Contrasts between chemical and physical estimates of baseflow help discern multiple sources of water contributing to rivers

NASA Astrophysics Data System (ADS)

Cartwright, I.; Gilfedder, B.; Hofmann, H.

2013-05-01

This study compares geochemical and physical methods of estimating baseflow in the upper reaches of the Barwon River, southeast Australia. Estimates of baseflow from physical techniques such as local minima and recursive digital filters are higher than those based on chemical mass balance using continuous electrical conductivity (EC). Between 2001 and 2011 the baseflow flux calculated using chemical mass balance is between 1.8 × 103 and 1.5 × 104 ML yr-1 (15 to 25% of the total discharge in any one year) whereas recursive digital filters yield baseflow fluxes of 3.6 × 103 to 3.8 × 104 ML yr-1 (19 to 52% of discharge) and the local minimum method yields baseflow fluxes of 3.2 × 103 to 2.5 × 104 ML yr-1 (13 to 44% of discharge). These differences most probably reflect how the different techniques characterise baseflow. Physical methods probably aggregate much of the water from delayed sources as baseflow. However, as many delayed transient water stores (such as bank return flow or floodplain storage) are likely to be geochemically similar to surface runoff, chemical mass balance calculations aggregate them with the surface runoff component. The mismatch between geochemical and physical estimates is greatest following periods of high discharge in winter, implying that these transient stores of water feed the river for several weeks to months. Consistent with these interpretations, modelling of bank storage indicates that bank return flows provide water to the river for several weeks after flood events. EC vs. discharge variations during individual flow events also imply that an inflow of low EC water stored within the banks or on the floodplain occurs as discharge falls. The joint use of physical and geochemical techniques allows a better understanding of the different components of water that contribute to river flow, which is important for the management and protection of water resources.

Numerical investigation of flow structure and pressure pulsation in the Francis-99 turbine during startup

NASA Astrophysics Data System (ADS)

Minakov, A.; Sentyabov, A.; Platonov, D.

2017-01-01

We performed numerical simulation of flow in a laboratory model of a Francis hydroturbine at startup regimes. Numerical technique for calculating of low frequency pressure pulsations in a water turbine is based on the use of DES (k-ω Shear Stress Transport) turbulence model and the approach of “frozen rotor”. The structure of the flow behind the runner of turbine was analysed. Shows the effect of flow structure on the frequency and intensity of non-stationary processes in the flow path. Two version of the inlet boundary conditions were considered. The first one corresponded measured time dependence of the discharge. Comparison of the calculation results with the experimental data shows the considerable delay of the discharge in this calculation. Second version corresponded linear approximation of time dependence of the discharge. This calculation shows good agreement with experimental results.

Comparison of the surface dielectric barrier discharge characteristics under different electrode gaps

NASA Astrophysics Data System (ADS)

Gao, Guoqiang; Dong, Lei; Peng, Kaisheng; Wei, Wenfu; Li, Chunmao; Wu, Guangning

2017-01-01

Currently, great interests are paid to the surface dielectric barrier discharge due to the diverse and interesting application. In this paper, the influences of the electrode gap on the discharge characteristics have been studied. Aspects of the electrical parameters, the optical emission, and the discharge induced gas flow were considered. The electrode gap varied from 0 mm to 21 mm, while the applied AC voltage was studied in the range of 17 kV-27 kV. Results indicate that with the increase of the electrode gap, the variation of discharge voltage exhibits an increasing trend, while the other parameters (i.e., the current, power, and induced flow velocity) increase first, and then decrease once the gap exceeded the critical value. Mechanisms of the electrode gap influencing these key parameters were discussed from the point of equivalent circuit. The experimental results reveal that an optimal discharge gap can be obtained, which is closely related to the applied voltage. Visualization of the induced flow with different electrode gaps was realized by the Schlieren diagnostic technique. Finally, the velocities of induced gas flow determined by the pitot tube were compared with the results of intensity-integral method, and good agreements were found.

High voltage pulse ignition of mercury discharge hollow cathodes

NASA Technical Reports Server (NTRS)

Wintucky, E. G.

1973-01-01

A high voltage pulse generated by a capacitor discharge into a step-up transformer has been demonstrated capable of consistently igniting hollow cathode mercury discharges at propellant flows and heater power levels much below those required by conventional cathode starting. Results are presented for 3.2-mm diameter enclosed and open keeper cathodes. Starting characteristics are shown to depend on keeper voltage, mercury flow rate, heater power, keeper orifice size, emissive materials, and electrode to which the pulse is applied. This starting technique has been used to start a cathode over 10,000 times without any degradation of starting capability.

Effect of pulsed corona discharge voltage and feed gas flow rate on dissolved ozone concentration

NASA Astrophysics Data System (ADS)

Prasetyaningrum, A.; Ratnawati, Jos, B.

2015-12-01

Ozonization is one of the methods extensively used for water purification and degradation of organic materials. Ozone (O3) is recognized as a powerful oxidizing agent. Due to its strong oxidability and better environmental friendless, ozone increasing being used in domestic and industrial applications. Current technology in ozone production utilizes several techniques (corona discharge, ultra violet radiation and electrolysis). This experiment aimed to evaluating effect of voltage and gas flow rate on ozone production with corona discharge. The system consists of two net-type stainless steel electrode placed in a dielectric barrier. Three pulsed voltage (20, 30, 40 KV) and flow rate (5, 10, 15 L/min) were prepare for operation variable at high frequency (3.7 kHz) with AC pulsed power supply. The dissolved ozone concentration depends on the applied high-voltage level, gas flow rate and the discharge exposure duration. The ozone concentration increases with decreasing gas flow rate. Dissolved ozone concentrations greater than 200 ppm can be obtained with a minimum voltage 40 kV.

Innovative model-based flow rate optimization for vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

König, S.; Suriyah, M. R.; Leibfried, T.

2016-11-01

In this paper, an innovative approach is presented to optimize the flow rate of a 6-kW vanadium redox flow battery with realistic stack dimensions. Efficiency is derived using a multi-physics battery model and a newly proposed instantaneous efficiency determination technique. An optimization algorithm is applied to identify optimal flow rates for operation points defined by state-of-charge (SoC) and current. The proposed method is evaluated against the conventional approach of applying Faraday's first law of electrolysis, scaled to the so-called flow factor. To make a fair comparison, the flow factor is also optimized by simulating cycles with different charging/discharging currents. It is shown through the obtained results that the efficiency is increased by up to 1.2% points; in addition, discharge capacity is also increased by up to 1.0 kWh or 5.4%. Detailed loss analysis is carried out for the cycles with maximum and minimum charging/discharging currents. It is shown that the proposed method minimizes the sum of losses caused by concentration over-potential, pumping and diffusion. Furthermore, for the deployed Nafion 115 membrane, it is observed that diffusion losses increase with stack SoC. Therefore, to decrease stack SoC and lower diffusion losses, a higher flow rate during charging than during discharging is reasonable.

Deterministic chaotic dynamics of Raba River flow (Polish Carpathian Mountains)

NASA Astrophysics Data System (ADS)

Kędra, Mariola

2014-02-01

Is the underlying dynamics of river flow random or deterministic? If it is deterministic, is it deterministic chaotic? This issue is still controversial. The application of several independent methods, techniques and tools for studying daily river flow data gives consistent, reliable and clear-cut results to the question. The outcomes point out that the investigated discharge dynamics is not random but deterministic. Moreover, the results completely confirm the nonlinear deterministic chaotic nature of the studied process. The research was conducted on daily discharge from two selected gauging stations of the mountain river in southern Poland, the Raba River.

OH and O radicals production in atmospheric pressure air/Ar/H2O gliding arc discharge plasma jet

NASA Astrophysics Data System (ADS)

N, C. ROY; M, R. TALUKDER; A, N. CHOWDHURY

2017-12-01

Atmospheric pressure air/Ar/H2O gliding arc discharge plasma is produced by a pulsed dc power supply. An optical emission spectroscopic (OES) diagnostic technique is used for the characterization of plasmas and for identifications of {{OH}} and {{O}} radicals along with other species in the plasmas. The OES diagnostic technique reveals the excitation T x ≈ 5550-9000 K, rotational T r ≈ 1350-2700 K and gas T g ≈ 850-1600 K temperatures, and electron density {n}{{e}}≈ ({1.1-1.9})× {10}14 {{{cm}}}-3 under different experimental conditions. The production and destruction of {{OH}} and {{O}} radicals are investigated as functions of applied voltage and air flow rate. Relative intensities of {{OH}} and {{O}} radicals indicate that their production rates are increased with increasing {{Ar}} content in the gas mixture and applied voltage. {n}{{e}} reveals that the higher densities of {{OH}} and {{O}} radicals are produced in the discharge due to more effective electron impact dissociation of {{{H}}}2{{O}} and {{{O}}}2 molecules caused by higher kinetic energies as gained by electrons from the enhanced electric field as well as by enhanced {n}{{e}}. The productions of {{OH}} and {{O}} are decreasing with increasing air flow rate due to removal of Joule heat from the discharge region but enhanced air flow rate significantly modifies discharge maintenance properties. Besides, {T}{{g}} significantly reduces with the enhanced air flow rate. This investigation reveals that {{Ar}} plays a significant role in the production of {{OH}} and {{O}} radicals.

Forward to the Future: Estimating River Discharge with McFLI

NASA Astrophysics Data System (ADS)

Gleason, C. J.; Durand, M. T.; Garambois, P. A.

2016-12-01

The global surface water budget is still poorly understood, and improving our understanding of freshwater budgets requires coordination between in situ observations, models, and remote sensing. The upcoming launch of the NASA/CNES Surface Water and Ocean Topography (SWOT) satellite has generated considerable excitement as a new tool enabling hydrologists to tackle some of the most pressing questions facing their discipline. One question in particular which SWOT seems well suited to answer is river discharge (flow rate) estimation in ungauged basins: SWOT's anticipated measurements of river surface height and area have ushered in a new technique in hydrology- what we are here calling Mass conserved Flow Law Inversions, or McFLI. McFLI algorithms leverage classic hydraulic flow expressions (e.g. Manning's Equation, hydraulic geometry) within mass conserved river reaches to construct a simplified but still underconstrained system of equations to be solved for an unknown discharge. Most existing McFLI techniques have been designed to take advantage of SWOT's measurements and Manning's Equation: SWOT will observe changes in cross sectional area and river surface slope over time, so the McFLI need only solve for baseflow area and Manning's roughness coefficient. Recently published preliminary results have indicated that McFLI can be a viable tool in a global hydrologist's toolbox (discharge errors less than 30% as compared to gauges are possible in most cases). Therefore, we here outline the progress to date for McFLI techniques, and highlight three key areas for future development: 1) Maximize the accuracy and robustness of McFLI by incorporating ancillary data from satellites, models, and in situ observations. 2) Develop new McFLI techniques using novel or underutilized flow laws. 3) Systematically test McFLI to define different inversion classes of rivers with well-defined error budgets based on geography and available data for use in gauged and ungauged basins alike.

Application of acoustical methods for estimating water flow and constituent loads in Perdido Bay, Florida

USGS Publications Warehouse

Grubbs, J.W.; Pittman, J.R.

1997-01-01

Water flow and quality data were collected from December 1994 to September 1995 to evaluate variations in discharge, water quality, and chemical fluxes (loads) through Perdido Bay, Florida. Data were collected at a cross section parallel to the U.S. Highway 98 bridge. Discharges measured with an acoustic Doppler current profiler (ADCP) and computed from stage-area and velocity ratings varied roughly between + or - 10,000 cubic feet per second during a typical tidal cycle. Large reversals in flow direction occurred rapidly (less than 1 hour), and complete reversals (resulting in near peak net-upstream or downstream discharges) occurred within a few hours of slack water. Observations of simultaneous upstream and downstream flow (bidirectional flow) were quite common in the ADCP measurements, with opposing directions of flow occurring predominantly in vertical layers. Continuous (every 15 minutes) discharge data were computed for the period from August 18, 1995, to September 28, 1995, and filtered daily mean discharge values were computed for the period from August 19 to September 26, 1995. Data were not computed prior to August 18, 1995, either because of missing data or because the velocity rating was poorly defined (because of insufficient data) for the period prior to landfall of hurricane Erin (August 3, 1995). The results of the study indicate that acoustical techniques can yield useful estimates of continuous (instantaneous) discharge in Perdido Bay. Useful estimates of average daily net flow rates can also be obtained, but the accuracy of these estimates will be limited by small rating shifts that introduce bias into the instantaneous values that are used to compute the net flows. Instantaneous loads of total nitrogen ranged from -180 to 220 grams per second for the samples collected during the study, and instantaneous loads of total phosphorous ranged from -10 to 11 grams per second (negative loads indicate net upstream transport). The chloride concentrations from the water samples collected from Perdido Bay indicated a significant amount of mixing of saltwater and freshwater. Mixing effects could greatly reduce the accuracy of estimates of net loads of nutrients or other substances. The study results indicate that acoustical techniques can yield acceptable estimates of instantaneous loads in Perdido Bay. However, estimates of net loads should be interpreted with great caution and may have unacceptably large errors, especially when saltwater and freshwater concentrations differ greatly.

Effect of pulsed corona discharge voltage and feed gas flow rate on dissolved ozone concentration

DOE Office of Scientific and Technical Information (OSTI.GOV)

Prasetyaningrum, A., E-mail: ajiprasetyaningrum@gmail.com; Ratnawati,; Jos, B.

Ozonization is one of the methods extensively used for water purification and degradation of organic materials. Ozone (O{sub 3}) is recognized as a powerful oxidizing agent. Due to its strong oxidability and better environmental friendless, ozone increasing being used in domestic and industrial applications. Current technology in ozone production utilizes several techniques (corona discharge, ultra violet radiation and electrolysis). This experiment aimed to evaluating effect of voltage and gas flow rate on ozone production with corona discharge. The system consists of two net-type stainless steel electrode placed in a dielectric barrier. Three pulsed voltage (20, 30, 40 KV) and flowmore » rate (5, 10, 15 L/min) were prepare for operation variable at high frequency (3.7 kHz) with AC pulsed power supply. The dissolved ozone concentration depends on the applied high-voltage level, gas flow rate and the discharge exposure duration. The ozone concentration increases with decreasing gas flow rate. Dissolved ozone concentrations greater than 200 ppm can be obtained with a minimum voltage 40 kV.« less

Numerical simulation of groundwater flow at Puget Sound Naval Shipyard, Naval Base Kitsap, Bremerton, Washington

USGS Publications Warehouse

Jones, Joseph L.; Johnson, Kenneth H.; Frans, Lonna M.

2016-08-18

Information about groundwater-flow paths and locations where groundwater discharges at and near Puget Sound Naval Shipyard is necessary for understanding the potential migration of subsurface contaminants by groundwater at the shipyard. The design of some remediation alternatives would be aided by knowledge of whether groundwater flowing at specific locations beneath the shipyard will eventually discharge directly to Sinclair Inlet of Puget Sound, or if it will discharge to the drainage system of one of the six dry docks located in the shipyard. A 1997 numerical (finite difference) groundwater-flow model of the shipyard and surrounding area was constructed to help evaluate the potential for groundwater discharge to Puget Sound. That steady-state, multilayer numerical model with homogeneous hydraulic characteristics indicated that groundwater flowing beneath nearly all of the shipyard discharges to the dry-dock drainage systems, and only shallow groundwater flowing beneath the western end of the shipyard discharges directly to Sinclair Inlet.Updated information from a 2016 regional groundwater-flow model constructed for the greater Kitsap Peninsula was used to update the 1997 groundwater model of the Puget Sound Naval Shipyard. That information included a new interpretation of the hydrogeologic units underlying the area, as well as improved recharge estimates. Other updates to the 1997 model included finer discretization of the finite-difference model grid into more layers, rows, and columns, all with reduced dimensions. This updated Puget Sound Naval Shipyard model was calibrated to 2001–2005 measured water levels, and hydraulic characteristics of the model layers representing different hydrogeologic units were estimated with the aid of state-of-the-art parameter optimization techniques.The flow directions and discharge locations predicted by this updated model generally match the 1997 model despite refinements and other changes. In the updated model, most groundwater discharge recharged within the boundaries of the shipyard is to the dry docks; only at the western end of the shipyard does groundwater discharge directly to Puget Sound. Particle tracking for the existing long-term monitoring well network suggests that only a few wells intercept groundwater that originates as recharge within the shipyard boundary.

Improving estimates of streamflow characteristics using LANDSAT-1 (ERTS-1) imagery. [Delmarva Peninsula

NASA Technical Reports Server (NTRS)

Hollyday, E. F. (Principal Investigator)

1975-01-01

The author has identified the following significant results. Streamflow characteristics in the Delmarva Peninsula derived from the records of daily discharge of 20 gaged basins are representative of the full range in flow conditions and include all of those commonly used for design or planning purposes. They include annual flood peaks with recurrence intervals of 2, 5, 10, 25, and 50 years, mean annual discharge, standard deviation of the mean annual discharge, mean monthly discharges, standard deviation of the mean monthly discharges, low-flow characteristics, flood volume characteristics, and the discharge equalled or exceeded 50 percent of the time. Streamflow and basin characteristics were related by a technique of multiple regression using a digital computer. A control group of equations was computed using basin characteristics derived from maps and climatological records. An experimental group of equations was computed using basin characteristics derived from LANDSAT imagery as well as from maps and climatological records. Based on a reduction in standard error of estimate equal to or greater than 10 percent, the equations for 12 stream flow characteristics were substantially improved by adding to the analyses basin characteristics derived from LANDSAT imagery.

Hollow cathode startup using a microplasma discharge

NASA Technical Reports Server (NTRS)

Aston, G.

1981-01-01

Attention is given to a microplasma discharge to initiate a hollow cathode discharge for such applications as plasma flow experiments, the electric propulsion of space vehicles, and as a replacement for filament cathodes in neutral beam injector ion sources. The technique results in a cathode that is easy to start, simple in design, and which does not require external RF exciters, inserts or heating elements. Future applications may include ion beam milling and ion implantation.

Towards a delimitation of southwestern Nigeria into hydrological regions

NASA Astrophysics Data System (ADS)

Ogunkoya, O. O.

1988-05-01

Fifteen third-order drainage basins (1:50,000) on the Basement Complex rocks of southwestern Nigeria are classified into hydrological regions using hydrologic response parameters of average daily mean specific discharge ( QA); daily mean specific discharges equalled or exceeded 90% ( Q90), 50% ( Q50) and 10% ( Q10) of the study period; variability index of flow ( VI); recession constant ( K) of flow from peak discharge at the end of the rainy season to minimum discharge in the dry season; total annual runoff ( RO); total runoff within the dry season ( DSRO); dry season runoff as a percentage of total annual runoff (% DSRO); runoff coefficient ( ROC); and, number of days during the study period when there was no flow ( NFD). An ordination technique and a classification algorithm derived from cluster analysis technique and incorporating the analysis of variance (ANOVA) tests to determine the level of significance of the homogeneity of derived classes, were used to classify the fifteen basins into five hydrologically homogeneous regions. The constituent basins of each region were observed to share common basin geology. It was observed that those drainage basins having at least 50% of their basin area underlain by quartzitic rocks form two groups and have the most desirable or optimal hydrologic response patterns, desirability or optimality being in terms of ability to potentially meet water resource development requirements (i.e. high perennial discharge, low variability and large groundwater contribution to stream flow). The basins predominantly underlain by granite-gneisses and amphibolitic rocks have much poorer hydrologic response patterns. Hydrological regionalization in southwestern Nigeria appears to be influenced by drainage basin geology while percentage area of the basin underlain by massive quartzites could be used as an index of occurrence of desirable hydrologic response pattern.

Is the difference between chemical and numerical estimates of baseflow meaningful?

NASA Astrophysics Data System (ADS)

Cartwright, Ian; Gilfedder, Ben; Hofmann, Harald

2014-05-01

Both chemical and numerical techniques are commonly used to calculate baseflow inputs to gaining rivers. In general the chemical methods yield lower estimates of baseflow than the numerical techniques. In part, this may be due to the techniques assuming two components (event water and baseflow) whereas there may also be multiple transient stores of water. Bank return waters, interflow, or waters stored on floodplains are delayed components that may be geochemically similar to the surface water from which they are derived; numerical techniques may record these components as baseflow whereas chemical mass balance studies are likely to aggregate them with the surface water component. This study compares baseflow estimates using chemical mass balance, local minimum methods, and recursive digital filters in the upper reaches of the Barwon River, southeast Australia. While more sophisticated techniques exist, these methods of estimating baseflow are readily applied with the available data and have been used widely elsewhere. During the early stages of high-discharge events, chemical mass balance overestimates groundwater inflows, probably due to flushing of saline water from wetlands and marshes, soils, or the unsaturated zone. Overall, however, estimates of baseflow from the local minimum and recursive digital filters are higher than those from chemical mass balance using Cl calculated from continuous electrical conductivity. Between 2001 and 2011, the baseflow contribution to the upper Barwon River calculated using chemical mass balance is between 12 and 25% of annual discharge. Recursive digital filters predict higher baseflow contributions of 19 to 52% of annual discharge. These estimates are similar to those from the local minimum method (16 to 45% of annual discharge). These differences most probably reflect how the different techniques characterise the transient water sources in this catchment. The local minimum and recursive digital filters aggregate much of the water from delayed sources as baseflow. However, as many of these delayed transient water stores (such as bank return flow, floodplain storage, or interflow) have Cl concentrations that are similar to surface runoff, chemical mass balance calculations aggregate them with the surface runoff component. The difference between the estimates is greatest following periods of high discharge in winter, implying that these transient stores of water feed the river for several weeks to months at that time. Cl vs. discharge variations during individual flow events also demonstrate that inflows of high-salinity older water occurs on the rising limbs of hydrographs followed by inflows of low-salinity water from the transient stores as discharge falls. The use of complementary techniques allows a better understanding of the different components of water that contribute to river flow, which is important for the management and protection of water resources.

Numerical simulations of river discharges, nutrient flux and nutrient dispersal in Jakarta Bay, Indonesia.

PubMed

van der Wulp, Simon A; Damar, Ario; Ladwig, Norbert; Hesse, Karl-J

2016-09-30

The present application of numerical modelling techniques provides an overview of river discharges, nutrient flux and nutrient dispersal in Jakarta Bay. A hydrological model simulated river discharges with a total of 90 to 377m(3)s(-1) entering Jakarta Bay. Daily total nitrogen and total phosphorus loads ranged from 40 to 174tons and 14 to 60tons, respectively. Flow model results indicate that nutrient gradients are subject to turbulent mixing by tides and advective transport through circulation driven by wind, barotropic and baroclinic pressure gradients. The bulk of nutrient loads originate from the Citarum and Cisadane rivers flowing through predominantly rural areas. Despite lower nutrient loads, river discharges from the urban area of Jakarta exhibit the highest impact of nutrient concentrations in the near shore area of Jakarta Bay and show that nutrient concentrations were not only regulated by nutrient loads but were strongly regulated by initial river concentrations and local flow characteristics. Copyright © 2016 Elsevier Ltd. All rights reserved.

Determination of discharge during pulsating flow

USGS Publications Warehouse

Thompson, T.H.

1968-01-01

Pulsating flow in an open channel is a manifestation of unstable-flow conditions in which a series of translatory waves of perceptible magnitude develops and moves rapidly downstream. Pulsating flow is a matter of concern in the design and operation of steep-gradient channels. If it should occur at high stages in a channel designed for stable flow, the capacity of the channel may be inadequate at a discharge that is much smaller than that for which the channel was designed. If the overriding translatory wave carries an appreciable part of the total flow, conventional stream-gaging procedures cannot be used to determine the discharge; neither the conventional instrumentation nor conventional methodology is adequate. A method of determining the discharge during pulsating flow was tested in the Santa Anita Wash flood control channel in Arcadia, Calif., April 16, 1965. Observations of the dimensions and velocities of translatory waves were made during a period of controlled reservoir releases of about 100, 200, and 300 cfs (cubic feet per second). The method of computing discharge was based on (1) computation of the discharge in the overriding waves and (2) computation of the discharge in the shallow-depth, or overrun, part of the flow. Satisfactory results were obtained by this method. However, the procedure used-separating the flow into two components and then treating the shallow-depth component as though it were steady--has no theoretical basis. It is simply an expedient for use until laboratory investigation can provide a satisfactory analytical solution to the problem of computing discharge during pulsating flow. Sixteen months prior to the test in Santa Anita Wash, a robot camera had been designed .and programmed to obtain the data needed to compute discharge by the method described above. The photographic equipment had been installed in Haines Creek flood control channel in Los Angeles, Calif., but it had not been completely tested because of the infrequency of flow in that channel. Because the Santa Anita Wash tests afforded excellent data for analysis, further development of the photographic ,technique at Haines Creek was discontinued. Three methods for obtaining the data needed to compute discharge during pulsating flow are proposed. In two of the methods--the photographic method and the depth-recorder method--the dimensions and velocities of translatory waves are recorded, and discharge is then computed by the procedure developed in this report. The third method?the constant-rate-dye-dilution method--yields the discharge more directly. The discharge is computed from the dye-injection rate and the ratio of the concentration of dye in the injected solution to the concentration of dye in the water sampled at a site downstream. The three methods should be developed and tested in ,the Santa Anita Wash flood control channel under controlled conditions similar to those in the test of April 1965.

Control system of an excitation power supply for fast axial flow CO2 lasersupda

NASA Astrophysics Data System (ADS)

Li, Bo; Jia, Xinting; Yuan, Hao; Gao, Yuhu; Wang, Youqing

2009-08-01

A switching power control system of fast axial flow CO2 lasers based on DSP is presented. The key techniques are described in detail, include the control principle, realization method and program design. The experiment showed that the system make the laser discharge stably and work in multi-mode. The discharge current can be adjusted from 3mA to 85mA continuously. 20-2000Hz frequency, 0-100% duty cycle laser pulse is achieved. The power supply can improve the processing efficiency and quality.

Estimates of Flow Duration, Mean Flow, and Peak-Discharge Frequency Values for Kansas Stream Locations

USGS Publications Warehouse

Perry, Charles A.; Wolock, David M.; Artman, Joshua C.

2004-01-01

Streamflow statistics of flow duration and peak-discharge frequency were estimated for 4,771 individual locations on streams listed on the 1999 Kansas Surface Water Register. These statistics included the flow-duration values of 90, 75, 50, 25, and 10 percent, as well as the mean flow value. Peak-discharge frequency values were estimated for the 2-, 5-, 10-, 25-, 50-, and 100-year floods. Least-squares multiple regression techniques were used, along with Tobit analyses, to develop equations for estimating flow-duration values of 90, 75, 50, 25, and 10 percent and the mean flow for uncontrolled flow stream locations. The contributing-drainage areas of 149 U.S. Geological Survey streamflow-gaging stations in Kansas and parts of surrounding States that had flow uncontrolled by Federal reservoirs and used in the regression analyses ranged from 2.06 to 12,004 square miles. Logarithmic transformations of climatic and basin data were performed to yield the best linear relation for developing equations to compute flow durations and mean flow. In the regression analyses, the significant climatic and basin characteristics, in order of importance, were contributing-drainage area, mean annual precipitation, mean basin permeability, and mean basin slope. The analyses yielded a model standard error of prediction range of 0.43 logarithmic units for the 90-percent duration analysis to 0.15 logarithmic units for the 10-percent duration analysis. The model standard error of prediction was 0.14 logarithmic units for the mean flow. Regression equations used to estimate peak-discharge frequency values were obtained from a previous report, and estimates for the 2-, 5-, 10-, 25-, 50-, and 100-year floods were determined for this report. The regression equations and an interpolation procedure were used to compute flow durations, mean flow, and estimates of peak-discharge frequency for locations along uncontrolled flow streams on the 1999 Kansas Surface Water Register. Flow durations, mean flow, and peak-discharge frequency values determined at available gaging stations were used to interpolate the regression-estimated flows for the stream locations where available. Streamflow statistics for locations that had uncontrolled flow were interpolated using data from gaging stations weighted according to the drainage area and the bias between the regression-estimated and gaged flow information. On controlled reaches of Kansas streams, the streamflow statistics were interpolated between gaging stations using only gaged data weighted by drainage area.

Experimental Determination of the Dynamic Hydraulic Transfer Function for the J-2X Oxidizer Turbopump. Part One; Methodology

NASA Technical Reports Server (NTRS)

Zoladz, Tom; Patel, Sandeep; Lee, Erik; Karon, Dave

2011-01-01

An advanced methodology for extracting the hydraulic dynamic pump transfer matrix (Yp) for a cavitating liquid rocket engine turbopump inducer+impeller has been developed. The transfer function is required for integrated vehicle pogo stability analysis as well as optimization of local inducer pumping stability. Laboratory pulsed subscale waterflow test of the J-2X oxygen turbo pump is introduced and our new extraction method applied to the data collected. From accurate measures of pump inlet and discharge perturbational mass flows and pressures, and one-dimensional flow models that represents complete waterflow loop physics, we are able to derive Yp and hence extract the characteristic pump parameters: compliance, pump gain, impedance, mass flow gain. Detailed modeling is necessary to accurately translate instrument plane measurements to the pump inlet and discharge and extract Yp. We present the MSFC Dynamic Lump Parameter Fluid Model Framework and describe critical dynamic component details. We report on fit minimization techniques, cost (fitness) function derivation, and resulting model fits to our experimental data are presented. Comparisons are made to alternate techniques for spatially translating measurement stations to actual pump inlet and discharge.

Experimental study of low-temperature plasma of electrical discharges with liquid electrodes

NASA Astrophysics Data System (ADS)

Zheltukhin, Viktor; Gaisin, Almaz

2016-09-01

Results of the experimental research of discharge between the liquid jet cathode (LJC) and the metal anode are presented. The discharge was studied over the voltage range U = 100 - 600 V, discharge current range I = 0 . 1 - 0 . 25 A, external pressure range P =105 Pa, discharge power Pd = 10 - 150 W. We used the techniques of infrared thermography and spectral measurements. Schlieren's photography is applied for describing the processes in liquid and gas phase. Results of the experimental researches of discharge current-voltage characteristic (CVC), the surface temperature distribution both on the LJC and the metal anode, a spectral measurements are showed. Effects of action both of breakdown and discharge on the jet flow as well as on the air flow near the discharge are described. It is found that the discharge CVC has an ascending behavior due to increase of plasma current density. The discharge is generated on the borders between the LJC and the metal anode as well as along the LJC misshaping this one. It is established that both the convection streams and an electrolyte drops are formed during the discharge burn. It is found that the discharge temperature in the vicinity of electrode surface reaches T 348 K. The work was funded by RFBR, according to the research projects No.,14-01-0755.

Contrasts between estimates of baseflow help discern multiple sources of water contributing to rivers

NASA Astrophysics Data System (ADS)

Cartwright, I.; Gilfedder, B.; Hofmann, H.

2014-01-01

This study compares baseflow estimates using chemical mass balance, local minimum methods, and recursive digital filters in the upper reaches of the Barwon River, southeast Australia. During the early stages of high-discharge events, the chemical mass balance overestimates groundwater inflows, probably due to flushing of saline water from wetlands and marshes, soils, or the unsaturated zone. Overall, however, estimates of baseflow from the local minimum and recursive digital filters are higher than those based on chemical mass balance using Cl calculated from continuous electrical conductivity measurements. Between 2001 and 2011, the baseflow contribution to the upper Barwon River calculated using chemical mass balance is between 12 and 25% of the annual discharge with a net baseflow contribution of 16% of total discharge. Recursive digital filters predict higher baseflow contributions of 19 to 52% of discharge annually with a net baseflow contribution between 2001 and 2011 of 35% of total discharge. These estimates are similar to those from the local minimum method (16 to 45% of annual discharge and 26% of total discharge). These differences most probably reflect how the different techniques characterise baseflow. The local minimum and recursive digital filters probably aggregate much of the water from delayed sources as baseflow. However, as many delayed transient water stores (such as bank return flow, floodplain storage, or interflow) are likely to be geochemically similar to surface runoff, chemical mass balance calculations aggregate them with the surface runoff component. The difference between the estimates is greatest following periods of high discharge in winter, implying that these transient stores of water feed the river for several weeks to months at that time. Cl vs. discharge variations during individual flow events also demonstrate that inflows of high-salinity older water occurs on the rising limbs of hydrographs followed by inflows of low-salinity water from the transient stores as discharge falls. The joint use of complementary techniques allows a better understanding of the different components of water that contribute to river flow, which is important for the management and protection of water resources.

Comparison of three artificial intelligence techniques for discharge routing

NASA Astrophysics Data System (ADS)

Khatibi, Rahman; Ghorbani, Mohammad Ali; Kashani, Mahsa Hasanpour; Kisi, Ozgur

2011-06-01

SummaryThe inter-comparison of three artificial intelligence (AI) techniques are presented using the results of river flow/stage timeseries, that are otherwise handled by traditional discharge routing techniques. These models comprise Artificial Neural Network (ANN), Adaptive Nero-Fuzzy Inference System (ANFIS) and Genetic Programming (GP), which are for discharge routing of Kizilirmak River, Turkey. The daily mean river discharge data with a period between 1999 and 2003 were used for training and testing the models. The comparison includes both visual and parametric approaches using such statistic as Coefficient of Correlation (CC), Mean Absolute Error (MAE) and Mean Square Relative Error (MSRE), as well as a basic scoring system. Overall, the results indicate that ANN and ANFIS have mixed fortunes in discharge routing, and both have different abilities in capturing and reproducing some of the observed information. However, the performance of GP displays a better edge over the other two modelling approaches in most of the respects. Attention is given to the information contents of recorded timeseries in terms of their peak values and timings, where one performance measure may capture some of the information contents but be ineffective in others. Thus, this makes a case for compiling knowledge base for various modelling techniques.

Using natural distributions of short-lived radium isotopes to quantify groundwater discharge and recharge

USGS Publications Warehouse

Krest, J.M.; Harvey, J.W.

2003-01-01

Radium activity in pore water of wetland sediments often differs from the amount expected from local production, decay, and exchange with solid phases. This disequilibrium results from vertical transport of radium with groundwater that flows between the underlying aquifer and surface water. In situations where groundwater recharge or discharge is significant, the rate of vertical water flow through wetland sediment can be determined from the radium disequilibrium by a combined model of transport, production, decay, and exchange with solid phases. We have developed and tested this technique at three sites in the freshwater portion of the Everglades by quantifying vertical advective velocities in areas with persistent groundwater recharge or discharge and estimating a coefficient of dispersion at a site that is subject to reversals between recharge and discharge. Groundwater velocities (v) were determined to be between 0 and -0.5 cm d-1 for a recharge site and 1.5 ?? 0.4 cm d-1 for a discharge site near Levee 39 in the Everglades. Strong gradients in 223Ra and 224Ra usually occurred at the base of the peat layer, which avoided the problems of other tracers (e.g., chloride) for which greatest sensitivity occurs near the peat surface - a zone readily disturbed by processes unrelated to groundwater flow. This technique should be easily applicable to any wetland system with different production rates of these isotopes in distinct sedimentary layers or surface water. The approach is most straightforward in systems where constant pore-water ionic strength can be assumed, simplifying the modeling of radium exchange.

Considering the summation of the effect of harmful substances during the calculation of the environmentally safe waste water discharge

NASA Astrophysics Data System (ADS)

Sokolov, A. K.

2017-09-01

This article presents the technique of assessing the maximum allowable (standard) discharge of waste waters with several harmful substances into a water reservoir. The technique makes it possible to take into account the summation of their effect provided that the limiting harmful indices are the same. The expressions for the determination of the discharge limit of waste waters have been derived from the conditions of admissibility of the effect of several harmful substances on the waters of a reservoir. Mathematical conditions of admissibility of the effect of wastewaters on a reservoir are given for the characteristic combinations of limiting harmful indices and hazard classes of several substances. The conditions of admissibility of effects are presented in the form of logical products of the sums of relative concentrations that should not exceed the value of 1. It is shown that the calculation of the process of wastewater dilution in a flowing water reservoir is possible only on the basis of a numerical method to assess the wastewater discharge limit. An example of the numerical calculation of the standard limit of industrial enterprise wastewater discharges that contain polysulfide oil, flocculant VPK-101, and fungicide captan is given to test this method. In addition to these three harmful substances, the water reservoir also contained a fourth substance, namely, Zellek-Super herbicide, above the waste discharge point. The summation of the harmful effect was taken into account for VPK-101, captan, and Zellek-Super. The reliability of the technique was tested by the calculation of concentrations of the four substances in the control point of the flowing reservoir during the estimated maximum allowable wastewater discharge. It is shown that the value of the maximum allowable discharge limit was almost two times higher for the example under consideration, taking into account that the effect of harmful substances was unidirectional, which provides a higher level of environmental safety for them.

Surface flow observations from a gauge-cam station on the Tiber river

NASA Astrophysics Data System (ADS)

Tauro, Flavia; Porfiri, Maurizio; Petroselli, Andrea; Grimaldi, Salvatore

2016-04-01

Understanding the kinematic organization of natural water bodies is central to hydrology and environmental engineering practice. Reliable and continuous flow observations are essential to comprehend flood generation and propagation mechanisms, erosion dynamics, sediment transport, and drainage network evolution. In engineering practice, flood warning systems largely rely on real-time discharge measurements, and flow velocity monitoring is important for the design and management of hydraulic structures, such as reservoirs and hydropower plants. Traditionally, gauging stations have been equipped with water level meters, and stage-discharge relationships (rating curves) have been established through few direct discharge measurements. Only in rare instances, monitoring stations have integrated radar technology for local measurement of surface flow velocity. Establishing accurate rating curves depends on the availability of a comprehensive range of discharge values, including measurements recorded during extreme events. However, discharge values during high-flow events are often difficult or even impossible to obtain, thereby hampering the reliability of discharge predictions. Fully remote observations have been enabled in the past ten years through optics-based velocimetry techniques. Such methodologies enable the estimation of the surface flow velocity field over extended regions from the motion of naturally occurring debris or floaters dragged by the current. Resting on the potential demonstrated by such approaches, here, we present a novel permanent gauge-cam station for the observation of the flow velocity field in the Tiber river. This new station captures one-minute videos every 10 minutes over an area of up to 20.6 × 15.5m2. In a feasibility study, we demonstrate that experimental images analyzed via particle tracking velocimetry and particle image velocimetry can be used to obtain accurate surface flow velocity estimations in close agreement with radar records. Future efforts will be devoted to the development of a comprehensive testbed infrastructure for investigating the potential of multiple optics-based approaches for surface hydrology.

Automatic dilution gaging of rapidly varying flow

USGS Publications Warehouse

Duerk, M.D.

1983-01-01

The analysis showed that the discharges measured by dye-dilution techniques were generally within ± 10 percent of the discharges determined from ratings established by current-meter measurements. Larger differences were noted at the start of and on the rising limb of four hydrographs. Of the 20 storms monitored, dilution measurements on 17 were of acceptable accuracy. Peak discharges from the open-channel site ranged from 0 to 12 percent departures from the existing rating whereas the comparison of peak discharge at the storm sewer site ranged from 0 to 5 percent departures from the existing rating.

A Riparian Approach to Dendrochronological Flow Reconstruction, Yellowstone River, Montana

NASA Astrophysics Data System (ADS)

Schook, D. M.; Rathburn, S. L.; Friedman, J. M.

2015-12-01

Tree ring-based flow reconstructions can reveal river discharge variability over durations far exceeding the gauged record, building perspective for both the measured record and future flows. We use plains cottonwood (Populus deltoides subsp. monilifera) tree rings collected from four rivers to reconstruct flow history of the Yellowstone River near its confluence with the Missouri River. Upland trees in dry regions are typically used in flow reconstruction because their annual growth is controlled by the same precipitation that drives downstream flow, but our study improves flow reconstruction by including floodplain trees that are directly affected by the river. Cores from over 1000 cottonwoods along the Yellowstone, Powder, Little Missouri, and Redwater Rivers were collected from within a 170 km radius to reconstruct flows using the Age Curve Standardization technique in a multiple regression analysis. The large sample from trees spanning many age classes allows us to use only the rings that were produced when each tree was less than 50 years old and growth was most strongly correlated to river discharge. Using trees from a range of rivers improves our ability to differentiate between growth resulting from local precipitation and river flow, and we show that cottonwood growth differs across these neighboring rivers having different watersheds. Using the program Seascorr, tree growth is found to better correlated to seasonal river discharge (R = 0.69) than to local precipitation (R = 0.45). Our flow reconstruction reveals that the most extreme multi-year or multi-decade drought periods of the last 250 years on either the Yellowstone (1817-1821) or Powder (1846-1865) Rivers are missed by the gauged discharge record. Across all sites, we document increased growth in the 20th century compared to the 19th, a finding unattainable with conventional methods but having important implications for flow management.

Field and laboratory determination of water-surface elevation and velocity using noncontact measurements

USGS Publications Warehouse

Nelson, Jonathan M.; Kinzel, Paul J.; Schmeeckle, Mark Walter; McDonald, Richard R.; Minear, Justin T.

2016-01-01

Noncontact methods for measuring water-surface elevation and velocity in laboratory flumes and rivers are presented with examples. Water-surface elevations are measured using an array of acoustic transducers in the laboratory and using laser scanning in field situations. Water-surface velocities are based on using particle image velocimetry or other machine vision techniques on infrared video of the water surface. Using spatial and temporal averaging, results from these methods provide information that can be used to develop estimates of discharge for flows over known bathymetry. Making such estimates requires relating water-surface velocities to vertically averaged velocities; the methods here use standard relations. To examine where these relations break down, laboratory data for flows over simple bumps of three amplitudes are evaluated. As anticipated, discharges determined from surface information can have large errors where nonhydrostatic effects are large. In addition to investigating and characterizing this potential error in estimating discharge, a simple method for correction of the issue is presented. With a simple correction based on bed gradient along the flow direction, remotely sensed estimates of discharge appear to be viable.

Interferometric estimation of ice sheet motion and topography

NASA Technical Reports Server (NTRS)

Joughlin, Ian; Kwok, Ron; Fahnestock, Mark; Winebrenner, Dale; Tulaczyk, Slawek; Gogenini, Prasad

1997-01-01

With ERS-1/2 satellite radar interferometry, it is possible to make measurements of glacier motion with high accuracy and fine spatial resolution. Interferometric techniques were applied to map velocity and topography for several outlet glaciers in Greenland. For the Humboldt and Petermann glaciers, data from several adjacent tracks were combined to make a wide-area map that includes the enhanced flow regions of both glaciers. The discharge flux of the Petermann glacier upstream of the grounding line was estimated, thereby establishing the potential use of ERS-1/2 interferometric data for monitoring ice-sheet discharge. Interferograms collected along a single track are sensitive to only one component of motion. By utilizing data from ascending and descending passes and by making a surface-parallel flow assumption, it is possible to measure the full three-dimensional vector flow field. The application of this technique for an area on the Ryder glacier is demonstrated. Finally, ERS-1/2 interferograms were used to observe a mini-surge on the Ryder glacier that occurred in autumn of 1995.

Monitoring of surface velocity of hyper-concentrated flow in a laboratory flume by means of fully-digital PIV

NASA Astrophysics Data System (ADS)

Termini, Donatella; Di Leonardo, Alice

2016-04-01

High flow conditions, which are generally characterized by high sediment concentrations, do not permit the use of traditional measurement equipment. Traditional techniques usually are based on the intrusive measure of the vertical profile of flow velocity and on the linking of water depth with the discharge through the rating curve. The major disadvantage of these measurement techniques is that they are difficult to use and not safe for operators especially in high flow conditions. The point is that, as literature shows (see as an example Moramarco and Termini, 2015), especially in such conditions, the measurement of surface velocity distribution is important to evaluate the mean flow velocity and, thus, the flow discharge. In the last decade, image-based techniques have been increasingly used for surface velocity measurements (among others Joeau et al., 2008). Experimental program has been recently conducted at the Hydraulic laboratory of the Department of Civil, Environmental, Aerospatial and of Materials Engineering (DICAM) - University of Palermo (Italy) in order to analyze the propagation phenomenon of hyper-concentrated flow in a defense channel. The experimental apparatus includes a high-precision camera and a system allowing the images recording. This paper investigates the utility and the efficiency of the digital image-technique for remote monitoring of surface velocity in hyper-concentrated flow by the aid of data collected during experiments conducted in the laboratory flume. In particular the present paper attention is focused on the estimation procedure of the velocity vectors and on their sensitivity with parameters (number of images, spatial resolution of interrogation area,) of the images processing procedure. References Jodeau M., A. Hauet, A. Paquier, Le Coz J., Dramais G., Application and evaluation of LS-PIV technique for the monitoring of river surface in high flow conditions, Flow Measurements and Instrumentation, Vol.19, No.2, 2008, pp.117-127. Moramarco T., Termini D., Entropic approach to estimate the mean flow velocity: experimental investigation in laboratory flumes, Environmental Fluid mechanics, Vol. 15, No.1, 2015.

Bioelectrographic testing of mineral samples: a comparison of techniques.

PubMed

Vainshelboim, Alex; Momoh, Kenneth S

2005-04-01

This study was initiated to determine the suitability of differing techniques to record optical properties of gemstones under electromagnetic stimulation. Such properties are of interest due to the historical use of gemstones in folkloric remedies, specifically as agents for concentrating, focusing, or otherwise conducting energy flows in the human body. The techniques researched produce a localized corona discharge around the tested material. The simplest technique, Tesla coil Kirlian photography (TCKP), uses a Tesla coil to introduce a strong electric current, and the circuit is completed by a glass electrode. The corona discharge is then photographed. The other technique used in the study is gas discharge visualization (GDV), which uses a pulsed current and a digital camera integral to the coil to produce digital images of the corona discharge. Gemstones were tested both whole and in powdered form. The sample gemstones were amethyst, aquamarine, garnet, golden citrine, pink tourmaline, and yellow topaz. Powdered gemstones were ground to a particle size of 2-5 microns; whole gemstones were roundcut to a diameter of 5 mm. In our tests, TCKP showed divergent effects for differing types of gemstone. The most extreme effects were exhibited by tourmaline, both in powdered and whole form. In addition, TCKP appeared to indicate differing effects for gemstones of the identical type but mined from differing locations. The GDV technique showed differing data among the gemstones for the measured parameters, indicating that a high relative intensity did not correspond to the size of the corona discharge. While both techniques showed promise in distinguishing differences in corona discharge behavior in gemstone samples, further work is necessary to determine the significance of differences in geographical sources or between gemstones of similar crystalline structure. The techniques explored show promise in characterizing the properties of gem materials under electromagnetic stimulation.

Field assessment of noncontact stream gauging using portable surface velocity radars (SVR)

NASA Astrophysics Data System (ADS)

Welber, Matilde; Le Coz, Jérôme; Laronne, Jonathan B.; Zolezzi, Guido; Zamler, Daniel; Dramais, Guillaume; Hauet, Alexandre; Salvaro, Martino

2016-02-01

The applicability of a portable, commercially available surface velocity radar (SVR) for noncontact stream gauging was evaluated through a series of field-scale experiments carried out in a variety of sites and deployment conditions. Comparisons with various concurrent techniques showed acceptable agreement with velocity profiles, with larger uncertainties close to the banks. In addition to discharge error sources shared with intrusive velocity-area techniques, SVR discharge estimates are affected by flood-induced changes in the bed profile and by the selection of a depth-averaged to surface velocity ratio, or velocity coefficient (α). Cross-sectional averaged velocity coefficients showed smaller fluctuations and closer agreement with theoretical values than those computed on individual verticals, especially in channels with high relative roughness. Our findings confirm that α = 0.85 is a valid default value, with a preferred site-specific calibration to avoid underestimation of discharge in very smooth channels (relative roughness ˜ 0.001) and overestimation in very rough channels (relative roughness > 0.05). Theoretically derived and site-calibrated values of α also give accurate SVR-based discharge estimates (within 10%) for low and intermediate roughness flows (relative roughness 0.001 to 0.05). Moreover, discharge uncertainty does not exceed 10% even for a limited number of SVR positions along the cross section (particularly advantageous to gauge unsteady flood flows and very large floods), thereby extending the range of validity of rating curves.

Controls on Thermal Discharge in Yellowstone NAtional Park, Wyoming

NASA Astrophysics Data System (ADS)

Mohrmann, Jacob Steven

2007-10-01

Significant fluctuations in discharge occur in hot springs in Yellowstone National Park on a seasonal to decadal scale (Ingebritsen et al., 2001) and an hourly scale (Vitale, 2002). The purpose of this study was to determine the interval of the fluctuations in discharge and to explain what causes those discharge patterns in three thermally influenced streams in Yellowstone National Park. By monitoring flow in these streams, whose primary source of input is thermal discharge, we were able to find several significant patterns of discharge fluctuations. Patterns were found by using two techniques of spectral analysis. The spectral analyses completed involved using the program "R" as well as Microsoft Excel, both of which use Fourier transforms. The Fourier transform is a linear operator that identifies frequencies in the original function. Stream flow data were collected using a FloDar open channel flow monitor. The flow meter collected data at15-minute intervals at White Creek and Rabbit Creek for a period of approximately two weeks each during the Fall. Flow data were also used from 15-minute data interval from a USGS gaging station at Tantalus Creek. Patterns of discharge fluctuation were found in each stream. By comparing spectral analysis results of flow data with spectral analysis of published tide data and barometric pressure data, connections were drawn between fluctuations in tidal and barometric-pressure patterns and flow patterns. Also, visual comparisons used to identify potential correspondence with earthquakes and precipitation events. At Tantalus Creek, patterns were affected only by barometric pressure changes. At White Creek, one pattern was attributed to barometric pressure fluctuations, and another pattern was found that could be associated with earth-tide forces. At Rabbit Creek, these patterns were absent. A pattern at 8.55 hours, which could not be attributed to barometric pressure or earth tide forces, was found at Rabbit and White Creeks. The 8.55 hour pattern in discharge found at both Rabbit and White Creeks may suggest a physical link between the sites, which are close (2.5 km). The time pattern could be a result of a shared hydrothermal aquifer, convectively heating and discharging at both streams. However, the common time pattern could also be the result of independent factors, which coincidentally caused a similar time pattern.

High voltage pulse ignition of mercury discharge hollow cathodes

NASA Technical Reports Server (NTRS)

Wintucky, E. G.

1973-01-01

A high voltage pulse generated by a capacitor discharge into a step-up transformer has been demonstrated capable of consistently igniting hollow cathode mercury discharges at propellant flows and heater power levels much below those required by conventional cathode starting. Results are presented for 3.2-mm diameter enclosed and open keeper cathodes. Starting characteristics are shown to depend on keeper voltage, mercury flow rate, heater power, keeper orifice size, emissive materials, and electrode to which the pulse is applied. This starting technique has been used to start a cathode over 10,000 times without any degradation of starting capability. The starting reliability, propellant and power savings offered by the high voltage pulse start should favorably impact performance of electron bombardment thrusters in missions requiring many on-off duty cycles.

Noncontact methods for measuring water-surface elevations and velocities in rivers: Implications for depth and discharge extraction

USGS Publications Warehouse

Nelson, Jonathan M.; Kinzel, Paul J.; McDonald, Richard R.; Schmeeckle, Mark

2016-01-01

Recently developed optical and videographic methods for measuring water-surface properties in a noninvasive manner hold great promise for extracting river hydraulic and bathymetric information. This paper describes such a technique, concentrating on the method of infrared videog- raphy for measuring surface velocities and both acoustic (laboratory-based) and laser-scanning (field-based) techniques for measuring water-surface elevations. In ideal laboratory situations with simple flows, appropriate spatial and temporal averaging results in accurate water-surface elevations and water-surface velocities. In test cases, this accuracy is sufficient to allow direct inversion of the governing equations of motion to produce estimates of depth and discharge. Unlike other optical techniques for determining local depth that rely on transmissivity of the water column (bathymetric lidar, multi/hyperspectral correlation), this method uses only water-surface information, so even deep and/or turbid flows can be investigated. However, significant errors arise in areas of nonhydrostatic spatial accelerations, such as those associated with flow over bedforms or other relatively steep obstacles. Using laboratory measurements for test cases, the cause of these errors is examined and both a simple semi-empirical method and computational results are presented that can potentially reduce bathymetric inversion errors.

Non-contact flow gauging for the extension and development of rating curves

NASA Astrophysics Data System (ADS)

Perks, Matthew; Large, Andy; Russell, Andy

2015-04-01

Accurate measurement of river discharge is fundamental to understanding hydrological processes, associated hazards and ecological responses within fluvial systems. Established protocols for determining river discharge are partial, predominantly invasive and logistically difficult during high flows. There is demand for new methods for accurate quantification of flow velocity under high-flow/flood conditions to in turn enable better post-event reconstruction of peak discharge. As a consequence considerable effort has been devoted to the development of innovative technologies for the representation of flow in open channels. Remotely operated fixed and mobile systems capable of providing quantitative estimates of instantaneous and time-averaged flow characteristics using non-contact methods has been a major development. Amongst the new approaches for stand-alone continuous monitoring of surface flows is Large Scale Particle Image Velocimetry (LSPIV). Here we adapt the LSPIV concept, to provide continuous discharge measurements in non-uniform channels with complex flow conditions. High Definition videos (1080p; 30fps) of the water surface are acquired at 5 minute intervals. The image is rectified to correct for perspective distortion using a new, open source tool which minimises errors resulting from oblique image capture. Naturally occurring artefacts on the water surface (e.g. bubbles, debris, etc.) are tracked with the Kanade-Lucas-Tomasi (KLT) algorithm. The data generated is in the form of a complex surface water velocity field which can be interrogated to extract a range of hydrological information such as the streamwise velocity at a cross-section of interest, or even allow the interrogation of hydrodynamic flow structures. Here we demonstrate that this approach is capable of generating river discharge data comparable to concurrent measurements made using existing, accepted technologies (e.g. ADCP). The outcome is better constraint and extension of rating curves. The approach is suited to water management authorities throughout Europe who seek ever-increasingly cost-effective and non-invasive techniques for maximising the monitoring capabilities of their operational network.

Streamflow record extension using power transformations and application to sediment transport

NASA Astrophysics Data System (ADS)

Moog, Douglas B.; Whiting, Peter J.; Thomas, Robert B.

1999-01-01

To obtain a representative set of flow rates for a stream, it is often desirable to fill in missing data or extend measurements to a longer time period by correlation to a nearby gage with a longer record. Linear least squares regression of the logarithms of the flows is a traditional and still common technique. However, its purpose is to generate optimal estimates of each day's discharge, rather than the population of discharges, for which it tends to underestimate variance. Maintenance-of-variance-extension (MOVE) equations [Hirsch, 1982] were developed to correct this bias. This study replaces the logarithmic transformation by the more general Box-Cox scaled power transformation, generating a more linear, constant-variance relationship for the MOVE extension. Combining the Box-Cox transformation with the MOVE extension is shown to improve accuracy in estimating order statistics of flow rate, particularly for the nonextreme discharges which generally govern cumulative transport over time. This advantage is illustrated by prediction of cumulative fractions of total bed load transport.

Improving the quantification of flash flood hydrographs and reducing their uncertainty using noncontact streamgauging methods

NASA Astrophysics Data System (ADS)

Branger, Flora; Dramais, Guillaume; Horner, Ivan; Le Boursicaud, Raphaël; Le Coz, Jérôme; Renard, Benjamin

2015-04-01

Continuous river discharge data are crucial for the study and management of floods. In most river discharge monitoring networks, these data are obtained at gauging stations, where the stage-discharge relation is modelled with a rating curve to derive discharge from the measurement of water level in the river. Rating curves are usually established using individual ratings (or gaugings). However, using traditional gauging methods during flash floods is challenging for many reasons including hazardous flow conditions (for both equipment and people), short duration of the flood events, transient flows during the time needed to perform the gauging, etc. The lack of gaugings implies that the rating curve is often extrapolated well beyond the gauged range for the highest floods, inducing large uncertainties in the computed discharges. We deployed two remote techniques for gauging floods and improving stage-discharge relations for high flow conditions at several hydrometric stations throughout the Ardèche river catchment in France : (1) permanent video-recording stations enabling the implementation of the image analysis LS-PIV technique (Large Scale Particle Image Velocimetry) ; (2) and mobile gaugings using handheld Surface Velocity Radars (SVR). These gaugings were used to estimate the rating curve and its uncertainty using the Bayesian method BaRatin (Le Coz et al., 2014). Importantly, this method explicitly accounts for the uncertainty of individual gaugings, which is especially relevant for remote gaugings since their uncertainty is generally much higher than that of standard intrusive gauging methods. Then, the uncertainty of streamflow records was derived by combining the uncertainty of the rating curve and the uncertainty of stage records. We assessed the impact of these methodological developments for peak flow estimation and for flood descriptors at various time steps. The combination of field measurement innovation and statistical developments allows efficiently quantifying and reducing the uncertainties of flood peak estimates and flood descriptors at gauging stations. The noncontact streamgauging techniques used in our field campaign strategy have complementary interests. Permanent LSPIV stations, once installed and calibrated, can monitor floods automatically and perform many gaugings during a single event, thus documenting the rise, peak and recession of floods. SVR gaugings are more "one shot" gaugings but can be deployed quickly and at minimal cost over a large territory. Both of these noncontact techniques contribute to a significant reduction of uncertainty on peak hydrographs and flood descriptors at different time steps for a given catchment. Le Coz, J.; Renard, B.; Bonnifait, L.; Branger, F. & Le Boursicaud, R. (2014), 'Combining hydraulic knowledge and uncertain gaugings in the estimation of hydrometric rating curves: A Bayesian approach', Journal of Hydrology 509, 573-587.

Differentiation of debris-flow and flash-flood deposits: implications for paleoflood investigations

USGS Publications Warehouse

Waythomas, Christopher F.; Jarrett, Robert D.; ,

1993-01-01

Debris flows and flash floods are common geomorphic processes in the Colorado Rocky Mountain Front Range and foothills. Usually, debris flows and flash floods are associated with excess summer rainfall or snowmelt, in areas were unconsolidated surficial deposits are relatively thick and slopes are steep. In the Front Range and foothills, flash flooding is limited to areas below about 2300m whereas, debris flow activity is common throughout the foothill and alpine zones and is not necessarily elevation limited. Because flash floods and debris flows transport large quantities of bouldery sediment, the resulting deposits appear somewhat similar even though such deposits were produced by different processes. Discharge estimates based on debris-flow deposits interpreted as flash-flood deposits have large errors because techniques for discharge retrodiction were developed for water floods with negligible sediment concentrations. Criteria for differentiating between debris-flow and flash-flood deposits are most useful for deposits that are fresh and well-exposed. However, with the passage of time, both debris-flow and flash-flood deposits become modified by the combined effects of weathering, colluviation, changes in surface morphology, and in some instances removal of interstitial sediment. As a result, some of the physical characteristics of the deposits become more alike. Criteria especially applicable to older deposits are needed. We differentiate flash-flood from debris-flow and other deposits using clast fabric measurements and other morphologic and sedimentologic techniques (e.g., deposit morphology, clast lithology, particle size and shape, geomorphic setting).

A Hybrid of Optical Remote Sensing and Hydrological Modeling Improves Water Balance Estimation

NASA Astrophysics Data System (ADS)

Gleason, Colin J.; Wada, Yoshihide; Wang, Jida

2018-01-01

Declining gauging infrastructure and fractious water politics have decreased available information about river flows globally. Remote sensing and water balance modeling are frequently cited as potential solutions, but these techniques largely rely on these same in-decline gauge data to make accurate discharge estimates. A different approach is therefore needed, and we here combine remotely sensed discharge estimates made via at-many-stations hydraulic geometry (AMHG) and the PCR-GLOBWB hydrological model to estimate discharge over the Lower Nile. Specifically, we first estimate initial discharges from 87 Landsat images and AMHG (1984-2015), and then use these flow estimates to tune the model, all without using gauge data. The resulting tuned modeled hydrograph shows a large improvement in flow magnitude: validation of the tuned monthly hydrograph against a historical gauge (1978-1984) yields an RMSE of 439 m3/s (40.8%). By contrast, the original simulation had an order-of-magnitude flow error. This improvement is substantial but not perfect: tuned flows have a 1-2 month wet season lag and a negative base flow bias. Accounting for this 2 month lag yields a hydrograph RMSE of 270 m3/s (25.7%). Thus, our results coupling physical models and remote sensing is a promising first step and proof of concept toward future modeling of ungauged flows, especially as developments in cloud computing for remote sensing make our method easily applicable to any basin. Finally, we purposefully do not offer prescriptive solutions for Nile management, and rather hope that the methods demonstrated herein can prove useful to river stakeholders in managing their own water.

River flow modeling using artificial neural networks in Kapuas river, West Kalimantan, Indonesia

NASA Astrophysics Data System (ADS)

Herawati, Henny; Suripin, Suharyanto

2017-11-01

Kapuas River is located in the province of West Kalimantan. Kapuas river length is 1,086 km and river basin areas about 100,000 Km2. The availability of river flow data in the Long River and very wide catchments are difficult to obtain, while river flow data are essential for planning waterworks. To predict the water flow in the catchment area requires a lot of hydrology coefficient, so it is very difficult to predict and obtain results that closer to the real conditions. This paper demonstrates that artificial neural network (ANN) could be used to predict the water flow. The ANN technique can be used to predict the incidence of water discharge that occurs in the Kapuas River based on rainfall and evaporation data. With the data available to do training on the artificial neural network model is obtained mean square error (MSE) 0.00007. The river flow predictions could be carried out after the training. The results showed differences in water discharge measurement and prediction of about 4%.

Low-flow characteristics for streams on the Islands of Kauaʻi, Oʻahu, Molokaʻi, Maui, and Hawaiʻi, State of Hawaiʻi

USGS Publications Warehouse

Cheng, Chui Ling

2016-08-03

Statistical models were developed to estimate natural streamflow under low-flow conditions for streams with existing streamflow data at measurement sites on the Islands of Kauaʻi, Oʻahu, Molokaʻi, Maui, and Hawaiʻi. Streamflow statistics used to describe the low-flow characteristics are flow-duration discharges that are equaled or exceeded between 50 and 95 percent of the time during the 30-year base period 1984–2013. Record-augmentation techniques were applied to develop statistical models relating concurrent streamflow data at the measurement sites and long-term data from nearby continuous-record streamflow-gaging stations that were in operation during the base period and were selected as index stations. Existing data and subsequent low-flow analyses of the available data help to identify streams in under-represented geographic areas and hydrogeologic settings where additional data collection is suggested.Low-flow duration discharges were estimated for 107 measurement sites (including long-term and short-term continuous-record streamflow-gaging stations, and partial-record stations) and 27 index stations. The adequacy of statistical models was evaluated with correlation coefficients and modified Nash-Sutcliff coefficients of efficiency, and a majority of the low-flow duration-discharge estimates are satisfactory based on these regression statistics.Molokaʻi and Hawaiʻi have the fewest number of measurement sites (that are not located on ephemeral stream reaches) at which flow-duration discharges were estimated, which can be partially explained by the limited number of index stations available on these islands that could be used for record augmentation. At measurement sites on some tributary streams, low-flow duration discharges could not be estimated because no adequate correlations could be developed with the index stations. These measurement sites are located on streams where duration-discharge estimates are available at long-term stations at other locations on the main stream channel to provide at least some definition of low-flow characteristics on that stream. In terms of general natural streamflow data availability, data are scarce in the leeward areas for all five islands as many leeward streams are dry or have minimal flow. Other under-represented areas include central Oʻahu, central Maui, and southeastern Maui.

Evaluation of Acoustic Doppler Current Profiler to Measure Discharge at New York Power Authority's Niagara Power Project, Niagara Falls, New York

USGS Publications Warehouse

Zajd, Henry J.

2007-01-01

The need for accurate real-time discharge in the International Niagara River hydro power system requires reliable, accurate and reproducible data. The U.S. Geological Survey has been widely using Acoustic Doppler Current Profilers (ADCP) to accurately measure discharge in riverine channels since the mid-1990s. The use of the ADCP to measure discharge has remained largely untested at hydroelectric-generation facilities such as the New York Power Authority's (NYPA) Niagara Power Project in Niagara Falls, N.Y. This facility has a large, engineered diversion channel with the capacity of high volume discharges in excess of 100,000 cubic feet per second (ft3/s). Facilities such as this could benefit from the use of an ADCP, if the ADCP discharge measurements prove to be more time effective and accurate than those obtained from the flow-calculation techniques that are currently used. Measurements of diversion flow by an ADCP in the 'Pant Leg' diversion channel at the Niagara Power Project were made on November 6, 7, and 8, 2006, and compared favorably (within 1 percent) with those obtained concurrently by a conventional Price-AA current-meter measurement during one of the ADCP measurement sessions. The mean discharge recorded during each 2-hour individual ADCP measurement session compared favorably with (3.5 to 6.8 percent greater than) the discharge values computed by the flow-calculation method presently in use by NYPA. The use of ADCP technology to measure discharge could ultimately permit increased power-generation efficiency at the NYPA Niagara Falls Power Project by providing improved predictions of the amount of water (and thus the power output) available.

Directional mass transport in an atmospheric pressure surface barrier discharge.

PubMed

Dickenson, A; Morabit, Y; Hasan, M I; Walsh, J L

2017-10-25

In an atmospheric pressure surface barrier discharge the inherent physical separation between the plasma generation region and downstream point of application reduces the flux of reactive chemical species reaching the sample, potentially limiting application efficacy. This contribution explores the impact of manipulating the phase angle of the applied voltage to exert a level of control over the electrohydrodynamic forces generated by the plasma. As these forces produce a convective flow which is the primary mechanism of species transport, the technique facilitates the targeted delivery of reactive species to a downstream point without compromising the underpinning species generation mechanisms. Particle Imaging Velocimetry measurements are used to demonstrate that a phase shift between sinusoidal voltages applied to adjacent electrodes in a surface barrier discharge results in a significant deviation in the direction of the plasma induced gas flow. Using a two-dimensional numerical air plasma model, it is shown that the phase shift impacts the spatial distribution of the deposited charge on the dielectric surface between the adjacent electrodes. The modified surface charge distribution reduces the propagation length of the discharge ignited on the lagging electrode, causing an imbalance in the generated forces and consequently a variation in the direction of the resulting gas flow.

The path to COVIS: A review of acoustic imaging of hydrothermal flow regimes

NASA Astrophysics Data System (ADS)

Bemis, Karen G.; Silver, Deborah; Xu, Guangyu; Light, Russ; Jackson, Darrell; Jones, Christopher; Ozer, Sedat; Liu, Li

2015-11-01

Acoustic imaging of hydrothermal flow regimes started with the incidental recognition of a plume on a routine sonar scan for obstacles in the path of the human-occupied submersible ALVIN. Developments in sonar engineering, acoustic data processing and scientific visualization have been combined to develop technology which can effectively capture the behavior of focused and diffuse hydrothermal discharge. This paper traces the development of these acoustic imaging techniques for hydrothermal flow regimes from their conception through to the development of the Cabled Observatory Vent Imaging Sonar (COVIS). COVIS has monitored such flow eight times a day for several years. Successful acoustic techniques for estimating plume entrainment, bending, vertical rise, volume flux, and heat flux are presented as is the state-of-the-art in diffuse flow detection.

Improving Water Balance Estimation in the Nile by Combining Remote Sensing and Hydrological Modelling: a Template for Ungauged Basins

NASA Astrophysics Data System (ADS)

Gleason, C. J.; Wada, Y.; Wang, J.

2017-12-01

Declining gauging infrastructure and fractious water politics have decreased available information about river flows globally, especially in international river basins. Remote sensing and water balance modelling are frequently cited as a potential solutions, but these techniques largely rely on the same in decline gauge data to constrain or parameterize discharge estimates, thus creating a circular approach to estimating discharge inapplicable to ungauged basins. To address this, we here combine a discontinued gauge, remotely sensed discharge estimates made via at-many-stations hydraulic geometry (AMHG) and Landsat data, and the PCR-GLOBWB hydrological model to estimate discharge for an ungauged time period for the Lower Nile (1978-present). Specifically, we first estimate initial discharges from 86 Landsat images and AMHG (1984-2015), and then use these flow estimates to tune the hydrologic model. Our tuning methodology is purposefully simple and can be easily applied to any model without the need for calibration/parameterization. The resulting tuned modelled hydrograph shows large improvement in flow magnitude over previous modelled hydrographs, and validation of tuned monthly model output flows against the historical gauge yields an RMSE of 343 m3/s (33.7%). By contrast, the original simulation had an order-of-magnitude flow error. This improvement is substantial but not perfect: modelled flows have a one-to two-month wet season lag and a negative bias. More sophisticated model calibration and training (e.g. data assimilation) is needed to improve upon our results, however, our results achieved by coupling physical models and remote sensing is a promising first step and proof of concept toward future modelling of ungauged flows. This is especially true as massive cloud computing via Google Earth Engine makes our method easily applicable to any basin without current gauges. Finally, we purposefully do not offer prescriptive solutions for Nile management, and rather hope that the methods demonstrated herein can prove useful to river stakeholders in managing their own water.

Evaluating a Radar-Based, Non Contact Streamflow Measurement System in the San Joaquin River at Vernalis, California

USGS Publications Warehouse

Cheng, Ralph T.; Gartner, Jeffrey W.; Mason, Jr., Robert R.; Costa, John E.; Plant, William J.; Spicer, Kurt R.; Haeni, F. Peter; Melcher, Nick B.; Keller, William C.; Hayes, Ken

2004-01-01

Accurate measurement of flow in the San Joaquin River at Vernalis, California, is vital to a wide range of Federal and State agencies, environmental interests, and water contractors. The U.S. Geological Survey uses a conventional stage-discharge rating technique to determine flows at Vernalis. Since the flood of January 1997, the channel has scoured and filled as much as 20 feet in some sections near the measurement site resulting in an unstable stage-discharge rating. In response to recent advances in measurement techniques and the need for more accurate measurement methods, the Geological Survey has undertaken a technology demonstration project to develop and deploy a radar-based streamflow measuring system on the bank of the San Joaquin River at Vernalis, California. The proposed flow-measurement system consists of a ground-penetrating radar system for mapping channel geometries, a microwave radar system for measuring surface velocities, and other necessary infrastructure. Cross-section information derived from ground penetrating radar provided depths similar to those measured by other instruments during the study. Likewise, surface-velocity patterns and magnitudes measured by the pulsed Doppler radar system are consistent with near surface current measurements derived from acoustic velocity instruments. Since the ratio of surface velocity to mean velocity falls to within a small range of theoretical value, using surface velocity as an index velocity to compute river discharge is feasable. Ultimately, the non-contact radar system may be used to make continuous, near-real-time flow measurements during high and medium flows. This report documents the data collected between April 14, 2002 and May 17, 2002 for the purposes of testing this radar based system. Further analyses of the data collected during this field effort will lead to further development and improvement of the system.

Microwave resonance lamp absorption technique for measuring temperature and OH number density in combustion environments

NASA Technical Reports Server (NTRS)

Lempert, Walter R.

1988-01-01

A simple technique for simultaneous determination of temperature and OH number density is described, along with characteristic results obtained from measurements using a premixed, hydrogen air flat flame burner. The instrumentation is based upon absorption of resonant radiation from a flowing microwave discharge lamp, and is rugged, relatively inexpensive, and very simple to operate.

Flow and pressure characteristics within a screw compressor

NASA Astrophysics Data System (ADS)

Guerrato, D.; Nouri, J. M.; Stosic, N.; Arcoumanis, C.

2007-10-01

The angle-resolved mean and turbulence characteristics of the axial air flow inside a screw compressor with both male and female rotors have been measured, using a laser Doppler velocimeter (LDV) with high spatial and temporal resolution at different radial and axial locations for speeds of 800-1600 rpm, discharge pressures of 1-1.6 bar and discharge temperatures of 33-90°C. The velocity measurements were performed through a special transparent window fixed near the discharge port. The results confirmed the ability of the LDV technique to characterise the flow inside the compressor working chamber; an angular resolution of 1.5° was able to fully describe the velocity field within the machine. The flow variation between the different working chambers was established as well as the spatial variation of the axial mean velocity and turbulence velocity fluctuation within the working chamber. The effect of discharge port opening on the axial mean and RMS velocities was found to be significant near the leading edge of the rotors causing an increase in the mean and RMS velocities of the order of 4.2Vp in mean (where Vp is the axial pitched velocity) for male rotor and 5.4Vp for, female rotor and this effect is less pronounced on the flow near the root of the rotor. Moreover, to obtain a better understanding of the flow motion, a high sampling rate pressure transducer was used to provide the internal angular static pressure variation. These measurements are used to validate the in-house CFD model of the fluid flow within twin screw compressors which, in turn, allows reliable optimisation of various compressor designs.

Measurement of discharge using tracers

USGS Publications Warehouse

Kilpatrick, Frederick A.; Cobb, Ernest D.

1984-01-01

The development of fluorescent dyes and fluorometers that can measure these dyes at very low concentrations has made dye-dilution methods practical for measuring discharge. These methods are particularly useful for determining discharge under certain flow conditions that are unfavorable for current meter measurements. These include small streams, canals, and pipes where:Turbulence is excessive for current meter measurement but conducive to good mixing.Moving rocks and debris are damaging to any instruments placed in the flow.Cross-sectional areas or velocities are indeterminant or changing.There are some unsteady flows such as exist with storm-runoff events on small streams.The flow is physically inaccessible or unsafe.From a practical standpoint, such measurements are limited primarily to small streams due to excessively long channel mixing lengths required of larger streams. Very good accuracy can be obtained provided:Adequate mixing length and time are allowed.Careful field and laboratory techniques are employed.Dye losses are not significant.This manual describes the slug-injection and constant-rate injection methods of performing tracer-dilution measurements. Emphasis is on the use of fluorescent dyes as tracers and the equipment, field methods, and Laboratory procedures for performing such measurements. The tracer-velocity method is also briefly discussed.

Measurement of discharge using tracers

USGS Publications Warehouse

Kilpatrick, F.A.; Cobb, Ernest D.

1985-01-01

The development of fluorescent dyes and fluorometers that can measure these dyes at very low concentrations has made dye-dilution methods practical for measuring discharge. These methods are particularly useful for determining discharge under certain flow conditions that are unfavorable for current meter measurements. These include small streams, canals, and pipes where 1. Turbulence is excessive for current-meter measurement but conducive to good mixing. 2. Moving rocks and debris may damage instruments placed in the flow. 3. Cross-sectional areas or velocities are indeterminate or changing. 4. The flow is unsteady, such as the flow that exists with storm-runoff events on small streams and urban storm-sewer systems. 5. The flow is physically inaccessible or unsafe. From a practical standpoint, such methods are limited primarily to small streams, because of the excessively long channel-mixing lengths required for larger streams. Very good accuracy can be obtained provided that 1. Adequate mixing length and time are allowed. 2. Careful field and laboratory techniques are used. 3. Dye losses are not significant. This manual describes the slug-injection and constant-rate injection methods of performing tracer-dilution measurements. Emphasis is on the use of fluorescent dyes as tracers and the equipment, field methods, and laboratory procedures for performing such measurements. The tracer-velocity method is also briefly discussed.

Investigation of the jet-wake flow of a highly loaded centrifugal compressor impeller

NASA Technical Reports Server (NTRS)

Eckardt, D.

1978-01-01

Investigations, aimed at developing a better understanding of the complex flow field in high performance centrifugal compressors were performed. Newly developed measuring techniques for unsteady static and total pressures as well as flow directions, and a digital data analysis system for fluctuating signals were thoroughly tested. The loss-affected mixing process of the distorted impeller discharge flow was investigated in detail, in the absolute and relative system, at impeller tip speeds up to 380 m/s. A theoretical analysis proved good coincidence of the test results with the DEAN-SENOO theory, which was extended to compressible flows.

Untangling Trends and Drivers of Changing River Discharge Along Florida's Gulf Coast

NASA Astrophysics Data System (ADS)

Glodzik, K.; Kaplan, D. A.; Klarenberg, G.

2017-12-01

Along the relatively undeveloped Big Bend coastline of Florida, discharge in many rivers and springs is decreasing. The causes are unclear, though they likely include a combination of groundwater extraction for water supply, climate variability, and altered land use. Saltwater intrusion from altered freshwater influence and sea level rise is causing transformative ecosystem impacts along this flat coastline, including coastal forest die-off and oyster reef collapse. A key uncertainty for understanding river discharge change is predicting discharge from rainfall, since Florida's karstic bedrock stores large amounts of groundwater, which has a long residence time. This study uses Dynamic Factor Analysis (DFA), a multivariate data reduction technique for time series, to find common trends in flow and reveal hydrologic variables affecting flow in eight Big Bend rivers since 1965. The DFA uses annual river flows as response time series, and climate data (annual rainfall and evapotranspiration by watershed) and climatic indices (El Niño Southern Oscillation [ENSO] Index and North Atlantic Oscillation [NAO] Index) as candidate explanatory variables. Significant explanatory variables (one evapotranspiration and three rainfall time series) explained roughly 50% of discharge variation across rivers. Significant trends (representing unexplained variation) were shared among rivers, with geographical grouping of five northern rivers and three southern rivers, along with a strong downward trend affecting six out of eight systems. ENSO and NAO had no significant impact. Advancing knowledge of these dynamics is necessary for forecasting how altered rainfall and temperatures from climate change may impact flows. Improved forecasting is especially important given Florida's reliance on groundwater extraction to support its growing population.

Distinguishing between debris flows and floods from field evidence in small watersheds

USGS Publications Warehouse

Pierson, Thomas C.

2005-01-01

Post-flood indirect measurement techniques to back-calculate flood magnitude are not valid for debris flows, which commonly occur in small steep watersheds during intense rainstorms. This is because debris flows can move much faster than floods in steep channel reaches and much slower than floods in low-gradient reaches. In addition, debris-flow deposition may drastically alter channel geometry in reaches where slope-area surveys are applied. Because high-discharge flows are seldom witnessed and automated samplers are commonly plugged or destroyed, determination of flow type often must be made on the basis of field evidence preserved at the site.

Temporally, spatially, and spectrally resolved barrier discharge produced in trapped helium gas at atmospheric pressure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiper, Alina Silvia; Popa, Gheorghe

2013-06-07

Experimental study was made on induced effects by trapped helium gas in the pulsed positive dielectric barrier discharge (DBD) operating in symmetrical electrode configuration at atmospheric pressure. Using fast photography technique and electrical measurements, the differences in the discharge regimes between the stationary and the flowing helium are investigated. It was shown experimentally that the trapped gas atmosphere (TGA) has notable impact on the barrier discharge regime compared with the influence of the flowing gas atmosphere. According to our experimental results, the DBD discharge produced in trapped helium gas can be categorized as a multi-glow (pseudo-glow) discharge, each discharge workingmore » in the sub-normal glow regime. This conclusion is made by considering the duration of current pulse (few {mu}s), their maximum values (tens of mA), the presence of negative slope on the voltage-current characteristic, and the spatio-temporal evolution of the most representative excited species in the discharge gap. The paper focuses on the space-time distribution of the active species with a view to better understand the pseudo-glow discharge mechanism. The physical basis for these effects was suggested. A transition to filamentary discharge is suppressed in TGA mode due to the formation of supplementary source of seed electrons by surface processes (by desorption of electrons due to vibrationally excited nitrogen molecules, originated from barriers surfaces) rather than volume processes (by enhanced Penning ionisation). Finally, we show that the pseudo-glow discharge can be generated by working gas trapping only; maintaining unchanged all the electrical and constructive parameters.« less

Growth and properties of amorphous silicon films grown using pulsed-flow reactive plasma beam epitaxy

NASA Technical Reports Server (NTRS)

Dalal, Vikram L.; Knox, Ralph; Kandalaft, Nabeeh; Baldwin, Greg

1991-01-01

The growth and properties of a-Si:H films grown using a novel deposition technique, reactive plasma beam epitaxy, are discussed. In this technique, a remote H plasma produced in a microwave-ECR reactor is used to grow a-Si:H films at low pressures. The H ions react with SiH4 introduced near the substrate to produce the film. The flow of SiH4 is pulsed on or off, thereby achieving in-situ annealing of the film during growth by H ions and radicals. The films produced by this technique appear to have good electronic quality, and are more stable than the standard glow discharge films.

Modeling of environmentally induced transients within satellites

NASA Technical Reports Server (NTRS)

Stevens, N. John; Barbay, Gordon J.; Jones, Michael R.; Viswanathan, R.

1987-01-01

A technique is described that allows an estimation of possible spacecraft charging hazards. This technique, called SCREENS (spacecraft response to environments of space), utilizes the NASA charging analyzer program (NASCAP) to estimate the electrical stress locations and the charge stored in the dielectric coatings due to spacecraft encounter with a geomagnetic substorm environment. This information can then be used to determine the response of the spacecraft electrical system to a surface discharge by means of lumped element models. The coupling into the electronics is assumed to be due to magnetic linkage from the transient currents flowing as a result of the discharge transient. The behavior of a spinning spacecraft encountering a severe substorm is predicted using this technique. It is found that systems are potentially vulnerable to upset if transient signals enter through the ground lines.

Remotely Characterizing the Topographic and Thermal Evolution of Kīlauea's Lava Flow Field

NASA Astrophysics Data System (ADS)

Rumpf, M. E.; Vaughan, R. G.; Poland, M. P.

2017-12-01

New technologies in satellite data acquisition and the continuous development of analysis software capabilities are greatly improving the ability of scientists to monitor volcanoes in near-real-time. Satellite-based thermal infrared (TIR) data are used to monitor and analyze new and ongoing volcanic activity by identifying and quantifying surface thermal characteristics and lava flow discharge rates. Improved detector sensitivities provide unprecedented spatial detail in visible to shortwave infrared (VSWIR) satellite imagery. The acquisition of stereo and tri-stereo visible imagery, as well as SAR, by an increasing number of satellite systems enables the creation of digital elevation models (DEMs) at higher temporal frequencies and resolutions than in the past. Free, user-friendly software programs, such as NASA's Ames Stereo Pipeline and Google Earth Engine, ease the accessibility and usability of satellite data to users unfamiliar with traditional analysis techniques. An effective and efficient integration of these technologies can be utilized towards volcano monitoring.Here, we use the active lava flows from the East Rift Zone vents of Kīlauea Volcano, Hawai`i as a testing ground for developing new techniques in multi-sensor volcano remote sensing. We use DEMs generated from stereo and tri-stereo images captured by the WorldView3 and Pleiades satellite systems to assess topographic changes over time at the active flow fields. Time-series data of lava flow area, thickness, and discharge rate developed from thermal emission measurements collected by ASTER, Landsat 8, and WorldView3 are compared to satellite-detected topographic changes and to ground observations of flow development to identify behavioral patterns and to monitor flow field evolution. We explore methods of combining these visual and TIR data sets collected by multiple satellite systems with a variety of resolutions and repeat times. Our ultimate goal is to develop integrative tools for near-real-time volcano monitoring. In addition, we recommend improvements to future satellite mission capabilities (e.g., repeat times, resolutions) to improve lava flow monitoring techniques.

Reciprocal functional interactions between the brainstem and the lower spinal cord

PubMed Central

Yazawa, Itaru

2014-01-01

The interplay of the neuronal discharge patterns regarding respiration and locomotion was investigated using electrophysiological techniques in a decerebrate and arterially perfused in situ mouse preparation. The phrenic, tibial, and/or peroneal nerve discharge became clearly organized into discharge episodes of increasing frequency and duration, punctuated by periods of quiescence as the perfusion flow rate increased at room temperature. The modulated sympathetic tone induced by the hyperoxic/normocapnic state was found to activate the locomotor pattern generator (LPG) via descending pathways and generate a left and right alternating discharge during discharge episodes in the motor nerves. The rhythm coupling of respiration and locomotion occurred at a 1:1 frequency ratio. Although the phrenic discharge synchronized with the tibial discharge at all flow rates tested, the time lag between peaks of the two discharges during locomotion was ≈400 ms rather than ≈200 ms, suggesting spinal feedback via ascending pathways. The incidence of the phrenic and tibial discharge episodes decreased by ≈50% after spinalization at the twelfth thoracic cord and the respiratory rhythm was more regular. These results indicate that: (i) locomotion can be generated in a hyperoxic/normocapnic state induced by specific respiratory conditions, (ii) the central mechanism regarding entrainment of respiratory and locomotor rhythms relies on spinal feedback via ascending pathways, initiated by the activated LPG generating locomotion, and (iii) the increase in respiratory rate seen during locomotion is caused not only by afferent mechanical and nociceptive inputs but also by impulses from the activated spinal cord producing a locomotor-like discharge via ascending pathways. PMID:24910591

Modeling Water-Surface Elevations and Virtual Shorelines for the Colorado River in Grand Canyon, Arizona

USGS Publications Warehouse

Magirl, Christopher S.; Breedlove, Michael J.; Webb, Robert H.; Griffiths, Peter G.

2008-01-01

Using widely-available software intended for modeling rivers, a new one-dimensional hydraulic model was developed for the Colorado River through Grand Canyon from Lees Ferry to Diamond Creek. Solving one-dimensional equations of energy and continuity, the model predicts stage for a known steady-state discharge at specific locations, or cross sections, along the river corridor. This model uses 2,680 cross sections built with high-resolution digital topography of ground locations away from the river flowing at a discharge of 227 m3/s; synthetic bathymetry was created for topography submerged below the 227 m3/s water surface. The synthetic bathymetry was created by adjusting the water depth at each cross section up or down until the model?s predicted water-surface elevation closely matched a known water surface. This approach is unorthodox and offers a technique to construct one-dimensional hydraulic models of bedrock-controlled rivers where bathymetric data have not been collected. An analysis of this modeling approach shows that while effective in enabling a useful model, the synthetic bathymetry can differ from the actual bathymetry. The known water-surface profile was measured using elevation data collected in 2000 and 2002, and the model can simulate discharges up to 5,900 m3/s. In addition to the hydraulic model, GIS-based techniques were used to estimate virtual shorelines and construct inundation maps. The error of the hydraulic model in predicting stage is within 0.4 m for discharges less than 1,300 m3/s. Between 1,300-2,500 m3/s, the model accuracy is about 1.0 m, and for discharges between 2,500-5,900 m3/s, the model accuracy is on the order of 1.5 m. In the absence of large floods on the flow-regulated Colorado River in Grand Canyon, the new hydraulic model and the accompanying inundation maps are a useful resource for researchers interested in water depths, shorelines, and stage-discharge curves for flows within the river corridor with 2002 topographic conditions.

Flow and geochemistry along shallow ground-water flowpaths in an agricultural area in southeastern Wisconsin

USGS Publications Warehouse

Saad, D.A.; Thorstenson, D.C.

1998-01-01

Ground water recharging at mid- and downgradient wells is oxic and contains dissolved nitrate, whereas the ground water discharging to the stream is anoxic and contains dissolved ammonium. Redox environments were defined at each well on the basis of relative concentrations of various dissolved redox-active species. Chemically permissible flowpaths inferred from the observed sequence of redox environments at well sites are consistent with flowpaths in the ground-water flow model. The transition from nitrate in recharging ground water to ammonium in ground water discharging to the stream suggests the possibility of nitrate reduction along the flowpath. None of the techniques employed in this study, however, were able to prove the occurrence of this reaction.

Looking Deeper Into Hydrologic Connectivity and Streamflow Generation: A Groundwater Hydrologist's Perspective.

NASA Astrophysics Data System (ADS)

Gardner, W. P.

2016-12-01

In this presentation the definition of hydraulic connection will be explored with a focus on the role of deep groundwater in streamflow generation and its time and space limits. Regional groundwater flow paths can be important sources of baseflow and potentially event response in surface water systems. This deep groundwater discharge plays an important role in determining how the watershed responds to climatic forcing, whether watersheds are a carbon source or sink and can be significant for watershed geochemistry and nutrient loading. These flow paths potentially "connect" to surface water systems and saturated soil zones at large distances, and over long time scales. However, these flow paths are challenging to detect, especially with hydraulic techniques. Here we will discuss some of the basic physical processes that affect the hydraulic signal along a groundwater flow path and their implications for the definition of hydrologic connection. Methods of measuring hydraulic connection using groundwater head response and their application in detecting regional groundwater discharge will be discussed. Environmental tracers are also a powerful method for identifying connected flowpaths in groundwater systems, and are commonly used to determine flow connection and flow rates in groundwater studies. Isotopic tracer methods for detecting deep, regional flow paths in watersheds will be discussed, along with observations of deep groundwater discharge in shallow alluvial systems around the world. The goal of this talk is to discuss hydraulic and hydrologic connection from a groundwater hydrologist's perspective, spark conversation on the meaning of hydrologic connection, the processes which govern hydraulic response and methods to measure flow connections and flux.

Measuring surface flow velocity with smartphones: potential for citizen observatories

NASA Astrophysics Data System (ADS)

Weijs, Steven V.; Chen, Zichong; Brauchli, Tristan; Huwald, Hendrik

2014-05-01

Stream flow velocity is an important variable for discharge estimation and research on sediment dynamics. Given the influence of the latter on rating curves (stage-discharge relations), and the relative scarcity of direct streamflow measurements, surface velocity measurements can offer important information for, e.g., flood warning, hydropower, and hydrological science and engineering in general. With the growing amount of sensing and computing power in the hands of more outdoorsy individuals, and the advances in image processing techniques, there is now a tremendous potential to obtain hydrologically relevant data from motivated citizens. This is the main focus of the interdisciplinary "WeSenseIt" project, a citizen observatory of water. In this subproject, we investigate the feasibility of stream flow surface velocity measurements from movie clips taken by (smartphone-) cameras. First results from movie-clip derived velocity information will be shown and compared to reference measurements.

Use of acoustic technology to define hydraulic characteristics of an estuary near the Mississippi Gulf Coast

USGS Publications Warehouse

Van Wilson, K.

2004-01-01

An Acoustic Doppler Current Profiler (ADCP) was used on the Jourdan River at Interstate Highway 10 near Kiln, Mississippi, in 1996 to measure three-dimensional velocity vectors and water depths and in 1998, in combination with a global positioning system, to define channel bathymetry in the vicinity of the bridge. During a 25-hour period on September 19-20, 1996, 117 consecutive measurements of stage and discharge were obtained throughout a complete tidal cycle. These measurements were obtained during the time of year when headwater flows were minimal, and, therefore, the tidal-affected flow conditions were noticeable. The stage ranged from only 0.7 to 2.8 ft above sea level, but discharge ranged from 3,980 ft3/s flowing upstream to 5,580 ft 3/s flowing downstream. The average discharge during the 25-hour period was only 80 ft3/s flowing downstream. By using the ADCP, full downstream flow, bi-directional flow, and full upstream flow conditions were identified. If conventional measurement techniques had been used, the bi-directional flow conditions could not have been detected since flow direction would have been based on what was seen at the water surface. These measurements were used to define the lower range of the stage-storage-volume relation inland of the highway. On June 10, 1998, the ADCP, in combination with a global positional system, was used to define channel bathymetry for the river reach from about 3,500 ft upstream to about 2,500 ft downstream of the bridge. The bathymetry was compared to past soundings obtained in the vicinity of the bridge; as much as 18 ft of total scour was indicated to have occurred at a bridge pier. Copyright ASCE 2004.

Time-series variations in CFC and 3H/3He ages in springs discharging from an eogenetic karst aquifer (Invited)

NASA Astrophysics Data System (ADS)

Martin, J. B.; Kurz, M. J.; Khadka, M. B.; Cohen, M. J.

2013-12-01

One of the hallmarks of karst aquifers is rapid mixing between surface water and groundwater, which results in changes in flow and water chemistry at springs. Aquifers with little matrix porosity (telogenetic karst) tend to respond to storm events within days to weeks (e.g., are flashy) while aquifers characterized by elevated matrix porosity (eogenetic karst) may take months or years to respond. This response time is an important control on remediation of storm-derived contaminants as well as the magnitude of water-rock reactions that may result from mixing of surface water and groundwater with different compositions. Responses of flashy springs may be observed through time-series measurements of various solute compositions of the discharge, but response at springs discharging from eogenetic aquifers are difficult to observe because the chemical composition of the recharged storm water may be altered during its residence in the subsurface. For these aquifers, conservative tracers such as chlorofluorocarbon and 3H/3He ratios may provide useful information on the mixing, residence time, and variation in the average age of discharged water. We are testing this hypothesis at six springs discharging from the Floridan Aquifer to the Ichetucknee River in north Florida. Samples were first collected September 3, 2009 during record low flow when the river was discharging 7.2 m3/sec and subsequently after about 400 mm of rain fell over the springshed from June 23 to 26, 2012 during Tropical Storm Debby. Following the storm, samples were collected July 27, 2012 (all six springs) when flow had increased to 10.5 m3/sec. Three of the six springs were sampled during the recession on October 25, 2012 (Q = 10.3 m3/sec), February 14, 2013 (Q = 8.7 m3/sec), and May 16, 2013 (Q = 8.6 m3/sec). CFC dates are available now for all sampling times but 3H/3He dates are only available through October 25, 2012. The two different tracers yield conflicting results with CFC ages generally increasing from the low flow to flood samples while 3H/3He ages decrease in five of the six springs with increasing discharge. The age of the water would be expected to decrease following the storm, suggesting that the CFC data may be contaminated. Assuming the drought discharge is solely groundwater and the measured reduction in the 3H/3He ages originates from mixing old groundwater with zero-aged water from the storm, the fraction of discharging storm water ranged from 4 to 25% of the total discharge. This variation in the fraction of the storm-derived water corresponds to estimated depths of flow paths to the springs based on dissolved oxygen and temperature data. Springs originating from deep flow paths have smaller fractions of storm water. Time-series measurements of ages of water discharging from springs appear to be a useful technique for estimating fractions of storm derived water and possibly flow paths in springs discharging from eogenetic karst aquifers.

User's manual for computer program BASEPLOT

USGS Publications Warehouse

Sanders, Curtis L.

2002-01-01

The checking and reviewing of daily records of streamflow within the U.S. Geological Survey is traditionally accomplished by hand-plotting and mentally collating tables of data. The process is time consuming, difficult to standardize, and subject to errors in computation, data entry, and logic. In addition, the presentation of flow data on the internet requires more timely and accurate computation of daily flow records. BASEPLOT was developed for checking and review of primary streamflow records within the U.S. Geological Survey. Use of BASEPLOT enables users to (1) provide efficiencies during the record checking and review process, (2) improve quality control, (3) achieve uniformity of checking and review techniques of simple stage-discharge relations, and (4) provide a tool for teaching streamflow computation techniques. The BASEPLOT program produces tables of quality control checks and produces plots of rating curves and discharge measurements; variable shift (V-shift) diagrams; and V-shifts converted to stage-discharge plots, using data stored in the U.S. Geological Survey Automatic Data Processing System database. In addition, the program plots unit-value hydrographs that show unit-value stages, shifts, and datum corrections; input shifts, datum corrections, and effective dates; discharge measurements; effective dates for rating tables; and numeric quality control checks. Checklist/tutorial forms are provided for reviewers to ensure completeness of review and standardize the review process. The program was written for the U.S. Geological Survey SUN computer using the Statistical Analysis System (SAS) software produced by SAS Institute, Incorporated.

A Multidisciplinary Initiative to Increase Inpatient Discharges Before Noon.

PubMed

Kane, Marlena; Weinacker, Ann; Arthofer, Rudolph; Seay-Morrison, Timothy; Elfman, Wesley; Ramirez, Mark; Ahuja, Neera; Pickham, David; Hereford, James; Welton, Mark

2016-12-01

The aim of this study is to evaluate the effect of 2 hospital-wide interventions on achieving a discharge-before-noon rate of 40%. A multidisciplinary team led by administrative and physician leadership developed a plan to diminish capacity constraints by minimizing late afternoon hospital discharges using 2 patient flow management techniques. The study was a preintervention/postintervention retrospective analysis observing all inpatients discharged across 19 inpatient units in a 484-bed, academic teaching hospital measuring calendar month discharge-before-noon percentage, patient satisfaction, and readmission rates. Patient satisfaction and readmission rates were used as baseline metrics. The discharge-before-noon percentage increased from 14% in the 11-month preintervention period to an average of 24% over the 11-month postintervention period, whereas patient satisfaction scores and readmission rates remained stable. Implementation of the 2 interventions successfully increased the percentage of discharges before noon yet did not achieve the goal of 40%. Patient satisfaction and readmission rates were not negatively impacted by the program.

Discharge stabilization studies of CO laser gas mixtures in quasi-steady supersonic flow

NASA Technical Reports Server (NTRS)

Srinivasan, G.; Smith, J. A.

1976-01-01

Experiments were conducted to study the applicability of a double discharge stabilization scheme in conditions appropriate for high energy CO lasers in supersonic flows. A Ludwieg tube impulse flow facility and a ballasted capacitor bank provided essentially steady flow and discharge conditions (d.c.) for times longer than ten electrode length-flow transit times. Steady, arc-free, volume discharges were produced in a Mach 3 test cavity using an auxiliary discharge to stabilize the main discharge in N2 and He/CO mixture. A signigicant result is the lack of observed plasma E/N changes in response to auxiliary discharge current changes. Also, where glow discharges were obtained, the energy loading achieved was very much less than the threshold level required for laser operation.

Dynamics of near-surface electric discharges and mechanisms of their interaction with the airflow

NASA Astrophysics Data System (ADS)

Leonov, Sergey B.; Adamovich, Igor V.; Soloviev, Victor R.

2016-12-01

The main focus of the review is on dynamics and kinetics of near-surface discharge plasmas, such as surface dielectric barrier discharges sustained by AC and repetitively pulsed waveforms, pulsed DC discharges, and quasi-DC discharges, generated in quiescent air and in the airflow. A number of technical issues related to plasma flow control applications are discussed in detail, including discharge development via surface ionization waves, charge transport and accumulation on dielectric surface, discharge contraction, different types of flow perturbations generated by surface discharges, and effect of high-speed flow on discharge dynamics. In the first part of the manuscript, plasma morphology and results of electrical and optical emission spectroscopy measurements are discussed. Particular attention is paid to dynamics of surface charge accumulation and dissipation, both in diffuse discharges and during development of ionization instabilities resulting in discharge contraction. Contraction leads to significant increase of both the surface area of charge accumulation and the energy coupled to the plasma. The use of alternating polarity pulse waveforms accelerates contraction of surface dielectric barrier discharges and formation of filamentary plasmas. The second part discusses the interaction of discharge plasmas with quiescent air and the external airflow. Four major types of flow perturbations have been identified: (1) low-speed near-surface jets generated by electrohydrodynamic interaction (ion wind); (2) spanwise and streamwise vortices formed by both electrohydrodynamic and thermal effects; (3) weak shock waves produced by rapid heating in pulsed discharges on sub-microsecond time scale; and (4) near-surface localized stochastic perturbations, on sub-millisecond time, detected only recently. The mechanism of plasma-flow interaction remains not fully understood, especially in filamentary surface dielectric barrier discharges. Localized quasi-DC surface discharges sustained in a high-speed flow are discussed in the third part of the review. Although dynamics of this type of the discharge is highly transient, due to its strong interaction with the flow, the resultant flow structure is stationary, including the oblique shock and the flow separation region downstream of the discharge. The oblique shock is attached to a time-averaged, wedge-shaped, near-wall plasma layer, with the shock angle controlled by the discharge power, which makes possible changing the flow structure and parameters in a controlled way. Finally, unresolved and open-ended issues are discussed in the summary.

Techniques for computing discharge at four Navigation Dams on the Illinois and Des Plaines Rivers in Illinois

USGS Publications Warehouse

Mades, Dean M.; Weiss, Linda S.; Gray, John R.

1991-01-01

Techniques for computing discharge are developed for Brandon Road Dam on the Des Plaines River and for Dresden Island, Marseilles, and Starved Rock Dams on the Illinois River. At Brandon Road Dam, streamflow is regulated by the operation of Tainter gates and headgates. At Dresden Island, Marseilles, and Starved Rock Dams, only Tainter gates are operated to regulate streamflow. The locks at all dams are equipped with culvert valves that are used to fill and empty the lock. The techniques facilitate determination of discharge at locations along the upper Illinois Waterway where no streamflow-gaging stations exist. The techniques are also useful for computing low flows when the water-surface slope between control structures on the river approaches zero and traditional methods of determining discharge based on slope are unsatisfactory. Two techniques can be used to compute discharge at the dams--gate ratings and tailwater ratings . A gate ratingdescribes the relation between discharge, gate opening, tailwater stage, and headwater stage. A tailwater rating describes the relation between tailwater stage and discharge. Gate ratings for Tainter gates at Dresden Island, Marseilles, and Starved Rock Dams are based on a total of 78 measurements of discharge that range from 569 to 86,400 cubic feet per second. Flood hydrographs developed from the gate ratings and Lockmaster records of gate opening and stage compare closely with streamflow records published for nearby streamflow-gaging stations. Additional measurements are needed to verify gate ratings for Tainter gates and headgates at Brandon Road Dam after the dam rehabilitation is completed. Extensive leakage past deteriorated headgates and sluice gates contributed to uncertainty in the ratings developed for this dam. A useful tailwater rating is developed for Marseilles Dam. Tailwater ratings for Dresden Island Dam and Starved Rock Dam are of limited use because of varying downstream channel-storage conditions. A tailwater rating could not be developed for Brandon Road Dam because its tailwater pool is substantially affected by the headwater pool of Dresden Island Dam.

Pulsed dielectric barrier discharge for Bacillus subtilis inactivation in water

NASA Astrophysics Data System (ADS)

Hernández-Arias, A. N.; Rodríguez-Méndez, B. G.; López-Callejas, R.; Valencia-Alvarado, R.; Mercado-Cabrera, A.; Peña-Eguiluz, R.; Barocio, S. R.; Muñoz-Castro, A. E.; de la Piedad Beneitez, A.

2012-06-01

The inactivation of Bacillus subtilis bacteria in water has been experimentally studied by means of a pulsed dielectric barrier discharge (PDBD) in a coaxial reactor endowed with an alumina dielectric. The plasma source is capable of operating at atmospheric pressure with gas, water or hybrid gas-liquid media at adjustable 25 kV pulses, 30 μs long and at a 500 Hz frequency. In order to evaluate the inactivation efficiency of the system, a set of experiments were designed on the basis of oxygen flow control. The initial data have showed a significant bacterial rate reduction of 103-107 CFU/mL. Additional results proved that applying an oxygen flow for a few seconds during the PDBD treatment inactivates the Bacillus subtilis population with 99.99% effectiveness. As a reference, without gas flow but with the same exposure times, this percentage is reduced to ~90%. The analysis of the relationship between inactivation rate and chemical species in the discharge has been carried out using optical emission spectroscopy as to identifying the main reactive species. Reactive oxygen species such as atomic oxygen and ozone tuned out to be the dominant germicidal species. Some proposed inactivation mechanisms of this technique are discussed.

Remote measurement of river discharge using thermal particle image velocimetry (PIV) and various sources of bathymetric information

USGS Publications Warehouse

Legleiter, Carl; Kinzel, Paul J.; Nelson, Jonathan M.

2017-01-01

Although river discharge is a fundamental hydrologic quantity, conventional methods of streamgaging are impractical, expensive, and potentially dangerous in remote locations. This study evaluated the potential for measuring discharge via various forms of remote sensing, primarily thermal imaging of flow velocities but also spectrally-based depth retrieval from passive optical image data. We acquired thermal image time series from bridges spanning five streams in Alaska and observed strong agreement between velocities measured in situ and those inferred by Particle Image Velocimetry (PIV), which quantified advection of thermal features by the flow. The resulting surface velocities were converted to depth-averaged velocities by applying site-specific, calibrated velocity indices. Field spectra from three clear-flowing streams provided strong relationships between depth and reflectance, suggesting that, under favorable conditions, spectrally-based bathymetric mapping could complement thermal PIV in a hybrid approach to remote sensing of river discharge; this strategy would not be applicable to larger, more turbid rivers, however. A more flexible and efficient alternative might involve inferring depth from thermal data based on relationships between depth and integral length scales of turbulent fluctuations in temperature, captured as variations in image brightness. We observed moderately strong correlations for a site-aggregated data set that reduced station-to-station variability but encompassed a broad range of depths. Discharges calculated using thermal PIV-derived velocities were within 15% of in situ measurements when combined with depths measured directly in the field or estimated from field spectra and within 40% when the depth information also was derived from thermal images. The results of this initial, proof-of-concept investigation suggest that remote sensing techniques could facilitate measurement of river discharge.

Buoyancy Effects on Flow Transition in Hydrogen Gas Jet Diffusion Flames

NASA Technical Reports Server (NTRS)

Albers, Burt W.; Agrawal, Ajay K.; Griffin, DeVon (Technical Monitor)

2000-01-01

Experiments were performed in earth-gravity to determine how buoyancy affected transition from laminar to turbulent flow in hydrogen gas jet diffusion flames. The jet exit Froude number characterizing buoyancy in the flame was varied from 1.65 x 10(exp 5) to 1.14 x 10(exp 8) by varying the operating pressure and/or burner inside diameter. Laminar fuel jet was discharged vertically into ambient air flowing through a combustion chamber. Flame characteristics were observed using rainbow schlieren deflectometry, a line-of-site optical diagnostic technique. Results show that the breakpoint length for a given jet exit Reynolds number increased with increasing Froude number. Data suggest that buoyant transitional flames might become laminar in the absence of gravity. The schlieren technique was shown as effective in quantifying the flame characteristics.

Influence of shock waves from plasma actuators on transonic and supersonic airflow

NASA Astrophysics Data System (ADS)

Mursenkova, I. V.; Znamenskaya, I. A.; Lutsky, A. E.

2018-03-01

This paper presents experimental and numerical investigations of high-current sliding surface discharges of nanosecond duration and their effect on high-speed flow as plasma actuators in a shock tube. This study deals with the effectiveness of a sliding surface discharge at low and medium air pressure. Results cover the electrical characteristics of the discharge and optical visualization of the discharge and high-speed post-discharge flow. A sliding surface discharge is first studied in quiescent air conditions and then in high-speed flow, being initiated in the boundary layer at a transverse flow velocity of 50-950 m s-1 behind a flat shock wave in air of density 0.04-0.45 kg m-3. The discharge is powered by a pulse voltage of 25-30 kV and the electric current is ~0.5 kA. Shadow imaging and particle image velocimetry (PIV) are used to measure the flow field parameters after the pulse surface discharge. Shadow imaging reveals shock waves originating from the channels of the discharge configurations. PIV is used to measure the velocity field resulting from the discharge in quiescent air and to determine the homogeneity of energy release along the sliding discharge channel. Semicylindrical shock waves from the channels of the sliding discharge have an initial velocity of more than 600 m s-1. The shock-wave configuration floats in the flow along the streamlined surface. Numerical simulation based on the equations of hydrodynamics matched with the experiment showed that 25%-50% of the discharge energy is instantly transformed into heat energy in a high-speed airflow, leading to the formation of shock waves. This energy is comparable to the flow enthalpy and can result in significant modification of the boundary layer and the entire flow.

Combined sewer overflows: an environmental source of hormones and wastewater micropollutants

USGS Publications Warehouse

Phillips, P.J.; Chalmers, A.T.; Gray, J.L.; Kolpin, D.W.; Foreman, W.T.; Wall, G.R.

2012-01-01

Data were collected at a wastewater treatment plant (WWTP) in Burlington, Vermont, USA, (serving 30,000 people) to assess the relative contribution of CSO (combined sewer overflow) bypass flows and treated wastewater effluent to the load of steroid hormones and other wastewater micropollutants (WMPs) from a WWTP to a lake. Flow-weighted composite samples were collected over a 13 month period at this WWTP from CSO bypass flows or plant influent flows (n = 28) and treated effluent discharges (n = 22). Although CSO discharges represent 10% of the total annual water discharge (CSO plus treated plant effluent discharges) from the WWTP, CSO discharges contribute 40–90% of the annual load for hormones and WMPs with high (>90%) wastewater treatment removal efficiency. By contrast, compounds with low removal efficiencies (<90%) have less than 10% of annual load contributed by CSO discharges. Concentrations of estrogens, androgens, and WMPs generally are 10 times higher in CSO discharges compared to treated wastewater discharges. Compound concentrations in samples of CSO discharges generally decrease with increasing flow because of wastewater dilution by rainfall runoff. By contrast, concentrations of hormones and many WMPs in samples from treated discharges can increase with increasing flow due to decreasing removal efficiency.

Combined Sewer Overflows: An Environmental Source of Hormones and Wastewater Micropollutants

PubMed Central

2012-01-01

Data were collected at a wastewater treatment plant (WWTP) in Burlington, Vermont, USA, (serving 30,000 people) to assess the relative contribution of CSO (combined sewer overflow) bypass flows and treated wastewater effluent to the load of steroid hormones and other wastewater micropollutants (WMPs) from a WWTP to a lake. Flow-weighted composite samples were collected over a 13 month period at this WWTP from CSO bypass flows or plant influent flows (n = 28) and treated effluent discharges (n = 22). Although CSO discharges represent 10% of the total annual water discharge (CSO plus treated plant effluent discharges) from the WWTP, CSO discharges contribute 40–90% of the annual load for hormones and WMPs with high (>90%) wastewater treatment removal efficiency. By contrast, compounds with low removal efficiencies (<90%) have less than 10% of annual load contributed by CSO discharges. Concentrations of estrogens, androgens, and WMPs generally are 10 times higher in CSO discharges compared to treated wastewater discharges. Compound concentrations in samples of CSO discharges generally decrease with increasing flow because of wastewater dilution by rainfall runoff. By contrast, concentrations of hormones and many WMPs in samples from treated discharges can increase with increasing flow due to decreasing removal efficiency. PMID:22540536

LAV@HAZARD: a Web-GIS Framework for Real-Time Forecasting of Lava Flow Hazards

NASA Astrophysics Data System (ADS)

Del Negro, C.; Bilotta, G.; Cappello, A.; Ganci, G.; Herault, A.

2014-12-01

Crucial to lava flow hazard assessment is the development of tools for real-time prediction of flow paths, flow advance rates, and final flow lengths. Accurate prediction of flow paths and advance rates requires not only rapid assessment of eruption conditions (especially effusion rate) but also improved models of lava flow emplacement. Here we present the LAV@HAZARD web-GIS framework, which combines spaceborne remote sensing techniques and numerical simulations for real-time forecasting of lava flow hazards. By using satellite-derived discharge rates to drive a lava flow emplacement model, LAV@HAZARD allows timely definition of parameters and maps essential for hazard assessment, including the propagation time of lava flows and the maximum run-out distance. We take advantage of the flexibility of the HOTSAT thermal monitoring system to process satellite images coming from sensors with different spatial, temporal and spectral resolutions. HOTSAT was designed to ingest infrared satellite data acquired by the MODIS and SEVIRI sensors to output hot spot location, lava thermal flux and discharge rate. We use LAV@HAZARD to merge this output with the MAGFLOW physics-based model to simulate lava flow paths and to update, in a timely manner, flow simulations. Thus, any significant changes in lava discharge rate are included in the predictions. A significant benefit in terms of computational speed was obtained thanks to the parallel implementation of MAGFLOW on graphic processing units (GPUs). All this useful information has been gathered into the LAV@HAZARD platform which, due to the high degree of interactivity, allows generation of easily readable maps and a fast way to explore alternative scenarios. We will describe and demonstrate the operation of this framework using a variety of case studies pertaining to Mt Etna, Sicily. Although this study was conducted on Mt Etna, the approach used is designed to be applicable to other volcanic areas around the world.

Understanding the distributed cognitive processes of intensive care patient discharge.

PubMed

Lin, Frances; Chaboyer, Wendy; Wallis, Marianne

2014-03-01

To better understand and identify vulnerabilities and risks in the ICU patient discharge process, which provides evidence for service improvement. Previous studies have identified that 'after hours' discharge and 'premature' discharge from ICU are associated with increased mortality. However, some of these studies have largely been retrospective reviews of various administrative databases, while others have focused on specific aspects of the process, which may miss crucial components of the discharge process. This is an ethnographic exploratory study. Distributed cognition and activity theory were used as theoretical frameworks. Ethnographic data collection techniques including informal interviews, direct observations and collecting existing documents were used. A total of 56 one-to-one interviews were conducted with 46 participants; 28 discharges were observed; and numerous documents were collected during a five-month period. A triangulated technique was used in both data collection and data analysis to ensure the research rigour. Under the guidance of activity theory and distributed cognition theoretical frameworks, five themes emerged: hierarchical power and authority, competing priorities, ineffective communication, failing to enact the organisational processes and working collaboratively to optimise the discharge process. Issues with teamwork, cognitive processes and team members' interaction with cognitive artefacts influenced the discharge process. Strategies to improve shared situational awareness are needed to improve teamwork, patient flow and resource efficiency. Tools need to be evaluated regularly to ensure their continuous usefulness. Health care professionals need to be aware of the impact of their competing priorities and ensure discharges occur in a timely manner. Activity theory and distributed cognition are useful theoretical frameworks to support healthcare organisational research. © 2013 John Wiley & Sons Ltd.

Characterization of microwave discharge plasmas for surface processing

NASA Astrophysics Data System (ADS)

Nikolic, Milka

We have developed several diagnostic techniques to characterize two types of microwave (MW) discharge plasmas: a supersonic flowing argon MW discharge maintained in a cylindrical quartz cavity at frequency ƒ = 2.45 GHz and a pulse repetitive MW discharge in air at ƒ = 9.5 GHz. Low temperature MW discharges have been proven to posses attractive properties for plasma cleaning and etching of niobium surfaces of superconductive radio frequency (SRF) cavities. Plasma based surface modification technologies offer a promising alternative for etching and cleaning of SRF cavities. These technologies are low cost, environmentally friendly and easily controllable, and present a possible alternative to currently used acid based wet technologies, such as buffered chemical polishing (BCP), or electrochemical polishing (EP). In fact, weakly ionized. non-equilibrium, and low temperature gas discharges represent a powerful tool for surface processing due to the strong chemical reactivity of plasma radicals. Therefore, characterizing these discharges by applying non-perturbing, in situ measurement techniques is of vital importance. Optical emission spectroscopy has been employed to analyze the molecular structure and evaluate rotational and vibrational temperatures in these discharges. The internal plasma structure was studied by applying a tomographic numerical method based on the two-dimensional Radon formula. An automated optical measurement system has been developed for reconstruction of local plasma parameters. It was found that excited argon states are concentrated near the tube walls, thus confirming the assumption that the post discharge plasma is dominantly sustained by a travelling surface wave. Employing a laser induced fluorescence technique in combination with the time synchronization device allowed us to obtain time-resolved population densities of some excited atomic levels in argon. We have developed a technique for absolute measurements of electron density based on the time-resolved absolute intensity of a Nitrogen spectral band belonging to the Second Positive System, the kinetic model and the detailed particle balance of the N2 (C 3piu) state. Measured electron density waveforms are in fair agreement with electron densities obtained using the Stark broadening technique. In addition, time dependent population densities of Ar I metastable and resonant levels were obtained by employing a kinetic model developed based on analysis of population density rates of excited Ar I p levels. Both the experimental results and numerical models for both types of gas discharges indicate that multispecies chemistry of gases plays an important role in understanding the dynamics and characterizing the properties of these discharges.

Estimating the gas and dye quantities for modified tracer technique measurements of stream reaeration coefficients

USGS Publications Warehouse

Rathbun, R.E.

1979-01-01

Measuring the reaeration coefficient of a stream with a modified tracer technique has been accomplished by injecting either ethylene or ethylene and propane together and a rhodamine-WT dye solution into the stream. The movement of the tracers through the stream reach after injection is described by a one-dimensional diffusion equation. The peak concentrations of the tracers at the downstream end of the reach depend on the concentrations of the tracers in the stream at the injection site, the longitudinal dispersion coefficient, the mean water velocity, the length of the reach, and the duration of the injection period. The downstream gas concentrations also depend on the gas desorption coefficients of the reach. The concentrations of the tracer gases in the stream at the injection site depend on the flow rates of the gases through the injection diffusers, the efficiency of the gas absorption process, and the stream discharge. The concentration of dye in the stream at the injection site depends on the flow rate of the dye solution, the concentration of the dye solution, and the stream discharge. Equations for estimating the gas flow rates, the quantities of the gases, the dye concentration, and the quantity of dye together with procedures for determining the variables in these equations are presented. (Woodard-USGS)

The Removal of NOx Using a Pulsed Streamer Corona Discharge in the Presence of Ethylene

DTIC Science & Technology

1996-07-25

be a stratospheric ozone destructor and a greenhouse gas (U.S EPA, 1993). Nitric oxide (NO) is an odorless gas and is only slightly soluble in water...gas can be bubbled for humidification , 5) flow meters, valves, and mass flow controllers, and 6) a stainless steel mixing chamber upstream from the...Reduction of Acid and Greenhouse Gases in Combustion of Flue Gases", Non-Thermal Plasma Techniques for Pollution Control, Part A, Eds: Penetrante

Mass and momentum turbulent transport experiments with confined swirling coaxial jets

NASA Technical Reports Server (NTRS)

Roback, R.; Johnson, B. V.

1983-01-01

Swirling coaxial jets mixing downstream, discharging into an expanded duct was conducted to obtain data for the evaluation and improvement of turbulent transport models currently used in a variety of computational procedures throughout the combustion community. A combination of laser velocimeter (LV) and laser induced fluorescence (LIF) techniques was employed to obtain mean and fluctuating velocity and concentration distributions which were used to derive mass and momentum turbulent transport parameters currently incorporated into various combustor flow models. Flow visualization techniques were also employed to determine qualitatively the time dependent characteristics of the flow and the scale of turbulence. The results of these measurements indicated that the largest momentum turbulent transport was in the r-z plane. Peak momentum turbulent transport rates were approximately the same as those for the nonswirling flow condition. The mass turbulent transport process for swirling flow was complicated. Mixing occurred in several steps of axial and radial mass transport and was coupled with a large radial mean convective flux. Mixing for swirling flow was completed in one-third the length required for nonswirling flow.

An Experimental Visualization and Image Analysis of Electrohydrodynamically Induced Vapor-Phase Silicon Oil Flow under DC Corona Discharge

NASA Astrophysics Data System (ADS)

Ohyama, Ryu-Ichiro; Fukumoto, Masaru

A DC corona discharge induced electrohydrodynamic (EHD) flow phenomenon for a multi-phase fluid containing a vapor-phase dielectric liquid in the fresh air was investigated. The experimental electrode system was a simple arrangement of needle-plate electrodes for the corona discharges and high-resistivity silicon oil was used as the vapor-phase liquid enclosure. The qualitative observation of EHD flow patterns was conducted by an optical processing on computer tomography and the time-series of discharge current pulse generations at corona discharge electrode were measured simultaneously. These experimental results were analyzed in relationship between the EHD flow motions and the current pulse generations in synchronization. The current pulses and the EHD flow motions from the corona discharge electrode presented a continuous mode similar to the ionic wind in the fresh air and an intermittent mode. In the intermittent mode, the observed EHD flow motion was synchronized with the separated discharge pulse generations. From these experimental results, it was expected that the existence of silicon oil vapor trapped charges gave an occasion to the intermittent generations of the discharge pulses and the secondary EHD flow.

Disturbance Source Separation in Shear Flows Using Blind Source Separation Methods

NASA Astrophysics Data System (ADS)

Gluzman, Igal; Cohen, Jacob; Oshman, Yaakov

2017-11-01

A novel approach is presented for identifying disturbance sources in wall-bounded shear flows. The method can prove useful for active control of boundary layer transition from laminar to turbulent flow. The underlying idea is to consider the flow state, as measured in sensors, to be a mixture of sources, and to use Blind Source Separation (BSS) techniques to recover the separate sources and their unknown mixing process. We present a BSS method based on the Degenerate Unmixing Estimation Technique. This method can be used to identify any (a priori unknown) number of sources by using the data acquired by only two sensors. The power of the new method is demonstrated via numerical and experimental proofs of concept. Wind tunnel experiments involving boundary layer flow over a flat plate were carried out, in which two hot-wire anemometers were used to separate disturbances generated by disturbance generators such as a single dielectric barrier discharge plasma actuator and a loudspeaker.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harding, Samuel F.; Romero-Gomez, Pedro D. J.; Richmond, Marshall C.

Standards provide recommendations for the best practices in the installation of current meters for measuring fluid flow in closed conduits. These include PTC-18 and IEC-41 . Both of these standards refer to the requirements of the ISO Standard 3354 for cases where the velocity distribution is assumed to be regular and the flow steady. Due to the nature of the short converging intakes of Kaplan hydroturbines, these assumptions may be invalid if current meters are intended to be used to characterize turbine flows. In this study, we examine a combination of measurement guidelines from both ISO standards by means ofmore » virtual current meters (VCM) set up over a simulated hydroturbine flow field. To this purpose, a computational fluid dynamics (CFD) model was developed to model the velocity field of a short converging intake of the Ice Harbor Dam on the Snake River, in the State of Washington. The detailed geometry and resulting wake of the submersible traveling screen (STS) at the first gate slot was of particular interest in the development of the CFD model using a detached eddy simulation (DES) turbulence solution. An array of virtual point velocity measurements were extracted from the resulting velocity field to simulate VCM at two virtual measurement (VM) locations at different distances downstream of the STS. The discharge through each bay was calculated from the VM using the graphical integration solution to the velocity-area method. This method of representing practical velocimetry techniques in a numerical flow field has been successfully used in a range of marine and conventional hydropower applications. A sensitivity analysis was performed to observe the effect of the VCM array resolution on the discharge error. The downstream VM section required 11–33% less VCM in the array than the upstream VM location to achieve a given discharge error. In general, more instruments were required to quantify the discharge at high levels of accuracy when the STS was introduced because of the increased spatial variability of the flow velocity.« less

Estimates of Lava Eruption Rates at Alba Patera, Mars

NASA Technical Reports Server (NTRS)

Baloga, S. M.; Pieri, D. C.

1985-01-01

The Martian volcanic complex Alba Patera exhibits a suite of well-defined, long and relatively narrow lava flows qualitatively resembling those found in Hawaii. Even without any information on the duration of the Martian flows, eruption rates (total volume discharge/duration of the extrusion) estimates are implied by the physical dimensions of the flows and the likely conjecture that Stephan-Boltzmann radiation is the dominating thermal loss mechanism. The ten flows in this analysis emanate radially from the central vent and were recently measured in length, plan areas, and average thicknesses by shadow measurement techniques. The dimensions of interest are shown. Although perhaps morphologically congruent to certain Hawaiian flows, the dramatically expanded physical dimensions of the Martian flows argues for some markedly distinct differences in lava flow composition for eruption characteristics.

Hydrologic assessment of the Upper Dorr Run Watershed, Hocking County, Ohio, 1998

USGS Publications Warehouse

Haefner, R.J.

1999-01-01

The Upper Dorr Run Watershed in Hocking County, Ohio, has been mined several times for coal and clay since 1913 and is a significant source of acid mine drainage to the Hocking River. To assess the surface-water hydrology of the site, a topographic map showing the location of springs and other hydrologic features of interest was prepared using aerial photography and field surveying and mapping techniques. Discharge and water-quality measurements at six springs and one stream site were made during field investigations in June 1998. Discharge and water quality observed at a downstream weir on Upper Dorr Run represents the combined discharge from springs plus ground-water inflow. Discharges from springs to surface water were generally small (less than 0.3 cubic foot per second), but one spring constituted 56 percent of the total discharge measured at the downstream weir. The total flow at an intermediate measurement site was less than the combined discharge of the upgradient springs because of evaporation, transpiration, and ground-water flow beneath the stream channel. The total flow at the weir was greater than the combined discharge of all springs, primarily because two potential sources of water were not included in field measurements. The water quality in Upper Dorr Run is strongly affected by acid mine drainage as indicated by pH less than 4, elevated acidity, and elevated concentrations of dissolved sulfate and dissolved iron. Concentrations of chemical constituents in the water were lower at the downstream weir than at the source springs because of residence times in ponds and chemical interactions between the water and the atmosphere. Acidity loads during the sampling period were significantly higher from the Lower Kittanning (No. 5) coal (272 kilograms per day) than from the Upper Kittanning (No. 6) coal (17.7 kilograms per day). Comparison of data obtained in 1998 to data obtained in 1982 showed that quality of water of selected sampling sites had not changed appreciably in 16 years.

Visualization of conduit-matrix conductivity differences in a karst aquifer using time-lapse electrical resistivity

NASA Astrophysics Data System (ADS)

Meyerhoff, Steven B.; Karaoulis, Marios; Fiebig, Florian; Maxwell, Reed M.; Revil, André; Martin, Jonathan B.; Graham, Wendy D.

2012-12-01

In the karstic upper Floridan aquifer, surface water flows into conduits of the groundwater system and may exchange with water in the aquifer matrix. This exchange has been hypothesized to occur based on differences in discharge at the Santa Fe River Sink-Rise system, north central Florida, but has yet to be visualized using any geophysical techniques. Using electrical resistivity tomography, we conducted a time-lapse study at two locations with mapped conduits connecting the Santa Fe River Sink to the Santa Fe River Rise to study changes of electrical conductivity during times of varying discharge over a six-week period. Our results show conductivity differences between matrix, conduit changes in resistivity occurring through time at the locations of mapped karst conduits, and changes in electrical conductivity during rainfall infiltration. These observations provide insight into time scales and matrix conduit conductivity differences, illustrating how surface water flow recharged to conduits may flow in a groundwater system in a karst aquifer.

Application of a parameter-estimation technique to modeling the regional aquifer underlying the eastern Snake River plain, Idaho

USGS Publications Warehouse

Garabedian, Stephen P.

1986-01-01

A nonlinear, least-squares regression technique for the estimation of ground-water flow model parameters was applied to the regional aquifer underlying the eastern Snake River Plain, Idaho. The technique uses a computer program to simulate two-dimensional, steady-state ground-water flow. Hydrologic data for the 1980 water year were used to calculate recharge rates, boundary fluxes, and spring discharges. Ground-water use was estimated from irrigated land maps and crop consumptive-use figures. These estimates of ground-water withdrawal, recharge rates, and boundary flux, along with leakance, were used as known values in the model calibration of transmissivity. Leakance values were adjusted between regression solutions by comparing model-calculated to measured spring discharges. In other simulations, recharge and leakance also were calibrated as prior-information regression parameters, which limits the variation of these parameters using a normalized standard error of estimate. Results from a best-fit model indicate a wide areal range in transmissivity from about 0.05 to 44 feet squared per second and in leakance from about 2.2x10 -9 to 6.0 x 10 -8 feet per second per foot. Along with parameter values, model statistics also were calculated, including the coefficient of correlation between calculated and observed head (0.996), the standard error of the estimates for head (40 feet), and the parameter coefficients of variation (about 10-40 percent). Additional boundary flux was added in some areas during calibration to achieve proper fit to ground-water flow directions. Model fit improved significantly when areas that violated model assumptions were removed. It also improved slightly when y-direction (northwest-southeast) transmissivity values were larger than x-direction (northeast-southwest) transmissivity values. The model was most sensitive to changes in recharge, and in some areas, to changes in transmissivity, particularly near the spring discharge area from Milner Dam to King Hill.

Probability analysis of the relation of salinity to freshwater discharge in the St. Sebastian River, Florida

USGS Publications Warehouse

Wicklein, S.M.; Gain, W.S.

1999-01-01

The St. Sebastian River lies in the southern part of the Indian River basin on the east coast of Florida. Increases in freshwater discharge due to urbanization and changes in land use have reduced salinity in the St. Sebastian River and, consequently, salinity in the Indian River, affecting the commercial fishing industry. Wind, water temperature, tidal flux, freshwater discharge, and downstream salinity all affect salinity in the St. Sebastian River estuary, but freshwater discharge is the only one of these hydrologic factors which might be affected by water-management practices. A probability analysis of salinity conditions in the St. Sebastian River estuary, taking into account the effects of freshwater discharge over a period from May 1992 to March 1996, was used to determine the likelihood (probability) that salinities, as represented by daily mean specific- conductance values, will fall below a given threshold. The effects of freshwater discharge on salinities were evaluated with a simple volumetric model fitted to time series of measured specific conductance, by using nonlinear optimization techniques. Specific-conductance values for two depths at monitored sites represent stratified flow which results from differences in salt concentration between freshwater and saltwater. Layering of freshwater and saltwater is assumed, and the model is applied independently to each layer with the assumption that the water within the layer is well mixed. The model of specific conductance as a function of discharge (a salinity response model) was combined with a model of residual variation to produce a total probability model. Flow distributions and model residuals were integrated to produce a salinity distribution and determine differences in salinity probabilities as a result of changes in water-management practices. Two possible management alternatives were analyzed: stormwater detention (reducing the peak rate of discharge but not reducing the overall flow volume) and stormwater retention (reducing peak discharges without later release). Detention of freshwater discharges increased the probability of specific- conductance values falling below a given limit (20,000 microsiemens per centimeter) for all sites but one. The retention of freshwater input to the system decreased the likelihood of falling below a selected limit of specific conductance at all sites. For limits of specific conductance (1,000 microsiemens per centimeter or 20,000 microsiemens per centimeter, depending on the site), the predicted days of occurrence below a limit decreased ranging from 17 to 68 percent of the predicted days of occurrence for unregulated flow. The primary finding to be drawn from the discharge-salinity analysis is that an empirical-response model alone does not provide adequate information to assess the response of the system to changes in flow regime. Whether a given level of discharge can produce a given response on a given day is not as important as the probability of that response on a given day and over a period of many days. A deterministic model of the St. Sebastian River estuary based only on discharge would predict that retention of discharge peaks should increase the average salinity conditions in the St. Sebastian River estuary. The probabilistic model produces a very different response indicating that salinity can decrease by a power of three as discharges increase, and that random factors can predominate and control salinity until discharges increase sufficiently to flush the entire system of saltwater.

Slope-Area Computation Program Graphical User Interface 1.0—A Preprocessing and Postprocessing Tool for Estimating Peak Flood Discharge Using the Slope-Area Method

USGS Publications Warehouse

Bradley, D. Nathan

2012-01-01

The slope-area method is a technique for estimating the peak discharge of a flood after the water has receded (Dalrymple and Benson, 1967). This type of discharge estimate is called an “indirect measurement” because it relies on evidence left behind by the flood, such as high-water marks (HWMs) on trees or buildings. These indicators of flood stage are combined with measurements of the cross-sectional geometry of the stream, estimates of channel roughness, and a mathematical model that balances the total energy of the flow between cross sections. This is in contrast to a “direct” measurement of discharge during the flood where cross-sectional area is measured and a current meter or acoustic equipment is used to measure the water velocity. When a direct discharge measurement cannot be made at a gage during high flows because of logistics or safety reasons, an indirect measurement of a peak discharge is useful for defining the high-flow section of the stage-discharge relation (rating curve) at the stream gage, resulting in more accurate computation of high flows. The Slope-Area Computation program (SAC; Fulford, 1994) is an implementation of the slope-area method that computes a peak-discharge estimate from inputs of water-surface slope (from surveyed HWMs), channel geometry, and estimated channel roughness. SAC is a command line program written in Fortran that reads input data from a formatted text file and prints results to another formatted text file. Preparing the input file can be time-consuming and prone to errors. This document describes the SAC graphical user interface (GUI), a crossplatform “wrapper” application that prepares the SAC input file, executes the program, and helps the user interpret the output. The SAC GUI is an update and enhancement of the slope-area method (SAM; Hortness, 2004; Berenbrock, 1996), an earlier spreadsheet tool used to aid field personnel in the completion of a slope-area measurement. The SAC GUI reads survey data, develops a plan-view plot, water-surface profile, cross-section plots, and develops the SAC input file. The SAC GUI also develops HEC-2 files that can be imported into HEC–RAS.

Analysis of river pollution data from low-flow period by means of multivariate techniques: a case study from the oil-shale industry region, northeastern Estonia.

PubMed

Truu, Jaak; Heinaru, Eeva; Talpsep, Ene; Heinaru, Ain

2002-01-01

The oil-shale industry has created serious pollution problems in northeastern Estonia. Untreated, phenol-rich leachate from semi-coke mounds formed as a by-product of oil-shale processing is discharged into the Baltic Sea via channels and rivers. An exploratory analysis of water chemical and microbiological data sets from the low-flow period was carried out using different multivariate analysis techniques. Principal component analysis allowed us to distinguish different locations in the river system. The riverine microbial community response to water chemical parameters was assessed by co-inertia analysis. Water pH, COD and total nitrogen were negatively related to the number of biodegradative bacteria, while oxygen concentration promoted the abundance of these bacteria. The results demonstrate the utility of multivariate statistical techniques as tools for estimating the magnitude and extent of pollution based on river water chemical and microbiological parameters. An evaluation of river chemical and microbiological data suggests that the ambient natural attenuation mechanisms only partly eliminate pollutants from river water, and that a sufficient reduction of more recalcitrant compounds could be achieved through the reduction of wastewater discharge from the oil-shale chemical industry into the rivers.

Regional ground-water discharge to large streams in the upper coastal plain of South Carolina and parts of North Carolina and Georgia

USGS Publications Warehouse

Aucott, W.R.; Meadows, R.S.; Patterson, G.G.

1987-01-01

Base flow was computed to estimate discharge from regional aquifers for six large streams in the upper Coastal Plain of South Carolina and parts of North Carolina and Georgia. Aquifers that sustain the base flow of both large and small streams are stratified into shallow and deep flow systems. Base-flow during dry conditions on main stems of large streams was assumed to be the discharge from the deep groundwater flow system. Six streams were analyzed: the Savannah, South and North Fork Edisto, Lynches, Pee Dee, and the Luber Rivers. Stream reaches in the Upper Coastal Plain were studied because of the relatively large aquifer discharge in these areas in comparison to the lower Coastal Plain. Estimates of discharge from the deep groundwater flow system to the six large streams averaged 1.8 cu ft/sec/mi of stream and 0.11 cu ft/sec/sq mi of surface drainage area. The estimates were made by subtracting all tributary inflows from the discharge gain between two gaging stations on a large stream during an extreme low-flow period. These estimates pertain only to flow in the deep groundwater flow system. Shallow flow systems and total base flow are > flow in the deep system. (USGS)

Correcting acoustic Doppler current profiler discharge measurement bias from moving-bed conditions without global positioning during the 2004 Glen Canyon Dam controlled flood on the Colorado River

USGS Publications Warehouse

Gartner, J.W.; Ganju, N.K.

2007-01-01

Discharge measurements were made by acoustic Doppler current profiler at two locations on the Colorado River during the 2004 controlled flood from Glen Canyon Dam, Arizona. Measurement hardware and software have constantly improved from the 1980s such that discharge measurements by acoustic profiling instruments are now routinely made over a wide range of hydrologic conditions. However, measurements made with instruments deployed from moving boats require reliable boat velocity data for accurate measurements of discharge. This is normally accomplished by using special acoustic bottom track pings that sense instrument motion over bottom. While this method is suitable for most conditions, high current flows that produce downstream bed sediment movement create a condition known as moving bed that will bias velocities and discharge to lower than actual values. When this situation exists, one solution is to determine boat velocity with satellite positioning information. Another solution is to use a lower frequency instrument. Discharge measurements made during the 2004 Glen Canyon controlled flood were subject to moving-bed conditions and frequent loss of bottom track. Due to site conditions and equipment availability, the measurements were conducted without benefit of external positioning information or lower frequency instruments. This paper documents and evaluates several techniques used to correct the resulting underestimated discharge measurements. One technique produces discharge values in good agreement with estimates from numerical model and measured hydrographs during the flood. ?? 2007, by the American Society of Limnology and Oceanography, Inc.

Advection within shallow pore waters of a coastal lagoon, Florida

USGS Publications Warehouse

Cable, J.E.; Martin, Jonathan B.; Swarzenski, Peter W.; Lindenberg, Mary K.; Steward, Joel

2004-01-01

Ground water sources can be a significant portion of a local water budget in estuarine environments, particularly in areas with high recharge rates, transmissive aquifers, and permeable marine sediments. However, field measurements of ground water discharge are often incongruent with ground water flow modeling results, leaving many scientists unsure which estimates are accurate. In this study, we find that both measurements and model results are reasonable. The difference between estimates apparently results from the sources of water being measured and not the techniques themselves. In two locations in the Indian River Lagoon estuarine system, we found seepage meter rates similar to rates calculated from the geochemical tracers 222Rn and 226Ra. Ground water discharge rates ranged from 4 to 9 cm/d using seepage meters and 3 to 20 cm/d using 222Rn and 226Ra. In contrast, in comparisons to other studies where finite element ground water flow modeling was used, much lower ground water discharge rates of ∼0.05 to 0.15 cm/d were estimated. These low rates probably represent discharge of meteoric ground water from land-recharged aquifers, while the much higher rates measured with seepage meters, 222Rn, and 226Ra likely include an additional source of surface waters that regularly flush shallow (< 1 m depth) sediments. This resultant total flow of mixed land-recharged water and recirculated surface waters contributes to the total biogeochemical loading in this shallow estuarine environment.

Techniques for estimating flood-peak discharges of rural, unregulated streams in Ohio

USGS Publications Warehouse

Koltun, G.F.; Roberts, J.W.

1990-01-01

Multiple-regression equations are presented for estimating flood-peak discharges having recurrence intervals of 2, 5, 10, 25, 50, and 100 years at ungaged sites on rural, unregulated streams in Ohio. The average standard errors of prediction for the equations range from 33.4% to 41.4%. Peak discharge estimates determined by log-Pearson Type III analysis using data collected through the 1987 water year are reported for 275 streamflow-gaging stations. Ordinary least-squares multiple-regression techniques were used to divide the State into three regions and to identify a set of basin characteristics that help explain station-to- station variation in the log-Pearson estimates. Contributing drainage area, main-channel slope, and storage area were identified as suitable explanatory variables. Generalized least-square procedures, which include historical flow data and account for differences in the variance of flows at different gaging stations, spatial correlation among gaging station records, and variable lengths of station record were used to estimate the regression parameters. Weighted peak-discharge estimates computed as a function of the log-Pearson Type III and regression estimates are reported for each station. A method is provided to adjust regression estimates for ungaged sites by use of weighted and regression estimates for a gaged site located on the same stream. Limitations and shortcomings cited in an earlier report on the magnitude and frequency of floods in Ohio are addressed in this study. Geographic bias is no longer evident for the Maumee River basin of northwestern Ohio. No bias is found to be associated with the forested-area characteristic for the range used in the regression analysis (0.0 to 99.0%), nor is this characteristic significant in explaining peak discharges. Surface-mined area likewise is not significant in explaining peak discharges, and the regression equations are not biased when applied to basins having approximately 30% or less surface-mined area. Analyses of residuals indicate that the equations tend to overestimate flood-peak discharges for basins having approximately 30% or more surface-mined area. (USGS)

Effective Discharge and Annual Sediment Yield on Brazos River

NASA Astrophysics Data System (ADS)

Rouhnia, M.; Salehi, M.; Keyvani, A.; Ma, F.; Strom, K. B.; Raphelt, N.

2012-12-01

Geometry of an alluvial river alters dynamically over the time due to the sediment mobilization on the banks and bottom of the river channel in various flow rates. Many researchers tried to define a single representative discharge for these morphological processes such as "bank-full discharge", "effective discharge" and "channel forming discharge". Effective discharge is the flow rate in which, the most sediment load is being carried by water, in a long term period. This project is aimed to develop effective discharge estimates for six gaging stations along the Brazos River from Waco, TX to Rosharon, TX. The project was performed with cooperation of the In-stream Flow Team of the Texas Water Development Board (TWDB). Project objectives are listed as: 1) developing "Flow Duration Curves" for six stations based on mean-daily discharge by downloading the required, additional data from U.S Geological Survey website, 2) developing "Rating Curves" for six gaging stations after sampling and field measurements in three different flow conditions, 3) developing a smooth shaped "Sediment Yield Histogram" with a well distinguished peak as effective discharge. The effective discharge was calculated using two methods of manually and automatic bin selection. The automatic method is based on kernel density approximation. Cross-sectional geometry measurements, particle size distributions and water field samples were processed in the laboratory to obtain the suspended sediment concentration associated with flow rate. Rating curves showed acceptable trends, as the greater flow rate we experienced, the more sediment were carried by water.

Refinement and application of acoustic impulse technique to study nozzle transmission characteristics

NASA Technical Reports Server (NTRS)

Salikuddin, M.; Brown, W. H.; Ramakrishnan, R.; Tanna, H. K.

1983-01-01

An improved acoustic impulse technique was developed and was used to study the transmission characteristics of duct/nozzle systems. To accomplish the above objective, various problems associated with the existing spark-discharge impulse technique were first studied. These included (1) the nonlinear behavior of high intensity pulses, (2) the contamination of the signal with flow noise, (3) low signal-to-noise ratio at high exhaust velocities, and (4) the inability to control or shape the signal generated by the source, specially when multiple spark points were used as the source. The first step to resolve these problems was the replacement of the spark-discharge source with electroacoustic driver(s). These included (1) synthesizing on acoustic impulse with acoustic driver(s) to control and shape the output signal, (2) time domain signal averaging to remove flow noise from the contaminated signal, (3) signal editing to remove unwanted portions of the time history, (4) spectral averaging, and (5) numerical smoothing. The acoustic power measurement technique was improved by taking multiple induct measurements and by a modal decomposition process to account for the contribution of higher order modes in the power computation. The improved acoustic impulse technique was then validated by comparing the results derived by an impedance tube method. The mechanism of acoustic power loss, that occurs when sound is transmitted through nozzle terminations, was investigated. Finally, the refined impulse technique was applied to obtain more accurate results for the acoustic transmission characteristics of a conical nozzle and a multi-lobe multi-tube supressor nozzle.

Laser cross-flow gas system

DOEpatents

Duncan, David B.

1992-01-01

A method and laser apparatus are disclosed which provide for a cross-flow of gas near one end of a laser discharge tube. The cross-flow of gas causes a concentration gradient which affects diffusion of contaminants in the discharge tube towards the cross-flow of the gas, which contaminants are then withdrawn from the discharge tube.

Properties of thermal air plasma with admixing of copper and carbon

NASA Astrophysics Data System (ADS)

Fesenko, S.; Veklich, A.; Boretskij, V.; Cressault, Y.; Gleizes, A.; Teulet, Ph

2014-11-01

This paper deals with investigations of air plasma with admixing of copper and carbon. Model plasma source unit with real breaking arc was used for the simulation of real discharges, which can be occurred during sliding of Cu-C composite electrodes on copper wire at electromotive vehicles. The complex technique of plasma property studies is developed. From one hand, the radial profiles of temperature and electron density in plasma of electric arc discharge in air between Cu-C composite and copper electrodes in air flow were measured by optical spectroscopy techniques. From another hand, the radial profiles of electric conductivity of plasma mixture were calculated by solution of energy balance equation. It was assumed that the thermal conductivity of air plasma is not depending on copper or carbon vapor admixtures. The electron density is obtained from electric conductivity profiles by calculation in assumption of local thermodynamic equilibrium in plasma. Computed in such way radial profiles of electron density in plasma of electric arc discharge in air between copper electrodes were compared with experimentally measured profiles. It is concluded that developed techniques of plasma diagnostics can be reasonably used in investigations of thermal plasma with copper and carbon vapors.

Electrostatic Propulsion Beam Divergence Effects on Spacecraft Surfaces. Volume 2, Addendum 1: Ion Time-of-flight Determinations of Doubly to Singly Ionized Mercury Ion Ratios from a Mercury Electron Bombardment Discharge

NASA Technical Reports Server (NTRS)

Sellen, J. M., Jr.; Kemp, R. F.; Hall, D. F.

1973-01-01

The analysis of ion exhaust beam current flow for multiply charged ion species and the application to propellant utilization for the thruster are discussed. The ion engine in use in the experiments is a twenty centimeter diameter electromagnet electron bombardment engine. The experimental technique to determine the multiply charged ion abundance ratios using ion time of flight is described. An analytical treatment of the discharge action in producing various ion species has been carried out.

The application of a non-thermal plasma generated by gas-liquid gliding arc discharge in sterilization

NASA Astrophysics Data System (ADS)

Du, Chang Ming; Wang, Jing; Zhang, Lu; Xia Li, Hong; Liu, Hui; Xiong, Ya

2012-01-01

Gliding arc discharge has been investigated in recent years as an innovative physicochemical technique for contaminated water treatment at atmospheric pressure and ambient temperature. In this study we tested a gas-liquid gliding arc discharge reactor, the bacterial suspension of which was treated circularly. When the bacterial suspension was passed through the electrodes and circulated at defined flow rates, almost 100% of the bacteria were killed in less than 3.0 min. Experimental results showed that it is possible to achieve an abatement of 7.0 decimal logarithm units within only 30 s. Circulation flow rates and types of feeding gas caused a certain impact on bacteria inactivation, but the influences are not obvious. So, under the promise of sterilization effect, industrial applications can select their appropriate operating conditions. All inactivation curves presented the same three-phase profile showing an apparent sterilization effect. Analysis of the scanning electron microscope images of bacterial cells supports the speculation that the gas-liquid gliding arc discharge plasma is acting under various mechanisms driven essentially by oxidation and the effect of electric field. These results enhance the possibility of applying gas-liquid gliding arc discharge decontamination systems to disinfect bacterial-contaminated water. Furthermore, correlational research indicates the potential applications of this technology in rapid sterilization of medical devices, spacecraft and food.

Application of wavelet analysis for monitoring the hydrologic effects of dam operation: Glen canyon dam and the Colorado River at lees ferry, Arizona

USGS Publications Warehouse

White, M.A.; Schmidt, J.C.; Topping, D.J.

2005-01-01

Wavelet analysis is a powerful tool with which to analyse the hydrologic effects of dam construction and operation on river systems. Using continuous records of instantaneous discharge from the Lees Ferry gauging station and records of daily mean discharge from upstream tributaries, we conducted wavelet analyses of the hydrologic structure of the Colorado River in Grand Canyon. The wavelet power spectrum (WPS) of daily mean discharge provided a highly compressed and integrative picture of the post-dam elimination of pronounced annual and sub-annual flow features. The WPS of the continuous record showed the influence of diurnal and weekly power generation cycles, shifts in discharge management, and the 1996 experimental flood in the post-dam period. Normalization of the WPS by local wavelet spectra revealed the fine structure of modulation in discharge scale and amplitude and provides an extremely efficient tool with which to assess the relationships among hydrologic cycles and ecological and geomorphic systems. We extended our analysis to sections of the Snake River and showed how wavelet analysis can be used as a data mining technique. The wavelet approach is an especially promising tool with which to assess dam operation in less well-studied regions and to evaluate management attempts to reconstruct desired flow characteristics. Copyright ?? 2005 John Wiley & Sons, Ltd.

Estimating sediment discharge: Appendix D

USGS Publications Warehouse

Gray, John R.; Simões, Francisco J. M.

2008-01-01

Sediment-discharge measurements usually are available on a discrete or periodic basis. However, estimates of sediment transport often are needed for unmeasured periods, such as when daily or annual sediment-discharge values are sought, or when estimates of transport rates for unmeasured or hypothetical flows are required. Selected methods for estimating suspended-sediment, bed-load, bed- material-load, and total-load discharges have been presented in some detail elsewhere in this volume. The purposes of this contribution are to present some limitations and potential pitfalls associated with obtaining and using the requisite data and equations to estimate sediment discharges and to provide guidance for selecting appropriate estimating equations. Records of sediment discharge are derived from data collected with sufficient frequency to obtain reliable estimates for the computational interval and period. Most sediment- discharge records are computed at daily or annual intervals based on periodically collected data, although some partial records represent discrete or seasonal intervals such as those for flood periods. The method used to calculate sediment- discharge records is dependent on the types and frequency of available data. Records for suspended-sediment discharge computed by methods described by Porterfield (1972) are most prevalent, in part because measurement protocols and computational techniques are well established and because suspended sediment composes the bulk of sediment dis- charges for many rivers. Discharge records for bed load, total load, or in some cases bed-material load plus wash load are less common. Reliable estimation of sediment discharges presupposes that the data on which the estimates are based are comparable and reliable. Unfortunately, data describing a selected characteristic of sediment were not necessarily derived—collected, processed, analyzed, or interpreted—in a consistent manner. For example, bed-load data collected with different types of bed-load samplers may not be comparable (Gray et al. 1991; Childers 1999; Edwards and Glysson 1999). The total suspended solids (TSS) analytical method tends to produce concentration data from open-channel flows that are biased low with respect to their paired suspended-sediment concentration values, particularly when sand-size material composes more than about a quarter of the material in suspension. Instantaneous sediment-discharge values based on TSS data may differ from the more reliable product of suspended- sediment concentration values and the same water-discharge data by an order of magnitude (Gray et al. 2000; Bent et al. 2001; Glysson et al. 2000; 2001). An assessment of data comparability and reliability is an important first step in the estimation of sediment discharges. There are two approaches to obtaining values describing sediment loads in streams. One is based on direct measurement of the quantities of interest, and the other on relations developed between hydraulic parameters and sediment- transport potential. In the next sections, the most common techniques for both approaches are briefly addressed.

Technique for estimating the 2- to 500-year flood discharges on unregulated streams in rural Missouri

USGS Publications Warehouse

Alexander, Terry W.; Wilson, Gary L.

1995-01-01

A generalized least-squares regression technique was used to relate the 2- to 500-year flood discharges from 278 selected streamflow-gaging stations to statistically significant basin characteristics. The regression relations (estimating equations) were defined for three hydrologic regions (I, II, and III) in rural Missouri. Ordinary least-squares regression analyses indicate that drainage area (Regions I, II, and III) and main-channel slope (Regions I and II) are the only basin characteristics needed for computing the 2- to 500-year design-flood discharges at gaged or ungaged stream locations. The resulting generalized least-squares regression equations provide a technique for estimating the 2-, 5-, 10-, 25-, 50-, 100-, and 500-year flood discharges on unregulated streams in rural Missouri. The regression equations for Regions I and II were developed from stream-flow-gaging stations with drainage areas ranging from 0.13 to 11,500 square miles and 0.13 to 14,000 square miles, and main-channel slopes ranging from 1.35 to 150 feet per mile and 1.20 to 279 feet per mile. The regression equations for Region III were developed from streamflow-gaging stations with drainage areas ranging from 0.48 to 1,040 square miles. Standard errors of estimate for the generalized least-squares regression equations in Regions I, II, and m ranged from 30 to 49 percent.

Relations of Water Quality to Streamflow, Season, and Land Use for Four Tributaries to the Toms River, Ocean County, New Jersey, 1994-99

USGS Publications Warehouse

Baker, Ronald J.; Hunchak-Kariouk, Kathryn

2006-01-01

The effects of nonpoint-source contamination on the water quality of four tributaries to the Toms River in Ocean County, New Jersey, have been investigated in a 5-year study by the U.S. Geological Survey (USGS), in cooperation with the New Jersey Department of Environmental Protection (NJDEP). The purpose of the study was to relate the extent of land development to loads of nutrients and other contaminants to these streams, and ultimately to Barnegat Bay. Volumetric streamflow (discharge) was measured at 6 monitoring sites during 37 stormflow and base-flow sampling events over a 5-year period (May 1994-September 1999). Concentrations and yields (area-normalized instantaneous load values) of nitrogen and phosphorus species, total suspended solids, and fecal coliform bacteria were quantified, and pH, dissolved oxygen, and stream stage were monitored during base-flow conditions and storms. Sufficient data were collected to allow for a statistical evaluation of differences in water quality among streams in subbasins with high, medium, and low levels of land development. Long Swamp Creek, in a highly developed subbasin (64.2 percent developed); Wrangle Brook, in a moderately developed subbasin (34.5 percent); Davenport Branch, in a slightly developed subbasin (22.8 percent); and Jakes Branch, in an undeveloped subbasin (0 percent) are the subbasins selected for this study. No point-source discharges are known to be present on these streams. Water samples were collected and analyzed by the NJDEP, and discharge measurements and data analysis were conducted by the USGS. Total nitrogen concentrations were lower in Davenport Branch than in Long Swamp Creek and Wrangle Brook during base flow and stormflow. Concentrations of total nitrogen and nitrate were highest in Wrangle Brook (as high as 3.0 mg/L and 1.6 mg/L, respectively) as a result of high concentrations of nitrate in samples collected during base flow; nitrate loading from ground-water discharge is much higher in Wrangle Brook than in any of the other streams, possibly as a result of an experimental wastewater-(secondary effluent) disposal site that was in operation during the 1980's. Ammonia concentrations were higher in samples from Long Swamp Creek than in those from the other two monitoring sites under all flow conditions, and ammonia yields were higher during stormflow than base flow at all monitoring sites. Concentrations and yields of fecal coliform bacteria and total suspended solids were higher during stormflow than during base flow at all monitoring sites. Concentrations and yields were significantly higher in Long Swamp Creek, a highly developed subbasin and Wrangle Brook, a moderately developed subbasin than in Davenport Branch, a slightly developed subbasin. Concentrations and yields of phosphate species, which also are strongly related to stormflow, were higher during stormflow in Long Swamp Creek than in the other subbasins. Base-flow separation techniques were used on hydrographs generated for storms to distinguish the fraction of discharge and constituent loading attributable to storm runoff (overland flow) from the fraction contributed by ground-water discharge. Precipitation records were used to determine the total annual volumes of ground-water discharge and runoff at each monitoring site. These volumes were used in conjunction with water-quality data to calculate total annual loads of each constituent at each monitoring site, separated into ground-water discharge and runoff fractions. It was determined that loads of ammonia, nitrate, organic nitrogen, total nitrogen, and orthophosphate in ground-water discharge were significantly higher in the moderately developed Wrangle Brook subbasin than in the highly developed Long Swamp Creek subbasin, and that no relation was apparent between the percent of land development and constituent loads from ground-water discharge. The loading of each constituent contributed by ground-water discharge is specific

Quantifying the Journey of a Turbidity Current: How Water and Sediment Discharges Vary with Distance in Monterey Canyon

NASA Astrophysics Data System (ADS)

Chapplow, N.; Talling, P.; Cartigny, M.; Parsons, D. R.; Simmons, S.; Clare, M. A.; Paull, C. K.

2017-12-01

Turbidity currents transport vast quantities of sediment across the seafloor and form the largest sediment accumulations on Earth. Such flows pose a hazard to strategically important seafloor infrastructure and are important agents for the transport of organic carbon and nutrients that support deep-sea ecosystems. It is therefore important to quantify the scale of these flows, how much sediment they transport, and how their discharge evolves over time and space along their flow path. Two modes of flow evolution have been proposed based on experimental and numerical models. The first is termed ignition, where flows entrain seafloor sediment and become more voluminous and powerful and increase in discharge. The second is dissipation, where sediment falls out of suspension, flows decelerate and lose discharge. Field-scale turbidity currents have only been measured at a handful of sites worldwide, however, and never at multiple locations along their full course. Therefore, it has not been possible to determine when, where and why flows diverge into these two modes in the deep sea and how discharge of the flows varies. The ambitious multi-institution Coordinated Canyon Experiment measured turbidity currents at seven instrumented moorings along the Monterey Canyon, offshore California. Fifteen flows were recorded, including the fastest events yet measured at high resolution (>8 m/s). This remarkable dataset provides the first opportunity to quantify down-channel sediment and flow discharge evolution of turbidity currents in the deep sea. To understand whether flows ignite or dissipate, we derive total and sediment discharges for each of the flows at all seven mooring locations down the canyon. Discharges are calculated from measured velocities, and sediment concentrations derived using a novel inversion method. Two distinct flow modes are observed, where most flows rapidly dissipated in the upper reaches of the canyon, while three ran out for the full 50 km array length. We then explore why only these three flows ignited and discuss the implications for canyon and channel capacity and evolution.

CFD Based Prediction of Discharge Coefficient of Sonic Nozzle with Surface Roughness

NASA Astrophysics Data System (ADS)

Bagaskara, Agastya; Agoes Moelyadi, Mochammad

2018-04-01

Due to its simplicity and accuracy, sonic nozzle is widely used in gas flow measurement, gas flow meter calibration standard, and flow control. The nozzle obtains mass flow rate by measuring temperature and pressure in the inlet during choked flow condition and calculate the flow rate using the one-dimensional isentropic flow equation multiplied by a discharge coefficient, which takes into account multiple non-isentropic effects, which causes the reduction in mass flow. Proper determination of discharge coefficient is crucial to ensure the accuracy of mass flow measurement by the nozzle. Available analytical solution for the prediction of discharge coefficient assumes that the nozzle wall is hydraulically smooth which causes disagreement with experimental results. In this paper, the discharge coefficient of sonic nozzle is determined using computational fluid dynamics method by taking into account the roughness of the wall. It is found that the result shows better agreement with the experiment data compared to the analytical result.

Freshwater flow from estuarine creeks into northeastern Florida Bay

USGS Publications Warehouse

Hittle, Clinton; Patino, Eduardo; Zucker, Mark A.

2001-01-01

Water-level, water-velocity, salinity, and temperature data were collected from selected estuarine creeks to compute freshwater flow into northeastern Florida Bay. Calibrated equations for determining mean velocity from acoustic velocity were obtained by developing velocity relations based on direct acoustic measurements, acoustic line velocity, and water level. Three formulas were necessary to describe flow patterns for all monitoring sites, with R2 (coefficient of determination) values ranging from 0.957 to 0.995. Cross-sectional area calculations were limited to the main channel of the creeks and did not include potential areas of overbank flow. Techniques also were used to estimate discharge at noninstrumented sites by establishing discharge relations to nearby instrumented sites. Results of the relation between flows at instrumented and noninstrumented sites varied with R2 values ranging from 0.865 to 0.99. West Highway Creek was used to estimate noninstrumented sites in Long Sound, and Mud Creek was used to estimate East Creek in Little Madeira Bay. Mean monthly flows were used to describe flow patterns and to calculate net flow along the northeastern coastline. Data used in the study were collected from October 1995 through September 1999, which includes the El Nino event of 1998. During this period, about 80 percent of the freshwater flowing into the bay occurred during the wet season (May-October). The mean freshwater discharge for all five instrumented sites during the wet season from 1996 to 1999 is 106 cubic feet per second. The El Nino event caused a substantial increase (654 percent) in mean flows during the dry season (November-April) at the instrumented sites, ranging from 8.5 cubic feet per second in 1996-97 to 55.6 cubic feet per second in 1997-98. Three main flow signatures were identified when comparing flows at all monitoring stations. The most significant was the magnitude of discharges at Trout Creek, which carries about 50 percent of the total measured freshwater entering northeastern Florida Bay. The mean monthly wet-season (May-October) flow at Trout Creek is about 340 cubic feet per second, compared to 55 cubic feet per second at West Highway Creek, 52 cubic feet per second at Taylor River, 49 cubic feet per second at Mud Creek, and 33 cubic feet per second at McCormick Creek. The other two flow signatures are the decline of freshwater discharge at McCormick Creek at the start of the El Nino event, and the absence of net-negative flows at West Highway Creek. The observed flow distribution within the study area, suggests that the overall flow direction of freshwater in the Everglades wetlands in the lower part of Taylor Slough may have a strong eastward flow component as water approaches the coastline. Data analysis also indicates that Trout Creek could potentially be used as a long-term monitoring station to estimate total freshwater flow into northeastern Florida Bay, provided that the remaining questions regarding flow patterns at McCormick Creek and the creeks in Long Sound are answered and that no major changes in flow characteristics occur in the future.

Variational Assimilation of Sparse and Uncertain Satellite Data For 1D Saint-Venant River Models

NASA Astrophysics Data System (ADS)

Garambois, P. A.; Brisset, P.; Monnier, J.; Roux, H.

2016-12-01

Profusion of satellites are providing increasingly accurate measurements of continental water cyle, and water bodies variations while in situ observability is declining. The future Surface Water and Ocean Topography (SWOT) mission will provide maps of river surface elevations widths and slopes with an almost global coverage and temporal revisits. This will offer the possibility to address a larger variety of inverse problems in surface hydrology. Data assimilation techniques, that are broadly used in several scientific fields, aim to optimally combine models, system observations and prior information. Variational assimilation consists in iterative minimization of a discrepency measure between model outputs and observations, here for retrieving boundary conditions and parameters of a 1D Saint Venant model. Nevertheless, inferring river discharge and hydraulic parameters thanks to the observation of river surface is not straightforward. This is particularly true in the case of sparse and uncertain observations of flow state variables since they are governed by nonlinear physical processes. This paper investigates the identifiability of hydraulic controls given sparse and uncertain satellite observations of a river. The identifiability of river discharge alone and with roughness is tested for several spatio temporal patterns of river observations, including SWOT like observations. A new 1D Shallow water model with variational data assimilation, within the DassFlow chain is presented as well as postprocessing and observation operator dedicated to the future SWOT and SWOT simulator data. In view to decrease inverse problem dimensionality discharge is represented in a reduced basis. Moreover we introduce an original and reduced parametrization of the flow resistance that can account for various flow regimes along with a cross section design dedicated to remote sensing. We show which discharge temporal frequencies can be identified w.r.t observation ones and at which accuracy. Eventually the important question of the discharge identifiability potential between observation times and depending on the spatio-temporal sampling is adressed with respect to the wave lengths of the hydrological signals.

Wind tunnel experiments on flow separation control of an Unmanned Air Vehicle by nanosecond discharge plasma aerodynamic actuation

NASA Astrophysics Data System (ADS)

Kang, Chen; Hua, Liang

2016-02-01

Plasma flow control (PFC) is a new kind of active flow control technology, which can improve the aerodynamic performances of aircrafts remarkably. The flow separation control of an unmanned air vehicle (UAV) by nanosecond discharge plasma aerodynamic actuation (NDPAA) is investigated experimentally in this paper. Experimental results show that the applied voltages for both the nanosecond discharge and the millisecond discharge are nearly the same, but the current for nanosecond discharge (30 A) is much bigger than that for millisecond discharge (0.1 A). The flow field induced by the NDPAA is similar to a shock wave upward, and has a maximal velocity of less than 0.5 m/s. Fast heating effect for nanosecond discharge induces shock waves in the quiescent air. The lasting time of the shock waves is about 80 μs and its spread velocity is nearly 380 m/s. By using the NDPAA, the flow separation on the suction side of the UAV can be totally suppressed and the critical stall angle of attack increases from 20° to 27° with a maximal lift coefficient increment of 11.24%. The flow separation can be suppressed when the discharge voltage is larger than the threshold value, and the optimum operation frequency for the NDPAA is the one which makes the Strouhal number equal one. The NDPAA is more effective than the millisecond discharge plasma aerodynamic actuation (MDPAA) in boundary layer flow control. The main mechanism for nanosecond discharge is shock effect. Shock effect is more effective in flow control than momentum effect in high speed flow control. Project supported by the National Natural Science Foundation of China (Grant Nos. 61503302, 51207169, and 51276197), the China Postdoctoral Science Foundation (Grant No. 2014M562446), and the Natural Science Foundation of Shaanxi Province, China (Grant No. 2015JM1001).

Investigating the spatio-temporal variability in groundwater and surface water interactions: a multi-technique approach

NASA Astrophysics Data System (ADS)

Unland, N. P.; Cartwright, I.; Andersen, M. S.; Rau, G. C.; Reed, J.; Gilfedder, B. S.; Atkinson, A. P.; Hofmann, H.

2013-09-01

The interaction between groundwater and surface water along the Tambo and Nicholson rivers, southeast Australia, was investigated using 222Rn, Cl, differential flow gauging, head gradients, electrical conductivity (EC) and temperature profiles. Head gradients, temperature profiles, Cl concentrations and 222Rn activities all indicate higher groundwater fluxes to the Tambo River in areas of increased topographic variation where the potential to form large groundwater-surface water gradients is greater. Groundwater discharge to the Tambo River calculated by Cl mass balance was significantly lower (1.48 × 104 to 1.41 × 103 m3 day-1) than discharge estimated by 222Rn mass balance (5.35 × 105 to 9.56 × 103 m3 day-1) and differential flow gauging (5.41 × 105 to 6.30 × 103 m3 day-1) due to bank return waters. While groundwater sampling from the bank of the Tambo River was intended to account for changes in groundwater chemistry associated with bank infiltration, variations in bank infiltration between sample sites remain unaccounted for, limiting the use of Cl as an effective tracer. Groundwater discharge to both the Tambo and Nicholson rivers was the highest under high-flow conditions in the days to weeks following significant rainfall, indicating that the rivers are well connected to a groundwater system that is responsive to rainfall. Groundwater constituted the lowest proportion of river discharge during times of increased rainfall that followed dry periods, while groundwater constituted the highest proportion of river discharge under baseflow conditions (21.4% of the Tambo in April 2010 and 18.9% of the Nicholson in September 2010).

URBAN WET-WEATHER FLOW MANAGEMENT: RESEARCH DIRECTIONS

EPA Science Inventory

There are three types of urban wet-weather flow (WWF) discharges: 1) combined-sewer overflow (CSO), which is a mixture of storm drainage and municipal-industrial wastewater discharged from combined sewers or dry-weather flow discharged from combined sewers due to clogged intercep...

Laser cross-flow gas system

DOEpatents

Duncan, D.B.

1992-11-24

A method and laser apparatus are disclosed which provide for a cross-flow of gas near one end of a laser discharge tube. The cross-flow of gas causes a concentration gradient which affects diffusion of contaminants in the discharge tube towards the cross-flow of the gas, which contaminants are then withdrawn from the discharge tube. 1 figure.

Modeling highly transient flow, mass, and heat transport in the Chattahoochee River near Atlanta, Georgia

USGS Publications Warehouse

Jobson, Harvey E.; Keefer, Thomas N.

1979-01-01

A coupled flow-temperature model has been developed and verified for a 27.9-km reach of the Chattahoochee River between Buford Dam and Norcross, Ga. Flow in this reach of the Chattahoochee is continuous but highly regulated by Buford Dam, a flood-control and hydroelectric facility located near Buford, Ga. Calibration and verification utilized two sets of data collected under highly unsteady discharge conditions. Existing solution techniques, with certain minor improvements, were applied to verify the existing technology of flow and transport modeling. The linear, implicit finite-difference flow model was calibrated by use of a depth profile obtained at steady low flow and unsteady flow data obtained in March 1976. During the calibration period, the model was generally able to reproduce observed stages to within 0.15 m and discharges at less than 100 m 3 /s, to within 5 percent. Peak discharges of about 200 m 3 /s were under-estimated by about 20 percent. During the verification period, October 1975, the flow model reproduced observed stage changes to within about 0.15 m, and its timing and over-all performance was considered to be very good. Dye was added to the upstream end of the river reach at a constant rate while the river flow was highly unsteady. The numerical solution of either the conservative or nonconservative form of the mass-transport equation did an excellent job of simulating the observed concentrations of dye in the river. The temperature model was capable of predicting temperature changes through this reach of as large as 5.8?C with a RMS (root-mean-square) error of 0.32?C in October 1975 and 0.20?C in March 1976. Hydropulsation has a significant effect on the water temperature below Buford Dam. These effects are very complicated because they are quite dependent on the timing of the release with respect to both the time of day and past releases.

Numerical modeling of pollutant transport using a Lagrangian marker particle technique

NASA Technical Reports Server (NTRS)

Spaulding, M.

1976-01-01

A derivation and code were developed for the three-dimensional mass transport equation, using a particle-in-cell solution technique, to solve coastal zone waste discharge problems where particles are a major component of the waste. Improvements in the particle movement techniques are suggested and typical examples illustrated. Preliminary model comparisons with analytic solutions for an instantaneous point release in a uniform flow show good results in resolving the waste motion. The findings to date indicate that this computational model will provide a useful technique to study the motion of sediment, dredged spoils, and other particulate waste commonly deposited in coastal waters.

Tidal impacts on the subtidal flow division at the main bifurcation in the Yangtze River Delta

NASA Astrophysics Data System (ADS)

Zhang, Wei; Feng, Haochuan; Hoitink, A. J. F.; Zhu, Yuliang; Gong, Fei; Zheng, Jinhai

2017-09-01

Flow division at bifurcations in the Yangtze Estuary has received ample attention, since it may control the pathways of terrestrial sediments over downstream river branches including the 12.5 m Deepwater Navigation channel. While some efforts have been made to interpret flow division at the bifurcations of the Yangtze Estuary, little attention has been paid to the role of tides. Flow division at estuarine bifurcations is made complicated by tides that propagate from the outlet of the tidal channels into the delta. To quantify the tidal influence on the distribution of river discharge, and more generally, to understand the mechanisms governing the subtidal flow division at the tidally affected bifurcation in the Yangtze River Delta, a two-dimensional hydrodynamic model is employed. In this model, the landward boundary is chosen beyond the tidal limit, where the tidal motion has faded out entirely. The seaward boundary is chosen such that the river discharge does not influence the water level. Subtidal discharges are decomposed using the method of factor separation, to distinguish between the effects of tides, river discharge and river-tide interactions on the subtidal flow division. Results indicate that tides modify the river discharge distribution over distributary channels in the Yangtze River Delta, particularly in the dry season. A significant difference in the subtidal flow division during spring tide and neap tide shows that the tidally averaged flow division over the distributaries in the delta greatly depends on tidal amplitude. By varying the river discharge at the landward boundary and amplitudes and phases of the principal tidal constituents at the seaward boundary of the established model, the sensitivities of the subtidal flow division to the river discharge and tidal amplitude variation were investigated in detail. Generally, the tidal impacts on the subtidal flow division are around 12% to 22%, with river discharge varying from 30,000 m3s-1 to 20,000 m3s-1. This effect on the flow distribution can even overwhelm the effects induced by river discharge based on geometry only, when the flow discharge is lowest. Furthermore, the fortnightly tidal cycle plays an important role in enhancing the inequality of the subtidal flow division caused by the M2 tidal component solely at the tidal bifurcation in the Yangtze River Delta during low flow.

Role of turbulence fluctuations on uncertainties of acoutic Doppler current profiler discharge measurements

USGS Publications Warehouse

Tarrab, Leticia; Garcia, Carlos M.; Cantero, Mariano I.; Oberg, Kevin

2012-01-01

This work presents a systematic analysis quantifying the role of the presence of turbulence fluctuations on uncertainties (random errors) of acoustic Doppler current profiler (ADCP) discharge measurements from moving platforms. Data sets of three-dimensional flow velocities with high temporal and spatial resolution were generated from direct numerical simulation (DNS) of turbulent open channel flow. Dimensionless functions relating parameters quantifying the uncertainty in discharge measurements due to flow turbulence (relative variance and relative maximum random error) to sampling configuration were developed from the DNS simulations and then validated with field-scale discharge measurements. The validated functions were used to evaluate the role of the presence of flow turbulence fluctuations on uncertainties in ADCP discharge measurements. The results of this work indicate that random errors due to the flow turbulence are significant when: (a) a low number of transects is used for a discharge measurement, and (b) measurements are made in shallow rivers using high boat velocity (short time for the boat to cross a flow turbulence structure).

Monitoring of stage and velocity, for computation of discharge in the Summit Conduit near Summit, Illinois, 2010-2012

USGS Publications Warehouse

Johnson, Kevin K.; Goodwin, Greg E.

2013-01-01

Lake Michigan diversion accounting is the process used by the U. S. Army Corps of Engineers to quantify the amount of water that is diverted from the Lake Michigan watershed into the Illinois and Mississippi River Basins. A network of streamgages within the Chicago area waterway system monitor tributary river flows and the major river flow on the Chicago Sanitary and Ship Canal near Lemont as one of the instrumental tools used for Lake Michigan diversion accounting. The mean annual discharges recorded by these streamgages are used as additions or deductions to the mean annual discharge recorded by the main stream gaging station currently used in the Lake Michigan diversion accounting process, which is the Chicago Sanitary and Ship Canal near Lemont, Illinois (station number 05536890). A new stream gaging station, Summit Conduit near Summit, Illinois (station number 414757087490401), was installed on September 23, 2010, for the purpose of monitoring stage, velocity, and discharge through the Summit Conduit for the U.S. Army Corps of Engineers in accordance with Lake Michigan diversion accounting. Summit Conduit conveys flow from a small part of the lower Des Plaines River watershed underneath the Des Plaines River directly into the Chicago Sanitary and Ship Canal. Because the Summit Conduit discharges into the Chicago Sanitary and Ship Canal upstream from the stream gaging station at Lemont, Illinois, but does not contain flow diverted from the Lake Michigan watershed, it is considered a flow deduction to the discharge measured by the Lemont stream gaging station in the Lake Michigan diversion accounting process. This report offers a technical summary of the techniques and methods used for the collection and computation of the stage, velocity, and discharge data at the Summit Conduit near Summit, Illinois stream gaging station for the 2011 and 2012 Water Years. The stream gaging station Summit Conduit near Summit, Illinois (station number 414757087490401) is an example of a nonstandard stream gage. Traditional methods of equating stage to discharge historically were not effective. Examples of the nonstandard conditions include the converging tributary flows directly upstream of the gage; the trash rack and walkway near the opening of the conduit introducing turbulence and occasionally entraining air bubbles into the flow; debris within the conduit creating conditions of variable backwater and the constant influx of smaller debris that escapes the trash rack and catches or settles in the conduit and on the equipment. An acoustic Doppler velocity meter was installed to measure stage and velocity to compute discharge. The stage is used to calculate area based the stage-area rating. The index-velocity from the acoustic Doppler velocity meter is applied to the velocity-velocity rating and the product of the two rated values is a rated discharge by the index-velocity method. Nonstandard site conditions prevalent at the Summit Conduit stream gaging station generally are overcome through the index-velocity method. Despite the difficulties in gaging and measurements, improvements continue to be made in data collection, transmission, and measurements. Efforts to improve the site and to improve the ratings continue to improve the quality and quantity of the data available for Lake Michigan diversion accounting.

Numerical Simulation of a Nanosecond Pulse Discharge in Mach 5 Flow

DTIC Science & Technology

2013-01-01

Numerical Simulation of a Nanosecond Pulse Discharge in Mach 5 Flow Jonathan Poggie∗and Nicholas J. Bisek† Air Force Research Laboratory, Wright...was developed for nanosecond- pulse discharges , including real- istic air kinetics, electron energy transport, and compressible bulk gas flow. A reduced...shock waves originating near the sheath edge, consistent with experimental observations. I. Introduction In a nanosecond- pulse discharge , the input

Large-scale thermal energy storage using sodium hydroxide /NaOH/

NASA Technical Reports Server (NTRS)

Turner, R. H.; Truscello, V. C.

1977-01-01

A technique employing NaOH phase change material for large-scale thermal energy storage to 900 F (482 C) is described; the concept consists of 12-foot diameter by 60-foot long cylindrical steel shell with closely spaced internal tubes similar to a shell and tube heat exchanger. The NaOH heat storage medium fills the space between the tubes and outer shell. To charge the system, superheated steam flowing through the tubes melts and raises the temperature of NaOH; for discharge, pressurized water flows through the same tube bundle. A technique for system design and cost estimation is shown. General technical and economic properties of the storage unit integrated into a solar power plant are discussed.

Change in hyporheic zone residence time under different surface flow states

NASA Astrophysics Data System (ADS)

Liu, Suning; Chui, Ting Fong May

2017-04-01

Hyporheic zone (HZ), which is the ecotone immediately below or adjacent to a stream, plays an important role in a stream ecological system. One of the most common metrics in evaluating the functioning of an HZ is residence time (RT) which is the duration a water molecule or a solute remains within the HZ. Many factors, such as meandering of a stream, heterogeneity of streambed, can influence the RT of an HZ. Stream discharge is another governing but less discussed factor. Different discharge values produce different flow states (i.e.., subcritical, critical and supercritical) and alluvial stream bed forms. This study examined the changes of RT in discharges of different states and their corresponding induced bed forms. It employed a toolbox developed by Stonedahl et al. (2015) within Netlogo to simulate the RT of an HZ, considering three discharge values in each of the supercritical, critical and subcritical states. It approximated the bed forms as sinusoidal waves with amplitudes and periods selected for each flow state. The simulated results suggest that the RT is minimum when the flow is critical, and it is longer for both subcritical and supercritical flows. For subcritical flow, the RT, as well as the fraction remained within the streambed during particle tracing, increases with the increase in discharge value. However, there is no such variation among the different discharge values of supercritical flow. Therefore, for supercritical flow, one combination of discharge value and bed form might be sufficient and representative. However, for subcritical flow, the variations of discharge values and their induced bed forms should be considered. Reference: Stonedahl, S.H., Roche, K.R., Stonedahl, F., & Packman, A.I. (2015). Visualizing Hyporheic Flow Through Bedforms Using Dye Experiments and Simulation. J. Vis. Exp. (105), e53285. doi: 10.3791/53285

Transportation and Hydrology Studies of the U.S. Geological Survey in New England

USGS Publications Warehouse

Lombard, Pamela J.

2016-03-23

In New England, the USGS is conducting investigations to improve flood flow estimation techniques, to define channel characteristics at bankfull discharge, and to document storm tide as a result of major coastal storms. Current locally focused investigations include examination of flow frequency in rural, urban, and small watersheds; documentation of extreme inland floods along with flood-frequency updates; examination of the effects of roadway blasting on groundwater quality; and determinations of the effects of road salting on the quality of runoff and receiving waters.

Impeller flow field characterization with a laser two-focus velocimeter

NASA Astrophysics Data System (ADS)

Brozowski, L. A.; Ferguson, T. V.; Rojas, L.

1993-07-01

Use of Computational Fluid Dynamics (CFD) codes, prevalent in the rocket engine turbomachinery industry, necessitates data of sufficient quality and quantity to benchmark computational codes. Existing data bases for typical rocket engine configurations, in particular impellers, are limited. In addition, traditional data acquisition methods have several limitations: typically transducer uncertainties are 0.5% of transducer full scale and traditional pressure probes are unable to provide flow characteristics in the circumferential (blade-to-blade) direction. Laser velocimetry circumvents these limitations by providing +0.5% uncertainty in flow velocity and +0.5% uncertainty in flow angle. The percent of uncertainty in flow velocity is based on the measured value, not full range capability. The laser electronics multiple partitioning capability allows data acquired between blades as the impeller rotates, to be analyzed separately, thus providing blade-to-blade flow characterization. Unlike some probes, the non-intrusive measurements made with the laser velocimeter does not disturb the flow. To this end,, and under Contract (NAS8-38864) to the National Aeronautics and Space Administration (NASA) at Marshall Space Flight Center (MSFC), an extensive test program was undertaken at Rocketdyne. Impellers from two different generic rocket engine pump configurations were examined. The impellers represent different spectrums of pump design: the Space Shuttle Main Engine (SSME) high pressure fuel turbopump (HPFTP) impeller was designed in the 1 1970's the Consortium for CFD application in Propulsion Technology Pump Stage Technology Team (Pump Consortium) optimized impeller was designed with the aid of modern computing techniques. The tester configuration for each of the impellers consisted of an axial inlet, an inducer, a diffuser, and a crossover discharge. While the tested configurations were carefully chosen to be representative of generic rocket engine pumps, several features of both testers were intentionally atypical. A crossover discharge, downstream of the impeller, rather than a volute discharge was used to minimize asymmetric flow conditions that might be reflected in the impeller discharge flow data. Impeller shroud wear ring radial clearances were purposely close to minimize leakage flow, thus increasing confidence in using the inlet data as an input to CFD programs. The empirical study extensively examined the flow fields of the two impellers via performance of laser two-focus velocimeter surveys in an axial plane upstream of the impellers and in multiple radial planes downstream of the impellers. Both studies were performed at the impeller design flow coefficients. Inlet laser surveys that provide CFD code inlet boundary conditions were performed in one axial plane, with ten radial locations surveyed. Three wall static pressures, positioned circumferentially around the impeller inlet, were used to identify asymmetrical pressure distributions in the inlet survey plane.

Simulation of ground-water flow and evaluation of water-management alternatives in the Assabet River Basin, Eastern Massachusetts

USGS Publications Warehouse

DeSimone, Leslie A.

2004-01-01

Water-supply withdrawals and wastewater disposal in the Assabet River Basin in eastern Massachusetts alter the flow and water quality in the basin. Wastewater discharges and stream-flow depletion from ground-water withdrawals adversely affect water quality in the Assabet River, especially during low-flow months (late summer) and in headwater areas. Streamflow depletion also contributes to loss of aquatic habitat in tributaries to the river. In 19972001, water-supply withdrawals averaged 9.9 million gallons per day (Mgal/d). Wastewater discharges to the Assabet River averaged 11 Mgal/d and included about 5.4 Mgal/d that originated from sources outside of the basin. The effects of current (2004) and future withdrawals and discharges on water resources in the basin were investigated in this study. Steady-state and transient ground-water-flow models were developed, by using MODFLOW-2000, to simulate flow in the surficial glacial deposits and underlying crystalline bedrock in the basin. The transient model simulated the average annual cycle at dynamic equilibrium in monthly intervals. The models were calibrated to 19972001 conditions of water withdrawals, wastewater discharges, water levels, and nonstorm streamflow (base flow plus wastewater discharges). Total flow through the simulated hydrologic system averaged 195 Mgal/d annually. Recharge from precipitation and ground-water discharge to streams were the dominant inflow and outflow, respectively. Evapotranspiration of ground water from wetlands and non-wetland areas also were important losses from the hydrologic system. Water-supply withdrawals and infiltration to sewers averaged 5 and 1.3 percent, respectively, of total annual out-flows and were larger components (12 percent in September) of the hydrologic system during low-flow months. Water budgets for individual tributary and main stem subbasins identified areas, such as the Fort Meadow Brook and the Assabet Main Stem Upper subbasins, where flows resulting from anthropo-genic activities were relatively large percentages, compared to other subbasins, (more than 20 percent in September) of total out-flows. Wastewater flows in the Assabet River accounted for 55, 32, and 20 percent of total nonstorm streamflow (base flow plus wastewater discharge) out of the Assabet Main Stem Upper, Middle, and Lower subbasins, respectively, in an average September. The ground-water-flow models were used to evaluate water-management alternatives by simulating hypothetical scenarios of altered withdrawals and discharges. A scenario that included no water management quantified nonstorm stream-flows that would result without withdrawals, discharges, septic-system return flow, or consumptive use. Tributary flows in this scenario increased in most subbasins by 2 to 44 percent relative to 19972001 conditions. The increases resulted mostly from variable combinations of decreased withdrawals and decreased infiltration to sewers. Average annual nonstorm streamflow in the Assabet River decreased slightly in this scenario, by 2 to 3 percent annually, because gains in ground-water discharge were offset by the elimination of wastewater discharges. A second scenario quantified the effects of increasing withdrawals and discharges to currently permitted levels. In this simulation, average annual tributary flows decreased in most subbasins, by less than 1 to 10 percent relative to 19972001 conditions. In the Assabet River, flows increased slightly, 1 to 5 percent annually, and the percentage of wastewater in the river increased to 69, 42, and 27 percent of total nonstorm streamflow out of the Assabet Main Stem Upper, Middle, and Lower subbasins, respectively, in an average September. A third set of scenarios quantified the effects of ground-water discharge of wastewater at four hypothetical sites, while maintaining 19972000 wastewater discharges to the Assabet River. Wastewater, discharged at a constant rate that varied among sites from 0.3 to 1

The three scales of submarine groundwater flow and discharge across passive continental margins

USGS Publications Warehouse

Bratton, John F.

2010-01-01

Increased study of submarine groundwater systems in recent years has provided a wealth of new data and techniques, but some ambiguity has been introduced by insufficient distinguishing of the relevant spatial scales of the phenomena studied. Submarine groundwater flow and discharge on passive continental margins can be most productively studied and discussed by distinct consideration of the following three spatial scales: (1) the nearshore scale, spanning approximately 0–10 m offshore and including the unconfined surficial aquifer; (2) the embayment scale, spanning approximately 10 m to as much as 10 km offshore and including the first confined submarine aquifer and its terminus; and (3) the shelf scale, spanning the width and thickness of the aquifers of the entire continental shelf, from the base of the first confined aquifer downward to the basement, and including influences of geothermal convection and glacio-eustatic change in sea level.

Effect of Doppler flow meter position on discharge measurement in surcharged manholes.

PubMed

Yang, Haoming; Zhu, David Z; Liu, Yanchen

2018-02-01

Determining the proper installation location of flow meters is important for accurate measurement of discharge in sewer systems. In this study, flow field and flow regimes in two types of manholes under surcharged flow were investigated using a commercial computational fluid dynamics (CFD) code. The error in measuring the flow discharge using a Doppler flow meter (based on the velocity in a Doppler beam) was then estimated. The values of the corrective coefficient were obtained for the Doppler flow meter at different locations under various conditions. Suggestions for selecting installation positions are provided.

Can hydraulic-modelled rating curves reduce uncertainty in high flow data?

NASA Astrophysics Data System (ADS)

Westerberg, Ida; Lam, Norris; Lyon, Steve W.

2017-04-01

Flood risk assessments rely on accurate discharge data records. Establishing a reliable rating curve for calculating discharge from stage at a gauging station normally takes years of data collection efforts. Estimation of high flows is particularly difficult as high flows occur rarely and are often practically difficult to gauge. Hydraulically-modelled rating curves can be derived based on as few as two concurrent stage-discharge and water-surface slope measurements at different flow conditions. This means that a reliable rating curve can, potentially, be derived much faster than a traditional rating curve based on numerous stage-discharge gaugings. In this study we compared the uncertainty in discharge data that resulted from these two rating curve modelling approaches. We applied both methods to a Swedish catchment, accounting for uncertainties in the stage-discharge gauging and water-surface slope data for the hydraulic model and in the stage-discharge gauging data and rating-curve parameters for the traditional method. We focused our analyses on high-flow uncertainty and the factors that could reduce this uncertainty. In particular, we investigated which data uncertainties were most important, and at what flow conditions the gaugings should preferably be taken. First results show that the hydraulically-modelled rating curves were more sensitive to uncertainties in the calibration measurements of discharge than water surface slope. The uncertainty of the hydraulically-modelled rating curves were lowest within the range of the three calibration stage-discharge gaugings (i.e. between median and two-times median flow) whereas uncertainties were higher outside of this range. For instance, at the highest observed stage of the 24-year stage record, the 90% uncertainty band was -15% to +40% of the official rating curve. Additional gaugings at high flows (i.e. four to five times median flow) would likely substantially reduce those uncertainties. These first results show the potential of the hydraulically-modelled curves, particularly where the calibration gaugings are of high quality and cover a wide range of flow conditions.

Low-flow characteristics of streams under natural and diversion conditions, Waipiʻo Valley, Island of Hawaiʻi, Hawaiʻi

USGS Publications Warehouse

Fontaine, Richard A.

2012-01-01

Over the past 100 years, natural streamflow in Waipiʻo Valley has been reduced by the transfer of water out of the valley by Upper and Lower Hāmākua Ditches. The physical condition and diversion practices along the two ditch systems have varied widely over the years, and as a result, so have their effects on natural streamflow in Waipiʻo Valley. Recent renovation and improvements to Lower Hāmākua Ditch system, along with proposals for its future operation and water-diversion strategies, have unknown implications. The purpose of this report is to quantify the availability of streamflow and to determine the effects of current and proposed diversion strategies on the low-flow hydrology in Waipiʻo Valley. In this report, the low-flow hydrology of Waipiʻo Valley is described in terms of flow-duration statistics. Flow-duration statistics were computed for three locations in the Waipiʻo Valley study area where long-term surface-water gaging stations have been operated. Using a variety of streamflow record-extension techniques, flow-duration statistics were estimated at an additional 13 locations where only few historical data are available or where discharge measurements were made as part of this study. Flow-duration statistics were computed to reflect natural conditions, current (2000-2005) diversion conditions, and proposed future diversion conditions at the 16 locations. At the downstream limit of the study area, on Wailoa Stream at an altitude of 190 feet, a baseline for evaluating the availability of streamflow is provided by computed flow-duration statistics that are representative of natural, no-diversion conditions. At the Wailoa gaging station, 95- and 50-percentile discharges under natural conditions were determined to be 86 and 112 cubic feet per second, respectively. Under 1965-1969 diversion conditions, natural 95- and 50-percentile discharges were reduced by 52 and 53 percent, to 41 and 53 cubic feet per second, respectively. Under current (2000-2005) diversion conditions, natural 95- and 50-percentile discharges were reduced by 21 and 24 percent, to 68 and 85 cubic feet per second, respectively. Under proposed future diversion conditions, natural 95- and 50-percentile discharges would be reduced by 33 and 24 percent, to 58 and 85 cubic feet per second, respectively. Compared to discharges that reflect current (2000-2005) diversion conditions, proposed future diversion conditions would reduce 95-percentile discharges, which are representative of moderate drought levels in the stream, by 15 percent. No change would be expected in 50-percentile discharges, which are representative of normal conditions. The effects of current (2000-2005) and proposed future diversion conditions on the natural flow of streams in the Waipiʻo Valley study area differ, depending on the location. Under current (2000-2005) diversion conditions, reductions in natural 95- or 50-percentile discharges of greater than 30 percent were found in Kawainui Stream downstream from Upper Hamakua Ditch to an altitude of about 1,435 feet and in the reach of Waimā Stream between Upper and Lower Hāmākua Ditches. Under proposed future diversion conditions, reductions in natural 95- or 50-percentile discharges of greater than 30 percent were found in Kawainui Stream downstream from Upper Hamakua Ditch to an altitude of about 1,435 feet, in the reach of Waimā Stream between Upper and Lower Hāmākua Ditches, and along most stream reaches downstream from Lower Hāmākua Ditch, except for Waimā Stream.

Ground-water flow paths and traveltime to three small embayments within the Peconic Estuary, eastern Suffolk County, New York

USGS Publications Warehouse

Schubert, Christopher E.

1999-01-01

The Peconic Estuary, at the eastern end of Long Island, has been plagued by a recurrent algal bloom that has caused the severe decline of local marine resources. Although the onset, duration, and cessation of the bloom remain unpredictable, ground-water discharge has been shown to affect surface-water quality in the western part of the estuary. Results from a study on the North Fork of Long Island indicate that local hydrogeologic factors cause differences in ground-water age and characteristics of discharge to the estuary. The need for information on the local patterns and rates of ground-water discharge to the Peconic Estuary prompted analysis of ground-water flow paths and traveltime to three small embayments within the estuary.Meetinghouse Creek, near the west end of the North Fork; Sag Harbor Cove, in the central part of the South Fork; and West Neck Bay, on Shelter Island.Ground-water-flow models were developed, and particle-tracking procedures were applied to the results of each model, to define the flow paths and traveltime of ground water to the three embayments. The steady-state flow models represent the two-dimensional ground-water-flow system along a vertical section through the uplands of each embayment and simulate long-term hydrologic conditions. The particle-tracking procedure used model-generated ground-water levels and flow rates to calculate the water-particle pathlines and times-of-travel through each flow system from the point of entry (recharge) to the point of exit at streams, the shore, or subsea-discharge areas.Results for the Meetinghouse Creek study area indicate that about 50 percent of the total recharge that enters the system flows southward to Meetinghouse Creek; half of this amount discharges as base flow to the fresh-water reach of the creek, and half as shoreline underflow to the estuarine reach. About 85 percent of the total discharge to Meetinghouse Creek has flowed entirely within the upper glacial aquifer, and about 15 percent has flowed through the Magothy aquifer. The average age of all ground water discharged to Meetinghouse Creek is about 60 years; the average age of base flow to the freshwater reach of the creek is about 7 years, and the average age of shoreline underflow to the estuarine reach is about 120 years. The results for the Sag Harbor Cove study area indicate that about 30 percent of the total recharge that enters the system flows northward to Sag Harbor Cove; about half of this amount discharges as shoreline underflow, and half as subsea underflow. About 40 percent of the total discharge to Sag Harbor Cove has flowed entirely within the upper glacial aquifer, and about 60 percent has flowed through the Pleistocene marine clay unit, Pleistocene(?) sand unit, or Magothy aquifer. The average age of all ground water discharged to Sag Harbor Cove is about 110 years; the average age of shoreline underflow is about 25 years, and the average age of subsea underflow is about 190 years.Results for the West Neck Bay study area indicate that about 65 percent of the total recharge that enters the system flows westward to West Neck Bay; virtually all of this amount discharges as shoreline underflow, but a negligible percentage discharges as subsea underflow. Virtually all discharge to West Neck Bay has flowed entirely within the upper glacial aquifer, although a minor amount has flowed through the Pleistocene marine clay unit. The average age of shoreline underflow to West Neck Bay is about 15 years, and the average age of subsea underflow is about 1,800 years.Ground water that discharges to streams and the shores represented in the models is mostly relatively young water that has flowed entirely within the shallow zones of the flow systems, whereas ground water that discharges to the subsea-discharge areas is mostly old water that has flowed through the deep zones. Data obtained from these models allows evaluation of each embayment.s vulnerability to contaminants introduced at the water table and can guide the development of source-area-protection strategies for the corresponding watersheds.

Simulated groundwater flow paths, travel time, and advective transport of nitrogen in the Kirkwood-Cohansey aquifer system, Barnegat Bay–Little Egg Harbor Watershed, New Jersey

USGS Publications Warehouse

Voronin, Lois M.; Cauller, Stephen J.

2017-07-31

Elevated concentrations of nitrogen in groundwater that discharges to surface-water bodies can degrade surface-water quality and habitats in the New Jersey Coastal Plain. An analysis of groundwater flow in the Kirkwood-Cohansey aquifer system and deeper confined aquifers that underlie the Barnegat Bay–Little Egg Harbor (BB-LEH) watershed and estuary was conducted by using groundwater-flow simulation, in conjunction with a particle-tracking routine, to provide estimates of groundwater flow paths and travel times to streams and the BB-LEH estuary.Water-quality data from the Ambient Groundwater Quality Monitoring Network, a long-term monitoring network of wells distributed throughout New Jersey, were used to estimate the initial nitrogen concentration in recharge for five different land-use classes—agricultural cropland or pasture, agricultural orchard or vineyard, urban non-residential, urban residential, and undeveloped. Land use at the point of recharge within the watershed was determined using a geographic information system (GIS). Flow path starting locations were plotted on land-use maps for 1930, 1973, 1986, 1997, and 2002. Information on the land use at the time and location of recharge, time of travel to the discharge location, and the point of discharge were determined for each simulated flow path. Particle-tracking analysis provided the link from the point of recharge, along the particle flow path, to the point of discharge, and the particle travel time. The travel time of each simulated particle established the recharge year. Land use during the year of recharge was used to define the nitrogen concentration associated with each flow path. The recharge-weighted average nitrogen concentration for all flow paths that discharge to the Toms River upstream from streamflow-gaging station 01408500 or to the BB-LEH estuary was calculated.Groundwater input into the Barnegat Bay–Little Egg Harbor estuary from two main sources— indirect discharge from base flow to streams that eventually flow into the bay and groundwater discharge directly into the estuary and adjoining coastal wetlands— is summarized by quantity, travel time, and estimated nitrogen concentration. Simulated average groundwater discharge to streams in the watershed that flow into the BB-LEH estuary is approximately 400 million gallons per day. Particle-tracking results indicate that the travel time of 56 percent of this discharge is less than 7 years. Fourteen percent of the groundwater discharge to the streams in the BB-LEH watershed has a travel time of less than 7 years and originates in urban land. Analysis of flow-path simulations indicate that approximately 13 percent of the total groundwater flow through the study area discharges directly to the estuary and adjoining coastal wetlands (approximately 64 million gallons per day). The travel time of 19 percent of this discharge is less than 7 years. Ten percent of this discharge (1 percent of the total groundwater flow through the study area) originates in urban areas and has a travel time of less than 7 years. Groundwater that discharges to the streams that flow into the BB-LEH, in general, has shorter travel times, and a higher percentage of it originates in urban areas than does direct groundwater discharge to the Barnegat Bay–Little Egg Harbor estuary.The simulated average nitrogen concentration in groundwater that discharges to the Toms River, upstream from streamflow-gaging station 01408500 was computed and compared to summary concentrations determined from analysis of multiple surface-water samples. The nitrogen concentration in groundwater that discharges directly to the estuary and adjoining coastal wetlands is a current data gap. The particle tracking methodology used in this study provides an estimate of this concentration."

Effect of turbulent flow on an atmospheric-pressure AC powered gliding arc discharge

NASA Astrophysics Data System (ADS)

Kong, Chengdong; Gao, Jinlong; Zhu, Jiajian; Ehn, Andreas; Aldén, Marcus; Li, Zhongshan

2018-06-01

A high-power gliding arc (GA) discharge was generated in a turbulent air flow driven by a 35 kHz alternating current electric power supply. The effects of the flow rate on the characteristics of the GA discharge were investigated using combined optical and electrical diagnostics. Phenomenologically, the GA discharge exhibits two types of discharge, i.e., glow type and spark type, depending on the flow rates and input powers. The glow-type discharge, which has peak currents of hundreds of milliamperes, is sustained at low flow rates. The spark-type discharge, which is characterized by a sharp current spike of several amperes with duration of less than 1 μs, occurs more frequently as the flow rate increases. Higher input power can suppress spark-type discharges in moderate turbulence, but this effect becomes weak under high turbulent conditions. Physically, the transition between glow- and spark-type is initiated by the short cutting events and the local re-ignition events. Short cutting events occur owing to the twisting, wrinkling, and stretching of the plasma columns that are governed by the relatively large vortexes in the flow. Local re-ignition events, which are defined as re-ignition along plasma columns, are detected in strong turbulence due to increment of the impedance of the plasma column and consequently the internal electric field strength. It is suggested that the vortexes with length scales smaller than the size of the plasma can penetrate into the plasma column and promote mixing with surroundings to accelerate the energy dissipation. Therefore, the turbulent flow influences the GA discharges by ruling the short cutting events with relatively large vortexes and the local re-ignition events with small vortexes.

Was the Deepwater Horizon Well Discharge Churn Flow? Implications on the Estimation of the Oil Discharge and Droplet Size Distribution

NASA Astrophysics Data System (ADS)

Boufadel, Michel C.; Gao, Feng; Zhao, Lin; Özgökmen, Tamay; Miller, Richard; King, Thomas; Robinson, Brian; Lee, Kenneth; Leifer, Ira

2018-03-01

Improved understanding of the character of an uncontrolled pipeline flow is critical for the estimation of the oil discharge and droplet size distribution both essential for evaluating oil spill impact. Measured oil and gas properties at the wellhead of the Macondo255 and detailed numerical modeling suggested that the flow within the pipe could have been "churn," whereby oil and gas tumble violently within the pipe and is different from the bubbly flow commonly assumed for that release. The churn flow would have produced 5 times the energy loss in the pipe compared to bubbly flow, and its plume would have entrained 35% more water than that of the bubbly flow. Both findings suggest that the oil discharge in Deepwater Horizon could have been overestimated, by up to 200%. The resulting oil droplet size distribution of churn flow is likely smaller than that of bubbly flow.

Schlieren optical visualization for transient EHD induced flow in a stratified dielectric liquid under gas-phase ac corona discharges

NASA Astrophysics Data System (ADS)

Ohyama, R.; Inoue, K.; Chang, J. S.

2007-01-01

A flow pattern characterization of electrohydrodynamically (EHD) induced flow phenomena of a stratified dielectric fluid situated in an ac corona discharge field is conducted by a Schlieren optical system. A high voltage application to a needle-plate electrode arrangement in gas-phase normally initiates a conductive type EHD gas flow. Although the EHD gas flow motion initiated from the corona discharge electrode has been well known as corona wind, no comprehensive study has been conducted for an EHD fluid flow motion of the stratified dielectric liquid that is exposed to the gas-phase ac corona discharge. The experimentally observed result clearly presents the liquid-phase EHD flow phenomenon induced from the gas-phase EHD flow via an interfacial momentum transfer. The flow phenomenon is also discussed in terms of the gas-phase EHD number under the reduced gas pressure (reduced interfacial momentum transfer) conditions.

Statistical properties of gravity-driven granular discharge flow under the influence of an obstacle

NASA Astrophysics Data System (ADS)

Endo, Keita; Katsuragi, Hiroaki

2017-06-01

Two-dimensional granular discharge flow driven by gravity under the influence of an obstacle is experimentally investigated. A horizontal exit of width W is opened at the bottom of vertical Hele-Shaw cell filled with stainless-steel particles to start the discharge flow. In this experiment, a circular obstacle is placed in front of the exit. Thus, the distance between the exit and obstacle L is also an important parameter. During the discharge, granular-flow state is acquired by a high-speed camera. The bulk discharge-flow rate is also measured by load cell sensors. The obtained high-speed-image data are analyzed to clarify the particle-level granular-flow dynamics. Using the measured data, we find that the obstacle above the exit affects the granular- flow field. Specifically, the existence of obstacle results in large horizontal granular temperature and small packing fraction. This tendency becomes significant when L is smaller than approximately 6Dg when W ≃ 4Dg, where Dg is diameter of particles.

Imaging lateral groundwater flow in the shallow subsurface using stochastic temperature fields

NASA Astrophysics Data System (ADS)

Fairley, Jerry P.; Nicholson, Kirsten N.

2006-04-01

Although temperature has often been used as an indication of vertical groundwater movement, its usefulness for identifying horizontal fluid flow has been limited by the difficulty of obtaining sufficient data to draw defensible conclusions. Here we use stochastic simulation to develop a high-resolution image of fluid temperatures in the shallow subsurface at Borax Lake, Oregon. The temperature field inferred from the geostatistical simulations clearly shows geothermal fluids discharging from a group of fault-controlled hydrothermal springs, moving laterally through the subsurface, and mixing with shallow subsurface flow originating from nearby Borax Lake. This interpretation of the data is supported by independent geochemical and isotopic evidence, which show a simple mixing trend between Borax Lake water and discharge from the thermal springs. It is generally agreed that stochastic simulation can be a useful tool for extracting information from complex and/or noisy data and, although not appropriate in all situations, geostatistical analysis may provide good definition of flow paths in the shallow subsurface. Although stochastic imaging techniques are well known in problems involving transport of species, e.g. delineation of contaminant plumes from soil gas survey data, we are unaware of previous applications to the transport of thermal energy for the purpose of inferring shallow groundwater flow.

Heavy metal contamination in an urban stream fed by contaminated air-conditioning and stormwater discharges.

PubMed

O'Sullivan, Aisling; Wicke, Daniel; Cochrane, Tom

2012-03-01

Urban waterways are impacted by diffuse stormwater runoff, yet other discharges can unintentionally contaminate them. The Okeover stream in Christchurch, New Zealand, receives air-conditioning discharge, while its ephemeral reach relies on untreated stormwater flow. Despite rehabilitation efforts, the ecosystem is still highly disturbed. It was assumed that stormwater was the sole contamination source to the stream although water quality data were sparse. We therefore investigated its water and sediment quality and compared the data with appropriate ecotoxicological thresholds from all water sources. Concentrations of metals (Zn, Cu and Pb) in stream baseflow, stormwater runoff, air-conditioning discharge and stream-bed sediments were quantified along with flow regimes to ascertain annual contaminant loads. Metals were analysed by ICP-MS following accredited techniques. Zn, Cu and Pb concentrations from stormflow exceeded relevant guidelines for the protection of 90% of aquatic species by 18-, 9- and 5-fold, respectively, suggesting substantial ecotoxicity potential. Sporadic copper (Cu) inputs from roof runoff exceeded these levels up to 3,200-fold at >4,000 μg L⁻¹ while Cu in baseflow from air-conditioning inputs exceeded them 5.4-fold. There was an 11-fold greater annual Cu load to the stream from air-conditioning discharge compared to stormwater runoff. Most Zn and Cu were dissolved species possibly enhancing metal bioavailability. Elevated metal concentrations were also found throughout the stream sediments. Environmental investigations revealed unsuspected contamination from air-conditioning discharge that contributed greater Cu annual loads to an urban stream compared to stormwater inputs. This discovery helped reassess treatment strategies for regaining ecological integrity in the ecosystem.

Concentration Measurements in Self-Excited Momentum Dominated Low-Density Gas Jets

NASA Technical Reports Server (NTRS)

Yildirim, B. S.; Pasumarthi, K. S.; Agrawal, A. K.

2004-01-01

Flow structure of self-excited, laminar, axisymmetric, momentum-dominated helium jets discharged vertically into ambient air was investigated using high-speed rainbow schlieren deflectometry technique. Measurements were obtained at temporal resolution of 1 ms and spatial resolution of 0.19 mm for two test cases with Richardson number of 0.034 and 0.018. Power spectra revealed that the oscillation frequency was independent of spatial coordinates, suggesting global oscillations in the flow. Abel inversion algorithm was used to reconstruct the concentration field of helium. Instantaneous concentration contours revealed changes in the flow field and evolution of vortical structures during an oscillation cycle. Temporal evolution plots of helium concentration at different axial locations provided detailed information about the instability in the flow field.

Low-Flow Characteristics and Discharge Profiles for Selected Streams in the Cape Fear River Basin, North Carolina, Through 1998

USGS Publications Warehouse

Weaver, J.C.; Pope, B.F.

2001-01-01

An understanding of the magnitude and frequency of low-flow discharges is an important part of evaluating surface-water resources and planning for municipal and industrial economic expansion. Low-flow characteristics are summarized in this report for 67 continuous-record gaging stations and 121 partial-record measuring sites in the Cape Fear River Basin of North Carolina. Records of discharge collected through the 1998 water year were used in the analyses. Flow characteristics included in the summary are (1) average annual unit flow; (2) 7Q10 low-flow discharge, the minimum average discharge for a 7-consecutive-day period occurring, on average, once in 10 years; (3) 30Q2 low-flow discharge; (4) W7Q10 low-flow discharge, similar to 7Q10 discharge except that only flow during November through March is considered; and (5) 7Q2 low-flow discharge. Low-flow characteristics in the Cape Fear River Basin vary widely in response to changes in geology and soil types. The area of the basin with the lowest potentials for sustained base flows is underlain by the Triassic basin in parts of Durham, Wake, and Chatham Counties. Typically, these soils are derived from basalt and fine-grained sedimentary rocks that allow very little infiltration of water into the shallow aquifers for storage and later release to streams during periods of base flow. The area of the basin with the highest base flows is the Sand Hills region in parts of Moore, Harnett, Hoke, and Cumberland Counties. Streams in the Sand Hills have the highest unit low flows in the study area as well as in much of North Carolina. Well-drained sandy soils in combination with higher topographic relief relative to other areas in the Coastal Plain contribute to the occurrence of high potentials for sustained base flows. A number of sites in the upper part of the Cape Fear River Basin underlain by the Carolina Slate Belt and Triassic basin, as well many sites in lower areas of the Coastal Plain (particularly the Northeast Cape Fear River Basin), have zero or minimal (defined as less than 0.05 cubic foot per second) 7Q10 discharges. In this area, the poorly sustained base flows are reflective of either (1) thin soils that have very little storage of water to sustain streams during base-flow periods (Carolina Slate Belt), or (2) soils having very low infiltration rates (Triassic basin). As a result, there is insufficient water stored in the surficial aquifers for release to streams during extended dry periods. Within the part of the study area underlain by the Carolina Slate Belt, streams draining basins 5 square miles or less may have zero or minimal 7Q10 discharges. The part of the study area underlain by the Triassic basin has a higher drainage-area threshold at 35 square miles, below which streams will likely have zero or minimal 7Q10 discharges. Occurrences of zero or minimal 7Q10 discharges in the Coastal Plain were noted, though on a more widespread basis. In this area, low flows are more likely affected by the presence of poorly drained soils in combination with very low topographic relief relative to other areas in the Coastal Plain, particularly the Sand Hills. In eastern Harnett County and northeastern Cumberland County, basins with less than 3 square miles may be prone to having zero or minimal 7Q10 discharges. Soils in this area have been described as a mixture of sandy and clay soils. In the Northeast Cape Fear River Basin, particularly on the western side of the river, streams draining less than 8 square miles may have zero or minimal 7Q10 discharges. The poorly drained clay soils along with very little topographic relief results in the low potential for sustained base flows in this part of the study area. Drainage area and low-flow discharge profiles are presented for 13 streams in the Cape Fear River Basin; these profiles reflect a wide range in basin size, characteristics, and streamflow conditions. In addition to the Haw River and Cape Fear River main stem, pro

Streamflow and streambed scour in 2010 at bridge 339, Copper River, Alaska

USGS Publications Warehouse

Conaway, Jeffrey S.; Brabets, Timothy P.

2011-01-01

The distribution of the Copper River's discharge through the bridges was relatively stable until sometime between 1969-70 and 1982-85. The majority of the total Copper River discharge in 1969-70 passed through three bridges on the western side of the delta, but by 1982-1985, 25 to 62 percent of the flow passed through bridge 342 on the eastern side of the Copper River Delta. In 2004, only 8 percent of the flow passed through the western bridges, while 90 percent of the discharge flowed through two bridges on the eastern side of the delta. Migration of the river across the delta and redistribution of discharge has resulted in streambed scour at some bridges, overtopping of the road during high flows, prolonged highway closures, and formation of new channels through forests. Scour monitoring at the eastern bridges has recorded as much as 44 feet of fill at one pier and 33 feet of scour at another. In 2009, flow distribution began to shift from the larger bridge 342 to bridge 339. In 2010, flow in excess of four times the design discharge scoured the streambed at bridge 339 to a level such that constant on-site monitoring was required to evaluate the potential need for bridge closure. In 2010, instantaneous flow through bridge 339 was never less than 30 percent and was as high as 49 percent of the total Copper River discharge. The percentage of flow through bridge 339 decreased when the overall Copper River discharge increased. The increased discharge through bridge 339 is attributed to a shift in the approach channel 3,500 feet upstream. Bridge channel alignment and analysis of flow distribution as of October 2010 indicate these hydrologic hazards will persist in 2011.

Death Valley regional groundwater flow system, Nevada and California-Hydrogeologic framework and transient groundwater flow model

USGS Publications Warehouse

Belcher, Wayne R.; Sweetkind, Donald S.

2010-01-01

A numerical three-dimensional (3D) transient groundwater flow model of the Death Valley region was developed by the U.S. Geological Survey for the U.S. Department of Energy programs at the Nevada Test Site and at Yucca Mountain, Nevada. Decades of study of aspects of the groundwater flow system and previous less extensive groundwater flow models were incorporated and reevaluated together with new data to provide greater detail for the complex, digital model. A 3D digital hydrogeologic framework model (HFM) was developed from digital elevation models, geologic maps, borehole information, geologic and hydrogeologic cross sections, and other 3D models to represent the geometry of the hydrogeologic units (HGUs). Structural features, such as faults and fractures, that affect groundwater flow also were added. The HFM represents Precambrian and Paleozoic crystalline and sedimentary rocks, Mesozoic sedimentary rocks, Mesozoic to Cenozoic intrusive rocks, Cenozoic volcanic tuffs and lavas, and late Cenozoic sedimentary deposits of the Death Valley regional groundwater flow system (DVRFS) region in 27 HGUs. Information from a series of investigations was compiled to conceptualize and quantify hydrologic components of the groundwater flow system within the DVRFS model domain and to provide hydraulic-property and head-observation data used in the calibration of the transient-flow model. These studies reevaluated natural groundwater discharge occurring through evapotranspiration (ET) and spring flow; the history of groundwater pumping from 1913 through 1998; groundwater recharge simulated as net infiltration; model boundary inflows and outflows based on regional hydraulic gradients and water budgets of surrounding areas; hydraulic conductivity and its relation to depth; and water levels appropriate for regional simulation of prepumped and pumped conditions within the DVRFS model domain. Simulation results appropriate for the regional extent and scale of the model were provided by acquiring additional data, by reevaluating existing data using current technology and concepts, and by refining earlier interpretations to reflect the current understanding of the regional groundwater flow system. Groundwater flow in the Death Valley region is composed of several interconnected, complex groundwater flow systems. Groundwater flow occurs in three subregions in relatively shallow and localized flow paths that are superimposed on deeper, regional flow paths. Regional groundwater flow is predominantly through a thick Paleozoic carbonate rock sequence affected by complex geologic structures from regional faulting and fracturing that can enhance or impede flow. Spring flow and ET are the dominant natural groundwater discharge processes. Groundwater also is withdrawn for agricultural, commercial, and domestic uses. Groundwater flow in the DVRFS was simulated using MODFLOW-2000, the U.S. Geological Survey 3D finitedifference modular groundwater flow modeling code that incorporates a nonlinear least-squares regression technique to estimate aquifer parameters. The DVRFS model has 16 layers of defined thickness, a finite-difference grid consisting of 194 rows and 160 columns, and uniform cells 1,500 meters (m) on each side. Prepumping conditions (before 1913) were used as the initial conditions for the transient-state calibration. The model uses annual stress periods with discrete recharge and discharge components. Recharge occurs mostly from infiltration of precipitation and runoff on high mountain ranges and from a small amount of underflow from adjacent basins. Discharge occurs primarily through ET and spring discharge (both simulated as drains) and water withdrawal by pumping and, to a lesser amount, by underflow to adjacent basins simulated by constant-head boundaries. All parameter values estimated by the regression are reasonable and within the range of expected values. The simulated hydraulic heads of the final calibrated transient mode

High levels of endocrine pollutants in US streams during low flow due to insufficient wastewater dilution

NASA Astrophysics Data System (ADS)

Rice, Jacelyn; Westerhoff, Paul

2017-08-01

Wastewater discharges from publicly owned treatment works are a significant source of endocrine disruptors and other contaminants to the aquatic environment in the US. Although remaining pollutants in wastewater pose environmental risks, treated wastewater is also a primary source of stream flow, which in turn is critical in maintaining many aquatic and riparian wildlife habitats. Here we calculate the dilution factor--the ratio of flow in the stream receiving discharge to the flow of wastewater discharge--for over 14,000 receiving streams in the continental US using streamflow observations and a spatially explicit watershed-scale hydraulic model. We found that wastewater discharges make up more than 50% of in-stream flow for over 900 streams. However, in 1,049 streams that experienced exceptional low-flow conditions, the dilution factors in 635 of those streams fell so low during those conditions that the safety threshold for concentrations of one endocrine disrupting compound was exceeded, and in roughly a third of those streams, the threshold was exceeded for two compounds. We suggest that streams are vulnerable to public wastewater discharge of contaminants under low-flow conditions, at a time when wastewater discharges are likely to be most important for maintaining stream flow for smaller sized river systems.

Dye tracing techniques used to determine ground-water flow in a carbonate aquifer system near Elizabethtown, Kentucky

USGS Publications Warehouse

Mull, D.S.; Smoot, J.L.; Liebermann, T.D.

1988-01-01

Because of the vulnerability of karst aquifers to contamination and the need for water managers to know recharge areas and groundwater flow characteristics for springs and wells used for public water supply, qualitative and quantitative dye tracing techniques were used during a groundwater investigation in the Elizabethtown area, Hardin County, in north-central Kentucky. The principal aquifer in the Elizabethtown area is thick, nearly horizontal beds of limestone, and thin beds of shale of Mississippi age. As much as 65% of all water pumped for the city water supply is obtained from two springs and two wells that obtain water from these rocks. Sinkholes were classified according to their ability to funnel runoff directly into the groundwater flow system, based primarily on the nature of the swallet draining the sinkhole. The presence of bedrock in the sinkhole nearly always ensured a well defined swallet leading to the subsurface. Qualitative and quantitative dye tracing techniques and equipment are discussed in detail. Qualitative dye tracing with fluorescein dye and passive dye detectors, consisting of activated coconut charcoal identified point to point connection between representative sinkholes, sinking streams, and karst windows and the city springs and wells. Qualitative tracing confirmed the presence of infiltrated surface water from a perennial stream, Valley Creek, in water from city wells and generally confirmed the direction of groundwater flow as shown by a water level contour map. Quantitative dye tracing with rhodamin WT, automatic samplers, discharge measurements, and fluorometric analyses were used to determine flow characteristics such as traveltime for arrival of the leading edge, peak concentration, trailing edge, and persistence of the dye cloud at the spring resurgence. Analyses of the dye recovery curves for quantitative dye traces completed between the same sinkholes and a city spring, and during different flow conditions showed that the arrival time of the leading edge of the dye cloud ranged from 5 to 24 hours and that the traveltime of the centroid of the dye cloud ranged from 6 to 31 hours when discharge was 4.6 and 0.53 cu ft/second, respectively. (Lantz-PTT)

ESTIMATING LOW-FLOW FREQUENCIES OF UNGAGED STREAMS IN NEW ENGLAND.

USGS Publications Warehouse

Wandle, S. William

1987-01-01

Equations to estimate low flows were developed using multiple-regression analysis with a sample of 48 river basins, which were selected from the U. S. Geological Survey's network of gaged river basins in Massachusetts, New Hampshire, Rhode Island, Vermont, and southwestern Maine. Low-flow characteristics are represented by the 7Q2 and 7Q10 (the annual minimum 7-day mean low flow at the 2- and 10-year recurrence intervals). These statistics for each of the 48 basins were determined from a low-flow frequency analysis of streamflow records for 1942-71, or from a graphical or mathematical relationship if the record did not cover this 30-year period. Estimators for the mean and variance of the 7-day low flows at the index and short-term sites were used for two stations where discharge measurements of base flow were available and for two sites where the graphical technique was unsatisfactory.

Numerical modelling of ozone production in a wire-cylinder corona discharge and comparison with a wire-plate corona discharge

NASA Astrophysics Data System (ADS)

Wang, Pengxiang; Chen, Junhong

2009-02-01

The effect of electrode configuration on ozone production in the direct-current corona discharge of dry and humid air is studied by a numerical model that combines the electron distribution in the corona plasma, plasma chemistry and transport phenomena. Two electrode configurations are considered: wire-cylinder discharge with air flowing along the wire axis and wire-plate discharge with air flowing transverse to the wire. The ozone distributions in both types of discharges are compared. For both electrode configurations, the ozone production rate is higher in the negative corona than in the positive corona and it decreases with an increase in relative humidity. More importantly, the detailed ozone distribution in the neighbourhood of the discharge wire, together with the ozone kinetics, reveals the possible difference in the ozone production from the two discharges. With the same operating conditions and sufficiently short flow residence time, the ozone production rate is nearly the same for both electrode configurations. When the flow residence time is longer than the characteristic time for homogeneous ozone destruction, the net ozone production is higher in the wire-cylinder discharge than in the wire-plate discharge due to relatively less ozone destruction.

Low-flow characteristics and profiles for the Rocky River in the Yadkin-Pee Dee River basin, North Carolina, through 2002

USGS Publications Warehouse

Weaver, J. Curtis; Fine, Jason M.

2003-01-01

An understanding of the magnitude and frequency of low-flow discharges is an important part of protecting surface-water resources and planning for municipal and industrial economic expansion. Low-flow characteristics are summarized for 12 continuous-record gaging stations and 44 partial-record measuring sites in the Rocky River basin in North Carolina. Records of discharge collected through the 2002 water year at continuous-record gaging stations and through the 2001 water year at partial-record measuring sites were used. Flow characteristics included in the summary are (1) average annual unit flow; (2) 7Q10 low-flow discharge, the minimum average discharge for a 7-consecutive-day period occurring, on average, once in 10 years; (3) 30Q2 low-flow discharge; (4) W7Q10 low-flow discharge, which is similar to 7Q10 discharge but is based only on flow during the winter months of November through March; and (5) 7Q2 low-flow discharge. The Rocky River basin drains 1,413 square miles (mi2) of the southern Piedmont Province in North Carolina. The Rocky River is about 91 miles long and merges with the Yadkin River in eastern Stanly County to form the Pee Dee River, which discharges into the Atlantic Ocean in South Carolina. Low-flow characteristics compiled for selected sites in the Rocky River basin indicated that the potential for sustained base flows in the upper half of the basin is relatively higher than for streams in the lower half of the basin. The upper half of the basin is underlain by the Charlotte Belt, where streams have been identified as having moderate potentials for sustained base flows. In the lower half of the basin, many streams were noted as having little to no potential for sustained base flows. Much of the decrease in base-flow potential is attributed to the underlying rock types of the Carolina Slate Belt. Of the 19 sites in the basin having minimal (defined as less than 0.05 cubic foot per second) or zero 7Q10 discharges, 18 sites are located in the lower half of the basin underlain by the Carolina Slate Belt. Assessment of these 18 sites indicates that streams that have drainage areas less than about 25 square miles are likely to have minimal or zero 7Q10 discharges. No drainage-area threshold for minimal or zero 7Q10 discharges was identified for the upper half of the basin, which is underlain by the Charlotte Belt. Tributaries to the Rocky River include the West Branch Rocky River (22.8 mi2), Clarke Creek (28.2 mi2), Mallard Creek (41.2 mi2), Coddle Creek (78.8 mi2), Reedy Creek (43.0 mi2), Irish Buffalo/Coldwater Creeks (110 mi2), Dutch Buffalo Creek (99 mi2), Long Creek (200 mi2), Richardson Creek (234 mi2), and Lanes Creek (135 mi2). In the 20-mile reach upstream from the mouth (about 22 percent of the river length), the drainage area increases by 648 mi2, or about 46 percent of the total drainage area as a result of the confluences with Long Creek, Richardson Creek, and Lanes Creek. Low-flow discharge profiles for the Rocky River include 7Q10, 30Q2, W7Q10, and 7Q2 discharges in a continuous profile with contributions from major tributaries included. At the gaging stations above Irish Buffalo Creek and near Stanfield, the 7Q10 discharges are 25.2 and 42.3 cubic feet per second, corresponding to 0.09 and 0.07 cubic feet per second per square mile, respectively. At the gaging station near Norwood, the 7Q10 discharge is 45.8 cubic feet per second, equivalent to 0.03 cubic foot per second per square mile. Low-flow discharge profiles reflect the presence of several major flow diversions in the reaches upstream from Stanfield and an apparent losing reach between the continuous-record gaging stations near Stanfield and Norwood, North Carolina.

Riparian vegetation controls on braided stream dynamics

NASA Astrophysics Data System (ADS)

Gran, Karen; Paola, Chris

2001-12-01

Riparian vegetation can significantly influence the morphology of a river, affecting channel geometry and flow dynamics. To examine the effects of riparian vegetation on gravel bed braided streams, we conducted a series of physical experiments at the St. Anthony Falls Laboratory with varying densities of bar and bank vegetation. Water discharge, sediment discharge, and grain size were held constant between runs. For each run, we allowed a braided system to develop, then seeded the flume with alfalfa (Medicago sativa), allowed the seeds to grow, and then continued the run. We collected data on water depth, surface velocity, and bed elevation throughout each run using image-based techniques designed to collect data over a large spatial area with minimal disturbance to the flow. Our results show that the influence of vegetation on overall river patterns varied systematically with the spatial density of plant stems. Vegetation reduced the number of active channels and increased bank stability, leading to lower lateral migration rates, narrower and deeper channels, and increased channel relief. These effects increased with vegetation density. Vegetation influenced flow dynamics, increasing the variance of flow direction in vegetated runs and increasing scour depths through strong downwelling where the flow collided with relatively resistant banks. This oblique bank collision also provides a new mechanism for producing secondary flows. We found it to be more important than the classical curvature-driven mechanism in vegetated runs.

An Experimental Study of the Ionization of Low-Density Gas Flows by Induced Discharges

NASA Technical Reports Server (NTRS)

Barger, R. L.; Brooks, J. D.; Beasley, W. D.

1960-01-01

Induced discharges are advantageous for ionizing low-density flows in that they introduce no electrode contamination into the flow and they provide a relatively high degree of ionization with good coupling of power into the gas. In this investigation a 40-megacycle oscillator was used to produce and maintain induced discharges in argon and mercury-vapor flows. Methods for preventing blowout of the discharge were determined, and power measurements were made with an in-line wattmeter. Some results with damped oscillations pulsed at 1,000 pulses per second are also presented.

Ion flow experiments in a multipole discharge chamber

NASA Technical Reports Server (NTRS)

Kaufman, H. R.; Robinson, R. S.; Frisa, L. E.

1982-01-01

It has been customary to assume that ions flow nearly equally in all directions from the ion production region within an electron-bombardment discharge chamber. Ion flow measurements in a multipole discharge chamber have shown that this assumption is not true. In general, the electron current through a magnetic field can alter the electron density, and hence the ion density, in such a way that ions tend to be directed away from the region bounded by the magnetic field. When this mechanism is understood, it becomes evident that many past discharge chamber designs have operated with a preferentially directed flow of ions.

Flow determination of a pump-turbine at zero discharge

NASA Astrophysics Data System (ADS)

Edinger, G.; Erne, S.; Doujak, E.; Bauer, C.

2014-03-01

When starting up a reversible Francis pump-turbine in pump mode, the machine may operate at zero flow at a given gate opening. Besides reversal flow and prerotation in the draft tube cone, the onset of a fully separated flow in the vaned diffuser is observable at zero- discharge condition. In this paper, the occurrence of prerotation and reversal flow in the conical draft tube and the flow in one stay vane channel of a pump-turbine are examined experimentally and compared to numerical simulations. In order to assess the strongly three-dimensional flow in the stay vane channel, measurements with a 2D laser doppler velocimeter (LDV) were performed at various positions. The inlet flow in the draft tube cone, which becomes significantly at zero discharge in pump mode, is investigated by velocity measurements at two different positions. Pressure fluctuations in the draft tube cone induced by complex flow patterns are also recorded and analyzed. It is found that the swirl number at zero discharge does not significant differ from the values obtained at very low load pumping. Experimental investigations combined with CFD have shown that in the stay vane channel flow velocity components different from zero occur even at no discharge. Streamline plots show the fully separated flow structure.

Parameters of the plasma of a dc pulsating discharge in a supersonic air flow

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shibkov, V. M., E-mail: shibkov@phys.msu.ru; Shibkova, L. V.; Logunov, A. A.

A dc discharge in a cold (T = 200 K) supersonic air flow at a static pressure of 200–400 Torr was studied experimentally. The excited unsteady pulsating discharge has the form of a thin plasma channel with a diameter of ≤1 mm, stretched downstream the flow. Depending on the discharge current, the pulsation frequency varies from 800 to 1600 Hz and the electron temperature varies from 8000 to 15000 K.

Establishing a Multi-scale Stream Gaging Network in the Whitewater River Basin, Kansas, USA

USGS Publications Warehouse

Clayton, J.A.; Kean, J.W.

2010-01-01

Investigating the routing of streamflow through a large drainage basin requires the determination of discharge at numerous locations in the channel network. Establishing a dense network of stream gages using conventional methods is both cost-prohibitive and functionally impractical for many research projects. We employ herein a previously tested, fluid-mechanically based model for generating rating curves to establish a stream gaging network in the Whitewater River basin in south-central Kansas. The model was developed for the type of channels typically found in this watershed, meaning that it is designed to handle deep, narrow geomorphically stable channels with irregular planforms, and can model overbank flow over a vegetated floodplain. We applied the model to ten previously ungaged stream reaches in the basin, ranging from third- to sixth-order channels. At each site, detailed field measurements of the channel and floodplain morphology, bed and bank roughness, and vegetation characteristics were used to quantify the roughness for a range of flow stages, from low flow to overbank flooding. Rating curves that relate stage to discharge were developed for all ten sites. Both fieldwork and modeling were completed in less than 2 years during an anomalously dry period in the region, which underscores an advantage of using theoretically based (as opposed to empirically based) discharge estimation techniques. ?? 2010 Springer Science+Business Media B.V.

Designing ecological flows to gravely braided rivers in alpine environments

NASA Astrophysics Data System (ADS)

Egozi, R.; Ashmore, P.

2009-04-01

Designing ecological flows in gravelly braided streams requires estimating the channel forming discharge in order to maintain the braided reach physical (allocation of flow and bed load) and ecological (maintaining the habitat diversity) functions. At present, compared to single meander streams, there are fewer guiding principles for river practitioners that can be used to manage braided streams. Insight into braiding morphodynamics using braiding intensity indices allows estimation of channel forming discharge. We assess variation in braiding intensity by mapping the total number of channels (BIT) and the number of active (transporting bed load) channels (BIA) at different stages of typical diurnal melt-water hydrographs in a pro-glacial braided river, Sunwapta River, Canada. Results show that both BIA and BIT vary with flow stage but over a limited range of values. Furthermore, maximum BIT occurs below peak discharge. At this stage there is a balance between channel merging from inundation and occupation of new channels as the stage rises. This stage is the channel forming discharge because above this stage the existing braided pattern cannot discharge the volume of water without causing morphological changes (e.g., destruction of bifurcations, channel avulsion). Estimation of the channel forming discharge requires a set of braiding intensity measurements over a range of flow stages. The design of ecological flows must take into consideration flow regime characteristics rather than just the channel forming discharge magnitude.

True Airspeed Measurement by Ionization-Tracer Technique

NASA Technical Reports Server (NTRS)

Boyd, B.; Dorsch, R. G.; Brodie, G. H.

1952-01-01

Ion bundles produced in a pulse-excited corona discharge are used as tracers with a radar-like pulse transit-time measuring instrument in order to provide a measurement of airspeed that is independent of all variables except time and distance. The resulting instrumentation need not project into the air stream and, therefore, will not cause any interference in supersonic flow. The instrument was tested at Mach numbers ranging from 0.3 to 3.8. Use of the proper instrumentation and technique results in accuracy of the order of 1 percent.

Estimating flood discharge using witness movies in post-flood hydrological surveys

NASA Astrophysics Data System (ADS)

Le Coz, Jérôme; Hauet, Alexandre; Le Boursicaud, Raphaël; Pénard, Lionel; Bonnifait, Laurent; Dramais, Guillaume; Thollet, Fabien; Braud, Isabelle

2015-04-01

The estimation of streamflow rates based on post-flood surveys is of paramount importance for the investigation of extreme hydrological events. Major uncertainties usually arise from the absence of information on the flow velocities and from the limited spatio-temporal resolution of such surveys. Nowadays, after each flood occuring in populated areas home movies taken from bridges, river banks or even drones are shared by witnesses through Internet platforms like YouTube. Provided that some topography data and additional information are collected, image-based velocimetry techniques can be applied to some of these movie materials, in order to estimate flood discharges. As a contribution to recent post-flood surveys conducted in France, we developed and applied a method for estimating velocities and discharges based on the Large Scale Particle Image Velocimetry (LSPIV) technique. Since the seminal work of Fujita et al. (1998), LSPIV applications to river flows were reported by a number of authors and LSPIV can now be considered a mature technique. However, its application to non-professional movies taken by flood witnesses remains challenging and required some practical developments. The different steps to apply LSPIV analysis to a flood home movie are as follows: (i) select a video of interest; (ii) contact the author for agreement and extra information; (iii) conduct a field topography campaign to georeference Ground Control Points (GCPs), water level and cross-sectional profiles; (iv) preprocess the video before LSPIV analysis: correct lens distortion, align the images, etc.; (v) orthorectify the images to correct perspective effects and know the physical size of pixels; (vi) proceed with the LSPIV analysis to compute the surface velocity field; and (vii) compute discharge according to a user-defined velocity coefficient. Two case studies in French mountainous rivers during extreme floods are presented. The movies were collected on YouTube and field topography surveys were achieved. Identifying fixed GCPs is more difficult in rural environments than in urban areas. Image processing was performed using free software only, especially Fudaa-LSPIV (Le Coz et al., 2014) was used for steps (v), (vi), and (vii). The results illustrate the typical issues and advantages of flood home movies taken by witnesses for improving post-flood discharge estimation. In spite of the non-ideal conditions related to such movies, the LSPIV technique was successfully applied. Corrections for lens distortion and limited camera movements (shake) are not difficult to achieve. Locating precisely the video viewpoint is often easy whereas precise timing may be not, especially when the author cannot be contacted or when the camera clock is false. Based on sensitivity analysis, the determination of the water level appears to be the main source of uncertainty in the results. Nevertheless, the information content of the results remains highly valuable for post-flood studies, in particular for improving the high-flow extrapolation of hydrometric rating curves. This kind of application opens interesting avenues for participative research in flood hydrology, as well as the study of other extreme geophysical events. Typically, as part of the FloodScale ANR research project (2012-2015), specific communication actions have been focused on the determination of flood discharges within the Ardèche river catchement (France) using home movies shared by observers and volunteers. Safety instructions and a simplified field procedure were shared through local media and were made available in French and English on the project website. This way, simple flood observers or even some enthusiastic flood chasers can contribute to participative hydrological science in the same way the so-called storm chasers have significantly contributed to meteorological science since the Tornado Intercept Project (1972). Website : http://floodscale.irstea.fr/donnees-en/videos-amateurs-de-rivieres-en-crue/ Fujita, I., Muste, M., and Kruger, A. (1998). Large-scale particle image velocimetry for flow analysis in hydraulic engineering applications. Journal of Hydraulic Research, 36(3):397-414. Le Coz, J., Jodeau, M., Hauet, A., Marchand, B., Le Boursicaud, R. (2014). Image-based velocity and discharge measurements in field and laboratory river engineering studies using the free FUDAA-LSPIV software, Proceedings of the International Conference on Fluvial Hydraulics, RIVER FLOW 2014, 1961-1967.

An Investigation of Ionic Flows in a Sphere-Plate Electrode Gap

NASA Astrophysics Data System (ADS)

Z. Alisoy, H.; Alagoz, S.; T. Alisoy, G.; B. Alagoz, B.

2013-10-01

This paper presents analyses of ion flow characteristics and ion discharge pulses in a sphere-ground plate electrode system. As a result of variation in electric field intensity in the electrode gap, the ion flows towards electrodes generate non-uniform discharging pulses. Inspection of these pulses provides useful information on ionic stream kinetics, the effective thickness of ion cover around electrodes, and the timing of ion clouds discharge pulse sequences. A finite difference time domain (FDTD) based space-charge motion simulation is used for the numerical analysis of the spatio-temporal development of ionic flows following the first Townsend avalanche, and the simulation results demonstrate expansion of the positive ion flow and compression of the negative ion flow, which results in non-uniform discharge pulse characteristics.

Effect of Dam operation on monthly and annual trends of flow discharge in the Qom Rood Watershed, Iran

NASA Astrophysics Data System (ADS)

Yaghmaei, Hiva; Sadeghi, Seyed Hamidreza; Moradi, Hamidreza; Gholamalifard, Mehdi

2018-02-01

Trends in flow discharge, temperature and rainfall from the Qom Rood Watershed, Iran, for a period of 1979-2016 were analyzed at monthly and annual time scales. Trend analyses were conducted using the Mann-Kendall test, the double-mass curve of mean annual discharge versus rainfall, and rainfall-runoff relationship before and after the 15 Khordad Dam operation. Multiple regression of flow discharge against rainfall and temperature was used to determine the residual trend at four meteorological and hydrological stations located upstream and downstream of the Qom Rood Watershed. Results showed that the temperature at the upstream and downstream stations did not have any significant trend, but a significant decreasing trend (P < .05) in rainfall was detected only in May (z = -1.66) at the downstream stations. There was a significant positive trend (P < .05) in rainfall in February (z = 2.22) and July (z = 2.15) at the upstream stations, and in October (z = 2.3) and November (z = 1.8) at the downstream stations. However, there was a noticeable decrease in monthly and annual flow discharge, and residual trend at 99% significance level at the downstream stations. At the upstream stations, the flow discharges had significant (P < .05) declining trend in all months, but annual flow discharge did not change significantly. Analysis of double mass curve between runoff and rainfall at the downstream stations showed an inconsistency in the line slope concordant with the time of 15 Khordad Dam operation. Annual mean discharge at the upstream stations did not show a significant change before and after 15 Khordad Dam operation. However, annual flow magnitude decreased significantly by 87.5 and 81.7% in Shad Abad and KoohSefid, respectively. These results confirmed that natural driving forces did not affect flow discharge changes and the observed decreasing tendency in flow discharge at the downstream stations was due to 15 Khordad Dam, and at the upstream stations due to diversion/storage dams. These findings highlighted the role of human interference in changing the hydrologic regime in the study area based on which appropriate adaptive decisions can be made.

Variable partitioning of flow and sediment transfer through a large river diffluence-confluence unit across a monsoonal flood pulse

NASA Astrophysics Data System (ADS)

Hackney, C. R.; Aalto, R. E.; Darby, S. E.; Parsons, D. R.; Leyland, J.; Nicholas, A. P.; Best, J.

2016-12-01

Bifurcations represent key morphological nodes within the channel networks of anabranching and braided fluvial channels, playing an important role in controlling local bed morphology, the routing of sediment and water, and defining the stability of the downstream reaches. Herein, we detail field observations of the three-dimensional flow structure, bed morphological changes and partitioning of both flow discharge and suspended sediment through a large diffluence-confluence unit on the Mekong River, Cambodia, across a range of flow stages (from 13,500 m3 s-1 to 27,000 m3 s-1) over the monsoonal flood-pulse cycle. We show that the discharge asymmetry (a measure of the disparity between discharges distributed down the left and right branches of the bifurcation) varies with flow discharge and that the influence of upstream curvature-induced cross-stream water surface slope and bed morphological changes are first-order controls in modulating the asymmetry in bifurcation discharge. Flow discharge is shown to play a key role in defining the morphodynamics of the diffluence-confluence unit downstream of the bifurcation. Our data show that during peak flows (Q 27,000 m3 s-1), the downstream island complex acts as a net sink of suspended sediment (with 2600 kg s-1 being deposited between the diffluence and confluence), whereas during lower flows, on both the rising and falling limbs of the flood wave, the sediment balance is in quasi-equilibrium. We propose a new conceptual model of bifurcation stability that incorporates varying flood discharge and in which the long term stability of the bifurcation, as well as the larger channel planform and morphology of the diffluence-confluence unit, are controlled by the variations in flood discharge.

The influence of flow discharge variations on the morphodynamics of a diffluence-confluence unit on the Mekong River

NASA Astrophysics Data System (ADS)

Hackney, Christopher; Darby, Stephen; Parsons, Daniel; Leyland, Julian; Aalto, Rolf; Nicholas, Andrew; Best, Jim

2017-04-01

Bifurcations represent key morphological nodes within the channel networks of anabranching and braided fluvial channels, playing an important role in controlling local bed morphology, the routing of sediment and water, and defining the stability of the downstream reaches. Herein, we detail field observations of the three-dimensional flow structure, bed morphological changes and partitioning of both flow discharge and suspended sediment through a large diffluence-confluence unit on the Mekong River, Cambodia, across a range of flow stages (from 13,500 m3 s-1 to 27,000 m3 s-1) over the monsoonal flood-pulse cycle. We show that the discharge asymmetry (a measure of the disparity between discharges distributed down the left and right branches of the bifurcation) varies with flow discharge and that the influence of upstream curvature-induced cross-stream water surface slope and bed morphological changes are first-order controls in modulating the asymmetry in bifurcation discharge. Flow discharge is shown to play a key role in defining the morphodynamics of the diffluence-confluence unit downstream of the bifurcation. Our data show that during high flows (Q 27,000 m3 s-1), the downstream island complex acts as a net sink of suspended sediment (with 2600 kg s-1 being deposited between the diffluence and confluence), whereas during lower flows, on both the rising and falling limbs of the flood wave, the sediment balance is in quasi-equilibrium. We propose, therefore, that the long term stability of the bifurcation, as well as the larger channel planform and morphology of the diffluence-confluence unit, is therefore controlled by annual monsoonal flood pulses and the associated variations in discharge.

Temperature and pressure measurements at cold exit of counter-flow vortex tube with flow visualization of reversed flow

NASA Astrophysics Data System (ADS)

Yusof, Mohd Hazwan bin; Katanoda, Hiroshi; Morita, Hiromitsu

2015-02-01

In order to clarify the structure of the cold flow discharged from the counter-flow vortex tube (VT), the temperature and pressure of the cold flow were measured, and the existence and behavior of the reversed flow at the cold exit was studied using a simple flow visualization technique consisting of a 0.75mm-diameter needle, and an oil paint droplet. It is observed through this experiment that the Pitot pressure at the cold exit center can either be lower or higher than atmospheric pressure, depending on the inlet pressure and the cold fraction, and that a reversed flow is observed when the Pitot pressure at the cold exit center is lower than atmospheric pressure. In addition, it is observed that when reducing the cold fraction from unity at any arbitrary inlet pressure, the region of reversed and colder flow in the central part of cold exit extends in the downstream direction.

Acceleration processes in the quasi-steady magnetoplasmadynamic discharge. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Boyle, M. J.

1974-01-01

The flow field characteristics within the discharge chamber and exhaust of a quasi-steady magnetoplasmadynamic (MPD) arcjet were examined to clarify the nature of the plasma acceleration process. The observation of discharge characteristics unperturbed by insulator ablation and terminal voltage fluctuations, first requires the satisfaction of three criteria: the use of refractory insulator materials; a mass injection geometry tailored to provide propellant to both electrode regions of the discharge; and a cathode of sufficient surface area to permit nominal MPD arcjet operation for given combinations of arc current and total mass flow. The axial velocity profile and electromagnetic discharge structure were measured for an arcjet configuration which functions nominally at 15.3 kA and 6 g/sec argon mass flow. An empirical two-flow plasma acceleration model is advanced which delineates inner and outer flow regions and accounts for the observed velocity profile and calculated thrust of the accelerator.

Patterning and Characterization of Carbon Nanotubes Grown in a Microwave Plasma Enhanced Chemical Vapor Deposition Chamber

DTIC Science & Technology

2009-03-01

display [6] of walls can go from two (D- MWCNTs ) to no limit. The distance between the tubes is approximately 0.34 nm closely matching the graphene sheet... MWCNT . . . . . . . . . . . . . . . . . . 9 2.5. Chiral Vector . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 2.6. Arc Discharge Reactor...17 2.15. MWCNTs from 260 nm Ni Dots . . . . . . . . . . . . . . . . . 19 2.16. Process Flow for Eom Technique

The Effect of Flow Distribution on the Concentration of NO Produced by Pulsed Arc Discharge

NASA Astrophysics Data System (ADS)

Hu, Hui; Bao, Bin; Wang, Heli; Liang, Haiyan; He, Junjia; He, Zhenghao; Li, Jin

2007-12-01

As a new method to cure acute respiratory distress syndrome (ARDS), high blood pressure and some illnesses related to the lung, NO has recently received more attention. Thermal plasmas produced by arc discharge can create medical NO, but the concentration of NO2 produced by arc discharge must be controlled simultaneously. This paper investigates the characteristics and regulations of NO production at different flow distribution by pulsed arc discharge in dry air with a special pulsed power. The experimental results show that the flow distribution has a considerable effect on the NO concentration, the stabilization of NO. The production of NO2 could be controlled and the ratio of NO2/NO was decreased to about 10% in the arc discharge. Therefore, the arc discharge could produce stable inhaled NO for medical treatment by changing the flow distribution.

Breakdown characteristics of atmospheric dielectric barrier discharge in gas flow condition

NASA Astrophysics Data System (ADS)

Fan, Zhihui; Yan, Huijie; Wang, Yuying; Liu, Yidi; Guo, Hongfei; Ren, Chunsheng

2018-05-01

Experimental investigations of the breakdown characteristics of plate-to-plate dielectric barrier discharge excited by an AC source at different gas flow conditions are carried out. The ignition voltage for the appearance of the very first discharge filament and the breakdown voltage in each discharge half cycle in continuous operation are examined. As revealed by the results of the indoor air experiment, the ignition voltage manifests a monotonous increase with the increase in the gas flow rate, while the breakdown voltage has a marked decline at the low gas flow rate and increases slightly as the gas flow rate is higher than 10 m/s. As regards the obvious decreases in the ignition voltage and breakdown voltage, the decrease in the humidity with the increase in the gas flow rate plays a dominant role. As regards the increase in breakdown voltage, the memory effect from the preceding discharge is considered. The losses of metastable particles, together with particles having high translational energy in the gas flow, are considered to be the most critical factors.

The study of excited oxygen molecule gas species production and quenching on thermal protection system materials

NASA Technical Reports Server (NTRS)

Nordine, Paul C.; Fujimoto, Gordon T.; Greene, Frank T.

1987-01-01

The detection of excited oxygen and ozone molecules formed by surface catalyzed oxygen atom recombination and reaction was investigated by laser induced fluorescence (LIF), molecular beam mass spectrometric (MBMS), and field ionization (FI) techniques. The experiment used partially dissociated oxygen flows from a microwave discharge at pressures in the range from 60 to 400 Pa or from an inductively coupled RF discharge at atmospheric pressure. The catalyst materials investigated were nickel and the reaction cured glass coating used for Space Shuttle reusable surface insulation tiles. Nonradiative loss processes for the laser excited states makes LIF detection of O2 difficult such that formation of excited oxygen molecules could not be detected in the flow from the microwave discharge or in the gaseous products of atom loss on nickel. MBMS experiments showed that ozone was a product of heterogeneous O atom loss on nickel and tile surfaces at low temperatures and that ozone is lost on these materials at elevated temperatures. FI was separately investigated as a method by which excited oxygen molecules may be conveniently detected. Partial O2 dissociation decreases the current produced by FI of the gas.

Control of plasma-liquid interaction of atmospheric DC glow discharge using liquid electrode

NASA Astrophysics Data System (ADS)

Shirai, Naoki; Aoki, Ryuta; Nito, Aihito; Aoki, Takuya; Uchida, Satoshi; Tochikubo, Fumiyoshi

2014-10-01

Atmospheric plasma in contact with liquid have a variety of interesting phenomena and applications. Previously, we investigated the fundamental characteristics of an atmospheric dc glow discharge using a liquid electrode with a miniature helium flow. We tried to control the plasma-liquid interaction by changing the plasma parameter such as gas species, liquid, and applied voltage. Sheath flow system enables another gas (N2, O2, Ar) flow to around the helium core flow. It can control the gas species around the discharge. When liquid (NaCl aq.) cathode DC discharge is generated, Na emission (588 nm) can be observed from liquid surface with increasing discharge current. Na emission strongly depends on the discharge current and liquid temperature. However, when Ar sheath flow is used, the intensity of Na becomes weak. When liquid anode DC discharge is generated, self-organized luminous pattern formation can be observed at the liquid surface. The pattern depends on existence of oxygen gas in gap. By changing the oxygen gas ratio in the gap, variety of pattern formation can be observed. The discharge in contact with liquid also can be used for synthesis of metal nanoparticles at plasma-liquid interface. Size and shape of nanoparticles depend on discharge gases. This work was supported financially in part by a Grant-in-Aid for Scientific Research on Innovative Areas (No 21110007) from MEXT, Japan.

A Novel Uncertainty Framework for Improving Discharge Data Quality Using Hydraulic Modelling.

NASA Astrophysics Data System (ADS)

Mansanarez, V.; Westerberg, I.; Lyon, S. W.; Lam, N.

2017-12-01

Flood risk assessments rely on accurate discharge data records. Establishing a reliable stage-discharge (SD) rating curve for calculating discharge from stage at a gauging station normally takes years of data collection efforts. Estimation of high flows is particularly difficult as high flows occur rarely and are often practically difficult to gauge. Hydraulically-modelled rating curves can be derived based on as few as two concurrent stage-discharge and water-surface slope measurements at different flow conditions. This means that a reliable rating curve can, potentially, be derived much faster than a traditional rating curve based on numerous stage-discharge gaugings. We introduce an uncertainty framework using hydraulic modelling for developing SD rating curves and estimating their uncertainties. The proposed framework incorporates information from both the hydraulic configuration (bed slope, roughness, vegetation) and the information available in the stage-discharge observation data (gaugings). This method provides a direct estimation of the hydraulic configuration (slope, bed roughness and vegetation roughness). Discharge time series are estimated propagating stage records through posterior rating curve results.We applied this novel method to two Swedish hydrometric stations, accounting for uncertainties in the gaugings for the hydraulic model. Results from these applications were compared to discharge measurements and official discharge estimations.Sensitivity analysis was performed. We focused analyses on high-flow uncertainty and the factors that could reduce this uncertainty. In particular, we investigated which data uncertainties were most important, and at what flow conditions the gaugings should preferably be taken.

Techniques for estimating flood-peak discharges from urban basins in Missouri

USGS Publications Warehouse

Becker, L.D.

1986-01-01

Techniques are defined for estimating the magnitude and frequency of future flood peak discharges of rainfall-induced runoff from small urban basins in Missouri. These techniques were developed from an initial analysis of flood records of 96 gaged sites in Missouri and adjacent states. Final regression equations are based on a balanced, representative sampling of 37 gaged sites in Missouri. This sample included 9 statewide urban study sites, 18 urban sites in St. Louis County, and 10 predominantly rural sites statewide. Short-term records were extended on the basis of long-term climatic records and use of a rainfall-runoff model. Linear least-squares regression analyses were used with log-transformed variables to relate flood magnitudes of selected recurrence intervals (dependent variables) to selected drainage basin indexes (independent variables). For gaged urban study sites within the State, the flood peak estimates are from the frequency curves defined from the synthesized long-term discharge records. Flood frequency estimates are made for ungaged sites by using regression equations that require determination of the drainage basin size and either the percentage of impervious area or a basin development factor. Alternative sets of equations are given for the 2-, 5-, 10-, 25-, 50-, and 100-yr recurrence interval floods. The average standard errors of estimate range from about 33% for the 2-yr flood to 26% for the 100-yr flood. The techniques for estimation are applicable to flood flows that are not significantly affected by storage caused by manmade activities. Flood peak discharge estimating equations are considered applicable for sites on basins draining approximately 0.25 to 40 sq mi. (Author 's abstract)

The effect of DC voltage polarity on ionic wind in ambient air for cooling purposes

NASA Astrophysics Data System (ADS)

Chen, She; van den Berg, R. G. W.; Nijdam, S.

2018-05-01

Gas flows can be induced by gas discharges like DC coronas because neutral molecules gain momentum by ion-neutral collisions. This can be used for active cooling and has advantages over mechanical fans. We investigate ionic wind by a DC corona discharge under different conditions with an emphasis on the effects of voltage polarity and the transition between different discharge regimes. We also consider the gas temperature of a DC corona which is important when it is to be used for cooling purposes. Although DC coronas are usually characterized as low temperature plasmas, gas heating can have a significant impact on flow generation, especially at higher operating voltages. In this paper, a 5–20 kV DC voltage of positive and negative polarity is applied to a needle–cylinder electrode. The ionic wind velocity at the exit of the cylinder electrode is measured by hot wire anemometry and the emission spectrum is used to study the gas temperature. It is found that the flow velocity induced by positive coronas is higher than that by negative coronas for voltages above 10–15 kV, which is also demonstrated by a phenomenological EHD force model. Furthermore, a heated column is observed by Schlieren technique for both voltage polarities. An improved self-consistent ionic wind model considering heat transfer is built to study the temperature distribution. The simulation results indicate that the gas flow velocity is lower on the symmetry axis when the temperature gradient is taken into account, something which is usually ignored in ionic wind simulations.

Force and pressure-recovery characteristics at supersonic speeds of a conical nose inlet with bypasses discharging outward from the body axis

NASA Technical Reports Server (NTRS)

Beke, Andrew; Allen, J L

1953-01-01

Aerodynamic and performance characteristics of a conical spike nacelle-type inlet with two bypasses are presented at Mach numbers of 1.6, 1.8, and 2.0 for angles of attach up to 90 degrees. The bypasses were located 6 inlet diameters downstream of the inlet and were designed to discharge the bypass mass flow outward from the body axis. The inlet was designed to attain a mass-flow ratio of unity at a Mach number of 2.0. It is shown that discharging the bypass mass flow outward from the body nearly doubles the critical drag of a similar configuration but with bypass discharge in an axial direction. As a result of this greater drag, the net force on the model in the flight direction is reduced when comparison is made with the axial discharge case. The lift and pitching-moment coefficients are slightly higher than those for a configuration without bypasses. Approximately 25 % of the maximum inlet mass flow was discharged through the bypasses, and the pressure-recovery and mass-flow characteristics were in qualitative and quantitative agreement with the results of an investigation of a similar configuration with axial discharge.

A novel approach to flow estimation in tidal rivers

NASA Astrophysics Data System (ADS)

Moftakhari, H. R.; Jay, D. A.; Talke, S. A.; Kukulka, T.; Bromirski, P. D.

2013-08-01

Reliable estimation of river discharge to the ocean from large tidal rivers is vital for water resources management and climate analyses. Due to the difficulties inherent in measuring tidal-river discharge, flow records are often limited in length and/or quality and tidal records often predate discharge records. Tidal theory indicates that tides and river discharge interact through quadratic bed friction, which diminishes and distorts the tidal wave as discharge increases. We use this phenomenon to develop a method of estimating river discharge for time periods with tidal data but no flow record. Employing sequential 32 day harmonic analyses of tidal properties, we calibrate San Francisco (SF), CA tide data to the Sacramento River delta outflow index from 1930 to 1990, and use the resulting relationship to hindcast river flow from 1858 to 1929. The M2 admittance (a ratio of the observed M2 tidal constituent to its astronomical forcing) best reproduces high flows, while low-flow periods are better represented by amplitude ratios based on higher harmonics (e.g.,M4/M22). Results show that the annual inflow to SF Bay is now 30% less than before 1900 and confirm that the flood of January 1862 was the largest since 1858.

Temporal changes in VOC discharge to surface water from a fractured rock aquifer during well installation and operation, Greenville, South Carolina

USGS Publications Warehouse

Vroblesky, D.A.; Robertson, J.F.

1996-01-01

Analysis of the vapor in passive vapor samplers retrieved from a streambed in fractured rock terrain implied that volatile organic carbon (VOC) discharge from ground water to surface water substantially increased following installation of a contaminant recovery well using air rotary drilling. The air rotary technique forced air into the aquifer near the stream. The injection produced an upward hydraulic gradient that appears to have transported water and contaminants from deeper parts of the aquifer through fractures into shallow parts of the aquifer. Once in the shallow flow regime, the contamination was transported to the stream, where it discharged during the next several weeks following well installation. After the recovery well was activated and began continuously pumping contaminated ground water to a treatment facility, the VOC concentrations in the stream bottom passive vapor samplers decreased to below detectable concentrations, suggesting that the withdrawal had captured the contaminated ground water that previously had discharged to the stream.

Modeling sediment concentration of rill flow

NASA Astrophysics Data System (ADS)

Yang, Daming; Gao, Peiling; Zhao, Yadong; Zhang, Yuhang; Liu, Xiaoyuan; Zhang, Qingwen

2018-06-01

Accurate estimation of sediment concentration is essential to establish physically-based erosion models. The objectives of this study were to evaluate the effects of flow discharge (Q), slope gradient (S), flow velocity (V), shear stress (τ), stream power (ω) and unit stream power (U) on sediment concentration. Laboratory experiments were conducted using a 10 × 0.1 m rill flume under four flow discharges (2, 4, 8 and 16 L min-1), and five slope gradients (5°, 10°, 15°, 20° and 25°). The results showed that the measured sediment concentration varied from 87.08 to 620.80 kg m-3 with a mean value of 343.13 kg m-3. Sediment concentration increased as a power function with flow discharge and slope gradient, with R2 = 0.975 and NSE = 0.945. The sediment concentration was more sensitive to slope gradient than to flow discharge. The sediment concentration was well predicted by unit stream power (R2 = 0.937, NSE = 0.865), whereas less satisfactorily by flow velocity (R2 = 0.470, NSE = 0.539) and stream power (R2 = 0.773, NSE = 0.732). In addition, using the equations to simulate the measured sediment concentration of other studies, the result further indicated that slope gradient, flow discharge and unit stream power were good predictors of sediment concentration. In general, slope gradient, flow discharge and unit stream power seem to be the preferred predictors for estimating sediment concentration.

Evaluation of Spatial Pattern of Altered Flow Regimes on a River Network Using a Distributed Hydrological Model

PubMed Central

Ryo, Masahiro; Iwasaki, Yuichi; Yoshimura, Chihiro; Saavedra V., Oliver C.

2015-01-01

Alteration of the spatial variability of natural flow regimes has been less studied than that of the temporal variability, despite its ecological importance for river ecosystems. Here, we aimed to quantify the spatial patterns of flow regime alterations along a river network in the Sagami River, Japan, by estimating river discharge under natural and altered flow conditions. We used a distributed hydrological model, which simulates hydrological processes spatiotemporally, to estimate 20-year daily river discharge along the river network. Then, 33 hydrologic indices (i.e., Indicators of Hydrologic Alteration) were calculated from the simulated discharge to estimate the spatial patterns of their alterations. Some hydrologic indices were relatively well estimated such as the magnitude and timing of maximum flows, monthly median flows, and the frequency of low and high flow pulses. The accuracy was evaluated with correlation analysis (r > 0.4) and the Kolmogorov–Smirnov test (α = 0.05) by comparing these indices calculated from both observed and simulated discharge. The spatial patterns of the flow regime alterations varied depending on the hydrologic indices. For example, both the median flow in August and the frequency of high flow pulses were reduced by the maximum of approximately 70%, but these strongest alterations were detected at different locations (i.e., on the mainstream and the tributary, respectively). These results are likely caused by different operational purposes of multiple water control facilities. The results imply that the evaluation only at discharge gauges is insufficient to capture the alteration of the flow regime. Our findings clearly emphasize the importance of evaluating the spatial pattern of flow regime alteration on a river network where its discharge is affected by multiple water control facilities. PMID:26207997

Classifying the hydrologic function of prairie potholes with remote sensing and GIS

USGS Publications Warehouse

Rover, Jennifer R.; Wright, C.K.; Euliss, Ned H.; Mushet, David M.; Wylie, Bruce K.

2011-01-01

A sequence of Landsat TM/ETM+ scenes capturing the substantial surface water variations exhibited by prairie pothole wetlands over a drought to deluge period were analyzed in an attempt to determine the general hydrologic function of individual wetlands (recharge, flow-through, and discharge). Multipixel objects (water bodies) were clustered according to their temporal changes in water extents. We found that wetlands receiving groundwater discharge responded differently over the time period than wetlands that did not. Also, wetlands located within topographically closed discharge basins could be distinguished from discharge basins with overland outlets. Field verification data showed that discharge wetlands with closed basins were most distinct and identifiable with reasonable accuracies (user’s accuracy = 97%, producer’s accuracy = 71%). The classification of other hydrologic function types had lower accuracies reducing the overall accuracy for the four hydrologic function classes to 51%. A simplified classification approach identifying only two hydrologic function classes was 82%. Although this technique has limited success for detecting small wetlands, Landsat-derived multipixel-object clustering can reliably differentiate wetlands receiving groundwater discharge and provides a new approach to quantify wetland dynamics in landscape scale investigations and models.

Export of nutrients and major ionic solutes from a rain forest catchment in the Central Amazon Basin

NASA Astrophysics Data System (ADS)

Lesack, Lance F. W.

1993-03-01

The relative roles of base flow runoff versus storm flow runoff versus subsurface outflow in controlling total export of solutes from a 23.4-ha catchment of undisturbed rain forest in the central Amazon Basin were evaluated from water and solute flux measurements performed over a 1 year period. Solutes exported via 173 storms during the study were estimated from stream water samples collected during base flow conditions and during eight storms, and by utilizing a hydrograph separation technique in combination with a mixing model to partition storm flow from base flow fluxes. Solutes exported by subsurface outflow were estimated from groundwater samples from three nests of piezometers installed into the streambed, and concurrent measurements of hydraulic conductivity and hydraulic head gradients. Base flow discharge represented 92% of water outflow from the basin and was the dominant pathway of solute export. Although storm flow discharge represented only 5% of total water outflow, storm flow solute fluxes represented up to 25% of the total annual export flux, though for many solutes the portion was less. Subsurface outflow represented only 2.5% of total water outflow, and subsurface solute fluxes never represented more than 5% of the total annual export flux. Measurement errors were relatively high for storm flow and subsurface outflow fluxes, but cumulative measurement errors associated with the total solute fluxes exported from the catchment, in most cases, ranged from only ±7% to 14% because base flow fluxes were measured relatively well. The export fluxes of most solutes are substantially less than previously reported for comparable small catchments in the Amazon basin, and these differences cannot be reconciled by the fact that storm flow and subsurface outflows were not appropriately measured in previous studies.

Satellite-driven modeling approach for monitoring lava flow hazards during the 2017 Etna eruption

NASA Astrophysics Data System (ADS)

Del Negro, C.; Bilotta, G.; Cappello, A.; Ganci, G.; Herault, A.; Zago, V.

2017-12-01

The integration of satellite data and modeling represents an efficient strategy that may provide immediate answers to the main issues raised at the onset of a new effusive eruption. Satellite-based thermal remote sensing of hotspots related to effusive activity can effectively provide a variety of products suited to timing, locating, and tracking the radiant character of lava flows. Hotspots show the location and occurrence of eruptive events (vents). Discharge rate estimates may indicate the current intensity (effusion rate) and potential magnitude (volume). High-spatial resolution multispectral satellite data can complement field observations for monitoring the front position (length) and extension of flows (area). Physics-based models driven, or validated, by satellite-derived parameters are now capable of fast and accurate forecast of lava flow inundation scenarios (hazard). Here, we demonstrate the potential of the integrated application of satellite remote-sensing techniques and lava flow models during the 2017 effusive eruption at Mount Etna in Italy. This combined approach provided insights into lava flow field evolution by supplying detailed views of flow field construction (e.g., the opening of ephemeral vents) that were useful for more accurate and reliable forecasts of eruptive activity. Moreover, we gave a detailed chronology of the lava flow activity based on field observations and satellite images, assessed the potential extent of impacted areas, mapped the evolution of lava flow field, and executed hazard projections. The underside of this combination is the high sensitivity of lava flow inundation scenarios to uncertainties in vent location, discharge rate, and other parameters, which can make interpreting hazard forecasts difficult during an effusive crisis. However, such integration at last makes timely forecasts of lava flow hazards during effusive crises possible at the great majority of volcanoes for which no monitoring exists.

A Froude-scaled model of a bedrock-alluvial channel reach: 1. Hydraulics

NASA Astrophysics Data System (ADS)

Hodge, Rebecca A.; Hoey, Trevor B.

2016-09-01

The controls on hydraulics in bedrock-alluvial rivers are relatively poorly understood, despite the importance of the flow in determining rates and patterns of sediment transport and consequent erosion. To measure hydraulics within a bedrock-alluvial channel, we developed a 1:10 Froude-scaled laboratory model of an 18 × 9 m bedrock-alluvial river reach using terrestrial laser scanning and 3-D printing. In the reported experiments, water depth and velocity were recorded at 18 locations within the channel at each of five different discharges. Additional data from runs with sediment cover in the flume were used to evaluate the hydraulic impact of sediment cover; the deposition and erosion of sediment patches in these runs are analyzed in the companion paper. In our data (1) spatial variation in both flow velocity and Froude number increases with discharge; (2) bulk flow resistance and Froude number become independent of discharge at higher discharges; (3) local flow velocity and Reynolds stress are correlated to the range of local bed topography at some, but not most, discharges; (4) at lower discharges, local topography induces vertical flow structures and slower velocities, but these effects decrease at higher discharges; and (5) there is a relationship between the linear combination of bed and sediment roughness and local flow velocity. These results demonstrate the control that bedrock topography exerts over both local and reach-scale flow conditions, but spatially distributed hydraulic data from bedrock-alluvial channels with different topographies are needed to generalize these findings.

Neutralization of an ion beam from the end-Hall ion source by a plasma electron source based on a discharge in crossed E × H fields

NASA Astrophysics Data System (ADS)

Dostanko, A. P.; Golosov, D. A.

2009-10-01

The possibility of using a plasma electron source (PES) with a discharge in crossed E × H field for compensating the ion beam from an end-Hall ion source (EHIS) is analyzed. The PES used as a neutralizer is mounted in the immediate vicinity of the EHIS ion generation and acceleration region at 90° to the source axis. The behavior of the discharge and emission parameters of the EHIS is determined for operation with a filament neutralizer and a plasma electron source. It is found that the maximal discharge current from the ion source attains a value of 3.8 A for operation with a PES and 4 A for operation with a filament compensator. It is established that the maximal discharge current for the ion source strongly depends on the working gas flow rate for low flow rates (up to 10 ml/min) in the EHIS; for higher flow rates, the maximum discharge current in the EHIS depends only on the emissivity of the PES. Analysis of the emission parameters of EHISs with filament and plasma neutralizers shows that the ion beam current and the ion current density distribution profile are independent of the type of the electron source and the ion current density can be as high as 0.2 mA/cm2 at a distance of 25 cm from the EHIS anode. The balance of currents in the ion source-electron source system is considered on the basis of analysis of operation of EHISs with various sources of electrons. It is concluded that the neutralization current required for operation of an ion source in the discharge compensation mode must be equal to or larger than the discharge current of the ion source. The use of PES for compensating the ion beam from an end-Hall ion source proved to be effective in processes of ion-assisted deposition of thin films using reactive gases like O2 or N2. The application of the PES technique makes it possible to increase the lifetime of the ion-assisted deposition system by an order of magnitude (the lifetime with a Ti cathode is at least 60 h and is limited by the replacement life of the deposited cathode insertion).

Computation of peak discharge at culverts

USGS Publications Warehouse

Carter, Rolland William

1957-01-01

Methods for computing peak flood flow through culverts on the basis of a field survey of highwater marks and culvert geometry are presented. These methods are derived from investigations of culvert flow as reported in the literature and on extensive laboratory studies of culvert flow. For convenience in computation, culvert flow has been classified into six types, according to the location of the control section and the relative heights of the head-water and tail-water levels. The type of flow which occurred at any site can be determined from the field data and the criteria given in this report. A discharge equation has been developed for each flow type by combining the energy and continuity equations for the distance between an approach section upstream from the culvert and a terminal section within the culvert barrel. The discharge coefficient applicable to each flow type is listed for the more common entrance geometries. Procedures for computing peak discharge through culverts are outlined in detail for each of the six flow types.

Quantity and quality of ground-water discharge to the South Platte River, Denver to Fort Lupton, Colorado, August 1992 through July 1993

USGS Publications Warehouse

McMahon, P.B.; Lull, K.J.; Dennehy, K.F.; Collins, J.A.

1995-01-01

Water-quality studies conducted by the Metro Wastewater Reclamation District have indicated that during low flow in segments of the South Platte River between Denver and Fort Lupton, concentrations of dissolved oxygen are less than minimum concen- trations set by the State of Colorado. Low dissolved-oxygen concentrations are observed in two reaches of the river-they are about 3.3 to 6.4 miles and 17 to 25 miles downstream from the Metro Waste- water Reclamation District effluent outfalls. Concentrations of dissolved oxygen recover between these two reaches. Studies conducted by the U.S. Geological Survey have indicated that ground-water discharge to the river may contribute to these low dissolved-oxygen concentrations. As a result, an assessment was made of the quantity and quality of ground-water discharge to the South Platte River from Denver to Fort Lupton. Measurements of surface- water and ground-water discharge and collections of surface water and ground water for water-quality analyses were made from August 1992 through January 1993 and in May and July 1993. The quantity of ground-water discharge to the South Platte River was determined indirectly by mass balance of surface-water inflows and outflows and directly by instantaneous measurements of ground-water discharge across the sediment/water interface in the river channel. The quality of surface water and ground water was determined by sampling and analysis of water from the river and monitoring wells screened in the alluvial aquifer adjacent to the river and by sampling and analysis of water from piezometers screened in sediments underlying the river channel. The ground-water flow system was subdivided into a large-area and a small-area flow system. The precise boundaries of the two flow systems are not known. However, the large-area flow system is considered to incorporate all alluvial sediments in hydrologic connection with the South Platte River. The small- area flow system is considered to incorporate the alluvial aquifer in the vicinity of the river. Flow-path lengths in the large-area flow system were considered to be on the order of hundreds of feet to more than a mile, whereas in the small-area flow system, they were considered to be on the order of feet to hundreds of feet. Mass-balance estimates of incremental ground-water discharge from the large- area flow system ranged from -27 to 17 cubic feet per second per mile in three reaches of the river; the median rate was 4.6 cubic feet per second per mile. The median percentage of surface-water discharge derived from ground-water discharge in the river reaches studied was 13 percent. Instantaneous measurements of ground-water discharge from the small-area flow system ranged from -1,360 to 1,000 cubic feet per second per mile, with a median value of -5.8 cubic feet per second per mile. Hourly measurements of discharge from the small-area flow system indicated that the high rates of discharge were transient and may have been caused by daily fluctuations in river stage due to changing effluent-discharge rates from the Metro Wastewater Reclamation District treatment plant. Higher river stages caused surface water to infiltrate bed sediments underlying the river channel, and lower river stages allowed ground water to discharge into the river. Although stage changes apparently cycled large quantities of water in and out of the small- area flow system, the process probably provided no net gain or loss of water to the river. In general, mass balance and instantaneous measurements of ground-water discharge indicated that the ground- water flow system in the vicinity of the river consisted of a large-area flow system that provided a net addition of water to the river and a small- area flow system that cycled water in and out of the riverbed sediments, but provided no net addition of water to the river. The small-area flow system was superimposed on the large-area flow system. The median values of pH and dissolved oxygen

Hydrodynamics and morphodynamics of a mobile bed confluence under equilibrium conditions for different values of the flow discharge ratio

NASA Astrophysics Data System (ADS)

Birjukova Canelas, Olga; Lage Ferreira, Rui Miguel; Heleno Cardoso, António

2017-04-01

Under steady water and sediment feeding in laboratory conditions, sediment fluxes tend to reach a steady state and bed morphology tends to equilibrium. This laboratory study states two objectives: i) to provide a detailed three-dimensional characterization of the flow field at a movable bed confluence and ii) to contribute to the characterization of the effect of the flow discharge ratio (Qr = Qt/Qm, Qt - tributary flow discharge and Qm - main channel flow discharge) on the flow field. While the junction angle between the main channel and the tributary as well as the sediment discharge ratio were kept constant, two scenarios corresponding to two different flow discharge ratios with dominant main channel flow discharge (Qm > Qt) were analyzed. Prior to the flow velocity measurements, both channels were fed with water and sand mixtures and tests were run until the equilibrium condition was reached, i.e. until the moment where the difference between the total supplied sand discharge and the total outgoing sand discharge was smaller than ± 5%. During the experiments, bed topography was systematically recorded. Then, the flow was stopped, the water was slowly drained and the bed was carefully fixed with a cement and vernix coat and allowed to dry to guarantee that it remained stable from there on, while the clear water (free of sand) discharges were fed again to the fixed bed converging channels. A 3D side looking Acoustic Doppler Velocimeter (ADV), installed on a remotely controlled and precisely positioned (± 0.1 mm) robotic arm, was used to measure the instantaneous velocities at a very dense mesh. Once the velocities measured and recorded, the water surface levels were surveyed. For the case with more dominant tributary flow (Qr = 0.17), as expected, the scour hole formed at the tributary mouth is much deeper and larger and extends towards the outer bank of the post-confluence channel, as well as upstream the junction corner. The avalanche slopes are, consequently, steeper. On the other hand, for the case with a weaker tributary flow (Qr = 0.08), no erosion is observed immediately upstream the junction. Moreover, the bank-attached sediment bar downstream the junction is considerably more developed in longitudinal and vertical directions. In both scenarios, a strong horizontal vortical structure was observed immediately downstream the junction. More detailed analysis of the origin and the characteristics of these and other flow patterns is still under investigation. Acknowledgements This research as partially supported by Portuguese and European funds, within programs COMPETE2020 and PORL-FEDER, through project PTDC/ECM-HID/6387/2014 granted by the National Foundation for Science and Technology (FCT).

Plasma-enhanced mixing and flameholding in supersonic flow

PubMed Central

Firsov, Alexander; Savelkin, Konstantin V.; Yarantsev, Dmitry A.; Leonov, Sergey B.

2015-01-01

The results of experimental study of plasma-based mixing, ignition and flameholding in a supersonic model combustor are presented in the paper. The model combustor has a length of 600 mm and cross section of 72 mm width and 60 mm height. The fuel is directly injected into supersonic airflow (Mach number M=2, static pressure Pst=160–250 Torr) through wall orifices. Two series of tests are focused on flameholding and mixing correspondingly. In the first series, the near-surface quasi-DC electrical discharge is generated by flush-mounted electrodes at electrical power deposition of Wpl=3–24 kW. The scope includes parametric study of ignition and flame front dynamics, and comparison of three schemes of plasma generation: the first and the second layouts examine the location of plasma generators upstream and downstream from the fuel injectors. The third pattern follows a novel approach of combined mixing/ignition technique, where the electrical discharge distributes along the fuel jet. The last pattern demonstrates a significant advantage in terms of flameholding limit. In the second series of tests, a long discharge of submicrosecond duration is generated across the flow and along the fuel jet. A gasdynamic instability of thermal cavity developed after a deposition of high-power density in a thin plasma filament promotes the air–fuel mixing. The technique studied in this work has weighty potential for high-speed combustion applications, including cold start/restart of scramjet engines and support of transition regime in dual-mode scramjet and at off-design operation. PMID:26170434

Advances in the regionalization approach: geostatistical techniques for estimating flood quantiles

NASA Astrophysics Data System (ADS)

Chiarello, Valentina; Caporali, Enrica; Matthies, Hermann G.

2015-04-01

The knowledge of peak flow discharges and associated floods is of primary importance in engineering practice for planning of water resources and risk assessment. Streamflow characteristics are usually estimated starting from measurements of river discharges at stream gauging stations. However, the lack of observations at site of interest as well as the measurement inaccuracies, bring inevitably to the necessity of developing predictive models. Regional analysis is a classical approach to estimate river flow characteristics at sites where little or no data exists. Specific techniques are needed to regionalize the hydrological variables over the considered area. Top-kriging or topological kriging, is a kriging interpolation procedure that takes into account the geometric organization and structure of hydrographic network, the catchment area and the nested nature of catchments. The continuous processes in space defined for the point variables are represented by a variogram. In Top-kriging, the measurements are not point values but are defined over a non-zero catchment area. Top-kriging is applied here over the geographical space of Tuscany Region, in Central Italy. The analysis is carried out on the discharge data of 57 consistent runoff gauges, recorded from 1923 to 2014. Top-kriging give also an estimation of the prediction uncertainty in addition to the prediction itself. The results are validated using a cross-validation procedure implemented in the package rtop of the open source statistical environment R The results are compared through different error measurement methods. Top-kriging seems to perform better in nested catchments and larger scale catchments but no for headwater or where there is a high variability for neighbouring catchments.

Identifying three-dimensional nested groundwater flow systems in a Tóthian basin

NASA Astrophysics Data System (ADS)

Wang, Xu-Sheng; Wan, Li; Jiang, Xiao-Wei; Li, Hailong; Zhou, Yangxiao; Wang, Junzhi; Ji, Xiaohui

2017-10-01

Nested groundwater flow systems have been revealed in Tóth's theory as the structural property of basin-scale groundwater circulation but were only well known with two-dimensional (2D) profile models. The method of searching special streamlines across stagnation points for partitioning flow systems, which has been successfully applied in the 2D models, has never been implemented for three-dimensional (3D) Tóthian basins because of the difficulty in solving the dual stream functions. Alternatively, a new method is developed to investigate 3D nested groundwater flow systems without determination of stagnation points. Connective indices are defined to quantify the connection between individual recharge and discharge zones along streamlines. Groundwater circulation cells (GWCCs) are identified according to the distribution of the connective indices and then grouped into local, intermediate and regional flow systems. This method requires existing solution of the flow velocity vector and is implemented via particle tracking technique. It is applied in a hypothetical 3D Tóthian basin with an analytical solution of the flow field and in a real-world basin with a numerical modeling approach. Different spatial patterns of flow systems compared to 2D profile models are found. The outcrops boundaries of GWCCs on water table may significantly deviate from and are not parallel to the nearby water table divides. Topological network is proposed to represent the linked recharge-discharge zones through closed and open GWCCs. Sensitivity analysis indicates that the development of GWCCs depends on the basin geometry, hydraulic parameters and water table shape.

Robust, non-invasive methods for metering groundwater well extraction in remote environments

NASA Astrophysics Data System (ADS)

Bulovic, Nevenka; Keir, Greg; McIntyre, Neil

2017-04-01

Quantifying the rate of extraction from groundwater wells can be essential for regional scale groundwater management and impact assessment. This is especially the case in regions heavily dependent on groundwater such as the semi-arid Surat and Bowen Basins in Queensland, Australia. Of the 30 000+ groundwater wells in this area, the majority of which are used for stock watering and domestic purposes, almost none have flow metering devices installed. As part of a research project to estimate regional groundwater extraction, we have undertaken a small scale flow metering program on a selected set of wells. Conventional in-line flow meters were unsuitable for our project, as both non-invasiveness and adaptability / suitability to a variety of discharge pipe characteristics was critical. We describe the use of two metering technologies not widely used in groundwater applications, non-invasive, clamp-on ultrasonic transit time flow meters and tipping bucket flow meters, as semi-permanent installations on discharge pipes of various artesian and sub-artesian groundwater wells. We present examples of detailed extraction rate time-series, which are of particular value in developing predictive models of water well extraction in data limited areas where water use dynamics and drivers are poorly understood. We conclude by discussing future project trajectories, which include expansion of the monitoring network through development of novel metering techniques and telemetry across large areas of poor connectivity.

Expiratory flow limitation relates to symptoms during COPD exacerbations requiring hospital admission.

PubMed

Jetmalani, Kanika; Timmins, Sophie; Brown, Nathan J; Diba, Chantale; Berend, Norbert; Salome, Cheryl M; Wen, Fu-Qiang; Chen, Peng; King, Gregory G; Farah, Claude S

2015-01-01

Expiratory flow limitation (EFL) is seen in some patients presenting with a COPD exacerbation; however, it is unclear how EFL relates to the clinical features of the exacerbation. We hypothesized that EFL when present contributes to symptoms and duration of recovery during a COPD exacerbation. Our aim was to compare changes in EFL with symptoms in subjects with and without flow-limited breathing admitted for a COPD exacerbation. A total of 29 subjects with COPD were recruited within 48 hours of admission to West China Hospital for an acute exacerbation. Daily measurements of post-bronchodilator spirometry, resistance, and reactance using the forced oscillation technique and symptom (Borg) scores until discharge were made. Flow-limited breathing was defined as the difference between inspiratory and expiratory respiratory system reactance (EFL index) greater than 2.8 cmH2O·s·L(-1). The physiological predictors of symptoms during recovery were determined by mixed-effect analysis. Nine subjects (31%) had flow-limited breathing on admission despite similar spirometry compared to subjects without flow-limited breathing. Spirometry and resistance measures did not change between enrolment and discharge. EFL index values improved in subjects with flow-limited breathing on admission, with resolution in four patients. In subjects with flow-limited breathing on admission, symptoms were related to inspiratory resistance and EFL index values. In subjects without flow-limited breathing, symptoms related to forced expiratory volume in 1 second/forced vital capacity. In the whole cohort, EFL index values at admission was related to duration of stay (Rs=0.4, P=0.03). The presence of flow-limited breathing as well as abnormal respiratory system mechanics contribute independently to symptoms during COPD exacerbations.

Statistical summaries of selected Iowa streamflow data through September 2013

USGS Publications Warehouse

Eash, David A.; O'Shea, Padraic S.; Weber, Jared R.; Nguyen, Kevin T.; Montgomery, Nicholas L.; Simonson, Adrian J.

2016-01-04

Statistical summaries of streamflow data collected at 184 streamgages in Iowa are presented in this report. All streamgages included for analysis have at least 10 years of continuous record collected before or through September 2013. This report is an update to two previously published reports that presented statistical summaries of selected Iowa streamflow data through September 1988 and September 1996. The statistical summaries include (1) monthly and annual flow durations, (2) annual exceedance probabilities of instantaneous peak discharges (flood frequencies), (3) annual exceedance probabilities of high discharges, and (4) annual nonexceedance probabilities of low discharges and seasonal low discharges. Also presented for each streamgage are graphs of the annual mean discharges, mean annual mean discharges, 50-percent annual flow-duration discharges (median flows), harmonic mean flows, mean daily mean discharges, and flow-duration curves. Two sets of statistical summaries are presented for each streamgage, which include (1) long-term statistics for the entire period of streamflow record and (2) recent-term statistics for or during the 30-year period of record from 1984 to 2013. The recent-term statistics are only calculated for streamgages with streamflow records pre-dating the 1984 water year and with at least 10 years of record during 1984–2013. The streamflow statistics in this report are not adjusted for the effects of water use; although some of this water is used consumptively, most of it is returned to the streams.

Gas turbine engine exhaust diffuser including circumferential vane

DOEpatents

Orosa, John A.; Matys, Pawel

2015-05-19

A flow passage defined between an inner and an outer boundary for guiding a fluid flow in an axial direction. A flow control vane is supported at a radial location between the inner and outer boundaries. A fluid discharge opening is provided for discharging a flow of the compressed fluid from a trailing edge of the vane, and a fluid control surface is provided adjacent to the fluid discharge opening and extends in the axial direction at the trailing edge of the vane. The fluid control surface has a curved trailing edge forming a Coanda surface. The fluid discharge opening is selectively provided with a compressed fluid to produce a Coanda effect along the control surface. The Coanda effect has a component in the radial direction effecting a turning of the fluid flow in the flow path radially inward or outward toward one of the inner and outer boundaries.

14C age reassessment of groundwater from the discharge zone due to cross-flow mixing in the deep confined aquifer

NASA Astrophysics Data System (ADS)

Mao, Xumei; Wang, Hua; Feng, Liang

2018-05-01

In a groundwater flow system, the age of groundwater should gradually increase from the recharge zone to the discharge zone within the same streamline. However, it is occasionally observed that the groundwater age becomes younger in the discharge zone in the piedmont alluvial plain, and the oldest age often appears in the middle of the plain. A new set of groundwater chemistry and isotopes was employed to reassess the groundwater 14C ages from the discharge zone in the North China Plain (NCP). Carbonate precipitation, organic matter oxidation and cross-flow mixing in the groundwater from the recharge zone to the discharge zone are recognized according to the corresponding changes of HCO3- (or DIC) and δ13C in the same streamline of the third aquifer of the NCP. The effects of carbonate precipitation and organic matter oxidation are calibrated with a 13C mixing model and DIC correction, but these corrected 14C ages seem unreasonable because they grow younger from the middle plain to the discharge zone in the NCP. The relationship of Cl- content and the recharge distance is used to estimate the expected Cl- content in the discharge zone, and ln(a14C)/Cl is proposed to correct the a14C in groundwater for the effect of cross-flow mixing. The 14C ages were reassessed with the corrected a14C due to the cross-flow mixing varying from 1.25 to 30.58 ka, and the groundwater becomes older gradually from the recharge zone to the discharge zone. The results suggest that the reassessed 14C ages are more reasonable for the groundwater from the discharge zone due to cross-flow mixing.

Singlet delta oxygen production in a 2D micro-discharge array in air: effect of gas residence time and discharge power

NASA Astrophysics Data System (ADS)

Nayak, Gaurav; Santos Sousa, João; Bruggeman, Peter J.

2017-03-01

The production of singlet delta oxygen (O2(a 1Δg)) is of growing interest for many applications. We report on the measurement of O2(a 1Δg) and ozone (O3) in a room temperature atmospheric pressure discharge in dry air. The plasma source is a 2D array of micro-discharges generated by an alternating current voltage at 20 kHz. The study focuses on the effect of gas flow through the discharge. The maximum investigated flow rate allows reducing the gas residence time in the discharge zone to half the discharge period. Results indicate that the residence time and discharge power have a major effect on the O2(a 1Δg) production. Different O2(a 1Δg) density dependencies on power are observed for different flow rates. Effects of collisional quenching on the as-produced and measured O2(a 1Δg) densities are discussed. The flow rate also allows for control of the O2(a 1Δg) to O3 density ratio in the effluent from 0.7 to conditions of pure O3.

An Evaluation of Selected Extraordinary Floods in the United States Reported by the U.S. Geological Survey and Implications for Future Advancement of Flood Science

USGS Publications Warehouse

Costa, John E.; Jarrett, Robert D.

2008-01-01

Thirty flood peak discharges determine the envelope curve of maximum floods documented in the United States by the U.S. Geological Survey. These floods occurred from 1927 to 1978 and are extraordinary not just in their magnitude, but in their hydraulic and geomorphic characteristics. The reliability of the computed discharge of these extraordinary floods was reviewed and evaluated using current (2007) best practices. Of the 30 flood peak discharges investigated, only 7 were measured at daily streamflow-gaging stations that existed when the flood occurred, and 23 were measured at miscellaneous (ungaged) sites. Methods used to measure these 30 extraordinary flood peak discharges consisted of 21 slope-area measurements, 2 direct current-meter measurements, 1 culvert measurement, 1 rating-curve extension, and 1 interpolation and rating-curve extension. The remaining four peak discharges were measured using combinations of culvert, slope-area, flow-over-road, and contracted-opening measurements. The method of peak discharge determination for one flood is unknown. Changes to peak discharge or rating are recommended for 20 of the 30 flood peak discharges that were evaluated. Nine floods retained published peak discharges, but their ratings were downgraded. For two floods, both peak discharge and rating were corrected and revised. Peak discharges for five floods that are subject to significant uncertainty due to complex field and hydraulic conditions, were re-rated as estimates. This study resulted in 5 of the 30 peak discharges having revised values greater than about 10 percent different from the original published values. Peak discharges were smaller for three floods (North Fork Hubbard Creek, Texas; El Rancho Arroyo, New Mexico; South Fork Wailua River, Hawaii), and two peak discharges were revised upward (Lahontan Reservoir tributary, Nevada; Bronco Creek, Arizona). Two peak discharges were indeterminate because they were concluded to have been debris flows with peak discharges that were estimated by an inappropriate method (slope-area) (Big Creek near Waynesville, North Carolina; Day Creek near Etiwanda, California). Original field notes and records could not be found for three of the floods, however, some data (copies of original materials, records of reviews) were available for two of these floods. A rating was assigned to each of seven peak discharges that had no rating. Errors identified in the reviews include misidentified flow processes, incorrect drainage areas for very small basins, incorrect latitude and longitude, improper field methods, arithmetic mistakes in hand calculations, omission of measured high flows when developing rating curves, and typographical errors. Common problems include use of two-section slope-area measurements, poor site selection, uncertainties in Manning's n-values, inadequate review, lost data files, and insufficient and inadequately described high-water marks. These floods also highlight the extreme difficulty in making indirect discharge measurements following extraordinary floods. Significantly, none of the indirect measurements are rated better than fair, which indicates the need to improve methodology to estimate peak discharge. Highly unsteady flow and resulting transient hydraulic phenomena, two-dimensional flow patterns, debris flows at streamflow-gaging stations, and the possibility of disconnected flow surfaces are examples of unresolved problems not well handled by current indirect discharge methodology. On the basis of a comprehensive review of 50,000 annual peak discharges and miscellaneous floods in California, problems with individual flood peak discharges would be expected to require a revision of discharge or rating curves at a rate no greater than about 0.10 percent of all floods. Many extraordinary floods create complex flow patterns and processes that cannot be adequately documented with quasi-steady, uniform one-dimensional analyses. These floods are most accura

Unsteady streamflow simulation using a linear implicit finite-difference model

USGS Publications Warehouse

Land, Larry F.

1978-01-01

A computer program for simulating one-dimensional subcritical, gradually varied, unsteady flow in a stream has been developed and documented. Given upstream and downstream boundary conditions and channel geometry data, roughness coefficients, stage, and discharge can be calculated anywhere within the reach as a function of time. The program uses a linear implicit finite-difference technique that discritizes the partial differential equations. Then it arranges the coefficients of the continuity and momentum equations into a pentadiagonal matrix for solution. Because it is a reasonable compromise between computational accuracy, speed and ease of use,the technique is one of the most commonly used. The upstream boundary condition is a depth hydrograph. However, options also allow the boundary condition to be discharge or water-surface elevation. The downstream boundary condition is a depth which may be constant, self-setting, or unsteady. The reach may be divided into uneven increments and the cross sections may be nonprismatic and may vary from one to the other. Tributary and lateral inflow may enter the reach. The digital model will simulate such common problems as (1) flood waves, (2) releases from dams, and (3) channels where storage is a consideration. It may also supply the needed flow information for mass-transport simulation. (Woodard-USGS)

Glow Discharge Plasma Demonstrated for Separation Control in the Low-Pressure Turbine

NASA Technical Reports Server (NTRS)

Ashpis, David e.; Hultgren, Lennart S.

2004-01-01

Flow separation in the low-pressure turbine (LPT) is a major barrier that limits further improvements of aerodynamic designs of turbine airfoils. The separation is responsible for performance degradation, and it prevents the design of highly loaded airfoils. The separation can be delayed, reduced, or eliminated completely if flow control techniques are used. Successful flow control technology will enable breakthrough improvements in gas turbine performance and design. The focus of this research project was the development and experimental demonstration of active separation control using glow discharge plasma (GDP) actuators in flow conditions simulating the LPT. The separation delay was shown to be successful, laying the foundation for further development of the technologies to practical application in the LPT. In a fluid mechanics context, the term "flow control" means a technology by which a very small input results in a very large effect on the flow. In this project, the interest is to eliminate or delay flow separation on LPT airfoils by using an active flow control approach, in which disturbances are dynamically inserted into the flow, they interact with the flow, and they delay separation. The disturbances can be inserted using a localized, externally powered, actuating device, examples are acoustic, pneumatic, or mechanical devices that generate vibrations, flow oscillations, or pulses. A variety of flow control devices have been demonstrated in recent years in the context of the external aerodynamics of aircraft wings and airframes, where the incoming flow is quiescent or of a very low turbulence level. However, the flow conditions in the LPT are significantly different because there are high levels of disturbances in the incoming flow that are characterized by high free-stream turbulence intensity. In addition, the Reynolds number, which characterizes the viscous forces in the flow and is related to the flow speed, is very low in the LPT passages.

Derivation of Lake Areas and Elevations for the Mackenzie Basin Using Satellite Remote Sensing

NASA Technical Reports Server (NTRS)

Birkett, Charon; Kite, Geoff

1997-01-01

Modelling hydrological processes in large watersheds flowing to the Arctic ocean is one step towards larger-scale modelling of the global water and energy cycles. Models of the Mackenzie River Basin (Northern Canada) are currently available but omit explicit routing of river flows through the three main lakes - Athabasca, Great Slave Lake and Great Bear Lake (Kite et al, 1994). These lakes occupy an area of 65,000 sq km but little gauge information is available. The levels of the lakes are only measured at a few points on the circumferences and river flows are only measured downstream. The hydraulic relationships between level/discharge and level/area/volume are uncertain. It has been previously shown that satellite remote sensing can be utilised in providing measurements of both lake surface area using imaging techniques and lake level using radar altimetry (Birkett, 1994). Here, we explore the application of these techniques to derive the lake levels and areas for the Mackenzie Basin lakes.

Discharge estimation in arid areas with the help of optical satellite data

NASA Astrophysics Data System (ADS)

Mett, M.; Aufleger, M.

2009-04-01

The MENA region is facing severe water scarcity. Overexploitation of groundwater resources leads to an ongoing drawdown of the water tables, salinisation and desertification of vast areas. To make matters worse enormous birth-rates, economic growth and refugees from conflict areas let the need for water explode. In the context of climate change this situation will even worsen and armed conflicts are within the bounds of possibility. To ease water scarcity many innovative techniques like artificial groundwater recharge are being developed or already state of the art. But missing hydrological information (for instance discharge data) often prevents design and efficient operation of such measures. Especially in poor countries hydrological measuring devices like gage stations are often missing, in a bad status or professionals of the water sector are absent. This leads to the paradox situation that in many arid regions water resources are indeed available but they cannot be utilised because they are not known. Nowadays different approaches are being designed to obtain hydrological information from perennial river systems with the help of satellite techniques. Mostly they are based on hydraulic parameters like river dimensions, roughness and water levels which can be derived from satellite data. By using conventional flow formulas and additional field investigations the discharge can be estimated. Another methodology derived information about maximum flow depth and flow width from optical sensors of high resolution to calculate discharge of the rivers whilst the flood. Attempts to derive discharge information from structural components of the river and fluviomorphologic changes due to changing flow regimes are in the focus of recent research. One attempt used Synthetic Aperture Radar (SAR) data to estimate discharge in braided river systems. Other attempts used airborne SAR imagery to obtain information about sinuosity and total river width of perennial braided river systems which were related to specific discharges. Such approaches cannot be applied in arid areas with ephemeral discharges. In this groundbreaking proposal, discharge data for arid riverine landscapes (dry wadi systems) will be derived from remotely sensed structural patterns and fluvio-morphologic changes. The main idea of the research work is as follows: In arid areas seldom precipitation events lead to flash floods which may significantly alter the geomorphology of a wadi river system. This is due to the mainly sparse vegetation cover in arid areas which enables mobilization and transport of large amounts of bed material whilst flood events. For example maximum river width of single channels, total river width of braided river networks and sinuosity of river beds change during a floods. Also river branches can be dislocated. These morphologic changes can be observed and judged from space. There is a correlation between intensity and duration of a flood and the resulting changes in riverbed structure. The kind of changes gives evidence about stream power and flow behaviour of the observed river systems. Satellite images from date A are compared with data from date B regarding morphologic changes and specific river patterns. Satellite data of different spatial and spectral solutions will be used from environmental and commercial satellites such as Landsat, SPOT, ASTER, IKONOS and so on. If a change in river morphology can be observed it was due to a flood event. Multitemporal analysis (change detection) with the help of digital image processing now enables to observe the nature and intensity of morphological changes. Structural patterns are extracted from the images and compared to field observations from the two exemplarily test sites in Jordan and Oman. Comprehensive field work was already performed to summarise detailed fluvial structures and to gather hydrologic data for each test site. The whole river networks will be visualised and extracted from the images with the help of spectral classification for further investigation such as fractal analysis of the river patterns. The "Morphologic Activity Index (MAI)" combines the above acquired information to one specific parameter for the examined test site. MAI contains information about general river patterns, river energy and the behaviour of the river system. MAI will be necessary for calibrating the calculated river discharges with discharge measurements which were taken on ground whilst the flood. With the available satellite images it will be possible to perform discharge estimation for duration of at least two or three decades. Statistical approaches and time series analysis will allow deriving information about the general flow behaviour (e.g. repeat interval of discharge and probable maximum flood) which are essential for planning infrastructural measures. First results from the test sites in Jordan and Oman showed the applicability of satellite data analysis regarding morphologic changes. The goal of the presented research work is to develop a fast and economic methodology to derive spatial distributed discharge information for large and inaccessible arid areas.

Numerical modeling of a glow discharge through a supersonic bow shock in air

NASA Astrophysics Data System (ADS)

Rassou, S.; Packan, D.; Elias, P.-Q.; Tholin, F.; Chemartin, L.; Labaune, J.

2017-03-01

The interaction between a glow discharge and the bow shock of a Mach 3 air flow around a truncated conical model with a central spike is modeled, and comparison is made with prior experimental results. The KRONOS workflow for plasma modeling in flow fields, which has recently been developed at ONERA, was used for the modeling. Based on the quasi-neutral approximation, it couples hypersonic and reactive flow fields with electron chemistry, including the effect of non-Maxwellian electron energy distribution function. The model used for the discharge involves 12 species and 82 reactions, including ionization, electronic and vibrational excitation, and attachment. The simulations reproduce the main features of the discharge observed experimentally well, in particular, the very recognizable topology of the discharge. It was found from the simulations that behind the bow shock, in the afterglow, the negative ion flow ensures the electrical conduction and the establishment of the glow discharge. The influence of kinetic rates on the voltage-current characteristics is discussed.

Stream gage descriptions and streamflow statistics for sites in the Tigris River and Euphrates River Basins, Iraq

USGS Publications Warehouse

Saleh, Dina K.

2010-01-01

Statistical summaries of streamflow data for all long-term streamflow-gaging stations in the Tigris River and Euphrates River Basins in Iraq are presented in this report. The summaries for each streamflow-gaging station include (1) a station description, (2) a graph showing annual mean discharge for the period of record, (3) a table of extremes and statistics for monthly and annual mean discharge, (4) a graph showing monthly maximum, minimum, and mean discharge, (5) a table of monthly and annual mean discharges for the period of record, (6) a graph showing annual flow duration, (7) a table of monthly and annual flow duration, (8) a table of high-flow frequency data (maximum mean discharge for 3-, 7-, 15-, and 30-day periods for selected exceedance probabilities), and (9) a table of low-flow frequency data (minimum mean discharge for 3-, 7-, 15-, 30-, 60-, 90-, and 183-day periods for selected non-exceedance probabilities).

Streamflow characteristics for selected stations in and near the Grand Mesa, Uncompahgre, and Gunnison National Forests, southwestern Colorado

USGS Publications Warehouse

Kuhn, Gerhard

2002-01-01

The U.S Geological Survey, in cooperation with the Grand Mesa, Uncompahgre, and Gunnison National Forests, began a study in 2000 to develop selected streamflow characteristics for 60 streamflow-gaging stations in and near the Grand Mesa, Uncompahgre, and Gunnison National Forests. The study area is located in southwestern Colorado within the Gunnison River, Dolores River, and Plateau Creek Basins, which are tributaries of the Colorado River. In addition to presenting the compiled daily, monthly, and annual discharge data for the 60 stations, the report presents tabular and graphical results for the following computed streamflow characteristics: (1) Instantaneous peak-flow frequency; (2) flow duration for daily mean discharges on an annual (water year) basis and on a monthly basis, and flow duration for the annual and monthly mean discharges; (3) low-flow and high-flow frequency of daily mean discharges for periods of 1, 3, 7, 15, 30, 60, 120, and 183 consecutive days; and (4) annual and monthly mean and median discharges for each year and month of record, and frequency of the annual and monthly mean and median discharges. All discharge data and results from the streamflow-characteristics analyses are presented in Microsoft Excel workbooks on the enclosed CD-ROM.

Leading edge vortex control on a delta wing with dielectric barrier discharge plasma actuators

NASA Astrophysics Data System (ADS)

Shen, Lu; Wen, Chih-yung

2017-06-01

This paper presents an experimental investigation of the application of dielectric barrier discharge (DBD) plasma actuators on a slender delta wing to control the leading edge vortices (LEVs). The experiments are conducted in a wind tunnel with a Reynolds number of 50 000 based on the chord length. The smoke flow visualization reveals that the DBD plasma actuators at the leading edges significantly modify the vortical flow structure over the delta wing. It is noted that symmetric control at both semi-spans and asymmetric control at a single semi-span leads to opposite effects on the local LEVs. Particle image velocimetry (PIV) indicates that the shear layer is deformed by the actuators. Therefore, both the strength and the shape of the LEV cores are deeply affected. The six-component force measurement shows that the DBD plasma actuators have a limited effect on lift and drag while inducing relatively large moments. This suggests that the DBD plasma actuator is a promising technique for delta wing maneuvering.

Determination of base-flow characteristics at selected streamflow-gaging stations on the Mad River, Ohio

USGS Publications Warehouse

Koltun, G.F.

1995-01-01

This report describes the results of a study to estimate characteristics of base flow and sustained ground-water discharge at five streamflow-gaging stations on the Mad River in Ohio. The five streamflow-gaging stations are located at Zanesfield, near Urbana, at St. Paris Pike (at Eagle City), near Springfield, and near Dayton. The median of the annual-mean base flows, determined by means of hydrograph separation, ranged from 0.64 (ft3/s)/mi2 (cubic feet per second per square mile) at Zanesfield to 0.74 (ft3/s)/mi2 at St. Paris Pike. The median percentage of annual total streamflow attributed to base flow ranged from 61.8 percent at Zanesfield to 76.1 percent near Urbana. Estimates of an upper limit (or threshold) at which base flows can be considered to be composed predominately of sustained ground-water discharge were made by constructing and analyzing base- flow-duration curves. The sustained ground-water discharges (base flows less than or equal to the estimated sustained ground-water-discharge thresholds) are assumed to originate from ground-water- flow systems that are minimally affected by seasonal climatic changes. The median sustained ground- water discharge ranged from 0.11 (ft3/s)/mi2 at Zanesfield to 0.26 (ft3/s)/mi2 at St. Paris Pike (at Eagle City) and near Springfield. The median sustained ground-water discharge, expressed as a percentage of the median annual-mean base flow, ranged from 17.2 percent at Zanesfield to 38.6 percent near Springfield.

Estimates of natural streamflow at two streamgages on the Esopus Creek, New York, water years 1932 to 2012

USGS Publications Warehouse

Burns, Douglas A.; Gazoorian, Christopher L.

2015-01-01

Natural discharge at the Mount Marion streamgage was estimated by summing the natural discharge estimated for the Coldbrook streamgage and the discharge estimated for the intervening basin area through application of the New York Streamflow Estimation Tool, recently developed for estimating unaltered streamflow at ungaged locations in the State. Estimates of natural daily discharge at the Mount Marion streamgage were about three times greater than gaged daily discharge throughout the moderate- to low-flow range from October 1, 1970, to September 30, 2012, the period of record for full water years at this streamgage. The relative difference between the two discharge time series declined as flow increased beyond the moderate range, but gaged daily discharge was still 25 to 43 percent less than estimated natural daily discharge for the high-flow metrics calculated in this analysis, and the mean relative difference was 43 percent for the annual 1-day maximum discharge. Overall, these estimates of natural discharge reflect the absence of effects of the Shandaken Tunnel and Ashokan Reservoir on flows in the Esopus Creek over broad time frames. However, caution is warranted if one is attempting to apply the natural estimates at short time scales because the regression prediction intervals indicate that uncertainty at a daily time step ranges from about 40 to 80 percent.

Assessing dry weather flow contribution in TSS and COD storm events loads in combined sewer systems.

PubMed

Métadier, M; Bertrand-Krajewski, J L

2011-01-01

Continuous high resolution long term turbidity measurements along with continuous discharge measurements are now recognised as an appropriate technique for the estimation of in sewer total suspended solids (TSS) and Chemical Oxygen Demand (COD) loads during storm events. In the combined system of the Ecully urban catchment (Lyon, France), this technique is implemented since 2003, with more than 200 storm events monitored. This paper presents a method for the estimation of the dry weather (DW) contribution to measured total TSS and COD event loads with special attention devoted to uncertainties assessment. The method accounts for the dynamics of both discharge and turbidity time series at two minutes time step. The study is based on 180 DW days monitored in 2007-2008. Three distinct classes of DW days were evidenced. Variability analysis and quantification showed that no seasonal effect and no trend over the year were detectable. The law of propagation of uncertainties is applicable for uncertainties estimation. The method has then been applied to all measured storm events. This study confirms the interest of long term continuous discharge and turbidity time series in sewer systems, especially in the perspective of wet weather quality modelling.

Emergency Assessment of Debris-Flow Hazards from Basins Burned by the Piru, Simi, and Verdale Fires of 2003, Southern California

USGS Publications Warehouse

Cannon, Susan H.; Gartner, Joseph E.; Rupert, Michael G.; Michael, John A.

2003-01-01

These maps present preliminary assessments of the probability of debris-flow activity and estimates of peak discharges that can potentially be generated by debris-flows issuing from basins burned by the Piru, Simi and Verdale Fires of October 2003 in southern California in response to the 25-year, 10-year, and 2-year 1-hour rain storms. The probability maps are based on the application of a logistic multiple regression model that describes the percent chance of debris-flow production from an individual basin as a function of burned extent, soil properties, basin gradients and storm rainfall. The peak discharge maps are based on application of a multiple-regression model that can be used to estimate debris-flow peak discharge at a basin outlet as a function of basin gradient, burn extent, and storm rainfall. Probabilities of debris-flow occurrence for the Piru Fire range between 2 and 94% and estimates of debris flow peak discharges range between 1,200 and 6,640 ft3/s (34 to 188 m3/s). Basins burned by the Simi Fire show probabilities for debris-flow occurrence between 1 and 98%, and peak discharge estimates between 1,130 and 6,180 ft3/s (32 and 175 m3/s). The probabilities for debris-flow activity calculated for the Verdale Fire range from negligible values to 13%. Peak discharges were not estimated for this fire because of these low probabilities. These maps are intended to identify those basins that are most prone to the largest debris-flow events and provide information for the preliminary design of mitigation measures and for the planning of evacuation timing and routes.

Recharge Area, Base-Flow and Quick-Flow Discharge Rates and Ages, and General Water Quality of Big Spring in Carter County, Missouri, 2000-04

USGS Publications Warehouse

Imes, Jeffrey L.; Plummer, Niel; Kleeschulte, Michael J.; Schumacher, John G.

2007-01-01

Exploration for lead deposits has occurred in a mature karst area of southeast Missouri that is highly valued for its scenic beauty and recreational opportunities. The area contains the two largest springs in Missouri (Big Spring and Greer Spring), both of which flow into federally designated scenic rivers. Concerns about potential mining effects on the area ground water and aquatic biota prompted an investigation of Big Spring. Water-level measurements made during 2000 helped define the recharge area of Big Spring, Greer Spring, Mammoth Spring, and Boze Mill Spring. The data infer two distinct potentiometric surfaces. The shallow potentiometric surface, where the depth-to-water is less than about 250 feet, tends to mimic topographic features and is strongly controlled by streams. The deep potentiometric surface, where the depth-to-water is greater than about 250 feet represents ground-water hydraulic heads within the more mature karst areas. A highly permeable zone extends about 20 mile west of Big Spring toward the upper Hurricane Creek Basin. Deeper flowing water in the Big Spring recharge area is directed toward this permeable zone. The estimated sizes of the spring recharge areas are 426 square miles for Big Spring, 352 square miles for Greer Spring, 290 square miles for Mammoth Spring, and 54 square miles for Boze Mill Spring. A discharge accumulation curve using Big Spring daily mean discharge data shows no substantial change in the discharge pattern of Big Spring during the period of record (water years 1922 through 2004). The extended periods when the spring flow deviated from the trend line can be attributed to prolonged departures from normal precipitation. The maximum possible instantaneous flow from Big Spring has not been adequately defined because of backwater effects from the Current River during high-flow conditions. Physical constraints within the spring conduit system may restrict its maximum flow. The largest discharge measured at Big Spring during the period of record (water years 1922 through 2004) was 1,170 cubic feet per second on December 7, 1982. The daily mean water temperature of Big Spring was monitored during water years 2001 through 2004 and showed little variability, ranging from 13 to 15? C (degree Celsius). Water temperatures generally vary less than 1? C throughout the year. The warmest temperatures occur during October and November and decrease until April, indicating Big Spring water temperature does show a slight seasonal variation. The use of the traditional hydrograph separation program HYSEP to determine the base flow and quick flow or runoff components at Big Spring failed to yield base-flow and quick-flow discharge curves that matched observations of spring characteristics. Big Spring discharge data were used in combination with specific conductance data to develop an improved hydrograph separation method for the spring. The estimated annual mean quick flow ranged from 15 to 48 cubic feet per second for the HYSEP analysis and ranged from 26 to 154 cubic feet per second for the discharge and specific conductance method for water years 2001 to 2004. Using the discharge and specific conductance method, the estimated base-flow component rises abruptly as the spring hydrograph rises, attains a peak value on the same day as the discharge peak, and then declines abruptly from its peak value. Several days later, base flow begins to increase again at an approximately linear trend, coinciding with the time at which the percentage of quick flow has reached a maximum after each recharge-induced discharge peak. The interval between the discharge peak and the peak in percentage quick flow ranges from 8 to 11 days for seven hydrograph peaks, consistent with quick-flow traveltime estimates by dye-trace tests from the mature karst Hurricane Creek Basin in the central part of the recharge area. Concentrations of environmental tracers chlorofluorocarbons (CFCs: CFC-11, CFC-12, CFC-113)

Modeling highly transient flow, mass, and heat transport in the Chattahoochee River near Atlanta, Georgia

USGS Publications Warehouse

Jobson, Harvey E.; Keefer, Thomas N.

1979-01-01

A coupled flow-temperature model has been developed and verified for a 27.9-km reach of the Chattahoochee River between Buford Dam and Norcross, Ga. Flow in this reach of the Chattahoochee is continuous but highly regulated by Buford Dam, a flood-control and hydroelectric facility located near Buford, Ga. Calibration and verification utilized two sets of data collected under highly unsteady discharge conditions. Existing solution techniques, with certain minor improvements, were applied to verify the existing technology of flow and transport modeling. A linear, implicit finite-difference flow model was coupled with implicit, finite-difference transport and temperature models. Both the conservative and nonconservative forms of the transport equation were solved, and the difference in the predicted concentrations of dye were found to be insignificant. The temperature model, therefore, was based on the simpler nonconservative form of the transport equation. (Woodard-USGS)

Flow measurements in sewers based on image analysis: automatic flow velocity algorithm.

PubMed

Jeanbourquin, D; Sage, D; Nguyen, L; Schaeli, B; Kayal, S; Barry, D A; Rossi, L

2011-01-01

Discharges of combined sewer overflows (CSOs) and stormwater are recognized as an important source of environmental contamination. However, the harsh sewer environment and particular hydraulic conditions during rain events reduce the reliability of traditional flow measurement probes. An in situ system for sewer water flow monitoring based on video images was evaluated. Algorithms to determine water velocities were developed based on image-processing techniques. The image-based water velocity algorithm identifies surface features and measures their positions with respect to real world coordinates. A web-based user interface and a three-tier system architecture enable remote configuration of the cameras and the image-processing algorithms in order to calculate automatically flow velocity on-line. Results of investigations conducted in a CSO are presented. The system was found to measure reliably water velocities, thereby providing the means to understand particular hydraulic behaviors.

Free surface profiles in river flows: Can standard energy-based gradually-varied flow computations be pursued?

NASA Astrophysics Data System (ADS)

Cantero, Francisco; Castro-Orgaz, Oscar; Garcia-Marín, Amanda; Ayuso, José Luis; Dey, Subhasish

2015-10-01

Is the energy equation for gradually-varied flow the best approximation for the free surface profile computations in river flows? Determination of flood inundation in rivers and natural waterways is based on the hydraulic computation of flow profiles. This is usually done using energy-based gradually-varied flow models, like HEC-RAS, that adopts a vertical division method for discharge prediction in compound channel sections. However, this discharge prediction method is not so accurate in the context of advancements over the last three decades. This paper firstly presents a study of the impact of discharge prediction on the gradually-varied flow computations by comparing thirteen different methods for compound channels, where both energy and momentum equations are applied. The discharge, velocity distribution coefficients, specific energy, momentum and flow profiles are determined. After the study of gradually-varied flow predictions, a new theory is developed to produce higher-order energy and momentum equations for rapidly-varied flow in compound channels. These generalized equations enable to describe the flow profiles with more generality than the gradually-varied flow computations. As an outcome, results of gradually-varied flow provide realistic conclusions for computations of flow in compound channels, showing that momentum-based models are in general more accurate; whereas the new theory developed for rapidly-varied flow opens a new research direction, so far not investigated in flows through compound channels.

Investigation of operating parameters on CO2 splitting by dielectric barrier discharge plasma

NASA Astrophysics Data System (ADS)

Pan, CHEN; Jun, SHEN; Tangchun, RAN; Tao, YANG; Yongxiang, YIN

2017-12-01

Experiments of CO2 splitting by dielectric barrier discharge (DBD) plasma were carried out, and the influence of CO2 flow rate, plasma power, discharge voltage, discharge frequency on CO2 conversion and process energy efficiency were investigated. It was shown that the absolute quantity of CO2 decomposed was only proportional to the amount of conductive electrons across the discharge gap, and the electron amount was proportional to the discharge power; the energy efficiency of CO2 conversion was almost a constant at a lower level, which was limited by CO2 inherent discharge character that determined a constant gap electric field strength. This was the main reason why CO2 conversion rate decreased as the CO2 flow rate increase and process energy efficiency was decreased a little as applied frequency increased. Therefore, one can improve the CO2 conversion by less feed flow rate or larger discharge power in DBD plasma, but the energy efficiency is difficult to improve.

Synthesis and spectroscopic characterization of gold nanoparticles via plasma-liquid interaction technique

NASA Astrophysics Data System (ADS)

Khatoon, N.; Yasin, H. M.; Younus, M.; Ahmed, W.; Rehman, N. U.; Zakaullah, M.; Iqbal, M. Zafar

2018-01-01

Fabrication of non-functionalized gold nanoparticles is interesting owing to their potential applications in sensing and biomedicine. We report on the synthesis of surfactant-free gold nanoparticles (AuNPs) by Plasma-Liquid Interaction (PLI) technique, using micro-atmospheric pressure D.C. plasma. The effects of discharge parameters, such as discharge current, precursor concentration and gas flow rates on the structure and morphology of AuNPs have been investigated. Optical Emission Spectroscopy (OES) was employed to estimate the UV radiation intensity and OH radical density. Scanning electron microscopy (SEM) and ultraviolet-visible (UV-Vis) optical spectroscopy were employed to study the morphology and structure of AuNPs. The normalized intensities of UV radiation and OH radical density found to increase with increase in discharge current. We observed that the particle size can be tuned by controlling any of the following parameters: intensity of the UV radiation, OH radical density, and concentration of the Au precursor. Interestingly, we found that addition of 1% Ar in the feedstock gas results in formation of relatively uniform size distribution of nanoparticles. The surfactant-free AuNPs, due to their bare-surface, exhibit excellent surface-enhanced Raman scattering (SERS) properties. The SERS study of Rhodamine 6G using AuNPs as substrates, shows significant Raman enhancement and fluorescence quenching, which makes our technique a potentially powerful route to detection of trace amounts of dangerous explosives and other materials.

Assessing the ecological base and peak flow of the alpine streams in Central Taiwan

NASA Astrophysics Data System (ADS)

Wei, C.; Yang, P. S.; Tian, P. L.

2009-04-01

The ecological base and peak flow are crucial for the assessment and design for habitat rehabilitation and recovery. The amount of discharge affects the aquatic creatures and may severely damage the existence and balance of the community under extreme conditions. Aquatic insects are selected as the target species in this study to evaluate the influence of the discharge and to estimate the ecological base and peak flow. The distribution of the number of species and abundance (density) versus discharge is assessed to define the critical discharge. Two streams located at the alpine area in central Taiwan are selected as the study area to evaluate the base and peak flow. From the preliminary data (Aug 2008 to Dec 2008) collected from one stream Creek C originating from Sitou Area in Central Taiwan shows that the abundance of several species varies with the discharge. The dominate family and genus of aquatic insects is Baetidae (Order Ephemeroptera) and Baetis spp. that accounts for 32.47% and 31.11%, respectively. The Hilsenhoff family biotic index (FBI) shows that the water quality is classified to "Good" and "Very Good" level while the river pollution index (RPI) indicates that the stream is non-polluted. The discharge of base flow interpreted from the 95% curve of duration for the daily discharge is 0.0234 cms. Consistent observations are yet to be collected to yield more accurate result and ecological peak flow in rainy and typhoon seasons.

OVERVIEW OF EPA'S WET-WEATHER FLOW RESEARCH PROGRAM

EPA Science Inventory

Surface waters receive three types of urban wet-weather flow discharges: combined-sewer overflow (CSO), stormwater, and sanitary-sewer overflow (SSO); all are principally untreated discharges that occur during storm-flow events. WWFs have proven to generate a substantial amount o...

Ground-water discharge determined from estimates of evapotranspiration, Death Valley regional flow system, Nevada and California

USGS Publications Warehouse

Laczniak, Randell J.; Smith, J. LaRue; Elliott, Peggy E.; DeMeo, Guy A.; Chatigny, Melissa A.; Roemer, Gaius J.

2001-01-01

The Death Valley regional flow system (DVRFS) is one of the larger ground-water flow systems in the southwestern United States and includes much of southern Nevada and the Death Valley region of eastern California. Centrally located within the ground-water flow system is the Nevada Test Site (NTS). The NTS, a large tract covering about 1,375 square miles, historically has been used for testing nuclear devices and currently is being studied as a potential repository for the long-term storage of high-level nuclear waste generated in the United States. The U.S. Department of Energy, as mandated by Federal and State regulators, is evaluating the risk associated with contaminants that have been or may be introduced into the subsurface as a consequence of any past or future activities at the NTS. Because subsurface contaminants can be transported away from the NTS by ground water, components of the ground-water budget are of great interest. One such component is regional ground-water discharge. Most of the ground water leaving the DVRFS is limited to local areas where geologic and hydrologic conditions force ground water upward toward the surface to discharge at springs and seeps. Available estimates of ground-water discharge are based primarily on early work done as part of regional reconnaissance studies. These early efforts covered large, geologically complex areas and often applied substantially different techniques to estimate ground-water discharge. This report describes the results of a study that provides more consistent, accurate, and scientifically defensible measures of regional ground-water losses from each of the major discharge areas of the DVRFS. Estimates of ground-water discharge presented in this report are based on a rigorous quantification of local evapotranspiration (ET). The study identifies areas of ongoing ground-water ET, delineates different ET areas based on similarities in vegetation and soil-moisture conditions, and determines an ET rate for each delineated area. Each area, referred to as an ET unit, generally consists of one or more assemblages of local phreatophytes or a unique moist soil environment. Ten ET units are identified throughout the DVRFS based on differences in spectral-reflectance characteristics. Spectral differences are determined from satellite imagery acquired June 21, 1989, and June 13, 1992. The units identified include areas of open playa, moist bare soils, sparse to dense vegetation, and open water. ET rates estimated for each ET unit range from a few tenths of a foot per year for open playa to nearly 9 feet per year for open water. Mean annual ET estimates are computed for each discharge area by summing estimates of annual ET from each ET unit within a discharge area. The estimate of annual ET from each ET unit is computed as the product of an ET unit's acreage and estimated ET rate. Estimates of mean annual ET range from 450 acre-feet in the Franklin Well area to 30,000 acre-feet in Sarcobatus Flat. Ground-water discharge is estimated as annual ET minus that part of ET attributed to local precipitation. Mean annual ground-water discharge estimates range from 350 acre-feet in the Franklin Well area to 18,000 acre-feet in Ash Meadows. Generally, these estimates are greater for the northern discharge areas (Sarcobatus Flat and Oasis Valley) and less for the southern discharge areas (Franklin Lake, Shoshone area, and Tecopa/ California Valley area) than those previously reported.

Effect of Seeding Particles on the Shock Structure of a Supersonic Jet

NASA Astrophysics Data System (ADS)

Porta, David; Echeverría, Carlos; Stern, Catalina

2012-11-01

The original goal of our work was to measure. With PIV, the velocity field of a supersonic flow produced by the discharge of air through a 4mm cylindrical nozzle. The results were superposed to a shadowgraph and combined with previous density measurements made with a Rayleigh scattering technique. The idea was to see if there were any changes in the flow field, close to the high density areas near the shocks. Shadowgraphs were made with and without seeding particles, (spheres of titanium dioxide). Surprisingly, it was observed that the flow structure with particles was shifted in the direction opposite to the flow with respect to the flow structure obtained without seeds. This result might contradict the belief that the seeding particles do not affect the flow and that the speed of the seeds correspond to the local speed of the flow. We acknowledge support from DGAPA UNAM through project IN117712 and from Facultad de Ciencias UNAM.

Optical Flow-Field Techniques Used for Measurements in High-Speed Centrifugal Compressors

NASA Technical Reports Server (NTRS)

Skoch, Gary J.

1999-01-01

The overall performance of a centrifugal compressor depends on the performance of the impeller and diffuser as well as on the interactions occurring between these components. Accurate measurements of the flow fields in each component are needed to develop computational models that can be used in compressor design codes. These measurements must be made simultaneously over an area that covers both components so that researchers can understand the interactions occurring between the two components. Optical measurement techniques are being used at the NASA Lewis Research Center to measure the velocity fields present in both the impeller and diffuser of a 4:1 pressure ratio centrifugal compressor operating at several conditions ranging from design flow to surge. Laser Doppler Velocimetry (LDV) was used to measure the intrablade flows present in the impeller, and the results were compared with analyses obtained from two three-dimensional viscous codes. The development of a region of low throughflow velocity fluid within this high-speed impeller was examined and compared with a similar region first observed in a large low-speed centrifugal impeller at Lewis. Particle Image Velocimetry (PIV) is a relatively new technique that has been applied to measuring the diffuser flow fields. PIV can collect data rapidly in the diffuser while avoiding the light-reflection problems that are often encountered when LDV is used. The Particle Image Velocimeter employs a sheet of pulsed laser light that is introduced into the diffuser in a quasi-radial direction through an optical probe inserted near the diffuser discharge. The light sheet is positioned such that its centerline is parallel to the hub and shroud surfaces and such that it is parallel to the diffuser vane, thereby avoiding reflections from the solid surfaces. Seed particles small enough to follow the diffuser flow are introduced into the compressor at an upstream location. A high-speed charge-coupled discharge (CCD) camera is synchronized to the laser pulse rate; this allows it to capture images of seed particle position that are separated by a small increment in time. A crosscorrelation of a particle's position in two consecutive images provides an estimate of flow velocity and direction. Multiple image pairs obtained in rapid succession at a particular flow condition provide enough measurements for statistical significance. PIV provides simultaneous velocity measurements over the entire plane that is illuminated by the light sheet instead of at a single point, as is the case when LDV is used. PIV has a further advantage in that the laser light pulse can be triggered by an external source such as a high-response pressure transducer. This feature will allow PIV to synchronize flow imaging to physical phenomena such as rotating stall or stall precursor waves. We hope that this technique can be used to obtain images of the flow field during and just prior to stall.

FAST TRACK COMMUNICATION: Effects of Penning ionization on the discharge patterns of atmospheric pressure plasma jets

NASA Astrophysics Data System (ADS)

Li, Qing; Zhu, Wen-Chao; Zhu, Xi-Ming; Pu, Yi-Kang

2010-09-01

Atmospheric pressure plasma jets, generated in a coaxial dielectric barrier discharge configuration, have been investigated with different flowing gases. Discharge patterns in different tube regions were compared in the flowing gases of helium, neon and krypton. To explain the difference of these discharge patterns, a theoretical analysis is presented to reveal the possible basic processes. A comparison of experimental and theoretical results identifies that Penning ionization is mainly responsible for the discharge patterns of helium and neon plasma jets.

Modeling of glow discharge in a gas flow

NASA Astrophysics Data System (ADS)

Galeev, I. G.; Asadullin, T. Ya

2017-11-01

The discharge plasma of positive column in electronegative gas flow has been described by two-dimensional integro-differential system of equations written in the approximation of “narrow channel”. An efficient algorithm of solving this system of equations is suggested. In this work an implicit method is used of solution with selection gradient of the electric field along the channel. The simulation of discharge characteristics was conducted under various boundary conditions at the inlet of the discharge area and with various full discharge currents.

Surface Microwave and Surface Transversal Pulsed-Periodic Discharges in Supersonic Flow

DTIC Science & Technology

2004-03-01

plasmas of different types of gas discharges near the surface of Aerodynamic models and in the boundary layers. Also, the contractor will develop modes...regions near the surface. The following experimental work will be done in supersonic air flow (Mɚ) at pressures between 1 and 200 Torr: a...198 CHAPTER IX NUMERICAL CALCULATION OF CHARACTERISTICS OF SUPERSONIC FLOW NEAR A FLAT PLATE WITH MICROWAVE DISCHARGE ON ITS SURFACE

Spatially resolved measurement of singlet delta oxygen by radar resonance-enhanced multiphoton ionization.

PubMed

Wu, Yue; Zhang, Zhili; Ombrello, Timothy M

2013-07-01

Coherent microwave Rayleigh scattering (Radar) from resonance-enhanced multiphoton ionization (REMPI) was demonstrated to directly and nonintrusively measure singlet delta oxygen, O(2)(a(1)Δ(g)), with high spatial resolution. Two different approaches, photodissociation of ozone and microwave discharge plasma in an argon and oxygen flow, were utilized for O(2)(a(1)Δ(g)) generation. The d(1)Π(g)←a(1)Δ(g) (3-0) and d(1)Π(g)←a(1)Δ(g) (1-0) bands of O(2)(a(1)Δ(g)) were detected by Radar REMPI for two different flow conditions. Quantitative absorption measurements using sensitive off-axis integrated cavity output spectroscopy (ICOS) was used simultaneously to evaluate the accuracy and sensitivity of the Radar REMPI technique. The detection limit of Radar REMPI was found to be comparable to the ICOS technique with a detection threshold of approximately 10(14) molecules/cm(3) but with a spatial resolution that was 8 orders of magnitude smaller than the ICOS technique.

Karst hydrology and chemical contamination

DOE Office of Scientific and Technical Information (OSTI.GOV)

Field, M.S.

1993-01-01

Ground-water flow in karst aquifers is very different from flow in granular or fractured aquifers. Chemical contamination may be fed directly to a karst aquifer via overland flow to a sinkhole with little or no attenuation and may contaminate downgradient wells, springs, and sinkholes within a few hours or a few days. Contaminants may also become temporarily stored in the epikarstic zone for eventual release to the aquifer. Flood pulses may flush the contaminants to cause transiently higher levels of contamination in the aquifer and discharge points. The convergent nature of flow in karst aquifers may result in contaminants becomingmore » concentrated in conduits. Once contaminants have reached the subsurface conduits, they are likely to be rapidly transported to spring outlets. Traditional aquifer remediation techniques for contaminated aquifers are less applicable to karst aquifers.« less

ESTIMATING FLOW AND FLUX OF GROUND-WATER DISCHARGE USING WATER TEMPERATURE AND VELOCITY. (R827961)

EPA Science Inventory

The nature of ground water discharge to a stream has important implications for nearby ground water flow, especially with respect to contaminant transport and well-head protection. Measurements of ground water discharge were accomplished in this study using (1) differences bet...

Characterization of a Plasmoid in the Afterglow of a Supersonic Flowing Microwave Discharge

NASA Technical Reports Server (NTRS)

Drake, D. J.; Miller, S.; Nikolic, M.; Popovic, S.; Vuskovic, L.

2009-01-01

We performed a detailed characterization a plasmoid in the afterglow region of an Ar supersonic microwave cavity discharge. The supersonic flow was generated using a convergent-divergent nozzle upstream of the discharge region. A cylindrical cavity was used to sustain a discharge in the pressure range of 100-600 Pa. Optical emission spectroscopy was used to observe populations of excited and ionic species in the plasmoid region. Plasmoid formation in the supersonic flowing afterglow located downstream from the primary microwave cavity discharge was characterized by measuring the radial and axial distributions of Argon excited states and Argon ions. More experiments are being carried out on the plasmoid to understand the discharge parameters within the region, i.e. rotational temperature, vibrational temperature, electron density, and how the electrodynamic and aerodynamic effects combine to form this plasmoid.

Assessing the ecological base flow in an experimental watershed of Central Taiwan

NASA Astrophysics Data System (ADS)

Wei, Chiang; Yang, Ping-Shih; Tian, Pei-Ling

2010-05-01

The ecological base flow is crucial for the assessment and design for habitat rehabilitation and recovery. The amount of discharge affects the aquatic creatures and may damage the existence and balance of the community under extreme low conditions. Aquatic insect is selected as the target species in this study to evaluate the influence of the discharge and to estimate the ecological base flow. The distribution of the number of species and abundance (density) versus discharge is assessed to define the critical discharge. A stream located at the alpine area in central Taiwan is selected as the study area to evaluate the base flow. From the preliminary data (Aug 2008 to May 2009) collected from Creek C of Sitou watershed (area: 1.3 km^2) shows that the abundance of several species varies with the discharge. The dominate family and genus of aquatic insects is Baetidae (Order Ephemeroptera) and Baetis spp. that accounts for 26.3 and 17.2 %, respectively. The Hilsenhoff family biotic index (FBI) shows that the water quality is classified to "Excellent" and "Good" level while the EPT Index (Index of three orders: Ephemeroptera, Plecoptera, and Trichoptera) indicates that the stream is non-polluted. The discharge of base flow interpreted from the 90%, 95% and 96% curve of duration for the daily discharge is 0.1582, 0.0476 and 0.0378 cms; the threshold value evaluated by curve of abundance vs. discharge is 0.0154 cms. Consistent observations are yet to be collected to yield more accurate results.

40 CFR 419.47 - Pretreatment standards for new sources (PSNS).

Code of Federal Regulations, 2010 CFR

2010-07-01

... forth in § 419.46 (a) and (b). (b) The following standard is applied to the cooling tower discharge part... flow to the POTW; and (3) by the ratio of the cooling tower discharge flow to the total refinery flow...

40 CFR 419.17 - Pretreatment standards for new sources (PSNS).

Code of Federal Regulations, 2010 CFR

2010-07-01

... forth in § 419.16 (a) and (b). (b) The following standard is applied to the cooling tower discharge part... flow to the POTW; and (3) by the ratio of the cooling tower discharge flow to the total refinery flow...

40 CFR 419.57 - Pretreatment standards for new sources (PSNS).

Code of Federal Regulations, 2010 CFR

2010-07-01

... forth in § 419.56 (a) and (b). (b) The following standard is applied to the cooling tower discharge part... flow to the POTW; and (3) by the ratio of the cooling tower discharge flow to the total refinery flow...

Properties of radio-frequency heated argon confined uranium plasmas

NASA Technical Reports Server (NTRS)

1976-01-01

Pure uranium hexafluoride (UF6) was injected into an argon confined, steady state, rf-heated plasma within a fused silica peripheral wall test chamber. Exploratory tests conducted using an 80 kW rf facility and different test chamber flow configurations permitted selection of the configuration demonstrating the best confinement characteristics and minimum uranium compound wall coating. The overall test results demonstrated applicable flow schemes and associated diagnostic techniques were developed for the fluid mechanical confinement and characterization of uranium within an rf plasma discharge when pure UF6 is injected for long test times into an argon-confined, high-temperature, high-pressure, rf-heated plasma.

Nested-scale discharge and groundwater level monitoring to improve predictions of flow route discharges and nitrate loads

NASA Astrophysics Data System (ADS)

van der Velde, Y.; Rozemeijer, J. C.; de Rooij, G. H.; van Geer, F. C.; Torfs, P. J. J. F.; de Louw, P. G. B.

2010-10-01

Identifying effective measures to reduce nutrient loads of headwaters in lowland catchments requires a thorough understanding of flow routes of water and nutrients. In this paper we assess the value of nested-scale discharge and groundwater level measurements for predictions of catchment-scale discharge and nitrate loads. In order to relate field-site measurements to the catchment-scale an upscaling approach is introduced that assumes that scale differences in flow route fluxes originate from differences in the relationship between groundwater storage and the spatial structure of the groundwater table. This relationship is characterized by the Groundwater Depth Distribution (GDD) curve that relates spatial variation in groundwater depths to the average groundwater depth. The GDD-curve was measured for a single field site (0.009 km2) and simple process descriptions were applied to relate the groundwater levels to flow route discharges. This parsimonious model could accurately describe observed storage, tube drain discharge, overland flow and groundwater flow simultaneously with Nash-Sutcliff coefficients exceeding 0.8. A probabilistic Monte Carlo approach was applied to upscale field-site measurements to catchment scales by inferring scale-specific GDD-curves from hydrographs of two nested catchments (0.4 and 6.5 km2). The estimated contribution of tube drain effluent (a dominant source for nitrates) decreased with increasing scale from 76-79% at the field-site to 34-61% and 25-50% for both catchment scales. These results were validated by demonstrating that a model conditioned on nested-scale measurements simulates better nitrate loads and better predictions of extreme discharges during validation periods compared to a model that was conditioned on catchment discharge only.

Evaluating the conservation potential of tributaries for native fishes in the Upper Colorado River Basin

USGS Publications Warehouse

Laub, Brian G.; Thiede, Gary P.; Macfarlane, William W.; Budy, Phaedra

2018-01-01

We explored the conservation potential of tributaries in the upper Colorado River basin by modeling native fish species richness as a function of river discharge, temperature, barrier‐free length, and distance to nearest free‐flowing main‐stem section. We investigated a historic period prior to large‐scale water development and a contemporary period. In the historic period, species richness was log‐linearly correlated to variables capturing flow magnitude, particularly mean annual discharge. In the contemporary period, the log‐linear relationship between discharge and species richness was still evident but weaker. Tributaries with lower average temperature and separated from free‐flowing main‐stem sections often had fewer native species compared to tributaries with similar discharge but with warmer temperature and directly connected to free‐flowing main stems. Thus, tributaries containing only a small proportion of main‐stem discharge, especially those at lower elevations with warmer temperatures and connected to free‐flowing main stems, can support a relatively high species richness. Tributaries can help maintain viable populations by providing ecological processes disrupted on large regulated rivers, such as natural flow and temperature regimes, and may present unique conservation opportunities. Efforts to improve fish passage, secure environmental flows, and restore habitat in these tributaries could greatly contribute to conservation of native fish richness throughout the watershed.

High Voltage SPT Performance

NASA Technical Reports Server (NTRS)

Manzella, David; Jacobson, David; Jankovsky, Robert

2001-01-01

A 2.3 kW stationary plasma thruster designed to operate at high voltage was tested at discharge voltages between 300 and 1250 V. Discharge specific impulses between 1600 and 3700 sec were demonstrated with thrust between 40 and 145 mN. Test data indicated that discharge voltage can be optimized for maximum discharge efficiency. The optimum discharge voltage was between 500 and 700 V for the various anode mass flow rates considered. The effect of operating voltage on optimal magnet field strength was investigated. The effect of cathode flow rate on thruster efficiency was considered for an 800 V discharge.

Application of effective discharge analysis to environmental flow decision-making

USGS Publications Warehouse

McKay, S. Kyle; Freeman, Mary C.; Covich, A.P.

2016-01-01

Well-informed river management decisions rely on an explicit statement of objectives, repeatable analyses, and a transparent system for assessing trade-offs. These components may then be applied to compare alternative operational regimes for water resource infrastructure (e.g., diversions, locks, and dams). Intra- and inter-annual hydrologic variability further complicates these already complex environmental flow decisions. Effective discharge analysis (developed in studies of geomorphology) is a powerful tool for integrating temporal variability of flow magnitude and associated ecological consequences. Here, we adapt the effectiveness framework to include multiple elements of the natural flow regime (i.e., timing, duration, and rate-of-change) as well as two flow variables. We demonstrate this analytical approach using a case study of environmental flow management based on long-term (60 years) daily discharge records in the Middle Oconee River near Athens, GA, USA. Specifically, we apply an existing model for estimating young-of-year fish recruitment based on flow-dependent metrics to an effective discharge analysis that incorporates hydrologic variability and multiple focal taxa. We then compare three alternative methods of environmental flow provision. Percentage-based withdrawal schemes outcompete other environmental flow methods across all levels of water withdrawal and ecological outcomes.

Application of Effective Discharge Analysis to Environmental Flow Decision-Making.

PubMed

McKay, S Kyle; Freeman, Mary C; Covich, Alan P

2016-06-01

Well-informed river management decisions rely on an explicit statement of objectives, repeatable analyses, and a transparent system for assessing trade-offs. These components may then be applied to compare alternative operational regimes for water resource infrastructure (e.g., diversions, locks, and dams). Intra- and inter-annual hydrologic variability further complicates these already complex environmental flow decisions. Effective discharge analysis (developed in studies of geomorphology) is a powerful tool for integrating temporal variability of flow magnitude and associated ecological consequences. Here, we adapt the effectiveness framework to include multiple elements of the natural flow regime (i.e., timing, duration, and rate-of-change) as well as two flow variables. We demonstrate this analytical approach using a case study of environmental flow management based on long-term (60 years) daily discharge records in the Middle Oconee River near Athens, GA, USA. Specifically, we apply an existing model for estimating young-of-year fish recruitment based on flow-dependent metrics to an effective discharge analysis that incorporates hydrologic variability and multiple focal taxa. We then compare three alternative methods of environmental flow provision. Percentage-based withdrawal schemes outcompete other environmental flow methods across all levels of water withdrawal and ecological outcomes.

Improving catchment discharge predictions by inferring flow route contributions from a nested-scale monitoring and model setup

NASA Astrophysics Data System (ADS)

van der Velde, Y.; Rozemeijer, J. C.; de Rooij, G. H.; van Geer, F. C.; Torfs, P. J. J. F.; de Louw, P. G. B.

2011-03-01

Identifying effective measures to reduce nutrient loads of headwaters in lowland catchments requires a thorough understanding of flow routes of water and nutrients. In this paper we assess the value of nested-scale discharge and groundwater level measurements for the estimation of flow route volumes and for predictions of catchment discharge. In order to relate field-site measurements to the catchment-scale an upscaling approach is introduced that assumes that scale differences in flow route fluxes originate from differences in the relationship between groundwater storage and the spatial structure of the groundwater table. This relationship is characterized by the Groundwater Depth Distribution (GDD) curve that relates spatial variation in groundwater depths to the average groundwater depth. The GDD-curve was measured for a single field site (0.009 km2) and simple process descriptions were applied to relate groundwater levels to flow route discharges. This parsimonious model could accurately describe observed storage, tube drain discharge, overland flow and groundwater flow simultaneously with Nash-Sutcliff coefficients exceeding 0.8. A probabilistic Monte Carlo approach was applied to upscale field-site measurements to catchment scales by inferring scale-specific GDD-curves from the hydrographs of two nested catchments (0.4 and 6.5 km2). The estimated contribution of tube drain effluent (a dominant source for nitrates) decreased with increasing scale from 76-79% at the field-site to 34-61% and 25-50% for both catchment scales. These results were validated by demonstrating that a model conditioned on nested-scale measurements improves simulations of nitrate loads and predictions of extreme discharges during validation periods compared to a model that was conditioned on catchment discharge only.

Sensitivity Testing of the NSTAR Ion Thruster

NASA Technical Reports Server (NTRS)

Sengupta, Anita; Anderson, John; Brophy, John

2007-01-01

During the Extended Life Test of the DS1 flight spare ion thruster, the engine was subjected to sensitvity testing in order to characterize the macroscopic dependence of discharge chamber sensitivity to a +\\-3% vatiation in main flow, cathode flow and beam current, and to +\\5% variation in beam and accelerator voltage, was determined for the minimum- (THO), half- (TH8) and full power (TH15) throttle levels. For each power level investigared, 16 high/low operating conditions were chosen to vary the flows, beam current, and grid voltages in in a matrix that mapped out the entire parameter space. The matrix of data generated was used to determine the partial derivative or senitivity of the dependent parameters--discharge voltage, discharge current, discharge loss, double-to-single-ion current ratio, and neutralizer-keeper voltage--to the variation in the independent parameters--main flow, cathode flow, beam current, and beam voltage. The sensititivities of each dependent parameter with respect to each independent parameter were determined using a least-square fit routine. Variation in these sensitivities with thruster runtime was recorded over the duration of the ELT, to detemine if discharge performance changed with thruster wear. Several key findings have been ascertained from the sensitivity testing. Discharge operation is most sensitve to changes in cathode flow and to a lesser degree main flow. The data also confirms that for the NSTAR configuration plasma production is limited by primary electron input due to the fixed neutral population. Key sensitivities along with their change with thruster wear (operating time) will be presented. In addition double ion content measurements with an ExB probe will also be presented to illustrate beam ion production and content sensitivity to the discharge chamber operating parameteres.

Using the Electronic Medical Record to Enhance Physician-Nurse Communication Regarding Patients' Discharge Status.

PubMed

Driscoll, Molly; Gurka, David

2015-01-01

The fast-paced environment of hospitals contributes to communication failures between health care providers while impacting patient care and patient flow. An effective mechanism for sharing patients' discharge information with health care team members is required to improve patient throughput. The communication of a patient's discharge plan was identified as crucial in alleviating patient flow delays at a tertiary care, academic medical center. By identifying the patients who were expected to be discharged the following day, the health care team could initiate discharge preparations in advance to improve patient care and patient flow. The patients' electronic medical record served to convey dynamic information regarding the patients' discharge status to the health care team via conditional discharge orders. Two neurosciences units piloted a conditional discharge order initiative. Conditional discharge orders were designed in the electronic medical record so that the conditions for discharge were listed in a dropdown menu. The health care team was trained on the conditional discharge order protocol, including when to write them, how to find them in the patients' electronic medical record, and what actions should be prompted by these orders. On average, 24% of the patients discharged had conditional discharge orders written the day before discharge. The average discharge time for patients with conditional discharge orders decreased by 83 minutes (0.06 day) from baseline. Qualitatively, the health care team reported improved workflows with conditional orders. The conditional discharge orders allowed physicians to communicate pending discharges electronically to the multidisciplinary team. The initiative positively impacted patient discharge times and workflows.

Discharge characteristics of embankment-shaped weirs

USGS Publications Warehouse

Kindsvater, Carl E.

1964-01-01

An embankment-shaped weir is an embankment overtopped by flood waters. Among the engineering problems frequently resulting from. this occurrence is the need to compute the peak discharge from postflood yield observations. The research described in this. report was concerned with the theoretical and experimental bases for the computation procedure. The research had two main objectives. One was to determine the relationship between embankment form and roughness and some of the more important discharge characteristics. The second was to define, theoretically and experimentally, the relationship between free-flow discharge and the boundary layer on the roadway. The first objective was accomplished with the experimental determination of coefficients of discharge and other significant flow characteristics for a variety of boundary and flow conditions. The second objective was accomplished with the development and experimental verification of a discharge equation which involved the boundary layer displacement thickness. This phase of the research included a general investigation of boundary layer growth on the roadway. It is included that both free- and submerged-flow discharge are virtually independent of the influence of embankment shape and relative height. The influence of boundary resistance is appreciable only for smaller heads. The most practical solution for discharge is one which is based on. the simple weir equation and experimentally determined coefficients. A completely analytical equation of discharge is impractical. The report contains the results of 936 experiments on the discharge characteristics of 17 different models; plus 106 boundary-layer velocity traverses on 4 different models. The data are summarized in both graphical and tabular form.

Death Valley regional ground-water flow system, Nevada and California -- hydrogeologic framework and transient ground-water flow model

USGS Publications Warehouse

Belcher, Wayne R.

2004-01-01

A numerical three-dimensional (3D) transient ground-water flow model of the Death Valley region was developed by the U.S. Geological Survey for the U.S. Department of Energy programs at the Nevada Test Site and at Yucca Mountain, Nevada. Decades of study of aspects of the ground-water flow system and previous less extensive ground-water flow models were incorporated and reevaluated together with new data to provide greater detail for the complex, digital model. A 3D digital hydrogeologic framework model (HFM) was developed from digital elevation models, geologic maps, borehole information, geologic and hydrogeologic cross sections, and other 3D models to represent the geometry of the hydrogeologic units (HGUs). Structural features, such as faults and fractures, that affect ground-water flow also were added. The HFM represents Precambrian and Paleozoic crystalline and sedimentary rocks, Mesozoic sedimentary rocks, Mesozoic to Cenozoic intrusive rocks, Cenozoic volcanic tuffs and lavas, and late Cenozoic sedimentary deposits of the Death Valley Regional Ground-Water Flow System (DVRFS) region in 27 HGUs. Information from a series of investigations was compiled to conceptualize and quantify hydrologic components of the ground-water flow system within the DVRFS model domain and to provide hydraulic-property and head-observation data used in the calibration of the transient-flow model. These studies reevaluated natural ground-water discharge occurring through evapotranspiration and spring flow; the history of ground-water pumping from 1913 through 1998; ground-water recharge simulated as net infiltration; model boundary inflows and outflows based on regional hydraulic gradients and water budgets of surrounding areas; hydraulic conductivity and its relation to depth; and water levels appropriate for regional simulation of prepumped and pumped conditions within the DVRFS model domain. Simulation results appropriate for the regional extent and scale of the model were provided by acquiring additional data, by reevaluating existing data using current technology and concepts, and by refining earlier interpretations to reflect the current understanding of the regional ground-water flow system. Ground-water flow in the Death Valley region is composed of several interconnected, complex ground-water flow systems. Ground-water flow occurs in three subregions in relatively shallow and localized flow paths that are superimposed on deeper, regional flow paths. Regional ground-water flow is predominantly through a thick Paleozoic carbonate rock sequence affected by complex geologic structures from regional faulting and fracturing that can enhance or impede flow. Spring flow and evapotranspiration (ET) are the dominant natural ground-water discharge processes. Ground water also is withdrawn for agricultural, commercial, and domestic uses. Ground-water flow in the DVRFS was simulated using MODFLOW-2000, a 3D finite-difference modular ground-water flow modeling code that incorporates a nonlinear least-squares regression technique to estimate aquifer parameters. The DVRFS model has 16 layers of defined thickness, a finite-difference grid consisting of 194 rows and 160 columns, and uniform cells 1,500 m on each side. Prepumping conditions (before 1913) were used as the initial conditions for the transient-state calibration. The model uses annual stress periods with discrete recharge and discharge components. Recharge occurs mostly from infiltration of precipitation and runoff on high mountain ranges and from a small amount of underflow from adjacent basins. Discharge occurs primarily through ET and spring discharge (both simulated as drains) and water withdrawal by pumping and, to a lesser amount, by underflow to adjacent basins, also simulated by drains. All parameter values estimated by the regression are reasonable and within the range of expected values. The simulated hydraulic heads of the final calibrated transient model gener

Variance of discharge estimates sampled using acoustic Doppler current profilers from moving boats

USGS Publications Warehouse

Garcia, Carlos M.; Tarrab, Leticia; Oberg, Kevin; Szupiany, Ricardo; Cantero, Mariano I.

2012-01-01

This paper presents a model for quantifying the random errors (i.e., variance) of acoustic Doppler current profiler (ADCP) discharge measurements from moving boats for different sampling times. The model focuses on the random processes in the sampled flow field and has been developed using statistical methods currently available for uncertainty analysis of velocity time series. Analysis of field data collected using ADCP from moving boats from three natural rivers of varying sizes and flow conditions shows that, even though the estimate of the integral time scale of the actual turbulent flow field is larger than the sampling interval, the integral time scale of the sampled flow field is on the order of the sampling interval. Thus, an equation for computing the variance error in discharge measurements associated with different sampling times, assuming uncorrelated flow fields is appropriate. The approach is used to help define optimal sampling strategies by choosing the exposure time required for ADCPs to accurately measure flow discharge.

Fluvial sediments a summary of source, transportation, deposition, and measurement of sediment discharge

USGS Publications Warehouse

Colby, B.R.

1963-01-01

This paper presents a broad but undetailed picture of fluvial sediments in streams, reservoirs, and lakes and includes a discussion of the processes involved in the movement of sediment by flowing water. Sediment is fragmental material that originates from the chemical or physical disintegration of rocks. The disintegration products may have many different shapes and may range in size from large boulders to colloidal particles. In general, they retain about the same mineral composition as the parent rocks. Rock fragments become fluvial sediment when they are entrained in a stream of water. The entrainment may occur as sheet erosion from land surfaces, particularly for the fine particles, or as channel erosion after the surface runoff has accumulated in streams. Fluvial sediments move in streams as bedload (particles moving within a few particle diameters of the streambed) or as suspended sediment in the turbulent flow. The discharge of bedload varies with several factors, which may include particle size and a type of effective shear on the surface of the streambed. The discharge of suspended sediment depends partly on concentration of moving sediment near the streambed and hence on discharge of bedload. However, the concentration of fine sediment near the streambed varies widely, even for equal flows, and, therefore, the discharge of fine sediment normally cannot be computed theoretically. The discharge of suspended sediment also depends on velocity, turbulence, depth of flow, and fall velocity of the particles. In general, the coarse sediment transported by a stream moves intermittently and is discharged at a rate that depends on properties of the flow and of the sediment. If an ample supply of coarse sediment is available at the surface of the streambed, the discharge of the coarse sediment, such as sand, can be roughly computed from properties of the available sediment and of the flow. On the other hand, much of the fine sediment in a stream usually moves nearly continuously at about the velocity of the flow, and even low flows can transport large amounts of fine sediment. Hence, the discharge of fine sediments, being largely dependent on the availability of fine sediment upstream rather than on the properties of the sediment and of the flow at a cross section, can seldom be computed from properties, other than concentrations based directly on samples, that can be observed at the cross section. Sediment particles continually change their positions in the flow; some fall to the streambed, and others are removed from the bed. Sediment deposits form locally or over large areas if the volume rate at which particles settle to the bed exceeds the volume rate at which particles are removed from the bed. In general, large particles are deposited more readily than small particles, whether the point of deposition is behind a rock, on a flood plain, within a stream channel, or at the entrance to a reservoir, a lake, or the ocean. Most samplers used for sediment observations collect a water-sediment mixture from the water surface to within a few tenths of a foot of the streambed. They thus sample most of the suspended sediment, especially if the flow is deep or if the sediment is mostly fine; but they exclude the bedload and some of the suspended sediment in a layer near the streambed where the suspended-sediment concentrations are highest. Measured sediment discharges are usually based on concentrations that are averages of several individual sediment samples for a cross section. If enough average concentrations for a cross section have been determined, the measured sediment discharge can be computed by interpolating sediment concentrations between sampling times. If only occasional samples were collected, an average relation between sediment discharge and flow can be used with a flow-duration curve to compute roughly the average or the total sediment discharges for any periods of time for which the flow-duration c

Discharge rating equation and hydraulic characteristics of standard Denil fishways

USGS Publications Warehouse

Odeh, M.

2003-01-01

This paper introduces a new equation to predict discharge capacity in the commonly used Denil fishway using water surface elevation in the upstream reservoir and fishway width and slope as the independent variables. A dimensionless discharge coefficient based only on the physical slope of the fishway is introduced. The discharge equation is based on flow physics, dimensional analysis, and experiments with three full-scale fishways of different sizes. Hydraulic characteristics of flow inside these fishways are discussed. Water velocities decreased by more than 50% and remained relatively unchanged in the fully developed flow downstream of the vena contracta region, near the upstream baffle where fish exit the fishway. Engineers and biologists need to be aware of this fact and ensure that fish can negotiate the vena contracta velocities rather than velocities within the developed flow region only. Discharge capacity was directly proportional to the fishway width and slope. The new equation is a design tool for engineers and field biologists, especially when designing a fishway based on flow availability in conjunction with the swimming capabilities of target fish species.

Discrete simulations of spatio-temporal dynamics of small water bodies under varied stream flow discharges

NASA Astrophysics Data System (ADS)

Daya Sagar, B. S.

2005-01-01

Spatio-temporal patterns of small water bodies (SWBs) under the influence of temporally varied stream flow discharge are simulated in discrete space by employing geomorphologically realistic expansion and contraction transformations. Cascades of expansion-contraction are systematically performed by synchronizing them with stream flow discharge simulated via the logistic map. Templates with definite characteristic information are defined from stream flow discharge pattern as the basis to model the spatio-temporal organization of randomly situated surface water bodies of various sizes and shapes. These spatio-temporal patterns under varied parameters (λs) controlling stream flow discharge patterns are characterized by estimating their fractal dimensions. At various λs, nonlinear control parameters, we show the union of boundaries of water bodies that traverse the water body and non-water body spaces as geomorphic attractors. The computed fractal dimensions of these attractors are 1.58, 1.53, 1.78, 1.76, 1.84, and 1.90, respectively, at λs of 1, 2, 3, 3.46, 3.57, and 3.99. These values are in line with general visual observations.

Occurrence of Volcanic CO2 by Groundwater Flow Systems in the Eifel Mountains, Germany

NASA Astrophysics Data System (ADS)

Weyer, K.; May, F.; Ellis, J. C.

2011-12-01

Weyer (2010) showed why and how discharge areas of regional groundwater flow systems are also discharge points of natural and stored CO2. As groundwater flow systems reach to great depth by penetrating aquitards and caprocks any successful design of on-shore geological carbon storage must regard the migration effects groundwater flow systems exert on stored CO2. Eventually all of the CO2 will be dissolved by groundwater and migrate to the discharge areas of these flow systems. By implication there will rarely be the anticipated permanent storage of CO2 in the subsurface. Instead the deep ground water flow will transport the dissolved CO2 into surface waters. A telling example of such a system is the Green River in Utah with its natural discharge points of volcanic CO2 and the artificial discharge point Crystal Geyser, a flowing abandoned well located at the bank of the Green River. The advantage of this situation is that there have been hydrogeological tools developed which allow the determination of the flow path of the groundwater flow systems and their approximate time scale to reach their groundwater discharge areas. These time spans may be as large as 50,000 to 100,000 years. In any case residence times of a thousand years and more would suffice in mitigating the atmospheric effect of CO2 discharge. The above concepts have so far not created much resonance in the scientific and practical world of geologic CO2 storage. Therefore the investigation of groundwater dynamics at areas with natural discharge of volcanic CO2 provides a test for the effect groundwater flow systems will exert on the geologic storage of CO2. The Eifel Mountains in Germany present such a natural laboratory as it contains over a hundred known Tertiary and Quaternary volcanoes. Its discharge points of water carrying CO2 are well-known as they have been used for generations for the production of carbonated mineral waters. For the western part of the Eifel-Mountains, May (2002) listed all known natural CO2 discharge points with coordinates. The high resolution digital topographical maps of the area outline the elevation of the groundwater table in these mountains as the topography controls the elevation of the groundwater table. The detailed network of rivers, creeks and lakes denotes the location of groundwater discharge areas draining into the surface waters. Büchel and Mertens (1982) provided the locations of volcanic eruption centers in the western part of the Eifel Mountains. After combining the above information in a series of small scale DEMs created with 'SURFER' it became directly obvious that all known natural CO2 discharge points are directly related to discharge areas while the occurrence of volcanic eruption centers is concentrated in the recharge areas for regional groundwater flow. Quod erat demonstrandum. Büchel, G., H. Mertes (1982). Die Eruptionszentren des Westeifeler Vulkanfeldes. Zeitschr. DGG, 131: 409-429. May, Franz (2002). Säuerlinge der Vulkaneifel und der Südeifel. Mainzer geowissen. Mitt., 31: 7-58. Weyer, K. U. (2010). Differing physical processes in off-shore and on-shore CO2 storage. Private publication based on a poster presented at GHGT-10, Amsterdam. 8 pp, July 2010.

The simultaneous discharge of liquid and grains from a silo

NASA Astrophysics Data System (ADS)

Cervantes-Álvarez, A. M.; Hidalgo-Caballero, S.; Pacheco-Vázquez, F.

2018-04-01

The flow rate of water through an orifice at the bottom of a container depends on the hydrostatic pressure whereas for a dry granular material it is nearly constant. But what happens during the simultaneous discharge of grains and liquid from a silo? By measuring the flow rate as a function of time, we found that (i) different regimes appear, going from the constant flow rate to a hydrostatic-like discharge depending on the aperture size and grain diameter, (ii) the mixed material is always discharged faster than dry grains but slower than liquid, (iii) for the mixture, the liquid level drops faster than the grain level, but they are always linearly proportional to one another, and (iv) a sudden growth in the flow rate happens during the transition from a biphasic discharge to a single phase discharge. These results are associated to the competition between the decrease in hydrostatic pressure above the granular bed and the hydrodynamic resistance. A model combining Darcy's law with Bernoulli and mass conservation equations is proposed, and the numerical results are in good agreement with experiments.

Surface water discharge and salinity monitoring of coastal estuaries in Everglades National Park, USA, in support of the Comprehensive Everglades Restoration Plan

USGS Publications Warehouse

Woods, Jeff

2010-01-01

Discharge and salinity were measured along the southwest and the southeast coast of Florida in Everglades National Park (ENP) within several rivers and creeks from 1996 through 2008. Data were collected using hydro-acoustic instruments and continuous water-quality monitors at fixed monitoring stations. Water flowed through ENP within two distinct drainage basins; specifically, Shark Slough and Taylor Slough. Discharge to the southwest coast through Shark Slough was substantially larger than discharge to the southeast coast through Taylor Slough. Correlation analysis between coastal flows and regulated flows at water-management structures upstream from ENP suggests rainfall has a larger impact on discharge through Shark Slough than releases from the S-12 water management structures. In contrast, flow releases from water management structures upstream from Taylor Slough appear to be more closely related to discharge along the southeast coast. Salinity varied within a wide range (0 to 50 parts per thousand) along both coastlines. Periods of hypersalinity were greater along the southeast coast due to shallow compartmentalized basins within Florida Bay, which restrict circulation.

Climate-change potential effects on the hydrological regime of freshwater springs in the Italian Northern Apennines.

PubMed

Cervi, Federico; Petronici, Francesca; Castellarin, Attilio; Marcaccio, Marco; Bertolini, Andrea; Borgatti, Lisa

2018-05-01

In large areas of the Italian Northern Apennines, hundreds of low-yield springs provide water for drinking and industrial purposes, with short groundwater flow paths being formed within fractured sedimentary rock units. This hydrogeological setting results in spring water discharges that closely follow meteoric water recharge patterns, leading to low-flow periods concentrated in the summer/early autumn. Therefore, the springs' outflow can be very sensitive to a shortage in water recharge, as it was the case in 2003 and 2017, when a prolonged period of drought caused severe water management issues. This work analyses how a group of such springs responds to climate change. In particular, we first validated a hydrological rainfall-runoff model on the basis of daily discharge data collected between 2013 and 2016. Then, outflows were simulated for baseline (1984-2013) and future periods (2021-2050) using weather data provided by five RCM-GCM combinations. Finally, we performed statistical analyses aiming to examine the intra-annual variability in discharge rates, low-flow indices, flow-duration curves and the length of low-flows. Results show no evidence of change in mean annual discharges, but future climate estimates suggest a slight change to seasonal discharges in the future, with a marked increase of discharge during winter and spring, and a decrease in summer and autumn. Q(95) and 7Q10 low-flow indices (i.e. the daily discharge exceeded 95% of the time and the minimum weekly discharge associated with a 10-year recurrence interval, respectively) are significantly affected by the climate change (-21.8% and -25.0%, respectively), while droughts are expected to be more frequent: the number of years with a consecutive low-flow between 51 and 100days to increase by a third, and between 101 and 150 to duplicate. Copyright © 2017 Elsevier B.V. All rights reserved.

A self-consistent model of ionic wind generation by negative corona discharges in air with experimental validation

NASA Astrophysics Data System (ADS)

Chen, She; Nobelen, J. C. P. Y.; Nijdam, S.

2017-09-01

Ionic wind is produced by a corona discharge when gaseous ions are accelerated in the electric field and transfer their momentum to neutral molecules by collisions. This technique is promising because a gas flow can be generated without the need for moving parts and can be easily miniaturized. The basic theory of ionic wind sounds simple but the details are far from clear. In our experiment, a negative DC voltage is applied to a needle-cylinder electrode geometry. Hot wire anemometry is used to measure the flow velocity at the downstream exit of the cylinder. The flow velocity fluctuates but the average velocity increases with the voltage. The current consists of a regular train of pulses with short rise time, the well-known Trichel pulses. To reveal the ionic wind mechanism in the Trichel pulse stage, a three-species corona model coupled with gas dynamics is built. The drift-diffusion equations of the plasma together with the Navier-Stokes equations of the flow are solved in COMSOL Multiphysics. The electric field, net number density of charged species, electrohydrodynamic (EHD) body force and flow velocity are calculated in detail by a self-consistent model. Multiple time scales are employed: hundreds of microseconds for the plasma characteristics and longer time scales (˜1 s) for the flow behavior. We found that the flow velocity as well as the EHD body force have opposite directions in the ionization region close to the tip and the ion drift region further away from the tip. The calculated mean current, Trichel pulse frequency and flow velocity are very close to our experimental results. Furthermore, in our simulations we were able to reproduce the mushroom-like minijets observed in experiments.

Comparison of thermal, salt and dye tracing to estimate shallow flow velocities: Novel triple-tracer approach

NASA Astrophysics Data System (ADS)

Abrantes, João R. C. B.; Moruzzi, Rodrigo B.; Silveira, Alexandre; de Lima, João L. M. P.

2018-02-01

The accurate measurement of shallow flow velocities is crucial to understand and model the dynamics of sediment and pollutant transport by overland flow. In this study, a novel triple-tracer approach was used to re-evaluate and compare the traditional and well established dye and salt tracer techniques with the more recent thermal tracer technique in estimating shallow flow velocities. For this purpose a triple tracer (i.e. dyed-salted-heated water) was used. Optical and infrared video cameras and an electrical conductivity sensor were used to detect the tracers in the flow. Leading edge and centroid velocities of the tracers were measured and the correction factors used to determine the actual mean flow velocities from tracer measured velocities were compared and investigated. Experiments were carried out for different flow discharges (32-1813 ml s-1) on smooth acrylic, sand, stones and synthetic grass bed surfaces with 0.8, 4.4 and 13.2% slopes. The results showed that thermal tracers can be used to estimate shallow flow velocities, since the three techniques yielded very similar results without significant differences between them. The main advantages of the thermal tracer were that the movement of the tracer along the measuring section was more easily visible than it was in the real image videos and that it was possible to measure space-averaged flow velocities instead of only one velocity value, with the salt tracer. The correction factors used to determine the actual mean velocity of overland flow varied directly with Reynolds and Froude numbers, flow velocity and slope and inversely with flow depth and bed roughness. In shallow flows, velocity estimation using tracers entails considerable uncertainty and caution must be taken with these measurements, especially in field studies where these variables vary appreciably in space and time.

Experimental calibration and validation of sewer/surface flow exchange equations in steady and unsteady flow conditions

NASA Astrophysics Data System (ADS)

Rubinato, Matteo; Martins, Ricardo; Kesserwani, Georges; Leandro, Jorge; Djordjević, Slobodan; Shucksmith, James

2017-09-01

The linkage between sewer pipe flow and floodplain flow is recognised to induce an important source of uncertainty within two-dimensional (2D) urban flood models. This uncertainty is often attributed to the use of empirical hydraulic formulae (the one-dimensional (1D) weir and orifice steady flow equations) to achieve data-connectivity at the linking interface, which require the determination of discharge coefficients. Because of the paucity of high resolution localised data for this type of flows, the current understanding and quantification of a suitable range for those discharge coefficients is somewhat lacking. To fulfil this gap, this work presents the results acquired from an instrumented physical model designed to study the interaction between a pipe network flow and a floodplain flow. The full range of sewer-to-surface and surface-to-sewer flow conditions at the exchange zone are experimentally analysed in both steady and unsteady flow regimes. Steady state measured discharges are first analysed considering the relationship between the energy heads from the sewer flow and the floodplain flow; these results show that existing weir and orifice formulae are valid for describing the flow exchange for the present physical model, and yield new calibrated discharge coefficients for each of the flow conditions. The measured exchange discharges are also integrated (as a source term) within a 2D numerical flood model (a finite volume solver to the 2D Shallow Water Equations (SWE)), which is shown to reproduce the observed coefficients. This calibrated numerical model is then used to simulate a series of unsteady flow tests reproduced within the experimental facility. Results show that the numerical model overestimated the values of mean surcharge flow rate. This suggests the occurrence of additional head losses in unsteady conditions which are not currently accounted for within flood models calibrated in steady flow conditions.

PONDCALC - A Tool to Estimate Discharge from the Alviso Salt Ponds, California

USGS Publications Warehouse

Shellenbarger, Gregory; Schoellhamer, David H.; Lionberger, Megan A.

2007-01-01

Former commercial salt ponds in Alviso, California, now are operated by the U.S. Fish and Wildlife Service (USFWS) to provide habitat for birds. The USFWS has modified the operation of the ponds to prevent exceedingly high salinity. Ponds that were formerly hydraulically isolated from South San Francisco Bay and adjacent sloughs now are managed as flow-through ponds, and some are allowed to discharge to the Bay and sloughs. This discharge is allowed under a permit issued by the Regional Water Quality Control Board. As a requirement of the permit, the USFWS must estimate the amount of discharge from each discharge pond for the period May through November of each year. To facilitate the accurate estimation of pond discharge, a calculation methodology (hereafter referred to as 'calculator' or PONDCALC) for the discharging Alviso ponds has been developed as a Microsoft Excel file and is presented in this report. The presence of flap gates on one end of the discharge culverts, which allow only outflow from a pond, complicates the hydraulic analysis of flow through the culverts. The equation typically used for culvert flow contains an energy loss coefficient that had to be determined empirically using measured water discharge and head at the discharge structure of one of the ponds. A standard weir-flow equation is included in PONDCALC for discharge calculation in the ponds having weir box structures in addition to culverts. The resulting methodology is applicable only to the five Alviso ponds (A2W, A3W, A7, A14, and A16) that discharge to South San Francisco Bay or adjacent sloughs under the management practices for 2005.

Over atmospheric pressure flowing afterglow

NASA Astrophysics Data System (ADS)

Ganciu, Mihai; Orphal, Johannes; Vervloet, Michel; Pointu, Anne-Marie; Touzeau, Michel

2002-10-01

A Tabletop discharge * created above atmospheric pressure in a N2 gas flow, uses some 10 kV very fast high voltage pulses applied between needle electrodes with some 10 kHz repetition rate. It is followed by a post-discharge, in a plastic tube with 6-mm internal diameter. Adjusting the flow and the repetition rate, the post-discharge exhibits a surprisingly long size, 9-10 m, as shown by the tube fluorescence. Preliminary spectroscopic measurements demonstrate that fluorescence is due to internal gas excited molecules (CN and NH) that are locally created by active species interaction with organic impurities. The discharge emission spectrum evidences a high nitrogen atom production rate, much higher than attainable rate with a Dielectric Barrier Discharge with same applied voltage pulses. For small air quantities added in the post-discharge, spectrum exhibits rich UV range corresponding to NO excited states. Further studies will be devoted to the post-discharge kinetics and to possible applications to medical sterilization. *M. Ganciu, private communication

Experimental study of a vertical jet in a vegetated crossflow.

PubMed

Ben Meftah, Mouldi; De Serio, Francesca; Malcangio, Daniela; Mossa, Michele; Petrillo, Antonio Felice

2015-12-01

Aquatic ecosystems have long been used as receiving environments of wastewater discharges. Effluent discharge in a receiving water body via single jet or multiport diffuser, reflects a number of complex phenomena, affecting the ecosystem services. Discharge systems need to be designed to minimize environmental impacts. Therefore, a good knowledge of the interaction between effluents, discharge systems and receiving environments is required to promote best environmental management practice. This paper reports innovative 3D flow velocity measurements of a jet discharged into an obstructed crossflow, simulating natural vegetated channel flows for which correct environmental management still lacks in literature. In recent years, numerous experimental and numerical studies have been conducted on vegetated channels, on the one hand, and on turbulent jets discharged into unvegetated crossflows, on the other hand. Despite these studies, however, there is a lack of information regarding jets discharged into vegetated crossflow. The present study aims at obtaining a more thorough understanding of the interaction between a turbulent jet and an obstructed crossflow. In order to achieve such an objective, a series of laboratory experiments was carried out in the Department of Civil, Environmental, Building Engineering and Chemistry of the Technical University of Bari - Italy. The physical model consists of a vertical jet discharged into a crossflow, obstructed by an array of vertical, rigid, circular and threaded steel cylinders. Analysis of the measured flow velocities shows that the array of emergent rigid vegetation significantly affects the jet and the ambient flow structures. It reduces the mean channel velocity, allowing the jet to penetrate higher into the crossflow. It significantly increases the transversal flow motion, promoting a major lateral spreading of the jet within the crossflow. Due to the vegetation array effects, the jet undergoes notable variations in its vortical structure. The variation of the flow patterns affects the mixing process and consequently the dilution of pollutants discharged in receiving water bodies. Copyright © 2015 Elsevier Ltd. All rights reserved.

Uncertainty in low-flow data from three streamflow-gaging stations on the upper Verde River, Arizona

USGS Publications Warehouse

Anning, D.W.; ,

2004-01-01

The evaluation of uncertainty in low-flow data collected from three streamflow-gaging stations on the upper Verde River, Arizona, was presented. In downstream order, the stations are Verde River near Paulden, Verde River near Clarkdale, and Verde River near Camp Verde. A monitoring objective of the evaluation was to characterize discharge of the lower flow regime through a variety of procedures such as frequency analysis and base-flow analysis. For Verde River near Paulden and near Camp Verde, the uncertainty of daily low flows can be reduced by decreasing the uncertainty of discharge-measurement frequency, or building an artificial control that would have a stable stage-discharge relation over time.

Plasma-enhanced mixing and flameholding in supersonic flow.

PubMed

Firsov, Alexander; Savelkin, Konstantin V; Yarantsev, Dmitry A; Leonov, Sergey B

2015-08-13

The results of experimental study of plasma-based mixing, ignition and flameholding in a supersonic model combustor are presented in the paper. The model combustor has a length of 600 mm and cross section of 72 mm width and 60 mm height. The fuel is directly injected into supersonic airflow (Mach number M=2, static pressure P(st)=160-250 Torr) through wall orifices. Two series of tests are focused on flameholding and mixing correspondingly. In the first series, the near-surface quasi-DC electrical discharge is generated by flush-mounted electrodes at electrical power deposition of W(pl)=3-24 kW. The scope includes parametric study of ignition and flame front dynamics, and comparison of three schemes of plasma generation: the first and the second layouts examine the location of plasma generators upstream and downstream from the fuel injectors. The third pattern follows a novel approach of combined mixing/ignition technique, where the electrical discharge distributes along the fuel jet. The last pattern demonstrates a significant advantage in terms of flameholding limit. In the second series of tests, a long discharge of submicrosecond duration is generated across the flow and along the fuel jet. A gasdynamic instability of thermal cavity developed after a deposition of high-power density in a thin plasma filament promotes the air-fuel mixing. The technique studied in this work has weighty potential for high-speed combustion applications, including cold start/restart of scramjet engines and support of transition regime in dual-mode scramjet and at off-design operation. © 2015 The Author(s) Published by the Royal Society. All rights reserved.

Parametric investigation of enclosed keeper discharge characteristics

NASA Technical Reports Server (NTRS)

Sheheen, T. W.; Finke, R. C.

1973-01-01

Volt-ampere discharge characteristics of an enclosed keeper hollow cathode discharge were measured as a function of the mercury flow rate and external circuit impedance. Discharge currents were varied from 0 to 1 ampere and voltages were 7 to 39 volts. Batteries and a vacuum tube control circuit were used to obtain characteristics curves that were independent of power supply impedance. Variation of the neutral flow results in changes in the discharge which interact with the impedance of the external circuit, and under some conditions, give rise to multiple operating points.

Hydrological characterization of cave drip waters in a porous limestone: Golgotha Cave, Western Australia

NASA Astrophysics Data System (ADS)

Mahmud, Kashif; Mariethoz, Gregoire; Baker, Andy; Treble, Pauline C.

2018-02-01

Cave drip water response to surface meteorological conditions is complex due to the heterogeneity of water movement in the karst unsaturated zone. Previous studies have focused on the monitoring of fractured rock limestones that have little or no primary porosity. In this study, we aim to further understand infiltration water hydrology in the Tamala Limestone of SW Australia, which is Quaternary aeolianite with primary porosity. We build on our previous studies of the Golgotha Cave system and utilize the existing spatial survey of 29 automated cave drip loggers and a lidar-based flow classification scheme, conducted in the two main chambers of this cave. We find that a daily sampling frequency at our cave site optimizes the capture of drip variability with the least possible sampling artifacts. With the optimum sampling frequency, most of the drip sites show persistent autocorrelation for at least a month, typically much longer, indicating ample storage of water feeding all stalactites investigated. Drip discharge histograms are highly variable, showing sometimes multimodal distributions. Histogram skewness is shown to relate to the wetter-than-average 2013 hydrological year and modality is affected by seasonality. The hydrological classification scheme with respect to mean discharge and the flow variation can distinguish between groundwater flow types in limestones with primary porosity, and the technique could be used to characterize different karst flow paths when high-frequency automated drip logger data are available. We observe little difference in the coefficient of variation (COV) between flow classification types, probably reflecting the ample storage due to the dominance of primary porosity at this cave site. Moreover, we do not find any relationship between drip variability and discharge within similar flow type. Finally, a combination of multidimensional scaling (MDS) and clustering by k means is used to classify similar drip types based on time series analysis. This clustering reveals four unique drip regimes which agree with previous flow type classification for this site. It highlights a spatial homogeneity in drip types in one cave chamber, and spatial heterogeneity in the other, which is in agreement with our understanding of cave chamber morphology and lithology.

Power law time dependence of river flood decay and its relationship to long term discharge frequency distribution. [California

NASA Technical Reports Server (NTRS)

Schubert, G.; Lingenfelter, R. E.

1973-01-01

Investigations have continued into the possibility that significant information on stream flow rates can be obtained from aerial and satellite imagery of river meander patterns by seeking a correlation between the meander and discharge spectra of rivers. Such a correlation could provide the basis for a simple and inexpensive technique for remote sensing of the water resources of large geographical areas, eliminating the need for much hydrologic recording. The investigation of the nature of the meander and discharge spectra and their interrelationship can also contribute to a more fundamental understanding of the processes of both river meander formation and drainage of large basins. It has been found that floods decay with an inverse power law dependence on time. The exponent of this dependence varies from river to river and even from station to station along the same river. This power law time dependence makes possible the forecasting of river discharge with an uncertainty of about 5% for as long as a month following the flood peak.

Full-Field Measurements of Self-Excited Oscillations in Momentum-Dominated Helium Jets

NASA Technical Reports Server (NTRS)

Yildirim, B. S.; Agrawal, A. K.

2005-01-01

Flow structure of momentum-dominated helium jets discharged vertically into ambient air was investigated using a high-speed rainbow schlieren deflectometry (RSD) apparatus operated at up to 2000 Hz. The operating parameters, i.e., Reynolds number and Richardson number were varied independently to examine the self-excited, flow oscillatory behavior over a range of experimental conditions. Measurements revealed highly periodic oscillations in the laminar region at a unique frequency as well as high regularity in the flow transition and initial turbulent regions. The buoyancy was shown to affect the oscillation frequency and the distance from the jet exit to the flow transition plane. Instantaneous helium concentration contours across the field of view revealed changes in the jet flow structure and the evolution of the vortical structures during an oscillation cycle. A cross-correlation technique was applied to track the vortices and to find their convection velocity. Time-traces of helium concentration at different axial locations provided detailed information about the oscillating flow.

Low-flow characteristics and profiles for the Deep River in the Cape Fear River basin, North Carolina

USGS Publications Warehouse

Weaver, J.C.

1997-01-01

Drainage area and low-flow discharge profiles are presented for the Deep River. The drainage-area profile shows downstream increases in basin size. At the mouth, the drainage area for the Deep River is 1,441 square miles. Low-flow discharge profiles for the Deep River include 7Q10, 30Q2, W7Q10, and 7Q2 discharges in a continuous profile with contributions from major tributaries included.

Water-discharge determinations for the tidal reach of the Willamette River from Ross Island Bridge to Mile 10.3, Portland, Oregon

USGS Publications Warehouse

Dempster, G.R.; Lutz, Gale A.

1968-01-01

Water-discharge, velocity, and slope variations for a 3.7-mile-Iong tidal reach of the Willamette River at Portland, Oreg., were defined from discharge measurements and river stage data collected between July 1962 and January 1965. Observed water discharge during tide-affected flows, during floods, and during backwater from the Columbia River and recorded stages at each end of the river reach were used to determine water discharge from two mathematical models. These models use a finite-difference method to solve the equations of moderately unsteady open-channel streamflow, and discharges are computed by an electronic digital computer. Discharges computed by using the mathematical models compare satisfactorily with observed discharges, except during the period of backwater from the annual flood of the Columbia River. The flow resistance coefficients used in the models vary with discharge; for one model, the coefficients for discharges above 30,000 cfs (cubic feet per second) are 12 and 24 percent less than the coefficient used for discharges below 30,000 cfs. Daily mean discharges were determined by use of one mathematical model for approximately two-thirds of the water year, October 1963 through September 1964. Agreement of computed with routed daily mean discharges is fair; above 30,000 cfs, average differences between the two discharges are about 10 percent, and below 30,000 cfs, computed daily discharges are consistently greater (by as much as 25 percent) than routed discharges. The other model was used to compute discharges for the unusually high flood flows of December 1964.

Calculated hydrographs for unsteady research flows at selected sites along the Colorado River downstream from Glen Canyon Dam, Arizona, 1990 and 1991

USGS Publications Warehouse

Griffin, Eleanor R.; Wiele, Stephen M.

1996-01-01

A one-dimensional model of unsteady discharge waves was applied to research flowr that were released from Glen Canyon Dam in support of the Glen Canyon Environmental Studies. These research flows extended over periods of 11 days during which the discharge followed specific, regular patterns repeated on a daily cycle that were similar to the daily releases for power generation. The model was used to produce discharge hydrographs at 38 selected sites in Marble and Grand Canyons for each of nine unsteady flows released from the dam in 1990 and 1991. In each case, the discharge computed from stage measurements and the associated stage-discharge relation at the streamflow-gaging station just below the dam (09379910 Colorado River Hlow Glen Canyon Dam) was routed to Diamond Creek, which is 386 kilometers downstream. Steady and unsteady tributary inflows downstream from the dam were included in the model calculations. Steady inflow to the river from tributaries downstream from the dam was determined for each case by comparing the steady base flow preceding and following the unsteady flow measured at six streamflow-gaging stations between Glen Canyon Dam and Diamond Creek. During three flow periods, significant unsteady inflow was received from the Paria River, or the Little Colorado River, or both. The amount and timing of unsteady inflow was determined using the discharge computed from records of streamflow-gaging stations on the tributaries. Unsteady flow then was added to the flow calculated by the model at the appropriate location. Hydrographs were calculated using the model at 5 streamflow-gaging stations downstream from the dam and at 33 beach study sites. Accuracy of model results was evaluated by comparing the results to discharge hydrographs computed from the records of the five streamflow-gaging stations between Lees Ferry and Lake Mead. Results show that model predictions of wave speed and shape agree well with data from the five streamflow-gaging stations.

Technique for simulating peak-flow hydrographs in Maryland

USGS Publications Warehouse

Dillow, Jonathan J.A.

1998-01-01

The efficient design and management of many bridges, culverts, embankments, and flood-protection structures may require the estimation of time-of-inundation and (or) storage of floodwater relating to such structures. These estimates can be made on the basis of information derived from the peak-flow hydrograph. Average peak-flow hydrographs corresponding to a peak discharge of specific recurrence interval can be simulated for drainage basins having drainage areas less than 500 square miles in Maryland, using a direct technique of known accuracy. The technique uses dimensionless hydrographs in conjunction with estimates of basin lagtime and instantaneous peak flow. Ordinary least-squares regression analysis was used to develop an equation for estimating basin lagtime in Maryland. Drainage area, main channel slope, forest cover, and impervious area were determined to be the significant explanatory variables necessary to estimate average basin lagtime at the 95-percent confidence interval. Qualitative variables included in the equation adequately correct for geographic bias across the State. The average standard error of prediction associated with the equation is approximated as plus or minus (+/-) 37.6 percent. Volume correction factors may be applied to the basin lagtime on the basis of a comparison between actual and estimated hydrograph volumes prior to hydrograph simulation. Three dimensionless hydrographs were developed and tested using data collected during 278 significant rainfall-runoff events at 81 stream-gaging stations distributed throughout Maryland and Delaware. The data represent a range of drainage area sizes and basin conditions. The technique was verified by applying it to the simulation of 20 peak-flow events and comparing actual and simulated hydrograph widths at 50 and 75 percent of the observed peak-flow levels. The events chosen are considered extreme in that the average recurrence interval of the selected peak flows is 130 years. The average standard errors of prediction were +/- 61 and +/- 56 percent at the 50 and 75 percent of peak-flow hydrograph widths, respectively.

Wave Augmented Diffuser for Centrifugal Compressor

NASA Technical Reports Server (NTRS)

Skoch, Gary J. (Inventor); Paxson, Daniel E. (Inventor)

2001-01-01

A wave augmented diffuser for a centrifugal compressor surrounds the outlet of an impeller that rotates on a drive shaft having an axis of rotation. The impeller brings flow in in an axial direction and imparts kinetic energy to the flow discharging it in radial and tangential directions. The flow is discharged into a plurality of circumferentially disposed wave chambers. The wave chambers are periodically opened and closed by a rotary valve such that the flow through the diffuser is unsteady. The valve includes a plurality of valve openings that are periodically brought into and out of fluid communication with the wave chambers. When the wave chambers are closed, a reflected compression wave moves upstream towards the diffuser bringing the flow into the wave chamber to rest. This action recovers the kinetic energy from the flow and limits any boundary layer growth. The flow is then discharged in an axial direction through an opening in the valve plate when the valve plate is rotated to an open position. The diffuser thus efficiently raises the static pressure of the fluid and discharges an axially directed flow at a radius that is predominantly below the maximum radius of the diffuser.

High resolution mapping of riffle-pool dynamics based on ADCP and close-range remote sensing data

NASA Astrophysics Data System (ADS)

Salmela, Jouni; Kasvi, Elina; Alho, Petteri

2017-04-01

Present development of mobile laser scanning (MLS) and close-range photogrammetry with unmanned aerial vehicle (UAV) enable us to create seamless digital elevation models (DEMs) of the riverine environment. Remote-controlled flow measurement platforms have also improved spatio-temporal resolution of the flow field data. In this study, acoustic Doppler current profiler (ADCP) attached to remote-controlled mini-boat, UAV-based bathymetry and MLS techniques were utilized to create the high-resolution DEMs of the river channel. These high-resolution measurements can be used in many fluvial applications such as computational fluid dynamics, channel change detection, habitat mapping or hydro-electric power plant planning. In this study we aim: 1) to analyze morphological changes of river channel especially riffle and pool formations based on fine-scale DEMs and ADCP measurements, 2) to analyze flow fields and their effect on morphological changes. The interest was mainly focused on reach-scale riffle-pool dynamics within two-year period of 2013 and 2014. The study was performed in sub-arctic meandering Pulmankijoki River located in Northern Finland. The river itself has shallow and clear water and sandy bed sediment. Discharge remains typically below 10 m3s-1 most of the year but during snow melt period in spring the discharge may exceed 70 m3s-1. We compared DEMs and ADCP measurements to understand both magnitude and spatio-temporal change of the river bed. Models were accurate enough to study bed form changes and locations and persistence of riffles and pools. We analyzed their locations with relation to flow during the peak and low discharge. Our demonstrated method has improved significantly spatio-temporal resolution of riverine DEMs compared to other cross-sectional and photogrammetry based models. Together with flow field measurements we gained better understanding of riverbed-water interaction

Flow control of an elongated jet in cross-flow: Film cooling effectiveness enhancement using surface dielectric barrier discharge plasma actuator

NASA Astrophysics Data System (ADS)

Audier, P.; Fénot, M.; Bénard, N.; Moreau, E.

2016-02-01

The case presented here deals with plasma flow control applied to a cross-flow configuration, more specifically to a film cooling system. The ability of a plasma dielectric barrier discharge actuator for film cooling effectiveness enhancement is investigated through an experimental set-up, including a film injection from an elongated slot into a thermally uniform cross-flow. Two-dimensional particle image velocimetry and infrared-thermography measurements are performed for three different blowing ratios of M = 0.4, 0.5, and 1. Results show that the effectiveness can be increased when the discharge is switched on, as predicted by the numerical results available in literature. Whatever the blowing ratio, the actuator induces a deflection of the jet flow towards the wall, increases its momentum, and delays its diffusion in the cross-flow.

Local Modelling of Groundwater Flow Using Analytic Element Method Three-dimensional Transient Unconfined Groundwater Flow With Partially Penetrating Wells and Ellipsoidal Inhomogeneites

NASA Astrophysics Data System (ADS)

Jankovic, I.; Barnes, R. J.; Soule, R.

2001-12-01

The analytic element method is used to model local three-dimensional flow in the vicinity of partially penetrating wells. The flow domain is bounded by an impermeable horizontal base, a phreatic surface with recharge and a cylindrical lateral boundary. The analytic element solution for this problem contains (1) a fictitious source technique to satisfy the head and the discharge conditions along the phreatic surface, (2) a fictitious source technique to satisfy specified head conditions along the cylindrical boundary, (3) a method of imaging to satisfy the no-flow condition across the impermeable base, (4) the classical analytic solution for a well and (5) spheroidal harmonics to account for the influence of the inhomogeneities in hydraulic conductivity. Temporal variations of the flow system due to time-dependent recharge and pumping are represented by combining the analytic element method with a finite difference method: analytic element method is used to represent spatial changes in head and discharge, while the finite difference method represents temporal variations. The solution provides a very detailed description of local groundwater flow with an arbitrary number of wells of any orientation and an arbitrary number of ellipsoidal inhomogeneities of any size and conductivity. These inhomogeneities may be used to model local hydrogeologic features (such as gravel packs and clay lenses) that significantly influence the flow in the vicinity of partially penetrating wells. Several options for specifying head values along the lateral domain boundary are available. These options allow for inclusion of the model into steady and transient regional groundwater models. The head values along the lateral domain boundary may be specified directly (as time series). The head values along the lateral boundary may also be assigned by specifying the water-table gradient and a head value at a single point (as time series). A case study is included to demonstrate the application of the model in local modeling of the groundwater flow. Transient three-dimensional capture zones are delineated for a site on Prairie Island, MN. Prairie Island is located on the Mississippi River 40 miles south of the Twin Cities metropolitan area. The case study focuses on a well that has been known to contain viral DNA. The objective of the study was to assess the potential for pathogen migration toward the well.

One-dimensional analytical solution for hydraulic head and numerical solution for solute transport through a horizontal fracture for submarine groundwater discharge.

PubMed

He, Cairong; Wang, Tongke; Zhao, Zhixue; Hao, Yonghong; Yeh, Tian-Chyi J; Zhan, Hongbin

2017-11-01

Submarine groundwater discharge (SGD) has been recognized as a major pathway of groundwater flow to coastal oceanic environments. It could affect water quality and marine ecosystems due to pollutants and trace elements transported through groundwater. Relations between different characteristics of aquifers and SGD have been investigated extensively before, but the role of fractures in SGD still remains unknown. In order to better understand the mechanism of groundwater flow and solute transport through fractures in SGD, one-dimensional analytical solutions of groundwater hydraulic head and velocity through a synthetic horizontal fracture with periodic boundary conditions were derived using a Laplace transform technique. Then, numerical solutions of solute transport associated with the given groundwater velocity were developed using a finite-difference method. The results indicated that SGD associated with groundwater flow and solute transport was mainly controlled by sea level periodic fluctuations, which altered the hydraulic head and the hydraulic head gradient in the fracture. As a result, the velocity of groundwater flow associated with SGD also fluctuated periodically. We found that the pollutant concentration associated with SGD oscillated around a constant value, and could not reach a steady state. This was particularly true at locations close to the seashore. This finding of the role of fracture in SGD will assist pollution remediation and marine conservation in coastal regions. Copyright © 2017 Elsevier B.V. All rights reserved.

One-dimensional analytical solution for hydraulic head and numerical solution for solute transport through a horizontal fracture for submarine groundwater discharge

NASA Astrophysics Data System (ADS)

He, Cairong; Wang, Tongke; Zhao, Zhixue; Hao, Yonghong; Yeh, Tian-Chyi J.; Zhan, Hongbin

2017-11-01

Submarine groundwater discharge (SGD) has been recognized as a major pathway of groundwater flow to coastal oceanic environments. It could affect water quality and marine ecosystems due to pollutants and trace elements transported through groundwater. Relations between different characteristics of aquifers and SGD have been investigated extensively before, but the role of fractures in SGD still remains unknown. In order to better understand the mechanism of groundwater flow and solute transport through fractures in SGD, one-dimensional analytical solutions of groundwater hydraulic head and velocity through a synthetic horizontal fracture with periodic boundary conditions were derived using a Laplace transform technique. Then, numerical solutions of solute transport associated with the given groundwater velocity were developed using a finite-difference method. The results indicated that SGD associated with groundwater flow and solute transport was mainly controlled by sea level periodic fluctuations, which altered the hydraulic head and the hydraulic head gradient in the fracture. As a result, the velocity of groundwater flow associated with SGD also fluctuated periodically. We found that the pollutant concentration associated with SGD oscillated around a constant value, and could not reach a steady state. This was particularly true at locations close to the seashore. This finding of the role of fracture in SGD will assist pollution remediation and marine conservation in coastal regions.

Glow discharge sources for atomic and molecular analyses

NASA Astrophysics Data System (ADS)

Storey, Andrew Patrick

Two types of glow discharges were used and characterized for chemical analysis. The flowing atmospheric pressure afterglow (FAPA) source, based on a helium glow discharge (GD), was utilized to analyze samples with molecular mass spectrometry. A second GD, operated at reduced pressure in argon, was employed to map the elemental composition of a solid surface with novel optical detection systems, enabling new applications and perspectives for GD emission spectrometry. Like many plasma-based ambient desorption-ionization sources being used around the world, the FAPA requires a supply of helium to operate effectively. With increased pressures on global helium supply and pricing, the use of an interrupted stream of helium for analysis was explored for vapor and solid samples. In addition to the mass spectra generated by the FAPA source, schlieren imaging and infrared thermography were employed to map the behavior of the source and its surroundings under the altered conditions. Additionally, a new annular microplasma variation of the FAPA source was developed and characterized. A spectroscopic imaging system that utilized an adjustable-tilt interference filter was used to map the elemental composition of a sample surface by glow discharge emission spectroscopy. This apparatus was compared to other GD imaging techniques for mapping elemental surface composition. The wide bandpass filter resulted in significant spectral interferences that could be partially overcome with chemometric data processing. Because time-resolved GD emission spectroscopy can provide fine depth-profiling measurements, a natural extension of GD imaging would be its application to three-dimensional characterization of samples. However, the simultaneous cathodic sputtering that occur across the sample results in a sampling process that is not completely predictable. These issues are frequently encountered when laterally varied samples are explored with glow discharge imaging techniques. These insights are described with respect to their consequences for both imaging and conventional GD spectroscopic techniques.

Habitat sequencing and the importance of discharge in inferences

Treesearch

Robert H. Hilderbrand; A. Dennis Lemly; C. Andrew Dolloff

1999-01-01

The authors constructed stream maps for a low-­gradient trout stream in southwestern Virginia during autumn (base flow) and spring (elevated flows) to compare spatial and temporal variation in stream habitats. Pool-riffle sequencing and total area occupied by pools and riffles changed substantially depending on the level of discharge: reduced discharge resulted in an...

Test stand for gas-discharge chamber of TEA CO2 lasers with pulse-periodical energy supply

NASA Astrophysics Data System (ADS)

Shorin, Vladimyr P.; Bystrov, N. D.; Zhuravlyov, O. A.; Nekrasov, V. V.

1997-05-01

Test stand for function optimization (incomposition of gas- dynamic circuit (GDC) of operating characteristics of full- size discharge chamber of flowing TEA carbon-dioxide lasers (power up to 100 kW) was created in Samara State Aerospace University (former Kuibyshev Aviation Institute). Test stand includes an inside-type GDC, low inductive generators of voltage pulses of preionization and main discharges, two-flow rate system of gas supply and noise immunity diagnostic system. Module construction of units of GDC, power supplies of preionization and main discharges allows to change configuration of stand's systems for providing given properties of gas flow and its energy supply. This test stand can also be used in servicing of laser system. The diagnostic system of this stand allows us to analyze energy properties of discharge by means of oscillographic measurements of voltage and current with following processing of discharges' volt- ampere characteristics by means of a computer; rate of non- stationary gas-dynamic disturbances in discharge gap of discharge chamber was measured by means of pulse holographic system (UlG-1M) with data processing of schliren- and interferogram (density fluctuation sensitivity approximately 10-2) and sensor measurement system of gas-dynamic shock and acoustics process with resonance frequency exceeding 100 kHz. Research results of process of plasma plate wave and channel structures interaction with mediums, including actuation non-stationary gas-dynamic flows, cavitation erosion of preionization electrodes' dielectric substructure, ancillary heating of channels by main volumetric discharge are presented as well.

Assessing colloid-bound metal export in response to short term changes in runoff from a forested catchment

NASA Astrophysics Data System (ADS)

Neubauer, E.; Kammer, F. v. d.; Knorr, K.-H.; Pfeiffer, S.; Reichert, M.; Hofmann, T.

2012-04-01

Soils can act as a source of metals and natural organic matter (NOM) in runoff from catchments. Amounts and intensity of rainfall may influence NOM export from catchments. The presence of NOM and other colloids in water may not only enhance metal export, but also significantly change metal speciation. In this study, we investigated the response of metal-colloid associations to short-term discharge variations in the runoff from a small forested catchment (Lehstenbach, Bavaria, Germany). Here, the discharge from the catchment outlet responds within hours to rain events. Near-surface flow in organic-rich layers and peat soils has been identified to increase dissolved organic carbon (DOC) concentrations during stormwater runoff. Flow Field-Flow Fractionation coupled to ICP-MS (FlowFFF-ICPMS) is a high-resolution size separation technique which was used for the detection and quantification of colloids and associated metals. Colloid-associated metals, dissolved metals and metals associated with low-molecular weight organic ligands were also separated by filtration (0.2 µm) and ultrafiltration (1000 g/mol MWCO). During baseflow DOC concentration was <6 mg/L and the pH ranged between 4.6 and 5.0. The DOC concentration exported at a given discharge was subject to strong seasonal variation and depended on the water level before the discharge event. DOC concentrations were up to 8 fold higher during stormwater runoff compared to baseflow. The export of aluminum, arsenic, rare earth elements (REE) and uranium from the catchment increased during stormwater runoff showing a strong correlation with NOM concentrations. This result was supported by FlowFFF-ICPMS data revealing that NOM was the only colloid type available for metal complexation during all hydrological conditions. A clear temporal pattern in the association with the NOM was observed for most of the metals under study: During baseflow, 70-100% (Fe), 90% (Al), 60-100% (REE) and 80-85% (U) were associated with the NOM. During stormwater runoff, the dissolved species concentration and those associated with small organic ligands (<1000 g/mol) increased. The pH drop during the stormwater runoff (pH <4) is most likely the main factor for weaker metal-NOM binding. However, only 25 to 50% of the arsenic was associated with NOM, but no relation to discharge, or pH was exhibited. The results show that fluxes of most trace metals from the catchment are governed by NOM-colloids, even though substantial concentrations are dissolved or associated to low-molecular weight organic substances during stormwater runoff.

Radio-frequency capacitive discharge with flowing liquid electrodes at reduced gas pressures

NASA Astrophysics Data System (ADS)

Gaisin, Al. F.; Son, E. E.; Petryakov, S. Yu.

2017-07-01

Results are presented from experimental studies of the electrophysical and spectral characteristics of the low-temperature plasma of a radio-frequency capacitive discharge excited between two flowing liquid electrodes at gas pressures of 103-105 Pa. The plasma composition, the electron density, and the vibrational and rotational temperatures of gas molecules are estimated. The types and shapes of discharge are described, and the thermal and gas-hydrodynamic processes in the discharge zone are analyzed.

Apparatus and techniques for measuring bedload

USGS Publications Warehouse

Hubbell, David Wellington

1964-01-01

The need for accurate determinations of the total sediment discharge of particles of bedload size has prompted this investigation of available and possible measuring apparatus and procedures. The accuracy of measurements of sediment discharge made with trap-type samplers is affected by the variability of sampler efficiency, by the oscillatory variation of bedload discharge, and by sampler placement. Equations that were developed for determining total discharge from measured bedioad discharge and measured suspended-sediment discharge are simplest if the bedload apparatus measures only the true bedload. Early bedload samplers are generally unsatisfactory. Recently developed or suggested apparatus include various improved samplers of the pressure-difference type, a pumping sampler, a magnetic sampler, acoustical instruments that measure the magnitude of the sound of particle collisions, an ultrasonic bedload sampler designed to measure and integrate electronically the concentration and velocity, and a tiltmeter designed to measure the total sediment discharge from the ground tilt that results from the passage of flow. All the pressure-difference samplers are improvements over early samplers, but none are void of the inherent shortcomings of trap-type apparatus; probably the Sphinx (Dutch) and VUV (Hungarian) samplers are the most satisfactory. The acoustical instruments are capable of measuring only the relative discharge. The ultrasonic sampler and the tiltmeter are not adequate without further development. Some new possible apparatus and means for measuring or aiding in measuring bedload discharge are small pit samplers, ultrasonic sounders, pressure transducers, and photography. A small pit sampler for measuring bedload discharge was designed to provide self-placement and portability ; however, its practicability and efficiency are undetermined. Exploratory films show that by using slowmotion photography the discharge of particles larger than about pea size can be determined provided the flow is clear; however, photography generally is not practical. Ultrasonic sounders provide continuous and accurate data on bed configuration and dune movement for use in equations that were developed for computing the bedload discharge. Computations with the equations indicate that the interpretation of the sounding data needs further study. Pressure transducers placed beneath the bed surface possibly can be used to provide information on dune movement; however, their installation would be difficult. The time required for collecting data on bed configuration and dune movement throughout a cross section could be substantially reduced by using several transducers simultaneously in conjunction with an ultrasonic sounder. A modified ultrasonic sounder that provides information on the shape and velocity of large particles and a method for determining the discharge of such particles were proposed; the method seems most feasible for particles of high sphericity.

Preliminary stage-discharge relations for Tombigbee River at Aliceville lock and dam, near Pickensville, Alabama

USGS Publications Warehouse

Nelson, G.H.; Ming, C.O.

1983-01-01

The construction of Aliceville lock and dam and other related channel alterations, completed in 1979, has resulted in changes to the stage-discharge relations in the vicinity. The scarcity of current-meter measurements, coupled with backwater conditions, makes definition of a single stage-discharge relation impossible. However, limit curves can be defined that would encompass such a relation. Backwater is defined as water backed up or retarded in its course as compared with water flowing under normal or natural conditions. This results in a rise in stage above normal water level while the discharge remains unaffected. Backwater is usually caused by temporary obstruction(s) to flow downstream. Backwater at Aliceville Dam results from a variety of river conditions. Some of these conditions are large tributary inflow, return of flood plain flows to the main channel during recessions, and operations at Gainesville Dam during low flows. The discharges obtained from 26 current-meter measurements, along with computed discharges through the dam, are plotted versus stage. The plot illustrates, by the scatter of data points, the variations in backwater. Curves are drawn to envelope the extreme plot patterns showing possible ranges of several feet in stage for any given discharge. The upper end of the curves were extrapolated based on the results of a step-backwater analysis.

Discharge Oscillations in a Permanent Magnet Cylindrical Hall-Effect Thruster

NASA Technical Reports Server (NTRS)

Polzin, K. A.; Sooby, E. S.; Raitses, Y.; Merino, E.; Fisch, N. J.

2009-01-01

Measurements of the discharge current in a cylindrical Hall thruster are presented to quantify plasma oscillations and instabilities without introducing an intrusive probe into the plasma. The time-varying component of the discharge current is measured using a current monitor that possesses a wide frequency bandwidth and the signal is Fourier transformed to yield the frequency spectra present, allowing for the identification of plasma oscillations. The data show that the discharge current oscillations become generally greater in amplitude and complexity as the voltage is increased, and are reduced in severity with increasing flow rate. The breathing mode ionization instability is identified, with frequency as a function of discharge voltage not increasing with discharge voltage as has been observed in some traditional Hall thruster geometries, but instead following a scaling similar to a large-amplitude, nonlinear oscillation mode recently predicted in for annular Hall thrusters. A transition from lower amplitude oscillations to large relative fluctuations in the oscillating discharge current is observed at low flow rates and is suppressed as the mass flow rate is increased. A second set of peaks in the frequency spectra are observed at the highest propellant flow rate tested. Possible mechanisms that might give rise to these peaks include ionization instabilities and interactions between various oscillatory modes.

Geohydrology and evapotranspiration at Franklin Lake playa, Inyo County, California; with a section on estimating evapotranspiration using the energy-budget eddy-correlation technique

USGS Publications Warehouse

Czarnecki, John B.; Stannard, David I.

1997-01-01

Franklin Lake playa is one of the principal discharge areas of the ground-water-flow system associated with Yucca Mountain, Nevada, the potential site of a high-level nuclear-waste repository. By using the energy-budget eddy-correlation technique, measurements made between June 1983 and April 1984 to estimate evapotranspiration were found to range from 0.1 centimeter per day during winter months to about 0.3 centimeter per day during summer months; the annual average was 0.16 centimeter per day. These estimates were compared with evapotranspiration estimates calculated from six other methods.

Experimental Investigation of Centrifugal Compressor Stabilization Techniques

NASA Technical Reports Server (NTRS)

Skoch, Gary J.

2003-01-01

Results from a series of experiments to investigate techniques for extending the stable flow range of a centrifugal compressor are reported. The research was conducted in a high-speed centrifugal compressor at the NASA Glenn Research Center. The stabilizing effect of steadily flowing air-streams injected into the vaneless region of a vane-island diffuser through the shroud surface is described. Parametric variations of injection angle, injection flow rate, number of injectors, injector spacing, and injection versus bleed were investigated for a range of impeller speeds and tip clearances. Both the compressor discharge and an external source were used for the injection air supply. The stabilizing effect of flow obstructions created by tubes that were inserted into the diffuser vaneless space through the shroud was also investigated. Tube immersion into the vaneless space was varied in the flow obstruction experiments. Results from testing done at impeller design speed and tip clearance are presented. Surge margin improved by 1.7 points using injection air that was supplied from within the compressor. Externally supplied injection air was used to return the compressor to stable operation after being throttled into surge. The tubes, which were capped to prevent mass flux, provided 9.3 points of additional surge margin over the baseline surge margin of 11.7 points.

Hydrodynamic simulation and particle-tracking techniques for identification of source areas to public-water intakes on the St. Clair-Detroit river waterway in the Great Lakes Basin

USGS Publications Warehouse

Holtschlag, David J.; Koschik, John A.

2004-01-01

Source areas to public water intakes on the St. Clair-Detroit River Waterway were identified by use of hydrodynamic simulation and particle-tracking analyses to help protect public supplies from contaminant spills and discharges. This report describes techniques used to identify these areas and illustrates typical results using selected points on St. Clair River and Lake St. Clair. Parameterization of an existing two-dimensional hydrodynamic model (RMA2) of the St. Clair-Detroit River Waterway was enhanced to improve estimation of local flow velocities. Improvements in simulation accuracy were achieved by computing channel roughness coefficients as a function of flow depth, and determining eddy viscosity coefficients on the basis of velocity data. The enhanced parameterization was combined with refinements in the model mesh near 13 public water intakes on the St. Clair-Detroit River Waterway to improve the resolution of flow velocities while maintaining consistency with flow and water-level data. Scenarios representing a range of likely flow and wind conditions were developed for hydrodynamic simulation. Particle-tracking analyses combined advective movements described by hydrodynamic scenarios with random components associated with sub-grid-scale movement and turbulent mixing to identify source areas to public water intakes.

Classifying low flow hydrological regimes at a regional scale

NASA Astrophysics Data System (ADS)

Kirkby, M. J.; Gallart, F.; Kjeldsen, T. R.; Irvine, B. J.; Froebrich, J.; Lo Porto, A.; de Girolamo, A.; Mirage Team

2011-12-01

The paper uses a simple water balance model that partitions the precipitation between actual evapotranspiration, quick flow and delayed flow, and has sufficient complexity to capture the essence of climate and vegetation controls on this partitioning. Using this model, monthly flow duration curves have been constructed from climate data across Europe to address the relative frequency of ecologically critical low flow stages in semi-arid rivers, when flow commonly persists only in disconnected pools in the river bed. The hydrological model is based on a dynamic partitioning of precipitation to estimate water available for evapotranspiration and plant growth and for residual runoff. The duration curve for monthly flows has then been analysed to give an estimate of bankfull flow based on recurrence interval. Arguing from observed ratios of cross-sectional areas at flood and low flows, hydraulic geometry suggests that disconnected flow under "pool" conditions is approximately 0.1% of bankfull flow. Flow duration curves define a measure of bankfull discharge on the basis of frequency. The corresponding frequency for pools is then read from the duration curve, using this (0.1%) ratio to estimate pool discharge from bank full discharge. The flow duration curve then provides an estimate of the frequency of poorly connected pool conditions, corresponding to this discharge, that constrain survival of river-dwelling arthropods and fish. The methodology has here been applied across Europe at 15 km resolution, and the potential is demonstrated for applying the methodology under alternative climatic scenarios.

Topological structures of vortex flow on a flying wing aircraft, controlled by a nanosecond pulse discharge plasma actuator

NASA Astrophysics Data System (ADS)

Du, Hai; Shi, Zhiwei; Cheng, Keming; Wei, Dechen; Li, Zheng; Zhou, Danjie; He, Haibo; Yao, Junkai; He, Chengjun

2016-06-01

Vortex control is a thriving research area, particularly in relation to flying wing or delta wing aircraft. This paper presents the topological structures of vortex flow on a flying wing aircraft controlled by a nanosecond plasma dielectric barrier discharge actuator. Experiments, including oil flow visualization and two-dimensional particle image velocimetry (PIV), were conducted in a wind tunnel with a Reynolds number of 0.5 × 106. Both oil and PIV results show that the vortex can be controlled. Oil topological structures on the aircraft surface coincide with spatial PIV flow structures. Both indicate vortex convergence and enhancement when the plasma discharge is switched on, leading to a reduced region of separated flow.

Streamflow Characteristics of Streams in the Helmand Basin, Afghanistan

USGS Publications Warehouse

Williams-Sether, Tara

2008-01-01

Statistical summaries of streamflow data for all historical streamflow-gaging stations for the Helmand Basin upstream from the Sistan Wetlands are presented in this report. The summaries for each streamflow-gaging station include (1) manuscript (station description), (2) graph of the annual mean discharge for the period of record, (3) statistics of monthly and annual mean discharges, (4) graph of the annual flow duration, (5) monthly and annual flow duration, (6) probability of occurrence of annual high discharges, (7) probability of occurrence of annual low discharges, (8) probability of occurrence of seasonal low discharges, (9) annual peak discharge and corresponding gage height for the period of record, and (10) monthly and annual mean discharges for the period of record.

Sediment Dynamics Affecting the Threatened Santa Ana Sucker in the Highly-modified Santa Ana River and Inset Channel, Southern California, USA

NASA Astrophysics Data System (ADS)

Minear, J. T.; Wright, S. A.

2015-12-01

In this study, we investigate the sediment dynamics of the low-flow channel of the Santa Ana River that is formed by wastewater discharges and contains some of the last remaining habitat of the Santa Ana Sucker (Catostomus santaanae). The Santa Ana River is a highly-modified river draining the San Bernardino Mountains and Inland Empire metropolitan area east of Los Angeles. Home to over 4 million people, the watershed provides habitat for the federally-threatened Santa Ana Sucker, which presently reside within the mainstem Santa Ana River in a reach supported by year-round constant discharges from water treatment plants. The nearly constant low-flow wastewater discharges and infrequent runoff events create a small, approximately 8 m wide, inset channel within the approximately 300 m wide mainstem channel that is typically dry except for large flood flows. The sediment dynamics within the inset channel are characterized by constantly evolving bed substrate and sediment transport rates, and occasional channel avulsions. The sediment dynamics have large influence on the Sucker, which rely on coarse-substrate (gravel and cobble) for their food production. In WY 2013 through the present, we investigated the sediment dynamics of the inset channel using repeat bathymetric and substrate surveys, bedload sampling, and discharge measurements. We found two distinct phases of the inset channel behavior: 1. 'Reset' flows, where sediment-laden mainstem discharges from upstream runoff events result in sand deposition in the inset channel or avulse the inset channel onto previously dry riverbed; and 2. 'Winnowing' flows, whereby the sand within the inset channel is removed by clear-water low flows from the wastewater treatment plant discharges. Thus, in contrast to many regulated rivers where high flows are required to flush fine sediments from the bed (for example, downstream from dams), in the Santa Ana River the low flows from wastewater treatment plants serve as the flushing flows that gradually remove sand and expose the coarser substrate. In effect, the inset channel is analogous to a flume subject to periodic sediment loading events from upstream (runoff events) with long periods of negligible upstream sediment supply between the events (wastewater discharges).

Techniques and equipment required for precise stream gaging in tide-affected fresh-water reaches of the Sacramento River, California

USGS Publications Warehouse

Smith, Winchell

1971-01-01

Current-meter measurements of high accuracy will be required for calibration of an acoustic flow-metering system proposed for installation in the Sacramento River at Chipps Island in California. This report presents an analysis of the problem of making continuous accurate current-meter measurements in this channel where the flow regime is changing constantly in response to tidal action. Gaging-system requirements are delineated, and a brief description is given of the several applicable techniques that have been developed by others. None of these techniques provides the accuracies required for the flowmeter calibration. A new system is described--one which has been assembled and tested in prototype and which will provide the matrix of data needed for accurate continuous current-meter measurements. Analysis of a large quantity of data on the velocity distribution in the channel of the Sacramento River at Chipps Island shows that adequate definition of the velocity can be made during the dominant flow periods--that is, at times other than slack-water periods--by use of current meters suspended at elevations 0.2 and 0.8 of the depth below the water surface. However, additional velocity surveys will be necessary to determine whether or not small systematic corrections need be applied during periods of rapidly changing flow. In the proposed system all gaged parameters, including velocities, depths, position in the stream, and related times, are monitored continuously as a boat moves across the river on the selected cross section. Data are recorded photographically and transferred later onto punchcards for computer processing. Computer programs have been written to permit computation of instantaneous discharges at any selected time interval throughout the period of the current meter measurement program. It is anticipated that current-meter traverses will be made at intervals of about one-half hour over periods of several days. Capability of performance for protracted periods was, consequently, one of the important elements in system design. Analysis of error sources in the proposed system indicates that errors in individual computed discharges can be kept smaller than 1.5 percent if the expected precision in all measured parameters is maintained.

75 FR 30395 - Stakeholder Input; National Pollutant Discharge Elimination System (NPDES) Permit Requirements...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-01

..., 2005 draft Peak Flows Policy. This draft Policy attempted to clarify EPA's interpretation that the... treatment plants that are recombined with the flows from the secondary treatment units prior to discharge... peak flow as part of an SSO rulemaking to allow for a holistic and integrated approach to reducing SSOs...

Measurements of population densities of metastable and resonant levels of argon using laser induced fluorescence

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nikolić, M.; Newton, J.; Sukenik, C. I.

2015-01-14

We present a new approach to measure population densities of Ar I metastable and resonant excited states in low temperature Ar plasmas at pressures higher than 1 Torr. This approach combines the time resolved laser induced fluorescence technique with the kinetic model of Ar. The kinetic model of Ar is based on calculating the population rates of metastable and resonant levels by including contributions from the processes that affect population densities of Ar I excited states. In particular, we included collisional quenching processes between atoms in the ground state and excited states, since we are investigating plasma at higher pressures. Wemore » also determined time resolved population densities of Ar I 2 p excited states by employing optical emission spectroscopy technique. Time resolved Ar I excited state populations are presented for the case of the post-discharge of the supersonic flowing microwave discharge at pressures of 1.7 and 2.3 Torr. The experimental set-up consists of a pulsed tunable dye laser operating in the near infrared region and a cylindrical resonance cavity operating in TE{sub 111} mode at 2.45 GHz. Results show that time resolved population densities of Ar I metastable and resonant states oscillate with twice the frequency of the discharge.« less

Low current plasmatron fuel converter having enlarged volume discharges

DOEpatents

Rabinovich, Alexander; Alexeev, Nikolai; Bromberg, Leslie; Cohn, Daniel R.; Samokhin, Andrei

2005-04-19

A novel apparatus and method is disclosed for a plasmatron fuel converter (""plasmatron"") that efficiently uses electrical energy to produce hydrogen rich gas. The volume and shape of the plasma discharge is controlled by a fluid flow established in a plasma discharge volume. A plasmatron according to this invention produces a substantially large effective plasma discharge volume allowing for substantially greater volumetric efficiency in the initiation of chemical reactions within a volume of bulk fluid reactant flowing through the plasmatron.

Low current plasmatron fuel converter having enlarged volume discharges

DOEpatents

Rabinovich, Alexander [Swampscott, MA; Alexeev, Nikolai [Moscow, RU; Bromberg, Leslie [Sharon, MA; Cohn, Daniel R [Chestnut Hill, MA; Samokhin, Andrei [Moscow, RU

2009-10-06

A novel apparatus and method is disclosed for a plasmatron fuel converter ("plasmatron") that efficiently uses electrical energy to produce hydrogen rich gas. The volume and shape of the plasma discharge is controlled by a fluid flow established in a plasma discharge volume. A plasmatron according to this invention produces a substantially large effective plasma discharge volume allowing for substantially greater volumetric efficiency in the initiation of chemical reactions within a volume of bulk fluid reactant flowing through the plasmatron.

Temporal hydrological and hydrochemical behaviour of the regional discharge area of a carbonate system - why we can not see fast responses?

NASA Astrophysics Data System (ADS)

Bodor, Petra; Eröss, Anita; Kovács, József; Mádl-Szönyi, Judit

2016-04-01

The subsurface part of the hydrologic cycle, the saturated groundwater flow can be mostly studied in regional discharge areas. In these regions the water has already spent geologically long time under the surface, therefore the upwelling water reflect the effect of the geometry and boundary conditions of the whole flow field, its geology and chemical processes. According to these conditions, the discharging waters can be characterized with different values and variability of physicochemical parameters (temperature, total dissolved solids, cations, anions, gas content etc.). This question has special interest in carbonate systems where the concept of regional groundwater flow was only introduced in the last few years. Hydrographs and chemographs are frequently used in karst studies to demonstrate the effect of variability of the system and to derive information for the nature of flow inside the karst (channel, fracture or matrix). Usually these graphs show abrupt changes after precipitation events, but this is typical for epigenic karsts. However, discharge areas, where hypogenic karsts developed, can behave differently due to their feeding flow systems. These systems and their effects are not so well studied yet. In this study we examined hydrographs and chemographs of the regional discharge area of a deep and thick carbonate range of Buda Thermal Karst and tried to understand those mechanisms which determine the hydrological and hydrochemical behaviour of the region. Here cold, lukewarm and also thermal waters discharge along the River Danube. The variability of physicochemical parameters (temperature, electric conductivity, pH, volume discharge, water level, dissolved CO2 and 222Rn, δ18O, δD) of the discharging water was studied to understand influencing mechanisms. We tried to understand the effect of precipitation (short and long term) and the effect of River Danube with geomathematical methods for the lukewarm components of the discharging water. Based on the results, it was found that the hydrological and hydrochemical parameters of the regional discharge zone are only slightly variable compared to the other parts of the system. The local effect of precipitation is not detectable at the area, and it has only buffered influence in the recharge zone based on comparison with integrated precipitation. However, this buffered effect is eliminated at the discharge zone. It means that these regional discharge zones of carbonates are less sensitive to the change in short and long term climatic conditions. This can be explained easily by their position in the gravity-driven flow systems. However, the transient effect of the river influences the discharge conditions, therefore the hydrological and hydrochemical conditions. These findings display the quasi permanent flow conditions regarding the regional discharge areas of carbonates with the superimposed transient effect of the river. The research was supported by the NK 101356 OTKA research grant.

Base flow recession from unsaturated-saturated porous media considering lateral unsaturated discharge and aquifer compressibility

NASA Astrophysics Data System (ADS)

Liang, Xiuyu; Zhan, Hongbin; Zhang, You-Kuan; Schilling, Keith

2017-09-01

Unsaturated flow is an important process in base flow recessions and its effect is rarely investigated. A mathematical model for a coupled unsaturated-saturated flow in a horizontally unconfined aquifer with time-dependent infiltrations is presented. The effects of the lateral discharge of the unsaturated zone and aquifer compressibility are specifically taken into consideration. Semianalytical solutions for hydraulic heads and discharges are derived using Laplace transform and Cosine transform. The solutions are compared with solutions of the linearized Boussinesq equation (LB solution) and the linearized Laplace equation (LL solution), respectively. A larger dimensionless constitutive exponent κD (a smaller retention capacity) of the unsaturated zone leads to a smaller discharge during the infiltration period and a larger discharge after the infiltration. The lateral discharge of the unsaturated zone is significant when κD≤1, and becomes negligible when κD≥100. The compressibility of the aquifer has a nonnegligible impact on the discharge at early times. For late times, the power index b of the recession curve -dQ/dt˜ aQb, is 1 and independent of κD, where Q is the base flow and a is a constant lumped aquifer parameter. For early times, b is approximately equal to 3 but it approaches infinity when t→0. The present solution is applied to synthetic and field cases. The present solution matched the synthetic data better than both the LL and LB solutions, with a minimum relative error of 16% for estimate of hydraulic conductivity. The present solution was applied to the observed streamflow discharge in Iowa, and the estimated values of the aquifer parameters were reasonable.

Repetitively Pulsed Nonequilibrium Plasmas for Plasma-Assisted Combustion, Flow Control, and Molecular Lasers

NASA Astrophysics Data System (ADS)

Adamovich, Igor

2006-10-01

The paper presents results of three experiments using high voltage, short pulse duration, high repetition rate discharge plasmas. High electric field during the pulse (E/N˜500-1000 Td) allows efficient ionization and molecular dissociation. Between the pulses, additional energy can be coupled to the decaying plasma using a DC field set below the breakdown threshold. While the DC sustainer discharge adds 90-95% of all the power to the flow, it does not produce any additional ionization. The pulser and the sustainer discharges are fully overlapped in space. Low duty cycle of the pulsed ionizer, ˜1/1000, allows sustaining diffuse and uniform pulser-sustainer plasmas at high pressures and power loadings. The first experiment using the pulsed discharge is ignition of premixed hydrocarbon-air flows, which occurs at low pulsed discharge powers, ˜100 W, and very low plasma temperatures, 100-200^0 C. The second experiment is Lorentz force acceleration of low-temperature supersonic flows. The pulsed discharge was used to generate electrical conductivity in M=3 nitrogen and air flows, while the sustainer discharge produced transverse current in the presence of magnetic field of B=1.5 T. Retarding Lorentz force applied to the flow produced a static pressure increase of up to 15-20%, while accelerating force of the same magnitude resulted in static pressure rise of up to 7-8%, i.e. a factor of two smaller. The third experiment is singlet delta oxygen (SDO) generation in a high-pressure pulser-sustainer discharge. SDO yield was inferred from the integrated intensity of SDO infrared emission spectra calibrated using a blackbody source. The measured yield exceeds the laser threshold yield by about a factor of three, which makes possible achieving positive gain in the laser cavity. The highest gain measured so far is 0.03%/cm.

Computer programs for describing the recession of ground-water discharge and for estimating mean ground-water recharge and discharge from streamflow records-update

USGS Publications Warehouse

Rutledge, A.T.

1998-01-01

The computer programs included in this report can be used to develop a mathematical expression for recession of ground-water discharge and estimate mean ground-water recharge and discharge. The programs are intended for analysis of the daily streamflow record of a basin where one can reasonably assume that all, or nearly all, ground water discharges to the stream except for that which is lost to riparian evapotranspiration, and where regulation and diversion of flow can be considered to be negligible. The program RECESS determines the master reces-sion curve of streamflow recession during times when all flow can be considered to be ground-water discharge and when the profile of the ground-water-head distribution is nearly stable. The method uses a repetitive interactive procedure for selecting several periods of continuous recession, and it allows for nonlinearity in the relation between time and the logarithm of flow. The program RORA uses the recession-curve displacement method to estimate the recharge for each peak in the streamflow record. The method is based on the change in the total potential ground-water discharge that is caused by an event. Program RORA is applied to a long period of record to obtain an estimate of the mean rate of ground-water recharge. The program PART uses streamflow partitioning to estimate a daily record of base flow under the streamflow record. The method designates base flow to be equal to streamflow on days that fit a requirement of antecedent recession, linearly interpolates base flow for other days, and is applied to a long period of record to obtain an estimate of the mean rate of ground-water discharge. The results of programs RORA and PART correlate well with each other and compare reasonably with results of the corresponding manual method.

Remote determination of the velocity index and mean streamwise velocity profiles

NASA Astrophysics Data System (ADS)

Johnson, E. D.; Cowen, E. A.

2017-09-01

When determining volumetric discharge from surface measurements of currents in a river or open channel, the velocity index is typically used to convert surface velocities to depth-averaged velocities. The velocity index is given by, k=Ub/Usurf, where Ub is the depth-averaged velocity and Usurf is the local surface velocity. The USGS (United States Geological Survey) standard value for this coefficient, k = 0.85, was determined from a series of laboratory experiments and has been widely used in the field and in laboratory measurements of volumetric discharge despite evidence that the velocity index is site-specific. Numerous studies have documented that the velocity index varies with Reynolds number, flow depth, and relative bed roughness and with the presence of secondary flows. A remote method of determining depth-averaged velocity and hence the velocity index is developed here. The technique leverages the findings of Johnson and Cowen (2017) and permits remote determination of the velocity power-law exponent thereby, enabling remote prediction of the vertical structure of the mean streamwise velocity, the depth-averaged velocity, and the velocity index.

Data for calibrating unsteady-flow sediment-transport models, East Fork River, Wyoming, 1975

USGS Publications Warehouse

Mahoney, Holly A.; Andrews, Edmund D.; Emmett, William W.; Leopold, Luna Bergere; Meade, Robert H.; Myrick, Robert M.; Nordin, Carl F.

1976-01-01

In 1975, data to calibrate a one-dimensional unsteady-flow and sediment-transport routing model were collected on a reach of the East Fork River of western Wyoming. The reach, 3.1 miles (5 kilometers) in length, wan immediately upstream from a previously established bedload sampling station. Nineteen channel cross sections were sounded at regular intervals during the spring-runoff period. Four stage recorders provided continuous records of water-surface elevations. Samples of bed material at most of the cross sections were obtained prior to high water. Streamflow and sediment-discharge measurements were collected at four of the sections.The physiography and hydrology of the contributing watershed, the study reach, and the equipment and techniques used in data collection are described briefly. The bulk of the report is a presentation of data for the several-week period of late May to early June 1975, for which concurrent water discharge data, bedload transport and size data, and cross-section depth measurements were collected. In addition, some data collected in 1973 and 1974 and before and after the calibration period in 1975 are included for completeness.

Ground-based thermography of fluvial systems at low and high discharge reveals potential complex thermal heterogeneity driven by flow variation and bioroughness

USGS Publications Warehouse

Cardenas, M.B.; Harvey, J.W.; Packman, A.I.; Scott, D.T.

2008-01-01

Temperature is a primary physical and biogeochemical variable in aquatic systems. Field-based measurement of temperature at discrete sampling points has revealed temperature variability in fluvial systems, but traditional techniques do not readily allow for synoptic sampling schemes that can address temperature-related questions with broad, yet detailed, coverage. We present results of thermal infrared imaging at different stream discharge (base flow and peak flood) conditions using a handheld IR camera. Remotely sensed temperatures compare well with those measured with a digital thermometer. The thermal images show that periphyton, wood, and sandbars induce significant thermal heterogeneity during low stages. Moreover, the images indicate temperature variability within the periphyton community and within the partially submerged bars. The thermal heterogeneity was diminished during flood inundation, when the areas of more slowly moving water to the side of the stream differed in their temperature. The results have consequences for thermally sensitive hydroelogical processes and implications for models of those processes, especially those that assume an effective stream temperature. Copyright ?? 2008 John Wiley & Sons, Ltd.

Effect of Off-Body Laser Discharge on Drag Reduction of Hemisphere Cylinder in Supersonic Flow

NASA Technical Reports Server (NTRS)

Kianvashrad, Nadia; Knight, Doyle; Wilkinson, Stephen P.; Chou, Amanda; Horne, Robert A.; Herring, Gregory C.; Beeler, George B.; Jangda, Moazzam

2017-01-01

The interaction of an off-body laser discharge with a hemisphere cylinder in supersonic flow is investigated. The objectives are 1) experimental determination of the drag reduction and energetic efficiency of the laser discharge, and 2) assessment of the capability for accurate simulation of the interaction. The combined computational and experimental study comprises two phases. In the first phase, laser discharge in quiescent air was examined. The temporal behavior of the shock wave formed by the laser discharge was compared between experiment and simulation and good agreement is observed. In the second phase, the interaction of the laser discharge with a hemisphere cylinder was investigated numerically. Details of the pressure drag reduction and the physics of the interaction of the heated region with the bow shock are included. The drag reduction due to this interaction persisted for about five characteristic times where one characteristic time represents the time for the flow to move a distance equal to the hemisphere radius. The energetic efficiency of laser discharge for the case with 50 mJ energy absorbed by the gas is calculated as 3.22.

Effectiveness of combined sewer overflow treatment for dissolved oxygen improvement in the Chicago waterways.

PubMed

Alp, E; Melching, C S; Zhang, H; Lanyon, R

2007-01-01

An Use Attainability Analysis (UAA) has been initiated to evaluate what water-quality standards can be achieved in the Chicago Waterway System (CWS). There are nearly 200 combined sewer overflow (CSO) locations discharging to the CWS by gravity. Three CSO pumping stations also drain approximately 140 km2. Because of the dynamic nature of the CWS the DUFLOW model that is capable of simulating hydraulics and water-quality processes under unsteady-flow conditions was used to evaluate the effectiveness of water-quality improvement techniques identified by the UAA including CSO treatment. Several CSO treatment levels were applied at gravity flow CSOs to evaluate improvement in dissolved oxygen (DO). The results show that pollutant removal at CSOs improves DO to a certain degree, but it still was not sufficient to bring DO concentrations to 5 mg/L or higher for 90% of the time during wet weather at most locations on the CWS. Flow from the pumping stations results in substantial stress on DO since a huge amount of un-treated water with a high pollution load is discharged into the CWS in a short period of time at a certain location. The simulation results indicate that CSO treatment does not effectively improve DO during wet-weather periods on the CWS.

Determination of Flood Discharges in Rivers as a Prerequisite for Calculating Rates of Geomorphic Change in Drainage Basins During Extreme Events

NASA Astrophysics Data System (ADS)

Smith, J. D.; Kean, J. W.

2003-12-01

Accurate empirical determination of river discharge during an extreme event is very difficult even at a gage site. Moreover, the procurement of extreme flow measurements at many locations in an ungaged drainage basin often is necessary to relate the surface-water flow in the drainage network during a flood to the spatial distribution of intense rainfall. Consequently, paleo-hydrologic methods have to be employed to estimate peak discharges. These methods, however, require the application of some type of flow model. Often the flow models used with paleo-hydrologic data are over simplified and embody low-flow or extrapolated roughness coefficients that are inappropriate for the high flow of interest and that substantially reduce the reliability of the estimated discharge. Models that permit calculation of flow resistance from measured or calculated pre-flood, post-flood, or evolving channel and floodplain geometries and roughnesses can yield the most accurate results for these extreme situations. We have developed a procedure for directly calculating flow discharge as a function of stage in reaches a few tens of river widths in length. The foundation for this approach is a set of algorithms that permits computation of the form drag on topographic elements and woody vegetation. Its application requires an initial survey of the channel and floodplain topography and roughness. The method can be used either with stage determined from a set of pressure gages distributed throughout a drainage basin to monitor discharge in a drainage network or with paleo-hydrologic data to determine discharge from extreme events. Currently, our method of determining discharge from stage is being tested at various sites in the drainage basin of the Whitewater River, Kansas. Two of these sites are just downstream of USGS gages, and a third is a short distance downstream from the outlet pipe of a man-made lake. These tests are for a full range of hydrologic conditions in order to demonstrate that the model-based method for converting stage to discharge can be employed with confidence (1) in ungaged drainage basins where a large number of discharge measurements are required for hydrologic research, (2) at locations where rated USGS stage gages are too expensive, (3) near the sites of USGS stage gages for floods during which the discharge exceeds those for which the gage has been rated, and (4) for situations where paleo-flood methods have to be used to obtain a peak discharge. Model calculated rating curves are compared to measured ones for one of the USGS gage sites. Model calculations also are used to show that Manning's and other friction coefficients are functions of stage at this site. An approach such as the one described here is essential for the quantitative investigation of fluvial geomorphic processes caused by very large floods.

Electro-hydrodynamics and kinetic modelling of polluted air flow activated by multi-tip-to-plane corona discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meziane, M.; Eichwald, O.; Ducasse, O.

The present paper is devoted to the 2D simulation of an Atmospheric Corona Discharge Reactor (ACDR) involving 10 pins powered by a DC high voltage and positioned 7 mm above a grounded metallic plane. The corona reactor is periodically crossed by thin mono filamentary streamers with a natural repetition frequency of some tens of kHz. The simulation involves the electro-dynamic, chemical kinetic, and neutral gas hydrodynamic phenomena that influence the kinetics of the chemical species transformation. Each discharge stage (including the primary and the secondary streamers development and the resulting thermal shock) lasts about one hundred nanoseconds while the post-dischargemore » stages occurring between two successive discharge phases last one hundred microseconds. The ACDR is crossed by a lateral air flow including 400 ppm of NO. During the considered time scale of 10 ms, one hundred discharge/post-discharge cycles are simulated. The simulation involves the radical formation and thermal exchange between the discharges and the background gas. The results show how the successive discharges activate the flow gas and how the induced turbulence phenomena affect the redistribution of the thermal energy and the chemical kinetics inside the ACDR.« less

Quantifying the fate of agricultural nitrogen in an unconfined aquifer: Stream-based observations at three measurement scales

NASA Astrophysics Data System (ADS)

Gilmore, Troy E.; Genereux, David P.; Solomon, D. Kip; Solder, John E.; Kimball, Briant A.; Mitasova, Helena; Birgand, François

2016-03-01

We compared three stream-based sampling methods to study the fate of nitrate in groundwater in a coastal plain watershed: point measurements beneath the streambed, seepage blankets (novel seepage-meter design), and reach mass-balance. The methods gave similar mean groundwater seepage rates into the stream (0.3-0.6 m/d) during two 3-4 day field campaigns despite an order of magnitude difference in stream discharge between the campaigns. At low flow, estimates of flow-weighted mean nitrate concentrations in groundwater discharge ([NO3-]FWM) and nitrate flux from groundwater to the stream decreased with increasing degree of channel influence and measurement scale, i.e., [NO3-]FWM was 654, 561, and 451 µM for point, blanket, and reach mass-balance sampling, respectively. At high flow the trend was reversed, likely because reach mass-balance captured inputs from shallow transient high-nitrate flow paths while point and blanket measurements did not. Point sampling may be better suited to estimating aquifer discharge of nitrate, while reach mass-balance reflects full nitrate inputs into the channel (which at high flow may be more than aquifer discharge due to transient flow paths, and at low flow may be less than aquifer discharge due to channel-based nitrate removal). Modeling dissolved N2 from streambed samples suggested (1) about half of groundwater nitrate was denitrified prior to discharge from the aquifer, and (2) both extent of denitrification and initial nitrate concentration in groundwater (700-1300 µM) were related to land use, suggesting these forms of streambed sampling for groundwater can reveal watershed spatial relations relevant to nitrate contamination and fate in the aquifer.

Base-flow data in the Arnold Air Force Base area, Tennessee, June and October 2002

USGS Publications Warehouse

Robinson, John A.; Haugh, Connor J.

2004-01-01

Arnold Air Force Base (AAFB) occupies about 40,000 acres in Coffee and Franklin Counties, Tennessee. The primary mission of AAFB is to support the development of aerospace systems. This mission is accomplished through test facilities at Arnold Engineering Development Center (AEDC), which occupies about 4,000 acres in the center of AAFB. Base-flow data including discharge, temperature, and specific conductance were collected for basins in and near AAFB during high base-flow and low base-flow conditions. Data representing high base-flow conditions from 109 sites were collected on June 3 through 5, 2002, when discharge measurements at sites with flow ranged from 0.005 to 46.4 ft3/s. Data representing low base-flow conditions from 109 sites were collected on October 22 and 23, 2002, when discharge measurements at sites with flow ranged from 0.02 to 44.6 ft3/s. Discharge from the basin was greater during high base-flow conditions than during low base-flow conditions. In general, major tributaries on the north side and southeastern side of the study area (Duck River and Bradley Creek, respectively) had the highest flows during the study. Discharge data were used to categorize stream reaches and sub-basins. Stream reaches were categorized as gaining, losing, wet, dry, or unobserved for each base-flow measurement period. Gaining stream reaches were more common during the high base-flow period than during the low base-flow period. Dry stream reaches were more common during the low base-flow period than during the high base-flow period. Losing reaches were more predominant in Bradley Creek and Crumpton Creek. Values of flow per square mile for the study area of 0.55 and 0.37 (ft3/s)/mi2 were calculated using discharge data collected on June 3 through 5, 2002, and October 22 and 23, 2002, respectively. Sub-basin areas with surplus or deficient flow were defined within the basin. Drainage areas for each stream measurement site were delineated and measured from topographic maps. Change in flow per square mile for each sub-basin was calculated using data from each base-flow measurement period. The calculated values were used to define the areas of surplus or deficient flow for high and low base-flow conditions. Many areas of deficient flow were present throughout the study area under high and low base-flow conditions. Most areas of deficient flow were in the headwater basins. Fewer areas of surplus flow were present under low base-flow conditions than during the high base-flow conditions. The flow per square mile for each major tributary basin in the study area also was calculated. The values of flow per square mile for the Dry Creek, Spring Creek, and Wiley Creek basins were greatest under both high and low base-flow conditions.

The comparative analysis of the current-meter method and the pressure-time method used for discharge measurements in the Kaplan turbine penstocks

NASA Astrophysics Data System (ADS)

Adamkowski, A.; Krzemianowski, Z.

2012-11-01

The paper presents experiences gathered during many years of utilizing the current-meter and pressure-time methods for flow rate measurements in many hydropower plants. The integration techniques used in these both methods are different from the recommendations contained in the relevant international standards, mainly from the graphical and arithmetical ones. The results of the comparative analysis of both methods applied at the same time during the hydraulic performance tests of two Kaplan turbines in one of the Polish hydropower plant are presented in the final part of the paper. In the case of the pressure-time method application, the concrete penstocks of the tested turbines required installing a special measuring instrumentation inside the penstock. The comparison has shown a satisfactory agreement between the results of discharge measurements executed using the both considered methods. Maximum differences between the discharge values have not exceeded 1.0 % and the average differences have not been greater than 0.5 %.

Tuning Electrochemical Properties of Li-Rich Layered Oxide Cathodes by Adjusting Co/Ni Ratios and Mechanism Investigation Using in situ X-ray Diffraction and Online Continuous Flow Differential Electrochemical Mass Spectrometry.

PubMed

Shen, ShouYu; Hong, YuHao; Zhu, FuChun; Cao, ZhenMing; Li, YuYang; Ke, FuSheng; Fan, JingJing; Zhou, LiLi; Wu, LiNa; Dai, Peng; Cai, MingZhi; Huang, Ling; Zhou, ZhiYou; Li, JunTao; Wu, QiHui; Sun, ShiGang

2018-04-18

Owing to high specific capacity of ∼250 mA h g -1 , lithium-rich layered oxide cathode materials (Li 1+ x Ni y Co z Mn (3- x-2 y-3 z)/4 O 2 ) have been considered as one of the most promising candidates for the next-generation cathode materials of lithium ion batteries. However, the commercialization of this kind of cathode materials seriously restricted by voltage decay upon cycling though Li-rich materials with high cobalt content have been widely studied and show good capacity. This research successfully suppresses voltage decay upon cycling while maintaining high specific capacity with low Co/Ni ratio in Li-rich cathode materials. Online continuous flow differential electrochemical mass spectrometry (OEMS) and in situ X-ray diffraction (XRD) techniques have been applied to investigate the structure transformation of Li-rich layered oxide materials during charge-discharge process. The results of OEMS revealed that low Co/Ni ratio lithium-rich layered oxide cathode materials released no lattice oxygen at the first charge process, which will lead to the suppression of the voltage decay upon cycling. The in situ XRD results displayed the structure transition of lithium-rich layered oxide cathode materials during the charge-discharge process. The Li 1.13 Ni 0.275 Mn 0.580 O 2 cathode material exhibited a high initial medium discharge voltage of 3.710 and a 3.586 V medium discharge voltage with the lower voltage decay of 0.124 V after 100 cycles.

Low-flow characteristics of streams on the Kitsap Peninsula and selected adjacent islands, Washington

USGS Publications Warehouse

Cummans, J.E.

1976-01-01

Low-flow-frequency data are tabulated for 90 streamflow sites on the Kitsap Peninsula and adjacent islands, Washington. Also listed are data for 56 additional sites which have insufficient measurements for frequency analysis but which have been observed having no flow at least once during the low-flow period. The streams drain relatively small basins; only three streams have drainage areas greater than 20.0 square miles, and only nine other streams have drainage areas greater than 10.0 square miles. Mean annual precipitation during the period 1931-60 ranged from about 25 inches near Hansville to about 70 inches near Tahuya. Low-flow-frequency curves plotted from records of streamflow at eight long-term gaging stations were used to determine data for low-flow durations of 7, 30, 60, 90, and 183 days. Regression techniques then were used to estimate low flows with frequencies up to 20 years for stations with less than 10 years of record and for miscellaneous sites where discharge measurements have been made. (Woodard-USGS)

Radionuclides in groundwater flow system understanding

NASA Astrophysics Data System (ADS)

Erőss, Anita; Csondor, Katalin; Horváth, Ákos; Mádl-Szőnyi, Judit; Surbeck, Heinz

2017-04-01

Using radionuclides is a novel approach to characterize fluids of groundwater flow systems and understand their mixing. Particularly, in regional discharge areas, where different order flow systems convey waters with different temperature, composition and redox-state to the discharge zone. Radium and uranium are redox-sensitive parameters, which causes fractionation along groundwater flow paths. Discharging waters of regional flow systems are characterized by elevated total dissolved solid content (TDS), temperature and by reducing conditions, and therefore with negligible uranium content, whereas local flow systems have lower TDS and temperature and represent oxidizing environments, and therefore their radium content is low. Due to the short transit time, radon may appear in local systems' discharge, where its source is the soil zone. However, our studies revealed the importance of FeOOH precipitates as local radon sources throughout the adsorption of radium transported by the thermal waters of regional flow systems. These precipitates can form either by direct oxidizing of thermal waters at discharge, or by mixing of waters with different redox state. Therefore elevated radon content often occurs in regional discharge areas as well. This study compares the results of geochemical studies in three thermal karst areas in Hungary, focusing on radionuclides as natural tracers. In the Buda Thermal Karst, the waters of the distinct discharge areas are characterized by different temperature and chemical composition. In the central discharge area both lukewarm (20-35°C, 770-980 mg/l TDS) and thermal waters (40-65°C, 800-1350 mg/l TDS), in the South only thermal water discharge (33-43°C, 1450-1700 mg/l TDS) occur. Radionuclides helped to identify mixing of fluids and to infer the temperature and chemical composition of the end members for the central discharge area. For the southern discharge zone mixing components could not be identified, which suggests different cave formation. The Bükk karst area is largely compartmentalized owing to the complex geological and structural build-up. Majority of the waters is low mineralized (TDS < 600 mg/l) regardless of their temperatures (8-77 °C). This may indicate deep but relatively fast/short flow paths. Thermal wells, characterized by higher TDS (1000-2500 mg/l) and radium content (400-1900 mBq/l), show the effects of hydrocarbon reservoir fluids. In the Villány Thermal Karst area the majority of the springs have lukewarm (20-26°C) waters with 712-930 mg/l TDS. Natural thermal water discharge (52-62°C, 1100 mg/l TDS) can be found only in Harkány. Here the highest concentration of radionuclides (226Ra: 230 mBq/l, 238+234U: 66 mBq/l, 222Rn: 43 Bq/l) suggest mixing of different flow systems. The results reflect the effect of different hydrogeological environments and flow regimes but similarities also could be revealed. The National Research, Development and Innovation Fund has provided financial support to the Villány project under the grant agreement no. PD 116227. The Bükk research was supported by the European Union and the State of Hungary, co-financed by the European Social Fund in the framework of TÁMOP-4.2.4.A/ 2-11/1-2012-0001 National Excellence Program. The Buda Thermal Karst research was funded by Shell International E&P and by the Hungarian Scientific Research Fund under the grant agreement no. NK 101356.

Dielectric barrier discharge plasma actuator for flow control

NASA Astrophysics Data System (ADS)

Opaits, Dmitry Florievich

Electrohydrodynamic (EHD) and magnetohydrodynamic phenomena are being widely studied for aerodynamic applications. The major effects of these phenomena are heating of the gas, body force generation, and enthalpy addition or extraction, [1, 2, 3]. In particular, asymmetric dielectric barrier discharge (DBD) plasma actuators are known to be effective EHD device in aerodynamic control, [4, 5]. Experiments have demonstrated their effectiveness in separation control, acoustic noise reduction, and other aeronautic applications. In contrast to conventional DBD actuators driven by sinusoidal voltages, we proposed and used a voltage profile consisting of nanosecond pulses superimposed on dc bias voltage. This produces what is essentially a non-self-sustained discharge: the plasma is generated by repetitive short pulses, and the pushing of the gas occurs primarily due to the bias voltage. The advantage of this non-self-sustained discharge is that the parameters of ionizing pulses and the driving bias voltage can be varied independently, which adds flexibility to control and optimization of the actuators performance. Experimental studies were conducted of a flow induced in a quiescent room air by a single DBD actuator. A new approach for non-intrusive diagnostics of plasma actuator induced flows in quiescent gas was proposed, consisting of three elements coupled together: the Schlieren technique, burst mode of plasma actuator operation, and 2-D numerical fluid modeling. During the experiments, it was found that DBD performance is severely limited by surface charge accumulation on the dielectric. Several ways to mitigate the surface charge were found: using a reversing DC bias potential, three-electrode configuration, slightly conductive dielectrics, and semi conductive coatings. Force balance measurements proved the effectiveness of the suggested configurations and advantages of the new voltage profile (pulses+bias) over the traditional sinusoidal one at relatively low voltages. In view of practical applications certain questions have been also addressed, such as electrodynamic effects which accompany scaling of the actuators to real size models, and environmental effects of ozone production by the plasma actuators.

Modern and Unconventional Approaches to Karst Hydrogeology

NASA Astrophysics Data System (ADS)

Sukop, M. C.

2017-12-01

Karst hydrogeology is frequently approached from a hydrograph/statistical perspective where precipitation/recharge inputs are converted to output hydrographs and the conversion process reflects the hydrology of the system. Karst catchments show hydrological response to short-term meteorological events and to long-term variation of large-scale atmospheric circulation. Modern approaches to analysis of these data include, for example, multiresolution wavelet techniques applied to understand relations between karst discharge and climate fields. Much less effort has been directed towards direct simulation of flow fields and transport phenomena in karst settings. This is primarily due to the lack of information on the detailed physical geometry of most karst systems. New mapping, sampling, and modeling techniques are beginning to enable direct simulation of flow and transport. A Conduit Flow Process (CFP) add-on to the USGS ModFlow model became available in 2007. FEFLOW and similar models are able to represent flows in individual conduits. Lattice Boltzmann models have also been applied to flow modeling in karst systems. Regarding quantitative measurement of karst system geometry, at scales to 0.1 m, X-ray computed tomography enables good detection of detailed (sub-millimeter) pore space in karstic rocks. Three-dimensional printing allows reconstruction of fragile high porosity rocks, and surrogate samples generated this way can then be subjected to laboratory testing. Borehole scales can be accessed with high-resolution ( 0.001 m) Digital Optical Borehole Imaging technologies and can provide virtual samples more representative of the true nature of karst aquifers than can obtained from coring. Subsequent extrapolation of such samples can generate three-dimensional models suitable for direct modeling of flow and transport. Finally, new cave mapping techniques are beginning to provide information than can be applied to direct simulation of flow. Due to flow rates and cave diameter, very high Reynolds number flows may be encountered.

Low-flow characteristics of streams in Virginia

USGS Publications Warehouse

Hayes, Donald C.

1991-01-01

Streamflow data were collected and low-flow characteristics computed for 715 gaged sites in Virginia Annual minimum average 7-consecutive-day flows range from 0 to 2,195 cubic feet per second for a 2-year recurrence interval and from 0 to 1,423 cubic feet per second for a 10-year recurrence interval. Drainage areas range from 0.17 to 7,320 square miles. Existing and discontinued gaged sites are separated into three types: long-term continuous-record sites, short-term continuous-record sites, and partial-record sites. Low-flow characteristics for long-term continuous-record sites are determined from frequency curves of annual minimum average 7-consecutive-day flows . Low-flow characteristics for short-term continuous-record sites are estimated by relating daily mean base-flow discharge values at a short-term site to concurrent daily mean discharge values at nearby long-term continuous-record sites having similar basin characteristics . Low-flow characteristics for partial-record sites are estimated by relating base-flow measurements to daily mean discharge values at long-term continuous-record sites. Information from the continuous-record sites and partial-record sites in Virginia are used to develop two techniques for estimating low-flow characteristics at ungaged sites. A flow-routing method is developed to estimate low-flow values at ungaged sites on gaged streams. Regional regression equations are developed for estimating low-flow values at ungaged sites on ungaged streams. The flow-routing method consists of transferring low-flow characteristics from a gaged site, either upstream or downstream, to a desired ungaged site. A simple drainage-area proration is used to transfer values when there are no major tributaries between the gaged and ungaged sites. Standard errors of estimate for108 test sites are 19 percent of the mean for estimates of low-flow characteristics having a 2-year recurrence interval and 52 percent of the mean for estimates of low-flow characteristics having a 10-year recurrence interval . A more complex transfer method must be used when major tributaries enter the stream between the gaged and ungaged sites. Twenty-four stream networks are analyzed, and predictions are made for 84 sites. Standard errors of estimate are 15 percent of the mean for estimates of low-flow characteristics having a 2-year recurrence interval and 22 percent of the mean for estimates of low-flow characteristics having a 10-year recurrence interval. Regional regression equations were developed for estimating low-flow values at ungaged sites on ungaged streams. The State was divided into eight regions on the basis of physiography and geographic grouping of the residuals computed in regression analyses . Basin characteristics that were significant in the regression analysis were drainage area, rock type, and strip-mined area. Standard errors of prediction range from 60 to139 percent for estimates of low-flow characteristics having a 2-year recurrence interval and 90 percent to 172 percent for estimates of low-flow characteristics having a 10-year recurrence interval.

Chemistry of groundwater discharge inferred from longitudinal river sampling

NASA Astrophysics Data System (ADS)

Batlle-Aguilar, J.; Harrington, G. A.; Leblanc, M.; Welch, C.; Cook, P. G.

2014-02-01

We present an approach for identifying groundwater discharge chemistry and quantifying spatially distributed groundwater discharge into rivers based on longitudinal synoptic sampling and flow gauging of a river. The method is demonstrated using a 450 km reach of a tropical river in Australia. Results obtained from sampling for environmental tracers, major ions, and selected trace element chemistry were used to calibrate a steady state one-dimensional advective transport model of tracer distribution along the river. The model closely reproduced river discharge and environmental tracer and chemistry composition along the study length. It provided a detailed longitudinal profile of groundwater inflow chemistry and discharge rates, revealing that regional fractured mudstones in the central part of the catchment contributed up to 40% of all groundwater discharge. Detailed analysis of model calibration errors and modeled/measured groundwater ion ratios elucidated that groundwater discharging in the top of the catchment is a mixture of local groundwater and bank storage return flow, making the method potentially useful to differentiate between local and regional sourced groundwater discharge. As the error in tracer concentration induced by a flow event applies equally to any conservative tracer, we show that major ion ratios can still be resolved with minimal error when river samples are collected during transient flow conditions. The ability of the method to infer groundwater inflow chemistry from longitudinal river sampling is particularly attractive in remote areas where access to groundwater is limited or not possible, and for identification of actual fluxes of salts and/or specific contaminant sources.

Estimated loads and yields of suspended soils and water-quality constituents in Kentucky streams

USGS Publications Warehouse

Crain, Angela S.

2001-01-01

Loads and yields of suspended solids, nutrients, major ions, trace elements, organic carbon, fecal coliform, dissolved oxygen, and alkalinity were estimated for 22 streams in 11 major river basins in Kentucky. Mean daily discharge was estimated at ungaged stations or stations with incomplete discharge records using drainage-area ratio, regression analysis, or a combination of the two techniques. Streamflow was partitioned into total and base flow and used to estimate loads and yields for suspended solids and water-quality constituents by use of the ESTIMATOR and FLUX computer programs. The relative magnitude of constituent transport to streams from groundand surface-water sources was determined for the 22 stations. Nutrient and suspended solids yields for drainage basins with relatively homogenous land use were used to estimate the total-flow and base-flow yields of nutrient and suspended solids for forested, agricultural, and urban land. Yields of nutrients?nitrite plus nitrate, ammonia plus organic nitrogen, and total phosphorus?in forested drainage basins were generally less than 1 ton per square mile per year ((ton/mi2)/yr) and were generally less than 2 (ton/mi2)/yr in agricultural drainage basins. The smallest total-flow yields for nitrogen (nitrite plus nitrate) was estimated at Levisa Fork at Paintsville in which 95 percent of the land is forested. This site also had one of the smallest total-flow yields for ammonia plus organic nitrogen. In general, nutrient yields from forested lands were lower than those from urban and agricultural land. Some of the largest estimated total-flow yields of nutrients among agricultural basins were for streams in the Licking River Basin, the North Fork Licking River near Milford, and the South Fork Licking River at Cynthiana. Agricultural land constitutes greater than 75 percent of the drainage area in these two basins. Possible sources of nutrients discharging into the Licking River are farm and residential fertilizers. Estimated base-flow yields of suspended solids and nutrients at several basins in the larger Green River and Lower Cumberland River Basins were about half of their estimated total-flow yields. The karst terrain in these basins makes the ground water highly susceptible to contamination, especially if a confining unit is thin or absent.

Application of Bayesian geostatistics for evaluation of mass discharge uncertainty at contaminated sites

NASA Astrophysics Data System (ADS)

Troldborg, Mads; Nowak, Wolfgang; Lange, Ida V.; Santos, Marta C.; Binning, Philip J.; Bjerg, Poul L.

2012-09-01

Mass discharge estimates are increasingly being used when assessing risks of groundwater contamination and designing remedial systems at contaminated sites. Such estimates are, however, rather uncertain as they integrate uncertain spatial distributions of both concentration and groundwater flow. Here a geostatistical simulation method for quantifying the uncertainty of the mass discharge across a multilevel control plane is presented. The method accounts for (1) heterogeneity of both the flow field and the concentration distribution through Bayesian geostatistics, (2) measurement uncertainty, and (3) uncertain source zone and transport parameters. The method generates conditional realizations of the spatial flow and concentration distribution. An analytical macrodispersive transport solution is employed to simulate the mean concentration distribution, and a geostatistical model of the Box-Cox transformed concentration data is used to simulate observed deviations from this mean solution. By combining the flow and concentration realizations, a mass discharge probability distribution is obtained. The method has the advantage of avoiding the heavy computational burden of three-dimensional numerical flow and transport simulation coupled with geostatistical inversion. It may therefore be of practical relevance to practitioners compared to existing methods that are either too simple or computationally demanding. The method is demonstrated on a field site contaminated with chlorinated ethenes. For this site, we show that including a physically meaningful concentration trend and the cosimulation of hydraulic conductivity and hydraulic gradient across the transect helps constrain the mass discharge uncertainty. The number of sampling points required for accurate mass discharge estimation and the relative influence of different data types on mass discharge uncertainty is discussed.

Discharge ratings for control gates at Mississippi River lock and dam 12, Bellevue, Iowa

USGS Publications Warehouse

Heinitz, Albert J.

1986-01-01

The water level of the navigation pools on the Mississippi River are maintained by the operation of tainter and roller gates at the locks and dams. Discharge ratings for the gates on Lock and Dam 12, at Bellevue, Iowa, were developed from current-meter discharge measurements made in the forebays of the gate structures. Methodology is given to accurately compute the gate openings of the tainter gates. Discharge coefficients, in equations that express discharge as a function of tailwater head , forebay head, and height of gate opening, were determined for conditions of submerged-orifice and fee-weir flow. A comparison of the rating discharges to the hydraulic-model rating discharges is given for submerged orifice flow for the tainter and roller gates.

Performance of a CW double electric discharge for supersonic CO lasers

NASA Technical Reports Server (NTRS)

Stanton, A. C.; Hanson, R. K.; Mitchner, M.

1980-01-01

The results of an experimental investigation of a CW double discharge in supersonic CO mixtures are reported. Stable discharges in CO/N2 and CO/Ar mixtures, with a maximum energy loading of 0.5 eV/CO molecule, were achieved in a small-scale continuous-flow supersonic channel. Detailed measurements of the discharge characteristics were performed, including electrostatic probe measurements of floating potential and electron number density and spectroscopic measurements of the CO vibrational population distributions. The results of these measurements indicate that the vibrational excitation efficiency of the discharge is approximately 60%, for moderate levels of main discharge current. These experiments, on a small scale, demonstrate that the double-discharge scheme provides adequate vibrational energy loading for efficient CO laser operation under CW supersonic flow conditions.

Culvert analysis program for indirect measurement of discharge

USGS Publications Warehouse

Fulford, Janice M.; ,

1993-01-01

A program based on the U.S. Geological Survey (USGS) methods for indirectly computing peak discharges through culverts allows users to employ input data formats used by the water surface profile program (WSPRO). The program can be used to compute discharge rating surfaces or curves that describe the behavior of flow through a particular culvert or to compute discharges from measurements of upstream of the gradually varied flow equations and has been adapted slightly to provide solutions that minimize the need for the user to determine between different flow regimes. The program source is written in Fortran 77 and has been run on mini-computers and personal computers. The program does not use or require graphics capability, a color monitor, or a mouse.

Boundary Layer Flow Control with a One Atmosphere Uniform Glow Discharge Surface Plasma

NASA Technical Reports Server (NTRS)

Roth, J. Reece; Sherman, Daniel M.; Wilkinson, Stephen P.

1998-01-01

Low speed wind tunnel data have been acquired for planar panels covered by a uniform, glow-discharge surface plasma in atmospheric pressure air known as the One Atmosphere Uniform Glow Discharge Plasma (OAUGDP). Streamwise and spanwise arrays of flush, plasma-generating surface electrodes have been studied in laminar, transitional, and fully turbulent boundary layer flow. Plasma between symmetric streamwise electrode strips caused large increases in panel drag, whereas asymmetric spanwise electrode configurations produced a significant thrust. Smoke wire flow visualization and mean velocity diagnostics show the primary cause of the phenomena to be a combination of mass transport and vortical structures induced by strong paraelectric ElectroHydroDynamic (EHD) body forces on the flow.

Discharge coefficient correlations for circular-arc venturi flowmeters at critical /sonic/ flow

NASA Technical Reports Server (NTRS)

Arnberg, B. T.; Britton, C. L.; Seidl, W. F.

1973-01-01

Experimental data are analyzed to support theoretical predictions for discharge coefficients in circular-arc venturi flow meters operating in the critical sonic flow regime at throat Reynolds numbers above 150 thousand. The data tend to verify the predicted 0.25% decrease in the discharge coefficient during transition from a laminar to turbulent boundary layer. Four different test gases and three flow measurement facilities were used in the experiments with 17 venturis with throat sizes from 0.15 to 1.37 in. and Beta ratios ranging from 0.014 to 0.25. Recommendations are given as to how the effectiveness of future studies in the field could be improved.

A Bayesian geostatistical approach for evaluating the uncertainty of contaminant mass discharges from point sources

NASA Astrophysics Data System (ADS)

Troldborg, M.; Nowak, W.; Binning, P. J.; Bjerg, P. L.

2012-12-01

Estimates of mass discharge (mass/time) are increasingly being used when assessing risks of groundwater contamination and designing remedial systems at contaminated sites. Mass discharge estimates are, however, prone to rather large uncertainties as they integrate uncertain spatial distributions of both concentration and groundwater flow velocities. For risk assessments or any other decisions that are being based on mass discharge estimates, it is essential to address these uncertainties. We present a novel Bayesian geostatistical approach for quantifying the uncertainty of the mass discharge across a multilevel control plane. The method decouples the flow and transport simulation and has the advantage of avoiding the heavy computational burden of three-dimensional numerical flow and transport simulation coupled with geostatistical inversion. It may therefore be of practical relevance to practitioners compared to existing methods that are either too simple or computationally demanding. The method is based on conditional geostatistical simulation and accounts for i) heterogeneity of both the flow field and the concentration distribution through Bayesian geostatistics (including the uncertainty in covariance functions), ii) measurement uncertainty, and iii) uncertain source zone geometry and transport parameters. The method generates multiple equally likely realizations of the spatial flow and concentration distribution, which all honour the measured data at the control plane. The flow realizations are generated by analytical co-simulation of the hydraulic conductivity and the hydraulic gradient across the control plane. These realizations are made consistent with measurements of both hydraulic conductivity and head at the site. An analytical macro-dispersive transport solution is employed to simulate the mean concentration distribution across the control plane, and a geostatistical model of the Box-Cox transformed concentration data is used to simulate observed deviations from this mean solution. By combining the flow and concentration realizations, a mass discharge probability distribution is obtained. Tests show that the decoupled approach is both efficient and able to provide accurate uncertainty estimates. The method is demonstrated on a Danish field site contaminated with chlorinated ethenes. For this site, we show that including a physically meaningful concentration trend and the co-simulation of hydraulic conductivity and hydraulic gradient across the transect helps constrain the mass discharge uncertainty. The number of sampling points required for accurate mass discharge estimation and the relative influence of different data types on mass discharge uncertainty is discussed.

Flow discharge prediction in compound channels using linear genetic programming

NASA Astrophysics Data System (ADS)

Azamathulla, H. Md.; Zahiri, A.

2012-08-01

SummaryFlow discharge determination in rivers is one of the key elements in mathematical modelling in the design of river engineering projects. Because of the inundation of floodplains and sudden changes in river geometry, flow resistance equations are not applicable for compound channels. Therefore, many approaches have been developed for modification of flow discharge computations. Most of these methods have satisfactory results only in laboratory flumes. Due to the ability to model complex phenomena, the artificial intelligence methods have recently been employed for wide applications in various fields of water engineering. Linear genetic programming (LGP), a branch of artificial intelligence methods, is able to optimise the model structure and its components and to derive an explicit equation based on the variables of the phenomena. In this paper, a precise dimensionless equation has been derived for prediction of flood discharge using LGP. The proposed model was developed using published data compiled for stage-discharge data sets for 394 laboratories, and field of 30 compound channels. The results indicate that the LGP model has a better performance than the existing models.

Hydrology of the coastal springs ground-water basin and adjacent parts of Pasco, Hernando, and Citrus Counties, Florida

USGS Publications Warehouse

Knochenmus, Lari A.; Yobbi, Dann K.

2001-01-01

The coastal springs in Pasco, Hernando, and Citrus Counties, Florida consist of three first-order magnitude springs and numerous smaller springs, which are points of substantial ground-water discharge from the Upper Floridan aquifer. Spring flow is proportional to the water-level altitude in the aquifer and is affected primarily by the magnitude and timing of rainfall. Ground-water levels in 206 Upper Floridan aquifer wells, and surface-water stage, flow, and specific conductance of water from springs at 10 gaging stations were measured to define the hydrologic variability (temporally and spatially) in the Coastal Springs Ground-Water Basin and adjacent parts of Pasco, Hernando, and Citrus Counties. Rainfall at 46 stations and ground-water withdrawals for three counties, were used to calculate water budgets, to evaluate long-term changes in hydrologic conditions, and to evaluate relations among the hydrologic components. Predictive equations to estimate daily spring flow were developed for eight gaging stations using regression techniques. Regression techniques included ordinary least squares and multiple linear regression techniques. The predictive equations indicate that ground-water levels in the Upper Floridan aquifer are directly related to spring flow. At tidally affected gaging stations, spring flow is inversely related to spring-pool altitude. The springs have similar seasonal flow patterns throughout the area. Water-budget analysis provided insight into the relative importance of the hydrologic components expected to influence spring flow. Four water budgets were constructed for small ground-water basins that form the Coastal Springs Ground-Water Basin. Rainfall averaged 55 inches per year and was the only source of inflow to the Basin. The pathways for outflow were evapotranspiration (34 inches per year), runoff by spring flow (8 inches per year), ground-water outflow from upward leakage (11 inches per year), and ground-water withdrawal (2 inches per year). Recharge (rainfall minus evapotranspiration) to the Upper Floridan aquifer consists of vertical leakage through the surficial deposits. Discharge is primarily through springs and diffuse upward leakage that maintains the extensive swamps along the Gulf of Mexico. The ground-water basins had slightly different partitioning of hydrologic components, reflecting variation among the regions. Trends in hydrologic data were identified using nonparametric statistical techniques to infer long-term changes in hydrologic conditions, and yielded mixed results. No trend in rainfall was detected during the past century. No trend in spring flow was detected in 1931-98. Although monotonic trends were not detected, rainfall patterns are naturally variable from month to month and year to year; this variability is reflected in ground-water levels and spring flows. A decreasing trend in ground-water levels was detected in the Weeki Wachee well (1966-98), but the trend was statistically weak. At current ground-water withdrawal rates, there is no discernible affect on ground-water levels and spring flows. Sporadic data records, lack of continuous data, and inconsistent periods of record among the hydrologic components impeded analysis of long-term changes to the hydrologic system and interrelations among components. The ongoing collection of hydrologic data from index sites could provide much needed information to assess the hydrologic factors affecting the quantity and quality of spring flow in the Coastal Springs Ground-Water Basin.

Flow resistance and hydraulic geometry in contrasting reaches of a bedrock channel

NASA Astrophysics Data System (ADS)

Ferguson, R. I.; Sharma, B. P.; Hardy, R. J.; Hodge, R. A.; Warburton, J.

2017-03-01

Assumptions about flow resistance in bedrock channels have to be made for mechanistic modeling of river incision, paleoflood estimation, flood routing, and river engineering. Field data on bedrock flow resistance are very limited and calculations generally use standard alluvial-river assumptions such as a fixed value of Manning's n. To help inform future work, we measured how depth, velocity, and flow resistance vary with discharge in four short reaches of a small bedrock channel, one with an entirely rock bed and the others with 20-70% sediment cover, and in the alluvial channel immediately upstream. As discharge and submergence increase in each of the partly or fully alluvial reaches there is a rapid increase in velocity and a strong decline in both n and the Darcy-Weisbach friction factor f. The bare-rock reach follows a similar trend from low to medium discharge but has increasing resistance at higher discharges because of the macroroughness of its rock walls. Flow resistance at a given discharge differs considerably between reaches and is highest where the partial sediment cover is coarsest and most extensive. Apart from the effect of rough rock walls, the flow resistance trends are qualitatively consistent with logarithmic and variable-power equations and with nondimensional hydraulic geometry, but quantitative agreement using sediment D84 as the roughness height is imperfect.

The Graded Alluvial River: Variable Flow and the Dominant Discharge

NASA Astrophysics Data System (ADS)

Blom, A.; Arkesteijn, L.; Viparelli, E.

2016-12-01

We derive analytical formulations for the graded or equilibrium longitudinal profile of a mixed-sediment alluvial river under variable flow. The formulations are applicable to reaches upstream from the backwater zone. The model is based on the conservation equations for the mass of two distinct sediment modes, sand and gravel, at the bed surface to account for the effects of grain size selective transport and abrasion of gravel particles. The effects of a variable flow rate are included by (a) treating the flow as a continuously changing yet steady water discharge (i.e. here termed an alternating steady discharge) and (b) assuming the time scale of changes in channel slope and bed surface texture to be much larger than the one of changes in flow rate. The equations are simplified realizing that at equilibrium the river profile finds itself in a dynamic steady state with oscillations around constant mean values of channel slope and bed surface texture. A generalized sediment transport relation representing the stochastic nature of sediment transport allows for explicit or analytical solutions to the streamwise decrease of both the channel slope and the bed surface mean grain size under variable flow for reaches unaffected by backwater effects. This modelling approach also provides a definition of a channel-forming or dominant water discharge, i.e., that steady water discharge that is equivalent in its effect on the equilibrium channel slope to the full hydrograph.

Seepage investigation on selected reaches of Fish Creek, Teton County, Wyoming, 2004

USGS Publications Warehouse

Wheeler, Jerrod D.; Eddy-Miller, Cheryl A.

2005-01-01

A seepage investigation was conducted on Fish Creek, a tributary to the Snake River in Teton County in western Wyoming, near Wilson. Mainstem, return flow, tributary, spring, and diversion sites were selected and measured on six reaches along Fish Creek. Flow was measured under two flow regimes, high flow in August 2004 and base flow in November 2004. During August 17-19, 2004, 20 sites had quantifiable discharge with median values ranging from 0.93 to 384 ft3/s for the 14 mainstem sites on Fish Creek, and from 0.35 to 12.2 ft3/s for the 5 return, spring, and tributary sites (inflows). The discharge was 2.23 ft3/s for the single diversion site (outflow). Estimated gains or losses from ground water were calculated for all reaches using the median discharge values and the estimated measurement errors. Reach 1 had a calculated gain in discharge from ground water (23.8 ?3.3 ft3/s). Reaches 2-6 had no calculated gains in flow, greater than the estimated error, that could be attributed to ground water. A second set of measurements were made under base-flow conditions during November 3-4, 2004. Twelve of the 20 sites visited in August 2004 were flowing and were measured. All of the Reach 1 sites near Teton Village were dry. Median discharge values ranged from 10.3 to 70.0 ft3/s on the nine Fish Creek mainstem sites, and from 2.32 to 3.71 ft3/s on the three return, spring, and tributary sites (inflows). Reaches 2, 3 and 6 had a gain from ground water. Reaches 4 and 5 had no calculated gains in flow, greater than the estimated error, that could be attributed to ground water.

Denitrification in nitrate-rich streams: Application of N2:Ar and 15N-tracer methods in intact cores

USGS Publications Warehouse

Smith, Lesley K.; Voytek, M.A.; Böhlke, J.K.; Harvey, J.W.

2006-01-01

Rates of benthic denitrification were measured using two techniques, membrane inlet mass spectrometry (MIMS) and isotope ratio mass spectrometry (IRMS), applied to sediment cores from two NO3--rich streams draining agricultural land in the upper Mississippi River Basin. Denitrification was estimated simultaneously from measurements of N 2:Ar (MIMS) and 15N[N2] (IRMS) after the addition of low-level 15NO3- tracer ( 15N:N = 0.03-0.08) in stream water overlying intact sediment cores. Denitrification rates ranged from about 0 to 4400 lmol N??m -2??h-1 in Sugar Creek and from 0 to 1300 ??mol N??m-2??h-1 in Iroquois River, the latter of which possesses greater streamflow discharge and a more homogeneous streambed and water column. Within the uncertainties of the two techniques, there is good agreement between the MIMS and IRMS results, which indicates that the production of N2 by the coupled process of nitrification/denitrification was relatively unimportant and surface-water NO3- was the dominant source of NO3- for benthic denitrification in these streams. Variation in stream NO3- concentration (from about 20 ??mol/L during low discharge to 1000 ??mol/L during high discharge) was a significant control of benthic denitrification rates, judging from the more abundant MIMS data. The interpretation that NO3- concentration directly affects denitrification rate was corroborated by increased rates of denitrification in cores amended with NO 3-. Denitrification in Sugar Creek removed ???11% per day of the instream NO3- in late spring and removed roughly 15-20% in late summer. The fraction of NO3- removed in Iroquois River was less than that of Sugar Creek. Although benthic denitrification rates were relatively high during periods of high stream flow, when NO3 concentrations were also high, the increase in benthic denitrification could not compensate for the much larger increase in stream NO3- fluxes during high flow. Consequently, fractional NO3- losses were relatively low during high flow. ?? 2006 by the Ecological Society of America.

Decontamination of Chemical/Biological Warfare (CBW) Agents Using an Atmospheric Pressure Plasma Jet (APPJ)

NASA Astrophysics Data System (ADS)

Herrmann, Hans W.

1998-11-01

The atmospheric pressure plasma jet (APPJ) is a non-thermal, high pressure, uniform glow discharge that produces a high velocity effluent stream of highly reactive chemical species. The discharge operates on a feedstock gas (e.g. He/O_2/H_2O) which flows between an outer, grounded, cylindrical electrode and an inner, coaxial electrode powered at 13.56 MHz RF. While passing through the plasma, the feedgas becomes excited, dissociated or ionized by electron impact. Once the gas exits the discharge volume, ions and electrons are rapidly lost by recombination, but the fast-flowing effluent still contains metastables (e.g. O2*, He*) and radicals (e.g. O, OH). These reactive species have been shown to be effective neutralizers of surrogates for anthrax spores, mustard blister agent and VX nerve gas. Unlike conventional, wet decontamination methods, the plasma effluent does not cause corrosion of most surfaces and does not damage wiring, electronics, nor most plastics. This makes it highly suitable for decontamination of high value sensitive equipment such as is found in vehicle interiors (i.e. tanks, planes...) for which there is currently no good decontamination technique. Furthermore, the reactive species rapidly degrade into harmless products leaving no lingering residue or harmful byproducts. Physics of the APPJ will be discussed and results of surface decontamination experiments using simulant and actual CBW agents will be presented.

Comparison of acoustic doppler current profiler and Price AA mechanical current meter measurements made during the 2011 Mississippi River Flood

USGS Publications Warehouse

O'Brien, Patrick; Mueller, David; Pratt, Thad

2012-01-01

The Mississippi River and Tributaries project performed as designed during the historic 2011 Mississippi River flood, with many of the operational decisions based on discharge targets as opposed to stage. Measurement of discharge at the Tarbert Landing, Mississippi range provides critical information used in operational decisions for the floodways located in Louisiana. Historically, discharge measurements have been made using a Price AA current meter and the mid-section method, and a long record exists based on these types of measurements, including historical peak discharges. Discharge measurements made using an acoustic Doppler current profiler from a moving boat have been incorporated into the record since the mid 1990's, and are used along with the Price AA mid-section measurements. During the 2011 flood event, both methods were used and appeared to provide different results at times. The apparent differences between the measurement techniques are due to complex hydrodynamics at this location that created large spatial and temporal fluctuations in the flow. The data and analysis presented herein show the difference between the two methods to be within the expected accuracy of the measurements when the measurements are made concurrently. The observed fluctuations prevent valid comparisons of data collected sequentially or even with different observation durations.

Goodenough Spring, Texas, USA: Discharge and water chemistry of a large spring deeply submerged under the binational Amistad Reservoir

NASA Astrophysics Data System (ADS)

Kamps, Ray H.; Tatum, Gregg S.; Gault, Mike; Groeger, Alan W.

2009-06-01

Goodenough Spring (Texas, USA) is a large spring near the border of the American state of Texas and the Mexican state of Coahuila, discharging into the international Amistad Reservoir on the river Rio Grande (Rio Bravo). Discharge was routinely measured from 1928 until 1968 to partition the flow of the river between the two countries in accordance with water-use treaties. Samples were analyzed for water-quality parameters in 1967-1968 prior to inundation under 45 m of Amistad Reservoir in 1968. Subsequently, discharge has been estimated indirectly by the International Boundary and Water Commission (IBWC). For the first direct measurements of the spring in 37 years, velocity and cross-sectional measurements were made and water samples collected in the summer of 2005 using advanced self-contained underwater breathing apparatus (SCUBA) techniques. Spring discharge was calculated at 2.03 m3 s-1, approximately one-half of the historical mean of 3.94 m3 s-1. In situ and laboratory analyses of samples for temperature, pH, dissolved oxygen, specific conductance, alkalinity, nitrate-nitrogen, dissolved solids, chloride, sulfate, fluoride, phosphorus, calcium, sodium, potassium, magnesium, and iron showed the water quality to be very good for human consumption and crop irrigation. Measurement values are relatively unchanged from those reported 37 years prior.

Quantifying changes in the contribution of upstream snow and glacier melt to downstream low flows in the River Rhine

NASA Astrophysics Data System (ADS)

Stahl, K.; Kohn, I.; Boehm, M.; Seibert, J.; Freudiger, D.; Gerlinger, K.; Weiler, M.

2016-12-01

Low flows impact river ecosystems and impair water use. In the mid- and downstream reaches of one of the largest rivers in Europe, the River Rhine, low flows can threaten a variety of ecosystem services and direct uses. Low flows in summer and fall are sustained by the snow and ice melt contribution from the glacierized mountain headwaters upstream. This study explores changes in the discharge components of rain, snowmelt and ice melt during extreme low flow events from a downstream perspective. Quantification of the discharge components is based on a novel method of runoff component tracking that was implemented into a model chain, consisting of the HBV model, which includes a glacier mass balance model allowing for areal glacier changes, for the headwaters and the distributed hydrological model LARSIM for the remaining Rhine basin. A transient model run at daily resolution was calibrated to glacier volume change, basin-wide snow cover and snow water equivalent and discharge variability at many gauging stations over the period 1901-2006. The analysis of the resulting discharge components revealed that over the course of the 20th Century, the loss of glacier volume and glacier area in the headwaters appears to have compensated an increasingly negative glacier mass balance, resulting in little long-term change to the ice melt component in summer streamflow - thus showing no clear `peak-water' trend. While the glacier ice melt component was less than two percent of the average annual discharge of the mid and lower reaches of the River Rhine, models suggest its fraction was much higher during extreme low flow events. The low flows of the summers of 1921, 1947, and 2003 were comprised of record daily ice melt fractions of more than one fifth of the daily discharge along the mid and lower reaches from Basel to the mouth. A scenario model run with suppressed glacier area change suggests that the ice melt discharge component would have doubled if the same meteorological event as in 2003 had occurred in the early 1900s when glacier areas were still much larger. Impacts on ecology and water use most likely would have also been less severe. The modeled changes in discharge components thus allow a quantification of the low flow hazard that may loom ahead as the glaciers continue to decline.

Negative DC corona discharge current characteristics in a flowing two-phase (air + suspended smoke particles) fluid

NASA Astrophysics Data System (ADS)

Berendt, Artur; Domaszka, Magdalena; Mizeraczyk, Jerzy

2017-04-01

The electrical characteristics of a steady-state negative DC corona discharge in a two-phase fluid (air with suspended cigarette smoke particles) flowing along a chamber with a needle-to-plate electrode arrangement were experimentally investigated. The two-phase flow was transverse in respect to the needle-to-plate axis. The velocity of the transverse two-phase flow was limited to 0.8 m/s, typical of the electrostatic precipitators. We found that three discharge current modes of the negative corona exist in the two-phase (air + smoke particles) fluid: the Trichel pulses mode, the "Trichel pulses superimposed on DC component" mode and the DC component mode, similarly as in the corona discharge in air (a single-phase fluid). The shape of Trichel pulses in the air + suspended particles fluid is similar to that in air. However, the Trichel pulse amplitudes are higher than those in "pure" air while their repetition frequency is lower. As a net consequence of that the averaged corona discharge current in the two-phase fluid is lower than in "pure" air. It was also found that the average discharge current decreases with increasing suspended particle concentration. The calculations showed that the dependence of the average negative corona current (which is a macroscopic corona discharge parameter) on the particle concentration can be explained by the particle-concentration dependencies of the electric charge of Trichel pulse and the repetition frequency of Trichel pulses, both giving a microscopic insight into the electrical phenomena in the negative corona discharge. Our investigations showed also that the average corona discharge current in the two-phase fluid is almost unaffected by the transverse fluid flow up to a velocity of 0.8 m/s. Contribution to the topical issue "The 15th International Symposium on High Pressure Low Temperature Plasma Chemistry (HAKONE XV)", edited by Nicolas Gherardi and Tomáš Hoder

A Preliminary Evaluation of Near-Transducer Velocities Collected with Low-Blank Acoustic Doppler Current Profiler

USGS Publications Warehouse

Gartner, J.W.; Ganju, N.K.; ,

2002-01-01

Many streams and rivers for which the US Geological Survey must provide discharge measurements are too shallow to apply existing acoustic Doppler current profiler techniques for flow measurements of satisfactory quality. Because the same transducer is used for both transmitting and receiving acoustic signals in most Doppler current profilers, some small time delay is required for acoustic "ringing" to be damped out of transducers before meaningful measurements can be made. The result of that time delay is that velocity measurements cannot be made close to the transducer thus limiting the usefulness of these instruments in shallow regions. Manufacturers and users are constantly striving for improvements to acoustic instruments which would permit useful discharge measurements in shallow rivers and streams that are still often measured with techniques and instruments more than a century old. One promising area of advance appeared to be reduction of time delay (blank) required between transmitting and receiving signals during acoustic velocity measurements. Development of a low- or zero-blank transducer by RD Instruments3 held promise that velocity measurements could be made much closer to the transducer and thus in much shallower water. Initial experience indicates that this is not the case; limitation of measurement quality appears to be related to the physical presence of the transducer itself within the flow field. The limitation may be the result of changes to water flow pattern close to the transducer rather than transducer ringing characteristics as a function of blanking distance. Results of field experiments are discussed that support this conclusion and some minimum measurement distances from transducer are suggested based on water current speed and ADCP sample modes.

Tide-induced fingering flow during submarine groundwater discharge

NASA Astrophysics Data System (ADS)

Greskowiak, Janek

2013-04-01

Submarine groundwater discharge (SGD) is a relevant component of the hydrological cycle (Moore, 2010). The discharge of fresh groundwater that originated from precipitation on the land typically occurs at the near shore scale (~ 10m-100m) and the embayment scale (~ 100m - 10km) (Bratton, 2010). In the recent years a number of studies revealed that tidal forcing has an important effect on the fresh SGD pattern in the beach zone, i.e., it leads to the formation of an upper saline recirculation cell and a lower "freshwater discharge tube" (Boufadel, 2000, Robinson et al., 2007; Kuan et al., 2012). Thereby the discharge of the fresh groundwater occurs near the low-tide mark. The shape and extent of the upper saline recirculation cell is mainly defined by the tidal amplitude, beach slope, fresh groundwater discharge rate and hydraulic conductivity (Robinson et al., 2007). In spite of fact that in this case sea water overlies less denser freshwater, all previous modeling studies suggested that the saline recirculation cell and the freshwater tube are rather stable. However, new numerical investigations indicate that there maybe realistic cases where the upper saline recirculation cell becomes unstable as a result of the density contrast to the underlying freshwater tube. In these cases salt water fingers develop and move downward, thereby penetrating the freshwater tube. To the author's knowledge, the present study is the first that illustrate the possibility of density induced fingering flow during near shore SGD. A total of 240 high resolution simulations with the density dependent groundwater modelling software SEAWAT-2000 (Langevin et al., 2007) has been carried out to identify the conditions under which salt water fingering starts to occur. The simulations are based on the field-scale model setup employed in Robinson et al. (2007). The simulation results indicate that a very flat beach slope of less than 1:35, a hydraulic conductivity of 10 m/d and already a tidal range of 2 m initiates fingering flow. Flatter beach slope, higher hydraulic conductivity and increasing tidal range support this behavior. In the cases of fingering flow, freshwater is squeezed upward and pinches out within the inter-tidal zone. Once pinched out, the discharge point slowly moves along at the beach surface towards the low-tide mark. Overall, the fingering process further complicates the flow pattern and the mixing of salt and freshwater in the inter-tidal zone compared to the cases where the saline recirculation cell remains stable. This may have an important implication for the hydrogeochemical processes in this zone and thus the mass flux of reactive chemicals from the land to the ocean. Boufadel, M. C. (2000). A mechanistic study of nonlinear solute transport in a groundwater-surface water system under steady state and transient hydraulic conditions, Water Resour. Res., 36(9), 2549 2565. Bratton, J.F. (2010). The Three Scales of Submarine Groundwater Flow and Discharge across Passive Continental Margins, The Journal of Geology, 2010, 118, 565-575. Kuan, W. K., G. Jin, P. Xin, C. Robinson, B. Gibbes, and L. Li (2012). Tidal influence on seawater intrusion in unconfined coastal aquifers, Water Resour. Res., 48, W02502, doi:10.1029/2011WR010678. Langevin, C.D., D.T. Thorne, Jr., A.M. Dausman, M.C. Sukop, and G. Weixing (2007). Seawat version 4: a computer program for simulation of multi-species solute and heat transport, Technical Report, U.S. Geological Survey Techniques and Methods Book 6, Chapter A22, 39 pp. Robinson, C., L. Li, and H. Prommer (2007). Tide-induced recirculation across the aquifer-ocean interface, Water Resour. Res., 43, W07428, doi:10.1029/2006WR005679. Moore, W.S. (2010). The Effect of Submarine Groundwater Discharge on the Ocean, Annu. Rev. Mar. Sci., 2, 59-88.

Characteristics of and Areas Contributing Recharge to Public-Supply Springs in Massachusetts

USGS Publications Warehouse

Hansen, Bruce P.; Smith, Kirk P.

2004-01-01

The geohydrologic and physical characteristics were determined for 28 public-supply springs, 27 of which are in western Massachusetts. Discharge ranged from zero at various small intermittent springs to more than 240 gallons per minute at Waubeeka Springs in Williamstown, Massachusetts. To determine the annual variability of spring discharge, discharge from 12 springs was measured during different seasonal conditions from June 2001 to November 2002, and the discharge from Red Mill Spring in Clarksburg, Massachusetts was recorded continuously from April 2002 to November 2002. The area contributing recharge to each spring was delineated on the basis of the geohydrologic conditions determined from reconnaissance investigations; these areas ranged from 0.010 to 0.682 square mile. Ground-water recharge, estimated on the basis of average discharge and the areas contributing recharge, ranged from 0.5 to 24.4 inches per year. High ground-water recharge rates for some of the high-discharge springs indicate that the areas contributing recharge for these springs may be too small. Detailed water-table mapping in the vicinity of two low-discharge springs indicates that the area contributing recharge to some of the smaller springs may be smaller than the area indicated by reconnaissance investigation. Monthly flow durations and low flow statistics were determined for the index streamflow-gaging stations for a 25-year period from 1976 to 2000. Annual hydrographs were prepared for each index station from median streamflows at the 50-percent monthly flow duration, normalized by drainage area. A median monthly flow of 1 ft3/s/mi2 was used to split hydrographs into a high-flow period (November?May), and a low-flow period (June?October). The hydrographs were used to classify index stations into groups with similar median monthly flow durations. Index stations were divided into four regional groups, roughly paralleling the coast, to characterize streamflows for November to May; and into two groups, on the basis of base-flow index and percentage of sand and gravel in the contributing area, for June to October.

Accuracy of patient's turnover time prediction using RFID technology in an academic ambulatory surgery center.

PubMed

Marchand-Maillet, Florence; Debes, Claire; Garnier, Fanny; Dufeu, Nicolas; Sciard, Didier; Beaussier, Marc

2015-02-01

Patients flow in outpatient surgical unit is a major issue with regards to resource utilization, overall case load and patient satisfaction. An electronic Radio Frequency Identification Device (RFID) was used to document the overall time spent by the patients between their admission and discharge from the unit. The objective of this study was to evaluate how a RFID-based data collection system could provide an accurate prediction of the actual time for the patient to be discharged from the ambulatory surgical unit after surgery. This is an observational prospective evaluation carried out in an academic ambulatory surgery center (ASC). Data on length of stay at each step of the patient care, from admission to discharge, were recorded by a RFID device and analyzed according to the type of surgical procedure, the surgeon and the anesthetic technique. Based on these initial data (n = 1520), patients were scheduled in a sequential manner according to the expected duration of the previous case. The primary endpoint was the difference between actual and predicted time of discharge from the unit. A total of 414 consecutive patients were prospectively evaluated. One hundred seventy four patients (42%) were discharged at the predicted time ± 30 min. Only 24% were discharged behind predicted schedule. Using an automatic record of patient's length of stay would allow an accurate prediction of the discharge time according to the type of surgery, the surgeon and the anesthetic procedure.

Construction and calibration of a groundwater-flow model to assess groundwater availability in the uppermost principal aquifer systems of the Williston Basin, United States and Canada

USGS Publications Warehouse

Davis, Kyle W.; Long, Andrew J.

2018-05-31

The U.S. Geological Survey developed a groundwater-flow model for the uppermost principal aquifer systems in the Williston Basin in parts of Montana, North Dakota, and South Dakota in the United States and parts of Manitoba and Saskatchewan in Canada as part of a detailed assessment of the groundwater availability in the area. The assessment was done because of the potential for increased demands and stresses on groundwater associated with large-scale energy development in the area. As part of this assessment, a three-dimensional groundwater-flow model was developed as a tool that can be used to simulate how the groundwater-flow system responds to changes in hydrologic stresses at a regional scale.The three-dimensional groundwater-flow model was developed using the U.S. Geological Survey’s numerical finite-difference groundwater model with the Newton-Rhapson solver, MODFLOW–NWT, to represent the glacial, lower Tertiary, and Upper Cretaceous aquifer systems for steady-state (mean) hydrological conditions for 1981‒2005 and for transient (temporally varying) conditions using a combination of a steady-state period for pre-1960 and transient periods for 1961‒2005. The numerical model framework was constructed based on existing and interpreted hydrogeologic and geospatial data and consisted of eight layers. Two layers were used to represent the glacial aquifer system in the model; layer 1 represented the upper one-half and layer 2 represented the lower one-half of the glacial aquifer system. Three layers were used to represent the lower Tertiary aquifer system in the model; layer 3 represented the upper Fort Union aquifer, layer 4 represented the middle Fort Union hydrogeologic unit, and layer 5 represented the lower Fort Union aquifer. Three layers were used to represent the Upper Cretaceous aquifer system in the model; layer 6 represented the upper Hell Creek hydrogeologic unit, layer 7 represented the lower Hell Creek aquifer, and layer 8 represented the Fox Hills aquifer. The numerical model was constructed using a uniform grid with square cells that are about 1 mile (1,600 meters) on each side with a total of about 657,000 active cells.Model calibration was completed by linking Parameter ESTimation (PEST) software with MODFLOW–NWT. The PEST software uses statistical parameter estimation techniques to identify an optimum set of input parameters by adjusting individual model input parameters and assessing the differences, or residuals, between observed (measured or estimated) data and simulated values. Steady-state model calibration consisted of attempting to match mean simulated values to measured or estimated values of (1) hydraulic head, (2) hydraulic head differences between model layers, (3) stream infiltration, and (4) discharge to streams. Calibration of the transient model consisted of attempting to match simulated and measured temporally distributed values of hydraulic head changes, stream base flow, and groundwater discharge to artesian flowing wells. Hydraulic properties estimated through model calibration included hydraulic conductivity, vertical hydraulic conductivity, aquifer storage, and riverbed hydraulic conductivity in addition to groundwater recharge and well skin.The ability of the numerical model to accurately simulate groundwater flow in the Williston Basin was assessed primarily by its ability to match calibration targets for hydraulic head, stream base flow, and flowing well discharge. The steady-state model also was used to assess the simulated potentiometric surfaces in the upper Fort Union aquifer, the lower Fort Union aquifer, and the Fox Hills aquifer. Additionally, a previously estimated regional groundwater-flow budget was compared with the simulated steady-state groundwater-flow budget for the Williston Basin. The simulated potentiometric surfaces typically compared well with the estimated potentiometric surfaces based on measured hydraulic head data and indicated localized groundwater-flow gradients that were topographically controlled in outcrop areas and more generalized regional gradients where the aquifers were confined. The differences between the measured and simulated (residuals) hydraulic head values for 11,109 wells were assessed, which indicated that the steady-state model generally underestimated hydraulic head in the model area. This underestimation is indicated by a positive mean residual of 11.2 feet for all model layers. Layer 7, which represents the lower Hell Creek aquifer, is the only layer for which the steady-state model overestimated hydraulic head. Simulated groundwater-level changes for the transient model matched within plus or minus 2.5 feet of the measured values for more than 60 percent of all measurements and to within plus or minus 17.5 feet for 95 percent of all measurements; however, the transient model underestimated groundwater-level changes for all model layers. A comparison between simulated and estimated base flows for the steady-state and transient models indicated that both models overestimated base flow in streams and underestimated annual fluctuations in base flow.The estimated and simulated groundwater budgets indicate the model area received a substantial amount of recharge from precipitation and stream infiltration. The steady-state model indicated that reservoir seepage was a larger component of recharge in the Williston Basin than was previously estimated. Irrigation recharge and groundwater inflow from outside the Williston Basin accounted for a relatively small part of total groundwater recharge when compared with recharge from precipitation, stream infiltration, and reservoir seepage. Most of the estimated and simulated groundwater discharge in the Williston Basin was to streams and reservoirs. Simulated groundwater withdrawal, discharge to reservoirs, and groundwater outflow in the Williston Basin accounted for a smaller part of total groundwater discharge.The transient model was used to simulate discharge to 571 flowing artesian wells within the model area. Of the 571 established flowing artesian wells simulated by the model, 271 wells did not flow at any time during the simulation because hydraulic head was always below the land-surface altitude. As hydraulic head declined throughout the simulation, 68 of these wells responded by ceasing to flow by the end of 2005. Total mean simulated discharge for the 571 flowing artesian wells was 55.1 cubic feet per second (ft3/s), and the mean simulated flowing well discharge for individual wells was 0.118 ft3/s. Simulated discharge to individual flowing artesian wells increased from 0.039 to 0.177 ft3/s between 1961 and 1975 and decreased to 0.102 ft3/s by 2005. The mean residual for 34 flowing wells with measured discharge was 0.014 ft3/s, which indicates the transient model overestimated discharge to flowing artesian wells in the model area.Model limitations arise from aspects of the conceptual model and from simplifications inherent in the construction and calibration of a regional-scale numerical groundwater-flow model. Simplifying assumptions in defining hydraulic parameters in space and hydrologic stresses and time-varying observational data in time can limit the capabilities of this tool to simulate how the groundwater-flow system responds to changes in hydrologic stresses, particularly at the local scale; nevertheless, the steady-state model adequately simulated flow in the uppermost principal aquifer systems in the Williston Basin based on the comparison between the simulated and estimated groundwater-flow budget, the comparison between simulated and estimated potentiometric surfaces, and the results of the calibration process.

Transient well flow in layered aquifer systems: the uniform well-face drawdown solution

NASA Astrophysics Data System (ADS)

Hemker, C. J.

1999-11-01

Previously a hybrid analytical-numerical solution for the general problem of computing transient well flow in vertically heterogeneous aquifers was proposed by the author. The radial component of flow was treated analytically, while the finite-difference technique was used for the vertical flow component only. In the present work the hybrid solution has been modified by replacing the previously assumed uniform well-face gradient (UWG) boundary condition in such a way that the drawdown remains uniform along the well screen. The resulting uniform well-face drawdown (UWD) solution also includes the effects of a finite diameter well, wellbore storage and a thin skin, while partial penetration and vertical heterogeneity are accommodated by the one-dimensional discretization. Solutions are proposed for well flow caused by constant, variable and slug discharges. The model was verified by comparing wellbore drawdowns and well-face flux distributions with published numerical solutions. Differences between UWG and UWD well flow will occur in all situations with vertical flow components near the well, which is demonstrated by considering: (1) partially penetrating wells in confined aquifers, (2) fully penetrating wells in unconfined aquifers with delayed response and (3) layered aquifers and leaky multiaquifer systems. The presented solution can be a powerful tool for solving many well-hydraulic problems, including well tests, flowmeter tests, slug tests and pumping tests. A computer program for the analysis of pumping tests, based on the hybrid analytical-numerical technique and UWG or UWD conditions, is available from the author.

Amplification of postwildfire peak flow by debris

NASA Astrophysics Data System (ADS)

Kean, J. W.; McGuire, L. A.; Rengers, F. K.; Smith, J. B.; Staley, D. M.

2016-08-01

In burned steeplands, the peak depth and discharge of postwildfire runoff can substantially increase from the addition of debris. Yet methods to estimate the increase over water flow are lacking. We quantified the potential amplification of peak stage and discharge using video observations of postwildfire runoff, compiled data on postwildfire peak flow (Qp), and a physically based model. Comparison of flood and debris flow data with similar distributions in drainage area (A) and rainfall intensity (I) showed that the median runoff coefficient (C = Qp/AI) of debris flows is 50 times greater than that of floods. The striking increase in Qp can be explained using a fully predictive model that describes the additional flow resistance caused by the emergence of coarse-grained surge fronts. The model provides estimates of the amplification of peak depth, discharge, and shear stress needed for assessing postwildfire hazards and constraining models of bedrock incision.

Amplification of postwildfire peak flow by debris

USGS Publications Warehouse

Kean, Jason W.; McGuire, Luke; Rengers, Francis K.; Smith, Joel B.; Staley, Dennis M.

2016-01-01

In burned steeplands, the peak depth and discharge of postwildfire runoff can substantially increase from the addition of debris. Yet methods to estimate the increase over water flow are lacking. We quantified the potential amplification of peak stage and discharge using video observations of postwildfire runoff, compiled data on postwildfire peak flow (Qp), and a physically based model. Comparison of flood and debris flow data with similar distributions in drainage area (A) and rainfall intensity (I) showed that the median runoff coefficient (C = Qp/AI) of debris flows is 50 times greater than that of floods. The striking increase in Qp can be explained using a fully predictive model that describes the additional flow resistance caused by the emergence of coarse-grained surge fronts. The model provides estimates of the amplification of peak depth, discharge, and shear stress needed for assessing postwildfire hazards and constraining models of bedrock incision.

Simulated effects of development on regional ground-water/surface-water interactions in the northern Coastal Plain of New Jersey

NASA Astrophysics Data System (ADS)

Pucci, Amleto A.; Pope, Daryll A.

1995-05-01

Stream flow in the Coastal Plain of New Jersey is primarily controlled by ground-water discharge. Ground-water flow in a 400 square mile area (1035 km 2) of the Potomac-Raritan-Magothy aquifer system (PRMA) in the northern Coastal Plain of New Jersey was simulated to examine development effects on water resources. Simulations showed that historical development caused significant capture of regional ground-water discharge to streams and wetlands. The Cretaceous PRMA primarily is composed of fine to coarse sand, clays and silts which form the Upper and Middle aquifers and their confining units. The aquifer outcrops are the principal areas of recharge and discharge for the regional flow system and have many traversing streams and surface-water bodies. A quasi-three-dimensional numerical model that incorporated ground-water/surface-water interactions and boundary flows from a larger regional model was used to represent the PRMA. To evaluate the influence of ground-water development on interactions in different areas, hydrogeologically similar and contiguous model stream cells were aggregated as 'stream zones'. The model representation of surface-water and ground-water interaction was limited in the areas of confining unit outcrops and because of this, simulated ground-water discharge could not be directly compared with base flow. Significant differences in simulated ground-water and surface-water interactions between the predevelopment and developed system, include; (1) redistribution of recharge and discharge areas; (2) reduced ground-water discharge to streams. In predevelopment, the primary discharge for the Upper and Middle aquifers is to low-lying streams and wetlands; in the developed system, the primary discharge is to ground-water withdrawals. Development reduces simulated ground-water discharge to streams in the Upper Aquifer from 61.4 to 10% of the Upper Aquifer hydrologic budget (28.9%, if impounded stream flow is included). Ground-water discharge to streams in the Middle Aquifer decreases from 80.0 to 22% of the Middle Aquifer hydrologic budget. The utility of assessing ground-water/surface-water interaction in a regional hydrogeologic system by simulation responses to development is demonstrated and which can compensate for lack of long-term stream-gaging data in determining management decisions.

Revisiting a classification scheme for U.S.-Mexico alluvial basin-fill aquifers.

PubMed

Hibbs, Barry J; Darling, Bruce K

2005-01-01

Intermontane basins in the Trans-Pecos region of westernmost Texas and northern Chihuahua, Mexico, are target areas for disposal of interstate municipal sludge and have been identified as possible disposal sites for low-level radioactive waste. Understanding ground water movement within and between these basins is needed to assess potential contaminant fate and movement. Four associated basin aquifers are evaluated and classified; the Red Light Draw Aquifer, the Northwest Eagle Flat Aquifer, the Southeast Eagle Flat Aquifer, and the El Cuervo Aquifer. Encompassed on all but one side by mountains and local divides, the Red Light Draw Aquifer has the Rio Grande as an outlet for both surface drainage and ground water discharge. The river juxtaposed against its southern edge, the basin is classified as a topographically open, through-flowing basin. The Northwest Eagle Flat Aquifer is classified as a topographically closed and drained basin because surface drainage is to the interior of the basin and ground water discharge occurs by interbasin ground water flow. Mountains and ground water divides encompass this basin aquifer on all sides; yet, depth to ground water in the interior of the basin is commonly >500 feet. Negligible ground water discharge within the basin indicates that ground water discharges from the basin by vertical flow and underflow to a surrounding basin or basins. The most likely mode of discharge is by vertical, cross-formational flow to underlying Permian rocks that are more porous and permeable and subsequent flow along regional flowpaths beneath local ground water divides. The Southeast Eagle Flat Aquifer is classified as a topographically open and drained basin because surface drainage and ground water discharge are to the adjacent Wildhorse Flat area. Opposite the Eagle Flat and Red Light Draw aquifers is the El Cuervo Aquifer of northern Chihuahua, Mexico. The El Cuervo Aquifer has interior drainage to Laguna El Cuervo, which is a phreatic playa that also serves as a focal point of ground water discharge. Our evidence suggests that El Cuervo Aquifer may lose a smaller portion of its discharge by interbasin ground water flow to Indian Hot Springs, near the Rio Grande. Thus, El Cuervo Aquifer is a topographically closed basin that is either partially drained if a component of its ground water discharge reaches Indian Hot Springs or undrained if all its natural ground water discharge is to Laguna El Cuervo.

Two-dimensional, steady-state model of ground-water flow, Nevada Test Site and vicinity, Nevada-California

USGS Publications Warehouse

Waddell, R.K.

1982-01-01

A two-dimensional, steady-state model of ground-water flow beneath the Nevada Test Site and vicinity has been developed using inverse techniques. The area is underlain by clastic and carbonate rocks of Precambrian and Paleozoic age and by volcanic rocks and alluvium of Tertiary and Quaternary age that have been juxtaposed by normal and strike-slip faulting. Aquifers are composed of carbonate and volcanic rocks and alluvium. Characteristics of the flow system are determined by distribution of low-conductivity rocks (barriers); by recharge originating in the Spring Mountains, Pahranagat, Timpahute, and Sheep Ranges, and in Pahute Mesa; and by underflow beneath Pahute Mesa from Gold Flat and Kawich Valley. Discharge areas (Ash Meadows, Oasis Valley, Alkali Flat, and Furnace Creek Ranch) are upgradient from barriers. Sensitivities of simulated hydraulic heads and fluxes to variations in model parameters were calculated to guide field studies and to help estimate errors in predictions from transport modeling. Hydraulic heads and fluxes are very sensitive to variations in the greater magnitude recharge/discharge terms. Transmissivity at a location may not be the most important transmissivity for determining flux there. Transmissivities and geometries of large barriers that impede flow from Pahute Mesa have major effects on fluxes elsewhere; as their transmissivities are decreased, flux beneath western Jackass Flats and Yucca Mountains is increased as water is diverted around the barriers. Fortymile Canyon is underlain by highly transmissive rocks that cause potentiometric contours to vee upgradient; increasing their transmissivity increases flow through them, and decreases it beneath Yucca Mountain. (USGS)

Base flow of streams in the outcrop area of southeastern sand aquifer, South Carolina, Georgia, Alabama, and Mississippi

USGS Publications Warehouse

Stricker, Virginia

1983-01-01

The base flow component of streamflow was separated from hydrographs for unregulated streams in the Cretaceous and Tertiary clastic outcrop area of South Carolina, Georgia, Alabama, and Mississippi. The base flow values are used in estimating recharge to the sand aquifer. Relations developed between mean annual base flow and stream discharge at the 60- and 65-percent streamflow duration point can be used to approximate mean annual base flow in lieu of hydrograph separation methods for base flows above 10 cu ft/s. Base flow recession curves were used to derive estimates of hydraulic diffusivity of the aquifer which was converted to transmissivity using estimated specific yield. These base-flow-derived transmissivities are in general agreement with transmissivities derived from well data. The shape of flow duration curves of streams is affected by the lithology of the Coastal Plain sediments. Steep flow duration curves appear to be associated with basins underlain by clay or chalk where a low percentage of the discharge is base flow while flatter curves appear to be associated with basins underlain by sand and gravel where a high percentage of the discharge is base flow. (USGS)

Electron concentration distribution in a glow discharge in air flow

NASA Astrophysics Data System (ADS)

Mukhamedzianov, R. B.; Gaisin, F. M.; Sabitov, R. A.

1989-04-01

Electron concentration distributions in a glow discharge in longitudinal and vortex air flows are determined from the attenuation of the electromagnetic wave passing through the plasma using microwave probes. An analysis of the distribution curves obtained indicates that electron concentration decreases in the direction of the anode. This can be explained by charge diffusion toward the chamber walls and electron recombination and sticking within the discharge.

Thermographic Data Analyses for Karst Watersheds

NASA Technical Reports Server (NTRS)

Campbell, C. Warren; McCaleb, Rebecca C. (Technical Monitor)

2001-01-01

Aerial thermography is an emerging technology unsurpassed for locating groundwater discharges. Thermography can be used to locate submerged discharges that are extremely difficult to find by other means. In two large projects, thermography was used to identify almost every significant spring at sites underlain by karst aquifers. This technology effectively converts Brown's Type 5 topology to types 1 or 2 (all discharges known), which has a significant impact on dye tracing. At a north Alabama site, springs located by thermography quadrupled the known groundwater discharge in and around the site. For submerged discharges, thermographic temperatures can be measured down the center of the groundwater plume that rises to the surface in the winter. Using the Cornell Mixing (CORMIX) model, flow rate for one submerged spring was estimated. Once identified, estimates of spring recharge area were desired. The size of the area of recharge was estimated by hydrograph separation of flow data from nearby, unregulated surface streams. Monthly recharge estimates were also made and used to show that in north Alabama the mean annual recharge/discharge occurs during May and December. Spring flow measurements for the same county of north Alabama were averaged to obtain mean flows. Then measurements for May only, were averaged. The two averages usually agreed to within 20 percent. This provides evidence that hydrograph separation determinations of recharge are valid.

Surface Water Data at Los Alamos National Laboratory: 2002 Water Year

DOE Office of Scientific and Technical Information (OSTI.GOV)

D.A. Shaull; D. Ortiz; M.R. Alexander

2003-03-03

The principal investigators collected and computed surface water discharge data from 34 stream-gaging stations that cover most of Los Alamos National Laboratory and one at Bandelier National Monument. Also included are discharge data from three springs--two that flow into Canon de Valle and one that flows into Water Canyon--and peak flow data from 16 stations.

Surface Water Data at Los Alamos National Laboratory 2006 Water Year

DOE Office of Scientific and Technical Information (OSTI.GOV)

R.P. Romero, D. Ortiz, G. Kuyumjian

2007-08-01

The principal investigators collected and computed surface water discharge data from 44 stream-gaging stations that cover most of Los Alamos National Laboratory and one at Bandelier National Monument. Also included are discharge data from three springs--two that flow into Canon de Valle and one that flows into Water Canyon--and peak flow data for 44 stations.

Impeller tandem blade study with grid embedding for local grid refinement

NASA Technical Reports Server (NTRS)

Bache, George

1992-01-01

Flow non-uniformity at the discharge of high power density impellers can result in significant unsteady interactions between impeller blades and downstream diffuser vanes. These interactions result in degradation of both performance and pump reliability. The MSFC Pump Technology Team has recognized the importance of resolving this problem and has thus initiated the development and testing of a high head coefficient impeller. One of the primary goals of this program is to improve impeller performance and discharge flow uniformity. The objective of the present work is complimentary. Flow uniformity and performance gains were sought through the application of a tandem blade arrangement. The approach adopted was to numerically establish flow characteristics at the impeller discharge for the baseline MSFC impeller and then parametrically evaluate tandem blade configurations. A tandem design was sought that improves both impeller performance and discharge uniformity. The Navier-Stokes solver AEROVISC was used to conduct the study. Grid embedding is used to resolve local gradients while attempting to minimize model size. Initial results indicate that significant gains in flow uniformity can be achieved through the tandem blade concept and that blade clocking rather than slot location is the primary driver for flow uniformity.

Influence of perched groundwater on base flow

USGS Publications Warehouse

Niswonger, Richard G.; Fogg, Graham E.

2008-01-01

Analysis with a three‐dimensional variably saturated groundwater flow model provides a basic understanding of the interplay between streams and perched groundwater. A simplified, layered model of heterogeneity was used to explore these relationships. Base flow contribution from perched groundwater was evaluated with regard to varying hydrogeologic conditions, including the size and location of the fine‐sediment unit and the hydraulic conductivity of the fine‐sediment unit and surrounding coarser sediment. Simulated base flow was sustained by perched groundwater with a maximum monthly discharge in excess of 15 L/s (0.6 feet3/s) over the length of the 2000‐m stream reach. Generally, the rate of perched‐groundwater discharge to the stream was proportional to the hydraulic conductivity of sediment surrounding the stream, whereas the duration of discharge was proportional to the hydraulic conductivity of the fine‐sediment unit. Other aspects of the perched aquifer affected base flow, such as the depth of stream penetration and the size of the fine‐sediment unit. Greater stream penetration decreased the maximum base flow contribution but increased the duration of contribution. Perched groundwater provided water for riparian vegetation at the demand rate but reduced the duration of perched‐groundwater discharge nearly 75%.

Design flow duration curves for environmental flows estimation in Damodar River Basin, India

NASA Astrophysics Data System (ADS)

Verma, Ravindra Kumar; Murthy, Shankar; Verma, Sangeeta; Mishra, Surendra Kumar

2017-06-01

In this study, environmental flows (EFs) are estimated for six watersheds of Damodar River Basin (DRB) using flow duration curve (FDC) derived using two approaches: (a) period of record and (b) stochastic approaches for daily, 7-, 30-, 60-day moving averages, and 7-daily mean annual flows observed at Tenughat dam, Konar dam, Maithon dam, Panchet dam, Damodar bridge, Burnpur during 1981-2010 and at Phusro during 1988-2010. For stochastic FDCs, 7-day FDCs for 10, 20-, 50- and 100-year return periods were derived for extraction of discharge values at every 5% probability of exceedance. FDCs derived using the first approach show high probability of exceedance (5-75%) for the same discharge values. Furthermore, discharge values of 60-day mean are higher than those derived using daily, 7-, and 30-day mean values. The discharge values of 95% probability of exceedance (Q95) derived from 7Q10 (ranges from 2.04 to 5.56 cumec) and 7Q100 (ranges from 3.4 to 31.48 cumec) FDCs using the second approach are found more appropriate as EFs during drought/low flow and normal precipitation years.

Combined Endoscopic Transorbital and Endonasal Repair of High Flow Orbital Apex/Middle Fossa Cerebrospinal Fluid Leak with a Nasoseptal Flap.

PubMed

Lucke-Wold, Brandon; Mendez, Gustavo; Cua, David; Akins, Paul; Gillham, Haley; Ciporen, Jeremy

2018-01-01

High flow orbital apex or middle fossa cerebrospinal fluid (CSF) leaks can be life threatening and complex to repair. These leaks associated with large dural defects are most commonly repaired with an open temporalis muscle patch or free flaps, but these flaps do not always stop the leak. A 65-year-old patient presented two years after orbital exenteration and radiation for squamous cell carcinoma. He developed multi-organism meningitis and pneumocephalus secondary to a large high-flow orbital apex/middle fossa CSF leak. To repair the leak, a combined endoscopic transorbital/endonasal approach with pedicled nasospetal flap and dermis fat graft was used. We describe the unique endoscopic technique that was used to treat the life threatening high flow orbital apex/middle fossa CSF leak. The technique allowed the use of the transposed pedicled flap, which is an alternative to the free flap in controlling CSF leak. Cisternogram post-operatively and clinical exam confirmed resolution of CSF leak. Although a critically ill patient at admission with a modified Rankin scale (MRS) of 5, he was discharged home on continued IV antibiotic therapy with a MRS of 3. Endoscopic evaluation at three months after treatment showed the effectiveness of the flap and he continued to improve clinically. This is the first case to describe a combined endoscopic transorbital and endonasal repair of high flow orbital apex/middle fossa CSF leak with a pedicled nasoseptal flap. These techniques can be utilized during initial reconstruction after orbital exenteration or as a salvage flap.

[Analysis of hydrodynamics parameters of runoff erosion and sediment-yielding on unpaved road].

PubMed

Huang, Peng-Fei; Wang, Wen-Long; Luo, Ting; Wang, Zhen; Wang, Zheng-Li; Li, Ren

2013-02-01

By the method of field runoff washout experiment, a simulation study was conducted on the relationships between the soil detachment rate and the hydrodynamic parameters on unpaved road, and the related quantitative formulas were established. Under the conditions of different flow discharges and road gradients, the averaged soil detachment rate increased with increasing flow discharge and road gradient, and the relationships between them could be described by a power function. As compared with road gradient, flow discharge had greater effects on the soil detachment rate. The soil detachment rate had a power relation with water flow velocity and runoff kinetic energy, and the runoff kinetic energy was of importance to the soil detachment rate. The soil detachment rate was linearly correlated with the unit runoff kinetic energy. The averaged soil erodibility was 0.120 g m-1.J-F-1, and the averaged critical unit runoff kinetic energy was 2.875 g.m-1.J-1. Flow discharge, road gradient, and unit runoff kinetic energy could be used to accurately describe the soil erosion process and calculate the soil erosion rate on unpaved road.

New insight into the residual inactivation of Microcystis aeruginosa by dielectric barrier discharge

PubMed Central

Li, Lamei; Zhang, Hong; Huang, Qing

2015-01-01

We report the new insight into the dielectric barrier discharge (DBD) induced inactivation of Microcystis aeruginosa, the dominant algae which caused harmful cyanobacterial blooms in many developing countries. In contrast with the previous work, we employed flow cytometry to examine the algal cells, so that we could assess the dead and living cells with more accuracy, and distinguish an intermediate state of algal cells which were verified as apoptotic. Our results showed that the numbers of both dead and apoptotic cells increased with DBD treatment delay time, and hydrogen peroxide produced by DBD was the main reason for the time-delayed inactivation effect. However, apart from the influence of hydrogen peroxide, the DBD-induced initial injures on the algal cells during the discharge period also played a considerable role in the inactivation of the DBD treated cells, as indicated by the measurement of intracellular reactive oxygen species (ROS) inside the algal cells. We therefore propose an effective approach to utilization of non-thermal plasma technique that makes good use of the residual inactivation effect to optimize the experimental conditions in terms of discharge time and delay time, so that more efficient treatment of cyanobacterial blooms can be achieved. PMID:26347270

Assessing the impacts of dams and levees on the hydrologic record of the Middle and Lower Mississippi River, USA

USGS Publications Warehouse

Remo, Jonathan W.F.; Ickes, Brian; Ryherd, Julia K.; Guida, Ross J.; Therrell, Matthew D.

2018-01-01

The impacts of dams and levees on the long-term (>130 years) discharge record was assessed along a ~1200 km segment of the Mississippi River between St. Louis, Missouri, and Vicksburg, Mississippi. To aid in our evaluation of dam impacts, we used data from the U.S. National Inventory of Dams to calculate the rate of reservoir expansion at five long-term hydrologic monitoring stations along the study segment. We divided the hydrologic record at each station into three periods: (1) a pre-rapid reservoir expansion period; (2) a rapid reservoir expansion period; and (3) a post-rapid reservoir expansion period. We then used three approaches to assess changes in the hydrologic record at each station. Indicators of hydrologic alteration (IHA) and flow duration hydrographs were used to quantify changes in flow conditions between the pre- and post-rapid reservoir expansion periods. Auto-regressive interrupted time series analysis (ARITS) was used to assess trends in maximum annual discharge, mean annual discharge, minimum annual discharge, and standard deviation of daily discharges within a given water year. A one-dimensional HEC-RAS hydraulic model was used to assess the impact of levees on flood flows. Our results revealed that minimum annual discharges and low-flow IHA parameters showed the most significant changes. Additionally, increasing trends in minimum annual discharge during the rapid reservoir expansion period were found at three out of the five hydrologic monitoring stations. These IHA and ARITS results support previous findings consistent with the observation that reservoirs generally have the greatest impacts on low-flow conditions. River segment scale hydraulic modeling revealed levees can modestly increase peak flood discharges, while basin-scale hydrologic modeling assessments by the U.S. Army Corps of Engineers showed that tributary reservoirs reduced peak discharges by a similar magnitude (2 to 30%). This finding suggests that the effects of dams and levees on peak flood discharges are in part offsetting one another along the modeled river segments and likely other substantially leveed segments of the Mississippi River.

Assessing the impacts of dams and levees on the hydrologic record of the Middle and Lower Mississippi River, USA

NASA Astrophysics Data System (ADS)

Remo, Jonathan W. F.; Ickes, Brian S.; Ryherd, Julia K.; Guida, Ross J.; Therrell, Matthew D.

2018-07-01

The impacts of dams and levees on the long-term (>130 years) discharge record was assessed along a 1200 km segment of the Mississippi River between St. Louis, Missouri, and Vicksburg, Mississippi. To aid in our evaluation of dam impacts, we used data from the U.S. National Inventory of Dams to calculate the rate of reservoir expansion at five long-term hydrologic monitoring stations along the study segment. We divided the hydrologic record at each station into three periods: (1) a pre-rapid reservoir expansion period; (2) a rapid reservoir expansion period; and (3) a post-rapid reservoir expansion period. We then used three approaches to assess changes in the hydrologic record at each station. Indicators of hydrologic alteration (IHA) and flow duration hydrographs were used to quantify changes in flow conditions between the pre- and post-rapid reservoir expansion periods. Auto-regressive interrupted time series analysis (ARITS) was used to assess trends in maximum annual discharge, mean annual discharge, minimum annual discharge, and standard deviation of daily discharges within a given water year. A one-dimensional HEC-RAS hydraulic model was used to assess the impact of levees on flood flows. Our results revealed that minimum annual discharges and low-flow IHA parameters showed the most significant changes. Additionally, increasing trends in minimum annual discharge during the rapid reservoir expansion period were found at three out of the five hydrologic monitoring stations. These IHA and ARITS results support previous findings consistent with the observation that reservoirs generally have the greatest impacts on low-flow conditions. River segment scale hydraulic modeling revealed levees can modestly increase peak flood discharges, while basin-scale hydrologic modeling assessments by the U.S. Army Corps of Engineers showed that tributary reservoirs reduced peak discharges by a similar magnitude (2 to 30%). This finding suggests that the effects of dams and levees on peak flood discharges are in part offsetting one another along the modeled river segments and likely other substantially leveed segments of the Mississippi River.

Transient well flow in vertically heterogeneous aquifers

NASA Astrophysics Data System (ADS)

Hemker, C. J.

1999-11-01

A solution for the general problem of computing well flow in vertically heterogeneous aquifers is found by an integration of both analytical and numerical techniques. The radial component of flow is treated analytically; the drawdown is a continuous function of the distance to the well. The finite-difference technique is used for the vertical flow component only. The aquifer is discretized in the vertical dimension and the heterogeneous aquifer is considered to be a layered (stratified) formation with a finite number of homogeneous sublayers, where each sublayer may have different properties. The transient part of the differential equation is solved with Stehfest's algorithm, a numerical inversion technique of the Laplace transform. The well is of constant discharge and penetrates one or more of the sublayers. The effect of wellbore storage on early drawdown data is taken into account. In this way drawdowns are found for a finite number of sublayers as a continuous function of radial distance to the well and of time since the pumping started. The model is verified by comparing results with published analytical and numerical solutions for well flow in homogeneous and heterogeneous, confined and unconfined aquifers. Instantaneous and delayed drainage of water from above the water table are considered, combined with the effects of partially penetrating and finite-diameter wells. The model is applied to demonstrate that the transient effects of wellbore storage in unconfined aquifers are less pronounced than previous numerical experiments suggest. Other applications of the presented solution technique are given for partially penetrating wells in heterogeneous formations, including a demonstration of the effect of decreasing specific storage values with depth in an otherwise homogeneous aquifer. The presented solution can be a powerful tool for the analysis of drawdown from pumping tests, because hydraulic properties of layered heterogeneous aquifer systems with partially penetrating wells may be estimated without the need to construct transient numerical models. A computer program based on the hybrid analytical-numerical technique is available from the author.

Use of the continuous slope-area method to estimate runoff in a network of ephemeral channels, southeast Arizona, USA

USGS Publications Warehouse

Stewart, Anne M.; Callegary, James B.; Smith, Christopher F.; Gupta, Hoshin V.; Leenhouts, James M.; Fritzinger, Robert A.

2012-01-01

The continuous slope-area (CSA) method is an innovative gaging method for indirect computation of complete-event discharge hydrographs that can be applied when direct measurement methods are unsafe, impractical, or impossible to apply. This paper reports on use of the method to produce event-specific discharge hydrographs in a network of sand-bedded ephemeral stream channels in southeast Arizona, USA, for water year 2008. The method provided satisfactory discharge estimates for flows that span channel banks, and for moderate to large flows, with about 10–16% uncertainty, respectively for total flow volume and peak flow, as compared to results obtained with an alternate method. Our results also suggest that the CSA method may be useful for estimating runoff of small flows, and during recessions, but with increased uncertainty.

Rotor bore and turbine rotor wheel/spacer heat exchange flow circuit

DOEpatents

Caruso, Philip M.; Eldrid, Sacheverel Quentin; Ladhani, Azad A.; DeMania, Alan Richard; Palmer, Gene David; Wilson, Ian David; Rathbun, Lisa Shirley; Akin, Robert Craig

2002-01-01

In a turbine having closed-circuit steam-cooling passages about the rim of the rotor during steady-state operation, compressor discharge air is supplied to the rotor bore for passage radially outwardly into the wheel space cavities between the wheels and spacers. Communicating slots and channels in the spacers and wheels at circumferentially spaced positions enable egress of the compressor discharge air into the hot gas flow path. At turbine startup, cooling air flows through the closed-circuit steam passages to cool the outer rim of the rotor while compressor discharge air pre-warms the wheels and spacers. At steady-state, cooling steam is supplied in the closed-circuit steam-cooling passages and compressor discharge air is supplied through the bore and into the wheel space cavities to cool the rotor.

A prototype of an electric-discharge gas flow oxygen-iodine laser: I. Modeling of the processes of singlet oxygen generation in a transverse cryogenic slab RF discharge

NASA Astrophysics Data System (ADS)

Vagin, N. P.; Ionin, A. A.; Kochetov, I. V.; Napartovich, A. P.; Sinitsyn, D. V.; Yuryshev, N. N.

2017-03-01

The existing kinetic model describing self-sustained and electroionization discharges in mixtures enriched with singlet oxygen has been modified to calculate the characteristics of a flow RF discharge in molecular oxygen and its mixtures with helium. The simulations were performed in the gas plug-flow approximation, i.e., the evolution of the plasma components during their motion along the channel was represented as their evolution in time. The calculations were carried out for the O2: He = 1: 0, 1: 1, 1: 2, and 1: 3 mixtures at an oxygen partial pressure of 7.5 Torr. It is shown that, under these conditions, volumetric gas heating in a discharge in pure molecular oxygen prevails over gas cooling via heat conduction even at an electrode temperature as low as 100 K. When molecular oxygen is diluted with helium, the behavior of the gas temperature changes substantially: heat removal begins to prevail over volumetric gas heating, and the gas temperature at the outlet of the discharge zone drops to 220-230 K at room gas temperature at the inlet, which is very important in the context of achieving the generation threshold in an electric-discharge oxygen-iodine laser based on a slab cryogenic RF discharge.

Effects of gas temperature in the plasma layer on RONS generation in array-type dielectric barrier discharge at atmospheric pressure

NASA Astrophysics Data System (ADS)

Yoon, Sung-Young; Yi, Changho; Eom, Sangheum; Park, Seungil; Kim, Seong Bong; Ryu, Seungmin; Yoo, Suk Jae

2017-12-01

In this work, we studied the control of plasma-produced species under a fixed gas composition (i.e., ambient air) in a 10 kHz-driven array-type dielectric barrier atmospheric-pressure plasma discharge. Instead of the gas composition, only the gas velocity was controlled. Thus, the plasma-maintenance cost was considerably lower than methods such as external N2 or O2 injection. The plasma-produced species were monitored using Fourier transformed infrared spectroscopy. The discharge properties were measured using a voltage probe, current probe, infrared camera, and optical emission spectroscopy. The results showed that the major plasma products largely depend on the gas temperature in the plasma discharge layer. The gas temperature in the plasma discharge layer was significantly different to the temperature of the ceramic adjacent to the plasma discharge layer, even in the small discharge power density of ˜15 W/cm2 or ˜100 W/cm3. Because the vibrational excitation of N2 was suppressed by the higher gas flow, the major plasma-produced species shifted from NOx in low flow to O3 in high flow.

Continuous estimation of baseflow in snowmelt-dominated streams and rivers in the Upper Colorado River Basin: A chemical hydrograph separation approach

USGS Publications Warehouse

Miller, Matthew P.; Susong, David D.; Shope, Christopher L.; Heilweil, Victor M.; Stolp, Bernard J.

2014-01-01

Effective science-based management of water resources in large basins requires a qualitative understanding of hydrologic conditions and quantitative measures of the various components of the water budget, including difficult to measure components such as baseflow discharge to streams. Using widely available discharge and continuously collected specific conductance (SC) data, we adapted and applied a long established chemical hydrograph separation approach to quantify daily and representative annual baseflow discharge at fourteen streams and rivers at large spatial (> 1,000 km2 watersheds) and temporal (up to 37 years) scales in the Upper Colorado River Basin. On average, annual baseflow was 21-58% of annual stream discharge, 13-45% of discharge during snowmelt, and 40-86% of discharge during low-flow conditions. Results suggest that reservoirs may act to store baseflow discharged to the stream during snowmelt and release that baseflow during low-flow conditions, and that irrigation return flows may contribute to increases in fall baseflow in heavily irrigated watersheds. The chemical hydrograph separation approach, and associated conceptual model defined here provide a basis for the identification of land use, management, and climate effects on baseflow.

Emergency Assessment of Debris-Flow Hazards from Basins Burned by the Padua Fire of 2003, Southern California

USGS Publications Warehouse

Cannon, Susan H.; Gartner, Joseph E.; Rupert, Michael G.; Michael, John A.

2004-01-01

Results of a present preliminary assessment of the probability of debris-flow activity and estimates of peak discharges that can potentially be generated by debris flows issuing from basins burned by the Padua Fire of October 2003 in southern California in response to 25-year, 10-year, and 2-year recurrence, 1-hour duration rain storms are presented. The resulting probability maps are based on the application of a logistic multiple-regression model (Cannon and others, 2004) that describes the percent chance of debris-flow production from an individual basin as a function of burned extent, soil properties, basin gradients, and storm rainfall. The resulting peak discharge maps are based on application of a multiple-regression model (Cannon and others, 2004) that can be used to estimate debris-flow peak discharge at a basin outlet as a function of basin gradient, burn extent, and storm rainfall. Probabilities of debris-flow occurrence for the Padua Fire range between 0 and 99% and estimates of debris-flow peak discharges range between 1211 and 6,096 ft3/s (34 to 173 m3/s). These maps are intended to identify those basins that are most prone to the largest debris-flow events and provide information for the preliminary design of mitigation measures and for the planning of evacuation timing and routes.

Introduction to investigations of the negative corona and EHD flow in gaseous two-phase fluids

NASA Astrophysics Data System (ADS)

Jerzy, MIZERACZYK; Artur, BERENDT

2018-05-01

Research interests have recently been directed towards electrical discharges in multi-phase environments. Natural electrical discharges, such as lightning and coronas, occur in the Earth’s atmosphere, which is actually a mixture of gaseous phase (air) and suspended solid and liquid particulate matters (PMs). An example of an anthropogenic gaseous multi-phase environment is the flow of flue gas through electrostatic precipitators (ESPs), which are generally regarded as a mixture of a post-combustion gas with solid PM and microdroplets suspended in it. Electrical discharges in multi-phase environments, the knowledge of which is scarce, are becoming an attractive research subject, offering a wide variety of possible discharges and multi-phase environments to be studied. This paper is an introduction to electrical discharges in multi-phase environments. It is focused on DC negative coronas and accompanying electrohydrodynamic (EHD) flows in a gaseous two-phase fluid formed by air (a gaseous phase) and solid PM (a solid phase), run under laboratory conditions. The introduction is based on a review of the relevant literature. Two cases will be considered: the first case is of a gaseous two-phase fluid, initially motionless in a closed chamber before being subjected to a negative corona (with the needle-to-plate electrode arrangement), which afterwards induces an EHD flow in the chamber, and the second, of a gaseous two-phase fluid flowing transversely with respect to the needle-to-plate electrode axis along a chamber with a corona discharge running between the electrodes. This review-based introductory paper should be of interest to theoretical researchers and modellers in the field of negative corona discharges in single- or two-phase fluids, and for engineers who work on designing EHD devices (such as ESPs, EHD pumps, and smoke detectors).

Constant-head pumping test of a multiaquifer well to determine characteristics of individual aquifers

USGS Publications Warehouse

Bennett, Gordon D.; Patten, E.P.

1962-01-01

This report describes the theory and field procedures for determining the transmissibility and storage coefficients and the original hydrostatic head of each aquifer penetrated by a multiaquifer well. The procedure involves pumping the well in such a manner that the drawdown of water level is constant while the discharges of the different aquifers are measured by means of borehole flowmeters. The theory is developed by analogy to the heat-flow problem solved by Smith. The internal discharge between aquifers after the well is completed is analyzed as the first step. Pumping at constant, drawdown constitutes the second step. Transmissibility and storage coefficients are determined by a method described by Jacob and Lohman, after the original internal discharge to or from the aquifer has been compensated for in the calculations. The original hydrostatic head of each aquifer is then determined by resubstituting the transmissibility and storage coefficients into the first step of the analysis. The method was tested on a well in Chester County, Pa., but the results were not entirely satisfactory, owing to the lack of sufficiently accurate methods of flow measurement and, probably, to the effects of entrance losses in the well. The determinations of the transmissibility coefficient and static head can be accepted as having order-of-magnitude significance, but the determinations of the storage coefficient, which is highly sensitive to experimental error, must be rejected. It is felt that better results may be achieved in the future, as more reliable devices for metering the flow become available and as more is learned concerning the nature of entrance losses. If accurate data can be obtained, recently developed techniques of digital or analog computation may permit determination of the response of each aquifer in the well to any form of pumping.

Factors contributing to the process of intensive care patient discharge: an ethnographic study informed by activity theory.

PubMed

Lin, Frances; Chaboyer, Wendy; Wallis, Marianne; Miller, Anne

2013-08-01

Patient flow from intensive care to acute care units is often problematic and many discharges from intensive care to acute care are unsuccessful on the first attempt. The aim of this study was to explore the factors that influence intensive care patient discharge. This ethnographic study was undertaken in an Australian metropolitan tertiary hospital that had a 14-bed level 3 intensive care unit. Intensive care and acute care unit medical and nursing staff, and other hospital staff who were involved in the intensive care patient discharge process participated in this study. A total of 28 discharges were observed, and 56 one on one interviews were conducted. Data collection techniques including direct observations, semi-structured interviews, and collection of existing documents were used. Activity theory was the theoretical framework that underpinned this study. Three patient activity systems were identified: intensive care patient discharge activity, acute care unit accepting patient activity, and hospital bed management activity. Analysis of the interactions among these activity systems revealed conflicting objects (goals), communication breakdowns, and teamwork issues. Discharge delay was found to be a significant problem, which was associated with limited acute care unit bed availability. Strategies to improve acute care unit bed availability are needed. Routine after-hours ICU discharge could raise patient safety concerns which need to be considered. All team members' input in discharge decision making should be encouraged. Problems identified in clinical handover call for actions to change the handover practice. Activity theory successfully guided the study by providing a practical and descriptive framework for the study, facilitating the understanding of the interrelationships among the activity systems. Copyright © 2012 Elsevier Ltd. All rights reserved.

Linking the pacific decadal oscillation to seasonal stream discharge patterns in Southeast Alaska

USGS Publications Warehouse

Neal, E.G.; Todd, Walter M.; Coffeen, C.

2002-01-01

This study identified and examined differences in Southeast Alaskan streamflow patterns between the two most recent modes of the Pacific decadal oscillation (PDO). Identifying relationships between the PDO and specific regional phenomena is important for understanding climate variability, interpreting historical hydrological variability, and improving water-resources forecasting. Stream discharge data from six watersheds in Southeast Alaska were divided into cold-PDO (1947-1976) and warm-PDO (1977-1998) subsets. For all watersheds, the average annual streamflows during cold-PDO years were not significantly different from warm-PDO years. Monthly and seasonal discharges, however, did differ significantly between the two subsets, with the warm-PDO winter flows being typically higher than the cold-PDO winter flows and the warm-PDO summer flows being typically lower than the cold-PDO flows. These results were consistent with and driven by observed temperature and snowfall patterns for the region. During warm-PDO winters, precipitation fell as rain and ran-off immediately, causing higher than normal winter streamflow. During cold-PDO winters, precipitation was stored as snow and ran off during the summer snowmelt, creating greater summer streamflows. The Mendenhall River was unique in that it experienced higher flows for all seasons during the warm-PDO relative to the cold-PDO. The large amount of Mendenhall River discharge caused by glacial melt during warm-PDO summers offset any flow reduction caused by lack of snow accumulation during warm-PDO winters. The effect of the PDO on Southeast Alaskan watersheds differs from other regions of the Pacific Coast of North America in that monthly/seasonal discharge patterns changed dramatically with the switch in PDO modes but annual discharge did not. ?? 2002 Elsevier Science B.V. All rights reserved.

Gas and plasma dynamics of RF discharge jet of low pressure in a vacuum chamber with flat electrodes and inside tube, influence of RF discharge on the steel surface parameters

NASA Astrophysics Data System (ADS)

Khristoliubova, V. I.; Kashapov, N. F.; Shaekhov, M. F.

2016-06-01

Researches results of the characteristics of the RF discharge jet of low pressure and the discharge influence on the surface modification of high speed and structural steels are introduced in the article. Gas dynamics, power and energy parameters of the RF low pressure discharge flow in the discharge chamber and the electrode gap are studied in the presence of the materials. Plasma flow rate, discharge power, the concentration of electrons, the density of RF power, the ion current density, and the energy of the ions bombarding the surface materials are considered for the definition of basic properties crucial for the process of surface modification of materials as they were put in the plasma jet. The influence of the workpiece and effect of products complex configuration on the RF discharge jet of low pressure is defined. The correlation of the input parameters of the plasma unit on the characteristics of the discharge is established.

PHYSICAL EFFECTS OCCURRING DURING GENERATION AND AMPLIFICATION OF LASER RADIATION: Efficiency of the vibrational excitation of CO2 molecules pumped by a capacitative discharge

NASA Astrophysics Data System (ADS)

Baranov, G. A.; Efremov, Yu V.; Smirnov, A. S.; Frolov, K. S.; Shevchenko, Yu I.

1989-02-01

An investigation was made of the distributions of the gain and input energy per unit volume along the discharge chamber length in a CO2-N2-He mixture stream excited by an rf discharge. The dependences of the gain and discharge luminescence intensity on the coordinate x were determined along the direction of the gas flow. The discharge luminescence intensity was shown to characterize the input energy distribution along the X axis. Calculations were made of the small-signal gain in the rf discharge. Experimental data on the distributions of the input energy and of the electric field in the discharge and the average values of the kinetic coefficients were used in the calculations. The efficiency of pumping CO2 lasers with an rf discharge was found to be close to the dc pumping efficiency. The results obtained provide evidence of promising prospects for using an rf discharge in fast-flow industrial lasers.

Discharge indices for water quality loads

USGS Publications Warehouse

Vogel, Richard M.; Stedinger, Jery R.; Hooper, Richard P.

2003-01-01

Effective discharge has been used to describe the streamflow level that is responsible for transporting the most sediment over the long term. Careful inspection reveals that this concept may not have been well defined, and different interpretations have led to conflicting representations. Because total load is ultimately the quantity of interest, we define a new index, the half‐load discharge, which is that discharge above and below which half the total long‐term load is transported. The value of the half‐load discharge is derived for a reasonable model of flows and constituent concentration. The effective discharge has generally been thought to be a relatively common or frequent flood. The half‐load discharge is generally a much greater and less frequent flow than commonly used estimators of the effective discharge. Relations provided here for the frequency and magnitude of the half‐load discharge provide evidence that it is relatively rare floods that transport most of the sediment over the long term. These ideas apply to other constituents as well.

A stage-normalized function for the synthesis of stage-discharge relations for the Colorado River in Grand Canyon, Arizona

USGS Publications Warehouse

Wiele, Stephen M.; Torizzo, Margaret

2003-01-01

A method was developed to construct stage-discharge rating curves for the Colorado River in Grand Canyon, Arizona, using two stage-discharge pairs and a stage-normalized rating curve. Stage-discharge rating curves formulated with the stage-normalized curve method are compared to (1) stage-discharge rating curves for six temporary stage gages and two streamflow-gaging stations developed by combining stage records with modeled unsteady flow; (2) stage-discharge rating curves developed from stage records and discharge measurements at three streamflow-gaging stations; and (3) stages surveyed at known discharges at the Northern Arizona Sand Bar Studies sites. The stage-normalized curve method shows good agreement with field data when the discharges used in the construction of the rating curves are at least 200 cubic meters per second apart. Predictions of stage using the stage-normalized curve method are also compared to predictions of stage from a steady-flow model.

Surface-Water and Ground-Water Interactions in the Central Everglades, Florida

USGS Publications Warehouse

Harvey, Judson W.; Newlin, Jessica T.; Krest, James M.; Choi, Jungyill; Nemeth, Eric A.; Krupa, Steven L.

2004-01-01

Recharge and discharge are hydrological processes that cause Everglades surface water to be exchanged for subsurface water in the peat soil and the underlying sand and limestone aquifer. These interactions are thought to be important to water budgets, water quality, and ecology in the Everglades. Nonetheless, relatively few studies of surface water and ground water interactions have been conducted in the Everglades, especially in its vast interior areas. This report is a product of a cooperative investigation conducted by the USGS and the South Florida Water Management District (SFWMD) aimed at developing and testing techniques that would provide reliable estimates of recharge and discharge in interior areas of WCA-2A (Water Conservation Area 2A) and several other sites in the central Everglades. The new techniques quantified flow from surface water to the subsurface (recharge) and the opposite (discharge) using (1) Darcy-flux calculations based on measured vertical gradients in hydraulic head and hydraulic conductivity of peat; (2) modeling transport through peat and decay of the naturally occurring isotopes 224Ra and 223Ra (with half-lives of 4 and 11 days, respectively); and (3) modeling transport and decay of naturally occurring and 'bomb-pulse' tritium (half-life of 12.4 years) in ground water. Advantages and disadvantages of each method for quantifying recharge and discharge were compared. In addition, spatial and temporal variability of recharge and discharge were evaluated and controlling factors identified. A final goal was to develop appropriately simplified (that is, time averaged) expressions of the results that will be useful in addressing a broad range of hydrological and ecological problems in the Everglades. Results were compared with existing information about water budgets from the South Florida Water Management Model (SFWMM), a principal tool used by the South Florida Water Management District to plan many of the hydrological aspects of the Everglades restoration. A century of water management for flood control and water storage in the Everglades resulted in the creation of the Water Conservation Areas (WCAs). Construction of the major canals began in the 1910s and the systems of levees that enclose the basins and structures that move water between basins were largely completed by the 1950s. The abandoned wetlands that remained outside of the Water Conservation areas tended to dry out and subside by 10 feet or more, which created abrupt transitions in land-surface elevations and water levels across the levees. The increases in topographic and hydraulic gradients near the margins of the WCAs, along with rapid pumping of water between basins to achieve management objectives, have together altered the patterns of recharge and discharge in the Everglades. The most evident change is the increase in the magnitude of recharge (on the upgradient side) and discharge (on the downgradient side) of levees separating WCA-2A from other basins or areas outside. Recharge and discharge in the vast interior of WCA-2A also likely have increased, but fluxes in the interior wetlands are more subtle and more difficult to quantify compared with areas close to the levees. Surface-water and ground-water interactions differ in fundamental ways between wetlands near WCA-2A's boundaries and wetlands in the basin's interior. The levees that form the WCA's boundaries have introduced step functions in the topographic and hydraulic gradients that are important as a force to drive water flow across the wetland ground surface. The resulting recharge and discharge fluxes tend to be unidirectional (connecting points of recharge on the upgradient side of the levee with points of discharge on the downgradient side), and fluxes are also relatively steady in magnitude compared with fluxes in the interior. Recharge flow paths are also relatively deep in their extent near levees, with fluxes passing entirely through the 1-m peat layer and inte

A flowing partially penetrating well in a finite-thickness aquifer: a mixed-type initial boundary value problem

NASA Astrophysics Data System (ADS)

Chang, Chien-Chieh; Chen, Chia-Shyun

2003-02-01

An analytical approach using integral transform techniques is developed to deal with a well hydraulics model involving a mixed boundary of a flowing partially penetrating well, where constant drawdown is stipulated along the well screen and no-flux condition along the remaining unscreened part. The aquifer is confined of finite thickness. First, the mixed boundary is changed into a homogeneous Neumann boundary by discretizing the well screen into a finite number of segments, each of which at constant drawdown is subject to unknown a priori well bore flux. Then, the Laplace and the finite Fourier transforms are used to solve this modified model. Finally, the prescribed constant drawdown condition is reinstated to uniquely determine the well bore flux function, and to restore the relation between the solution and the original model. The transient and the steady-state solutions for infinite aquifer thickness can be derived from the semi-analytical solution, complementing the currently available dual integral solution. If the distance from the edge of the well screen to the bottom/top of the aquifer is 100 times greater than the well screen length, aquifer thickness can be assumed infinite for times of practical significance, and groundwater flow can reach a steady-state condition, where the well will continuously supply water under a constant discharge. However, if aquifer thickness is smaller, the well discharge decreases with time. The partial penetration effect is most pronounced in the vicinity of the flowing well, decreases with increasing horizontal distance, and vanishes at distances larger than 1-2 times the aquifer thickness divided by the square root of aquifer anisotropy. The horizontal hydraulic conductivity and the specific storage coefficient can be determined from vertically averaged drawdown as measured by fully penetrating observation wells. The vertical hydraulic conductivity can be determined from the well discharge under two particular partial penetration conditions.

Finite difference model for aquifer simulation in two dimensions with results of numerical experiments

USGS Publications Warehouse

Trescott, Peter C.; Pinder, George Francis; Larson, S.P.

1976-01-01

The model will simulate ground-water flow in an artesian aquifer, a water-table aquifer, or a combined artesian and water-table aquifer. The aquifer may be heterogeneous and anisotropic and have irregular boundaries. The source term in the flow equation may include well discharge, constant recharge, leakage from confining beds in which the effects of storage are considered, and evapotranspiration as a linear function of depth to water. The theoretical development includes presentation of the appropriate flow equations and derivation of the finite-difference approximations (written for a variable grid). The documentation emphasizes the numerical techniques that can be used for solving the simultaneous equations and describes the results of numerical experiments using these techniques. Of the three numerical techniques available in the model, the strongly implicit procedure, in general, requires less computer time and has fewer numerical difficulties than do the iterative alternating direction implicit procedure and line successive overrelaxation (which includes a two-dimensional correction procedure to accelerate convergence). The documentation includes a flow chart, program listing, an example simulation, and sections on designing an aquifer model and requirements for data input. It illustrates how model results can be presented on the line printer and pen plotters with a program that utilizes the graphical display software available from the Geological Survey Computer Center Division. In addition the model includes options for reading input data from a disk and writing intermediate results on a disk.

Gaining the necessary geologic, hydrologic, and geochemical understanding for additional brackish groundwater development, coastal San Diego, California, USA

USGS Publications Warehouse

Danskin, Wesley R.

2012-01-01

Local water agencies and the United States Geological Survey are using a combination of techniques to better understand the scant freshwater resources and the much more abundant brackish resources in coastal San Diego, California, USA. Techniques include installation of multiple-depth monitoring well sites; geologic and paleontological analysis of drill cuttings; geophysical logging to identify formations and possible seawater intrusion; sampling of pore-water obtained from cores; analysis of chemical constituents including trace elements and isotopes; and use of scoping models including a three-dimensional geologic framework model, rainfall-runoff model, regional groundwater flow model, and coastal density-dependent groundwater flow model. Results show that most fresh groundwater was recharged during the last glacial period and that the coastal aquifer has had recurring intrusions of fresh and saline water. These intrusions disguise the source, flowpaths, and history of ground water near the coast. The flow system includes a freshwater lens resting on brackish water; a 100-meter-thick flowtube of freshwater discharging under brackish estuarine water and above highly saline water; and broad areas of fine-grained coastal sediment filled with fairly uniform brackish water. Stable isotopes of hydrogen and oxygen indicate the recharged water flows through many kilometers of fractured crystalline rock before entering the narrow coastal aquifer.

SARAL/Altika for inland water: current and potential applications

NASA Astrophysics Data System (ADS)

Tarpanelli, Angelica; Brocca, Luca; Barbetta, Silvia; Moramarco, Tommaso; Santos da Silva, Joécila; Calmant, Stephane

2015-04-01

Although representing less than 1% of the total amount of water on Earth the freshwater is essential for terrestrial life and human needs. Over one third of the world's population is not served by adequate supplies of clean water and for this reason freshwater wars are becoming one of the most pressing environmental issues exacerbating the already difficult tensions between the riparian nations. Notwithstanding the foregoing, we have surprisingly poor knowledge of the spatial and temporal dynamics of surface discharge. In-situ gauging networks quantify the instantaneous water volume in the main river channels but provide few information about the spatial dynamics of surface water extent, such as floodplain flows and the dynamics of wetlands. The growing reduction of hydrometric monitoring networks over the world, along with the inaccessibility of many remote areas and the difficulties for data sharing among developing countries feed the need to develop new procedures for river discharge estimation based on remote sensing technology. The major challenge in this case is the possibility of using Earth Observation data without ground measurements. Radar altimeters are a valuable tool to retrieve hydrological information from space such as water level of inland water. More than a decade of research on the application of radar altimetry has demonstrated its advantages also for monitoring continental water, providing global coverage and regular temporal sampling. The high accuracy of altimetry data provided by the latest spatial missions and the convincing results obtained in the previous applications suggest that these data may be employed for hydraulic/hydrological applications as well. If used in synergy with the modeling, the potential benefits of the altimetry measurements can grow significantly. The new SARAL French-Indian mission, providing improvements in terms of vertical accuracy and spatial resolution of the onboard altimeter Altika, can offer a great contribute for monitoring inland water and especially for the assessment of the discharge. Expressed in terms of water level variations using mathematical formulas or calibrated relationships, the discharge can be estimated by different methods. In the last years, empirical formulae relating the flow to the hydraulic variables (width, flow depth, slope) along with more complex methods that use hydrological modelling and assimilation techniques were applied to this end. Recently, a simplified approach based on relationship between the discharge and the hydraulic conditions and a method using MODIS images for the river flow velocity estimation were successful applied to altimetry data derived from the previous satellite missions (ERS-2, ENVISAT) for different case studies. With the aim to investigate the benefits that can be achieved by SARAL mission, the same two procedures are here applied by using Altika altimetry data for some pilot rivers. Results are analyzed and discussed in terms of performance measures in discharge estimation.

Significance of flow clustering and sequencing on sediment transport: 1D sediment transport modelling

NASA Astrophysics Data System (ADS)

Hassan, Kazi; Allen, Deonie; Haynes, Heather

2016-04-01

This paper considers 1D hydraulic model data on the effect of high flow clusters and sequencing on sediment transport. Using observed flow gauge data from the River Caldew, England, a novel stochastic modelling approach was developed in order to create alternative 50 year flow sequences. Whilst the observed probability density of gauge data was preserved in all sequences, the order in which those flows occurred was varied using the output from a Hidden Markov Model (HMM) with generalised Pareto distribution (GP). In total, one hundred 50 year synthetic flow series were generated and used as the inflow boundary conditions for individual flow series model runs using the 1D sediment transport model HEC-RAS. The model routed graded sediment through the case study river reach to define the long-term morphological changes. Comparison of individual simulations provided a detailed understanding of the sensitivity of channel capacity to flow sequence. Specifically, each 50 year synthetic flow sequence was analysed using a 3-month, 6-month or 12-month rolling window approach and classified for clusters in peak discharge. As a cluster is described as a temporal grouping of flow events above a specified threshold, the threshold condition used herein is considered as a morphologically active channel forming discharge event. Thus, clusters were identified for peak discharges in excess of 10%, 20%, 50%, 100% and 150% of the 1 year Return Period (RP) event. The window of above-peak flows also required cluster definition and was tested for timeframes 1, 2, 10 and 30 days. Subsequently, clusters could be described in terms of the number of events, maximum peak flow discharge, cumulative flow discharge and skewness (i.e. a description of the flow sequence). The model output for each cluster was analysed for the cumulative flow volume and cumulative sediment transport (mass). This was then compared to the total sediment transport of a single flow event of equivalent flow volume. Results illustrate that clustered flood events generated sediment loads up to an order of magnitude greater than that of individual events of the same flood volume. Correlations were significant for sediment volume compared to both maximum flow discharge (R2<0.8) and number of events (R2 -0.5 to -0.7) within the cluster. The strongest correlations occurred for clusters with a greater number of flow events only slightly above-threshold. This illustrates that the numerical model can capture a degree of the non-linear morphological response to flow magnitude. Analysis of the relationship between morphological change and the skewness of flow events within each cluster was also determined, illustrating only minor sensitivity to cluster peak distribution skewness. This is surprising and discussion is presented on model limitations, including the capability of sediment transport formulae to effectively account for temporal processes of antecedent flow, hysteresis, local supply etc.

Mach 5 bow shock control by a nanosecond pulse surface dielectric barrier discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nishihara, M.; Takashima, K.; Rich, J. W.

2011-06-15

Bow shock perturbations in a Mach 5 air flow, produced by low-temperature, nanosecond pulse, and surface dielectric barrier discharge (DBD), are detected by phase-locked schlieren imaging. A diffuse nanosecond pulse discharge is generated in a DBD plasma actuator on a surface of a cylinder model placed in air flow in a small scale blow-down supersonic wind tunnel. Discharge energy coupled to the actuator is 7.3-7.8 mJ/pulse. Plasma temperature inferred from nitrogen emission spectra is a few tens of degrees higher than flow stagnation temperature, T = 340 {+-} 30 K. Phase-locked Schlieren images are used to detect compression waves generatedmore » by individual nanosecond discharge pulses near the actuator surface. The compression wave propagates upstream toward the baseline bow shock standing in front of the cylinder model. Interaction of the compression wave and the bow shock causes its displacement in the upstream direction, increasing shock stand-off distance by up to 25%. The compression wave speed behind the bow shock and the perturbed bow shock velocity are inferred from the Schlieren images. The effect of compression waves generated by nanosecond discharge pulses on shock stand-off distance is demonstrated in a single-pulse regime (at pulse repetition rates of a few hundred Hz) and in a quasi-continuous mode (using a two-pulse sequence at a pulse repetition rate of 100 kHz). The results demonstrate feasibility of hypersonic flow control by low-temperature, repetitive nanosecond pulse discharges.« less

Aerospace Thematic Workshop (4th): Fundamentals of Aerodynamic Flow and Combustion Control by Plasmas

DTIC Science & Technology

2013-04-01

Supersonic Flow Control by Microwave Discharge and Non-equilibrium Processes in Viscous Gas Flows Elena Kustova (Saint Petersburg State University...implying new technologies (direct injection, turbocharging, exhaust gas recirculation, ...) and introducing new physics ( liquid films, flame propagation...combustion  Discharges physics and kinetics A visit was also organized in the afternoon of April 10 to the supersonic and hypersonic wind tunnels

Effects of flow regime on benthic algae and macroinvertebrates - A comparison between regulated and unregulated rivers.

PubMed

Schneider, Susanne C; Petrin, Zlatko

2017-02-01

Natural fluctuations in flow are important for maintaining the ecological integrity of riverine ecosystems. However, the flow regime of many rivers has been modified. We assessed the impact of water chemistry, habitat and streamflow characteristics on macroinvertebrates and benthic algae, comparing 20 regulated with 20 unregulated sites. Flow regime, calculated from daily averaged discharge over the five years preceding sampling, was generally more stable at regulated sites, with higher relative discharges in winter, lower relative discharges in spring and smaller differences between upper and lower percentiles. However, no consistent differences in benthic algal or macroinvertebrate structural and functional traits occurred between regulated and unregulated sites. When regulated and unregulated sites were pooled, overall flow regime, calculated as principal components of discharge characteristics over the five years preceding sampling, affected macroinvertebrate species assemblages, but not indices used for ecosystem status assessment or functional feeding groups. This indicates that, while species identity shifted with changing flow regime, the exchanged taxa had similar feeding habits. In contrast to macroinvertebrates, overall flow regime did not affect benthic algae. Our results indicate that overall flow regime affected the species pool of macroinvertebrates from which recolonization after extreme events may occur, but not of benthic algae. When individual components of flow regime were analyzed separately, high June (i.e. three months before sampling) flow maxima were associated with low benthic algal taxon richness, presumably due to scouring. Macroinvertebrate taxon richness decreased with lower relative minimum discharges, presumably due to temporary drying of parts of the riverbed. However, recolonization after such extreme events presumably is fast. Generally, macroinvertebrate and benthic algal assemblages were more closely related to water physico-chemical than to hydrological variables. Our results suggest that macroinvertebrate and benthic algal indices commonly used for ecological status assessment are applicable also in regulated rivers. Copyright © 2016 Elsevier B.V. All rights reserved.

US researchers study effectiveness of Fluidized Sand Biofilters

USDA-ARS?s Scientific Manuscript database

Intensive aquaculture facilities generally produce two separate waste flows: 1) a high volume dilute discharge from culture tanks or pump sumps, and 2) a moderately small and solids-concentrated discharge typically backwashed from mechanical filtration units. The high volume dilute flow can appear p...

Modeling of corona discharge combined with Mn²⁺ catalysis for the removal of SO₂ from simulated flue gas.

PubMed

Jiwu, Li; Lei, Fan

2013-05-01

This study investigated a mass-transfer process of the removal of SO₂ from simulated flue gas by corona discharge combined with Mn(2+) catalysis in wet reactor, including gas migration, liquid phase diffusion, and chemical reaction. The novelty formula of desulphurization efficiency and the flow rate of flue gas, discharge voltage, reaction enhancement factor, and the flow rate of water were established. It is reported that desulphurization efficiency remarkably increased with the increasing of enhancement factor and discharge voltage at 4000 mg m(-3) of SO₂ and 0.05 m(3)s(-1) of gas flow rate. However, the desulphurization efficiency had a slightly increase with the increasing of water flow rate. It is realizable that the energy consumption could be reduced to be lower than 0.3 kJ m(-3), which was acceptable for industrial application. The experimental data were well in accord with the calculated results of theoretical model. Copyright © 2013 Elsevier Ltd. All rights reserved.

Oil flow at the scroll compressor discharge: visualization and CFD simulation

NASA Astrophysics Data System (ADS)

Xu, Jiu; Hrnjak, Pega

2017-08-01

Oil is important to the compressor but has other side effect on the refrigeration system performance. Discharge valves located in the compressor plenum are the gateway for the oil when leaving the compressor and circulate in the system. The space in between: the compressor discharge plenum has the potential to separate the oil mist and reduce the oil circulation ratio (OCR) in the system. In order to provide information for building incorporated separation feature for the oil flow near the compressor discharge, video processing method is used to quantify the oil droplets movement and distribution. Also, CFD discrete phase model gives the numerical approach to study the oil flow inside compressor plenum. Oil droplet size distributions are given by visualization and simulation and the results show a good agreement. The mass balance and spatial distribution are also discussed and compared with experimental results. The verification shows that discrete phase model has the potential to simulate the oil droplet flow inside the compressor.

Kinetics study of the reaction of OH radicals with C5-C8 cycloalkanes at 240-340 K using the relative rate/discharge flow/mass spectrometry technique.

PubMed

Singh, Sumitpal; de Leon, Maria Fatima; Li, Zhuangjie

2013-10-24

Rate constants of reactions of hydroxyl radical with cyclopentane (k1), cyclohexane (k2), cycloheptane (k3), and cyclooctane (k4) have been acquired at 240-340 K and a total pressure of about 1 Torr using the technique of relative rate combined with discharge flow and mass spectrometry (RR/DF/MS). At 298 K, the rate constants are determined using two reference compounds, which are averaged to be k1 = (4.81 ± 0.88) × 10(-12), k2 = (6.41 ± 0.85) × 10(-12), k3 = (10.30 ± 1.44) × 10(-12), and k4 = (1.42 ± 0.27) × 10(-11) cm(3) molecule(-1) s(-1). The Arrhenius expressions at 240-340 K for these reactions are determined to be k1(T) = (2.43 ± 0.50) × 10(-11)exp[-(481 ± 58)/T], k2(T) = (3.96 ± 0.60) × 10(-11)exp[-554 ± 42)/T], k3(T) = (5.74 ± 0.66) × 10(-11)exp[-527 ± 33)/T], and k4(T) = (1.12 ± 0.21) × 10(-10)exp[-626 ± 53)/T]. Using the kcycloalkane+OH(277 K) values measured in the present work, the atmospheric lifetime for cyclopentane, cyclohexane, cycloheptane, and cyclooctane is estimated to be about 78, 64, 38, and 29 h, respectively.

Congenital extrahepatic portosystemic shunt (Abernethy malformation) treated endovascularly with vascular plug shunt closure.

PubMed

Passalacqua, Matthew; Lie, Kevin T; Yarmohammadi, Hooman

2012-01-01

A 3-year-old boy, who presented with progressive cyanosis and hypoxia, was diagnosed with a large congenital extrahepatic portosystemic shunt, interrupted IVC with azygos continuation, and multiple congenital anomalies. Traditionally open and laparoscopic surgical techniques have been used to treat this malformation. Endovascular repair using a 16-mm Amplatzer vascular plug (AGA Medical Corporation, Golden Valley, Minnesota, USA) was used to occlude the shunt. Immediate post-placement venography demonstrated cessation of flow within the shunt and increased portal venous flow. The patient's hypoxia and cyanosis decreased significantly, and he was discharged on the 5th post-procedure day in stable clinical condition. Three months follow-up evaluation demonstrated the vascular plug in place, unchanged in position.

Debris flow-induced topographic changes: effects of recurrent debris flow initiation.

PubMed

Chen, Chien-Yuan; Wang, Qun

2017-08-12

Chushui Creek in Shengmu Village, Nantou County, Taiwan, was analyzed for recurrent debris flow using numerical modeling and geographic information system (GIS) spatial analysis. The two-dimensional water flood and mudflow simulation program FLO-2D were used to simulate debris flow induced by rainfall during typhoon Herb in 1996 and Mindulle in 2004. Changes in topographic characteristics after the debris flows were simulated for the initiation of hydrological characteristics, magnitude, and affected area. Changes in topographic characteristics included those in elevation, slope, aspect, stream power index (SPI), topographic wetness index (TWI), and hypsometric curve integral (HI), all of which were analyzed using GIS spatial analysis. The results show that the SPI and peak discharge in the basin increased after a recurrence of debris flow. The TWI was higher in 2003 than in 2004 and indicated higher potential of landslide initiation when the slope of the basin was steeper. The HI revealed that the basin was in its mature stage and was shifting toward the old stage. Numerical simulation demonstrated that the parameters' mean depth, maximum depth, affected area, mean flow rate, maximum flow rate, and peak flow discharge were increased after recurrent debris flow, and peak discharge occurred quickly.

Simulation of flow and evaluation of bridge scour at Horse Island Chute Bridge near Chester, Illinois

USGS Publications Warehouse

Huizinga, Richard J.; Rydlund, Jr., Paul H.

2001-01-01

The evaluation of scour at bridges throughout the State of Missouri has been ongoing since 1991, and most of these evaluations have used one-dimensional hydraulic analysis and application of conventional scour depth equations. Occasionally, the conditions of a site dictate that a more thorough hydraulic assessment is required. To provide the hydraulic parameters required to determine the potential scour depths at the bridge over Horse Island Chute near Chester, Illinois, a two-dimensional finite-element surface-water model (FESWMS-2DH) was used to simulate flood flows in the vicinity of the Missouri State Highway 51 crossing of the Mississippi River and Horse Island Chute. The model was calibrated using flood-flow information collected during the 1993 flood. A flood profile along the Illinois side of the Mississippi River on August 5, 1993, with a corresponding measured discharge of 944,000 cubic feet per second was used to calibrate the model. Two additional flood-flow simulations were run: the flood peak that occurred on August 6, 1993, with a maximum discharge of 1,000,000 cubic feet per second, and the discharge that caused impending overtopping of the road embankment in the vicinity of the Horse Island Chute bridge, with a discharge of 894,000 cubic feet per second (impendent discharge). Hydraulic flow parameters obtained from the simulations were applied to scour depth equations to determine general contraction and local pier and abutment scour depths at the Horse Island Chute bridge. The measured discharge of 944,000 cubic feet per second resulted in 13.3 feet of total combined contraction and local pier scour at Horse Island Chute bridge. The maximum discharge of 1,000,000 cubic feet per second resulted in 15.8 feet of total scour and the impendent discharge of 894,000 cubic feet per second resulted in 11.6 feet of total scour.

Pulsed electrothermal thruster

NASA Technical Reports Server (NTRS)

Burton, Rodney L. (Inventor); Goldstein, Yeshayahu S. A. (Inventor); Tidman, Derek A. (Inventor); Winsor, Niels K. (Inventor)

1989-01-01

A plasma electrothermal thruster includes a capillary passage in which a plasma discharge is formed and directed out of an open end of the passage into a supersonic nozzle. Liquid supplied to the capillary passage becomes partially atomized to cool a confining surface of the passage. The plasma discharge is formed as the atomized liquid flows out of the open end into a supersonic equilibrium nozzle. The discharge can have a duration greater than the two way travel time of acoustic energy in the capillary to cause the plasma to flow continuously through the nozzle during the time of the discharge pulse.

Estimating river discharge uncertainty by applying the Rating Curve Model

NASA Astrophysics Data System (ADS)

Barbetta, S.; Melone, F.; Franchini, M.; Moramarco, T.

2012-04-01

The knowledge of the flow discharge at a river site is necessary for planning and management of water resources as well as for monitoring and real-time forecasting purposes when significant flood events occur. In the hydrological practice, the operational discharge measurement in medium and large rivers is mostly based on indirect approaches by converting the observed stage into discharge values using steady-flow rating curves. However, the stage-discharge relationship can be unknown for hydrometric sections where flow velocity measurements, particularly during high floods, are not available. To overcome this issue, a simplified approach named Rating Curve Model (RCM) and proposed by Moramarco et al. (Moramarco, T., Barbetta, S., F. Melone, F. & Singh, V.P., Relating local stage and remote discharge with significant lateral inflow, J. Hydrol. Engng ASCE, 10[1], 58?69, 2005) can be conveniently used. RCM turned out able to assess, with a high level of accuracy, the discharge hydrograph at a river site where only the stage is monitored while the flow is recorded at a different section along the river, even when significant lateral flows occur. The simple structure of the model is depending on three parameters of which two can be considered characteristic of the river reach and one of the wave travel time of floods. Considering that RCM well lends itself to predict the stage-discharge relationship at a river site wherein only stages are recorded, an uncertainty analysis on river discharge estimate is of interest for the hydrological practice definitely. To this aim, the uncertainty characterizing the RCM outcomes is addressed in this work by considering two different procedures based on the Monte Carlo approach and the Generalized Likelihood Uncertainty Estimation (GLUE) method, respectively. The statistical distribution of parameters is found and a random re-sampling of parameters is done for assessing the 90% confidence interval (CI) of discharge estimates. In particular, for the latter approach the Nash-Sutcliffe coefficient is used as likelihood measure. Two equipped river reaches of the Upper-Middle Tiber River basin, central Italy, are investigated as case studies. The results provided by the selected methodologies are discussed and compared showing that all the computed CIs are satisfied in term of percentage of included observed discharges with similar percentages characterizing the bands assessed by both Monte Carlo approach and GLUE procedure.

Karst hydrogeology and hydrochemistry of the Cave Springs basin near Chattanooga, Tennessee

USGS Publications Warehouse

Pavlicek, D.J.

1996-01-01

The Cave Springs ground-water basin, located near Chattanooga, Tennessee, was chosen as one of the Valley and Ridge physiographic province type area studies for the Appalachian Valley-Piedmont Regional Aquifer-System Analysis study in 1990. Karstic Paleozoic carbonate rocks, residual clay-rich regolith, and coarse alluvium form the aquifer framework. Recharge from rainfall dispersed over the basin enters the karst aquifer through the thick regolith. The area supplying recharge to the Cave Springs Basin is approximately 7 square miles. Recharge from North Chickamauga Creek may contribute recharge to the Cave Springs Basin along losing reaches. The flow medium consists of mixed dolomite and limestone with cavernous and fracture porosity. Flow type as determined by the coefficient of variation of long-term continuous specific conductance (18 and 15 percent) from two wells completed in cavernous intervals about 150 feet northeast of Cave Springs, indicates an aquifer with conduit flow. Flow type, based on the ratio (6:1) of spring flood-flow discharge to spring base-flow discharge, indicates an aquifer with diffuse flow. Conduit flow probably dominates the aquifer system west of Cave Springs Ridge from the highly transmissive, unconfined, alluvium capped aquifer and along losing reaches of North Chickamauga Creek. Diffuse flow probably predominates in the areas along and east of Cave Springs Ridge covered with the thick, clay-rich regolith that forms a leaky confining layer. Based on average annual long-term precipitation and runoff records, the amount of water available for recharge to Cave Springs is 11.8 cubic feet per second. The mean annual long-term discharge of Cave Springs is 16.4 cubic feet per second which leaves 4.6 cubic feet per second of recharge unaccounted for. As determined by low-flow stream discharge measurements, recharge along losing reaches of North Chickamauga Creek may be an important source of unaccounted-for-recharge to the Cave Springs Basin. Selected ground-water samples in the study area are characterized by calcium bicarbonate type water and calcium magnesium bicarbonate type water. Calcium bicarbonate type water characterizes Lick Branch and Poe Branch. North Chickamauga Creek water is calcium magnesium sulfate type water and reflects interaction with the pyrite-containing siliciclastic rocks of the Cumberland Plateau or acid mine drainage. Seasonal high spring discharge is associated with lower specific conductance and lower temperatures, which lag in response to increasing spring discharge by approximately 2 months. Seasonal decrease in spring discharge is accompanied by an incident increase in specific conductance and temperature increase, which leads by about 4 months.

Automatic tracer-dilution method used for stage-discharge ratings and streamflow hydrographs on small Iowa streams

USGS Publications Warehouse

Soenksen, P.J.

1990-01-01

Tracer-dilution discharge measurements were made during 14 flow periods at six stations from 1986 through 1988 water years. Ratings were developed at three stations with the aid of these measurements. A loop rating was identified at one station during rapidly-changing flow conditions. Incomplete mixing and dye loss to sediment apparently were problems at some stations. Stage hydrographs were recorded for 38 flows at seven stations. Limited data on background fluorescence during high flows were also obtained.

Evaluation of a prototype surface flow bypass for juvenile salmon and steelhead at the powerhouse of Lower Granite Dam, Snake River, Washington, 1996-2000

USGS Publications Warehouse

Johnson, G.E.; Anglea, S.M.; Adams, N.S.; Wik, T.O.

2005-01-01

A surface flow bypass takes advantage of the natural surface orientation of most juvenile salmon Oncorhynchus spp. and steelhead O. mykiss by providing a route in the upper water column that downstream migrant fishes can use to pass a hydroelectric dam safely. A prototype structure, called the surface bypass and collector (SBC), was retrofitted on the powerhouse of Lower Granite Dam and was evaluated annually with biotelemetry and hydroacoustic techniques during the 5-year life span of the structure (1996-2000) to determine the entrance configuration that maximized passage efficiency and minimized forebay residence time. The best tested entrance configuration had maximum inflow (99 m 3/s) concentrated in a single surface entrance (5 m wide, 8.5 m deep). We identified five important considerations for future surface flow bypass development in the lower Snake River and elsewhere: (1) an extensive flow net should be formed in the forebay by use of relatively high surface flow bypass discharge (>7% of total project discharge); (2) a gradual increase in water velocity with increasing proximity to the surface flow bypass (ideally, acceleration 3 m/s) to entrain the subject juvenile fishes; (4) the shape and orientation of the surface entrance(s) should be adapted to fit site-specific features; and (5) construction of a forebay wall to increase fish availability to the surface flow bypass should be considered. The efficiency of the SBC was not high enough (maximum of 62% relative to passage at turbine units 4-5) for the SBC to operate as a stand-alone bypass. Anywhere that surface-oriented anadromous fish must negotiate hydroelectric dams, surface flow bypass systems can provide cost-effective use of typically limited water supplies to increase the nonturbine passage, and presumably survival, of downstream migrants. ??Copyright by the American Fisheries Society 2005.

Comparison of Numerical Approaches to a Steady-State Landscape Equation

NASA Astrophysics Data System (ADS)

Bachman, S.; Peckham, S.

2008-12-01

A mathematical model of an idealized fluvial landscape has been developed, in which a land surface will evolve to preserve dendritic channel networks as the surface is lowered. The physical basis for this model stems from the equations for conservation of mass for water and sediment. These equations relate the divergence of the 2D vector fields showing the unit-width discharge of water and sediment to the excess rainrate and tectonic uplift on the land surface. The 2D flow direction is taken to be opposite to the water- surface gradient vector. These notions are combined with a generalized Manning-type flow resistance formula and a generalized sediment transport law to give a closed mathematical system that can, in principle, be solved for all variables of interest: discharge of water and sediment, land surface height, vertically- averaged flow velocity, water depth, and shear stress. The hydraulic geometry equations (Leopold et. al, 1964, 1995) are used to incorporate width, depth, velocity, and slope of river channels as powers of the mean-annual river discharge. Combined, they give the unit- width discharge of the stream as a power, γ, of the water surface slope. The simplified steady-state model takes into account three components among those listed above: conservation of mass for water, flow opposite the gradient, and a slope-discharge exponent γ = -1 to reflect mature drainage networks. The mathematical representation of this model appears as a second-order hyperbolic partial differential equation (PDE) where the diffusivity is inversely proportional to the square of the local surface slope. The highly nonlinear nature of this PDE has made it very difficult to solve both analytically and numerically. We present simplistic analytic solutions to this equation which are used to test the validity of the numerical algorithms. We also present three such numerical approaches which have been used in solving the differential equation. The first is based on a nonlinear diffusion filtering technique (Welk et. al, 2007) that has been applied successfully in the context of image processing. The second uses a Ritz finite element approach to the Euler-Lagrange formulation of the PDE in which an eighth degree polynomial is solved whose coefficients are locally dependent on slope and elevation. Lastly, we show a variant to the diffusion filtering approach in which a single-stage Runge-Kutta method is used to iterate a time-derivative to steady- state. The relative merits and drawbacks of these approaches are discussed, as well as stability and consistency requirements.

Fundamental experiment of ion thruster using ECR discharge

NASA Astrophysics Data System (ADS)

Yasui, Toshiaki; Kitayama, Jiro; Tahara, Hirokazu; Onoe, Ken-Ichi; Yoshikawa, Takao

A microwave ion thruster has the potential to overcome a lifetime problem of electric propulsion by eliminating electrodes. Two types of microwave ion thruster have been investigated to examine the operational characteristics. The one is the thruster using cavity-resonance microwave discharge, and the other is the thruster using Electron Cyclotron Resonance (ECR) discharge. Cavity-resonance microwave discharge produced plasmas by strong electric field in the resonant cavity and sustained plasmas at argon mass flow rates above 10 sccm. However, ECR discharge was capable of sustaining plasmas at lower mass flow rate, because ECR discharge efficiently produced plasmas by resonance absorption. From these generated microwave plasmas, ions were electrostatically extracted by two multiaperture grids. In ECR discharge, the maximum ion beam current of 75 mA and the highest mass utilization efficiency of 18.7% were achieved at a total extraction voltage of 950 V.

General field and office procedures for indirect discharge measurements

USGS Publications Warehouse

Benson, M.A.; Dalrymple, Tate

2001-04-01

The discharge of streams is usually measured by the current-meter method. During flood periods, however, it is frequently impossible or impractical to measure the discharges by this method when they occur. Consequently, many peak discharges must be determined after the passage of the flood by indirect methods, such as slope-area, contracted-opening, flow-over-dam, and flow-through-culvert, rather than by direct current-meter measurement. Indirect methods of determining peak discharge are based on hydraulic equations which relate the discharge to the water-surface profile and the geometry of the channel. A field survey is made after the flood to determine the location and elevation of high-water marks and the characteristics of the channel. Detailed descriptions of the general procedures used in collecting the field data and in computing the discharge are given in this report. Each of the methods requires special procedures described in subsequent chapters.

Concentration Measurements in Self-Excited, Momentum-Dominated Helium Jets

NASA Technical Reports Server (NTRS)

Yildirim, Bekir Sedat

2004-01-01

Flow structure of momentum-dominated pure helium jets discharged vertically into ambient air was investigated using high-speed rainbow schlieren deflectometry (RSD) technique. Effects of the operating parameters, i.e., Reynolds number (Re) and Richardson number (Ri), on the oscillatory behavior of the flow were examined over a range of experimental conditions. To seek the individual effect of these parameters, one of them was fixed and the other was varied with certain constraints. Measurements revealed highly periodic oscillations in the laminar region as well as high regularity in transition and turbulent regions. Maximum spectral power profiles at different axial locations indicated the oscillation amplitude increasing until the breakdown of the jet in the turbulent regime. The transition from the laminar to turbulent flow was also investigated. Fast Fourier transform analysis performed in the transition regime showed that the flow oscillates at a unique frequency, which was the same in the upstream laminar flow region. Measured deflection angle data were used in Abel inversion algorithm to construct the helium concentration fields. Instantaneous helium concentration contours revealed changes in the flow structure and evolution of vortical structures during an oscillation cycle. Temporal evolution plots of helium concentration at different axial location showed repeatable oscillations at all axial and radial locations up to the turbulent regime. A cross-correlation technique, applied to find the spatial displacements of the vortical structures, provided correlation coefficient peaks between consecutive schlieren images. Results show that the vortical structure convected and accelerated only in the axial direction.

Surface-water and groundwater interactions in an extensively mined watershed, upper Schuylkill River, Pennsylvania, USA

USGS Publications Warehouse

Cravotta, Charles A.; Goode, Daniel J.; Bartles, Michael D.; Risser, Dennis W.; Galeone, Daniel G.

2014-01-01

Streams crossing underground coal mines may lose flow, while abandoned mine drainage (AMD) restores flow downstream. During 2005-12, discharge from the Pine Knot Mine Tunnel, the largest AMD source in the upper Schuylkill River Basin, had near-neutral pH and elevated concentrations of iron, manganese, and sulfate. Discharge from the tunnel responded rapidly to recharge but exhibited a prolonged recession compared to nearby streams, consistent with rapid infiltration and slow release of groundwater from the mine. Downstream of the AMD, dissolved iron was attenuated by oxidation and precipitation while dissolved CO2 degassed and pH increased. During high-flow conditions, the AMD and downstream waters exhibited decreased pH, iron, and sulfate with increased acidity that were modeled by mixing net-alkaline AMD with recharge or runoff having low ionic strength and low pH. Attenuation of dissolved iron within the river was least effective during high-flow conditions because of decreased transport time coupled with inhibitory effects of low pH on oxidation kinetics. A numerical model of groundwater flow was calibrated using groundwater levels in the Pine Knot Mine and discharge data for the Pine Knot Mine Tunnel and the West Branch Schuylkill River during a snowmelt event in January 2012. Although the calibrated model indicated substantial recharge to the mine complex took place away from streams, simulation of rapid changes in mine pool level and tunnel discharge during a high flow event in May 2012 required a source of direct recharge to the Pine Knot Mine. Such recharge produced small changes in mine pool level and rapid changes in tunnel flow rate because of extensive unsaturated storage capacity and high transmissivity within the mine complex. Thus, elimination of stream leakage could have a small effect on the annual discharge from the tunnel, but a large effect on peak discharge and associated water quality in streams.

Overview of surface-water resources at the U.S. Coast Guard Support Center Kodiak, Alaska, 1987-89

USGS Publications Warehouse

Solin, G.L.

1996-01-01

Hydrologic data at a U.S. Coast Guard Support Center on Kodiak Island, Alaska, were collected from 1987 though 1989 to determine hydrologic conditions and if contamination of soils, ground water, or surface water has occurred. This report summarizes the surface-water-discharge data collected during the study and estimates peak, average, and low-flow values for Buskin River near its mouth. Water-discharge measurements were made at least once at 48 sites on streams in or near the Center. Discharges were measured in the Buskin River near its mouth five times during 1987-89 and ranged from 27 to 367 cubic feet per second. Tributaries of Buskin River below Buskin Lake that had discharges greater than 1 cubic foot per second include Bear Creek, Alder Creek, Magazine Creek, Devils Creek and an outlet from Lake Louise. Streams having flows generally greater than 0.1 cubic foot per second but less than 1 cubic foot per second include an unnamed tributary to Buskin River, an unnamed tributary to Lake Catherine and a drainage channel at Kodiak airport. Most other streams flowing into Buskin River, and all streams on Nyman Peninsula, usually had little or no flow except during periods of rainfall or snowmelt. During a low-flow period in February 1989, discharge measurements in Buskin River and its tributaries indicate that three reaches of Buskin River below Buskin Lake lost water to the ground-water system, whereas two reaches gained water; the net gain in streamflow attributed to ground-water inflow at a location near the mouth was estimated to be 2.2 cubic feet per second. The 100-year peak flow for Buskin River near its mouth was estimated to be 4,460 cubic feet per second. Average discharge was estimated to be 125 cubic feet per second and the 7-day 10-year low flow was estimated to be 5.8 cubic feet per second.

An analysis of effect of land use change on river flow variability

NASA Astrophysics Data System (ADS)

Zhang, Tao; Liu, Yuting; Yang, Xinyue; Wang, Xiang

2018-02-01

Land use scenario analysis, SWAT model, flow characteristic indices and flow variability technology were used to analyze the effect of land use quantity and location change on river flow. Results showed that river flow variation caused by land use change from forest to crop was larger than that caused by land use change from forest to grass; Land use change neither from upstream to downstream nor from downstream to upstream had little effect on annual average discharge and maximum annual average discharge. But it had obvious effect on maximum daily discharge; Land use change which occurred in upstream could lead to producing larger magnitude flood more easily; Land use change from forest to crop or grass could increase the number of large magnitude floods and their total duration. And it also could increase the number of small magnitude floods but decrease their duration.

Use of radars to monitor stream discharge by noncontact methods

USGS Publications Warehouse

Costa, J.E.; Cheng, R.T.; Haeni, F.P.; Melcher, N.; Spicer, K.R.; Hayes, E.; Plant, W.; Hayes, K.; Teague, C.; Barrick, D.

2006-01-01

Conventional measurements of river flows are costly, time‐consuming, and frequently dangerous. This report evaluates the use of a continuous wave microwave radar, a monostatic UHF Doppler radar, a pulsed Doppler microwave radar, and a ground‐penetrating radar to measure river flows continuously over long periods and without touching the water with any instruments. The experiments duplicate the flow records from conventional stream gauging stations on the San Joaquin River in California and the Cowlitz River in Washington. The purpose of the experiments was to directly measure the parameters necessary to compute flow: surface velocity (converted to mean velocity) and cross‐sectional area, thereby avoiding the uncertainty, complexity, and cost of maintaining rating curves. River channel cross sections were measured by ground‐penetrating radar suspended above the river. River surface water velocity was obtained by Bragg scattering of microwave and UHF Doppler radars, and the surface velocity data were converted to mean velocity on the basis of detailed velocity profiles measured by current meters and hydroacoustic instruments. Experiments using these radars to acquire a continuous record of flow were conducted for 4 weeks on the San Joaquin River and for 16 weeks on the Cowlitz River. At the San Joaquin River the radar noncontact measurements produced discharges more than 20% higher than the other independent measurements in the early part of the experiment. After the first 3 days, the noncontact radar discharge measurements were within 5% of the rating values. On the Cowlitz River at Castle Rock, correlation coefficients between the USGS stream gauging station rating curve discharge and discharge computed from three different Doppler radar systems and GPR data over the 16 week experiment were 0.883, 0.969, and 0.992. Noncontact radar results were within a few percent of discharge values obtained by gauging station, current meter, and hydroacoustic methods. Time series of surface velocity obtained by different radars in the Cowlitz River experiment also show small‐amplitude pulsations not found in stage records that reflect tidal energy at the gauging station. Noncontact discharge measurements made during a flood on 30 January 2004 agreed with the rated discharge to within 5%. Measurement at both field sites confirm that lognormal velocity profiles exist for a wide range of flows in these rivers, and mean velocity is approximately 0.85 times measured surface velocity. Noncontact methods of flow measurement appear to (1) be as accurate as conventional methods, (2) obtain data when standard contact methods are dangerous or cannot be obtained, and (3) provide insight into flow dynamics not available from detailed stage records alone.

The Design of Pumpjets for Hydrodynamic Propulsion

NASA Technical Reports Server (NTRS)

Bruce, E. P.; Gearhart, W. S.; Ross, J. R.; Treaster, A. L.

1974-01-01

A procedure for use in the design of a wake adapted pumpjet mounted on the aft end of a body of revolution is presented. To this end, a pumpjet is designed for the Akron airship. The propulsor mass flow is selected to minimize kinetic energy losses through the duct and in the discharge jet. The shaft speed and disk size are selected to satisfy specified limits of cavitation performance and to provide acceptable blade loading. The streamtubes which pass through a propulsor mounted on a tapered afterbody follow essentially conical surfaces. A method is provided for defining these surfaces as a function of shroud geometry, rotor head distribution, and the energy distribution of the ingested mass flow. The three-dimensional effects to which the conical flow subjects the cylindrical blade design sections are described and a technique is presented which permits incorporation of these effects in the blade design procedure.

Integration of UAV photogrammetry and SPH modelling of fluids to study runoff on real terrains.

PubMed

Barreiro, Anxo; Domínguez, Jose M; C Crespo, Alejandro J; González-Jorge, Higinio; Roca, David; Gómez-Gesteira, Moncho

2014-01-01

Roads can experience runoff problems due to the intense rain discharge associated to severe storms. Two advanced tools are combined to analyse the interaction of complex water flows with real terrains. UAV (Unmanned Aerial Vehicle) photogrammetry is employed to obtain accurate topographic information on small areas, typically on the order of a few hectares. The Smoothed Particle Hydrodynamics (SPH) technique is applied by means of the DualSPHysics model to compute the trajectory of the water flow during extreme rain events. The use of engineering solutions to palliate flood events is also analysed. The study case simulates how the collected water can flow into a close road and how precautionary measures can be effective to drain water under extreme conditions. The amount of water arriving at the road is calculated under different protection scenarios and the efficiency of a ditch is observed to decrease when sedimentation reduces its depth.

Integration of UAV Photogrammetry and SPH Modelling of Fluids to Study Runoff on Real Terrains

PubMed Central

Barreiro, Anxo; Domínguez, Jose M.; C. Crespo, Alejandro J.; González-Jorge, Higinio; Roca, David; Gómez-Gesteira, Moncho

2014-01-01

Roads can experience runoff problems due to the intense rain discharge associated to severe storms. Two advanced tools are combined to analyse the interaction of complex water flows with real terrains. UAV (Unmanned Aerial Vehicle) photogrammetry is employed to obtain accurate topographic information on small areas, typically on the order of a few hectares. The Smoothed Particle Hydrodynamics (SPH) technique is applied by means of the DualSPHysics model to compute the trajectory of the water flow during extreme rain events. The use of engineering solutions to palliate flood events is also analysed. The study case simulates how the collected water can flow into a close road and how precautionary measures can be effective to drain water under extreme conditions. The amount of water arriving at the road is calculated under different protection scenarios and the efficiency of a ditch is observed to decrease when sedimentation reduces its depth. PMID:25372035

Predicting Flood Hazards in Systems with Multiple Flooding Mechanisms

NASA Astrophysics Data System (ADS)

Luke, A.; Schubert, J.; Cheng, L.; AghaKouchak, A.; Sanders, B. F.

2014-12-01

Delineating flood zones in systems that are susceptible to flooding from a single mechanism (riverine flooding) is a relatively well defined procedure with specific guidance from agencies such as FEMA and USACE. However, there is little guidance in delineating flood zones in systems that are susceptible to flooding from multiple mechanisms such as storm surge, waves, tidal influence, and riverine flooding. In this study, a new flood mapping method which accounts for multiple extremes occurring simultaneously is developed and exemplified. The study site in which the method is employed is the Tijuana River Estuary (TRE) located in Southern California adjacent to the U.S./Mexico border. TRE is an intertidal coastal estuary that receives freshwater flows from the Tijuana River. Extreme discharge from the Tijuana River is the primary driver of flooding within TRE, however tide level and storm surge also play a significant role in flooding extent and depth. A comparison between measured flows at the Tijuana River and ocean levels revealed a correlation between extreme discharge and ocean height. Using a novel statistical method based upon extreme value theory, ocean heights were predicted conditioned up extreme discharge occurring within the Tijuana River. This statistical technique could also be applied to other systems in which different factors are identified as the primary drivers of flooding, such as significant wave height conditioned upon tide level, for example. Using the predicted ocean levels conditioned upon varying return levels of discharge as forcing parameters for the 2D hydraulic model BreZo, the 100, 50, 20, and 10 year floodplains were delineated. The results will then be compared to floodplains delineated using the standard methods recommended by FEMA for riverine zones with a downstream ocean boundary.

Low-flow characteristics and flow-duration statistics for selected USGS continuous-record streamgaging stations in North Carolina through 2012

USGS Publications Warehouse

Weaver, J. Curtis

2015-03-12

In 2013, the U.S. Geological Survey, in cooperation with the North Carolina Division of Water Resources, compiled updated low-flow characteristics and flow-duration statistics for selected continuous-record streamgages in North Carolina. The compilation of updated streamflow statistics provides regulators and planners with relevant hydrologic information reflective of the recent droughts, which can be used to better manage the quantity and quality of streams in North Carolina. Streamflow records available through the 2012 water year1 were used to determine the annual (based on climatic year2) and winter 7-day, 10-year (7Q10, W7Q10) low-flow discharges, the 30-day, 2-year (30Q2) low-flow discharge, and the 7-day, 2-year (7Q2) low-flow discharge. Consequently, streamflow records available through March 31, 2012 (or the 2011 climatic year) were used to determine the updated low-flow characteristics. Low-flow characteristics were published for 177 unregulated sites, 56 regulated sites, and 33 sites known or considered to be affected by varying degrees of minor regulation and (or) diversions upstream from the streamgages (266 sites total). The updated 7Q10 discharges were compared for 63 streamgages across North Carolina where (1) long-term streamflow record consisted of 30 or more climatic years of data available as of the 1998 climatic year, and (2) streamflows were not known to be regulated. The 7Q10 discharges did not change for 3 sites, whereas increases and decreases were noted at 5 and 55 sites, respectively. Positive changes (increases) ranged from 4.3 percent (site 362) to 34.1 percent (site 112) with a median of 13.2 percent. Negative percentage changes (decreases) ranged from –3.3 percent (site 514) to –80.0 percent (site 308) with a median of –22.2 percent. The median percentage change for all 63 streamgages was –18.4 percent. Streamflow statistics determined as a part of this compilation included minimum, mean, maximum, and flow-duration statistics of daily mean discharges for categorical periods. Flow-duration statistics based on the daily mean discharge records were compiled in this study for the 5th, 10th, 25th, 50th, 75th, 90th, and 95th percentiles. Flow-duration statistics were determined for each complete water year of record at a streamgage as well as the available period of record (or selected periods if flows were regulated) and selected seasonal, monthly, and calendar day periods. In addition to the streamflow statistics compiled for each of the water years, the number of days the daily mean discharge was at or below the 10th percentile was summed for each water year as well as the number of events during the water year when streamflow was consistently at or below the 10th percentile. All low-flow characteristics for the streamgages were added into the StreamStatsDB, which is a database accessible to users through the recently released USGS StreamStats application for North Carolina. The minimum, mean, maximum, and flow-duration statistics of daily mean discharges based on the available (or selected if regulated flows) period of record were updated in the North Carolina StreamStatsDB. However, for the selected seasonal, monthly, calendar day, and annual water year periods, tab-delimited American Standard Code for Information Interchange (ASCII) tables of the streamflow statistics are available online to users from a link provided in the StreamStats application. 1The annual period from October 1 through September 30, designated by the year in which the period ends. 2The annual period from April 1 through March 31, designated by the year in which the period begins.

Quantification of the effect of surface heating on shock wave modification by a plasma actuator in a low-density supersonic flow over a flat plate

NASA Astrophysics Data System (ADS)

Joussot, Romain; Lago, Viviana; Parisse, Jean-Denis

2015-05-01

This paper describes experimental and numerical investigations focused on the shock wave modification induced by a dc glow discharge. The model is a flat plate in a Mach 2 air flow, equipped with a plasma actuator composed of two electrodes. A weakly ionized plasma was created above the plate by generating a glow discharge with a negative dc potential applied to the upstream electrode. The natural flow exhibited a shock wave with a hyperbolic shape. Pitot measurements and ICCD images of the modified flow revealed that when the discharge was ignited, the shock wave angle increased with the discharge current. The spatial distribution of the surface temperature was measured with an IR camera. The surface temperature increased with the current and decreased along the model. The temperature distribution was reproduced experimentally by placing a heating element instead of the active electrode, and numerically by modifying the boundary condition at the model surface. For the same surface temperature, experimental investigations showed that the shock wave angle was lower with the heating element than for the case with the discharge switched on. The results show that surface heating is responsible for roughly 50 % of the shock wave angle increase, meaning that purely plasma effects must also be considered to fully explain the flow modifications observed.

Development and evaluation of an ultrasonic ground water seepage meter.

PubMed

Paulsen, R J; Smith, C F; O'Rourke, D; Wong, T F

2001-01-01

Submarine ground water discharge can influence significantly the near-shore transport and flux of chemicals into the oceans. Quantification of the sources and rates of such discharge requires a ground water seepage meter that provides continuous measurements at high resolution over an extended period of time. An ultrasonic flowmeter has been adapted for such measurements in the submarine environment. Connected to a steel collection funnel, the meter houses two piezoelectric transducers mounted at opposite ends of a cylindrical flow tube. By monitoring the perturbations of fluid flow on the propagation of sound waves inside the flow tube, the ultrasonic meter can measure both forward and reverse fluid flows in real time. Laboratory and field calibrations show that the ultrasonic meter can resolve ground water discharges on the order of 0.1 microm/sec, and it is sufficiently robust for deployment in the field for several days. Data from West Neck Bay, Shelter Island, New York, elucidate the temporal and spatial heterogeneity of submarine ground water discharge and its interplay with tidal loading. A negative correlation between the discharge and tidal elevation was generally observed. A methodology was also developed whereby data for the sound velocity as a function of temperature can be used to infer the salinity and source of the submarine discharge. Independent measurements of electrical conductance were performed to validate this methodology.

Effects of hydropeaking on the spawning behaviour of Atlantic salmon Salmo salar and brown trout Salmo trutta.

PubMed

Vollset, K W; Skoglund, H; Wiers, T; Barlaup, B T

2016-06-01

An in situ camera set-up was used to study the spawning activity of Atlantic salmon Salmo salar and brown trout Salmo trutta throughout two consecutive seasons in a spawning area affected by hydropower-related pulse flows due to hydropeaking. The purpose was to test whether the flow variation discouraged spawning in shallow areas or motivated spawning into areas with elevated risk of incubation mortality. There were more S. salar observed on the spawning ground during days with high discharge. The presence of S. salar in the spawning grounds was not affected by the hydropeaking cycles of the preceding night. Female S. salar were observed preparing nests within the first hour after water discharge had increased to levels suitable for spawning. In contrast, the number of S. trutta was not correlated with flow and nest preparation was also observed at a discharge corresponding to the lowest discharge levels during a hydropeaking cycle. Survival was generally high in nests excavated the following winter, with only 5·4% suffering mortality due to dewatering. The results suggest that S. salar may respond rapidly to variable-flow conditions and utilize short windows with suitable flows for spawning. Smaller S. trutta may utilize low-flow conditions to spawn in areas that are not habitable by larger S. salar during low flow. © 2016 The Fisheries Society of the British Isles.

Quantifying Temperature Effects on Snow, Plant and Streamflow Dynamics in Headwater Catchments

NASA Astrophysics Data System (ADS)

Wainwright, H. M.; Sarah, T.; Siirila-Woodburn, E. R.; Newcomer, M. E.; Williams, K. H.; Hubbard, S. S.; Enquist, B. J.; Steltzer, H.; Carroll, R. W. H.

2017-12-01

Quantifying Temperature Effects on Snow, Plant and Streamflow Dynamics in Headwater Catchments Snow-dominated headwater catchments are critical for water resource throughout the world; particularly in Western US. Under climate change, temperature increases are expected to be amplified in mountainous regions. We use a data-driven approach to better understand the coupling among inter-annual variability in temperature, snow and plant community dynamics and stream discharge. We apply data mining methods (e.g., principal component analysis, random forest) to historical spatiotemporal datasets, including the SNOTEL data, Landsat-based normalized difference vegetation index (NDVI) and airborne LiDAR-based snow distribution. Although both snow distribution and NDVI are extremely heterogeneous spatially, the inter-annual variability and temporal responses are spatially consistent, providing an opportunity to quantify the effect of temperature in the catchment-scale. We demonstrate our approach in the East River Watershed of the Upper Colorado River Basin, including Rocky Mountain Biological Laboratory, where the changes in plant communities and their dynamics have been extensively documented. Results indicate that temperature - particularly spring temperature - has a significant control not only on the timing of snowmelt, plant NDVI and peak flow but also on the magnitude of peak NDVI, peak flow and annual discharge. Monthly temperature in spring explains the variability of snowmelt by the equivalent standard deviation of 3.4-4.4 days, and total discharge by 10-11%. In addition, the high correlation among June temperature, peak NDVI and annual discharge suggests a primary role of spring evapotranspiration on plant community phenology, productivity, and streamflow volume. On the other hand, summer monsoon precipitation does not contribute significantly to annual discharge, further emphasizing the importance of snowmelt. This approach is mostly based on a set of datasets typically available throughout the US, providing a powerful approach to link remote sensing techniques with long-term monitoring of temperature, snowfall, plant, and streamflow dynamics.

Studies of oxygen-helium discharges for use in electric oxygen-iodine lasers

NASA Astrophysics Data System (ADS)

Zimmerman, Joseph William

In recent work, the performance of the Electric Oxygen-Iodine Laser (ElectricOIL), developed in partnership by researchers at the University of Illinois and CU Aerospace, has been greatly improved through systematic study of various components of this new laser technology. One major contribution to the advancement of ElectricOIL technology has been the development of electric discharges capable of producing significant flow rates of the precursor electronically-excited molecular oxygen, O2(a1Delta). O2(a 1Delta) serves as an energy reservoir in the laser system, pumping atomic iodine by near-resonant energy transfer producing gain and laser on the I(2P1/2) → I(2P3/2 ) transition at 1315 nm. Initial experimental work with radio-frequency discharges showed the importance of controlling O-atom flow rates to reduce quenching losses of energy stored in O2(a1Delta), and determined proper selection of the helium diluent ratio and specific power deposition (power per O2 flow rate). Further experimental investigations with transverse capacitive radio-frequency discharges in O2/He/NO mixtures in the pressure range of 1-100 Torr and power range of 0.1-1.2 kW have indicated that O2(a1Delta) production is a strong function of geometry (transverse gap), excitation frequency, and pressure. These parameters along with gas flow mixture dictate the current density at which the discharge operates, and its modal characteristics (normal vs. abnormal, homogeneous vs. inhomogeneous). A key result is that to encourage efficient O2(a1Delta) production these parameters should be selected in order to promote a homogeneous (low current density) discharge. The discharge behavior is characterized using terminal current-voltage-characteristics, microwave interferometer measurements, and plasma emission intensity measurements. Numerous spectroscopic measurements of O2(a1Delta), oxygen atoms, and discharge excited states are made in order to describe the discharge performance dependent on various parameters. The influence of NO on O-atom flow rates and O2(a1Delta) production is investigated. Progress of laser power extraction since initial reports in 2005 is overviewed.

Recent developments in CO2 lasers

NASA Astrophysics Data System (ADS)

Du, Keming

1993-05-01

CO2 lasers have been used in industry mainly for such things as cutting, welding, and surface processing. To conduct a broad spectrum of high-speed and high-quality applications, most of the developments in industrial CO2 lasers at the ILT are aimed at increasing the output power, optimizing the beam quality, and reducing the production costs. Most of the commercial CO2 lasers above 5 kW are transverse-flow systems using dc excitation. The applications of these lasers are limited due to the lower beam quality, the poor point stability, and the lower modulation frequency. To overcome the problems we developed a fast axial- flow CO2 laser using rf excitation with an output of 13 kW. In section 2 some of the results are discussed concerning the gas flow, the discharge, the resonator design, optical effects of active medium, the aerodynamic window, and the modulation of the output power. The first CO2 lasers ever built are diffusion-cooled systems with conventional dc excited cylindrical discharge tubes surrounded by cooling jackets. The output power per unit length is limited to 50 W/m by those lasers with cylindrical tubes. In the past few years considerable increases in the output power were achieved, using new mechanical geometries, excitation- techniques, and resonator designs. This progress in diffusion-cooled CO2 lasers is presented in section 3.

Culvert Analysis Program Graphical User Interface 1.0--A preprocessing and postprocessing tool for estimating flow through culvert

USGS Publications Warehouse

Bradley, D. Nathan

2013-01-01

The peak discharge of a flood can be estimated from the elevation of high-water marks near the inlet and outlet of a culvert after the flood has occurred. This type of discharge estimate is called an “indirect measurement” because it relies on evidence left behind by the flood, such as high-water marks on trees or buildings. When combined with the cross-sectional geometry of the channel upstream from the culvert and the culvert size, shape, roughness, and orientation, the high-water marks define a water-surface profile that can be used to estimate the peak discharge by using the methods described by Bodhaine (1968). This type of measurement is in contrast to a “direct” measurement of discharge made during the flood where cross-sectional area is measured and a current meter or acoustic equipment is used to measure the water velocity. When a direct discharge measurement cannot be made at a streamgage during high flows because of logistics or safety reasons, an indirect measurement of a peak discharge is useful for defining the high-flow section of the stage-discharge relation (rating curve) at the streamgage, resulting in more accurate computation of high flows. The Culvert Analysis Program (CAP) (Fulford, 1998) is a command-line program written in Fortran for computing peak discharges and culvert rating surfaces or curves. CAP reads input data from a formatted text file and prints results to another formatted text file. Preparing and correctly formatting the input file may be time-consuming and prone to errors. This document describes the CAP graphical user interface (GUI)—a modern, cross-platform, menu-driven application that prepares the CAP input file, executes the program, and helps the user interpret the output

Online monitoring and conditional regression tree test: Useful tools for a better understanding of combined sewer network behavior.

PubMed

Bersinger, T; Bareille, G; Pigot, T; Bru, N; Le Hécho, I

2018-06-01

A good knowledge of the dynamic of pollutant concentration and flux in a combined sewer network is necessary when considering solutions to limit the pollutants discharged by combined sewer overflow (CSO) into receiving water during wet weather. Identification of the parameters that influence pollutant concentration and flux is important. Nevertheless, few studies have obtained satisfactory results for the identification of these parameters using statistical tools. Thus, this work uses a large database of rain events (116 over one year) obtained via continuous measurement of rainfall, discharge flow and chemical oxygen demand (COD) estimated using online turbidity for the identification of these parameters. We carried out a statistical study of the parameters influencing the maximum COD concentration, the discharge flow and the discharge COD flux. In this study a new test was used that has never been used in this field: the conditional regression tree test. We have demonstrated that the antecedent dry weather period, the rain event average intensity and the flow before the event are the three main factors influencing the maximum COD concentration during a rainfall event. Regarding the discharge flow, it is mainly influenced by the overall rainfall height but not by the maximum rainfall intensity. Finally, COD discharge flux is influenced by the discharge volume and the maximum COD concentration. Regression trees seem much more appropriate than common tests like PCA and PLS for this type of study as they take into account the thresholds and cumulative effects of various parameters as a function of the target variable. These results could help to improve sewer and CSO management in order to decrease the discharge of pollutants into receiving waters. Copyright © 2017 Elsevier B.V. All rights reserved.

Coherent anti-Stokes Raman scattering and spontaneous Raman scattering diagnostics of nonequilibrium plasmas and flows

NASA Astrophysics Data System (ADS)

Lempert, Walter R.; Adamovich, Igor V.

2014-10-01

The paper provides an overview of the use of coherent anti-Stokes Raman scattering (CARS) and spontaneous Raman scattering for diagnostics of low-temperature nonequilibrium plasmas and nonequilibrium high-enthalpy flows. A brief review of the theoretical background of CARS, four-wave mixing and Raman scattering, as well as a discussion of experimental techniques and data reduction, are included. The experimental results reviewed include measurements of vibrational level populations, rotational/translational temperature, electric fields in a quasi-steady-state and transient molecular plasmas and afterglow, in nonequilibrium expansion flows, and behind strong shock waves. Insight into the kinetics of vibrational energy transfer, energy thermalization mechanisms and dynamics of the pulse discharge development, provided by these experiments, is discussed. Availability of short pulse duration, high peak power lasers, as well as broadband dye lasers, makes possible the use of these diagnostics at relatively low pressures, potentially with a sub-nanosecond time resolution, as well as obtaining single laser shot, high signal-to-noise spectra at higher pressures. Possibilities for the development of single-shot 2D CARS imaging and spectroscopy, using picosecond and femtosecond lasers, as well as novel phase matching and detection techniques, are discussed.

Fibre-optic distributed temperature sensing in combined sewer systems.

PubMed

Schilperoort, R P S; Clemens, F H L R

2009-01-01

This paper introduces the application of fibre-optic distributed temperature sensing (DTS) in combined sewer systems. The DTS-technique uses a fibre-optic cable that is inserted into a combined sewer system in combination with a laser instrument that performs measurements and logs the data. The DTS-technique allows monitoring in-sewer temperatures with dense spatial and temporal resolutions. The installation of a fibre-optic cable in a combined sewer system has proven feasible. The use of a single instrument in an easy accessible and safe location that can simultaneously monitor up to several hundreds of monitoring locations makes the DTS set-up easy in use and nearly free of maintenance. Temperature data from a one-week monitoring campaign in an 1,850 m combined sewer system shows the level of detail with which in-sewer processes that affect wastewater temperatures can be studied. Individual discharges from house-connections can be tracked in time and space. With a dedicated cable configuration the confluence of wastewater flows can be observed with a potential to derive the relative contributions of contributary flows to a total flow. Also, the inflow and in-sewer propagation of stormwater can be monitored.

Study of a plate-electrode XeCl laser with a pulse repetition rate up to 5 kHz

DOE Office of Scientific and Technical Information (OSTI.GOV)

Voevodin, Denis D; Vysotskii, Andrei V; Lazhintsev, Boris V

2012-11-30

The results of the study of a repetitively pulsed XeCl laser with a high rate of pulse repetition and the electrode assembly based on a multi-section discharge gap with inductance-capacitance stabilisation of the discharge are presented. The multi-section discharge gap is formed by 25 pairs of anode - cathode plates. The discharge formed in the interelectrode gap had the dimensions 250 Multiplication-Sign 12 Multiplication-Sign 2 mm. The studies were performed using the HCl - Xe - Ne laser mixture at the total pressure up to 3.5 atm. The limit value of the radiation pulse repetition rate was equal to 5more » kHz. The meansquare deviation of the pulse energy increased from 0.8 % to 1.6 % in the range of repetition rates from 1 to 4.5 kHz and did not exceed 2.4 % at the frequency 5 kHz. The maximal energy of the laser pulse and the efficiency coefficient were equal to 7.9 mJ and 1.6 %, respectively. The maximal power of laser radiation (31 W) was obtained at the repetition rate 5 kHz. A new technique of measuring the gas flow velocity in the interelectrode gap is proposed. The velocity of gas circulation at the maximal pressure of the mixture did not exceed 18 m s{sup -1}. Optical inhomogeneities were observed, caused by a high concentration of electrons in the discharge plasma, by the acoustic wave, arising in the discharge gap, and by the heating of the gas in the discharge. (lasers)« less

Sediment motion and velocity in a glacier-fed stream

NASA Astrophysics Data System (ADS)

Mao, L.; Dell'Agnese, A.; Comiti, F.

2017-08-01

Current understanding of coarse sediment transport (e.g. threshold for motion, travel length and virtual velocity) in mountain rivers is still quite limited, and even less is known about glacial streams. However, the hydrological characteristics of these systems (strong daily discharge fluctuations, high water turbidity) pose challenges to the use of tracers to monitor bed sediment dynamics, as tagged clasts are usually located after bedload events when flow stage has receded, e.g. by means of portable antennas in the case of Passive Integrated Transponders (PIT). The use of stationary antennas, still scarcely in use worldwide, to detect PIT-tagged particles has potential advantages in glacier-fed streams. If water discharge is monitored continuously, a stationary antenna provides real time data on the actual discharge at the moment of tracer particles passage. This study focuses on incipient motion and virtual velocity of bed particles measured by a stationary antennas system in a steep mountain channel (Saldur River, drainage area 18.6 km2, Italian Alps) where significant daily discharge fluctuations and bedload transport occur as a result of a nivo-glacial regime. Four stationary antennas were installed 50-m apart in the study reach. A total of 629 PIT-tagged clasts were inserted in the studied reach between 2011 and 2014, ranging in size from 35 mm to 580 mm, with an overall recovery rate of around 44%. Critical discharge for sediment entrainment was obtained by detecting the movement of tracers placed immediately upstream of antennas. Virtual velocity was derived by knowing distances between the antennas and travel time of tracers. Results on initiation of motion show that the relationship between the size of transported tracers and the discharge measured at the time clasts were passing the stationary antenna is very weak. The influence of antecedent flows on incipient motion was thus investigated by dividing the highest discharge recorded between each PIT deployment and the subsequent entrainment by the actual critical discharge at the time of movement (ratio Qmax/Qc). Results show that approximately 50% of tracers moved at Qmax/Qc ≤ 1.2, and that 73% of tracers moved at Qmax/Qc < 1.5. Therefore, about 30% of tracers had to previously experience a discharge substantially greater than the one that actually mobilized them. Also, coarser particles moved at higher Qmax/Qc ratios, suggesting that higher antecedent flows may be needed to destabilize bed clustering. Results on the virtual velocity of the PIT-tagged clasts employed in the field show that the virtual velocity turned out to be highly variable (ranging from 101 to 10- 5 m min- 1) and weakly related to either particle size or flow discharge. However, virtual velocity was well correlated with the highest flow discharge experienced by each tracer normalized by a percentile of the flow duration curve. This evidence further stresses the importance of flow history on sediment entrainment and transport. Finally, the pros and cons of the deployed monitoring technology are discussed.

Flow Classification and Cave Discharge Characteristics in Unsaturated Karst Formation

NASA Astrophysics Data System (ADS)

Mariethoz, G.; Mahmud, K.; Baker, A.; Treble, P. C.

2015-12-01

In this study we utilize the spatial array of automated cave drip monitoring in two large chambers of the Golgotha Cave, SW Australia, developed in Quaternary aeolianite (dune limestone), with the aim of understanding infiltration water movement via the relationships between infiltration, stalactite morphology and groundwater recharge. Mahmud et al. (2015) used the Terrestrial LiDAR measurements to analyze stalactite morphology and to characterize possible flow locations in this cave. Here we identify the stalactites feeding the drip loggers and classify each as matrix (soda straw or icicle), fracture or combined-flow. These morphology-based classifications are compared with flow characteristics from the drip logger time series and the discharge from each stalactite is calculated. The total estimated discharge from each area is compared with infiltration estimates to better understand flow from the surface to the cave ceilings of the studied areas. The drip discharge data agrees with the morphology-based flow classification in terms of flow and geometrical characteristics of cave ceiling stalactites. No significant relationships were observed between the drip logger discharge, skewness and coefficient of variation with overburden thickness, due to the possibility of potential vadose-zone storage volume and increasing complexity of the karst architecture. However, these properties can be used to characterize different flow categories. A correlation matrix demonstrates that similar flow categories are positively correlated, implying significant influence of spatial distribution. The infiltration water comes from a larger surface area, suggesting that infiltration is being focused to the studied ceiling areas of each chamber. Most of the ceiling in the cave site is dry, suggesting the possibility of capillary effects with water moving around the cave rather than passing through it. Reference:Mahmud et al. (2015), Terrestrial Lidar Survey and Morphological Analysis to Identify Infiltration Properties in the Tamala Limestone, Western Australia, IEEE JSTARS, DOI: 10.1109/JSTARS.2015.2451088, in Press.

Numerical study of groundwater flow cycling controlled by seawater/freshwater interaction in a coastal karst aquifer through conduit network using CFPv2.

PubMed

Xu, Zexuan; Hu, Bill X; Davis, Hal; Kish, Stephen

2015-11-01

In this study, a groundwater flow cycling in a karst springshed and an interaction between two springs, Spring Creek Springs and Wakulla Springs, through a subground conduit network are numerically simulated using CFPv2, the latest research version of MODFLOW-CFP (Conduit Flow Process). The Spring Creek Springs and Wakulla Springs, located in a marine estuary and 11 miles inland, respectively, are two major groundwater discharge spots in the Woodville Karst Plain (WKP), North Florida, USA. A three-phase conceptual model of groundwater flow cycling between the two springs and surface water recharge from a major surface creek (Lost Creek) was proposed in various rainfall conditions. A high permeable subground karst conduit network connecting the two springs was found by tracer tests and cave diving. Flow rate of discharge, salinity, sea level and tide height at Spring Creek Springs could significantly affect groundwater discharge and water stage at Wakulla Springs simultaneously. Based on the conceptual model, a numerical hybrid discrete-continuum groundwater flow model is developed using CFPv2 and calibrated by field measurements. Non-laminar flows in conduits and flow exchange between conduits and porous medium are implemented in the hybrid coupling numerical model. Time-variable salinity and equivalent freshwater head boundary conditions at the submarine spring as well as changing recharges have significant impacts on seawater/freshwater interaction and springs' discharges. The developed numerical model is used to simulate the dynamic hydrological process and quantitatively represent the three-phase conceptual model from June 2007 to June 2010. Simulated results of two springs' discharges match reasonably well to measurements with correlation coefficients 0.891 and 0.866 at Spring Creeks Springs and Wakulla Springs, respectively. The impacts of sea level rise on regional groundwater flow field and relationship between the inland springs and submarine springs are evaluated as well in this study. Copyright © 2015 Elsevier B.V. All rights reserved.

Numerical study of groundwater flow cycling controlled by seawater/freshwater interaction in a coastal karst aquifer through conduit network using CFPv2

NASA Astrophysics Data System (ADS)

Xu, Zexuan; Hu, Bill X.; Davis, Hal; Kish, Stephen

2015-11-01

In this study, a groundwater flow cycling in a karst springshed and an interaction between two springs, Spring Creek Springs and Wakulla Springs, through a subground conduit network are numerically simulated using CFPv2, the latest research version of MODFLOW-CFP (Conduit Flow Process). The Spring Creek Springs and Wakulla Springs, located in a marine estuary and 11 miles inland, respectively, are two major groundwater discharge spots in the Woodville Karst Plain (WKP), North Florida, USA. A three-phase conceptual model of groundwater flow cycling between the two springs and surface water recharge from a major surface creek (Lost Creek) was proposed in various rainfall conditions. A high permeable subground karst conduit network connecting the two springs was found by tracer tests and cave diving. Flow rate of discharge, salinity, sea level and tide height at Spring Creek Springs could significantly affect groundwater discharge and water stage at Wakulla Springs simultaneously. Based on the conceptual model, a numerical hybrid discrete-continuum groundwater flow model is developed using CFPv2 and calibrated by field measurements. Non-laminar flows in conduits and flow exchange between conduits and porous medium are implemented in the hybrid coupling numerical model. Time-variable salinity and equivalent freshwater head boundary conditions at the submarine spring as well as changing recharges have significant impacts on seawater/freshwater interaction and springs' discharges. The developed numerical model is used to simulate the dynamic hydrological process and quantitatively represent the three-phase conceptual model from June 2007 to June 2010. Simulated results of two springs' discharges match reasonably well to measurements with correlation coefficients 0.891 and 0.866 at Spring Creeks Springs and Wakulla Springs, respectively. The impacts of sea level rise on regional groundwater flow field and relationship between the inland springs and submarine springs are evaluated as well in this study.

HOW WELL CAN YOU ESTIMATE LOW FLOW AND BANKFULL DISCHARGE FROM STREAM CHANNEL HABITAT DATA?

EPA Science Inventory

Modeled estimates of stream discharge are becoming more important because of reductions in the number of gauging stations and increases in flow alteration from land development and climate change. Field measurements of channel morphology are available at thousands of streams and...

A prototype of an electric-discharge gas flow oxygen−iodine laser: I. Modeling of the processes of singlet oxygen generation in a transverse cryogenic slab RF discharge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vagin, N. P.; Ionin, A. A., E-mail: aion@sci.lebedev.ru; Kochetov, I. V.

The existing kinetic model describing self-sustained and electroionization discharges in mixtures enriched with singlet oxygen has been modified to calculate the characteristics of a flow RF discharge in molecular oxygen and its mixtures with helium. The simulations were performed in the gas plug-flow approximation, i.e., the evolution of the plasma components during their motion along the channel was represented as their evolution in time. The calculations were carried out for the O{sub 2}: He = 1: 0, 1: 1, 1: 2, and 1: 3 mixtures at an oxygen partial pressure of 7.5 Torr. It is shown that, under these conditions,more » volumetric gas heating in a discharge in pure molecular oxygen prevails over gas cooling via heat conduction even at an electrode temperature as low as ~100 K. When molecular oxygen is diluted with helium, the behavior of the gas temperature changes substantially: heat removal begins to prevail over volumetric gas heating, and the gas temperature at the outlet of the discharge zone drops to ~220–230 K at room gas temperature at the inlet, which is very important in the context of achieving the generation threshold in an electric-discharge oxygen−iodine laser based on a slab cryogenic RF discharge.« less

On discharge from poppet valves: effects of pressure and system dynamics

NASA Astrophysics Data System (ADS)

Winroth, P. M.; Ford, C. L.; Alfredsson, P. H.

2018-02-01

Simplified flow models are commonly used to design and optimize internal combustion engine systems. The exhaust valves and ports are modelled as straight pipe flows with a corresponding discharge coefficient. The discharge coefficient is usually determined from steady-flow experiments at low pressure ratios and at fixed valve lifts. The inherent assumptions are that the flow through the valve is insensitive to the pressure ratio and may be considered as quasi-steady. The present study challenges these two assumptions through experiments at varying pressure ratios and by comparing measurements of the discharge coefficient obtained under steady and dynamic conditions. Steady flow experiments were performed in a flow bench, whereas the dynamic measurements were performed on a pressurized, 2 l, fixed volume cylinder with one or two moving valves. In the latter experiments an initial pressure (in the range 300-500 kPa) was established whereafter the valve(s) was opened with a lift profile corresponding to different equivalent engine speeds (in the range 800-1350 rpm). The experiments were only concerned with the blowdown phase, i.e. the initial part of the exhaustion process since no piston was simulated. The results show that the process is neither pressure-ratio independent nor quasi-steady. A measure of the "steadiness" has been defined, relating the relative change in the open flow area of the valve to the relative change of flow conditions in the cylinder, a measure that indicates if the process can be regarded as quasi-steady or not.

Median and Low-Flow Characteristics for Streams under Natural and Diverted Conditions, Northeast Maui, Hawaii

USGS Publications Warehouse

Gingerich, Stephen B.

2005-01-01

Flow-duration statistics under natural (undiverted) and diverted flow conditions were estimated for gaged and ungaged sites on 21 streams in northeast Maui, Hawaii. The estimates were made using the optimal combination of continuous-record gaging-station data, low-flow measurements, and values determined from regression equations developed as part of this study. Estimated 50- and 95-percent flow duration statistics for streams are presented and the analyses done to develop and evaluate the methods used in estimating the statistics are described. Estimated streamflow statistics are presented for sites where various amounts of streamflow data are available as well as for locations where no data are available. Daily mean flows were used to determine flow-duration statistics for continuous-record stream-gaging stations in the study area following U.S. Geological Survey established standard methods. Duration discharges of 50- and 95-percent were determined from total flow and base flow for each continuous-record station. The index-station method was used to adjust all of the streamflow records to a common, long-term period. The gaging station on West Wailuaiki Stream (16518000) was chosen as the index station because of its record length (1914-2003) and favorable geographic location. Adjustments based on the index-station method resulted in decreases to the 50-percent duration total flow, 50-percent duration base flow, 95-percent duration total flow, and 95-percent duration base flow computed on the basis of short-term records that averaged 7, 3, 4, and 1 percent, respectively. For the drainage basin of each continuous-record gaged site and selected ungaged sites, morphometric, geologic, soil, and rainfall characteristics were quantified using Geographic Information System techniques. Regression equations relating the non-diverted streamflow statistics to basin characteristics of the gaged basins were developed using ordinary-least-squares regression analyses. Rainfall rate, maximum basin elevation, and the elongation ratio of the basin were the basin characteristics used in the final regression equations for 50-percent duration total flow and base flow. Rainfall rate and maximum basin elevation were used in the final regression equations for the 95-percent duration total flow and base flow. The relative errors between observed and estimated flows ranged from 10 to 20 percent for the 50-percent duration total flow and base flow, and from 29 to 56 percent for the 95-percent duration total flow and base flow. The regression equations developed for this study were used to determine the 50-percent duration total flow, 50-percent duration base flow, 95-percent duration total flow, and 95-percent duration base flow at selected ungaged diverted and undiverted sites. Estimated streamflow, prediction intervals, and standard errors were determined for 48 ungaged sites in the study area and for three gaged sites west of the study area. Relative errors were determined for sites where measured values of 95-percent duration discharge of total flow were available. East of Keanae Valley, the 95-percent duration discharge equation generally underestimated flow, and within and west of Keanae Valley, the equation generally overestimated flow. Reduction in 50- and 95-percent flow-duration values in stream reaches affected by diversions throughout the study area average 58 to 60 percent.

Study of a DC gas discharge with a copper cathode in a water flow

NASA Astrophysics Data System (ADS)

Tazmeev, G. Kh.; Timerkaev, B. A.; Tazmeev, Kh. K.

2017-07-01

A dc gas discharge between copper electrodes in the current range of 5-20 A was studied experimentally. The discharge gap length was varied within 45-70 mm. The cathode was a 10-mm-diameter rod placed in the water flowing out from a dielectric tube. Three discharge configurations differing in the position of the cathode upper end with respect to the water surface were considered: (i) above water; (ii) flush with the water surface, and (iii) under water. The electric and optical characteristics of the discharge in the second configuration were studied in more detail. It is established that the discharge properties are similar to those of an electric arc. Considerable cathode erosion was observed in the third configuration. It is revealed that fine-dispersed copper grains form in the course of erosion.

Experimental study of flow distribution and pressure loss with circumferential inlet and outlet manifolds

NASA Technical Reports Server (NTRS)

Dittrich, R. T.

1972-01-01

Water flow tests with circumferential inlet and outlet manifolds were conducted to determine factors affecting fluid distribution and pressure losses. Various orifice sizes and manifold geometries were tested over a range of flow velocities. With inlet manifolds, flow distribution was related directly to orifice discharge coefficients. A correlation indicated that nonuniform distribution resulted when the velocity head ratio at the orifice was not in the range of constant discharge coefficient. With outlet manifolds, nonuniform flow was related to static pressure variations along the manifold. Outlet manifolds had appreciably greater pressure losses than comparable inlet manifolds.

Discharge characteristics and hydrodynamics behaviors of atmospheric plasma jets produced in various gas flow patterns

NASA Astrophysics Data System (ADS)

Setsuhara, Yuichi; Uchida, Giichiro; Nakajima, Atsushi; Takenaka, Kosuke; Koga, Kazunori; Shiratani, Masaharu

2015-09-01

Atmospheric nonequilibrium plasma jets have been widely employed in biomedical applications. For biomedical applications, it is an important issue to understand the complicated mechanism of interaction of the plasma jet with liquid. In this study, we present analysis of the discharge characteristics of a plasma jet impinging onto the liquid surface under various gas flow patterns such as laminar and turbulence flows. For this purpose, we analyzed gas flow patters by using a Schlieren gas-flow imaging system in detail The plasma jet impinging into the liquid surface expands along the liquid surface. The diameter of the expanded plasma increases with gas flow rate, which is well explained by an increase in the diameter of the laminar gas-flow channel. When the gas flow rate is further increased, the gas flow mode transits from laminar to turbulence in the gas flow channel, which leads to the shortening of the plasm-jet length. Our experiment demonstrated that the gas flow patterns strongly affect the discharge characteristics in the plasma-jet system. This study was partly supported by a Grant-in-Aid for Scientific Research on Innovative Areas ``Plasma Medical Innovation'' (24108003) from the Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT).

Continuum simulation of the discharge of the granular silo: a validation test for the μ(I) visco-plastic flow law.

PubMed

Staron, L; Lagrée, P-Y; Popinet, S

2014-01-01

Using a continuum Navier-Stokes solver with the μ(I) flow law implemented to model the viscous behavior, and the discrete Contact Dynamics algorithm, the discharge of granular silos is simulated in two dimensions from the early stages of the discharge until complete release of the material. In both cases, the Beverloo scaling is recovered. We first do not attempt a quantitative comparison, but focus on the qualitative behavior of velocity and pressure at different locations in the flow. A good agreement for the velocity is obtained in the regions of rapid flows, while areas of slow creep are not entirely captured by the continuum model. The pressure field shows a general good agreement, while bulk deformations are found to be similar in both approaches. The influence of the parameters of the μ(I) flow law is systematically investigated, showing the importance of the dependence on the inertial number I to achieve quantitative agreement between continuum and discrete discharge. However, potential problems involving the systems size, the configuration and "non-local" effects, are suggested. Yet the general ability of the continuum model to reproduce qualitatively the granular behavior is found to be very encouraging.

Determination of flow losses in the Cape Fear River between B. Everett Jordan Lake and Lillington, North Carolina, 2008-2010

USGS Publications Warehouse

Weaver, J. Curtis; McSwain, Kristen Bukowski

2013-01-01

During 2008-2010, the U.S. Geological Survey conducted a hydrologic investigation in cooperation with the Triangle J Council of Governments Cape Fear River Flow Study Committee and the North Carolina Division of Water Resources to collect hydrologic data in the Cape Fear River between B. Everett Jordan Lake and Lillington in central North Carolina to help determine if suspected flow losses occur in the reach. Flow loss analyses were completed by summing the daily flow releases at Jordan Lake Dam with the daily discharges at Deep River at Moncure and Buckhorn Creek near Corinth, then subtracting these values from the daily discharges at Cape Fear River at Lillington. Examination of long-term records revealed that during 10,227 days of the 1983-2010 water years, 408 days (4.0 percent) had flow loss when conditions were relatively steady with respect to the previous day's records. The flow loss that occurred on these 40 days ranged from 0.49 to 2,150 cubic feet per second with a median flow loss of 37.2 cubic feet per second. The months with the highest number of days with flow losses were June (16. percent), September (16.9 percent), and October (19.4 percent). A series of synoptic discharge measurements made on six separate days in 2009 provided "snapshots" of overall flow conditions along the study reach. The largest water diversion is just downstream from the confluence of the Haw and Deep Rivers, and discharges substantially decrease in the main stem downstream from the intake point. Downstream from Buckhorn Dam, minimal gain or loss between the dam and Raven Rock State Park was noted. Analyses of discharge measurements and ratings for two streamgages-one at Deep River at Moncure and the other at Cape Fear River at Lillington-were completed to address the accuracy of the relation between stage and discharge at these sites. The ratings analyses did not indicate a particular time during the 1982-2011 water years in which a consistent bias occurred in the computations of discharge records that would indicate false flow losses. A total of 34 measured discharges at a streamgage on the Haw River below B. Everett Jordan Lake near Moncure were compared with the reported hourly flow releases from Jordan Lake Dam. Because 28 of 34 measurements were within plus or minus 10 percent of the hourly flow releases reported by the U.S Army Corps of Engineers, use of the current discharge computation tables for reporting Jordan Lake Dam flow releases is generally supported. A stage gage was operated on the Cape Fear River at Buckhorn Dam near Corinth to collect continuous stage-only records. Throughout the study period, flow over the dam was observed along its length, and flow loss within the study reach is not attributed to river-level fluctuations at the dam. Water-use information and (or) data were obtained for five industrial facilities, a regional power utility, two municipalities, one small hydropower facility on the Deep River, and one quarry operation also adjacent to the Deep River. The largest water users are the regional power producer, a small hydropower operation, and the two municipalities. The total water-use diversions for these facilities range from almost 25.5 to 38.5 cubic feet per second (39.5 to 59.5 million gallons per day) during the winter and summer periods, respectively. This range is equivalent to 69 to 104 percent of the 37 cubic feet per second median flow loss. The Lockville hydropower station is on the Deep River about 1 mile downstream from the streamgage near Moncure. Run-of-river operations at the facility do not appear to affect flow losses in the study reach. The largest water user in the study area is a regional power producer at a coal-fired power-generation plant located immediately adjacent to the Cape Fear River just downstream from the confluence of the Haw an Deep Rivers. Comparisons of daily water withdrawals, sup-plied by the regional power producer, and discharge records at a streamgage on the diversion canal indicated many days when consumption exceeded the producer's estimates for the cooling towers. Uncertainty surrounding reasonable estimates of consumption remained in effect at the end of the study. Data concerning evaporative losses were compiled using two approaches-an analysis of available pan-evaporation data from a National Weather Service cooperative observer station in Chapel Hill, North Carolina; and a compilation of reference open-water evaporation computed by the State Climate Office of North Carolina. The potential flow loss by evaporation from the main stem and the Deep River was estimated to be in the range of 4 to 14 cubic feet per second during May through October, equivalent to 10 to 38 percent of the 37 cubic feet per second median flow loss. Daily water-use diversions and evaporation losses were compared to flow-loss occurrences during the period April 2008 through September 2010. In comparing the surface-water, water-use, and evaporation data compiled for 2008-2010, it is evident that documented water diversions combined with flow losses by open-water evaporation can exceed the net flow gain in the study area and result in flow losses from the reach. Analysis of data from a streamgage downstream from the regional power plant on the diversion canal adjacent to the Cape Fear River provided insight into the occurrence of an apparent flow loss at the streamgage at Lillington. Assessment of the daily discharges and subsequent hydrographs for the canal streamgage indicated at least 24 instances during the study when the flows suddenly changed by magnitudes of 100 to more that 200 cubic feet per second, resulting in a noted time-lag effect on the downstream discharges at the Lillington streamgage, beginning 8 to 16 hours after the sudden flow change. A fiber-optic distributed temperature-sensing survey was conducted on the Cape Fear River at the Raven Rock State Park reach August 12-14, 2009, to determine if the presence of diabase dikes were preferentially directing groundwater discharge. No temperature anomalies of colder water were measured during the survey, which indicated that at the time of the survey that particular reach of the Cape Fear River was a "no-flow" or losing stream. An aerial thermal-infrared survey was conducted on the Haw and Cape Fear Rivers on February 27, 2010, from Jordan Lake Dam to Lillington to qualitatively delineate areas of groundwater discharge on the basis of the contrast between warm groundwater discharge and cold surface-water temperatures. Dis-charge generally was noted as diffuse seepage, but in a few cases springs were detected as inflow at a discrete point of discharge. Two reaches of the Cape Fear River (regional power plant and Bradley Road reaches) were selected for groundwater monitoring with a transect of piezometers installed within the flood plain. Groundwater-level altitudes at these reaches were analyzed for 1 water year (October 1, 2009, to September 30, 2010). Data collected as part of this study represent only a brief period of time and may not represent all conditions and all years; however, the data indicate that, during the dry summer months, the Cape Fear River within the study area is losing an undetermined quantity of water through seepage. Analyses completed during this investigation indicate a study reach with complex flow patterns affected by numerous concurrent factors resulting in flow losses. The causes of flow loss could not be solely attributed to any one factor. Among the factors considered, the occurrences of water diversions and evaporative losses were determined to be sufficient on some days (particularly during the base-flow period) to exceed the net gain in flows between the upstream and downstream ends of the study area. Losses by diversions and evaporation can exceed the median flow loss of 3 cubic feet per second, which indicates that flow loss from the study reach is real. Groundwater data collected during 2009-2010 indicate the possibility of localized flow loss during the summer, particularly in the impounded reach above Buckhorn Dam. However, no indication of unusual patterns was noted that would cause substantial flow loss by groundwater and surface-water interaction at the river bottom.

Quantifying landscape change following the 1999 jökulhlaup at Sólheimajökull, southern Iceland

NASA Astrophysics Data System (ADS)

Staines, Kate E. H.

2010-05-01

Glacial outburst floods (jökulhlaups) occur periodically in glaciated areas worldwide as the result of subglacial volcanism, geothermal activity, natural dam-failures, high rainfall events and the release of stored meltwater. Despite their relative low frequency, the high discharge magnitudes and flow velocities can lead to widespread, intensive and long-lasting landscape change. Indeed, in the jökulhlaup-prone regions of southern Iceland, outburst floods are hypothesised to largely control long-term proglacial landscape evolution, with low-magnitude/high-frequency ablation-controlled meltwater flow having a minimal impact. Jökulhlaups also pose a major threat to populations, infrastructures and property. It is predicted with climate change that the frequency and potentially the magnitude of jökulhlaups will increase. It is therefore important to study jökulhlaup flow processes and understand how landscapes are impacted by and recover from these floods. Ultimately, this will better inform policy, flood prediction and hazard management in populated regions at risk from jökulhlaups. Currently, our understanding of jökulhlaup flow processes and the links between these processes and resulting landforms is limited. This is in parts due to the difficulty in directly measuring these high-magnitude, high-velocity floods. Research into jökulhlaup flow characteristics has consequently focussed on reconstructing flow parameters through a variety of palaeohydraulic techniques. However, these often produce conflicting and inaccurate reconstructions of flow inundation, peak discharge and flow rheology as key characteristics of jökulhlaups are frequently neglected (e.g. sediment transport, flow attenuation, sediment bulking and de-bulking). Furthermore, there has been little research into quantifying landscape change, response and recovery following jökulhlaups. The degree of preservation of flood deposits is determined in large parts by the pre-flood sensitivity of the landscape and its recovery potential. Factors controlling these include the recurrence interval and magnitude of past jökulhlaups, glacier surging, glacial advance and retreat cycles and fluctuations in glacier discharge. This study aims to quantify the immediate landscape change associated with a jökulhlaup and examine the response of the landscape in the years following the flood. The study site is the outwash plain (sandur) of Sólheimajökull, an outlet glacier of the Mýrdalsjökull ice cap in southern Iceland. The most recent jökulhlaup, triggered by the eruption of the subglacial volcano Katla, was in July 1999. Field surveys of a boulder fan deposited during the flood at the snout of Sólheimajökull will be used to reconstruct flow palaeocompetence, with cross-sections of the river channel used to calculate peak discharge. From orthorectified pre- and immediate post-flood aerial imagery, digital elevation models will be generated and used to quantify net elevation change (i.e. sediment loss or gain) across the flooded area. Geomorphological maps of the proglacial area from before and in the decade following the flood have been produced and will be used to quantify changes in the main river channel, in terms of braiding and sinuosity parameters.

Flow and chloride transport in the tidal Hudson River, NY

USGS Publications Warehouse

Weiss, Lawrence A.; Schaffranek, Raymond W.; de Vries, M. Peter

1994-01-01

A one-dimensional dynamic-flow model and a one-dimensional solute-transport model were used to evaluate the effects of hypothetical public-supply water withdrawals on saltwater intrusion in a 133-mile reach of the tidal Hudson River between Green Island dam, near Troy, N.Y., and Hastings-on-Hudson, N.Y. Regression techniques were used in analyses of current and extreme historical conditions, and numerical models were used to investigate the effect of various water withdrawals. Of four withdrawal scenarios investigated, simulations of a 27-day period during which discharges at Green Island dam averaged 7,090 ft3/s indicate that increasing the present Chelsea pumping-station withdrawal rate of 100 Mgal/d (million gallons per day) to 300 Mgal/d would have the least effect on upstream saltwater movement. A 90-day simulation, during which discharges at Green Island dam averaged 25,200 ft3/s, indicates that withdrawals of 1,940 Mgal/d at Chelsea would not measurably increase chloride concentrations at Chelsea under normal tidal and meteorological conditions, but withdrawals of twice that rate (3,880 Mgal/d) could increase the chloride concentration at Chelsea to 250 mg/L.

Technique for predicting ground-water discharge to surface coal mines and resulting changes in head

USGS Publications Warehouse

Weiss, L.S.; Galloway, D.L.; Ishii, Audrey L.

1986-01-01

Changes in seepage flux and head (groundwater level) from groundwater drainage into a surface coal mine can be predicted by a technique that considers drainage from the unsaturated zone. The user applies site-specific data to precalculated head and seepage-flux profiles. Groundwater flow through hypothetical aquifer cross sections was simulated using the U.S. Geological Survey finite-difference model, VS2D, which considers variably saturated two-dimensional flow. Conceptual models considered were (1) drainage to a first cut, and (2) drainage to multiple cuts, which includes drainage effects of an area surface mine. Dimensionless head and seepage flux profiles from 246 simulations are presented. Step-by-step instructions and examples are presented. Users are required to know aquifer characteristics and to estimate size and timing of the mine operation at a proposed site. Calculated groundwater drainage to the mine is from one excavated face only. First cut considers confined and unconfined aquifers of a wide range of permeabilities; multiple cuts considers unconfined aquifers of higher permeabilities only. The technique, developed for Illinois coal-mining regions that use area surface mining and evaluated with an actual field example, will be useful in assessing potential hydrologic impacts of mining. Application is limited to hydrogeologic settings and mine operations similar to those considered. Fracture flow, recharge, and leakage are nor considered. (USGS)

Coarse-grained debris flow dynamics on erodible beds

NASA Astrophysics Data System (ADS)

Lanzoni, Stefano; Gregoretti, Carlo; Stancanelli, Laura Maria

2017-03-01

A systematic set of flume experiments is used to investigate the features of velocity profiles within the body of coarse-grained debris flows and the dependence of the transport sediment concentration on the relevant parameters (runoff discharge, bed slope, grain size, and form). The flows are generated in a 10 m long laboratory flume, initially filled with a layer consisting of loose debris. After saturation, a prescribed water discharge is suddenly supplied over the granular bed, and the runoff triggers a debris flow wave that reaches nearly steady conditions. Three types of material have been used in the tests: gravel with mean grain size of 3 and 5 mm, and 3 mm glass spheres. Measured parameters included: triggering water discharge, volumetric sediment discharge, sediment concentration, flow depth, and velocity profiles. The dynamic similarity with full-sized debris flows is discussed on the basis of the relevant dimensionless parameters. Concentration data highlight the dependence on the slope angle and the importance of the quasi-static friction angle. The effects of flow rheology on the shape of velocity profiles are analyzed with attention to the role of different stress-generating mechanisms. A remarkable collapse of the dimensionless profiles is obtained by scaling the debris flow velocity with the runoff velocity, and a power law characterization is proposed following a heuristic approach. The shape of the profiles suggests a smooth transition between the different rheological regimes (collisional and frictional) that establish in the upper and lower regions of the flow and is compatible with the presence of multiple length scales dictated by the type of contacts (instantaneous or long lasting) between grains.

Pahoehoe and aa in Hawaii: volumetric flow rate controls the lava structure

NASA Astrophysics Data System (ADS)

Rowland, Scott K.; Walker, George Pl

1990-11-01

The historical records of Kilauea and Mauna Loa volcanoes reveal that the rough-surfaced variety of basalt lava called aa forms when lava flows at a high volumetric rate (>5 10 m3/s), and the smooth-surfaced variety called pahoehoe forms at a low volumetric rate (<5 10 m3/s). This relationship is well illustrated by the 1983 1990 and 1969 1974 eruptions of Kilauea and the recent eruptions of Mauna Loa. It is also illustrated by the eruptions that produced the remarkable paired flows of Mauna Loa, in which aa formed during an initial short period of high discharge rate (associated with high fountaining) and was followed by the eruption of pahoehoe over a sustained period at a low discharge rate (with little or no fountaining). The finest examples of paired lava flows are those of 1859 and 1880 1881. We attribute aa formation to rapid and concentrated flow in open channels. There, rapid heat loss causes an increase in viscosity to a threshold value (that varies depending on the actual flow velocity) at which, when surface crust is torn by differential flow, the underlying lava is unable to move sufficiently fast to heal the tear. We attribute pahoehoe formation to the flowage of lava at a low volumetric rate, commonly in tubes that minimize heat loss. Flow units of pahoehoe are small (usually <1 m thick), move slowly, develop a chilled skin, and become virtually static before the viscosity has risen, to the threshold value. We infer that the high-discharge-rate eruptions that generate aa flows result from the rapid emptying of major or subsidiary magma chambers. Rapid near-surface vesiculation of gas-rich magma leads to eruptions with high discharge rates, high lava fountains, and fast-moving channelized flows. We also infer that long periods of sustained flow at a low discharge rate, which favor pahoehoe, result from the development of a free and unimpeded pathway from the deep plumbing system of the volcano and the separation of gases from the magma before eruption. Achievement of this condition requires one or more episodes of rapid magma excursion through the rift zone to establish a stable magma pathway.

Influence of permafrost distribution on groundwater flow in the context of climate-driven permafrost thaw: example from Yukon Flats Basin, Alaska, United States

USGS Publications Warehouse

Walvoord, Michelle Ann; Voss, Clifford I.; Wellman, Tristan P.

2012-01-01

Understanding the role of permafrost in controlling groundwater flow paths and fluxes is central in studies aimed at assessing potential climate change impacts on vegetation, species habitat, biogeochemical cycling, and biodiversity. Recent field studies in interior Alaska show evidence of hydrologic changes hypothesized to result from permafrost degradation. This study assesses the hydrologic control exerted by permafrost, elucidates modes of regional groundwater flow for various spatial permafrost patterns, and evaluates potential hydrologic consequences of permafrost degradation. The Yukon Flats Basin (YFB), a large (118,340 km2) subbasin within the Yukon River Basin, provides the basis for this investigation. Model simulations that represent an assumed permafrost thaw sequence reveal the following trends with decreasing permafrost coverage: (1) increased groundwater discharge to rivers, consistent with historical trends in base flow observations in the Yukon River Basin, (2) potential for increased overall groundwater flux, (3) increased spatial extent of groundwater discharge in lowlands, and (4) decreased proportion of suprapermafrost (shallow) groundwater contribution to total base flow. These trends directly affect the chemical composition and residence time of riverine exports, the state of groundwater-influenced lakes and wetlands, seasonal river-ice thickness, and stream temperatures. Presently, the YFB is coarsely mapped as spanning the continuous-discontinuous permafrost transition that model analysis shows to be a critical threshold; thus, the YFB may be on the verge of major hydrologic change should the current permafrost extent decrease. This possibility underscores the need for improved characterization of permafrost and other hydrogeologic information in the region via geophysical techniques, remote sensing, and ground-based observations.

Studies of the Electrohydrodynamic Force Produced in a Dielectric Barrier Discharge for Flow Control. Report no. 2, Phase 3

DTIC Science & Technology

2010-02-01

applied between the electrodes at a repetition rate of a few kHz (for spanwise as well as streamwise configurations of the DBD actuators with respect to...the electronic version) 1. Introduction Surface dielectric barrier discharges ( DBDs ) at atmospheric pressure can generate a flow or modify the...to the momentum transfer from charged particles to neutral molecules in a gas discharge. In recent papers [7–9], we presented studies of surface DBDs

Widely tunable gas laser for remote sensing

NASA Technical Reports Server (NTRS)

Rothe, D. E.

1988-01-01

An advanced, highly efficient and reliable Rare-Gas Halide laser was developed. It employs the following: (1) novel prepulse techniques and impedance matching for efficient energy transfer; (2) magnetic switches for high reliability; (3) x-ray preionization for discharge uniformity and beam quality; and (4) an integrated gas flow loop for compactness. When operated as a XeCl laser, the unit produces 2 J per pulse with good beam uniformity. Optical pulse duration is 100 ns. Pulse repetition rate was tested up to 25 Hz. Efficiency is 3 percent.

New Techniques to Evaluate the Incendiary Behavior of Insulators

NASA Technical Reports Server (NTRS)

Buhler, Charles; Calle, Carlos; Clements, Sid; Trigwell, Steve; Ritz, Mindy

2008-01-01

New techniques for evaluating the incendiary behavior of insulators is presented. The onset of incendive brush discharges in air is evaluated using standard spark probe techniques for the case simulating approaches of an electrically grounded sphere to a charged insulator in the presence of a flammable atmosphere. However, this standard technique is unsuitable for the case of brush discharges that may occur during the charging-separation process for two insulator materials. We present experimental techniques to evaluate this hazard in the presence of a flammable atmosphere which is ideally suited to measure the incendiary nature of micro-discharges upon separation, a measurement never before performed. Other measurement techniques unique to this study include; surface potential measurements of insulators before, during and after contact and separation, as well as methods to verify fieldmeter calibrations using a charge insulator surface opposed to standard high voltage plates. Key words: Kapton polyimide film, incendiary discharges, brush discharges, contact and frictional electrification, ignition hazards, insulators, contact angle, surface potential measurements.

Zero Liquid Discharge approach in plating industry: treatment of degreasing effluents by electrocoagulation and anodic oxidation.

PubMed

Hermon, S; Grange, D; Pellet, Y; Lloret, G; Oyonarte, S; Bosch, F; Coste, M

2008-01-01

Degreasing waste effluents issued from a surface treatment plant were treated by electrochemical techniques in an attempt to reduce COD so that clean water can be returned to the rinse bath. Electrocoagulation, both with iron and aluminium anodes, and anodic oxidation with boron doped diamond (BDD) anodes were tested. In the electrocoagulation tests, the nature of the anodes did not impact significantly the reduction of COD. Electrocoagulation showed good COD removal rates, superior to 80%, but it was not able to reduce COD down to low levels. Anodic oxidation was able to reduce COD down to discharge limits; the oxidation efficiency was superior to 50%. Economical calculations show that anodic oxidation is best used as a polishing step after electrocoagulation. The bulk of the COD would be reduced by electrocoagulation and, then, anodic oxidation would reduce COD below discharge limits. The maximum treatable flow is somewhat hindered by the small sizes of current BDD installation but it would reach 600 m(3)/year if anodic oxidation is coupled with electrocoagulation, the operational cost being 2.90 Euros /m(3). (c) IWA Publishing 2008.

Membranes produced by plasma enhanced chemical vapor deposition technique for low temperature fuel cell applications

NASA Astrophysics Data System (ADS)

Ennajdaoui, Aboubakr; Roualdes, Stéphanie; Brault, Pascal; Durand, Jean

A plasma polymerization process using a continuous glow discharge has been implemented for preparing proton conducting membranes from trifluoromethane sulfonic acid and styrene. The chemical and physical structure of plasma membranes has been investigated using FTIR and SEM. The films are homogeneous with a good adhesion on commercial gas diffusion layer (E-Tek ®). Their deposition rate can be increased with increasing flow rate and input power. The thermogravimetric analysis under air of plasma polymers has showed a thermal stability up to 140 °C. Compared to the pulsed glow discharge studied in a previous paper, the continuous glow discharge has enabled to enhance the proton conductivity of membranes by a factor 3 (up to 1.7 mS cm -1). Moreover, the low methanol permeability (methanol diffusion coefficient down to 5 × 10 -13 m 2 s -1) of membranes has been confirmed by this study. In an industrial context, a reactor prototype has been developed to manufacture by plasma processes all active layers of fuel cell cores to be integrated in original compact PEMFC or DMFC.

Estimates of ground-water discharge as determined from measurements of evapotranspiration, Ash Meadows area, Nye County, Nevada

USGS Publications Warehouse

Laczniak, R.J.; DeMeo, G.A.; Reiner, S.R.; Smith, J. LaRue; Nylund, W.E.

1999-01-01

Ash Meadows is one of the major discharge areas within the regional Death Valley ground-water flow system of southern Nevada and adjacent California. Ground water discharging at Ash Meadows is replenished from inflow derived from an extensive recharge area that includes the eastern part of the Nevada Test Site (NTS). Currently, contaminants introduced into the subsurface by past nuclear testing at NTS are the subject of study by the U.S. Department of Energy's Environmental Restoration Program. The transport of any contaminant in contact with ground water is controlled in part by the rate and direction of ground-water flow, which itself depends on the location and quantity of ground water discharging from the flow system. To best evaluate any potential risk associated with these test-generated contaminants, studies were undertaken to accurately quantify discharge from areas downgradient from the NTS. This report presents results of a study to refine the estimate of ground-water discharge at Ash Meadows. The study estimates ground-water discharge from the Ash Meadows area through a rigorous quantification of evapotranspiration (ET). To accomplish this objective, the study identifies areas of ongoing ground-water ET, delineates unique areas of ET defined on the basis of similarities in vegetation and soil-moisture conditions, and computes ET rates for each of the delineated areas. A classification technique using spectral-reflectance characteristics determined from satellite images recorded in 1992 identified seven unique units representing areas of ground-water ET. The total area classified encompasses about 10,350 acres dominated primarily by lush desert vegetation. Each unique area, referred to as an ET unit, generally consists of one or more assemblages of local phreatophytes. The ET units identified range from sparse grasslands to open water. Annual ET rates are computed by energy-budget methods from micrometeorological measurements made at 10 sites within six of the seven identified ET units. Micrometeorological data were collected for a minimum of 1 year at each site during 1994 through 1997. Evapotranspiration ranged from 0.6 foot per year in a sparse, dry saltgrass environment to 8.6 feet per year over open water. Ancillary data, including water levels, were collected during this same period to gain additional insight into the evapotranspiration process. Water levels measured in shallow wells showed annual declines of more than 10 feet and daily declines as high as 0.3 foot attributed to water losses associated with evapotranspiration. Mean annual ET from the Ash Meadows area is estimated at 21,000 acre-feet. An estimate of ground-water discharge, based on this ET estimate, is presented as a range to account for uncertainties in the contribution of local precipitation. The estimates given for mean annual ground-water discharge range from 18,000 to 21,000 acre-feet. The low estimate assumes a large contribution from local precipitation in computed ET rates; whereas, the high estimate assumes no contribution from local precipitation. The range presented is only slightly higher than previous estimates of ground-water discharge from the Ash Meadows area based primarily on springflow measurements.

Self-pulsing discharge of a plasma brush operated in atmospheric-pressure argon

NASA Astrophysics Data System (ADS)

Li, Xuechen; Liu, Runfu; Jia, Pengying; Bao, Wenting; Shang, Yong

2013-06-01

A plasma brush excited by DC voltage is developed with argon as working gas in the ambient air. The time evolution of the discharge current, the light emission, and the sustaining voltage are analyzed under different conditions. The self-pulsing phenomenon of the discharge is observed with oscillated voltage and intermittent current. The self-pulsing frequency ranges from several tens hertz to several hundred hertz depending on the output power and the gas flow rate. It increases with the increasing of the gas flow rate, while it decreases as the output power increases. The phenomenon is explained qualitatively based on a spatially resolved measurement about the discharge.

Observatory enabled discovery of diffuse discharge temperature structure

NASA Astrophysics Data System (ADS)

Bemis, K. G.; Lee, R.; Ivakin, A. N.

2016-12-01

Underwater cabled observatories provide long term but short time and spatial scale measurements of hydrothermal discharge properties. For the first time, an intricate picture of diffuse discharge has been captured at both Axial Volcano (Axial) and the Main Endeavour Field (MEF) on the Juan de Fuca Ridge. This study combines thermistor (3D array, 2D array and spot) and acoustic data to compare the statistical and distribution characteristics of diffuse discharge for narrow crack flow (at ASHES field on Axial) and distributive flow out of a sulfide structure (at Grotto vent in MEF). Two surprising observations seem to apply to both styles of diffuse discharge: (1) thermal variance scales with the mean temperature suggesting coherent flow structures exist in the form of plumes, wakes or boundary layers, and (2) thermal hot spots are persistently localized in space, despite tidal current disruption. Thermal variance was measured at ASHES using a 3D thermistor array (TMPSF) with 10 s sampling over two years and at Grotto using 2D thermistor arrays with 1 hr sampling over several years and a ROV-held CTD (Seabird 39plus) with 0.5 second sampling over several minutes. For locations with temperatures greater than ambient, the variance in temperature scales with the mean temperature. This unusual statistical property is characteristic of self-similar flows like plumes, wakes, and boundary layers and arises from the bounded mixing of a cooling high temperature fluid with a cold ambient fluid. Thus this observation implies an underlying coherence to the diffuse discharge that has not yet been adequately captured or described. A coherent flow like a plume should have a discoverable spatial pattern, albeit one that may vary with the influence of tides. Acoustic observations ( 1m diameter footprint) of the Grotto sulfide edifice found stable local hot spots of diffuse discharge that sway with tides. In contrast, the 3D thermistor array at ASHES sees very localized (single thermistor) hot spots that persist for months. Is this a fundamental difference between two styles of diffuse discharge? Alternate conceptual models of diffuse discharge are used to place localized observations in a spatial context and develop a rigorous understanding of the spatial and temporal pattern of diffuse discharge for both crack and distributive styles.

DC discharges in atmospheric air for bio-decontamination - spectroscopic methods for mechanism identification

NASA Astrophysics Data System (ADS)

Machala, Z.; Jedlovský, I.; Chládeková, L.; Pongrác, B.; Giertl, D.; Janda, M.; Ikurová, L. Å.; Polčic, P.

2009-08-01

Three types of DC electrical discharges in atmospheric air (streamer corona, transient spark and glow discharge) were tested for bio-decontamination of bacteria and yeasts in water solution, and spores on surfaces. Static vs. flowing treatment of contaminated water were compared, in the latter the flowing water either covered the grounded electrode or passed through the high voltage needle electrode. The bacteria were killed most efficiently in the flowing regime by transient spark. Streamer corona was efficient when the treated medium flew through the active corona region. The spores on plastic foil and paper surfaces were successfully inactivated by negative corona. The microbes were handled and their population evaluated by standard microbiology cultivation procedures. The emission spectroscopy of the discharges and TBARS (thiobarbituric acid reactive substances) absorption spectrometric detection of the products of lipid peroxidation of bacterial cell membranes indicated a major role of radicals and reactive oxygen species among the bio-decontamination mechanisms.

Quantitative characterization of arc discharge as vacuum interface

DOE PAGES

Huang, S.; Zhu, K.; Lu, Y. R.; ...

2014-12-19

An arc discharge with channel diameters of 3 mm and 6 mm and lengths between 30mm and 60mm was experimentally investigated for its potential to function as plasma window, i.e., interface vacuum regions of different pressures. In this study, electron temperature of the plasma channel measured spectroscopically varied in the range of 7000K to 15000K, increasing with discharge current while decreasing with gas flow rate. The plasma window had a slightly positive I-V characteristics over the whole range of investigated current 30A–70 A. Measurements of pressure separation capability, which were determined by input current, gas flow rate, discharge channel diameter,more » and length, were well explained by viscosity effect and “thermal-block” effect. The experimental results of global parameters including temperature, gas flow rate, and voltage had a good agreement with the simulation results calculated by an axis-symmetry Fluent-based magneto-hydrodynamic model.« less

Pool Formation in Boulder-Bed Streams: Implications From 1-D and 2-D Numerical Modeling

NASA Astrophysics Data System (ADS)

Harrison, L. R.; Keller, E. A.

2003-12-01

In mountain rivers of Southern California, boulder-large roughness elements strongly influence flow hydraulics and pool formation and maintenance. In these systems, boulders appear to control the stream morphology by converging flow and producing deep pools during channel forming discharges. Our research goal is to develop quantitative relationships between boulder roughness elements, temporal patterns of scour and fill, and geomorphic processes that are important in producing pool habitat. The longitudinal distribution of shear stress, unit stream power and velocity were estimated along a 48 m reach on Rattlesnake Creek, using the HEC-RAS v 3.0 and River 2-D numerical models. The reach has an average slope of 0.02 and consists of a pool-riffle sequence with a large boulder constriction directly above the pool. Model runs were performed for a range of stream discharges to test if scour and fill thresholds for pool and riffle environments could be identified. Results from the HEC-RAS simulations identified that thresholds in shear stress, unit stream power and mean velocity occur above a discharge of 5.0 cms. Results from the one-dimensional analysis suggest that the reversal in competency is likely due to changes in cross-sectional width at varying flows. River 2-D predictions indicated that strong transverse velocity gradients were present through the pool at higher modeled discharges. At a flow of 0.5 cms (roughly 1/10th bankfull discharge), velocities are estimated at 0.6 m/s and 1.3 m/s for the pool and riffle, respectively. During discharges of 5.15 cms (approximate bankfull discharge), the maximum velocity in the pool center increased to nearly 3.0 m/s, while the maximum velocity over the riffle is estimated at approximately 2.5 cms. These results are consistent with those predicted by HEC-RAS, though the reversal appears to be limited to a narrow jet that occurs through the pool head and pool center. Model predictions suggest that the velocity reversal is produced by a boulder-bedrock constriction that rapidly decreases the channel width above the pool by roughly 25 percent. The width constriction creates highly turbulent flow capable of scouring bed material through the pool. The high velocity core that is produced through the pool center appears to be enhanced by the formation of a large eddy directly below the boulder. Values of unit stream power and shear stress indicate that the pool exit is an area of deposition of bed material due to a decrease in tractive force. The presence of a strong transverse velocity gradient suggests that only a portion of the flow is responsible for scouring bed material. After we eliminate the dead water zone, the lowest five percent of the velocity range, patterns of effective width between pools and riffles begin to emerge. The ratio of flow width between adjacent pools and riffles is one measure of flow convergence. At a discharge of 0.5 cms, the ratio of effective width between pools and riffles is roughly 1:1, implying that there is uniform flow with little flow convergence. At a discharge of 5.15 cms the width ratio between the pool and riffle is about 1:3, demonstrating the strong convergent flow patterns at the pool head. The observed effective width relationship suggests that when considering restoration designs, boulders should be placed in areas that replicate natural convergence and divergence patterns in order to maximize pool area and depth.

Problems associated with estimating ground water discharge and recharge from stream-discharge records

USGS Publications Warehouse

Halford, K.J.; Mayer, G.C.

2000-01-01

Ground water discharge and recharge frequently have been estimated with hydrograph-separation techniques, but the critical assumptions of the techniques have not been investigated. The critical assumptions are that the hydraulic characteristics of the contributing aquifer (recession index) can be estimated from stream-discharge records; that periods of exclusively ground water discharge can be reliably identified; and that stream-discharge peaks approximate the magnitude and tinting of recharge events. The first assumption was tested by estimating the recession index from st earn-discharge hydrographs, ground water hydrographs, and hydraulic diffusivity estimates from aquifer tests in basins throughout the eastern United States and Montana. The recession index frequently could not be estimated reliably from stream-discharge records alone because many of the estimates of the recession index were greater than 1000 days. The ratio of stream discharge during baseflow periods was two to 36 times greater than the maximum expected range of ground water discharge at 12 of the 13 field sites. The identification of the ground water component of stream-discharge records was ambiguous because drainage from bank-storage, wetlands, surface water bodies, soils, and snowpacks frequently exceeded ground water discharge and also decreased exponentially during recession periods. The timing and magnitude of recharge events could not be ascertained from stream-discharge records at any of the sites investigated because recharge events were not directly correlated with stream peaks. When used alone, the recession-curve-displacement method and other hydrograph-separation techniques are poor tools for estimating ground water discharge or recharge because the major assumptions of the methods are commonly and grossly violated. Multiple, alternative methods of estimating ground water discharge and recharge should be used because of the uncertainty associated with any one technique.

An evaluation of Dynamic TOPMODEL for low flow simulation

NASA Astrophysics Data System (ADS)

Coxon, G.; Freer, J. E.; Quinn, N.; Woods, R. A.; Wagener, T.; Howden, N. J. K.

2015-12-01

Hydrological models are essential tools for drought risk management, often providing input to water resource system models, aiding our understanding of low flow processes within catchments and providing low flow predictions. However, simulating low flows and droughts is challenging as hydrological systems often demonstrate threshold effects in connectivity, non-linear groundwater contributions and a greater influence of water resource system elements during low flow periods. These dynamic processes are typically not well represented in commonly used hydrological models due to data and model limitations. Furthermore, calibrated or behavioural models may not be effectively evaluated during more extreme drought periods. A better understanding of the processes that occur during low flows and how these are represented within models is thus required if we want to be able to provide robust and reliable predictions of future drought events. In this study, we assess the performance of dynamic TOPMODEL for low flow simulation. Dynamic TOPMODEL was applied to a number of UK catchments in the Thames region using time series of observed rainfall and potential evapotranspiration data that captured multiple historic droughts over a period of several years. The model performance was assessed against the observed discharge time series using a limits of acceptability framework, which included uncertainty in the discharge time series. We evaluate the models against multiple signatures of catchment low-flow behaviour and investigate differences in model performance between catchments, model diagnostics and for different low flow periods. We also considered the impact of surface water and groundwater abstractions and discharges on the observed discharge time series and how this affected the model evaluation. From analysing the model performance, we suggest future improvements to Dynamic TOPMODEL to improve the representation of low flow processes within the model structure.

Force Measurements of Single and Double Barrier DBD Plasma Actuators in Quiescent Air

NASA Technical Reports Server (NTRS)

Hoskinson, Alan R.; Hershkowitz, Noah; Ashpis, David E.

2008-01-01

We have performed measurements of the force induced by both single (one electrode insulated) and double (both electrodes insulated) dielectric barrier discharge plasma actuators in quiescent air. We have shown that, for single barrier actuators, as the electrode diameter decreased below those values previously studied the induced Force increases exponentially rather than linearly. This behavior has been experimentally verified using two different measurement techniques: stagnation probe measurements of the induced flow velocity and direct measurement of the force using an electronic balance. In addition, we have shown the the induced force is independent of the material used for the exposed electrode. The same techniques have shown that the induced force of a double barrier actuator increases with decreasing narrow electrode diameter.

Impacts of changing hydrology on permanent gully growth: experimental results

NASA Astrophysics Data System (ADS)

Day, Stephanie S.; Gran, Karen B.; Paola, Chris

2018-06-01

Permanent gullies grow through head cut propagation in response to overland flow coupled with incision and widening in the channel bottom leading to hillslope failures. Altered hydrology can impact the rate at which permanent gullies grow by changing head cut propagation, channel incision, and channel widening rates. Using a set of small physical experiments, we tested how changing overland flow rates and flow volumes alter the total volume of erosion and resulting gully morphology. Permanent gullies were modeled as both detachment-limited and transport-limited systems, using two different substrates with varying cohesion. In both cases, the erosion rate varied linearly with water discharge, such that the volume of sediment eroded was a function not of flow rate, but of total water volume. This implies that efforts to reduce peak flow rates alone without addressing flow volumes entering gully systems may not reduce erosion. The documented response in these experiments is not typical when compared to larger preexisting channels where higher flow rates result in greater erosion through nonlinear relationships between water discharge and sediment discharge. Permanent gullies do not respond like preexisting channels because channel slope remains a free parameter and can adjust relatively quickly in response to changing flows.

21 CFR 1020.20 - Cold-cathode gas discharge tubes.

Code of Federal Regulations, 2014 CFR

2014-04-01

... discharge tubes designed to demonstrate the effects of a flow of electrons or the production of x-radiation... electron flow is produced and sustained by ionization of contained gas atoms and ion bombardment of the... the ions of one sign produced in air when all electrons liberated by photons in a volume element of...

21 CFR 1020.20 - Cold-cathode gas discharge tubes.

Code of Federal Regulations, 2012 CFR

2012-04-01

... discharge tubes designed to demonstrate the effects of a flow of electrons or the production of x-radiation... electron flow is produced and sustained by ionization of contained gas atoms and ion bombardment of the... the ions of one sign produced in air when all electrons liberated by photons in a volume element of...

21 CFR 1020.20 - Cold-cathode gas discharge tubes.

Code of Federal Regulations, 2013 CFR

2013-04-01

... discharge tubes designed to demonstrate the effects of a flow of electrons or the production of x-radiation... electron flow is produced and sustained by ionization of contained gas atoms and ion bombardment of the... the ions of one sign produced in air when all electrons liberated by photons in a volume element of...

21 CFR 1020.20 - Cold-cathode gas discharge tubes.

Code of Federal Regulations, 2011 CFR

2011-04-01

... discharge tubes designed to demonstrate the effects of a flow of electrons or the production of x-radiation... electron flow is produced and sustained by ionization of contained gas atoms and ion bombardment of the... the ions of one sign produced in air when all electrons liberated by photons in a volume element of...

Emplacement and Growth of the August 2014 to February 2015 Nornahraun Lava Flow Field North Iceland

NASA Astrophysics Data System (ADS)

Thordarson, T.; Hoskuldsson, A.; Jónsdottir, I.; Pedersen, G.; Gudmundsson, M. T.; Dürig, T.; Riishuus, M. S.; Moreland, W.; Gudnason, J.; Gallagher, C. R.; Askew, R. A.

2015-12-01

The 31.08.2014 to 27.02.2015 Nornahraun eruption in North Iceland is the largest eruption in Iceland in 232 years, producing an 85km2 lava flow field with a volume of 1.5-2km3. The eruption began on a 2 km long fissure that cut through the 1797AD Holuhraun vent system, spreading lava onto the flat (slope <0.4°) Dyngjujokull outwash plane. At mean magma discharge of 250 m3 the lava was transported from the vents via a 3.5km long lava channel, feeding a 1-2km wide rubbly pāhoehoe to 'a'a flow front advancing to the NE at rate of 1-2 km/day. This lava flow came to halt on 12 September at a distance of 18km from the vents and for the next 5 days it was subjected to endogenous growth reaching a mean thickness 12m and a volume 0.35km3. Mean magma discharge dropped to 150 m3/s on 18th and the vent activity was reduced to a 500 m long central segment of the fissure. A new lava flow formed, advancing along the southern margins of the first, coming to rest on 22 September at 11.5 km from the vents (vol. 0.09km3). On 23rd the third flow formed, advanced along south and north margins of the flow field, reaching a maximum length of 6.7 km as it came to rest on the 26th (vol. 0.06km3). Increase in magma discharge to about 220 m3/s is observed between 27 September and 8 October forming the 4th lava flow along the south margins of the flow field. This flow surged out to a distance of 15km in 12 days (vol. 0.22km3). Flow 5 formed between 9 to 30 October at mean discharge of 140 m3/s, advancing along the south side of flow 4 and reaching length of 11 km (vol. 0.30km3). Similarly, the sixth flow formed along flow 5 between 1-14 November at mean discharge of 110 m3/s and reaching length of 7.5km (vol. 0.11km3). This signaled the end of this gradual clockwise widening of the flow field, which coincided with partial crusting over of the lava channel and initiation of insulated flows that were emplaced on top of the earlier formed flows for the reminder of the eruption.

Effective discharge analysis of ecological processes in streams

USGS Publications Warehouse

Doyle, Martin W.; Stanley, Emily H.; Strayer, David L.; Jacobson, Robert B.; Schmidt, John C.

2005-01-01

Discharge is a master variable that controls many processes in stream ecosystems. However, there is uncertainty of which discharges are most important for driving particular ecological processes and thus how flow regime may influence entire stream ecosystems. Here the analytical method of effective discharge from fluvial geomorphology is used to analyze the interaction between frequency and magnitude of discharge events that drive organic matter transport, algal growth, nutrient retention, macroinvertebrate disturbance, and habitat availability. We quantify the ecological effective discharge using a synthesis of previously published studies and modeling from a range of study sites. An analytical expression is then developed for a particular case of ecological effective discharge and is used to explore how effective discharge varies within variable hydrologic regimes. Our results suggest that a range of discharges is important for different ecological processes in an individual stream. Discharges are not equally important; instead, effective discharge values exist that correspond to near modal flows and moderate floods for the variable sets examined. We suggest four types of ecological response to discharge variability: discharge as a transport mechanism, regulator of habitat, process modulator, and disturbance. Effective discharge analysis will perform well when there is a unique, essentially instantaneous relationship between discharge and an ecological process and poorly when effects of discharge are delayed or confounded by legacy effects. Despite some limitations the conceptual and analytical utility of the effective discharge analysis allows exploring general questions about how hydrologic variability influences various ecological processes in streams.

Tracking groundwater discharge to a large river using tracers and geophysics.

PubMed

Harrington, Glenn A; Gardner, W Payton; Munday, Tim J

2014-01-01

Few studies have investigated large reaches of rivers in which multiple sources of groundwater are responsible for maintaining baseflow. This paper builds upon previous work undertaken along the Fitzroy River, one of the largest perennial river systems in north-western Australia. Synoptic regional-scale sampling of both river water and groundwater for a suite of environmental tracers ((4) He, (87) Sr/(86) Sr, (222) Rn and major ions), and subsequent modeling of tracer behavior in the river, has enabled definition and quantification of groundwater input from at least three different sources. We show unambiguous evidence of both shallow "local" groundwater, possibly recharged to alluvial aquifers beneath the adjacent floodplain during recent high-flow events, and old "regional" groundwater introduced via artesian flow from deep confined aquifers. We also invoke hyporheic exchange and either bank return flow or parafluvial flow to account for background (222) Rn activities and anomalous chloride trends along river reaches where there is no evidence of the local or regional groundwater inputs. Vertical conductivity sections acquired through an airborne electromagnetic (AEM) survey provide insights to the architecture of the aquifers associated with these sources and general groundwater quality characteristics. These data indicate fresh groundwater from about 300 m below ground preferentially discharging to the river, at locations consistent with those inferred from tracer data. The results demonstrate how sampling rivers for multiple environmental tracers of different types-including stable and radioactive isotopes, dissolved gases and major ions-can significantly improve conceptualization of groundwater-surface water interaction processes, particularly when coupled with geophysical techniques in complex hydrogeological settings. © 2013, National Ground Water Association.

Generalized additive regression models of discharge and mean velocity associated with direct-runoff conditions in Texas: Utility of the U.S. Geological Survey discharge measurement database

USGS Publications Warehouse

Asquith, William H.; Herrmann, George R.; Cleveland, Theodore G.

2013-01-01

A database containing more than 17,700 discharge values and ancillary hydraulic properties was assembled from summaries of discharge measurement records for 424 U.S. Geological Survey streamflow-gauging stations (stream gauges) in Texas. Each discharge exceeds the 90th-percentile daily mean streamflow as determined by period-of-record, stream-gauge-specific, flow-duration curves. Each discharge therefore is assumed to represent discharge measurement made during direct-runoff conditions. The hydraulic properties of each discharge measurement included concomitant cross-sectional flow area, water-surface top width, and reported mean velocity. Systematic and statewide investigation of these data in pursuit of regional models for the estimation of discharge and mean velocity has not been previously attempted. Generalized additive regression modeling is used to develop readily implemented procedures by end-users for estimation of discharge and mean velocity from select predictor variables at ungauged stream locations. The discharge model uses predictor variables of cross-sectional flow area, top width, stream location, mean annual precipitation, and a generalized terrain and climate index (OmegaEM) derived for a previous flood-frequency regionalization study. The mean velocity model uses predictor variables of discharge, top width, stream location, mean annual precipitation, and OmegaEM. The discharge model has an adjusted R-squared value of about 0.95 and a residual standard error (RSE) of about 0.22 base-10 logarithm (cubic meters per second); the mean velocity model has an adjusted R-squared value of about 0.67 and an RSE of about 0.063 fifth root (meters per second). Example applications and computations using both regression models are provided. - See more at: http://ascelibrary.org/doi/abs/10.1061/%28ASCE%29HE.1943-5584.0000635#sthash.jhGyPxgZ.dpuf

Perennial flow through convergent hillslopes explains chemodynamic solute behavior in a shale headwater catchment

NASA Astrophysics Data System (ADS)

Herndon, E.; Steinhoefel, G.; Dere, A. L. D.; Sullivan, P. L.

2017-12-01

Streams experience changing hydrologic connectivity to heterogeneous water sources under different flow regimes. It remains unclear how seasonal flow paths link these different sources and regulate concentration-discharge behavior. Previous research at the Susquehanna Shale Hills Critical Zone Observatory (SSHCZO) in central Pennsylvania, USA identified chemostatic solutes (e.g., K, Mg, Na, Cl) whose concentrations varied little across a wide range of discharge values and chemodynamic solutes (e.g., Fe and Mn) whose concentrations decreased sharply with increasing stream discharge. To elucidate inputs to the stream when concentrations of chemodynamic solutes were high, we investigated stream water and shallow groundwater (< 4 m) chemistry at the SSHCZO in early autumn when discharge was negligible. The stream consisted of isolated puddles that were chemically variable along the length of the channel but similar to underlying shallow groundwater. Chemodynamic solute concentrations in the stream and groundwater were high in the upper catchment but decreased by an order of magnitude towards the outlet. In contrast, chemostatic solute concentrations varied little. Groundwater was minimally connected to the stream in an area of upwelling near the stream headwaters; however, the water table remained over a meter below the stream bed along the rest of the channel. We conclude that well water sampled from the upper catchment is young, shallow interflow that upwells to generate metal-rich stream headwaters during the dry season. High concentrations of chemodynamic solutes measured during low discharge occur when metal-rich headwaters are flushed to the catchment outlet during periodic rain events. Interflow during the dry season originates from water that infiltrates through organic-rich swales; thus, metals in the stream at low flow are ultimately derived from convergent hillslopes where biological processes have concentrated chemodynamic elements. We infer that chemodynamic solutes are diluted at high discharge due to increased flow through planar hillslopes and inputs from regional groundwater that rises to enter the stream. This study highlights how spatially heterogeneous biogeochemistry and seasonally variable flow paths regulate concentration-discharge behavior within catchments.

Large springs of east Tennessee

USGS Publications Warehouse

Sun, Pao-chang P.; Criner, J.H.; Poole, J.L.

1963-01-01

Springs constitute an important source of water in east Tennessee, and many individual springs are capable of supplying the large quantities needed for municipal and industrial supplies. Most of the springs in east Tennessee issue from solution openings and fractured and faulted zones in limestone and dolomite of the Knox Group, Chickamauga Limestone, and Conasauga Group. The ability of these rocks to yield a sustained flow of water to springs is dependent on a system of interconnected openings through which water can infiltrate from the land surface and move to points of natural discharge. Ninety springs were selected for detailed study, and 84 of these are analyzed in terms of magnitude and variability of discharge. Of the 84 springs analyzed, 4 flow at an average rate of 10 to 100 cfs (cubic feet per second), 62 at an average rate of 1 to 10 cfs, and 18 at an average rate of 1 cfs or less. Of the 90 springs, 75 are variable in their discharge; that is, the ratio of their fluctuations to their average discharges exceeds 100 percent. Mathematical analysis of the flow recession curve of Mill Spring near Jefferson City shows that the hydrologic system contributing to the flow of the spring has an effective capacity of about 70 million cubic feet of water. The rate of depletion of this volume of water, in the absence of significant precipitation, averages 0.0056 cfs per day between the time when the hydrologic system is full and the time when the spring ceases to flow. From such a curve it is possible to determine at any time the residual volume of water remaining in the system and the expected rate of decrease in discharge from that time to cessation of flow. Correlation of discharge measurements of 22 springs with those of Mill Spring shows that rough approximations of discharge can be projected for springs for which few measurements are available. Seventeen of the springs analyzed in this manner show good correlation with Mill Spring: that is, their coefficients of correlation were 0.70 or better as compared with a perfect correlation factor of 1.00.

Numerical simulation of dune-flat bed transition and stage‐discharge relationship with hysteresis effect

USGS Publications Warehouse

Shimizu, Yasuyuki; Giri, Sanjay; Yamaguchi, Satomi; Nelson, Jonathan M.

2009-01-01

This work presents recent advances on morphodynamic modeling of bed forms under unsteady discharge. This paper includes further development of a morphodynamic model proposed earlier by Giri and Shimizu (2006a). This model reproduces the temporal development of river dunes and accurately replicates the physical properties associated with bed form evolution. Model results appear to provide accurate predictions of bed form geometry and form drag over bed forms for arbitrary steady flows. However, accurate predictions of temporal changes of form drag are key to the prediction of stage‐discharge relation during flood events. Herein, the model capability is extended to replicate the dune–flat bed transition, and in turn, the variation of form drag produced by the temporal growth or decay of bed forms under unsteady flow conditions. Some numerical experiments are performed to analyze hysteresis of the stage‐discharge relationship caused by the transition between dune and flat bed regimes during rising and falling stages of varying flows. The numerical model successfully simulates dune–flat bed transition and the associated hysteresis of the stage‐discharge relationship; this is in good agreement with physical observations but has been treated in the past only using empirical methods. A hypothetical relationship for a sediment parameter (the mean step length) is proposed to a first level of approximation that enables reproduction of the dune–flat bed transition. The proposed numerical model demonstrates its ability to address an important practical problem associated with bed form evolution and flow resistance in varying flows.

The case of the 1981 eruption of Mount Etna: An example of very fast moving lava flows

NASA Astrophysics Data System (ADS)

Coltelli, Mauro; Marsella, Maria; Proietti, Cristina; Scifoni, Silvia

2012-01-01

Mount Etna despite being an extremely active volcano which, during the last 400 years, has produced many lava flow flank eruptions has rarely threatened or damaged populated areas. The reconstruction of the temporal evolution of potentially hazardous flank eruptions represents a useful contribution to reducing the impact of future eruptions by and analyzing actions to be taken for protecting sensitive areas. In this work, we quantitatively reconstructed the evolution of the 1981 lava flow field of Mt Etna, which threatened the town of Randazzo. This reconstruction was used to evaluate the cumulated volume, the time averaged discharge rate trend and to estimate its maximum value. The analysis was conducted by comparing pre- and post-eruption topographic surfaces, extracted by processing historical photogrammetric data sets and by utilizing the eruption chronology to establish the lava flow front positions at different times. An unusually high discharge rate (for Etna) of 640 m3/s was obtained, which corresponds well with the very fast advance rate observed for the main lava flow. A comparison with other volcanoes, presenting high discharge rate, was proposed for finding a clue to unveil the 1981 Etna eruptive mechanism. A model was presented to explain the high discharge rate, which includes an additional contribution to the lava discharge caused by the interception of a shallow magma reservoir by a dike rising from depth and the subsequent emptying of the reservoir.

Flow measuring structures

NASA Astrophysics Data System (ADS)

Boiten, W.

1993-11-01

The use of flow measuring structures is one of the various methods for the continuous measurement of discharges in open channels. In this report a brief summary of these methods is presented to get some insight in the selection of the most appropriate method. Then the distinct functions of water control structures are described. The flow measuring structures are classified according to international rules. The fields of application are dealt with and the definitions of weir flow are given. Much attention is paid to the aspects of how to select the most suitable flow measuring structure. The accuracy in the evaluation of the discharge has been related to the different error sources. A review of international standards on flow measuring structures concludes the report.

Study of Plasma Flows Generated in Plasma Focus Discharge in Different Regimes of Working Gas Filling

NASA Astrophysics Data System (ADS)

Voitenko, D. A.; Ananyev, S. S.; Astapenko, G. I.; Basilaia, A. D.; Markolia, A. I.; Mitrofanov, K. N.; Myalton, V. V.; Timoshenko, A. P.; Kharrasov, A. M.; Krauz, V. I.

2017-12-01

Results are presented from experimental studies of the plasma flows generated in the KPF-4 Phoenix Mather-type plasma focus device (Sukhum Physical Technical Institute). In order to study how the formation and dynamics of the plasma flow depend on the initial distribution of the working gas, a system of pulsed gas puffing into the discharge volume was developed. The system allows one to create profiled gas distributions, including those with a reduced gas density in the region of plasma flow propagation. Results of measurements of the magnetic field, flow profile, and flow deceleration dynamics at different initial distributions of the gas pressure are presented.

Continuous pressure letdown system

DOEpatents

Sprouse, Kenneth M.; Matthews, David R.; Langowski, Terry

2010-06-08

A continuous pressure letdown system connected to a hopper decreases a pressure of a 2-phase (gas and solid) dusty gas stream flowing through the system. The system includes a discharge line for receiving the dusty gas from the hopper, a valve, a cascade nozzle assembly positioned downstream of the discharge line, a purge ring, an inert gas supply connected to the purge ring, an inert gas throttle, and a filter. The valve connects the hopper to the discharge line and controls introduction of the dusty gas stream into the discharge line. The purge ring is connected between the discharge line and the cascade nozzle assembly. The inert gas throttle controls a flow rate of an inert gas into the cascade nozzle assembly. The filter is connected downstream of the cascade nozzle assembly.

Discharge Characterization of 40 cm-Microwave ECR Ion Source and Neutralizer

NASA Technical Reports Server (NTRS)

Foster, John E.; Patterson, Michael J.; Britton, Melissa

2003-01-01

Discharge characteristics of a 40 cm, 2.45 GHz Electron Cyclotron Resonance (ECR) ion thruster discharge chamber and neutralizer were acquired. Thruster bulk discharge plasma characteristics were assessed using a single Langmuir probe. Total extractable ion current was measured as a function of input microwave power and flow rate. Additionally, radial ion current density profiles at the thruster.s exit plane were characterized using five equally spaced Faraday probes. Distinct low and high density operating modes were observed as discharge input power was varied from 0 to 200 W. In the high mode, extractable ion currents as high as 0.82 A were measured. Neutralizer emission current was characterized as a function of flow rate and microwave power. Neutralizer extraction currents as high as 0.6 A were measured.

Experimental Investigation of the Induced Airflow of Corona Discharge

NASA Astrophysics Data System (ADS)

Huang, Yong; Zhang, Xin; Wang, Xun-Nian; Wang, Wan-Bo; Huang, Zong-Bo; Li, Hua-Xing

2013-09-01

In order to improve the acceleration effect of corona discharge acting on air, we present an experimental study on the induced airflow produced by corona discharge between two parallel electrodes. The parameters investigated are the type of electrodes, actuation voltage and the distance in the absence of free airflow. The induced flow velocity is measured directly in the accelerated region using the particle image velocimetry technology. The results show that if corona discharge is not developed into arc discharge, the induced airflow velocity increases nearly linearly with the applied voltage and the maximum induced airflow velocity near the needle electrode reaches 36 m/s. It is expected that in the future, the result can be referred to in the research about effect of active flow control to reach much higher induced airflow speed.

CO2 Dissociation by Low Current Gliding Discharge in the Reverse Vortex Flow

NASA Astrophysics Data System (ADS)

Gutsol, Alexander

2012-10-01

If performed with high energy efficiency, plasma-chemical dissociation of carbon dioxide can be a way of converting and storing energy when there is an excess of electric energy, for example generated by solar elements of wind turbines. CO2 dissociation with efficiency of up to 90% was reported earlier for low pressure microwave discharge in supersonic flow. A new plasma-chemical system uses a low current gliding discharge in the reverse vortex flow of plasma gas. The system is a development of the Gliding Arc in Tornado reactor. The system was used to study dissociation of CO2 in wide ranges of the following experimental parameters: reactor pressure (15-150 kPa), discharge current (50-500 mA), gas flow rate (3-30 liters per minute), and electrode gap length (1-10 cm). Additionally, the effect of thermal energy recuperation on CO2 dissociation efficiency was tested. Plasma chemical efficiency of CO2 dissociation is very low (about 3%) in a short discharge at low pressures (about 15 kPa) when it is defined by electronic excitation. The highest efficiency (above 40%) was reached at pressures 50-70 kPa in a long discharge with thermal energy recuperation. It means that the process is controlled by thermal dissociation with subsequent effective quenching. Plasma chemical efficiency was determined from the data of chromatographic analysis and oscilloscope electric power integration, and also was checked calorimetrically by the thermal balance of the system.

Providing peak river flow statistics and forecasting in the Niger River basin

NASA Astrophysics Data System (ADS)

Andersson, Jafet C. M.; Ali, Abdou; Arheimer, Berit; Gustafsson, David; Minoungou, Bernard

2017-08-01

Flooding is a growing concern in West Africa. Improved quantification of discharge extremes and associated uncertainties is needed to improve infrastructure design, and operational forecasting is needed to provide timely warnings. In this study, we use discharge observations, a hydrological model (Niger-HYPE) and extreme value analysis to estimate peak river flow statistics (e.g. the discharge magnitude with a 100-year return period) across the Niger River basin. To test the model's capacity of predicting peak flows, we compared 30-year maximum discharge and peak flow statistics derived from the model vs. derived from nine observation stations. The results indicate that the model simulates peak discharge reasonably well (on average + 20%). However, the peak flow statistics have a large uncertainty range, which ought to be considered in infrastructure design. We then applied the methodology to derive basin-wide maps of peak flow statistics and their associated uncertainty. The results indicate that the method is applicable across the hydrologically active part of the river basin, and that the uncertainty varies substantially depending on location. Subsequently, we used the most recent bias-corrected climate projections to analyze potential changes in peak flow statistics in a changed climate. The results are generally ambiguous, with consistent changes only in very few areas. To test the forecasting capacity, we ran Niger-HYPE with a combination of meteorological data sets for the 2008 high-flow season and compared with observations. The results indicate reasonable forecasting capacity (on average 17% deviation), but additional years should also be evaluated. We finish by presenting a strategy and pilot project which will develop an operational flood monitoring and forecasting system based in-situ data, earth observations, modelling, and extreme statistics. In this way we aim to build capacity to ultimately improve resilience toward floods, protecting lives and infrastructure in the region.

Calibration of hydrological models using flow-duration curves

NASA Astrophysics Data System (ADS)

Westerberg, I. K.; Guerrero, J.-L.; Younger, P. M.; Beven, K. J.; Seibert, J.; Halldin, S.; Freer, J. E.; Xu, C.-Y.

2011-07-01

The degree of belief we have in predictions from hydrologic models will normally depend on how well they can reproduce observations. Calibrations with traditional performance measures, such as the Nash-Sutcliffe model efficiency, are challenged by problems including: (1) uncertain discharge data, (2) variable sensitivity of different performance measures to different flow magnitudes, (3) influence of unknown input/output errors and (4) inability to evaluate model performance when observation time periods for discharge and model input data do not overlap. This paper explores a calibration method using flow-duration curves (FDCs) to address these problems. The method focuses on reproducing the observed discharge frequency distribution rather than the exact hydrograph. It consists of applying limits of acceptability for selected evaluation points (EPs) on the observed uncertain FDC in the extended GLUE approach. Two ways of selecting the EPs were tested - based on equal intervals of discharge and of volume of water. The method was tested and compared to a calibration using the traditional model efficiency for the daily four-parameter WASMOD model in the Paso La Ceiba catchment in Honduras and for Dynamic TOPMODEL evaluated at an hourly time scale for the Brue catchment in Great Britain. The volume method of selecting EPs gave the best results in both catchments with better calibrated slow flow, recession and evaporation than the other criteria. Observed and simulated time series of uncertain discharges agreed better for this method both in calibration and prediction in both catchments. An advantage with the method is that the rejection criterion is based on an estimation of the uncertainty in discharge data and that the EPs of the FDC can be chosen to reflect the aims of the modelling application, e.g. using more/less EPs at high/low flows. While the method appears less sensitive to epistemic input/output errors than previous use of limits of acceptability applied directly to the time series of discharge, it still requires a reasonable representation of the distribution of inputs. Additional constraints might therefore be required in catchments subject to snow and where peak-flow timing at sub-daily time scales is of high importance. The results suggest that the calibration method can be useful when observation time periods for discharge and model input data do not overlap. The method could also be suitable for calibration to regional FDCs while taking uncertainties in the hydrological model and data into account.

Snowmelt discharge characteristics Sierra Nevada, California

USGS Publications Warehouse

Peterson, David; Smith, Richard; Stewart, Iris; Knowles, Noah; Soulard, Chris; Hager, Stephen

2005-01-01

Alpine snow is an important water resource in California and the western U.S. Three major features of alpine snowmelt are the spring pulse (the first surge in snowmelt-driven river discharge in spring), maximum snowmelt discharge, and base flow (low river discharge supported by groundwater in fall). A long term data set of hydrologic measurements at 24 gage locations in 20 watersheds in the Sierra Nevada was investigated to relate patterns of snowmelt with stream discharge In wet years, the daily variations in snowmelt discharge at all the gage locations in the Sierra Nevada correlate strongly with the centrally located Merced River at Happy Isles, Yosemite National Park (i.e., in 1983, the mean of the 23 correlations was R= 0.93 + 0.09) ; in dry years, however, this correlation breaks down (i.e., in year 1977, R=0.72 + 0.24). A general trend towards earlier snowmelt was found and modeled using correlations with the timing of the spring pulse and the river discharge center of mass. For the 24 river and creek gage locations in this study, the spring pulse appeared to be a more sensitive measure of early snowmelt than the center of mass. The amplitude of maximum daily snowmelt discharge correlates strongly with initial snow water equivalent. Geologic factors, base rock permeability and soil-to-bedrock ratio, influence snowmelt flow pathways. Although both surface and ground water flows and water levels increase in wet years compared to dry years, the increase was greater for surface water in a watershed with relatively impermeable base rock than for surface water in a watershed with highly permeable base rock The relation was the opposite for base flow (ground water). The increase was greater for groundwater in a watershed with permeable rock compared to ground water in a watershed with impermeable rock. A similar, but weaker, surface/groundwater partitioning was observed in relatively impermeable granitic watersheds with differing soil-to-bedrock ratios. The increase in surface flow was greater in a watershed with a low, compared to a high, soil-to-bedrock ratio; whereas the increase in ground water flow was greater in a watershed with a high, compared to a low, soil-to-bedrock ratio. Transects that include long-term observations of shallow well-water depth and chemistry would complement traditional hydroclimate data and provide a more complete understanding of hydrologic controls of snowmelt.

Dissolved organic matter composition of winter flow in the Yukon River basin: Implications of permafrost thaw and increased groundwater discharge

USGS Publications Warehouse

O'Donnell, Jonathan A.; Aiken, George R.; Walvoord, Michelle Ann; Butler, Kenna D.

2012-01-01

Groundwater discharge to rivers has increased in recent decades across the circumpolar region and has been attributed to thawing permafrost in arctic and subarctic watersheds. Permafrost-driven changes in groundwater discharge will alter the flux of dissolved organic carbon (DOC) in rivers, yet little is known about the chemical composition and reactivity of dissolved organic matter (DOM) of groundwater in permafrost settings. Here, we characterize DOM composition of winter flow in 60 rivers and streams of the Yukon River basin to evaluate the biogeochemical consequences of enhanced groundwater discharge associated with permafrost thaw. DOC concentration of winter flow averaged 3.9 ± 0.5 mg C L−1, yet was highly variable across basins (ranging from 20 mg C L−1). In comparison to the summer-autumn period, DOM composition of winter flow had lower aromaticity (as indicated by specific ultraviolet absorbance at 254 nm, or SUVA254), lower hydrophobic acid content, and a higher proportion of hydrophilic compounds (HPI). Fluorescence spectroscopy and parallel factor analysis indicated enrichment of protein-like fluorophores in some, but not all, winter flow samples. The ratio of DOC to dissolved organic nitrogen, an indicator of DOM biodegradability, was positively correlated with SUVA254 and negatively correlated with the percentage of protein-like compounds. Using a simple two-pool mixing model, we evaluate possible changes in DOM during the summer-autumn period across a range of conditions reflecting possible increases in groundwater discharge. Across three watersheds, we consistently observed decreases in DOC concentration and SUVA254 and increases in HPI with increasing groundwater discharge. Spatial patterns in DOM composition of winter flow appear to reflect differences in the relative contributions of groundwater from suprapermafrost and subpermafrost aquifers across watersheds. Our findings call for more explicit consideration of DOC loss and stabilization pathways associated with changing subsurface hydrology in watersheds underlain by thawing permafrost.

3D SPH numerical simulation of the wave generated by the Vajont rockslide

NASA Astrophysics Data System (ADS)

Vacondio, R.; Mignosa, P.; Pagani, S.

2013-09-01

A 3D numerical modeling of the wave generated by the Vajont slide, one of the most destructive ever occurred, is presented in this paper. A meshless Lagrangian Smoothed Particle Hydrodynamics (SPH) technique was adopted to simulate the highly fragmented violent flow generated by the falling slide in the artificial reservoir. The speed-up achievable via General Purpose Graphic Processing Units (GP-GPU) allowed to adopt the adequate resolution to describe the phenomenon. The comparison with the data available in literature showed that the results of the numerical simulation reproduce satisfactorily the maximum run-up, also the water surface elevation in the residual lake after the event. Moreover, the 3D velocity field of the flow during the event and the discharge hydrograph which overtopped the dam, were obtained.

Plasma core reactor simulations using RF uranium seeded argon discharges

NASA Technical Reports Server (NTRS)

Roman, W. C.

1976-01-01

Experimental results are described in which pure uranium hexafluoride was injected into an argon-confined, steady-state, RF-heated plasma to investigate characteristics of plasma core nuclear reactors. The 80 kW (13.56 MHz) and 1.2 MW (5.51 MHz) rf induction heater facilities were used to determine a test chamber flow scheme which offered best uranium confinement with minimum wall coating. The cylindrical fused-silica test chamber walls were 5.7-cm-ID by 10-cm-long. Test conditions included RF powers of 2-85 kW, chamber pressures of 1-12 atm, and uranium hexafluoride mass-flow rates of 0.005-0.13 g/s. Successful techniques were developed for fluid-mechanical confinement of RF-heated plasmas with pure uranium hexafluoride injection.

Hyporheic zone influences on concentration-discharge relationships in a headwater sandstone stream

NASA Astrophysics Data System (ADS)

Hoagland, Beth; Russo, Tess A.; Gu, Xin; Hill, Lillian; Kaye, Jason; Forsythe, Brandon; Brantley, Susan L.

2017-06-01

Complex subsurface flow dynamics impact the storage, routing, and transport of water and solutes to streams in headwater catchments. Many of these hydrogeologic processes are indirectly reflected in observations of stream chemistry responses to rain events, also known as concentration-discharge (CQ) relations. Identifying the relative importance of subsurface flows to stream CQ relationships is often challenging in headwater environments due to spatial and temporal variability. Therefore, this study combines a diverse set of methods, including tracer injection tests, cation exchange experiments, geochemical analyses, and numerical modeling, to map groundwater-surface water interactions along a first-order, sandstone stream (Garner Run) in the Appalachian Mountains of central Pennsylvania. The primary flow paths to the stream include preferential flow through the unsaturated zone ("interflow"), flow discharging from a spring, and groundwater discharge. Garner Run stream inherits geochemical signatures from geochemical reactions occurring along each of these flow paths. In addition to end-member mixing effects on CQ, we find that the exchange of solutes, nutrients, and water between the hyporheic zone and the main stream channel is a relevant control on the chemistry of Garner Run. CQ relationships for Garner Run were compared to prior results from a nearby headwater catchment overlying shale bedrock (Shale Hills). At the sandstone site, solutes associated with organo-mineral associations in the hyporheic zone influence CQ, while CQ trends in the shale catchment are affected by preferential flow through hillslope swales. The difference in CQ trends document how the lithology and catchment hydrology control CQ relationships.

Effects of Changes in Irrigation Practices and Aquifer Development on Groundwater Discharge to the Jobos Bay National Estuarine Research Reserve near Salinas, Puerto Rico

USGS Publications Warehouse

Kuniansky, Eve L.; Rodriguez, Jose M.

2010-01-01

Since 1990, about 75 acres of black mangroves have died in the Jobos Bay National Estuarine Research Reserve near Salinas, Puerto Rico. Although many factors can contribute to the mortality of mangroves, changes in irrigation practices, rainfall, and water use resulted in as much as 25 feet of drawdown in the potentiometric surface of the aquifer in the vicinity of the reserve between 1986 and 2002. To clarify the issue, the U.S. Geological Survey, in cooperation with the Puerto Rico Department of Natural and Environmental Resources, conducted a study to ascertain how aquifer development and changes in irrigation practices have affected groundwater levels and groundwater flow to the Mar Negro area of the reserve. Changes in groundwater flow to the mangrove swamp and bay from 1986 to 2004 were estimated in this study by developing and calibrating a numerical groundwater flow model. The transient simulations indicate that prior to 1994, high irrigation return flows more than offset the effect of reduced groundwater withdrawals. In this case, the simulated discharge to the coast in the modeled area was 19 million gallons per day. From 1994 through 2004, furrow irrigation was completely replaced by micro-drip irrigation, thus eliminating return flows and the simulated average coastal discharge was 7 million gallons per day, a reduction of 63 percent. The simulated average groundwater discharge to the coastal mangrove swamps in the reserve from 1986 to 1993 was 2 million gallons per day, compared to an average simulated discharge of 0.2 million gallons per day from 1994 to 2004. The average annual rainfall for each of these periods was 38 inches. The groundwater discharge to the coastal mangrove swamps in the Jobos Bay National Estuarine Research Reserve was estimated at about 0.5 million gallons per day for 2003-2004 because of higher than average annual rainfall during these 2 years. The groundwater flow model was used to test five alternatives for increasing groundwater discharge to the coastal mangrove swamps to approximately 1.4 million gallons per day: (1) artificially recharging the aquifer with injection wells or (2) by increasing irrigation return flow by going back to furrow irrigation; (3) termination of groundwater withdrawals near the mangroves; (4) reduction of groundwater withdrawals at irrigation wells by 50 percent; and (5) a combination of alternatives 2 and 4 increasing irrigation return flows and decreasing irrigation withdrawals. Each alternative assumed average climatic conditions and groundwater withdrawals at 2004 rates. Alternative 1 required 1.5 million gallons per day of injected water. Alternative 2 required flooding 958 acres with a rate of 1.84 million gallons per day if no crops are grown. Alternative 3 required the termination of 2.44 million gallons per day of withdrawals to achieve 1.34 million gallons per day of discharge to the mangroves. Alternative 4 did not achieve the objective with only 0.80 million gallons per day simulated discharge to the mangroves, while requiring a 1.26 million gallon per day reduction in groundwater withdrawals. Alternative 5 required flooding fields with additional 1.13 million gallons of day and the same reduction in groundwater withdrawals, but did achieve the objective of about 1.4 million gallons per day discharge to the mangroves. Alternative 1, incorporating injection wells near the reserve required the least amount of water to raise groundwater levels and maintain discharge of 1.4 million gallons per day through the mangroves.

A digital underwater video camera system for aquatic research in regulated rivers

USGS Publications Warehouse

Martin, Benjamin M.; Irwin, Elise R.

2010-01-01

We designed a digital underwater video camera system to monitor nesting centrarchid behavior in the Tallapoosa River, Alabama, 20 km below a peaking hydropower dam with a highly variable flow regime. Major components of the system included a digital video recorder, multiple underwater cameras, and specially fabricated substrate stakes. The innovative design of the substrate stakes allowed us to effectively observe nesting redbreast sunfish Lepomis auritus in a highly regulated river. Substrate stakes, which were constructed for the specific substratum complex (i.e., sand, gravel, and cobble) identified at our study site, were able to withstand a discharge level of approximately 300 m3/s and allowed us to simultaneously record 10 active nests before and during water releases from the dam. We believe our technique will be valuable for other researchers that work in regulated rivers to quantify behavior of aquatic fauna in response to a discharge disturbance.

The Effect of Rainfall Measurement Technique and Its Spatiotemporal Resolution on Discharge Predictions in the Netherlands

NASA Astrophysics Data System (ADS)

Uijlenhoet, R.; Brauer, C.; Overeem, A.; Sassi, M.; Rios Gaona, M. F.

2014-12-01

Several rainfall measurement techniques are available for hydrological applications, each with its own spatial and temporal resolution. We investigated the effect of these spatiotemporal resolutions on discharge simulations in lowland catchments by forcing a novel rainfall-runoff model (WALRUS) with rainfall data from gauges, radars and microwave links. The hydrological model used for this analysis is the recently developed Wageningen Lowland Runoff Simulator (WALRUS). WALRUS is a rainfall-runoff model accounting for hydrological processes relevant to areas with shallow groundwater (e.g. groundwater-surface water feedback). Here, we used WALRUS for case studies in a freely draining lowland catchment and a polder with controlled water levels. We used rain gauge networks with automatic (hourly resolution but low spatial density) and manual gauges (high spatial density but daily resolution). Operational (real-time) and climatological (gauge-adjusted) C-band radar products and country-wide rainfall maps derived from microwave link data from a cellular telecommunication network were also used. Discharges simulated with these different inputs were compared to observations. We also investigated the effect of spatiotemporal resolution with a high-resolution X-band radar data set for catchments with different sizes. Uncertainty in rainfall forcing is a major source of uncertainty in discharge predictions, both with lumped and with distributed models. For lumped rainfall-runoff models, the main source of input uncertainty is associated with the way in which (effective) catchment-average rainfall is estimated. When catchments are divided into sub-catchments, rainfall spatial variability can become more important, especially during convective rainfall events, leading to spatially varying catchment wetness and spatially varying contribution of quick flow routes. Improving rainfall measurements and their spatiotemporal resolution can improve the performance of rainfall-runoff models, indicating their potential for reducing flood damage through real-time control.

Streamflow losses along the Balcones Fault Zone, Nueces River basin, Texas

USGS Publications Warehouse

Land, L.F.; Boning, C.W.; Harmsen, Lynn; Reeves, R.D.

1983-01-01

Statistical evaluations of historical daily flow records for the streams that have gaging stations upstream and downstream from the recharge zone provided mathematical relationships that expressed downstream flow in terms of other significant parameters. For each stream, flow entering the recharge zone is most significant in defining downstream flow; for some streams, antecedent flows at the upstream site and ground-water levels are also significantly related to downstream flow. The analyses also determined the discharges required upstream from the recharge zone to sustain flow downstream from that zone. These discharges ranged from 355 cubic feet per second for the combined Frio and Dry Frio Rivers to 33 cubic feet per second for the Nueces River. The entire flows of lesser magnitude are generally lost to recharge to the aquifer.

Hysteretic behavior of stage-discharge relationships in urban streams

NASA Astrophysics Data System (ADS)

Miller, A. J.; Lindner, G. A.

2009-12-01

Reliable stage-discharge relationships or rating curves are of critical importance for accurate calculation of streamflow and maintenance of long-term flow records. Urban streams offer particular challenges for the maintenance of accurate rating curves. It is often difficult or impossible to collect direct discharge measurements at high flows, many of which are generated by short-duration high-intensity summer thunderstorms, both because of dangerous conditions in the channel and also because the stream rises and falls so rapidly that field crews cannot reach sites in time and sometimes cannot make measurements rapidly enough to keep pace with changing water levels even when they are on site during a storm. Work in urban streams in the Baltimore metropolitan area has shown that projection of rating curves beyond the range of measured flows can lead to overestimation of flood peaks by as much as 100%, and these can only be corrected when adequate field data are available to support modeling efforts. Even moderate flows that are above safe wading depth and velocity may best be estimated using hydraulic models. Current research for NSF CNH project 0709659 includes the application of 2-d depth-averaged hydraulic models to match existing rating curves over a range of low to moderate flows and to extend rating curves for higher flows, based on field collection of high-water marks. Although it is generally assumed that stage-discharge relationships are single-valued, we find that modeling results in small urban streams often generate hysteretic relationships, with higher discharges on the rising limb of the hydrograph than on the falling limb. The difference between discharges for the same stage on the rising and falling limb can be on the order of 20-30% even for in-channel flows that are less than 1 m deep. As safety considerations dictate that it is preferable to make direct discharge measurements on the falling limb of the hydrograph, the higher direct measurements used in many rating curves probably have been collected on the falling limb and therefore may not capture the correct stage-discharge relationship for the rising limb. In some cases model results selected only from the falling limb are able to match the existing rating curve very closely. Although hysteresis may be explained with reference to the innate properties of the flood wave, other factors also lead to hysteretic behavior. Downstream constrictions and obstructions associated with urban infrastructure may cause substantial backwater effects, particularly during flood flows. Flood conditions at tributary confluences also can exert a controlling influence upstream. Based on our results we recommend that at some sites it is advisable to develop separate rating curves for the rising and falling limbs, and to develop a range of modeling scenarios for predicting the range of potential uncertainty.

The Spatial and Temporal Variability of Meltwater Flow Paths: Insights From a Grid of Over 100 Snow Lysimeters

NASA Astrophysics Data System (ADS)

Webb, R. W.; Williams, M. W.; Erickson, T. A.

2018-02-01

Snowmelt is an important part of the hydrologic cycle and ecosystem dynamics for headwater systems. However, the physical process of water flow through snow is a poorly understood aspect of snow hydrology as meltwater flow paths tend to be highly complex. Meltwater flow paths diverge and converge as percolating meltwater reaches stratigraphic layer interfaces creating high spatial variability. Additionally, a snowpack is temporally heterogeneous due to rapid localized metamorphism that occurs during melt. This study uses a snowmelt lysimeter array at tree line in the Niwot Ridge study area of northern Colorado. The array is designed to address the issue of spatial and temporal variability of basal discharge at 105 locations over an area of 1,300 m2. Observed coefficients of variation ranged from 0 to almost 10 indicating more variability than previously observed, though this variability decreased throughout each melt season. Snowmelt basal discharge also significantly increases as snow depth decreases displaying a cluster pattern that peaks during weeks 3-5 of the snowmelt season. These results are explained by the flow of meltwater along snow layer interfaces. As the snowpack becomes less stratified through the melt season, the pattern transforms from preferential flow paths to uniform matrix flow. Correlation ranges of the observed basal discharge correspond to a mean representative elementary area of 100 m2, or a characteristic length of 10 m. Snowmelt models representing processes at scales less than this will need to explicitly incorporate the spatial variability of snowmelt discharge and meltwater flow paths through snow between model pixels.

Effect of inner guide on performances of cross flow turbine

NASA Astrophysics Data System (ADS)

Kokubu, K.; Yamasaki, K.; Honda, H.; Kanemoto, T.

2012-11-01

To get the sustainable society, the hydropower with not only the large but also the mini/micro capacity has been paid attention to the power generation. The cross-flow turbines can work efficiently at the comparatively low head and/or low discharge in the onshore and the offshore, and the runner and the casing profiles have been optimizing. In this paper, the turbine composed of the optimal profiles has prepared to provide for the mini/micro hydropower, and the performances have been investigated at the low head. The hydraulic efficiency is maximal at the normal guide vane opening and deteriorates at the lower and the higher discharge than the normal discharge. Such deteriorations are brought from the unacceptable flow conditions crossing in the runner, that is, the flow direction does not meet the setting angle of the blade at the inner radius. To improve dramatically the performances, the inner guide, which guards the shaft from the water jet and adjusts the flow direction, was installed in the runner.

Numerical investigation and thermodynamic analysis of the effect of electrolyte flow rate on performance of all vanadium redox flow batteries

NASA Astrophysics Data System (ADS)

Khazaeli, Ali; Vatani, Ali; Tahouni, Nassim; Panjeshahi, Mohammad Hassan

2015-10-01

In flow batteries, electrolyte flow rate plays a crucial role on the minimizing mass transfer polarization which is at the compensation of higher pressure drop. In this work, a two-dimensional numerical method is applied to investigate the effect of electrolyte flow rate on cell voltage, maximum depth of discharge and pressure drop a six-cell stack of VRFB. The results show that during the discharge process, increasing electrolyte flow rate can raise the voltage of each cell up to 50 mV on average. Moreover, the maximum depth of discharge dramatically increases with electrolyte flow rate. On the other hand, the pressure drop also positively correlates with electrolyte flow rate. In order to investigate all these effects simultaneously, average energy and exergy efficiencies are introduced in this study for the transient process of VRFB. These efficiencies give insight into choosing an appropriate strategy for the electrolyte flow rate. Finally, the energy efficiency of electricity storage using VRFB is investigated and compared with other energy storage systems. The results illustrate that this kind of battery has at least 61% storage efficiency based on the second law of thermodynamics, which is considerably higher than that of their counterparts.