A standardised graphic method for describing data privacy frameworks in primary care research using a flexible zone model.

PubMed

Kuchinke, Wolfgang; Ohmann, Christian; Verheij, Robert A; van Veen, Evert-Ben; Arvanitis, Theodoros N; Taweel, Adel; Delaney, Brendan C

2014-12-01

To develop a model describing core concepts and principles of data flow, data privacy and confidentiality, in a simple and flexible way, using concise process descriptions and a diagrammatic notation applied to research workflow processes. The model should help to generate robust data privacy frameworks for research done with patient data. Based on an exploration of EU legal requirements for data protection and privacy, data access policies, and existing privacy frameworks of research projects, basic concepts and common processes were extracted, described and incorporated into a model with a formal graphical representation and a standardised notation. The Unified Modelling Language (UML) notation was enriched by workflow and own symbols to enable the representation of extended data flow requirements, data privacy and data security requirements, privacy enhancing techniques (PET) and to allow privacy threat analysis for research scenarios. Our model is built upon the concept of three privacy zones (Care Zone, Non-care Zone and Research Zone) containing databases, data transformation operators, such as data linkers and privacy filters. Using these model components, a risk gradient for moving data from a zone of high risk for patient identification to a zone of low risk can be described. The model was applied to the analysis of data flows in several general clinical research use cases and two research scenarios from the TRANSFoRm project (e.g., finding patients for clinical research and linkage of databases). The model was validated by representing research done with the NIVEL Primary Care Database in the Netherlands. The model allows analysis of data privacy and confidentiality issues for research with patient data in a structured way and provides a framework to specify a privacy compliant data flow, to communicate privacy requirements and to identify weak points for an adequate implementation of data privacy. Copyright © 2014 Elsevier Ireland Ltd. All rights reserved.

Experimental analysis of the flow in a two stage axial compressor at off-design conditions

NASA Astrophysics Data System (ADS)

Massardo, Aristide; Satta, Antonio

1987-05-01

The experimental analysis of the flow that develops in a two-stage axial flow compressor at off-design conditions is presented. The measurements are performed upstream, between, and downstream of the four blade rows of the compressor. The analysis shows the off-design effects on the local conditions of the flow field. Low-energy flow zones are identified, and the development of annulus-boundary-layer, secondary, and tip-clearance flows is shown. The tip-clearance flows are also present in the stator rows with various outlying conditions (stationary or rotating hub).

Unsaturated flow characterization utilizing water content data collected within the capillary fringe

USGS Publications Warehouse

Baehr, Arthur; Reilly, Timothy J.

2014-01-01

An analysis is presented to determine unsaturated zone hydraulic parameters based on detailed water content profiles, which can be readily acquired during hydrological investigations. Core samples taken through the unsaturated zone allow for the acquisition of gravimetrically determined water content data as a function of elevation at 3 inch intervals. This dense spacing of data provides several measurements of the water content within the capillary fringe, which are utilized to determine capillary pressure function parameters via least-squares calibration. The water content data collected above the capillary fringe are used to calculate dimensionless flow as a function of elevation providing a snapshot characterization of flow through the unsaturated zone. The water content at a flow stagnation point provides an in situ estimate of specific yield. In situ determinations of capillary pressure function parameters utilizing this method, together with particle-size distributions, can provide a valuable supplement to data libraries of unsaturated zone hydraulic parameters. The method is illustrated using data collected from plots within an agricultural research facility in Wisconsin.

Shallow subsurface storm flow in a forested headwater catchment: Observations and modeling using a modified TOPMODEL

USGS Publications Warehouse

Scanlon, Todd M.; Raffensperger, Jeff P.; Hornberger, George M.; Clapp, Roger B.

2000-01-01

Transient, perched water tables in the shallow subsurface are observed at the South Fork Brokenback Run catchment in Shenandoah National Park, Virginia. Crest piezometers installed along a hillslope transect show that the development of saturated conditions in the upper 1.5 m of the subsurface is controlled by total precipitation and antecedent conditions, not precipitation intensity, although soil heterogeneities strongly influence local response. The macroporous subsurface storm flow zone provides a hydrological pathway for rapid runoff generation apart from the underlying groundwater zone, a conceptualization supported by the two‐storage system exhibited by hydrograph recession analysis. A modified version of TOPMODEL is used to simulate the observed catchment dynamics. In this model, generalized topographic index theory is applied to the subsurface storm flow zone to account for logarithmic storm flow recessions, indicative of linearly decreasing transmissivity with depth. Vertical drainage to the groundwater zone is required, and both subsurface reservoirs are considered to contribute to surface saturation.

Bed Erosion Process in Geophysical Viscoplastic Fluid

NASA Astrophysics Data System (ADS)

Luu, L. H.; Philippe, P.; Chambon, G.; Vigneaux, P.; Marly, A.

2017-12-01

The bulk behavior of materials involved in geophysical fluid dynamics such as snow avalanches or debris flows has often been modeled as viscoplastic fluid that starts to flow once its stress state overcomes a critical yield value. This experimental and numerical study proposes to interpret the process of erosion in terms of solid-fluid transition for these complex materials. The experimental setup consists in a closed rectangular channel with a cavity in its base. By means of high-resolution optical velocimetry (PIV), we properly examine the typical velocity profiles of a model elasto-viscoplastic flow (Carbopol) at the vicinity of the solid-fluid interface, separating a yielded flowing layer above from an unyielded dead zone below. In parallel, numerical simulations in this expansion-contraction geometry with Augmented Lagrangian and Finite-Differences methods intend to discuss the possibility to describe the specific flow related to the existence of a dead zone, with a simple Bingham rheology. First results of this comparative analysis show a good numerical ability to capture the main scalings and flow features, such as the non-monotonous evolution of the shear stress in the boundary layer between the central plug zone and the dead zone at the bottom of the cavity.

Estimation of Unsaturated Zone Traveltimes for Rainier Mesa and Shoshone Mountain, Nevada Test Site, Nevada, Using a Source-Responsive Preferential-Flow Model

USGS Publications Warehouse

Ebel, Brian A.; Nimmo, John R.

2009-01-01

Traveltimes for contaminant transport by water from a point in the unsaturated zone to the saturated zone are a concern at Rainier Mesa and Shoshone Mountain in the Nevada Test Site, Nevada. Where nuclear tests were conducted in the unsaturated zone, contaminants must traverse hundreds of meters of variably saturated rock before they enter the saturated zone in the carbonate rock, where the regional groundwater system has the potential to carry them substantial distances to a location of concern. The unsaturated-zone portion of the contaminant transport path may cause a significant delay, in addition to the time required to travel within the saturated zone, and thus may be important in the overall evaluation of the potential hazard from contamination. Downward contaminant transport through the unsaturated zone occurs through various processes and pathways; this can lead to a broad distribution of contaminant traveltimes, including exceedingly slow and unexpectedly fast extremes. Though the bulk of mobile contaminant arrives between the time-scale end members, the fastest contaminant transport speed, in other words the speed determined by the combination of possible processes and pathways that would bring a measureable quantity of contaminant to the aquifer in the shortest time, carries particular regulatory significance because of its relevance in formulating the most conservative hazard-prevention scenarios. Unsaturated-zone flow is usually modeled as a diffusive process responding to gravity and pressure gradients as mediated by the unsaturated hydraulic properties of the materials traversed. The mathematical formulation of the diffuse-flow concept is known as Richards' equation, which when coupled to a solute transport equation, such as the advection-dispersion equation, provides a framework to simulate contaminant migration in the unsaturated zone. In recent decades awareness has increased that much fluid flow and contaminant transport within the unsaturated zone takes place as preferential flow, faster than would be predicted by the coupled Richards' and advection-dispersion equations with hydraulic properties estimated by traditional means. At present the hydrologic community has not achieved consensus as to whether a modification of Richards' equation, or a fundamentally different formulation, would best quantify preferential flow. Where the fastest contaminant transport speed is what needs to be estimated, there is the possibility of simplification of the evaluation process. One way of doing so is by a two-step process in which the first step is to evaluate whether significant preferential flow and solute transport is possible for the media and conditions of concern. The second step is to carry out (a) a basic Richards' and advection-dispersion equation analysis if it is concluded that preferential flow is not possible or (b) an analysis that considers only the fastest possible preferential-flow processes, if preferential flow is possible. For the preferential-flow situation, a recently published model describable as a Source-Responsive Preferential-Flow (SRPF) model is an easily applied option. This report documents the application of this two-step process to flow through the thick unsaturated zones of Rainier Mesa and Shoshone Mountain in the Nevada Test Site. Application of the SRPF model involves distinguishing between continuous and intermittent water supply to preferential flow paths. At Rainier Mesa and Shoshone Mountain this issue is complicated by the fact that contaminant travel begins at a location deep in the subsurface, where there may be perched water that may or may not act like a continuous supply, depending on such features as the connectedness of fractures and the nature of impeding layers. We have treated this situation by hypothesizing both continuous and intermittent scenarios for contaminant transport to the carbonate aquifer and reporting estimation of the fastest speed for both of th

Estimation of unsaturated zone traveltimes for Rainier Mesa and Shoshone Mountain, Nevada Test Site, Nevada, using a source-responsive preferential-flow model

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

Brian A. Ebel; John R. Nimmo

2009-09-11

Traveltimes for contaminant transport by water from a point in the unsaturated zone to the saturated zone are a concern at Rainier Mesa and Shoshone Mountain in the Nevada Test Site, Nevada. Where nuclear tests were conducted in the unsaturated zone, contaminants must traverse hundreds of meters of variably saturated rock before they enter the saturated zone in the carbonate rock, where the regional groundwater system has the potential to carry them substantial distances to a location of concern. The unsaturated-zone portion of the contaminant transport path may cause a significant delay, in addition to the time required to travelmore » within the saturated zone, and thus may be important in the overall evaluation of the potential hazard from contamination. Downward contaminant transport through the unsaturated zone occurs through various processes and pathways; this can lead to a broad distribution of contaminant traveltimes, including exceedingly slow and unexpectedly fast extremes. Though the bulk of mobile contaminant arrives between the time-scale end members, the fastest contaminant transport speed, in other words the speed determined by the combination of possible processes and pathways that would bring a measureable quantity of contaminant to the aquifer in the shortest time, carries particular regulatory significance because of its relevance in formulating the most conservative hazard-prevention scenarios. Unsaturated-zone flow is usually modeled as a diffusive process responding to gravity and pressure gradients as mediated by the unsaturated hydraulic properties of the materials traversed. The mathematical formulation of the diffuse-flow concept is known as Richards' equation, which when coupled to a solute transport equation, such as the advection-dispersion equation, provides a framework to simulate contaminant migration in the unsaturated zone. In recent decades awareness has increased that much fluid flow and contaminant transport within the unsaturated zone takes place as preferential flow, faster than would be predicted by the coupled Richards' and advection-dispersion equations with hydraulic properties estimated by traditional means. At present the hydrologic community has not achieved consensus as to whether a modification of Richards' equation, or a fundamentally different formulation, would best quantify preferential flow. Where the fastest contaminant transport speed is what needs to be estimated, there is the possibility of simplification of the evaluation process. One way of doing so is by a two-step process in which the first step is to evaluate whether significant preferential flow and solute transport is possible for the media and conditions of concern. The second step is to carry out (a) a basic Richards' and advection-dispersion equation analysis if it is concluded that preferential flow is not possible or (b) an analysis that considers only the fastest possible preferential-flow processes, if preferential flow is possible. For the preferential-flow situation, a recently published model describable as a Source-Responsive Preferential-Flow (SRPF) model is an easily applied option. This report documents the application of this two-step process to flow through the thick unsaturated zones of Rainier Mesa and Shoshone Mountain in the Nevada Test Site. Application of the SRPF model involves distinguishing between continuous and intermittent water supply to preferential flow paths. At Rainier Mesa and Shoshone Mountain this issue is complicated by the fact that contaminant travel begins at a location deep in the subsurface, where there may be perched water that may or may not act like a continuous supply, depending on such features as the connectedness of fractures and the nature of impeding layers. We have treated this situation by hypothesizing both continuous and intermittent scenarios for contaminant transport to the carbonate aquifer and reporting estimation of the fastest speed for both of these end members.« less

Numerical study of the effects of icing on viscous flow over wings

NASA Technical Reports Server (NTRS)

Sankar, L. N.

1994-01-01

An improved hybrid method for computing unsteady compressible viscous flows is presented. This method divides the computational domain into two zones. In the outer zone, the unsteady full-potential equation (FPE) is solved. In the inner zone, the Navier-Stokes equations are solved using a diagonal form of an alternating-direction implicit (ADI) approximate factorization procedure. The two zones are tightly coupled so that steady and unsteady flows may be efficiently solved. Characteristic-based viscous/inviscid interface boundary conditions are employed to avoid spurious reflections at that interface. The resulting CPU times are less than 60 percent of that required for a full-blown Navier-Stokes analysis for steady flow applications and about 60 percent of the Navier-Stokes CPU times for unsteady flows in non-vector processing machines. Applications of the method are presented for a rectangular NACA 0012 wing in low subsonic steady flow at moderate and high angles of attack, and for an F-5 wing in steady and unsteady subsonic and transonic flows. Steady surface pressures are in very good agreement with experimental data and are essentially identical to Navier-Stokes predictions. Density contours show that shocks cross the viscous/inviscid interface smoothly, so that the accuracy of full Navier-Stokes equations can be retained with a significant savings in computational time.

Coronary physiological assessment combining fractional flow reserve and index of microcirculatory resistance in patients undergoing elective percutaneous coronary intervention with grey zone fractional flow reserve.

PubMed

Niida, Takayuki; Murai, Tadashi; Yonetsu, Taishi; Kanaji, Yoshihisa; Usui, Eisuke; Matsuda, Junji; Hoshino, Masahiro; Araki, Makoto; Yamaguchi, Masao; Hada, Masahiro; Ichijyo, Sadamitsu; Hamaya, Rikuta; Kanno, Yoshinori; Isobe, Mitsuaki; Kakuta, Tsunekazu

2018-03-08

The aim of this study is to investigate the association between fractional flow reserve (FFR) values and change in coronary physiological indices after elective percutaneous coronary intervention (PCI). Decision making for revascularization when FFR is 0.75-0.80 is controversial. A retrospective analysis was performed of 296 patients with stable angina pectoris who underwent physiological examinations before and after PCI. To investigate the differences of coronary flow improvement between territories with low-FFR (<0.75) and grey-zone FFR (0.75-0.80), serial changes in physiological indices including mean transit time (Tmn), coronary flow reserve (CFR), and index of microcirculatory resistance (IMR) were compared between these two groups. Compared to low-FFR territories, grey-zone FFR territories showed significantly lower prevalence of Tmn shortening, CFR improvement, and decrease in IMR (Tmn shorting, 63.9% vs. 87.0%, P < .001; CFR improvement, 63.0% vs. 75.7%, P = .019; IMR decrease, 51.3% vs. 63.3%, P = .040) and lower extent of their absolute changes (Tmn shorting, 0.06 (-0.03 to 0.16) vs. 0.22 (0.07-0.45), P < .001; CFR improvement, 0.45 (-0.32 to 1.87) vs. 1.08 (0.02-2.44), P < .01; IMR decrease, 0.2 (-44.0 to 31.3) vs. 2.9 (-2.9 to 11.8), P = .022). Multivariate analysis showed that pre-PCI IMR predicted improved coronary flow profile in both groups, whereas pre-PCI FFR predicted increased coronary flow indices in low-FFR territories. Worsening of physiological indices after PCI was not uncommon in territories showing grey-zone FFR. Physiological assessment combining FFR and IMR may help identify patients who may benefit by PCI, particularly those in the grey zone. © 2018 Wiley Periodicals, Inc.

Tritium and 36Cl as constraints on fast fracture flow and percolation flux in the unsaturated zone at Yucca Mountain

NASA Astrophysics Data System (ADS)

Guerin, Marianne

2001-10-01

An analysis of tritium and 36Cl data collected at Yucca Mountain, Nevada suggests that fracture flow may occur at high velocities through the thick unsaturated zone. The mechanisms and extent of this "fast flow" in fractures at Yucca Mountain are investigated with data analysis, mixing models and several one-dimensional modeling scenarios. The model results and data analysis provide evidence substantiating the weeps model [Gauthier, J.H., Wilson, M.L., Lauffer, F.C., 1992. Proceedings of the Third Annual International High-level Radioactive Waste Management Conference, vol. 1, Las Vegas, NV. American Nuclear Society, La Grange Park, IL, pp. 891-989] and suggest that fast flow in fractures with minimal fracture-matrix interaction may comprise a substantial proportion of the total infiltration through Yucca Mountain. Mixing calculations suggest that bomb-pulse tritium measurements, in general, represent the tail end of travel times for thermonuclear-test-era (bomb-pulse) infiltration. The data analysis shows that bomb-pulse tritium and 36Cl measurements are correlated with discrete features such as horizontal fractures and areas where lateral flow may occur. The results presented here imply that fast flow in fractures may be ubiquitous at Yucca Mountain, occurring when transient infiltration (storms) generates flow in the connected fracture network.

Tritium and 36Cl as constraints on fast fracture flow and percolation flux in the unsaturated zone at Yucca Mountain.

PubMed

Guerin, M

2001-10-01

An analysis of tritium and 36Cl data collected at Yucca Mountain, Nevada suggests that fracture flow may occur at high velocities through the thick unsaturated zone. The mechanisms and extent of this "fast flow" in fractures at Yucca Mountain are investigated with data analysis, mixing models and several one-dimensional modeling scenarios. The model results and data analysis provide evidence substantiating the weeps model [Gauthier, J.H., Wilson, M.L., Lauffer, F.C., 1992. Proceedings of the Third Annual International High-level Radioactive Waste Management Conference, vol. 1, Las Vegas, NV. American Nuclear Society, La Grange Park, IL, pp. 891-989] and suggest that fast flow in fractures with minimal fracture-matrix interaction may comprise a substantial proportion of the total infiltration through Yucca Mountain. Mixing calculations suggest that bomb-pulse tritium measurements, in general, represent the tail end of travel times for thermonuclear-test-era (bomb-pulse) infiltration. The data analysis shows that bomb-pulse tritium and 36Cl measurements are correlated with discrete features such as horizontal fractures and areas where lateral flow may occur. The results presented here imply that fast flow in fractures may be ubiquitous at Yucca Mountain, occurring when transient infiltration (storms) generates flow in the connected fracture network.

MPS solidification model. Analysis and calculation of macrosegregation in a casting ingot

NASA Technical Reports Server (NTRS)

Poirier, D. R.; Maples, A. L.

1985-01-01

Work performed on several existing solidification models for which computer codes and documentation were developed is presented. The models describe the solidification of alloys in which there is a time varying zone of coexisting solid and liquid phases; i.e., the S/L zone. The primary purpose of the models is to calculate macrosegregation in a casting or ingot which results from flow of interdendritic liquid in this S/L zone during solidification. The flow, driven by solidification contractions and by gravity acting on density gradients in the interdendritic liquid, is modeled as flow through a porous medium. In Model 1, the steady state model, the heat flow characteristics are those of steady state solidification; i.e., the S/L zone is of constant width and it moves at a constant velocity relative to the mold. In Model 2, the unsteady state model, the width and rate of movement of the S/L zone are allowed to vary with time as it moves through the ingot. Each of these models exists in two versions. Models 1 and 2 are applicable to binary alloys; models 1M and 2M are applicable to multicomponent alloys.

Coupled semivariogram uncertainty of hydrogeological and geophysical data on capture zone uncertainty analysis

USGS Publications Warehouse

Rahman, A.; Tsai, F.T.-C.; White, C.D.; Willson, C.S.

2008-01-01

This study investigates capture zone uncertainty that relates to the coupled semivariogram uncertainty of hydrogeological and geophysical data. Semivariogram uncertainty is represented by the uncertainty in structural parameters (range, sill, and nugget). We used the beta distribution function to derive the prior distributions of structural parameters. The probability distributions of structural parameters were further updated through the Bayesian approach with the Gaussian likelihood functions. Cokriging of noncollocated pumping test data and electrical resistivity data was conducted to better estimate hydraulic conductivity through autosemivariograms and pseudo-cross-semivariogram. Sensitivities of capture zone variability with respect to the spatial variability of hydraulic conductivity, porosity and aquifer thickness were analyzed using ANOVA. The proposed methodology was applied to the analysis of capture zone uncertainty at the Chicot aquifer in Southwestern Louisiana, where a regional groundwater flow model was developed. MODFLOW-MODPATH was adopted to delineate the capture zone. The ANOVA results showed that both capture zone area and compactness were sensitive to hydraulic conductivity variation. We concluded that the capture zone uncertainty due to the semivariogram uncertainty is much higher than that due to the kriging uncertainty for given semivariograms. In other words, the sole use of conditional variances of kriging may greatly underestimate the flow response uncertainty. Semivariogram uncertainty should also be taken into account in the uncertainty analysis. ?? 2008 ASCE.

Assessing Landslide Mobility Using GIS: Application to Kosrae, Micronesia

NASA Astrophysics Data System (ADS)

Reid, M. E.; Brien, D. L.; Godt, J.; Schmitt, R. G.; Harp, E. L.

2015-12-01

Deadly landslides are often mobile landslides, as exemplified by the disastrous landslide that occurred near Oso, Washington in 2014 killing 43. Despite this association, many landslide susceptibility maps do not identify runout areas. We developed a simple, GIS-based method for identifying areas potentially overrun by mobile slides and debris flows. Our method links three processes within a DEM landscape: landslide initiation, transport, and debris-flow inundation (from very mobile slides). Given spatially distributed shear strengths, we first identify initiation areas using an infinite-slope stability analysis. We then delineate transport zones, or regions of potential entrainment and/or deposition, using a height/length runout envelope. Finally, where these transport zones intersect the channel network, we start debris-flow inundation zones. The extent of inundation is computed using the USGS model Laharz, modified to include many debris-flow locations throughout a DEM. Potential debris-flow volumes are computed from upslope initiation areas and typical slide thicknesses. We applied this approach to the main island of Kosrae State, Federated States of Micronesia (FSM). In 2002, typhoon Chata'an triggered numerous landslides on the neighboring islands of Chuuk State, FSM, resulting in 43 fatalities. Using an infinite-slope stability model calibrated to the Chuuk event, we identified potential landslide initiation areas on Kosrae. We then delineated potential transport zones using a 20º runout envelope, based on runout observations from Chuuk. Potential debris-flow inundation zones were then determined using Laharz. Field inspections on Kosrae revealed that our resulting susceptibility map correctly classified areas covered by previous debris-flow deposits and did not include areas covered by fluvial deposits. Our map has the advantage of providing a visual tool to portray initiation, transport, and runout zones from mobile landslides.

Analysis of an anisotropic coastal aquifer system using variable-density flow and solute transport simulation

USGS Publications Warehouse

Souza, W.R.; Voss, C.I.

1987-01-01

The groundwater system in southern Oahu, Hawaii consists of a thick, areally extensive freshwater lens overlying a zone of transition to a thick saltwater body. This system is analyzed in cross section with a variable-density groundwater flow and solute transport model on a regional scale. The simulation is difficult, because the coastal aquifer system has a saltwater transition zone that is broadly dispersed near the discharge area, but is very sharply defined inland. Steady-state simulation analysis of the transition zone in the layered basalt aquifer of southern Oahu indicates that a small transverse dispersivity is characteristic of horizontal regional flow. Further, in this system flow is generally parallel to isochlors and steady-state behavior is insensitive to the longitudinal dispersivity. Parameter analysis identifies that only six parameters control the complex hydraulics of the system: horizontal and vertical hydraulic conductivity of the basalt aquifer; hydraulic conductivity of the confining "caprock" layer; leakance below the caprock; specific yield; and aquifer matrix compressibility. The best-fitting models indicate the horizontal hydraulic conductivity is significantly greater than the vertical hydraulic conductivity. These models give values for specific yield and aquifer compressibility which imply a considerable degree of compressive storage in the water table aquifer. ?? 1987.

Primary weathering rates, water transit times, and concentration-discharge relations: A theoretical analysis for the critical zone

NASA Astrophysics Data System (ADS)

Ameli, Ali A.; Beven, Keith; Erlandsson, Martin; Creed, Irena F.; McDonnell, Jeffrey J.; Bishop, Kevin

2017-01-01

The permeability architecture of the critical zone exerts a major influence on the hydrogeochemistry of the critical zone. Water flow path dynamics drive the spatiotemporal pattern of geochemical evolution and resulting streamflow concentration-discharge (C-Q) relation, but these flow paths are complex and difficult to map quantitatively. Here we couple a new integrated flow and particle tracking transport model with a general reversible Transition State Theory style dissolution rate law to explore theoretically how C-Q relations and concentration in the critical zone respond to decline in saturated hydraulic conductivity (Ks) with soil depth. We do this for a range of flow rates and mineral reaction kinetics. Our results show that for minerals with a high ratio of equilibrium concentration (Ceq) to intrinsic weathering rate (Rmax), vertical heterogeneity in Ks enhances the gradient of weathering-derived solute concentration in the critical zone and strengthens the inverse stream C-Q relation. As CeqRmax decreases, the spatial distribution of concentration in the critical zone becomes more uniform for a wide range of flow rates, and stream C-Q relation approaches chemostatic behavior, regardless of the degree of vertical heterogeneity in Ks. These findings suggest that the transport-controlled mechanisms in the hillslope can lead to chemostatic C-Q relations in the stream while the hillslope surface reaction-controlled mechanisms are associated with an inverse stream C-Q relation. In addition, as CeqRmax decreases, the concentration in the critical zone and stream become less dependent on groundwater age (or transit time).

NaturAnalogs for the Unsaturated Zone

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

A. Simmons; A. Unger; M. Murrell

2000-03-08

The purpose of this Analysis/Model Report (AMR) is to document natural and anthropogenic (human-induced) analog sites and processes that are applicable to flow and transport processes expected to occur at the potential Yucca Mountain repository in order to build increased confidence in modeling processes of Unsaturated Zone (UZ) flow and transport. This AMR was prepared in accordance with ''AMR Development Plan for U0135, Natural Analogs for the UZ'' (CRWMS 1999a). Knowledge from analog sites and processes is used as corroborating information to test and build confidence in flow and transport models of Yucca Mountain, Nevada. This AMR supports the Unsaturatedmore » Zone (UZ) Flow and Transport Process Model Report (PMR) and the Yucca Mountain Site Description. The objectives of this AMR are to test and build confidence in the representation of UZ processes in numerical models utilized in the UZ Flow and Transport Model. This is accomplished by: (1) applying data from Boxy Canyon, Idaho in simulations of UZ flow using the same methodologies incorporated in the Yucca Mountain UZ Flow and Transport Model to assess the fracture-matrix interaction conceptual model; (2) Providing a preliminary basis for analysis of radionuclide transport at Pena Blanca, Mexico as an analog of radionuclide transport at Yucca Mountain; and (3) Synthesizing existing information from natural analog studies to provide corroborating evidence for representation of ambient and thermally coupled UZ flow and transport processes in the UZ Model.« less

Tularosa Basin Play Fairway Analysis: Partial Basin and Range Heat and Zones of Critical Stress Maps

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

Adam Brandt

Interpolated maps of heat flow, temperature gradient, and quartz geothermometers are included as TIF files. Zones of critical stress map is also included as a TIF file. The zones are given a 5km diameter buffer. The study area is only a part of the Basin and Range, but it does includes the Tularosa Basin.

A multitracer system for multizone ventilation measurement

NASA Astrophysics Data System (ADS)

Sherman, Max

1990-09-01

Mass transfer due to pressure-driven air flow is one of the most important processes for determining both environmental quality and energy requirements in buildings. Heat, moisture, and contaminants are all transported by air movement between indoors and outdoors as well as between different zones within a building. Measurement of these air flows is critical to understanding the performance of buildings. Virtually all measurements of ventilation are made using the dilution of a tracer gas. The vast majority of such measurements have been made in a single zone, using a single tracer gas. For the past several years LBL has been developing the MultiTracer Measurement System (MTMS) to provide full multizone air flow information in an accurate, real-time manner. MTMS is based on a quadrupole mass spectrometer to provide high-speed concentration analysis of multiple tracer gases in the (low) ppm level that are injected into multiple zones using mass-flow controllers. The measurement and injection system is controlled by a PC and can measure all concentrations in all zones (and adjust the injected tracer flows) within 2 min and can operate unattended for weeks. The resulting injection rate and concentration data can be analyzed to infer the bulk air movement between zones. The system also measures related quantities such as weather and zonal temperature to assist in the data interpretation. Using MTMS, field measurements have been made for the past two years.

Model Fit to Experimental Data for Foam-Assisted Deep Vadose Zone Remediation

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

Roostapour, A.; Lee, G.; Zhong, Lirong

2014-01-15

Foam has been regarded as a promising means of remeidal amendment delivery to overcome subsurface heterogeneity in subsurface remediation processes. This study investigates how a foam model, developed by Method of Characteristics and fractional flow analysis in the companion paper of Roostapour and Kam (2012), can be applied to make a fit to a set of existing laboratory flow experiments (Zhong et al., 2009) in an application relevant to deep vadose zone remediation. This study reveals a few important insights regarding foam-assisted deep vadose zone remediation: (i) the mathematical framework established for foam modeling can fit typical flow experiments matchingmore » wave velocities, saturation history , and pressure responses; (ii) the set of input parameters may not be unique for the fit, and therefore conducting experiments to measure basic model parameters related to relative permeability, initial and residual saturations, surfactant adsorption and so on should not be overlooked; and (iii) gas compressibility plays an important role for data analysis, thus should be handled carefully in laboratory flow experiments. Foam kinetics, causing foam texture to reach its steady-state value slowly, may impose additional complications.« less

Simultaneous injection-effective mixing analysis of palladium.

PubMed

Teshima, Norio; Noguchi, Daisuke; Joichi, Yasutaka; Lenghor, Narong; Ohno, Noriko; Sakai, Tadao; Motomizu, Shoji

2010-01-01

A novel concept of simultaneous injection-effective mixing analysis (SIEMA) is proposed, and a SIEMA method applied to the spectrophotometric determination of palladium using a water-soluble chromogenic reagent has been demonstrated. The flow configuration of SIEMA is a hybrid format of flow injection analysis (FIA), sequential injection analysis (SIA) and multicommutation in flow-based analysis. Sample and reagent solutions are aspirated into each holding coil through each solenoid valve by a syringe pump, and then the zones are simultaneously dispensed (injected) into a mixing coil by reversed flow toward a detector through a confluence point. This results in effective mixing and rapid detection with low reagent consumption.

Regeneratively cooled transition duct with transversely buffered impingement nozzles

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

Morrison, Jay A; Lee, Ching-Pang; Crawford, Michael E

2015-04-21

A cooling arrangement (56) having: a duct (30) configured to receive hot gases (16) from a combustor; and a flow sleeve (50) surrounding the duct and defining a cooling plenum (52) there between, wherein the flow sleeve is configured to form impingement cooling jets (70) emanating from dimples (82) in the flow sleeve effective to predominately cool the duct in an impingement cooling zone (60), and wherein the flow sleeve defines a convection cooling zone (64) effective to cool the duct solely via a cross-flow (76), the cross-flow comprising cooling fluid (72) exhausting from the impingement cooling zone. In themore » impingement cooling zone an undimpled portion (84) of the flow sleeve tapers away from the duct as the undimpled portion nears the convection cooling zone. The flow sleeve is configured to effect a greater velocity of the cross-flow in the convection cooling zone than in the impingement cooling zone.« less

Evidence of Enhanced Subrosion in a Fault Zone and Characterization of Hazard Zones with Elastic Parameters derived from SH-wave reflection Seismics and VSP

NASA Astrophysics Data System (ADS)

Wadas, S. H.; Tanner, D. C.; Tschache, S.; Polom, U.; Krawczyk, C. M.

2017-12-01

Subrosion, the dissolution of soluble rocks, e.g., sulfate, salt, or carbonate, requires unsaturated water and fluid pathways that enable the water to flow through the subsurface and generate cavities. Over time, different structures can occur that depend on, e.g., rock solubility, flow rate, and overburden type. The two main structures are sinkholes and depressions. To analyze the link between faults, groundwater flow, and soluble rocks, and to determine parameters that are useful to characterize hazard zones, several shear-wave (SH) reflection seismic profiles were surveyed in Thuringia in Germany, where Permian sulfate rocks and salt subcrop close to the surface. From the analysis of the seismic sections we conclude that areas affected by tectonic deformation phases are prone to enhanced subrosion. The deformation of fault blocks leads to the generation of a damage zone with a dense fracture network. This increases the rock permeability and thus serves as a fluid pathway for, e.g., artesian-confined groundwater. The more complex the fault geometry and the more interaction between faults, the more fractures are generated, e.g., in a strike slip-fault zone. The faults also act as barriers for horizontal groundwater flow perpendicular to the fault surfaces and as conduits for groundwater flow along the fault strike. In addition, seismic velocity anomalies and attenuation of seismic waves are observed. Low velocities <200 m/s and high attenuation may indicate areas affected by subrosion. Other parameters that characterize the underground stability are the shear modulus and the Vp/Vs ratio. The data revealed zones of low shear modulus <100 MPa and high Vp/Vs ratio >2.5, which probably indicate unstable areas due to subrosion. Structural analysis of S-wave seismics is a valuable tool to detect near-surface faults in order to determine whether or not an area is prone to subrosion. The recognition of even small fault blocks can help to better understand the hydrodynamic groundwater conditions, which is another key factor to understand the subrosion process. The elastic parameters derived from seismic velocities can help to identify possible zones of instability.

Air Change Rates and Interzonal Flows in Residences, and the Need for Multi-Zone Models for Exposure and Health Analysis

EPA Science Inventory

Air change rates (ACRs) and interzonal flows are key determinants of indoor air quality (IAQ) and building energy use. This paper characterizes ACRs and interzonal flows in 126 houses, and evaluates effects of these parameters on IAQ. ACRs measured using weeklong tracer measureme...

Aerodynamic and heat transfer analysis of the low aspect ratio turbine using a 3D Navier-Stokes code

NASA Astrophysics Data System (ADS)

Choi, D.; Knight, C. J.

1991-06-01

The single-stage, high-pressure ratio Garrett Low Aspect Ratio Turbine (LART) test data obtained in a shock tunnel are employed as a basis for evaluating a new three-dimensional Navier Stokes code based on the O-H grid system. It uses Coakley's two-equation turbulence modeling with viscous sublayer resolution. For the nozzle guide vanes, calculations were made based on two grid zones: an O-grid zone wrapping around airfoil and an H-grid zone outside of the O-grid zone, including the regions upstream of the leadig edge and downstream of the trailing edge. For the rotor blade row, a third O-grid zone was added for the tip-gap region leakage flow. The computational results compare well with experiment. These comparisons include heat transfer distributions on the airfoils and end-walls. The leakage flow through the tip-gap clearance is well resolved.

Geometric situation of points of division of regions of direct and return currency in channels with the presence of heating zone limited on the longitudinal coordinate

NASA Astrophysics Data System (ADS)

Gerasimov, A.; Kirpichnikov, A.; Sabirova, F.

2018-03-01

The analysis of energy balance equation for viscous laminar flow of fluid or gas in the cylindrical channel in the area (zone) of warm up bounded along the longitudinal coordinate is made. It was found that at laminar flow of fluid or gas in a round pipe, in each warm up area bounded along the longitudinal coordinate there are the areas of direct and reverse flows separated by a plane that is a locus of points where temperature is maximal for each fixed value of radial coordinate r.

Optical properties of zirconium oxynitride films: The effect of composition, electronic and crystalline structures

NASA Astrophysics Data System (ADS)

Carvalho, P.; Borges, J.; Rodrigues, M. S.; Barradas, N. P.; Alves, E.; Espinós, J. P.; González-Elipe, A. R.; Cunha, L.; Marques, L.; Vasilevskiy, M. I.; Vaz, F.

2015-12-01

This work is devoted to the investigation of zirconium oxynitride (ZrOxNy) films with varied optical responses prompted by the variations in their compositional and structural properties. The films were prepared by dc reactive magnetron sputtering of Zr, using Ar and a reactive gas mixture of N2 + O2 (17:3). The colour of the films changed from metallic-like, very bright yellow-pale and golden yellow, for low gas flows to red-brownish for intermediate gas flows. Associated to this colour change there was a significant decrease of brightness. With further increase of the reactive gas flow, the colour of the samples changed from red-brownish to dark blue or even to interference colourations. The variations in composition disclosed the existence of four different zones, which were found to be closely related with the variations in the crystalline structure. XRD analysis revealed the change from a B1 NaCl face-centred cubic zirconium nitride-type phase for films prepared with low reactive gas flows, towards a poorly crystallized over-stoichiometric nitride phase, which may be similar to that of Zr3N4 with some probable oxygen inclusions within nitrogen positions, for films prepared with intermediate reactive gas flows. For high reactive gas flows, the films developed an oxynitride-type phase, similar to that of γ-Zr2ON2 with some oxygen atoms occupying some of the nitrogen positions, evolving to a ZrO2 monoclinic type structure within the zone where films were prepared with relatively high reactive gas flows. The analysis carried out by reflected electron energy loss spectroscopy (REELS) revealed a continuous depopulation of the d-band and an opening of an energy gap between the valence band (2p) and the Fermi level close to 5 eV. The ZrN-based coatings (zone I and II) presented intrinsic colourations, with a decrease in brightness and a colour change from bright yellow to golden yellow, red brownish and dark blue. Associated to these changes, there was also a shift of the reflectivity minimum to lower energies, with the increase of the non-metallic content. The samples lying in the two last zones (zone III, oxynitride and zone IV, oxide films) revealed a typical semi-transparent-optical behaviour showing interference-like colourations only due to the complete depopulation of the d band at the Fermi level. The samples lying in these zones presented also an increase of the optical bandgap from 2 to 3.6 eV.

A computational analysis of different endograft designs for Zone 0 aortic arch repair.

PubMed

van Bakel, Theodorus M; Arthurs, Christopher J; van Herwaarden, Joost A; Moll, Frans L; Eagle, Kim A; Patel, Himanshu J; Trimarchi, Santi; Figueroa, C Alberto

2018-03-15

Aortic arch repair remains a major surgical challenge. Multiple manufacturers are developing branched endografts for Zone 0 endovascular repair, extending the armamentarium for minimally invasive treatment of aortic arch pathologies. We hypothesize that the design of the Zone 0 endograft has a significant impact on the postoperative haemodynamic performance, particularly in the cervical arteries. The goal of our study was to compare the postoperative haemodynamic performance of different Zone 0 endograft designs. Patient-specific, clinically validated, computational fluid dynamics simulations were performed in a 71-year-old woman with a 6.5-cm saccular aortic arch aneurysm. Additionally, 4 endovascular repair scenarios using different endograft designs were created. Haemodynamic performance was evaluated by calculation of postoperative changes in blood flow and platelet activation potential (PLAP) in the cervical arteries. Preoperative cervical blood flow and mean PLAP were 1080 ml/min and 151.75, respectively. Cervical blood flow decreased and PLAP increased following endovascular repair in all scenarios. Endografts with 2 antegrade inner branches performed better compared to single-branch endografts. Scenario 3 performed the worst with a decrease in the total cervical blood flow of 4.8%, a decrease in the left hemisphere flow of 6.7% and an increase in the mean PLAP of 74.3%. Endograft design has a significant impact on haemodynamic performance following Zone 0 endovascular repair, potentially affecting cerebral blood flow during follow-up. Our results demonstrate the use of computational modelling for virtual testing of therapeutic interventions and underline the need to monitor the long-term outcomes in this cohort of patients.

Simulation of wake effects between two wind farms

NASA Astrophysics Data System (ADS)

Hansen, K. S.; Réthoré, P.-E.; Palma, J.; Hevia, B. G.; Prospathopoulos, J.; Peña, A.; Ott, S.; Schepers, G.; Palomares, A.; van der Laan, M. P.; Volker, P.

2015-06-01

SCADA data, recorded on the downstream wind farm, has been used to identify flow cases with visible clustering effects. The inflow condition is derived from a partly undisturbed wind turbine, due to lack of mast measurements. The SCADA data analysis concludes that centre of the deficit for the downstream wind farm with disturbed inflow has a distinct visible maximum deficit zone located only 5-10D downstream from the entrance. This zone, representing 20-30% speed reduction, increases and moves downstream for increasing cluster effect and is not visible outside a flow sector of 20-30°. The eight flow models represented in this benchmark include both RANS models, mesoscale models and engineering models. The flow cases, identified according to the wind speed level and inflow sector, have been simulated and validated with the SCADA results. The model validation concludes that all models more or less are able to predict the location and size of the deficit zone inside the downwind wind farm.

Numerical simulation of steady state three-dimensional groundwater flow near lakes

USGS Publications Warehouse

Winter, Thomas C.

1978-01-01

Numerical simulation of three-dimensional groundwater flow near lakes shows that the continuity of the boundary encompassing the local groundwater flow system associated with a lake is the key to understanding the interaction of a lake with the groundwater system. The continuity of the boundary can be determined by the presence of a stagnation zone coinciding with the side of the lake nearest the downgradient side of the groundwater system. For most settings modeled in this study the stagnation zone underlies the lakeshore, and it generally follows its curvature. The length of the stagnation zone is controlled by the geometry of the lake's drainage basin divide on the side of the lake nearest the downgradient side of the groundwater system. In the case of lakes that lose water to the groundwater system, three-dimensional modeling also allows for estimating the area of lake bed through which outseepage takes place. Analysis of the effects of size and lateral and vertical distribution of aquifers within the groundwater system on the outseepage from lakes shows that the position of the center point of the aquifer relative to the littoral zone on the side of the lake nearest the downgradient side of the groundwater system is a critical factor. If the center point is downslope from this part of the littoral zone, the local flow system boundary tends to be weak or outseepage occurs. If the center point is upslope from this littoral zone, the stagnation zone tends to be stronger (to have a higher head in relation to lake level), and outseepage is unlikely to occur.

Numerical simulation of the vortical flow around a pitching airfoil

NASA Astrophysics Data System (ADS)

Fu, Xiang; Li, Gaohua; Wang, Fuxin

2017-04-01

In order to study the dynamic behaviors of the flapping wing, the vortical flow around a pitching NACA0012 airfoil is investigated. The unsteady flow field is obtained by a very efficient zonal procedure based on the velocity-vorticity formulation and the Reynolds number based on the chord length of the airfoil is set to 1 million. The zonal procedure divides up the whole computation domain in to three zones: potential flow zone, boundary layer zone and Navier-Stokes zone. Since the vorticity is absent in the potential flow zone, the vorticity transport equation needs only to be solved in the boundary layer zone and Navier-Stokes zone. Moreover, the boundary layer equations are solved in the boundary layer zone. This arrangement drastically reduces the computation time against the traditional numerical method. After the flow field computation, the evolution of the vortices around the airfoil is analyzed in detail.

Characterizing a middle to upper crustal shear zone: Microstructures, quartz c-axis fabrics, deformation temperatures and flow vorticity analysis of the northern Ailao Shan-Red River shear zone, China

NASA Astrophysics Data System (ADS)

Wu, Wenbin; Liu, Junlai; Zhang, Lisheng; Qi, Yinchuan; Ling, Chengyang

2017-05-01

Structural and microstructural characteristics, deformation temperatures and flow vorticities of the northern Ailao Shan (ALS) high-grade metamorphic belt provide significant information regarding the nature and tectonic evolution of the Ailao Shan-Red River (ASRR) shear zone. Mineral deformation mechanisms, quartz lattice-preferred orientation (LPO) patterns and the opening angles of quartz c-axis fabrics of samples from the Gasa section indicate that the northern ALS high-grade metamorphic belt has experienced progressive shear deformation. The early stage shearing is characterized by a gradual decrease of deformation temperatures from >650 °C at the northeastern unit to ca. 300 °C at the southwestern unit, that results in the formation of migmatites, mylonitic gneisses, thin bedded mylonites, mylonitic schists and phyllonites from the NE to SW across the strike of the shear zone. The late stage low-temperature (300-400 °C) shearing is superimposed on the early deformation throughout the belt with the formation of discrete, small-scale shear zones, especially in the thin-banded mylonitic rocks along both margins. The kinematic vorticity values estimated by rotated rigid porphyroclast method and oblique grain-shaped/quartz c-axis-fabric method imply that the general shear-dominated flow (0.49-0.77) progressively changed to a simple shear-dominated flow (0.77-1) toward the late stage of ductile deformation. The two stages of shearing are consistent with early shortening-dominated and late extrusion-controlled regional tectonic processes. The transition between them occurred at ca. 27 Ma in the ALS high-grade metamorphic belt along the ASRR shear zone. The large amount of strike-slip displacement along the ASRR shear zone is predominantly attributed to accelerated flow along the shear zone during the late extrusion-controlled tectonic process.

UAV-based remote sensing surveys of lava flow fields: a case study from Etna's 1974 channel-fed lava flows

NASA Astrophysics Data System (ADS)

Favalli, Massimiliano; Fornaciai, Alessandro; Nannipieri, Luca; Harris, Andrew; Calvari, Sonia; Lormand, Charline

2018-03-01

During an eruption, time scales of topographic change are fast and involve vertical and planimetric evolution of millimeters to meters as the event progresses. Repeat production of high spatial resolution terrain models of lava flow fields over time scales of a few hours is thus a high-value capability in tracking the buildup of the deposit. Among the wide range of terrestrial and aerial methods available to collect such topographic data, the use of an unmanned aerial vehicle (UAV) as an acquisition platform, together with structure from motion (SfM) photogrammetry, has become especially useful. This approach allows high-frequency production of centimeter-scale terrain models over kilometer-scale areas, including dangerous and inaccessible zones, with low cost and minimal hazard to personnel. This study presents the application of such an integrated UAV-SfM method to generate a high spatial resolution digital terrain model and orthomosaic of Mount Etna's January-February 1974 lava flow field. The SfM method, applied to images acquired using a UAV platform, enabled the extraction of a very high spatial resolution (20 cm) digital elevation model and the generation of a 3-cm orthomosaic covering an area of 1.35 km2. This spatial resolution enabled us to analyze the morphology of sub-meter-scale features, such as folds, blocks, and cracks, over kilometer-scale areas. The 3-cm orthomosaic allowed us to further push the analysis to centimeter-scale grain size distribution of the lava surface. Using these data, we define three types of crust structure and relate them to positions within a channel-fed ´áā flow system. These crust structures are (i) flow parallel shear lines, (ii) raft zones, and (iii) folded zones. Flow parallel shear lines are found at the channel edges, and are 2-m-wide and 0.25-m-deep zones running along the levee base and in which cracking is intense. They result from intense shearing between the moving channel lava and the static levee lava. In zones where initial levees are just beginning to form, these subtle features are the only marker that delimits the moving lava from the stagnant marginal lava. Rafts generally form as the system changes from a stable to a transitional channel regime. Over this 170-m-long zone, the channel broadens from 8 to 70 m and rafts are characterized by topographically higher and poorly cracked areas, surrounded by lower, heavily cracked areas. We interpret the rafts as forming due to breakup of crust zones, previously moving in a coherent manner in the narrow proximal channel reach. Folded zones involve arcuate, cross-flow ridges with their apexes pointing down-flow, where ridges have relatively small clasts and depressions are of coarser-grained breccia. Our folds have wavelengths of 10 m and amplitudes of 1 m; are found towards the flow front, down-flow of the raft zones; and are associated with piling up of lava behind a static or slowly moving flow front. The very high spatial resolution topographic data available from UAV-SfM allow us to resolve surfaces where roughness has a vertical and horizontal scale of variation that is less than 1 m. This is the case over pāhoehoe and ´áā flow surfaces, and thus allows us to explore those new structures that are only apparent in the sub-metric data. Moreover, during future eruptions, the possibility to acquire such information in near-real time will allow a prompt analysis of developing lava flow fields and structures therein, such as developing lava channel systems, so as to contribute to timely hazard assessment, modeling, and projections.

Correlation between Reynolds number and eccentricity effect in stenosed artery models.

PubMed

Javadzadegan, Ashkan; Shimizu, Yasutomo; Behnia, Masud; Ohta, Makoto

2013-01-01

Flow recirculation and shear strain are physiological processes within coronary arteries which are associated with pathogenic biological pathways. Distinct Quite apart from coronary stenosis severity, lesion eccentricity can cause flow recirculation and affect shear strain levels within human coronary arteries. The aim of this study is to analyse the effect of lesion eccentricity on the transient flow behaviour in a model of a coronary artery and also to investigate the correlation between Reynolds number (Re) and the eccentricity effect on flow behaviour. A transient particle image velocimetry (PIV) experiment was implemented in two silicone based models with 70% diameter stenosis, one with eccentric stenosis and one with concentric stenosis. At different times throughout the flow cycle, the eccentric model was always associated with a greater recirculation zone length, maximum shear strain rate and maximum axial velocity; however, the highest and lowest impacts of eccentricity were on the recirculation zone length and maximum shear strain rate, respectively. Analysis of the results revealed a negative correlation between the Reynolds number (Re) and the eccentricity effect on maximum axial velocity, maximum shear strain rate and recirculation zone length. As Re number increases the eccentricity effect on the flow behavior becomes negligible.

Nanoindentation study on the characteristic of shear transformation zone in a Pd-based bulk metallic glass during serrated flow

NASA Astrophysics Data System (ADS)

Liao, G. K.; Long, Z. L.; Zhao, M. S. Z.; Peng, L.; Chai, W.; Ping, Z. H.

2018-04-01

This paper presents the research on the evolution of shear transformation zone (STZ) in a Pd-based bulk metallic glass (BMG) during serrated flow under nanoindentation. A novel method of estimating the STZ volume through statistical analysis of the serrated flow behavior was proposed for the first time. Based on the proposed method, the STZ volume of the studied BMG at various peak loads have been systematically investigated. The results indicate that the measured STZ volumes are in good agreement with that documented in literature, and the STZ size exhibits an increasing trend during indentation. Moreover, the correlation between the serrated flow dynamics and the STZ activation has also been evaluated. It is found that the STZ activation can promote the formation of self-organized critical (SOC) state during serrated flow.

An analytic description of electrodynamic dispersion in free-flow zone electrophoresis.

PubMed

Dutta, Debashis

2015-07-24

The present work analyzes the electrodynamic dispersion of sample streams in a free-flow zone electrophoresis (FFZE) chamber resulting due to partial or complete blockage of electroosmotic flow (EOF) across the channel width by the sidewalls of the conduit. This blockage of EOF has been assumed to generate a pressure-driven backflow in the transverse direction for maintaining flow balance in the system. A parallel-plate based FFZE device with the analyte stream located far away from the channel side regions has been considered to simplify the current analysis. Applying a method-of-moments formulation, an analytic expression was derived for the variance of the sample zone at steady state as a function of its position in the separation chamber under these conditions. It has been shown that the increase in stream broadening due to the electrodynamic dispersion phenomenon is additive to the contributions from molecular diffusion and sample injection, and simply modifies the coefficient for the hydrodynamic dispersion term for a fixed lateral migration distance of the sample stream. Moreover, this dispersion mechanism can dominate the overall spatial variance of analyte zones when a significant fraction of the EOF is blocked by the channel sidewalls. The analysis also shows that analyte streams do not undergo any hydrodynamic broadening due to unwanted pressure-driven cross-flows in an FFZE chamber in the absence of a transverse electric field. The noted results have been validated using Monte Carlo simulations which further demonstrate that while the sample concentration profile at the channel outlet approaches a Gaussian distribution only in FFZE chambers substantially longer than the product of the axial pressure-driven velocity and the characteristic diffusion time in the system, the spatial variance of the exiting analyte stream is well described by the Taylor-Aris dispersion limit even in analysis ducts much shorter than this length scale. Copyright © 2015 Elsevier B.V. All rights reserved.

Slope stability in the critical zone: The relative influence of long vs. short-time scale soil and vegetation properties on debris-flow initiation during a catastrophic rainfall.

NASA Astrophysics Data System (ADS)

Rengers, F. K.; McGuire, L.; Coe, J. A.; Kean, J. W.; Baum, R. L.; Staley, D. M.; Godt, J.

2016-12-01

Within the critical zone there is a feedback between the state of soil and vegetation development, boundary conditions (e.g. topography, climate, hillslope aspect), and biogeochemical and geophysical process fluxes. Here we explore how one process—debris flows initiated by shallow landslides—is influenced by the critical zone development state and the imposed boundary conditions. In this study, we examine a rainstorm in September 2013 in the Colorado Front Range wherein 78% of 1138 debris flows were triggered on south-facing slopes. One hypothesis is that debris-flow initiation sites are controlled by long-term soil formation and bedrock weathering, which are aspect-dependent in the Front Range. A competing hypothesis is that debris flow initiation locations are controlled by present-day vegetation patterns within the critical zone. We tested these hypotheses with a regional investigation of the Green-Red Vegetation Index (GRVI), a metric used to identify the degree of vegetation cover. Although the majority of debris flows were observed on south-facing hillslopes, the GRVI analysis revealed that most debris-flow initiation locations had low tree density and high rainfall, regardless of hillslope aspect. We next numerically simulated soil pore pressure and slope stability using the September 2013 rainfall data at one site. Results suggest that spatial variations in soil depth and the relative extent of bedrock weathering on north- versus south-facing slopes are insufficient to explain the observed spatial variations in debris flow initiation. However, decreased debris flow initiation on north-facing slopes likely resulted from increased root reinforcement provided by trees on north-facing slopes. While the current vegetation regimes in the Colorado Front Range, and throughout much of the semi-arid southwestern U.S., are superimposed on a landscape where soil development and bedrock weathering (both of which affect slope stability) are responding to longer timescale processes, our analysis suggests landslide susceptibility was primarily governed by the local, geo-mechanical effects of vegetation during this extreme rainfall event.

Balancing practicality and hydrologic realism: a parsimonious approach for simulating rapid groundwater recharge via unsaturated-zone preferential flow

USGS Publications Warehouse

Mirus, Benjamin B.; Nimmo, J.R.

2013-01-01

The impact of preferential flow on recharge and contaminant transport poses a considerable challenge to water-resources management. Typical hydrologic models require extensive site characterization, but can underestimate fluxes when preferential flow is significant. A recently developed source-responsive model incorporates film-flow theory with conservation of mass to estimate unsaturated-zone preferential fluxes with readily available data. The term source-responsive describes the sensitivity of preferential flow in response to water availability at the source of input. We present the first rigorous tests of a parsimonious formulation for simulating water table fluctuations using two case studies, both in arid regions with thick unsaturated zones of fractured volcanic rock. Diffuse flow theory cannot adequately capture the observed water table responses at both sites; the source-responsive model is a viable alternative. We treat the active area fraction of preferential flow paths as a scaled function of water inputs at the land surface then calibrate the macropore density to fit observed water table rises. Unlike previous applications, we allow the characteristic film-flow velocity to vary, reflecting the lag time between source and deep water table responses. Analysis of model performance and parameter sensitivity for the two case studies underscores the importance of identifying thresholds for initiation of film flow in unsaturated rocks, and suggests that this parsimonious approach is potentially of great practical value.

Identifying fracture‐zone geometry using simulated annealing and hydraulic‐connection data

USGS Publications Warehouse

Day-Lewis, Frederick D.; Hsieh, Paul A.; Gorelick, Steven M.

2000-01-01

A new approach is presented to condition geostatistical simulation of high‐permeability zones in fractured rock to hydraulic‐connection data. A simulated‐annealing algorithm generates three‐dimensional (3‐D) realizations conditioned to borehole data, inferred hydraulic connections between packer‐isolated borehole intervals, and an indicator (fracture zone or background‐K bedrock) variogram model of spatial variability. We apply the method to data from the U.S. Geological Survey Mirror Lake Site in New Hampshire, where connected high‐permeability fracture zones exert a strong control on fluid flow at the hundred‐meter scale. Single‐well hydraulic‐packer tests indicate where permeable fracture zones intersect boreholes, and multiple‐well pumping tests indicate the degree of hydraulic connection between boreholes. Borehole intervals connected by a fracture zone exhibit similar hydraulic responses, whereas intervals not connected by a fracture zone exhibit different responses. Our approach yields valuable insights into the 3‐D geometry of fracture zones at Mirror Lake. Statistical analysis of the realizations yields maps of the probabilities of intersecting specific fracture zones with additional wells. Inverse flow modeling based on the assumption of equivalent porous media is used to estimate hydraulic conductivity and specific storage and to identify those fracture‐zone geometries that are consistent with hydraulic test data.

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.

Predicting Fluid Flow in Stressed Fractures: A Quantitative Evaluation of Methods

NASA Astrophysics Data System (ADS)

Weihmann, S. A.; Healy, D.

2015-12-01

Reliable estimation of fracture stability in the subsurface is crucial to the success of exploration and production in the petroleum industry, and also for wider applications to earthquake mechanics, hydrogeology and waste disposal. Previous work suggests that fracture stability is related to fluid flow in crystalline basement rocks through shear or tensile instabilities of fractures. Our preliminary scoping analysis compares the fracture stability of 60 partly open (apertures 1.5-3 cm) and electrically conductive (low acoustic amplitudes relative to matrix) fractures from a 16 m section of a producing zone in a basement well in Bayoot field, Yemen, to a non-producing zone in the same well (also 16 m). We determine the Critically Stressed Fractures (CSF; Barton et al., 1995) and dilatation tendency (Td; Ferrill et al., 1999). We find that: 1. CSF (Fig. 1) is a poor predictor of high fluid flow in the inflow zone; 88% of the fractures are predicted to be NOT critically stressed and yet they all occur within a zone of high fluid flow rate 2. Td (Fig. 2) is also a poor predictor of high fluid flow in the inflow zone; 67% of the fractures have a LOW Td(< 0.6) 3. For the non-producing zone CSF is a very reliable predictor (100% are not critically stressed) whereas the values of Tdare consistent with their location in non-producing interval (81% are < 0.6) (Fig. 3 & 4). In summary, neither method correlates well with the observed abundance of hydraulically conductive fractures within the producing zone. Within the non-producing zone CSF and Td make reasonably accurate predictions. Fractures may be filled or partially filled with drilling mud or a lower density and electrically conductive fill such as clay in the producing zone and therefore appear (partly) open. In situ stress, fluid pressure, rock properties (friction, strength) and fracture orientation data used as inputs for the CSF and Td calculations are all subject to uncertainty. Our results suggest that scope exists to systematically quantify and explore the impacts of these uncertainties for better predictions of geomechanical stability and fluid conductivity in the subsurface.

Which key properties controls the preferential transport in the vadose zone under transient hydrological conditions

NASA Astrophysics Data System (ADS)

Groh, J.; Vanderborght, J.; Puetz, T.; Gerke, H. H.; Rupp, H.; Wollschlaeger, U.; Stumpp, C.; Priesack, E.; Vereecken, H.

2015-12-01

Understanding water flow and solute transport in the unsaturated zone is of great importance for an appropriate land use management strategy. The quantification and prediction of water and solute fluxes through the vadose zone can help to improve management practices in order to limit potential risk on our fresh water resources. Water related solute transport and residence time is strongly affected by preferential flow paths in the soil. Water flow in soils depends on soil properties and site factors (climate or experiment conditions, land use) and are therefore important factors to understand preferential solute transport in the unsaturated zone. However our understanding and knowledge of which on-site properties or conditions define and enhance preferential flow and transport is still poor and mostly limited onto laboratory experimental conditions (small column length and steady state boundary conditions). Within the TERENO SOILCan lysimeter network, which was designed to study the effects of climate change on soil functions, a bromide tracer was applied on 62 lysimeter at eight different test sites between Dec. 2013 and Jan. 2014. The TERENO SOILCan infrastructure offers the unique possibility to study the occurrence of preferential flow and transport of various soil types under different natural transient hydrological conditions and land use (crop, bare and grassland) at eight TERENO SOILCan observatories. Working with lysimeter replicates at each observatory allows defining the spatial variability of preferential transport and flow. Additionally lysimeters in the network were transferred within and between observatories in order to subject them to different rainfall and temperature regimes and enable us to relate the soil type susceptibility of preferential flow and transport not only to site specific physical and land use properties, but also to different transient boundary conditions. Comparison and statistical analysis between preferential flow indicators 5% arrival time and potential key soil properties, site factors and boundary conditions will be presented in order to identify key properties which control the preferential transport in the vadose zone under transient hydrological conditions.

Extensive lava flow fields on Venus: Preliminary investigation of source elevation and regional slope variations

NASA Technical Reports Server (NTRS)

Magee-Roberts, K.; Head, James W., III; Lancaster, M. G.

1992-01-01

Large-volume lava flow fields have been identified on Venus, the most areally extensive of which are known as fluctus and have been subdivided into six morphologic types. Sheetlike flow fields (Type 1) lack the numerous, closely spaced, discrete lava flow lobes that characterize digitate flow fields. Transitional flow fields (Type 2) are similar to sheetlike flow fields but contain one or more broad flow lobes. Digitate flow fields are divided further into divergent (Types 3-5) and subparallel (Type 6) classes on the basis of variations in the amount of downstream flow divergence. As a result of our previous analysis of the detailed morphology, stratigraphy, and tectonic associations of Mylitta Fluctus, we have formulated a number of questions to apply to all large flow fields on Venus. In particular, we would like to address the following: (1) eruption conditions and style of flow emplacement (effusion rate, eruption duration), (2) the nature of magma storage zones (presence of neutral buoyancy zones, deep or shallow crustal magma chambers), (3) the origin of melt and possible link to mantle plumes, and (4) the importance of large flow fields in plains evolution. To answer these questions we have begun to examine variations in flow field dimension and morphology; the distribution of large flow fields in terms of elevation above the mean planetary radius; links to regional tectonic or volcanic structures (e.g., associations with large shield edifices, coronae, or rift zones); statigraphic relationships between large flow fields, volcanic plains, shields, and coronae; and various models of flow emplacement in order to estimate eruption parameters. In this particular study, we have examined the proximal elevations and topographic slopes of 16 of the most distinctive flow fields that represent each of the 6 morphologic types.

Solar-cycle Variations of Meridional Flows in the Solar Convection Zone Using Helioseismic Methods

NASA Astrophysics Data System (ADS)

Lin, Chia-Hsien; Chou, Dean-Yi

2018-06-01

The solar meridional flow is an axisymmetric flow in solar meridional planes, extending through the convection zone. Here we study its solar-cycle variations in the convection zone using SOHO/MDI helioseismic data from 1996 to 2010, including two solar minima and one maximum. The travel-time difference between northward and southward acoustic waves is related to the meridional flow along the wave path. Applying the ray approximation and the SOLA inversion method to the travel-time difference measured in a previous study, we obtain the meridional flow distributions in 0.67 ≤ r ≤ 0.96R ⊙ at the minimum and maximum. At the minimum, the flow has a three-layer structure: poleward in the upper convection zone, equatorward in the middle convection zone, and poleward again in the lower convection zone. The flow speed is close to zero within the error bar near the base of the convection zone. The flow distribution changes significantly from the minimum to the maximum. The change above 0.9R ⊙ shows two phenomena: first, the poleward flow speed is reduced at the maximum; second, an additional convergent flow centered at the active latitudes is generated at the maximum. These two phenomena are consistent with the surface meridional flow reported in previous studies. The change in flow extends all the way down to the base of the convection zone, and the pattern of the change below 0.9R ⊙ is more complicated. However, it is clear that the active latitudes play a role in the flow change: the changes in flow speed below and above the active latitudes have opposite signs. This suggests that magnetic fields could be responsible for the flow change.

Utilizing Controlled Vibrations in a Microgravity Environment to Understand and Promote Microstructural Homogeneity During Floating-Zone Crystal Growth

NASA Technical Reports Server (NTRS)

Anilkumar, A. V.; Bhowmick, J.; Grugel, R. N.

2001-01-01

Our previous experiments with NaNO3 float-zones revealed that steady thermocapillary flow can be balanced/offset by the controlled surface streaming flow induced by end-wall vibration. In the current experiments we are examining the effects of streaming flow on steadying/stabilizing nonsteady thermocapillary flow in such zones. To this effect we have set up a controlled NaNO3 half-zone experiment, where the processing parameters, like zone dimensions and temperature gradients, can be easily varied to generate nonsteady thermocapillary flows. In the present paper we present preliminary results of our investigations into stabilizing such flows by employing endwall vibration.

Utilizing Controlled Vibrations in a Microgravity Environment to Understand and Promote Microstructural Homogeneity During Float-Zone Crystal Growth

NASA Technical Reports Server (NTRS)

Anilkumar, A. V.; Bhowmick, J.; Grugel, R. N.a

2000-01-01

Our previous experiments with NaNO3 float-zones revealed that steady thermocapillary flow can be balanced/offset by the controlled surface streaming flow induced by end-wall vibration. In the current experiments we are examining the effects of streaming flow on steadying/stabilizing nonsteady thermocapillary flow in such zones. To this effect we have set up a controlled NaNO3 half-zone experiment, where the processing parameters, like zone dimensions and temperature gradients, can be easily varied to generate nonsteady thermocapillary flows. In the present paper we present preliminary results of our investigations into stabilizing such flows by employing end-wall vibration.

Flat slabs seen from above: aeromagnetic data in Central Mexico

NASA Astrophysics Data System (ADS)

Manea, M.; Manea, V. C.

2006-12-01

The aeromagnetic map of Mexico shows a magnetic "quiet zone" in Guerrero and Oaxaca (Central Mexico), characterized by a general lack of short-wavelength magnetic anomalies. In order to investigate the magnetic quiet zone in relation with the thermal sources, spectral analysis has been applied to the aeromagnetic data. The results show the existence of deep magnetic sources (30-40 km) which we consider to be the Currie depth (corresponding to a temperature of 575-600°). Above the Curie temperature spontaneous magnetization vanishes and the minerals exhibit only a small paramagnetic susceptibility. Our estimates of magnetic basal depth are consistent with the heat flow measurements in the area (20-30 mW/m2). In order to explain such deep magnetic source and small heat flow estimates, we infer the thermal structure associated with the subduction of the Cocos plate beneath Central Mexico, using a finite element approach. The modeling results show that the 575-600°C isotherm is subhorisontal due to the flat slab regime in the area. Also, the heat flow estimates from thermal models and spectral analysis of aeromagnetic anomalies are in good agreement. We conclude that the magnetic quiet zone is associated with a flat slab subduction regime in Central Mexico, and proved to be an important constraint for the thermal structure associated with subduction zones.

Thermal impact of magmatism in subduction zones

NASA Astrophysics Data System (ADS)

Rees Jones, David W.; Katz, Richard F.; Tian, Meng; Rudge, John F.

2018-01-01

Magmatism in subduction zones builds continental crust and causes most of Earth's subaerial volcanism. The production rate and composition of magmas are controlled by the thermal structure of subduction zones. A range of geochemical and heat flow evidence has recently converged to indicate that subduction zones are hotter at lithospheric depths beneath the arc than predicted by canonical thermomechanical models, which neglect magmatism. We show that this discrepancy can be resolved by consideration of the heat transported by magma. In our one- and two-dimensional numerical models and scaling analysis, magmatic transport of sensible and latent heat locally alters the thermal structure of canonical models by ∼300 K, increasing predicted surface heat flow and mid-lithospheric temperatures to observed values. We find the advection of sensible heat to be larger than the deposition of latent heat. Based on these results we conclude that thermal transport by magma migration affects the chemistry and the location of arc volcanoes.

New insights into the Edwards Aquifer—Brackish-water simulation, drought, and the role of uncertainty analysis

USGS Publications Warehouse

Foster, Linzy K.; White, Jeremy T.

2016-02-03

The Edwards aquifer consists of three water-quality zones. The freshwater zone of the Edwards aquifer is bounded to the south by a zone of brackish water (transition zone) where the aquifer transitions from fresh to saline water. The saline zone is downdip from the transition zone. There is concern that a recurrence of extreme drought, such as the 7-year drought from 1950 through 1956, could cause the transition zone to move toward (encroach upon) the freshwater zone, causing production wells near the transition zone to pump saltier water. There is also concern of drought effects on spring flows from Comal and San Marcos Springs. These concerns were evaluated through the development of a new numerical model of the Edwards aquifer.

Calculating terrain indices along streams: A new method for separating stream sides

Treesearch

T. J. Grabs; K. G. Jencso; B. L. McGlynn; J. Seibert

2010-01-01

There is increasing interest in assessing riparian zones and their hydrological and biogeochemical buffering capacity with indices derived from hydrologic landscape analysis of digital elevation data. Upslope contributing area is a common surrogate for lateral water flows and can be used to assess the variability of local water inflows to riparian zones and streams....

Using an Integrated Hydrologic Model to Assess the Ecohydrological Impacts of Change on a Mountain Headwaters Critical Zone

NASA Astrophysics Data System (ADS)

Collins, C.; Maxwell, R. M.; Visser, A.

2016-12-01

The critical zone is the region of the Earth's crust where hydrogeology, ecology, and climate interact. As many critical zone processes are fundamental, the significance of studying critical zone processes goes beyond understanding the local ecohydrological setting. Therefore studying critical zone governing processes requires an interdisciplinary approach that integrates simulation and observation. In this study, a high-resolution integrated hydrologic model, ParFlow-CLM, was developed for the Providence Creek watershed. Providence Creek is a highly instrumented critical zone observatory (CZO) located in the southern Sierra Nevada Mountains, a region currently experiencing a range of short-term responses (i.e. tree mortality) to a severe four-year drought. Sources of plant water use, pathways and residence times of water through the subsurface are identified using a suite of isotopic signatures and numerical particle tracking. Implications of using a fully coupled integrated hydrologic model accompanied by tracer analysis include better understanding of water partitioning and water storage in the regolith and vegetation water use during drought time conditions. The importance of subsurface storage, plant available water and lateral flow during the 2012-2015 drought to mitigate vegetation stress are addressed and verified against observed tree mortality. The stream flow response to tree mortality in the aftermath of the drought, analogous to the Colorado Mountain Pine Beetle case, provides insight into the potential effects of proposed forest management practices.

Viscous and Interacting Flow Field Effects.

DTIC Science & Technology

1980-06-01

in the inviscid flow analysis using free vortex sheets whose shapes are determined by iteration. The outer iteration employs boundary layer...Methods, Inc. which replaces the source distribution in the separation zone by a vortex wake model . This model is described in some detail in (2), but...in the potential flow is obtained using linearly varying vortex singularities distributed on planar panels. The wake is represented by sheets of

A field technique for estimating aquifer parameters using flow log data

USGS Publications Warehouse

Paillet, Frederick L.

2000-01-01

A numerical model is used to predict flow along intervals between producing zones in open boreholes for comparison with measurements of borehole flow. The model gives flow under quasi-steady conditions as a function of the transmissivity and hydraulic head in an arbitrary number of zones communicating with each other along open boreholes. The theory shows that the amount of inflow to or outflow from the borehole under any one flow condition may not indicate relative zone transmissivity. A unique inversion for both hydraulic-head and transmissivity values is possible if flow is measured under two different conditions such as ambient and quasi-steady pumping, and if the difference in open-borehole water level between the two flow conditions is measured. The technique is shown to give useful estimates of water levels and transmissivities of two or more water-producing zones intersecting a single interval of open borehole under typical field conditions. Although the modeling technique involves some approximation, the principle limit on the accuracy of the method under field conditions is the measurement error in the flow log data. Flow measurements and pumping conditions are usually adjusted so that transmissivity estimates are most accurate for the most transmissive zones, and relative measurement error is proportionately larger for less transmissive zones. The most effective general application of the borehole-flow model results when the data are fit to models that systematically include more production zones of progressively smaller transmissivity values until model results show that all accuracy in the data set is exhausted.A numerical model is used to predict flow along intervals between producing zones in open boreholes for comparison with measurements of borehole flow. The model gives flow under quasi-steady conditions as a function of the transmissivity and hydraulic head in an arbitrary number of zones communicating with each other along open boreholes. The theory shows that the amount of inflow to or outflow from the borehole under any one flow condition may not indicate relative zone transmissivity. A unique inversion for both hydraulic-head and transmissivity values is possible if flow is measured under two different conditions such as ambient and quasi-steady pumping, and if the difference in open-borehole water level between the two flow conditions is measured. The technique is shown to give useful estimates of water levels and transmissivities of two or more water-producing zones intersecting a single interval of open borehole under typical field conditions. Although the modeling technique involves some approximation, the principle limit on the accuracy of the method under field conditions is the measurement error in the flow log data. Flow measurements and pumping conditions are usually adjusted so that transmissivity estimates are most accurate for the most transmissive zones, and relative measurement error is proportionately larger for less transmissive zones. The most effective general application of the borehole-flow model results when the data are fit to models that symmetrically include more production zones of progressively smaller transmissivity values until model results show that all accuracy in the data set is exhausted.

Mixing effects on nitrogen and oxygen concentrations and the relationship to mean residence time in a hyporheic zone of a riffle-pool sequence

USGS Publications Warehouse

Naranjo, Ramon C.; Niswonger, Richard G.; Clinton Davis,

2015-01-01

Flow paths and residence times in the hyporheic zone are known to influence biogeochemical processes such as nitrification and denitrification. The exchange across the sediment-water interface may involve mixing of surface water and groundwater through complex hyporheic flow paths that contribute to highly variable biogeochemically active zones. Despite the recognition of these patterns in the literature, conceptualization and analysis of flow paths and nitrogen transformations beneath riffle-pool sequences often neglect to consider bed form driven exchange along the entire reach. In this study, the spatial and temporal distribution of dissolved oxygen (DO), nitrate (NO3-) and ammonium (NH4+) were monitored in the hyporheic zone beneath a riffle-pool sequence on a losing section of the Truckee River, NV. Spatially-varying hyporheic exchange and the occurrence of multi-scale hyporheic mixing cells are shown to influence concentrations of DO and NO3- and the mean residence time (MRT) of riffle and pool areas. Distinct patterns observed in piezometers are shown to be influenced by the first large flow event following a steady 8 month period of low flow conditions. Increases in surface water discharge resulted in reversed hydraulic gradients and production of nitrate through nitrification at small vertical spatial scales (0.10 to 0.25 m) beneath the sediment-water interface. In areas with high downward flow rates and low MRT, denitrification may be limited. The use of a longitudinal two-dimensional flow model helped identify important mechanisms such as multi-scale hyporheic mixing cells and spatially varying MRT, an important driver for nitrogen transformation in the riverbed. Our observations of DO and NO3- concentrations and model simulations highlight the role of multi-scale hyporheic mixing cells on MRT and nitrogen transformations in the hyporheic zone of riffle-pool sequences. This article is protected by copyright. All rights reserved.

A knowledge-based approach to automated flow-field zoning for computational fluid dynamics

NASA Technical Reports Server (NTRS)

Vogel, Alison Andrews

1989-01-01

An automated three-dimensional zonal grid generation capability for computational fluid dynamics is shown through the development of a demonstration computer program capable of automatically zoning the flow field of representative two-dimensional (2-D) aerodynamic configurations. The applicability of a knowledge-based programming approach to the domain of flow-field zoning is examined. Several aspects of flow-field zoning make the application of knowledge-based techniques challenging: the need for perceptual information, the role of individual bias in the design and evaluation of zonings, and the fact that the zoning process is modeled as a constructive, design-type task (for which there are relatively few examples of successful knowledge-based systems in any domain). Engineering solutions to the problems arising from these aspects are developed, and a demonstration system is implemented which can design, generate, and output flow-field zonings for representative 2-D aerodynamic configurations.

An experimental study of a self-confined flow with ring-vorticity distribution. Ph.D. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Lin, K. M.; Moore, F. K.

1976-01-01

A new form of self-confined flow was investigated in which a recirculation zone forms away from any solid boundary. An inviscid flow analysis indicated that in a purely meridional axisymmetric flow a stationary, spherical, self-confined region should occur in the center of a streamlined divergent-convergent enlargement zone. The spherical confinement region would be at rest and at constant pressure. Experimental investigations were carried out in a specially built test apparatus to establish the desired confined flow. The streamlined divergent-convergent interior shape of the test section was fabricated according to the theoretical calculation for a particular streamline. The required inlet vorticity distribution was generated by producing a velocity profile with a shaped gauze screen in the straight pipe upstream of the test section. Fluid speed and turbulence intensity were measured with a constant-temperature hot-wire anemometer system. The measured results indicated a very orderly and stable flow field.

The prediction of radiofrequency ablation zone volume using vascular indices of 3-dimensional volumetric colour Doppler ultrasound in an in vitro blood-perfused bovine liver model

PubMed Central

Lanctot, Anthony C; McCarter, Martin D; Roberts, Katherine M; Glueck, Deborah H; Dodd, Gerald D

2017-01-01

Objective: To determine the most reliable predictor of radiofrequency (RF) ablation zone volume among three-dimensional (3D) volumetric colour Doppler vascular indices in an in vitro blood-perfused bovine liver model. Methods: 3D colour Doppler volume data of the local hepatic parenchyma were acquired from 37 areas of 13 bovine livers connected to an in vitro oxygenated blood perfusion system. Doppler vascular indices of vascularization index (VI), flow index (FI) and vascularization flow index (VFI) were obtained from the volume data using 3D volume analysis software. 37 RF ablations were performed at the same locations where the ultrasound data were obtained from. The relationship of these vascular indices and the ablation zone volumes measured from gross specimens were analyzed using a general linear mixed model fit with random effect for liver and backward stepwise regression analysis. Results: FI was significantly associated with ablation zone volumes measured on gross specimens (p = 0.0047), but explained little of the variance (Rβ2 = 0.21). Ablation zone volume decreased by 0.23 cm3 (95% confidence interval: −0.38, −0.08) for every 1 increase in FI. Neither VI nor VFI was significantly associated with ablation zone volumes (p > 0.05). Conclusion: Although FI was associated with ablation zone volumes, it could not sufficiently explain their variability, limiting its clinical applicability. VI, FI and VFI are not clinically useful in the prediction of RF ablation zone volume in the liver. Advances in knowledge: Despite a significant association of FI with ablation zone volumes, VI, FI and VFI cannot be used for their prediction. Different Doppler vascular indices need to be investigated for clinical use. PMID:27925468

Graphical User Interface Development for Representing Air Flow Patterns

NASA Technical Reports Server (NTRS)

Chaudhary, Nilika

2004-01-01

In the Turbine Branch, scientists carry out experimental and computational work to advance the efficiency and diminish the noise production of jet engine turbines. One way to do this is by decreasing the heat that the turbine blades receive. Most of the experimental work is carried out by taking a single turbine blade and analyzing the air flow patterns around it, because this data indicates the sections of the turbine blade that are getting too hot. Since the cost of doing turbine blade air flow experiments is very high, researchers try to do computational work that fits the experimental data. The goal of computational fluid dynamics is for scientists to find a numerical way to predict the complex flow patterns around different turbine blades without physically having to perform tests or costly experiments. When visualizing flow patterns, scientists need a way to represent the flow conditions around a turbine blade. A researcher will assign specific zones that surround the turbine blade. In a two-dimensional view, the zones are usually quadrilaterals. The next step is to assign boundary conditions which define how the flow enters or exits one side of a zone. way of setting up computational zones and grids, visualizing flow patterns, and storing all the flow conditions in a file on the computer for future computation. Such a program is necessary because the only method for creating flow pattern graphs is by hand, which is tedious and time-consuming. By using a computer program to create the zones and grids, the graph would be faster to make and easier to edit. Basically, the user would run a program that is an editable graph. The user could click and drag with the mouse to form various zones and grids, then edit the locations of these grids, add flow and boundary conditions, and finally save the graph for future use and analysis. My goal this summer is to create a graphical user interface (GUI) that incorporates all of these elements. I am writing the program in Java, a language that is portable among platforms, because it can run on different operating systems such as Windows and Unix without having to be rewritten. I had no prior experience of programming in Java at the start of my internship; I am continuously learning as I create the program. I have written the part of the program that enables a user to draw several zones, edit them, and store their locations. The next phase of my project is to allow the user to click on the side of a zone and create a boundary condition for it. A previous intern wrote a program that allows the user to input boundary conditions. I can integrate the two programs to create a larger, more usable program. After that, I will develop a way for the user to save the graph for future reference. Another eventual goal is to make the GUI capable of creating three-dimensional zones as well. Researchers such as my mentor, Dr. David Ashpis, need a quick, user-friendly

Aerodynamic drag characterization and deposition studies of irregular particles. Part 3: Analysis of flow and temperature field inside the Combustion Deposition Entrained Reactor (CDER)

NASA Astrophysics Data System (ADS)

Celik, I.; Katragadda, S.; Nagarajan, R.

1990-01-01

An experimental and numerical analysis was performed of the temperature and flow field involved in co-axial, confined, non-reacting heated jets in a drop tube reactor. An electrically heated 2-inch (50.8 mm) diameter drop tube reactor was utilized to study the jet characteristics. Profiles of gas temperature, typically in the range of 800 to 1600 K were measured in the mixing zone of the jet with a K-Type thermocouple. Measured temperatures were corrected for conduction, convection, and radiation heat losses. Because of limited access to the mixing zone, characterization of the flow field at high temperatures with laser Doppler or hot wire anemometry were impractical. A computer program which solves the full equations of motion and energy was employed to simulate the temperature and flow fields. The location of the recirculation region, the flow regimes, and the mixing phenomena were studied. The wall heating, laminar and turbulent flow regimes were considered in the simulations. The predictions are in fairly good agreement with the corrected temperature measurements provided that the flow is turbulent. The results of this study demonstrate how a numerical method and measurement can be used together to analyze the flow conditions inside a reactor which has limited access because of very high temperatures.

Stochastic Ground Water Flow Simulation with a Fracture Zone Continuum Model

USGS Publications Warehouse

Langevin, C.D.

2003-01-01

A method is presented for incorporating the hydraulic effects of vertical fracture zones into two-dimensional cell-based continuum models of ground water flow and particle tracking. High hydraulic conductivity features are used in the model to represent fracture zones. For fracture zones that are not coincident with model rows or columns, an adjustment is required for the hydraulic conductivity value entered into the model cells to compensate for the longer flowpath through the model grid. A similar adjustment is also required for simulated travel times through model cells. A travel time error of less than 8% can occur for particles moving through fractures with certain orientations. The fracture zone continuum model uses stochastically generated fracture zone networks and Monte Carlo analysis to quantify uncertainties with simulated advective travel times. An approach is also presented for converting an equivalent continuum model into a fracture zone continuum model by establishing the contribution of matrix block transmissivity to the bulk transmissivity of the aquifer. The methods are used for a case study in west-central Florida to quantify advective travel times from a potential wetland rehydration site to a municipal supply wellfield. Uncertainties in advective travel times are assumed to result from the presence of vertical fracture zones, commonly observed on aerial photographs as photolineaments.

System and method for treatment of a medium

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

Singh, Surinder Prabhjot; Acharya, Harish Radhakrishna; Perry, Robert James

2017-05-23

A system and method for treatment of a medium is disclosed. The system includes a plurality of separator zones and a plurality of heat transfer zones. Each of the separator zone and the heat transfer zone among the plurality of separator zones and heat transfer zones respectively, are disposed alternatively in a flow duct. Further, each separator zone includes an injector device for injecting a sorbent into the corresponding separator zone. Within the corresponding separator zone, the injected sorbent is reacted with a gaseous medium flowing in the flow duct, so as to generate a reacted gaseous medium and amore » reacted sorbent. Further, each heat transfer zone exchanges heat between the reacted gaseous medium fed from the corresponding separator zone and a heat transfer medium.« less

IN SITU FIELD TESTING OF PROCESSES

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

J.S.Y. YANG

2004-11-08

The purpose of this scientific analysis report is to update and document the data and subsequent analyses from ambient field-testing activities performed in underground drifts and surface-based boreholes through unsaturated zone (UZ) tuff rock units. In situ testing, monitoring, and associated laboratory studies are conducted to directly assess and evaluate the waste emplacement environment and the natural barriers to radionuclide transport at Yucca Mountain. This scientific analysis report supports and provides data to UZ flow and transport model reports, which in turn contribute to the Total System Performance Assessment (TSPA) of Yucca Mountain, an important document for the license applicationmore » (LA). The objectives of ambient field-testing activities are described in Section 1.1. This report is the third revision (REV 03), which supercedes REV 02. The scientific analysis of data for inputs to model calibration and validation as documented in REV 02 were developed in accordance with the Technical Work Plan (TWP) ''Technical Work Plan for: Performance Assessment Unsaturated Zone'' (BSC 2004 [DIRS 167969]). This revision was developed in accordance with the ''Technical Work Plan for: Unsaturated Zone Flow Analysis and Model Report Integration'' (BSC 2004 [DIRS 169654], Section 1.2.4) for better integrated, consistent, transparent, traceable, and more complete documentation in this scientific analysis report and associated UZ flow and transport model reports. No additional testing or analyses were performed as part of this revision. The list of relevant acceptance criteria is provided by ''Technical Work Plan for: Unsaturated Zone Flow Analysis and Model Report Integration'' (BSC 2004 [DIRS 169654]), Table 3-1. Additional deviations from the TWP regarding the features, events, and processes (FEPs) list are discussed in Section 1.3. Documentation in this report includes descriptions of how, and under what conditions, the tests were conducted. The descriptions and analyses provide data useful for refining and confirming the understanding of flow, drift seepage, and transport processes in the UZ. The UZ testing activities included measurement of permeability distribution, quantification of the seepage of water into the drifts, evaluation of fracture-matrix interaction, study of flow along faults, testing of flow and transport between drifts, characterization of hydrologic heterogeneity along drifts, estimation of drying effects on the rock surrounding the drifts due to ventilation, monitoring of moisture conditions in open and sealed drifts, and determination of the degree of minimum construction water migration below drift. These field tests were conducted in two underground drifts at Yucca Mountain, the Exploratory Studies Facility (ESF) drift, and the cross-drift for Enhanced Characterization of the Repository Block (ECRB), as described in Section 1.2. Samples collected in boreholes and underground drifts have been used for additional hydrochemical and isotopic analyses for additional understanding of the UZ setting. The UZ transport tests conducted at the nearby Busted Butte site (see Figure 1-4) are also described in this scientific analysis report.« less

Estimated damage from the Cascadia Subduction Zone tsunami: A model comparisons using fragility curves

NASA Astrophysics Data System (ADS)

Wiebe, D. M.; Cox, D. T.; Chen, Y.; Weber, B. A.; Chen, Y.

2012-12-01

Building damage from a hypothetical Cascadia Subduction Zone tsunami was estimated using two methods and applied at the community scale. The first method applies proposed guidelines for a new ASCE 7 standard to calculate the flow depth, flow velocity, and momentum flux from a known runup limit and estimate of the total tsunami energy at the shoreline. This procedure is based on a potential energy budget, uses the energy grade line, and accounts for frictional losses. The second method utilized numerical model results from previous studies to determine maximum flow depth, velocity, and momentum flux throughout the inundation zone. The towns of Seaside and Canon Beach, Oregon, were selected for analysis due to the availability of existing data from previously published works. Fragility curves, based on the hydrodynamic features of the tsunami flow (inundation depth, flow velocity, and momentum flux) and proposed design standards from ASCE 7 were used to estimate the probability of damage to structures located within the inundations zone. The analysis proceeded at the parcel level, using tax-lot data to identify construction type (wood, steel, and reinforced-concrete) and age, which was used as a performance measure when applying the fragility curves and design standards. The overall probability of damage to civil buildings was integrated for comparison between the two methods, and also analyzed spatially for damage patterns, which could be controlled by local bathymetric features. The two methods were compared to assess the sensitivity of the results to the uncertainty in the input hydrodynamic conditions and fragility curves, and the potential advantages of each method discussed. On-going work includes coupling the results of building damage and vulnerability to an economic input output model. This model assesses trade between business sectors located inside and outside the induction zone, and is used to measure the impact to the regional economy. Results highlight critical businesses sectors and infrastructure critical to the economic recovery effort, which could be retrofitted or relocated to survive the event. The results of this study improve community understanding of the tsunami hazard for civil buildings.

High Explosive Detonation-Confiner Interactions

NASA Astrophysics Data System (ADS)

Short, Mark; Quirk, James J.

2018-01-01

The primary purpose of a detonation in a high explosive (HE) is to provide the energy to drive a surrounding confiner, typically for mining or munitions applications. The details of the interaction between an HE detonation and its confinement are essential to achieving the objectives of the explosive device. For the high pressures induced by detonation loading, both the solid HE and confiner materials will flow. The structure and speed of a propagating detonation, and ultimately the pressures generated in the reaction zone to drive the confiner, depend on the induced flow both within the confiner and along the HE-confiner material interface. The detonation-confiner interactions are heavily influenced by the material properties and, in some cases, the thickness of the confiner. This review discusses the use of oblique shock polar analysis as a means of characterizing the possible range of detonation-confiner interactions. Computations that reveal the fluid mechanics of HE detonation-confiner interactions for finite reaction-zone length detonations are discussed and compared with the polar analysis. This includes cases of supersonic confiner flow; subsonic, shock-driven confiner flow; subsonic, but shockless confiner flow; and sonic flow at the intersection of the detonation shock and confiner material interface. We also summarize recent developments, including the effects of geometry and porous material confinement, on detonation-confiner interactions.

Preliminary Hydrogeologic Characterization Results from the Wallula Basalt Pilot Study

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

B.P. McGrail; E. C. Sullivan; F. A. Spane

2009-12-01

The DOE's Big Sky Regional Carbon Sequestration Partnership has completed drilling the first continental flood basalt sequestration pilot borehole to a total depth (TD) of 4,110 feet on the Boise White Paper Mill property at Wallula, Washington. Site suitability was assessed prior to drilling by the 2007-2008 acquisition, processing and analysis of a four-mile, five-line three component seismic swath, which was processed as a single data-dense line. Analysis of the seismic survey data indicated a composite basalt formation thickness of {approx}8,000 feet and absence of major geologic structures (i.e., faults) along the line imaged by the seismic swath. Drilling ofmore » Wallula pilot borehole was initiated on January 13, 2009 and reached TD on April 6, 2009. Based on characterization results obtained during drilling, three basalt breccia zones were identified between the depth interval of 2,716 and 2,910 feet, as being suitable injection reservoir for a subsequent CO2 injection pilot study. The targeted injection reservoir lies stratigraphically below the massive Umtanum Member of the Grande Ronde Basalt, whose flow-interior section possesses regionally recognized low-permeability characteristics. The identified composite injection zone reservoir provides a unique and attractive opportunity to scientifically study the reservoir behavior of three inter-connected reservoir intervals below primary and secondary caprock confining zones. Drill cuttings, wireline geophysical logs, and 31one-inch diameter rotary sidewall cores provided geologic data for characterization of rock properties. XRF analyses of selected rock samples provided geochemical characterizations of the rocks and stratigraphic control for the basalt flows encountered by the Wallula pilot borehole. Based on the geochemical results, the pilot borehole was terminated in the Wapshilla Ridge 1 flow of the Grande Ronde Basalt Formation. Detailed hydrologic test characterizations of 12 basalt interflow reservoir zones and 3 flow-interior/caprock intervals were performed during drilling and immediately following reaching the final borehole drilling depth (i.e., 4,110 ft). In addition, six of the 12 basalt interflow zones were selected for detailed hydrochemical characterization. Results from the detailed hydrologic test characterization program provided the primary information on basalt interflow zone transmissivity/injectivity, and caprock permeability characteristics.« less

Use of demand for and spatial flow of ecosystem services to identify priority areas.

PubMed

Verhagen, Willem; Kukkala, Aija S; Moilanen, Atte; van Teeffelen, Astrid J A; Verburg, Peter H

2017-08-01

Policies and research increasingly focus on the protection of ecosystem services (ESs) through priority-area conservation. Priority areas for ESs should be identified based on ES capacity and ES demand and account for the connections between areas of ES capacity and demand (flow) resulting in areas of unique demand-supply connections (flow zones). We tested ways to account for ES demand and flow zones to identify priority areas in the European Union. We mapped the capacity and demand of a global (carbon sequestration), a regional (flood regulation), and 3 local ESs (air quality, pollination, and urban leisure). We used Zonation software to identify priority areas for ESs based on 6 tests: with and without accounting for ES demand and 4 tests that accounted for the effect of ES flow zone. There was only 37.1% overlap between the 25% of priority areas that encompassed the most ESs with and without accounting for ES demand. The level of ESs maintained in the priority areas increased from 23.2% to 57.9% after accounting for ES demand, especially for ESs with a small flow zone. Accounting for flow zone had a small effect on the location of priority areas and level of ESs maintained but resulted in fewer flow zones without ES maintained relative to ignoring flow zones. Accounting for demand and flow zones enhanced representation and distribution of ESs with local to regional flow zones without large trade-offs relative to the global ES. We found that ignoring ES demand led to the identification of priority areas in remote regions where benefits from ES capacity to society were small. Incorporating ESs in conservation planning should therefore always account for ES demand to identify an effective priority network for ESs. © 2016 The Authors. Conservation Biology published by Wiley Periodicals, Inc. on behalf of Society for Conservation Biology.

Catalytic reactor for low-Btu fuels

DOEpatents

Smith, Lance; Etemad, Shahrokh; Karim, Hasan; Pfefferle, William C.

2009-04-21

An improved catalytic reactor includes a housing having a plate positioned therein defining a first zone and a second zone, and a plurality of conduits fabricated from a heat conducting material and adapted for conducting a fluid therethrough. The conduits are positioned within the housing such that the conduit exterior surfaces and the housing interior surface within the second zone define a first flow path while the conduit interior surfaces define a second flow path through the second zone and not in fluid communication with the first flow path. The conduit exits define a second flow path exit, the conduit exits and the first flow path exit being proximately located and interspersed. The conduits define at least one expanded section that contacts adjacent conduits thereby spacing the conduits within the second zone and forming first flow path exit flow orifices having an aggregate exit area greater than a defined percent of the housing exit plane area. Lastly, at least a portion of the first flow path defines a catalytically active surface.

Primary weathering rates, water transit times and concentration-discharge relations: A theoretical analysis for the critical zone

NASA Astrophysics Data System (ADS)

Ameli, Ali; Erlandsson, Martin; Beven, Keith; Creed, Irena; McDonnell, Jeffrey; Bishop, Kevin

2017-04-01

The permeability architecture of the critical zone exerts a major influence on the hydrogeochemistry of the critical zone. Water flowpath dynamics drive the spatio-temporal pattern of geochemical evolution and resulting streamflow concentration-discharge (C-Q) relation, but these flowpaths are complex and difficult to map quantitatively. Here, we couple a new integrated flow and particle tracking transport model with a general reversible Transition-State-Theory style dissolution rate-law to explore theoretically how C-Q relations and concentration in the critical zone respond to decline in saturated hydraulic conductivity (Ks) with soil depth. We do this for a range of flow rates and mineral reaction kinetics. Our results show that for minerals with a high ratio of equilibrium concentration to intrinsic weathering rate, vertical heterogeneity in Ks enhances the gradient of weathering-derived solute concentration in the critical zone and strengthens the inverse stream C-Q relation. As the ratio of equilibrium concentration to intrinsic weathering rate decreases, the spatial distribution of concentration in the critical zone becomes more uniform for a wide range of flow rates, and stream C-Q relation approaches chemostatic behaviour, regardless of the degree of vertical heterogeneity in Ks. These findings suggest that the transport-controlled mechanisms in the hillslope can lead to chemostatic C-Q relations in the stream while the hillslope surface reaction-controlled mechanisms are associated with an inverse stream C-Q relation. In addition, as the ratio of equilibrium concentration to intrinsic weathering rate decreases, the concentration in the critical zone and stream become less dependent on groundwater age (or transit time)

Groundwater flow in the transition zone between freshwater and saltwater: a field-based study and analysis of measurement errors

NASA Astrophysics Data System (ADS)

Post, Vincent E. A.; Banks, Eddie; Brunke, Miriam

2018-02-01

The quantification of groundwater flow near the freshwater-saltwater transition zone at the coast is difficult because of variable-density effects and tidal dynamics. Head measurements were collected along a transect perpendicular to the shoreline at a site south of the city of Adelaide, South Australia, to determine the transient flow pattern. This paper presents a detailed overview of the measurement procedure, data post-processing methods and uncertainty analysis in order to assess how measurement errors affect the accuracy of the inferred flow patterns. A particular difficulty encountered was that some of the piezometers were leaky, which necessitated regular measurements of the electrical conductivity and temperature of the water inside the wells to correct for density effects. Other difficulties included failure of pressure transducers, data logger clock drift and operator error. The data obtained were sufficiently accurate to show that there is net seaward horizontal flow of freshwater in the top part of the aquifer, and a net landward flow of saltwater in the lower part. The vertical flow direction alternated with the tide, but due to the large uncertainty of the head gradients and density terms, no net flow could be established with any degree of confidence. While the measurement problems were amplified under the prevailing conditions at the site, similar errors can lead to large uncertainties everywhere. The methodology outlined acknowledges the inherent uncertainty involved in measuring groundwater flow. It can also assist to establish the accuracy requirements of the experimental setup.

Role of the sedimentary structure of the urban vadose zone (URVAZO) on the transfer of heavy metals of an urban stormwater basin

NASA Astrophysics Data System (ADS)

Angulo-Jaramillo, R.; Winiarski, T.; Goutaland, D.; Lassabatere, L.

2009-12-01

Stormwater infiltration basins have become a common alternative practice to traditional stormwater pipe networks in urban areas. They are often built in permeable subsurface soils (Urban Vadose Zone, URVAZO), such as alluvial deposits. These sedimentary deposits are highly heterogeneous and generate preferential flow paths that may cause either rapid or non-uniform transport of contaminants at great depths. The understanding of how subsurface vadose zone heterogeneities transfer contaminant and fluid flow to the aquifer still remains a challenge in urban hydrology. Indeed, urban stormwater may contain pollutants that can contaminate either soil or groundwater. The aim of this study is to evaluate the role of the lithological heterogeneity of a glaciofluvial deposit underlying an urban infiltration basin on the link between water flow and heavy metals retention. A trench wall (14m length x 3m depth) was exposed by excavating the glaciofluvial formation. By a hydrogeophysical approach based on a sedimentary structural units and in situ hydraulic characterization (Beerkan tests), a realistic hydrostratigraphic 2D model was defined. The trench was sampled on nine vertical sections of 1.5m length, with ten samples per vertical section following each lithofacies. A total of 90 samples were analyzed. Coarse (mechanical sieving) and fine (laser diffraction) particle size distribution analysis, as well as the concentration of three replicates of Pb, Cu, Zn and organic matter (OM) was measured for each sample. The principal component analysis shows a strong correlation between metal concentration and the lithofacies. This hydrostratigraphic model was implemented in the finite element program Hydrus2D. The soil heterogeneity exerts an impact on the heterogeneity of the water content field under slightly saturated conditions, as they induce capillary barrier effects. These capillary barrier effects may generate water accumulation in some lithofacies overlying matrix-free gravel; they lead to lateral flow patterns known as funneled flows. Knowledge of the geometry (orientation, dip) at the structural scale is therefore a prerequisite for evaluating the preferential flow paths. They can explain that the silt fraction may come from colloidal migration through the vadose zone. The use of coupled water-geochemical transfer models enables us to advance assumptions helping the comprehension of principal hydrogeochemical process in the urban vadose zone.

Domino structures evolution in strike-slip shear zones; the importance of the cataclastic flow

NASA Astrophysics Data System (ADS)

Moreira, N.; Dias, R.

2018-05-01

The Porto-Tomar-Ferreira do Alentejo dextral Shear Zone is one of the most important structures of the Iberian Variscides. In its vicinity, close to Abrantes (Central Portugal), a localized heterogeneous strain pattern developed in a decimetric metamorphic siliceous multilayer. This complex pattern was induced by the D2 dextral shearing of the early S0//S1 foliation in brittle-ductile conditions, giving rise to three main shear zone families. One of these families, with antithetic kinematics, delimits blocks with rigid clockwise rotation surrounded by coeval cataclasites, generating a local domino structure. The proposed geometrical and kinematic analysis, coupled with statistical studies, highlights the relation between subsidiary shear zones and the main shear zone. Despite the heterogeneous strain pattern, a quantitative approach of finite strain was applied based on the restoration of the initial fracture pattern. This approach shows the importance of the cataclastic flow coupled with the translational displacement of the domino domain in solving space problems related to the rigid block rotation. Such processes are key in allowing the rigid block rotation inside shear zones whenever the simple shear component is a fundamental mechanism.

Soil Moisture Flow and Nitrate Movement Simulation through Deep and Heterogeneous Vadose Zone using Dual-porosity Approach

NASA Astrophysics Data System (ADS)

Yadav, B. K.; Tomar, J.; Harter, T.

2014-12-01

We investigate nitrate movement from non-point sources in deep, heterogeneous vadose zones, using multi-dimensional variably saturated flow and transport simulations. We hypothesize that porous media heterogeneity causes saturation variability that leads to preferential flow systems such that a significant portion of the vadose zone does not significantly contribute to flow. We solve Richards' equation and the advection-dispersion equation to simulate soil moisture and nitrate transport regimes in plot-scale experiments conducted in the San Joaquin Valley, California. We compare equilibrium against non-equilibrium (dual-porosity) approaches. In the equilibrium approach we consider each soil layer to have unique hydraulic properties as a whole, while in the dual-porosity approach we assume that large fractions of the porous flow domain are immobile. However we consider exchange of water and solute between mobile and immobile zone using the appropriate mass transfer terms. The results indicate that flow and transport in a nearly 16 m deep stratified vadose zone comprised of eight layers of unconsolidated alluvium experiences highly non-uniform, localized preferential flow and transport patterns leading to accelerated nitrate transfer. The equilibrium approach largely under-predicted the leaching of nitrate to groundwater while the dual-porosity approach showed higher rates of nitrate leaching, consistent with field observations. The dual-porosity approach slightly over-predicted nitrogen storage in the vadose zone, which may be the result of limited matrix flow or denitrification not accounted for in the model. Results of this study may be helpful to better predict fertilizer and pesticide retention times in deep vadose zone, prior to recharge into the groundwater flow system. Keywords: Nitrate, Preferential flow, Heterogeneous vadose zone, Dual-porosity approach

Regional Survey of Structural Properties and Cementation Patterns of Fault Zones in the Northern Part of the Albuquerque Basin, New Mexico - Implications for Ground-Water Flow

USGS Publications Warehouse

Minor, Scott A.; Hudson, Mark R.

2006-01-01

Motivated by the need to document and evaluate the types and variability of fault zone properties that potentially affect aquifer systems in basins of the middle Rio Grande rift, we systematically characterized structural and cementation properties of exposed fault zones at 176 sites in the northern Albuquerque Basin. A statistical analysis of measurements and observations evaluated four aspects of the fault zones: (1) attitude and displacement, (2) cement, (3) lithology of the host rock or sediment, and (4) character and width of distinctive structural architectural components at the outcrop scale. Three structural architectural components of the fault zones were observed: (1) outer damage zones related to fault growth; these zones typically contain deformation bands, shear fractures, and open extensional fractures, which strike subparallel to the fault and may promote ground-water flow along the fault zone; (2) inner mixed zones composed of variably entrained, disrupted, and dismembered blocks of host sediment; and (3) central fault cores that accommodate most shear strain and in which persistent low- permeability clay-rich rocks likely impede the flow of water across the fault. The lithology of the host rock or sediment influences the structure of the fault zone and the width of its components. Different grain-size distributions and degrees of induration of the host materials produce differences in material strength that lead to variations in width, degree, and style of fracturing and other fault-related deformation. In addition, lithology of the host sediment appears to strongly control the distribution of cement in fault zones. Most faults strike north to north-northeast and dip 55? - 77? east or west, toward the basin center. Most faults exhibit normal slip, and many of these faults have been reactivated by normal-oblique and strike slip. Although measured fault displacements have a broad range, from 0.9 to 4,000 m, most are <100 m, and fault zones appear to have formed mainly at depths less than 1,000 m. Fault zone widths do not exceed 40 m (median width = 15.5 m). The mean width of fault cores (0.1 m) is nearly one order of magnitude less than that of mixed zones (0.75 m) and two orders of magnitude less than that of damage zones (9.7 m). Cements, a proxy for localized flow of ancient ground water, are common along fault zones in the basin. Silica cements are limited to faults that are near and strike north to northwest toward the Jemez volcanic field north of the basin, whereas carbonate fault cements are widely distributed. Coarse sediments (gravel and sand) host the greatest concentrations of cement within fault zones. Cements fill some extension fractures and, to a lesser degree, are concentrated along shear fractures and deformation bands within inner damage zones. Cements are commonly concentrated in mixed zones and inner damage zones on one side of a fault and thus are asymmetrically distributed within a fault zone, but cement does not consistently lie on the basinward side of faults. From observed spatial patterns of asymmetrically distributed fault zone cements, we infer that ancient ground-water flow was commonly localized along, and bounded by, faults in the basin. It is apparent from our study that the Albuquerque Basin contains a high concentration of faults. The geometry of, internal structure of, and cement and clay distribution in fault zones have created and will continue to create considerable heterogeneity of permeability within the basin aquifers. The characteristics and statistical range of fault zone features appear to be predictable and consistent throughout the basin; this predictability can be used in ground-water flow simulations that consider the influence of faults.

Analysis of Computational Fluid Dynamics and Particle Image Velocimetry Models of Distal-End Side-to-Side and End-to-Side Anastomoses for Coronary Artery Bypass Grafting in a Pulsatile Flow.

PubMed

Shintani, Yoshiko; Iino, Kenji; Yamamoto, Yoshitaka; Kato, Hiroki; Takemura, Hirofumi; Kiwata, Takahiro

2017-12-25

Intimal hyperplasia (IH) is a major cause of graft failure. Hemodynamic factors such as stagnation and disturbed blood flow are involved in IH formation. The aim of this study is to perform a comparative analysis of distal-end side-to-side (deSTS) and end-to-side (ETS) anastomoses using computational fluid dynamics (CFD) after validating the results via particle image velocimetry (PIV).Methods and Results:We investigated the characteristics of our target flow fields using CFD under steady and pulsatile flows. CFD via PIV under steady flow in a 10-times-actual-size model was validated. The CFD analysis revealed a recirculation zone in the heel region in the deSTS and ETS anastomoses and at the distal end of the graft, and just distal to the toe of the host artery in the deSTS anastomoses. The recirculation zone sizes changed with the phase shift. We found regions of low wall shear stress and high oscillating shear index in the same areas. The PIV and CFD results were similar. It was demonstrated that the hemodynamic characteristics of CFD and PIV is the difference between the deSTS and ETS anastomoses; that is, the deSTS flow peripheral to the distal end of the graft, at the distal end and just distal to the toe of the host artery is involved in the IH formation.

A numerical model investigation of the formation and persistence of an erosion hotspot

USGS Publications Warehouse

Hansen, Jeff E.; Elias, Edwin; List, Jeffrey H.; Barnard, Patrick L.

2011-01-01

A Delft3D-SWAN coupled flow and wave model was constructed for the San Francisco Bight with high-resolution at 7 km-long Ocean Beach, a high-energy beach located immediately south of the Golden Gate, the sole entrance to San Francisco Bay. The model was used to investigate tidal and wave-induced flows, basic forcing terms, and potential sediment transport in an area in the southern portion of Ocean Beach that has eroded significantly over the last several decades. The model predicted flow patterns that were favorable for sediment removal from the area and net erosion from the surf-zone. Analysis of the forcing terms driving surf-zone flows revealed that wave refraction over an exposed wastewater outfall pipe between the 12 and 15 m isobaths introduces a perturbation in the wave field that results in erosion-causing flows. Modeled erosion agreed well with five years of topographic survey data from the area.

Flow stagnation volume and abdominal aortic aneurysm growth: Insights from patient-specific computational flow dynamics of Lagrangian-coherent structures.

PubMed

Joly, Florian; Soulez, Gilles; Garcia, Damien; Lessard, Simon; Kauffmann, Claude

2018-01-01

Abdominal aortic aneurysms (AAA) are localized, commonly-occurring dilations of the aorta. When equilibrium between blood pressure (loading) and wall mechanical resistance is lost, rupture ensues, and patient death follows, if not treated immediately. Experimental and numerical analyses of flow patterns in arteries show direct correlations between wall shear stress and wall mechano-adaptation with the development of zones prone to thrombus formation. For further insights into AAA flow topology/growth interaction, a workout of patient-specific computational flow dynamics (CFD) is proposed to compute finite-time Lyapunov exponents and extract Lagrangian-coherent structures (LCS). This computational model was first compared with 4-D phase-contrast magnetic resonance imaging (MRI) in 5 patients. To better understand the impact of flow topology and transport on AAA growth, hyperbolic, repelling LCS were computed in 1 patient during 8-year follow-up, including 9 volumetric morphologic AAA measures by computed tomography-angiography (CTA). LCS defined barriers to Lagrangian jet cores entering AAA. Domains enclosed between LCS and the aortic wall were considered to be stagnation zones. Their evolution was studied during AAA growth. Good correlation - 2-D cross-correlation coefficients of 0.65, 0.86 and 0.082 (min, max, SD) - was obtained between numerical simulations and 4-D MRI acquisitions in 6 specific cross-sections from 4 patients. In follow-up study, LCS divided AAA lumens into 3 dynamically-isolated zones: 2 stagnation volumes lying in dilated portions of the AAA, and circulating volume connecting the inlet to the outlet. The volume of each zone was tracked over time. Although circulating volume remained unchanged during 8-year follow-up, the AAA lumen and main stagnation zones grew significantly (8 cm 3 /year and 6 cm 3 /year, respectively). This study reveals that transient transport topology can be quantified in patient-specific AAA during disease progression by CTA, in parallel with lumen morphology. It is anticipated that analysis of the main AAA stagnation zones by patient-specific CFD on a yearly basis could help to predict AAA growth and rupture. Copyright © 2017 Elsevier Ltd. All rights reserved.

Complex fragmentation and silicification structures in fault zones: quartz crystallization and repeated fragmentation in the Rusey fault zone (Cornwall/UK)

NASA Astrophysics Data System (ADS)

Yilmaz, Tim I.; Blenkinsop, Tom; Duschl, Florian; Kruhl, Jörn H.

2015-04-01

Silicified fault rocks typically show structures resulting from various stages of fragmentation and quartz crystallization. Both processes interact episodically and result in complex structures on various scales, which require a wide spectrum of analysis tools. Based on field and microstructural data, the spatial-temporal connection between deformation, quartz crystallization and fluid and material flow along the Rusey fault zone was investigated. The fault can be examined in detail in three dimensions on the north Cornwall coast, UK. It occurs within Carboniferous sandstones, siltstones, mudstones and slates of the Culm basin, and is likely to have had a long history. The fault rocks described here formed during the younger events, possibly due to Tertiary strike-slip reactivation. Frequent fragmentation, flow and crystallization events and their interaction led to various generations of complex-structured quartz units, among them quartz-mantled and partly silicified wall-rock fragments, microcrystalline quartz masses of different compositions and structures, and quartz vein patterns of various ages. Lobate boundaries of quartz masses indicate viscous flow. Fragments are separated by quartz infill, which contains cm-sized open pores, in which quartz crystals have pyramidal terminations. Based on frequent occurrence of feathery textures and the infill geometry, quartz crystallization from chalcedony appears likely, and an origin from silica gel is discussed. Fragmentation structures are generally fractal. This allows differentiation between various processes, such as corrosive wear, wear abrasion and hydraulic brecciation. Material transport along the brittle shear zone, and displacement of the wall-rocks, were at least partly governed by flow of mobile fluid-quartz-particle suspensions. The complex meso- to microstructures were generated by repeated processes of fragmentation, quartz precipitation and grain growth. In general, the brittle Rusey fault zone represents a zone of multiple fragmentation, fluid flow, crystallization and quartz dissolution and precipitation, and is regarded as key example of large-scale cyclic interaction of these processes. The geological evidence of interactions between processes implies that feedbacks and highly non-linear mechanical behaviour generated the complex meso- and microstructures. The fault zone rheology may also therefore have been complex.

Determination of the Zone Endangered by Methane Explosion in Goaf with Caving of Longwalls Ventilated on "Y" System

NASA Astrophysics Data System (ADS)

Brodny, Jarosław; Tutak, Magdalena

2016-12-01

One of the most dangerous and most commonly present risks in hard coal mines is methane hazard. During exploitation by longwall system with caving, methane is emitted to mine heading from the mined coal and coal left in a pile. A large amount of methane also flows from neighboring seams through cracks and fissures formed in rock mass. In a case of accumulation of explosive methane concentration in goaf zone and with appropriate oxygen concentration and occurrence of initials (e.g. spark or endogenous fire), it may come to the explosion of this gas. In the paper there are presented results of numerical analysis of mixture of air and methane streams flow through the real heading system of a mine, characterized by high methane hazard. The aim of the studies was to analyze the ventilation system of considered heading system and determination of braking zones in goaf zone, in which dangerous and explosive concertation of methane can occur with sufficient oxygen concentration equal to at least 12%. Determination of position of these zones is necessary for the selection of appropriate parameters of the ventilation system to ensure safety of the crew. Analysis of the scale of methane hazard allows to select such a ventilation system of exploitation and neighboring headings that ensures chemical composition of mining atmosphere required by regulation, and required efficiency of methane drainage. The obtained results clearly show that numerical methods, combined with the results of tests in real conditions can be successfully used for the analysis of variants of processes related to ventilation of underground mining, and also in the analysis of emergency states.

Experimental Investigation of Combustion Stabilization in Supersonic Flow Using Free Recirculation Zones

DTIC Science & Technology

1997-08-01

NUMBERS Experimental Investigation of Combustion Stabilization in Supersonic Flow Using Free F6170896W0291 Recirculation Zones 6. AUTHOR(S) Dr...stabilization in supersonic flow using free recirculation zones Special contract (SPC-96-4043) with Air Force Office of Scientific Research (AFMC), USA, EOARD...of three quarterly reports and presents experimental results on self-ignition and combustion stabilization in supersonic flow using free

Selective transport of palynomorphs in marine turbiditic deposits: An example from the Ascension-Monterey Canyon system offshore central California

USGS Publications Warehouse

McGann, Mary

2017-01-01

The pollen assemblage of a deep-sea core (15G) collected at lower bathyal depths (3491 m) on a levee of Monterey Canyon off central California was investigated to gain insights into the delivery processes of terrigenous material to submarine fans and the effect this transport has on the palynological record. Thirty-two samples were obtained down the length of the core, 19 from hemipelagic and mixed mud deposits considered to be the background record, and 13 others from displaced flow deposits. The pollen record obtained from the background samples documents variations in the terrestrial flora as it adapted to changing climatic conditions over the last 19,000 cal yrs BP. A Q-mode cluster analysis defined three pollen zones: a Glacial Pollen Zone (ca. 20,000–17,000 cal yr BP), an overlying Transitional Pollen Zone (ca. 17,000–11,500 cal yr BP), and an Interglacial Pollen Zone (ca. 11,500 cal yr BP to present). Another Q-mode cluster analysis, of both the background mud and flow deposits, also defined these three pollen zones, but four of the 13 turbiditic deposits were assigned to pollen zones older than expected by their stratigraphic position. This was due to these samples containing statistically significant fewer palynomorphs than the background muds as well as being enriched (∼10–35% in some cases) in hydraulically-efficient Pinus pollen. A selective bias in the pollen assemblage, such as demonstrated here, may result in incorrect interpretations (e.g., climatic shifts or environmental perturbations) based on the floral record, indicating turbiditic deposits should be avoided in marine palynological studies. Particularly in the case of fine-grained flow deposits that may not be visually distinct, granulometry and grain size frequency distribution curves may not be enough to identify these biased deposits. Determining the relative abundance and source of displaced shallow-water benthic foraminifera entrained in these sediments serves as an excellent additional tool to do so.

Constraining geometrical, hydrodynamical and mechanical properties of a fault zone at hourly time scales from ground surface tilt data

NASA Astrophysics Data System (ADS)

Schuite, Jonathan; Longuevergne, Laurent; Bour, Olivier; Burbey, Thomas J.; Boudin, Frédéric

2017-04-01

Flow through reservoirs such as fractured media is powered by pressure gradients which also generate measurable poroelastic deformation of the rock body. The combined analysis of ground surface deformation and sub-surface fluid pressure provides valuable insights of a reservoir's structure and hydromechanical properties, which are of interest for deep-seated CO2 or nuclear waste storage for instance. Amongst all surveying tools, surface tiltmeters offer the possibility to grasp hydraulically-induced deformation over a broad range of time scales with a remarkable precision (1 nanoradian). Here, we investigate the information content of transient surface tilt generated by flow in a kilometer scale sub-vertical fault zone and its surrounding fractured rock matrix. Our approach involves the combined analysis of field data and results of a fully coupled poroelastic model, where fault and matrix are represented as equivalent homogeneous domains. The signature of pressure changes in the fault zone due to pumping cycles is clearly recognizable in field tilt data and we aim to explain the peculiar features that appear in: 1) tilt time series alone from a set of 4 instruments; 2) the ratio of tilt over pressure. With the model, we evidence that the shape of tilt measurements on both sides of a fault zone is sensitive to its diffusivity and its elastic modulus. In particular, we show a few well placed tiltmeters (on each side of a fault) give more information on the medium's properties than well spatialized surface displacement maps. Furthermore, the ratio of tilt over pressure predominantly encompasses information about the system's dynamic behavior and extent of the fault zone, and allows separating contributions of flow in the different compartments. Hence, tiltmeters are well suited to characterize hydromechanical processes associated to fault zone hydrogeology at short time scales, where space-borne surveying methods fail to seize any deformation signal.

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.

Influence of the chemical and electronic structure on the electrical behavior of zirconium oxynitride films

NASA Astrophysics Data System (ADS)

Carvalho, P.; Chappé, J. M.; Cunha, L.; Lanceros-Méndez, S.; Alpuim, P.; Vaz, F.; Alves, E.; Rousselot, C.; Espinós, J. P.; González-Elipe, A. R.

2008-05-01

This work is devoted to the investigation of decorative zirconium oxynitride, ZrOxNy, films prepared by dc reactive magnetron sputtering, using a 17:3 nitrogen-to-oxygen-ratio gas mixture. The color of the films changed from metallic-like, very bright yellow pale, and golden yellow, for low gas mixture flows [from 0 to about 9SCCM (SCCM denotes cubic centimeter per minute at STP)] to red brownish for intermediate gas flows (values up to 12SCCM). Associated to this color change there is a significant decrease of brightness. With further increase of the reactive gas flow, the color of the samples changed from red brownish to dark blue (samples prepared with 13 and 14SCCM). The films deposited with gas flows above 14SCCM showed only apparent colorations due to interference effects. This change in optical behavior from opaque to transparent (characteristic of a transition from metallic to insulating-type materials), promoted by the change in gas flow values, revealed that significant changes were occurring in the film structure and electronic properties, thus opening new potential applications for the films, beyond those of purely decorative ones. Taking this into account, the electrical behavior of the films was investigated as a function of the reactive gas flow and correlated with the observed chemical, electronic, and structural features. The variations in composition disclosed the existence of four different zones, which were correlated to different crystalline structures. For the so-called zone I, x-ray diffraction revealed the development of films with a B1 NaCl face-centered cubic zirconium nitride-type phase, with some texture changes. Increasing the reactive gas flow, the structure of the films is that of a poorly crystallized overstoichiometric nitride phase, which may be similar to that of Zr3N4, but with some probable oxygen inclusions within nitrogen positions. This region was characterized as zone II. Zone III was indexed as an oxynitride-type phase, similar to that of γ-Zr2ON2 with some oxygen atoms occupying some of the nitrogen positions. Finally, occurring at the highest flow rates, zone IV was assigned to a ZrO2 monoclinic-type structure. The composition/structure variations were consistent with the chemical bonding analysis carried out by x-ray photoelectron spectroscopy, which showed oxygen doping in both Zr3N4- and ZrN-type grown films. The electronic properties of the films exhibited significant changes from zone to zone. Resistivity measurements revealed a very wide range of values, varying from relatively highly conductive materials (for zone I) with resistivity values around few hundreds of μΩcm to highly insulating films within zones III and IV, which presented resistivity values in the order of 1015μΩcm. Regarding zone II, corresponding to oxygen doped Zr3N4-type compounds, the observed behavior revealed resistivity values increasing steeply from about 103 up to 1015μΩcm, indicating a systematic transition from metallic to insulating regimes.

A calculation procedure for viscous flow in turbomachines, volume 2

NASA Technical Reports Server (NTRS)

Khalil, J.; Tabakoff, W.

1980-01-01

Turbulent flow within turbomachines having arbitrary blade geometries is examined. Effects of turbulence are modeled using two equations, one expressing the development of the turbulence kinetic energy and the other its dissipation rate. To account for complicated blade geometries, the flow equations are formulated in terms of a nonorthogonal boundary fitted coordinate system. The analysis is applied to a radial inflow turbine. The solution obtained indicates the severity of the complex interaction mechanism that occurs between the different flow regimes (i.e., boundary layers, recirculating eddies, separation zones, etc.). Comparison with nonviscous flow solutions tend to justify strongly the inadequacy of using the latter with standard boundary layer techniques to obtain viscous flow details within turbomachine rotors. Capabilities and limitations of the present method of analysis are discussed.

Experimental and numerical analysis of parallel reactant flow and transverse mixing with mineral precipitation in homogeneous and heterogeneous porous media

DOE PAGES

Fox, Don T.; Guo, Luanjing; Fujita, Yoshiko; ...

2015-12-17

Formation of mineral precipitates in the mixing interface between two reactant solutions flowing in parallel in porous media is governed by reactant mixing by diffusion and dispersion and is coupled to changes in porosity/permeability due to precipitation. The spatial and temporal distribution of mixing-dependent precipitation of barium sulfate in porous media was investigated with side-by-side injection of barium chloride and sodium sulfate solutions in thin rectangular flow cells packed with quartz sand. The results for homogeneous sand beds were compared to beds with higher or lower permeability inclusions positioned in the path of the mixing zone. In the homogeneous andmore » high permeability inclusion experiments, BaSO 4 precipitate (barite) formed in a narrow deposit along the length and in the center of the solution–solution mixing zone even though dispersion was enhanced within, and downstream of, the high permeability inclusion. In the low permeability inclusion experiment, the deflected BaSO 4 precipitation zone broadened around one side and downstream of the inclusion and was observed to migrate laterally toward the sulfate solution. A continuum-scale fully coupled reactive transport model that simultaneously solves the nonlinear governing equations for fluid flow, transport of reactants and geochemical reactions was used to simulate the experiments and provide insight into mechanisms underlying the experimental observations. Lastly, migration of the precipitation zone in the low permeability inclusion experiment could be explained by the coupling effects among fluid flow, reactant transport and localized mineral precipitation reaction.« less

Present heat flow and paleo-geothermal regime in the Canadian Arctic margin: analysis of industrial thermal data and coalification gradients

NASA Astrophysics Data System (ADS)

Majorowicz, Jacek A.; Embry, Ashton F.

1998-06-01

Calculations of the present geothermal gradient and terrestrial heat flow were made on 156 deep wells of the Canadian Arctic Archipelago. Corrected bottom hole temperature (BHT) data and drill stem test (DST) temperatures were used to determine the thermal gradients for sites for which the quality of data was sufficient. Thermal gradients evaluated for depths below the base of permafrost for the onshore wells and below sea bottom for the offshore wells were combined with the estimates of effective thermal conductivity to approximate heat flow for these sites. The present geothermal gradient is in the 15-50 mK/m range (mean = 31 ± 7 mK/m). Present heat flow is mainly in the 35-90 mW/m 2 range (mean = 53 ± 12 mW/m 2). Maps of the present geothermal gradient and present heat flow have been constructed for the basin. The analysis of vitrinite reflectance profiles and the calculation of logarithmic coalification gradients for 101 boreholes in the Sverdrup Basin showed large variations related in many cases to regional variations of present terrestrial heat flow. Paleo-geothermal gradients estimated from these data are mostly in the range of 15-50 mK/m (mean = 28 ± 9 mK/m) and paleo-heat flow is in the 40-90 mW/m 2 range (mean = 57 ± 18 mW/m 2) related to the time of maximum burial in the Early Tertiary. Mean values of the present heat flow and paleo-heat flow for the Sverdrup Basin are almost identical considering the uncertainties of the methods used (53 ± 12 versus 57 ± 18 mW/m 2, respectively). Present geothermal gradients and paleo-geothermal gradients are also close when means are compared (31 ± 7 versus 28 ± 9 mK/m respectively). A zone of high present heat flow and a paleo-heat flow zone coincide in places with the northeastern-southwestern incipient rift landward of the Arctic margin first described by Balkwill and Fox (1982). Correlation between present heat flow and paleo-heat flow for the time of maximum burial in the earliest Tertiary suggests that the high heat flow zone has prevailed since that time.

Assessing lateral flows and solute transport during floods in a conduit-flow-dominated karst system using the inverse problem for the advection-diffusion equation

NASA Astrophysics Data System (ADS)

Cholet, Cybèle; Charlier, Jean-Baptiste; Moussa, Roger; Steinmann, Marc; Denimal, Sophie

2017-07-01

The aim of this study is to present a framework that provides new ways to characterize the spatio-temporal variability of lateral exchanges for water flow and solute transport in a karst conduit network during flood events, treating both the diffusive wave equation and the advection-diffusion equation with the same mathematical approach, assuming uniform lateral flow and solute transport. A solution to the inverse problem for the advection-diffusion equations is then applied to data from two successive gauging stations to simulate flows and solute exchange dynamics after recharge. The study site is the karst conduit network of the Fourbanne aquifer in the French Jura Mountains, which includes two reaches characterizing the network from sinkhole to cave stream to the spring. The model is applied, after separation of the base from the flood components, on discharge and total dissolved solids (TDSs) in order to assess lateral flows and solute concentrations and compare them to help identify water origin. The results showed various lateral contributions in space - between the two reaches located in the unsaturated zone (R1), and in the zone that is both unsaturated and saturated (R2) - as well as in time, according to hydrological conditions. Globally, the two reaches show a distinct response to flood routing, with important lateral inflows on R1 and large outflows on R2. By combining these results with solute exchanges and the analysis of flood routing parameters distribution, we showed that lateral inflows on R1 are the addition of diffuse infiltration (observed whatever the hydrological conditions) and localized infiltration in the secondary conduit network (tributaries) in the unsaturated zone, except in extreme dry periods. On R2, despite inflows on the base component, lateral outflows are observed during floods. This pattern was attributed to the concept of reversal flows of conduit-matrix exchanges, inducing a complex water mixing effect in the saturated zone. From our results we build the functional scheme of the karst system. It demonstrates the impact of the saturated zone on matrix-conduit exchanges in this shallow phreatic aquifer and highlights the important role of the unsaturated zone on storage and transfer functions of the system.

A comparison of the Landsat image and LAHARZ-simulated lahar inundation hazard zone by the 2010 Merapi eruption

NASA Astrophysics Data System (ADS)

Lee, Seul-Ki; Lee, Chang-Wook; Lee, Saro

2015-06-01

Located above the Java subduction zone, Merapi Volcano is an active stratovolcano with a volcanic activity cycle of 1-5 years. Most Merapi eruptions are relatively small with volcanic explosivity index (VEI) of 1-3. However, the most recent eruption, which occurred in 2010, was quite violent with a VEI of 4 and 386 people were killed. In this study, lahars and pyroclastic flow zones were detected using optical Landsat images and the lahar and pyroclastic flow zone simulated using the LAHARZ program. To detect areal extents of lahar and pyroclastic flows using Landsat images, supervised classification was performed after atmospheric correction by using a cosine of the solar zenith correction (COST) model. As a result, the extracted dimensions of pyroclastic flows are nearly identical to the Calatrava Volcanic Province (CVP) monthly reports. Then, areas of potential lahar and pyroclastic flow inundation based on flow volume using the LAHARZ program were simulated and mapped. Finally, the detected lahars and pyroclastic flow zones were compared with the simulated potential zones using LAHARZ program and verified. Results showed satisfactory similarity (55.63 %) between the detected and simulated zone. The simulated zones using the LAHARZ program can be used as an essential volcanic hazard map for preventing life and property damages for Merapi Volcano and other hazardous volcanic areas. Also, the LAHARZ program can be used to map volcano hazards in other hazardous volcanic areas.

Fluid pressure development beneath the décollement at the Nankai subduction zone: its implications for slow earthquakes

NASA Astrophysics Data System (ADS)

Hirose, T.; Kamiya, N.; Yamamoto, Y.; Heuer, V.; Inagaki, F.; Kubo, Y.

2017-12-01

Pore fluid pressure along a fault zone is very important for understanding earthquake generation processes in subduction zones. However, quantitative constraints on the pore pressure are quite limited. Here we report two estimates of the pore pressure developed within the underthrust sediments in the Nankai Trough off Cape Muroto, Japan, using the shipboard data obtained during IODP Expedition 370 (Heuer et al., 2017). First estimates are based on the depth trend of porosity data in the lower Shikoku Basin (LSB) facies, in which the décollement zone has propagated. Porosities in the LSB facies generally decrease with depth, but turn to increase by 5-7% below the décollement zone at 760 mbsf. Deeper than 830 mbsf, porosities resume a general compaction trend. By applying the method followed by Screaton et al. (2002) in which the downward porosity-increase is reflected by an excess pore pressure, we estimated the highest excess pore pressure of 4.2 MPa (λ* = 0.4: a ratio of excess pore pressure to effective overburden stress) at 1020 mbsf within the underthrust sediments. Another estimate is based on the analysis of upwelling drilling-mud flow from the borehole, which is a direct evidence the development of overpressure. We assumed that the borehole penetrated a disc-shaped high pore pressure zone with 10 m thickness and the steady-state flow. Then the pore pressure for a given radius of the disc-shaped zone, which is necessary for explaining the observed flow rate, was calculated using Darcy's law. The calculation yields that the pore pressure exceeded by 2-4 MPa above hydrostatic in case of the 10-13 m2 permeability and the 100-1000 m radius of the disc-shaped zone. Our analysis indicates a significant development of excess pore pressure beneath the décollement zone, most likely at the depth of 1020 mbsf where the highest overpressure was estimated from the downhole porosity trend and also an anomaly in relative hydrocarbon gas concentrations. Friction experiments by Sawai et al. (2016) show that a transition from stable to unstable slip behavior appears with increasing pore fluid pressure that is a prerequisite for the generation of slow earthquakes. Thus, slow earthquakes that occurred off Cape Muroto (Obara & Kato, 2016) can be attributed with the observed significant overpressure beneath the décollement.

Using Heat as a Tracer to Estimate Saline Groundwater Fluxes from the Deep Aquifer System to the Shallow Aquifers and the Rio Grande in the Mesilla Basin, New Mexico, USA

NASA Astrophysics Data System (ADS)

Pepin, J. D.; Robertson, A.; Ferguson, C.; Burns, E. R.

2017-12-01

Heat is used as a tracer to estimate vertical groundwater flow and associated saline fluxes from deep (greater than 1 km) parts of the Mesilla Basin regional aquifer to the Rio Grande. Profiles of temperature with depth below ground surface are used to locate groundwater upflow zones and to estimate associated salinity fluxes. The results of this study will inform understanding of the impact of deep saline groundwater on regional water supplies. The Mesilla Basin in southern New Mexico, Texas, and Chihuahua, Mexico was designated by the U.S. as a priority transboundary aquifer in part because of the presence of the Rio Grande within the basin. Declining water levels, deteriorating water quality in both the aquifer and the river, and increasing use of water resources on both sides of the international border raise concerns about the sustainability of regional water supplies. The Rio Grande chloride concentration increases by about 130% (120 ppm to 280 ppm) as the river traverses the Mesilla Basin. Previous research attributed this reduction in water quality to the upwelling of deep sedimentary brines and geothermal waters within the basin. However, the spatial distribution of these upflow zones and their groundwater flow rates are poorly understood. Temperature profiles from 374 existing boreholes within the Mesilla Basin indicate that temperature-profile shape is affected by heat advection in the basin. Three distinct geothermal upflow zones were identified along regional fault zones in the study area based on the temperature profiles. Groundwater in these zones is considered thermal, having temperatures greater than 50°C at depths of less than 200 m. Identification of upflow-zone profiles combines analysis of temperature profiles, lithologic records, well-completion data, and profile derivatives. The Bredehoeft and Papadopulos (1965) one-dimensional heat-transport analytical solution will be applied to upflow-zone profiles to estimate the corresponding vertical groundwater flow rates. Temperature, heat flow, and salinity maps will be constructed to approximate the areal extents of identified upflow zones. These areal estimates will then be combined with the 1D vertical groundwater flow calculations and salinity data to quantify volumetric salinity fluxes to the shallow aquifer system and Rio Grande.

Sequence-Stratigraphic Analysis of the Regional Observation Monitoring Program (ROMP) 29A Test Corehole and Its Relation to Carbonate Porosity and Regional Transmissivity in the Floridan Aquifer System, Highlands County, Florida

USGS Publications Warehouse

Ward, W. C.; Cunningham, K.J.; Renken, R.A.; Wacker, M.A.; Carlson, J.I.

2003-01-01

An analysis was made to describe and interpret the lithology of a part of the Upper Floridan aquifer penetrated by the Regional Observation Monitoring Program (ROMP) 29A test corehole in Highlands County, Florida. This information was integrated into a one-dimensional hydrostratigraphic model that delineates candidate flow zones and confining units in the context of sequence stratigraphy. Results from this test corehole will serve as a starting point to build a robust three-dimensional sequence-stratigraphic framework of the Floridan aquifer system. The ROMP 29A test corehole penetrated the Avon Park Formation, Ocala Limestone, Suwannee Limestone, and Hawthorn Group of middle Eocene to Pliocene age. The part of the Avon Park Formation penetrated in the ROMP 29A test corehole contains two composite depositional sequences. A transgressive systems tract and a highstand systems tract were interpreted for the upper composite sequence; however, only a highstand systems tract was interpreted for the lower composite sequence of the deeper Avon Park stratigraphic section. The composite depositional sequences are composed of at least five high-frequency depositional sequences. These sequences contain high-frequency cycle sets that are an amalgamation of vertically stacked high-frequency cycles. Three types of high-frequency cycles have been identified in the Avon Park Formation: peritidal, shallow subtidal, and deeper subtidal high-frequency cycles. The vertical distribution of carbonate-rock diffuse flow zones within the Avon Park Formation is heterogeneous. Porous vuggy intervals are less than 10 feet, and most are much thinner. The volumetric arrangement of the diffuse flow zones shows that most occur in the highstand systems tract of the lower composite sequence of the Avon Park Formation as compared to the upper composite sequence, which contains both a backstepping transgressive systems tract and a prograding highstand systems tract. Although the porous and permeable layers are not thick, some intervals may exhibit lateral continuity because of their deposition on a broad low-relief ramp. A thick interval of thin vuggy zones and open faults forms thin conduit flow zones mixed with relatively thicker carbonate-rock diffuse flow zones between a depth of 1,070 and 1,244 feet below land surface (bottom of the test corehole). This interval is the most transmissive part of the Avon Park Formation penetrated in the ROMP 29A test corehole and is included in the highstand systems tract of the lower composite sequence. The Ocala Limestone is considered to be a semiconfining unit and contains three depositional sequences penetrated by the ROMP 29A test corehole. Deposited within deeper subtidal depositional cycles, no zones of enhanced porosity and permeability are expected in the Ocala Limestone. A thin erosional remnant of the shallow marine Suwannee Limestone overlies the Ocala Limestone, and permeability seems to be comparatively low because moldic porosity is poorly connected. Rocks that comprise the lower Hawthorn Group, Suwannee Limestone, and Ocala Limestone form a permeable upper zone of the Upper Floridan aquifer, and rocks of the lower Ocala Limestone and Avon Park Formation form a permeable lower zone of the Upper Floridan aquifer. On the basis of a preliminary analysis of transmissivity estimates for wells located north of Lake Okeechobee, spatial relations among groups of relatively high and low transmissivity values within the upper zone are evident. Upper zone transmissivity is generally less than 10,000 feet squared per day in areas located south of a line that extends through Charlotte, Sarasota, DeSoto, Highlands, Polk, Osceola, Okeechobee, and St. Lucie Counties. Transmissivity patterns within the lower zone of the Avon Park Formation cannot be regionally assessed because insufficient data over a wide areal extent have not been compiled.

Seismic evidence for flow in the hydrated mantle wedge of the Ryukyu subduction zone

PubMed Central

Nagaya, Takayoshi; Walker, Andrew M.; Wookey, James; Wallis, Simon R.; Ishii, Kazuhiko; Kendall, J. -Michael

2016-01-01

It is widely accepted that water-rich serpentinite domains are commonly present in the mantle above shallow subducting slabs and play key roles in controlling the geochemical cycling and physical properties of subduction zones. Thermal and petrological models show the dominant serpentine mineral is antigorite. However, there is no good consensus on the amount, distribution and alignment of this mineral. Seismic velocities are commonly used to identify antigorite-rich domains, but antigorite is highly-anisotropic and depending on the seismic ray path, its properties can be very difficult to distinguish from non-hydrated olivine-rich mantle. Here, we utilize this anisotropy and show how an analysis of seismic anisotropy that incorporates measured ray path geometries in the Ryukyu arc can constrain the distribution, orientation and amount of antigorite. We find more than 54% of the wedge must consist of antigorite and the alignment must change from vertically aligned to parallel to the slab. This orientation change suggests convective flow in the hydrated forearc mantle. Shear wave splitting analysis in other subduction zones indicates large-scale serpentinization and forearc mantle convection are likely to be more widespread than generally recognized. The view that the forearc mantle of cold subduction zones is dry needs to be reassessed. PMID:27436676

Seismic evidence for flow in the hydrated mantle wedge of the Ryukyu subduction zone.

PubMed

Nagaya, Takayoshi; Walker, Andrew M; Wookey, James; Wallis, Simon R; Ishii, Kazuhiko; Kendall, J-Michael

2016-07-20

It is widely accepted that water-rich serpentinite domains are commonly present in the mantle above shallow subducting slabs and play key roles in controlling the geochemical cycling and physical properties of subduction zones. Thermal and petrological models show the dominant serpentine mineral is antigorite. However, there is no good consensus on the amount, distribution and alignment of this mineral. Seismic velocities are commonly used to identify antigorite-rich domains, but antigorite is highly-anisotropic and depending on the seismic ray path, its properties can be very difficult to distinguish from non-hydrated olivine-rich mantle. Here, we utilize this anisotropy and show how an analysis of seismic anisotropy that incorporates measured ray path geometries in the Ryukyu arc can constrain the distribution, orientation and amount of antigorite. We find more than 54% of the wedge must consist of antigorite and the alignment must change from vertically aligned to parallel to the slab. This orientation change suggests convective flow in the hydrated forearc mantle. Shear wave splitting analysis in other subduction zones indicates large-scale serpentinization and forearc mantle convection are likely to be more widespread than generally recognized. The view that the forearc mantle of cold subduction zones is dry needs to be reassessed.

Passively actuated valve

DOEpatents

Modro, S. Michael; Ougouag, Abderrafi M.

2005-09-20

A passively actuated valve for isolating a high pressure zone from a low pressure zone and discontinuing the isolation when the pressure in the high pressure zone drops below a preset threshold. If the pressure in the high pressure zone drops below the preset threshold, the valve opens and allows flow from the high pressure zone to the low pressure zone. The valve remains open allowing pressure equalization and back-flow should a pressure inversion between the two pressure zone occur.

Spiral blood flow in aorta-renal bifurcation models.

PubMed

Javadzadegan, Ashkan; Simmons, Anne; Barber, Tracie

2016-01-01

The presence of a spiral arterial blood flow pattern in humans has been widely accepted. It is believed that this spiral component of the blood flow alters arterial haemodynamics in both positive and negative ways. The purpose of this study was to determine the effect of spiral flow on haemodynamic changes in aorta-renal bifurcations. In this regard, a computational fluid dynamics analysis of pulsatile blood flow was performed in two idealised models of aorta-renal bifurcations with and without flow diverter. The results show that the spirality effect causes a substantial variation in blood velocity distribution, while causing only slight changes in fluid shear stress patterns. The dominant observed effect of spiral flow is on turbulent kinetic energy and flow recirculation zones. As spiral flow intensity increases, the rate of turbulent kinetic energy production decreases, reducing the region of potential damage to red blood cells and endothelial cells. Furthermore, the recirculation zones which form on the cranial sides of the aorta and renal artery shrink in size in the presence of spirality effect; this may lower the rate of atherosclerosis development and progression in the aorta-renal bifurcation. These results indicate that the spiral nature of blood flow has atheroprotective effects in renal arteries and should be taken into consideration in analyses of the aorta and renal arteries.

A chaotic-dynamical conceptual model to describe fluid flow and contaminant transport in a fractured vadose zone. 1997 progress report and presentations at the annual meeting, Ernest Orlando Lawrence Berkeley National Laboratory, December 3--4, 1997

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

Faybishenko, B.; Doughty, C.; Geller, J.

1998-07-01

Understanding subsurface flow and transport processes is critical for effective assessment, decision-making, and remediation activities for contaminated sites. However, for fluid flow and contaminant transport through fractured vadose zones, traditional hydrogeological approaches are often found to be inadequate. In this project, the authors examine flow and transport through a fractured vadose zone as a deterministic chaotic dynamical process, and develop a model of it in these terms. Initially, the authors examine separately the geometric model of fractured rock and the flow dynamics model needed to describe chaotic behavior. Ultimately they will put the geometry and flow dynamics together to developmore » a chaotic-dynamical model of flow and transport in a fractured vadose zone. They investigate water flow and contaminant transport on several scales, ranging from small-scale laboratory experiments in fracture replicas and fractured cores, to field experiments conducted in a single exposed fracture at a basalt outcrop, and finally to a ponded infiltration test using a pond of 7 by 8 m. In the field experiments, they measure the time-variation of water flux, moisture content, and hydraulic head at various locations, as well as the total inflow rate to the subsurface. Such variations reflect the changes in the geometry and physics of water flow that display chaotic behavior, which they try to reconstruct using the data obtained. In the analysis of experimental data, a chaotic model can be used to predict the long-term bounds on fluid flow and transport behavior, known as the attractor of the system, and to examine the limits of short-term predictability within these bounds. This approach is especially well suited to the need for short-term predictions to support remediation decisions and long-term bounding studies. View-graphs from ten presentations made at the annual meeting held December 3--4, 1997 are included in an appendix to this report.« less

Application of carbonate cyclostratigraphy and borehole geophysics to delineate porosity and preferential flow in the karst limestone of the Biscayne aquifer, SE Florida

USGS Publications Warehouse

Cunningham, K.J.; Renken, R.A.; Wacker, M.A.; Zygnerski, M.R.; Robinson, E.; Shapiro, A.M.; Wingard, G.L.

2006-01-01

Combined analyses of cores, borehole geophysical logs, and cyclostratigraphy produced a new conceptual hydrogeologic framework for the triple-porosity (matrix, touching-vug, and conduit porosity) karst limestone of the Biscayne aquifer in a 0.65 km2 study area, SE Florida. Vertical lithofacies successions, which have recurrent stacking patterns, fit within high-frequency cycles. We define three ideal high-frequency cycles as: (1) upward-shallowing subtidal cycles, (2) upward-shallowing paralic cycles, and (3) aggradational subtidal cycles. Digital optical borehole images, tracers, and flow meters indicate that there is a predictable vertical pattern of porosity and permeability within the three ideal cycles, because the distribution of porosity and permeability is related to lithofacies. Stratiform zones of high permeability commonly occur just above flooding surfaces in the lower part of upward-shallowing subtidal and paralic cycles, forming preferential groundwater flow zones. Aggradational subtidal cycles are either mostly high-permeability zones or leaky, low-permeability units. In the study area, groundwater flow within stratiform high-permeability zones is through a secondary pore system of touching-vug porosity principally related to molds of burrows and pelecypods and to interburrow vugs. Movement of a dye-tracer pulse observed using a borehole fluid-temperature tool during a conservative tracer test indicates heterogeneous permeability. Advective movement of the tracer appears to be most concentrated within a thin stratiform flow zone contained within the lower part of a high-frequency cycle, indicating a distinctly high relative permeability for this zone. Borehole flow-meter measurements corroborate the relatively high permeability of the flow zone. Identification and mapping of such high-permeability flow zones is crucial to conceptualization of karst groundwater flow within a cyclostratigraphic framework. Many karst aquifers are included in cyclic platform carbonates. Clearly, a cyclostratigraphic approach that translates carbonate aquifer heterogeneity into a consistent framework of correlative units will improve simulation of karst groundwater flow. ?? 2006 Geological Society of America.

Suppression of flow pulsation activity by relaxation process of additive effect on viscous media transport

NASA Astrophysics Data System (ADS)

Kharlamov, S.; Dedeyev, P.; Meucci, L.; Shenderova, I.; Manastirniy, A.; Usenko, M.

2015-11-01

The article presents the analysis of the processes occurring together with the turbulent transfer of impulse in mixture of hydrocarbon fluid and polymer solutions (anti-turbulent additives). The study evaluates complex shear flows by popular theoretical and practical methods. Understanding of hydrodynamic and dissipative effects of laminar-turbulent transition tightening and turbulence suppression is provided. The peculiarities of "thin" flow structure in pipeline zones with complex shape walls are evaluated. Recommendations to forecast the local flow parameters, calculation of hydraulic resistance are given.

Entrainment-Zone Restratification and Flow Structures in Stratified Shear Turbulence

NASA Technical Reports Server (NTRS)

Reif, B. Anders Pettersson; Werne, Joseph; Andreassen, Oyvind; Meyer, Christian; Davis-Mansour, Melissa

2002-01-01

Late-time dynamics and morphology of a stratified turbulent shear layer are examined using 1) Reynolds-stress and heat-flux budgets, 2) the single-point structure tensors introduced by Kassinos et al. (2001), and 3) flow visualization via 3D volume rendering. Flux reversal is observed during restratification in the edges of the turbulent layer. We present a first attempt to quantify the turbulence-mean-flow interaction and to characterize the predominant flow structures. Future work will extend this analysis to earlier times and different values of the Reynolds and Richardson numbers.

Transition zone cells reach G2 phase before initiating elongation in maize root apex

PubMed Central

Alarcón, M. Victoria

2017-01-01

ABSTRACT Root elongation requires cell divisions in the meristematic zone and cell elongation in the elongation zone. The boundary between dividing and elongating cells is called the transition zone. In the meristem zone, initial cells are continuously dividing, but on the basal side of the meristem cells exit the meristem through the transition zone and enter in the elongation zone, where they stop division and rapidly elongate. Throughout this journey cells are accompanied by changes in cell cycle progression. Flow cytometry analysis showed that meristematic cells are in cycle, but exit when they enter the elongation zone. In addition, the percentage of cells in G2 phase (4C) strongly increased from the meristem to the elongation zone. However, we did not observe remarkable changes in the percentage of cells in cell cycle phases along the entire elongation zone. These results suggest that meristematic cells in maize root apex stop the cell cycle in G2 phase after leaving the meristem. PMID:28495964

Preferential Flow Paths In A Karstified Spring Catchment: A Study Of Fault Zones As Conduits To Rapid Groundwater Flow

NASA Astrophysics Data System (ADS)

Kordilla, J.; Terrell, A. N.; Veltri, M.; Sauter, M.; Schmidt, S.

2017-12-01

In this study we model saturated and unsaturated flow in the karstified Weendespring catchment, located within the Leinetal graben in Goettingen, Germany. We employ the finite element COMSOL Multiphysics modeling software to model variably saturated flow using the Richards equation with a van Genuchten type parameterization. As part of the graben structure, the Weende spring catchment is intersected by seven fault zones along the main flow path of the 7400 m cross section of the catchment. As the Weende spring is part of the drinking water supply in Goettingen, it is particularly important to understand the vulnerability of the catchment and effect of fault zones on rapid transport of contaminants. Nitrate signals have been observed at the spring only a few days after the application of fertilizers within the catchment at a distance of approximately 2km. As the underlying layers are known to be highly impermeable, fault zones within the area are likely to create rapid flow paths to the water table and the spring. The model conceptualizes the catchment as containing three hydrogeological limestone units with varying degrees of karstification: the lower Muschelkalk limestone as a highly conductive layer, the middle Muschelkalk as an aquitard, and the upper Muschelkalk as another conductive layer. The fault zones are parameterized based on a combination of field data from quarries, remote sensing and literary data. The fault zone is modeled considering the fracture core as well as the surrounding damage zone with separate, specific hydraulic properties. The 2D conceptual model was implemented in COMSOL to study unsaturated flow at the catchment scale using van Genuchten parameters. The study demonstrates the importance of fault zones for preferential flow within the catchment and its effect on the spatial distribution of vulnerability.

Boolean logic analysis for flow regime recognition of gas-liquid horizontal flow

NASA Astrophysics Data System (ADS)

Ramskill, Nicholas P.; Wang, Mi

2011-10-01

In order to develop a flowmeter for the accurate measurement of multiphase flows, it is of the utmost importance to correctly identify the flow regime present to enable the selection of the optimal method for metering. In this study, the horizontal flow of air and water in a pipeline was studied under a multitude of conditions using electrical resistance tomography but the flow regimes that are presented in this paper have been limited to plug and bubble air-water flows. This study proposes a novel method for recognition of the prevalent flow regime using only a fraction of the data, thus rendering the analysis more efficient. By considering the average conductivity of five zones along the central axis of the tomogram, key features can be identified, thus enabling the recognition of the prevalent flow regime. Boolean logic and frequency spectrum analysis has been applied for flow regime recognition. Visualization of the flow using the reconstructed images provides a qualitative comparison between different flow regimes. Application of the Boolean logic scheme enables a quantitative comparison of the flow patterns, thus reducing the subjectivity in the identification of the prevalent flow regime.

Relations between well-field pumping and induced canal leakage in east-central Miami-Dade County, Florida, 2010-2011

USGS Publications Warehouse

Nemec, Katherine; Antolino, Dominick J.; Turtora, Michael; Adam Foster,

2015-08-26

Results from the groundwater model and the stable isotope data analysis indicate the importance of considering geologic heterogeneity when investigating the relations between pumping and canal leakage, not only at this site, but also at other sites with similar heterogeneous geology. The model results were consistently sensitive to the hydrogeologic framework and changes in hydraulic conductivities. The model and the isotope data indicate that the majority of the groundwater/surface-water interactions occurred within the shallow flow zone. A relatively lower-permeability geologic layer occurring between the shallowest and deep preferential flow zones lessens the interactions between the production wells and the canal.

Numerical solution of nonlinear partial differential equations of mixed type. [finite difference approximation

NASA Technical Reports Server (NTRS)

Jameson, A.

1976-01-01

A review is presented of some recently developed numerical methods for the solution of nonlinear equations of mixed type. The methods considered use finite difference approximations to the differential equation. Central difference formulas are employed in the subsonic zone and upwind difference formulas are used in the supersonic zone. The relaxation method for the small disturbance equation is discussed and a description is given of difference schemes for the potential flow equation in quasi-linear form. Attention is also given to difference schemes for the potential flow equation in conservation form, the analysis of relaxation schemes by the time dependent analogy, the accelerated iterative method, and three-dimensional calculations.

Modeling variably saturated subsurface solute transport with MODFLOW-UZF and MT3DMS

USGS Publications Warehouse

Morway, Eric D.; Niswonger, Richard G.; Langevin, Christian D.; Bailey, Ryan T.; Healy, Richard W.

2013-01-01

The MT3DMS groundwater solute transport model was modified to simulate solute transport in the unsaturated zone by incorporating the unsaturated-zone flow (UZF1) package developed for MODFLOW. The modified MT3DMS code uses a volume-averaged approach in which Lagrangian-based UZF1 fluid fluxes and storage changes are mapped onto a fixed grid. Referred to as UZF-MT3DMS, the linked model was tested against published benchmarks solved analytically as well as against other published codes, most frequently the U.S. Geological Survey's Variably-Saturated Two-Dimensional Flow and Transport Model. Results from a suite of test cases demonstrate that the modified code accurately simulates solute advection, dispersion, and reaction in the unsaturated zone. Two- and three-dimensional simulations also were investigated to ensure unsaturated-saturated zone interaction was simulated correctly. Because the UZF1 solution is analytical, large-scale flow and transport investigations can be performed free from the computational and data burdens required by numerical solutions to Richards' equation. Results demonstrate that significant simulation runtime savings can be achieved with UZF-MT3DMS, an important development when hundreds or thousands of model runs are required during parameter estimation and uncertainty analysis. Three-dimensional variably saturated flow and transport simulations revealed UZF-MT3DMS to have runtimes that are less than one tenth of the time required by models that rely on Richards' equation. Given its accuracy and efficiency, and the wide-spread use of both MODFLOW and MT3DMS, the added capability of unsaturated-zone transport in this familiar modeling framework stands to benefit a broad user-ship.

Modeling variably saturated subsurface solute transport with MODFLOW-UZF and MT3DMS.

PubMed

Morway, Eric D; Niswonger, Richard G; Langevin, Christian D; Bailey, Ryan T; Healy, Richard W

2013-03-01

The MT3DMS groundwater solute transport model was modified to simulate solute transport in the unsaturated zone by incorporating the unsaturated-zone flow (UZF1) package developed for MODFLOW. The modified MT3DMS code uses a volume-averaged approach in which Lagrangian-based UZF1 fluid fluxes and storage changes are mapped onto a fixed grid. Referred to as UZF-MT3DMS, the linked model was tested against published benchmarks solved analytically as well as against other published codes, most frequently the U.S. Geological Survey's Variably-Saturated Two-Dimensional Flow and Transport Model. Results from a suite of test cases demonstrate that the modified code accurately simulates solute advection, dispersion, and reaction in the unsaturated zone. Two- and three-dimensional simulations also were investigated to ensure unsaturated-saturated zone interaction was simulated correctly. Because the UZF1 solution is analytical, large-scale flow and transport investigations can be performed free from the computational and data burdens required by numerical solutions to Richards' equation. Results demonstrate that significant simulation runtime savings can be achieved with UZF-MT3DMS, an important development when hundreds or thousands of model runs are required during parameter estimation and uncertainty analysis. Three-dimensional variably saturated flow and transport simulations revealed UZF-MT3DMS to have runtimes that are less than one tenth of the time required by models that rely on Richards' equation. Given its accuracy and efficiency, and the wide-spread use of both MODFLOW and MT3DMS, the added capability of unsaturated-zone transport in this familiar modeling framework stands to benefit a broad user-ship. Published 2012. This article is a U.S. Government work and is in the public domain in the USA.

Important observations and parameters for a salt water intrusion model

USGS Publications Warehouse

Shoemaker, W.B.

2004-01-01

Sensitivity analysis with a density-dependent ground water flow simulator can provide insight and understanding of salt water intrusion calibration problems far beyond what is possible through intuitive analysis alone. Five simple experimental simulations presented here demonstrate this point. Results show that dispersivity is a very important parameter for reproducing a steady-state distribution of hydraulic head, salinity, and flow in the transition zone between fresh water and salt water in a coastal aquifer system. When estimating dispersivity, the following conclusions can be drawn about the data types and locations considered. (1) The "toe" of the transition zone is the most effective location for hydraulic head and salinity observations. (2) Areas near the coastline where submarine ground water discharge occurs are the most effective locations for flow observations. (3) Salinity observations are more effective than hydraulic head observations. (4) The importance of flow observations aligned perpendicular to the shoreline varies dramatically depending on distance seaward from the shoreline. Extreme parameter correlation can prohibit unique estimation of permeability parameters such as hydraulic conductivity and flow parameters such as recharge in a density-dependent ground water flow model when using hydraulic head and salinity observations. Adding flow observations perpendicular to the shoreline in areas where ground water is exchanged with the ocean body can reduce the correlation, potentially resulting in unique estimates of these parameter values. Results are expected to be directly applicable to many complex situations, and have implications for model development whether or not formal optimization methods are used in model calibration.

Important observations and parameters for a salt water intrusion model.

PubMed

Shoemaker, W Barclay

2004-01-01

Sensitivity analysis with a density-dependent ground water flow simulator can provide insight and understanding of salt water intrusion calibration problems far beyond what is possible through intuitive analysis alone. Five simple experimental simulations presented here demonstrate this point. Results show that dispersivity is a very important parameter for reproducing a steady-state distribution of hydraulic head, salinity, and flow in the transition zone between fresh water and salt water in a coastal aquifer system. When estimating dispersivity, the following conclusions can be drawn about the data types and locations considered. (1) The "toe" of the transition zone is the most effective location for hydraulic head and salinity observations. (2) Areas near the coastline where submarine ground water discharge occurs are the most effective locations for flow observations. (3) Salinity observations are more effective than hydraulic head observations. (4) The importance of flow observations aligned perpendicular to the shoreline varies dramatically depending on distance seaward from the shoreline. Extreme parameter correlation can prohibit unique estimation of permeability parameters such as hydraulic conductivity and flow parameters such as recharge in a density-dependent ground water flow model when using hydraulic head and salinity observations. Adding flow observations perpendicular to the shoreline in areas where ground water is exchanged with the ocean body can reduce the correlation, potentially resulting in unique estimates of these parameter values. Results are expected to be directly applicable to many complex situations, and have implications for model development whether or not formal optimization methods are used in model calibration.

Investigation of the fluid flow dynamic parameters for Newtonian and non-Newtonian materials: an approach to understanding the fluid flow-like structures within fault zones

NASA Astrophysics Data System (ADS)

Tanaka, H.; Shiomi, Y.; Ma, K.-F.

2017-11-01

To understand the fault zone fluid flow-like structure, namely the ductile deformation structure, often observed in the geological field (e.g., Ramsay and Huber The techniques of modern structure geology, vol. 1: strain analysis, Academia Press, London, 1983; Hobbs and Ord Structure geology: the mechanics of deforming metamorphic rocks, Vol. I: principles, Elsevier, Amsterdam, 2015), we applied a theoretical approach to estimate the rate of deformation, the shear stress and the time to form a streak-line pattern in the boundary layer of viscous fluids. We model the dynamics of streak lines in laminar boundary layers for Newtonian and pseudoplastic fluids and compare the results to those obtained via laboratory experiments. The structure of deformed streak lines obtained using our model is consistent with experimental observations, indicating that our model is appropriate for understanding the shear rate, flow time and shear stress based on the profile of deformed streak lines in the boundary layer in Newtonian and pseudoplastic viscous materials. This study improves our understanding of the transportation processes in fluids and of the transformation processes in fluid-like materials. Further application of this model could facilitate understanding the shear stress and time history of the fluid flow-like structure of fault zones observed in the field.[Figure not available: see fulltext.

3D-printed and CNC milled flow-cells for chemiluminescence detection.

PubMed

Spilstead, Kara B; Learey, Jessica J; Doeven, Egan H; Barbante, Gregory J; Mohr, Stephan; Barnett, Neil W; Terry, Jessica M; Hall, Robynne M; Francis, Paul S

2014-08-01

Herein we explore modern fabrication techniques for the development of chemiluminescence detection flow-cells with features not attainable using the traditional coiled tubing approach. This includes the first 3D-printed chemiluminescence flow-cells, and a milled flow-cell designed to split the analyte stream into two separate detection zones within the same polymer chip. The flow-cells are compared to conventional detection systems using flow injection analysis (FIA) and high performance liquid chromatography (HPLC), with the fast chemiluminescence reactions of an acidic potassium permanganate reagent with morphine and a series of adrenergic phenolic amines. Copyright © 2014 Elsevier B.V. All rights reserved.

Approach for delineation of contributing areas and zones of transport to selected public-supply wells using a regional ground-water flow model, Palm Beach County, Florida

USGS Publications Warehouse

Renken, R.A.; Patterson, R.D.; Orzol, L.L.; Dixon, Joann

2001-01-01

Rapid urban development and population growth in Palm Beach County, Florida, have been accompanied with the need for additional freshwater withdrawals from the surficial aquifer system. To maintain water quality, County officials protect capture areas and determine zones of transport of municipal supply wells. A multistep process was used to help automate the delineation of wellhead protection areas. A modular ground-water flow model (MODFLOW) Telescopic Mesh Refinement program (MODTMR) was used to construct an embedded flow model and combined with particle tracking to delineate zones of transport to supply wells; model output was coupled with a geographic information system. An embedded flow MODFLOW model was constructed using input and output file data from a preexisting three-dimensional, calibrated model of the surficial aquifer system. Three graphical user interfaces for use with the geographic information software, ArcView, were developed to enhance the telescopic mesh refinement process. These interfaces include AvMODTMR for use with MODTMR; AvHDRD to build MODFLOW river and drain input files from dynamically segmented linear (canals) data sets; and AvWELL Refiner, an interface designed to examine and convert well coverage spatial data layers to a MODFLOW Well package input file. MODPATH (the U.S. Geological Survey particle-tracking postprocessing program) and MODTOOLS (the set of U.S. Geological Survey computer programs to translate MODFLOW and MODPATH output to a geographic information system) were used to map zones of transport. A steady-state, five-layer model of the Boca Raton area was created using the telescopic mesh refinement process and calibrated to average conditions during January 1989 to June 1990. A sensitivity analysis of various model parameters indicates that the model is most sensitive to changes in recharge rates, hydraulic conductivity for layer 1, and leakance for layers 3 and 4 (Biscayne aquifer). Recharge (58 percent); river (canal) leakance (29 percent); and inflow through the northern, western, and southern prescribed flux model boundaries (10 percent) represent the major inflow components. Principal outflow components in the Boca Raton well field area include well discharge (56 percent), river (canal) leakance (27 percent), and water that discharges along the coast (10 percent). A particle-tracking analysis using MODPATH was conducted to better understand well-field ground-water flow patterns and time of travel. MODTOOLS was used to construct zones-of-transport spatial data for municipal supply wells. Porosity estimates were uniformly increased to study the effect of porosity on zones of transport. Where porosity was increased, the size of the zones of transport were shown to decrease.

Field-testing competing runoff source and hydrochemical conceptualisations

NASA Astrophysics Data System (ADS)

Western, A. W.; Saffarpour, S.; Adams, R.; Costelloe, J. F.; McDonnell, J.

2014-12-01

There are competing conceptualisations of heterogeneity in catchment systems. It is often convenient to divide catchments into zones, for example the soil profile, groundwater aquifers (saturated zone), riparian zones, etc. We also often divide flow sources into distinct categories such as surface runoff, interflow and baseflow, implying a few distinct stores of water. In tracer hydrology we typically assume water from such zones has distinct and invariant chemistry that is used to infer the runoff source mixture through conservative mixing model techniques such as End-Member Mixing Analysis (EMMA). An alternative conceptualisation is that catchments consist of a large number of stores with varying residence times. In this case individual stores contribute a variable proportion of flow and may have a temporally varying composition due to processes such as evapo-concentration. Hence they have a variable influence on the hydrochemistry of runoff. In this presentation, examples from two field studies in southern Australia will be presented that examine the relationships between hydrologic and hydrochemical conceptualisations and the relative variation within and between different hydrologic zones. The implications for water quality behaviour will be examined and the additional behavioural complexities associated with interactions between runoff pathways for non-conservative chemical species will be discussed.

Sedimentary gravity flows from subaerial fan-deltas in Loreto Bay, Baja California Sur, Mexico

NASA Astrophysics Data System (ADS)

Navarro-Lozano, José O.; Nava-Sánchez, Enrique H.; Godínez-Orta, Lucio

2010-05-01

Fan-deltas from Loreto Bay show recent evidences of sedimentary gravity flows as a result from catastrophic events during hurricane rainfalls. The knowledge of hydrological characteristics of these flows is important for understanding the effects of storms on fan-deltas geomorphology in this region, as well as for the urban developing planning of the city of Loreto in order to avoid hazardous zones. The analysis of precipitation and hurricane tracks data for the period 1945 to 2009 indicates that hurricanes have caused catastrophic floods every 20 years. Stratigraphy from the channel incision shows a sequence of stream flow and debris flow controlled by changes in the competence and capacity of the stream, which are associated to the gentle slope (<2 °) of the fan-deltas. However fans from the north of the bay (Arce and Gúa) show deposits of debris flows associated to catastrophic floods, which have caused the incision channel to drift towards the southern part of the fans, while flows from Las Parras fan-delta, from the middle of the bay, are dominated by stream flows. These differences in the type of the flows are controlled by lithology, shape and size of the drainage basin, and slope of the transit zone in the feeder channel.

Traffic flow characteristic and capacity in intelligent work zones.

DOT National Transportation Integrated Search

2009-10-15

Intellgent transportation system (ITS) technologies are utilized to manage traffic flow and safety in : highway work zones. Traffic management plans for work zones require queuing analyses to determine : the anticipated traffic backups, but the predi...

Using heat as a tracer to estimate spatially distributed mean residence times in the hyporheic zone

NASA Astrophysics Data System (ADS)

Naranjo, R. C.; Pohll, G. M.; Stone, M. C.; Niswonger, R. G.; McKay, W. A.

2013-12-01

Biogeochemical reactions that occur in the hyporheic zone are highly dependent on the time solutes are in contact with riverbed sediments. In this investigation, we developed a two-dimensional longitudinal flow and solute transport model to estimate the spatial distribution of mean residence time in the hyporheic zone along a riffle-pool sequence to gain a better understanding of nitrogen reactions. A flow and transport model was developed to estimate spatially distributed mean residence times and was calibrated using observations of temperature and pressure. The approach used in this investigation accounts for the mixing of ages given advection and dispersion. Uncertainty of flow and transport parameters was evaluated using standard Monte-Carlo analysis and the generalized likelihood uncertainty estimation method. Results of parameter estimation indicate the presence of a low-permeable zone in the riffle area that induced horizontal flow at shallow depth within the riffle area. This establishes shallow and localized flow paths and limits deep vertical exchange. From the optimal model, mean residence times were found to be relatively long (9 - 40 days). The uncertainty of hydraulic conductivity resulted in a mean interquartile range of 13 days across all piezometers and was reduced by 24% with the inclusion of temperature and pressure observations. To a lesser extent, uncertainty in streambed porosity and dispersivity resulted in a mean interquartile range of 2.2- and 4.7 days, respectively. Alternative conceptual models demonstrate the importance of accounting for the spatial distribution of hydraulic conductivity in simulating mean residence times in a riffle-pool sequence. It is demonstrated that spatially variable mean residence time beneath a riffle-pool system does not conform to simple conceptual models of hyporheic flow through a riffle-pool sequence. Rather, the mixing behavior between the river and the hyporheic flow are largely controlled by layered heterogeneity and anisotropy of the subsurface.

Volcanic hazard at Vesuvius: An analysis for the revision of the current emergency plan

NASA Astrophysics Data System (ADS)

Rolandi, G.

2010-01-01

Mt Somma-Vesuvius is a composite volcano on the southern margin of the Campanian Plain which has been active since 39 ka BP and which poses a hazard and risk for the people living around its base. The volcano last erupted in 1944, and since this date has been in repose. As the level of volcanic risk perception is very high in the scientific community, in 1995 a hazard and risk evaluation, and evacuation plan, was published by the Italian Department of Civil Protection ( Dipartimento della Protezione Civile) . The plan considered the response to a worst-case scenario, taken to be a subplinian eruption on the scale of the 1631 AD eruption, and based on a volcanological reconstruction of this eruption, assumes that a future eruption will be preceded by about two weeks of ground uplift at the volcano's summit, and about one week of locally perceptible seismic activity. Moreover, by analogy with the 1631 events, the plan assumes that ash fall and pyroclastic flow should be recognized as the primary volcanic hazard. To design the response to this subplinian eruption, the emergency plan divided the Somma-Vesuvius region into three hazard zones affected by pyroclastic flows (Red Zone), tephra fall (Yellow and Green Zone), and floods (Blue Zone). The plan at present is the subject of much controversy, and, in our opinion, several assumptions need to be modified according to the following arguments: a) For the precursory unrest problem, recent scientific studies show that at present neither forecast capability is realistic, so that the assumption that a future eruption will be preceded by about two weeks of forecasts need to be modified; b) Regarding the exposure of the Vesuvius region to flow phenomena, the Red Zone presents much inconsistency near the outer border as it has been defined by the administrative limits of the eighteen municipality area lying on the volcano. As this outer limit shows no uniformity, a pressing need exists to define appropriately the flow hazard zone, since there are some important public structures not considered in the current Red Zone that could be exposed to flow risk; c) Modern wind records clearly indicate that at the time of a future eruption winds could blow not only from the west, but also from the east, so that the Yellow Zone (the area with the potential to be affected by significant tephra fall deposits) must be redefined. As a result the relationship between the Yellow Zone and Green Zone (the area within and beyond which the impact of tephra fall is expected to be insignificant) must be reconsidered mainly in the Naples area; d) The May 1998 landslide, caused in the Apennine region east of the volcano by continuous rain fall, led to the definition of a zone affected by re-mobilisation of tephra (Blue Zone), confined in the Nola valley. However, as described in the 1631 chronicles of the eruption, if generation of debris flows occurs during and after a future eruption, a much wider region east of the Somma-Vesuvius must be affected by events of this type.

Hydrogeologic characterization of a fractured granitic rock aquifer, Raymond, California

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

Cohen, Andrew J.B.

1993-10-01

The hydrogeologic properties of a shallow, fractured granitic rock aquifer in the foothills of the Sierra Nevada, California were investigated via the analysis of borehole geophysical logs and pumping tests. The drawdowns produced during these tests are not indicative of any simple conceptual aquifer model, and borehole logs show that the granite is intensely fractured. These observations are suggestive of a complex fracture-flow geometry which is extremely difficult to decipher. However, through the measurement of orientations of individual subsurface fractures from acoustic televiewer logs, and correlation between particular fractures and electrical resistivity and thermal-pulse flowmeter logs, it was found thatmore » the aquifer is, in general, comprised of two subhorizontal and nearly parallel zones of unloading fractures. Downhole flowmeter measurements taken in several wells provide further evidence for the inferred dual-layer structure of the aquifer, as well as yield quantitative measures of the contribution of flow from each zone. Analysis of drawdowns in pumped wells reveals that there are zones of relatively high transmissivity immediately around them. It was found that these properties, as well as a nearby zone of lower transmissivity, can account for their observed drawdowns. A numerical model was constructed to test whether these major heterogeneities could also account for the drawdowns in observation wells. This stepwise analysis of both the geophysical and hydrological data resulted in the formulation of a conceptual model of the aquifer which is consistent with observations, and which can account for its behavior when subjected to pumping.« less

An analytical approach to thermal modeling of Bridgman-type crystal growth. I - One-dimensional analysis

NASA Technical Reports Server (NTRS)

Naumann, R. J.

1982-01-01

A relatively simple one-dimensional thermal model of the Bridgman growth process has been developed which is applicable to the growth of small diameter samples with conductivities similar to those of metallic alloys. The heat flow in a translating rod is analyzed in a way that is applicable to Biot numbers less than unity. The model accommodates an adiabatic zone, different heat transfer coefficients in the hot and cold zones, and changes in sample material properties associated with phase change. The analysis is applied to several simplified cases. The effect of the rod's motion is studied in a three-zone furnace for a rod sufficiently long that end effects can be neglected; end effects are then investigated for a motionless rod. Finally, the addition of a fourth zone, an independently controlled booster heater between the main heater and the adiabatic zone, is evaluated for its ability to increase the gradient in the sample at the melt interface and to control the position of the interface.

Chromosomal rearrangements and gene flow over time in an inter-specific hybrid zone of the Sorex araneus group.

PubMed

Yannic, G; Basset, P; Hausser, J

2009-06-01

Most hybrid zones have existed for hundreds or thousands of years but have generally been observed for only a short time period. Studies extending over periods long enough to track evolutionary changes in the zones or assess the ultimate outcome of hybridization are scarce. Here, we describe the evolution over time of the level of genetic isolation between two karyotypically different species of shrews (Sorex araneus and Sorex antinorii) at a hybrid zone located in the Swiss Alps. We first evaluated hybrid zone movement by contrasting patterns of gene flow and changes in cline parameters (centre and width) using 24 microsatellite loci, between two periods separated by 10 years apart. Additionally, we tested the role of chromosomal rearrangements on gene flow by analysing microsatellite loci located on both rearranged and common chromosomes to both species. We did not detect any movement of the hybrid zone during the period analysed, suggesting that the zone is a typical tension zone. However, the gene flow was significantly lower among the rearranged than the common chromosomes for the second period, whereas the difference was only marginally significant for the first period. This further supports the role of chromosomal rearrangements on gene flow between these taxa.

Temporal dynamics in dominant runoff sources and flow paths in the Andean Páramo

NASA Astrophysics Data System (ADS)

Correa, Alicia; Windhorst, David; Tetzlaff, Doerthe; Crespo, Patricio; Célleri, Rolando; Feyen, Jan; Breuer, Lutz

2017-07-01

The relative importance of catchment's water provenance and flow paths varies in space and time, complicating the conceptualization of the rainfall-runoff responses. We assessed the temporal dynamics in source areas, flow paths, and age by End Member Mixing Analysis (EMMA), hydrograph separation, and Inverse Transit Time Proxies (ITTPs) estimation within a headwater catchment in the Ecuadorian Andes. Twenty-two solutes, stable isotopes, pH, and electrical conductivity from a stream and 12 potential sources were analyzed. Four end-members were required to satisfactorily represent the hydrological system, i.e., rainfall, spring water, and water from the bottom layers of Histosols and Andosols. Water from Histosols in and near the riparian zone was the highest source contributor to runoff throughout the year (39% for the drier season, 45% for the wetter season), highlighting the importance of the water that is stored in the riparian zone. Spring water contributions to streamflow tripled during the drier season, as evidenced by geochemical signatures that are consistent with deeper flow paths rather than shallow interflow through Andosols. Rainfall exhibited low seasonal variation in this contribution. Hydrograph separation revealed that 94% and 84% is preevent water in the drier and wetter seasons, respectively. From low-flow to high-flow conditions, all the sources increased their contribution except spring water. The relative age of stream water decreased during wetter periods, when the contributing area of the riparian zone expands. The multimethod and multitracer approach enabled to closely study the interchanging importance of flow processes and water source dynamics from an interannual perspective.

Methods for improved growth of group III nitride semiconductor compounds

DOEpatents

Melnik, Yuriy; Chen, Lu; Kojiri, Hidehiro

2015-03-17

Methods are disclosed for growing group III-nitride semiconductor compounds with advanced buffer layer technique. In an embodiment, a method includes providing a suitable substrate in a processing chamber of a hydride vapor phase epitaxy processing system. The method includes forming an AlN buffer layer by flowing an ammonia gas into a growth zone of the processing chamber, flowing an aluminum halide containing precursor to the growth zone and at the same time flowing additional hydrogen halide or halogen gas into the growth zone of the processing chamber. The additional hydrogen halide or halogen gas that is flowed into the growth zone during buffer layer deposition suppresses homogeneous AlN particle formation. The hydrogen halide or halogen gas may continue flowing for a time period while the flow of the aluminum halide containing precursor is turned off.

Removing volatile contaminants from the unsaturated zone by inducing advective air-phase transport

USGS Publications Warehouse

Baehr, A.L.; Hoag, G.E.; Marley, M.C.

1989-01-01

Organic liquids inadvertently spilled and then distributed in the unsaturated zone can pose a long-term threat to ground water. Many of these substances have significant volatility, and thereby establish a premise for contaminant removal from the unsaturated zone by inducing advective air-phase transport with wells screened in the unsaturated zone. In order to focus attention on the rates of mass transfer from liquid to vapour phases, sand columns were partially saturated with gasoline and vented under steady air-flow conditions. The ability of an equilibrium-based transport model to predict the hydrocarbon vapor flux from the columns implies an efficient rate of local phase transfer for reasonably high air-phase velocities. Thus the success of venting remediations will depend primarily on the ability to induce an air-flow field in a heterogeneous unsaturated zone that will intersect the distributed contaminant. To analyze this aspect of the technique, a mathematical model was developed to predict radially symmetric air flow induced by venting from a single well. This model allows for in-situ determinations of air-phase permeability, which is the fundamental design parameter, and for the analysis of the limitations of a single well design. A successful application of the technique at a site once contaminated by gasoline supports the optimism derived from the experimental and modeliing phases of this study, and illustrates the well construction and field methods used to document the volatile contaminant recovery. ?? 1989.

Basalt-flow imaging using a high-resolution directional borehole radar

USGS Publications Warehouse

Moulton, C.W.; Wright, D.L.; Hutton, S.R.; Smith, D.V.G.; Abraham, J.D.

2002-01-01

A new high-resolution directional borehole radar-logging tool (DBOR tool) was used to log three wells at the Idaho National Engineering and Environmental Laboratory (INEEL). The radar system uses identical directional cavity-backed monopole transmitting and receiving antennas that can be mechanically rotated while the tool is stationary or moving slowly in a borehole. Faster reconnaissance logging with no antenna rotation was also done to find zones of interest. The microprocessor-controlled motor/encoder in the tool can rotate the antennas azimuthally, to a commanded angle, accurate to a within few degrees. The three logged wells in the unsaturated zone at the INEEL had been cored with good core recovery through most zones. After coring, PVC casing was installed in the wells. The unsaturated zone consists of layered basalt flows that are interbedded with thin layers of coarse-to-fine grained sediments. Several zones were found that show distinctive signatures consistent with fractures in the basalt. These zones may correspond to suspected preferential flow paths. The DBOR data were compared to core, and other borehole log information to help provide better understanding of hydraulic flow and transport in preferential flow paths in the unsaturated zone basalts at the INEEL.

Influence of dendrite network defects on channel segregate growth

NASA Technical Reports Server (NTRS)

Simpson, M.; Yerebakan, M.; Flemings, M. C.

1985-01-01

The solidifying ingot interdendritic flow analysis in which channel segregates are assumed to be produced by interdendritic fluid flow dissolving channels in the primary dendrite network is presently refined by examining the flow through a dendrite network possessing a small defect. Attention is given to the section of the mushy zone in a solidifying casting. Since defects such as that presently treated are unavoidable in a real casting, a more reliable indication may be furnished of the occurrence of channel segregates.

Nonequilibrium thermo-chemical calculations using a diagonal implicit scheme

NASA Technical Reports Server (NTRS)

Imlay, Scott T.; Roberts, Donald W.; Soetrisno, Moeljo; Eberhardt, Scott

1991-01-01

A recently developed computer program for hypersonic vehicle flow analysis is described. The program uses a diagonal implicit algorithm to solve the equations of viscous flow for a gas in thermochemical nonequilibrium. The diagonal scheme eliminates the expense of inverting large block matrices that arise when species conservation equations are introduced. The program uses multiple zones of grids patched together and includes radiation wall and rarefied gas boundary conditions. Solutions are presented for hypersonic flows of air and hydrogen air mixtures.

Application of advanced geophysical logging methods in the characterization of a fractured-sedimentary bedrock aquifer, Ventura County, California

USGS Publications Warehouse

Williams, John H.; Lane, John W.; Singha, Kamini; Haeni, F. Peter

2002-01-01

An integrated suite of advanced geophysical logging methods was used to characterize the geology and hydrology of three boreholes completed in fractured-sedimentary bedrock in Ventura County, California. The geophysical methods included caliper, gamma, electromagnetic induction, borehole deviation, optical and acoustic televiewer, borehole radar, fluid resistivity, temperature, and electromagnetic flowmeter. The geophysical logging 1) provided insights useful for the overall geohydrologic characterization of the bedrock and 2) enhanced the value of information collected by other methods from the boreholes including core-sample analysis, multiple-level monitoring, and packer testing.The logged boreholes, which have open intervals of 100 to 200 feet, penetrate a sequence of interbedded sandstone and mudstone with bedding striking 220 to 250 degrees and dipping 15 to 40 degrees to the northwest. Fractures intersected by the boreholes include fractures parallel to bedding and fractures with variable strike that dip moderately to steeply. Two to three flow zones were detected in each borehole. The flow zones consist of bedding-parallel or steeply dipping fractures or a combination of bedding-parallel fractures and moderately to steeply dipping fractures. About 75 to more than 90 percent of the measured flow under pumped conditions was produced by only one of the flow zones in each borehole.

Description and application of capture zone delineation for a wellfield at Hilton Head Island, South Carolina

USGS Publications Warehouse

Landmeyer, J.E.

1994-01-01

Ground-water capture zone boundaries for individual pumped wells in a confined aquffer were delineated by using groundwater models. Both analytical and numerical (semi-analytical) models that more accurately represent the $round-water-flow system were used. All models delineated 2-dimensional boundaries (capture zones) that represent the areal extent of groundwater contribution to a pumped well. The resultant capture zones were evaluated on the basis of the ability of each model to realistically rapresent the part of the ground-water-flow system that contributed water to the pumped wells. Analytical models used were based on a fixed radius approach, and induded; an arbitrary radius model, a calculated fixed radius model based on the volumetric-flow equation with a time-of-travel criterion, and a calculated fixed radius model derived from modification of the Theis model with a drawdown criterion. Numerical models used induded the 2-dimensional, finite-difference models RESSQC and MWCAP. The arbitrary radius and Theis analytical models delineated capture zone boundaries that compared least favorably with capture zones delineated using the volumetric-flow analytical model and both numerical models. The numerical models produced more hydrologically reasonable capture zones (that were oriented parallel to the regional flow direction) than the volumetric-flow equation. The RESSQC numerical model computed more hydrologically realistic capture zones than the MWCAP numerical model by accounting for changes in the shape of capture zones caused by multiple-well interference. The capture zone boundaries generated by using both analytical and numerical models indicated that the curnmtly used 100-foot radius of protection around a wellhead in South Carolina is an underestimate of the extent of ground-water capture for pumped wetis in this particular wellfield in the Upper Floridan aquifer. The arbitrary fixed radius of 100 feet was shown to underestimate the upgradient contribution of ground-water flow to a pumped well.

Hyporheic hot moments: Dissolved oxygen dynamics in the hyporheic zone in response to surface flow perturbations

NASA Astrophysics Data System (ADS)

Kaufman, Matthew H.; Cardenas, M. Bayani; Buttles, Jim; Kessler, Adam J.; Cook, Perran L. M.

2017-08-01

Dissolved oxygen (DO) is a key environmental variable that drives and feeds back with numerous processes. In the aquatic sediment that makes up the hyporheic zone, DO may exhibit pronounced spatial gradients and complex patterns which control the distribution of a series of redox processes. Yet, little is known regarding the dynamics of hyporheic zone DO, especially under transitional flow regimes. Considering the natural tendency of rivers to be highly responsive to external forcing, these temporal dynamics are potentially just as important and pronounced as the spatial gradients. Here we use laboratory flume experiments and multiphysics flow and reactive transport modeling to investigate surface flow controls on the depth of oxygen penetration in the bed as well as the area of oxygenated sediment. We show that the hyporheic zone DO conditions respond over time scales of hours-to-days when subjected to practically instantaneous surface flow perturbations. Additionally, the flume experiments demonstrate that hyporheic zone DO conditions respond faster to surface flow acceleration than to deceleration. Finally, we found that the morphology of the dissolved oxygen plume front depends on surface flow acceleration or deceleration. This study thus shows that the highly dynamic nature of typical streams and rivers drives equally dynamic redox conditions in the hyporheic zone. Because the redox conditions and their distribution within the hyporheic zone are important from biological, ecological, and contaminant perspectives, this hyporheic redox dynamism has the potential to impact system scale aquatic chemical cycles.

The role of strain hardening in the transition from dislocation-mediated to frictional deformation of marbles within the Karakoram Fault Zone, NW India

NASA Astrophysics Data System (ADS)

Wallis, David; Lloyd, Geoffrey E.; Hansen, Lars N.

2018-02-01

The onset of frictional failure and potentially seismogenic deformation in carbonate rocks undergoing exhumation within fault zones depends on hardening processes that reduce the efficiency of aseismic dislocation-mediated deformation as temperature decreases. However, few techniques are available for quantitative analysis of dislocation slip system activity and hardening in natural tectonites. Electron backscatter diffraction maps of crystal orientations offer one such approach via determination of Schmid factors, if the palaeostress conditions can be inferred and the critical resolved shear stresses of slip systems are constrained. We analyse calcite marbles deformed in simple shear within the Karakoram Fault Zone, NW India, to quantify changes in slip system activity as the rocks cooled during exhumation. Microstructural evidence demonstrates that between ∼300 °C and 200-250 °C the dominant deformation mechanisms transitioned from dislocation-mediated flow to twinning and frictional failure. However, Schmid factor analysis, considering critical resolved shear stresses for yield of undeformed single crystals, indicates that the fraction of grains with sufficient resolved shear stress for glide apparently increased with decreasing temperature. Misorientation analysis and previous experimental data indicate that strain-dependent work hardening is responsible for this apparent inconsistency and promoted the transition from dislocation-mediated flow to frictional, and potentially seismogenic, deformation.

Groundwater recharge dynamics in unsaturated fractured chalk: a case study

NASA Astrophysics Data System (ADS)

Cherubini, Claudia; Pastore, Nicola; Giasi, Concetta I.; Allegretti, Nicolaetta M.

2016-04-01

The heterogeneity of the unsaturated zone controls its hydraulic response to rainfall and the extent to which pollutants are delayed or attenuated before reaching groundwater. It plays therefore a very important role in the recharge of aquifers and the transfer of pollutants because of the presence of temporary storage zones and preferential flows. A better knowledge of the physical processes in the unsaturated zone would allow an improved assessment of the natural recharge in a heterogeneous aquifer and of its vulnerability to surface-applied pollution. The case study regards the role of the thick unsaturated zone of the Cretaceous chalk aquifer in Picardy (North of France) that controls the hydraulic response to rainfall. In the North Paris Basin, much of the recharge must pass through a regional chalk bed that is composed of a porous matrix with embedded fractures. Different types of conceptual models have been formulated to explain infiltration and recharge processes in the unsaturated fractured rock. The present study analyses the episodic recharge in fractured Chalk aquifer using the kinematic diffusion theory to predict water table fluctuation in response to rainfall. From an analysis of the data, there is the evidence of 1) a seasonal behavior characterized by a constant increase in the water level during the winter/spring period and a recession period, 2) a series of episodic behaviors during the summer/autumn. Kinematic diffusion models are useful for predict preferential fluxes and dynamic conditions. The presented approach conceptualizes the unsaturated flow as a combination of 1) diffusive flow refers to the idealized portion of the pore space of the medium within the flow rate is driven essentially by local gradient of potential; 2) preferential flow by which water moves across macroscopic distances through conduits of macropore length.

Component testing of a ground based gas turbine steam cooled rich-burn primary zone combustor for emissions control of nitrogeneous fuels

NASA Technical Reports Server (NTRS)

Schultz, D. F.

1986-01-01

This effort summarizes the work performed on a steam cooled, rich-burn primary zone, variable geometry combustor designed for combustion of nitrogeneous fuels such as heavy oils or synthetic crude oils. The steam cooling was employed to determine its feasibility and assess its usefulness as part of a ground based gas turbine bottoming cycle. Variable combustor geometry was employed to demonstrate its ability to control primary and secondary zone equivalence ratios and overall pressure drop. Both concepts proved to be highly successful in achieving their desired objectives. The steam cooling reduced peak liner temperatures to less than 800 K. This low temperature offers the potential of both long life and reduced use of strategic materials for liner fabrication. These degrees of variable geometry were successfully employed to control air flow distribution within the combustor. A variable blade angle axial flow air swirler was used to control primary zone air flow, while the secondary and tertiary zone air flows were controlled by rotating bands which regulated air flow to the secondary zone quench holes and the dilutions holes respectively.

Photoreactor with self-contained photocatalyst recapture

DOEpatents

Gering, Kevin L.

2004-12-07

A system for the continuous use and recapture of a catalyst in liquid, comprising: a generally vertical reactor having a reaction zone with generally downwardly flowing liquid, and a catalyst recovery chamber adjacent the reaction zone containing a catalyst consisting of buoyant particles. The liquid in the reaction zone flows downward at a rate which exceeds the speed of upward buoyant migration of catalyst particles in the liquid, whereby catalyst particles introduced into the liquid in the reaction zone are drawn downward with the liquid. A slow flow velocity flotation chamber disposed below the reaction zone is configured to recapture the catalyst particles and allow them to float back into the catalyst recovery chamber for recycling into the reaction zone, rather than being swept downstream. A novel 3-dimensionally adjustable solar reflector directs light into the reaction zone to induce desired photocatalytic reactions within the liquid in the reaction zone.

Thermal Modeling of Bridgman Crystal Growth

NASA Technical Reports Server (NTRS)

Cothran, E.

1983-01-01

Heat Flow modeled for moving or stationary rod shaped sample inside directional-solidification furnace. Program effectively models one-dimensional heat flow in translating or motionless rod-shaped sample inside of directionalsolidification furnace in which adiabatic zone separates hot zone and cold zone. Applicable to systems for which Biot numbers in hot and cold zones are less than unity.

An overview of dry-wet climate variability among monsoon-westerly regions and the monsoon northernmost marginal active zone in China

NASA Astrophysics Data System (ADS)

Qian, Weihong; Ding, Ting; Hu, Haoran; Lin, Xiang; Qin, Aimin

2009-07-01

Climate in mainland China can be divided into the monsoon region in the southeast and the westerly region in the northwest as well as the intercross zone, i.e., the monsoon northernmost marginal active zone that is oriented from Southwest China to the upper Yellow River, North China, and Northeast China. In the three regions, dry-wet climate changes are directly linked to the interaction of the southerly monsoon flow on the east side of the Tibetan Plateau and the westerly flow on the north side of the Plateau from the inter-annual to inter-decadal timescales. Some basic features of climate variability in the three regions for the last half century and the historical hundreds of years are reviewed in this paper. In the last half century, an increasing trend of summer precipitation associated with the enhancing westerly flow is found in the westerly region from Xinjiang to northern parts of North China and Northeast China. On the other hand, an increasing trend of summer precipitation along the Yangtze River and a decreasing trend of summer precipitation along the monsoon northernmost marginal active zone are associated with the weakening monsoon flow in East Asia. Historical documents are widely distributed in the monsoon region for hundreds of years and natural climate proxies are constructed in the non-monsoon region, while two types of climate proxies can be commonly found over the monsoon northernmost marginal active zone. In the monsoon region, dry-wet variation centers are altered among North China, the lower Yangtze River, and South China from one century to another. Dry or wet anomalies are firstly observed along the monsoon northernmost marginal active zone and shifted southward or southeastward to the Yangtze River valley and South China in about a 70-year timescale. Severe drought events are experienced along the monsoon northernmost marginal active zone during the last 5 centuries. Inter-decadal dry-wet variations are depicted by natural proxies for the last 4-5 centuries in several areas over the non-monsoon region. Some questions, such as the impact of global warming on dry-wet regime changes in China, complex interactions between the monsoon and westerly flows in Northeast China, and the integrated multi-proxy analysis throughout all of China, are proposed.

A zonal computational procedure adapted to the optimization of two-dimensional thrust augmentor inlets

NASA Technical Reports Server (NTRS)

Lund, T. S.; Tavella, D. A.; Roberts, L.

1985-01-01

A viscous-inviscid interaction methodology based on a zonal description of the flowfield is developed as a mean of predicting the performance of two-dimensional thrust augmenting ejectors. An inviscid zone comprising the irrotational flow about the device is patched together with a viscous zone containing the turbulent mixing flow. The inviscid region is computed by a higher order panel method, while an integral method is used for the description of the viscous part. A non-linear, constrained optimization study is undertaken for the design of the inlet region. In this study, the viscous-inviscid analysis is complemented with a boundary layer calculation to account for flow separation from the walls of the inlet region. The thrust-based Reynolds number as well as the free stream velocity are shown to be important parameters in the design of a thrust augmentor inlet.

Weld pool development during GTA and laser beam welding of Type 304 stainless steel; Part II-experimental correlation

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

Zacharia, T.; David, S.A.; Vitek, J.M.

1989-12-01

In part I of the paper, the results of the heat flow and the fluid flow analysis were presented. Here, in Part II of the paper, predictions of the computational model are verified by comparing the numerically predicted and experimentally observed fusion zone size and shape. Stationary gas tungsten arc and laser beam welds were made on Type 304 stainless steel for different times to provide a variety of solidification conditions such as cooling rate and temperature gradient. Calculated temperatures and cooling rates are correlated with the experimentally observed fusion zone structure. In addition, the effect of sulfur on GTAmore » weld penetration was quantitatively evaluated by considering two heats of 304 stainless steel containing 90 and 240 ppm sulfur. Sulfur, as expected, increased the depth/width ratio by altering the surface tension gradient driven flow in the weld pool.« less

Effect of groundwater flow on remediation of dissolved-phase VOC contamination using air sparging.

PubMed

Reddy, K R; Adams, J A

2000-02-25

This paper presents two-dimensional laboratory experiments performed to study how groundwater flow may affect the injected air zone of influence and remedial performance, and how injected air may alter subsurface groundwater flow and contaminant migration during in situ air sparging. Tests were performed by subjecting uniform sand profiles contaminated with dissolved-phase benzene to a hydraulic gradient and two different air flow rates. The results of the tests were compared to a test subjected to a similar air flow rate but a static groundwater condition. The test results revealed that the size and shape of the zone of influence were negligibly affected by groundwater flow, and as a result, similar rates of contaminant removal were realized within the zone of influence with and without groundwater flow. The air flow, however, reduced the hydraulic conductivity within the zone of influence, reducing groundwater flow and subsequent downgradient contaminant migration. The use of a higher air flow rate further reduced the hydraulic conductivity and decreased groundwater flow and contaminant migration. Overall, this study demonstrated that air sparging may be effectively implemented to intercept and treat a migrating contaminant plume.

Conditions for the appearance of boundary-free circulation zones in supersonic axisymmetric accelerating flows

NASA Astrophysics Data System (ADS)

Savin, Andrey V.; Sokolov, Eugeny I.

2018-05-01

The mechanism of appearance of boundary-free circulation zones - circulating flows arising behind the Mach disk of an underexpanded supersonic jet is investigated. Ideas on the mechanism of formation of circulation zones and the criteria for their occurrence are formulated within the near-axis approximation. Technical possibilities of realization flows that satisfy these criteria are analyzed with the help of numerical simulation. A comparison is made with the results of a study of the formation of circulation zones in axisymmetric nozzles at the overexpansion mode.

Quasi 3D modeling of water flow in vadose zone and groundwater

USDA-ARS?s Scientific Manuscript database

The complexity of subsurface flow systems calls for a variety of concepts leading to the multiplicity of simplified flow models. One habitual simplification is based on the assumption that lateral flow and transport in unsaturated zone are not significant unless the capillary fringe is involved. In ...

76 FR 56413 - Building Energy Codes Cost Analysis

Federal Register 2010, 2011, 2012, 2013, 2014

2011-09-13

... the by-zone housing starts of Table 2. \\7\\ See http://rredc.nrel.gov/solar/old_data/nsrdb/tmy2... as an alternative investment rate. Thus the present value, (PV) of a cash flow in year Y (CFy) is...

Thermocapillary flow and melt/solid interfaces in floating-zone crystal growth under microgravity

NASA Technical Reports Server (NTRS)

Lan, C. W.; Kou, Sindo

1990-01-01

Computer simulation of steady-state axisymmetrical heat transfer and fluid flow was conducted to study thermocapillary flow and melt/solid interfaces in floating-zone crystal growth under microgravity. The effects of key variables on the extent of thermocapillary flow in the melt zone, the shapes of melt/solid interfaces and the length of the melt zone were discussed. These variables are: (1) the temperature coefficient of surface tension (or the Marangoni number), (2) the pulling speed (or the Peclet number), (3) the feed rod radius, (4) the ambient temperature distribution, (5) the heat transfer coefficient (or the Biot number), and (6) the thermal diffusivity of the material (or the Prandtl number).

Comparative Dynamics of Retrograde Actin Flow and Focal Adhesions: Formation of Nascent Adhesions Triggers Transition from Fast to Slow Flow

PubMed Central

Alexandrova, Antonina Y.; Arnold, Katya; Schaub, Sébastien; Vasiliev, Jury M.; Meister, Jean-Jacques; Bershadsky, Alexander D.; Verkhovsky, Alexander B.

2008-01-01

Dynamic actin network at the leading edge of the cell is linked to the extracellular matrix through focal adhesions (FAs), and at the same time it undergoes retrograde flow with different dynamics in two distinct zones: the lamellipodium (peripheral zone of fast flow), and the lamellum (zone of slow flow located between the lamellipodium and the cell body). Cell migration involves expansion of both the lamellipodium and the lamellum, as well as formation of new FAs, but it is largely unknown how the position of the boundary between the two flow zones is defined, and how FAs and actin flow mutually influence each other. We investigated dynamic relationship between focal adhesions and the boundary between the two flow zones in spreading cells. Nascent FAs first appeared in the lamellipodium. Within seconds after the formation of new FAs, the rate of actin flow decreased locally, and the lamellipodium/lamellum boundary advanced towards the new FAs. Blocking fast actin flow with cytochalasin D resulted in rapid dissolution of nascent FAs. In the absence of FAs (spreading on poly-L-lysine-coated surfaces) retrograde flow was uniform and the velocity transition was not observed. We conclude that formation of FAs depends on actin dynamics, and in its turn, affects the dynamics of actin flow by triggering transition from fast to slow flow. Extension of the cell edge thus proceeds through a cycle of lamellipodium protrusion, formation of new FAs, advance of the lamellum, and protrusion of the lamellipodium from the new base. PMID:18800171

Structural characteristics of cohesive flow deposits, and a sedimentological approach on their flow mechanisms.

NASA Astrophysics Data System (ADS)

Tripsanas, E. K.; Bryant, W. R.; Prior, D. B.

2003-04-01

A large number of Jumbo Piston cores (up to 20 m long), acquired from the continental slope and rise of the Northwest Gulf of Mexico (Bryant Canyon area and eastern Sigsbee Escarpment), have recovered various mass-transport deposits. The main cause of slope instabilities over these areas is oversteepening of the slopes due to the seaward mobilization of the underlying allochthonous salt masses. Cohesive flow deposits were the most common recoveries in the sediment cores. Four types of cohesive flow deposits have been recognized: a) fluid debris flow, b) mud flow, c) mud-matrix dominated debris flow, and d) clast-dominated debris flow deposits. The first type is characterized by its relatively small thickness (less than 1 m), a mud matrix with small (less than 0.5 cm) and soft mud-clasts, and a faint layering. The mud-clasts reveal a normal grading and become more abundant towards the base of each layer. That reveals that their deposition resulted by several successive surges/pulses, developed in the main flow, than the sudden “freezing” of the whole flow. The main difference between mud flow and mud-matrix dominated debris flow deposits is the presence of small to large mud-clasts in the later. Both deposits consist of a chaotic mud-matrix, and a basal shear laminated zone, where the strongest shearing of the flow was exhibited. Convolute laminations, fault-like surfaces, thrust faults, and microfaults are interpreted as occurring during the “freezing” of the flows and/or by adjustments of the rested deposits. Clast-dominated debris flow deposits consist of three zones: a) an upper plug-zone, characterized by large interlocked clasts, b) a mid-zone, of higher reworked, inversely graded clasts, floating in a mud-matrix, and c) a lower shear laminated zone. The structure of the last three cohesive flow deposits indicate that they represent deposition of typical Bingham flows, consisting of an upper plug-zone in which the yield stress is not exceeded and an underlain shearing zone, where the shear stress exceeded the yield strength of the sediments. Mud-matrix, and clast-dominated debris flow deposits are the pervasive ones. Intensely sheared thin layers (5- to 20 cm) with sharp bases, displayed as successive layers at the base of mud/debris flow deposits, or as isolated depositional units interbedded in hemipelagic sediments, are as interesting, as enigmatic. They are interpreted as basal self-lubricating layers, of having high shear stress and pore pressures, over which the mud/debris flows were able to travel for very long distances.

Staged membrane oxidation reactor system

DOEpatents

Repasky, John Michael; Carolan, Michael Francis; Stein, VanEric Edward; Chen, Christopher Ming-Poh

2014-05-20

Ion transport membrane oxidation system comprising (a) two or more membrane oxidation stages, each stage comprising a reactant zone, an oxidant zone, one or more ion transport membranes separating the reactant zone from the oxidant zone, a reactant gas inlet region, a reactant gas outlet region, an oxidant gas inlet region, and an oxidant gas outlet region; (b) an interstage reactant gas flow path disposed between each pair of membrane oxidation stages and adapted to place the reactant gas outlet region of a first stage of the pair in flow communication with the reactant gas inlet region of a second stage of the pair; and (c) one or more reactant interstage feed gas lines, each line being in flow communication with any interstage reactant gas flow path or with the reactant zone of any membrane oxidation stage receiving interstage reactant gas.

Staged membrane oxidation reactor system

DOEpatents

Repasky, John Michael; Carolan, Michael Francis; Stein, VanEric Edward; Chen, Christopher Ming-Poh

2013-04-16

Ion transport membrane oxidation system comprising (a) two or more membrane oxidation stages, each stage comprising a reactant zone, an oxidant zone, one or more ion transport membranes separating the reactant zone from the oxidant zone, a reactant gas inlet region, a reactant gas outlet region, an oxidant gas inlet region, and an oxidant gas outlet region; (b) an interstage reactant gas flow path disposed between each pair of membrane oxidation stages and adapted to place the reactant gas outlet region of a first stage of the pair in flow communication with the reactant gas inlet region of a second stage of the pair; and (c) one or more reactant interstage feed gas lines, each line being in flow communication with any interstage reactant gas flow path or with the reactant zone of any membrane oxidation stage receiving interstage reactant gas.

Staged membrane oxidation reactor system

DOEpatents

Repasky, John Michael; Carolan, Michael Francis; Stein, VanEric Edward; Chen, Christopher Ming-Poh

2012-09-11

Ion transport membrane oxidation system comprising (a) two or more membrane oxidation stages, each stage comprising a reactant zone, an oxidant zone, one or more ion transport membranes separating the reactant zone from the oxidant zone, a reactant gas inlet region, a reactant gas outlet region, an oxidant gas inlet region, and an oxidant gas outlet region; (b) an interstage reactant gas flow path disposed between each pair of membrane oxidation stages and adapted to place the reactant gas outlet region of a first stage of the pair in flow communication with the reactant gas inlet region of a second stage of the pair; and (c) one or more reactant interstage feed gas lines, each line being in flow communication with any interstage reactant gas flow path or with the reactant zone of any membrane oxidation stage receiving interstage reactant gas.

An Experimental Investigation of an Airfoil Traversing Across a Shear Flow

NASA Astrophysics Data System (ADS)

Hamedani, Borhan A.; Naguib, Ahmed; Koochesfahani, Manoochehr

2017-11-01

While the aerodynamics of an airfoil in a uniform approach flow is well understood, less attention has been paid to airfoils in non-uniform flows. An aircraft encounters such flow, for example, during landing through the air wake of an aircraft carrier. The present work is focused on investigating the fundamental aerodynamics of airfoils in such an environment using canonical flow experiments. To generate a shear approach flow, a shaped honeycomb block is employed in a wind tunnel setup. Direct force measurements are performed on a NACA 0012 airfoil, with an aspect ratio of 1.8, as the airfoil traverses steadily across the shear region. Measurements are conducted at a chord Reynolds number Rec 75k, based on the mean approach stream velocity at the center of the shear zone, for a range of airfoil traverse velocities and angles of attack (0 - 12 degree). The results are compared to those obtained for the same airfoil when placed statically at different points along the traverse path inside the shear zone. The comparison enables examination of the applicability of quasi-steady analysis in computing the forces on the moving airfoil. This work is supported by ONR Grant Number N00014-16-1-2760.

Experimental study of the solid-liquid interface in a yield-stress fluid flow upstream of a step

NASA Astrophysics Data System (ADS)

Luu, Li-Hua; Pierre, Philippe; Guillaume, Chambon

2014-11-01

We present an experimental study where a yield-stress fluid is implemented to carefully examine the interface between a liquid-like unyielded region and a solid-like yielded region. The studied hydrodynamics consists of a rectangular pipe-flow disturbed by the presence of a step. Upstream of the step, a solid-liquid interface between a dead zone and a flow zone appears. This configuration can both model geophysical erosion phenomenon in debris flows or find applications for industrial extrusion processes. We aim to investigate the dominant physical mechanism underlying the formation of the static domain, by combining the rheological characterization of the yield-stress fluid with local measurements of the related hydrodynamic parameters. In this work, we use a model fluid, namely polymer micro-gel Carbopol, that exhibits a Hershel-Bulkley viscoplastic rheology. Exploiting the fluid transparency, the flow is monitored by Particle Image Velocimetry thanks to internal visualization technique. In particular, we demonstrate that the flow above the dead zone roughly behaves as a plug flow whose velocity profile can successfully be described by a Poiseuille equation including a Hershel-Bulkley rheology (PHB theory), with exception of a thin zone at the close vicinity of the static domain. The border inside the flow zone above which the so-called PHB flow starts, is found to be the same regardless of the flow rate and to move with a constant velocity that increases with the flow rate. We interpret this feature as a slip frontier.

Using chemical, hydrologic, and age dating analysis to delineate redox processes and flow paths in the riparian zone of a glacial outwash aquifer‐stream system

USGS Publications Warehouse

Puckett, Larry J.; Cowdery, Timothy K.; McMahon, Peter B.; Tornes, Lan H.; Stoner, Jeffrey D.

2002-01-01

A combination of chemical and dissolved gas analyses, chlorofluorocarbon age dating, and hydrologic measurements were used to determine the degree to which biogeochemical processes in a riparian wetland were responsible for removing NO3−from groundwaters discharging to the Otter Tail River in west central Minnesota. An analysis of river chemistry and flow data revealed that NO3− concentrations in the river increased in the lower half of the 8.3 km study reach as the result of groundwater discharge to the river. Groundwater head measurements along a study transect through the riparian wetland revealed a zone of groundwater discharge extending out under the river. On the basis of combined chemical, dissolved gas, age date, and hydrologic results, it was determined that water chemistry under the riparian wetland was controlled largely by upgradient groundwaters that followed flow paths up to 16 m deep and discharged under the wetland, creating a pattern of progressively older, more chemically reduced, low NO3− water the farther one progressed from the edge of the wetland toward the river. These findings pose challenges for researchers investigating biogeochemical processes in riparian buffer zones because the progressively older groundwaters entered the aquifer in earlier years when less NO3− fertilizer was being used. NO3− concentrations originally present in the groundwater had also decreased in the upgradient aquifer as a result of denitrification and progressively stronger reducing conditions there. The resulting pattern of decreasing NO3− concentrations across the riparian zone may be incorrectly interpreted as evidence of denitrification losses there instead of in the upgradient aquifer. Consequently, it is important to understand the hydrogeologic setting and age structure of the groundwaters being sampled in order to avoid misinterpreting biogeochemical processes in riparian zones.

GLOBAL HELIOSEISMIC EVIDENCE FOR A DEEPLY PENETRATING SOLAR MERIDIONAL FLOW CONSISTING OF MULTIPLE FLOW CELLS

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

Schad, A.; Roth, M.; Timmer, J., E-mail: ariane.schad@kis.uni-freiburg.de

2013-12-01

We use a novel global helioseismic analysis method to infer the meridional flow in the deep Solar interior. The method is based on the perturbation of eigenfunctions of Solar p modes due to meridional flow. We apply this method to time series obtained from Dopplergrams measured by the Michelson Doppler Imager aboard the Solar and Heliospheric Observatory covering the observation period 2004-2010. Our results show evidence that the meridional flow reaches down to the base of the convection zone. The flow profile has a complex spatial structure consisting of multiple flow cells distributed in depth and latitude. Toward the Solarmore » surface, our results are in good agreement with flow measurements from local helioseismology.« less

Genetic analysis of an ephemeral intraspecific hybrid zone in the hypervariable tree, Metrosideros polymorpha, on Hawai'i Island.

PubMed

Stacy, E A; Johansen, J B; Sakishima, T; Price, D K

2016-09-01

Intraspecific hybrid zones involving long-lived woody species are rare and can provide insights into the genetic basis of early-diverging traits in speciation. Within the landscape-dominant Hawaiian tree, Metrosideros polymorpha, are morphologically distinct successional varieties, incana and glaberrima, that dominate new and old lava flows, respectively, below 1200 me on volcanically active Hawai'i Island, with var. glaberrima also extending to higher elevations and bogs. Here, we use morphological measurements on 86 adult trees to document the presence of an incana-glaberrima hybrid zone on the 1855 Mauna Loa lava flow on east Hawai'i Island and parent-offspring analysis of 1311 greenhouse seedlings from 71 crosses involving 72 adults to estimate heritabilities and genetic correlations among vegetative traits. Both the variation in adult leaf pubescence at the site and the consistency between adult and offspring phenotypes suggest the presence of two hybrid classes, F1s and var. incana backcrosses, as would be expected on a relatively young lava flow. Nine nuclear microsatellite loci failed to distinguish parental and hybrid genotypes. All four leaf traits examined showed an additive genetic basis with moderate to strong heritabilities, and genetic correlations were stronger for the more range-restricted var. incana. The differences between varieties in trait values, heritabilities and genetic correlations, coupled with high genetic variation within but low genetic variation between varieties, are consistent with a multi-million-year history of alternating periods of disruptive selection in contrasting environments and admixture in ephemeral hybrid zones. Finally, the contrasting genetic architectures suggest different evolutionary trajectories of leaf traits in these forms.

Quantitative assessment of key parameters in qualitative vulnerability methods applied in karst systems based on an integrated numerical modelling approach

NASA Astrophysics Data System (ADS)

Doummar, Joanna; Kassem, Assaad

2017-04-01

In the framework of a three-year PEER (USAID/NSF) funded project, flow in a Karst system in Lebanon (Assal) dominated by snow and semi arid conditions was simulated and successfully calibrated using an integrated numerical model (MIKE-She 2016) based on high resolution input data and detailed catchment characterization. Point source infiltration and fast flow pathways were simulated by a bypass function and a high conductive lens respectively. The approach consisted of identifying all the factors used in qualitative vulnerability methods (COP, EPIK, PI, DRASTIC, GOD) applied in karst systems and to assess their influence on recharge signals in the different hydrological karst compartments (Atmosphere, Unsaturated zone and Saturated zone) based on the integrated numerical model. These parameters are usually attributed different weights according to their estimated impact on Groundwater vulnerability. The aim of this work is to quantify the importance of each of these parameters and outline parameters that are not accounted for in standard methods, but that might play a role in the vulnerability of a system. The spatial distribution of the detailed evapotranspiration, infiltration, and recharge signals from atmosphere to unsaturated zone to saturated zone was compared and contrasted among different surface settings and under varying flow conditions (e.g., in varying slopes, land cover, precipitation intensity, and soil properties as well point source infiltration). Furthermore a sensitivity analysis of individual or coupled major parameters allows quantifying their impact on recharge and indirectly on vulnerability. The preliminary analysis yields a new methodology that accounts for most of the factors influencing vulnerability while refining the weights attributed to each one of them, based on a quantitative approach.

Genetic analysis of an ephemeral intraspecific hybrid zone in the hypervariable tree, Metrosideros polymorpha, on Hawai‘i Island

PubMed Central

Stacy, E A; Johansen, J B; Sakishima, T; Price, D K

2016-01-01

Intraspecific hybrid zones involving long-lived woody species are rare and can provide insights into the genetic basis of early-diverging traits in speciation. Within the landscape-dominant Hawaiian tree, Metrosideros polymorpha, are morphologically distinct successional varieties, incana and glaberrima, that dominate new and old lava flows, respectively, below 1200 me on volcanically active Hawai‘i Island, with var. glaberrima also extending to higher elevations and bogs. Here, we use morphological measurements on 86 adult trees to document the presence of an incana–glaberrima hybrid zone on the 1855 Mauna Loa lava flow on east Hawai‘i Island and parent–offspring analysis of 1311 greenhouse seedlings from 71 crosses involving 72 adults to estimate heritabilities and genetic correlations among vegetative traits. Both the variation in adult leaf pubescence at the site and the consistency between adult and offspring phenotypes suggest the presence of two hybrid classes, F1s and var. incana backcrosses, as would be expected on a relatively young lava flow. Nine nuclear microsatellite loci failed to distinguish parental and hybrid genotypes. All four leaf traits examined showed an additive genetic basis with moderate to strong heritabilities, and genetic correlations were stronger for the more range-restricted var. incana. The differences between varieties in trait values, heritabilities and genetic correlations, coupled with high genetic variation within but low genetic variation between varieties, are consistent with a multi-million-year history of alternating periods of disruptive selection in contrasting environments and admixture in ephemeral hybrid zones. Finally, the contrasting genetic architectures suggest different evolutionary trajectories of leaf traits in these forms. PMID:27301333

Analysis of flow disturbance in a stenosed carotid artery bifurcation using two-equation transitional and turbulence models.

PubMed

Tan, F P P; Soloperto, G; Bashford, S; Wood, N B; Thom, S; Hughes, A; Xu, X Y

2008-12-01

In this study, newly developed two-equation turbulence models and transitional variants are employed for the prediction of blood flow patterns in a diseased carotid artery where the growth, progression, and structure of the plaque at rupture are closely linked to low and oscillating wall shear stresses. Moreover, the laminar-turbulent transition in the poststenotic zone can alter the separation zone length, wall shear stress, and pressure distribution over the plaque, with potential implications for stresses within the plaque. Following the validation with well established experimental measurements and numerical studies, a magnetic-resonance (MR) image-based model of the carotid bifurcation with 70% stenosis was reconstructed and simulated using realistic patient-specific conditions. Laminar flow, a correlation-based transitional version of Menter's hybrid k-epsilon/k-omega shear stress transport (SST) model and its "scale adaptive simulation" (SAS) variant were implemented in pulsatile simulations from which analyses of velocity profiles, wall shear stress, and turbulence intensity were conducted. In general, the transitional version of SST and its SAS variant are shown to give a better overall agreement than their standard counterparts with experimental data for pulsatile flow in an axisymmetric stenosed tube. For the patient-specific case reported, the wall shear stress analysis showed discernable differences between the laminar flow and SST transitional models but virtually no difference between the SST transitional model and its SAS variant.

Hydromechanical heterogeneities of a mature fault zone: impacts on fluid flow.

PubMed

Jeanne, Pierre; Guglielmi, Yves; Cappa, Frédéric

2013-01-01

In this paper, fluid flow is examined for a mature strike-slip fault zone with anisotropic permeability and internal heterogeneity. The hydraulic properties of the fault zone were first characterized in situ by microgeophysical (VP and σc ) and rock-quality measurements (Q-value) performed along a 50-m long profile perpendicular to the fault zone. Then, the local hydrogeological context of the fault was modified to conduct a water-injection test. The resulting fluid pressures and flow rates through the different fault-zone compartments were then analyzed with a two-phase fluid-flow numerical simulation. Fault hydraulic properties estimated from the injection test signals were compared to the properties estimated from the multiscale geological approach. We found that (1) the microgeophysical measurements that we made yield valuable information on the porosity and the specific storage coefficient within the fault zone and (2) the Q-value method highlights significant contrasts in permeability. Fault hydrodynamic behavior can be modeled by a permeability tensor rotation across the fault zone and by a storativity increase. The permeability tensor rotation is linked to the modification of the preexisting fracture properties and to the development of new fractures during the faulting process, whereas the storativity increase results from the development of micro- and macrofractures that lower the fault-zone stiffness and allows an increased extension of the pore space within the fault damage zone. Finally, heterogeneities internal to the fault zones create complex patterns of fluid flow that reflect the connections of paths with contrasting properties. © 2013, The Author(s). Ground Water © 2013, National Ground Water Association.

Identification of the inflow zone of unruptured cerebral aneurysms: comparison of 4D flow MRI and 3D TOF MRA data.

PubMed

Futami, K; Sano, H; Misaki, K; Nakada, M; Ueda, F; Hamada, J

2014-07-01

The hemodynamics of the inflow zone of cerebral aneurysms may be a key factor in coil compaction and recanalization after endovascular coil embolization. We performed 4D flow MR imaging in conjunction with 3D TOF MRA and compared their ability to identify the inflow zone of unruptured cerebral aneurysms. This series comprised 50 unruptured saccular cerebral aneurysms in 44 patients. Transluminal color-coded 3D MRA images were created by selecting the signal-intensity ranges on 3D TOF MRA images that corresponded with both the luminal margin and the putative inflow. 4D flow MR imaging demonstrated the inflow zone and yielded inflow velocity profiles for all 50 aneurysms. In 18 of 24 lateral-projection aneurysms (75%), the inflow zone was located distally on the aneurysmal neck. The maximum inflow velocity ranged from 285 to 922 mm/s. On 4D flow MR imaging and transluminal color-coded 3D MRA studies, the inflow zone of 32 aneurysms (64%) was at a similar location. In 91% of aneurysms whose neck section plane angle was <30° with respect to the imaging section direction on 3D TOF MRA, depiction of the inflow zone was similar on transluminal color-coded 3D MRA and 4D flow MR images. 4D flow MR imaging can demonstrate the inflow zone and provide inflow velocity profiles. In aneurysms whose angle of the neck-section plane is obtuse vis-a-vis the imaging section on 3D TOF MRA scans, transluminal color-coded 3D MRA may depict the inflow zone reliably. © 2014 by American Journal of Neuroradiology.

Quantifying Preferential Flow and Seasonal Storage in an Unsaturated Fracture-Facial Domain

NASA Astrophysics Data System (ADS)

Nimmo, J. R.; Malek-Mohammadi, S.

2012-12-01

Preferential flow through deep unsaturated zones of fractured rock is hydrologically important to a variety of contaminant transport and water-resource issues. The unsaturated zone of the English Chalk Aquifer provides an important opportunity for a case study of unsaturated preferential flow in isolation from other flow modes. The chalk matrix has low hydraulic conductivity and stays saturated, owing to its fine uniform pores and the wet climate of the region. Therefore the substantial fluxes observed in the unsaturated chalk must be within fractures and interact minimally with matrix material. Price et al. [2000] showed that irregularities on fracture surfaces provide a significant storage capacity in the chalk unsaturated zone, likely accounting for volumes of water required to explain unexpected dry-season water-table stability during substantial continuing streamflow observed by Lewis et al. [1993] In this presentation we discuss and quantify the dynamics of replenishment and drainage of this unsaturated zone fracture-face storage domain using a modification of the source-responsive model of Nimmo [2010]. This model explains the processes in terms of two interacting flow regimes: a film or rivulet preferential flow regime on rough fracture faces, active on an individual-storm timescale, and a regime of adsorptive and surface-tension influences, resembling traditional diffuse formulations of unsaturated flow, effective mainly on a seasonal timescale. The modified model identifies hydraulic parameters for an unsaturated fracture-facial domain lining the fractures. Besides helping to quantify the unsaturated zone storage described by Price et al., these results highlight the importance of research on the topic of unsaturated-flow relations within a near-fracture-surface domain. This model can also facilitate understanding of mechanisms for reinitiation of preferential flow after temporary cessation, which is important in multi-year preferential flow through deep unsaturated zones [Pruess, 1999]. Lewis, M.A., H.K. Jones, D.M.J. Macdonald, M. Price, J.A. Barker, T.R. Shearer, A.J. Wesselink, and D.J. Evans (1993), Groundwater storage in British aquifers--Chalk, National Rivers Authority R&D Note, 169, Bristol, UK. Nimmo, J.R. (2010), Theory for Source-Responsive and Free-Surface Film Modeling of Unsaturated Flow, Vadose Zone Journal, 9(2), 295-306, doi:10.2136/vzj2009.0085. Price, M., R.G. Low, and C. McCann (2000), Mechanisms of water storage and flow in the unsaturated zone of the Chalk aquifer, Journal of Hydrology, 233(1-4), 54-71. Pruess, K. (1999), A mechanistic model for water seepage through thick unsaturated zones in fractured rocks of low matrix permeability, Water Resources Research, 35(4), 1039-1051.

Quantifying Hydro-biogeochemical Model Sensitivity in Assessment of Climate Change Effect on Hyporheic Zone Processes

NASA Astrophysics Data System (ADS)

Song, X.; Chen, X.; Dai, H.; Hammond, G. E.; Song, H. S.; Stegen, J.

2016-12-01

The hyporheic zone is an active region for biogeochemical processes such as carbon and nitrogen cycling, where the groundwater and surface water mix and interact with each other with distinct biogeochemical and thermal properties. The biogeochemical dynamics within the hyporheic zone are driven by both river water and groundwater hydraulic dynamics, which are directly affected by climate change scenarios. Besides that, the hydraulic and thermal properties of local sediments and microbial and chemical processes also play important roles in biogeochemical dynamics. Thus for a comprehensive understanding of the biogeochemical processes in the hyporheic zone, a coupled thermo-hydro-biogeochemical model is needed. As multiple uncertainty sources are involved in the integrated model, it is important to identify its key modules/parameters through sensitivity analysis. In this study, we develop a 2D cross-section model in the hyporheic zone at the DOE Hanford site adjacent to Columbia River and use this model to quantify module and parametric sensitivity on assessment of climate change. To achieve this purpose, We 1) develop a facies-based groundwater flow and heat transfer model that incorporates facies geometry and heterogeneity characterized from a field data set, 2) derive multiple reaction networks/pathways from batch experiments with in-situ samples and integrate temperate dependent reactive transport modules to the flow model, 3) assign multiple climate change scenarios to the coupled model by analyzing historical river stage data, 4) apply a variance-based global sensitivity analysis to quantify scenario/module/parameter uncertainty in hierarchy level. The objectives of the research include: 1) identifing the key control factors of the coupled thermo-hydro-biogeochemical model in the assessment of climate change, and 2) quantify the carbon consumption in different climate change scenarios in the hyporheic zone.

An integral turbulent kinetic energy analysis of free shear flows

NASA Technical Reports Server (NTRS)

Peters, C. E.; Phares, W. J.

1973-01-01

Mixing of coaxial streams is analyzed by application of integral techniques. An integrated turbulent kinetic energy (TKE) equation is solved simultaneously with the integral equations for the mean flow. Normalized TKE profile shapes are obtained from incompressible jet and shear layer experiments and are assumed to be applicable to all free turbulent flows. The shear stress at the midpoint of the mixing zone is assumed to be directly proportional to the local TKE, and dissipation is treated with a generalization of the model developed for isotropic turbulence. Although the analysis was developed for ducted flows, constant-pressure flows were approximated with the duct much larger than the jet. The axisymmetric flows under consideration were predicted with reasonable accuracy. Fairly good results were also obtained for the fully developed two-dimensional shear layers, which were computed as thin layers at the boundary of a large circular jet.

Analysis of vertical flow during ambient and pumped conditions in four monitoring wells at the Pantex Plant, Carson County, Texas, July-September 2008

USGS Publications Warehouse

Stanton, Gregory P.; Thomas, Jonathan V.; Stoval, Jeffery

2009-01-01

Logs collected in monitoring well PTX06–1068 during ambient conditions indicate a static environment with no flow. During pumping there was upward vertical flow at rates ranging from 0.4 to 4.8 gallons per minute. During pumping, a gradual trend of more positive flowmeter values (upward flow) with distance up the well was observed. Estimated total transmissivity for four production zones identified from Flow–B numerical model results taken together was calculated to be about 200 feet squared per day.

Hydrogeology of the Potsdam Sandstone in northern New York

USGS Publications Warehouse

Williams, John H.; Reynolds, Richard J.; Franzi, David A.; Romanowicz, Edwin A.; Paillet, Frederick L.

2010-01-01

The Potsdam Sandstone of Cambrian age forms a transboundary aquifer that extends across northern New York and into southern Quebec. The Potsdam Sandstone is a gently dipping sequence of arkose, subarkose, and orthoquartzite that unconformably overlies Precambrian metamorphic bedrock. The Potsdam irregularly grades upward over a thickness of 450 m from a heterogeneous feldspathic and argillaceous rock to a homogeneous, quartz-rich and matrix-poor rock. The hydrogeological framework of the Potsdam Sandstone was investigated through an analysis of records from 1,500 wells and geophysical logs from 40 wells, and through compilation of GIS coverages of bedrock and surficial geology, examination of bedrock cores, and construction of hydrogeological sections. The upper several metres of the sandstone typically is weathered and fractured and, where saturated, readily transmits groundwater. Bedding-related fractures in the sandstone commonly form sub-horizontal flow zones of relatively high transmissivity. The vertical distribution of sub-horizontal flow zones is variable; spacings of less than 10 m are common. Transmissivity of individual flow zones may be more than 100 m2/d but typically is less than 10 m2/d. High angle fractures, including joints and faults, locally provide vertical hydraulic connection between flow zones. Hydraulic head gradients in the aquifer commonly are downward; a laterally extensive series of sub-horizontal flow zones serve as drains for the groundwater flow system. Vertical hydraulic head differences between shallow and deep flow zones range from 1 m to more than 20 m. The maximum head differences are in recharge areas upgradient from the area where the Chateauguay and Chazy Rivers, and their tributaries, have cut into till and bedrock. Till overlies the sandstone in much of the study area; its thickness is generally greatest in the western part, where it may exceed 50 m. A discontinuous belt of bedrock pavements stripped of glacial drift extends across the eastern part of the study area; the largest of these is Altona Flat Rock. Most recharge to the sandstone aquifer occurs in areas of thin, discontinuous till and exposed bedrock; little recharge occurs in areas where this unit is overlain by thick till and clay. Discharge from the sandstone aquifer provides stream and river baseflow and is the source of many springs. A series of springs that are used for municipal bottled water and fish-hatchery supply discharge from 1,000 to 5,000 L/min adjacent to several tributaries east of the Chateauguay River. The major recharge areas for the Chateauguay springs are probably upgradient to the southeast, where the till cover is thin or absent.

An analytical study on groundwater flow in drainage basins with horizontal wells

NASA Astrophysics Data System (ADS)

Wang, Jun-Zhi; Jiang, Xiao-Wei; Wan, Li; Wang, Xu-Sheng; Li, Hailong

2014-06-01

Analytical studies on release/capture zones are often limited to a uniform background groundwater flow. In fact, for basin-scale problems, the undulating water table would lead to the development of hierarchically nested flow systems, which are more complex than a uniform flow. Under the premise that the water table is a replica of undulating topography and hardly influenced by wells, an analytical solution of hydraulic head is derived for a two-dimensional cross section of a drainage basin with horizontal injection/pumping wells. Based on the analytical solution, distributions of hydraulic head, stagnation points and flow systems (including release/capture zones) are explored. The superposition of injection/pumping wells onto the background flow field leads to the development of new internal stagnation points and new flow systems (including release/capture zones). Generally speaking, the existence of n injection/pumping wells would result in up to n new internal stagnation points and up to 2n new flow systems (including release/capture zones). The analytical study presented, which integrates traditional well hydraulics with the theory of regional groundwater flow, is useful in understanding basin-scale groundwater flow influenced by human activities.

Importance of unsaturated zone flow for simulating recharge in a humid climate

USGS Publications Warehouse

Hunt, R.J.; Prudic, David E.; Walker, J.F.; Anderson, M.P.

2008-01-01

Transient recharge to the water table is often not well understood or quantified. Two approaches for simulating transient recharge in a ground water flow model were investigated using the Trout Lake watershed in north-central Wisconsin: (1) a traditional approach of adding recharge directly to the water table and (2) routing the same volume of water through an unsaturated zone column to the water table. Areas with thin (less than 1 m) unsaturated zones showed little difference in timing of recharge between the two approaches; when water was routed through the unsaturated zone, however, less recharge was delivered to the water table and more discharge occurred to the surface because recharge direction and magnitude changed when the water table rose to the land surface. Areas with a thick (15 to 26 m) unsaturated zone were characterized by multimonth lags between infiltration and recharge, and, in some cases, wetting fronts from precipitation events during the fall overtook and mixed with infiltration from the previous spring snowmelt. Thus, in thicker unsaturated zones, the volume of water infiltrated was properly simulated using the traditional approach, but the timing was different from simulations that included unsaturated zone flow. Routing of rejected recharge and ground water discharge at land surface to surface water features also provided a better simulation of the observed flow regime in a stream at the basin outlet. These results demonstrate that consideration of flow through the unsaturated zone may be important when simulating transient ground water flow in humid climates with shallow water tables.

Protection of extreme ultraviolet lithography masks. II. Showerhead flow mitigation of nanoscale particulate contamination [Protection of EUV lithography masks II: Showerhead flow mitigation of nanoscale particulate contamination

DOE PAGES

Klebanoff, Leonard E.; Torczynski, John R.; Geller, Anthony S.; ...

2015-03-27

An analysis is presented of a method to protect the reticle (mask) in an extreme ultraviolet (EUV) mask inspection tool using a showerhead plenum to provide a continuous flow of clean gas over the surface of a reticle. The reticle is suspended in an inverted fashion (face down) within a stage/holder that moves back and forth over the showerhead plenum as the reticle is inspected. It is essential that no particles of 10-nm diameter or larger be deposited on the reticle during inspection. Particles can originate from multiple sources in the system, and mask protection from each source is explicitlymore » analyzed. The showerhead plate has an internal plenum with a solid conical wall isolating the aperture. The upper and lower surfaces of the plate are thin flat sheets of porous-metal material. These porous sheets form the top and bottom showerheads that supply the region between the showerhead plate and the reticle and the region between the conical aperture and the Optics Zone box with continuous flows of clean gas. The model studies show that the top showerhead provides robust reticle protection from particles of 10-nm diameter or larger originating from the Reticle Zone and from plenum surfaces contaminated by exposure to the Reticle Zone. Protection is achieved with negligible effect on EUV transmission. Furthermore, the bottom showerhead efficiently protects the reticle from nanoscale particles originating from the Optics Zone.« less

Modelling Fault Zone Evolution: Implications for fluid flow.

NASA Astrophysics Data System (ADS)

Moir, H.; Lunn, R. J.; Shipton, Z. K.

2009-04-01

Flow simulation models are of major interest to many industries including hydrocarbon, nuclear waste, sequestering of carbon dioxide and mining. One of the major uncertainties in these models is in predicting the permeability of faults, principally in the detailed structure of the fault zone. Studying the detailed structure of a fault zone is difficult because of the inaccessible nature of sub-surface faults and also because of their highly complex nature; fault zones show a high degree of spatial and temporal heterogeneity i.e. the properties of the fault change as you move along the fault, they also change with time. It is well understood that faults influence fluid flow characteristics. They may act as a conduit or a barrier or even as both by blocking flow across the fault while promoting flow along it. Controls on fault hydraulic properties include cementation, stress field orientation, fault zone components and fault zone geometry. Within brittle rocks, such as granite, fracture networks are limited but provide the dominant pathway for flow within this rock type. Research at the EU's Soultz-sous-Forệt Hot Dry Rock test site [Evans et al., 2005] showed that 95% of flow into the borehole was associated with a single fault zone at 3490m depth, and that 10 open fractures account for the majority of flow within the zone. These data underline the critical role of faults in deep flow systems and the importance of achieving a predictive understanding of fault hydraulic properties. To improve estimates of fault zone permeability, it is important to understand the underlying hydro-mechanical processes of fault zone formation. In this research, we explore the spatial and temporal evolution of fault zones in brittle rock through development and application of a 2D hydro-mechanical finite element model, MOPEDZ. The authors have previously presented numerical simulations of the development of fault linkage structures from two or three pre-existing joints, the results of which compare well to features observed in mapped exposures. For these simple simulations from a small number of pre-existing joints the fault zone evolves in a predictable way: fault linkage is governed by three key factors: Stress ratio of s1 (maximum compressive stress) to s3(minimum compressive stress), original geometry of the pre-existing structures (contractional vs. dilational geometries) and the orientation of the principle stress direction (σ1) to the pre-existing structures. In this paper we present numerical simulations of the temporal and spatial evolution of fault linkage structures from many pre-existing joints. The initial location, size and orientations of these joints are based on field observations of cooling joints in granite from the Sierra Nevada. We show that the constantly evolving geometry and local stress field perturbations contribute significantly to fault zone evolution. The location and orientations of linkage structures previously predicted by the simple simulations are consistent with the predicted geometries in the more complex fault zones, however, the exact location at which individual structures form is not easily predicted. Markedly different fault zone geometries are predicted when the pre-existing joints are rotated with respect to the maximum compressive stress. In particular, fault surfaces range from evolving smooth linear structures to producing complex ‘stepped' fault zone geometries. These geometries have a significant effect on simulations of along and across-fault flow.

Microstructural Evolution during Mid-Crustal Shear Zone Thickening and Thinning, Mount Irene Detachment Zone, Fiordland, New Zealand

NASA Astrophysics Data System (ADS)

Negrini, M.; Smith, S. A. F.; Scott, J.; Rooney, J. S.; Demurtas, M.

2016-12-01

Recent work has shown that ductile shear zones experience cyclic variations in stress and strain rate due to, for example, elastic loading from earthquake slip on brittle faults or the presence of rigid particles and asperities within the shear zone. Such non-steady state flow conditions can promote microstructural changes including a decrease in grain sizes followed by a switch in the main deformation mechanisms. Understanding the microstructural changes that occur during non steady-state deformation is therefore critical in evaluating shear zone rheology. The Mount Irene shear zone formed during Cretaceous extension in the middle crust and was active at temperatures of 600°C and pressures of 6 kbar. The shear zone localized in a basal calcite marble layer typically 3-5 m thick containing hundreds of thin (mm-cm) calc-silicate bands that are now parallel to the shear zone boundaries. The lower boundary of the shear zone preserves meter-scale undulations that cause the shear zone to be squeezed in to regions that are <1.5 m thick. The calc-silicate bands act as "flow markers" and allow individual shear zone layers to be traced continuously through thick and thin regions, implying that the mylonites experienced cyclic variations in stress and strain rate. Calc-mylonite samples collected from the same layer close to the base of the shear zone reveal that layer thinning was accompanied by progressive microstructural changes including intense twinning, stretching and flattening of large calcite porphyroclasts as well as the development of interconnected networks of recrystallized calcite aggregates. EBSD analysis shows that the recrystallized aggregates contain polygonal calcite grains with microstructures (e.g. grain quadruple junctions) similar to those reported for neighbor-switching processes associated with grain boundary sliding and superplasticity. Ongoing and future work will utilize samples from across the full thickness of the shear zone to determine key microstructural changes and deformation mechanisms that accommodated shear zone thinning and thickening during non-steady state deformation.

Extended residence time centrifugal contactor design modification and centrifugal contactor vane plate valving apparatus for extending mixing zone residence time

DOEpatents

Wardle, Kent E.

2017-06-06

The present invention provides an annular centrifugal contactor, having a housing adapted to receive a plurality of flowing liquids; a rotor on the interior of the housing; an annular mixing zone, wherein the annular mixing zone has a plurality of fluid retention reservoirs with ingress apertures near the bottom of the annular mixing zone and egress apertures located above the ingress apertures of the annular mixing zone; and an adjustable vane plate stem, wherein the stem can be raised to restrict the flow of a liquid into the rotor or lowered to increase the flow of the liquid into the rotor.

Geostatistics applied to cross-well reflection seismic for imaging carbonate aquifers

NASA Astrophysics Data System (ADS)

Parra, Jorge; Emery, Xavier

2013-05-01

Cross-well seismic reflection data, acquired from a carbonate aquifer at Port Mayaca test site near the eastern boundary of Lake Okeechobee in Martin County, Florida, are used to delineate flow units in the region intercepted by two wells. The interwell impedance determined by inversion from the seismic reflection data allows us to visualize the major boundaries between the hydraulic units. The hydraulic (flow) unit properties are based on the integration of well logs and the carbonate structure, which consists of isolated vuggy carbonate units and interconnected vug systems within the carbonate matrix. The vuggy and matrix porosity logs based on Formation Micro-Imager (FMI) data provide information about highly permeable conduits at well locations. The integration of the inverted impedance and well logs using geostatistics helps us to assess the resolution of the cross-well seismic method for detecting conduits and to determine whether these conduits are continuous or discontinuous between wells. A productive water zone of the aquifer outlined by the well logs was selected for analysis and interpretation. The ELAN (Elemental Log Analysis) porosity from two wells was selected as primary data and the reflection seismic-based impedance as secondary data. The direct and cross variograms along the vertical wells capture nested structures associated with periodic carbonate units, which correspond to connected flow units between the wells. Alternatively, the horizontal variogram of impedance (secondary data) provides scale lengths that correspond to irregular boundary shapes of flow units. The ELAN porosity image obtained by cokriging exhibits three similar flow units at different depths. These units are thin conduits developed in the first well and, at about the middle of the interwell separation region, these conduits connect to thicker flow units that are intercepted by the second well. In addition, a high impedance zone (low porosity) at a depth of about 275 m, after being converted to ELAN porosity, is characterized as a more confined low porosity structure. This continuous zone corresponds to a permeability barrier in the carbonate aquifer that separates the three connected conduits observed in the cokriging image. In the zones above and below this permeability barrier, the water production is very high, which agrees with water well observations at the Port Mayaca aquifer.

Design of suitable carrier buffer for free-flow zone electrophoresis by charge-to-mass ratio and band broadening analysis.

PubMed

Kong, Fan-Zhi; Yang, Ying; He, Yu-Chen; Zhang, Qiang; Li, Guo-Qing; Fan, Liu-Yin; Xiao, Hua; Li, Shan; Cao, Cheng-Xi

2016-09-01

In this work, charge-to-mass ratio (C/M) and band broadening analyses were combined to provide better guidance for the design of free-flow zone electrophoresis carrier buffer (CB). First, the C/M analyses of hemoglobin and C-phycocyanin (C-PC) under different pH were performed by CLC Protein Workbench software. Second, band dispersion due to the initial bandwidth, diffusion, and hydrodynamic broadening were discussed, respectively. Based on the analyses of the C/M and band broadening, a better guidance for preparation of free-flow zone electrophoresis CB was obtained. Series of experiments were performed to validate the proposed method. The experimental data showed high accordance with our prediction allowing the CB to be prepared easily with our proposed method. To further evaluate this method, C-PC was purified from crude extracts of Spirulina platensis with the selected separation condition. Results showed that C-PC was well separated from other phycobiliproteins that have similar physicochemical properties, and analytical grade product with purity up to 4.5 (A620/A280) was obtained. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

COST ANALYSIS OF PERMEABLE REACTIVE BARRIERS FOR REMEDIATION OF GROUND WATER

EPA Science Inventory

ABSTRACT

Permeable reactive barriers (PRB's) are an emerging, alternative in-situ approach for remediating contaminated groundwater that combine subsurface fluid flow management with a passive chemical treatment zone. PRB's are a potentially more cost effective treatment...

Method for siting detectors within a facility

DOEpatents

Gleason, Nathaniel Jeremy Meyer

2007-12-11

A method, system and article of manufacture of siting one or more detectors in a facility represented with zones are provided. Signals S.sub.i,j representing an effect in zone j in response to a release of contaminant in zone i for one or more flow conditions are provided. A candidate architecture has one or more candidate zones. A limiting case signal is determined for each flow condition for multiple candidate architectures. The limiting case signal is a smallest system signal of multiple system signals associated with a release in a zone. Each system signal is a maximum one of the signals representing the effect in the candidate zones from the release in one zone for the flow condition. For each candidate architecture, a robust limiting case signal is determined based on a minimum of the limiting case signals. One candidate architecture is selected based on the robust limiting case signals.

Applicability of Channel flow as an extrusion mechanism of the Higher Himalayan Shear Zone from Sutlej, Zanskar, Dhauliganga and Goriganga Sections, Indian Himalaya

NASA Astrophysics Data System (ADS)

Mukherjee, Soumyajit

2010-05-01

Applicability of Channel flow as an extrusion mechanism of the Higher Himalayan Shear Zone from Sutlej, Zanskar, Dhauliganga and Goriganga Sections, Indian Himalaya Soumyajit Mukherjee Department of Earth Sciences, Indian Institute of Technology Bombay Powai, Mumbai- 400076, INDIA, e-mail: soumyajitm@gmail.com Mukherjee & Koyi (1,2) evaluated the applicability of channel flow extrusion of the Higher Himalayan Shear Zone (HHSZ) in the Zanskar and the Sutlej sections based on field- and micro-structural studies, analytical- and analog models. Further work on the Dhauliganga and the Goriganga sections of the HHSZ reveal complicated structural geology that is untenable to explain simply in terms of channel flow. For example, in the former section, flexure slip folds exist in a zone spatially separated from the upper strand of the South Tibetan Detachment System (STDSU). On the other hand, in the later section, an STDSU- in the sense of Mukherjee and Koyi (1)- is absent. Instead, a steep extensional shear zone with northeasterly dipping shear plane cuts the pre-existing shear fabrics throughout the HHSZ. However, the following common structural features in the HHSZ were observed in these sections. (1) S-C fabrics are the most ubiquitous ductile shear sense indicators in field. (2) Brittle shearing along the preexisting ductile primary shear planes in a top-to-SW sense. (3) Less ubiquitous ductile compressional shearing in the upper part of the shear zone including the STDSU. (4) A phase of local brittle-ductile extension throughout the shear zone as revealed by boudins of various morphologies. (5) The shear zone is divisible into a southern non-migmatitic and a northern migmatitic zone. No special structural dissimilarity is observed across this lithological boundary. Keywords: Channel flow, Extrusion, Higher Himalaya, Structural Geology, Shear zone, Deformation References 1. Mukherjee S, Koyi HA (in press) Higher Himalayan Shear Zone, Sutlej section: structural geology and extrusion mechanism by various combinations of simple shear, pure shear and channel flow in shifting modes. International Journal of Earth Sciences. 2. Mukherjee S, Koyi HA (in press) Higher Himalayan Shear Zone, Zanskar Indian Himalaya: microstructural studies and extrusion mechanism by a combination of simple shear and channel flow. International Journal of Earth Sciences.

Eruption and emplacement dynamics of a thick trachytic lava flow of the Sancy volcano (France)

NASA Astrophysics Data System (ADS)

Latutrie, Benjamin; Harris, Andrew; Médard, Etienne; Gurioli, Lucia

2017-01-01

A 70-m-thick, 2200-m-long (51 × 106 m3) trachytic lava flow unit underlies the Puy de Cliergue (Mt. Dore, France). Excellent exposure along a 400-m-long and 60- to 85-m-high section allows the flow interior to be accessed on two sides of a glacial valley that cuts through the unit. We completed an integrated morphological, structural, textural, and chemical analysis of the unit to gain insights into eruption and flow processes during emplacement of this thick silicic lava flow, so as to elucidate the chamber and flow dynamic processed that operate during the emplacement of such systems. The unit is characterized by an inverse chemical stratification, where there is primitive lava beneath the evolved lava. The interior is plug dominated with a thin basal shear zone overlying a thick basal breccia, with ramping affecting the entire flow thickness. To understand these characteristics, we propose an eruption model that first involves processes operating in the magma chamber whereby a primitive melt is injected into an evolved magma to create a mixed zone at the chamber base. The eruption triggered by this event first emplaced a trachytic dome, into which banded lava from the chamber base was injected. Subsequent endogenous dome growth led to flow down the shallow slope to the east on which the highly viscous (1012 Pa s) coulée was emplaced. The flow likely moved extremely slowly, being emplaced over a period of 4-10 years in a glacial manner, where a thick (>60-m) plug slid over a thin (5-m-thick) basal shear zone. Excellent exposure means that the Puy de Cliergue complex can be viewed as a case type location for understanding and defining the eruption and emplacement of thick, high-viscosity, silicic lava flow systems.

Prediction of groundwater flowing well zone at An-Najif Province, central Iraq using evidential belief functions model and GIS.

PubMed

Al-Abadi, Alaa M; Pradhan, Biswajeet; Shahid, Shamsuddin

2015-10-01

The objective of this study is to delineate groundwater flowing well zone potential in An-Najif Province of Iraq in a data-driven evidential belief function model developed in a geographical information system (GIS) environment. An inventory map of 68 groundwater flowing wells was prepared through field survey. Seventy percent or 43 wells were used for training the evidential belief functions model and the reset 30 % or 19 wells were used for validation of the model. Seven groundwater conditioning factors mostly derived from RS were used, namely elevation, slope angle, curvature, topographic wetness index, stream power index, lithological units, and distance to the Euphrates River in this study. The relationship between training flowing well locations and the conditioning factors were investigated using evidential belief functions technique in a GIS environment. The integrated belief values were classified into five categories using natural break classification scheme to predict spatial zoning of groundwater flowing well, namely very low (0.17-0.34), low (0.34-0.46), moderate (0.46-0.58), high (0.58-0.80), and very high (0.80-0.99). The results show that very low and low zones cover 72 % (19,282 km(2)) of the study area mostly clustered in the central part, the moderate zone concentrated in the west part covers 13 % (3481 km(2)), and the high and very high zones extended over the northern part cover 15 % (3977 km(2)) of the study area. The vast spatial extension of very low and low zones indicates that groundwater flowing wells potential in the study area is low. The performance of the evidential belief functions spatial model was validated using the receiver operating characteristic curve. A success rate of 0.95 and a prediction rate of 0.94 were estimated from the area under relative operating characteristics curves, which indicate that the developed model has excellent capability to predict groundwater flowing well zones. The produced map of groundwater flowing well zones could be used to identify new wells and manage groundwater storage in a sustainable manner.

Hydrogeological characterization of soil/weathered zone and underlying fractured bedrocks in DNAPL contaminated areas using the electromagnetic flowmeter

NASA Astrophysics Data System (ADS)

Kang, E.; Yeo, I.

2011-12-01

Flowmeter tests were carried out to characterize hydrogeology at DNAPL contaminated site in Wonju, Korea. Aquifer and slug tests determined hydraulic conductivity of soil/weathered zone and underlying fractured bed rocks to be 2.95×10-6 to 7.11×10-6 m/sec and 9.14×10-7 to 2.59×10-6 m/sec, respectively. Ambient flowmeter tests under natural hydraulic conditions revealed that the inflow and outflow take place through the borehole of soil/weathered zone with a tendency of down flow in the borehole. In particular, the most permeable layer of 22 to 30 m below the surface was found to form a major groundwater flow channel. On the contrary, a slight inflow and outflow was observed in the borehole, and the groundwater that inflows in the bottom section of the fractured bedrock flows up and exits through to the most permeable layer. Hydraulic heads measured at nearby multi-level boreholes confirmed the down flow in the soil/weathered zone and the up flow in fractured bedrocks. It was also revealed that the groundwater flow converges to the most permeable layer. TCE concentration in groundwater was measured at different depths, and in the borehole of the soil/weathered zone, high TCE concentration was found with higher than 10 mg/L near to the water table and decreased to about 6 mg/L with depth. The fractured bedrocks have a relatively constant low TCE concentration through a 20 m thick screen at less than l mg/L. The hydrogeology of the up flow in the soil/weathered zone and the down flow in underlying fractured bedrock leads the groundwater flow, and subsequently TCE plume, mainly to the most permeable layer that also restricts the advective transport of TCE plume to underlying fractured bedrocks. The cross borehole flowmeter test was carried out to find any hydrogeological connection between the soil/weathered zone and underlying fractured bedrocks. When pumping groundwater from the soil/weathered zone, no induced flow by groundwater extraction was observed at the underlying fractured bedrocks, and the hydraulic connection was identified only within the soil/weathered zone. However, when pumping groundwater from the fractured bedrocks, the hydraulic response was observed in the soil/weathered zone rather than another fractured bedrock borehole. Thus, when pump-and-treat is adopted for remediating the dissolved plume of DNAPL, the pumping well should be placed in the soil/weathered zone. Otherwise, the pumping of groundwater from the underlying fractured bedrocks will disperse the TCE plume into underlying fractured bedrocks.

Method development and strategy for the characterization of complexly faulted and fractured rhyolitic tuffs, Yucca Mountain, Nevada

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

Karasaki, K.; Galloway, D.

1991-06-01

The planned high-level nuclear waste repository at Yucca Mountain, Nevada, would exist in unsaturated, fractured welded tuff. One possible contaminant pathway to the accessible environment is transport by groundwater infiltrating to the water table and flowing through the saturated zone. Therefore, an effort to characterize the hydrology of the saturated zone is being undertaken in parallel with that of the unsaturated zone. As a part of the saturated zone investigation, there wells-UE-25c{number_sign}1, UE-25c{number_sign}2, and UE-25c{number_sign}3 (hereafter called the c-holes)-were drilled to study hydraulic and transport properties of rock formations underlying the planned waste repository. The location of the c-holes ismore » such that the formations penetrated in the unsaturated zone occur at similar depths and with similar thicknesses as at the planned repository site. In characterizing a highly heterogeneous flow system, several issues emerge. (1) The characterization strategy should allow for the virtual impossibility to enumerate and characterize all heterogeneities. (2) The methodology to characterize the heterogeneous flow system at the scale of the well tests needs to be established. (3) Tools need to be developed for scaling up the information obtained at the well-test scale to the larger scale of the site. In the present paper, the characterization strategy and the methods under development are discussed with the focus on the design and analysis of the field experiments at the c-holes.« less

One-dimensional flow model of the river-hyporheic zone system

NASA Astrophysics Data System (ADS)

Pokrajac, D.

2016-12-01

The hyporheic zone is a shallow layer beneath natural streams that is characterized by intense exchange of water, nutrients, pollutants and thermal energy. Understanding these exchange processes is crucial for successful modelling of the river hydrodynamics and morphodynamics at various scales from the river corridor up to the river network scale (Cardenas, 2015). Existing simulation models of hyporheic exchange processes are either idealized models of the tracer movement through the river-hyporheic zone system (e.g. TSM, Bencala and Walters, 1983) or detailed models of turbulent flow in a stream, coupled with a conventional 2D Darcian groundwater model (e.g. Cardenas and Wilson, 2007). This paper presents an alternative approach which involves a simple 1-D simulation model of the hyporheic zone system based on the classical SWE equations coupled with the newly developed porous media analogue. This allows incorporating the effects of flow unsteadiness and non-Darcian parameterization od the drag term in the hyporheic zone model. The conceptual model of the stream-hyporheic zone system consists of a 1D model of the open channel flow in the river, coupled with a 1D model of the flow in the hyporheic zone via volume flux due to the difference in the water level in the river and the hyporheic zone. The interaction with the underlying groundwater aquifer is neglected, but coupling the present model with any conventional groundwater model is straightforward. The paper presents the derivation of the 1D flow equations for flow in the hyporheic zone, the details of the numerical scheme used for solving them and the model validation by comparison with published experimental data. References Bencala, K. E., and R. A. Walters (1983) "Simulation of solute transport in a mountain pool-and-riffle stream- a transient storage model", Water Resources Reseach 19(3): 718-724. Cardenas, M. B. (2015) "Hyporheic zone hydrologic science: A historical account of its emergence and a prospectus", Water Resources Research 51: 3601-3616 Cardenas, M. B., and J. L. Wilson (2007) "Dunes, turbulent eddies, and interfacial exchange with permeable sediments", Water Resour. Res. 43:W08412

Pore network properties of sandstones in a fault damage zone

NASA Astrophysics Data System (ADS)

Bossennec, Claire; Géraud, Yves; Moretti, Isabelle; Mattioni, Luca; Stemmelen, Didier

2018-05-01

The understanding of fluid flow in faulted sandstones is based on a wide range of techniques. These depend on the multi-method determination of petrological and structural features, porous network properties and both spatial and temporal variations and interactions of these features. The question of the multi-parameter analysis on fluid flow controlling properties is addressed for an outcrop damage zone in the hanging wall of a normal fault zone on the western border of the Upper Rhine Graben, affecting the Buntsandstein Group (Early Triassic). Diagenetic processes may alter the original pore type and geometry in fractured and faulted sandstones. Therefore, these may control the ultimate porosity and permeability of the damage zone. The classical model of evolution of hydraulic properties with distance from the major fault core is nuanced here. The hydraulic behavior of the rock media is better described by a pluri-scale model including: 1) The grain scale, where the hydraulic properties are controlled by sedimentary features, the distance from the fracture, and the impact of diagenetic processes. These result in the ultimate porous network characteristics observed. 2) A larger scale, where the structural position and characteristics (density, connectivity) of the fracture corridors are strongly correlated with both geo-mechanical and hydraulic properties within the damage zone.

Shedding Light on the Grey Zone of Speciation along a Continuum of Genomic Divergence.

PubMed

Roux, Camille; Fraïsse, Christelle; Romiguier, Jonathan; Anciaux, Yoann; Galtier, Nicolas; Bierne, Nicolas

2016-12-01

Speciation results from the progressive accumulation of mutations that decrease the probability of mating between parental populations or reduce the fitness of hybrids-the so-called species barriers. The speciation genomic literature, however, is mainly a collection of case studies, each with its own approach and specificities, such that a global view of the gradual process of evolution from one to two species is currently lacking. Of primary importance is the prevalence of gene flow between diverging entities, which is central in most species concepts and has been widely discussed in recent years. Here, we explore the continuum of speciation thanks to a comparative analysis of genomic data from 61 pairs of populations/species of animals with variable levels of divergence. Gene flow between diverging gene pools is assessed under an approximate Bayesian computation (ABC) framework. We show that the intermediate "grey zone" of speciation, in which taxonomy is often controversial, spans from 0.5% to 2% of net synonymous divergence, irrespective of species life history traits or ecology. Thanks to appropriate modeling of among-locus variation in genetic drift and introgression rate, we clarify the status of the majority of ambiguous cases and uncover a number of cryptic species. Our analysis also reveals the high incidence in animals of semi-isolated species (when some but not all loci are affected by barriers to gene flow) and highlights the intrinsic difficulty, both statistical and conceptual, of delineating species in the grey zone of speciation.

Groundwater-flow model of the Ozark Plateaus aquifer system, northwestern Arkansas, southeastern Kansas, southwestern Missouri, and northeastern Oklahoma

USGS Publications Warehouse

Czarnecki, John B.; Gillip, Jonathan A.; Jones, Perry M.; Yeatts, Daniel S.

2009-01-01

To assess the effect that increased water use is having on the long-term availability of groundwater within the Ozark Plateaus aquifer system, a groundwater-flow model was developed using MODFLOW 2000 for a model area covering 7,340 square miles for parts of Arkansas, Kansas, Missouri, and Oklahoma. Vertically the model is divided into five units. From top to bottom these units of variable thickness are: the Western Interior Plains confining unit, the Springfield Plateau aquifer, the Ozark confining unit, the Ozark aquifer, and the St. Francois confining unit. Large mined zones contained within the Springfield Plateau aquifer are represented in the model as extensive voids with orders-of-magnitude larger hydraulic conductivity than the adjacent nonmined zones. Water-use data were compiled for the period 1960 to 2006, with the most complete data sets available for the period 1985 to 2006. In 2006, total water use from the Ozark aquifer for Missouri was 87 percent (8,531,520 cubic feet per day) of the total pumped from the Ozark aquifer, with Kansas at 7 percent (727,452 cubic feet per day), and Oklahoma at 6 percent (551,408 cubic feet per day); water use for Arkansas within the model area was minor. Water use in the model from the Springfield Plateau aquifer in 2005 was specified from reported and estimated values as 569,047 cubic feet per day. Calibration of the model was made against average water-level altitudes in the Ozark aquifer for the period 1980 to 1989 and against waterlevel altitudes obtained in 2006 for the Springfield Plateau and Ozark aquifers. Error in simulating water-level altitudes was largest where water-level altitude gradients were largest, particularly near large cones of depression. Groundwater flow within the model area occurs generally from the highlands of the Springfield Plateau in southwestern Missouri toward the west, with localized flow occurring towards rivers and pumping centers including the five largest pumping centers near Joplin, Missouri; Carthage, Missouri; Noel, Missouri; Pittsburg, Kansas; and Miami, Oklahoma.Hypothetical scenarios involving various increases in groundwater-pumping rates were analyzed with the calibrated groundwater-flow model to assess changes in the flow system from 2007 to the year 2057. Pumping rates were increased between 0 and 4 percent per year starting with the 2006 rates for all wells in the model. Sustained pumping at 2006 rates was feasible at the five pumping centers until 2057; however, increases in pumping resulted in dewatering the aquifer and thus pumpage increases were not sustainable in Carthage and Noel for the 1 percent per year pumpage increase and greater hypothetical scenarios, and in Joplin and Miami for the 4 percent per year pumpage increase hypothetical scenarios.Zone-budget analyses were performed to assess the groundwater flow into and out of three zones specified within the Ozark-aquifer layer of the model. The three zones represented the model part of the Ozark aquifer in Kansas (zone 1), Oklahoma (zone 2), and Missouri and Arkansas (zone 3). Groundwater pumping causes substantial reductions in water in storage and induces flow through the Ozark confining unit for all hypothetical scenarios evaluated. Net simulated flow in 2057 from Kansas (zone 1) to Missouri (zone 3) ranges from 74,044 cubic feet per day for 2006 pumping rates (hypothetical scenario 1) to 625,319 cubic feet per day for a 4 percent increase in pumping per year (hypothetical scenario 5). Pumping from wells completed in the Ozark aquifer is the largest component of flow out of zone 3 in Missouri and Arkansas, and varies between 88 to 91 percent of the total flow out of zone 3 for all of the hypothetical scenarios. The largest component of flow into Oklahoma (zone 2) comes from the overlying Ozark confining unit, which is consistently about 45 percent of the total. Flow from the release of water in storage, from general-head boundaries, and from zones 1 and 3 is considerably smaller values that range from 3 to 22 percent of the total flow into zone 2. The largest flow out of the Oklahoma part of the model occurs from pumping from wells and ranges from 52 to 69 percent of the total.

Fault zone hydrogeology

NASA Astrophysics Data System (ADS)

Bense, V. F.; Gleeson, T.; Loveless, S. E.; Bour, O.; Scibek, J.

2013-12-01

Deformation along faults in the shallow crust (< 1 km) introduces permeability heterogeneity and anisotropy, which has an important impact on processes such as regional groundwater flow, hydrocarbon migration, and hydrothermal fluid circulation. Fault zones have the capacity to be hydraulic conduits connecting shallow and deep geological environments, but simultaneously the fault cores of many faults often form effective barriers to flow. The direct evaluation of the impact of faults to fluid flow patterns remains a challenge and requires a multidisciplinary research effort of structural geologists and hydrogeologists. However, we find that these disciplines often use different methods with little interaction between them. In this review, we document the current multi-disciplinary understanding of fault zone hydrogeology. We discuss surface- and subsurface observations from diverse rock types from unlithified and lithified clastic sediments through to carbonate, crystalline, and volcanic rocks. For each rock type, we evaluate geological deformation mechanisms, hydrogeologic observations and conceptual models of fault zone hydrogeology. Outcrop observations indicate that fault zones commonly have a permeability structure suggesting they should act as complex conduit-barrier systems in which along-fault flow is encouraged and across-fault flow is impeded. Hydrogeological observations of fault zones reported in the literature show a broad qualitative agreement with outcrop-based conceptual models of fault zone hydrogeology. Nevertheless, the specific impact of a particular fault permeability structure on fault zone hydrogeology can only be assessed when the hydrogeological context of the fault zone is considered and not from outcrop observations alone. To gain a more integrated, comprehensive understanding of fault zone hydrogeology, we foresee numerous synergistic opportunities and challenges for the discipline of structural geology and hydrogeology to co-evolve and address remaining challenges by co-locating study areas, sharing approaches and fusing data, developing conceptual models from hydrogeologic data, numerical modeling, and training interdisciplinary scientists.

The Impact of Operating Room Layout on Circulating Nurse's Work Patterns and Flow Disruptions: A Behavioral Mapping Study.

PubMed

Bayramzadeh, Sara; Joseph, Anjali; San, Dee; Khoshkenar, Amin; Taaffe, Kevin; Jafarifiroozabadi, Roxana; Neyens, David M

2018-01-01

To assess how the adjacencies of functionally different areas within operating rooms (ORs) can influence the circulating nurse's (CN) workflow patterns and disruptions. The CN plays a significant role in promoting patient safety during surgical procedures by observing, monitoring, and managing potential threats at and around the surgical field. Their work requires constant movement to different parts of the OR to support team members. The layout of the OR and crowded and cluttered environment might impact the CN's workflow and cause disruptions during the surgery. A convenience sample of 25 surgeries were video recorded and thematically coded for CN's activities, locations, and flow disruptions. The OR layout was categorized into transitional zones and functional zones (workstations, supply zones, support zones, and sterile areas around the surgical table). CN's activities were classified into patient-, equipment-, material-, and information-related activities. Flow disruptions included those related to environmental hazards and layout. The CN traveled through multiple zones during 91% of the activities. The CN's workstation acted as a main hub from which the CN made frequent trips to both sides of the surgical table, the foot of the OR table, supply zones, and support zones. Transitional zones accounted for 58.3% of all flow disruption that the CN was involved in whereas 28% occurred in areas surrounding the OR bed. The similarity of the movement and flow disruption patterns, despite variations in OR layout, highlighted the adjacencies required between major zones that CNs regularly visit. These optimum adjacencies should be considered while designing ORs such that they are more efficient and safer.

Vesicular komatiites, 3.5-Ga Komati Formation, Barberton Greenstone Belt, South Africa: inflation of submarine lavas and origin of spinifex zones

NASA Astrophysics Data System (ADS)

Dann, Jesse

2001-08-01

Komatiites of the 3.5-Ga Komati Formation are ultramafic lavas (>23% MgO) erupted in a submarine, lava plain environment. Newly discovered vesicular komatiites have vesicular upper crusts disrupted by synvolcanic structures that are similar to inflation-related structures of modern lava flows. Detailed outcrop maps reveal flows with upper vesicular zones, 2-15 m thick, which were (1) rotated by differential inflation, (2) intruded by dikes from the interior of the flow, (3) extended, forming a flooded graben, and/or (4) entirely engulfed. The largest inflated structure is a tumulus with 20 m of surface relief, which was covered by a compound flow unit of spinifex flow lobes. The lava that inflated and rotated the upper vesicular crust did not vesiculate, but crystallized as a thick spinifex zone with fist-size skeletal olivine. Instead of representing rapidly cooled lava, the spinifex zone cooled slowly beneath an insulating upper crust during inflation. Overpressure of the inflating lava may have inhibited vesiculation. This work describes the oldest vesicular komatiites known, illustrates the first field evidence for inflated structures in komatiite flows, proposes a new factor in the development of spinifex zones, and concludes that the inflation model is useful for understanding the evolution of komatiite submarine flow fields.

AnalyzeHOLE - An Integrated Wellbore Flow Analysis Tool

USGS Publications Warehouse

Halford, Keith

2009-01-01

Conventional interpretation of flow logs assumes that hydraulic conductivity is directly proportional to flow change with depth. However, well construction can significantly alter the expected relation between changes in fluid velocity and hydraulic conductivity. Strong hydraulic conductivity contrasts between lithologic intervals can be masked in continuously screened wells. Alternating intervals of screen and blank casing also can greatly complicate the relation between flow and hydraulic properties. More permeable units are not necessarily associated with rapid fluid-velocity increases. Thin, highly permeable units can be misinterpreted as thick and less permeable intervals or not identified at all. These conditions compromise standard flow-log interpretation because vertical flow fields are induced near the wellbore. AnalyzeHOLE, an integrated wellbore analysis tool for simulating flow and transport in wells and aquifer systems, provides a better alternative for simulating and evaluating complex well-aquifer system interaction. A pumping well and adjacent aquifer system are simulated with an axisymmetric, radial geometry in a two-dimensional MODFLOW model. Hydraulic conductivities are distributed by depth and estimated with PEST by minimizing squared differences between simulated and measured flows and drawdowns. Hydraulic conductivity can vary within a lithology but variance is limited with regularization. Transmissivity of the simulated system also can be constrained to estimates from single-well, pumping tests. Water-quality changes in the pumping well are simulated with simple mixing models between zones of differing water quality. These zones are differentiated by backtracking thousands of particles from the well screens with MODPATH. An Excel spreadsheet is used to interface the various components of AnalyzeHOLE by (1) creating model input files, (2) executing MODFLOW, MODPATH, PEST, and supporting FORTRAN routines, and (3) importing and graphically displaying pertinent results.

Computational and experimental analysis of the flow in an annular centrifugal contactor

NASA Astrophysics Data System (ADS)

Wardle, Kent E.

The annular centrifugal contactor has been developed for solvent extraction processes for recycling used nuclear fuel. The compact size and high efficiency of these contactors have made them the choice for advanced reprocessing schemes and a key equipment for a proposed future advanced fuel cycle facility. While a sufficient base of experience exists to facilitate successful operation of current contactor technology, a more complete understanding of the fluid flow within the contactor would enable further advancements in design and operation of future units and greater confidence for use of such contactors in a variety of other solvent extraction applications. This research effort has coupled computational fluid dynamics modeling with a variety of experimental measurements and observations to provide a valid detailed analysis of the flow within the centrifugal contactor. CFD modeling of the free surface flow in the annular mixing zone using the Volume of Fluid (VOF) volume tracking method combined with Large Eddy Simulation (LES) of turbulence was found to have very good agreement with the experimental measurements and observations. A detailed study of the flow and mixing for different housing vane geometries was performed and it was found that the four straight mixing vane geometry had greater mixing for the flow rate simulated and more predictable operation over a range of low to moderate flow rates. The separation zone was also modeled providing a useful description of the flow in this region and identifying critical design features. It is anticipated that this work will form a foundation for additional efforts at improving the design and operation of centrifugal contactors and provide a framework for progress towards simulation of solvent extraction processes.

High-Speed Friction Stir Welding of AA7075-T6 Sheet: Microstructure, Mechanical Properties, Micro-texture, and Thermal History

NASA Astrophysics Data System (ADS)

Zhang, Jingyi; Upadhyay, Piyush; Hovanski, Yuri; Field, David P.

2018-01-01

Friction stir welding (FSW) is a cost-effective and high-quality joining process for aluminum alloys (especially heat-treatable alloys) that is historically operated at lower joining speeds (up to hundreds of millimeters per minute). In this study, we present a microstructural analysis of friction stir welded AA7075-T6 blanks with high welding speeds up to 3 M/min. Textures, microstructures, mechanical properties, and weld quality are analyzed using TEM, EBSD, metallographic imaging, and Vickers hardness. The higher welding speed results in narrower, stronger heat-affected zones (HAZs) and also higher hardness in the nugget zones. The material flow direction in the nugget zone is found to be leaning towards the welding direction as the welding speed increases. Results are coupled with welding parameters and thermal history to aid in the understanding of the complex material flow and texture gradients within the welds in an effort to optimize welding parameters for high-speed processing.

Visualization of entry flow separation for oscillating flow in tubes

NASA Technical Reports Server (NTRS)

Qiu, Songgang; Simon, Terence W.

1992-01-01

Neutrally buoyant helium-filled soap bubbles with laser illumination are used to document entry flow separation for oscillating flow in tubes. For a symmetric entry case, the size of the separation zone appears to mildly depend on Reynolds number in the acceleration phase, but is roughly Reynolds number independent in the deceleration phase. For the asymmetric entry case, the separation zone was larger and appeared to grow somewhat during the deceleration phase. The separation zones for both entry geometry cases remain relatively small throughout the cycle. This is different from what would be observed in all-laminar, oscillator flows and is probably due to the high turbulence of the flow, particularly during the deceleration phase of the cycle.

Subsurface Flow and Moisture Dynamics in Response to Swash Motions: Effects of Beach Hydraulic Conductivity and Capillarity

NASA Astrophysics Data System (ADS)

Geng, Xiaolong; Heiss, James W.; Michael, Holly A.; Boufadel, Michel C.

2017-12-01

A combined field and numerical study was conducted to investigate dynamics of subsurface flow and moisture response to waves in the swash zone of a sandy beach located on Cape Henlopen, DE. A density-dependent variably saturated flow model MARUN was used to simulate subsurface flow beneath the swash zone. Values of hydraulic conductivity (K) and characteristic pore size (α, a capillary fringe property) were varied to evaluate their effects on subsurface flow and moisture dynamics in response to swash motions in beach aquifers. The site-specific modeling results were validated against spatiotemporal measurements of moisture and pore pressure in the beach. Sensitivity analyses indicated that the hydraulic conductivity and capillary fringe thickness of the beach greatly influenced groundwater flow pathways and associated transit times in the swash zone. A higher value of K enhanced swash-induced seawater infiltration into the beach, thereby resulting in a faster expansion of a wedge of high moisture content induced by swash cycles, and a flatter water table mound beneath the swash zone. In contrast, a thicker capillary fringe retained higher moisture content near the beach surface, and thus, significantly reduced the available pore space for infiltration of seawater. This attenuated wave effects on pore water flow in the unsaturated zone of the beach. Also, a thicker capillary fringe enhanced horizontal flow driven by the larger-scale hydraulic gradient caused by tides.

Multiple sample characterization of coals and other substances by controlled-atmosphere programmed temperature oxidation

DOEpatents

LaCount, Robert B.

1993-01-01

A furnace with two hot zones holds multiple analysis tubes. Each tube has a separable sample-packing section positioned in the first hot zone and a catalyst-packing section positioned in the second hot zone. A mass flow controller is connected to an inlet of each sample tube, and gas is supplied to the mass flow controller. Oxygen is supplied through a mass flow controller to each tube to either or both of an inlet of the first tube and an intermediate portion between the tube sections to intermingle with and oxidize the entrained gases evolved from the sample. Oxidation of those gases is completed in the catalyst in each second tube section. A thermocouple within a sample reduces furnace temperature when an exothermic condition is sensed within the sample. Oxidized gases flow from outlets of the tubes to individual gas cells. The cells are sequentially aligned with an infrared detector, which senses the composition and quantities of the gas components. Each elongated cell is tapered inward toward the center from cell windows at the ends. Volume is reduced from a conventional cell, while permitting maximum interaction of gas with the light beam. Reduced volume and angulation of the cell inlets provide rapid purgings of the cell, providing shorter cycles between detections. For coal and other high molecular weight samples, from 50% to 100% oxygen is introduced to the tubes.

Knowledge-based zonal grid generation for computational fluid dynamics

NASA Technical Reports Server (NTRS)

Andrews, Alison E.

1988-01-01

Automation of flow field zoning in two dimensions is an important step towards reducing the difficulty of three-dimensional grid generation in computational fluid dynamics. Using a knowledge-based approach makes sense, but problems arise which are caused by aspects of zoning involving perception, lack of expert consensus, and design processes. These obstacles are overcome by means of a simple shape and configuration language, a tunable zoning archetype, and a method of assembling plans from selected, predefined subplans. A demonstration system for knowledge-based two-dimensional flow field zoning has been successfully implemented and tested on representative aerodynamic configurations. The results show that this approach can produce flow field zonings that are acceptable to experts with differing evaluation criteria.

A study of the viscous and nonadiabatic flow in radial turbines

NASA Technical Reports Server (NTRS)

Khalil, I.; Tabakoff, W.

1981-01-01

A method for analyzing the viscous nonadiabatic flow within turbomachine rotors is presented. The field analysis is based upon the numerical integration of the incompressible Navier-Stokes equations together with the energy equation over the rotors blade-to-blade stream channels. The numerical code used to solve the governing equations employs a nonorthogonal boundary fitted coordinate system that suits the most complicated blade geometries. Effects of turbulence are modeled with two equations; one expressing the development of the turbulence kinetic energy and the other its dissipation rate. The method of analysis is applied to a radial inflow turbine. The solution obtained indicates the severity of the complex interaction mechanism that occurs between different flow regimes (i.e., boundary layers, recirculating eddies, separation zones, etc.). Comparison with nonviscous flow solutions tend to justify strongly the inadequacy of using the latter with standard boundary layer techniques to obtain viscous flow details within turbomachine rotors. Capabilities and limitations of the present method of analysis are discussed.

Advancement and Implementation of Integrated Computational Materials Engineering (ICME) for Aerospace Applications

DTIC Science & Technology

2010-03-01

of sub-routines Thermal history • Abaqus FEM engine mature applied within ABAQUS Residual stress & Distortion • Unknown maturity for HTC • Focused...investment. The committee’s ICME vision is comprehensive, expansive , and involves the entire materials community. The scope of this white paper is...Software • Continuum FEM for fluid flow, heat Mold Fill • FEM implementation mature flow and stress analysis Thermal & mushy zone history • Needs

Two-zone countercurrent smelter system and process

DOEpatents

Cox, J.H.; Fruehan, R.J.; Elliott, J.F.

1995-01-03

A process for continuously smelting iron ore by use of coal to yield molten iron or semi-steel is disclosed. The process comprises the steps of establishing a melt covered by slag; inducing the slag and the molten iron to flow countercurrently to one another, toward opposite ends of the smelter; maintaining iron oxide-reducing conditions in that zone of the smelter towards which the slag flows; maintaining carbon-oxidizing conditions in that zone of the smelter towards which the molten iron flows; continuously or semicontinuously tapping the slag from the reducing zone end of the smelter; continuously or semicontinuously tapping the molten iron from the oxidizing zone end of the smelter; and adding to both zones iron ore, coal, oxygen, and flux at addition rates sufficient to keep the molten iron in the reducing zone substantially saturated with carbon, maintain in the slag being tapped an FeO content of about 5 weight percent or less, and maintain in the molten iron being tapped a carbon content of about 0.5 to 5 weight percent. A slag dam preferably is included in the smelter, to impede the backflow of the slag from the reducing zone to the oxidizing zone. A metal bath dam with one or more flow-through portals also is preferably used, submerged below the slag dam, to impede the backflow of the hot metal. 8 figures.

Two-zone countercurrent smelter system and process

DOEpatents

Cox, James H.; Fruehan, Richard J.; Elliott, deceased, John F.

1995-01-01

A process for continuously smelting iron ore by use of coal to yield molten iron or semi-steel is disclosed. The process comprises the steps of establishing a melt covered by slag; inducing the slag and the molten iron to flow countercurrently to one another, toward opposite ends of the smelter; maintaining iron oxide-reducing conditions in that zone of the smelter towards which the slag flows; maintaining carbon-oxidizing conditions in that zone of the smelter towards which the molten iron flows; continuously or semicontinuously tapping the slag from the reducing zone end of the smelter; continuously or semicontinuously tapping the molten iron from the oxidizing zone end of the smelter; and adding to both zones iron ore, coal, oxygen, and flux at addition rates sufficient to keep the molten iron in the reducing zone substantially saturated with carbon, maintain in the slag being tapped an FeO content of about 5 weight percent or less, and maintain in the molten iron being tapped a carbon content of about 0.5 to 5 weight percent. A slag dam preferably is included in the smelter, to impede the backflow of the slag from the reducing zone to the oxidizing zone. A metal bath dam with one or more flow-through portals also is preferably used, submerged below the slag dam, to impede the backflow of the hot metal.

Velocity profiles and plug zones in a free surface viscoplastic flow : experimental study and comparison to shallow flow models

NASA Astrophysics Data System (ADS)

Freydier, Perrine; Chambon, Guillaume; Naaim, Mohamed

2016-04-01

Rheological studies concerning natural muddy debris flows have shown that these materials can be modelled as non-Newtonian viscoplastic fluids. These complex flows are generally represented using models based on a depth-integrated approach (Shallow Water) that take into account closure terms depending on the shape of the velocity profile. But to date, there is poor knowledge about the shape of velocity profiles and the position of the interface between sheared and unsheared regions (plug) in these flows, especially in the vicinity of the front. In this research, the internal dynamics of a free-surface viscoplastic flow down an inclined channel is investigated and compared to the predictions of a Shallow Water model based on the lubrication approximation. Experiments are conducted in an inclined channel whose bottom is constituted by an upward-moving conveyor belt with controlled velocity, which allows generating and observing gravity-driven stationary surges in the laboratory frame. Carbopol microgel has been used as a homogeneous and transparent viscoplastic fluid. High-resolution measurements of velocity field is performed through optical velocimetry techniques both in the uniform zone and within the front zone where flow thickness is variable and where recirculation takes place. Specific analyses have been developed to determine the position of the plug within the surge. Flow height is accessible through image processing and ultrasonic sensors. Sufficiently far from the front, experimental results are shown to be in good agreement with theoretical predictions regarding the velocity profiles and the flow height evolution. In the vicinity of the front, however, analysis of measured velocity profiles shows an evolution of the plug different from that predicted by lubrication approximation. Accordingly, the free surface shape also deviates from the predictions of the classical Shallow Water model. These results highlight the necessity to take into account higher-order corrective terms in Shallow Water models in order to better account for the internal dynamics of the fluid layer.

Controls on Mixing-Dependent Denitrification in Hyporheic Zones

NASA Astrophysics Data System (ADS)

Hester, E. T.; Young, K. I.; Widdowson, M. A.

2013-12-01

Interaction of surface water and groundwater in hyporheic sediments of river systems is known to create unique biogeochemical conditions that can attenuate contaminants flowing downstream. Oxygen, carbon, and the contaminants themselves (e.g., excess nitrate) often advect together through the hyporheic zone from sources in surface water. However, the ability of the hyporheic zone to attenuate contaminants in upwelling groundwater plumes as they exit to rivers is less known. Such reactions may be more dependent on mixing of carbon and oxygen sources from surface water with contaminants from deeper groundwater. We simulated hyporheic flow cells and upwelling groundwater together with mixing-dependent denitrification of an upwelling nitrate plume in shallow riverbed sediments using MODFLOW and SEAM3D. For our first set of model scenarios, we set biogeochemical boundary conditions to be consistent with situations where only mixing-dependent denitrification occurred within the model domain. This occurred where dissolved organic carbon (DOC) advecting from surface water through hyporheic flow cells meets nitrate upwelling from deeper groundwater. This would be common where groundwater is affected by septic systems which contribute nitrate that upwells into streams that do not have significant nitrate sources from upstream. We conducted a sensitivity analysis that showed that mixing-dependent denitrification increased with parameters that increase mixing itself, such as the degree of heterogeneity of sediment hydraulic conductivity (K). Mixing-dependent denitrification also increased with certain biogeochemical boundary concentrations such as increasing DOC or decreasing dissolved oxygen (DO) advecting from surface water. For our second set of model scenarios, we set biogeochemical boundary conditions to be consistent with common situations where non-mixing-dependent denitrification also occurred within the model domain. For example, when nitrate concentrations are substantial in water advecting from surface water, non-mixing-dependent denitrification can occur within the hyporheic flow cells. This would be common where surface water and groundwater have high nitrate concentrations in agricultural areas. We conducted a sensitivity analysis for this set of model scenarios as well, to evaluate controls on the relative balance of mixing-dependent and non-mixing-dependent denitrification. We found that non-mixing-dependent denitrification often has higher potential to consume nitrate than mixing-dependent denitrification. This is because non-mixing-dependent denitrification is not confined to the relatively small mixing zone between upwelling groundwater and hyporheic flow cells, and hence often has longer residence times available for consumption of existing oxygen followed by consumption of nitrate. Nevertheless, the potential for hyporheic zones to attenuate upwelling nitrate plumes appears to be substantial, yet is variable depending on geomorphic, hydraulic, and biogeochemical conditions.

Experimental Investigation of 3-D flow fields around the mouth of the Dwarf Seahorse during attacks on planktonic prey

NASA Astrophysics Data System (ADS)

Gemmell, Brad; Buskey, Edward; Sheng, Jian

2009-11-01

Copepods are an important planktonic food source for fish species. High predation has led to the development of effective escape responses with short reaction times (less than 2 ms), maximum escape velocities of over 500 body lengths per second and shear sensitivity as low as 1.5s-1. Using high speed digital holography (2 kfps), we measure 3-D distributions of velocity generated by a dwarf seahorse (Hippocampus zosterae) during attacks on its copepod prey, Acartia tonsa. It is found that successful attacks often produce smaller or even no detectable hydrodynamic disturbances around the strike zone, when compared to unsuccessful attempts. In this paper, we will provide quantitative characterization of this ``low-flow'' zone. Further, to elucidate the role of a possible geometrical advantage of the seahorse's head in minimizing its bow wave, high-speed time resolved PIV measurements are conducted in a low-speed water tunnel. On-going analysis will provide insights and implications in understanding the dynamics of flows around the stagnation point at high Reynolds number flow. Sponsored by NSF.

Advanced control of liquid water region in diffusion media of polymer electrolyte fuel cells through a dimensionless number

NASA Astrophysics Data System (ADS)

Wang, Yun; Chen, Ken S.

2016-05-01

In the present work, a three-dimension (3-D) model of polymer electrolyte fuel cells (PEFCs) is employed to investigate the complex, non-isothermal, two-phase flow in the gas diffusion layer (GDL). Phase change in gas flow channels is explained, and a simplified approach accounting for phase change is incorporated into the fuel cell model. It is found that the liquid water contours in the GDL are similar along flow channels when the channels are subject to two-phase flow. Analysis is performed on a dimensionless parameter Da0 introduced in our previous paper [Y. Wang and K. S. Chen, Chemical Engineering Science 66 (2011) 3557-3567] and the parameter is further evaluated in a realistic fuel cell. We found that the GDL's liquid water (or liquid-free) region is determined by the Da0 number which lumps several parameters, including the thermal conductivity and operating temperature. By adjusting these factors, a liquid-free GDL zone can be created even though the channel stream is two-phase flow. Such a liquid-free zone is adjacent to the two-phase region, benefiting local water management, namely avoiding both severe flooding and dryness.

The characteristics of hydrogeochemical zonation of groundwater in inland plain

NASA Astrophysics Data System (ADS)

Xin-yu, HOU; Li-ting, XING; Yi, YANG; Wen-jing, ZHANG; Guang-yao, CHI

2018-05-01

To find out the hydrochemical zoning of groundwaterin the inland plain, taking Jiyang plain as an example, based on mathematical statistics, ion ratio coefficient and isotopic analysis method, the characteristics of water chemical composition and its zoning at different depths of 500m were studied. The result shows: ①The groundwater flow system in the study area can be divided into local flow system, intermediate flow system and regional flow system. ②The hydrochemical type of shallow groundwater is complex. The hydrochemical types of middle confined water are mainly ClṡSO4—MgṡNa and SO4ṡCl—NaṡMg. The deep confined water is mainly HCO3. ③The TDS of shallow groundwater increases gradually along the direction of groundwater flow. ④The shallow saltwater and freshwater are alternately distributed in horizontal direction, and saltwater is distributed sporadically in the interfluve area with sporadic punctate or banded, and hydrochemical types are mainly ClṡSO4—NaṡMgṡCa. Conclusion: Groundwater in the study area is affected by complicated hydrogeochemical action, mainly in the form of filtration, cation exchange and evaporation. The inland plain area is characterized by hydrogeochemical zonation in horizontal and vertical.

Advanced control of liquid water region in diffusion media of polymer electrolyte fuel cells through a dimensionless number

DOE PAGES

Wang, Yun; Chen, Ken S.

2016-03-21

In the present study, a three-dimension (3-D) model of polymer electrolyte fuel cells (PEFCs) is employed to investigate the complex, non-isothermal, two-phase flow in the gas diffusion layer (GDL). Phase change in gas flow channels is explained, and a simplified approach accounting for phase change is incorporated into the fuel cell model. It is found that the liquid water contours in the GDL are similar along flow channels when the channels are subject to two-phase flow. Here, analysis is performed on a dimensionless parameter Da 0 introduced in our previous paper and the parameter is further evaluated in a realisticmore » fuel cell. We found that the GDL's liquid water (or liquid-free) region is determined by the Da 0 number which lumps several parameters, including the thermal conductivity and operating temperature. By adjusting these factors, a liquid-free GDL zone can be created even though the channel stream is two-phase flow. Such a liquid-free zone is adjacent to the two-phase region, benefiting local water management, namely avoiding both severe flooding and dryness.« less

Lithologic and physicochemical properties and hydraulics of flow in and near the freshwater/saline-water transition zone, San Antonio segment of the Edwards aquifer, south-central Texas, based on water-level and borehole geophysical log data, 1999-2007

USGS Publications Warehouse

Lambert, Rebecca B.; Hunt, Andrew G.; Stanton, Gregory P.; Nyman, Michael B.

2010-01-01

The freshwater zone of the San Antonio segment of the Edwards aquifer in south-central Texas (hereinafter, the Edwards aquifer) is bounded to the south and southeast by a zone of transition from freshwater to saline water (hereinafter, the transition zone). The boundary between the two zones is the freshwater/saline-water interface (hereinafter, the interface), defined as the 1,000-milligrams per liter dissolved solids concentration threshold. This report presents the findings of a study, done by the U.S. Geological Survey in cooperation with the San Antonio Water System, to obtain lithologic properties (rock properties associated with known stratigraphic units) and physicochemical properties (fluid conductivity and temperature) and to analyze the hydraulics of flow in and near the transition zone of the Edwards aquifer on the basis of water-level and borehole geophysical log data collected from 15 monitoring wells in four transects during 1999-2007. No identifiable relation between conductivity values from geophysical logs in monitoring wells in all transects and equivalent freshwater heads in the wells at the times the logs were run is evident; and no identifiable relation between conductivity values and vertical flow in the boreholes concurrent with the times the logs were run is evident. The direction of the lateral equivalent freshwater head gradient and thus the potential lateral flow at the interface in the vicinity of the East Uvalde transect fluctuates between into and out of the freshwater zone, depending on recharge and withdrawals. Whether the prevailing direction on average is into or out of the freshwater zone is not clearly indicated. Equivalent freshwater head data do not indicate a prevailing direction of the lateral gradient at the interface in the vicinity of the Tri-County transect. The prevailing direction on average of the lateral gradient and thus potential lateral flow at the interface in the vicinity of the Kyle transect likely is from the transition zone into the freshwater zone. The hypothesis regarding the vertical gradient at the East Uvalde transect, and thus the potential for vertical flow near an interface conceptualized as a surface sloping upward in the direction of the dip of the stratigraphic units, is that the potential for vertical flow fluctuates between into and out of the freshwater zone, depending on recharge and withdrawals. At the Tri-County transect, a downward gradient on the fresh-water side of the interface and an upward gradient on the saline-water side are evidence of opposing potentials that appear to have stabilized the position of the interface over the range of hydrologic conditions that occurred at the times the logs were run. At the Fish Hatchery transect, an upward gradient on the saline-water side of the interface, coupled with the assumption of a sloping interface, implies a vertical gradient from the transition zone into the freshwater zone. This potential for vertical movement of the interface apparently was opposed by the potential (head) on the freshwater side of the interface that kept the interface relatively stable over the range of hydrologic conditions during which the logs were run. The five flow logs for Kyle transect freshwater well KY1 all indicate upward flow that originates from the Glen Rose Limestone, the uppermost unit of the Trinity aquifer; and one log for well KY2 shows upward flow entering the borehole from the Trinity aquifer. These flow data constitute evidence of the potential for flow from the Trinity aquifer into the Edwards aquifer in the vicinity of the Kyle transect. Subsurface temperature data indicate that flow on average is more active, or vigorous, on the freshwater side of the interface than on the saline-water side. A hydraulic connection between the transition zone and the freshwater zone is indicated by similar patterns in the hydrographs of the 15 transect monitoring wells in and near the transition zone and three county index wel

Prominence of ichnologically influenced macroporosity in the karst Biscayne aquifer: Stratiform "super-K" zones

USGS Publications Warehouse

Cunningham, K.J.; Sukop, M.C.; Huang, H.; Alvarez, P.F.; Curran, H.A.; Renken, R.A.; Dixon, J.F.

2009-01-01

A combination of cyclostratigraphic, ichnologic, and borehole geophysical analyses of continuous core holes; tracer-test analyses; and lattice Boltzmann flow simulations was used to quantify biogenic macroporosity and permeability of the Biscayne aquifer, southeastern Florida. Biogenic macroporosity largely manifests as: (1) ichnogenic macroporosity primarily related to postdepositional burrowing activity by callianassid shrimp and fossilization of components of their complex burrow systems (Ophiomorpha); and (2) biomoldic macroporosity originating from dissolution of fossil hard parts, principally mollusk shells. Ophiomorpha-dominated ichno-fabric provides the greatest contribution to hydrologic characteristics in the Biscayne aquifer in a 345 km2 study area. Stratiform tabular-shaped units of thalassinidean-associated macroporosity are commonly confined to the lower part of upward-shallowing high-frequency cycles, throughout aggradational cycles, and, in one case, they stack vertically within the lower part of a high-frequency cycle set. Broad continuity of many of the macroporous units concentrates groundwater flow in extremely permeable passage-ways, thus making the aquifer vulnerable to long-distance transport of contaminants. Ichnogenic macroporosity represents an alternative pathway for concentrated groundwater flow that differs considerably from standard karst flow-system paradigms, which describe groundwater movement through fractures and cavernous dissolution features. Permeabilities were calculated using lattice Boltzmann methods (LBMs) applied to computer renderings assembled from X-ray computed tomography scans of various biogenic macroporous limestone samples. The highest simulated LBM permeabilities were about five orders of magnitude greater than standard laboratory measurements using air-permeability methods, which are limited in their application to extremely permeable macroporous rock samples. Based on their close conformance to analytical solutions for pipe flow, LBMs offer a new means of obtaining accurate permeability values for such materials. We suggest that the stratiform ichnogenic groundwater flow zones have permeabilities even more extreme (???2-5 orders of magnitude higher) than the Jurassic "super-K" zones of the giant Ghawar oil field. The flow zones of the Pleistocene Biscayne aquifer provide examples of ichnogenic macroporosity for comparative analysis of origin and evolution in other carbonate aquifers, as well as petroleum reservoirs. ?? 2008 Geological Society of America.

Analysis of atmospheric flow over a surface protrusion using the turbulence kinetic energy equation

NASA Technical Reports Server (NTRS)

Frost, W.; Harper, W. L.; Fichtl, G. H.

1975-01-01

Atmospheric flow fields resulting from a semi-elliptical surface obstruction in an otherwise horizontally homogeneous statistically stationary flow are modelled with the boundary-layer/Boussinesq-approximation of the governing equation of fluid mechanics. The turbulence kinetic energy equation is used to determine the dissipative effects of turbulent shear on the mean flow. Mean-flow results are compared with those given in a previous paper where the same problem was attacked using a Prandtl mixing-length hypothesis. Iso-lines of turbulence kinetic energy and turbulence intensity are plotted in the plane of the flow. They highlight regions of high turbulence intensity in the stagnation zone and sharp gradients in intensity along the transition from adverse to favourable pressure gradient.

Process dominance shift in solute chemistry as revealed by long-term high-frequency water chemistry observations of groundwater flowing through weathered argillite underlying a steep forested hillslope

NASA Astrophysics Data System (ADS)

Kim, Hyojin; Bishop, James K. B.; Dietrich, William E.; Fung, Inez Y.

2014-09-01

Significant solute flux from the weathered bedrock zone - which underlies soils and saprolite - has been suggested by many studies. However, controlling processes for the hydrochemistry dynamics in this zone are poorly understood. This work reports the first results from a four-year (2009-2012) high-frequency (1-3 day) monitoring of major solutes (Ca, Mg, Na, K and Si) in the perched, dynamic groundwater in a 4000 m2 zero-order basin located at the Angelo Coast Range Reserve, Northern California. Groundwater samples were autonomously collected at three wells (downslope, mid-slope, and upslope) aligned with the axis of the drainage. Rain and throughfall samples, profiles of well headspace pCO2, vertical profiles and time series of groundwater temperature, and contemporaneous data from an extensive hydrologic and climate sensor network provided the framework for data analysis. All runoff at this soil-mantled site occurs by vertical unsaturated flow through a 5-25 m thick weathered argillite and then by lateral flows to the adjacent channel as groundwater perched over fresher bedrock. Driven by strongly seasonal rainfall, over each of the four years of observations, the hydrochemistry of the groundwater at each well repeats an annual cycle, which can be explained by two end-member processes. The first end-member process, which dominates during the winter high-flow season in mid- and upslope areas, is CO2 enhanced cation exchange reaction in the vadose zone in the more shallow conductive weathered bedrock. This process rapidly increases the cation concentrations of the infiltrated rainwater, which is responsible for the lowest cation concentration of groundwater. The second-end member process occurs in the deeper perched groundwater and either dominates year-round (at the downslope well) or becomes progressively dominant during low flow season at the two upper slope wells. This process is the equilibrium reaction with minerals such as calcite and clay minerals, but not with primary minerals, suggesting the critical role of the residence time of the water. Collectively, our measurements reveal that the hydrochemistry dynamics of the groundwater in the weathered bedrock zone is governed by two end-member processes whose dominance varies with critical zone structure, the relative importance of vadose versus groundwater zone processes, and thus with the seasonal variation of the chemistry of recharge and runoff.

Deep arid system hydrodynamics 1. Equilibrium states and response times in thick desert vadose zones

USGS Publications Warehouse

Walvoord, Michelle Ann; Plummer, Mitchell A.; Phillips, Fred M.; Wolfsberg, Andrew V.

2002-01-01

Quantifying moisture fluxes through deep desert soils remains difficult because of the small magnitude of the fluxes and the lack of a comprehensive model to describe flow and transport through such dry material. A particular challenge for such a model is reproducing both observed matric potential and chloride profiles. We propose a conceptual model for flow in desert vadose zones that includes isothermal and nonisothermal vapor transport and the role of desert vegetation in supporting a net upward moisture flux below the root zone. Numerical simulations incorporating this conceptual model match typical matric potential and chloride profiles. The modeling approach thereby reconciles the paradox between the recognized importance of plants, upward driving forces, and vapor flow processes in desert vadose zones and the inadequacy of the downward‐only liquid flow assumption of the conventional chloride mass balance approach. Our work shows that water transport in thick desert vadose zones at steady state is usually dominated by upward vapor flow and that long response times, of the order of 104–105 years, are required to equilibrate to existing arid surface conditions. Simulation results indicate that most thick desert vadose zones have been locked in slow drying transients that began in response to a climate shift and establishment of desert vegetation many thousands of years ago.

Recharge processes and vertical transfer investigated through long-term monitoring of dissolved gases in shallow groundwater

NASA Astrophysics Data System (ADS)

de Montety, V.; Aquilina, L.; Labasque, T.; Chatton, E.; Fovet, O.; Ruiz, L.; Fourré, E.; de Dreuzy, J. R.

2018-05-01

We investigated temporal variations and vertical evolution of dissolved gaseous tracers (CFC-11, CFC-12, SF6, and noble gases), as well as 3H/3He ratio to determine groundwater recharge processes of a shallow unconfined, hard-rock aquifer in an agricultural catchment. We sampled dissolved gas concentration at 4 locations along the hillslope of a small experimental watershed, over 6 hydrological years, between 2 and 6 times per years, for a total of 20 field campaigns. We collected groundwater samples in the fluctuation zone and the permanently saturated zone using piezometers from 5 to 20 m deep. The purpose of this work is i) to assess the benefits of using gaseous tracers like CFCs and SF6 to study very young groundwater with flows suspected to be heterogeneous and variable in time, ii) to characterize the processes that control dissolved gas concentrations in groundwater during the recharge of the aquifer, and iii) to understand the evolution of recharge flow processes by repeated measurement campaigns, taking advantage of a long monitoring in a site devoted to recharge processes investigation. Gas tracer profiles are compared at different location of the catchment and for different hydrologic conditions. In addition, we compare results from CFCs and 3H/3He analysis to define the flow model that best explains tracer concentrations. Then we discuss the influence of recharge events on tracer concentrations and residence time and propose a temporal evolution of residence times for the unsaturated zone and the permanently saturated zone. These results are used to gain a better understanding of the conceptual model of the catchment and flow processes especially during recharge events.

Flow separation in a straight draft tube, particle image velocimetry

NASA Astrophysics Data System (ADS)

Duquesne, P.; Maciel, Y.; Ciocan, G. D.; Deschênes, C.

2014-03-01

As part of the BulbT project, led by the Consortium on Hydraulic Machines and the LAMH (Hydraulic Machine Laboratory of Laval University), the efficiency and power break off in a bulb turbine has been investigated. Previous investigations correlated the break off to draft tube losses. Tuft visualizations confirmed the emergence of a flow separation zone at the wall of the diffuser. Opening the guide vanes tends to extend the recirculation zone. The flow separations were investigated with two-dimensional and two-component particle image velocimetry (PIV) measurements designed based on the information collected from tuft visualizations. Investigations were done for a high opening blade angle with a N11 of 170 rpm, at best efficiency point and at two points with a higher Q11. The second operating point is inside the efficiency curve break off and the last operating point corresponds to a lower efficiency and a larger recirculation region in the draft tube. The PIV measurements were made near the wall with two cameras in order to capture two measurement planes simultaneously. The instantaneous velocity fields were acquired at eight different planes. Two planes located near the bottom wall were parallel to the generatrix of the conical part of the diffuser, while two other bottom planes diverged more from the draft tube axis than the cone generatrix. The last four planes were located on the draft tube side and diverged more from the draft tube axis than the cone generatrix. By combining the results from the various planes, the separation zone is characterized using pseudo-streamlines of the mean velocity fields, maps of the Reynolds stresses and maps of the reverse-flow parameter. The analysis provides an estimation of the separation zone size, shape and unsteady character, and their evolution with the guide vanes opening.

Computational fluid dynamics-habitat suitability index (CFD-HSI) modelling as an exploratory tool for assessing passability of riverine migratory challenge zones for fish

USGS Publications Warehouse

Haro, Alexander J.; Chelminski, Michael; Dudley, Robert W.

2015-01-01

We developed two-dimensional computational fluid hydraulics-habitat suitability index (CFD-HSI) models to identify and qualitatively assess potential zones of shallow water depth and high water velocity that may present passage challenges for five major anadromous fish species in a 2.63-km reach of the main stem Penobscot River, Maine, as a result of a dam removal downstream of the reach. Suitability parameters were based on distribution of fish lengths and body depths and transformed to cruising, maximum sustained and sprint swimming speeds. Zones of potential depth and velocity challenges were calculated based on the hydraulic models; ability of fish to pass a challenge zone was based on the percent of river channel that the contiguous zone spanned and its maximum along-current length. Three river flows (low: 99.1 m3 sec-1; normal: 344.9 m3 sec-1; and high: 792.9 m3 sec-1) were modelled to simulate existing hydraulic conditions and hydraulic conditions simulating removal of a dam at the downstream boundary of the reach. Potential depth challenge zones were nonexistent for all low-flow simulations of existing conditions for deeper-bodied fishes. Increasing flows for existing conditions and removal of the dam under all flow conditions increased the number and size of potential velocity challenge zones, with the effects of zones being more pronounced for smaller species. The two-dimensional CFD-HSI model has utility in demonstrating gross effects of flow and hydraulic alteration, but may not be as precise a predictive tool as a three-dimensional model. Passability of the potential challenge zones cannot be precisely quantified for two-dimensional or three-dimensional models due to untested assumptions and incomplete data on fish swimming performance and behaviours.

Shear zone formation within the billet and metal flow through the die orifice in unlubricated axisymmetric forward and backward extrusion

NASA Astrophysics Data System (ADS)

Valberg, Henry; Costa, Andrè L. M.

2017-10-01

Metal flow inside the billet is known to be completely different in forward (FWE) and backward (BWE) Al-extrusion. A practical implication of this is that contamination near to the surface of the extrusion billet, or on the peripheral surface skin, tends to flow out of the die more readily in BWE than in FWE. It is therefore common in BWE to use a scalping operation on the billet to remove eventual sub-surface contamination that may be present. This additional working operation may be required in order to avoid surface quality problems on BWE profiles. In spite of the importance of metal flow in metals extrusion, there are still lack of knowledge about the topic. With recent progress in FEM-analysis for modelling deformation processing, however, it is now possible to perform accurate studies on metal flow phenomena by simulation on the computer. In our study, we are using the 3D FEM-program DEFORM® to model axisymmetric FWE and BWE in case of non-lubricated extrusion through a flat-faced die. Our primary focus is to consider the difference in appearance of shear zones present inside the extrusion billet for the two processes, including metal flow in the die mouth.

Geostatistical analysis of regional hydraulic conductivity variations in the Snake River Plain aquifer, eastern Idaho

USGS Publications Warehouse

Welhan, J.A.; Reed, M.F.

1997-01-01

The regional spatial correlation structure of bulk horizontal hydraulic conductivity (Kb) estimated from published transmissivity data from 79 open boreholes in the fractured basalt aquifer of the eastern Snake River Plain was analyzed with geostatistical methods. The two-dimensional spatial correlation structure of In Kb shows a pronounced 4:1 range anisotropy, with a maximum correlation range in the north-northwest- south-southeast direction of about 6 km. The maximum variogram range of In Kb is similar to the mean length of flow groups exposed at the surface. The In Kb range anisotropy is similar to the mean width/length ratio of late Quaternary and Holocene basalt lava flows and the orientations of the major volcanic structural features on the eastern Snake River Plain. The similarity between In Kb correlation scales and basalt flow dimensions and between basalt flow orientations and correlation range anisotropy suggests that the spatial distribution of zones of high hydraulic conductivity may be controlled by the lateral dimensions, spatial distribution, and interconnection between highly permeable zones which are known to occur between lava flows within flow groups. If hydraulic conductivity and lithology are eventually shown to be cross correlative in this geologic setting, it may be possible to stochastically simulate hydraulic conductivity distributions, which are conditional on a knowledge of volcanic stratigraphy.

Quantitative geometric description of fracture systems in an andesite lava flow using terrestrial laser scanner data

NASA Astrophysics Data System (ADS)

Massiot, Cécile; Nicol, Andrew; Townend, John; McNamara, David D.; Garcia-Sellés, David; Conway, Chris E.; Archibald, Garth

2017-07-01

Permeability hosted in andesitic lava flows is dominantly controlled by fracture systems, with geometries that are often poorly constrained. This paper explores the fracture system geometry of an andesitic lava flow formed during its emplacement and cooling over gentle paleo-topography, on the active Ruapehu volcano, New Zealand. The fracture system comprises column-forming and platy fractures within the blocky interior of the lava flow, bounded by autobreccias partially observed at the base and top of the outcrop. We use a terrestrial laser scanner (TLS) dataset to extract column-forming fractures directly from the point-cloud shape over an outcrop area of ∼3090 m2. Fracture processing is validated using manual scanlines and high-resolution panoramic photographs. Column-forming fractures are either steeply or gently dipping with no preferred strike orientation. Geometric analysis of fractures derived from the TLS, in combination with virtual scanlines and trace maps, reveals that: (1) steeply dipping column-forming fracture lengths follow a scale-dependent exponential or log-normal distribution rather than a scale-independent power-law; (2) fracture intensities (combining density and size) vary throughout the blocky zone but have similar mean values up and along the lava flow; and (3) the areal fracture intensity is higher in the autobreccia than in the blocky zone. The inter-connected fracture network has a connected porosity of ∼0.5 % that promote fluid flow vertically and laterally within the blocky zone, and is partially connected to the autobreccias. Autobreccias may act either as lateral permeability connections or barriers in reservoirs, depending on burial and alteration history. A discrete fracture network model generated from these geometrical parameters yields a highly connected fracture network, consistent with outcrop observations.

Recuperator construction for a gas turbine engine

DOEpatents

Kang, Yungmo; McKeirnan, Jr., Robert D.

2006-12-12

A counter-flow recuperator formed from annular arrays of recuperator core segments. The recuperator core segments are formed from two opposing sheets of fin fold material coined to form a primary surface zone disposed between two flattened manifold zones. Each primary surface zone has undulating corrugations including a uniform, full height central portion and a transition zone disposed between the central portion and one of the manifold zones. Corrugations of the transition zone rise from zero adjacent to the manifold zone and increase along a transition length to full crest height at the central portion. The transition lengths increase in a direction away from an inner edge containing the air inlet so as to equalize air flow to the distal regions of the primary surface zone.

Numerical modeling of fluid flow in a fault zone: a case of study from Majella Mountain (Italy).

NASA Astrophysics Data System (ADS)

Romano, Valentina; Battaglia, Maurizio; Bigi, Sabina; De'Haven Hyman, Jeffrey; Valocchi, Albert J.

2017-04-01

The study of fluid flow in fractured rocks plays a key role in reservoir management, including CO2 sequestration and waste isolation. We present a numerical model of fluid flow in a fault zone, based on field data acquired in Majella Mountain, in the Central Apennines (Italy). This fault zone is considered a good analogue for the massive presence of fluid migration in the form of tar. Faults are mechanical features and cause permeability heterogeneities in the upper crust, so they strongly influence fluid flow. The distribution of the main components (core, damage zone) can lead the fault zone to act as a conduit, a barrier, or a combined conduit-barrier system. We integrated existing information and our own structural surveys of the area to better identify the major fault features (e.g., type of fractures, statistical properties, geometrical and petro-physical characteristics). In our model the damage zones of the fault are described as discretely fractured medium, while the core of the fault as a porous one. Our model utilizes the dfnWorks code, a parallelized computational suite, developed at Los Alamos National Laboratory (LANL), that generates three dimensional Discrete Fracture Network (DFN) of the damage zones of the fault and characterizes its hydraulic parameters. The challenge of the study is the coupling between the discrete domain of the damage zones and the continuum one of the core. The field investigations and the basic computational workflow will be described, along with preliminary results of fluid flow simulation at the scale of the fault.

Small Gas Turbine Combustor Primary Zone Study

NASA Technical Reports Server (NTRS)

Sullivan, R. E.; Young, E. R.; Miles, G. A.; Williams, J. R.

1983-01-01

A development process is described which consists of design, fabrication, and preliminary test evaluations of three approaches to internal aerodynamic primary zone flow patterns: (1) conventional double vortex swirl stabilization; (2) reverse flow swirl stabilization; and (3) large single vortex flow system. Each concept incorporates special design features aimed at extending the performance capability of the small engine combustor. Since inherent geometry of these combustors result in small combustion zone height and high surface area to volume ratio, design features focus on internal aerodynamics, fuel placement, and advanced cooling. The combustors are evaluated on a full scale annular combustor rig. A correlation of the primary zone performance with the overall performance is accomplished using three intrusion type gas sampling probes located at the exit of the primary zone section. Empirical and numerical methods are used for designing and predicting the performance of the three combustor concepts and their subsequent modifications. The calibration of analytical procedures with actual test results permits an updating of the analytical design techniques applicable to small reverse flow annular combustors.

Recirculation zone length in renal artery is affected by flow spirality and renal-to-aorta flow ratio.

PubMed

Javadzadegan, Ashkan; Fulker, David; Barber, Tracie

2017-07-01

Haemodynamic perturbations such as flow recirculation zones play a key role in progression and development of renal artery stenosis, which typically originate at the aorta-renal bifurcation. The spiral nature of aortic blood flow, division of aortic blood flow in renal artery as well as the exercise conditions have been shown to alter the haemodynamics in both positive and negative ways. This study focuses on the combinative effects of spiral component of blood flow, renal-to-aorta flow ratio and the exercise conditions on the size and distribution of recirculation zones in renal branches using computational fluid dynamics technique. Our findings show that the recirculation length was longest when the renal-to-aorta flow ratio was smallest. Spiral flow and exercise conditions were found to be effective in reducing the recirculation length in particular in small renal-to-aorta flow ratios. These results support the hypothesis that in renal arteries with small flow ratios where a stenosis is already developed an artificially induced spiral flow within the aorta may decelerate the progression of stenosis and thereby help preserve kidney function.

Analysis and calculation of macrosegregation in a casting ingot, exhibits C and E

NASA Technical Reports Server (NTRS)

Poirier, D. R.; Maples, A. L.

1984-01-01

A computer model which describes the solidification of a binary metal alloy in an insulated rectangular mold with a temperature gradient is presented. A numerical technique, applicable to a broad class of moving boundary problems, was implemented therein. The solidification model described is used to calculate the macrosegregation within the solidified casting by coupling the equations for liquid flow in the solid/liquid or mushy zone with the energy equation for heat flow throughout the ingot and thermal convection in the bulk liquid portion. The rate of development of the solid can be automatically calculated by the model. Numerical analysis of such solidification parameters as enthalpy and boundary layer flow is displayed. On-line user interface and software documentation are presented.

Development of Hydrologic Characterization Technology of Fault Zones (in Japanese; English)

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

Karasaki, Kenzi; Onishi, Tiemi; Wu, Yu-Shu

2008-03-31

Through an extensive literature survey we find that there is very limited amount of work on fault zone hydrology, particularly in the field using borehole testing. The common elements of a fault include a core, and damage zones. The core usually acts as a barrier to the flow across it, whereas the damage zone controls the flow either parallel to the strike or dip of a fault. In most of cases the damage zone isthe one that is controlling the flow in the fault zone and the surroundings. The permeability of damage zone is in the range of two tomore » three orders of magnitude higher than the protolith. The fault core can have permeability up to seven orders of magnitude lower than the damage zone. The fault types (normal, reverse, and strike-slip) by themselves do not appear to be a clear classifier of the hydrology of fault zones. However, there still remains a possibility that other additional geologic attributes and scaling relationships can be used to predict or bracket the range of hydrologic behavior of fault zones. AMT (Audio frequency Magneto Telluric) and seismic reflection techniques are often used to locate faults. Geochemical signatures and temperature distributions are often used to identify flow domains and/or directions. ALSM (Airborne Laser Swath Mapping) or LIDAR (Light Detection and Ranging) method may prove to be a powerful tool for identifying lineaments in place of the traditional photogrammetry. Nonetheless not much work has been done to characterize the hydrologic properties of faults by directly testing them using pump tests. There are some uncertainties involved in analyzing pressure transients of pump tests: both low permeability and high permeability faults exhibit similar pressure responses. A physically based conceptual and numerical model is presented for simulating fluid and heat flow and solute transport through fractured fault zones using a multiple-continuum medium approach. Data from the Horonobe URL site are analyzed to demonstrate the proposed approach and to examine the flow direction and magnitude on both sides of a suspected fault. We describe a strategy for effective characterization of fault zone hydrology. We recommend conducting a long term pump test followed by a long term buildup test. We do not recommend isolating the borehole into too many intervals. We do recommend ensuring durability and redundancy for long term monitoring.« less

Stochastic capture zone analysis of an arsenic-contaminated well using the generalized likelihood uncertainty estimator (GLUE) methodology

NASA Astrophysics Data System (ADS)

Morse, Brad S.; Pohll, Greg; Huntington, Justin; Rodriguez Castillo, Ramiro

2003-06-01

In 1992, Mexican researchers discovered concentrations of arsenic in excess of World Heath Organization (WHO) standards in several municipal wells in the Zimapan Valley of Mexico. This study describes a method to delineate a capture zone for one of the most highly contaminated wells to aid in future well siting. A stochastic approach was used to model the capture zone because of the high level of uncertainty in several input parameters. Two stochastic techniques were performed and compared: "standard" Monte Carlo analysis and the generalized likelihood uncertainty estimator (GLUE) methodology. The GLUE procedure differs from standard Monte Carlo analysis in that it incorporates a goodness of fit (termed a likelihood measure) in evaluating the model. This allows for more information (in this case, head data) to be used in the uncertainty analysis, resulting in smaller prediction uncertainty. Two likelihood measures are tested in this study to determine which are in better agreement with the observed heads. While the standard Monte Carlo approach does not aid in parameter estimation, the GLUE methodology indicates best fit models when hydraulic conductivity is approximately 10-6.5 m/s, with vertically isotropic conditions and large quantities of interbasin flow entering the basin. Probabilistic isochrones (capture zone boundaries) are then presented, and as predicted, the GLUE-derived capture zones are significantly smaller in area than those from the standard Monte Carlo approach.

Anomalous heat flow belt along the continental margin of Brazil

NASA Astrophysics Data System (ADS)

Hamza, Valiya M.; Vieira, Fabio P.; Silva, Raquel T. A.

2018-01-01

A comprehensive analysis of thermal gradient and heat flow data was carried out for sedimentary basins situated in the continental margin of Brazil (CMB). The results point to the existence of a narrow belt within CMB, where temperature gradients are higher than 30 °C/km and the heat flow is in excess of 70 mW/m2. This anomalous geothermal belt is confined between zones of relatively low to normal heat flow in the adjacent continental and oceanic regions. The width of the belt is somewhat variable, but most of it falls within the range of 100-300 km. The spatial extent is relatively large in the southern (in the basins of Pelotas, Santos and Campos) and northern (in the basins of Potiguar and Ceará) parts, when compared with those in the central parts (in the basins of South Bahia, Sergipe and Alagoas). The characteristics of heat flow anomalies appear to be compatible with those produced by thermal sources at depths in the lower crust. Hence, magma emplacement at the transition zone between lower crust and upper mantle is considered the likely mechanism producing such anomalies. Seismicity within the belt is relatively weak, with focal depths less than 10 km for most of the events. Such observations imply that "tectonic bonding" between continental and oceanic segments, at the transition zone of CMB, is relatively weak. Hence, it is proposed that passive margins like CMB be considered as constituting a type of plate boundary that is aseismic at sub-crustal levels, but allows for escape of significant amounts of earth's internal heat at shallow depths.

Al/Cu Dissimilar Friction Stir Welding with Ni, Ti, and Zn Foil as the Interlayer for Flow Control, Enhancing Mechanical and Metallurgical Properties

NASA Astrophysics Data System (ADS)

Sahu, Prakash Kumar; Pal, Sukhomay; Pal, Surjya K.

2017-07-01

This research investigates the effects of Ni, Ti, and Zn foil as interlayer, inserted between the faying edges of Al and Cu plates, for controlled intermetallic compound (IMC) formation. The weld tensile strength with Ti and Zn as interlayer is superior to Al base metal strength. This is due to controlled flow of IMCs by diffused Ti interlayer and thin, continuous, and uniform IMC formation in the case of Zn interlayer. Improved flexural stress was observed with interlayer. Weld microhardness varied with different interlayers and purely depends on IMCs present at the indentation point, flow of IMCs, and interlayer hardness. Specimens with interlayer failed at the interface of the nugget and thermomechanical-affected zone (TMAZ) with complete and broken three-dimensional (3-D) grains, indicating transgranular fracture. Phase analysis revealed that Al/Cu IMCs are impeded by Ni and Ti interlayer. The minor binary and ternary IMC phases form adjacent to the interlayer due to diffusion of the material with Al/Cu. Line scan and elemental mapping indicate thin, continuous, and uniform IMCs with enhanced weld metallurgical and mechanical properties for the joints with Zn interlayer. Macrostructural analysis revealed IMC flow variations with and without interlayer. Variation in grain size at different zones is also observed for different interlayers.

Aerothermodynamic Analysis of a Reentry Brazilian Satellite

NASA Astrophysics Data System (ADS)

Santos, Wilson F. N.

2012-12-01

This work deals with a computational investigation on the small ballistic reentry Brazilian vehicle SAtélite de Reentrada Atmosférica (SARA). Hypersonic flows over the vehicle SARA at zero-degree angle of attack in chemical equilibrium and thermal nonequilibrium are modeled by the direct simulation Monte Carlo method, which has become the main technique for studying complex multidimensional rarefied flows, and which properly accounts for the nonequilibrium aspects of the flows. The emphasis of this paper is to examine the behavior of the primary properties during the high-altitude portion of SARA reentry. In this way, velocity, density, pressure, and temperature field are investigated for altitudes of 100, 95, 90, 85, and 80 km. In addition, comparisons based on geometry are made between axisymmetric and planar two-dimensional configurations. Some significant differences between these configurations were noted on the flowfield structure in the reentry trajectory. The analysis showed that the flow disturbances have different influence on velocity, density, pressure, and temperature along the stagnation streamline ahead of the capsule nose. It was found that the stagnation region is a thermally stressed zone. It was also found that the stagnation region is a zone of strong compression, high wall pressure. Wall pressure distributions are compared with those of available experimental data, and good agreement is found along the spherical nose for the altitude range investigated.

Pronounced zonation of seismic anisotropy in the Western Hellenic subduction zone and its geodynamic significance

NASA Astrophysics Data System (ADS)

Olive, Jean-Arthur; Pearce, Frederick; Rondenay, Stéphane; Behn, Mark D.

2014-04-01

Many subduction zones exhibit significant retrograde motion of their arc and trench. The observation of fast shear-wave velocities parallel to the trench in such settings has been inferred to represent trench-parallel mantle flow beneath a retreating slab. Here, we investigate this process by measuring seismic anisotropy in the shallow Aegean mantle. We carry out shear-wave splitting analysis on a dense array of seismometers across the Western Hellenic Subduction Zone, and find a pronounced zonation of anisotropy at the scale of the subduction zone. Fast SKS splitting directions subparallel to the trench-retreat direction dominate the region nearest to the trench. Fast splitting directions abruptly transition to trench-parallel above the corner of the mantle wedge, and rotate back to trench-normal over the back-arc. We argue that the trench-normal anisotropy near the trench is explained by entrainment of an asthenospheric layer beneath the shallow-dipping portion of the slab. Toward the volcanic arc this signature is overprinted by trench-parallel anisotropy in the mantle wedge, likely caused by a layer of strained serpentine immediately above the slab. Arcward steepening of the slab and horizontal divergence of mantle flow due to rollback may generate an additional component of sub-slab trench-parallel anisotropy in this region. Poloidal flow above the retreating slab is likely the dominant source of back-arc trench-normal anisotropy. We hypothesize that trench-normal anisotropy associated with significant entrainment of the asthenospheric mantle near the trench may be widespread but only observable at shallow-dipping subduction zones where stations nearest the trench do not overlie the mantle wedge.

Hydrological connectivity in the karst critical zone: an integrated approach

NASA Astrophysics Data System (ADS)

Chen, X.; Zhang, Z.; Soulsby, C.; Cheng, Q.; Binley, A. M.; Tao, M.

2017-12-01

Spatial heterogeneity in the subsurface is high, evidenced by specific landform features (sinkholes, caves etc.) and resulting in high variability of hydrological processes in space and time. This includes complex exchange of various flow sources (e.g. hillslope springs and depression aquifers) and fast conduit flow and slow fracture flow. In this paper we integrate various "state-of-the-art" methods to understand the structure and function of this understudied critical zone environment. Geophysical, hydrometric and hydrogeochemical tools are used to characterize the hydrological connectivity of the cockpit karst critical zone in a small catchment of Chenqi, Guizhou province, China. Geophysical surveys, using electrical resistivity tomography (ERT), identified the complex conduit networks that link flows between hillslopes and depressions. Statistical time series analysis of water tables and discharge responses at hillslope springs and in depression wells and underground channels showed different threshold responses of hillslope and depression flows. This reflected the differing relative contribution of fast and slow flow paths during rainfall events of varying magnitude in the hillslope epikarst and depression aquifer in dry and wet periods. This showed that the hillslope epikarst receives a high proportion of rainfall recharge and is thus a main water resource in the catchment during the drought period. In contrast, the depression aquifer receives fast, concentrated hillslope flows during large rainfall events during the wet period, resulting in the filling of depression conduits and frequent flooding. Hydrological tracer studies using water temperatures and stable water isotopes (δD and δ18O) corroborated this and provided quantitative information of the mixing proportions of various flow sources and insights into water travel times. This revealed how higher contributions of event "new" water (from hillslope springs and depression conduits displaces "old" pre-event water primarily from low permeability fissures and fractures), particularly during heavy rainfall. As the various water sources have contrasting water quality characteristics, these mixing and exchange processes have important implications for understanding and managing water quality in karst waters.

Susceptibility to enhanced chemical migration from depression-focused preferential flow, High Plains aquifer

USGS Publications Warehouse

Gurdak, Jason J.; Walvoord, Michelle Ann; McMahon, Peter B.

2008-01-01

Aquifer susceptibility to contamination is controlled in part by the inherent hydrogeologic properties of the vadose zone, which includes preferential-flow pathways. The purpose of this study was to investigate the importance of seasonal ponding near leaky irrigation wells as a mechanism for depression-focused preferential flow and enhanced chemical migration through the vadose zone of the High Plains aquifer. Such a mechanism may help explain the widespread presence of agrichemicals in recently recharged groundwater despite estimates of advective chemical transit times through the vadose zone from diffuse recharge that exceed the historical period of agriculture. Using a combination of field observations, vadose zone flow and transport simulations, and probabilistic neural network modeling, we demonstrated that vadose zone transit times near irrigation wells range from 7 to 50 yr, which are one to two orders of magnitude faster than previous estimates based on diffuse recharge. These findings support the concept of fast and slow transport zones and help to explain the previous discordant findings of long vadose zone transit times and the presence of agrichemicals at the water table. Using predictions of aquifer susceptibility from probabilistic neural network models, we delineated approximately 20% of the areal extent of the aquifer to have conditions that may promote advective chemical transit times to the water table of <50 yr if seasonal ponding and depression-focused flow exist. This aquifer-susceptibility map may help managers prioritize areas for groundwater monitoring or implementation of best management practices.

Using high-frequency sensors to identify hydroclimatological controls on storm-event variability in catchment nutrient fluxes and source zone activation

NASA Astrophysics Data System (ADS)

Blaen, Phillip; Khamis, Kieran; Lloyd, Charlotte; Krause, Stefan

2017-04-01

At the river catchment scale, storm events can drive highly variable behaviour in nutrient and water fluxes, yet short-term dynamics are frequently missed by low resolution sampling regimes. In addition, nutrient source contributions can vary significantly within and between storm events. Our inability to identify and characterise time dynamic source zone contributions severely hampers the adequate design of land use management practices in order to control nutrient exports from agricultural landscapes. Here, we utilise an 8-month high-frequency (hourly) time series of streamflow, nitrate concentration (NO3) and fluorescent dissolved organic matter concentration (FDOM) derived from optical in-situ sensors located in a headwater agricultural catchment. We characterised variability in flow and nutrient dynamics across 29 storm events. Storm events represented 31% of the time series and contributed disproportionately to nutrient loads (43% of NO3 and 36% of CDOM) relative to their duration. Principal components analysis of potential hydroclimatological controls on nutrient fluxes demonstrated that a small number of components, representing >90% of variance in the dataset, were highly significant model predictors of inter-event variability in catchment nutrient export. Hysteresis analysis of nutrient concentration-discharge relationships suggested spatially discrete source zones existed for NO3 and FDOM, and that activation of these zones varied on an event-specific basis. Our results highlight the benefits of high-frequency in-situ monitoring for characterising complex short-term nutrient dynamics and unravelling connections between hydroclimatological variability and river nutrient export and source zone activation under extreme flow conditions. These new process-based insights are fundamental to underpinning the development of targeted management measures to reduce nutrient loading of surface waters.

Spatio-Temporal Modelling of Dust Transport over Surface Mining Areas and Neighbouring Residential Zones.

PubMed

Matejicek, Lubos; Janour, Zbynek; Benes, Ludek; Bodnar, Tomas; Gulikova, Eva

2008-06-06

Projects focusing on spatio-temporal modelling of the living environment need to manage a wide range of terrain measurements, existing spatial data, time series, results of spatial analysis and inputs/outputs from numerical simulations. Thus, GISs are often used to manage data from remote sensors, to provide advanced spatial analysis and to integrate numerical models. In order to demonstrate the integration of spatial data, time series and methods in the framework of the GIS, we present a case study focused on the modelling of dust transport over a surface coal mining area, exploring spatial data from 3D laser scanners, GPS measurements, aerial images, time series of meteorological observations, inputs/outputs form numerical models and existing geographic resources. To achieve this, digital terrain models, layers including GPS thematic mapping, and scenes with simulation of wind flows are created to visualize and interpret coal dust transport over the mine area and a neighbouring residential zone. A temporary coal storage and sorting site, located near the residential zone, is one of the dominant sources of emissions. Using numerical simulations, the possible effects of wind flows are observed over the surface, modified by natural objects and man-made obstacles. The coal dust drifts with the wind in the direction of the residential zone and is partially deposited in this area. The simultaneous display of the digital map layers together with the location of the dominant emission source, wind flows and protected areas enables a risk assessment of the dust deposition in the area of interest to be performed. In order to obtain a more accurate simulation of wind flows over the temporary storage and sorting site, 3D laser scanning and GPS thematic mapping are used to create a more detailed digital terrain model. Thus, visualization of wind flows over the area of interest combined with 3D map layers enables the exploration of the processes of coal dust deposition at a local scale. In general, this project could be used as a template for dust-transport modelling which couples spatial data focused on the construction of digital terrain models and thematic mapping with data generated by numerical simulations based on Reynolds averaged Navier-Stokes equations.

Spatio-Temporal Modelling of Dust Transport over Surface Mining Areas and Neighbouring Residential Zones

PubMed Central

Matejicek, Lubos; Janour, Zbynek; Benes, Ludek; Bodnar, Tomas; Gulikova, Eva

2008-01-01

Projects focusing on spatio-temporal modelling of the living environment need to manage a wide range of terrain measurements, existing spatial data, time series, results of spatial analysis and inputs/outputs from numerical simulations. Thus, GISs are often used to manage data from remote sensors, to provide advanced spatial analysis and to integrate numerical models. In order to demonstrate the integration of spatial data, time series and methods in the framework of the GIS, we present a case study focused on the modelling of dust transport over a surface coal mining area, exploring spatial data from 3D laser scanners, GPS measurements, aerial images, time series of meteorological observations, inputs/outputs form numerical models and existing geographic resources. To achieve this, digital terrain models, layers including GPS thematic mapping, and scenes with simulation of wind flows are created to visualize and interpret coal dust transport over the mine area and a neighbouring residential zone. A temporary coal storage and sorting site, located near the residential zone, is one of the dominant sources of emissions. Using numerical simulations, the possible effects of wind flows are observed over the surface, modified by natural objects and man-made obstacles. The coal dust drifts with the wind in the direction of the residential zone and is partially deposited in this area. The simultaneous display of the digital map layers together with the location of the dominant emission source, wind flows and protected areas enables a risk assessment of the dust deposition in the area of interest to be performed. In order to obtain a more accurate simulation of wind flows over the temporary storage and sorting site, 3D laser scanning and GPS thematic mapping are used to create a more detailed digital terrain model. Thus, visualization of wind flows over the area of interest combined with 3D map layers enables the exploration of the processes of coal dust deposition at a local scale. In general, this project could be used as a template for dust-transport modelling which couples spatial data focused on the construction of digital terrain models and thematic mapping with data generated by numerical simulations based on Reynolds averaged Navier-Stokes equations. PMID:27879911

Numerical modelling and data assimilation of the Larsen B ice shelf, Antarctic Peninsula.

PubMed

Vieli, Andreas; Payne, Antony J; Du, Zhijun; Shepherd, Andrew

2006-07-15

In this study, the flow and rheology of pre-collapse Larsen B ice shelf are investigated by using a combination of flow modelling and data assimilation. Observed shelf velocities from satellite interferometry are used to constrain an ice shelf model by using a data assimilation technique based on the control method. In particular, the ice rheology field and the velocities at the inland shelf boundary are simultaneously optimized to get a modelled flow and stress field that is consistent with the observed flow. The application to the Larsen B ice shelf shows that a strong weakening of the ice in the shear zones, mostly along the margins, is necessary to fit the observed shelf flow. This pattern of bands with weak ice is a very robust feature of the inversion, whereas the ice rheology within the main shelf body is found to be not well constrained. This suggests that these weak zones play a major role in the control of the flow of the Larsen B ice shelf and may be the key to understanding the observed pre-collapse thinning and acceleration of Larsen B. Regarding the sensitivity of the stress field to rheology, the consistency of the model with the observed flow seems crucial for any further analysis such as the application of fracture mechanics or perturbation model experiments.

Microcrustacea in flowing water - experimental-analysis of washout times and a field-test

USGS Publications Warehouse

Richardson, W.B.

1992-01-01

1. Flow-chamber experiments were conducted to evaluate the ability of microcrustacea to maintain position in moving water. These results were compared to distributions of zooplankton and water velocity in a stream pool to determine the relationship of animal density to water movement and swimming ability.^2. Cladocerans exhibited negative rheotaxis (directed behaviour against a current) but poor ability to maintain position at velocities >2.5 Cm s-1. Daphnia and scapholeberis were better at avoiding washout than moina and diaphanosoma. At velocities 2.5 Cm s-1, scapholeberis >3.2 Cm s-1 and eucyclops >7.75 Cm s-1. Washout time of daphnia and scapholeberis was positively related to body size and negatively to water velocity and possession of eggs. Washout was inversely related to water velocity for eucyclops.^4. Highest densities of microcrustacea in a stream pool were found in non-flowing or downstream zones of the pool. Benthic (hydracarina, harpacticoid copepods, ostracods) and fast-swimming (cyclopoids) forms were most common in flowing zones. Facultatively benthic cladocera were abundant in regions of no flow. Rotifers and immature copepods were most abundant at the downstream end of the pool.^5. Behavioural mechanisms for remaining in stream pools at times of high flow appear to include: (i) flow avoidance (simocephalus, chydorus, scapholeberis and cyclopoids), (ii) use of benthic habitat (ostracods, harpacticoids, hydracarina), (iii) strong swimming ability (cyclopoids).

Prediction of recirculation zones in isothermal coaxial jet flows relevant to combustors

NASA Technical Reports Server (NTRS)

Nallasamy, M.

1987-01-01

The characteristics of the recirculation zones in confined coaxial turbulent jets are investigated numerically employing the kappa - epsilon turbulence model. The geometrical arrangement corresponds to the experimental study of Owen (AIAA J. 1976) and the investigation is undertaken to provide information for isothermal flow relevant to combustor flows. For the first time, the shape, size, and location of the recirculation zones for the above experimental configuration are correctly predicted. The processes leading to the observed results are explained. Detailed comparisons of the prediction with measurements are made. It is shown that the recirculation zones are very sensitive to the central jet exit configuration and the velocity ratio of the jets.

Heat flow in eastern Egypt - The thermal signature of a continental breakup

NASA Technical Reports Server (NTRS)

Morgan, P.; Boulos, F. K.; Hennin, S. F.; El-Sherif, A. A.; El-Sayed, A. A.

1985-01-01

It is noted that the Red Sea is a modern example of continental fragmentation and incipient ocean formation. A consistent pattern of high heat flow in the Red Sea margins and coastal zone, including Precambrian terrane up to at least 30 km from the Red Sea, has emerged from the existing data. It is noted that this pattern has important implications for the mode and mechanism of Red Sea opening. High heat flow in the Red Sea shelf requires either a high extension of the crust in this zone (probably with major basic magmatic activity) or young oceanic crust beneath this zone. High heat flow in the coastal thermal anomaly zone may be caused by lateral conduction from the offshore lithosphere and/or from high mantle heat flow. It is suggested that new oceanic crust and highly extended continental crust would be essentially indistinguishable with the available data in the Red Sea margins, and are for many purposes essentially identical.

Free flowing and cohesive powders agitation in a cylindrical convective blender- kinetics experiments and Markov chain modelling

NASA Astrophysics Data System (ADS)

Legoix, Léonard; Milhé, Mathieu; Gatumel, Cendrine; Berthiaux, Henri

2017-06-01

An original methodology for studying powder flow in a cylindrical convective blender has been developed. A free-flowing and a cohesive powder were studied, at a fixed stirring speed, in rolling regime. For both powders, three apparent flow mechanisms were evidenced: convection in the volume swept by the blades, diffusion/shearing between the agitated zone and the stagnant one, as well as in the stagnant zone itself, and avalanches at the powder bed surface between agitated and stagnant zones. After defining six zones in the blender, tracing experiments were carried out by placing appropriate tracers in different starting zones and sampling the whole bed at different stirring times, which lead to mixing kinetics of the powders into themselves. A Markov chains model of the blender allowed the quantification of the three mechanisms respective magnitude by fitting the experimental data. This simple model has a good agreement with the free-flowing powder data, but is not able to represent well the observations for the cohesive powder. Bed consolidation should probably be taken into account for this kind of powders and thus a linear Markov model is not sufficient.

Uncertainty in the modelling of spatial and temporal patterns of shallow groundwater flow paths: The role of geological and hydrological site information

NASA Astrophysics Data System (ADS)

Woodward, Simon J. R.; Wöhling, Thomas; Stenger, Roland

2016-03-01

Understanding the hydrological and hydrogeochemical responses of hillslopes and other small scale groundwater systems requires mapping the velocity and direction of groundwater flow relative to the controlling subsurface material features. Since point observations of subsurface materials and groundwater head are often the basis for modelling these complex, dynamic, three-dimensional systems, considerable uncertainties are inevitable, but are rarely assessed. This study explored whether piezometric head data measured at high spatial and temporal resolution over six years at a hillslope research site provided sufficient information to determine the flow paths that transfer nitrate leached from the soil zone through the shallow saturated zone into a nearby wetland and stream. Transient groundwater flow paths were modelled using MODFLOW and MODPATH, with spatial patterns of hydraulic conductivity in the three material layers at the site being estimated by regularised pilot point calibration using PEST, constrained by slug test estimates of saturated hydraulic conductivity at several locations. Subsequent Null Space Monte Carlo uncertainty analysis showed that this data was not sufficient to definitively determine the spatial pattern of hydraulic conductivity at the site, although modelled water table dynamics matched the measured heads with acceptable accuracy in space and time. Particle tracking analysis predicted that the saturated flow direction was similar throughout the year as the water table rose and fell, but was not aligned with either the ground surface or subsurface material contours; indeed the subsurface material layers, having relatively similar hydraulic properties, appeared to have little effect on saturated water flow at the site. Flow path uncertainty analysis showed that, while accurate flow path direction or velocity could not be determined on the basis of the available head and slug test data alone, the origin of well water samples relative to the material layers and site contour could still be broadly deduced. This study highlights both the challenge of collecting suitably informative field data with which to characterise subsurface hydrology, and the power of modern calibration and uncertainty modelling techniques to assess flow path uncertainty in hillslopes and other small scale systems.

In Situ NAPL Modification for Contaminant Source-Zone Passivation, Mass Flux Reduction, and Remediation

NASA Astrophysics Data System (ADS)

Mateas, D. J.; Tick, G.; Carroll, K. C.

2016-12-01

A remediation method was developed to reduce the aqueous solubility and mass-flux of target NAPL contaminants through the in-situ creation of a NAPL mixture source-zone. This method was tested in the laboratory using equilibrium batch tests and two-dimensional flow-cell experiments. The creation of two different NAPL mixture source zones were tested in which 1) volumes of relatively insoluble n-hexadecane (HEX) or vegetable oil (VO) were injected into a trichloroethene (TCE) contaminant source-zone; and 2) pre-determined HEX-TCE and VO-TCE mixture ratio source zones were emplaced into the flow cell prior to water flushing. NAPL-aqueous phase batch tests were conducted prior to the flow-cell experiments to evaluate the effects of various NAPL mixture ratios on equilibrium aqueous-phase concentrations of TCE and toluene (TOL) and to design optimal NAPL (HEX or VO) injection volumes for the flow-cell experiments. Uniform NAPL mixture source-zones were able to quickly decrease contaminant mass-flux, as demonstrated by the emplaced source-zone experiments. The success of the HEX and VO injections to also decrease mass flux was dependent on the ability of these injectants to homogeneously mix with TCE source-zone. Upon injection, both HEX and VO migrated away from the source-zone, to some extent. However, the lack of a steady-state dissolution phase and the inefficient mass-flux-reduction/mass-removal behavior produced after VO injection suggest that VO was more effective than HEX for mixing and partitioning within the source-zone region to form a more homogeneous NAPL mixture with TCE. VO appears to be a promising source-zone injectant-NAPL due to its negligible long-term toxicity and lower mobilization potential.

Fluid-Structure Interaction Effects on Mass Flow Rates in Solid Rocket Motors

DTIC Science & Technology

2015-09-02

FEA ) is explored. A propellant flap in a cross flow is analyzed. Comparisons are made between an analytical solution, a solely CFD solution, a manual...finite element analysis ( FEA ) is explored.  A  propellant flap in a cross flow is analyzed.  Comparisons are made between an analytical  solution, a...Condition Zones ..................................................................... 11  Figure 6: Pressure Boundary Condition Applied to  FEA  model

Characterization of a high-transmissivity zone by well test analysis: Steady state case

USGS Publications Warehouse

Tiedeman, Claire; Hsieh, Paul A.; Christian, Sarah B.

1995-01-01

A method is developed to analyze steady horizontal flow to a well pumped from a confined aquifer composed of two homogeneous zones with contrasting transmissivities. Zone 1 is laterally unbounded and encloses zone 2, which is elliptical in shape and is several orders of magnitude more transmissive than zone 1. The solution for head is obtained by the boundary integral equation method. Nonlinear least squares regression is used to estimate the model parameters, which include the transmissivity of zone 1, and the location, size, and orientation of zone 2. The method is applied to a hypothetical aquifer where zone 2 is a long and narrow zone of vertical fractures. Synthetic data are generated from three different well patterns, representing different areal coverage and proximity to the fracture zone. When zone 1 of the hypothetical aquifer is homogeneous, the method correctly estimates all model parameters. When zone 1 is a randomly heterogeneous transmissivity field, some parameter estimates, especially the length of zone 2, become highly uncertain. To reduce uncertainty, the pumped well should be close to the fracture zone, and surrounding observation wells should cover an area similar in dimension to the length of the fracture zone. Some prior knowledge of the fracture zone, such as that gained from a surface geophysical survey, would greatly aid in designing the well test.

Stability and modal analysis of shock/boundary layer interactions

NASA Astrophysics Data System (ADS)

Nichols, Joseph W.; Larsson, Johan; Bernardini, Matteo; Pirozzoli, Sergio

2017-02-01

The dynamics of oblique shock wave/turbulent boundary layer interactions is analyzed by mining a large-eddy simulation (LES) database for various strengths of the incoming shock. The flow dynamics is first analyzed by means of dynamic mode decomposition (DMD), which highlights the simultaneous occurrence of two types of flow modes, namely a low-frequency type associated with breathing motion of the separation bubble, accompanied by flapping motion of the reflected shock, and a high-frequency type associated with the propagation of instability waves past the interaction zone. Global linear stability analysis performed on the mean LES flow fields yields a single unstable zero-frequency mode, plus a variety of marginally stable low-frequency modes whose stability margin decreases with the strength of the interaction. The least stable linear modes are grouped into two classes, one of which bears striking resemblance to the breathing mode recovered from DMD and another class associated with revolving motion within the separation bubble. The results of the modal and linear stability analysis support the notion that low-frequency dynamics is intrinsic to the interaction zone, but some continuous forcing from the upstream boundary layer may be required to keep the system near a limit cycle. This can be modeled as a weakly damped oscillator with forcing, as in the early empirical model by Plotkin (AIAA J 13:1036-1040, 1975).

Permeability and seismic velocity anisotropy across a ductile-brittle fault zone in crystalline rock

NASA Astrophysics Data System (ADS)

Wenning, Quinn C.; Madonna, Claudio; de Haller, Antoine; Burg, Jean-Pierre

2018-05-01

This study characterizes the elastic and fluid flow properties systematically across a ductile-brittle fault zone in crystalline rock at the Grimsel Test Site underground research laboratory. Anisotropic seismic velocities and permeability measured every 0.1 m in the 0.7 m across the transition zone from the host Grimsel granodiorite to the mylonitic core show that foliation-parallel P- and S-wave velocities systematically increase from the host rock towards the mylonitic core, while permeability is reduced nearest to the mylonitic core. The results suggest that although brittle deformation has persisted in the recent evolution, antecedent ductile fabric continues to control the matrix elastic and fluid flow properties outside the mylonitic core. The juxtaposition of the ductile strain zone next to the brittle zone, which is bounded inside the two mylonitic cores, causes a significant elastic, mechanical, and fluid flow heterogeneity, which has important implications for crustal deformation and fluid flow and for the exploitation and use of geothermal energy and geologic waste storage. The results illustrate how physical characteristics of faults in crystalline rocks change in fault zones during the ductile to brittle transitions.

Thermal Models of the Costa Rica - Nicaragua Subduction Zone: the Effect of a Three-Dimensional Oceanic Plate Structure and Hydrothermal Circulation in the Temperature Distribution and Mantle Wedge Dynamics

NASA Astrophysics Data System (ADS)

Rosas, J. C.; Currie, C. A.; He, J.

2014-12-01

Over the last years several 2D thermo-mechanical models of the Costa Rica - Nicaragua Subduction Zone (CNSZ) have studied the thermal distribution of sections of the fault. Such investigations allow us to understand temperature-related aspects of subduction zones, like volcanism and megathrust earthquake locations. However, certain features of the CNSZ limit the range of applicability of 2D models. In the CNSZ, geochemical trends and seismic anisotropy studies reveal a 3D mantle wedge flow that departs from the 2D corner flow. The origin of this flow are dip variations (20o to 25o between Nicaragua and Costa Rica) and the presence of a slab window in Panama that allows material to flow into the mantle wedge. Also, the Central America trench has abrupt variations in surface heat flux that contrasts with steady changes in plate age and convergence rate. These variations have been attributed to hydrothermal circulation (HC), which effectively removes heat from the oceanic crust.In this project we analyze the thermal structure of the CNSZ. The objective is to study dehydration and metamorphic reactions, as well as the length of the megathrust seismogenic zone. We created 3D finite-element models that employ a dislocation creep rheology for the mantle wedge. Two aspects make our models different from previous studies: an up-to-date 3D slab geometry, and an implementation of HC by introducing a conductive proxy in the subducting aquifer, allowing us to model convective heat transport without the complex, high-Rayleigh number calculations. A 3D oceanic boundary condition that resembles the along-strike changes in surface heat flux is also employed. Results show a maximum mantle wedge flow rate of 4.69 cm/yr in the along-strike direction, representing more than 50% of the slab convergence rate. With respect to 2D models, analysis shows this flow changes temperatures by ~100 C in the mantle wedge near areas of strong slab curvature. Along the subducting interface, there is also a change of 10-40 C, which can have a significant impact on dehydration and metamorphic reactions. Also, 2D models have proven that HC controls temperatures along the subduction thrust, which controls the length of the seismogenic zone. In general, the combined effect of 3D mantle wedge flow and HC is expected to have a significant impact on the thermal structure.

A Temporal and Spatial Analysis of Wave-Generated Foam Patterns in the Surf Zone

DTIC Science & Technology

2017-01-10

region, rectange B depicts the gap region, rectangle C is the plunging breaker, circle D represents a foam hole, rectangle E depict a top box...structures: The hidden skeleton of fluid flows . Phys. Today, 66, 41–47. 35 V. CONCLUSION Unique surf zone imagery, acquired from a UAV at Sand City...MacMahan, J. H., E . B . Thornton, T. P. Stanton, and A. J. H. M. Reniers, 2005: RIPEX: Observations of a rip current system. Mar. Geol., 218, 113–134

Electropherogram of capillary zone electrophoresis with effective mobility axis as a transverse axis and its analytical utility. I. Transformation applying the hypothetical electroosmotic flow.

PubMed

Ikuta, N; Yamada, Y; Hirokawa, T

2000-01-01

For capillary zone electrophoresis, a new method of transformation from migration time to effective mobility was proposed, in which the mobility increase due to Joule heating and the relaxation effect of the potential gradient were eliminated successfully. The precision of the mobility evaluated by the proposed transformation was discussed in relation to the analysis of rare earth ions. By using the transformation, almost the same pherograms could be obtained even from the pherograms obtained originally at different applied voltages.

Comprehensive protein profiling by multiplexed capillary zone electrophoresis using cross-linked polyacrylamide coated capillaries.

PubMed

Liu, Shaorong; Gao, Lin; Pu, Qiaosheng; Lu, Joann J; Wang, Xingjia

2006-02-01

We have recently developed a new process to create cross-linked polyacrylamide (CPA) coatings on capillary walls to suppress protein-wall interactions. Here, we demonstrate CPA-coated capillaries for high-efficiency (>2 x 10(6) plates per meter) protein separations by capillary zone electrophoresis (CZE). Because CPA virtually eliminates electroosmotic flow, positive and negative proteins cannot be analyzed in a single run. A "one-sample-two-separation" approach is developed to achieve a comprehensive protein analysis. High throughput is achieved through a multiplexed CZE system.

Stratigraphy of the Oliocene Sullivan Buttes Latite constrains transition zone development in Chino Valley, Arizona

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

Ward, S.A.; Riggs, N.R.

The 26.7--23.4 Ma Sullivan Buttes Latite of Chino Valley, Yavapai County, Arizona, erupted during the development of the Transition Zone between the Basin and Range and Colorado Plateau provinces. Detailed mapping and stratigraphic analysis of a portion of the volcanic field indicate volcanism began with the eruption of a shoshonite lava flow and associated cinder cone. Amphibole latite domes then erupted fallouts, surges, and mass flow breccias and culminated activity with a lava flow. Extrusive units from a biotite oxidized latite center to the east interfinger with the older amphibole lattice volcaniclastics. Sullivan Buttes Latite units erupted onto Precambrian andmore » lower Paleozoic strata and Tertiary gravels; the scarp of upper Paleozoic strata equivalent to the paleo' Mogollon Rim had retreated from the area by the time of emplacement of the oldest Sullivan Buttes Latite unit. Subsequent 15--10 Ma Hickey Formation basalts flowed onto an erosion surface cut into Sullivan Buttes deposits, and the nearby Verde River downcut through younger 4.62 Ma Perkinsville Formation basalt. Both situations demonstrate erosion and degradation post Sullivan Buttes activity. Normal faults offsetting Hickey Formation basalts and all older units constrain Basin and Range structural activity to 15 Ma or younger. These stratigraphic relationships of the Sullivan Buttes Latite in the context of Transition Zone development concur with 65--18 Ma retreat of the upper Paleozoic scarp and below-scarp aggradation, 18--12 Ma Basin and Range faulting, and subsequent degradation.« less

Geohydrology of the Stockton Formation and cross-contamination through open boreholes, Hatboro Borough and Warminster Township, Pennsylvania

USGS Publications Warehouse

Sloto, R.A.; Macchiaroli, Paola; Towle, M.T.

1996-01-01

The study area consists of a 9-square-mile area underlain by sedimentary rocks of the middle arkose member of the Stockton Formation of Upper Triassic age. In the Hatboro area, the Stockton Formation strikes approximately N. 65 degrees E. and dps approximately 9 degrees NW. The rocks are chiefly arkosic sandstone and siltstone. Rocks of the Stocton Formation form a complex, heterogeneous, multiaquifer system consisting of a series of gently dipping lithologic units with different hydraulic properties. Most ground water in the unweathered zone moves through a network of interconnecting secondary openigns-fractures, bedding plans, and joints. Ground water is unconfined in the shallower part of the aquifer and semiconfined or confined in the deeper part of the aquifer. Nearly all deep wells in the Stockton Formation are open to several water-bearing zones and are multiaquifer wells. Each water-bearing zone usually has a different hydraulic head. Where differences in hydraulic head exist between water-bearing zones, water in the well bore flows under nonpumping conditions in the direction of decreasing head. Determination of the potential for borehole flow was based on caliper, natural-gamma, single- point-resistance, fluid-resistivity, and (or) fluid-temperature logs that were run in 162 boreholes 31 to 655 feet deep. The direction and rate of borehole-fluid movement were determined in 83 boreholes by the bring-tracing method and in 10 boreholes by use of a heat-pulse flowmeter. Borehole flow was measurable in 65 of the 93 boreholes (70 percent). Fluid movement at rates up to 17 gallons per minute was measured. Downward flow was measured in 36 boreholes, and upward flow was measured in 23 boreholes, not including those boreholes in which two directions of flow were measured. Both upward and downward vertical flow was measured in six boreholes; these boreholes are 396 to 470 feet deep and were among the deepest boreholes logged. Fluid movement was upward in the upper part of the borehole and downward in the lower part of the borehole in two boreholes. Fluid movement wad downward in the upper part of the borehole and upward in the lower part of the borehole in three boreholes. Groung-water contamination by volatile organic compounds (VOC's) is widespread in the study area. Detectable concentrations of VOC's were present in water samples from 24 wells sampled in Hatboro Brough and in water samples for 10 of 14 wells (71 percent) samples in Warminster Township. Samples of borehole flow from nine boreholes in the industrial area of Hatboro were collected for laboratory analysis to estimate the quantity of VOC's in borehole flow. Downward flow was measured in all of these boreholes. Concentrations of TCE, TCA, and 1,1-DCE as great at 5,800, 1,400 and 260 micrograms per liter, respectively, show that some water moving downward in the aquifer through these open boreholes is highly contaminated and that open boreholes may contribute substantially to ground-water contamination. An estimated 14.7 gallons per year of VOC's were moving downward through the nine open boreholes sampled from the contaminated, upper part of the aquifer to the lower part, which is tapped by public supply wells. Borehole geophysical logs were used as a guide to design and construct monitor-well networks at three National Priorities List sites in the area. An open borehole was dirlled, and a suite of geophysical logs was run. Interpretation of geophysical logs enabled the identification of water-bearing zones that produce and receive water; these are zones that should not be connected. From the logs, discrete intervals to be monitored were selected. In the Stockton Formation, the same water-bearing zone may not be intersected in adjacent boreholes, especially if it is a vertical fracture with a diffident magnetic orientation than that of the adjacent boreholes. In most areas of the stockton Formation, depth of water-bearing zones in an are

Use of individualistic streamflow-vegetation relations along the Fremont River, Utah, USA to assess impacts of flow alteration on wetland and riparian area

USGS Publications Warehouse

Auble, G.T.; Scott, M.L.; Friedman, J.M.

2005-01-01

We analyzed the transverse pattern of vegetation along a reach of the Fremont River in Capitol Reef National Park, Utah, USA using models that support both delineation of wetland extent and projection of the changes in wetland area resulting from upstream hydrologic alteration. We linked stage-discharge relations developed by a hydraulic model to a flow-duration curve derived from the flow history in order to calculate the inundation duration of 361 plots (0.5 × 2 m). Logistic regression was used to relate plant species occurrence in plots to inundation duration. A weighted average of the wetland indicator values of species was used to characterize plots as Aquatic, Wetland, Transitional, or Upland. Finally, we assessed how alterations in the flow duration curve would change the relative widths of these four zones. The wetland indicator values of species and the wetland prevalence index scores of plots were strongly correlated with inundation duration. Our results support the concept that plants classified as wetland species typically occur on sites inundated at least two weeks every two years. The portion of the riparian zone along the high-gradient study reach of the Fremont River that satisfied the vegetation criterion for a regulatory wetland was narrow (2 m wide). Both the unvegetated Aquatic zone (7.8 m) and the Transitional zone (8 m) were substantially wider. The Transitional zone included the maxima of several species and was, therefore, not merely a combination of elements of the Wetland and Upland zones. Multiplicative increases or decreases in streamflow regime produced a wetter, or drier, bottomland vegetation, respectively. Systematic reductions in flow variability reduced the width of both the Wetland and Transitional zones and increased the width of the Upland zone. Our approach is widely applicable to inform water management decisions involving changes in flow regime.

Fault and fracture patterns in low porosity chalk and their potential influence on sub-surface fluid flow-A case study from Flamborough Head, UK

NASA Astrophysics Data System (ADS)

Sagi, D. A.; De Paola, N.; McCaffrey, K. J. W.; Holdsworth, R. E.

2016-10-01

To better understand fault zone architecture and fluid flow in mesoscale fault zones, we studied normal faults in chalks with displacements up to 20 m, at two representative localities in Flamborough Head (UK). At the first locality, chalk contains cm-thick, interlayered marl horizons, whereas at the second locality marl horizons were largely absent. Cm-scale displacement faults at both localities display ramp-flat geometries. Mesoscale fault patterns in the marl-free chalk, including a larger displacement fault (20 m) containing multiple fault strands, show widespread evidence of hydraulically-brecciated rocks, whereas clays smears along fault planes, and injected into open fractures, and a simpler fault zone architecture is observed where marl horizons are present. Hydraulic brecciation and veins observed in the marl-free chalk units suggest that mesoscale fault patterns acted as localized fault conduit allowing for widespread fluid flow. On the other hand, mesoscale fault patterns developed in highly fractured chalk, which contains interlayered marl horizons can act as localized barriers to fluid flow, due to the sealing effect of clays smears along fault planes and introduced into open fractures in the damage zone. To support our field observations, quantitative analyses carried out on the large faults suggest a simple fault zone in the chalk with marl units with fracture density/connectivity decreasing towards the protolith. Where marls are absent, density is high throughout the fault zone, while connectivity is high only in domains nearest the fault core. We suggest that fluid flow in fractured chalk is especially influenced by the presence of marls. When present, it can smear onto fault planes, forming localised barriers. Fluid flow along relatively large displacement faults is additionally controlled by the complexity of the fault zone, especially the size/geometry of weakly and intensely connected damage zone domains.

Compressible Flow Phenomena at Inception of Lateral Density Currents Fed by Collapsing Gas-Particle Mixtures

NASA Astrophysics Data System (ADS)

Valentine, Greg A.; Sweeney, Matthew R.

2018-02-01

Many geological flows are sourced by falling gas-particle mixtures, such as during collapse of lava domes, and impulsive eruptive jets, and sustained columns, and rock falls. The transition from vertical to lateral flow is complex due to the range of coupling between particles of different sizes and densities and the carrier gas, and due to the potential for compressible flow phenomena. We use multiphase modeling to explore these dynamics. In mixtures with small particles, and with subsonic speeds, particles follow the gas such that outgoing lateral flows have similar particle concentration and speed as the vertical flows. Large particles concentrate immediately upon impact and move laterally away as granular flows overridden by a high-speed jet of expelled gas. When a falling flow is supersonic, a bow shock develops above the impact zone, and this produces a zone of high pressure from which lateral flows emerge as overpressured wall jets. The jets form complex structures as the mixtures expand and accelerate and then recompress through a recompression zone that mimics a Mach disk shock in ideal gas jets. In mixtures with moderate to high ratios of fine to coarse particles, the latter tend to follow fine particles through the expansion-recompression flow fields because of particle-particle drag. Expansion within the flow fields can lead to locally reduced gas pressure that could enhance substrate erosion in natural flows. The recompression zones form at distances, and have peak pressures, that are roughly proportional to the Mach numbers of impacting flows.

Energy efficiency analysis of reactor for torrefaction of biomass with direct heating

NASA Astrophysics Data System (ADS)

Kuzmina, J. S.; Director, L. B.; Shevchenko, A. L.; Zaichenko, V. M.

2016-11-01

Paper presents energy analysis of reactor for torrefaction with direct heating of granulated biomass by exhaust gases. Various schemes of gas flow through the reactor zones are presented. Performed is a comparative evaluation of the specific energy consumption for the considered schemes. It has been shown that one of the most expensive processes of torrefaction technology is recycling of pyrolysis gases.

Hydrogeologic framework and salinity distribution of the Floridan aquifer system of Broward County, Florida

USGS Publications Warehouse

Reese, Ronald S.; Cunningham, Kevin J.

2014-01-01

Concerns about water-level decline and seawater intrusion in the surficial Biscayne aquifer, currently the principal source of water supply to Broward County, prompted a study to refine the hydrogeologic framework of the underlying Floridan aquifer system to evaluate its potential as an alternative source of supply. This report presents cross sections that illustrate the stratigraphy and hydrogeology in eastern Broward County; maps of the upper surfaces and thicknesses of several geologic formations or units within the Floridan aquifer system; and maps of two of the potentially productive water-bearing zones within the system, the Upper Floridan aquifer and the Avon Park permeable zone. An analysis of data on rock depositional textures, associated pore networks, and flow zones in the Floridan aquifer system shows that groundwater moves through the system in two ways. These data support a conceptual, dual-porosity model of the system wherein groundwater moves either as concentrated flow in discrete, thin bedding-plane vugs or zones of vuggy megaporosity, or as diffuse flow through rocks with primarily interparticle and moldic-particle porosity. Because considerable exchange of groundwater may occur between the zones of vuggy and matrix-dominated porosity, understanding the distribution of that porosity and flow zone types is important to evaluating the suitability of the several units within the Floridan aquifer system for managing the water through practices such as aquifer storage and recovery (ASR). The salinity of the water in the Floridan aquifer system is highest in the central part of the study area, and lower toward the north and south. Although salinity generally increases with depth, in the western part of the study area a zone of relatively high saline water is perched above water of lower salinity in the underlying Avon Park permeable zone. Overall, the areas of highest salinity in the aquifer system coincide with those with the lowest estimated transmissivity, so that the occurrence of perched saline water in the system may be the consequence of incompletely flushed connate water or intruded seawater. A seismic reflection profile along the Hillsboro Canal, at the northern edge of the study area, shows seven seismic-sag structures that are interpreted as downward deformation of overlying strata into collapsed deep cave systems. These structures may compromise the integrity of the confinement created by the underlying strata by allowing upconing of saline water from depth, which has implications for successful application of ASR and use of the Floridan aquifer system as an alternative water supply.

Heat and Mass Transfer in the Over-Shower Zone of a Cooling Tower with Flow Rotation

NASA Astrophysics Data System (ADS)

Kashani, M. M. Hemmasian; Dobrego, K. V.

2013-11-01

The influence of flow rotation in the over-shower zone of a natural draft wet cooling tower (NDCT) on heat and mass transfer in this zone is investigated numerically. The 3D geometry of an actual NDCT and three models of the induced rotation velocity fields are utilized for calculations. Two phases (liquid and gaseous) and three components are taken into consideration. The interphase heat exchange, heat transfer to the walls, condensation-evaporation intensity field, and other parameters are investigated as functions of the induced rotation intensity (the inclination of the velocity vector at the periphery). It is shown that the induced flow rotation intensifies the heat and mass transfer in the over-shower zone of an NDCT. Flow rotation leads to specific redistribution of evaporation-condensation areas in an NDCT and stimulates water condensation near its walls.

Apparatus and method for continuous production of materials

DOEpatents

Chang, Chih-hung; Jin, Hyungdae

2014-08-12

Embodiments of a continuous-flow injection reactor and a method for continuous material synthesis are disclosed. The reactor includes a mixing zone unit and a residence time unit removably coupled to the mixing zone unit. The mixing zone unit includes at least one top inlet, a side inlet, and a bottom outlet. An injection tube, or plurality of injection tubes, is inserted through the top inlet and extends past the side inlet while terminating above the bottom outlet. A first reactant solution flows in through the side inlet, and a second reactant solution flows in through the injection tube(s). With reference to nanoparticle synthesis, the reactant solutions combine in a mixing zone and form nucleated nanoparticles. The nucleated nanoparticles flow through the residence time unit. The residence time unit may be a single conduit, or it may include an outer housing and a plurality of inner tubes within the outer housing.

Geomorphic controls on hyporheic exchange flow in mountain streams.

Treesearch

T. Kasahara; S.M. Wondzell

2003-01-01

Hyporheic exchange flows were simulated using MODFLOW and MODPATH to estimate relative effects of channel morphologic features on the extent of the hyporheic zone, on hyporheic exchange flow, and on the residence time of stream water in the hyporheic zone. Four stream reaches were compared in order to examine the influence of stream size and channel constraint. Within...

Modeling Water Waves with Smoothed Particle Hydrodynamics

DTIC Science & Technology

2013-09-30

SPH Model for Water Waves and Other Free Surface Flows ...Lagrangian nature of SPH allows the modeling of wave breaking, surf zones, ship waves, and wave-structure interaction, where the free surface becomes...proving to be a competent modeling scheme for free surface flows in three dimensions including the complex flows of the surf zone. As the GPU

An investigation on near wall transport characteristics in an adiabatic upward gas-liquid two-phase slug flow

NASA Astrophysics Data System (ADS)

Zheng, Donghong; Che, Defu

2007-08-01

The near-wall transport characteristics, inclusive of mass transfer coefficient and wall shear stress, which have a great effect on gas-liquid two-phase flow induced internal corrosion of low alloy pipelines in vertical upward oil and gas mixing transport, have been both mechanistically and experimentally investigated in this paper. Based on the analyses on the hydrodynamic characteristics of an upward slug unit, the mass transfer in the near wall can be divided into four zones, Taylor bubble nose zone, falling liquid film zone, Taylor bubble wake zone and the remaining liquid slug zone; the wall shear stress can be divided into two zones, the positive wall shear stress zone associated with the falling liquid film and the negative wall shear stress zone associated with the liquid slug. Based on the conventional mass transfer and wall shear stress characteristics formulas of single phase liquid full-pipe turbulent flow, corrected normalized mass transfer coefficient formula and wall shear stress formula are proposed. The calculated results are in good agreement with the experimental data. The shear stress and the mass transfer coefficient in the near wall zone are increased with the increase of superficial gas velocity and decreased with the increase of superficial liquid velocity. The mass transfer coefficients in the falling liquid film zone and the wake zone of leading Taylor bubble are lager than those in the Taylor bubble nose zone and the remaining liquid slug zone, and the wall shear stress associated falling liquid film is larger than that associated the liquid slug. The mass transfer coefficient is within 10-3 m/s, and the wall shear stress below 103 Pa. It can be concluded that the alternate wall shear stress due to upward gas-liquid slug flow is considered to be the major cause of the corrosion production film fatigue cracking.

Turbulent transport modeling of shear flows around an aerodynamic wing. Development of turbulent near-wall model and its application to recirculating flows

NASA Technical Reports Server (NTRS)

Amano, R. S.

1982-01-01

Progress in implementing and refining two near-wall turbulence models in which the near-wall region is divided into either two or three zones is outlined. These models were successfully applied to the computation of recirculating flows. The research was further extended to obtaining experimental results of two different recirculating flow conditions in order to check the validity of the present models. Two different experimental apparatuses were set up: axisymmetric turbulent impinging jets on a flat plate, and turbulent flows in a circular pipe with a abrupt pipe expansion. It is shown that generally better results are obtained by using the present near-wall models, and among the models the three-zone model is superior to the two-zone model.

Near-census Delineation of Laterally Organized Geomorphic Zones and Associated Sub-width Fluvial Landforms

NASA Astrophysics Data System (ADS)

Pasternack, G. B.; Hopkins, C.

2017-12-01

A river channel and its associated riparian corridor exhibit a pattern of nested, geomorphically imprinted, lateral inundation zones (IZs). Each zone plays a key role in fluvial geomorphic processes and ecological functions. Within each zone, distinct landforms (aka geomorphic or morphological units, MUs) reside at the 0.1-10 channel width scale. These features are basic units linking river corridor morphology with local ecosystem services. Objective, automated delineation of nested inundation zones and morphological units remains a significant scientific challenge. This study describes and demonstrates new, objective methods for solving this problem, using the 35-km alluvial lower Yuba River as a testbed. A detrended, high-resolution digital elevation model constructed from near-census topographic and bathymetric data was produced and used in a hypsograph analysis, a commonly used method in oceanographic studies capable of identifying slope breaks at IZ transitions. Geomorphic interpretation mindful of the river's setting was required to properly describe each IZ identified by the hypsograph analysis. Then, a 2D hydrodynamic model was used to determine what flow yields the wetted area that most closely matches each IZ domain. The model also provided meter-scale rasters of depth and velocity useful for MU mapping. Even though MUs are discharge-independent landforms, they can be revealed by analyzing their overlying hydraulics at low flows. Baseflow depth and velocity rasters are used along with a hydraulic landform classification system to quantitatively delineate in-channel bed MU types. In-channel bar and off-channel flood and valley MUs are delineated using a combination of hydraulic and geomorphic indicators, such as depth and velocity rasters for different discharges, topographic contours, NAIP imagery, and a raster of vegetation. The ability to objectively delineate inundation zones and morphological units in tandem allows for better informed river management and restoration strategies as well as scientific studies about abiotic-biotic linkages.

Regional-scale analysis of karst underground flow deduced from tracing experiments: examples from carbonate aquifers in Malaga province, southern Spain

NASA Astrophysics Data System (ADS)

Barberá, J. A.; Mudarra, M.; Andreo, B.; De la Torre, B.

2018-02-01

Tracer concentration data from field experiments conducted in several carbonate aquifers (Malaga province, southern Spain) were analyzed following a dual approach based on the graphical evaluation method (GEM) and solute transport modeling to decipher flow mechanisms in karst systems at regional scale. The results show that conduit system geometry and flow conditions are the principal factors influencing tracer migration through the examined karst flow routes. Solute transport is mainly controlled by longitudinal advection and dispersion throughout the conduit length, but also by flow partitioning between mobile and immobile fluid phases, while the matrix diffusion process appears to be less relevant. The simulation of tracer breakthrough curves (BTCs) suggests that diffuse and concentrated flow through the unsaturated zone can have equivalent transport properties under extreme recharge, with high flow velocities and efficient mixing due to the high hydraulic gradients generated. Tracer mobilization within the saturated zone under low flow conditions mainly depends on the hydrodynamics (rather than on the karst conduit development), which promote a lower longitudinal advection and retardation in the tracer migration, resulting in a marked tailing effect of BTCs. The analytical advection-dispersion equation better approximates the effective flow velocity and longitudinal dispersion estimations provided by the GEM, while the non-equilibrium transport model achieves a better adjustment of most asymmetric and long-tailed BTCs. The assessment of karst underground flow properties from tracing tests at regional scale can aid design of groundwater management and protection strategies, particularly in large hydrogeological systems (i.e. transboundary carbonate aquifers) and/or in poorly investigated ones.

A New Mixing Diagnostic and Gulf Oil Spill Movement

NASA Astrophysics Data System (ADS)

Mezić, Igor; Loire, S.; Fonoberov, Vladimir A.; Hogan, P.

2010-10-01

Chaotic advection has served as the paradigm for mixing in fluid flows with simple time dependence. Its skeletal structure is based on analysis of invariant attracting and repelling manifolds in fluid flows. Here we develop a finite-time theory for two-dimensional incompressible fluid flows with arbitrary time dependence and introduce a new mixing diagnostic based on it. Besides stretching events around attracting and repelling manifolds, this allows us to detect hyperbolic mixing zones. We used the new diagnostic to forecast the spatial location and timing of oil washing ashore in Plaquemines Parish and Grand Isle, Louisiana, and Pensacola, Florida, in May 2010 and the flow of oil toward Panama City Beach, Florida, in June 2010.

Validation Data for Mechanical System Algorithms Used in Building Energy Analysis Programs.

DTIC Science & Technology

1982-02-01

15 Zone Design 15 Built-Up Air Handler 15 Ventilation Requirements 16 The DES 16 Duct Design 17 Air -Delivery System 17 VAV Operation 17 Constant Volume...observed to operate well at reduced air flows, even at low flow in the so- called surge region. Recommendations 1. The HVAC system and component...With Inlet Guide Vanes Operating Within a Built-Up Air Handler 31 Test 2 -- Boiler Operation, Capacity, Efficiency, and Stand-By Losses 32 Test 3

An investigation of deformation and fluid flow at subduction zones using newly developed instrumentation and finite element modeling

NASA Astrophysics Data System (ADS)

Labonte, Alison Louise

Detecting seafloor deformation events in the offshore convergent margin environment is of particular importance considering the significant seismic hazard at subduction zones. Efforts to gain insight into the earthquake cycle have been made at the Cascadia and Costa Rica subduction margins through recent expansions of onshore GPS and seismic networks. While these studies have given scientists the ability to quantify and locate slip events in the seismogenic zone, there is little technology available for adequately measuring offshore aseismic slip. This dissertation introduces an improved flow meter for detecting seismic and aseismic deformation in submarine environments. The value of such hydrologic measurements for quantifying the geodetics at offshore margins is verified through a finite element modeling (FEM) study in which the character of deformation in the shallow subduction zone is determined from previously recorded hydrologic events at the Costa Rica Pacific margin. Accurately sensing aseismic events is one key to determining the stress state in subduction zones as these slow-slip events act to load or unload the seismogenic zone during the interseismic period. One method for detecting seismic and aseismic strain events is to monitor the hydrogeologic response to strain events using fluid flow meters. Previous instrumentation, the Chemical Aqueous Transport (CAT) meter which measures flow rates through the sediment-water interface, can detect transient events at very low flowrates, down to 0.0001 m/yr. The CAT meter performs well in low flow rate environments and can capture gradual changes in flow rate, as might be expected during ultra slow slip events. However, it cannot accurately quantify high flow rates through fractures and conduits, nor does it have the temporal resolution and accuracy required for detecting transient flow events associated with rapid deformation. The Optical Tracer Injection System (OTIS) developed for this purpose is an electronic flow meter that can measure flow rates of 0.1 to >500 m/yr at a temporal resolution of 30 minutes to 0.5 minutes, respectively. Test deployments of the OTIS at cold seeps in the transpressional Monterey Bay demonstrated the OTIS functionality over this range of flow environments. Although no deformation events were detected during these test deployments, the OTIS's temporally accurate measurements at the vigorously flowing Monterey Bay cold seep rendered valuable insight into the plumbing of the seep system. In addition to the capability to detect transient flow events, a primary functional requirement of the OTIS was the ability to communicate and transfer data for long-term real-time monitoring deployments. Real-time data transfer from the OTIS to the desktop was successful during a test deployment of the Nootka Observatory, an acoustically-linked moored-buoy system. A small array of CAT meters was also deployed at the Nootka transform-Cascadia subduction zone triple junction. Four anomalous flow rate events were observed across all four meters during the yearlong deployment. Although the records have low temporal accuracy, a preliminary explanation for the regional changes in flow rate is made through comparison between flow rate records and seismic records. The flow events are thought to be a result of a tectonic deformation event, possibly with an aseismic component. Further constraints are not feasible given the unknown structure of faulting near the triple junction. In a final proof of concept study, I find that use these hydrologic instruments, which capture unique aseismic flow rate patterns, is a valuable method for extracting information about deformation events on the decollement in the offshore subduction zone margin. Transient flow events observed in the frontal prism during a 1999--2000 deployment of CAT meters on the Costa Rica Pacific margin suggest episodic slow-slip deformation events may be occurring in the shallow subduction zone. The FEM study to infer the character of the hypothetical deformation event driving flow transients verify that indeed, a shallow slow-slip event can reproduce the unique flow rate patterns observed. Along (trench) strike variability in the rupture initiation location, and bidirectional propagation, is one way to explain the opposite sign of flow rate transients observed at different along-strike distances. The larger question stimulated by this dissertation project, is: What are the controls on fault mechanics in offshore subduction zone environments? It appears the shallow subduction zone plate interface doesn't behave solely in response to frictional properties of the sediment lining the decollement. Shallow episodic slip at the Costa Rica Pacific margin and further north off Nicaragua, where a slow earthquake broke through the shallow 'stable-sliding' zone and resulted in a tsunami, are potentially conceived through the normally faulted incoming basement topography. Scientists should seek to map out the controls of faulting mechanics, whatever they may be, at all temporal and spatial scales in order to understand these dynamic subduction zone systems. The quest to understanding these controls, in part, requires the characterization of aseismic and seismic strain occurring over time and space. The techniques presented in this dissertation advance scientists' capability for quantifying such strains. With the new instrumentation presented here, long-term real-time observatory networks on the seafloor, and modeling for characterization of deformation events, the pieces of the subduction zone earthquake cycle puzzle may start to come together.

Aggradation and degradation of alluvial sand deposits, 1965 to 1986, Colorado River, Grand Canyon National Park, Arizona

USGS Publications Warehouse

Schmidt, John C.; Graf, Julia B.

1990-01-01

Alluvial sand deposits along the Colorado River in Grand Canyon National Park are used as campsites and are substrate for vegetation. The largest and most numerous of these deposits are formed in zones of recirculating current that are created downstream from where the channel is constricted by debris fans at tributary mouths. Alluvial sand deposits are classified by location and form. Separation and reattachment deposits are downstream from constrictions within recirculation zones. Separation deposits are near the point of flow separation and typically mantle large debris fans. Reattachment deposits are near the point of flow reattachment and project upstream beneath much of the zone of recirculating current. Upper-pool deposits are upstream from a constriction and are associated with backwaters. Channel-margin deposits line the channel and have the form of terraces. Some are created in small recirculation zones. Reattachment and channel-margin deposits are largest and most numerous in wide reaches, although small channel-margin deposits are used as campsites in the narrow Muav Gorge. Separation deposits are more uniformly distributed throughout Grand Canyon National Park than are other types of deposits. In some narrow reaches where the number of alluvial sand deposits used as campsites is small, separation deposits are a high percentage of the total. During high flows, both separation and reattachment deposits are initially scoured but are subsequently redeposited during flow recession. Sand is also exchanged between the main channel and recirculation zones. The rate of recession of high flows can affect the elevation of alluvial deposits that are left exposed after a flood has passed. Fluctuating flows that follow a period of steady discharge cause initial erosion of separation and reattachment deposits. A part of this eroded sand is transported to the main channel. Therefore, sand is exchanged between the main channel and recirculation zones and redistributed within recirculation zones over a broad range of discharges. Comparison of aerial photographs and reinterpretation of published data concerning changes of alluvial sand deposits following recession of high flows in 1983 and 1984 indicate that sand was eroded from recirculation zones in narrow reaches. In wide reaches, however, aggradation in recirculation zones may have occurred. In narrow reaches, the decrease of reattachment deposits was greater than that of separation deposits. In all reaches, the percentage of separation deposits that maintained a constant area was greater than for other deposits. Separation deposits, therefore, appear to be the most stable of the deposit types. Fluctuating flows between October 1985 and January 1986, which followed the higher and steadier flows of 1983 to 1985, caused erosion throughout the park. For separation deposits, erosion was greatest at those sites where deposition from the 1983 high flows had been greatest. The existing pattern of low campsite availability in narrow reaches and high campsite availability in wide reaches was thus accentuated by the sequence of flows between 1983 and 1985.

The response of a laminar boundary layer in supersonic flow to small amplitude progressive waves

NASA Technical Reports Server (NTRS)

Duck, Peter W.

1989-01-01

The effect of a small amplitude progressive wave on the laminar boundary layer on a semi-infinite flat plate, due to a uniform supersonic freestream flow, is considered. The perturbation to the flow divides into two streamwise zones. In the first, relatively close to the leading edge of the plate, on a transverse scale comparable to the boundary layer thickness, the perturbation flow is described by a form of the unsteady linearized compressible boundary layer equations. In the freestream, this component of flow is governed by the wave equation, the solution of which provides the outer velocity conditions for the boundary layer. This system is solved numerically, and also the asymptotic structure in the far downstream limit is studied. This reveals a breakdown and a subsequent second streamwise zone, where the flow disturbance is predominantly inviscid. The two zones are shown to match in a proper asymptotic sense.

Methodology for CFD Design Analysis of National Launch System Nozzle Manifold

NASA Technical Reports Server (NTRS)

Haire, Scot L.

1993-01-01

The current design environment dictates that high technology CFD (Computational Fluid Dynamics) analysis produce quality results in a timely manner if it is to be integrated into the design process. The design methodology outlined describes the CFD analysis of an NLS (National Launch System) nozzle film cooling manifold. The objective of the analysis was to obtain a qualitative estimate for the flow distribution within the manifold. A complex, 3D, multiple zone, structured grid was generated from a 3D CAD file of the geometry. A Euler solution was computed with a fully implicit compressible flow solver. Post processing consisted of full 3D color graphics and mass averaged performance. The result was a qualitative CFD solution that provided the design team with relevant information concerning the flow distribution in and performance characteristics of the film cooling manifold within an effective time frame. Also, this design methodology was the foundation for a quick turnaround CFD analysis of the next iteration in the manifold design.

DEAD ZONE IN THE POLAR-CAP ACCELERATOR OF PULSARS

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

Chen, Alexander Y.; Beloborodov, Andrei M.

We study plasma flows above pulsar polar caps using time-dependent simulations of plasma particles in the self-consistent electric field. The flow behavior is controlled by the dimensionless parameter {alpha} = j/c{rho}{sub GJ}, where j is the electric current density and {rho}{sub GJ} is the Goldreich-Julian charge density. The region of the polar cap where 0 < {alpha} < 1 is a {sup d}ead zone{sup -}in this zone, particle acceleration is inefficient and pair creation is not expected even for young, rapidly rotating pulsars. Pulsars with polar caps near the rotation axis are predicted to have a hollow-cone structure of radiomore » emission, as the dead zone occupies the central part of the polar cap. Our results apply to charge-separated flows of electrons (j < 0) or ions (j > 0). In the latter case, we consider the possibility of a mixed flow consisting of different ion species, and observe the development of two-stream instability. The dead zone at the polar cap is essential for the development of an outer gap near the null surface {rho}{sub GJ} = 0.« less

Effect of Pin Tool Shape on Metal Flow During Friction Stir Welding

NASA Technical Reports Server (NTRS)

McClure, J. C.; Coronado, E.; Aloor, S.; Nowak, B.; Murr, L. M.; Nunes, Arthur C., Jr.; Munafo, Paul M. (Technical Monitor)

2002-01-01

It has been shown that metal moves behind the rotating Friction Stir Pin Tool in two separate currents or streams. One current, mostly on the advancing side, enters a zone of material that rotates with the pin tool for one or more revolutions and eventually is abandoned behind the pin tool in crescent-shaped pieces. The other current, largely on the retreating side of the pin tool is moved by a wiping process to the back of the pin tool and fills in between the pieces of the rotational zone that have been shed by the rotational zone. This process was studied by using a faying surface copper trace to clarify the metal flow. Welds were made with pin tools having various thread pitches. Decreasing the thread pitch causes the large scale top-to-bottorn flow to break up into multiple vortices along the pin and an unthreaded pin tool provides insufficient vertical motion for there to be a stable rotational zone and flow of material via the rotational zone is not possible leading to porosity on the advancing side of the weld.

The Model Analysis of Inclusion Moving in the Swirl Flow Zone Sourcing from the Inner-Swirl-Type Turbulence Controller in Tundish

NASA Astrophysics Data System (ADS)

Jin, Yan; Ye, Chen; Luo, Xiao; Yuan, Hui; Cheng, Changgui

2017-05-01

In order to improve the inclusion removal property of the tundish, the mathematic model for simulation of the flow field sourced from inner-swirl-type turbulence controller (ISTTC) was developed, in which there were six blades arranged with an eccentric angle (θ) counterclockwise. Based on the mathematical and water model, the effect of inclusion removal in the swirling flow field formed by ISTTC was analyzed. It was found that ISTTC had got the better effect of inhibiting turbulence in tundish than traditional turbulence inhibitor (TI). As the blades eccentric angle (θ) of ISTTC increasing, the intensity of swirling flow above it increased. The maximum rotate speed of fluid in swirling flow band driven by ISTTC (θ=45°) was equal to 25 rmp. Based on the force analysis of inclusion in swirling flow sourced from ISTTC, the removal effect of medium size inclusion by ISTTC was attributed to the centripetal force (Fct) of swirling flow, but removal effect of ISTTC to small size inclusion was more depend on its better turbulence depression behavior.

Finite Element Method Analysis of An Out Flow With Free Surface In Transition Zones

NASA Astrophysics Data System (ADS)

Saoula, R. Iddir S.; Mokhtar, K. Ait

The object of this work is to present this part of the fluid mechanics that relates to out-flows of the fluid to big speeds in transitions. Results usually gotten by the classic processes can only have a qualitative aspect. The method fluently used for the count of these out-flows to big speeds is the one of characteristics, this approach remains interesting so much that doesn't appear within the out-flow of intersections of shock waves, as well as of reflections of these. In the simple geometry case, the method of finite differences satisfying result, But when the complexity of this geometry imposes itself, it is the method of finite elements that is proposed to solve this type of prob- lem, in particular for problems Trans critic. The goal of our work is to analyse free surface flows in channels no prismatic has oblong transverse section in zone of tran- sition. (Convergent, divergent). The basic mathematical model of this study is Saint Venant derivatives partial equations. To solve these equations we use the finite ele- ment method, the element of reference is the triangular element with 6 nodes which are quadratic in speed and linear in height (pressure). Our results and their obtains by others are very close to experimental results.

Preliminary control system design and analysis for the Space Station Furnace Facility thermal control system

NASA Technical Reports Server (NTRS)

Jackson, M. E.

1995-01-01

This report presents the Space Station Furnace Facility (SSFF) thermal control system (TCS) preliminary control system design and analysis. The SSFF provides the necessary core systems to operate various materials processing furnaces. The TCS is defined as one of the core systems, and its function is to collect excess heat from furnaces and to provide precise cold temperature control of components and of certain furnace zones. Physical interconnection of parallel thermal control subsystems through a common pump implies the description of the TCS by coupled nonlinear differential equations in pressure and flow. This report formulates the system equations and develops the controllers that cause the interconnected subsystems to satisfy flow rate tracking requirements. Extensive digital simulation results are presented to show the flow rate tracking performance.

An investigation into the mechanism for enhanced mechanical properties in friction stir welded AA2024-T3 joints coated with cold spraying

NASA Astrophysics Data System (ADS)

Li, N.; Li, W. Y.; Yang, X. W.; Feng, Y.; Vairis, A.

2018-05-01

Using cold spraying (CS), a surface layer with a modified microstructure and enhanced mechanical properties was formed on a 3.2 mm thick friction stir welded (FSWed) AA2024-T3 joint. The combined effect of "shot peening effect (SPE)" and "heat flow effect (HFE)" during CS were used to enhance joint mechanical properties. The microstructure evolution of the FSWed AA2024-T3 joints in the surface layer following CS coatings and their effect on mechanical properties were systematically characterized with electron back-scattered diffraction, transmission electron microscopy, differential scanning calorimetry and mechanical tests. Based on these experiments, a grain refinement, finer and more S phases, and improved amount of Guinier-Preston-Bagaryatsky (GPB) zones produced by CS treatments are proposed. The deposition of aluminum coating on the joint, lead to hardness recovery in the stir zone and the development of two low hardness zones as the density of GPB increased. The tensile properties of FSWed AA2024-T3 joints improved with the application of the aluminum coatings. Experiments and analysis of the enhanced mechanical properties mechanism indicate that SPE with a high plastic deformation and HFE with an intensive heat flow are necessary for the production of refined grains and increased numbers of GPB zones.

Effects of nose bluntness and shock-shock interactions on blunt bodies in viscous hypersonic flows

NASA Technical Reports Server (NTRS)

Singh, D. J.; Tiwari, S. N.

1990-01-01

A numerical study was conducted to investigate the effects of blunt leading edges on the viscous flow field around a hypersonic vehicle such as the proposed National Aero-Space Plane. Attention is focused on two specific regions of the flow field. In the first region, effects of nose bluntness on the forebody flow field are investigated. The second region of the flow considered is around the leading edges of the scramjet inlet. In this region, the interaction of the forebody shock with the shock produced by the blunt leading edges of the inlet compression surfaces is analyzed. Analysis of these flow regions is required to accurately predict the overall flow field as well as to get necessary information on localized zones of high pressure and intense heating. The results for the forebody flow field are discussed first, followed by the results for the shock interaction in the inlet leading edge region.

Computational fluid dynamics of airfoils and wings

NASA Technical Reports Server (NTRS)

Garabedian, P.; Mcfadden, G.

1982-01-01

It is pointed out that transonic flow is one of the fields where computational fluid dynamics turns out to be most effective. Codes for the design and analysis of supercritical airfoils and wings have become standard tools of the aircraft industry. The present investigation is concerned with mathematical models and theorems which account for some of the progress that has been made. The most successful aerodynamics codes are those for the analysis of flow at off-design conditions where weak shock waves appear. A major breakthrough was achieved by Murman and Cole (1971), who conceived of a retarded difference scheme which incorporates artificial viscosity to capture shocks in the supersonic zone. This concept has been used to develop codes for the analysis of transonic flow past a swept wing. Attention is given to the trailing edge and the boundary layer, entropy inequalities and wave drag, shockless airfoils, and the inverse swept wing code.

Computational fluid dynamics assessment: Volume 2, Isothermal simulations of the METC bench-scale coal-water slurry combustor: Final report

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

Celik, I.; Chattree, M.

1988-09-01

The isothermal turbulent, swirling flow inside the METC pressurized bench-scale combustor has been simulated using ISOPCGC-2. The effects of the swirl numbers, the momentum ratio of the primary to secondary streams, the annular wall thickness, and the quarl angle on the flow and mixing patterns have been investigated. The results that with the present configuration of the combustor, an annular recirculation zone is present up to secondary swirl number of four. A central (on axis) recirculation zone can be obtained by increasing the momentum of the secondary stream by decreasing the annular area at the reactor inlet. The mixing ofmore » the primary (fuel carrier) air with the secondary air improves only slightly due to swirl unless a central recirculation zone is present. Good mixing is achieved in the quarl region when a central recirculation zone is present. A preliminary investigation of the influence of placing flow regulators inside the the combustor shows that they influence the flow field significantly and that there is a potential of obtaining optimum flow conditions using these flow regulators. 58 refs., 47 figs., 12 tabs.« less

Thermal structure and geodynamics of subduction zones

NASA Astrophysics Data System (ADS)

Wada, Ikuko

The thermal structure of subduction zones depends on the age-controlled thermal state of the subducting slab and mantle wedge flow. Observations indicate that the shallow part of the forearc mantle wedge is stagnant and the slab-mantle interface is weakened. In this dissertation, the role of the interface strength in controlling mantle wedge flow, thermal structure, and a wide range of subduction zone processes is investigated through two-dimensional finite-element modelling and a global synthesis of geological and geophysical observations. The model reveals that the strong temperature-dependence of the mantle strength always results in full slab-mantle decoupling along the weakened part of the interface and hence complete stagnation of the overlying mantle. The interface immediately downdip of the zone of decoupling is fully coupled, and the overlying mantle is driven to flow at a rate compatible with the subduction rate. The sharpness of the transition from decoupling to coupling depends on the rheology assumed and increases with the nonlinearity of the flow system. This bimodal behaviour of the wedge flow gives rise to a strong thermal contrast between the cold stagnant and hot flowing parts of the mantle wedge. The maximum depth of decoupling (MDD) thus dictates the thermal regime of the forearc. Observed surface heat flow patterns and petrologically and geochemically estimated mantle wedge temperatures beneath the volcanic arc require an MDD of 70--80 km in most, if not all, subduction zones regardless of their thermal regime of the slab. The common MDD of 70--80 km explains the observed systematic variations of the petrologic, seismological, and volcanic processes with the thermal state of the slab and thus explains the rich diversity of subduction zones in a unified fashion. Models for warm-slab subduction zones such as Cascadia and Nankai predict shallow dehydration of the slab beneath the cold stagnant part of the mantle wedge, which provides ample fluid for mantle wedge serpentinization in the forearc but little fluid for melt generation beneath the arc. In contrast, models for colder-slab subduction zones such as NE Japan and Kamchatka predict deeper dehydration, which provides greater fluid supply for melt generation beneath the arc and allows deeper occurrence of intraslab earthquakes but less fluid for forearc mantle wedge serpentinization. The common MDD also explains the intriguing uniform configuration of subduction zones, that is, the volcanic arc always tends to be situated where the slab is at about 100 km depth. The sudden onset of mantle wedge flow downdip of the common MDD overshadows the thermal effect of the slab, and the resultant thermal field and slab dehydration control the location of the volcanic arc. The recognition of the fundamental importance of the MDD has important implications to the study of geodynamics and earthquake hazard in subduction zones.

Beyond the classic thermoneutral zone

PubMed Central

Kingma, Boris RM; Frijns, Arjan JH; Schellen, Lisje; van Marken Lichtenbelt, Wouter D

2014-01-01

The thermoneutral zone is defined as the range of ambient temperatures where the body can maintain its core temperature solely through regulating dry heat loss, i.e., skin blood flow. A living body can only maintain its core temperature when heat production and heat loss are balanced. That means that heat transport from body core to skin must equal heat transport from skin to the environment. This study focuses on what combinations of core and skin temperature satisfy the biophysical requirements of being in the thermoneutral zone for humans. Moreover, consequences are considered of changes in insulation and adding restrictions such as thermal comfort (i.e. driver for thermal behavior). A biophysical model was developed that calculates heat transport within a body, taking into account metabolic heat production, tissue insulation, and heat distribution by blood flow and equates that to heat loss to the environment, considering skin temperature, ambient temperature and other physical parameters. The biophysical analysis shows that the steady-state ambient temperature range associated with the thermoneutral zone does not guarantee that the body is in thermal balance at basal metabolic rate per se. Instead, depending on the combination of core temperature, mean skin temperature and ambient temperature, the body may require significant increases in heat production or heat loss to maintain stable core temperature. Therefore, the definition of the thermoneutral zone might need to be reformulated. Furthermore, after adding restrictions on skin temperature for thermal comfort, the ambient temperature range associated with thermal comfort is smaller than the thermoneutral zone. This, assuming animals seek thermal comfort, suggests that thermal behavior may be initiated already before the boundaries of the thermoneutral zone are reached. PMID:27583296

Beyond the classic thermoneutral zone: Including thermal comfort.

PubMed

Kingma, Boris Rm; Frijns, Arjan Jh; Schellen, Lisje; van Marken Lichtenbelt, Wouter D

2014-01-01

The thermoneutral zone is defined as the range of ambient temperatures where the body can maintain its core temperature solely through regulating dry heat loss, i.e., skin blood flow. A living body can only maintain its core temperature when heat production and heat loss are balanced. That means that heat transport from body core to skin must equal heat transport from skin to the environment. This study focuses on what combinations of core and skin temperature satisfy the biophysical requirements of being in the thermoneutral zone for humans. Moreover, consequences are considered of changes in insulation and adding restrictions such as thermal comfort (i.e. driver for thermal behavior). A biophysical model was developed that calculates heat transport within a body, taking into account metabolic heat production, tissue insulation, and heat distribution by blood flow and equates that to heat loss to the environment, considering skin temperature, ambient temperature and other physical parameters. The biophysical analysis shows that the steady-state ambient temperature range associated with the thermoneutral zone does not guarantee that the body is in thermal balance at basal metabolic rate per se. Instead, depending on the combination of core temperature, mean skin temperature and ambient temperature, the body may require significant increases in heat production or heat loss to maintain stable core temperature. Therefore, the definition of the thermoneutral zone might need to be reformulated. Furthermore, after adding restrictions on skin temperature for thermal comfort, the ambient temperature range associated with thermal comfort is smaller than the thermoneutral zone. This, assuming animals seek thermal comfort, suggests that thermal behavior may be initiated already before the boundaries of the thermoneutral zone are reached.

Simulation of dispersion in layered coastal aquifer systems

USGS Publications Warehouse

Reilly, T.E.

1990-01-01

A density-dependent solute-transport formulation is used to examine ground-water flow in layered coastal aquifers. The numerical experiments indicate that although the transition zone may be thought of as an impermeable 'sharp' interface with freshwater flow parallel to the transition zone in homogeneous aquifers, this is not the case for layered systems. Freshwater can discharge through the transition zone in the confining units. Further, for the best simulation of layered coastal aquifer systems, either a flow-direction-dependent dispersion formulation is required, or the dispersivities must change spatially to reflect the tight thin confining unit. ?? 1990.

Free-Flow Zone Electrophoresis of Peptides and Proteins in PDMS Microchip for Narrow pI Range Sample Prefractionation Coupled with Mass Spectrometry

PubMed Central

Song, Yong-Ak; Chan, Michael; Celio, Chris; Tannenbaum, Steven R.; Wishnok, John S.; Han, Jongyoon

2010-01-01

In this paper, we are evaluating the strategy of sorting peptides / proteins based on the charge to mass without resorting to ampholytes and / or isoelectric focusing, using a single- and two-step free-flow zone electrophoresis. We developed a simple fabrication method to create a salt bridge for free-flow zone electrophoresis in PDMS chips by surface printing a hydrophobic layer on a glass substrate. Since the surface-printed hydrophobic layer prevents plasma bonding between the PDMS chip and the substrate, an electrical junction gap can be created for free-flow zone electrophoresis. With this device, we demonstrated a separation of positive and negative peptides and proteins at a given pH in standard buffer systems, and validated the sorting result with LC/MS. Furthermore, we coupled two sorting steps via off-chip titration, and isolated peptides within specific pI ranges from sample mixtures, where the pI range was simply set by the pH values of the buffer solutions. This free-flow zone electrophoresis sorting device, with its simplicity of fabrication, and a sorting resolution of 0.5 pH unit, can potentially be a high-throughput sample fractionation tool for targeted proteomics using LC/MS. PMID:20163146

Computational analysis of hybrid Norwood circulation with distal aortic arch obstruction and reverse Blalock-Taussig shunt.

PubMed

Ceballos, Andres; Argueta-Morales, I Ricardo; Divo, Eduardo; Osorio, Ruben; Caldarone, Christopher A; Kassab, Alain J; Decampli, William M

2012-11-01

The hemodynamics characteristics of the hybrid Norwood (HN) procedure differ from those of the conventional Norwood and are not fully understood. We present a multiscale model of HN circulation to understand local hemodynamics and effects of aortic arch stenosis and a reverse Blalock-Taussig shunt (RBTS) on coronary and carotid perfusion. Four 3-dimensional models of four HN anatomic variants were developed, with and without 90% distal preductal arch stenosis and with and without a 4-mm RBTS. A lumped parameter model of the circulation was coupled to a local 3-dimensional computational fluid dynamics model. Outputs from the lumped parameter model provided waveform boundary conditions for the computational fluid dynamics model. A 90% distal arch stenosis reduced pressure and net flow-rate through the coronary and carotid arteries by 30%. Addition of the RBTS completely restored pressure and flow rate to baseline in these vessels. Zones of flow stagnation, flow reversal, and recirculation in the presence of stenosis were rendered more orderly by addition of the RBTS. In the absence of stenosis, presence of the shunt resulted in extensive zones of disturbed flow within the RBTS and arch. We found that a 4-mm × 21-mm RBTS completely compensated for the effects of a 90% discrete stenosis of the distal aortic arch in the HN. Placed preventatively, the RBTS and arch displayed zones with thrombogenic potential showing recirculation and stagnation that persist for a substantial fraction of the cardiac cycle, indicating that anticoagulation should be considered with a prophylactic RBTS. Copyright © 2012 The Society of Thoracic Surgeons. Published by Elsevier Inc. All rights reserved.

Tilt Current Meter Field Validation in the Surf Zone

NASA Astrophysics Data System (ADS)

Anarde, K.; Myres, H.; Figlus, J.

2016-12-01

Tilt current meters (TCMs) are a low-cost way of measuring current velocities in coastal waters. They consist of a slightly buoyant floater, tilt sensor assembly, and internal logger tethered to a fixed base. TCMs measure the tilt of the sensor induced by the forces of the flowing water to infer local current velocity. They have been successfully deployed to measure unidirectional flows in rivers and slowly oscillating flows in tidally influenced bodies of water where the inertia of the instrument does not create a problem. Here we attempt to validate an array of TCMs for use in the surf zone where waves, wave bores, and alongshore currents dominate the hydrodynamics in relatively shallow water (0.3 - 2.0 m) with relatively high oscillatory frequencies. A series of test deployments using seven measuring pods outfitted with TCMs and pressure transducers were conducted in the surf zone off Galveston Island, Texas. Field experiments were supported by laboratory tests of the instrument assemblies in a moveable-bed wave flume. Instrument pod design was optimized over the series of tests to minimize issues caused by scouring, sedimentation, and overturning. The end design consists of a low-profile concrete base plate secured to the bed by sand stakes. Field measurements of tilt and bearing were calibrated against co-located acoustic Doppler velocimeter (ADV) and wave-current profiler (ADCP) measurements as well as laboratory-supplied calibration curves. While optimization of the setup is ongoing, the initial field studies show good correlation between instrument pairs. If successfully validated, the TCMs will be used as part of an instrument array designed to measure overland flow dynamics during extreme storms. Other potential uses include detailed analysis of spatial and temporal gradients in nearshore hydrodynamics such as the complex flow scenarios through tidal inlets and around barrier islands.

Analytics of crystal growth in space

NASA Technical Reports Server (NTRS)

Chang, C. E.; Lefever, R. A.; Wilcox, W. R.

1975-01-01

The variation of radial impurity distribution induced by surface tension driven flow increases as the zone length decreases in silicon crystals grown by floating zone melting. In combined buoyancy driven and surface tension driven convection at the gravity of earth, the buoyancy contribution becomes relatively smaller as the zone diameter decreases and eventually convection is dominated by the surface tension driven flow (in the case of silicon, for zones of less than about 0.8 cm in diameter). Preliminary calculations for sapphire suggest the presence of an oscillatory surface tension driven convection as a result of an unstable melt surface temperature that results when the zone is heated by a radiation heater.

Rip currents and alongshore flows in single channels dredged in the surf zone

NASA Astrophysics Data System (ADS)

Moulton, Melissa; Elgar, Steve; Raubenheimer, Britt; Warner, John C.; Kumar, Nirnimesh

2017-05-01

To investigate the dynamics of flows near nonuniform bathymetry, single channels (on average 30 m wide and 1.5 m deep) were dredged across the surf zone at five different times, and the subsequent evolution of currents and morphology was observed for a range of wave and tidal conditions. In addition, circulation was simulated with the numerical modeling system COAWST, initialized with the observed incident waves and channel bathymetry, and with an extended set of wave conditions and channel geometries. The simulated flows are consistent with alongshore flows and rip-current circulation patterns observed in the surf zone. Near the offshore-directed flows that develop in the channel, the dominant terms in modeled momentum balances are wave-breaking accelerations, pressure gradients, advection, and the vortex force. The balances vary spatially, and are sensitive to wave conditions and the channel geometry. The observed and modeled maximum offshore-directed flow speeds are correlated with a parameter based on the alongshore gradient in breaking-wave-driven-setup across the nonuniform bathymetry (a function of wave height and angle, water depths in the channel and on the sandbar, and a breaking threshold) and the breaking-wave-driven alongshore flow speed. The offshore-directed flow speed increases with dissipation on the bar and reaches a maximum (when the surf zone is saturated) set by the vertical scale of the bathymetric variability.

Rip currents and alongshore flows in single channels dredged in the surf zone

USGS Publications Warehouse

Moulton, Melissa; Elgar, Steve; Raubenheimer, Britt; Warner, John C.; Kumar, Nirnimesh

2017-01-01

To investigate the dynamics of flows near nonuniform bathymetry, single channels (on average 30 m wide and 1.5 m deep) were dredged across the surf zone at five different times, and the subsequent evolution of currents and morphology was observed for a range of wave and tidal conditions. In addition, circulation was simulated with the numerical modeling system COAWST, initialized with the observed incident waves and channel bathymetry, and with an extended set of wave conditions and channel geometries. The simulated flows are consistent with alongshore flows and rip-current circulation patterns observed in the surf zone. Near the offshore-directed flows that develop in the channel, the dominant terms in modeled momentum balances are wave-breaking accelerations, pressure gradients, advection, and the vortex force. The balances vary spatially, and are sensitive to wave conditions and the channel geometry. The observed and modeled maximum offshore-directed flow speeds are correlated with a parameter based on the alongshore gradient in breaking-wave-driven-setup across the nonuniform bathymetry (a function of wave height and angle, water depths in the channel and on the sandbar, and a breaking threshold) and the breaking-wave-driven alongshore flow speed. The offshore-directed flow speed increases with dissipation on the bar and reaches a maximum (when the surf zone is saturated) set by the vertical scale of the bathymetric variability.

Electrically heated particulate filter with zoned exhaust flow control

DOEpatents

Gonze, Eugene V [Pinckney, MI

2012-06-26

A system includes a particulate matter (PM) filter that includes X zones. An electrical heater includes Y heater segments that are associated with respective ones of the X zones. The electrical heater is arranged upstream from and proximate with the PM filter. A valve assembly includes Z sections that are associated with respective ones of the X zones. A control module adjusts flow through each of the Z sections during regeneration of the PM filter via control of the valve assembly. X, Y and Z are integers.

Understanding the Hydromechanical Behavior of a Fault Zone From Transient Surface Tilt and Fluid Pressure Observations at Hourly Time Scales

NASA Astrophysics Data System (ADS)

Schuite, Jonathan; Longuevergne, Laurent; Bour, Olivier; Burbey, Thomas J.; Boudin, Frédérick; Lavenant, Nicolas; Davy, Philippe

2017-12-01

Flow through reservoirs such as fractured media is powered by head gradients which also generate measurable poroelastic deformation of the rock body. The combined analysis of surface deformation and subsurface pressure provides valuable insights of a reservoir's structure and hydromechanical properties, which are of interest for deep-seated CO2 or nuclear waste storage for instance. Among all surveying tools, surface tiltmeters offer the possibility to grasp hydraulically induced deformations over a broad range of time scales with a remarkable precision. Here we investigate the information content of transient surface tilt generated by the pressurization a kilometer scale subvertical fault zone. Our approach involves the combination of field data and results of a fully coupled poromechanical model. The signature of pressure changes in the fault zone due to pumping cycles is clearly recognizable in field tilt data and we aim to explain the peculiar features that appear in (1) tilt time series alone from a set of four instruments and 2) the ratio of tilt over pressure. We evidence that the shape of tilt measurements on both sides of a fault zone is sensitive to its diffusivity and its elastic modulus. The ratio of tilt over pressure predominantly encompasses information about the system's dynamic behavior and extent of the fault zone and allows separating contributions of flow in the different compartments. Hence, tiltmeters are well suited to characterize hydromechanical processes associated with fault zone hydrogeology at short time scales, where spaceborne surveying methods fail to recognize any deformation signal.

Size matters: The effects of displacement magnitude on the fluid flow properties of faults in poorly lithified sediments

NASA Astrophysics Data System (ADS)

Loveless, S. E.; Bense, V.; Turner, J.

2011-12-01

Many aquifers worldwide occur in poorly lithified sediments, often in regions that experience active tectonic deformation. Faulting of these sediments introduces heterogeneities that may affect aquifer porosity and permeability, and consequently subsurface fluid flow and groundwater storage. The specific hydrogeological effects of faults depend upon the fault architecture and deformation mechanisms. These are controlled by factors such as rheology, stratigraphy and burial depth. Here, we analyse fault permeability in poorly lithified sediments as a function of fault displacement. We have carried out detailed outcrop studies of minor normal faults at five study sites within the rapidly extending Corinth rift, Central Greece. Gravel conglomerates of giant Gilbert delta facies form productive but localised shallow aquifers within the region. Exposures reveal dense (average 20 faults per 100 m) networks of minor (0.1 to 50 m displacement) normal faults within the uplifted sequences, proximal to many of the crustal-scale normal faults. Analysis of 42 faults shows that fault zones are primarily composed of smeared beds that can either retain their definition or mix with surrounding sediment. Lenses or blocks of sediment are common in fault zones that cut beds with contrasting rheology, and a few faults have a clay core and/or damage zone. Fault thickness increases at a rate of about 0.4 m per 10 m increase in displacement. Comparison of sediment micro-structures from the field, hand samples and thin sections show grain-scale sediment mixing, fracturing of clasts, and in some cases cementation, within fault zones. In faults with displacements >12 m we also find a number of roughly parallel, highly indurated shear planes, up to 20 mm in thickness, composed of highly fragmented clasts and a fine grained matrix. Image analysis of thin sections from hand samples collected in the field was used to quantify the porosity of fault zones and adjacent undeformed sediment. These data show a reduction in average porosity from 21% (± 4) in undisturbed sediments to 14% (± 8) within fault zones. We find that fault zone porosity decreases by approximately 5% per 1 m displacement (up to 2 m displacement), as sediments undergo greater micro-scale deformation. Porosity within the shear planes of larger displacement faults (> 12 m) is significantly less than 5%. In summary, with an increase in fault displacement there is an increase in fault thickness and decrease in fault zone porosity, in addition to the occurrence of extremely low porosity shear planes. Consequently, the impact of faults in poorly lithified sediment on fluid flow is, to a large degree, dependent upon the magnitude of fault displacement.

Are the Columbia River Basalts, Columbia Plateau, Idaho, Oregon, and Washington, USA, a viable geothermal target? A preliminary analysis

USGS Publications Warehouse

Burns, Erick R.; Williams, Colin F.; Tolan, Terry; Kaven, Joern Ole

2016-01-01

The successful development of a geothermal electric power generation facility relies on (1) the identification of sufficiently high temperatures at an economically viable depth and (2) the existence of or potential to create and maintain a permeable zone (permeability >10-14 m2) of sufficient size to allow efficient long-term extraction of heat from the reservoir host rock. If both occur at depth under the Columbia Plateau, development of geothermal resources there has the potential to expand both the magnitude and spatial extent of geothermal energy production. However, a number of scientific and technical issues must be resolved in order to evaluate the likelihood that the Columbia River Basalts, or deeper geologic units under the Columbia Plateau, are viable geothermal targets.Recent research has demonstrated that heat flow beneath the Columbia Plateau Regional Aquifer System may be higher than previously measured in relatively shallow (<600 m depth) wells, indicating that sufficient temperatures for electricity generation occur at depths 5 km. The remaining consideration is evaluating the likelihood that naturally high permeability exists, or that it is possible to replicate the high average permeability (approximately 10-14 to 10-12 m2) characteristic of natural hydrothermal reservoirs. From a hydraulic perspective, Columbia River Basalts are typically divided into dense, impermeable flow interiors and interflow zones comprising the top of one flow, the bottom of the overlying flow, and any sedimentary interbed. Interflow zones are highly variable in texture but, at depths <600 m, some of them form highly permeable regional aquifers with connectivity over many tens of kilometers. Below depths of ~600 m, permeability reduction occurs in many interflow zones, caused by the formation of low-temperature hydrothermal alteration minerals (corresponding to temperatures above ~35 °C). However, some high permeability (>10-14 m2) interflows are documented at depths up to ~1,400 m. If the elevated permeability in these zones persists to greater depths, they may provide natural permeability of sufficient magnitude to allow their exploitation as conventional geothermal reservoirs. Alternatively, if the permeability in these interflow zones is less than 10-14 m2 at depth, it may be possible to use hydraulic and thermal stimulation to enhance the permeability of both the interflow zones and the natural jointing within the low-permeability interior portions of individual basalt flows in order to develop Enhanced/Engineered Geothermal System (EGS) reservoirs. The key challenge for an improved Columbia Plateau geothermal assessment is acquiring and interpreting comprehensive field data that can provide quantitative constraints on the recovery of heat from the Columbia River Basalts at depths greater than those currently tested by deep boreholes.

Heat flow, morphology, pore fluids and hydrothermal circulation in a typical Mid-Atlantic Ridge flank near Oceanographer Fracture Zone

NASA Astrophysics Data System (ADS)

Le Gal, V.; Lucazeau, F.; Cannat, M.; Poort, J.; Monnin, C.; Battani, A.; Fontaine, F.; Goutorbe, B.; Rolandone, F.; Poitou, C.; Blanc-Valleron, M.-M.; Piedade, A.; Hipólito, A.

2018-01-01

Hydrothermal circulation affects heat and mass transfers in the oceanic lithosphere, not only at the ridge axis but also on their flanks, where the magnitude of this process has been related to sediment blanket and seamounts density. This was documented in several areas of the Pacific Ocean by heat flow measurements and pore water analysis. However, as the morphology of Atlantic and Indian ridge flanks is generally rougher than in the Pacific, these regions of slow and ultra-slow accretion may be affected by hydrothermal processes of different regimes. We carried out a survey of two regions on the eastern and western flanks of the Mid-Atlantic Ridge between Oceanographer and Hayes fracture zones. Two hundred and eight new heat flow measurements were obtained along six seismic profiles, on 5 to 14 Ma old seafloor. Thirty sediment cores (from which porewaters have been extracted) have been collected with a Kullenberg corer equipped with thermistors thus allowing simultaneous heat flow measurement. Most heat flow values are lower than those predicted by purely conductive cooling models, with some local variations and exceptions: heat flow values on the eastern flank of the study area are more variable than on the western flank, where they tend to increase westward as the sedimentary cover in the basins becomes thicker and more continuous. Heat flow is also higher, on average, on the northern sides of both the western and eastern field regions and includes values close to conductive predictions near the Oceanographer Fracture Zone. All the sediment porewaters have a chemical composition similar to that of bottom seawater (no anomaly linked to fluid circulation has been detected). Heat flow values and pore fluid compositions are consistent with fluid circulation in volcanic rocks below the sediment. The short distances between seamounts and short fluid pathways explain that fluids flowing in the basaltic aquifer below the sediment have remained cool and unaltered. Finally, relief at small-scale is calculated using variogram of bathymetry and compared for different regions affected by hydrothermal circulation.

Chemical constituents in groundwater from multiple zones in the eastern Snake River Plain aquifer, Idaho National Laboratory, Idaho, 2009-13

USGS Publications Warehouse

Bartholomay, Roy C.; Hopkins, Candice B.; Maimer, Neil V.

2015-01-01

Tritium concentrations in relation to basaltic flow units indicate the presence of wastewater influence in multiple basalt flow groups; however, tritium is most abundant in the South Late Matuyama flow group in the southern boundary wells. The concentrations of wastewater constituents in deep zones in wells Middle 2051, USGS 132, USGS 105, and USGS 103 support the concept of groundwater flow deepening in the southwestern corner of the INL, as indicated by the INL groundwater-flow model.

An analytical model for flow induced by a constant-head pumping in a leaky unconfined aquifer system with considering unsaturated flow

NASA Astrophysics Data System (ADS)

Lin, Ye-Chen; Li, Ming-Hsu; Yeh, Hund-Der

2017-09-01

A new mathematical model is developed to describe the flow in response to a constant-head pumping (or constant-head test, CHT) in a leaky unconfined aquifer system of infinite lateral extent with considering unsaturated flow. The model consists of an unsaturated zone on the top, an unconfined aquifer in the middle, and a second aquifer (aquitard) at the bottom. The unsaturated flow is described by Richard's equation, and the flows in unconfined aquifer and second layer are governed by the groundwater flow equation. The well partially penetrates the unconfined aquifer with a constant head in the well due to CHT. The governing equations of the model are linearized by the perturbation method and Gardner's exponential model is adopted to describe the soil retention curves. The solution of the model for drawdown distribution is obtained by applying the methods of Laplace transform and Weber transform. Then the solution for the wellbore flowrate is derived from the drawdown solution with Darcy's law. The issue of the equivalence of normalized drawdown predicted by the present solution for constant-head pumping and Tartakovsky and Neuman's (2007) solution for constant-rate pumping is discussed. On the basis of the wellbore flowrate solution, the results of the sensitivity analysis indicate that the wellbore flowrate is very sensitive to the changes in the radial hydraulic conductivity and the thickness of the saturated zone. Moreover, the results predicted from the present wellbore flowrate solution indicate that this new solution can reduce to Chang's et al. (2010a) solution for homogenous aquifers when the dimensionless unsaturated exponent approaches 100. The unsaturated zone can be considered as infinite extent in the vertical direction if the thickness ratio of the unsaturated zone to the unconfined aquifer is equal to or greater than one. As for the leakage effect, it can be ignored when the vertical hydraulic conductivity ratio (i.e., the vertical hydraulic conductivity of the lower layer over that of the unconfined aquifer) is smaller than 0.1. The present solution is compared with the numerical solution from FEMWATER for validation and the results indicate good match between these two solutions. Finally, the present solution is applied to a set of field drawdown data obtained from a CHT for the estimation of hydrogeologic parameters.

A hydrometric and geochemical approach to test the transmissivity feedback hypothesis during snowmelt

USGS Publications Warehouse

Kendall, K.A.; Shanley, J.B.; McDonnell, Jeffery J.

1999-01-01

To test the transmissivity feedback hypothesis of runoff generation, surface and subsurface waters were monitored and sampled during the 1996 snowmelt at various topographic positions in a 41 ha forested headwater catchment at Sleepers River, Vermont. Two conditions that promote transmissivity feedback existed in the catchment during the melt period. First, saturated hydraulic conductivity increased toward land surface, from a geometric mean of 3.6 mm h-1 in glacial till to 25.6 mm h-1 in deep soil to 54.0 mm h-1 in shallow soil. Second, groundwater levels rose to within 0.3 m of land surface at all riparian sites and most hillslope sites at peak melt. The importance of transmissivity feedback to streamflow generation was tested at the catchment scale by examination of physical and chemical patterns of groundwater in near-stream (discharge) and hillslope (recharge/lateral flow) zones, and within a geomorphic hollow (convergent flow). The presence of transmissivity feedback was supported by the abrupt increase in streamflow as the water table rose into the surficial, transmissive zone; a flattening of the groundwater level vs. streamflow curve occurred at most sites. This relation had a clockwise hysteresis (higher groundwater level for given discharge on rising limb than at same discharge on falling limb) at riparian sites, suggesting that the riparian zone was the dominant source area during the rising limb of the melt hydrograph. Hysteresis was counterclockwise at hillslope sites, suggesting that hillslope drainage controlled the snowmelt recession. End member mixing analysis using Ca, Mg, Na, dissolved organic carbon (DOC), and Si showed that stream chemistry could be explained as a two-component mixture of groundwater high in base cations and an O-horizon/overland flow water high in DOC. The dominance of shallow flow paths during events was indicated by the high positive correlation of DOC with streamflow (r2 = 0.82). Despite the occurrence of transmissivity feedback, hillslope till and soil water were ruled out as end members primarily because their distinctive high-Si composition had little or no effect on streamwater composition. Till water from the geomorphic hollow had a chemistry very close to streamwater base flow, and may represent the base flow end member better than the more concentrated riparian groundwater. During snowmelt, streamwater composition shifted as this base flow was diluted - not by shallow groundwater from the hillslope, but rather by a more surficial O-horizon/overland flow water.Surface and subsurface waters were analyzed to test the transmissivity feedback of runoff generation during the 1996 snowmelt in a catchment at Sleepers River, Vermont. The importance of transmissivity feedback to stream flow generation was tested by examination of physical and chemical patterns of groundwater in near-stream and hillslope zones within a geomorphic hollow. End member mixing analysis of Ca, Mg, Na, dissolved organic carbon (DOC), and Si showed that stream chemistry could be explained as a two-component mixture of groundwater high in base cations and an O-horizon/overland flow water high in DOC. The dominance of shallow water paths during the events was indicated by the high positive correlation of DOC with streamflow (r2 = 0.82).

Stratigraphy, structure, and some petrographic features of Tertiary volcanic rocks in the USW G-2 drill hole, Yucca Mountain, Nye County, Nevada

USGS Publications Warehouse

Maldonado, Florian; Koether, S.L.

1983-01-01

A continuously cored drill hole designated as USW G-2, located at Yucca Mountain in southwestern Nevada, penetrated 1830.6 m of Tertiary volcanic strata composed of abundant silicic ash-flow tuffs, minor lava and flow breccias, and subordinate volcaniclastic rocks. The volcanic strata penetrated are comprised of the following in descending order: Paintbrush Tuff (Tiva Canyon Member, Yucca Mountain Member, bedded tuff, Pah Canyon Member, and Topopah Spring Member), tuffaceous beds of Calico Hills, Crater Flat Tuff (Prow Pass Member, Bullfrog Member, and Tram unit), lava and flow breccia (rhyodacitic), tuff of Lithic Ridge, bedded and ash-flow tuff, lava and flow breccia (rhyolitic, quartz latitic, and dacitic), bedded tuff, conglomerate and ash-flow tuff, and older tuffs of USW G-2. Comparison of unit thicknesses at USW G-2 to unit thicknesses at previously drilled holes at Yucca Mountain indicate the following: (1) thickening of the Paintbrush Tuff members and tuffaceous beds of Calico Hills toward the northern part of Yucca Mountain; (2) thickening of the Prow Pass Member but thinning of the Bullfrog Member and Tram unit; (3) thinning of the tuff of Lithic Ridge; (4) presence of approximately 280 m of lava and flow breccia not previously penetrated by any drill hole; and (5) presence of an ash-flow tuff unit at the bottom of the drill hole not previously intersected, apparently the oldest unit penetrated at Yucca Mountain to date. Petrographic features of some of the units include: (1) decrease in quartz and K-feldspar and increases in biotite and plagioclase with depth in the tuffaceous beds of Calico Hills; (2) an increase in quartz phenocrysts from the top to the bottom members of the Crater Flat Tuff; (3) a low quartz content in the tuff of Lithic Ridge, suggesting tapping of the magma chamber at quartz-poor levels; (4) a change in zeolitic alteration from heulandite to clinoptilolite to mordenite with increasing depth; (5) lavas characterized by a rhyolitic top and dacitic base, suggesting reverse compositional zoning; and (6) presence of hydrothermal mineralization in the lavas that could be related to an intrusive under Yucca Mountain or to volcanism associated with the Timber Mountain-Claim Canyon caldera complex. A fracture analysis of the core resulted n tabulation of 7,848 fractures, predominately open and high angle. The fractures were filled or coated with material in various combinations and include the following in decreasing abundance: CaCo3, iron oxides and hydroxides, SiO2, manganese oxides and hydroxides, clays and zeolites. An increase in the intensity of fracturing can be correlated with the following: (1) densely welded zones, (2) lithophysal zones, (3) vitrophyre, (4) silicified zones, (5) fault zones, and (6) cooling joints. Numerous fault zones were penetrated by the drill hole, predominately in the lithophysal zone of the Topopah Spring Member and below the tuffaceous beds of Calico Hills. The faults are predominately high angle with both a vertical and lateral component. Three major faults were penetrated, two of which intersect the ground surface, with displacements of at least 20 m and possibly as much as 52 m. The faults and some fractures are probably related to the regional doming of the area associated with the volcanism-tectonism of the Timber Mountain-Claim Canyon caldera complex, and to Basin and Range tectonism.

Structure of hydrogen-rich transverse jets in a vitiated turbulent flow

DOE PAGES

Lyra, Sgouria; Wilde, Benjamin; Kolla, Hemanth; ...

2014-11-24

Our paper reports the results of a joint experimental and numerical study of the flow characteristics and flame structure of a hydrogen rich jet injected normal to a turbulent, vitiated crossflow of lean methane combustion products. Simultaneous high-speed stereoscopic PIV and OH PLIF measurements were obtained and analyzed alongside three-dimensional direct numerical simulations of inert and reacting JICF with detailed H2/COH2/CO chemistry. Both the experiment and the simulation reveal that, contrary to most previous studies of reacting JICF stabilized in low-to-moderate temperature air crossflow, the present conditions lead to a burner-attached flame that initiates uniformly around the burner edge. Significantmore » asymmetry is observed, however, between the reaction zones located on the windward and leeward sides of the jet, due to the substantially different scalar dissipation rates. The windward reaction zone is much thinner in the near field, while also exhibiting significantly higher local and global heat release than the much broader reaction zone found on the leeward side of the jet. The unsteady dynamics of the windward shear layer, which largely control the important jet/crossflow mixing processes in that region, are explored in order to elucidate the important flow stability implications arising in the inert and reacting JICF. The paper concludes with an analysis of the ignition, flame characteristics, and global structure of the burner-attached flame. FurthermoreChemical explosive mode analysis (CEMA) shows that the entire windward shear layer, and a large region on the leeward side of the jet, are highly explosive prior to ignition and are dominated by non-premixed flame structures after ignition. The predominantly mixing limited nature of the flow after ignition is examined by computing the Takeno flame index, which shows that ~70% of the heat release occurs in non-premixed regions.« less

Local Helioseismology of Emerging Active Regions: A Case Study

NASA Astrophysics Data System (ADS)

Kosovichev, Alexander G.; Zhao, Junwei; Ilonidis, Stathis

2018-04-01

Local helioseismology provides a unique opportunity to investigate the subsurface structure and dynamics of active regions and their effect on the large-scale flows and global circulation of the Sun. We use measurements of plasma flows in the upper convection zone, provided by the Time-Distance Helioseismology Pipeline developed for analysis of solar oscillation data obtained by Helioseismic and Magnetic Imager (HMI) on Solar Dynamics Observatory (SDO), to investigate the subsurface dynamics of emerging active region NOAA 11726. The active region emergence was detected in deep layers of the convection zone about 12 hours before the first bipolar magnetic structure appeared on the surface, and 2 days before the emergence of most of the magnetic flux. The speed of emergence determined by tracking the flow divergence with depth is about 1.4 km/s, very close to the emergence speed in the deep layers. As the emerging magnetic flux becomes concentrated in sunspots local converging flows are observed beneath the forming sunspots. These flows are most prominent in the depth range 1-3 Mm, and remain converging after the formation process is completed. On the larger scale converging flows around active region appear as a diversion of the zonal shearing flows towards the active region, accompanied by formation of a large-scale vortex structure. This process occurs when a substantial amount of the magnetic flux emerged on the surface, and the converging flow pattern remains stable during the following evolution of the active region. The Carrington synoptic flow maps show that the large-scale subsurface inflows are typical for active regions. In the deeper layers (10-13 Mm) the flows become diverging, and surprisingly strong beneath some active regions. In addition, the synoptic maps reveal a complex evolving pattern of large-scale flows on the scale much larger than supergranulation

Effect of enhanced manganese oxidation in the hyporheic zone on basin-scale geochemical mass balance

USGS Publications Warehouse

Harvey, Judson W.; Fuller, Christopher C.

1998-01-01

We determined the role of the hyporheic zone (the subsurface zone where stream water and shallow groundwater mix) in enhancing microbially mediated oxidation of dissolved manganese (to form manganese precipitates) in a drainage basin contaminated by copper mining. The fate of manganese is of overall importance to water quality in Pinal Creek Basin, Arizona, because manganese reactions affect the transport of trace metals. The basin-scale role of the hyporheic zone is difficult to quantify because stream-tracer studies do not always reliably characterize the cumulative effects of the hyporheic zone. This study determined cumulative effects of hyporheic reactions in Pinal Creek basin by characterizing manganese uptake at several spatial scales (stream-reach scale, hyporheic-flow-path scale, and sediment-grain scale). At the stream-reach scale a one-dimensional stream-transport model (including storage zones to represent hyporheic flow paths) was used to determine a reach-averaged time constant for manganese uptake in hyporheic zones, 1/λs, of 1.3 hours, which was somewhat faster but still similar to manganese uptake time constants that were measured directly in centimeter-scale hyporheic flow paths (1/λh= 2.6 hours), and in laboratory batch experiments using streambed sediment (1/λ = 2.7 hours). The modeled depths of subsurface storage zones (ds = 4–17 cm) and modeled residence times of water in storage zones (ts = 3–12 min) were both consistent with direct measurements in hyporheic flow paths (dh = 0–15 cm, th = 1–25 min). There was also good agreement between reach-scale modeling and direct measurements of the percentage removal of dissolved manganese in hyporheic flow paths (fs = 8.9%, andfh = 9.3%rpar;. Manganese uptake experiments in the laboratory using sediment from Pinal Creek demonstrated (through comparison of poisoned and unpoisoned treatments) that the manganese removal process was enhanced by microbially mediated oxidation. The cumulative effect of hyporheic exchange in Pinal Creek basin was to remove approximately 20% of the dissolved manganese flowing out of the drainage basin. Our results illustrate that the cumulative significance of reactive uptake in the hyporheic zone depends on the balance between chemical reaction rates, hyporheic porewater residence time, and turnover of streamflow through hyporheic flow paths. The similarity between the hyporheic reaction timescale (1/λs ≈ 1.3 hours), and the hyporheic porewater residence timescale (ts ≈ 8 min) ensured that there was adequate time for the reaction to progress. Furthermore, it was the similarity between the turnover length for stream water flow through hyporheic flow paths (Ls = stream velocity/storage-zone exchange coefficient ≈ 1.3 km) and the length of Pinal Creek (L ≈ 7 km), which ensured that all stream water passed through hyporheic flow paths several times. As a means to generalize our findings to other sites where similar types of hydrologic and chemical information are available, we suggest a cumulative significance index for hyporheic reactions, Rs = λstsL/Ls (dimensionless); higher values indicate a greater potential for hyporheic reactions to influence geochemical mass balance. Our experience in Pinal Creek basin suggests that values of Rs > 0.2 characterize systems where hyporheic reactions are likely to influence geochemical mass balance at the drainage-basin scale.

Lava inundation zone maps for Mauna Loa, Island of Hawaiʻi, Hawaii

USGS Publications Warehouse

Trusdell, Frank A.; Zoeller, Michael H.

2017-10-12

Lava flows from Mauna Loa volcano, on the Island of Hawaiʻi, constitute a significant hazard to people and property. This report addresses those lava flow hazards, mapping 18 potential lava inundation zones on the island.

Methods to prioritize placement of riparian buffers for improved water quality

Treesearch

Mark D. Tomer; Michael G. Dosskey; Michael R. Burkart; David E. James; Matthew J. Helmers; Dean E. Eisenhauer

2008-01-01

Agroforestry buffers in riparian zones can improve stream water quality, provided they intercept and remove contaminants from surface runoff and/or shallow groundwater. Soils, topography, surficial geology, and hydrology determine the capability of forest buffers to intercept and treat these flows. This paper describes two landscape analysis techniques for identifying...

Oxy-fired boiler unit and method of operating the same

DOEpatents

Lou, Xinsheng; Zhang, Jundong; Joshi, Abhinaya; McCombe, James A.; Levasseur, Armand A.

2016-12-06

An oxy-combustion boiler unit is disclosed which includes a furnace for combusting fuel and for emitting flue gas resulting from combustion. The furnace has first, second and third combustion zones, and an air separation unit for separating oxygen gas from air and providing a first portion of the separated oxygen to a first oxidant flow, a second portion to a second oxidant flow, and a third portion of the separated oxygen gas to the first, second, and third zones of the furnace. A controller can cause the separated oxygen gas to be distributed so that the first and second oxygen flows have a desired oxygen content, and so that the first, second, and third zones of the furnace receive a desired amount of oxygen based on a combustion zone stoichiometry control.

An Angus/Argo study of the neovolcanic zone along the East Pacific rise from the Clipperton fracture zone to 12°N

NASA Astrophysics Data System (ADS)

Uchupi, E.; Schwab, W. C.; Ballard, R. D.; Cheminee, J. L.; Francheteau, J.; Hekinian, R.; Blackman, D. K.; Sigurdsson, H.

1988-09-01

Still photographs and video images collected along the Neovolcanic Zone of the East Pacific Rise from 10°15'N to 11°53'N show that recent volcanic sheet flows, possibly less than 100 years old, are superimposed on an older sediment-laden pillow terrane. This recent activity is restricted to a narrow zone that crosses two topographic highs at 10°55'N and 11°26'N and diminishes along-axis away from these highs. The association of recent sheet flows with older flows and collapse structures on the overlapping spreading centers at 11°45'N supports the evolutionary model for the occurrence and evolution of overlapping spreading centers by MacDonald and others (1986, 1988).

Microwave plasma generation of hydrogen atoms for rocket propulsion

NASA Technical Reports Server (NTRS)

Chapman, R.; Filpus, J.; Morin, T.; Snellenberger, R.; Asmussen, J.; Hawley, M.; Kerber, R.

1981-01-01

A flow microwave plasma reaction system is used to study the conversion of hydrogen to hydrogen atoms as a function of pressure, power density, cavity tuning, cavity mode, and time in the plasma zone. Hydrogen atom concentration is measured down-stream from the plasma by NOCl titration. Extensive modeling of the plasma and recombination zones is performed with the plasma zone treated as a backmix reaction system and the recombination zone treated as a plug flow. The thermodynamics and kinetics of the recombination process are examined in detail to provide an understanding of the conversion of recombination energy to gas kinetic energy. It is found that cavity tuning, discharge stability, and optimum power coupling are critically dependent on the system pressure, but nearly independent of the flow rate.

A natural example of fluid-mediated brittle-ductile cyclicity in quartz veins from Olkiluoto Island, SW Finland

NASA Astrophysics Data System (ADS)

Marchesini, Barbara; Garofalo, Paolo S.; Viola, Giulio; Mattila, Jussi; Menegon, Luca

2017-04-01

Brittle faults are well known as preferential conduits for localised fluid flow in crystalline rocks. Their study can thus reveal fundamental details of the physical-chemical properties of the flowing fluid phase and of the mutual feedbacks between mechanical properties of faults and fluids. Crustal deformation at the brittle-ductile transition may occur by a combination of competing brittle fracturing and viscous flow processes, with short-lived variations in fluid pressure as a viable mechanism to produce this cyclicity switch. Therefore, a detailed study of the fluid phases potentially present in faults can help to better constrain the dynamic evolution of crustal strength within the seismogenic zone, as a function of varying fluid phase characteristics. With the aim to 1) better understand the complexity of brittle-ductile cyclicity under upper to mid-crustal conditions and 2) define the physical and chemical features of the involved fluid phase, we present the preliminary results of a recently launched (micro)structural and geochemical project. We study deformed quartz veins associated with brittle-ductile deformation zones on Olkiluoto Island, chosen as the site for the Finnish deep repository for spent nuclear fuel excavated in the Paleoproterozoic crust of southwestern Finland. The presented results stem from the study of brittle fault zone BFZ300, which is a mixed brittle and ductile deformation zone characterized by complex kinematics and associated with multiple generations of quartz veins, and which serves as a pertinent example of the mechanisms of fluid flow-deformation feedbacks during brittle-ductile cyclicity in nature. A kinematic and dynamic mesostructural study is being integrated with the detailed analysis of petrographic thin sections from the fault core and its immediate surroundings with the aim to reconstruct the mechanical deformation history along the entire deformation zone. Based on the observed microstructures, it was possible to recognize three distinct episodes of ductile deformation alternating with at least three brittle episodes. Preliminary fluid inclusion data show that, during crystallization and brittle-viscous deformation, quartz crystals hosted homogeneous and heterogeneous (boiling) aqueous fluids with a large salinity (11.7-0 wt% NaCleq) and Thtot (410-200 °C) range. Boiling occurred at 200-260 °C. Variations of fluid temperature and density (hence, viscosity) may thus have induced localized cyclic switches between brittle and ductile deformation in quartz, with implications on the bulk regional crustal strength. Preliminary EBSD analysis also supports the hypothesis of cyclic switches between brittle and viscous deformation.

A New Methodology for Turbulence Modelers Using DNS Database Analysis

NASA Technical Reports Server (NTRS)

Parneix, S.; Durbin, P.

1996-01-01

Many industrial applications in such fields as aeronautical, mechanical, thermal, and environmental engineering involve complex turbulent flows containing global separations and subsequent reattachment zones. Accurate prediction of this phenomena is very important because separations influence the whole fluid flow and may have an even bigger impact on surface heat transfer. In particular, reattaching flows are known to be responsible for large local variations of the local wall heat transfer coefficient as well as modifying the overall heat transfer. For incompressible, non-buoyant situations, the fluid mechanics have to be accurately predicted in order to have a good resolution of the temperature field.

Analysis of ground-water flow in the Madison aquifer using fluorescent dyes injected in Spring Creek and Rapid Creek near Rapid City, South Dakota, 2003-04

USGS Publications Warehouse

Putnam, Larry D.; Long, Andrew J.

2007-01-01

The Madison aquifer, which contains fractures and solution openings in the Madison Limestone, is used extensively for water supplies for the city of Rapid City and other suburban communities in the Rapid City, S. Dak., area. The 48 square-mile study area includes the west-central and southwest parts of Rapid City and the outcrops of the Madison Limestone extending from south of Spring Creek to north of Rapid Creek. Recharge to the Madison Limestone occurs when streams lose flow as they cross the outcrop. The maximum net loss rate for Spring and Rapid Creek loss zones are 21 and 10 cubic feet per second (ft3/s), respectively. During 2003 and 2004, fluorescent dyes were injected in the Spring and Rapid Creek loss zones to estimate approximate locations of preferential flow paths in the Madison aquifer and to measure the response and transit times at wells and springs. Four injections of about 2 kilograms of fluorescein dye were made in the Spring Creek loss zone during 2003 (sites S1, S2, and S3) and 2004 (site S4). Injection at site S1 was made in streamflow just upstream from the loss zone over a 12-hour period when streamflow was about equal to the maximum loss rate. Injections at sites S2, S3, and S4 were made in specific swallow holes located in the Spring Creek loss zone. Injection at site R1 in 2004 of 3.5 kilograms of Rhodamine WT dye was made in streamflow just upstream from the Rapid Creek loss zone over about a 28-hour period. Selected combinations of 27 wells, 6 springs, and 3 stream sites were monitored with discrete samples following the injections. For injections at sites S1-S3, when Spring Creek streamflow was greater than or equal to 20 ft3/s, fluorescein was detected in samples from five wells that were located as much as about 2 miles from the loss zone. Time to first arrival (injection at site S1) ranged from less than 1 to less than 10 days. The maximum fluorescein concentration (injection at site S1) of 120 micrograms per liter (ug/L) at well CO, which is located adjacent to the loss zone, was similar to the concentration in the stream. Fluorescein arrived at well NON (injection at site S1), which is located about 2 miles northeast of the loss zone, within about 1.6 days, and the maximum concentration was 44 ug/L. For injection at site S4, when streamflow was about 12 ft3/s, fluorescein was detected in samples from six wells and time to first arrival ranged from 0.2 to 16 days. Following injection at site S4 in 2004, the length of time that dye remained in the capture zone of well NON, which is located approximately 2 miles from the loss zone, was almost an order of magnitude greater than in 2003. For injection at site R1, Rhodamine WT was detected at well DRU and spring TI-SP with time to first arrival of about 0.5 and 1.1 days and maximum concentrations of 6.2 and 0.91 ug/L, respectively. Well DRU and spring TI-SP are located near the center of the Rapid Creek loss zone where the creek has a large meander. Measurable concentrations were observed for spring TI-SP as many as 109 days after the dye injection. The direction of a conduit flow path in the Spring Creek area was to the northeast with ground-water velocities that ranged from 770 to 6,500 feet per day. In the Rapid Creek loss zone, a conduit flow path east of the loss zone was not evident from the dye injection.

Flow to partially penetrating wells in unconfined heterogeneous aquifers: Mean head and interpretation of pumping tests

NASA Astrophysics Data System (ADS)

Dagan, G.; Lessoff, S. C.

2011-06-01

A partially penetrating well of length Lw and radius Rw starts to pump at constant discharge Qw at t = 0 from an unconfined aquifer of thickness D. The aquifer is of random and stationary conductivity characterized by KG (geometric mean), σY2 (log conductivity variance), and I and Iv (the horizontal and vertical integral scales). The flow problem is solved under a few simplifying assumptions commonly adopted in the literature for homogeneous media: Rw/Lw ≪ 1, linearization of the free surface condition, and constant drainable porosity n. Additionally, it is assumed that Rw/I < 1 and Lw/Iv ≫ 1 (to simplify the well boundary conditions) and that a first-order approximation in σY2 (extended to finite σY2 on a conjectural basis) is adopted. The solution is obtained for the mean head field and the associated water table equation. The main result of the analysis is that the flow domain can be divided into three zones for : (1) the neighborhood of the well R ≪ I, where = (Qw/LwKA)h0(R, z, tKefuv/nD), with h0 being the zero-order solution pertaining to a homogeneous and isotropic aquifer, KA being the conductivity arithmetic mean, and Kefuv being the effective vertical conductivity in mean uniform flow, (2) an exterior zone R ⪆ I in which ?H? = (Qw/LwKefuh)h0(R?, z, tKefuv/nD), with Kefuh being the horizontal effective conductivity, and (3) an intermediate zone in which the solution requires a few numerical quadratures, not carried out here. The application to pumping tests reveals that identification of the aquifer parameters for homogeneous and anisotropic aquifers by commonly used methods can be applied for the drawdown measured in an observation well of length Low?Iv (to ensure exchange of space and ensemble head averages) in the second zone in order to identify Kefuh, Kefuv, and n. In contrast, the use of the drawdown in the well (first zone) leads to an overestimation of Kefuh by the factor KA/Kefuh.

Oxygen Carbon Dynamics within the Hyporheic Zone of a Headwater Stream

NASA Astrophysics Data System (ADS)

Pennington, R.; Haggerty, R.; Wondzell, S. M.; Serchan, S. P.; Reeder, W. J.; Tonina, D.

2016-12-01

Streams and rivers influence global carbon fluxes; on an aerial basis, they have disproportionately high export rates compared to land. Various mechanisms exist for the movement of terrestrially derived carbon to the stream network including transport of organic and inorganic carbon with groundwater and hillslope runoff. A secondary process that has received little attention is carbon dynamics of hyporheic flow along flow paths that pass beneath the vegetated riparian zone. Through use of high frequency monitoring of dissolved inorganic carbon and dissolved oxygen we find that the riparian zone is a net source of carbon throughout the year. Increases in DIC relative stream water are generally more than double decreases in O2 on a molar basis. Metabolic quotients of C to O2 are close to 1.0, therefore respiration of dissolved or particulate organic carbon along flow paths would result in an equal magnitude increase in inorganic carbon to decrease in O2. Diffusion from the high CO2 soil atmosphere into hyporheic water has been considered, however 2-D reactive transport modeling using PFLOTRAN indicates that soil diffusion processes are unlikely to produce observed increases in carbon and that alternative transport mechanisms including root respiration or diel water level fluctuations are necessary for mass balance. Results of the analysis will feed into a comprehensive distributed model of the system that explores carbon dynamics at the reach scale.

Play-fairway analysis for geothermal exploration: Examples from the Great Basin, western USA

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

Siler, Drew L; Faulds, James E

2013-10-27

Elevated permeability within fault systems provides pathways for circulation of geothermal fluids. Future geothermal development depends on precise and accurate location of such fluid flow pathways in order to both accurately assess geothermal resource potential and increase drilling success rates. The collocation of geologic characteristics that promote permeability in a given geothermal system define the geothermal ‘fairway’, the location(s) where upflow zones are probable and where exploration efforts including drilling should be focused. We define the geothermal fairway as the collocation of 1) fault zones that are ideally oriented for slip or dilation under ambient stress conditions, 2) areas withmore » a high spatial density of fault intersections, and 3) lithologies capable of supporting dense interconnected fracture networks. Areas in which these characteristics are concomitant with both elevated temperature and fluids are probable upflow zones where economic-scale, sustainable temperatures and flow rates are most likely to occur. Employing a variety of surface and subsurface data sets, we test this ‘play-fairway’ exploration methodology on two Great Basin geothermal systems, the actively producing Brady’s geothermal system and a ‘greenfield’ geothermal prospect at Astor Pass, NV. These analyses, based on 3D structural and stratigraphic framework models, reveal subsurface characteristics about each system, well beyond the scope of standard exploration methods. At Brady’s, the geothermal fairways we define correlate well with successful production wells and pinpoint several drilling targets for maintaining or expanding production in the field. In addition, hot-dry wells within the Brady’s geothermal field lie outside our defined geothermal fairways. At Astor Pass, our play-fairway analysis provides for a data-based conceptual model of fluid flow within the geothermal system and indicates several targets for exploration drilling.« less

Analysis of radar images of the active volcanic zone at Krafla, Iceland: The effects of look azimuth biasing

NASA Technical Reports Server (NTRS)

Garvin, J. B.; Williams, R. S., Jr.

1989-01-01

The geomorphic expression of Mid-Ocean-Ridge (MOR) volcanism in a subaerial setting occurs uniquely on Earth in Iceland, and the most recent MOR eruptive activity has been concentrated in the Northeastern Volcanic Zone in an area known as Krafla. Within the Krafla region are many of the key morphologic elements of MOR-related basaltic volcanism, as well as volcanic explosion craters, subglacial lava shields, tectonic fissure swarms known as gjar, and basaltic-andesite flows with well developed ogives (pressure-ridges). The objective was to quantify the degree to which the basic volcanic and structural features can be mapped from directional SAR imagery as a function of the look azimuth. To accomplish this, the current expression of volcanic and tectonic constructs was independently mapped within the Krafla region on the E, W, and N-looking SAR images, as well as from SPOT Panchromatic imagery acquired in 1987. The initial observations of the E, W, and N images indicates that fresh a'a lava surfaces are extremely radar bright (rough at 3 cm to meter scales) independent of look direction; this suggests that these flows do not have strong flow direction related structures at meter and cm scales, which is consistent with typical Icelandic a'a lava surfaces in general. The basic impression from a preliminary analysis of the effects of look azimuth biasing on interpretation of the geology of an active MOR volcanic zone is that up to 30 percent of the diagnostic features can be missed at any given look direction, but that having two orthogonal look direction images is probably sufficient to prevent gross misinterpretation.

Large-scale asymmetric introgression of cytoplasmic DNA reveals Holocene range displacement in a North American boreal pine complex

PubMed Central

Godbout, Julie; Yeh, Francis C; Bousquet, Jean

2012-01-01

Jack pine (Pinus banksiana) and lodgepole pine (Pinus contorta var. latifolia) are two North American boreal hard pines that hybridize in their zone of contact in western Canada. The main objective of this study was to characterize their patterns of introgression resulting from past and recent gene flow, using cytoplasmic markers having maternal or paternal inheritance. Mitochondrial DNA (mtDNA) and chloroplast DNA (cpDNA) diversity was assessed in allopatric populations of each species and in stands from the current zone of contact containing morphological hybrids. Cluster analyses were used to identify genetic discontinuities among groups of populations. A canonical analysis was also conducted to detect putative associations among cytoplasmic DNA variation, tree morphology, and site ecological features. MtDNA introgression was extensive and asymmetric: it was detected in P. banksiana populations from the hybrid zone and from allopatric areas, but not in P. contorta populations. Very weak cpDNA introgression was observed, and only in P. banksiana populations. The mtDNA introgression pattern indicated that central Canada was first colonized by migrants from a P. contorta glacial population located west of the Rocky Mountains, before being replaced by P. banksiana migrating westward during the Holocene. In contrast, extensive pollen gene flow would have erased the cpDNA traces of this ancient presence of P. contorta. Additional evidence for this process was provided by the results of canonical analysis, which indicated that the current cpDNA background of trees reflected recent pollen gene flow from the surrounding dominant species rather than historical events that took place during the postglacial colonization. PMID:22957188

A comparative CFD study on the hemodynamics of flow through an idealized symmetric and asymmetric stenosed arteries

NASA Astrophysics Data System (ADS)

Prashantha, B.; Anish, S.

2017-04-01

The aim of the present study is to numerically evaluate the hemodynamic factors which affect the formation of atherosclerosis and plaque rupture in the human artery. An increase of atherosclerosis in the artery causes geometry changes, which results in hemodynamic changes such as flow separation, reattachment and adhesion of new cells (chemotactic) in the artery. Hence, geometry plays an important role in the determining the nature of hemodynamic patterns. Influence of stenosis in the non-bifurcating artery, under pulsatile flow condition has been studied on an idealized geometry. Analysis of flow through symmetric and asymmetric stenosis in the artery revealed the significance of oscillating shear index (OSI), flow separation, low wall shear stress (WSS) zones and secondary flow patterns on plaque formation. The observed characteristic of flow in the post-stenotic region highlight the importance of plaque eccentricity on the formation of secondary stenosis on the arterial wall.

Physical mechanisms of longitudinal vortexes formation, appearance of zones with high heat fluxes and early transition in hypersonic flow over delta wing with blunted leading edges

NASA Astrophysics Data System (ADS)

Alexandrov, S. V.; Vaganov, A. V.; Shalaev, V. I.

2016-10-01

Processes of vortex structures formation and they interactions with the boundary layer in the hypersonic flow over delta wing with blunted leading edges are analyzed on the base of experimental investigations and numerical solutions of Navier-Stokes equations. Physical mechanisms of longitudinal vortexes formation, appearance of abnormal zones with high heat fluxes and early laminar turbulent transition are studied. These phenomena were observed in many high-speed wind tunnel experiments; however they were understood only using the detailed analysis of numerical modeling results with the high resolution. Presented results allowed explaining experimental phenomena. ANSYS CFX code (the DAFE MIPT license) on the grid with 50 million nodes was used for the numerical modeling. The numerical method was verified by comparison calculated heat flux distributions on the wing surface with experimental data.

Rates of volcanic activity along the southwest rift zone of Mauna Loa volcano, Hawaii.

USGS Publications Warehouse

Lipman, P.W.

1981-01-01

Flow-by-flow mapping of the 65 km long subaerial part of the southwest rift zone and adjacent flanks of Mauna Loa Volcano, Hawaii, and about 50 new 14C dates on charcoal from beneath these flows permit estimates of rates of lava accumulation and volcanic growth over the past 10 000 years. The sequence of historic eruptions along the southwest rift zone, beginning in 1868, shows a general pattern of uprift migration and increasing eruptive volume, culminating in the great 1950 eruption. No event comparable to 1950, in terms of volume or vent length, is evident for at least the previous 1000 years. Rates of lava accumulation along the zone have been subequal to those of Kilauea Volcano during the historic period but they were much lower in late prehistoric time (unpubl. Kilauea data by R. T. Holcomb). Rates of surface covering and volcanic growth have been markedly asymmetric along Mauna Loa's southwest rift zone. Accumulation rates have been about half again as great on the northwest side of the rift zone in comparison with the southeast side. The difference apparently reflects a westward lateral shift of the rift zone of Mauna Loa away from Kilauea Volcano, which may have acted as a barrier to symmetrical growth of the rift zone. -Author

DISTRIBUTION OF THE TEMPERATURE IN THE ASH-GAS FLOW DURING KORYAKSKY VOLCANO ERUPTION IN 2009

NASA Astrophysics Data System (ADS)

Gordeev, E.; Droznin, V.

2009-12-01

The observations of the ash-gas plumes during the Koryaksky eruption in March 2009 by the high resolution thermovision camera allowed obtaining thermal distributions inside the ash-gas flows. The plume structure is formed by single emissions. They rise at the rate of 5.5-7 m/s. The plume structure in general is represented as 3 zones: 1. a zone of high heat exchange; 2. a zone of floating up; 3. a zone of lateral movement. The plume temperature within the zone of lateral movement exceeds the atmospheric temperature by 3-5 oC, within the zone of floating up it exceeds by 20 oC. Its rate within the zone of floating up comprises 5-7 m/s. At the boundary between the zones of high heat exchange and floating up where we know the plume section, from heat balance equation we can estimate steam rate and heat power of the fluid thermal flow. Power of the overheated steam was estimated as Q=35 kg/s. It forms the ash-gas plume from the eruption and has temperature equal to 450 oC. The total volume of water steam produced during 100 days of eruption was estimated 3*105 t, its energy - 109 MJ.

Geothermal energy prospectivity of the Torrens Hinge Zone: evidence from new heat flow data

NASA Astrophysics Data System (ADS)

Matthews, Chris

2009-09-01

The Torrens Hinge Zone is a long but narrow (up to 40km wide) geological transition zone between the relatively stable Eastern Gawler Craton `Olympic Domain' to the west, and the sedimentary basin known as the Adelaide Geosyncline to the east. The author hypothesised from first principles that the Torrens Hinge Zone should be prospective for high geothermal gradients due to the likely presence of high heat flow and insulating cover rocks. A method to test this hypothesis was devised, which involved the determination of surface heat flow on a pattern grid using purpose-drilled wells, precision temperature logging and detailed thermal conductivity measurements. The results of this structured test have validated the hypothesis, with heat flow values over 90mW/m2 recorded in five of six wells drilled. With several kilometres thickness of moderate conductivity sediments overlying the crystalline basement in this region, predicted temperature at 5000m ranges between 200 and 300°C.

Microscale cavitation as a mechanism for nucleating earthquakes at the base of the seismogenic zone.

PubMed

Verberne, Berend A; Chen, Jianye; Niemeijer, André R; de Bresser, Johannes H P; Pennock, Gillian M; Drury, Martyn R; Spiers, Christopher J

2017-11-21

Major earthquakes frequently nucleate near the base of the seismogenic zone, close to the brittle-ductile transition. Fault zone rupture at greater depths is inhibited by ductile flow of rock. However, the microphysical mechanisms responsible for the transition from ductile flow to seismogenic brittle/frictional behaviour at shallower depths remain unclear. Here we show that the flow-to-friction transition in experimentally simulated calcite faults is characterized by a transition from dislocation and diffusion creep to dilatant deformation, involving incompletely accommodated grain boundary sliding. With increasing shear rate or decreasing temperature, dislocation and diffusion creep become too slow to accommodate the imposed shear strain rate, leading to intergranular cavitation, weakening, strain localization, and a switch from stable flow to runaway fault rupture. The observed shear instability, triggered by the onset of microscale cavitation, provides a key mechanism for bringing about the brittle-ductile transition and for nucleating earthquakes at the base of the seismogenic zone.

Vadose Zone Transport Field Study: Summary Report

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

Ward, Andy L.; Conrad, Mark E.; Daily, William D.

2006-07-31

From FY 2000 through FY 2003, a series of vadose zone transport field experiments were conducted as part of the U.S. Department of Energy’s Groundwater/Vadose Zone Integration Project Science and Technology Project, now known as the Remediation and Closure Science Project, and managed by the Pacific Northwest National Laboratory (PNNL). The series of experiments included two major field campaigns, one at a 299-E24-11 injection test site near PUREX and a second at a clastic dike site off Army Loop Road. The goals of these experiments were to improve our understanding of vadose zone transport processes; to develop data sets tomore » validate and calibrate vadose zone flow and transport models; and to identify advanced monitoring techniques useful for evaluating flow-and-transport mechanisms and delineating contaminant plumes in the vadose zone at the Hanford Site. This report summarizes the key findings from the field studies and demonstrates how data collected from these studies are being used to improve conceptual models and develop numerical models of flow and transport in Hanford’s vadose zone. Results of these tests have led to a better understanding of the vadose zone. Fine-scale geologic heterogeneities, including grain fabric and lamination, were observed to have a strong effect on the large-scale behavior of contaminant plumes, primarily through increased lateral spreading resulting from anisotropy. Conceptual models have been updated to include lateral spreading and numerical models of unsaturated flow and transport have revised accordingly. A new robust model based on the concept of a connectivity tensor was developed to describe saturation-dependent anisotropy in strongly heterogeneous soils and has been incorporated into PNNL’s Subsurface Transport Over Multiple Phases (STOMP) simulator. Application to field-scale transport problems have led to a better understanding plume behavior at a number of sites where lateral spreading may have dominated waste migration (e.g. BC Cribs and Trenches). The improved models have been also coupled with inverse models and newly-developed parameter scaling techniques to allow estimation of field-scale and effective transport parameters for the vadose zone. The development and utility of pedotransfer functions for describing fine-scale hydrogeochemical heterogeneity and for incorporating this heterogeneity into reactive transport models was explored. An approach based on grain-size statistics appears feasible and has been used to describe heterogeneity in hydraulic properties and sorption properties, such as the cation exchange capacity and the specific surface area of Hanford sediments. This work has also led to the development of inverse modeling capabilities for time-dependent, subsurface, reactive transport with transient flow fields using an automated optimization algorithm. In addition, a number of geophysical techniques investigated for their potential to provide detailed information on the subtle changes in lithology and bedding surfaces; plume delineation, leak detection. High-resolution resistivity is now being used for detecting saline plumes at several waste sites at Hanford, including tank farms. Results from the field studies and associated analysis have appeared in more than 46 publications generated over the past 4 years. These publications include test plans and status reports, in addition to numerous technical notes and peer reviewed papers.« less

Simulation of ground-water flow and stream-aquifer relations in the vicinity of the Savannah River Site, Georgia and South Carolina, predevelopment through 1992

USGS Publications Warehouse

Clarke, John S.; West, Christopher T.

1998-01-01

Ground-water flow and stream-aquifer relations were simulated for seven aquifers in Coastal Plain sediments in the vicinity of the U.S. Department of Energy, Savannah River Site (SRS), in Georgia and South Carolina to evaluate the potential for ground water containing hazardous materials to migrate from the SRS into Georgia through aquifers underlying the Savannah River (trans-river flow). The work was completed as part of a cooperative study between the U.S. Geological Survey, the U.S. Department of Energy, and Georgia Department of Natural Resources. The U.S. Geological Survey three-dimensional finite-difference ground-water flow model, MODFLOW, was used to simulate ground-water flow in three aquifer systems containing seven discrete aquifers: (1) the Floridan aquifer system, consisting of the Upper Three Runs and Gordon aquifers in sediments of Eocene age; (2) the Dublin aquifer system, consisting of the Millers Pond, and upper and lower Dublin aquifers in sediments of Paleocene and Late Cretaceous age; and (3) the Midville aquifer system, consisting of the upper and lower Midville aquifers of sediments in Late Cretaceous age. Ground-water flow was simulated using a series of steady-state simulations of predevelopment (pre-1953) conditions and six pumping periods--1953-60, 1961-70, 1971-75, 1976-80, 1981-86, and 1987-92--results are presented for predevelopment (prior to 1953) and modern-day (1987-92) conditions. Total simulated predevelopment inflow is 1,023 million gallons per day (Mgal/d), of which 76 percent is contributed by leakage from the Upper Three Runs aquifer. Over most of the study area, pumpage induced changes in ground-water levels, ground-water discharge to streams, and water-budget components were small during 1953-92, and changes in aquifer storage were insignificant. Simulated drawdown between predevelopment and modern-day conditions is small (less than 7 feet) and of limited areal extent--the largest simulated declines occur in the upper and lower Dublin aquifers in the vicinity of the Sandoz plant site in South Carolina. These declines extend beneath the Savannah River and change the configuration of the simulated potentiometric surface and flow paths near the river. Predevelopment and modern-day flowpaths were simulated near the Savannah River by using the U.S. Geological Survey particle-tracking code MODPATH. Eastward and westward zones of trans-river flow were identified in three principal areas as follows: --zone 1-from the Fall Line southward to the confluence of Hollow Creek and the Savannah River; --zone 2-from the zone 1 boundary southward to the southern border of the SRS (not including the Lower Three Runs Creek section); and --zone 3-from the zone 2 boundary, southward into the northern part of Screven County, Ga. All zones for all model layers were located within or immediately adjacent to the Savannah River alluvial valley and most were located in the immediate vicinity of the Savannah River. Recharge areas for each of the zones of trans-river flow generally are in the vicinity of major interstream drainage divides. Mean time-of-travel simulated for predevelopment conditions ranges from 300 to 24,000 years for westward trans-river flow zones; and from 550 to 41,000 years for eastward zones. Corresponding travel times under modern-day conditions range from 300 to 34,000 years for westward zones and from 580 to 31,000 years for eastward zones. Differences in travel times between predevelopment and modern-day simulations result from changes in hydraulic gradients due to ground-water pumpage that alter flow paths in the vicinity of the river. Recharge to Georgia trans-river flow zones originating on the SRS was simulated for the Gordon and upper Dublin aquifers during predevelopment, and in the Gordon aquifer during 1987-92. During 1987-92, SRS recharge was simulated in 6 model cells covering a 2-square mile area, located away from areas of ground-water contamination. Si

Direct numerical simulations of flow-chemistry interactions in statistically turbulent premixed flames

NASA Astrophysics Data System (ADS)

Arias, Paul; Uranakar, Harshavardhana; Chaudhuri, Swetaprovo; Im, Hong

2015-11-01

The effects of Damköhler number and Karlovitz number on the flame dynamics of three-dimensional statistically planar turbulent premixed flames are investigated by direct numerical simulation incorporating detailed chemistry and transport for a hydrogen-air mixture. The mean inlet velocity was dynamically adjusted to ensure a stable flame within the computational domain, allowing the investigation of time-averaged quantities of interest. A particular interest was on understanding the effects of turbulence on the displacement speed of the flame relative to the local fluid flow. Results show a linear dependence on the displacement speed as a function of total strain, consistent with earlier work on premixed-laminar flames. Additional analysis on the local flame thickness reveals that the effect of turbulence is twofold: (1) the increase in mixing results in flame thinning due to the enhancement of combustion at early onset of the flame, and (2) for large Reynolds number flows, the penetration of the turbulence far into the preheat zone and into the reaction zone results in localized flame broadening.

Inequity in ecosystem service delivery: Socioeconomic gaps in the public-private conservation network

USGS Publications Warehouse

Villamagna, Amy M.; Mogollón, Beatriz; Angermeier, Paul L.

2017-01-01

Conservation areas, both public and private, are critical tools to protect biodiversity and deliver important ecosystem services (ES) to society. Although societal benefits from such ES are increasingly used to promote public support of conservation, the number of beneficiaries, their identity, and the magnitude of benefits are largely unknown for the vast majority of conservation areas in the United States public-private conservation network. The location of conservation areas in relation to people strongly influences the direction and magnitude of ES flows as well as the identity of beneficiaries. We analyzed benefit zones, the areas to which selected ES could be conveyed to beneficiaries, to assess who benefits from a typical conservation network. Better knowledge of ES flows and beneficiaries will help land conservationists make a stronger case for the broad collateral benefits of conservation and help to address issues of social-environmental justice. To evaluate who benefits the most from the current public-private conservation network, we delineated the benefit zones for local ES (within 16 km) that are conveyed along hydrological paths from public (federal and state) and private (easements) conservation lands in the states of North Carolina and Virginia, USA. We also discuss the challenges and demonstrate an approach for delineating nonhydrological benefits that are passively conveyed to beneficiaries. We mapped and compared the geographic distribution of benefit zones within and among conservation area types. We further compared beneficiary demographics across benefit zones of the conservation area types and found that hydrological benefit zones of federal protected areas encompass disproportionately fewer minority beneficiaries compared to statewide demographic patterns. In contrast, benefit zones of state protected areas and private easements encompassed a much greater proportion of minority beneficiaries (~22–25%). Benefit zones associated with private conservation lands included beneficiaries of significantly greater household income than benefit zones of other types of conservation areas. Our analysis of ES flows revealed significant socioeconomic gaps in how the current public-private conservation network benefits the public. These gaps warrant consideration in regional conservation plans and suggest that private conservation initiatives may be best suited for responding to the equity challenge. Enhancing the ecosystem benefits and the equity of benefit delivery from private conservation networks could build public and political support for long-term conservation strategies and ultimately enhance conservation efficacy.

Temporally resolved planar measurements of transient phenomena in a partially pre-mixed swirl flame in a gas turbine model combustor

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

Boxx, I.; Stoehr, M.; Meier, W.

This paper presents observations and analysis of the time-dependent behavior of a 10 kW partially pre-mixed, swirl-stabilized methane-air flame exhibiting self-excited thermo-acoustic oscillations. This analysis is based on a series of measurements wherein particle image velocimetry (PIV) and planar laser-induced fluorescence (PLIF) of the OH radical were performed simultaneously at 5 kHz repetition rate over durations of 0.8 s. Chemiluminescence imaging of the OH{sup *} radical was performed separately, also at 5 kHz over 0.8 s acquisition runs. These measurements were of sufficient sampling frequency and duration to extract usable spatial and temporal frequency information on the medium to large-scalemore » flow-field and heat-release characteristics of the flame. This analysis is used to more fully characterize the interaction between the self-excited thermo-acoustic oscillations and the dominant flow-field structure of this flame, a precessing vortex core (PVC) present in the inner recirculation zone. Interpretation of individual measurement sequences yielded insight into various physical phenomena and the underlying mechanisms driving flame dynamics. It is observed for this flame that location of the reaction zone tracks large-scale fluctuations in axial velocity and also conforms to the passage of large-scale vortical structures through the flow-field. Local extinction of the reaction zone in regions of persistently high principal compressive strain is observed. Such extinctions, however, are seen to be self healing and thus do not induce blowout. Indications of auto-ignition in regions of unburned gas near the exit are also observed. Probable auto-ignition events are frequently observed coincident with the centers of large-scale vortical structures, suggesting the phenomenon is linked to the enhanced mixing and longer residence times associated with fluid at the core of the PVC as it moves through the flame. (author)« less

Six-flow operations for catalyst development in Fischer-Tropsch synthesis: Bridging the gap between high-throughput experimentation and extensive product evaluation

NASA Astrophysics Data System (ADS)

Sartipi, Sina; Jansma, Harrie; Bosma, Duco; Boshuizen, Bart; Makkee, Michiel; Gascon, Jorge; Kapteijn, Freek

2013-12-01

Design and operation of a "six-flow fixed-bed microreactor" setup for Fischer-Tropsch synthesis (FTS) is described. The unit consists of feed and mixing, flow division, reaction, separation, and analysis sections. The reactor system is made of five heating blocks with individual temperature controllers, assuring an identical isothermal zone of at least 10 cm along six fixed-bed microreactor inserts (4 mm inner diameter). Such a lab-scale setup allows running six experiments in parallel, under equal feed composition, reaction temperature, and conditions of separation and analysis equipment. It permits separate collection of wax and liquid samples (from each flow line), allowing operation with high productivities of C5+ hydrocarbons. The latter is crucial for a complete understanding of FTS product compositions and will represent an advantage over high-throughput setups with more than ten flows where such instrumental considerations lead to elevated equipment volume, cost, and operation complexity. The identical performance (of the six flows) under similar reaction conditions was assured by testing a same catalyst batch, loaded in all microreactors.

Hydrologic connections and dynamics of water movement in the classical Karst (Kras) Aquifer: evidence from frequent chemical and stable isotope sampling

USGS Publications Warehouse

Doctor, Daniel H.

2008-01-01

A review of past research on the hydrogeology of the Classical Karst (Kras) region and new information obtained from a two- year study using environmental tracers are presented in this paper. The main problems addressed are 1) the sources of water to the Kras aquifer resurgence zone-including the famous Timavo springs-under changing flow regimes; 2) a quantification of the storage volumes of the karst massif corresponding to flow regimes defined by hydrograph recessions of the Timavo springs; and 3) changing dynamics between deep phreatic conduit flow and shallow phreatic and epiphreatic storage within the aquifer resurgence zone as determined through changes in chemical and isotopic composition at springs and wells. Particular focus was placed on addressing the long-standing question of the influence of the Soca River on the ground waters of the aquifer resurgence zone. The results indicate that the alluvial aquifer supplied by the sinking of the Soca River on the northwestern edge of the massif contributes approximately 75% of the mean annual outflow to the smaller springs of the aquifer resurgence zone, and as much as 53% to the mean annual outflow of the Timavo springs. As a whole, the Soca River is estimated to contribute 56% of the average outflow of the Kras aquifer resurgence. The proportions of Soca River water increase under drier conditions, and decrease under wetter conditions. Time series analysis of oxygen stable isotope records indicate that the transit time of Soca River water to the Timavo springs, Sardos spring, and well B-4 is on the order of 1-2 months, depending on hydrological conditions. The total baseflow storage of the Timavo springs is estimated to be 518 million m3, and represents 88.5% of the storage capacity estimated for all flow regimes of the springs. The ratio of baseflow storage volume to the average annual volume discharged at the Timavo springs is 0.54. The Reka River sinking in Slovenia supplies substantial allogenic recharge to the aquifer; however, its influence on the northwest resurgence zone is limited to the Timavo springs, and is only a significant component of the spring discharge under flood conditions for relatively brief periods (several days to weeks). Sustainability of the trans-boundary aquifer of the Kras will benefit from maintaining high water quality in the Soca River, as well as focused water tracing experiments within the epiphreatic zone of the aquifer to better delineate the recharge zone and to identify sources of potential contamination to the Brestovica water supply well.

Response of hyporheic zones to transient forcing

NASA Astrophysics Data System (ADS)

Singh, T.; Wu, L.; Gomez-Velez, J. D.; Krause, S.; Hannah, D. M.; Lewandowski, J.; Nuetzmann, G.

2017-12-01

Exchange of water, solutes, and energy between river channels and hyporheic zones (HZs) modulates biogeochemical cycling, regulates stream temperature and impacts ecological structure and function. Numerical modelling of HZ processes is required as field observations are challenging for transient flow. To gain a deeper mechanistic understanding of the effects of transient discharge on hyporheic exchange, we performed a systematic analysis using numerical experiments. In this case, we vary (i) the characteristics of time-varying flood events; (ii) river bedform geometry; (iii) river hydraulic geometry; and (iv) the magnitude and direction of groundwater fluxes (neutral, gaining and losing conditions). We conceptualize the stream bed as a two-dimensional system. Whereby the flow is driven by a dynamically changing head distribution at the water-sediment interface and is modulated by steady groundwater flow. Our model estimates both net values for a single bedform and spatial distributions of (i) the flow field; (ii) mean residence times; and (iii) the concentration of a conservative tracer. A detailed sensitivity analysis was performed by changing channel slope, flood characteristics, groundwater upwelling/downwelling fluxes and biogeochemical time-scales in different bedforms such as ripples, dunes and alternating bars. Results show that change of parameters can have a substantial impact on exchange fluxes which can lead to the expansion, contraction, emergence and/or dissipation of HZs . Our results also reveal that groundwater fluxes have different impacts on HZs during flood events, depending on the channel slope and bedform topography. It is found that topographies with smaller aspect ratios and shallower slopes are more affected by groundwater upwelling/downwelling fluxes during flood events. The analysis of biogeochemical transformations shows that discharge events can potentially affects the efficiencies of nitrate removal. Taking into consideration multiple morphological characteristics along with hydrological controls are important to improve model conceptualizations at the reach and watershed scale.

Improved solution for saturated-unsaturated flow to a partially penetrating well in a compressible unconfined aquifer

NASA Astrophysics Data System (ADS)

Mishra, P. K.; Neuman, S. P.

2009-12-01

Tartakovsky and Neuman [2007] developed an analytical solution for flow to a partially penetrating well pumping at a constant rate from a compressible unconfined aquifer considering an unsaturated zone of infinite thickness. In their solution three-dimensional, axially symmetric unsaturated flow was described by a linearized version of Richards’ equation in which both relative hydraulic conductivity and water content vary exponentially with incremental capillary pressure head relative to its air entry value. Both exponential functions were characterized by a common exponent. We present an improved solution in which relative hydraulic conductivity and water content are characterized by separate parameters and the unsaturated zone has finite thickness. Our four-parameter representation of these functions is more flexible than the three-parameter version of Mathias and Butler [2006], who consider flow in the unsaturated zone to be strictly vertical and the pumping well to be fully penetrating. We investigate the effects of unsaturated zone thickness and constitutive parameters on drawdown in the unsaturated and saturated zones as functions of position and time. We then use our new solution to analyze data from synthetic and real pumping tests.

Unscrambling the Omlette: a New Bubble and Crystal Clustering Mechanism in Chaotically Mixed Magma Flows

NASA Astrophysics Data System (ADS)

Robertson, J.; Metcalfe, G.; Wang, S.; Barnes, S. J.

2014-12-01

The concentration of bubbles, crystals or droplets into small volumes of magma is a key trigger for many interesting magmatic processes. For example, gas slugs driving Strombolian eruptions form from the coalesence of exsolved bubbles within a volcanic conduit, while Ni-Cu-PGE magmatic sulfide deposits require a concentration of dense sulfide droplets from a large volume of magma to form a massive ore body. However the physical mechanism for this clustering remains unresolved - especially since small particles in active magma flows are expected to mostly track flow streamlines rather than clustering. We have uncovered a previously unreported clustering mechanism which is applicable to magmatic flows. This mechanism involves the interaction of particles with two kinds of chaotic flow structure: (a) high-strain regions within the well-mixed chaotic zones of the flow, and (b) unmixed islands of stability within the chaotic flow, known as Kolmogorov-Arnold-Moser (KAM) regions. The first figure shows the difference between chaotic and KAM regions in a chaotic laminar pipe flow. Trapping occurs when particles are scattered from high-strain regions in the chaotic zones and become trapped in the KAM regions, leading to a rapid concentration of particles relative to their original distribution (shown in the second series of figures). Using a combination of these analogue experiments and theoretical analysis we outline the conditions under which this clustering process can occur. We examine the onset of secondary density-related instabilities and the effects of increased particle-particle interaction within the clustered particles, and highlight the impact of particle clustering on the dynamics of magma ascent and emplacement.

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.

Environmental controls on microbial abundance and activity on the greenland ice sheet: a multivariate analysis approach.

PubMed

Stibal, Marek; Telling, Jon; Cook, Joe; Mak, Ka Man; Hodson, Andy; Anesio, Alexandre M

2012-01-01

Microbes in supraglacial ecosystems have been proposed to be significant contributors to regional and possibly global carbon cycling, and quantifying the biogeochemical cycling of carbon in glacial ecosystems is of great significance for global carbon flow estimations. Here we present data on microbial abundance and productivity, collected along a transect across the ablation zone of the Greenland ice sheet (GrIS) in summer 2010. We analyse the relationships between the physical, chemical and biological variables using multivariate statistical analysis. Concentrations of debris-bound nutrients increased with distance from the ice sheet margin, as did both cell numbers and activity rates before reaching a peak (photosynthesis) or a plateau (respiration, abundance) between 10 and 20 km from the margin. The results of productivity measurements suggest an overall net autotrophy on the GrIS and support the proposed role of ice sheet ecosystems in carbon cycling as regional sinks of CO(2) and places of production of organic matter that can be a potential source of nutrients for downstream ecosystems. Principal component analysis based on chemical and biological data revealed three clusters of sites, corresponding to three 'glacier ecological zones', confirmed by a redundancy analysis (RDA) using physical data as predictors. RDA using data from the largest 'bare ice zone' showed that glacier surface slope, a proxy for melt water flow, accounted for most of the variation in the data. Variation in the chemical data was fully explainable by the determined physical variables. Abundance of phototrophic microbes and their proportion in the community were identified as significant controls of the carbon cycling-related microbial processes.

Determination of protection zones for Dutch groundwater wells against virus contamination--uncertainty and sensitivity analysis.

PubMed

Schijven, J F; Mülschlegel, J H C; Hassanizadeh, S M; Teunis, P F M; de Roda Husman, A M

2006-09-01

Protection zones of shallow unconfined aquifers in The Netherlands were calculated that allow protection against virus contamination to the level that the infection risk of 10(-4) per person per year is not exceeded with a 95% certainty. An uncertainty and a sensitivity analysis of the calculated protection zones were included. It was concluded that protection zones of 1 to 2 years travel time (206-418 m) are needed (6 to 12 times the currently applied travel time of 60 days). This will lead to enlargement of protection zones, encompassing 110 unconfined groundwater well systems that produce 3 x 10(8) m3 y(-1) of drinking water (38% of total Dutch production from groundwater). A smaller protection zone is possible if it can be shown that an aquifer has properties that lead to greater reduction of virus contamination, like more attachment. Deeper aquifers beneath aquitards of at least 2 years of vertical travel time are adequately protected because vertical flow in the aquitards is only 0.7 m per year. The most sensitive parameters are virus attachment and inactivation. The next most sensitive parameters are grain size of the sand, abstraction rate of groundwater, virus concentrations in raw sewage and consumption of unboiled drinking water. Research is recommended on additional protection by attachment and under unsaturated conditions.

Numerical simulation and comparison of two ventilation methods for a restaurant - displacement vs mixed flow ventilation

NASA Astrophysics Data System (ADS)

Chitaru, George; Berville, Charles; Dogeanu, Angel

2018-02-01

This paper presents a comparison between a displacement ventilation method and a mixed flow ventilation method using computational fluid dynamics (CFD) approach. The paper analyses different aspects of the two systems, like the draft effect in certain areas, the air temperatureand velocity distribution in the occupied zone. The results highlighted that the displacement ventilation system presents an advantage for the current scenario, due to the increased buoyancy driven flows caused by the interior heat sources. For the displacement ventilation case the draft effect was less prone to appear in the occupied zone but the high heat emissions from the interior sources have increased the temperature gradient in the occupied zone. Both systems have been studied in similar conditions, concentrating only on the flow patterns for each case.

CONTINUOUS GAS ANALYZER

DOEpatents

Katz, S.; Weber, C.W.

1960-02-16

A reagent gas and a sample gas are chemically combined on a continuous basis in a reaction zone maintained at a selected temperature. The reagent gas and the sample gas are introduced to the reaction zone at preselected. constant molar rates of flow. The reagent gas and the selected gas in the sample mixture combine in the reaction zone to form a product gas having a different number of moles from the sum of the moles of the reactants. The difference in the total molar rates of flow into and out of the reaction zone is measured and indicated to determine the concentration of the selected gas.

Method and system for the removal of oxides of nitrogen and sulfur from combustion processes

DOEpatents

Walsh, John V.

1987-12-15

A process for removing oxide contaminants from combustion gas, and employing a solid electrolyte reactor, includes: (a) flowing the combustion gas into a zone containing a solid electrolyte and applying a voltage and at elevated temperature to thereby separate oxygen via the solid electrolyte, (b) removing oxygen from that zone in a first stream and removing hot effluent gas from that zone in a second stream, the effluent gas containing contaminant, (c) and pre-heating the combustion gas flowing to that zone by passing it in heat exchange relation with the hot effluent gas.

CFD Analysis in Advance of the NASA Juncture Flow Experiment

NASA Technical Reports Server (NTRS)

Lee, H. C.; Pulliam, T. H.; Neuhart, D. H.; Kegerise, M. A.

2017-01-01

NASA through its Transformational Tools and Technologies Project (TTT) under the Advanced Air Vehicle Program, is supporting a substantial effort to investigate the formation and origin of separation bubbles found on wing-body juncture zones. The flow behavior in these regions is highly complex, difficult to measure experimentally, and challenging to model numerically. Multiple wing configurations were designed and evaluated using Computational Fluid Dynamics (CFD), and a series of wind tunnel risk reduction tests were performed to further down-select the candidates for the final experiment. This paper documents the CFD analysis done in conjunction with the 6 percent scale risk reduction experiment performed in NASA Langley's 14- by 22-Foot Subsonic Tunnel. The combined CFD and wind tunnel results ultimately helped the Juncture Flow committee select the wing configurations for the final experiment.

Evaluating the reliability of the stream tracer approach to characterize stream-subsurface water exchange

USGS Publications Warehouse

Harvey, Judson W.; Wagner, Brian J.; Bencala, Kenneth E.

1996-01-01

Stream water was locally recharged into shallow groundwater flow paths that returned to the stream (hyporheic exchange) in St. Kevin Gulch, a Rocky Mountain stream in Colorado contaminated by acid mine drainage. Two approaches were used to characterize hyporheic exchange: sub-reach-scale measurement of hydraulic heads and hydraulic conductivity to compute streambed fluxes (hydrometric approach) and reachscale modeling of in-stream solute tracer injections to determine characteristic length and timescales of exchange with storage zones (stream tracer approach). Subsurface data were the standard of comparison used to evaluate the reliability of the stream tracer approach to characterize hyporheic exchange. The reach-averaged hyporheic exchange flux (1.5 mL s−1 m−1), determined by hydrometric methods, was largest when stream base flow was low (10 L s−1); hyporheic exchange persisted when base flow was 10-fold higher, decreasing by approximately 30%. Reliability of the stream tracer approach to detect hyporheic exchange was assessed using first-order uncertainty analysis that considered model parameter sensitivity. The stream tracer approach did not reliably characterize hyporheic exchange at high base flow: the model was apparently more sensitive to exchange with surface water storage zones than with the hyporheic zone. At low base flow the stream tracer approach reliably characterized exchange between the stream and gravel streambed (timescale of hours) but was relatively insensitive to slower exchange with deeper alluvium (timescale of tens of hours) that was detected by subsurface measurements. The stream tracer approach was therefore not equally sensitive to all timescales of hyporheic exchange. We conclude that while the stream tracer approach is an efficient means to characterize surface-subsurface exchange, future studies will need to more routinely consider decreasing sensitivities of tracer methods at higher base flow and a potential bias toward characterizing only a fast component of hyporheic exchange. Stream tracer models with multiple rate constants to consider both fast exchange with streambed gravel and slower exchange with deeper alluvium appear to be warranted.

High aeration rate enhances flow stratification in full-scale oxidation ditch.

PubMed

Diamantis, Vasileios; Papaspyrou, Ioannis; Melidis, Parasxos; Aivasidis, Alexander

2010-02-01

Aerated channel reactors with a uniform field of aeration may display flow stratification and short-circuit phenomena in wastewater treatment systems. In this study, we present data suggesting that flow stratification is closely related to the aeration rate and the arrangement of aerators. A full-scale oxidation ditch, with a total volume of 6,500 m(3) and a membrane-diffused aerated zone of 60 x 7 x 5 m (length-width-depth), was selected for water velocity measurements. Two profiles of the oxidation ditch were studied in detail: the first one was at the end of the aerated zone and the second one at the end of the anoxic zone. The results of this work demonstrate that the horizontal water velocity at the end of the aerated zone displayed significant stratification, with maximum velocity near the water surface (0.5-0.7 m/s) and almost zero velocity at a depth of 2.5 m. At the end of the anoxic zone, water velocity was uniform and equal to 0.27-0.31 m/s. Increasing the aeration rate from 1,800 to 4,300 m(3)/h, almost 90% of the water flow was found to discharge through the upper-half of the channel reactor profile. Different options to mitigate flow stratification of the oxidation ditch are discussed in this paper.

Preferential flow, diffuse flow, and perching in an interbedded fractured-rock unsaturated zone

NASA Astrophysics Data System (ADS)

Nimmo, John R.; Creasey, Kaitlyn M.; Perkins, Kim S.; Mirus, Benjamin B.

2017-03-01

Layers of strong geologic contrast within the unsaturated zone can control recharge and contaminant transport to underlying aquifers. Slow diffuse flow in certain geologic layers, and rapid preferential flow in others, complicates the prediction of vertical and lateral fluxes. A simple model is presented, designed to use limited geological site information to predict these critical subsurface processes in response to a sustained infiltration source. The model is developed and tested using site-specific information from the Idaho National Laboratory in the Eastern Snake River Plain (ESRP), USA, where there are natural and anthropogenic sources of high-volume infiltration from floods, spills, leaks, wastewater disposal, retention ponds, and hydrologic field experiments. The thick unsaturated zone overlying the ESRP aquifer is a good example of a sharply stratified unsaturated zone. Sedimentary interbeds are interspersed between massive and fractured basalt units. The combination of surficial sediments, basalts, and interbeds determines the water fluxes through the variably saturated subsurface. Interbeds are generally less conductive, sometimes causing perched water to collect above them. The model successfully predicts the volume and extent of perching and approximates vertical travel times during events that generate high fluxes from the land surface. These developments are applicable to sites having a thick, geologically complex unsaturated zone of substantial thickness in which preferential and diffuse flow, and perching of percolated water, are important to contaminant transport or aquifer recharge.

Preferential flow, diffuse flow, and perching in an interbedded fractured-rock unsaturated zone

USGS Publications Warehouse

Nimmo, John R.; Creasey, Kaitlyn M; Perkins, Kimberlie; Mirus, Benjamin B.

2017-01-01

Layers of strong geologic contrast within the unsaturated zone can control recharge and contaminant transport to underlying aquifers. Slow diffuse flow in certain geologic layers, and rapid preferential flow in others, complicates the prediction of vertical and lateral fluxes. A simple model is presented, designed to use limited geological site information to predict these critical subsurface processes in response to a sustained infiltration source. The model is developed and tested using site-specific information from the Idaho National Laboratory in the Eastern Snake River Plain (ESRP), USA, where there are natural and anthropogenic sources of high-volume infiltration from floods, spills, leaks, wastewater disposal, retention ponds, and hydrologic field experiments. The thick unsaturated zone overlying the ESRP aquifer is a good example of a sharply stratified unsaturated zone. Sedimentary interbeds are interspersed between massive and fractured basalt units. The combination of surficial sediments, basalts, and interbeds determines the water fluxes through the variably saturated subsurface. Interbeds are generally less conductive, sometimes causing perched water to collect above them. The model successfully predicts the volume and extent of perching and approximates vertical travel times during events that generate high fluxes from the land surface. These developments are applicable to sites having a thick, geologically complex unsaturated zone of substantial thickness in which preferential and diffuse flow, and perching of percolated water, are important to contaminant transport or aquifer recharge.

Radiocarbon dates for lava flows from northeast rift zone of Mauna Loa Volcano, Hilo 7 1/2 minute quadrangle, Island of Hawaii

USGS Publications Warehouse

Buchanan-Banks, J. M.; Lockwood, J.P.; Rubin, M.

1989-01-01

Twenty-eight 14C analyses are reported for carbonized roots and other plant material collected from beneath 15 prehistoric lava flows erupted from the northeast rift zone (NERZ) of Mauna Loa Volcano (ML). The new 14C dates establish ages for 13 previously undated lava flows, and correct or add to information previously reported. Limiting ages on other flows that lie either above or below the dated flows are also established. These dates help to unravel the eruptive history of ML's NERZ. -from Authors

Steady flows in the chromosphere and transition-zone above active regions as observed by OSO-8

NASA Technical Reports Server (NTRS)

Lites, B. W.

1980-01-01

Two years of data from the University of Colorado ultraviolet spectrometer aboard OSO-8 were searched for steady line-of-sight flows in the chromosphere and transition-zone above active regions. The most conspicuous pattern that emerges from this data set is that many sunspots show persistent blueshifts of transition-zone lines indicating velocities of about 20 km/s with respect to the surrounding plage areas. The data show much smaller shifts in ultraviolet emission lines arising from the chromosphere: the shifts are frequently to the blue, but sometimes redshifts do occur. Plage areas often show a redshift of the transition-zone lines relative to the surrounding quiet areas, and a strong gradient of the vertical component of the velocity is evident in many plages. One area of persistent blueshift was observed in the transition-zone above an active region filament. The energy requirement of these steady flows over sunspots is discussed.

Reductive dechlorination of chlorinated ethenes under oxidation-reduction conditions and potentiometric surfaces in two trichloroethene-contaminated zones at the Double Eagle and Fourth Street Superfund sites in Oklahoma City, Oklahoma

USGS Publications Warehouse

Braun, Christopher L.

2004-01-01

The Double Eagle Refining Superfund site and the Fourth Street Abandoned Refinery Superfund site are in northeast Oklahoma City, Oklahoma, adjacent to one another. The Double Eagle facility became a Superfund site on the basis of contamination from lead and volatile organic compounds; the Fourth Street facility on the basis of volatile organic compounds, pesticides, and acid-base neutral compounds. The study documented in this report was done to investigate whether reductive dechlorination of chlorinated ethenes under oxidation-reduction conditions is occurring in two zones of the Garber-Wellington aquifer (shallow zone 30–60 to 75 feet below land surface, deep zone 75 to 160 feet below land surface) at the sites; and to construct potentiometric surfaces of the two water-yielding zones to determine the directions of groundwater flow at the sites. The presence in some wells of intermediate products of reductive dechlorination, dichloroethene and vinyl chloride, is an indication that reductive dechlorination of trichloroethene is occurring. Dissolved oxygen concentrations (less than 0.5 milligram per liter) indicate that consumption of dissolved oxygen likely had occurred in the oxygen-reducing microbial process associated with reductive dechlorination. Concentrations of nitrate and nitrite nitrogen (generally less than 2.0 and 0.06 milligrams per liter, respectively) indicate that nitrate reduction probably is not a key process in either aquifer zone. Concentrations of ferrous iron greater than 1.00 milligram per liter in the majority of wells sampled indicate that iron reduction is probable. Concentrations of sulfide less than 0.05 milligram per liter in all wells indicate that sulfate reduction probably is not a key process in either zone. The presence of methane in ground water is an indication of strongly reducing conditions that facilitate reductive dechlorination. Methane was detected in all but one well. In the shallow zone in the eastern part of the study area, ground water flowing from the northwest and south coalesces in a potentiometric trough, then moves westward and ultimately northwestward. In the western part of the study area, ground water in the shallow zone flows northwest. In the deep zone in the eastern part of the study area, ground water generally flows northwestward; and in the western part of the study area, ground water in the deep zone generally flows northward.

Origin and emplacement of the andesite of Burroughs Mountain, a zoned, large-volume lava flow at Mount Rainier, Washington, USA

USGS Publications Warehouse

Stockstill, K.R.; Vogel, T.A.; Sisson, T.W.

2002-01-01

Burroughs Mountain, situated at the northeast foot of Mount Rainier, WA, exposes a large-volume (3.4 km3) andesitic lava flow, up to 350 m thick and extending 11 km in length. Two sampling traverses from flow base to eroded top, over vertical sections of 245 and 300 m, show that the flow consists of a felsic lower unit (100 m thick) overlain sharply by a more mafic upper unit. The mafic upper unit is chemically zoned, becoming slightly more evolved upward; the lower unit is heterogeneous and unzoned. The lower unit is also more phenocryst-rich and locally contains inclusions of quenched basaltic andesite magma that are absent from the upper unit. Widespread, vuggy, gabbronorite-to-diorite inclusions may be fragments of shallow cumulates, exhumed from the Mount Rainier magmatic system. Chemically heterogeneous block-and-ash-flow deposits that conformably underlie the lava flow were the earliest products of the eruptive episode. The felsic-mafic-felsic progression in lava composition resulted from partial evacuation of a vertically-zoned magma reservoir, in which either (1) average depth of withdrawal increased, then decreased, during eruption, perhaps due to variations in effusion rate, or (2) magmatic recharge stimulated ascent of a plume that brought less evolved magma to shallow levels at an intermediate stage of the eruption. Pre-eruptive zonation resulted from combined crystallization- differentiation and intrusion(s) of less evolved magma into the partly crystallized resident magma body. The zoned lava flow at Burroughs Mountain shows that, at times, Mount Rainier's magmatic system has developed relatively large, shallow reservoirs that, despite complex recharge events, were capable of developing a felsic-upward compositional zonation similar to that inferred from large ash-flow sheets and other zoned lava flows. ?? 2002 Elsevier Science B.V. All rights reserved.

Development of computational fluid dynamics--habitat suitability (CFD-HSI) models to identify potential passage--Challenge zones for migratory fishes in the Penobscot River

USGS Publications Warehouse

Haro, Alexander J.; Dudley, Robert W.; Chelminski, Michael

2012-01-01

A two-dimensional computational fluid dynamics-habitat suitability (CFD–HSI) model was developed to identify potential zones of shallow depth and high water velocity that may present passage challenges for five anadromous fish species in the Penobscot River, Maine, upstream from two existing dams and as a result of the proposed future removal of the dams. Potential depth-challenge zones were predicted for larger species at the lowest flow modeled in the dam-removal scenario. Increasing flows under both scenarios increased the number and size of potential velocity-challenge zones, especially for smaller species. This application of the two-dimensional CFD–HSI model demonstrated its capabilities to estimate the potential effects of flow and hydraulic alteration on the passage of migratory fish.

An Angus/Argo study of the neovolcanic zone along the East Pacific rise from the Clipperton fracture zone to 12°N

USGS Publications Warehouse

Uchupi, E.; Schwab, W.C.; Ballard, Richard D.; Cheminee, J.L.; Francheteau, Jean; Hekinian, R.; Blackman, D.K.; Sigurdsson, Haraldur

1988-01-01

Still photographs and video images collected along the Neovolcanic Zone of the East Pacific Rise from 10°15′N to 11°53′N show that recent volcanic sheet flows, possibly less than 100 years old, are superimposed on an older sediment-laden pillow terrane. This recent activity is restricted to a narrow zone that crosses two topographic highs at 10°55′N and 11°26′N and diminishes along-axis away from these highs. The association of recent sheet flows with older flows and collapse structures on the overlapping spreading centers at 11°45′N supports the evolutionary model for the occurrence and evolution of overlapping spreading centers by MacDonald and others (1986, 1988).

Hydroelastic effects in the aorta bifurcation zone

NASA Technical Reports Server (NTRS)

Volmir, A. S.; Gersheyn, M. S.; Purinya, B. A.

1980-01-01

The mechanical behavior of the vessels and blood is mathematically analyzed at the point of aortic bifurcation using a homogeneous single layer channel as a model of the aorta. Allowance is made for the fact that the aortic intima is considerably less rigid than the other layers. For analysis of blood flow in the major arteries, the blood is treated as a viscous Newtonian fluid whose movements are described by Navier-Stokes equations and a continuity equation. Blood flow dynamics at the aortic bifurcation are discussed on the basis of the results.

Application of Analysis and Modeling for Surface Water-Ground Water System: Preliminary Study of Artificial Recharge in Jeju Island, Korea

NASA Astrophysics Data System (ADS)

Kim, Y.; Koo, M.; Lee, K.; Ko, K.; Barry, J. M.

2008-12-01

The primary goal of this study is to secure sustainable groundwater resources with application of the analysis and modeling of coupled surface water-groundwater system to Jeju Island in the form of artificial recharge. Artificial recharge technology is a feasible method to augment groundwater resources in Jeju Island, Korea. Jeju-friendly Aquifer Recharge Technology (J-ART) that will be developed in this study is a technology for securing sustainable water resources by capturing ephemeral stream water with no interference in the environment such as natural recharge or eco-system, capturing the water in the reservoirs, recharging it through designed borehole after appropriate treatment, and then making it to be used at down-gradient production wells. Precipitation pattern in the study area is shifting to more sparsely-distributed and heavier rain type in summer season which reduces infiltration and/or groundwater recharge but increases runoff and flash flood on stream. Stream water as a source for J-ART is available only a few times a year since the stream bed is highly feasible to be percolated. To characterize quantitatively stream water, automatic temporal data collection system for water level, water velocity, and water qualities of total 8 parameters including temperature, water depth, pH, EC, DO, turbidity, NO3-N and Cl-. Characterizing groundwater flow from recharge area to discharge area should be achieved to evaluate the efficiency of J-ART. Jeju volcanic island has very thick unsaturated zone which is approximately 50 percent of the elevation on which it is. This hydrogeological property is good to inject source water through unsaturated zone to increase transport time, to get main basal aquifer, and to naturally filter the injected water during the transport. However, characterizing groundwater flow through the thick unsaturated zone with repeatedly overlapping permeable/impermeable layers would be a challenge. Estimation method of the infiltration velocity of soil water, groundwater age dating, and evaluation method for groundwater flow/circulation using stable isotopes are developed to evaluate artificial recharge. Input parameters for groundwater flow model are collected and analyzed quantitatively to develop model for simulating groundwater flow and thermal transport during artificial recharge. Self-potential survey method is reviewed theoretically as a geophysical evaluation method to characterize unsaturated flow during artificial recharge.

Blueschist preservation in a retrograded, high-pressure, low-temperature metamorphic terrane, Tinos, Greece: Implications for fluid flow paths in subduction zones

NASA Astrophysics Data System (ADS)

Breeding, Christopher M.; Ague, Jay J.; BröCker, Michael; Bolton, Edward W.

2003-01-01

The preservation of high-pressure, low-temperature (HP-LT) mineral assemblages adjacent to marble unit contacts on the Cycladic island of Tinos in Greece was investigated using a new type of digital outcrop mapping and numerical modeling of metamorphic fluid infiltration. Mineral assemblage distributions in a large blueschist outcrop, adjacent to the basal contact of a 150-meter thick marble horizon, were mapped at centimeter-scale resolution onto digital photographs using a belt-worn computer and graphics editing software. Digital mapping reveals that while most HP-LT rocks in the outcrop were pervasively retrograded to greenschist facies, the marble-blueschist contact zone underwent an even more intense retrogression. Preservation of HP-LT mineral assemblages was mainly restricted to a 10-15 meter zone (or enclave) adjacent to the intensely retrograded lithologic contact. The degree and distribution of the retrograde overprint suggests that pervasively infiltrating fluids were channelized into the marble-blueschist contact and associated veins and flowed around the preserved HP-LT enclave. Numerical modeling of Darcian flow, based on the field observations, suggests that near the marble horizon, deflections in fluid flow paths caused by flow channelization along the high-permeability marble-blueschist contact zone likely resulted in very large fluid fluxes along the lithologic contact and significantly smaller fluxes (as much as 8 times smaller than the input flux) within the narrow, low-flux regions where HP-LT minerals were preserved adjacent to the contact. Our results indicate that lithologic contacts are important conduits for metamorphic fluid flow in subduction zones. Channelization of retrograde fluids into these discrete flow conduits played a critical role in the preservation of HP-LT assemblages.

Flow visualization and flow field measurements of a 1/12 scale tilt rotor aircraft in hover

NASA Technical Reports Server (NTRS)

Coffen, Charles D.; George, Albert R.; Hardinge, Hal; Stevenson, Ryan

1991-01-01

The results are given of flow visualization studies and inflow velocity field measurements performed on a 1/12 scale model of the XV-15 tilt rotor aircraft in the hover mode. The complex recirculating flow due to the rotor-wake-body interactions characteristic of tilt rotors was studied visually using neutrally buoyant soap bubbles and quantitatively using hot wire anemometry. Still and video photography were used to record the flow patterns. Analysis of the photos and video provided information on the physical dimensions of the recirculating fountain flow and on details of the flow including the relative unsteadiness and turbulence characteristics of the flow. Recirculating flows were also observed along the length of the fuselage. Hot wire anemometry results indicate that the wing under the rotor acts to obstruct the inflow causing a deficit in the inflow velocities over the inboard region of the model. Hot wire anemometry also shows that the turbulence intensities in the inflow are much higher in the recirculating fountain reingestion zone.

Linking fault pattern with groundwater flow in crystalline rocks at the Grimsel Test Site (Switzerland)

NASA Astrophysics Data System (ADS)

Schneeberger, Raphael; Berger, Alfons; Mäder, Urs K.; Niklaus Waber, H.; Kober, Florian; Herwegh, Marco

2017-04-01

Water flow across crystalline bedrock is of major interest for deep-seated geothermal energy projects as well as for underground disposal of radioactive waste. In crystalline rocks enhanced fluid flow is related to zones of increased permeability, i.e. to fractures that are associated to fault zones. The flow regime around the Grimsel Test Site (GTS, Central Aar massif) was assessed by establishing a 3D fault zone pattern on a local scale in the GTS underground facility (deca-meter scale) and on a regional scale at the surface (km-scale). The study reveals the existence of a dense fault zone network consisting of several km long and few tens of cm to meter wide, sub-vertically oriented major faults that are connected by tens to hundreds of meters long minor bridging faults. This geometrical information was used as input for the generation of a 3D fault zone network model. The faults originate from ductile shear zones that were reactivated as brittle faults under retrograde conditions during exhumation. Embrittlement and associated dilatancy along the faults provide the pathways for today's groundwater flow. Detection of the actual 3D flow paths is, however, challenging since flow seem to be not planar but rather tube-like. Two strategies are applied to constrain the 3D geometry of the flow tubes: (i) Characterization of the groundwater infiltrating into the GTS (location, yield, hydraulic head, and chemical composition) and (ii) stress modelling on the base of the 3D structural model to unravel potential domains of enhanced fluid flow such as fault plane intersections and domains of dilatancy. At the Grimsel Test Site, hydraulic and structural data demonstrate that the groundwater flow is head-driven from the surface towards the GTS located some 450 m below the surface. The residence time of the groundwater in this surface-near section is >60 years as evidenced by absence of detectable tritium. However, hydraulic heads obtained from interval pressure measurements within boreholes are variable and do not correspond to the overburden above the interval. Underground mapping revealed close spatial relation between water inflow points and faults, major water inflows occur in strongly deformed areas of the GTS. Furthermore, persistent differences in the groundwater chemical composition between infiltration points indicate that connectivity between different water flow paths is poor. Different findings indicate complex flow path geometries. However, domains of enhanced dilatancy and domains with increased number of fault intersections correlate with areas in the underground with 'high' water inflow.

Contrastive analysis of cooling performance between a high-level water collecting cooling tower and a typical cooling tower

NASA Astrophysics Data System (ADS)

Wang, Miao; Wang, Jin; Wang, Jiajin; Shi, Cheng

2018-02-01

A three-dimensional (3D) numerical model is established and validated for cooling performance optimization between a high-level water collecting natural draft wet cooling tower (HNDWCT) and a usual natural draft wet cooling tower (UNDWCT) under the actual operation condition at Wanzhou power plant, Chongqing, China. User defined functions (UDFs) of source terms are composed and loaded into the spray, fill and rain zones. Considering the conditions of impact on three kinds of corrugated fills (Double-oblique wave, Two-way wave and S wave) and four kinds of fill height (1.25 m, 1.5 m, 1.75 m and 2 m), numerical simulation of cooling performance are analysed. The results demonstrate that the S wave has the highest cooling efficiency in three fills for both towers, indicating that fill characteristics are crucial to cooling performance. Moreover, the cooling performance of the HNDWCT is far superior to that of the UNDWCT with fill height increases of 1.75 m and above, because the air mass flow rate in the fill zone of the HNDWCT improves more than that in the UNDWCT, as a result of the rain zone resistance declining sharply for the HNDWCT. In addition, the mass and heat transfer capacity of the HNDWCT is better in the tower centre zone than in the outer zone near the tower wall under a uniform fill layout. This behaviour is inverted for the UNDWCT, perhaps because the high-level collection devices play the role of flow guiding in the inner zone. Therefore, when non-uniform fill layout optimization is applied to the HNDWCT, the inner zone increases in height from 1.75 m to 2 m, the outer zone reduces in height from 1.75 m to 1.5 m, and the outlet water temperature declines approximately 0.4 K compared to that of the uniform layout.

Superplastic flow lubricates carbonate faults during earthquake slip

NASA Astrophysics Data System (ADS)

De Paola, Nicola; Holdsworth, Robert; Viti, Cecilia; Collettini, Cristiano; Faoro, Igor; Bullock, Rachael

2014-05-01

Tectonic earthquakes are hosted in the shallower portion of crustal fault zones, where fracturing and cataclasis are thought to be the dominant processes during frictional sliding. Aseismic shear in lower crust and lithospheric mantle shear zones is accomplished by crystal plasticity, including superplastic flow acting at low strain rates on ultrafine-grained rocks. Superplasticity has also been observed at high strain rates for a range of nano-phase alloys and ceramics, and could potentially occur in fine-grained geological materials, if deformed at high strain rates and temperatures. We performed a set of displacement-controlled experiments to explore whether superplastic flow can effectively weaken faults, and facilitate earthquake propagation. The experiments were performed on fine-grained synthetic gouges (63 < f < 93 μm) of undeformed, protolith carbonate rocks using a rotary shear apparatus, at target speed v = 1 ms-1, normal stresses σn = 12-18 MPa, displacements d from 0.009 to 1.46 m, room temperature and humidity conditions. Samples were recovered after each experiment to study the slip zone microstructures. The integration of experimental data and microstructural observations shows that during sliding at seismic velocity, brittle fracturing and cataclasis control shear localization and grain size reduction in the slip zone at relatively low temperatures (T ≤ 100 °C). Stress levels predicted by such behaviours match those measured during the experiments. As temperatures rise due to frictional heating (T ≥ 500 °C), dislocation creep mechanisms start to accommodate intragranular strain, and play a key role in producing nanoscale subgrains (< 200 nm) in the slip zone. At this stage, despite of the presence of nanoparticles in the slip zone and the attainment of seismic slip rates, the measured frictional strength of experimental faults still lies within Byerlee's range of values μ = 0.8. This suggests that the slip zone bulk strength at this stage is controlled by cataclastic frictional sliding rather than by dislocation creep or nanopowder lubrication mechanisms. When T ≥ 800 °C are attained, micro-textures diagnostic of diffusion-dominated grain boundary sliding are widespread within the slip zone, and suggest bulk superplastic flow. Flow stresses predicted by superplasticity constitutive laws at the slip zone temperatures, grain sizes and strain rates attained during the experiments match those we measured in the laboratory (μ = 0.16). We propose therefore that the activation of diffusion creep at high temperatures (T ≥ 800 °C) leads to slip zone-localised superplastic flow and that this causes the dynamic weakening of carbonate faults at seismic slip rates. Note, however, that both cataclasis and dislocation creep operating at lower temperatures, during the earlier stages of slip, are critical, precursory processes needed to produce the nanoscale grain sizes required to activate grainsize sensitive mechanisms during superplastic flow. Finally, the re-strengthening observed during the decelerating phase of deformation can be explained by the falling temperature "switching off" slip zone-localized superplasticity, leading to a return to frictional sliding. These results indicate that superplastic flow can effectively weaken faults, and facilitate earthquake propagation in the upper crust.

Viscosity changes of riparian water controls diurnal fluctuations of stream-flow and DOC concentration

NASA Astrophysics Data System (ADS)

Schwab, Michael; Klaus, Julian; Pfister, Laurent; Weiler, Markus

2015-04-01

Diurnal fluctuations in stream-flow are commonly explained as being triggered by the daily evapotranspiration cycle in the riparian zone, leading to stream flow minima in the afternoon. While this trigger effect must necessarily be constrained by the extent of the growing season of vegetation, we here show evidence of daily stream flow maxima in the afternoon in a small headwater stream during the dormant season. We hypothesize that the afternoon maxima in stream flow are induced by viscosity changes of riparian water that is caused by diurnal temperature variations of the near surface groundwater in the riparian zone. The patterns were observed in the Weierbach headwater catchment in Luxembourg. The catchment is covering an area of 0.45 km2, is entirely covered by forest and is dominated by a schistous substratum. DOC concentration at the outlet of the catchment was measured with the field deployable UV-Vis spectrometer spectro::lyser (scan Messtechnik GmbH) with a high frequency of 15 minutes over several months. Discharge was measured with an ISCO 4120 Flow Logger. During the growing season, stream flow shows a frequently observed diurnal pattern with discharge minima in the afternoon. During the dormant season, a long dry period with daily air temperature amplitudes of around 10 ° C occurred in March and April 2014, with discharge maxima in the afternoon. The daily air temperature amplitude led to diurnal variations in the water temperature of the upper 10 cm of the riparian zone. Higher riparian water temperatures cause a decrease in water viscosity and according to the Hagen-Poiseuille equation, the volumetric flow rate is inversely proportional to viscosity. Based on the Hagen-Poiseuille equation and the viscosity changes of water, we calculated higher flow rates of near surface groundwater through the riparian zone into the stream in the afternoon which explains the stream flow maxima in the afternoon. With the start of the growing season, the viscosity induced diurnal effect is overlain by the stronger influence of evapotranspiration. Diurnal DOC fluctuations show daily maxima in the afternoon. While daily variations in DOC concentrations are often explained by faster in-stream biogeochemical processes during daylight, we here propose that the viscosity effect in the riparian zone could explain the afternoon peaks in DOC concentrations. Our records show that daily water temperature variations and therefore viscosity changes only occur in the near surface parts of the riparian zone, where the DOC concentrations are higher than in deeper parts of the riparian zone. We calculated, that the viscosity induced higher flow rates from the near surface parts of the riparian zone can explain the DOC concentration maxima in the afternoon. As the viscosity effect does not disappear during the growing season but is just smaller than the evapotranspiration effect, the DOC concentration pattern is not changing between the dormant and growing seasons. The different controls of diurnal fluctuations of stream-flow and water quality concentrations need to be carefully considered in order to better understand the different patterns in catchment hydrology.

Structural analysis characterization of permeability pathways across reservoir-seal interface - South-Eastern Utah; Results from integrated sedimentological, structural, and geochemical studies.

NASA Astrophysics Data System (ADS)

Petrie, E. S.; Evans, J. P.; Richey, D.; Flores, S.; Barton, C.; Mozley, P.

2015-12-01

Sedimentary rocks in the San Rafael Swell, Utah, were deformed by Laramide compression and subsequent Neogene extension. We evaluate the effect of fault damage zone morphology as a function of structural position, and changes in mechanical stratigraphy on the distribution of secondary minerals across the reservoir-seal pair of the Navajo Sandstone and overlying Carmel Formation. We decipher paleo-fluid migration and examine the effect faults and fractures have on reservoir permeability and efficacy of top seal for a range of geo-engineering applications. Map-scale faults have an increased probability of allowing upward migration of fluids along the fault plane and within the damage zone, potentially bypassing the top seal. Field mapping, mesoscopic structural analyses, petrography, and geochemical observations demonstrate that fault zone thickness increases at structural intersections, fault relay zones, fault-related folds, and fault tips. Higher densities of faults with meters of slip and dense fracture populations are present in relay zones relative to single, discrete faults. Curvature analysis of the San Rafael monocline and fracture density data show that fracture density is highest where curvature is highest in the syncline hinge and near faults. Fractures cross the reservoir-seal interface where fracture density is highest and structural diagensis includes mineralization events and bleaching and calcite and gypsum mineralization. The link between fracture distributions and structural setting implys that transmissive fractures have predictable orientations and density distributions. At the m- to cm- scale, deformation-band faults and joints in the Navajo Sandstone penetrate the reservoir-seal interface and transition into open-mode fractures in the caprock seal. Scanline analysis and petrography of veins provide evidence for subsurface mineralization and fracture reactivation, suggesting that the fractures act as loci for fluid flow through time. Heterolithic caprock seals with variable fracture distributions and morphology highlight the strong link between the variation in material properties and the response to changing stress conditions. The variable connectivity of fractures and the changes in fracture density plays a critical role in subsurface fluid flow.

Effects of Packed Structure and Operation Conditions on Liquid Flow Behavior in Blast Furnace Hearth

NASA Astrophysics Data System (ADS)

Zuo, Haibin; Hong, Jun; Zhang, Jianliang; Zheng, Jin

The circulating flow of molten iron is an important reason that results in the erosion of blast furnace hearth. In order to prolong the campaign life of blast furnace, it is necessary to analysis the flow state of molten iron. The three-dimensional mathematical model at steady state which takes the standard k-e and porous zone model into consideration is applied to simulate the flow field under different conditions. The results showed that floating of the deadman did strengthen molten iron circulating flow. Increasing the deadman diameter will increase the erosion of hearth and bottom. Deepen the depth of the taphole and reduce the taphole diameter can reduce the circulating flow. Effect of the taphole angle from 10° to 15° is not significant. The results can be used to provide guidance for protecting the blast furnace hearth.

Hybrid Stochastic Forecasting Model for Management of Large Open Water Reservoir with Storage Function

NASA Astrophysics Data System (ADS)

Kozel, Tomas; Stary, Milos

2017-12-01

The main advantage of stochastic forecasting is fan of possible value whose deterministic method of forecasting could not give us. Future development of random process is described better by stochastic then deterministic forecasting. Discharge in measurement profile could be categorized as random process. Content of article is construction and application of forecasting model for managed large open water reservoir with supply function. Model is based on neural networks (NS) and zone models, which forecasting values of average monthly flow from inputs values of average monthly flow, learned neural network and random numbers. Part of data was sorted to one moving zone. The zone is created around last measurement average monthly flow. Matrix of correlation was assembled only from data belonging to zone. The model was compiled for forecast of 1 to 12 month with using backward month flows (NS inputs) from 2 to 11 months for model construction. Data was got ridded of asymmetry with help of Box-Cox rule (Box, Cox, 1964), value r was found by optimization. In next step were data transform to standard normal distribution. The data were with monthly step and forecast is not recurring. 90 years long real flow series was used for compile of the model. First 75 years were used for calibration of model (matrix input-output relationship), last 15 years were used only for validation. Outputs of model were compared with real flow series. For comparison between real flow series (100% successfully of forecast) and forecasts, was used application to management of artificially made reservoir. Course of water reservoir management using Genetic algorithm (GE) + real flow series was compared with Fuzzy model (Fuzzy) + forecast made by Moving zone model. During evaluation process was founding the best size of zone. Results show that the highest number of input did not give the best results and ideal size of zone is in interval from 25 to 35, when course of management was almost same for all numbers from interval. Resulted course of management was compared with course, which was obtained from using GE + real flow series. Comparing results showed that fuzzy model with forecasted values has been able to manage main malfunction and artificially disorders made by model were founded essential, after values of water volume during management were evaluated. Forecasting model in combination with fuzzy model provide very good results in management of water reservoir with storage function and can be recommended for this purpose.

A detached eddy simulation model for the study of lateral separation zones along a large canyon-bound river

NASA Astrophysics Data System (ADS)

Alvarez, Laura V.; Schmeeckle, Mark W.; Grams, Paul E.

2017-01-01

Lateral flow separation occurs in rivers where banks exhibit strong curvature. In canyon-bound rivers, lateral recirculation zones are the principal storage of fine-sediment deposits. A parallelized, three-dimensional, turbulence-resolving model was developed to study the flow structures along lateral separation zones located in two pools along the Colorado River in Marble Canyon. The model employs the detached eddy simulation (DES) technique, which resolves turbulence structures larger than the grid spacing in the interior of the flow. The DES-3D model is validated using Acoustic Doppler Current Profiler flow measurements taken during the 2008 controlled flood release from Glen Canyon Dam. A point-to-point validation using a number of skill metrics, often employed in hydrological research, is proposed here for fluvial modeling. The validation results show predictive capabilities of the DES model. The model reproduces the pattern and magnitude of the velocity in the lateral recirculation zone, including the size and position of the primary and secondary eddy cells, and return current. The lateral recirculation zone is open, having continuous import of fluid upstream of the point of reattachment and export by the recirculation return current downstream of the point of separation. Differences in magnitude and direction of near-bed and near-surface velocity vectors are found, resulting in an inward vertical spiral. Interaction between the recirculation return current and the main flow is dynamic, with large temporal changes in flow direction and magnitude. Turbulence structures with a predominately vertical axis of vorticity are observed in the shear layer becoming three-dimensional without preferred orientation downstream.

Changes in air flow patterns using surfactants and thickeners during air sparging: bench-scale experiments.

PubMed

Kim, Juyoung; Kim, Heonki; Annable, Michael D

2015-01-01

Air injected into an aquifer during air sparging normally flows upward according to the pressure gradients and buoyancy, and the direction of air flow depends on the natural hydrogeologic setting. In this study, a new method for controlling air flow paths in the saturated zone during air sparging processes is presented. Two hydrodynamic parameters, viscosity and surface tension of the aqueous phase in the aquifer, were altered using appropriate water-soluble reagents distributed before initiating air sparging. Increased viscosity retarded the travel velocity of the air front during air sparging by modifying the viscosity ratio. Using a one-dimensional column packed with water-saturated sand, the velocity of air intrusion into the saturated region under a constant pressure gradient was inversely proportional to the viscosity of the aqueous solution. The air flow direction, and thus the air flux distribution was measured using gaseous flux meters placed at the sand surface during air sparging experiments using both two-, and three-dimensional physical models. Air flow was found to be influenced by the presence of an aqueous patch of high viscosity or suppressed surface tension in the aquifer. Air flow was selective through the low-surface tension (46.5 dyn/cm) region, whereas an aqueous patch of high viscosity (2.77 cP) was as an effective air flow barrier. Formation of a low-surface tension region in the target contaminated zone in the aquifer, before the air sparging process is inaugurated, may induce air flow through the target zone maximizing the contaminant removal efficiency of the injected air. In contrast, a region with high viscosity in the air sparging influence zone may minimize air flow through the region prohibiting the region from de-saturating. Copyright © 2014 Elsevier B.V. All rights reserved.

Segregation of male-sterility alleles across a species boundary.

PubMed

Weller, S G; Sakai, A K; Culley, T M; Duong, L; Danielson, R E

2014-02-01

Hybrid zones may serve as bridges permitting gene flow between species, including alleles influencing the evolution of breeding systems. Using greenhouse crosses, we assessed the likelihood that a hybrid zone could serve as a conduit for transfer of nuclear male-sterility alleles between a gynodioecious species and a hermaphroditic species with very rare females in some populations. Segregation patterns in progeny of crosses between rare females of hermaphroditic Schiedea menziesii and hermaphroditic plants of gynodioecious Schiedea salicaria heterozygous at the male-sterility locus, and between female S. salicaria and hermaphroditic plants from the hybrid zone, were used to determine whether male-sterility was controlled at the same locus in the parental species and the hybrid zone. Segregations of females and hermaphrodites in approximately equal ratios from many of the crosses indicate that the same nuclear male-sterility allele occurs in the parent species and the hybrid zone. These rare male-sterility alleles in S. menziesii may result from gene flow from S. salicaria through the hybrid zone, presumably facilitated by wind pollination in S. salicaria. Alternatively, rare male-sterility alleles might result from a reversal from gynodioecy to hermaphroditism in S. menziesii, or possibly de novo evolution of male sterility. Phylogenetic analysis indicates that some species of Schiedea have probably evolved separate sexes independently, but not in the lineage containing S. salicaria and S. menziesii. High levels of selfing and expression of strong inbreeding depression in S. menziesii, which together should favour females in populations, argue against a reversal from gynodioecy to hermaphroditism in S. menziesii. © 2014 The Authors. Journal of Evolutionary Biology © 2014 European Society For Evolutionary Biology.

Flow-dependent vascular heat transfer during microwave thermal ablation.

PubMed

Chiang, Jason; Hynes, Kieran; Brace, Christopher L

2012-01-01

Microwave tumor ablation is an attractive option for thermal ablation because of its inherent benefits over radiofrequency ablation (RFA) in the treatment of solid tumors such as hepatocellular carcinoma (HCC). Microwave energy heats tissue to higher temperatures and at a faster rate than RFA, creating larger, more homogenous ablation zones. In this study, we investigate microwave heating near large vasculature using coupled fluid-flow and thermal analysis. Low-flow conditions are predicted to be more likely to cause cytotoxic heating and, therefore, vessel thrombosis and endothelial damage of downstream tissues. Such conditions may be more prevalent in patient with severe cirrhosis or compromised blood flow. High-flow conditions create the more familiar heat-sink effect that can protect perivascular tissues from the intended thermal damage. These results may help guide placement and use of microwave ablation technologies in future studies.

Mantle shear-wave tomography and the fate of subducted slabs.

PubMed

Grand, Steven P

2002-11-15

A new seismic model of the three-dimensional variation in shear velocity throughout the Earth's mantle is presented. The model is derived entirely from shear bodywave travel times. Multibounce shear waves, core-reflected waves and SKS and SKKS waves that travel through the core are used in the analysis. A unique aspect of the dataset used in this study is the use of bodywaves that turn at shallow depths in the mantle, some of which are triplicated. The new model is compared with other global shear models. Although competing models show significant variations, several large-scale structures are common to most of the models. The high-velocity anomalies are mostly associated with subduction zones. In some regions the anomalies only extend into the shallow lower mantle, whereas in other regions tabular high-velocity structures seem to extend to the deepest mantle. The base of the mantle shows long-wavelength high-velocity zones also associated with subduction zones. The heterogeneity seen in global tomography models is difficult to interpret in terms of mantle flow due to variations in structure from one subduction zone to another. The simplest interpretation of the seismic images is that slabs in general penetrate to the deepest mantle, although the flow is likely to be sporadic. The interruption in slab sinking is likely to be associated with the 660 km discontinuity.

Effect of pin tool design on the material flow of dissimilar AA7075-AA6061 friction stir welds

NASA Astrophysics Data System (ADS)

Hasan, Mohammed M.; Ishak, M.; Rejab, M. R. M.

2017-10-01

Tool design is the most influential aspect in the friction stir welding (FSW) technology. Influence of pin tool geometry on material flow pattern are studied in this work during the FSW of dissimilar AA7075 and AA6061 aluminium alloys. Three truncated pin tool profiles (threaded, threaded with single flat, and unthreaded with single flat) were used to prepare the weldments. The workpieces were joined using a custom-made clamping system under 1100 rpm of spindle speed, 300 mm/min of traverse rate and 3° of tilt angle. The metallographic analysis showed that defect-free welds can be produced using the three pin tools with significant changes in the mixing stir zone structure. The results declared that the introducing of the flat on the cone of the probe deviates the pattern of the onion rings without changing the chemical composition of the created layers. This in turn improves the hardness distribution and tensile strength of the welded joint. It was also noted that both heat affected zone (HAZ) and thermal-mechanical affected zone (TMAZ) are similar in composition to their corresponding base materials (BM).

Soil Microbial Community Contribution to Small Headwater Stream Metabolism.

NASA Astrophysics Data System (ADS)

Clapcott, J. E.; Gooderham, J. P.; Barmuta, L. A.; Davies, P. E.

2005-05-01

The temporal dynamics of sediment respiration were examined in seven small headwater streams in forested catchments in 2004. A strong seasonal response was observed with higher respiration rates in depositional zones than in gravel runs. The data were also examined in the context of proportional habitat distributions that highlighted the importance of high flow events in shaping whole stream metabolic budgets. This study specifically examines the question of terrestrial soil respiration contribution to whole stream metabolism by the controlled inundation of terrestrial soils. The experiment included six experimentally inundated terrestrial zones, six terrestrial controls, and six in-stream depositional zones. Sediment bacterial respiration was measured using 14C leucine incorporation and cotton strip bioassays were also employed to provide an indicative measure of sediment microbial activity. Despite high variability and exhibiting significantly lower bacterial activity than in-stream sediments, modelling using flow data and habitat mapping illustrated the important contribution of terrestrial soil respiration to the whole stream metabolic budgets of small headwater streams. In addition, microbial community composition examined using phospholipid fatty acid analysis clearly differentiated between terrestrial and aquatic communities. Freshly inundated terrestrial communities remained similar to un-inundated controls after 28 days.

Evaporative cooling of air in an adiabatic channel with partially wetted zones

NASA Astrophysics Data System (ADS)

Terekhov, V. I.; Gorbachev, M. V.; Khafaji, H. Q.

2016-03-01

The paper deals with the numerical study of heat and mass transfer in the process of direct evaporation air cooling in the laminar flow of forced convection in a channel between two parallel insulated plates with alternating wet and dry zones along the length. The system of Navier-Stokes equations and equations of energy and steam diffusion are being solved in two-dimensional approximation. At the channel inlet, all thermal gas-dynamic parameters are constant over the cross section, and the channel walls are adiabatic. The studies were carried out with varying number of dry zones ( n = 0-16), their relative length ( s/l = 0-1) and Reynolds number Re = 50-1000 in the flow of dry air (φ0 = 0) with a constant temperature at the inlet (T 0 = 30 °C). The main attention is paid to optimization analysis of evaporation cell characteristics. It is shown that an increase in the number of alternating steps leads to an increase in the parameters of thermal and humid efficiency. With an increase in Re number and a decrease in the extent of wet areas, the efficiency parameter reduces.

Macro- and microscale variables regulate stent haemodynamics, fibrin deposition and thrombomodulin expression

PubMed Central

Jiménez, Juan M.; Prasad, Varesh; Yu, Michael D.; Kampmeyer, Christopher P.; Kaakour, Abdul-Hadi; Wang, Pei-Jiang; Maloney, Sean F.; Wright, Nathan; Johnston, Ian; Jiang, Yi-Zhou; Davies, Peter F.

2014-01-01

Drug eluting stents are associated with late stent thrombosis (LST), delayed healing and prolonged exposure of stent struts to blood flow. Using macroscale disturbed and undisturbed fluid flow waveforms, we numerically and experimentally determined the effects of microscale model strut geometries upon the generation of prothrombotic conditions that are mediated by flow perturbations. Rectangular cross-sectional stent strut geometries of varying heights and corresponding streamlined versions were studied in the presence of disturbed and undisturbed bulk fluid flow. Numerical simulations and particle flow visualization experiments demonstrated that the interaction of bulk fluid flow and stent struts regulated the generation, size and dynamics of the peristrut flow recirculation zones. In the absence of endothelial cells, deposition of thrombin-generated fibrin occurred primarily in the recirculation zones. When endothelium was present, peristrut expression of anticoagulant thrombomodulin (TM) was dependent on strut height and geometry. Thinner and streamlined strut geometries reduced peristrut flow recirculation zones decreasing prothrombotic fibrin deposition and increasing endothelial anticoagulant TM expression. The studies define physical and functional consequences of macro- and microscale variables that relate to thrombogenicity associated with the most current stent designs, and particularly to LST. PMID:24554575

Deep thermal disturbances related to the sub-surface groundwater flow (Western Alps, France)

NASA Astrophysics Data System (ADS)

Mommessin, Grégoire; Dzikowski, Marc; Menard, Gilles; Monin, Nathalie

2013-04-01

In mountain area, the bedrock of the valley side is affected by a thickness of decompressed rock in subsurface (decompressed zone). Groundwater flowing in this zone disrupts the depth geothermal gradients. The evolution of thermal gradients under the decompressed zone depends of groundwater temperature changes into the decompressed zone. In this study, the phenomenon is studied from data acquired in exploration drilling prior to the construction of the France - Italy transalpine tunnel (High Speed Line project between Lyon and Turin). The study area is located in the Vanoise siliceous series between Modane and Avrieux (Western Alps, France). Of 31 boreholes, we selected 14 wells showing a natural thermal disturbance (not due to the drilling) linked to the groundwater flow in decompressed zone. The drill holes have a length between 200 and 1380m and well logs were carried out (gamma log, acoustic log, temperature log, flowmeter log). The rocks are constituted mainly by quartzite with high thermal conductivity or by schist and gneiss with low thermal conductivity. The decompressed zone concerns the quartzite with thicknesses ranging from 50m to 750m where groundwater flow imposes a constant temperature throughout the rock thickness. In the very low permeability rocks under the decompressed zone, the thermal gradient shows variations with depth. These variations suggest a water temperature change in the decompressed zone probably due to a paleoclimate event. We used the derived of the equation describing the propagation of a temperature in a 1D semi-infinite, in response to a sudden temperature disturbance at the boundary of the medium, to estimate the age and the amplitude of temperature change in the decompressed zone. The medium under the decompressed zone is supposed to be initially in a steady state and only conductive. Numerical tests assess that the 1D model is applicable in the slope context. The results obtained from 13 wells data show a few warming degrees (1 to 4°K) of the decompressed zone occurring about two to four centuries BP. The latest high altitude drilling shows about two degrees cooling of the decompressed zone two centuries ago. The groundwater temperature warming can be due to a type of recharge change with a reduction of the snowmelt contribution or it can be provided by an increase of atmospheric and rainfall temperature. The observed cooling in the latest drilling can be interpreted as a groundwater flow change caused by the permafrost melting. The temperature change occurs during the end of Little Ice Age.

Radial Anisotropy in the Mantle Transition Zone and Its Implications

NASA Astrophysics Data System (ADS)

Chang, S. J.; Ferreira, A. M.

2016-12-01

Seismic anisotropy is a useful tool to investigate mantle flow, mantle convection, and the presence of melts in mantle, since it provides information on the direction of mantle flow or the orientation of melts by combining it with laboratory results in mineral physics. Although the uppermost and lowermost mantle with strong anisotropy have been well studied, anisotropic properties of the mantle transition zone is still enigmatic. We use a recent global radially anisotropic model, SGLOBE-rani, to examine the patterns of radial anisotropy in the mantle transition zone. Strong faster SV velocity anomalies are found in the upper transition zone beneath subduction zones in the western Pacific, which decrease with depth, thereby nearly isotropic in the lower transition zone. This may imply that the origin for the anisotropy is the lattice-preferred orientation of wadsleyite, the dominant anisotropic mineral in the upper transition zone. The water content in the upper transition zone may be inferred from radial anisotropy because of the report that anisotropic intensity depends on the water content in wadsleyite.

Flow on the symmetry plane of a total cavo-pulmonary connection.

PubMed

Bolzon, G; Pedrizzetti, G; Grigioni, M; Zovatto, L; Daniele, C; D'Avenio, G

2002-05-01

The flow inside a total cavo-pulmonary connection, a bypass operation of the right heart adopted in the presence of congenital malformation, is here studied for a specific geometry which has been recently introduced in clinics. The analysis has been performed by preliminary experimental observation and a novel Navier-Stokes formulation on the symmetry plane. This method, once some basic hypotheses are verified, allows to reproduce the flow on the symmetry plane of a three-dimensional field by using an extension of the two-dimensional approach. The analysis has confirmed the existence of a central vortex showing that it is not a real vortex (i.e. a place with accumulation of vorticity) but, rather, a weakly dissipative recirculating zone. It is surrounded by a shear layer that becomes spontaneously unsteady at moderately high Reynolds number. The topological changes and energy dissipation have been analysed in both cases of unbalanced and of balanced pulmonary artery and caval flows.

Turbulence and wave particle interactions in solar-terrestrial plasmas

NASA Technical Reports Server (NTRS)

Dulk, G. A.

1982-01-01

Theoretical modelling of two dimensional compressible convection in the Sun shows that convective flows can extend over many pressure scale heights without the nonlinear motions becoming supersonic, and that compressional work arising from pressure fluctuations can be comparable to that by buoyancy forces. These results are contrary to what was supposed in prevailing mixing length models for solar convection, and they imply a much greater degree of organized flow extending over the full depth of the convection zone. The nonlinear penetration of motions into the stable region below the convection zone was emphasized. These compressible flows are dominated by downward directed plumes in the unstable zone. Their strong penetration into the region of stable stratification below excites a broad spectrum of internal gravity waves there, and these in turn feed back upon the convection in the unstable zone to produce a rich time dependence.

Dead Zone Accretion Flows in Protostellar Disks

NASA Technical Reports Server (NTRS)

Turner, Neal; Sano, T.

2008-01-01

Planets form inside protostellar disks in a dead zone where the electrical resistivity of the gas is too high for magnetic forces to drive turbulence. We show that much of the dead zone nevertheless is active and flows toward the star while smooth, large-scale magnetic fields transfer the orbital angular momentum radially outward. Stellar X-ray and radionuclide ionization sustain a weak coupling of the dead zone gas to the magnetic fields, despite the rapid recombination of free charges on dust grains. Net radial magnetic fields are generated in the magnetorotational turbulence in the electrically conducting top and bottom surface layers of the disk, and reach the midplane by ohmic diffusion. A toroidal component to the fields is produced near the midplane by the orbital shear. The process is similar to the magnetization of the solar tachocline. The result is a laminar, magnetically driven accretion flow in the region where the planets form.

Improved forward and inverse analyses of saturated-unsaturated flow toward a well in a compressible unconfined aquifer

NASA Astrophysics Data System (ADS)

Mishra, Phoolendra Kumar; Neuman, Shlomo P.

2010-07-01

We present an analytical solution for flow to a partially penetrating well in a compressible unconfined aquifer that allows inferring its saturated and unsaturated hydraulic properties from drawdowns recorded in the saturated and/or unsaturated zone. We improve upon a previous such solution due to Tartakovsky and Neuman (2007) by (1) adopting a more flexible representation of unsaturated zone constitutive properties and (2) allowing the unsaturated zone to have finite thickness. Both solutions account for horizontal as well as vertical flows throughout the system. We investigate the effects of unsaturated zone constitutive parameters and thickness on drawdowns in the saturated and unsaturated zones as functions of position and time; demonstrate the development of significant horizontal hydraulic gradients in the unsaturated zone in response to pumping; validate our solution against numerical simulations of drawdown in a synthetic aquifer having unsaturated properties described by the van Genuchten-Mualem constitutive model; use our solution to analyze drawdown data from a pumping test conducted by the U.S. Geological Survey at Cape Cod, Massachusetts; and compare our estimates of van Genuchten-Mualem parameters with laboratory values obtained for similar materials in the area.

Transient flow conditions in probabilistic wellhead protection: importance and ways to manage spatial and temporal uncertainty in capture zone delineation

NASA Astrophysics Data System (ADS)

Enzenhoefer, R.; Rodriguez-Pretelin, A.; Nowak, W.

2012-12-01

"From an engineering standpoint, the quantification of uncertainty is extremely important not only because it allows estimating risk but mostly because it allows taking optimal decisions in an uncertain framework" (Renard, 2007). The most common way to account for uncertainty in the field of subsurface hydrology and wellhead protection is to randomize spatial parameters, e.g. the log-hydraulic conductivity or porosity. This enables water managers to take robust decisions in delineating wellhead protection zones with rationally chosen safety margins in the spirit of probabilistic risk management. Probabilistic wellhead protection zones are commonly based on steady-state flow fields. However, several past studies showed that transient flow conditions may substantially influence the shape and extent of catchments. Therefore, we believe they should be accounted for in the probabilistic assessment and in the delineation process. The aim of our work is to show the significance of flow transients and to investigate the interplay between spatial uncertainty and flow transients in wellhead protection zone delineation. To this end, we advance our concept of probabilistic capture zone delineation (Enzenhoefer et al., 2012) that works with capture probabilities and other probabilistic criteria for delineation. The extended framework is able to evaluate the time fraction that any point on a map falls within a capture zone. In short, we separate capture probabilities into spatial/statistical and time-related frequencies. This will provide water managers additional information on how to manage a well catchment in the light of possible hazard conditions close to the capture boundary under uncertain and time-variable flow conditions. In order to save computational costs, we take advantage of super-positioned flow components with time-variable coefficients. We assume an instantaneous development of steady-state flow conditions after each temporal change in driving forces, following an idea by Festger and Walter, 2002. These quasi steady-state flow fields are cast into a geostatistical Monte Carlo framework to admit and evaluate the influence of parameter uncertainty on the delineation process. Furthermore, this framework enables conditioning on observed data with any conditioning scheme, such as rejection sampling, Ensemble Kalman Filters, etc. To further reduce the computational load, we use the reverse formulation of advective-dispersive transport. We simulate the reverse transport by particle tracking random walk in order to avoid numerical dispersion to account for well arrival times.

Lava Flow Hazard Assessment, as of August 2007, for Kilauea East Rift Zone Eruptions, Hawai`i Island

USGS Publications Warehouse

Kauahikaua, Jim

2007-01-01

The most recent episode in the ongoing Pu'u 'O'o-Kupaianaha eruption of Kilauea Volcano is currently producing lava flows north of the east rift zone. Although they pose no immediate threat to communities, changes in flow behavior could conceivably cause future flows to advance downrift and impact communities thus far unaffected. This report reviews lava flow hazards in the Puna District and discusses the potential hazards posed by the recent change in activity. Members of the public are advised to increase their general awareness of these hazards and stay up-to-date on current conditions.

Modeling unsaturated zone flow and runoff processes by integrating MODFLOW-LGR and VSF, and creating the new CFL package

USGS Publications Warehouse

Borsia, I.; Rossetto, R.; Schifani, C.; Hill, Mary C.

2013-01-01

In this paper two modifications to the MODFLOW code are presented. One concerns an extension of Local Grid Refinement (LGR) to Variable Saturated Flow process (VSF) capability. This modification allows the user to solve the 3D Richards’ equation only in selected parts of the model domain. The second modification introduces a new package, named CFL (Cascading Flow), which improves the computation of overland flow when ground surface saturation is simulated using either VSF or the Unsaturated Zone Flow (UZF) package. The modeling concepts are presented and demonstrated. Programmer documentation is included in appendices.

Turbulence characteristics of swirling flowfields. Ph.D. Thesis. Final Report

NASA Technical Reports Server (NTRS)

Jackson, T. W.; Lilley, D. G.

1985-01-01

The time mean and turbulence properties of a confined swirling jet using the six orientation, single hot wire technique were obtained. The effect of swirl on a confined, expanding jet is to reduce the size of the corner recirculation zone and generate a central recirculation zone followed by a precessing vortex core. The effect of introducing a contraction nozzle of area ratio four, located two test section diameters downstream of the inlet, is to dramatically reduce the size and shape of the central recirculation zone for the swirling flows considered. The shear stresses are found to increase by an order of magnitude in the region of the contraction nozzle because of large radial gradients of axial velocity. Reduction of the expansion ratio to D/o = 1 causes the time mean flow field to be homogeneous throughout the entire test section with the tangential velocity dominating in the swirling cases. No recirculation zones were observed for these particular flows. Turbulence levels and dissipation rates were found to be low except in the entrance regions and in areas of acceleration in the swirling flow cases.

Five-hole pitot probe time-mean velocity measurements in confined swirling flows

NASA Technical Reports Server (NTRS)

Yoon, H. K.; Lilley, D. G.

1983-01-01

Nonswirling and swirling nonreacting flows in an axisymmetric test section with an expansion ratio D/d = 2, which may be equipped with contraction nozzles of area ratios 2 and 4, are investigated. The effects of a number of geometric parameters on the flow-field are investigated, among them side-wall expansion angles of 90 and 45 deg, swirl vane angles of 0, 38, 45, 60, and 70 deg, and contraction nozzle locations L/D = 1 and 2 (if present). Data are acquired by means of a five-hole pitot probe enabling three time-mean velocity components in the axial, radial, and azimuthal directions to be measured. The velocities are extensively plotted and artistic impressions of recirculation zones are set forth. The presence of a swirler is found to shorten the corner recirculation zone and to generate a central recirculation zone followed by a precessing vortex core. A gradual inlet expansion has the effect of encouraging the flow to remain close to the sidewall and shortening the extent of the corner recirculation zone in all cases investigated.

Measurement of Sedimentary Interbed Hydraulic Properties and Their Hydrologic Influence near the Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory

USGS Publications Warehouse

Perkins, Kim S.

2003-01-01

Disposal of wastewater to unlined infiltration ponds near the Idaho Nuclear Technology and Engineering Center (INTEC), formerly known as the Idaho Chemical Processing Plant, at the Idaho National Engineering and Environmental Laboratory (INEEL) has resulted in the formation of perched water bodies in the unsaturated zone (Cecil and others, 1991). The unsaturated zone at INEEL comprises numerous basalt flows interbedded with thinner layers of coarse- to fine-grained sediments and perched ground-water zones exist at various depths associated with massive basalts, basalt-flow contacts, sedimentary interbeds, and sediment-basalt contacts. Perched ground water is believed to result from large infiltration events such as seasonal flow in the Big Lost River and wastewater discharge to infiltration ponds. Evidence from a large-scale tracer experiment conducted in 1999 near the Radioactive Waste Management Complex (RWMC), approximately 13 km from the INTEC, indicates that rapid lateral flow of perched water in the unsaturated zone may be an important factor in contaminant transport at the INEEL (Nimmo and others, 2002b). Because sedimentary interbeds, and possibly baked-zone alterations at sediment-basalt contacts (Cecil and other, 1991) play an important role in the generation of perched water it is important to assess the hydraulic properties of these units.

Experimental Evaluation of the Heat Sink Effect in Hepatic Microwave Ablation.

PubMed

Ringe, Kristina I; Lutat, Carolin; Rieder, Christian; Schenk, Andrea; Wacker, Frank; Raatschen, Hans-Juergen

2015-01-01

To demonstrate and quantify the heat sink effect in hepatic microwave ablation (MWA) in a standardized ex vivo model, and to analyze the influence of vessel distance and blood flow on lesion volume and shape. 108 ex vivo MWA procedures were performed in freshly harvested pig livers. Antennas were inserted parallel to non-perfused and perfused (700,1400 ml/min) glass tubes (diameter 5mm) at different distances (10, 15, 20mm). Ablation zones (radius, area) were analyzed and compared (Kruskal-Wallis Test, Dunn's multiple comparison Test). Temperature changes adjacent to the tubes were measured throughout the ablation cycle. Maximum temperature decreased significantly with increasing flow and distance (p<0.05). Compared to non-perfused tubes, ablation zones were significantly deformed by perfused tubes within 15 mm distance to the antenna (p<0.05). At a flow rate of 700 ml/min ablation zone radius was reduced to 37.2% and 80.1% at 10 and 15 mm tube distance, respectively; ablation zone area was reduced to 50.5% and 89.7%, respectively. Significant changes of ablation zones were demonstrated in a pig liver model. Considerable heat sink effect was observed within a diameter of 15 mm around simulated vessels, dependent on flow rate. This has to be taken into account when ablating liver lesions close to vessels.

Enhancing resolution of free-flow zone electrophoresis via a simple sheath-flow sample injection.

PubMed

Yang, Ying; Kong, Fan-Zhi; Liu, Ji; Li, Jun-Min; Liu, Xiao-Ping; Li, Guo-Qing; Wang, Ju-Fang; Xiao, Hua; Fan, Liu-Yin; Cao, Cheng-Xi; Li, Shan

2016-07-01

In this work, a simple and novel sheath-flow sample injection method (SFSIM) is introduced to reduce the band broadening of free-flow zone electrophoresis separation in newly developed self-balance free-flow electrophoresis instrument. A needle injector was placed in the center of the separation inlet, into which the BGE and sample solution were pumped simultaneously. BGE formed sheath flow outside the sample stream, resulting in less band broadening related to hydrodynamics and electrodynamics. Hemoglobin and C-phycocyanin were successfully separated by the proposed method in contrast to the poor separation of free-flow electrophoresis with the traditional injection method without sheath flow. About 3.75 times resolution enhancement could be achieved by sheath-flow sample injection method. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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.

Hydrologic evaluation methodology for estimating water movement through the unsaturated zone at commercial low-level radioactive waste disposal site

USGS Publications Warehouse

Meyer, P.D.; Rockhold, M.L.; Nichols, W.E.; Gee, G.W.

1996-01-01

This report identifies key technical issues related to hydrologic assessment of water flow in the unsaturated zone at low-level radioactive waste (LLW) disposal facilities. In addition, a methodology for incorporating these issues in the performance assessment of proposed LLW disposal facilities is identified and evaluated. The issues discussed fall into four areas:Estimating the water balance at a site (i.e., infiltration, runoff, water storage, evapotranspiration, and recharge);Analyzing the hydrologic performance of engineered components of a facility;Evaluating the application of models to the prediction of facility performance; andEstimating the uncertainty in predicted facility performance.An estimate of recharge at a LLW site is important since recharge is a principal factor in controlling the release of contaminants via the groundwater pathway. The most common methods for estimating recharge are discussed in Chapter 2. Many factors affect recharge; the natural recharge at an undisturbed site is not necessarily representative either of the recharge that will occur after the site has been disturbed or of the flow of water into a disposal facility at the site. Factors affecting recharge are discussed in Chapter 2.At many sites engineered components are required for a LLW facility to meet performance requirements. Chapter 3 discusses the use of engineered barriers to control the flow of water in a LLW facility, with a particular emphasis on cover systems. Design options and the potential performance and degradation mechanisms of engineered components are also discussed.Water flow in a LLW disposal facility must be evaluated before construction of the facility. In addition, hydrologic performance must be predicted over a very long time frame. For these reasons, the hydrologic evaluation relies on the use of predictive modeling. In Chapter 4, the evaluation of unsaturated water flow modeling is discussed. A checklist of items is presented to guide the evaluation. Several computer simulation codes that were used in the examples (Chapter 6) are discussed with respect to this checklist. The codes used include HELP, UNSAT-H, and VAM3DCG.To provide a defensible estimate of water flow in a LLW disposal facility, the uncertainty associated with model predictions must be considered. Uncertainty arises because of the highly heterogeneous nature of most subsurface environments and the long time frame required in the analysis. Sources of uncertainty in hydrologic evaluation of the unsaturated zone and several approaches for analysis are discussed in Chapter 5. The methods of analysis discussed include a bounding approach, sensitivity analysis, and Monte Carlo simulation.To illustrate the application of the discussion in Chapters 2 through 5, two examples are presented in Chapter 6. The first example is of a below ground vault located in a humid environment. The second example looks at a shallow land burial facility located in an arid environment. The examples utilize actual site-specific data and realistic facility designs. The two examples illustrate the issues unique to humid and arid sites as well as the issues common to all LLW sites. Strategies for addressing the analytical difficulties arising in any complex hydrologic evaluation of the unsaturated zone are demonstrated.The report concludes with some final observations and recommendations.

Large-scale bedforms induced by supercritical flows and wave-wave interference in the intertidal zone (Cap Ferret, France)

NASA Astrophysics Data System (ADS)

Vaucher, Romain; Pittet, Bernard; Humbert, Thomas; Ferry, Serge

2017-11-01

The Cap Ferret sand spit is situated along the wave-dominated, tidally modulated Atlantic coast of western France, characterized by a semidiurnal macrotidal range. It displays peculiar dome-like bedforms that can be observed at low tide across the intertidal zone. These bedforms exhibit a wavelength of ca. 1.2 m and an elevation of ca. 30 cm. They occur only when the incident wave heights reach 1.5-2 m. The internal stratifications are characterized by swaley-like, sub-planar, oblique-tangential, oblique-tabular, as well as hummocky-like stratifications. The tabular and tangential stratifications comprise prograding oblique sets (defined as foresets and backsets) that almost always show variations in their steepness. Downcutting into the bottomsets of the oblique-tangential stratifications is common. The sets of laminae observed in the bedforms share common characteristics with those formed by supercritical flows in flume experiments of earlier studies. These peculiar bedforms are observed at the surf-swash transition zone where the backwash flow reaches supercritical conditions. This type of flow can explain their internal architecture but not their general dome-like (three-dimensional) morphology. Wave-wave interference induced by the geomorphology (i.e. tidal channel) of the coastal environment is proposed as explanation for the localized formation of such bedforms. This study highlights that the combination of supercritical flows occurring in the surf-swash transition zone and wave-wave interferences can generate dome-like bedforms in intertidal zones.

Large-scale bedforms induced by supercritical flows and wave-wave interference in the intertidal zone (Cap Ferret, France)

NASA Astrophysics Data System (ADS)

Vaucher, Romain; Pittet, Bernard; Humbert, Thomas; Ferry, Serge

2018-06-01

The Cap Ferret sand spit is situated along the wave-dominated, tidally modulated Atlantic coast of western France, characterized by a semidiurnal macrotidal range. It displays peculiar dome-like bedforms that can be observed at low tide across the intertidal zone. These bedforms exhibit a wavelength of ca. 1.2 m and an elevation of ca. 30 cm. They occur only when the incident wave heights reach 1.5-2 m. The internal stratifications are characterized by swaley-like, sub-planar, oblique-tangential, oblique-tabular, as well as hummocky-like stratifications. The tabular and tangential stratifications comprise prograding oblique sets (defined as foresets and backsets) that almost always show variations in their steepness. Downcutting into the bottomsets of the oblique-tangential stratifications is common. The sets of laminae observed in the bedforms share common characteristics with those formed by supercritical flows in flume experiments of earlier studies. These peculiar bedforms are observed at the surf-swash transition zone where the backwash flow reaches supercritical conditions. This type of flow can explain their internal architecture but not their general dome-like (three-dimensional) morphology. Wave-wave interference induced by the geomorphology (i.e. tidal channel) of the coastal environment is proposed as explanation for the localized formation of such bedforms. This study highlights that the combination of supercritical flows occurring in the surf-swash transition zone and wave-wave interferences can generate dome-like bedforms in intertidal zones.

When interflow also percolates: downslope travel distances and hillslope process zones.

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

Jackson, C. Rhett; Bitew, Menberu; Du, Enhao

2014-02-17

In hillslopes with soils characterized by deep regoliths, such as Ultisols,Oxisols, and Alfisols, interflow occurs episodically over impeding layers near and parallel to the soil surface such as low-conductivity B horizons (e.g.Newman et al., 1998; Buttle andMcDonald, 2002; Du et al., In Review), till layers (McGlynn et al., 1999; Bishop et al., 2004), hardpans (McDaniel et al., 2008), C horizons (Detty and McGuire, 2010), and permeable bedrock (Tromp van Meerveld et al., 2007). As perched saturation develops within and above these impeding but permeable horizons, flow moves laterally downslope, but the perched water also continues to percolate through the impedingmore » horizon to the unsaturated soils and saprolite below. Perched water and solutes will eventually traverse the zone of perched saturation above the impeding horizon and then enter and percolate through the impeding horizon. In such flow situations, only lower hillslope segments with sufficient downslope travel distance will deliver water to the riparian zone within the time scale of a storm.farther up the slope, lateral flow within the zone of perched saturation. will act mainly to shift the point of percolation (location where a water packet leaves the downslope flow zone in the upper soil layer and enters the impeding layer) down the hillslope from the point of infiltration. In flatter parts of the hillslope or in areas with little contrast between the conductivities of the upper and impeding soil layers, lateral flow distances will be negligible.« less

Redox zonation for different groundwater flow paths during bank filtration: a case study at Liao River, Shenyang, northeastern China

NASA Astrophysics Data System (ADS)

Su, Xiaosi; Lu, Shuai; Yuan, Wenzhen; Woo, Nam Chil; Dai, Zhenxue; Dong, Weihong; Du, Shanghai; Zhang, Xinyue

2018-03-01

The spatial and temporal distribution of redox zones in an aquifer is important when designing groundwater supply systems. Redox zonation can have direct or indirect control of the biological and chemical reactions and mobility of pollutants. In this study, redox conditions are characterized by interpreting the hydrogeological conditions and water chemistry in groundwater during bank infiltration at a site in Shenyang, northeast China. The relevant redox processes and zonal differences in a shallow flow path and deeper flow path at the field scale were revealed by monitoring the redox parameters and chemistry of groundwater near the Liao River. The results show obvious horizontal and vertical components of redox zones during bank filtration. Variations in the horizontal extent of the redox zone were controlled by the different permeabilities of the riverbed sediments and aquifer with depth. Horizontally, the redox zone was situated within 17 m of the riverbank for the shallow flow path and within 200 m for the deep flow path. The vertical extent of the redox zone was affected by precipitation and seasonal river floods and extended to 10 m below the surface. During bank filtration, iron and manganese oxides or hydroxides were reductively dissolved, and arsenic that was adsorbed onto the medium surface or coprecipitated is released into the groundwater. This leads to increased arsenic content in groundwater, which poses a serious threat to water supply security.

Physical Controls on Biogeochemical Processes in Intertidal Zones of Beach Aquifers

NASA Astrophysics Data System (ADS)

Heiss, James W.; Post, Vincent E. A.; Laattoe, Tariq; Russoniello, Christopher J.; Michael, Holly A.

2017-11-01

Marine ecosystems are sensitive to inputs of chemicals from submarine groundwater discharge. Tidally influenced saltwater-freshwater mixing zones in beach aquifers can host biogeochemical transformations that modify chemical loads prior to discharge. A numerical variable-density groundwater flow and reactive transport model was used to evaluate the physical controls on reactivity for mixing-dependent and mixing-independent reactions in beach aquifers, represented as denitrification and sulfate reduction, respectively. A sensitivity analysis was performed across typical values of tidal amplitude, hydraulic conductivity, terrestrial freshwater flux, beach slope, dispersivity, and DOC reactivity. For the model setup and conditions tested, the simulations demonstrate that denitrification can remove up to 100% of terrestrially derived nitrate, and sulfate reduction can transform up to 8% of seawater-derived sulfate prior to discharge. Tidally driven mixing between saltwater and freshwater promotes denitrification along the boundary of the intertidal saltwater circulation cell in pore water between 1 and 10 ppt. The denitrification zone occupies on average 49% of the mixing zone. Denitrification rates are highest on the landward side of the circulation cell and decrease along circulating flow paths. Reactivity for mixing-dependent reactions increases with the size of the mixing zone and solute supply, while mixing-independent reactivity is controlled primarily by solute supply. The results provide insights into the types of beaches most efficient in altering fluxes of chemicals prior to discharge and could be built upon to help engineer beaches to enhance reactivity. The findings have implications for management to protect coastal ecosystems and the estimation of chemical fluxes to the ocean.

Combining the Neuman and Boulton models for flow to a well in an unconfined aquifer

USGS Publications Warehouse

Moench, Allen F.

1995-01-01

A Laplace transform solution is presented for flow to a well in a homogeneous, water-table aquifer with noninstanta-neous drainage of water from the zone above the water table. The Boulton convolution integral is combined with Darcy's law and used as an upper boundary condition to replace the condition used by Neuman. Boulton's integral derives from the assumption that water drained from the unsaturated zone is released gradually in a manner that varies exponentially with time in response to a unit decline in hydraulic head, whereas the condition used by Newman assumes that the water is released instantaneously. The result is a solution that reduces to the solution obtained by Neuman as the rate of release of water from the zone above the water table increases. A dimensionless fitting parameter, γ, is introduced that incorporates vertical hydraulic conductivity, saturated thickness, specific yield, and an empirical constant α1, similar to Boulton's α. Results show that theoretical drawdown in water-table piezometers is amplified by noninstantaneous drainage from the unsaturated zone to a greater extent than drawdown in piezometers located at depth in the saturated zone. This difference provides a basis for evaluating γ by type-curve matching in addition to the other dimensionless parameters. Analysis of drawdown in selected piezometers from the published results of two aquifer tests conducted in relatively homogeneous glacial outwash deposits but with significantly different hydraulic conductivities reveals improved comparison between the theoretical type curves and the hydraulic head measured in water-table piezometers.

Hydrogeology of a Danish Riparian Lowland: the Importance of Groundwater Upwelling on Nitrate Removal

NASA Astrophysics Data System (ADS)

Steiness, M.; van't Veen, S. G. W.; Jessen, S.; Engesgaard, P. K.

2016-12-01

Riparian zones are critical interfaces between streams and uplands with many of the characteristics for being key areas for nitrate removal. The hydrogeology is a controlling factor for the source, flow paths, magnitude of groundwater discharge to the stream, nitrate loading, and therefore the occurrence of "hot spots" with increased denitrification. A riparian lowland was investigated through field studies (geophysics, hydrogeology), water quality assessment, and flow and reactive transport modelling. One of the objectives was to understand the role of the landscape and hydrogeology on diffusive versus focused groundwater discharge and also nitrate removal. The investigated riparian zone is characterized by diffusive flow of groundwater to the stream from the northern bank (from a maize field) and groundwater upwelling in several places with overland flow to the stream from south (wetland area). Nitrate is effectively removed by pyrite oxidation (as shown by the reactive transport model high sulphate concentrations) on the northern side, whereas the groundwater-fed springs carry up to 74 mg/L nitrate. Groundwater flow modeling shows that upwelling may account for almost 25 % of the flow to the stream. Two other riparian zones were subsequently included and, on the catchment scale, the occurrence of diffusive and focused discharge is found to be common suggesting that riparian zones in this area are only partly effective in removing nitrate.

Flow zone characterisation in a fractured aquifer using spring and open-well T and EC monitoring.

NASA Astrophysics Data System (ADS)

Agbotui, Prodeo; West, Landis; Bottrell, Simon

2017-04-01

The Cretaceous Chalk is a very important aquifer in England, and its relatively high transmissivity derives essentially from a well-developed network of solutionally-enhanced fractures and conduits. Like other fractured aquifers, characterisation and delineation of flow pathways and hence catchment boundaries is important. Determination of flow pathways for source catchment delineation (e.g. identification of safeguarding zones around wells) is critical for the effective management and protection of the groundwater resource. It also determines the areal extent of contamination from known sources, and enables the targeted sampling of flow zones e.g. for monitored natural attenuation (MNA). A rather simplistic conceptualisation of the unconfined chalk aquifer of East Yorkshire is currently used as a basis for numerical simulations: linearly reducing hydraulic conductivity (K) with depth below the maximum groundwater elevation, reducing to a minimum value below the zone of groundwater table fluctuation. This study represents an attempt to improve this conceptualisation via improved characterisation of permeable zones within the aquifer. The methods used are: pumping test drawdown analyses for transmissivity, ambient open-well dilution testing; rainfall, groundwater head, and spring / open-well specific electrical conductance (SEC) and temperature monitoring. Pumping test analyses yield overall well transmissivity; the open-well dilution/monitoring approach identifies inflow, outflow, crossflow zones and direction and rate of flow in wells; seasonal changes in flows in wells and springs reflect the annual recharge and recession cycle and the impact of seasonal hydraulic head variation on the activation/deactivation of permeable pathways. Variations in spring and well-water electrical conductivity / temperature provide insight into groundwater residence times and the degree of isolation of groundwater from atmospheric and soil zone sources of CO2. The results of the study combined with stratigraphic information on the aquifer, allows the characterisation of the development of bedding-controlled features such as solutionally-enhanced fractures or conduits, and the role of steeply inclined normal faults. The results have implications for catchment management because it will inform a refinement and improvement of the regulatory body) groundwater model for assessment, evaluation and protection of groundwater resource. The method and techniques used can be applicable for characterising fractured aquifers in other jurisdictions.

Safety evaluation of joint and conventional lane merge configurations for freeway work zones.

PubMed

Ishak, Sherif; Qi, Yan; Rayaprolu, Pradeep

2012-01-01

Inefficient operation of traffic in work zone areas not only leads to an increase in travel time delays, queue length, and fuel consumption but also increases the number of forced merges and roadway accidents. This study evaluated the safety performance of work zones with a conventional lane merge (CLM) configuration in Louisiana. Analysis of variance (ANOVA) was used to compare the crash rates for accidents involving fatalities, injuries, and property damage only (PDO) in each of the following 4 areas: (1) advance warning area, (2) transition area, (3) work area, and (4) termination area. The analysis showed that the advance warning area had higher fatality, injury, and PDO crash rates when compared to the transition area, work area, and termination area. This finding confirmed the need to make improvements in the advance warning area where merging maneuvers take place. Therefore, a new lane merge configuration, called joint lane merge (JLM), was proposed and its safety performance was examined and compared to the conventional lane merge configuration using a microscopic simulation model (VISSIM), which was calibrated with real-world data from an existing work zone on I-55 and used to simulate a total of 25 different scenarios with different levels of demand and traffic composition. Safety performance was evaluated using 2 surrogate measures: uncomfortable decelerations and speed variance. Statistical analysis was conducted to determine whether the differences in safety performance between both configurations were significant. The safety analysis indicated that JLM outperformed CLM in most cases with low to moderate flow rates and that the percentage of trucks did not have a significant impact on the safety performance of either configuration. Though the safety analysis did not clearly indicate which lane merge configuration is safer for the overall work zone area, it was able to identify the possibly associated safety changes within the work zone area under different traffic conditions. Copyright © 2012 Taylor & Francis Group, LLC

Stress loading from viscous flow in the lower crust and triggering of aftershocks following the 1994 Northridge, California, earthquake

USGS Publications Warehouse

Deng, J.; Hudnut, K.; Gurnis, M.; Hauksson, E.

1999-01-01

Following the M(w) 6.7 Northridge earthquake, significant postseismic displacements were resolved with GPS. Using a three-dimensional viscoelastic model, we suggest that this deformation is mainly driven by viscous flow in the lower crust. Such flow can transfer stress to the upper crust and load the rupture zone of the main shock at a decaying rate. Most aftershocks within the rupture zone, especially those that occurred after the first several weeks of the main shock, may have been triggered by continuous stress loading from viscous flow. The long-term decay time of aftershocks (about 2 years) approximately matches the decay of viscoelastic loading, and thus is controlled by the viscosity of the lower crust. Our model provides a physical interpretation of the observed correlation between aftershock decay rate and surface heat flow.Following the Mw 6.7 Northridge earthquake, significant postseismic displacements were resolved with GPS. Using a three-dimensional viscoelastic model, we suggest that this deformation is mainly driven by viscous flow in the lower crust. Such flow can transfer stress to the upper crust and load the rupture zone of the main shock at a decaying rate. Most aftershocks within the rupture zone, especially those that occurred after the first several weeks of the main shock, may have been triggered by continuous stress loading from viscous flow. The long-term decay time of aftershocks (about 2 years) approximately matches the decay of viscoelastic loading, and thus is controlled by the viscosity of the lower crust. Our model provides a physical interpretation of the observed correlation between aftershock decay rate and surface heat flow.

TOMOGRAPHY OF PLASMA FLOWS IN THE UPPER SOLAR CONVECTION ZONE USING TIME-DISTANCE INVERSION COMBINING RIDGE AND PHASE-SPEED FILTERING

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

Svanda, Michal, E-mail: michal@astronomie.cz; Astronomical Institute, Charles University in Prague, Faculty of Mathematics and Physics, V Holesovickach 2, CZ-18000 Prague 8

2013-09-20

The consistency of time-distance inversions for horizontal components of the plasma flow on supergranular scales in the upper solar convection zone is checked by comparing the results derived using two k-{omega} filtering procedures-ridge filtering and phase-speed filtering-commonly used in time-distance helioseismology. I show that both approaches result in similar flow estimates when finite-frequency sensitivity kernels are used. I further demonstrate that the performance of the inversion improves (in terms of a simultaneously better averaging kernel and a lower noise level) when the two approaches are combined together in one inversion. Using the combined inversion, I invert for horizontal flows inmore » the upper 10 Mm of the solar convection zone. The flows connected with supergranulation seem to be coherent only for the top {approx}5 Mm; deeper down there is a hint of change of the convection scales toward structures larger than supergranules.« less

Analysis of the results of hydraulic-fracture stimulation of two crystalline bedrock boreholes, Grand Portage, Minnesota

USGS Publications Warehouse

Paillet, Dr. Fredrick L.; Olson, James D.

1994-01-01

Hydraulic fracture-stimulation procedures typical of those provided by contractors in the water-well industry were applied to two boreholes in basaltic and gabbroic rocks near Grand Portage, Minnesota.These boreholes were considered incapable of supplying adequate ground water for even a single household although geophysical logs showed both boreholes were intersected by many apparently permeable fractures. Tests made before and after stimulation indicated that the two boreholes would produce about 0.05 and 0.25 gallon per minute before stimulation, and about 1.5 and 1.2 gallons per minute after stimulation. These increases would be enough to obtain adequate domestic water supplies from the two boreholes but would not furnish enough water for more than a single household from either borehole. Profiles of high-resolution flow made during pumping after stimulation indicated that the stimulation enhanced previously small inflows or stimulated new inflow from seven fractures or fracture zones in one borehole and from six fractures or fracture zones in the other.Geophysical logs obtained after stimulation showed no specific changes in these 13 fractures that could be related to stimulation other than the increases in flow indicated by the flowmeter logs. The results indicate that the stimulation has increased inflow to the two boreholes by improving the connectivity of favorably orientated fractures with larger scale flow zones in the surrounding rocks. Three of four possible diagnostics related to measured pressure and flow during the stimulation treatments were weakly correlated with the increases in production associated with each treatment interval. These correlations are not statistically significant on the basis of the limited sample of 16 treatment intervals in two boreholes, but the results indicate that significant correlations might be established from a much larger data set.

The mode of emplacement of Neogene flood basalts in eastern Iceland: Facies architecture and structure of simple aphyric basalt groups

NASA Astrophysics Data System (ADS)

Óskarsson, Birgir V.; Riishuus, Morten S.

2014-12-01

Simple flows (tabular) in the Neogene flood basalt sections of Iceland are described and their mode of emplacement assessed. The flows belong to three aphyric basalt groups: the Kumlafell group, the Hólmatindur group and the Hjálmadalur group. The groups can be traced over 50 km and originate in the Breiðdalur-Thingmuli volcanic zone. The groups have flow fields that display mixed volcanic facies architecture and can be classified after dominating type morphology. The Kumlafell and the Hólmatindur groups have predominantly simple flows of pāhoehoe and rubbly pāhoehoe morphologies with minor compound or lobate pāhoehoe flows. The Hjálmadalur group has simple flows of rubbly pāhoehoe, but also includes minor compound or lobate flows of rubble and 'a'ā. Simple flows are most common in the distal and medial areas from the vents, while more lobate flows in proximal areas. The simple flows are formed by extensive sheet lobes that are several kilometers long with plane-parallel contacts, some reaching thicknesses of ~ 40 m (aspect ratios < 0.01). They have overlapping contacts and are free of tubes and inflation structures. Their internal structure consists generally of a simple upper vesicular crust, a dense core and a thin basal vesicular zone. The brecciated flow-top is formed by clinker and crustal rubble, the clinker often welded or agglutinated. The simple flows erupted from seemingly short-lived fissures and have the characteristics of cooling-limited flows. We estimate the effusion rates to be ~ 105 m3/s for the simple flows of the Kumlafell and Hólmatindur groups and ~ 104 m3/s for the Hjálmadalur group. The longest flows advanced 15-20 km from the fissures, with lava streams of fast propagating flows inducing tearing and brecciation of the chilled crust. Compound or lobate areas appear to reflect areas of low effusion rates or the interaction of the lava with topographic barriers or wetlands, resulting in chaotic flowage. Slowing lobes with brecciated flow-tops developed into 'a'ā flows. The groups interdigitated with lava groups from the Reyðarfjörður volcanic zone to the east, and the exhumed Breiðdalur-Thingmuli volcanic zone which appear to have formed as a flank lineament parallel the main rift zone. Flood basalt volcanism in flank areas may support a mantle anomaly more pronounced and/or perhaps more widespread in the Neogene of Iceland than today. Eruptions of simple flows have not been observed in modern times and are significant for models of crustal accretion in Iceland and other Large Igneous Provinces.

[Doppler echocardiography of tricuspid insufficiency. Methods of quantification].

PubMed

Loubeyre, C; Tribouilloy, C; Adam, M C; Mirode, A; Trojette, F; Lesbre, J P

1994-01-01

Evaluation of tricuspid incompetence has benefitted considerably from the development of Doppler ultrasound. In addition to direct analysis of the valves, which provides information about the mechanism involved, this method is able to provide an accurate evaluation, mainly through use of the Doppler mode. In addition to new criteria being evaluated (mainly the convergence zone of the regurgitant jet), some indices are recognised as good quantitative parameters: extension of the regurgitant jet into the right atrium, anterograde tricuspid flow, laminar nature of the regurgitant flow, analysis of the flow in the supra-hepatic veins, this is only semi-quantitative, since the calculation of the regurgitation fraction from the pulsed Doppler does not seem to be reliable; This accurate semi-quantitative evaluation is made possible by careful and consistent use of all the criteria available. The authors set out to discuss the value of the various evaluation criteria mentioned in the literature and try to define a practical approach.

Application of vadose-zone monitoring system for real-time characterization of leachate percolation in and under a municipal landfill.

PubMed

Aharoni, Imri; Siebner, Hagar; Dahan, Ofer

2017-09-01

Leachates from solid-waste landfills are considered a severe threat to groundwater quality. The fate of pollutants in the waste and underlying unsaturated zone is crucial for evaluating environmental risks and selecting a restoration strategy. In this study, a vadose-zone monitoring system (VMS) installed in a municipal landfill was used, for the first time, to continuously track leachates percolation dynamics and assess their chemical transformation across the entire thickness of the waste body (15m) and underlying unsaturated zone (16m) to the water table. Winter rains were found to quickly infiltrate through the waste and underlying vadose zone despite a clay cover that was implemented as part of a restoration and leachate-prevention strategy. Within the waste body, the flow pattern was controlled by preferential flow paths, which changed frequently. It is hypothesized that ongoing decomposition of the waste creates dynamic variations in the waste's physical structure and flow pattern. Water samples collected from the waste layer indicated the formation of highly polluted leachates. The chemical composition in the waste body showed extreme variability between sampling points with respect to DOC (407-31,464mg/L), BOD/COD ratios (0.07-0.55), Fe 2+ (6.8-1154mg/L), ammonium (68-2924mg/L) and heavy metal concentrations. Environmental hot spots creating concentrated, aggressive, "acid-phase" leachates still exist in the waste more than 13years after closing the landfill. However, continuous changes in the flow pattern and moisture distribution affected the creation and decay of such environments. In the underlying sandy vadose zone, some sections repeatedly exhibited stronger and faster flow characteristics than others. These local fluxes of concentrated leachates rapidly transported heavy contaminant loads toward the groundwater. However results showed evidence of continual attenuation processes in the deep vadose zone, with the anaerobic digestion of organic matter, as well as the significant retention of heavy metals. Copyright © 2017 Elsevier Ltd. All rights reserved.

A preliminary study of the effect of equivalence ratio on a low emissions gas turbine combustor using KIVA-2

NASA Astrophysics Data System (ADS)

Yang, S. L.; Chen, R.; Cline, M. C.

The staged turbine combustor (STC) concept has drawn more and more attention since the late 70's because of its potential in reducing pollutant emissions where a high power output is required. A numerical study is performed to investigate the chemically reactive flow with sprays inside a STC combustor using a modified version of the KIVA-II code. This STC combustor consists of a fuel nozzle (FN), a rich-burn (RB) zone, a converging connecting section, a quick-quench (QQ) zone, a diverging connecting section, and a lean-combustion (LC) zone. An advanced airblast fuel nozzle, which has two fuel injection passages and four air flow passages for providing swirl, is used in this study. The effect of the equivalence ratio phi on the performance of the STC combustor is reported in this paper for phi range of 1.2 to 2.0. Preliminary results reveal some major features of the flow and temperature fields inside the STC combustor. Distributions of velocity, temperature, and some critical species information inside the FN/RB zone illustrate the effect of phi on the flame temperature and the NO(x) formation in rich burning. The co- and counter-rotating bulk flow, and the sandwiched-ring-shape temperature field in the QQ/LC zone, typical of the confined inclined jet-in-cross flow, are clearly shown from the computation. The predicted mass-weighted standard deviation and the pattern factor of temperature show that the mixing performance of the STC combustor is very good. The temperature of the fluid leaving the LC zone is very uniform. As expected. lower value of the emission index of NO can be achieved with larger value of phi. Prediction of the NO(x) emission shows that there is no excessive thermal NO(x) produced in the QQ/LC zone for all the cases studied.

The role of fluid pressure on frictional behavior at the base of the seismogenic zone

USGS Publications Warehouse

Hirth, Greg; Beeler, Nicholas M.

2015-01-01

To characterize stress and deformation style at the base of the seismogenic zone, we investigate how the mechanical properties of fluid-rock systems respond to variations in temperature and strain rate. The role of fluids on the processes responsible for the brittle-ductile transition in quartz-rich rocks has not been explored at experimental conditions where the kinetic competition between microcracking and viscous flow is similar to that expected in the Earth. Our initial analysis of this competition suggests that the effective stress law for sliding friction should not work as efficiently near the brittle-ductile transition as it does at shallow conditions

Distribution and floristics of moss- and lichen-dominated soil crusts in a patterned Callitris glaucophylla woodland in eastern Australia

NASA Astrophysics Data System (ADS)

Eldridge, David J.

1999-05-01

The distribution and abundance of soil crust lichens and bryophytes was examined in a patterned Callitris glaucophylla woodland in eastern Australia. Twenty-one lichen species and 26 bryophyte species were collected within thirty quadrats along a sequence of runoff, interception and runoff zones. Crust cover was significantly greatest in the interception zones (79.0 %), followed by the runoff zones (24.0 %), and lowest in the groved, runon zones (6.6 %). Lichens and bryophytes were distributed across all geomorphic zones, and, although there were significantly more moss species in the interception zones (mean = 9.1) compared with either the runoff (4.2) or runon (3.2) zones, the number of lichen species did not vary between zones. Ordination of a reduced data set of 32 species revealed a separation of taxa into distinct groups corresponding to the three geomorphic zones. Canonical correspondence analysis (CCA) of the 32 species and thirteen environmental variables revealed that the most important factors associated with the distribution of species were sheet and scarp erosion, soil stability and coherence, litter cover and crust cover. Surface cracking, microtopography and plant cover were of intermediate importance. The CCA biplot revealed that the timbered runon zones (groves) were dominated by `shade-tolerant' mosses Fissidens vittatus and Barbula hornschuchiana, whilst the heavily eroded runoff zones supported sparse populations of `erosion tolerant' lichens ( Endocarpon rogersii) and mosses (Bryum argenteum and Didymodon torquatus). Interception zones supported a rich suite of `crust forming' mosses and lichens capable of tolerating moderate inundation by overland flow. Two other groups of taxa were identified by this analysis: the `pioneer' group, comprising mainly nitrogen-fixing lichens which occupy the zone of active erosion at the lower edge of the groves, and the `opportunists' dominated by liverworts, occupying the shallow depressions or bays at the margins of the groves and the interception zones. This study confirms that the non-vascular lichens and bryophytes in these arid soil crusts, are, like the vascular plants, strongly patterned according to geomorphic zone, being most strongly associated with soil surface and erosional features.

Evaluation of a commercial electro-kinetically pumped sheath-flow nanospray interface coupled to an automated capillary zone electrophoresis system.

PubMed

Peuchen, Elizabeth H; Zhu, Guije; Sun, Liangliang; Dovichi, Norman J

2017-03-01

Capillary zone electrophoresis-electrospray ionization-mass spectrometry (CZE-ESI-MS) is attracting renewed attention for proteomic and metabolomic analysis. An important reason for this interest is the maturation and commercialization of interfaces for coupling CZE with ESI-MS. One of these interfaces is an electro-kinetically pumped sheath flow nanospray interface developed by the Dovichi group, in which a very low sheath flow is generated based on electroosmosis within a glass emitter. CMP Scientific has commercialized this interface as the EMASS-II ion source. In this work, we compared the performance of the EMASS-II ion source with our in-house system. The performance of the systems is equivalent. We also coupled the EMASS-II ion source with a PrinCE Next|480 capillary electrophoresis autosampler and an Orbitrap mass spectrometer, and analyzed this system's performance in terms of sensitivity, reproducibility, and separation performance for separation of tryptic digests, intact proteins, and amino acids. The system produced reproducible analysis of BSA digest; the RSDs of peptide intensity and migration time across 24 runs were less than 20 and 6%, respectively. The system produced a linear calibration curve of intensity across a 30-fold range of tryptic digest concentration. The combination of a commercial autosampler and electrospray interface efficiently separated amino acids, peptides, and intact proteins, and only required 5 μL of sample for analysis. Graphical Abstract The commercial and locally constructed versions of the interface provide similar numbers of protein identifications from a Xenopus laevis fertilized egg digest.

An object-oriented model of the cardiopulmonary system with emphasis on the gravity effect.

PubMed

Chuong Ngo; Herranz, Silvia Briones; Misgeld, Berno; Vollmer, Thomas; Leonhardt, Steffen

2016-08-01

We introduce a novel comprehensive model of the cardiopulmonary system with emphasis on perfusion and ventilation distribution along the vertical thorax axis under the gravity effect. By using an object-oriented environment, the complex physiological system can be represented by a network of electrical, lumped-element compartments. The lungs are divided into three zones: upper, middle, and lower zone. Blood flow increases with the distance from the apex to the base of the lungs. The upper zone is characterized by a complete collapse of the pulmonary capillary vasculature; thus, there is no flow in this zone. The second zone has a "waterfall effect" where the blood flow is determined by the difference between the pulmonary-arterial and alveolar pressures. At resting position, the upper lobes of the lungs are more expanded than the middle and lower lobes. However, during spontaneous breathing, ventilation is nonuniform with more air entering the lower lobes than the middle and upper lobes. A simulative model of the complete system is developed which shows results in good agreement with the literature.

Hydrologic conditions, recharge, and baseline water quality of the surficial aquifer system at Jekyll Island, Georgia, 2012-13

USGS Publications Warehouse

Gordon, Debbie W.; Torak, Lynn J.

2016-03-08

Groundwater levels and specific-conductance measurements showed the dependence of freshwater resources on rainfall to recharge the water-table zone of the surficial aquifer system and to influence groundwater flow on Jekyll Island. The unseasonably dry conditions during November 2012 to April 2013 induced saline water infiltration to the water-table zone from the marshland separating the Jekyll River from the island. A strong correlation (R2 = 0.97) of specific conductance to chloride concentration in water samples from wells installed in the water-table zone provided support for the determination of seasonal directions of groundwater flow by confirming salinity changes in the water-table zone. Unseasonably wet conditions during the late spring to August caused groundwater-flow reversals in some areas. The high dependence of the water-table zone in the surficial aquifer system on precipitation to replenish the aquifer with freshwater underscored the importance of monitoring groundwater levels, water quality, and water use to identify aquifer-discharge conditions that have the potential to promote seawater encroachment and degrade freshwater resources on Jekyll Island.

Petrographic Analysis and Geochemical Source Correlation of Pigeon Peak, Sutter Buttes, CA

NASA Astrophysics Data System (ADS)

Novotny, N. M.; Hausback, B. P.

2013-12-01

The Sutter Buttes are a volcanic complex located in the center of the Great Valley north of Sacramento. They are comprised of numerous inter-intruding andesite and rhyolite lava domes of varying compositions surrounded by a shallow rampart of associated tephras. The Pigeon Peak block-and-ash flow sequence is located in the rampart and made up of a porphyritic Biotite bearing Hornblende Andesite. The andesite blocks demonstrate a high degree of propylization in hornblende crystals, highly zoned plagioclase, trace olivine, and display a red to gray color gradation. DAR is an andesite dome located less than one mile from Pigeon Peak. Of the 15 to 25 andesite lava domes within four miles from Pigeon Peak, only DAR displays trace olivine, red to grey color stratification, low biotite content, and propylitized hornblende. These characteristic similarities suggest that DAR may be the source for Pigeon Peak. My investigation used microprobe analysis of the DAR and Pigeon Peak feldspar crystals to identify the magmatic history of the magma body before emplacement. Correlation of the anorthite zoning within the feldspars from both locations support my hypothesis that DAR is the source of the Pigeon Peak block-and-ash flow.

On the coupled unsaturated-saturated flow process induced by vertical, horizontal, and slant wells in unconfined aquifers

NASA Astrophysics Data System (ADS)

Liang, Xiuyu; Zhan, Hongbin; Zhang, You-Kuan; Liu, Jin

2017-03-01

Conventional models of pumping tests in unconfined aquifers often neglect the unsaturated flow process. This study concerns the coupled unsaturated-saturated flow process induced by vertical, horizontal, and slant wells positioned in an unconfined aquifer. A mathematical model is established with special consideration of the coupled unsaturated-saturated flow process and the well orientation. Groundwater flow in the saturated zone is described by a three-dimensional governing equation and a linearized three-dimensional Richards' equation in the unsaturated zone. A solution in the Laplace domain is derived by the Laplace-finite-Fourier-transform and the method of separation of variables, and the semi-analytical solutions are obtained using a numerical inverse Laplace method. The solution is verified by a finite-element numerical model. It is found that the effects of the unsaturated zone on the drawdown of a pumping test exist at any angle of inclination of the pumping well, and this impact is more significant in the case of a horizontal well. The effects of the unsaturated zone on the drawdown are independent of the length of the horizontal well screen. The vertical well leads to the largest water volume drained from the unsaturated zone (W) during the early pumping time, and the effects of the well orientation on W values become insignificant at the later time. The screen length of the horizontal well does not affect W for the whole pumping period. The proposed solutions are useful for the parameter identification of pumping tests with a general well orientation (vertical, horizontal, and slant) in unconfined aquifers affected from above by the unsaturated flow process.

Mixing zone hydrodynamics in a large confluence: a case study of the Snake and Clearwater Rivers confluence

NASA Astrophysics Data System (ADS)

Shehata, M. M.; Petrie, J.

2015-12-01

Confluences are a basic component in all fluvial systems, which are often characterized by complex flow and sediment transport patterns. Addressing confluences, however, started only recently in parallel with new advances of flow measurement tools and computational techniques. A limited number of field studies exist investigating flow hydrodynamics through confluences, particularly for large confluences with central zone widths of 100 m or greater. Previous studies have indicated that the size of the confluent rivers and the post-confluence zone may impact flow and sediment transport processes in the confluence zone, which consequently could impact the biodiversity within the river network. This study presents the results of a field study conducted at the confluence of the Snake and the Clearwater rivers near the towns of Clarkston, WA and Lewiston, ID (average width of 700 m at the confluence center). This confluence supports many different and, sometimes, conflicting purposes including commercial navigation, recreation, and fish and wildlife conservation. The confluence properties are affected by dredging operations carried out periodically to maintain the minimum water depth required for safe flow conveyance and navigation purposes. Also, a levee system was constructed on the confluence banks as an extra flood control measure. In the recent field work, an Acoustic Doppler Current Profiler was used to measure water velocity profiles at cross sections in the confluence region. Fixed and moving vessel measurements were taken at selected locations to evaluate both the spatial and temporal variation in velocity throughout the confluence. The confluence bathymetry was surveyed with a multi-beam sonar to investigate existent bed morphological elements. The results identify the velocity pattern in the mixing zone between the two rivers. The present findings are compared to previous studies on small confluences to demonstrate the influence of scale on flow processes.

Percolation characteristics of solvent invasion in rough fractures under miscible conditions

NASA Astrophysics Data System (ADS)

Korfanta, M.; Babadagli, T.; Develi, K.

2017-10-01

Surface roughness and flow rate effects on the solvent transport under miscible conditions in a single fracture are studied. Surface replicas of seven different rocks (marble, granite, and limestone) are used to represent different surface roughness characteristics each described by different mathematical models including three fractal dimensions. Distribution of dyed solvent is investigated at various flow rate conditions to clarify the effect of roughness on convective and diffusive mixing. After a qualitative analysis using comparative images of different rocks, the area covered by solvent with respect to time is determined to conduct a semi-quantitative analysis. In this exercise, two distinct zones are identified, namely the straight lines obtained for convective (early times) and diffusive (late times) flow. The bending point between these two lines is used to point the transition between the two zones. Finally, the slopes of the straight lines and the bending points are correlated to five different roughness parameters and the rate (Peclet number). It is observed that both surface roughness and flow rate have significant effect on solvent spatial distribution. The largest area covered is obtained at moderate flow rates and hence not only the average surface roughness characteristic is important, but coessentially total fracture surface area needs to be considered when evaluating fluid distribution. It is also noted that the rate effect is critically different for the fracture samples of large grain size (marbles and granite) compared to smaller grain sizes (limestones). Variogram fractal dimension exhibits the strongest correlation with the maximum area covered by solvent, and display increasing trend at the moderate flow rates. Equations with variogram surface fractal dimension in combination with any other surface fractal parameter coupled with Peclet number can be used to predict maximum area covered by solvent in a single fracture, which in turn can be utilized to model oil recovery, waste disposal, and groundwater contamination processes in the presence of fractures.

Saturated-unsaturated flow in a compressible leaky-unconfined aquifer

NASA Astrophysics Data System (ADS)

Mishra, Phoolendra K.; Vesselinov, Velimir V.; Kuhlman, Kristopher L.

2012-06-01

An analytical solution is developed for three-dimensional flow towards a partially penetrating large-diameter well in an unconfined aquifer bounded below by a leaky aquitard of finite or semi-infinite extent. The analytical solution is derived using Laplace and Hankel transforms, then inverted numerically. Existing solutions for flow in leaky unconfined aquifers neglect the unsaturated zone following an assumption of instantaneous drainage due to Neuman. We extend the theory of leakage in unconfined aquifers by (1) including water flow and storage in the unsaturated zone above the water table, and (2) allowing the finite-diameter pumping well to partially penetrate the aquifer. The investigation of model-predicted results shows that aquitard leakage leads to significant departure from the unconfined solution without leakage. The investigation of dimensionless time-drawdown relationships shows that the aquitard drawdown also depends on unsaturated zone properties and the pumping-well wellbore storage effects.

Radial flow towards well in leaky unconfined aquifer

NASA Astrophysics Data System (ADS)

Mishra, P. K.; Kuhlman, K. L.

2012-12-01

An analytical solution is developed for three-dimensional flow towards a partially penetrating large- diameter well in an unconfined aquifer bounded below by a leaky aquitard of finite or semi-infinite extent. The analytical solution is derived using Laplace and Hankel transforms, then inverted numerically. Existing solutions for flow in leaky unconfined aquifers neglect the unsaturated zone following an assumption of instantaneous drainage due to Neuman. We extend the theory of leakage in unconfined aquifers by (1) including water flow and storage in the unsaturated zone above the water table, and (2) allowing the finite-diameter pumping well to partially penetrate the aquifer. The investigation of model-predicted results shows that aquitard leakage leads to significant departure from the unconfined solution without leakage. The investigation of dimensionless time-drawdown relationships shows that the aquitard drawdown also depends on unsaturated zone properties and the pumping-well wellbore storage effects.

Estimating the Spatial Extent of Unsaturated Zones in Heterogeneous River-Aquifer Systems

NASA Astrophysics Data System (ADS)

Schilling, Oliver S.; Irvine, Dylan J.; Hendricks Franssen, Harrie-Jan; Brunner, Philip

2017-12-01

The presence of unsaturated zones at the river-aquifer interface has large implications on numerous hydraulic and chemical processes. However, the hydrological and geological controls that influence the development of unsaturated zones have so far only been analyzed with simplified conceptualizations of flow processes, or homogeneous conceptualizations of the hydraulic conductivity in either the aquifer or the riverbed. We systematically investigated the influence of heterogeneous structures in both the riverbed and the aquifer on the development of unsaturated zones. A stochastic 1-D criterion that takes both riverbed and aquifer heterogeneity into account was developed using a Monte Carlo sampling technique. The approach allows the reliable estimation of the upper bound of the spatial extent of unsaturated areas underneath a riverbed. Through systematic numerical modeling experiments, we furthermore show that horizontal capillary forces can reduce the spatial extent of unsaturated zones under clogged areas. This analysis shows how the spatial structure of clogging layers and aquifers influence the propensity for unsaturated zones to develop: In riverbeds where clogged areas are made up of many small, spatially disconnected patches with a diameter in the order of 1 m, unsaturated areas are less likely to develop compared to riverbeds where large clogged areas exist adjacent to unclogged areas. A combination of the stochastic 1-D criterion with an analysis of the spatial structure of the clogging layers and the potential for resaturation can help develop an appropriate conceptual model and inform the choice of a suitable numerical simulator for river-aquifer systems.

Aerothermal modeling program, phase 1

NASA Technical Reports Server (NTRS)

Srinivasan, R.; Reynolds, R.; Ball, I.; Berry, R.; Johnson, K.; Mongia, H.

1983-01-01

The combustor performance submodels for complex flows are evaluated. The benchmark test cases for complex nonswirling flows are identified and analyzed. The introduction of swirl into the flow creates much faster mixing, caused by radial pressure gradients and increase in turbulence generation. These phenomena are more difficult to predict than the effects due to geometrical streamline curvatures, like the curved duct, and sudden expansion. Flow fields with swirl, both confined and unconfined are studied. The role of the dilution zone to achieve the turbine inlet radial profile plays an important part, therefore temperature field measurements were made in several idealized dilution zone configurations.

Using a conceptual model to assess the role of flow regulation in the hydromorphological evolution of riparian corridors

NASA Astrophysics Data System (ADS)

Martínez-Fernández, Vanesa; Gonzalez del Tánago, Marta; García de Jalón, diego

2017-04-01

Riparian corridors result from active vegetation-fluvial interactions, which are highly dependent on flow regime conditions and sediment dynamics. Colonization, establishment and survival of species are constrained by fluvial processes which vary according to topographic and sedimentological complexity of the corridor. In order to manage these dynamic and complex riparian systems there is a need for practical tools based on conceptual models. The objective of this study was to apply the conceptual model of riparian corridors lateral zonation in response to the dominant fluvial processes established by Gurnell et al. (2015) and verify its usefulness as a tool for assessing the effect of flow regulation. Two gravel rivers have been selected for this purpose from the north of Spain, the Porma River regulated by Boñar large dam and the unregulated Curueño River. The historical series of flows and the aerial photographs of 1956 and 2011 on which the river corridor has been delimited have been analyzed and identified the permanent inundated zone (1) and four areas of riparian vegetation dominated respectively by fluvial disturbance with coarse sediment erosion and deposition (zone 2), fluvial disturbance with finer sediment deposition (zone 3), inundation (zone 4) and soil moisture regime (zone 5). Likewise, a two-dimensional hydraulic simulation was performed with avenues of different return periods and calculated the prevailing hydraulic conditions (depths, velocities and drag forces) to characterize each of the vegetation zones mentioned in both rivers. The results show that the most active zone 2 (fluvial disturbance dominated showing coarse sediment erosion and deposition) disappears due to the regulation of flows and vegetation encroachment, while the riparian corridor is dominated by the less active zone where the vegetation is maintained by the humidity of sporadic floods and underground runoff. Moreover, by means of the hydraulic simulation we have found a close relationship between the different areas of fluvial processes recognized through its vegetation and hydraulic conditions, which predicts the expected evolution of vegetation at different scenarios of regulation.

Lengths and hazards from channel-fed lava flows on Mauna Loa, Hawai`i, determined from thermal and downslope modeling with FLOWGO

NASA Astrophysics Data System (ADS)

Rowland, Scott K.; Garbeil, Harold; Harris, Andrew J. L.

2005-08-01

Using the FLOWGO thermo-rheological model we have determined cooling-limited lengths of channel-fed (i.e. ‘a‘ā) lava flows from Mauna Loa. We set up the program to run autonomously, starting lava flows from every 4th line and sample in a 30-m spatial-resolution SRTM DEM within regions corresponding to the NE and SW rift zones and the N flank of the volcano. We consider that each model run represents an effective effusion rate, which for an actual flow coincides with it reaching 90% of its total length. We ran the model at effective effusion rates ranging from 1 to 1,000 m3 s-1, and determined the cooling-limited channel length for each. Keeping in mind that most flows extend 1 2 km beyond the end of their well-developed channels and that our results are non-probabilistic in that they give all potential vent sites an equal likelihood to erupt, lava coverage results include the following: SW rift zone flows threaten almost all of Mauna Loa’s SW flanks, even at effective effusion rates as low as 50 m3 s-1 (the average effective effusion rate for SW rift zone eruptions since 1843 is close to 400 m3 s-1). N flank eruptions, although rare in the recent geologic record, have the potential to threaten much of the coastline S of Keauhou with effective effusion rates of 50 100 m3 s-1, and the coast near Anaeho‘omalu if effective effusion rates are 400 500 m3 s-1 (the 1859 ‘a‘ā flow reached this coast with an effective effusion rate of ˜400 m3 s-1). If the NE rift zone continues to be active only at elevations >2,500 m, in order for a channel-fed flow to reach Hilo the effective effusion rate needs to be ≥400 m3 s-1 (the 1984 flow by comparison, had an effective effusion rate of 200 m3 s-1). Hilo could be threatened by NE rift zone channel-fed flows with lower effective effusion rates but only if they issue from vents at ˜2,000 m or lower. Populated areas on Mauna Loa’s SE flanks (e.g. Pāhala), could be threatened by SW rift zone eruptions with effective effusion rates of ˜100 m3 s-1.

Flow of a Non-Newtonian Liquid with a Free Surface

NASA Astrophysics Data System (ADS)

Borzenko, E. I.; Shrager, G. R.

2016-07-01

A fountain flow of a non-Newtonian liquid filling a vertical plane channel was investigated. The problem of this flow was solved by the finite-difference method on the basis of a system of complete equations of motion with natural boundary conditions on the free surface of the liquid. The stability of calculations was provided by regularization of the rheological Ostwald-de Waele law. It is shown that the indicated flow is divided into a zone of two-dimensional flow in the neighborhood of the free surface and a zone of one-dimensional flow at a distance from this surface. A parametric investigation of the dependence of the kinetic characteristics of the fountain flow and the behavior of its free surface on the determining criteria of this flow and its rheological parameters has been performed.

Disturbance, A Mechanism for Increased Microbial Diversity in a Yellowstone National Park Hot Spring Mixing Zone

NASA Astrophysics Data System (ADS)

Howells, A. E.; Oiler, J.; Fecteau, K.; Boyd, E. S.; Shock, E.

2014-12-01

The parameters influencing species diversity in natural ecosystems are difficult to assess due to the long and experimentally prohibitive timescales needed to develop causative relationships among measurements. Ecological diversity-disturbance models suggest that disturbance is a mechanism for increased species diversity, allowing for coexistence of species at an intermediate level of disturbance. Observing this mechanism often requires long timescales, such as the succession of a forest after a fire. In this study we evaluated the effect of mixing of two end member hydrothermal fluids on the diversity and structure of a microbial community where disturbance occurs on small temporal and spatial scales. Outflow channels from two hot springs of differing geochemical composition in Yellowstone National Park, one pH 3.3 and 36 °C and the other pH 7.6 and 61 °C flow together to create a mixing zone on the order of a few meters. Geochemical measurements were made at both in-coming streams and at a site of complete mixing downstream of the mixing zone, at pH 6.5 and 46 °C. Compositions were estimated across the mixing zone at 1 cm intervals using microsensor temperature and conductivity measurements and a mixing model. Qualitatively, there are four distinct ecotones existing over ranges in temperature and pH across the mixing zone. Community analysis of the 16S rRNA genes of these ecotones show a peak in diversity at maximal mixing. Principle component analysis of community 16S rRNA genes reflects coexistence of species with communities at maximal mixing plotting intermediate to communities at distal ends of the mixing zone. These spatial biological and geochemical observations suggest that the mixing zone is a dynamic ecosystem where geochemistry and biological diversity are governed by changes in the flow rate and geochemical composition of the two hot spring sources. In ecology, understanding how environmental disruption increases species diversity is a foundation for ecosystem conservation. By studying a hot spring environment where detailed measurements of geochemical variation and community diversity can be made at small spatial scales, the mechanisms by which maximal diversity is achieved can be tested and may assist in applications of diversity-disturbance models for larger ecosystems.

Six-flow operations for catalyst development in Fischer-Tropsch synthesis: Bridging the gap between high-throughput experimentation and extensive product evaluation

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

Sartipi, Sina, E-mail: S.Sartipi@tudelft.nl, E-mail: J.Gascon@tudelft.nl; Jansma, Harrie; Bosma, Duco

2013-12-15

Design and operation of a “six-flow fixed-bed microreactor” setup for Fischer-Tropsch synthesis (FTS) is described. The unit consists of feed and mixing, flow division, reaction, separation, and analysis sections. The reactor system is made of five heating blocks with individual temperature controllers, assuring an identical isothermal zone of at least 10 cm along six fixed-bed microreactor inserts (4 mm inner diameter). Such a lab-scale setup allows running six experiments in parallel, under equal feed composition, reaction temperature, and conditions of separation and analysis equipment. It permits separate collection of wax and liquid samples (from each flow line), allowing operation with highmore » productivities of C5+ hydrocarbons. The latter is crucial for a complete understanding of FTS product compositions and will represent an advantage over high-throughput setups with more than ten flows where such instrumental considerations lead to elevated equipment volume, cost, and operation complexity. The identical performance (of the six flows) under similar reaction conditions was assured by testing a same catalyst batch, loaded in all microreactors.« less

Analysis and calculation of macrosegregation in a casting ingot. MPS solidification model. Volume 1: Formulation and analysis

NASA Technical Reports Server (NTRS)

Maples, A. L.; Poirier, D. R.

1980-01-01

The physical and numerical formulation of a model for the horizontal solidification of a binary alloy is described. It can be applied in an ingot. The major purpose of the model is to calculate macrosegregation in a casting ingot which results from flow of interdendritic liquid during solidification. The flow, driven by solidification contractions and by gravity acting on density gradients in the interdendritic liquid, was modeled as flow through a porous medium. The symbols used are defined. The physical formulation of the problem leading to a set of equations which can be used to obtain: (1) the pressure field; (2) the velocity field: (3) mass flow and (4) solute flow in the solid plus liquid zone during solidification is presented. With these established, the model calculates macrosegregation after solidification is complete. The numerical techniques used to obtain solution on a computational grid are presented. Results, evaluation of the results, and recommendations for future development of the model are given. The macrosegregation and flow field predictions for tin-lead, aluminum-copper, and tin-bismuth alloys are included as well as comparisons of some of the predictions with published predictions or with empirical data.

Comparison of Series of Vugs and Non-vuggy Synthetic Porous Media on Formation Damage

NASA Astrophysics Data System (ADS)

Khan, H.; DiCarlo, D. A.; Prodanovic, M.

2017-12-01

Produced water reinjection (PWRI) is an established cost-effective oil field practice where produced water is injected without any cleanup, for water flooding or disposal. Resultantly the cost of fresh injection fluid and/or processing produced water is saved. A common problem with injection of unprocessed water is formation damage in the near injection zone due to solids (fines) entrapment, causing a reduction in permeability and porosity of the reservoir. Most studies have used homogeneous porous media with unimodal grain sizes, while real world porous media often has a wide range of pores, up to and including vugs in carbonaceous rocks. Here we fabricate a series of vugs in synthetic porous media by sintering glass beads with large dissolvable inclusions. The process is found to be repeatable, allowing a similar vug configuration to be tested for different flow conditions. Bi-modal glass bead particles (25 & 100 micron) are injected at two different flow rates and three different injection concentrations. Porosity, permeability and effluent concentration are determined using CT scanning, pressure measurements and particle counting (Coulter counter), respectively. Image analysis is performed on the CT images to determine the change in vug size for each flow condition. We find that for the same flow conditions, heterogeneous media with series of vugs have an equal or greater permeability loss compared to homogeneous porous media. A significant change in permeability is observed at the highest concentration and flow rate as more particles approach the filter quickly, resulting in a greater loss in permeability in the lower end of the core. Image analysis shows the highest loss in vug size occurs at the low flow rate and highest concentration. The lower vug is completely blocked for this flow case. For all flow cases lower values of porosity are observed after the core floods. At low flow rate and medium concentration, a drastic loss in porosity is observed in the lower part of the core, after the vuggy zone. This trough is also distinctly clear in the homogeneous core for the same flow conditions. This study focuses on understanding the effect of pore heterogeneity on formation damage. We conclude that more damage is done deeper in vuggy formations at high flow rates, resulting in shorter injection cycle prior to clean up.

30 CFR 250.415 - What must my casing and cementing programs include?

Code of Federal Regulations, 2010 CFR

2010-07-01

... included in API RP 65, Recommended Practice for Cementing Shallow Water Flow Zones in Deep Water Wells... and are in either of the following two areas: (1) An “area with an unknown shallow water flow potential” is a zone or geologic formation where neither the presence nor absence of potential for a shallow...

Heat Transfer at the Reattachment Zone of Separated Laminar Boundary Layers

NASA Technical Reports Server (NTRS)

Chung, Paul M.; Viegas, John R.

1961-01-01

The flow and heat transfer are analyzed at the reattachment zone of two-dimensional separated laminar boundary layers. The fluid is considered to be flowing normal to the wall at reattachment. An approximate expression is derived for the heat transfer in the reattachment region and a calculated value is compared with an experimental measurement.

Delineation of recharge areas for selected wells in the St. Peter-Prairie du Chien-Jordan Aquifer, Rochester, Minnesota

USGS Publications Warehouse

Delin, G.N.; Almendinger, James Edward

1991-01-01

Hydrogeologic mapping and numerical modeling were used to delineate zones of contribution to wells, defined as all parts of a ground-water-flow system that could supply water to a well. The zones of contribution delineated by use of numerical modeling have similar orientation (parallel to regional flow directions) but significantly different areas than the zones of contribution delineated by use of hydrogeologic mapping. Differences in computed areas of recharge are attributed to the capability of the numerical model to more accurately represent (1) the three-dimensional flow system, (2) hydrologic boundaries like streams, (3) variable recharge, and (4) the influence of nearby pumped wells, compared to the analytical models.

Delineation of recharge areas for selected wells in the St. Peter-Prairie du Chien-Jordan aquifer, Rochester, Minnesota

USGS Publications Warehouse

Delin, G.N.; Almendinger, James Edward

1993-01-01

Hydrogeologic mapping and numerical modeling were used to delineate zones of contribution to wells, defined as all parts of a ground-water-flow system that could supply water to a well. The zones of contribution delineated by use of numerical modeling have similar orientation (parallel to regional flow directions) but significantly different areas than the zones of contribution delineated by use of hydrogeologic mapping. Differences in computed areas of recharge are attributed to the capability of the numerical model to more accurately represent (1) the three-dimensional flow system, (2) hydrologic boundaries such as streams, (3) variable recharge, and (4) the influence of nearby pumped wells, compared to the analytical models.

Characterization of fracture permeability with high-resolution vertical flow measurements during borehole pumping.

USGS Publications Warehouse

Paillet, Frederick L.; Hess, A.E.; Cheng, C.H.; Hardin, E.

1987-01-01

The distribution of fracture permeability in granitic rocks was investigated by measuring the distribution of vertical flow in boreholes during periods of steady pumping. Pumping tests were conducted at two sites chosen to provide examples of moderately fractured rocks near Mirror Lake, New Hampshire and intensely fractured rocks near Oracle, Arizona. A sensitive heat-pulse flowmeter was used for accurate measurements of vertical flow as low as 0.2 liter per minute. Results indicate zones of fracture permeability in crystalline rocks are composed of irregular conduits that cannot be approximated by planar fractures of uniform aperture, and that the orientation of permeability zones may be unrelated to the orientation of individual fractures within those zones.-Authors

Geologic and hydrogeologic frameworks of the Biscayne aquifer in central Miami-Dade County, Florida

USGS Publications Warehouse

Wacker, Michael A.; Cunningham, Kevin J.; Williams, John H.

2014-01-01

Evaluations of the lithostratigraphy, lithofacies, paleontology, ichnology, depositional environments, and cyclostratigraphy from 11 test coreholes were linked to geophysical interpretations, and to results of hydraulic slug tests of six test coreholes at the Snapper Creek Well Field (SCWF), to construct geologic and hydrogeologic frameworks for the study area in central Miami-Dade County, Florida. The resulting geologic and hydrogeologic frameworks are consistent with those recently described for the Biscayne aquifer in the nearby Lake Belt area in Miami-Dade County and link the Lake Belt area frameworks with those developed for the SCWF study area. The hydrogeologic framework is characterized by a triple-porosity pore system of (1) matrix porosity (mainly mesoporous interparticle porosity, moldic porosity, and mesoporous to megaporous separate vugs), which under dynamic conditions, produces limited flow; (2) megaporous, touching-vug porosity that commonly forms stratiform groundwater passageways; and (3) conduit porosity, including bedding-plane vugs, decimeter-scale diameter vertical solution pipes, and meter-scale cavernous vugs. The various pore types and associated permeabilities generally have a predictable vertical spatial distribution related to the cyclostratigraphy. The Biscayne aquifer within the study area can be described as two major flow units separated by a single middle semiconfining unit. The upper Biscayne aquifer flow unit is present mainly within the Miami Limestone at the top of the aquifer and has the greatest hydraulic conductivity values, with a mean of 8,200 feet per day. The middle semiconfining unit, mainly within the upper Fort Thompson Formation, comprises continuous to discontinuous zones with (1) matrix porosity; (2) leaky, low permeability layers that may have up to centimeter-scale vuggy porosity with higher vertical permeability than horizontal permeability; and (3) stratiform flow zones composed of fossil moldic porosity, burrow related vugs, or irregular vugs. Flow zones with a mean hydraulic conductivity of 2,600 feet per day are present within the middle semiconfining unit, but none of the flow zones are continuous across the study area. The lower Biscayne aquifer flow unit comprises a group of flow zones in the lower part of the aquifer. These flow zones are present in the lower part of the Fort Thompson Formation and in some cases within the limestone or sandstone or both in the uppermost part of the Pinecrest Sand Member of the Tamiami Formation. The mean hydraulic conductivity of major flow zones within the lower Biscayne aquifer flow unit is 5,900 feet per day, and the mean value for minor flow zones is 2,900 feet per day. A semiconfining unit is present beneath the Biscayne aquifer. The boundary between the two hydrologic units is at the top or near the top of the Pinecrest Sand Member of the Tamiami Formation. The lower semiconfining unit has a hydraulic conductivity of less than 350 feet per day. The most productive zones of groundwater flow within the two Biscayne aquifer flow units have a characteristic pore system dominated by stratiform megaporosity related to selective dissolution of an Ophiomorpha-dominated ichnofabric. In the upper flow unit, decimeter-scale vertical solution pipes that are common in some areas of the SCWF study area contribute to high vertical permeability compared to that in areas without the pipes. Cross-hole flowmeter data collected from the SCWF test coreholes show that the distribution of vuggy porosity, matrix porosity, and permeability within the Biscayne aquifer of the SCWF is highly heterogeneous and anisotropic. Groundwater withdrawals from production well fields in southeastern Florida may be inducing recharge of the Biscayne aquifer from canals near the well fields that are used for water-management functions, such as flood control and well-field pumping. The SCWF was chosen as a location within Miami-Dade County to study the potential for such recharge to the Biscayne aquifer from the C–2 (Snapper Creek) canal that roughly divides the well field in half. Geologic, hydrogeologic, and hydraulic information on the aquifer collected during construction of monitoring wells within the SCWF could be used to evaluate the groundwater flow budget at the well-field scale.

Full-scale demonstration of in situ cometabolic biodegradation of trichloroethylene in groundwater 1. Dynamics of a recirculating well system

NASA Astrophysics Data System (ADS)

Gandhi, Rahul K.; Hopkins, Gary D.; Goltz, Mark N.; Gorelick, Steven M.; McCarty, Perry L.

2002-04-01

Recirculating well systems provide an engine for the in situ treatment of subsurface contaminants. Although numerous recirculating wells have been installed in the field, for such systems, there is a paucity of comprehensive monitoring data and models constrained to data appearing in the research literature. Here we present an extensive data set combined with detailed inverse and simulation analyses for a two-well groundwater recirculation system used for in situ bioremediation at Edwards Air Force Base in southern California. The ``conveyor belt'' flow system, which was established for in situ treatment of trichloroethylene (TCE) in two bioactive zones, was created by pumping water upward in one well and downward in another well, each well being screened in both the upper and lower aquifers. A bromide tracer test was conducted and extensively monitored for 60 days. Combined inverse analysis was conducted on hydraulic heads from 38 monitoring wells, 32 bromide concentration histories, and a constraint on the degree of recirculation that was based on TCE concentration data. Four different formulations involving alternative weighting schemes used in a nonlinear weighted least squares simulation-regression analysis were explored. The best formulation provided parameter estimates with tight bounds on estimated covariances, suggesting that the model provides a reasonable description of the hydrogeologic system. Our investigation indicates the geometry of the recirculation zone and the degree of recirculation under two different sets of operating conditions. Surprisingly, our analysis suggests that the effects of aquifer heterogeneity are not significant at this site under the conditions of forced recirculation. Furthermore, anomalous flow through an open monitoring well created significant vertical short-circuiting between the generally insulated aquifers. Flow through this small open conduit was equivalent to as much as 33% of the flow through the pumping wells. Using the model as a guide, we treated the aquifer system and bioactive zones as an equivalent mixed reactor to develop simple expressions relating effluent concentrations to influent concentrations. We demonstrate how these expressions are useful in predicting the removal of TCE that had undergone in situ bioremediation in the recirculatory treatment well system. The finite element model developed in this work serves as the foundation for a reactive transport simulator that we developed to analyze bioremediation which occurred during a 444 day experiment [Gandhi et al., 2002].

Regional regression equations to estimate peak-flow frequency at sites in North Dakota using data through 2009

USGS Publications Warehouse

Williams-Sether, Tara

2015-08-06

Annual peak-flow frequency data from 231 U.S. Geological Survey streamflow-gaging stations in North Dakota and parts of Montana, South Dakota, and Minnesota, with 10 or more years of unregulated peak-flow record, were used to develop regional regression equations for exceedance probabilities of 0.5, 0.20, 0.10, 0.04, 0.02, 0.01, and 0.002 using generalized least-squares techniques. Updated peak-flow frequency estimates for 262 streamflow-gaging stations were developed using data through 2009 and log-Pearson Type III procedures outlined by the Hydrology Subcommittee of the Interagency Advisory Committee on Water Data. An average generalized skew coefficient was determined for three hydrologic zones in North Dakota. A StreamStats web application was developed to estimate basin characteristics for the regional regression equation analysis. Methods for estimating a weighted peak-flow frequency for gaged sites and ungaged sites are presented.

Uncertainty and sensitivity analysis for two-phase flow in the vicinity of the repository in the 1996 performance assessment for the Waste Isolation Pilot Plant: Undisturbed conditions

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

HELTON,JON CRAIG; BEAN,J.E.; ECONOMY,K.

2000-05-19

Uncertainty and sensitivity analysis results obtained in the 1996 performance assessment for the Waste Isolation Pilot Plant are presented for two-phase flow the vicinity of the repository under undisturbed conditions. Techniques based on Latin hypercube sampling, examination of scatterplots, stepwise regression analysis, partial correlation analysis and rank transformation are used to investigate brine inflow, gas generation repository pressure, brine saturation and brine and gas outflow. Of the variables under study, repository pressure is potentially the most important due to its influence on spallings and direct brine releases, with the uncertainty in its value being dominated by the extent to whichmore » the microbial degradation of cellulose takes place, the rate at which the corrosion of steel takes place, and the amount of brine that drains from the surrounding disturbed rock zone into the repository.« less

Technical Note: Approximate solution of transient drawdown for constant-flux pumping at a partially penetrating well in a radial two-zone confined aquifer

NASA Astrophysics Data System (ADS)

Huang, C.-S.; Yang, S.-Y.; Yeh, H.-D.

2015-06-01

An aquifer consisting of a skin zone and a formation zone is considered as a two-zone aquifer. Existing solutions for the problem of constant-flux pumping in a two-zone confined aquifer involve laborious calculation. This study develops a new approximate solution for the problem based on a mathematical model describing steady-state radial and vertical flows in a two-zone aquifer. Hydraulic parameters in these two zones can be different but are assumed homogeneous in each zone. A partially penetrating well may be treated as the Neumann condition with a known flux along the screened part and zero flux along the unscreened part. The aquifer domain is finite with an outer circle boundary treated as the Dirichlet condition. The steady-state drawdown solution of the model is derived by the finite Fourier cosine transform. Then, an approximate transient solution is developed by replacing the radius of the aquifer domain in the steady-state solution with an analytical expression for a dimensionless time-dependent radius of influence. The approximate solution is capable of predicting good temporal drawdown distributions over the whole pumping period except at the early stage. A quantitative criterion for the validity of neglecting the vertical flow due to a partially penetrating well is also provided. Conventional models considering radial flow without the vertical component for the constant-flux pumping have good accuracy if satisfying the criterion.

Effects from Unsaturated Zone Flow during Oscillatory Hydraulic Testing

NASA Astrophysics Data System (ADS)

Lim, D.; Zhou, Y.; Cardiff, M. A.; Barrash, W.

2014-12-01

In analyzing pumping tests on unconfined aquifers, the impact of the unsaturated zone is often neglected. Instead, desaturation at the water table is often treated as a free-surface boundary, which is simple and allows for relatively fast computation. Richards' equation models, which account for unsaturated flow, can be compared with saturated flow models to validate the use of Darcy's Law. In this presentation, we examine the appropriateness of using fast linear steady-periodic models based on linearized water table conditions in order to simulate oscillatory pumping tests in phreatic aquifers. We compare oscillatory pumping test models including: 1) a 2-D radially-symmetric phreatic aquifer model with a partially penetrating well, simulated using both Darcy's Law and Richards' Equation in COMSOL; and 2) a linear phase-domain numerical model developed in MATLAB. Both COMSOL and MATLAB models are calibrated to match oscillatory pumping test data collected in the summer of 2013 at the Boise Hydrogeophysical Research Site (BHRS), and we examine the effect of model type on the associated parameter estimates. The results of this research will aid unconfined aquifer characterization efforts and help to constrain the impact of the simplifying physical assumptions often employed during test analysis.

Hydrologic processes in deep vadose zones in interdrainage arid environments

USGS Publications Warehouse

Walvoord, Michelle Ann; Scanlon, Bridget R.; Hogan, James F.; Phillips, Fred M.; Scanlon, Bridget R.

2004-01-01

A unifying theory for the hydrology of desert vadose zones is particularly timely considering the rising population and water stresses in arid and semiarid regions. Conventional models cannot reconcile the apparent discrepancy between upward flow indicated by hydraulic gradient data and downward flow suggested by environmental tracer data in deep vadose zone profiles. A conceptual model described here explains both hydraulic and tracer data remarkably well by incorporating the hydrologic role of desert plants that encroached former juniper woodland 10 to 15 thousand years ago in the southwestern United States. Vapor transport also plays an important role in redistributing moisture through deep soils, particularly in coarse-grained sediments. Application of the conceptual model to several interdrainage arid settings reproduces measured matric potentials and chloride accumulation by simulating the transition from downward flow to upward flow just below the root zone initiated by climate and vegetation change. Model results indicate a slow hydraulic drying response in deep vadose zones that enables matric potential profiles to be used to distinguish whether precipitation episodically percolated below the root zone or was completely removed via evapotranspiration during the majority of the Holocene. Recharge declined dramatically during the Holocene in interdrainage basin floor settings of arid and semiarid basins. Current flux estimates across the water table in these environmental settings, are on the order of 0.01 to 0.1 mm yr-1 and may be recharge (downward) or discharge (upward) depending on vadose zone characteristics, such as soil texture, geothermal gradient, and water table depth. In summary, diffuse recharge through the basin floor probably contributes only minimally to the total recharge in arid and semiarid basins.

Spatial variability analysis of combining the water quality and groundwater flow model to plan groundwater and surface water management in the Pingtung plain

NASA Astrophysics Data System (ADS)

Chen, Ching-Fang; Chen, Jui-Sheng; Jang, Cheng-Shin

2014-05-01

As a result of rapid economic growth in the Pingtung Plain, the use of groundwater resources has changed dramatically. The groundwater is quite rich in the Pingtung plain and the most important water sources. During the several decades, a substantial amount of groundwater has been pumped for the drinking, irrigation and aquaculture water supplies. However, because the sustainable use concept of groundwater resources is lack, excessive pumping of groundwater causes the occurrence of serious land subsidence and sea water intrusion. Thus, the management and conservation of groundwater resources in the Pingtung plain are considerably critical. This study aims to assess the conjunct use effect of groundwater and surface water in the Pingtung plain on recharge by reducing the amount of groundwater extraction. The groundwater quality variability and groundwater flow models are combined to spatially analyze potential zones of groundwater used for multi-purpose in the Pingtung Plain. First, multivariate indicator kriging (MVIK) is used to analyze spatial variability of groundwater quality based on drinking, aquaculture and irrigation water quality standards, and probabilistically delineate suitable zones in the study area. Then, the groundwater flow model, Processing MODFLOW (PMWIN), is adopted to simulate groundwater flow. The groundwater flow model must be conducted by the calibration and verification processes, and the regional groundwater recovery is discussed when specified water rights are replaced by surface water in the Pingtung plain. Finally, the most suitable zones of reducing groundwater use are determined for multi-purpose according to combining groundwater quality and quantity. The study results can establish a sound and low-impact management plan of groundwater resources utilization for the multi-purpose groundwater use, and prevent decreasing ground water tables, and the occurrence of land subsidence and sea water intrusion in the Pingtung plain.

Drift-Scale Coupled Processes (DST and THC Seepage) Models

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

E. Gonnenthal; N. Spyoher

The purpose of this Analysis/Model Report (AMR) is to document the Near-Field Environment (NFE) and Unsaturated Zone (UZ) models used to evaluate the potential effects of coupled thermal-hydrologic-chemical (THC) processes on unsaturated zone flow and transport. This is in accordance with the ''Technical Work Plan (TWP) for Unsaturated Zone Flow and Transport Process Model Report'', Addendum D, Attachment D-4 (Civilian Radioactive Waste Management System (CRWMS) Management and Operating Contractor (M and O) 2000 [153447]) and ''Technical Work Plan for Nearfield Environment Thermal Analyses and Testing'' (CRWMS M and O 2000 [153309]). These models include the Drift Scale Test (DST) THCmore » Model and several THC seepage models. These models provide the framework to evaluate THC coupled processes at the drift scale, predict flow and transport behavior for specified thermal loading conditions, and predict the chemistry of waters and gases entering potential waste-emplacement drifts. The intended use of this AMR is to provide input for the following: (1) Performance Assessment (PA); (2) Abstraction of Drift-Scale Coupled Processes AMR (ANL-NBS-HS-000029); (3) UZ Flow and Transport Process Model Report (PMR); and (4) Near-Field Environment (NFE) PMR. The work scope for this activity is presented in the TWPs cited above, and summarized as follows: continue development of the repository drift-scale THC seepage model used in support of the TSPA in-drift geochemical model; incorporate heterogeneous fracture property realizations; study sensitivity of results to changes in input data and mineral assemblage; validate the DST model by comparison with field data; perform simulations to predict mineral dissolution and precipitation and their effects on fracture properties and chemistry of water (but not flow rates) that may seep into drifts; submit modeling results to the TDMS and document the models. The model development, input data, sensitivity and validation studies described in this AMR are required to fully document and address the requirements of the TWPs.« less

Drift-Scale Coupled Processes (DST and THC Seepage) Models

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

E. Sonnenthale

The purpose of this Analysis/Model Report (AMR) is to document the Near-Field Environment (NFE) and Unsaturated Zone (UZ) models used to evaluate the potential effects of coupled thermal-hydrologic-chemical (THC) processes on unsaturated zone flow and transport. This is in accordance with the ''Technical Work Plan (TWP) for Unsaturated Zone Flow and Transport Process Model Report'', Addendum D, Attachment D-4 (Civilian Radioactive Waste Management System (CRWMS) Management and Operating Contractor (M&O) 2000 [1534471]) and ''Technical Work Plan for Nearfield Environment Thermal Analyses and Testing'' (CRWMS M&O 2000 [153309]). These models include the Drift Scale Test (DST) THC Model and several THCmore » seepage models. These models provide the framework to evaluate THC coupled processes at the drift scale, predict flow and transport behavior for specified thermal loading conditions, and predict the chemistry of waters and gases entering potential waste-emplacement drifts. The intended use of this AMR is to provide input for the following: Performance Assessment (PA); Near-Field Environment (NFE) PMR; Abstraction of Drift-Scale Coupled Processes AMR (ANL-NBS-HS-000029); and UZ Flow and Transport Process Model Report (PMR). The work scope for this activity is presented in the TWPs cited above, and summarized as follows: Continue development of the repository drift-scale THC seepage model used in support of the TSPA in-drift geochemical model; incorporate heterogeneous fracture property realizations; study sensitivity of results to changes in input data and mineral assemblage; validate the DST model by comparison with field data; perform simulations to predict mineral dissolution and precipitation and their effects on fracture properties and chemistry of water (but not flow rates) that may seep into drifts; submit modeling results to the TDMS and document the models. The model development, input data, sensitivity and validation studies described in this AMR are required to fully document and address the requirements of the TWPs.« less

Characterization of unsaturated zone hydrogeologic units using matrix properties and depositional history in a complex volcanic environment

USGS Publications Warehouse

Flint, Lorraine E.; Buesch, David C.; Flint, Alan L.

2006-01-01

Characterization of the physical and unsaturated hydrologic properties of subsurface materials is necessary to calculate flow and transport for land use practices and to evaluate subsurface processes such as perched water or lateral diversion of water, which are influenced by features such as faults, fractures, and abrupt changes in lithology. Input for numerical flow models typically includes parameters that describe hydrologic properties and the initial and boundary conditions for all materials in the unsaturated zone, such as bulk density, porosity, and particle density, saturated hydraulic conductivity, moisture-retention characteristics, and field water content. We describe an approach for systematically evaluating the site features that contribute to water flow, using physical and hydraulic data collected at the laboratory scale, to provide a representative set of physical and hydraulic parameters for numerically calculating flow of water through the materials at a site. An example case study from analyses done for the heterogeneous, layered, volcanic rocks at Yucca Mountain is presented, but the general approach for parameterization could be applied at any site where depositional processes follow deterministic patterns. Hydrogeologic units at this site were defined using (i) a database developed from 5320 rock samples collected from the coring of 23 shallow (<100 m) and 10 deep (500–1000 m) boreholes, (ii) lithostratigraphic boundaries and corresponding relations to porosity, (iii) transition zones with pronounced changes in properties over short vertical distances, (iv) characterization of the influence of mineral alteration on hydrologic properties such as permeability and moisture-retention characteristics, and (v) a statistical analysis to evaluate where boundaries should be adjusted to minimize the variance within layers. Model parameters developed in this study, and the relation of flow properties to porosity, can be used to produce detailed and accurate representations of the core-scale hydrologic processes ongoing at Yucca Mountain.

Titer-plate formatted continuous flow thermal reactors: Design and performance of a nanoliter reactor

PubMed Central

Chen, Pin-Chuan; Park, Daniel S.; You, Byoung-Hee; Kim, Namwon; Park, Taehyun; Soper, Steven A.; Nikitopoulos, Dimitris E.; Murphy, Michael C.

2010-01-01

Arrays of continuous flow thermal reactors were designed, configured, and fabricated in a 96-device (12 × 8) titer-plate format with overall dimensions of 120 mm × 96 mm, with each reactor confined to a 8 mm × 8 mm footprint. To demonstrate the potential, individual 20-cycle (740 nL) and 25-cycle (990 nL) reactors were used to perform the continuous flow polymerase chain reaction (CFPCR) for amplification of DNA fragments of different lengths. Since thermal isolation of the required temperature zones was essential for optimal biochemical reactions, three finite element models, executed with ANSYS (v. 11.0, Canonsburg, PA), were used to characterize the thermal performance and guide system design: (1) a single device to determine the dimensions of the thermal management structures; (2) a single CFPCR device within an 8 mm × 8 mm area to evaluate the integrity of the thermostatic zones; and (3) a single, straight microchannel representing a single loop of the spiral CFPCR device, accounting for all of the heat transfer modes, to determine whether the PCR cocktail was exposed to the proper temperature cycling. In prior work on larger footprint devices, simple grooves between temperature zones provided sufficient thermal resistance between zones. For the small footprint reactor array, 0.4 mm wide and 1.2 mm high fins were necessary within the groove to cool the PCR cocktail efficiently, with a temperature gradient of 15.8°C/mm, as it flowed from the denaturation zone to the renaturation zone. With temperature tolerance bands of ±2°C defined about the nominal temperatures, more than 72.5% of the microchannel length was located within the desired temperature bands. The residence time of the PCR cocktail in each temperature zone decreased and the transition times between zones increased at higher PCR cocktail flow velocities, leading to less time for the amplification reactions. Experiments demonstrated the performance of the CFPCR devices as a function of flow velocity, fragment length, and copy number. A 99 bp DNA fragment was successfully amplified at flow velocities from 1 mm/s to 3 mm/s, requiring from 8.16 minutes for 20 cycles (24.48 s/cycle) to 2.72 minutes for 20 cycles (8.16 s/cycle), respectively. Yield compared to the same amplification sequence performed using a bench top thermal cycler decreased nonlinearly from 73% (at 1 mm/s) to 13% (at 3 mm/s) with shorter residence time at the optimal temperatures for the reactions due to increased flow rate primarily responsible. Six different DNA fragments with lengths between 99 bp and 997 bp were successfully amplified at 1 mm/s. Repeatable, successful amplification of a 99 bp fragment was achieved with a minimum of 8000 copies of the DNA template. This is the first demonstration and characterization of continuous flow thermal reactors within the 8 mm × 8 mm footprint of a 96-well micro-titer plate and is the smallest continuous flow PCR to date. PMID:20871807

Tracing long-term vadose zone processes at the Nevada Test Site, USA

PubMed Central

Hunt, James R.; Tompson, Andrew F. B.

2010-01-01

The nuclear weapons testing programme of the USA has released radionuclides to the subsurface at the Nevada Test Site. One of these tests has been used to study the hydrological transport of radionuclides for over 25 years in groundwater and the deep unsaturated zone. Ten years after the weapon’s test, a 16 year groundwater pumping experiment was initiated to study the mobility of radionuclides from that test in an alluvial aquifer. The continuously pumped groundwater was released into an unlined ditch where some of the water infiltrated into the 200 m deep vadose zone. The pumped groundwater had well-characterized tritium activities that were utilized to trace water migration in the shallow and deep vadose zones. Within the near-surface vadose zone, tritium levels in the soil water are modelled by a simple one-dimensional, analytical wetting front model. In the case of the near-surface soils at the Cambric Ditch experimental site, water flow and salt accumulation appear to be dominated by rooted vegetation, a mechanism not included within the wetting front model. Simulation results from a two-dimensional vadose groundwater flow model illustrate the dominance of vertical flow in the vadose zone and the recharge of the aquifer with the pumped groundwater. The long-time series of hydrological data provides opportunities to understand contaminant transport processes better in the vadose zone with an appropriate level of modelling. PMID:21785525

Modeling merging behavior at lane drops.

DOT National Transportation Integrated Search

2015-02-01

In work-zone configurations where lane drops are present, merging of traffic at the taper presents an operational concern. In : addition, as flow through the work zone is reduced, the relative traffic safety of the work zone is also reduced. Improvin...

Geometry of the Nojima fault at Nojima-Hirabayashi, Japan - I. A simple damage structure inferred from borehole core permeability

USGS Publications Warehouse

Lockner, David A.; Tanaka, Hidemi; Ito, Hisao; Ikeda, Ryuji; Omura, Kentaro; Naka, Hisanobu

2009-01-01

The 1995 Kobe (Hyogo-ken Nanbu) earthquake, M = 7.2, ruptured the Nojima fault in southwest Japan. We have studied core samples taken from two scientific drillholes that crossed the fault zone SW of the epicentral region on Awaji Island. The shallower hole, drilled by the Geological Survey of Japan (GSJ), was started 75 m to the SE of the surface trace of the Nojima fault and crossed the fault at a depth of 624 m. A deeper hole, drilled by the National Research Institute for Earth Science and Disaster Prevention (NIED) was started 302 m to the SE of the fault and crossed fault strands below a depth of 1140 m. We have measured strength and matrix permeability of core samples taken from these two drillholes. We find a strong correlation between permeability and proximity to the fault zone shear axes. The half-width of the high permeability zone (approximately 15 to 25 m) is in good agreement with the fault zone width inferred from trapped seismic wave analysis and other evidence. The fault zone core or shear axis contains clays with permeabilities of approximately 0.1 to 1 microdarcy at 50 MPa effective confining pressure (10 to 30 microdarcy at in situ pressures). Within a few meters of the fault zone core, the rock is highly fractured but has sustained little net shear. Matrix permeability of this zone is approximately 30 to 60 microdarcy at 50 MPa effective confining pressure (300 to 1000 microdarcy at in situ pressures). Outside this damage zone, matrix permeability drops below 0.01 microdarcy. The clay-rich core material has the lowest strength with a coefficient of friction of approximately 0.55. Shear strength increases with distance from the shear axis. These permeability and strength observations reveal a simple fault zone structure with a relatively weak fine-grained core surrounded by a damage zone of fractured rock. In this case, the damage zone will act as a high-permeability conduit for vertical and horizontal flow in the plane of the fault. The fine-grained core region, however, will impede fluid flow across the fault.

Stratigraphy of the unsaturated zone and the Snake River Plain aquifer at and near the Idaho National Engineering Laboratory, Idaho

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

Anderson, S.R.; Liszewski, M.J.

1997-08-01

The unsaturated zone and the Snake River Plain aquifer at and near the Idaho National Engineering Laboratory (INEL) are made up of at least 178 basalt-flow groups, 103 sedimentary interbeds, 6 andesite-flow groups, and 4 rhyolite domes. Stratigraphic units identified in 333 wells in this 890-mile{sup 2} area include 121 basalt-flow groups, 102 sedimentary interbeds, 6 andesite-flow groups, and 1 rhyolite dome. Stratigraphic units were identified and correlated using the data from numerous outcrops and 26 continuous cores and 328 natural-gamma logs available in December 1993. Basalt flows make up about 85% of the volume of deposits underlying the area.

Estimation of the Potential for Atrazine Transport in a Silt Loam Soil

USGS Publications Warehouse

Eckhardt, D.A.V.; Wagenet, R.J.

1996-01-01

The transport potential of the herbicide atrazine (2-chloro-4-ethyl-6-isopropyl-s-triazine) through a 1-meter-thick root zone of corn (Zea mays L.) in a silty-loam soil in Kansas was estimated for a 22-year period (1972-93) using the one-dimensional water-flow and solute-transport model LEACHM. Results demonstrate that, for this soil, atrazine transport is directly related to the amount and timing of rain that follows spring applications of atrazine. Two other critical transport factors were important in wet years - [1] variability in atrazine application rate, and [2] atrazine degradation rates below the root zone. Results demonstrate that the coincidence of heavy rain soon after atrazine application can cause herbicide to move below the rooting zone into depths at which biodegradation rates are assumed to be low but are often unknown. Atrazine that reaches below the rooting zone and persists in the underlying soil can subsequently be transported into ground water as soil water drains, typically after the growing season. A frequency analysis of atrazine concentrations in subsurface drainage, combined with field data, demonstrates the relative importance of critical transport factors and confirms a need for definitive estimates of atrazine-degradation rates below the root zone. The analysis indicates that periodic leaching of atrazine can be expected for this soil when rainfall that exceeds 20 cm/mo coincides with atrazine presence in soil.

Implementation of Solute Transport in the Vadose Zone into the `HYDRUS Package for MODFLOW'

NASA Astrophysics Data System (ADS)

Simunek, J.; Beegum, S.; Szymkiewicz, A.; Sudheer, K. P.

2017-12-01

The 'HYDRUS package for MODFLOW' was developed by Seo et al. (2007) and Twarakavi et al. (2008) to simultaneously evaluate transient water flow in both unsaturated and saturated zones. The package, which is based on the HYDRUS-1D model (Šimůnek et al., 2016) simulating unsaturated water flow in the vadose zone, was incorporated into MODFLOW (Harbaugh et al., 2000) simulating saturated groundwater flow. The HYDRUS package in the coupled model can be used to represent the effects of various unsaturated zone processes, including infiltration, evaporation, root water uptake, capillary rise, and recharge in homogeneous or layered soil profiles. The coupled model is effective in addressing spatially-variable saturated-unsaturated hydrological processes at the regional scale, allowing for complex layering in the unsaturated zone, spatially and temporarily variable water fluxes at the soil surface and in the root zone, and with alternating recharge and discharge fluxes (Twarakavi et al., 2008). One of the major limitations of the coupled model was that it could not be used to simulate at the same time solute transport. However, solute transport is highly dependent on water table fluctuations due to temporal and spatial variations in groundwater recharge. This is an important concern when the coupled model is used for analyzing groundwater contamination due to transport through the unsaturated zone. The objective of this study is to integrate the solute transport model (the solute transport part of HYDRUS-1D for the unsaturated zone and MT3DMS (Zheng and Wang, 1999; Zheng, 2009) for the saturated zone) into an existing coupled water flow model. The unsaturated zone component of the coupled model can consider solute transport involving many biogeochemical processes and reactions, including first-order degradation, volatilization, linear or nonlinear sorption, one-site kinetic sorption, two-site sorption, and two-kinetic sites sorption (Šimůnek and van Genuchten, 2008). Due to complex interactions at the groundwater table, certain modifications of the pressure head (compared to the original coupling) and solute concentration profiles were incorporated into the HYDRUS package. The developed integrated model is verified using HYDRUS-2D and analyzed for its computational time requirements.

Hydrological and Climate Controls on Hyporheic Contributions to River Net Ecosystem Productivity

NASA Astrophysics Data System (ADS)

Newcomer, M. E.; Hubbard, S. S.; Fleckenstein, J. H.; Maier, U.; Schmidt, C.; Laube, G.; Chen, N.; Ulrich, C.; Dwivedi, D.; Steefel, C. I.; Rubin, Y.

2016-12-01

Hyporheic zone contributions to river net ecosystem productivity (NEP) can represent a substantial source or sink for organic and inorganic carbon (C). Hyporheic zone processes are estimated to vary with network location as a function of river-aquifer interactions as well as with climatic factors supporting riverbed gross primary productivity (GPP) and ecosystem respiration. Even though hyporheic zone NEP is hypothesized to be a significant budgetary component to river-aquifer biogeochemical cycling, models of river NEP often parameterize hyporheic zone contributions as a space-time constant input of CO2 to rivers, leading to overestimation of hyporheic zone NEP and underestimation of C storage. This assumption is problematic during the summer growing season, when GPP is largest and C is stored in surface and subsurface biomass. We investigated the dynamic role of hyporheic zone NEP using the MIN3P flow and reactive transport model with surface water GPP and ecosystem respiration simulated as a function of light, depth, temperature, pH, and atmospheric CO2. We simulated hyporheic zone NEP for low-order and high-order streams, which collectively represent a range of characteristic flow paths and subsurface residence times. Downscaled climate predictions of temperature and atmospheric CO2 representing carbon emission futures were used to force the models and to compare future and current hyporheic zone NEP. Our results show that river-aquifer flow conditions determine the relative role of the river as either a store or sink of C through direct contributions of O2 and dissolved organic content from river GPP. Modeled results show that high discharge, high order rivers are net stores of CO2 from the atmosphere; however this is dependent on perturbation events that allow stored C from summer GPP to be released (i.e. rising water tables during winter storms). Lacking a perturbation event, C remains in pore-water storage as dissolved CO2 and biomass. Conversely, low-discharge mountainous streams with continuous hyporheic zone flow represent a net source of CO2, with future temperature rises stimulating additional heterotrophic activity. Our work contributes to a better understanding of how river and hyporheic zone processes significantly influence biogeochemical cycling under changing climate conditions.

Audio-frequency magnetotelluric imaging of the Hijima fault, Yamasaki fault system, southwest Japan

NASA Astrophysics Data System (ADS)

Yamaguchi, S.; Ogawa, Y.; Fuji-Ta, K.; Ujihara, N.; Inokuchi, H.; Oshiman, N.

2010-04-01

An audio-frequency magnetotelluric (AMT) survey was undertaken at ten sites along a transect across the Hijima fault, a major segment of the Yamasaki fault system, Japan. The data were subjected to dimensionality analysis, following which two-dimensional inversions for the TE and TM modes were carried out. This model is characterized by (1) a clear resistivity boundary that coincides with the downward projection of the surface trace of the Hijima fault, (2) a resistive zone (>500 Ω m) that corresponds to Mesozoic sediment, and (3) shallow and deep two highly conductive zones (30-40 Ω m) along the fault. The shallow conductive zone is a common feature of the Yamasaki fault system, whereas the deep conductor is a newly discovered feature at depths of 800-1,800 m to the southwest of the fault. The conductor is truncated by the Hijima fault to the northeast, and its upper boundary is the resistive zone. Both conductors are interpreted to represent a combination of clay minerals and a fluid network within a fault-related fracture zone. In terms of the development of the fluid networks, the fault core of the Hijima fault and the highly resistive zone may play important roles as barriers to fluid flow on the northeast and upper sides of the conductive zones, respectively.

Simulation results for a multirate mass transfer modell for immiscible displacement of two fluids in highly heterogeneous porous media

NASA Astrophysics Data System (ADS)

Tecklenburg, Jan; Neuweiler, Insa; Dentz, Marco; Carrera, Jesus; Geiger, Sebastian

2013-04-01

Flow processes in geotechnical applications do often take place in highly heterogeneous porous media, such as fractured rock. Since, in this type of media, classical modelling approaches are problematic, flow and transport is often modelled using multi-continua approaches. From such approaches, multirate mass transfer models (mrmt) can be derived to describe the flow and transport in the "fast" or mobile zone of the medium. The porous media is then modeled with one mobile zone and multiple immobile zones, where the immobile zones are connected to the mobile zone by single rate mass transfer. We proceed from a mrmt model for immiscible displacement of two fluids, where the Buckley-Leverett equation is expanded by a sink-source-term which is nonlocal in time. This sink-source-term models exchange with an immobile zone with mass transfer driven by capillary diffusion. This nonlinear diffusive mass transfer can be approximated for particular imbibition or drainage cases by a linear process. We present a numerical scheme for this model together with simulation results for a single fracture test case. We solve the mrmt model with the finite volume method and explicit time integration. The sink-source-term is transformed to multiple single rate mass transfer processes, as shown by Carrera et. al. (1998), to make it local in time. With numerical simulations we studied immiscible displacement in a single fracture test case. To do this we calculated the flow parameters using information about the geometry and the integral solution for two phase flow by McWorther and Sunnada (1990). Comparision to the results of the full two dimensional two phase flow model by Flemisch et. al. (2011) show good similarities of the saturation breakthrough curves. Carrera, J., Sanchez-Vila, X., Benet, I., Medina, A., Galarza, G., and Guimera, J.: On matrix diffusion: formulations, solution methods and qualitative effects, Hydrogeology Journal, 6, 178-190, 1998. Flemisch, B., Darcis, M., Erbertseder, K., Faigle, B., Lauser, A. et al.: Dumux: Dune for multi-{Phase, Component, Scale, Physics, ...} flow and transport in porous media, Advances in Water Resources, 34, 1102-1112, 2011. McWhorter, D. B., and Sunada, D. K.: Exact integral solutions for two-phase flow, Water Resources Research, 26(3), 399-413, 1990.

WTAQ - A computer program for aquifer-test analysis of confined and unconfined aquifers

USGS Publications Warehouse

Barlow, P.M.; Moench, A.F.

2004-01-01

Computer program WTAQ was developed to implement a Laplace-transform analytical solution for axial-symmetric flow to a partially penetrating, finite-diameter well in a homogeneous and anisotropic unconfined (water-table) aquifer. The solution accounts for wellbore storage and skin effects at the pumped well, delayed response at an observation well, and delayed or instantaneous drainage from the unsaturated zone. For the particular case of zero drainage from the unsaturated zone, the solution simplifies to that of axial-symmetric flow in a confined aquifer. WTAQ calculates theoretical time-drawdown curves for the pumped well and observation wells and piezometers. The theoretical curves are used with measured time-drawdown data to estimate hydraulic parameters of confined or unconfined aquifers by graphical type-curve methods or by automatic parameter-estimation methods. Parameters that can be estimated are horizontal and vertical hydraulic conductivity, specific storage, and specific yield. A sample application illustrates use of WTAQ for estimating hydraulic parameters of a hypothetical, unconfined aquifer by type-curve methods. Copyright ASCE 2004.

A hydrogeological conceptual approach to study urban groundwater flow in Bucharest city, Romania

NASA Astrophysics Data System (ADS)

Boukhemacha, Mohamed Amine; Gogu, Constantin Radu; Serpescu, Irina; Gaitanaru, Dragos; Bica, Ioan

2015-05-01

Management of groundwater systems in urban areas is necessary and can be reliably performed by means of mathematical modeling combined with geospatial analysis. A conceptual approach for the study of urban hydrogeological systems is presented. The proposed approach is based on the features of Bucharest city (Romania) and can be adapted to other urban areas showing similar characteristics. It takes into account the interaction between groundwater and significant urban infrastructure elements that can be encountered in modern cities such as subway tunnels and water-supply networks, and gives special attention to the sewer system. In this respect, an adaptation of the leakage factor approach is proposed, which uses a sewer-system zoning function related to the conduits' location in the aquifer system and a sewer-conduits classification function related to their structural and/or hydraulic properties. The approach was used to elaborate a single-layered steady state groundwater flow model for a pilot zone of Bucharest city.

Geochemistry of the Springfield Plateau aquifer of the Ozark Plateaus Province in Arkansas, Kansas, Missouri and Oklahoma, USA

USGS Publications Warehouse

Adamski, J.C.

2000-01-01

Geochemical data indicate that the Springfield Plateau aquifer, a carbonate aquifer of the Ozark Plateaus Province in central USA, has two distinct hydrochemical zones. Within each hydrochemical zone, water from springs is geochemically and isotopically different than water from wells. Geochemical data indicate that spring water generally interacts less with the surrounding rock and has a shorter residence time, probably as a result of flowing along discrete fractures and solution openings, than water from wells. Water type throughout most of the aquifer was calcium bicarbonate, indicating that carbonate-rock dissolution is the primary geochemical process occurring in the aquifer. Concentrations of calcium, bicarbonate, dissolved oxygen and tritium indicate that most ground water in the aquifer recharged rapidly and is relatively young (less than 40 years). In general, field-measured properties, concentrations of many chemical constituents, and calcite saturation indices were greater in samples from the northern part of the aquifer (hydrochemical zone A) than in samples from the southern part of the aquifer (hydrochemical zone B). Factors affecting differences in the geochemical composition of ground water between the two zones are difficult to identify, but could be related to differences in chert content and possibly primary porosity, solubility of the limestone, and amount and type of cementation between zone A than in zone B. In addition, specific conductance, pH, alkalinity, concentrations of many chemical constituents and calcite saturation indices were greater in samples from wells than in samples from springs in each hydrochemical zone. In contrast, concentrations of dissolved oxygen, nitrite plus nitrate, and chloride generally were greater in samples from springs than in samples from wells. Water from springs generally flows rapidly through large conduits with minimum water-rock interactions. Water from wells flow through small fractures, which restrict flow and increase water-rock interactions. As a result, springs tend to be more susceptible to surface contamination than wells. The results of this study have important implications for the geochemical and hydrogeological processes of similar carbonate aquifers in other geographical locations. Copyright (C) 2000 John Wiley and Sons, Ltd.Geochemical data indicate that the Springfield Plateau carbonate aquifer has two distinct hydrochemical zones. With each hydrochemical zone, water from springs is geochemically and isotopically different from the water from wells. Spring water generally interacts less with the surrounding rock and has a shorter residence time, probably as a result of flowing along discrete fractures and solution openings, than water from wells. Factors affecting the differences in the geochemical composition of groundwater between the two zones are difficult to identify, but could be related to differences in chert content and possibly primary porosity, solubility of the limestone, and amount and type of cementation between zones.

Internal flow inside droplets within a concentrated emulsion during droplet rearrangement

NASA Astrophysics Data System (ADS)

Leong, Chia Min; Gai, Ya; Tang, Sindy K. Y.

2018-03-01

Droplet microfluidics, in which each droplet serves as a micro-reactor, has found widespread use in high-throughput biochemical screening applications. These droplets are often concentrated at various steps to form a concentrated emulsion. As part of a serial interrogation and sorting process, such concentrated emulsions are typically injected into a tapered channel leading to a constriction that fits one drop at a time for the probing of droplet content in a serial manner. The flow physics inside the droplets under these flow conditions are not well understood but are critical for predicting and controlling the mixing of reagents inside the droplets as reactors. Here we investigate the flow field inside droplets of a concentrated emulsion flowing through a tapered microchannel using micro-particle image velocimetry. The confining geometry of the channel forces the number of rows of drops to reduce by one at specific and uniformly spaced streamwise locations, which are referred to as droplet rearrangement zones. Within each rearrangement zone, the phase-averaged velocity results show that the motion of the droplets involved in the rearrangement process, also known as a T1 event, creates vortical structures inside themselves and their adjacent droplets. These flow structures increase the circulation inside droplets up to 2.5 times the circulation in droplets at the constriction. The structures weaken outside of the rearrangement zones suggesting that the flow patterns created by the T1 process are transient. The time scale of circulation is approximately the same as the time scale of a T1 event. Outside of the rearrangement zones, flow patterns in the droplets are determined by the relative velocity between the continuous and disperse phases.

Using heat as a tracer to estimate spatially distributed mean residence times in the hyporheic zone of a riffle-pool sequence

USGS Publications Warehouse

Naranjo, Ramon C.

2013-01-01

Biochemical reactions that occur in the hyporheic zone are highly dependent on the time solutes that are in contact with sediments of the riverbed. In this investigation, we developed a 2-D longitudinal flow and solute-transport model to estimate the spatial distribution of mean residence time in the hyporheic zone. The flow model was calibrated using observations of temperature and pressure, and the mean residence times were simulated using the age-mass approach for steady-state flow conditions. The approach used in this investigation includes the mixing of different ages and flow paths of water through advection and dispersion. Uncertainty of flow and transport parameters was evaluated using standard Monte Carlo and the generalized likelihood uncertainty estimation method. Results of parameter estimation support the presence of a low-permeable zone in the riffle area that induced horizontal flow at a shallow depth within the riffle area. This establishes shallow and localized flow paths and limits deep vertical exchange. For the optimal model, mean residence times were found to be relatively long (9–40.0 days). The uncertainty of hydraulic conductivity resulted in a mean interquartile range (IQR) of 13 days across all piezometers and was reduced by 24% with the inclusion of temperature and pressure observations. To a lesser extent, uncertainty in streambed porosity and dispersivity resulted in a mean IQR of 2.2 and 4.7 days, respectively. Alternative conceptual models demonstrate the importance of accounting for the spatial distribution of hydraulic conductivity in simulating mean residence times in a riffle-pool sequence.

Optimization of Orifice Geometry for Cross-Flow Mixing in a Cylindrical Duct

NASA Technical Reports Server (NTRS)

Kroll, J. T.; Sowa, W. A.; Samuelsen, G. S.

1996-01-01

Mixing of gaseous jets in a cross-flow has significant applications in engineering, one example of which is the dilution zone of a gas turbine combustor. Despite years of study, the design of the jet injection in combustors is largely based on practical experience. The emergence of NO(x) regulations for stationary gas turbines and the anticipation of aero-engine regulations requires an improved understanding of jet mixing as new combustor concepts are introduced. For example, the success of the staged combustor to reduce the emission of NO(x) is almost entirely dependent upon the rapid and complete dilution of the rich zone products within the mixing section. It is these mixing challenges to which the present study is directed. A series of experiments was undertaken to delineate the optimal mixer orifice geometry. A cross-flow to core-flow momentum-flux ratio of 40 and a mass flow ratio of 2.5 were selected as representative of a conventional design. An experimental test matrix was designed around three variables: the number of orifices, the orifice length-to- width ratio, and the orifice angle. A regression analysis was performed on the data to arrive at an interpolating equation that predicted the mixing performance of orifice geometry combinations within the range of the test matrix parameters. Results indicate that the best mixing orifice geometry tested involves eight orifices with a long-to-short side aspect ratio of 3.5 at a twenty-three degree inclination from the center-line of the mixing section.

Ground-water levels and direction of ground-water flow in the central part of Bernalillo County, New Mexico, summer 1983

USGS Publications Warehouse

Kues, Georginna E.

1986-01-01

In 1980, toxic chemicals were detected in water samples from wells in and near Albuquerque 's San Jose well field. At the request of the Environmental Improvement Division of the New Mexico Health and Environment Department, the U.S. Geological Survey conducted a study to determine groundwater levels and flow direction. Water levels were measured in 44 wells in a 64 sq mi area along the Rio Grande and adjacent areas during a period of near maximum municipal pumpage. Based on the altitude of screened interval, wells were grouped into shallow (screened internal above an altitude of 4,800 ft) or deep (screened internal below an altitude of 4,800 ft) zones. Groundwater in the shallow zone generally moves from north to south parallel to flow in the Rio Grande. Groundwater in the deep zone generally moves from the northwest to the east and southeast. A poorly developed cone of depression within the deep zone was present in the northeast. Water levels in wells were as much as 18 feet higher in the shallow zone than in the deep zone in the vicinity of the San Jose well field, indicating a downward gradient. (Author 's abstract)

Experimental Evaluation of the Heat Sink Effect in Hepatic Microwave Ablation

PubMed Central

Ringe, Kristina I.; Lutat, Carolin; Rieder, Christian; Schenk, Andrea; Wacker, Frank; Raatschen, Hans-Juergen

2015-01-01

Purpose To demonstrate and quantify the heat sink effect in hepatic microwave ablation (MWA) in a standardized ex vivo model, and to analyze the influence of vessel distance and blood flow on lesion volume and shape. Materials and Methods 108 ex vivo MWA procedures were performed in freshly harvested pig livers. Antennas were inserted parallel to non-perfused and perfused (700,1400 ml/min) glass tubes (diameter 5mm) at different distances (10, 15, 20mm). Ablation zones (radius, area) were analyzed and compared (Kruskal-Wallis Test, Dunn’s multiple comparison Test). Temperature changes adjacent to the tubes were measured throughout the ablation cycle. Results Maximum temperature decreased significantly with increasing flow and distance (p<0.05). Compared to non-perfused tubes, ablation zones were significantly deformed by perfused tubes within 15mm distance to the antenna (p<0.05). At a flow rate of 700ml/min ablation zone radius was reduced to 37.2% and 80.1% at 10 and 15mm tube distance, respectively; ablation zone area was reduced to 50.5% and 89.7%, respectively. Conclusion Significant changes of ablation zones were demonstrated in a pig liver model. Considerable heat sink effect was observed within a diameter of 15mm around simulated vessels, dependent on flow rate. This has to be taken into account when ablating liver lesions close to vessels. PMID:26222431

Anisotropy in subduction zones: Insights from new source side S wave splitting measurements from India

NASA Astrophysics Data System (ADS)

Roy, Sunil K.; Kumar, M. Ravi; Davuluri, Srinagesh

2017-08-01

This study presents 106 splitting and 40 null measurements of source side anisotropy in subduction zones, utilizing direct S waves registered at two stations sited on the Indian continent, which show null shear wave splitting measurements for SKS phases. Our results suggest that trench-parallel anisotropy is dominant beneath the Philippines, Mariana, Izu-Bonin, and edge of the Java slab, while plate motion-parallel anisotropy is observed beneath the Solomon, Aegean, Japan, and Java slabs. Results from Kuril and Aleutian regions reveal trench-oblique anisotropy. We chose to interpret these observations primarily in terms of mantle flow beneath a subduction zone. While the two-dimensional (2-D) slab entrained flow model offers a simple explanation for trench-normal fast polarization azimuths (FPA), the trench-parallel FPA can be reconciled by extension due to slab rollback. The model that invokes age of the subducting lithosphere can explain anisotropy in the subslab, derived from rays recorded at the updip stations. However, when downdip stations are used, contributions from the slab and supraslab need to be considered. In Japan, anisotropy in the subslab mantle shallower than 300 km might be associated with trench-parallel mantle flow resulting in the alignment of FPA in the same direction. Anisotropy in the deeper part, above the transition zone, is probably associated with 2-D flow resulting in trench-normal FPA. Anisotropy in the Mariana Trench might be associated with trench-parallel mantle flow in the supraslab region, with similar deformation in the upper mantle and the transition zone.

Applying a general triclinic transpression model to highly partitioned brittle-ductile shear zones: A case study from the Torcal de Antequera massif, external Betics, southern Spain

NASA Astrophysics Data System (ADS)

Díaz-Azpiroz, M.; Barcos, L.; Balanyá, J. C.; Fernández, C.; Expósito, I.; Czeck, D. M.

2014-11-01

Oblique convergence and subsequent transpression kinematics can be considered as the general situation in most convergent and strike-slip tectonic boundaries. To better understand such settings, progressively more complex kinematic models have been proposed, which need to be tested against natural shear zones using standardized procedures that minimise subjectivism. In this work, a protocol to test a general triclinic transpression model is applied to the Torcal de Antequera massif (TAM), an essentially brittle shear zone. Our results, given as kinematic parameters of the transpressive flow (transpression obliquity, ϕ; extrusion obliquity, υ; and kinematic vorticity number, Wk), suggest that the bulk triclinic transpressive flow imposed on the TAM was partitioned into two different flow fields, following a general partitioning type. As such, one flow field produced narrow structural domains located at the limits of the TAM, where mainly dextral strike-slip simple-shear-dominated transpression took place (Outer domains, ODs). In contrast, the remaining part of the bulk flow produced pure-shear-dominated dextral triclinic transpression at the inner part of the TAM (Inner domain, ID). A graphical method relating internal (ϕ, Wk) to far-field (dip of the shear zone boundary, δ; angle of oblique convergence, α) transpression parameters is proposed to obtain the theoretical horizontal velocity vector (V→), which in the case of the TAM, ranges between 099 and 118. These results support the applicability of kinematic models of triclinic transpression to brittle-ductile shear zones and the potential utility of the proposed protocol.

Comparison of Mixing Calculations for Reacting and Non-Reacting Flows in a Cylindrical Duct

NASA Technical Reports Server (NTRS)

Oechsle, V. L.; Mongia, H. C.; Holdeman, J. D.

1994-01-01

A production 3-D elliptic flow code has been used to calculate non-reacting and reacting flow fields in an experimental mixing section relevant to a rich burn/quick mix/lean burn (RQL) combustion system. A number of test cases have been run to assess the effects of the variation in the number of orifices, mass flow ratio, and rich-zone equivalence ratio on the flow field and mixing rates. The calculated normalized temperature profiles for the non-reacting flow field agree qualitatively well with the normalized conserved variable isopleths for the reacting flow field indicating that non-reacting mixing experiments are appropriate for screening and ranking potential rapid mixing concepts. For a given set of jet momentum-flux ratio, mass flow ratio, and density ratio (J, MR, and DR), the reacting flow calculations show a reduced level of mixing compared to the non-reacting cases. In addition, the rich-zone equivalence ratio has noticeable effect on the mixing flow characteristics for reacting flows.

Detailed analysis of the flow in the inducer of a transonic centrifugal compressor

NASA Astrophysics Data System (ADS)

Buffaz, Nicolas; Trébinjac, Isabelle

2012-02-01

Numerical and experimental investigations were conducted in a transonic centrifugal compressor stage composed of a backswept splittered unshrouded impeller and a vaned diffuser. A detailed analysis of the flow in the inducer (i.e. the entry zone of the impeller between the main blade leading edge and the splitter blade leading edge) is proposed from choke to surge. Steady and unsteady simulations were performed using the code elsA, which uses a multi-domain approach on structured meshes and solves the compressible RANS equations, associated with a two-equation turbulence model k-l in the rotating frame of reference. The 1MW LMFA-ECL test rig was used for carrying out the tests in the compressor stage. Unsteady pressure measurements up to 150 kHz and Laser Doppler Anemometry measurements were performed in the inducer. A good agreement is obtained between the experimental and numerical data even if an over dissipation is noticed in the numerical results. The change in flow pattern from choke to surge is mainly due to a change in the tip leakage flow trajectory which straightens, leading to a flow blockage of an individual passage near shroud. A spectral analysis shows that only the blade passing frequency and its harmonics compose the various spectra obtained from choke to surge.

Impacts of exhalation flow on the microenvironment around the human body under different room temperatures

NASA Astrophysics Data System (ADS)

Jafari, Mohammad Javad; Gharari, Noradin; Azari, Mansour Rezazade; Ashrafi, Khosro

2018-04-01

Exhalation flow and room temperature can have a considerable effect on the microenvironment in the vicinity of human body. In this study, impacts of exhalation flow and room temperature on the microenvironment around a human body were investigated using a numerical simulation. For this purpose, a computational fluid dynamic program was applied to study thermal plume around a sitting human body at different room temperatures of a calm indoor room by considering the exhalation flow. The simulation was supported by some experimental measurements. Six different room temperatures (18 to 28 °C) with two nose exhalation modes (exhalation and non-exhalation) were investigated. Overhead and breathing zone velocities and temperatures were simulated in different scenarios. This study finds out that the exhalation through the nose has a significant impact on both quantitative and qualitative features of the human microenvironment in different room temperatures. At a given temperature, the exhalation through the nose can change the location and size of maximum velocity at the top of the head. In the breathing zone, the effect of exhalation through the nose on velocity and temperature distribution was pronounced for the point close to mouth. Also, the exhalation through the nose strongly influences the thermal boundary layer on the breathing zone while it only minimally influences the convective boundary layer on the breathing zone. Overall results demonstrate that it is important to take the exhalation flow into consideration in all areas, especially at a quiescent flow condition with low temperature.

The effect of abdominal pressure on urinary flow rate.

PubMed

Hasegawa, N; Kitagawa, Y; Takasaki, N; Miyazaki, S

1983-07-01

We examined the effect of abdominal pressure on urinary flow rate and urethral closure pressure in 46 subjects, ranging in age from 26 to 82 years. An increase in urinary flow rate caused by abdominal straining was not found when organic obstruction was present in the prostatic urethra in men or the proximal urethra in women, or when dysuria is caused by the lowered detrusor pressure. An increase in urinary flow rate caused by straining was noted when anterior urethral stricture or stress incontinence was present. The increase in urinary flow rate owing to straining was undetermined in the control group. The urethral closure pressure on the anti-stress incontinence zone increased as a result of straining at the same time and to the same degree as did the intravesical pressure. When the anti-stress incontinence zone was subjected to transurethral resection for canal formation urination became possible as a result of straining. The patients who were able to urinate with straining sometimes suffered temporary stress incontinence. The degree of straining did not determine whether the patient could urinate with straining. Therefore, it was concluded that abdominal pressure should be excluded from intravesical pressure in performing several urodynamic studies on the lower urinary tract, such as pressure flow studies, and that it is important to have a sufficient canal formation in the anti-stress incontinence zone when urination with straining is expected when performing an operation on patients with urethral obstruction in the anti-stress incontinence zone.

Quasi 3D modeling of water flow and solute transport in vadose zone and groundwater

NASA Astrophysics Data System (ADS)

Yakirevich, A.; Kuznetsov, M.; Weisbrod, N.; Pachepsky, Y. A.

2013-12-01

The complexity of subsurface flow systems calls for a variety of concepts leading to the multiplicity of simplified flow models. One commonly used simplification is based on the assumption that lateral flow and transport in unsaturated zone is insignificant unless the capillary fringe is involved. In such cases the flow and transport in the unsaturated zone above groundwater level can be simulated as a 1D phenomenon, whereas through groundwater they are viewed as 2D or 3D phenomena. A new approach for a numerical scheme for 3D variably saturated flow and transport is presented. A Quasi-3D approach allows representing flow in the 'vadose zone - aquifer' system by a series of 1D Richards' equations solved in variably-saturated zone and by 3D-saturated flow equation in groundwater (modified MODFLOW code). The 1D and 3D equations are coupled at the phreatic surface in a way that aquifer replenishment is calculated using the Richards' equation, and solving for the moving water table does not require definition of the specific yield parameter. The 3D advection-dispersion equation is solved in the entire domain by the MT3D code. Using implicit finite differences approximation to couple processes in the vadose zone and groundwater provides mass conservation and increase of computational efficiency. The above model was applied to simulate the impact of irrigation on groundwater salinity in the Alto Piura aquifer (Northern Peru). Studies on changing groundwater quality in arid and semi-arid lands show that irrigation return flow is one of the major factors contributing to aquifer salinization. Existing mathematical models do not account explicitly for the solute recycling during irrigation on a daily scale. Recycling occurs throughout the unsaturated and saturated zones, as function of the solute mass extracted from pumping wells. Salt concentration in irrigation water is calculated at each time step as a function of concentration of both surface water and groundwater extracted at specific locations. Three scenarios were considered: (i) use of furrow irrigation and groundwater extraction (the present situation); (ii) increase of groundwater pumping by 50% compared to the first scenario; and (iii) transition from furrow irrigation to drip irrigation, thus decreasing irrigation volume by around 60% compared to the first scenario. Results indicate that in different irrigation areas, the simulated increase rates of total dissolved solids in groundwater vary from 3 to17 mg/L/ year, depending on hydrogeological and hydrochemical conditions, volumes of water extracted, and proportion between surface water and groundwater applied. The transition from furrow irrigation to drip irrigation can decrease the negative impact of return flow on groundwater quality; however drip irrigation causes faster simulated soil salinization compared to furrow irrigation. The quasi 3D modeling appeared to be efficient in elucidating solute recycling effects on soil and groundwater salinity.

Determining sources of water and contaminants to wells in a carbonate aquifer near Martinsburg, Blair County, Pennsylvania, by use of geochemical indicators, analysis of anthropogenic contaminants, and simulation of ground-water flow

USGS Publications Warehouse

Lindsey, Bruce D.; Koch, Michele L.

2004-01-01

Water supply for the Borough of Martinsburg, Pa., is from two well fields (Wineland and Hershberger) completed in carbonate-bedrock aquifers in the Morrison Cove Valley. Water supply is plentiful; however, waters with high concentrations of nitrate are a concern. This report describes the sources of water and contaminants to the supply wells. A review of previous investigations was used to establish the aquifer framework and estimate aquifer hydraulic properties. Aquifer framework and simulation of ground-water flow in a 25-square-mile area using the MODFLOW model helped to further constrain aquifer hydraulic properties and identify water-source areas in the zone of contribution of ground water to the well fields. Flow simulation identified potential contaminant-source areas. Data on contaminants and geochemical characteristics of ground water at the well fields were compared to the results of flow simulation. The Woodbury Anticline controls the aquifer framework near the well fields and four carbonate-bedrock formations contain the primary aquifers. Three carbonate-bedrock aquifers of Ordovician age overlie the Gatesburg aquifer of Cambrian age on the flanks of the anticline. Fracture, not conduit, permeability was determined to be the dominant water-bearing characteristic of the bedrock. The horizontal hydraulic conductivity of the Gatesburg aquifer is about 36 feet per day. The other carbonate aquifers (Nittany/Stonehenge, Bellefonte/Axemann, and Coburn through Loysburg aquifers) overlying and flanking the Gatesburg aquifer have horizontal hydraulic conductivities of about 1 foot per day. Regional directions of ground-water flow are toward the major streams with Clover Creek as the major discharge point for ground water in the east. Ground-water flow to the well fields is anisotropic with a 5:1 preferential horizontal direction along strike of the axial fold of the anticline. Thus, the zone of contribution of ground water to the well fields is elongate in a north-south direction along the anticline axis, with the majority of the flow to the well fields originating from the south. Human activity in the areal extent of the zone of contribution to the well fields was the source of contaminants. The areal extent of the zone of contribution included both urban areas in the Borough and a large amount of agricultural land. By relating results of flow simulation, natural geochemistry, and analyses of anthropogenic (human-made) contaminants, the source areas for water and contaminants were determined with more confidence than by using only flow simulation. Analysis of natural geochemistry identified water sources from both limestone and dolomite aquifers. Geochemistry results also indicated fractures, not conduits, were the dominant source of water from aquifers; however, quantitative source identification was not possible. Chemical ratios of chloride and bromide were useful to show that all samples of ground water had sources with chemical contributions from land surface. Nitrogen isotope ratio analysis indicated animal manure as the possible primary source of nitrate in most ground water. Some of the nitrate in ground water had chemical fertilizer as a source. At the Wineland well field, chemical fertilizer was likely the source of nitrate. The nitrate in water from the Hershberger well field was from a mixture of fertilizer and animal-manure sources. Human sewage was ruled out as a major source of nitrate in water from the municipal wells by results showing 1) wastewater compounds in sewage were rarely detected and 2) a mass-balance calculation indicating the small contribution of nitrogen that could be attributed to septic systems.

Analyzing the effect of cutting parameters on surface roughness and tool wear when machining nickel based hastelloy - 276

NASA Astrophysics Data System (ADS)

Khidhir, Basim A.; Mohamed, Bashir

2011-02-01

Machining parameters has an important factor on tool wear and surface finish, for that the manufacturers need to obtain optimal operating parameters with a minimum set of experiments as well as minimizing the simulations in order to reduce machining set up costs. The cutting speed is one of the most important cutting parameter to evaluate, it clearly most influences on one hand, tool life, tool stability, and cutting process quality, and on the other hand controls production flow. Due to more demanding manufacturing systems, the requirements for reliable technological information have increased. For a reliable analysis in cutting, the cutting zone (tip insert-workpiece-chip system) as the mechanics of cutting in this area are very complicated, the chip is formed in the shear plane (entrance the shear zone) and is shape in the sliding plane. The temperature contributed in the primary shear, chamfer and sticking, sliding zones are expressed as a function of unknown shear angle on the rake face and temperature modified flow stress in each zone. The experiments were carried out on a CNC lathe and surface finish and tool tip wear are measured in process. Machining experiments are conducted. Reasonable agreement is observed under turning with high depth of cut. Results of this research help to guide the design of new cutting tool materials and the studies on evaluation of machining parameters to further advance the productivity of nickel based alloy Hastelloy - 276 machining.

Assessing TCE source bioremediation by geostatistical analysis of a flux fence.

PubMed

Cai, Zuansi; Wilson, Ryan D; Lerner, David N

2012-01-01

Mass discharge across transect planes is increasingly used as a metric for performance assessment of in situ groundwater remediation systems. Mass discharge estimates using concentrations measured in multilevel transects are often made by assuming a uniform flow field, and uncertainty contributions from spatial concentration and flow field variability are often overlooked. We extend our recently developed geostatistical approach to estimate mass discharge using transect data of concentration and hydraulic conductivity, so accounting for the spatial variability of both datasets. The magnitude and uncertainty of mass discharge were quantified by conditional simulation. An important benefit of the approach is that uncertainty is quantified as an integral part of the mass discharge estimate. We use this approach for performance assessment of a bioremediation experiment of a trichloroethene (TCE) source zone. Analyses of dissolved parent and daughter compounds demonstrated that the engineered bioremediation has elevated the degradation rate of TCE, resulting in a two-thirds reduction in the TCE mass discharge from the source zone. The biologically enhanced dissolution of TCE was not significant (~5%), and was less than expected. However, the discharges of the daughter products cis-1,2, dichloroethene (cDCE) and vinyl chloride (VC) increased, probably because of the rapid transformation of TCE from the source zone to the measurement transect. This suggests that enhancing the biodegradation of cDCE and VC will be crucial to successful engineered bioremediation of TCE source zones. © 2012, The Author(s). Ground Water © 2012, National Ground Water Association.

Internal architecture, permeability structure, and hydrologic significance of contrasting fault-zone types

NASA Astrophysics Data System (ADS)

Rawling, Geoffrey C.; Goodwin, Laurel B.; Wilson, John L.

2001-01-01

The Sand Hill fault is a steeply dipping, large-displacement normal fault that cuts poorly lithified Tertiary sediments of the Albuquerque basin, New Mexico, United States. The fault zone does not contain macroscopic fractures; the basic structural element is the deformation band. The fault core is composed of foliated clay flanked by structurally and lithologically heterogeneous mixed zones, in turn flanked by damage zones. Structures present within these fault-zone architectural elements are different from those in brittle faults formed in lithified sedimentary and crystalline rocks that do contain fractures. These differences are reflected in the permeability structure of the Sand Hill fault. Equivalent permeability calculations indicate that large-displacement faults in poorly lithified sediments have little potential to act as vertical-flow conduits and have a much greater effect on horizontal flow than faults with fractures.

Simulating Heterogeneous Infiltration and Contaminant leaching Processes at Chalk River, Ontario

NASA Astrophysics Data System (ADS)

Ali, M. A.; Ireson, A. M.; Keim, D.

2015-12-01

A study is conducted at a waste management area in Chalk River, Ontario to characterize flow and contaminant transport with the aim of contributing to improved hydrogeological risk assessment in the context of waste management. Field monitoring has been performed to gain insights into the unsaturated zone characteristics, moisture dynamics, and contaminant transport rates. The objective is to provide quantitative estimates of surface fluxes (quantification of infiltration and evaporation) and investigations of unsaturated zone processes controlling water infiltration and spatial variability in head distributions and flow rates. One particular issue is to examine the effectiveness of the clayey soil cap installed to prevent infiltration of water into the waste repository and the top sand soil cover above the clayey layer to divert the infiltrated water laterally. The spatial variability in the unsaturated zone properties and associated effects on water flow and contaminant transport observed at the site, have led to a concerted effort to develop improved model of flow and transport based on stochastic concepts. Results obtained through the unsaturated zone model investigations are combined with the hydrogeological and geochemical components and develop predictive tools to assess the long term fate of the contaminants at the waste management site.

Evaluating tsunami hazards from debris flows

USGS Publications Warehouse

Watts, P.; Walder, J.S.; ,

2003-01-01

Debris flows that enter water bodies may have significant kinetic energy, some of which is transferred to water motion or waves that can impact shorelines and structures. The associated hazards depend on the location of the affected area relative to the point at which the debris flow enters the water. Three distinct regions (splash zone, near field, and far field) may be identified. Experiments demonstrate that characteristics of the near field water wave, which is the only coherent wave to emerge from the splash zone, depend primarily on debris flow volume, debris flow submerged time of motion, and water depth at the point where debris flow motion stops. Near field wave characteristics commonly may be used as & proxy source for computational tsunami propagation. This result is used to assess hazards associated with potential debris flows entering a reservoir in the northwestern USA. ?? 2003 Millpress,.

Programming a hillslope water movement model on the MPP

NASA Technical Reports Server (NTRS)

Devaney, J. E.; Irving, A. R.; Camillo, P. J.; Gurney, R. J.

1987-01-01

A physically based numerical model was developed of heat and moisture flow within a hillslope on a parallel architecture computer, as a precursor to a model of a complete catchment. Moisture flow within a catchment includes evaporation, overland flow, flow in unsaturated soil, and flow in saturated soil. Because of the empirical evidence that moisture flow in unsaturated soil is mainly in the vertical direction, flow in the unsaturated zone can be modeled as a series of one dimensional columns. This initial version of the hillslope model includes evaporation and a single column of one dimensional unsaturated zone flow. This case has already been solved on an IBM 3081 computer and is now being applied to the massively parallel processor architecture so as to make the extension to the one dimensional case easier and to check the problems and benefits of using a parallel architecture machine.

Embedded function methods for compressible high speed turbulent flow

NASA Technical Reports Server (NTRS)

Walker, J. D. A.

1989-01-01

Fundamental issues relating to compressible turbulent flow are addressed. The focus has been on developing methods and testing concepts for attached flows rather than trying to force a conventional law of the wall into a zone of backflow. Although the dynamics of the near-wall flow in an attached turbulent boundary layer are relatively well documented, the dynamical features of a zone of reversed turbulent flow are not, nor are they well understood. Incompressibility introduces effects and issues that have been dealt with only marginally in the literature, therefore, the present work has been focussed on attached high-speed flows. The wall function method has been extended up through the supersonic to hypersonic speeds. Algorithms have been successfully introduced into the code that calculates the flow all the way to the wall, and testing is being carried out for progressively more complex flow situations.

Internal structure, fault rocks, and inferences regarding deformation, fluid flow, and mineralization in the seismogenic Stillwater normal fault, Dixie Valley, Nevada

USGS Publications Warehouse

Caine, Jonathan S.; Bruhn, R.L.; Forster, C.B.

2010-01-01

Outcrop mapping and fault-rock characterization of the Stillwater normal fault zone in Dixie Valley, Nevada are used to document and interpret ancient hydrothermal fluid flow and its possible relationship to seismic deformation. The fault zone is composed of distinct structural and hydrogeological components. Previous work on the fault rocks is extended to the map scale where a distinctive fault core shows a spectrum of different fault-related breccias. These include predominantly clast-supported breccias with angular clasts that are cut by zones containing breccias with rounded clasts that are also clast supported. These are further cut by breccias that are predominantly matrix supported with angular and rounded clasts. The fault-core breccias are surrounded by a heterogeneously fractured damage zone. Breccias are bounded between major, silicified slip surfaces, forming large pod-like structures, systematically oriented with long axes parallel to slip. Matrix-supported breccias have multiply brecciated, angular and rounded clasts revealing episodic deformation and fluid flow. These breccias have a quartz-rich matrix with microcrystalline anhedral, equant, and pervasively conformable mosaic texture. The breccia pods are interpreted to have formed by decompression boiling and rapid precipitation of hydrothermal fluids whose flow was induced by coseismic, hybrid dilatant-shear deformation and hydraulic connection to a geothermal reservoir. The addition of hydrothermal silica cement localized in the core at the map scale causes fault-zone widening, local sealing, and mechanical heterogeneities that impact the evolution of the fault zone throughout the seismic cycle. ?? 2010.

Vadose zone process that control landslide initiation and debris flow propagation

NASA Astrophysics Data System (ADS)

Sidle, Roy C.

2015-04-01

Advances in the areas of geotechnical engineering, hydrology, mineralogy, geomorphology, geology, and biology have individually advanced our understanding of factors affecting slope stability; however, the interactions among these processes and attributes as they affect the initiation and propagation of landslides and debris flows are not well understood. Here the importance of interactive vadose zone processes is emphasized related to the mechanisms, initiation, mode, and timing of rainfall-initiated landslides that are triggered by positive pore water accretion, loss of soil suction and increase in overburden weight, and long-term cumulative rain water infiltration. Both large- and small-scale preferential flow pathways can both contribute to and mitigate instability, by respectively concentrating and dispersing subsurface flow. These mechanisms are influenced by soil structure, lithology, landforms, and biota. Conditions conducive to landslide initiation by infiltration versus exfiltration are discussed relative to bedrock structure and joints. The effects of rhizosphere processes on slope stability are examined, including root reinforcement of soil mantles, evapotranspiration, and how root structures affect preferential flow paths. At a larger scale, the nexus between hillslope landslides and in-channel debris flows is examined with emphasis on understanding the timing of debris flows relative to chronic and episodic infilling processes, as well as the episodic nature of large rainfall and related stormflow generation in headwater streams. The hydrogeomorphic processes and conditions that determine whether or not landslides immediately mobilize into debris flows is important for predicting the timing and extent of devastating debris flow runout in steep terrain. Given the spatial footprint of individual landslides, it is necessary to assess vadose zone processes at appropriate scales to ascertain impacts on mass wasting phenomena. Articulating the appropriate level of detail of small-scale vadose zone processes into landslide models is a particular challenge. As such, understanding flow pathways in regoliths susceptible to mass movement is critical, including distinguishing between conditions conducive to vertical recharge of water through relatively homogeneous soil mantles and conditions where preferential flow dominates - either by rapid infiltration and lateral flow through interconnected preferential flow networks or via exfiltration through bedrock fractures. These different hydrologic scenarios have major implications for the occurrence, timing, and mode of slope failures.

The anatomy of a 'suture zone' in Amazonian butterflies: a coalescent-based test for vicariant geographic divergence and speciation.

PubMed

Dasmahapatra, Kanchon K; Lamas, Gerardo; Simpson, Fraser; Mallet, James

2010-10-01

Attempts by biogeographers to understand biotic diversification in the Amazon have often employed contemporary species distribution patterns to support particular theories, such as Pleistocene rainforest refugia, rather than to test among alternative hypotheses. Suture zones, narrow regions where multiple contact zones and hybrid zones between taxa cluster, have been seen as evidence for past expansion of whole biotas that have undergone allopatric divergence in vicariant refuges. We used coalescent analysis of mutilocus sequence data to examine population split times in 22 pairs of geminate taxa in ithomiine and heliconiine butterflies. We test a hypothesis of simultaneous divergence across a suture zone in NE Peru. Our results reveal a scattered time course of diversification in this suture zone, rather than a tight cluster of split times. Additionally, we find rapid diversification within some lineages such as Melinaea contrasting with older divergence within lineages such as the Oleriina (Hyposcada and Oleria). These results strongly reject simple vicariance as a cause of the suture zone. At the same time, observed lineage effects are incompatible with a series of geographically coincident vicariant events which should affect all lineages similarly. Our results suggest that Pleistocene climatic forcing cannot readily explain this Peruvian suture zone. Lineage-specific biological traits, such as characteristic distances of gene flow or varying rates of parapatric divergence, may be of greater importance. © 2010 Blackwell Publishing Ltd.

Preferential Flow and Transport of Cryptosporidium Parvum Oocysts Through Vadose Zone: Experiments and Modeling

NASA Astrophysics Data System (ADS)

Darnault, C. J.; Darnault, C. J.; Garnier, P.; Kim, Y.; Oveson, K.; Jenkins, M.; Ghiorse, W.; Baveye, P.; Parlange, J.; Steenhuis, T.

2001-12-01

Oocysts of the protozoan Cryptosporidium parvum, when they contaminate drinking water supplies, can cause outbreaks of Cryptosporidiosis, a common waterborne disease. Of the different pathways by which oocysts can wind up in drinking water, one has received very little attention to date; because soils are often considered to be perfect filters, the transport of oocysts through the subsoil to groundwater by preferential flow is generally ignored. To evaluate its significance, three set of laboratory experiments investigated transport of oocysts through vadose zone. Experiment set I was carried out in a vertical 50 cm-long column filled with silica sand, under conditions known to foster fingered flow. Experiment set II investigates the effect of gas-water interfaces by modifying the hydrodynamical conditions in the sand columns with water-repellent sand barriers. Experiment III involved undisturbed soil columns subjected to macropores flow. The sand and soil columns were subjected to artificial rainfall and were allowed to reach steady-state. At that point, feces of contaminated calves were applied at the surface, along with a known amount of KCl to serve as tracer, and rainfall was continued at the same rate. The breakthrough of oocysts and Cl-, monitored in the effluent, demonstrate the importance of preferential flow - fingered flow and macropore flow - on the transport of oocysts through vadose zone. Peak oocyst concentrations were not appreciably delayed, compared to Cl-, and in some cases, occurred even before the Cl- peak. However, the numbers of oocysts present in the effluents were still orders of magnitude higher than the 5 to 10 oocysts per liter that are considerable sufficient to cause cryptosporidiosis in healthy adults. The transport of oocysts was simulated based on a partitioning the soil profile in both a distribution zone and a preferential zone, In particular, the model simulates accurately the markedly asymmetric breakthrough patterns, and the long exponential tailing. The spatial distribution of oocysts suggest a close relationship between oocyst retention and the extent of gas-water interfaces; sharp increases in oocyst numbers are consistently observed in regions of the sand where the water content has steep gradients, and therefore where one expects capillary meniscii to have maximal extent. These observations imply that oocyst transport in the vadose zone is likely to be very limited in the absence of preferential flow. However, experimental results suggest that the transport of oocysts in the subsurface via preferential flow may create a significant risk of groundwater contamination in some situations.

Spatial zonation limits magnesite dissolution in porous media

NASA Astrophysics Data System (ADS)

Li, Li; Salehikhoo, Fatemeh; Brantley, Susan L.; Heidari, Peyman

2014-02-01

We investigate how mineral spatial distribution in porous media affects their dissolution rates. Specifically, we measure the dissolution rate of magnesite interspersed in different patterns in packed columns of quartz sand where the magnesite concentration (v/v) was held constant. The largest difference was observed between a “Mixed column” containing uniformly distributed magnesite and a “One-zone column” containing magnesite packed into one cylindrical center zone aligned parallel to the main flow of acidic inlet fluid (flow-parallel One-zone column). The columns were flushed with acid water at a pH of 4.0 at flow velocities of 3.6 or 0.36 m/d. Breakthrough data show that the rate of magnesite dissolution is 1.6-2 times slower in the One-zone column compared to the Mixed column. This extent of rate limitation is much larger than what was observed in our previous work (14%) for a similar One-zone column where the magnesite was packed in a layer aligned perpendicular to flow (flow-transverse One-zone column). Two-dimensional reactive transport modeling with CrunchFlow revealed that ion activity product (IAP) and local dissolution rates at the grid block scale (0.1 cm) vary by orders of magnitude. Much of the central magnesite zone in the One-zone flow-parallel column is characterized by close or equal to equilibrium conditions with IAP/Keq > 0.1. Two important surface areas are defined to understand the observed rates: the effective surface area (Ae) reflects the magnesite that effectively dissolves under far from equilibrium conditions (IAP/Keq < 0.1), while the interface surface area (AI) reflects the effective magnesite surface that lies along the quartz-magnesite interface. Modeling results reveal that the transverse dispersivity at the interface of the quartz and magnesite zones controls mass transport and therefore the values of Ae and AI. Under the conditions examined in this work, the value of Ae varies from 2% to 67% of the total magnesite BET surface area. Column-scale bulk rates R,B (in units of mol/s) vary linearly with Ae and AI. Using Ae to normalize rates, we calculate a rate constant (10-9.56 mol/m2/s) that is very close to the value of 10-10.0 mol/m2/s under well-mixed conditions at the grid block scale. This implies that the laboratory-field rate discrepancy can potentially be caused by differences in the effective surface area. If we know the effective surface area of dissolution, we will be able to use the rate constant measured in laboratory systems to calculate field rates for some systems. In this work, approximately 60-70% of the Ae is at the magnesite-quartz interface. This implies that in some field systems where the detailed information that we have for our columns is not available, the effective mineral surface area may be approximated by the area of grains residing at the interface of reactive mineral zones. Although it has long been known that spatial heterogeneities play a significant role in determining physical processes such as flow and solute transport, our data are the first that systematically and experimentally quantifies the importance of mineral spatial distribution (chemical heterogeneity) on dissolution.

Ground-water hydrology of the Chad Basin in Bornu and Dikwa Emirates, northeastern Nigeria, with special emphasis on the flow life of the artesian system

USGS Publications Warehouse

Miller, Raymond E.; Johnston, R.H.; Olowu, J.A.I.; Uzoma, J.U.

1968-01-01

Bornu and Dikwa Emirates lie in the Nigerian sector of the Chad Basin, a vast region of interior drainage encompassing about 600,000 square miles of north-central Africa. The report area includes about 25,000 square miles of the basin that lie in Nigeria. Most of the area is a featureless plain that slopes gently northeast and east from the uplands of central Nigeria towards Lake Chad. On its eastern side the lake has one surface outlet which overflows only during exceptionally high stages of the lake. This outlet spills into the channel of Bahr al Ghazal, which in turn drains into the Bod616 depression. Because the lake is shallow, the shoreline fluctuates markedly with high and low stages corresponding to the wet and dry seasons. The semiarid climate of Bornu and Dikwa Emirates is characterized by a long dry season and a short wet season that correspond to seasonal winds. Annual rainfall ranges from 15 inches in the northern part of the area to 32 inches in the southern. The Chad Basin in Dikwa and Bornu Emirates is underlain by interbedded sand and clay, collectively termed the Chad Formation. These alluvial and lactustrine sediments were deposited in or near Lake Chad whet it occupied a much greater area during Pliocene and Pleistocene time. The Chad Formation has a very slight primary dip in the direction of Lake Chad and conforms to the gentle slope of land surface. The known thickness of the formation ranges from a few feet where it overlies bedrock on the periphery of the basin to at least 1,800 feet at Maiduguri; however, its total thickness probably exceeds 2,000 feet in the central part of the basin. Three water-bearing units termed upper, middle, and lower zones occur within the Chad Formation. The upper zone yields water to numerous dug wells throughout the rural areas and also is .the major source of the Maiduguri municipal water .supply. The middle zone yields water from flowing artesian boreholes that have heads ranging from a few feet to 70 feet above land surface throughout a 13,000 square-mile area of the basin in Nigeria. The lower zone also yields water from flowing boreholes ; however, its areal extent has not been proved beyond the environs of Maiduguri. The present investigation is concerned primarily with the middle zone, which is the source of water for some 190 flowing boreholes used as little-watering points in the Nigerian sector of the Chad Basin. The thickness of loads of waterbearing sand in the middle zone ranges from less than 1 foot to 200 feet, and the artesian head ranges from land surface at Maiduguri to 70 feet above land surface at Lake Chad. The depth to the top of the middle zone in the area of flowing boreholes ranges from 500 to 1,250 feet below land surface. The waterbearing properties of the middle zone differ greatly from place to place. Also, the yields of individual flowing boreholes generally range from 50 to 20,000 imperial gallons per hour (gph). On the basis of water availability, the middle zone can be divided as follows : Areas of high-, moderate-, and low-yield artesian aquifer ; areas of low- and moderate-yield subartesian aquifer ; and an area where the yields from boreholes are insignificant or the aquifer is missing. Recommended maximum rates of long-term withdrawal from individual boreholes for the three artesian areas range from 100 to 5,000 gph with boreholes spaced 5 to 10 miles apart. By limiting flows to the recommended maximum rates, the boreholes should continue to flow for at least 30 years. The present average use per borehole (265 gph in 1965) is considerably less than the recommended maximum rates. Recharge to the upper zone occurs in significant but as yet unmeasured quantities, mostly in the vicinity of the major streams. Apparently, however, no significant amount of recharge reaches the middle zone from the Upper zone. Although the middle zone is, in effect, being 'mined' by existing flowing wells, the present (1965) rate of withdrawal i

Flame Structure and Emissions of Strongly-Pulsed Turbulent Diffusion Flames with Swirl

NASA Astrophysics Data System (ADS)

Liao, Ying-Hao

This work studies the turbulent flame structure, the reaction-zone structure and the exhaust emissions of strongly-pulsed, non-premixed flames with co-flow swirl. The fuel injection is controlled by strongly-pulsing the fuel flow by a fast-response solenoid valve such that the fuel flow is completely shut off between pulses. This control strategy allows the fuel injection to be controlled over a wide range of operating conditions, allowing the flame structure to range from isolated fully-modulated puffs to interacting puffs to steady flames. The swirl level is controlled by varying the ratio of the volumetric flow rate of the tangential air to that of the axial air. For strongly-pulsed flames, both with and without swirl, the flame geometry is strongly impacted by the injection time. Flames appear to exhibit compact, puff-like structures for short injection times, while elongated flames, similar in behaviors to steady flames, occur for long injection times. The flames with swirl are found to be shorter for the same fuel injection conditions. The separation/interaction level between flame puffs in these flames is essentially governed by the jet-off time. The separation between flame puffs decreases as swirl is imposed, consistent with the decrease in flame puff celerity due to swirl. The decreased flame length and flame puff celerity are consistent with an increased rate of air entrainment due to swirl. The highest levels of CO emissions are generally found for compact, isolated flame puffs, consistent with the rapid quenching due to rapid dilution with excess air. The imposition of swirl generally results in a decrease in CO levels, suggesting more rapid and complete fuel/air mixing by imposing swirl in the co-flow stream. The levels of NO emissions for most cases are generally below the steady-flame value. The NO levels become comparable to the steady-flame value for sufficiently short jet-off time. The swirled co-flow air can, in some cases, increase the NO emissions. The elevated NO emissions are due to a longer combustion residence time due to the flow recirculation within the swirl-induced recirculation zone. The reaction zone structure, based on OH planar laser-induced fluorescence (PLIF) is broadly consistent with the observation of luminous flame structure for these types of flames. In many cases, the reaction zone exhibits discontinuities at the instantaneous flame tip in the early period of fuel injection. These discontinuities in the reaction zone likely result from the non-ignition of injected fuel, due to a relatively slower reaction rate in comparison with the mixing rate. The discontinuity in the OH zone is generally seen to diminish with increased swirl level. Statistics generated from the OH PLIF signals show that the reaction zone area generally increases with increased swirl level, consistent with a broader and more convoluted OH-zone structure for flames with swirl. The reaction zone area for swirled flames generally exhibits a higher degree of fluctuation, suggesting a relatively stronger impact of flow turbulence on the flame structure for flames with swirl.

Experiments on Suppression of Thermocapillary Oscillations in Sodium Nitrate Floating Half-Zones by High-frequency End-wall Vibrations

NASA Technical Reports Server (NTRS)

Anilkumar, A.; Grugel, R. N.; Bhowmick, J.; Wang, T.

2004-01-01

Experiments to suppress thermocapillary oscillations using high-frequency vibrations were carried out in sodium nitrate floating half-zones. Such a half-zone is formed by melting one end of a vertically held sodium nitrate crystal rod in contact with a hot surface at the top. Thermocapillary convection occurs in the melt because of the temperature gradient at the free surface of the melt. In the experiments, when thermocapillary oscillations occurred, the bottom end of the crystal rod was vibrated at a high frequency to generate a streaming flow in a direction opposite to that of the thermocapillary convection. It is observed that, by generating a sufficiently strong streaming flow, the thermocapillary flow can be offset enough such that the associated thermocapillary oscillations can be quenched.

A simple landslide susceptibility analysis for hazard and risk assessment in developing countries

NASA Astrophysics Data System (ADS)

Guinau, M.; Vilaplana, J. M.

2003-04-01

In recent years, a number of techniques and methodologies have been developed for mitigating natural disasters. The complexity of these methodologies and the scarcity of material and data series justify the need for simple methodologies to obtain the necessary information for minimising the effects of catastrophic natural phenomena. The work with polygonal maps using a GIS allowed us to develop a simple methodology, which was developed in an area of 473 Km2 in the Departamento de Chinandega (NW Nicaragua). This area was severely affected by a large number of landslides (mainly debris flows), triggered by the Hurricane Mitch rainfalls in October 1998. With the aid of aerial photography interpretation at 1:40.000 scale, amplified to 1:20.000, and detailed field work, a landslide map at 1:10.000 scale was constructed. The failure zones of landslides were digitized in order to obtain a failure zone digital map. A terrain unit digital map, in which a series of physical-environmental terrain factors are represented, was also used. Dividing the studied area into two zones (A and B) with homogeneous physical and environmental characteristics, allows us to develop the proposed methodology and to validate it. In zone A, the failure zone digital map is superimposed onto the terrain unit digital map to establish the relationship between the different terrain factors and the failure zones. The numerical expression of this relationship enables us to classify the terrain by its landslide susceptibility. In zone B, this numerical relationship was employed to obtain a landslide susceptibility map, obviating the need for a failure zone map. The validity of the methodology can be tested in this area by using the degree of superposition of the susceptibility map and the failure zone map. The implementation of the methodology in tropical countries with physical and environmental characteristics similar to those of the study area allows us to carry out a landslide susceptibility analysis in areas where landslide records do not exist. This analysis is essential to landslide hazard and risk assessment, which is necessary to determine the actions for mitigating landslide effects, e.g. land planning, emergency aid actions, etc.

Effects of the Karacadag Volcanic Complex on the thermal structure and geothermal potential of southeast Anatolia

NASA Astrophysics Data System (ADS)

Bilim, Funda; Aydemir, Attila; Kosaroglu, Sinan; Bektas, Ozcan

2018-06-01

The Karacadag Volcanic Complex (KVC) is the largest volcanic unit in SE Turkey. It is also defined as a shield volcano on the northernmost part of the Arabian Plate. The main goal of this study is to investigate the geothermal potential of this region associated with the magnetic signature of this volcanic complex and surrounding area. Besides this primary objective, the possibility of there being volcanic intrusion into the buried fault zones under the volcanic cover are also investigated to determine the interrelations between the active tectonics and heat flow in the area. A spectral analysis method is applied to the magnetic anomalies of the volcanic rocks to identify the Curie point depth (CPD) and geothermal gradient, as well as to estimate heat flow and radiogenic heat production of radioactive minerals in the complex. A tilt angle map is also presented, in correlation with instrumentally recorded earthquake magnitudes, to indicate tectonic trends that are consistent with the maps of the thermal parameters in this study. In contrast with expectations for the KVC area, the region around Akcakale and Suruc Grabens is the most prolific zone for geothermal potential, despite them not showing strong magnetic anomalies. Curie point depths are shallow, down to 18 km, around the Akcakale Graben, and deeper, down to 22 km, around the Bitlis-Zagros Suture Zone where the geothermal gradients increase from 26 to 32 °C km-1 through the graben area. Heat flows in this zone are in the range from 75 to 90 mW m-2 depending on the thermal conductivity coefficient (2.3, 2.5, 2.7, and 3.0 W m-1 K-1) used. Radiogenic heat production values also indicate slightly changing spectra in the range 0.19 to 0.25 μW m-3). None of these parameters are focused around Mt. Karacadag. However, the earthquake epicenters (generally M ≤ 4) are aligned with the boundary faults of the Akcakale Graben where the CPD, geothermal gradient, and heat flow maps indicate relatively high potential. We thus suggest that this graben area would be good for future geothermal exploration. On the contrary, considering the low geothermal gradient and heat flow values, Mt. Karacadag can be accepted as being an extinct volcano, despite its apparent, high, magnetic anomalies.

Calculation of recirculating flow behind flame-holders

NASA Astrophysics Data System (ADS)

Zeng, Q.; Sheng, Y.; Zhou, Q.

1985-10-01

Adoptability of standard K-epsilon turbulence model for numerical calculation of recirculating flow is discussed. Many computations of recirculating flows behind bluff-bodies used as flame-holders in afterburner of aeroengine have been completed. Blocking-off method to treat the incline walls of the flame-holder gives good results. In isothermal recirculating flows the flame-holder wall is assumed to be isolated. Therefore, it is possible to remove the inactive zone from the calculation domain in programming to save computer time. The computation for a V-shaped flame-holder exhibits an interesting phenomenon that the recirculation zone extends to the cavity of the flame-holder.

Complex cytogeographical patterns reveal a dynamic tetraploid–octoploid contact zone

PubMed Central

Castro, Mariana; Castro, Sílvia; Figueiredo, Albano; Husband, Brian; Loureiro, João

2018-01-01

Abstract The distribution of cytotypes in mixed-ploidy species is crucial for evaluating ecological processes involved in the establishment and evolution of polyploid taxa. Here, we use flow cytometry and chromosome counts to explore cytotype diversity and distributions within a tetraploid–octoploid contact zone. We then use niche modelling and ploidy seed screening to assess the roles of niche differentiation among cytotypes and reproductive interactions, respectively, in promoting cytotype coexistence. Two cytotypes, tetraploids and octoploids, were dominant within the contact zone. They were most often distributed parapatrically or allopatrically, resulting in high geographic isolation. Still, 16.7 % of localities comprised two or more cytotypes, including the intermediate hexaploid cytotype. Tetraploids and octoploids had high environmental niche overlap and associated with similar climatic environments, suggesting they have similar ecological requirements. Given the geographical separation and habitat similarity among cytotypes, mixed-ploidy populations may be transitional and subject to the forces of minority cytotype exclusion which lead to pure-ploidy populations. However, seed ploidy analysis suggests that strong reproductive barriers may enforce assortative mating which favours stable cytotype coexistence. High cytogenetic diversity detected in the field suggests that unreduced gamete formation and hybridization events seem frequent in the studied polyploid complex and might be involved with the recurrent polyploid formation, governing, as well, the gene flow between cytogenetic entities. PMID:29593853

Complex cytogeographical patterns reveal a dynamic tetraploid-octoploid contact zone.

PubMed

Castro, Mariana; Castro, Sílvia; Figueiredo, Albano; Husband, Brian; Loureiro, João

2018-03-01

The distribution of cytotypes in mixed-ploidy species is crucial for evaluating ecological processes involved in the establishment and evolution of polyploid taxa. Here, we use flow cytometry and chromosome counts to explore cytotype diversity and distributions within a tetraploid-octoploid contact zone. We then use niche modelling and ploidy seed screening to assess the roles of niche differentiation among cytotypes and reproductive interactions, respectively, in promoting cytotype coexistence. Two cytotypes, tetraploids and octoploids, were dominant within the contact zone. They were most often distributed parapatrically or allopatrically, resulting in high geographic isolation. Still, 16.7 % of localities comprised two or more cytotypes, including the intermediate hexaploid cytotype. Tetraploids and octoploids had high environmental niche overlap and associated with similar climatic environments, suggesting they have similar ecological requirements. Given the geographical separation and habitat similarity among cytotypes, mixed-ploidy populations may be transitional and subject to the forces of minority cytotype exclusion which lead to pure-ploidy populations. However, seed ploidy analysis suggests that strong reproductive barriers may enforce assortative mating which favours stable cytotype coexistence. High cytogenetic diversity detected in the field suggests that unreduced gamete formation and hybridization events seem frequent in the studied polyploid complex and might be involved with the recurrent polyploid formation, governing, as well, the gene flow between cytogenetic entities.

The role of the hydrological cycle on the distribution patterns of fish assemblages in an Andean stream.

PubMed

Ríos-Pulgarín, M I; Barletta, M; Mancera-Rodríguez, N J

2016-07-01

The seasonal and interannual changes of the fish assemblage in the main channel and littoral zone of the Guarinó River, a torrential system located in the Colombian Andean foothills, were examined in relation to the physical and chemical environmental changes associated with the hydrological cycle and the El Niño-La Niña-Southern Oscillation (ENSO) between 2007 and 2010. Four samplings per year (in dry season and high water) were performed. Environmental variables (temperature, pH, conductivity, turbidity, oxygen, total nitrogen, orthophosphate, depth and flow rate) were contrasted with ANOVAs and a discriminant analysis to establish temporal patterns. Biological descriptors (richness, density and biomass) were contrasted with ANCOVAs. The temporal patterns of the taxonomic and functional composition and the density of the fish assemblages were examined with respect to environmental variables through canonical discriminant analysis per habitat. Interannual differences were significant with regard to density and richness for the main channel habitat; while in the littoral zone, the differences were significant between both the year and seasons. Discriminant analysis showed variations in species composition and relative abundance between the main channel and the littoral zone under contrasting hydrological conditions of El Niño-La Niña. High flows from 2008 to 2009 (La Niña) favoured resident species (e.g. Creagrutus magdalenae) and small benthic Siluriformes (e.g. Chaetostoma spp.), but was limited to migratory species (e.g. Prochilodus magdalenae). From 2009 to 2010 (El Niño), the most common species were reduced and rare species increased. River flow, temperature and oxygen were the variables that had the largest influences on the seasonal and interannual differences in the fish assemblage structure of the Guarinó River. The results suggested that the presence and abundance of species and functional groups in different habitats were regulated by stochastic conditions, such as droughts, floods and drag events associated with the Southern Oscillation phenomenon (ENSO), acting as a hydrological disturbance on the habitats and generating different responses according to the adaptive characteristics of the species. © 2015 The Fisheries Society of the British Isles.

Reconciling Environmental and Flood Control Goals on an Arid-Zone River: Case Study of the Limitrophe Region of the Lower Colorado River in the United States and Mexico

NASA Astrophysics Data System (ADS)

Glenn, Edward P.; Hucklebridge, Kate; Hinojosa-Huerta, Osvel; Nagler, Pamela L.; Pitt, Jennifer

2008-03-01

Arid zone rivers have highly variable flow rates, and flood control projects are needed to protect adjacent property from flood damage. On the other hand, riparian corridors provide important wildlife habitat, especially for birds, and riparian vegetation is adapted to the natural variability in flows on these rivers. While environmental and flood control goals might appear to be at odds, we show that both goals can be accommodated in the Limitrophe Region (the shared border between the United States and Mexico) on the Lower Colorado River. In 1999, the International Boundary and Water Commission proposed a routine maintenance project to clear vegetation and create a pilot channel within the Limitrophe Region to improve flow capacity and delineate the border. In 2000, however, Minute 306 to the international water treaty was adopted, which calls for consideration of environmental effects of IBWC actions. We conducted vegetation and bird surveys within the Limitrophe and found that this river segment is unusually rich in native cottonwood and willow trees, marsh habitat, and resident and migratory birds compared to flow-regulated segments of river. A flood-frequency analysis showed that the existing levee system can easily contain a 100 year flood even if vegetation is not removed, and the existing braided channel system has greater carrying capacity than the proposed pilot channel.

Harnessing electrical forces for separation. Capillary zone electrophoresis, isoelectric focusing, field-flow fractionation, split-flow thin-cell continuous-separation and other techniques.

PubMed

Giddings, J C

1989-10-20

A simple analysis, first presented twenty years ago, showed that the effectiveness of a field-driven separation like electrophoresis, as expressed by the maximum number of theoretical plates (N), is given by the dimensionless ratio of two energies N = -delta mu ext/2RT in which -delta mu ext is the electrical potential energy drop of a charged species and RT is the thermal energy (R is the gas constant and T is the absolute temperature). Quantity -delta mu ext is the product of the force F acting on the species and the path length X of separation. The exceptional power of electrophoresis, for which often N approximately 10(6), can be traced directly to the enormous magnitude of the electrical force F. This paper explores the fundamentals underlying several different means for utilizing these powerful electrical forces for separation, including capillary zone electrophoresis, gel electrophoresis, isoelectric focusing, electrical field-flow fractionation and split-flow thin continuous separation cells. Remarkably, the above equation and its relatives are found to describe the approximate performance of all these diverse electrically driven systems. Factors affecting both the resolving power and separation speed of the systems are addressed; from these considerations some broad optimization criteria emerge. The capabilities of the different methods are compared using numerical examples.

Reconciling environmental and flood control goals on an arid-zone river: case study of the limitrophe region of the lower colorado river in the United States and Mexico.

PubMed

Glenn, Edward P; Hucklebridge, Kate; Hinojosa-Huerta, Osvel; Nagler, Pamela L; Pitt, Jennifer

2008-03-01

Arid zone rivers have highly variable flow rates, and flood control projects are needed to protect adjacent property from flood damage. On the other hand, riparian corridors provide important wildlife habitat, especially for birds, and riparian vegetation is adapted to the natural variability in flows on these rivers. While environmental and flood control goals might appear to be at odds, we show that both goals can be accommodated in the Limitrophe Region (the shared border between the United States and Mexico) on the Lower Colorado River. In 1999, the International Boundary and Water Commission proposed a routine maintenance project to clear vegetation and create a pilot channel within the Limitrophe Region to improve flow capacity and delineate the border. In 2000, however, Minute 306 to the international water treaty was adopted, which calls for consideration of environmental effects of IBWC actions. We conducted vegetation and bird surveys within the Limitrophe and found that this river segment is unusually rich in native cottonwood and willow trees, marsh habitat, and resident and migratory birds compared to flow-regulated segments of river. A flood-frequency analysis showed that the existing levee system can easily contain a 100 year flood even if vegetation is not removed, and the existing braided channel system has greater carrying capacity than the proposed pilot channel.

The morphology and evolution of the Stromboli 2002-2003 lava flow field--An example of a basaltic flow field emplaced on a steep slope

USGS Publications Warehouse

Lodato, Luigi; Harris, A.; Spampinato, L.; Calvari, Sonia; Dehn, J.; Patrick, M.

2007-01-01

The use of a hand-held thermal camera during the 2002–2003 Stromboli effusive eruption proved essential in tracking the development of flow field structures and in measuring related eruption parameters, such as the number of active vents and flow lengths. The steep underlying slope on which the flow field was emplaced resulted in a characteristic flow field morphology. This comprised a proximal shield, where flow stacking and inflation caused piling up of lava on the relatively flat ground of the vent zone, that fed a medial–distal lava flow field. This zone was characterized by the formation of lava tubes and tumuli forming a complex network of tumuli and flows linked by tubes. Most of the flow field was emplaced on extremely steep slopes and this had two effects. It caused flows to slide, as well as flow, and flow fronts to fail frequently, persistent flow front crumbling resulted in the production of an extensive debris field. Channel-fed flows were also characterized by development of excavated debris levees in this zone (Calvari et al. 2005). Collapse of lava flow fronts and inflation of the upper proximal lava shield made volume calculation very difficult. Comparison of the final field volume with that expecta by integrating the lava effusion rates through time suggests a loss of ~70% erupted lava by flow front crumbling and accumulation as debris flows below sea level. Derived relationships between effusion rate, flow length, and number of active vents showed systematic and correlated variations with time where spreading of volume between numerous flows caused an otherwise good correlation between effusion rate, flow length to break down. Observations collected during this eruption are useful in helping to understand lava flow processes on steep slopes, as well as in interpreting old lava–debris sequences found in other steep-sided volcanoes subject to effusive activity.

Navier-Stokes Aerodynamic Simulation of the V-22 Osprey on the Intel Paragon MPP

NASA Technical Reports Server (NTRS)

Vadyak, Joseph; Shrewsbury, George E.; Narramore, Jim C.; Montry, Gary; Holst, Terry; Kwak, Dochan (Technical Monitor)

1995-01-01

The paper will describe the Development of a general three-dimensional multiple grid zone Navier-Stokes flowfield simulation program (ENS3D-MPP) designed for efficient execution on the Intel Paragon Massively Parallel Processor (MPP) supercomputer, and the subsequent application of this method to the prediction of the viscous flowfield about the V-22 Osprey tiltrotor vehicle. The flowfield simulation code solves the thin Layer or full Navier-Stoke's equation - for viscous flow modeling, or the Euler equations for inviscid flow modeling on a structured multi-zone mesh. In the present paper only viscous simulations will be shown. The governing difference equations are solved using a time marching implicit approximate factorization method with either TVD upwind or central differencing used for the convective terms and central differencing used for the viscous diffusion terms. Steady state or Lime accurate solutions can be calculated. The present paper will focus on steady state applications, although time accurate solution analysis is the ultimate goal of this effort. Laminar viscosity is calculated using Sutherland's law and the Baldwin-Lomax two layer algebraic turbulence model is used to compute the eddy viscosity. The Simulation method uses an arbitrary block, curvilinear grid topology. An automatic grid adaption scheme is incorporated which concentrates grid points in high density gradient regions. A variety of user-specified boundary conditions are available. This paper will present the application of the scalable and superscalable versions to the steady state viscous flow analysis of the V-22 Osprey using a multiple zone global mesh. The mesh consists of a series of sheared cartesian grid blocks with polar grids embedded within to better simulate the wing tip mounted nacelle. MPP solutions will be shown in comparison to equivalent Cray C-90 results and also in comparison to experimental data. Discussions on meshing considerations, wall clock execution time, load balancing, and scalability will be provided.