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Sample records for flow field study

  1. Ex-situ experimental studies on serpentine flow field design for redox flow battery systems

    NASA Astrophysics Data System (ADS)

    Jyothi Latha, T.; Jayanti, S.

    2014-02-01

    Electrolyte distribution using parallel flow field for redox flow battery (RFB) applications shows severe non-uniformity, while the conventional design of using the carbon felt itself as the flow distributor gives too high pressure drop. An optimized flow field design for uniform flow distribution at a minimal parasitic power loss is therefore needed for RFB systems. Since the materials and geometrical dimensions in RFBs are very different from those used in fuel cells, the hydrodynamics of the flow fields in RFBs is likely to be very different. In the present paper, we report on a fundamental study of the hydrodynamics of a serpentine flow field relevant to RFB applications. The permeability of the porous medium has been measured under different compression ratios and this is found to be in the range of 5-8 × 10-11 m2. The pressure drop in two serpentine flow fields of different geometric characteristics has been measured over a range of Reynolds numbers. Further analysis using computational fluid dynamics simulations brings out the importance of the compression of the porous medium as an additional parameter in determining the flow distribution and pressure drop in these flow fields.

  2. Numerical study of a scramjet engine flow field

    NASA Technical Reports Server (NTRS)

    Drummond, J. P.; Weidner, E. H.

    1981-01-01

    A computer program has been developed to analyze the turbulent reacting flow field in a two-dimensional scramjet engine configuration. The program numerically solves the full two-dimensional Navier-Stokes and species equations in the engine inlet and combustor, allowing consideration of flow separation and possible inlet-combustor interactions. The current work represents an intermediate step towards development of a three-dimensional program to analyze actual scramjet engine flow fields. Results from the current program are presented that predict the flow field for two inlet-combustor configurations, and comparisons of the program with experiment are given to allow assessment of the modeling that is employed.

  3. Study of He II boiling flow field around a heater

    NASA Astrophysics Data System (ADS)

    Murakami, M.; Takada, S.; Nozawa, M.

    2015-12-01

    We studied boiling phenomena in He II based on the flow velocity measurement data by using a PIV (Particle Image Velocimeter). Noisy and silent film boiling modes together with non-boiling state were generated on/around a horizontal planar or a cylindrical heater. For PIV tracer particles, we used H2-D2 solid particles that were neutrally buoyant in He II. Video images showing the development and collapse of vapour bubble or film and the motions of tracer particles were PIV-analysed. We found the PIV velocity field was composed of AC and DC velocity components of the normal fluid. The AC component follows the dynamic behaviour of vapour, and the DC results primarily from the thermal counter flow and secondarily is induced by the asymmetric vapour bubble motion. We also investigated unsteady velocity component. The objective of this series of study is to compare the characteristic features of the flow field of He II film boiling states and peculiar He I boiling state in He II and to make clear the difference in the heat transfer performance of each boiling mode.

  4. Study of flow fields induced by surface dielectric barrier discharge actuator in low-pressure air

    SciTech Connect

    Che, Xueke E-mail: st@mail.iee.ac.cn; Nie, Wansheng; Tian, Xihui; Hou, Zhiyong; He, Haobo; Zhou, Penghui; Zhou, Siyin; Yang, Chao; Shao, Tao E-mail: st@mail.iee.ac.cn

    2014-04-15

    Surface dielectric barrier discharge (SDBD) is a promising method for a flow control. Flow fields induced by a SDBD actuator driven by the ac voltage in static air at low pressures varying from 1.0 to 27.7 kPa are measured by the particle image velocimetry method. The influence of the applied ac voltage frequency and magnitude on the induced flow fields is studied. The results show that three different classes of flow fields (wall jet flow field, complex flow field, and vortex-shape flow field) can be induced by the SDBD actuator in the low-pressure air. Among them, the wall jet flow field is the same as the tangential jet at atmospheric pressure, which is, together with the vertical jet, the complex flow field. The vortex-shape flow field is composed of one vertical jet which points towards the wall and two opposite tangential jets. The complex and the vortex-shape flow fields can be transformed to the wall jet flow field when the applied ac voltage frequency and magnitude are changed. It is found that the discharge power consumption increases initially, decreases, and then increases again at the same applied ac voltage magnitude when the air pressure decreases. The tangential velocity of the wall jet flow field increases when the air pressure decreases. It is however opposite for the complex flow field. The variation of the applied ac voltage frequency influences differently three different flow fields. When the applied ac voltage magnitude increases at the same applied ac voltage frequency, the maximal jet velocity increases, while the power efficiency increases only initially and then decreases again. The discharge power shows either linear or exponential dependences on the applied ac voltage magnitude.

  5. Application of full field optical studies for pulsatile flow in a carotid artery phantom

    PubMed Central

    Nemati, M.; Loozen, G. B.; van der Wekken, N.; van de Belt, G.; Urbach, H. P.; Bhattacharya, N.; Kenjeres, S.

    2015-01-01

    A preliminary comparative measurement between particle imaging velocimetry (PIV) and laser speckle contrast analysis (LASCA) to study pulsatile flow using ventricular assist device in a patient-specific carotid artery phantom is reported. These full-field optical techniques have both been used to study flow and extract complementary parameters. We use the high spatial resolution of PIV to generate a full velocity map of the flow field and the high temporal resolution of LASCA to extract the detailed frequency spectrum of the fluid pulses. Using this combination of techniques a complete study of complex pulsatile flow in an intricate flow network can be studied. PMID:26504652

  6. Study of Spray Disintegration in Accelerating Flow Fields

    NASA Technical Reports Server (NTRS)

    Nurick, W. H.

    1972-01-01

    An analytical and experimental investigation was conducted to perform "proof of principlem experiments to establish the effects of propellant combustion gas velocity on propella'nt atomization characteristics. The propellants were gaseous oxygen (GOX) and Shell Wax 270. The fuel was thus the same fluid used in earlier primary cold-flow atomization studies using the frozen wax method. Experiments were conducted over a range in L* (30 to 160 inches) at two contraction ratios (2 and 6). Characteristic exhaust velocity (c*) efficiencies varied from SO to 90 percent. The hot fire experimental performance characteristics at a contraction ratio of 6.0 in conjunction with analytical predictions from the drovlet heat-up version of the Distributed Energy Release (DER) combustion computer proDam showed that the apparent initial dropsize compared well with cold-flow predictions (if adjusted for the gas velocity effects). The results also compared very well with the trend in perfomnce as predicted with the model. significant propellant wall impingement at the contraction ratio of 2.0 precluded complete evaluation of the effect of gross changes in combustion gas velocity on spray dropsize.

  7. Depolymerization study of sodium hyaluronate by flow field-flow fractionation/multiangle light scattering.

    PubMed

    Kwon, Ji Hye; Hwang, Euijin; Cho, Il-Hwan; Moon, Myeong Hee

    2009-09-01

    Thermal depolymerization of ultrahigh-molecular-weight (UHMW) sodium hyaluronate (NaHA) was studied systematically by using frit-inlet asymmetrical flow field-flow fractionation/multiangle light scattering/differential refractive index (FI-AFlFFF/MALS/DRI). FI-AFlFFF was utilized for the size separation of NaHA samples which had been thermally degraded for varied treatment times, followed by light-scattering detection to determine MW and structural information of degraded NaHA products. Analysis of NaHA products showed time-dependent depolymerization of raw molecules into smaller-MW components, as well as unfolding of compact structures of UHMW NaHA. To determine whether the observed decrease in MW of sodium hyaluronate originated from the chain degradation of UHMW molecules or from dissociation of entangled complex particles that may have been formed by intermolecular association, narrow size fractions (1 x 10(7)-6 x 10(7) and >6 x 10(7) MW) of NaHA molecules were collected during FlFFF separation and followed by thermal treatment. Subsequent FI-AFlFFF/MALS analysis of collected fractions after thermal treatment suggested that the ultrahigh-MW region (>10(7) Da) of NaHA is likely to result from supermolecular structures formed by aggregation of large molecules. PMID:19649622

  8. Computational study of generic hypersonic vehicle flow fields

    NASA Technical Reports Server (NTRS)

    Narayan, Johnny R.

    1994-01-01

    The geometric data of the generic hypersonic vehicle configuration included body definitions and preliminary grids for the forebody (nose cone excluded), midsection (propulsion system excluded), and afterbody sections. This data was to be augmented by the nose section geometry (blunt conical section mated with the noncircular cross section of the forebody initial plane) along with a grid and a detailed supersonic combustion ramjet (scramjet) geometry (inlet and combustor) which should be merged with the nozzle portion of the afterbody geometry. The solutions were to be obtained by using a Navier-Stokes (NS) code such as TUFF for the nose portion, a parabolized Navier-Stokes (PNS) solver such as the UPS and STUFF codes for the forebody, a NS solver with finite rate hydrogen-air chemistry capability such as TUFF and SPARK for the scramjet and a suitable solver (NS or PNS) for the afterbody and external nozzle flows. The numerical simulation of the hypersonic propulsion system for the generic hypersonic vehicle is the major focus of this entire work. Supersonic combustion ramjet is such a propulsion system, hence the main thrust of the present task has been to establish a solution procedure for the scramjet flow. The scramjet flow is compressible, turbulent, and reacting. The fuel used is hydrogen and the combustion process proceeds at a finite rate. As a result, the solution procedure must be capable of addressing such flows.

  9. Experimental study of flow field around a plunging flexible hydrofoil

    NASA Astrophysics Data System (ADS)

    Martin-Alarcon, Leonardo; Yang, Tao; Shu, Fangjun; Wei, Mingjun

    2011-11-01

    Recent developments in micro air vehicles (MAVs) have led to the improvement of computational fluid dynamics (CFD) simulations capable of simulating flexible flapping wing phenomena. For validation of these simulations, an experimental methodology is applied to characterize the flow physics involved with an immersed flexible flapping hydrofoil. Using a one-degree of freedom crank-shaft system, a silicone hydrofoil was actuated to flap under various kinematic conditions. The hydrofoil was subject to active plunging and passive pitching motion in both water and aqueous glycerin solutions. Phase-locked particle image velocimetry (PIV) measurements were obtained around the flapping hydrofoil. These measurements, along with force measurements using a six-axis load cell, are used to compare the results with those of the numerical simulations. By comparing the hydrofoil deformation, vortex evolution and force generation, good agreements between CFD and experimental results were observed. Supported by Army High Performance Computing Research Center.

  10. A Study of Liquid Metal Film Flow, Under Fusion Relevant Magnetic Fields

    SciTech Connect

    Narula, M.; Ying, A.; Abdou, M.A.

    2005-04-15

    The use of flowing liquid metal streams or 'liquid walls' as a plasma contact surface is a very attractive option and has received considerable attention over the past several years both in the plasma physics and fusion engineering programs. A key issue for the feasibility of flowing liquid metal plasma facing component (PFC) systems, lies in their magnetohydrodynamic (MHD) behavior. The spatially varying magnetic field environment, typical of a fusion device can lead to serious flow disrupting MHD forces that hinder the development of a smooth and controllable flow needed for PFC applications. The present study builds up on the ongoing research effort at UCLA, directed towards providing qualitative and quantitative data on liquid metal free surface flow behavior under fusion relevant magnetic fields, to aid in better understanding of flowing liquid metal PFC systems.

  11. Numerical studies on flow fields around buildings in an Urban street canyon and cross-road

    NASA Astrophysics Data System (ADS)

    Cheng, Xueling; Hu, Fei

    2005-03-01

    The questions on how vortices are constructed and on the relationship between the flow patterns and concentration distributions in real street canyons are the most pressing questions in pollution control studies. In this paper, the very large eddy simulation (VLES) and large eddy simulation (LES) are applied to calculate the flow and pollutant concentration fields in an urban street canyon and a cross-road respectively. It is found that the flow separations are not only related to the canyon aspect ratios, but also with the flow velocities and wall temperatures. And the turbulent dispersions are so strongly affected by the flow fields that the pollutant concentration distributions can be distinguished from the different aspect ratios, flow velocities and wall temperatures.

  12. Experimental studies of zonal flow and field in compact helical system plasma

    SciTech Connect

    Fujisawa, A.; Itoh, K.; Shimizu, A.; Nakano, H.; Ohshima, S.; Iguchi, H.; Matsuoka, K.; Okamura, S.; Minami, T.; Yoshimura, Y.; Nagaoka, K.; Ida, K.; Toi, K.; Takahashi, C.; Kojima, M.; Nishimura, S.; Isobe, M.; Suzuki, C.; Akiyama, T.; Ido, T.

    2008-05-15

    The experimental studies on zonal flows and turbulence have been carried out in Compact Helical System [K. Matsuoka, S. Kubo, M. Hosokawa et al., in Plasma Physics and Controlled Nuclear Fusion Research, Proc. 12th Int. Conf., Nice, 1988 (International Atomic Energy Agency, Vienna, 1989, Vol. 2, p. 411] using twin heavy ion beam probes. The paper presents the experimental observations of stationary zonal flow, nonlinear couplings between zonal flow and turbulence, and the role of zonal flow in the improved confinement, together with the recent discovery of zonal magnetic field. The presented experimental results strongly support the new paradigm that the plasma transport should be considered as a system of drift wave and zonal flows, and provides the first direct evidence for turbulence dynamo that the structured magnetic field can be really generated by turbulence.

  13. Fundamental study of flow field generated by rotorcraft blades using wide-field shadowgraph

    NASA Technical Reports Server (NTRS)

    Parthasarathy, S. P.; Cho, Y. I.; Back, L. H.

    1985-01-01

    The vortex trajectory and vortex wake generated by helicopter rotors are visualized using a wide-field shadowgraph technique. Use of a retro-reflective Scotchlite screen makes it possible to investigate the flow field generated by full-scale rotors. Tip vortex trajectories are visible in shadowgraphs for a range of tip Mach number of 0.38 to 0.60. The effect of the angle of attack is substantial. At an angle of attack greater than 8 degrees, the visibility of the vortex core is significant even at relatively low tip Mach numbers. The theoretical analysis of the sensitivity is carried out for a rotating blade. This analysis demonstrates that the sensitivity decreases with increasing dimensionless core radius and increases with increasing tip Mach number. The threshold value of the sensitivity is found to be 0.0015, below which the vortex core is not visible and above which it is visible. The effect of the optical path length is also discussed. Based on this investigation, it is concluded that the application of this wide-field shadowgraph technique to a large wind tunnel test should be feasible. In addition, two simultaneous shadowgraph views would allow three-dimensional reconstruction of vortex trajectories.

  14. Integrating Acoustic Imaging of Flow Regimes With Bathymetry: A Case Study, Main Endeavor Field

    NASA Astrophysics Data System (ADS)

    Bemis, K. G.; Rona, P. A.; Jackson, D. R.; Jones, C. D.

    2003-12-01

    A unified view of the seafloor and the hydrothermal flow regimes (plumes and diffuse flow) is constructed for three major vent clusters in the Main Endeavour Field (e.g., Grotto, S&M, and Salut) of the Endeavour Segment, Juan de Fuca Ridge. The Main Endeavour Field is one of RIDGE 2000's Integrated Study Sites. A variety of visualization techniques are used to reconstruct the plumes (3D) and the diffuse flow field (2D) based on our acoustic imaging data set (July 2000 cruise). Plumes are identified as volumes of high backscatter intensity (indicating high particulate content or sharp density contrasts due to temperature variations) that remained high intensity when successive acoustic pings were subtracted (indicating that the acoustic targets producing the backscatter were in motion). Areas of diffuse flow are detected using our acoustic scintillation technique (AST). For the Grotto vent region (where a new Doppler technique was used to estimate vertical velocities in the plume), we estimate the areal partitioning between black smoker and diffuse flow in terms of volume fluxes. The volumetric and areal regions, where plume and diffuse flow were imaged, are registered over the bathymetry and compared to geologic maps of each region. The resulting images provide a unified view of the seafloor by integrating hydrothermal flow with geology.

  15. Field-Flow Fractionation.

    ERIC Educational Resources Information Center

    Caldwell, Karin D.

    1988-01-01

    Describes a technique for separating samples that range over 15 orders of magnitude in molecular weight. Discusses theory, apparatus, and sample preparation techniques. Lists several types of field-flow fractionation (FFF) and their uses: sedimentation FFF, thermal FFF, flow FFF, electrical FFF, and steric FFF. (ML)

  16. Study on flow field in capacity regulating actuator for reciprocating compressor

    NASA Astrophysics Data System (ADS)

    Cao, J. L.; Hong, W. R.; Li, Y.; He, Z. K.

    2013-12-01

    The rated capacity of reciprocating compressor tends to be higher than the level needed, so the capacity regulation needs to be implemented to save unnecessary energy waste. Among the methods for reciprocating compressor capacity regulation, holding the suction valves open in partial stroke is a widely used method for its economy, full-range and easy-using characters. The capacity regulation system based on a hydraulic distributor has been successfully applied in industrial process. Hydraulic distributor is the core component of the complete set of stepless capacity regulation system. Continuous high-pressure hydraulic oil provided by hydraulic unit is converted into a pressure impulse wave with a controllable periodic time and pressure acting time when it flows through the hydraulic distributor, which is used to realize the suction valves regulation when it is in the compression stroke. Although the equipment is successfully used in industry fields, the fluid mechanics design of hydraulic distributor is still empirical as its complexity of the fluid field in inner circulation space. For better and more rational distributor design, the flow field in inner zones needs to be better analysed and studied. The manuscript concerned the subjects of path lines, pressure and velocity distribution in hydraulic distributor's flow channels using the CFD software FLUENT. The article explored the flow field characteristics and the flow performance with 5.0 MPa outlet pressure. In the end, a systematic conclusion would be given to guide the actor design.

  17. Background-oriented schlieren for the study of large flow fields

    NASA Astrophysics Data System (ADS)

    Trolinger, James D.; Buckner, Ben; L'Esperance, Drew

    2015-09-01

    Modern digital recording and processing techniques combined with new lighting methods and relatively old schlieren visualization methods move flow visualization to a new level, enabling a wide range of new applications and a possible revolution in the visualization of very large flow fields. This paper traces the evolution of schlieren imaging from Robert Hooke, who, in 1665, employed candles and lenses, to modern digital background oriented schlieren (BOS) systems, wherein image processing by computer replaces pure optical image processing. New possibilities and potential applications that could benefit from such a capability are examined. Example applications include viewing the flow field around full sized aircraft, large equipment and vehicles, monitoring explosions on bomb ranges, cooling systems, large structures and even buildings. Objectives of studies include aerodynamics, aero optics, heat transfer, and aero thermal measurements. Relevant digital cameras, light sources, and implementation methods are discussed.

  18. A numerical study on the flow and sound fields of centrifugal impeller located near a wedge

    NASA Astrophysics Data System (ADS)

    Jeon, Wan-Ho; Lee, Duck-Joo

    2003-09-01

    Centrifugal fans are widely used and the noise generated by these machines causes one of the serious problems. In general, the centrifugal fan noise is often dominated by tones at blade passage frequency and its higher harmonics. This is a consequence of the strong interaction between the flow discharged from the impeller and the cut-off in the casing. However, only a few researches have been carried out on predicting the noise because of the difficulty in obtaining detailed information about the flow field and considering the scattering effect of the casing. The objective of this study is to understand the generation mechanism of sound and to develop a prediction method for the unsteady flow field and the acoustic pressure field of the centrifugal impeller. A discrete vortex method is used to model the centrifugal impeller and a wedge and to calculate the flow field. The force of each element on the blade is calculated by the unsteady Bernoulli equation. Lowson's method is used to predict the acoustic source. In order to consider the scattering and diffraction effects of the casing, Kirchhoff-Helmholtz boundary element method (BEM) is developed. The source of Kirchhoff-Helmholtz BEM is newly developed, so the sound field of the centrifugal fan can be obtained. A centrifugal impeller and wedge are used in the numerical calculation and the results are compared with the experimental data. Reasonable results are obtained not only for the peak frequencies but also for the amplitudes of the tonal sound. The radiated acoustic field shows the diffraction and scattering effect of the wedge.

  19. Numerical Study for Detailed Flow Fields and Performance of the Savonius-Type Rotor

    NASA Astrophysics Data System (ADS)

    Zhou, Tong; Rempfer, Dietmar

    2011-11-01

    The Savonius-type rotor is simple in structure, has good starting characteristics, relatively low operating speeds, and an ability to accept wind from any direction, although it has a lower efficiency than other vertical axis wind turbines. So far a number of experimental investigations have been carried out to study the performance of the Savonius rotor, however, there is a lack of detailed descriptions of the flow field. The aim of this paper is to numerically explore the non-linear two-dimensional unsteady flow over a Savonius rotor and develop a simulation method for predicting its aerodynamic performance. The simulations are based on Star CCM+. The motion of the blades is solved by using a moving mesh. Different turbulence models are compared. Parameters such as mesh density, wall y+, and boundary conditions will be discussed. Numerical simulation results are compared with experimental data. Separation of the flow at the blade tips is well modeled. The characteristics of flow fields details are studied, including boundary layer, moment coefficient, and pressure distribution. The wall shear on each surface of the blades is studied to look into the position of the separation point. Computational fluid dynamics is proven to be an effective approach for the investigation of the Savonius-type rotor, on the premise of proper theory and reasonable assumption. It also provides a basis for optimization of the Savonius wind turbine.

  20. Subsurface flow in a soil-mantled subtropical dolomite karst slope: A field rainfall simulation study

    NASA Astrophysics Data System (ADS)

    Fu, Z. Y.; Chen, H. S.; Zhang, W.; Xu, Q. X.; Wang, S.; Wang, K. L.

    2015-12-01

    Soil and epikarst co-evolve resulting in complex structures, but their coupled structural effects on hydrological processes are poorly understood in karst regions. This study examined the plot-scale subsurface flow characteristics from an integrated soil-epikarst system perspective in a humid subtropical cockpit karst region of Southwest China. A trench was excavated to the epikarst lower boundary for collecting individual subsurface flows in five sections with different soil thicknesses. Four field rainfall simulation experiments were carried out under different initial moisture conditions (dry and wet) and rainfall intensities (114 mm h- 1 (high) and 46 mm h- 1 (low) on average). The soil-epikarst system was characterized by shallow soil overlaying a highly irregular epikarst surface with a near-steady infiltration rate of about 35 mm h- 1. The subsurface flows occurred mainly along the soil-epikarst interface and were dominated by preferential flow. The subsurface flow hydrographs showed strong spatial variability and had high steady-state coefficients (0.52 and 0.36 for high and low rainfall intensity events). Irregular epikarst surface combining with high vertical drainage capacity resulted in high threshold rainfall depths for subsurface flows: 67 mm and 263 mm for initial wet and dry conditions, respectively. The above results evidenced that the irregular and permeable soil-epikarst interface was a crucial component of soil-epikarst architecture and consequently should be taken into account in the hydrological modeling for karst regions.

  1. Integration of Hard and Soft Data to Characterize Field-Scale Hydraulic Properties for Flow and Transport Studies

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Field-scale flow and transport studies are frequently conducted to assess and quantify a variety of environmental and agricultural scenarios. The utility of field-scale flow and transport studies, however, is frequently limited by our inability to characterize the heterogeneous distribution of hydr...

  2. Numerical study of turbulent flow over complex aeolian dune fields: the White Sands National Monument.

    PubMed

    Anderson, William; Chamecki, Marcelo

    2014-01-01

    The structure and dynamics of fully developed turbulent flows responding to aeolian dune fields are studied using large-eddy simulation with an immersed boundary method. An aspect of particular importance in these flows is the downwind migration of coherent motions associated with Kelvin-Helmholtz instabilities that originate at the dune crests. These instabilities are responsible for enhanced downward transport of high-momentum fluid via the so-called turbulent sweep mechanism. However, the presence of such structures and their role in determining the bulk characteristics of fully developed dune field sublayer aerodynamics have received relatively limited attention. Moreover, many existing studies address mostly symmetric or mildly asymmetric dune forms. The White Sands National Monument is a field of aeolian gypsum sand dunes located in the Tularosa Basin in southern New Mexico. Aeolian processes at the site result in a complex, anisotropic dune field. In the dune field sublayer, the flow statistics resemble a mixing layer: At approximately the dune crest height, vertical profiles of streamwise velocity exhibit an inflection and turbulent Reynolds stresses are maximum; below this, the streamwise and vertical velocity fluctuations are positively and negatively skewed, respectively. We evaluate the spatial structure of Kelvin-Helmholtz instabilities present in the dune field sublayer (shear length L(s) and vortex spacing Λ(x)) and show that Λ(x)=m(dune)L(s), where m(dune)≈7.2 in the different sections considered (for turbulent mixing layers, 7

  3. Numerical calculations of flow fields

    NASA Technical Reports Server (NTRS)

    Anderson, D.; Vogel, J. M.

    1973-01-01

    Numerical calculations were made of flow fields generated by various aerodynamic configurations. Data cover flow fields generated by a finitely thick lifting three dimensional wing with subsonic tips moving at supersonic speeds, cross flow instability associated with lifting delta wing configurations such as space shuttles, and flow fields produced by a lifting elliptic cone. Finite difference techniques were used to determine elliptic cone flow.

  4. Sedimentation field flow fractionation and flow field flow fractionation as tools for studying the aging effects of WO₃ colloids for photoelectrochemical uses.

    PubMed

    Contado, Catia; Argazzi, Roberto

    2011-07-01

    WO₃ colloidal suspensions obtained through a simple sol-gel procedure were subjected to a controlled temperature aging process whose time evolution in terms of particle mass and size distribution was followed by sedimentation field flow fractionation (SdFFF) and flow field flow fractionation (FlFFF). The experiments performed at a temperature of 60 °C showed that in a few hours the initially transparent sol of WO₃ particles, whose size was less than 25 nm, undergoes a progressive size increase allowing nanoparticles to reach a maximum equivalent spherical size of about 130 nm after 5 h. The observed shift in particle size distribution maxima (SdFFF), the broadening of the curves (FlFFF) and the SEM-TEM observations suggest a mixed mechanism of growth-aggregation of initial nanocrystals to form larger particles. The photoelectrochemical properties of thin WO₃ films obtained from the aged suspensions at regular intervals, were tested in a biased photoelectrocatalytic cell with 1M H₂SO₄ under solar simulated irradiation. The current-voltage polarization curves recorded in the potential range 0-1.8 V (vs. SCE) showed a diminution of the maximum photocurrent from 3.7 mA cm⁻² to 2.8 mA cm⁻² with aging times of 1h and 5h, respectively. This loss of performance was mainly attributed to the reduction of the electroactive surface area of the sintered particles as suggested by the satisfactory linear correlation between the integrated photocurrent and the cyclic voltammetry cathodic wave area of the W(VI)→W(V) process measured in the dark. PMID:21168138

  5. Study on steric transition in asymmetrical flow field-flow fractionation and application to characterization of high-energy material.

    PubMed

    Dou, Haiyang; Lee, Yong-Ju; Jung, Euo Chang; Lee, Byung-Chul; Lee, Seungho

    2013-08-23

    In field-flow fractionation (FFF), there is the 'steric transition' phenomenon where the sample elution mode changes from the normal to steric/hyperlayer mode. Accurate analysis by FFF requires understanding of the steric transition phenomenon, particularly when the sample has a broad size distribution, for which the effect by combination of different modes may become complicated to interpret. In this study, the steric transition phenomenon in asymmetrical flow FFF (AF4) was studied using polystyrene (PS) latex beads. The retention ratio (R) gradually decreases as the particle size increases (normal mode) and reaches a minimum (Ri) at diameter around 0.5μm, after which R increases with increasing diameter (steric/hyperlayer mode). It was found that the size-based selectivity (Sd) tends to increase as the channel thickness (w) increases. The retention behavior of cyclo-1,3,5-trimethylene-2,4,6-trinitramine (commonly called 'research department explosive' (RDX)) particles in AF4 was investigated by varying experimental parameters including w and flow rates. AF4 showed a good reproducibility in size determination of RDX particles with the relative standard deviation of 4.1%. The reliability of separation obtained by AF4 was evaluated by transmission electron microscopy (TEM). PMID:23871284

  6. Experimental and numerical studies on plasma behavior flowing across perpendicular magnetic field

    NASA Astrophysics Data System (ADS)

    Takezaki, T.; Takahashi, K.; Sasaki, T.; Kikuchi, T.; Harada, N.

    2016-05-01

    To understand particle acceleration mechanisms in a collisionless shock, we have investigated the behaviors of a one-dimensional fast plasma flow in a perpendicular magnetic field by experimental and numerical simulations in a laboratory scale experiment. The velocity of the plasma flow generated by a taper-cone-shaped plasma focus device has varied by the gradient of the perpendicular magnetic field. The plasma flow has accelerated by applying the magnetic field with the negative gradient. To clarify the behavior of the plasma flow in the perpendicular magnetic field, numerical simulations based on an electromagnetic hybrid particle-in-cell (PIC) method have been carried out. These results indicate that the magnetic field gradient affects the plasma flow velocity.

  7. Flow field analysis studies downstream of a cooling hole on a flat plate

    NASA Astrophysics Data System (ADS)

    Ranakoti, Ganesh; Marathe, Parag

    2014-10-01

    Flow field analysis is carried out computationally on a flat plate with 35° stream-wise coolant injection through a cylindrical film cooling hole. ANSYS Fluent 13.0 is used to perform computations using k-ɛrealizable turbulence model with enhanced wall functions. The Reynolds number ReD based on free stream velocity and diameter of hole is 15885 with blowing ratio M=0.5 and density ratio D.R=1.2. Streamlines are studied downstream of the film cooling hole in the present study.

  8. A coupled field study of subsurface fracture flow and colloid transport

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Tang, Xiang-Yu; Weisbrod, Noam; Zhao, Pei; Reid, Brian J.

    2015-05-01

    Field studies of subsurface transport of colloids, which may act as carriers of contaminants, are still rare. This is particularly true for heterogeneous and fractured matrices. To address this knowledge gap, a 30-m long monitoring trench was constructed at the lower end of sloping farmland in central Sichuan, southwest China. During the summer of 2013, high resolution dynamic and temporal fracture flow discharging from the interface between fractured mudrock and impermeable sandstone was obtained at intervals of 5 min (for fast rising stages), 30-60 min (for slow falling stages) or 15 min (at all other times). This discharge was analyzed to elucidate fracture flow and colloid transport in response to rainfall events. Colloid concentrations were observed to increase quickly once rainfall started (∼15-90 min) and reached peak values of up to 188 mg/L. Interestingly, maximum colloid concentration occurred prior to the arrival of flow discharge peak (i.e. maximum colloid concentration was observed before saturation of the soil layer). Rainfall intensity (rather than its duration) was noted to be the main factor controlling colloid response and transport. Dissolved organic carbon concentration and δ18O dynamics in combination with soil water potential were used to apportion water sources of fracture flow at different stages. These approaches suggested the main source of the colloids discharged to be associated with the flushing of colloids from the soil mesopores and macropores. Beyond the scientific interest of colloid mobilization and transport at the field scale, these results have important implications for a region of about 160,000 km2 in southwest China that featured similar hydrogeologic settings as the experimental site. In this agriculture-dominated area, application of pesticides and fertilizers to farmland is prevalent. These results highlight the need to avoid such applications immediately before rainfall events in order to reduce rapid migration to

  9. Factors affecting milk flow traits in dairy cows: results of a field study.

    PubMed

    Sandrucci, A; Tamburini, A; Bava, L; Zucali, M

    2007-03-01

    The study of milk flow curves provides useful information for enhancing milking efficiency and protecting udder health by adapting milking machine and milking procedures to the physiological requirements of the cow. The aim of this experiment was to investigate, using field data, the relationships among traits of the milk flow curves, their sources of variation, and milking performances in terms of milk production, machine-on time, and udder health. A total of 2,486 milk flow curves of the whole udder were collected in 82 Italian Holstein-Friesian dairy herds in the Lombardy region of Italy. Approximately one-third (35.1%) of milk flow curves were classified as bimodal. Most flow characteristics were influenced by lactation number, days in milk, and peak flow but also strongly affected by premilking operations. Proper udder preparation, including forestripping and predipping, resulted in better milking performances compared with poor preparation, with greater milk yield per milking, shorter milking time, and lesser bimodality. Premilking delay time, between the start of teat stimulation and cup attachment, affected milking time significantly: The shortest milking time was obtained for a range of delay time between 1 and 60 s. As the delay time increased, the percentage of bimodality dropped significantly. Increasing the number of clusters per operator led to greater percentages of bimodal curves. The greater somatic cell count of cows with bimodal curves supports the hypothesis of the negative effect of bimodality on udder health and indicates the importance of avoiding its occurrence using proper pre-milking procedures. PMID:17297090

  10. An experimental study on the effects of tip clearance on flow field and losses in an axial flow compressor rotor

    NASA Technical Reports Server (NTRS)

    Lakshminarayana, B.; Zhang, J.; Murthy, K. N. S.

    1987-01-01

    Detailed measurement of the flow field in the tip region of a compressor rotor was carried out using a Laser Doppler Velocimeter (LDV) and a Kiel probe at two different tip clearance heights. At both clearance sizes, the relative stagnation pressure and the axial and tangential components of relative velocities were measured upstream, inside the passage and downstream of the rotor, up to about 20 percent of the blade span from the annulus wall. The velocities, outlet angles, losses, momentum thickness, and force defect thickness are compared for the two clearances. A detailed interpretation of the effect of tip clearance on the flow field is given. There are substantial differences in flow field, on momentum thickness, and performance as the clearance is varied. The losses increase linearly within the passage and their values increase in direct proportion to tip clearance height. No discernable vortex (discrete) is observed downstream of the rotor.

  11. Study of unsteady flow field over a forward-looking endoatmospheric hit-to-kill interceptor

    NASA Technical Reports Server (NTRS)

    Yang, H. Q.; Antonison, Mark

    1993-01-01

    Forward-looking recessed aperture interceptor has significant aero-optical and aero-thermal advantages. Previous experimental studies have shown that the flow field in front of a forward-looking cavity is unsteady and the bow shock oscillates at the cavity fundamental resonant frequency. In this study, an advanced CFD code is applied to study the above unsteady phenomena. The code is first validated against the experiments and good comparisons are found. The numerical parametric study shows that the existence of oscillatory bow shock is very sensitive to the cavity geometry. At a FOV of 60 deg, the initial transient quickly dampens out to a steady state. With a decrease of FOV, an unsteady oscillatory flow field is sustained after initial transient and the amplitude of oscillation is a function of FOV. For FOV of 20 deg, the amplitude of pressure oscillation is 25 percent of the mean value in the cavity. For a FOV of 10 deg, it can be as high as 50 percent.

  12. A study of methods which predict supersonic flow fields from body geometry, distance, and Mach number

    NASA Technical Reports Server (NTRS)

    Mack, R. J.

    1973-01-01

    A study of seven methods for predicting flow-field pressure signatures from the parameters Mach number, body geometry, and field-path distance has been made. The methods included the method of characteristics, which served as a standard of comparison; a shock-capturing method; three Whitham theory methods; a modified characteristics method; and a bicharacteristics method. Results from each method were also compared with recently obtained wind-tunnel data for a cone-cylinder model at Mach numbers of 2.96 and 4.63 with ratios of radial distance to cone length of 2 and 5. The comparisons at a Mach number of 2.96 showed that signatures from all the methods correlated well with wind-tunnel data and with the signatures predicted by the method of characteristics. At a Mach number of 4.63, however, the agreement between the signatures obtained in the wind tunnel and those predicted by theory varied from good to poor, as did the agreement between the signatures obtained by the method of characteristics and the other six methods. It should be noted that these results and comparisons indicate pressure prediction capabilities only for the near-field flow about bodies of revolution.

  13. Analytical study of mixing and reacting three-dimensional supersonic combustor flow fields

    NASA Technical Reports Server (NTRS)

    Baker, A. J.; Rogers, R. C.; Zelazny, S. W.

    1975-01-01

    An analytical investigation is presented of mixing and reacting hydrogen jets injected from multiple orifices transverse and parallel to a supersonic airstream. The COMOC computer program, based upon a finite-element solution algorithm, was developed to solve the governing equations for three-dimensional, turbulent, reacting, boundary-region, and confined flow fields. The computational results provide a three-dimensional description of the velocity, temperature, and species-concentration fields downstream of hydrogen injection. Detailed comparisons between cold-flow data and results of the computational analysis have established validity of the turbulent-mixing model based on the elementary mixing-length hypothesis. A method is established to initiate computations for reacting flow fields based upon cold-flow correlations and the appropriate experimental parameters of Mach number, injector spacing, and pressure ratio. Key analytical observations on mixing and combustion efficiency for reacting flows are presented and discussed.

  14. Aggregation behavior of fullerenes in aqueous solutions: a capillary electrophoresis and asymmetric flow field-flow fractionation study.

    PubMed

    Astefanei, Alina; Núñez, Oscar; Galceran, Maria Teresa; Kok, Wim Th; Schoenmakers, Peter J

    2015-10-01

    In this work, the electrophoretic behavior of hydrophobic fullerenes [buckminsterfullerene (C60), C70, and N-methyl-fulleropyrrolidine (C60-pyrr)] and water-soluble fullerenes [fullerol (C60(OH)24); polyhydroxy small gap fullerene, hydrated (C120(OH)30); C60 pyrrolidine tris acid (C60-pyrr tris acid); and (1,2-methanofullerene C60)-61-carboxylic acid (C60CHCOOH)] in micellar electrokinetic capillary chromatography (MECC) was evaluated. The aggregation behavior of the water-soluble compounds in MECC at different buffer and sodium dodecyl sulfate (SDS) concentrations and pH values of the background electrolyte (BGE) was studied by monitoring the changes observed in the electrophoretic pattern of the peaks. Broad and distorted peaks that can be attributed to fullerene aggregation were obtained in MECC which became narrower and more symmetric by working at low buffer and SDS concentrations (below the critical micelle concentration, capillary zone electrophoresis (CZE) conditions). For the characterization of the suspected aggregates formed (size and shape), asymmetrical flow field-flow fractionation (AF4) and transmission electron microscopy (TEM) were used. The results showed that the increase in the buffer concentration promoted the aggregation of the particles, while the presence of SDS micelles revealed multiple peaks corresponding to particles of different aggregation degrees. Furthermore, MECC has been applied for the first time for the analysis of C60 in two different cosmetic products (i.e., anti-aging serum and facial mask). PMID:26314484

  15. Study on aggregation behavior of Cytochrome C-conjugated silver nanoparticles using asymmetrical flow field-flow fractionation.

    PubMed

    Kim, Sun Tae; Lee, Yong-Ju; Hwang, Yu-Sik; Lee, Seungho

    2015-01-01

    In this study, 40 nm silver nanoparticles (AgNPs) were synthesized using the citrate reduction method and then the surface of AgNPs was modified by conjugating Cytochrome C (Cyto C) to improve stability and to enhance bioactivity and biocompatibility of AgNPs. It is known that Cyto C may undergo conformational changes under various conditions of pH, temperature, ionic strength, etc., resulting in aggregation of the particles. These parameters also affect the size and size distribution of Cyto C-conjugated AgNPs (Cyto C-AgNP). ζ-potential measurement revealed that the adsorption of Cyto C on the surface of AgNPs is saturated at the molar ratio [Cyto C]/[AgNPs] above about 300. Asymmetrical flow field-flow fractionation (AsFlFFF) analysis showed that hydrodynamic diameter of AgNPs increases by about 4 nm when the particle is saturated by Cyto C. The aggregation behavior of Cyto C-AgNP at various conditions of pH, temperature and ionic strength were investigated using AsFlFFF and UV-vis spectroscopy. It was found that the aggregation of Cyto C-AgNP increases with decreasing pH, increasing temperature and ionic strength due to denaturation of Cyto C on AgNPs and reduction in the thickness of electrostatic double layer on the surface of Cyto C-AgNP. PMID:25476400

  16. Experimental and computational studies of the relative flow field in a centrifugal blood pump.

    PubMed

    Ng, B T; Chan, W K; Yu, S C; Li, H D

    2000-01-01

    The relative flow field within the impeller passage of a centrifugal blood pump had been examined using flow visualization technique and computational fluid dynamics. It was found that for a seven-blade radial impeller design, the required flow rate and static pressure rise across the pump could be achieved but the flow field within the blades was highly undesirable. Two vortices were observed near the suction side and these could lead to thrombus formation. Preliminary results presented in this article are part of our overall effort to minimize undesirable flow patterns such flow separation and high shear stress regions within the centrifugal blood pump. This will facilitate the future progress in developing a long-term clinically effective blood pump. PMID:10999375

  17. Field, laboratory and numerical approaches to studying flow through mangrove pneumatophores

    NASA Astrophysics Data System (ADS)

    Chua, V. P.

    2014-12-01

    The circulation of water in riverine mangrove swamps is expected to be influenced by mangrove roots, which in turn affect the nutrients, pollutants and sediments transport in these systems. Field studies were carried out in mangrove areas along the coastline of Singapore where Avicennia marina and Sonneratia alba pneumatophore species are found. Geometrical properties, such as height, diameter and spatial density of the mangrove roots were assessed through the use of photogrammetric methods. Samples of these roots were harvested from mangrove swamps and their material properties, such as bending strength and Young's modulus were determined in the laboratory. It was found that the pneumatophores under hydrodynamic loadings in a mangrove environment could be regarded as fairly rigid. Artificial root models of pneumatophores were fabricated from downscaling based on field observations of mangroves. Flume experiments were performed and measurements of mean flow velocities, Reynolds stress and turbulent kinetic energy were made. The boundary layer formed over the vegetation patch is fully developed after x = 6 m with a linear mean velocity profile. High shear stresses and turbulent kinetic energy were observed at the interface between the top portion of the roots and the upper flow. The experimental data was employed to calibrate and validate three-dimensional simulations of flow in pneumatophores. The simulations were performed with the Delft3D-FLOW model, where the vegetation effect is introduced by adding a depth-distributed resistance force and modifying the k-ɛ turbulence model. The model-predicted profiles for mean velocity, turbulent kinetic energy and concentration were compared with experimental data. The model calibration is performed by adjusting the horizontal and vertical eddy viscosities and diffusivities. A skill assessment of the model is performed using statistical measures that include the Pearson correlation coefficient (r), the mean absolute error

  18. The Flow Field Downstream of a Dynamic Low Aspect Ratio Circular Cylinder: A Parametric Study

    NASA Astrophysics Data System (ADS)

    Gildersleeve, Samantha; Dan, Clingman; Amitay, Michael

    2015-11-01

    Flow past a static, low aspect ratio cylinder (pin) has shown the formation of vortical structures, namely the horseshoe and arch-type vortex. These vortical structures may have substantial effects in controlling flow separation over airfoils. In the present experiments, the flow field associated with a low aspect ratio cylinder as it interacts with a laminar boundary layer under static and dynamic conditions was investigated through a parametric study over a flat plate. As a result of the pin being actuated in the wall-normal direction, the structures formed in the wake of the pin were seen to be a strong function of actuation amplitude, driving frequency, and aspect ratio of the cylinder. The study was conducted at a Reynolds number of 1875, based on the local boundary layer thickness, with a free stream velocity of 10 m/s. SPIV data were collected for two aspect ratios of 0.75 and 1.125, actuation amplitudes of 6.7% and 16.7%, and driving frequencies of 175 Hz and 350 Hz. Results indicate that the presence and interactions between vortical structures are altered in comparison to the static case and suggest increased large-scale mixing when the pin is driven at the shedding frequency (350 Hz). Supported by the Boeing Company.

  19. Mach 10 computational study of a three-dimensional scramjet inlet flow field

    NASA Technical Reports Server (NTRS)

    Holland, Scott D.

    1995-01-01

    The present work documents the computational results for a combined computational and experimental parametric study of the internal aerodynamics of a generic three-dimensional sidewall-compression scramjet inlet configuration at Mach 10. The three-dimensional Navier-Stokes code SCRAMIN was chosen for the computational portion of the study because it uses a well-known and well-proven numerical scheme and has shown favorable comparison with experiment at Mach numbers between 2 and 6. One advantage of CFD was that it provided flow field data for a detailed examination of the internal flow characteristics in addition to the surface properties. The experimental test matrix at Mach 10 included three geometric contraction ratios (3, 5, and 9), three Reynolds numbers (0.55 x 10(exp 6) per foot, 1.14 x 10(exp 6) per foot, and 2.15 x 10(exp 6) per foot), and three cowl positions (at the throat and two forward positions). Computational data for two of these configurations (the contraction ratio of 3, Re = 2.15 x 10(exp 6) per foot, at two cowl positions) are presented along with a detailed analysis of the flow interactions in successive computational planes.

  20. Mach 10 computational study of a three-dimensional scramjet inlet flow field

    NASA Technical Reports Server (NTRS)

    Holland, Scott D.

    1995-01-01

    The present work documents the computational results for a combined computational and experimental parametric study of the internal aerodynamics of a generic three-dimensional sidewall-compression scramjet inlet configuration at Mach 10. The three-dimensional Navier-Stokes code SCRAMIN was chosen for the computational portion of the study because it uses a well-known and well-proven numerical scheme and has shown favorable comparison with experiment at Mach numbers between 2 and 6. One advantage of CFD was that it provided flow field data for a detailed examination of the internal flow characteristics in addition to the surface properties. The experimental test matrix at mach 10 included three geometric contraction ratios (3, 5, and 9), three Reynolds numbers (0.55 x 10(exp 6) per foot, 1.14 x 10(exp 6) per foot, and 2.15 x 10(exp 6) per foot), and three cowl positions (at the throat and two forward positions). Computational data for two of these configurations (the contraction ratio of 3, Re = 2.15 x 10 (exp 6) per foot, at two cowl positions) are presented along with a detailed analysis of the flow interactions in successive computational planes.

  1. A field study of unstable preferential flow during soil water redistribution

    NASA Astrophysics Data System (ADS)

    Wang, Zhi; Wu, Laosheng; Harter, Thomas; Lu, Jianhang; Jury, William A.

    2003-04-01

    Reversal of the matric potential gradient during redistribution of soil water following infiltration has been hypothesized as a cause of preferential flow by inducing a fluid instability at the leading edge of the wetting front. In this paper, we present results of 17 field experiments carried out to quantify the effects of redistribution on preferential flow in nonstructured soils. The experiments were performed in three field soils (Superstition sand, Delhi sand, and Hanford sandy loam) under saturating and nonsaturating water application rates. Water flow patterns were monitored at various times during redistribution with photography using anionic dyes and by intensive core sampling of bromide added during infiltration. The soil surface was either tilled or undisturbed, exposed or covered with a plastic membrane, and the top 20-cm fine layer was either left in place or removed in various treatments. The infiltration water containing tracers was applied continuously and uniformly to the surface of a 2 × 1.2 m2 field plot using a moving spray system. After the soil received 8 to 20 cm of water, a trench was dug adjacent to the plot and vertical soil profiles were exposed at different times and positions to visualize the redistribution process. Some profiles were intensively sampled by soil coring along the trench face and analyzed for water content and bromide concentration to quantify the redistribution of water in the wetted zones. The observed two- and three-dimensional distribution of the water tracers clearly indicated the development of unstable flow during redistribution in two of the three soil types studied but not in the coarsest-textured Superstition sand. Symptoms of instability included irregularly shaped fingers that tended to become narrower toward their tips, isolated patches, and highly concentrated areas of the tracers indicating signs of converging and intermittent flow. The measured tortuosity of the wetting front was near 1.0 at the end of

  2. Flow field studies on a micro-air-vehicle-scale cycloidal rotor in forward flight

    NASA Astrophysics Data System (ADS)

    Lind, Andrew H.; Jarugumilli, Tejaswi; Benedict, Moble; Lakshminarayan, Vinod K.; Jones, Anya R.; Chopra, Inderjit

    2014-12-01

    This paper examines the flow physics and principles of force production on a cycloidal rotor (cyclorotor) in forward flight. The cyclorotor considered here consists of two blades rotating about a horizontal axis, with cyclic pitch angle variation about the blade quarter-chord. The flow field at the rotor mid-span is analyzed using smoke flow visualization and particle image velocimeV are compared with flow fields predicted using 2D CFD and time-averaged force measurements acquired in an open-jet wind tunnel at three advance ratios. It is shown that the experimental flow field is nearly two dimensional at μ = 0.73 allowing for qualitative comparisons to be made with CFD. The incoming flow velocity decreases in magnitude as the flow passes through the retreating (upper) half of the rotor and is attributed to power extraction by the blades. A significant increase in flow velocity is observed across the advancing (lower) half of the rotor. The aerodynamic analysis demonstrates that the blades accelerate the flow through the lower aft region of the rotor, where they operate in a high dynamic pressure environment. This is consistent with CFD-predicted values of instantaneous aerodynamic forces which reveal that the aft section of the rotor is the primary region of force production. Phase-averaged flow field measurements showed two blade wakes in the flow, formed by each of the two blades. Analysis of the blades at several azimuthal positions revealed two significant blade-wake interactions. The locations of these blade-wake interactions are correlated with force peaks in the CFD-predicted instantaneous blade forces and highlight their importance to the generation of lift and propulsive force of the cyclorotor.

  3. Analytical and experimental study of axisymmetric truncated plug nozzle flow fields

    NASA Technical Reports Server (NTRS)

    Muller, T. J.; Sule, W. P.; Fanning, A. E.; Giel, T. V.; Galanga, F. L.

    1972-01-01

    Experimental and analytical investigation of the flow field and base pressure of internal-external-expansion truncated plug nozzles are discussed. Experimental results for two axisymmetric, conical plug-cylindrical shroud, truncated plug nozzles are presented for both open and closed wake operations. These results include extensive optical and pressure data covering nozzle flow field and base pressure characteristics, diffuser effects, lip shock strength, Mach disc behaviour, and the recompression and reverse flow regions. Transonic experiments for a special planar transonic section are presented. An extension of the analytical method of Hall and Mueller to include the internal shock wave from the shroud exit is presented for closed wake operation. Results of this analysis include effects on the flow field and base pressure of ambient pressure ratio, nozzle geometry, and the ratio of specific heats. Static thrust is presented as a function of ambient pressure ratio and nozzle geometry. A new transonic solution method is also presented.

  4. Preliminary study of the effect of the turbulent flow field around complex surfaces on their acoustic characteristics

    NASA Technical Reports Server (NTRS)

    Olsen, W. A.; Boldman, D.

    1978-01-01

    Fairly extensive measurements have been conducted of the turbulent flow around various surfaces as a basis for a study of the acoustic characteristics involved. In the experiments the flow from a nozzle was directed upon various two-dimensional surface configurations such as the three-flap model. A turbulent flow field description is given and an estimate of the acoustic characteristics is provided. The developed equations are based upon fundamental theories for simple configurations having simple flows. Qualitative estimates are obtained regarding the radiation pattern and the velocity power law. The effect of geometry and turbulent flow distribution on the acoustic emission from simple configurations are discussed.

  5. Morphological complexities and hazards during the emplacement of channel-fed `a`ā lava flow fields: A study of the 2001 lower flow field on Etna

    NASA Astrophysics Data System (ADS)

    Applegarth, L. J.; Pinkerton, H.; James, M. R.; Calvari, S.

    2010-08-01

    Long-lived basaltic eruptions often produce structurally complex, compound `a`ā flow fields. Here we reconstruct the development of a compound flow field emplaced during the 2001 eruption of Mt. Etna (Italy). Following an initial phase of cooling-limited advance, the reactivation of stationary flows by superposition of new units caused significant channel drainage. Later, blockages in the channel and effusion rate variations resulted in breaching events that produced two new major flow branches. We also examined small-scale, late-stage ‘squeeze-up’ extrusions that were widespread in the flow field. We classified these as ‘flows’, ‘tumuli’ or ‘spines’ on the basis of their morphology, which depended on the rheology, extrusion rate and cooling history of the lava. Squeeze-up flows were produced when the lava was fluid enough to drain away from the source bocca, but fragmented to produce blade-like features that differed markedly from `a`ā clinker. As activity waned, increased cooling and degassing led to lava arriving at boccas with a higher yield strength. In many cases this was unable to flow after extrusion, and laterally extensive, near-vertical sheets of lava developed. These are considered to be exogenous forms of tumuli. In the highest yield strength cases, near-solid lava was extruded from the flow core as a result of ramping, forming spines. The morphology and location of the squeeze-ups provides insight into the flow rheology at the time of their formation. Because they represent the final stages of activity of the flow, they may also help to refine estimates of the most advanced rheological states in which lava can be considered to flow. Our observations suggest that real-time monitoring of compound flow field evolution may allow complex processes such as channel breaching and bocca formation to be forecast. In addition, documenting the occurrence and morphology of squeeze-ups may allow us to determine whether there is any risk of a

  6. Internal flow field studies in a simulated cylindrical port rocket chamber

    NASA Astrophysics Data System (ADS)

    Dunlap, R.; Blackner, A. M.; Waugh, R. C.; Brown, R. S.; Willoughby, P. G.

    1990-12-01

    The present experimental characterization of the mean and fluctuating flow field along the length of a simulated cylindrical port rocket chamber employed flow simulations in which ambient-temperature nitrogen was uniformly injected along the walls of a porous-tube chamber connected to a choked sonic nozzle. The data obtained indicate that velocity fluctuations near the head of the chamber generally decrease in intensity relative to the centerline speed over the first five port diameters. Regular velocity fluctuations then appear near the wall, just ahead of the transition to turbulent flow; vortical disturbances are noted to exhibit pairing as they move away from the wall. Both buoyant flow influences and flow spinning are discovered in the forward portions of the chamber.

  7. Cyclical magnetic field flow fractionation

    NASA Astrophysics Data System (ADS)

    Tasci, T. O.; Johnson, W. P.; Gale, B. K.

    2012-04-01

    In this study, a new magnetic field flow fractionation (FFF) system was designed and modeled by using finite element simulations. Other than current magnetic FFF systems, which use static magnetic fields, our system uses cyclical magnetic fields. Results of the simulations show that our cyclical magnetic FFF system can be used effectively for the separation of magnetic nanoparticles. Cyclical magnetic FFF system is composed of a microfluidic channel (length = 5 cm, height = 30 μm) and 2 coils. Square wave currents of 1 Hz (with 90 deg of phase difference) were applied to the coils. By using Comsol Multiphysics 3.5a, magnetic field profile and corresponding magnetic force exerted on the magnetite nanoparticles were calculated. The magnetic force data were exported from Comsol to Matlab. In Matlab, a parabolic flow profile with maximum flow speed of 0.4 mL/h was defined. Particle trajectories were obtained by the calculation of the particle speeds resulted from both magnetic and hydrodynamic forces. Particle trajectories of the particles with sizes ranging from 10 to 50 nm were simulated and elution times of the particles were calculated. Results show that there is a significant difference between the elution times of the particles so that baseline separation of the particles can be obtained. In this work, it is shown that by the application of cyclical magnetic fields, the separation of magnetic nanoparticles can be done efficiently.

  8. Study of Fluid Flow Control in Protein Crystallization using Strong Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Ramachandran, Narayanan; Leslie, Fred; Ciszak, Ewa

    2002-01-01

    positioning the crystal growth cell so that the magnetic susceptibility force counteracts terrestrial gravity. The general objective is to test the hypothesis of convective control using a strong magnetic field and magnetic field gradient and to understand the nature of the various forces that come into play. Specifically we aim to delineate causative factors and to quantify them through experiments, analysis and numerical modeling. Once the basic understanding is obtained, the study will focus on testing the hypothesis on proteins of pyruvate dehydrogenase complex (PDC), proteins E1 and E3. Obtaining high crystal quality of these proteins is of great importance to structural biologists since their structures need to be determined. Specific goals for the investigation are: 1. To develop an understanding of convection control in diamagnetic fluids with concentration gradients through experimentation and numerical modeling. Specifically solutal buoyancy driven convection due to crystal growth will be considered. 2. To develop predictive measures for successful crystallization in a magnetic field using analyses and numerical modeling for use in future protein crystal growth experiments. This will establish criteria that can be used to estimate the efficacy of magnetic field flow damping on crystallization of candidate proteins. 3. To demonstrate the understanding of convection damping by high magnetic fields to a class of proteins that is of interest and whose structure is as yet not determined. 4. To compare quantitatively, the quality of the grown crystals with and without a magnetic field. X-ray diffraction techniques will be used for the comparative studies. In a preliminary set of experiments, we studied crystal dissolution effects in a 5 Tesla magnet available at NASA Marshall Space Flight Center (MSFC). Using a Schlieren setup, a 1mm crystal of Alum (Aluminum-Potassium Sulfate) was introduced in a 75% saturated solution and the resulting dissolution plume was observed

  9. Rheo-Optical Studies on a Polymer Liquid Crystal Under the Influence of Flow or Magnetic Fields.

    NASA Astrophysics Data System (ADS)

    Srinivasarao, Mohan

    1990-01-01

    The response of a lyotropic liquid crystal to an external perturbing field (flow or magnetic field) has been studied. Solutions of rodlike poly(1,4-phenylene -2,6-benzobisthiazole) (PBT) in methane sulfonic acid (MSA) have been used. The study is primarily limited to the anisotropic phase. Two molecular weights were used, both forming a liquid-crystalline phase above 3% by weight of the polymer in solution. Flow birefringence measurements were attempted to characterize flow-induced orientation in the nematic phase. However, a stable, uniform, steady-state flow condition was not reached. The transmitted intensities of polarized light, both with and without an analyzer, fluctuate rapidly, indicating that a stable, uniform flow did not obtain in torsional shear flow. By contrast, a constant stress was measured above 100 units of strain. During the course of this study, we were successful in obtaining monodomain nematic solutions. Monodomains were used to study the response of the material to external fields (flow or magnetic field). Experiments were done in the twist geometry in an effort to obtain the twist elastic constant for the solutions. We found that an instability is created on the application of a magnetic field, producing a phase grating. The instability has been characterized by light microscopy, fluorescence polarization and conoscopy. Theoretical description of this instability is unavailable as yet. We have demonstrated that the instability involves a three -dimensional flow pattern which gives rise to a reorientation of the director in three dimensions. Monodomains were used to study the flow properties of PBT solutions. Microscopic observations were made on textures created during flow. Conoscopy was used to study the director distortion at the onset of shear flows. We have established that alpha_2/ alpha_3 is less than zero, giving rise to unstable flow conditions. Situations with flow parallel and perpendicular to the director were examined. We have

  10. Flow field characteristics study of a flapping airfoil using computational fluid dynamics

    NASA Astrophysics Data System (ADS)

    Amiralaei, M. R.; Alighanbari, H.; Hashemi, S. M.

    2011-10-01

    The flow field of a flapping airfoil in Low Reynolds Number (LRN) flow regime is associated with complex nonlinear vortex shedding and viscous phenomena. The respective fluid dynamics of such a flow is investigated here through Computational Fluid Dynamics (CFD) based on the Finite Volume Method (FVM). The governing equations are the unsteady, incompressible two-dimensional Navier-Stokes (N-S) equations. The airfoil is a thin ellipsoidal geometry performing a modified figure-of-eight-like flapping pattern. The flow field and vortical patterns around the airfoil are examined in detail, and the effects of several unsteady flow and system parameters on the flow characteristics are explored. The investigated parameters are the amplitude of pitching oscillations, phase angle between pitching and plunging motions, mean angle of attack, Reynolds number (Re), Strouhal number (St) based on the translational amplitudes of oscillations, and the pitching axis location ( x / c ). It is shown that these parameters change the instantaneous force coefficients quantitatively and qualitatively. It is also observed that the strength, interaction, and convection of the vortical structures surrounding the airfoil are significantly affected by the variations of these parameters.

  11. Ground vortex flow field investigation

    NASA Technical Reports Server (NTRS)

    Kuhn, Richard E.; Delfrate, John H.; Eshleman, James E.

    1988-01-01

    Flow field investigations were conducted at the NASA Ames-Dryden Flow Visualization Facility (water tunnel) to investigate the ground effect produced by the impingement of jets from aircraft nozzles on a ground board in a STOL operation. Effects on the overall flow field with both a stationary and a moving ground board were photographed and compared with similar data found in other references. Nozzle jet impingement angles, nozzle and inlet interaction, side-by-side nozzles, nozzles in tandem, and nozzles and inlets mounted on a flat plate model were investigated. Results show that the wall jet that generates the ground effect is unsteady and the boundary between the ground vortex flow field and the free-stream flow is unsteady. Additionally, the forward projection of the ground vortex flow field with a moving ground board is one-third less than that measured over a fixed ground board. Results also showed that inlets did not alter the ground vortex flow field.

  12. Magnetic Nanoparticle Drug Carriers and their Study by Quadrupole Magnetic Field-Flow Fractionation

    PubMed Central

    Williams, P. Stephen; Carpino, Francesca; Zborowski, Maciej

    2009-01-01

    Magnetic nanoparticle drug carriers continue to attract considerable interest for drug targeting in the treatment of cancers and other pathological conditions. The efficient delivery of therapeutic levels of drug to a target site while limiting nonspecific, systemic toxicity requires optimization of the drug delivery materials, the applied magnetic field, and the treatment protocol. The history and current state of magnetic drug targeting is reviewed. While initial studies involved micron-sized and larger carriers, and work with these microcarriers continues, it is the sub-micron carriers or nanocarriers that are of increasing interest. An aspect of magnetic drug targeting using nanoparticle carriers that has not been considered is then addressed. This aspect involves the variation in the magnetic properties of the nanocarriers. Quadrupole magnetic field-flow fractionation (QMgFFF) is a relatively new technique for characterizing magnetic nanoparticles. It is unique in its capability of determining the distribution in magnetic properties of a nanoparticle sample in suspension. The development and current state of this technique is also reviewed. Magnetic nanoparticle drug carriers have been found by QMgFFF analysis to be highly polydisperse in their magnetic properties, and the strength of response of the particles to magnetic field gradients is predicted to vary by orders of magnitude. It is expected that the least magnetic fraction of a formulation will contribute the most to systemic toxicity, and the depletion of this fraction will result in a more effective drug carrying material. A material that has a reduced systemic toxicity will allow higher doses of cytotoxic drugs to be delivered to the tumor with reduced side effects. Preliminary experiments involving a novel method of refining a magnetic nanoparticle drug carrier to achieve this result are described. QMgFFF is used to characterize the refined and unrefined material. PMID:19591456

  13. Unsaturated flow dynamics during irrigation with wastewater: field and modelling study

    NASA Astrophysics Data System (ADS)

    Martinez-Hernandez, V.; de Miguel, A.; Meffe, R.; Leal, M.; González-Naranjo, V.; de Bustamante, I.

    2012-04-01

    . Data from the lysimeter and soil moisture probes were used to calibrate the model. The overall simulation time period included the dry (irrigation as main source of water) and the wet season (precipitation as main source of water). Future investigation concerning groundwater affections and contaminant transport at the field site will be based on the results obtained through the flow model developed in this study.

  14. Study of the flow field in the magnetic rod interfacial stress rheometer.

    PubMed

    Verwijlen, Tom; Moldenaers, Paula; Stone, Howard A; Vermant, Jan

    2011-08-01

    Several technological applications, consumer products, and biological systems derive their functioning from the presence of a complex fluid interface with viscoelastic interfacial rheological properties. Measurements of the "excess" rheological properties of such an interface are complicated by the intimate coupling of the bulk and interfacial flows. In the present work, analytical, numerical, and experimental results of the interfacial flow fields in a magnetic rod interfacial stress rheometer (ISR) are presented. Mathematical solutions are required to correct the experimentally determined apparent interfacial shear moduli and phase angles for the drag exerted by the surrounding phases, especially at low Boussinesq numbers. Starting from the Navier-Stokes equations and using the generalized Boussinesq-Scriven equation as a suitable boundary condition, the problem is solved both analytically and numerically. In addition, experimental data of the interfacial flow field are reported, obtained by following the trajectories of tracer particles at the interface with time. Good agreement is found between the three methods, indicating that both the analytical solution and the numerical simulations give an adequate description of the flow field and the resulting local interfacial shear rate at the rod. Based on these results, an algorithm to correct the experimental data of the ISR is proposed and evaluated, which can be extended to different types of interfacial shear rheometers and geometries. An increased accuracy is obtained and the measurement range of the ISR is expanded toward viscosities and elastic moduli of smaller magnitude. PMID:21696160

  15. Supersonic reacting internal flow fields

    NASA Technical Reports Server (NTRS)

    Drummond, J. Philip

    1989-01-01

    The national program to develop a trans-atmospheric vehicle has kindled a renewed interest in the modeling of supersonic reacting flows. A supersonic combustion ramjet, or scramjet, has been proposed to provide the propulsion system for this vehicle. The development of computational techniques for modeling supersonic reacting flow fields, and the application of these techniques to an increasingly difficult set of combustion problems are studied. Since the scramjet problem has been largely responsible for motivating this computational work, a brief history is given of hypersonic vehicles and their propulsion systems. A discussion is also given of some early modeling efforts applied to high speed reacting flows. Current activities to develop accurate and efficient algorithms and improved physical models for modeling supersonic combustion is then discussed. Some new problems where computer codes based on these algorithms and models are being applied are described.

  16. Inlet flow field investigation. Part 1: Transonic flow field survey

    NASA Technical Reports Server (NTRS)

    Yetter, J. A.; Salemann, V.; Sussman, M. B.

    1984-01-01

    A wind tunnel investigation was conducted to determine the local inlet flow field characteristics of an advanced tactical supersonic cruise airplane. A data base for the development and validation of analytical codes directed at the analysis of inlet flow fields for advanced supersonic airplanes was established. Testing was conducted at the NASA-Langley 16-foot Transonic Tunnel at freestream Mach numbers of 0.6 to 1.20 and angles of attack from 0.0 to 10.0 degrees. Inlet flow field surveys were made at locations representative of wing (upper and lower surface) and forebody mounted inlet concepts. Results are presented in the form of local inlet flow field angle of attack, sideflow angle, and Mach number contours. Wing surface pressure distributions supplement the flow field data.

  17. Visualization study on the static flow field around a straight-bladed vertical axis wind turbine

    NASA Astrophysics Data System (ADS)

    Li, Yan; Tagawa, Kotaro

    2010-03-01

    Visual experiments based on the smoke wire way were carried out on a small model of Straight-blade Vertical Axis Wind Turbine (SB-VAWT) to invest the relationship between the static flow field characteristics and the rotor azimuth angle. The test rotor had 3 blades with NACA0018 aerofoil. The rotor diameter and blade chord were 0.3m and 0.07m, respectively. Visual photos of the static flow path lines in and around the rotor were obtained at every 5 degrees of the azimuth angle. Further, numerical computations of the static flow filed were also carried out for comparison with the same situation as the visual tests and the static torques at different azimuth angles were calculated. According to the results of visual tests and computations, the dependence of the starting performance on the azimuth angle was discussed. The solidity is an important factor affecting the starting performance of the SB-VAWT.

  18. Visualization study on the static flow field around a straight-bladed vertical axis wind turbine

    NASA Astrophysics Data System (ADS)

    Li, Yan; Tagawa, Kotaro

    2009-12-01

    Visual experiments based on the smoke wire way were carried out on a small model of Straight-blade Vertical Axis Wind Turbine (SB-VAWT) to invest the relationship between the static flow field characteristics and the rotor azimuth angle. The test rotor had 3 blades with NACA0018 aerofoil. The rotor diameter and blade chord were 0.3m and 0.07m, respectively. Visual photos of the static flow path lines in and around the rotor were obtained at every 5 degrees of the azimuth angle. Further, numerical computations of the static flow filed were also carried out for comparison with the same situation as the visual tests and the static torques at different azimuth angles were calculated. According to the results of visual tests and computations, the dependence of the starting performance on the azimuth angle was discussed. The solidity is an important factor affecting the starting performance of the SB-VAWT.

  19. Constraining Eruptive Conditions From Lava Flow Morphometry: A Case Study With Field Evidence

    NASA Astrophysics Data System (ADS)

    Bowles, Z. R.; Clarke, A.; Greeley, R.

    2007-12-01

    Volcanism is widely recognized as one of the primary factors affecting the surfaces of solid planets and satellites throughout the solar system. Basaltic lava is thought to be the most common composition based on observed features typical of basaltic eruptions found on Earth. Lava flows are one of the most easily recognizable landforms on planetary surfaces and their features may provide information about eruption dynamics, lava rheology, and potential hazards. More recently, researchers have taken a multi-faceted approach to combine remote sensing, field observations and quantitative modeling to constrain volcanic activity on Earth and other planets. Here we test a number of published models, including empirically derived relationships from Mt. Etna and Kilauea, models derived from laboratory experiments, and theoretical models previously applied to remote sensing of planetary surfaces, against well-documented eruptions from the literature and field observations. We find that the Graetz (Hulme and Felder, 1977, Phil.Trans., 285, 227 - 234) method for estimating effusion rates compares favorably with published eruption data, while, on the other hand, inverting lava flow length prediction models to estimate effusion rates leads to several orders of magnitude in error. The Graetz method also better constrains eruption duration. Simple radial spreading laws predict Hawaiian lava flow lengths quite well, as do using the thickness of the lava flow front and chilled crust. There was no observed difference between results from models thought to be exclusive to aa or pahoehoe flow fields. Interpreting historic conditions should therefore follow simple relationships to observable morphologies no matter the composition or surface texture. We have applied the most robust models to understand the eruptive conditions and lava rheology of the Batamote Mountains near Ajo, AZ, an eroded shield volcano in southern Arizona. We find effusion rates on the order of 100 - 200 cubic

  20. Study of Fluid Flow Control in Protein Crystallization using Strong Magnetic Fields

    NASA Astrophysics Data System (ADS)

    Ramachandran, Narayanan; Leslie, Fred; Ciszak, Ewa

    2002-11-01

    positioning the crystal growth cell so that the magnetic susceptibility force counteracts terrestrial gravity. The general objective is to test the hypothesis of convective control using a strong magnetic field and magnetic field gradient and to understand the nature of the various forces that come into play. Specifically we aim to delineate causative factors and to quantify them through experiments, analysis and numerical modeling. Once the basic understanding is obtained, the study will focus on testing the hypothesis on proteins of pyruvate dehydrogenase complex (PDC), proteins E1 and E3. Obtaining high crystal quality of these proteins is of great importance to structural biologists since their structures need to be determined. Specific goals for the investigation are: 1. To develop an understanding of convection control in diamagnetic fluids with concentration gradients through experimentation and numerical modeling. Specifically solutal buoyancy driven convection due to crystal growth will be considered. 2. To develop predictive measures for successful crystallization in a magnetic field using analyses and numerical modeling for use in future protein crystal growth experiments. This will establish criteria that can be used to estimate the efficacy of magnetic field flow damping on crystallization of candidate proteins. 3. To demonstrate the understanding of convection damping by high magnetic fields to a class of proteins that is of interest and whose structure is as yet not determined. 4. To compare quantitatively, the quality of the grown crystals with and without a magnetic field. X-ray diffraction techniques will be used for the comparative studies. In a preliminary set of experiments, we studied crystal dissolution effects in a 5 Tesla magnet available at NASA Marshall Space Flight Center (MSFC). Using a Schlieren setup, a 1mm crystal of Alum (Aluminum-Potassium Sulfate) was introduced in a 75% saturated solution and the resulting dissolution plume was observed

  1. Study of Fluid Flow Control in Protein Crystallization using Strong Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Ramachandran, Narayanan; Leslie, Fred; Ciszak, Ewa

    2002-01-01

    positioning the crystal growth cell so that the magnetic susceptibility force counteracts terrestrial gravity. The general objective is to test the hypothesis of convective control using a strong magnetic field and magnetic field gradient and to understand the nature of the various forces that come into play. Specifically we aim to delineate causative factors and to quantify them through experiments, analysis and numerical modeling. Once the basic understanding is obtained, the study will focus on testing the hypothesis on proteins of pyruvate dehydrogenase complex (PDC), proteins E1 and E3. Obtaining high crystal quality of these proteins is of great importance to structural biologists since their structures need to be determined. Specific goals for the investigation are: 1. To develop an understanding of convection control in diamagnetic fluids with concentration gradients through experimentation and numerical modeling. Specifically solutal buoyancy driven convection due to crystal growth will be considered. 2. To develop predictive measures for successful crystallization in a magnetic field using analyses and numerical modeling for use in future protein crystal growth experiments. This will establish criteria that can be used to estimate the efficacy of magnetic field flow damping on crystallization of candidate proteins. 3. To demonstrate the understanding of convection damping by high magnetic fields to a class of proteins that is of interest and whose structure is as yet not determined. 4. To compare quantitatively, the quality of the grown crystals with and without a magnetic field. X-ray diffraction techniques will be used for the comparative studies. In a preliminary set of experiments, we studied crystal dissolution effects in a 5 Tesla magnet available at NASA Marshall Space Flight Center (MSFC). Using a Schlieren setup, a 1mm crystal of Alum (Aluminum-Potassium Sulfate) was introduced in a 75% saturated solution and the resulting dissolution plume was observed

  2. Bonneville Second Powerhouse Tailrace and High Flow Outfall: ADCP and drogue release field study

    SciTech Connect

    Cook, Christopher B.; Richmond, Marshall C.; Guensch, Gregory R.

    2001-03-20

    The Bonneville Project is one of four US Army Corps of Engineers operated dams along the Lower Columbia River. Each year thousands of smelt pass through this Project on their way to the Pacific Ocean. High flow outfalls, if specifically designed for fish passage, are thought to have as good or better smelt survival rates as spillways. To better understand the hydrodynamic flow field around an operating outfall, the Corps of Engineers commissioned measurement of water velocities in the tailrace of the Second Powerhouse. These data also are necessary for proper calibration and verification of three-dimensional numerical models currently under development at PNNL. Hydrodynamic characterization of the tailrace with and without the outfall operating was accomplished through use of a surface drogue and acoustic Doppler current profiler (ADCP). Both the ADCP and drogue were linked to a GPS (global positioning system); locating the data in both space and time. Measurements focused on the area nearest to the high flow outfall, however several ADCP transects and drogue releases were performed away from the outfall to document ambient flow field conditions when the outfall was not operating.

  3. Experimental study of the flow field inside a whirling annular seal

    NASA Technical Reports Server (NTRS)

    Morrison, Gerald L.; Deotte, Robert E., Jr.; Thames, H. Davis, III

    1992-01-01

    The flow field inside a whirling annular seal was measured using a 3-D Laser Doppler Anemometer (LDA) system. The seal investigated has a clearance of 1.27 mm, a length of 37.3 mm, and is mounted on a drive shaft with a 50 percent eccentricity ratio. This results in the rotor whirling at the same speed as the shaft rotation (whirl ratio = 1.0). The seal is operated at Reynolds number of 12,000 and a Taylor number of 6,300 (3,600 rpm). The 3-D LDA system is equipped with a rotary encoding system which is used to produce phase averaged measurements of the entire mean velocity vector field and Reynolds stress tensor field from 0.13 mm upstream to 0.13 mm downstream of the seal. The mean velocity field reveals a highly three dimensional flow field with large radial velocities near the inlet of the seal as well as a recirculation zone on the rotor surface. The location of maximum mean axial velocity migrates from the pressure side of the rotor at the inlet to the suction side at turbulence kinetic energy. However, turbulence production and dissipation attain equilibrium fairly quickly with remaining relatively constant over the last half of the seal.

  4. Integrated flow field (IFF) structure

    NASA Technical Reports Server (NTRS)

    Pien, Shyhing M. (Inventor); Warshay, Marvin (Inventor)

    2012-01-01

    The present disclosure relates in part to a flow field structure comprising a hydrophilic part and a hydrophobic part communicably attached to each other via a connecting interface. The present disclosure further relates to electrochemical cells comprising the aforementioned flow fields.

  5. An experimental study of the flow field surrounding a subsonic jet in a cross flow. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Dennis, Robert Foster

    1993-01-01

    An experimental investigation of the flow interaction of a 5.08 cm (2.00 in.) diameter round subsonic jet exhausting perpendicularly to a flat plate in a subsonic cross flow was conducted in the NASA Ames 7x1O ft. Wind Tunnel Number One. Flat plate surface pressures were measured at 400 locations in a 30.48 cm (12.0 in.) concentric circular array surrounding the jet exit. Results from these measurements are provided in tabular and graphical form for jet-to-crossflow velocity ratios ranging from 4 to 12, and for jet exit Mach numbers ranging from 0.50 to 0.93. Laser doppler velocimeter (LDV) three component velocity measurements were made in selected regions in the developed jet plume and near the flat plate surface, at a jet Mach number of 0.50 and jet-to-crossflow velocity ratios of 6 and 8. The results of both pressure and LDV measurements are compared with the results of previous experiments. In addition, pictures of the jet plume shape at jet velocity ratios ranging from 4 to 12 were obtained using schleiren photography. The LDV measurements are consistent with previous work, but more extensive measurements will be necessary to provide a detailed picture of the flow field. The surface pressure results compare closely with previous work and provide a useful characterization of jet induced surface pressures. The results demonstrate the primary influence of jet velocity ratio and the secondary influence of jet Mach number in determining such surface pressures.

  6. Study of Radially Varying Magnetic Field on Blood Flow through Catheterized Tapered Elastic Artery with Overlapping Stenosis

    NASA Astrophysics Data System (ADS)

    Nadeem, S.; Ijaz, S.

    2015-11-01

    A precise model has been developed for studying the influence of metallic nanoparticles on blood flow through catheterized tapered elastic arteries with radially varying magnetic field. The model is solved under the mild stenosis approximation by considering blood as viscous fluid. The influence of different flow parameters associated with this problem such as Hartmann number, nanoparticle volume fraction, Grashof number and heat source or sink parameter is analyzed by plotting the graphs of the wall shear stress, resistance impedance to blood flow and stream lines. The influence of the radially varying magnetic field on resistance impedance to flow is analyzed and it is observed that the significantly strong magnetic force tends to increase in resistance.

  7. A comparative study of nonreflecting far-field boundary condition procedures for unsteady transonic flow computation

    NASA Technical Reports Server (NTRS)

    Kwak, D.

    1981-01-01

    Various nonreflecting far-field boundary condition procedures are compared by implementing them in the computer code LTRAN2. This code solves the implicit finite-difference representation of the small-disturbance equations for transonic flows about airfoils. The first- and second-approximate nonreflecting conditions, as proposed by Engquist and Majda, are compared with the condition derived from the full-characteristic equation. The far-field boundary conditions and the description of the algorithm for implementing these conditions in LTRAN2 are discussed. Various cases are computed and compared with results from the older, more conventional procedures. One concludes that the full-characteristic equation produces the most effective results, thus allowing the far-field boundary to be located closer to the airfoil; this decreases the computer time required to obtain the solution because fewer mesh points are required.

  8. Oxidation flow reactors (OFRs): overview of recent field and modeling studies

    NASA Astrophysics Data System (ADS)

    Jimenez, Jose-Luis; Palm, Brett B.; Peng, Zhe; Hu, Weiwei; Ortega, Amber M.; Li, Rui; Campuzano-Jost, Pedro; Day, Douglas A.; Stark, Harald; Brune, William H.; de Gouw, Joost; Schroder, Jason

    2016-04-01

    Oxidation flow reactors (OFRs) are popular tools for studying SOA formation and aging in both laboratory and field experiments. In an OFR, the concentration of an oxidant (OH, O3, or NO3) can be increased, leading to hours-months of equivalent atmospheric oxidation during the several-minute OFR residence time. Using gas- and particle-phase measurements from several recent field campaigns, we demonstrate SOA formation after oxidation of ambient air in an OFR. Typically, more SOA formation is observed from nighttime air than daytime air. This indicates that the concentration of SOA-forming gases in ambient air is relatively higher at night. Measured ambient VOCs are not able to explain the magnitude of SOA formation in the OFR, suggesting that typically unmeasured S/IVOCs (possibly VOC oxidation products or direct emissions) play a substantial intermediary role in ambient SOA formation. We also present highlights from recent OFR oxidant chemistry modeling studies. HOx, Ox, and photolysis chemistry was modeled for two common OH production methods (utilizing 185+254 nm UV light, or 254 nm only). OH exposure (OHexp) can be estimated within a factor of ~2 using model-derived equations, and can be verified in situ using VOC decay measurements. OHexp is strongly dependent on external OH reactivity, which may cause significant OH suppression in some circumstances (e.g., lab/source studies with high precursor concentrations). UV light photolysis and reaction with oxygen atoms are typically not major reaction pathways. Modeling the fate of condensable low-volatility organic gases (LVOCs) formed in an OFR suggests that LVOC fate is dependent on particle condensational sink. E.g., for the range of particle condensational sink at a remote pine forest, anywhere from 20-80% of produced LVOCs were predicted to condense onto aerosols for an OHexp of ~1 day, with the remainder lost to OFR or sampling line walls. Similar to large chamber wall loss corrections, a correction is needed

  9. Numerical study of the flow field through a transonic linear turbine cascade at design and off-design conditions

    NASA Astrophysics Data System (ADS)

    El-Batsh, Hesham

    The flow field through a transonic linear turbine cascade is studied in this paper at design and off-design conditions. The compressible flow field is obtained by solving the equations governing the fluid flow and heat transfer. Two eddy-viscosity turbulence models are used to simulate the turbulence in turbine cascades: the standard k-e model and the Spalart Allmaras model. The standard k-e model is the most universal and popular model for industrial flow and heat transfer simulations. It has the shortcoming of accurately predicting the profile loss in turbomachinery applications. The Spalart Allmaras model is a relatively recent and simple one-equation model. In this paper, the model is tested for turbomachinery applications. The ability of the model to accurately predict the flow field in turbine cascade is tested. Blade loading, downstream wake distribution, total pressure loss coefficient, and exit flow angle are used in this study with comparisons to the standard k-e model and experimental data. The design condition and the off-design conditions are considered.

  10. A study of the round jet/plane wall flow field

    NASA Technical Reports Server (NTRS)

    Foss, J. F.; Kleis, S. J.

    1971-01-01

    Impingement angles, between the axisymmetric jet axis and the plane wall, from zero to 15 degrees have been examined for nozzle heights of 0.75, 1.0, 1.5 and 2.0 diameters and for: (1) a fully developed pipe flow, and (2) a relatively uniform exit velocity condition. Velocity measurements have been used to define isotach contours and to determine mass, momentum and energy flux values for the near field (within five diameters) of the jet. Surface pressure measurements have been used to define surface pressure forces and jet centerline trajectories. The geometric and flow conditions examined and the interpretation of the results have been motivated by the externally blown flap STOL aircraft application.

  11. WIND TUNNEL STUDY OF THE FLOW FIELD WITHIN AND AROUND OPEN-TOP CHAMBERS USED FOR AIR POLLUTION STUDIES

    EPA Science Inventory

    The EPA Meteorological Wind Tunnel was used to examine the flow field in and around models of open-top field plant growth chambers used to assess the effects of pollutant gases on plant growth. Baffles designed to reduce the ingress of ambient air into the chamber through the ope...

  12. Field Use of Soil Moisture Sensors to Study Water Flow Patterns

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Automated soil water content data are helpful to understand water flow in closed-depression landscapes, with gentle slopes and shallow water table depths. Non-automated neutron probe data are useful for extending analysis to broader spatial areas. The purpose of this study is to show how closed-depr...

  13. Numerical studies of the fluid and optical fields associated with complex cavity flows

    NASA Technical Reports Server (NTRS)

    Atwood, Christopher A.

    1992-01-01

    Numerical solutions for the flowfield about several cavity configurations have been computed using the Reynolds averaged Navier-Stokes equations. Comparisons between numerical and experimental results are made in two dimensions for free shear layers and a rectangular cavity, and in three dimensions for the transonic aero-window problem of the Stratospheric Observatory for Infrared Astronomy (SOFIA). Results show that dominant acoustic frequencies and magnitudes of the self excited resonant cavity flows compare well with the experiment. In addition, solution sensitivity to artificial dissipation and grid resolution levels are determined. Optical path distortion due to the flow field is modelled geometrically and is found to match the experiment. The fluid field was computed using a diagonalized scheme within an overset mesh framework. An existing code, OVERFLOW, was utilized with the additions of characteristic boundary condition and output routines required for reduction of the unsteady data. The newly developed code is directly applicable to a generalized three dimensional structured grid zone. Details are provided in a paper included in Appendix A.

  14. Experimental study of the flow field induced by a resonating piezoelectric flapping wing

    NASA Astrophysics Data System (ADS)

    Bidakhvidi, M. Ahmadi; Shirzadeh, R.; Steenackers, G.; Vanlanduit, S.

    2013-11-01

    Flexible plate structures with integrated piezoelectric patches offer interesting possibilities when considered as actuation mechanisms for energy harvesting devices, cooling devices and propulsion devices of micro-aerial vehicles. Most of the studies reported in literature are based on the assumption of a 2D aerodynamic flow. However, the flow behind a finite span wing is significantly more complex than that of an infinite span wing. In order to corroborate this statement, the present experimental study contains high-speed particle image velocimetry measurements performed on a piezoelectric finite span wing oscillating in air, at 84.8 Hz. The paper focuses on the situation of low Keulegan-Carpenter numbers (KC < 3). The dimensionless KC number describes the relative importance of the drag forces over inertia forces for objects that oscillate in a fluid flow at rest. The evolution of the unsteady vortex structures near the plate is characterized for different conditions. This allows a better understanding of the unsteady aerodynamics of flapping flight. The accomplished experimental data analysis has shown that the flow phenomena are strongly dependent on the KC values.

  15. Transport studies in polymer electrolyte fuel cell with porous metallic flow field at ultra high current density

    NASA Astrophysics Data System (ADS)

    Srouji, Abdul-Kader

    Achieving cost reduction for polymer electrolyte fuel cells (PEFC) requires a simultaneous effort in increasing power density while reducing precious metal loading. In PEFCs, the cathode performance is often limiting due to both the slow oxygen reduction reaction (ORR), and mass transport limitation caused by limited oxygen diffusion and liquid water flooding at high current density. This study is motivated by the achievement of ultra-high current density through the elimination of the channel/land (C/L) paradigm in PEFC flow field design. An open metallic element (OME) flow field capable of operating at unprecedented ultra-high current density (3 A/cm2) introduces new advantages and limitations for PEFC operation. The first part of this study compares the OME with a conventional C/L flow field, through performance and electrochemical diagnostic tools such as electrochemical impedance spectroscopy (EIS). The results indicate the uniqueness of the OME's mass transport improvement. No sign of operation limitation due to flooding is noted. The second part specifically examines water management at high current density using the OME flow field. A unique experimental setup is developed to measure steady-state and transient net water drag across the membrane, in order to characterize the fundamental aspects of water transport at high current density with the OME. Instead of flooding, the new limitation is identified to be anode side dry-out of the membrane, caused by electroosmotic drag. The OME improves water removal from the cathode, which immediately improves oxygen transport and performance. However, the low water content in the cathode reduces back diffusion of water to the membrane, and electroosmotic drag dominates at high current density, leading to dry-out. The third part employs the OME flow field as a tool that avoids C/L effects endemic to a typical flow field, in order to study oxygen transport resistance at the catalyst layer of a PEFC. In open literature, a

  16. Field study of spatial variability in unsaturated flow beneath and adjacent to playas

    NASA Astrophysics Data System (ADS)

    Scanlon, Bridget R.; Goldsmith, Richard S.

    We quantified unsaturated flow beneath playa and adjacent interplaya settings at a site in the Southern High Plains (United States) to resolve issues related to where and how water moves through the unsaturated zone. This is the first study in which the data density (39 boreholes) and the variety of techniques used (physical, chemical, and isotopic) were sufficient to quantify spatial variability in unsaturated flow. Water contents, water potentials, and tritium concentrations were much higher and chloride concentrations were much lower beneath playas than in interplaya settings, which indicated that playas focus recharge. These results refute previous hypotheses that playas act as evaporation pans or that recharge is restricted to the annular region around playas. Water fluxes estimated from environmental tracers ranged from 60 to 120mmyr-1 beneath playas and were <=0.1mmyr-1 during the past 2000-5000 years beneath natural interplaya areas not subjected to ponding. To evaluate the apparent inconsistency between high recharge rates and thick clay layers beneath playas, we applied bromide and FD&C blue dye to evaluate flow processes. These applied tracer experiments showed preferential flow along roots and desiccation cracks through structured clays in the shallow subsurface in playas.

  17. The design of a low-speed wind tunnel for studying the flow field of insects' flight

    NASA Astrophysics Data System (ADS)

    Zhao, Hong-yan; Zhang, Peng-fei; Ma, Yun; Ning, Jian-guo

    2015-03-01

    In this paper, low-speed smoke wind tunnel has been designed and fabricated for the insects' flow field visualization. The test section and the contraction section of the tunnel are optimized and determined as to size by the method of computational fluid dynamics. And fairing devices are equipped in different sections to reduce the turbulence intensity and increase the flow uniformity in the experimental sections. For the smoke visualization of small insects, the smokeemitting equipment has been specially designed and carefully debugged. Composed of wind tunnel, light source and high-speed camera, experimental platform for visualization and filming of insect flight flow field has been established. Besides, the feasible and stable method for insect fixing has been designed. With the smoke wind tunnel, flow filed visualization experiment for the honeybee's flapping was conducted and smoke flow filed in the experiment was recorded and analyzed. Near-filed and far-filed vortex structure when the honeybee fly can be recorded clearly. The experimental results indicate that the experimental platform is appropriate for flow filed study on insects flapping.

  18. Application of holography to the study of helicopter rotor flow fields

    NASA Technical Reports Server (NTRS)

    Baganoff, D.

    1981-01-01

    The feasibility of an experiment which is intended to measure the density field about a model helicopter rotor using holographic interferometry is considered. The numerical simulation used to study the experiment is described as well as the measurement technique itself. Data generated by the simulation are presented and prospects for both determining the density field from these data, and for actually obtaining such data in practice are assessed. A few significant problems which may be expected to arise are indicated and discussed.

  19. Analytical and numerical study on cooling flow field designs performance of PEM fuel cell with variable heat flux

    NASA Astrophysics Data System (ADS)

    Afshari, Ebrahim; Ziaei-Rad, Masoud; Jahantigh, Nabi

    2016-06-01

    In PEM fuel cells, during electrochemical generation of electricity more than half of the chemical energy of hydrogen is converted to heat. This heat of reactions, if not exhausted properly, would impair the performance and durability of the cell. In general, large scale PEM fuel cells are cooled by liquid water that circulates through coolant flow channels formed in bipolar plates or in dedicated cooling plates. In this paper, a numerical method has been presented to study cooling and temperature distribution of a polymer membrane fuel cell stack. The heat flux on the cooling plate is variable. A three-dimensional model of fluid flow and heat transfer in cooling plates with 15 cm × 15 cm square area is considered and the performances of four different coolant flow field designs, parallel field and serpentine fields are compared in terms of maximum surface temperature, temperature uniformity and pressure drop characteristics. By comparing the results in two cases, the constant and variable heat flux, it is observed that applying constant heat flux instead of variable heat flux which is actually occurring in the fuel cells is not an accurate assumption. The numerical results indicated that the straight flow field model has temperature uniformity index and almost the same temperature difference with the serpentine models, while its pressure drop is less than all of the serpentine models. Another important advantage of this model is the much easier design and building than the spiral models.

  20. Rotorcraft Downwash Flow Field Study to Understand the Aerodynamics of Helicopter Brownout

    NASA Technical Reports Server (NTRS)

    Wadcock, Alan J.; Ewing, Lindsay A.; Solis, Eduardo; Potsdam, Mark; Rajagopalan, Ganesh

    2008-01-01

    Rotorcraft brownout is caused by the entrainment of dust and sand particles in helicopter downwash, resulting in reduced pilot visibility during low, slow flight and landing. Recently, brownout has become a high-priority problem for military operations because of the risk to both pilot and equipment. Mitigation of this problem has focused on flight controls and landing maneuvers, but current knowledge and experimental data describing the aerodynamic contribution to brownout are limited. This paper focuses on downwash characteristics of a UH-60 Blackhawk as they pertain to particle entrainment and brownout. Results of a full-scale tuft test are presented and used to validate a high-fidelity Navier-Stokes computational fluid dynamics (CFD) calculation. CFD analysis for an EH-101 Merlin helicopter is also presented, and its flow field characteristics are compared with those of the UH-60.

  1. Study of VTOL in ground-effect flow field including temperature effect

    NASA Technical Reports Server (NTRS)

    Hill, W. G.; Jenkins, R. C.; Kalemaris, S. G.; Siclari, M. J.

    1982-01-01

    Detailed pressure, temperature, and velocity data were obtained for twin-fan configurations in-ground-effect and flow models to aid in predicting pressures and upwash forces on aircraft surfaces were developed. For the basic experiments, 49.5 mm-diameter jets were used, oriented normal to a simulated round plane, with pressurized, heated air providing a jet. The experimental data consisted of: (1) the effect of jet height and temperature on the ground, model, and upwash pressures, and temperatures, (2) the effect of simulated aircraft surfaces on the isolated flow field, (3) the jet-induced forces on a three-dimensional body with various strakes, (4) the effects of non-uniform coannular jets. For the uniform circular jets, temperature was varied from room temperature (24 C) to 232 C. Jet total pressure was varied between 9,300 Pascals and 31,500 Pascals. For the coannular jets, intended to represent turbofan engines, fan temperature was maintained at room temperature while core temperature was varied from room temperature to 437 C. Results are presented.

  2. Palladium Catalysis in Horizontal-Flow Treatment Wells: Field-Scale Design and Laboratory Study

    SciTech Connect

    Munakata, N; Cunningham, J A; Reinhard, M; Ruiz, R; Lebron, C

    2002-03-01

    This paper discusses the field-scale design and associated laboratory experiments for a new groundwater remediation system that combines palladium-catalyzed hydrodehalogenation with the use of dual horizontal-flow treatment wells (HFTWs). Palladium (Pd) catalysts can treat a wide range of halogenated compounds, often completely and rapidly dehalogenating them. The HFTW system recirculates water within the treatment zone and provides the opportunity for multiple treatment passes, thereby enhancing contaminant removal. The combined Pd/HFTW system is scheduled to go on line in mid-2002 at Edwards Air Force Base in southeastern California, with groundwater contaminated with 0.5 to 1.5 mg/L of trichloroethylene (TCE). Laboratory work, performed in conjunction with the field-scale design, provided reaction rates for field-scale design and information on long-term catalyst behavior. The apparent first-order reaction rate constant for TCE was 0.43/min, corresponding to a half-life of 1.6 min. Over the long term (1 to 2 months), the reaction rate decreased, indicating catalyst deactivation. The data show three distinct deactivation rates: a slow rate of 0.03/day over approximately the first month, followed by faster deactivation at 0.16 to 0.19/day. The final, fastest deactivation (0.55/day) was attributed to an artifact of the laboratory setup, which caused unnaturally high sulfide concentrations through bacterial reduction of sulfate to sulfide, a known catalyst poison. Sodium hypochlorite recovered the catalyst activity, and is expected to maintain activity in the field with periodic pulses to regenerate the catalyst and control growth of sulfate-reducing bacteria.

  3. Study of flow field of burning particles in a pyrotechnic flame based on particle image and particle velocity

    NASA Astrophysics Data System (ADS)

    Xue, R.; Xu, H. Q.; Li, Y.; Zhu, C. G.

    2014-11-01

    Studying the burning particles in the pyrotechnic flame is important to acquire the decomposition mechanism and spectral radiance of pyrotechnics. The high speed video (HSV) and particle image velocimetry (PIV) were used in this paper to analyze the flow field and velocity of burning particles in the flame of pyrotechnics. The binary image was obtained through gray scale treatment and adaptive threshold segmentation from HSV and PIV data, by which the coordinate of each particle was marked. On the basis, the movement trajectory of each particle during combustion was pursued by the most recent guidelines algorithm of cancroids matching. Through the method proposed in this study, the velocity variation of each particle was obtained, the approximate distribution of particle quantity at each zone was visualized and the mathematical model of pyrotechnic particle velocity flow field was established.

  4. Iron-rich colloids as carriers of phosphorus in streams: A field-flow fractionation study.

    PubMed

    Baken, Stijn; Regelink, Inge C; Comans, Rob N J; Smolders, Erik; Koopmans, Gerwin F

    2016-08-01

    Colloidal phosphorus (P) may represent an important fraction of the P in natural waters, but these colloids remain poorly characterized. In this work, we demonstrate the applicability of asymmetric flow field-flow fractionation (AF4) coupled to high resolution ICP-MS for the characterization of low concentrations of P-bearing colloids. Colloids from five streams draining catchments with contrasting properties were characterized by AF4-ICP-MS and by membrane filtration. All streams contain free humic substances (2-3 nm) and Fe-bearing colloids (3-1200 nm). Two soft water streams contain primary Fe oxyhydroxide-humic nanoparticles (3-6 nm) and aggregates thereof (up to 150 nm). In contrast, three harder water streams contain larger aggregates (40-1200 nm) which consist of diverse associations between Fe oxyhydroxides, humic substances, clay minerals, and possibly ferric phosphate minerals. Despite the diversity of colloids encountered in these contrasting streams, P is in most of the samples predominantly associated with Fe-bearing colloids (mostly Fe oxyhydroxides) at molar P:Fe ratios between 0.02 and 1.5. The molar P:Fe ratio of the waters explains the partitioning of P between colloids and truly dissolved species. Waters with a high P:Fe ratio predominantly contain truly dissolved species because the Fe-rich colloids are saturated with P, whereas waters with a low P:Fe ratio mostly contain colloidal P species. Overall, AF4-ICP-MS is a suitable technique to characterize the diverse P-binding colloids in natural waters. Such colloids may increase the mobility or decrease the bioavailability of P, and they therefore need to be considered when addressing the transport and environmental effects of P in catchments. PMID:27140905

  5. Passive treatment using coal combustion products: An innovative vertical flow constructed wetland field study

    SciTech Connect

    Nairn, R.W.; Mercer, M.N.; Everett, J.W.

    1999-07-01

    Designs of constructed wetlands for acid mine drainage (AMD) treatment have evolved substantially during the past decade. Current research focuses on the study of vertical-flow treatment systems containing labile organic substrates. Also known as successive alkalinity producing systems (SAPS), these systems emphasize contact of acidic waters with the substrate, thus maximizing biological alkalinity generation, via bacterial sulfate reduction, and abiotic alkalinity generation via carbonate dissolution processes. in this study, a coal combustion product (CCP) was utilized to generate supplementary alkalinity in addition to that provided by traditional substrate materials of spent mushroom substrate (SMS) and high CaCO{sub 3} content limestone. Although limestone is commonly utilized for abiotic alkalinity generation in AMC treatment wetlands, CCPs are not. The preliminary effectiveness of this innovative vertical flow passive treatment system was evaluated during the initial year of operation. The wetlands are successfully retaining iron, aluminum and manganese and are increasing pH, alkalinity, dissolved oxygen (from ,1.0 to >13 mg/L, due to biological productivity), and calcium (from 31 to 385 mg/L, presumably due to limestone and hydrated fly ash dissolution). No hydraulic conductivity problems have been encountered in the initial year of operation. CCPs may offer an attractive alternative, or supplementary, alkalinity generating source for AMD treatment wetlands.

  6. Flow field calculations for afterburner

    NASA Astrophysics Data System (ADS)

    Zhao, Jianxing; Liu, Quanzhong; Liu, Hong

    1995-04-01

    In this paper a calculation procedure for simulating the combustion flow in the afterburner with the heat shield, flame stabilizer and the contracting nozzle is described and evaluated by comparison with experimental data. The modified two-equation k ɛ model is employed to consider the turbulence effects, and the k ɛ g turbulent combustion model is used to determine the reaction rate. To take into account the influence of heat radiation on gas temperature distribution, heat flux model is applied to predictions of heat flux distributions. The solution domain spanned the entire region between centerline and afterburner wall, with the heat shield represented as a blockage to the mesh. The enthalpy equation and wall boundary of the heat shield require special handling for two passages in the afterburner. In order to make the computer program suitable to engineering applications, a subregional scheme is developed for calculating flow fields of complex geometries. The computational grids employed are 100×100 and 333×100 (non-uniformly distributed). The numerical results are compared with experimental data. Agreement between predictions and measurements shows that the numerical method and the computational program used in the study are fairly reasonable and appropriate for primary design of the afterburner.

  7. Performance of High-Flow-Rate Samplers for Respirable Crystalline Silica Measurement Under Field Conditions: Preliminary Study

    PubMed Central

    Coggins, Marie A.; Healy, Catherine B.; Lee, Taekhee; Harper, Martin

    2015-01-01

    Restoration stone work regularly involves work with high-silica-content materials (e.g., sandstone), but low-silica-content materials (<2 % quartz) such as limestone and lime mortar are also used. A combination of short sample duration and low silica content makes the quantification of worker exposure to respirable crystalline silica (RCS) difficult. This problem will be further compounded by the introduction of lower occupational exposure standards for RCS. The objective of this work was to determine whether higher-flow samplers might be an effective tool in characterizing lower RCS concentrations. A short study was performed to evaluate the performance of three high-flow samplers (FSP10, CIP10-R, and GK2.69) using side-by-side sampling with low-flow samplers (SIMPEDS and 10-mm nylon cyclones) for RCS exposure measurement at a restoration stonemasonry field site. A total of 19 side-by-side sample replicates for each high-flow and low-flow sampler pair were collected from work tasks involving limestone and sandstone. RESULTS. Most of the RCS (quartz) masses collected with the high-flow-rate samplers were above the limit of detection (62 % to 84 %) relative to the low-flow-rate samplers (58 % to 78 %). The average of the respirable mass concentration ratios for CIP10-R/SIMPEDS, GK2.69/10-mm nylon, FSP10/SIMPEDS, and FSP10/10-mm nylon pairs and the range of the quartz concentration ratios for the CIP10-R/SIMPEDS, CIP10-R/10-mm nylon, GK2.69/10-mm nylon, FSP10/SIMPEDS, and FSP10/10-mm nylon pairs included unity with an average close to unity, indicating no likely difference between the reported values for each sampler. Workers reported problems related to the weight of the sampling pumps for the high-flow-rate samplers. Respirable mass concentration data suggest that the high-flow-rate samplers evaluated would be appropriate for sampling respirable dust concentrations during restoration stone work. Results from the comparison of average quartz concentration ratios

  8. Bypass Flow Study

    SciTech Connect

    Richard Schultz

    2011-09-01

    The purpose of the fluid dynamics experiments in the MIR (Matched Index of-Refraction) flow system at Idaho National Laboratory (INL) is to develop benchmark databases for the assessment of Computational Fluid Dynamics (CFD) solutions of the momentum equations, scalar mixing, and turbulence models for the flow ratios between coolant channels and bypass gaps in the interstitial regions of typical prismatic standard fuel element (SFE) or upper reflector block geometries of typical Modular High-temperature Gas-cooled Reactors (MHTGR) in the limiting case of negligible buoyancy and constant fluid properties. The experiments use Particle Image Velocimetry (PIV) to measure the velocity fields that will populate the bypass flow study database.

  9. Architecture and emplacement of flood basalt flow fields: case studies from the Columbia River Basalt Group, NW USA

    NASA Astrophysics Data System (ADS)

    Vye-Brown, C.; Self, S.; Barry, T. L.

    2013-03-01

    The physical features and morphologies of collections of lava bodies emplaced during single eruptions (known as flow fields) can be used to understand flood basalt emplacement mechanisms. Characteristics and internal features of lava lobes and whole flow field morphologies result from the forward propagation, radial spread, and cooling of individual lobes and are used as a tool to understand the architecture of extensive flood basalt lavas. The features of three flood basalt flow fields from the Columbia River Basalt Group are presented, including the Palouse Falls flow field, a small (8,890 km2, ˜190 km3) unit by common flood basalt proportions, and visualized in three dimensions. The architecture of the Palouse Falls flow field is compared to the complex Ginkgo and more extensive Sand Hollow flow fields to investigate the degree to which simple emplacement models represent the style, as well as the spatial and temporal developments, of flow fields. Evidence from each flow field supports emplacement by inflation as the predominant mechanism producing thick lobes. Inflation enables existing lobes to transmit lava to form new lobes, thus extending the advance and spread of lava flow fields. Minimum emplacement timescales calculated for each flow field are 19.3 years for Palouse Falls, 8.3 years for Ginkgo, and 16.9 years for Sand Hollow. Simple flow fields can be traced from vent to distal areas and an emplacement sequence visualized, but those with multiple-layered lobes present a degree of complexity that make lava pathways and emplacement sequences more difficult to identify.

  10. Comparative study of the vorticity field in turbulent flows: Theory, experiments and computations. Final report

    SciTech Connect

    Hussain, F.

    1991-12-31

    We have carried out a comprehensive study of unexcited and excited elliptic jets, addressing the effects of initial conditions, aspect ratio, excitation frequency, and excitation amplitude. We have studied the dynamics of the preferred mode structure and interactions of coherent structure in the near field of elliptic jets. The dynamics of elliptic jets are quite different from the extensively studied plane and circular jets -- owing mainly to the fact that the azimuthal curvature variation of a vortical structure causes a nonuniform self-induction and hence complex three-dimensional deformation. Such deformation, combined with properly selected excitation, can substantially alter entrainment and other turbulence phenomenon, thus suggesting a preference for the elliptic shape in many jet applications. In the following, we mention a few key results.

  11. Thermal effects of groundwater flow through subarctic fens: A case study based on field observations and numerical modeling

    NASA Astrophysics Data System (ADS)

    Sjöberg, Ylva; Coon, Ethan; Sannel, A. Britta K.; Pannetier, Romain; Harp, Dylan; Frampton, Andrew; Painter, Scott L.; Lyon, Steve W.

    2016-03-01

    Modeling and observation of ground temperature dynamics are the main tools for understanding current permafrost thermal regimes and projecting future thaw. Until recently, most studies on permafrost have focused on vertical ground heat fluxes. Groundwater can transport heat in both lateral and vertical directions but its influence on ground temperatures at local scales in permafrost environments is not well understood. In this study we combine field observations from a subarctic fen in the sporadic permafrost zone with numerical simulations of coupled water and thermal fluxes. At the Tavvavuoma study site in northern Sweden, ground temperature profiles and groundwater levels were observed in boreholes. These observations were used to set up one- and two-dimensional simulations down to 2 m depth across a gradient of permafrost conditions within and surrounding the fen. Two-dimensional scenarios representing the fen under various hydraulic gradients were developed to quantify the influence of groundwater flow on ground temperature. Our observations suggest that lateral groundwater flow significantly affects ground temperatures. This is corroborated by modeling results that show seasonal ground ice melts 1 month earlier when a lateral groundwater flux is present. Further, although the thermal regime may be dominated by vertically conducted heat fluxes during most of the year, isolated high groundwater flow rate events such as the spring freshet are potentially important for ground temperatures. As sporadic permafrost environments often contain substantial portions of unfrozen ground with active groundwater flow paths, knowledge of this heat transport mechanism is important for understanding permafrost dynamics in these environments.

  12. A wind tunnel study of the flow field within and around open-top chambers used for air pollution studies

    NASA Astrophysics Data System (ADS)

    Davis, J. M.; Riordan, A. J.; Lawson, R. E.

    1983-02-01

    The EPA Meteorological Wind Tunnel was used to examine the flow field in and around models of open-top field-plant growth chambers used to assess the effects of pollutant gases on plant growth. Baffles designed to reduce the ingress of ambient air into the chamber through the open top were tested; the mean flow and turbulence in the simulated boundary layer with and without the chambers were compared (the chamber was operated with and without the pollutant flow system on); and the effects of surrounding chambers on the concentration field were measured. Results showed that a baffle with a reduced opening vertically above the test area maintained the highest uniform concentration in the test area. The major differences between the three (no chamber and the chamber with flow on and off) mean velocity profiles occurred below z/h = 2.0 ( h is chamber height) and at z/h ≤ 4.2. The three Reynolds stress profiles were similar above z/h = 2.0. Downwind of the chamber, the Reynolds stresses in the on-mode were greater than those in the off-mode above z/h = 1.1. The reverse was true below that point. Both longitudinal and vertical intensities above and downwind of the chamber were greater with the mixture flow system on rather than off, below about z/h < 1.5. Lateral variations in the mean wind indicated that the mean velocity was greater with the mixture flow system on except near the centerline where the reverse was true. The concentrations in the downwind wake resembled those for a cube. The location of a cylinder within a regular array had some effect on its internal gas concentration. Locations near the upwind and downwind edges of the array were associated with lower concentrations, although for all locations the highest internal values were always found at the lowest portion of the upwind wall. With active cylinders downwind, the gas plume emitted from a source cylinder at the windward edge of the array was forced 0.5 h higher and the centerline meandered laterally

  13. Study of Fluid Flow Control In Protein Crystallization Using Strong Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Ramachandran, N.; Leslie, F.; Ciszak, E.; Curreri, Peter A. (Technical Monitor)

    2002-01-01

    positioning the crystal growth cell so that the magnetic susceptibility force counteracts terrestrial gravity. The general objective is to test the hypothesis of convective control using a strong magnetic field and magnetic field gradient and to understand the nature of the various forces that come into play. Specifically we aim to delineate causative factors and to quantify them through experiments, analysis and numerical modeling. Once the basic understanding is obtained, the study will focus on testing the hypothesis on proteins of pyruvate dehydrogenase complex (PDC), proteins E1 and E3. Obtaining high crystal quality of these proteins is of great importance to structural biologists since their structures need to be determined.

  14. Heat-flow studies in the northwest geysers geothermal field, California

    USGS Publications Warehouse

    Williams, Colin F.; Galanis, S. Peter; Moses, Thomas H.; Grubb, Frederick V.

    1993-01-01

    Temperature and thermal conductivity data were acquired from 3 idle production wells in the Northwest Geysers. Heat-flow profiles derived from data recorded in the caprock which overlies the steam reservoir reveal a decrease of heat flow with depth in 2 of the 3 wells. These observations contradict the generally accepted theory that conductive heat flow is constant with depth within The Geysers caprock. There are several possible explanations for this, but the available data suggest that these profiles reflect a local recession or cooling of the reservoir top within the past 5000 to 10000 years.

  15. An Experimental Study of Continuous Plasma Flows Driven by a Confined Arc in a Transverse Magnetic Field

    NASA Technical Reports Server (NTRS)

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

    1961-01-01

    A crossed-field, continuous-flow plasma accelerator has been built and operated. The highest measured velocity of the flow, which was driven by the interaction of the electric and magnetic fields, was about 500 meters per second. Some of the problems discussed are ion slip, stability and uniformity of the discharge, effect of the magnetic field on electron emission, use of preionization, and electrode contamination.

  16. Numerical study of changing the geometry of the flow field of a PEM fuel cell

    NASA Astrophysics Data System (ADS)

    Khazaee, I.; Sabadbafan, H.

    2016-05-01

    The geometry of channels of a PEM fuel cell is an important parameter that affects the performance of it that the lower voltage loss in polarization curve can indicate the better performance. In this study a complete three-dimensional and single phase model is used to investigate the effect of increasing the number of serpentine channels in the bipolar plates and also increasing the area (depth) of channels of a PEM fuel cell with rectangular, triangular and elliptical cross-section geometry. A single set of conservation equations which are valid for the flow channels, gas-diffusion electrodes, catalyst layers, and the membrane region is developed and numerically solved using a finite volume based computational fluid dynamics technique. The results show that there are good agreement with the numerical results and experimental results of the previous work of authors. Also the results show that by increasing the number of channels from one to four and eight, the performance improved about 18 % and by decreasing the area of channels from 2 to 1 mm2 the performance improved about 13 %.

  17. Field and modelling studies of immiscible fluid flow above a contaminated water-table aquifer

    USGS Publications Warehouse

    Herkelrath, W.N.; Essaid, H.I.; Hess, K.M.

    1991-01-01

    A method was developed for measuring the spatial distribution of immiscible liquid contaminants in the subsurface. Fluid saturation distributions measured at a crude-oil spill site were used to test a numerical multiphase flow model.

  18. Silica Measurement with High Flow Rate Respirable Size Selective Samplers: A Field Study.

    PubMed

    Lee, Taekhee; Harper, Martin; Kashon, Michael; Lee, Larry A; Healy, Catherine B; Coggins, Marie A; Susi, Pam; O'Brien, Andrew

    2016-04-01

    High and low flow rate respirable size selective samplers including the CIP10-R (10 l min(-1)), FSP10 (11.2 l min(-1)), GK2.69 (4.4 l min(-1)), 10-mm nylon (1.7 l min(-1)), and Higgins-Dewell type (2.2 l min(-1)) were compared via side-by-side sampling in workplaces for respirable crystalline silica measurement. Sampling was conducted at eight different occupational sites in the USA and five different stonemasonry sites in Ireland. A total of 536 (268 pairs) personal samples and 55 area samples were collected. Gravimetric analysis was used to determine respirable dust mass and X-ray diffraction analysis was used to determine quartz mass. Ratios of respirable dust mass concentration, quartz mass concentration, respirable dust mass, and quartz mass from high and low flow rate samplers were compared. In general, samplers did not show significant differences greater than 30% in respirable dust mass concentration and quartz mass concentration when outliers (ratio <0.3 or >3.0) were removed from the analysis. The frequency of samples above the limit of detection and limit of quantification of quartz was significantly higher for the CIP10-R and FSP10 samplers compared to low flow rate samplers, while the GK2.69 cyclone did not show significant difference from low flow rate samplers. High flow rate samplers collected significantly more respirable dust and quartz than low flow rate samplers as expected indicating that utilizing high flow rate samplers might improve precision in quartz measurement. Although the samplers did not show significant differences in respirable dust and quartz concentrations, other practical attributes might make them more or less suitable for personal sampling. PMID:26608952

  19. Silica Measurement with High Flow Rate Respirable Size Selective Samplers: A Field Study

    PubMed Central

    Lee, Taekhee; Harper, Martin; Kashon, Michael; Lee, Larry A.; Healy, Catherine B.; Coggins, Marie A.; Susi, Pam; O’Brien, Andrew

    2016-01-01

    High and low flow rate respirable size selective samplers including the CIP10-R (10 l min−1), FSP10 (11.2 l min−1), GK2.69 (4.4 l min−1), 10-mm nylon (1.7 l min−1), and Higgins-Dewell type (2.2 l min−1) were compared via side-by-side sampling in workplaces for respirable crystalline silica measurement. Sampling was conducted at eight different occupational sites in the USA and five different stonemasonry sites in Ireland. A total of 536 (268 pairs) personal samples and 55 area samples were collected. Gravimetric analysis was used to determine respirable dust mass and X-ray diffraction analysis was used to determine quartz mass. Ratios of respirable dust mass concentration, quartz mass concentration, respirable dust mass, and quartz mass from high and low flow rate samplers were compared. In general, samplers did not show significant differences greater than 30% in respirable dust mass concentration and quartz mass concentration when outliers (ratio <0.3 or >3.0) were removed from the analysis. The frequency of samples above the limit of detection and limit of quantification of quartz was significantly higher for the CIP10-R and FSP10 samplers compared to low flow rate samplers, while the GK2.69 cyclone did not show significant difference from low flow rate samplers. High flow rate samplers collected significantly more respirable dust and quartz than low flow rate samplers as expected indicating that utilizing high flow rate samplers might improve precision in quartz measurement. Although the samplers did not show significant differences in respirable dust and quartz concentrations, other practical attributes might make them more or less suitable for personal sampling. PMID:26608952

  20. FLOW FIELDS IN SUPERSONIC INLETS

    NASA Technical Reports Server (NTRS)

    Sorenson, R. L.

    1994-01-01

    This computer program is designed to calculate the flow fields in two-dimensional and three-dimensional axisymmetric supersonic inlets. The method of characteristics is used to compute arrays of points in the flow field. At each point the total pressure, local Mach number, local flow angle, and static pressure are calculated. This program can be used to design and analyze supersonic inlets by determining the surface compression rates and throat flow properties. The program employs the method of characteristics for a perfect gas. The basic equation used in the program is the compatibility equation which relates the change in stream angle to the change in entropy and the change in velocity. In order to facilitate the computation, the flow field behind the bow shock wave is broken into regions bounded by shock waves. In each region successive rays are computed from a surface to a shock wave until the shock wave intersects a surface or falls outside the cowl lip. As soon as the intersection occurs a new region is started and the previous region continued only in the area in which it is needed, thus eliminating unnecessary calculations. The maximum number of regions possible in the program is ten, which allows for the simultaneous calculations of up to nine shock waves. Input to this program consists of surface contours, free-stream Mach number, and various calculation control parameters. Output consists of printed and/or plotted results. For plotted results an SC-4020 or similar plotting device is required. This program is written in FORTRAN IV to be executed in the batch mode and has been implemented on a CDC 7600 with a central memory requirement of approximately 27k (octal) of 60 bit words.

  1. Numerical study on the impact of ground heating and ambient wind speed on flow fields in street canyons

    NASA Astrophysics Data System (ADS)

    Li, Lei; Yang, Lin; Zhang, Li-Jie; Jiang, Yin

    2012-11-01

    The impact of ground heating on flow fields in street canyons under different ambient wind speed conditions was studied based on numerical methods. A series of numerical tests were performed, and three factors including height-to-width (H/W) ratio, ambient wind speed and ground heating intensity were taken into account. Three types of street canyon with H/W ratios of 0.5, 1.0 and 2.0, respectively, were used in the simulation and seven speed values ranging from 0.0 to 3.0 m s-1 were set for the ambient wind speed. The ground heating intensity, which was defined as the difference between the ground temperature and air temperature, ranged from 10 to 40 K with an increase of 10 K in the tests. The results showed that under calm conditions, ground heating could induce circulation with a wind speed of around 1.0 m s-1, which is enough to disperse pollutants in a street canyon. It was also found that an ambient wind speed threshold may exist for street canyons with a fixed H/W ratio. When ambient wind speed was lower than the threshold identified in this study, the impact of the thermal effect on the flow field was obvious, and there existed a multi-vortex flow pattern in the street canyon. When the ambient wind speed was higher than the threshold, the circulation pattern was basically determined by dynamic effects. The tests on the impact of heating intensity showed that a higher ground heating intensity could strengthen the vortical flow within the street canyon, which would help improve pollutant diffusion capability in street canyons.

  2. A study of leeside flow field heat transfer on Shuttle Orbiter configuration

    NASA Technical Reports Server (NTRS)

    Baranowski, L. C.; Kipp, H. W.

    1984-01-01

    A coupled inviscid and viscous theoretical solution of the flow about the entire configuration is the desirable and comprehensive approach to defining thermal environments about the space shuttle orbiter. Simplified methods for predicting entry heating on leeside surfaces of the orbiter are considered. Wind tunnel heat transfer and oil flow data at Mach 6 and 10 and Reynolds numbers ranging from 500,000 to 73 million were used to develop correlations for the wing upper surface and the top surface of the fuselage. These correlations were extrapolated to flight Reynolds number and compared with heating data obtained during the shuttle STS-2 reentry. Efforts directed toward the wing leeside surface resulted in an approach which generally agreed with the flight data. Heating predictions for the upper fuselage were less successful due to the extreme complexity of local flow interactions and the associated heating environment.

  3. A combined field and modeling study of groundwater flow in a tidal marsh

    NASA Astrophysics Data System (ADS)

    Xia, Yuqiang; Li, Hailong

    2011-05-01

    Bald mud beaches were found among the mangrove marshes in Dongzhaigang National Nature Reserve, Hainan, China. To investigate the possible reasons for this phenomenon, the intertidal zones of a mangrove transect and a bald beach transect with similar topography and same tidal actions were selected for comparison study. Along both transects, observed water table variations were significant in the high and low intertidal zones and negligible in the middle intertidal zones. Field investigations and observations invite two speculations: (1) existence of a high-permeability zone on each transect which underlies the low-permeability surface mud sediments and outcrops in the high intertidal zone, and (2) considerable inland freshwater recharge along the mangrove transect but negligible freshwater recharge along the bald beach transect. Two-dimensional numerical simulations based on these speculations gave results in line with the observed water table. The bald beach is most probably due to the lack of enough freshwater for generating a brackish beach soil condition essential to mangrove growth. It is also indicated that seawater infiltrated the high-permeability zone through its outcrop near the high intertidal zone, and discharged from the tidal river bank in the vicinity of the low tide line, thereby forming a tide-induced seawater-groundwater circulation which may provide considerable contribution to the total submarine groundwater discharge.

  4. Fundamental studies of materials, designs, and models development for polymer electrolyte membrane fuel cell flow field distributors

    NASA Astrophysics Data System (ADS)

    Nikam, Vaibhav Vilas

    Fuel cells are becoming a popular source of energy due to their promising performance and availability. However, the high cost of fuel cell stack forbids its deployment to end user. Moreover, bipolar plate is one of the critical components in current polymer electrolyte membrane fuel cell (PEMFC) system, causing severe increase in manufacturing cost. The objective of this research work is to develop new materials, design and manufacturing process for bipolar plates. The materials proposed for use were tested for corrosion resistance in simulated fuel cell conditions. After corrosion studies copper alloy (C17200) and Low Temperature Carburized (LTC) SS 316 were selected as an alternative material for bipolar plate. It was observed that though the copper alloy offered good resistance in corrosive atmosphere, the major advantage of using the alloys was good conductivity even after formation of corrosion layer compared to SS 316. However, LTC SS 316 achieved the best corrosion resistance (ever reported in current open literature at relatively low cost) with decreased contact resistance, as compared to SS 316. Due to the expensive and tedious machining for bipolar plate manufacturing, the conventional machining process was not used. Bipolar plates were manufactured from thin corrugated sheets formed of the alloy. This research also proposed a novel single channel convoluted flow field design which was developed by increasing the tortuosity of conventional serpentine design. The CFD model for novel single channel convoluted design showed uniform distribution of velocity over the entire three dimensional domain. The novel design was further studied using pressure drop and permeability models. These modeling calculations showed substantial benefit in using corrugated sheet design and novel single channel convoluted flow field design. All the concepts of materials (except for LTC SS 316), manufacturing and design are validated using various tests like long term stability

  5. Numerical study of magnetohydrodynamic viscous plasma flow in rotating porous media with Hall currents and inclined magnetic field influence

    NASA Astrophysics Data System (ADS)

    Bég, O. Anwar; Sim, Lik; Zueco, J.; Bhargava, R.

    2010-02-01

    A numerical solution is developed for the viscous, incompressible, magnetohydrodynamic flow in a rotating channel comprising two infinite parallel plates and containing a Darcian porous medium, the plates lying in the x-z plane, under constant pressure gradient. The system is subjected to a strong, inclined magnetic field orientated to the positive direction of the y-axis (rotational axis, normal to the x-z plane). The Navier-Stokes flow equations for a general rotating hydromagnetic flow are reduced to a pair of linear, viscous partial differential equations neglecting convective acceleration terms, for primary velocity (u‧) and secondary velocity (v‧) where these velocities are directed along the x and y axes. Only viscous terms are retained in the momenta equations. The model is non-dimensionalized and shown to be controlled by a number of dimensionless parameters. The resulting dimensionless ordinary differential equations are solved using a robust numerical method, Network Simulation Methodology. Full details of the numerics are provided. The present solutions are also benchmarked against the analytical solutions presented recently by Ghosh and Pop [Ghosh SK, Pop I. An analytical approach to MHD plasma behaviour of a rotating environment in the presence of an inclined magnetic field as compared to excitation frequency. Int J Appl Mech Eng 2006;11(4):845-856] for the case of a purely fluid medium (infinite permeability). We study graphically the influence of Hartmann number (Ha, magnetic field parameter), Ekman number (Ek, rotation parameter), Hall current parameter (Nh), Darcy number (Da, permeability parameter), pressure gradient (Np) and also magnetic field inclination (θ) on primary and secondary velocity fields. Additionally we investigate the effects of these multiphysical parameters on the dimensionless shear stresses at the plates. Both primary and secondary velocity are seen to be increased with a rise in Darcy number, owing to a simultaneous

  6. Thermal effects of groundwater flow through subarctic fens: A case study based on field observations and numerical modeling

    DOE PAGESBeta

    Sjöberg, Ylva; Coon, Ethan; K. Sannel, A. Britta; Pannetier, Romain; Harp, Dylan; Frampton, Andrew; Painter, Scott L.; Lyon, Steve W.

    2016-02-05

    Modeling and observation of ground temperature dynamics are the main tools for understanding current permafrost thermal regimes and projecting future thaw. Until recently, most studies on permafrost have focused on vertical ground heat fluxes. Groundwater can transport heat in both lateral and vertical directions but its influence on ground temperatures at local scales in permafrost environments is not well understood. In this paper, we combine field observations from a subarctic fen in the sporadic permafrost zone with numerical simulations of coupled water and thermal fluxes. At the Tavvavuoma study site in northern Sweden, ground temperature profiles and groundwater levels weremore » observed in boreholes. These observations were used to set up one- and two-dimensional simulations down to 2 m depth across a gradient of permafrost conditions within and surrounding the fen. Two-dimensional scenarios representing the fen under various hydraulic gradients were developed to quantify the influence of groundwater flow on ground temperature. Our observations suggest that lateral groundwater flow significantly affects ground temperatures. This is corroborated by modeling results that show seasonal ground ice melts 1 month earlier when a lateral groundwater flux is present. Further, although the thermal regime may be dominated by vertically conducted heat fluxes during most of the year, isolated high groundwater flow rate events such as the spring freshet are potentially important for ground temperatures. Finally, as sporadic permafrost environments often contain substantial portions of unfrozen ground with active groundwater flow paths, knowledge of this heat transport mechanism is important for understanding permafrost dynamics in these environments.« less

  7. Implementation and efficiency analysis of parallel computation using OpenACC: a case study using flow field simulations

    NASA Astrophysics Data System (ADS)

    Zhang, Shanghong; Yuan, Rui; Wu, Yu; Yi, Yujun

    2016-01-01

    The Open Accelerator (OpenACC) application programming interface is a relatively new parallel computing standard. In this paper, particle-based flow field simulations are examined as a case study of OpenACC parallel computation. The parallel conversion process of the OpenACC standard is explained, and further, the performance of the flow field parallel model is analysed using different directive configurations and grid schemes. With careful implementation and optimisation of the data transportation in the parallel algorithm, a speedup factor of 18.26× is possible. In contrast, a speedup factor of just 11.77× was achieved with the conventional Open Multi-Processing (OpenMP) parallel mode on a 20-kernel computer. These results demonstrate that optimised feature settings greatly influence the degree of speedup, and models involving larger numbers of calculations exhibit greater efficiency and higher speedup factors. In addition, the OpenACC parallel mode is found to have good portability, making it easy to implement parallel computation from the original serial model.

  8. Chemical speciation studies on DU contaminated soils using flow field flow fractionation linked to inductively coupled plasma mass spectrometry (FlFFF-ICP-MS).

    PubMed

    Brittain, S R; Cox, A G; Tomos, A D; Paterson, E; Siripinyanond, A; McLeod, C W

    2012-03-01

    Flow field flow fractionation (FlFFF) in combination with inductively coupled plasma mass spectrometry (ICP-MS) was used to study the chemical speciation of U and trace metals in depleted uranium (DU) contaminated soils. A chemical extraction procedure using sodium pyrophosphate, followed by isolation of humic and fulvic substances was applied to two dissimilar DU contaminated sample types (a sandy soil and a clay-rich soil), in addition to a control soil. The sodium pyrophosphate fractions of the firing range soils (Eskmeals and Kirkcudbright) were found to contain over 50% of the total U (measured after aqua regia digestion), compared to approximately 10% for the control soil. This implies that the soils from the contaminated sites contained a large proportion of the U within more easily mobile soil fractions. Humic and fulvic acid fractions each gave characteristic peak maxima for analytes of interest (Mn, Fe, Cu, Zn, Pb and U), with the fulvic acid fraction eluting at a smaller diameter (approximately 2.1 nm on average) than the humic fraction (approximately 2.4 nm on average). DU in the fulvic acid fraction gave a bimodal peak, not apparent for other trace elements investigated, including natural U. This implies that DU interacts with the fulvic acid fraction in a different way to all other elements studied. PMID:22237634

  9. Visualizing vector field topology in fluid flows

    NASA Technical Reports Server (NTRS)

    Helman, James L.; Hesselink, Lambertus

    1991-01-01

    Methods of automating the analysis and display of vector field topology in general and flow topology in particular are discussed. Two-dimensional vector field topology is reviewed as the basis for the examination of topology in three-dimensional separated flows. The use of tangent surfaces and clipping in visualizing vector field topology in fluid flows is addressed.

  10. Study on aggregation behavior of low density lipoprotein in hen egg yolk plasma by asymmetrical flow field-flow fractionation coupled with multiple detectors.

    PubMed

    Dou, Haiyang; Magnusson, Emma; Choi, Jaeyeong; Duan, Fei; Nilsson, Lars; Lee, Seungho

    2016-02-01

    In this study, asymmetrical flow field-flow fractionation (AF4) coupled online with UV, multiangle light scattering (MALS), and fluorescence (FS) detectors (AF4-UV-MALS-FS) was employed for separation and characterization of egg yolk plasma. AF4 provided separation of three major components of the egg yolk plasma i.e. soluble proteins, low density lipoproteins (LDL) and their aggregates, based on their respective hydrodynamic sizes. Identification of LDL was confirmed by staining the sample with a fluorescent dye, Nile Red. The effect of carrier liquids on aggregation of LDL was investigated. Collected fractions of soluble proteins were characterized using sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE). Moreover, the effect of heat and enzymatic treatment on egg yolk plasma was investigated. The results suggest that enzymatic treatment with phospholipase A2 (PLA2) significantly enhances the heat stability of LDL. The results show that AF4-UV-MALS-FS is a powerful tool for the fractionation and characterization of egg yolk plasma components. PMID:26304341

  11. a Numerical Study on the Magnetic Fluid Flow in a Channel Surrounding a Permanent Magnet Under Temperature Field

    NASA Astrophysics Data System (ADS)

    Li, X. L.; Yao, K. L.; Liu, Z. L.

    It was investigated that the magnetic fluid which can be the carrier of magnetic particles or magnetic drug carrier particles (MDCP) flows surrounding a permanent magnet in a channel under the influence of high gradient magnetic field and the temperature difference between upper and lower boundaries of the channel. It is considered that the magnetization of the fluid varies linearly with temperature and magnetic field intensity. The numerical solution of above model is described by a coupled and nonlinear system of PDEs. Results indicate that the presence of magnetic and temperature fields appreciably influence the flow field; vortexes arise almost around the magnetic source and also appear near the upper left and lower right boundaries. The temperature, local skin friction coefficient and rate of heat transfer are all affected by the magnitude and position of the magnetic source, they fluctuate evidently near the high gradient magnetic field area.

  12. An experimental study using flow visualization on the effect of an acoustic field on heat transfer from spheres

    NASA Technical Reports Server (NTRS)

    Leung, W. W.; Baroth, E. C.

    1986-01-01

    The physical mechanisms responsible for the heat transfer process in a thermal-acoustic field were investigated using the technique of holographic interferometry for flow visualization. Experimental results were obtained with sound pressure levels in the range of 120 to 150 decibels, relative to a pressure of 0.0002 dynes/sq cm. Steady state laminar flow was observed when the vibrational Reynolds number was below 400; separated flow was observed when it was above 400. In the presence of a horizontal sound field, the data indicate that the relation between the vibrational Nusselt number, Nu(v) and the vibrational Reynolds number, Re(v) is given by Nu(v) = Re(v) exp 0.22. In the presence of a vertical sound field, the corresponding relation is Nu(v) = Re(v) exp 0.15.

  13. HVOF gas flow field characteristics

    SciTech Connect

    Swank, W.D.; Fincke, J.R.; Haggard, D.C.; Irons, G.

    1994-12-31

    The effects of combustion chamber pressure and fuel/oxygen mixture ratio on the characteristics of a high pressure, supersonic HVOF gun are examined experimentally and theoretically. The measured temperature, velocity and entrained air fraction are obtained from an enthalpy probe/mass spectrometer system. Predictions of combustion chamber flame temperature and composition are calculated with an equilibrium combustion model. Nozzle and barrel exit conditions are calculated using a one-dimensional rocket performance model. The calculations are bounded by the assumption of frozen and equilibrium compositions. Comparisons between measurements and the predictions indicate that the flow field is far from chemical equilibrium. The aerodynamic force available for accelerating a particle is primarily controlled by the chamber pressure while the composition and temperature of the gas surrounding the particles is controlled by the mixture ratio.

  14. A field study of the effects of soil structure and irrigation method on preferential flow of pesticides in unsaturated soil

    NASA Astrophysics Data System (ADS)

    Ghodrati, Masoud; Jury, William A.

    1992-10-01

    A large number of field plot experiments were performed to characterize the downward flow of three pesticides (atrazine, napropamide and prometryn) and a water tracer (chloride) under various soil water regimes and soil surface conditions. Each experiment consisted of the uniform application of a 0.4-cm pulse of a solution containing a mixture of the four chemicals to the surface of a 1.5 × 1.5-m plot. The plot was then irrigated with 12 cm of water and soil samples were collected and analyzed to a depth of 150 cm. In all, 64 different plots were employed to study individual as well as interactive effects of such variables as irrigation method (continuous or intermittent sprinkling or ponding), pesticide formulation method (technical grade dissolved in water, wettable powder, or emulsifiable concentrate), and tillage (undisturbed or tilled and repacked surface layer) on pesticide transport. While all three pesticides were expected to be retained in the top 10-20 cm, there was considerable movement below this zone. When averaged over all the treatments, 18.8% of the recovered mass of atrazine, 9.4% of the prometryn and 16.4% of the napropamide were found between 30- and 150cm depth. Moreover, all pesticides were highly mobile in the surface 30 cm regardless of their adsorption coefficient. There were occureences of extreme mobility or "preferential flow" of pesticide under every experimental condition except where the pesticides were applied in wettable powder form to plots which had their surface tilled and repacked. This finding implies that there may be fine preferential flow pathways through which solution may move but particulates may not.

  15. Field study and simulation of diurnal temperature effects on infiltration and variably saturated flow beneath an ephemeral stream

    USGS Publications Warehouse

    Ronan, A.D.; Prudic, D.E.; Thodal, C.E.; Constantz, J.

    1998-01-01

    Two experiments were performed to investigate flow beneath an ephemeral stream and to estimate streambed infiltration rates. Discharge and stream-area measurements were used to determine infiltration rates. Stream and subsurface temperatures were used to interpret subsurface flow through variably saturated sediments beneath the stream. Spatial variations in subsurface temperatures suggest that flow beneath the streambed is dependent on the orientation of the stream in the canyon and the layering of the sediments. Streamflow and infiltration rates vary diurnally: Stream flow is lowest in late afternoon when stream temperature is greatest and highest in early morning when stream temperature is least. The lower afternoon streamflow is attributed to increased infiltration rates; evapotranspiration is insufficient to account for the decreased streamflow. The increased infiltration rates are attributed to viscosity effects on hydraulic conductivity from increased stream temperatures. The first set of field data was used to calibrate a two-dimensional variably saturated flow model that includes heat transport. The model was calibrated to (1) temperature fluctuations in the subsurface and (2) infiltration rates determined from measured stream flow losses. The second set of field data was to evaluate the ability to predict infiltration rates on the basis of temperature measurements alone. Results indicate that the variably saturated subsurface flow depends on downcanyon layering of the sediments. They also support the field observations in indicating that diurnal changes in infiltration can be explained by temperature dependence of hydraulic conductivity. Over the range of temperatures and flows monitored, diurnal stream temperature changes can be used to estimate streambed infiltration rates. It is often impractical to maintain equipment for determining infiltration rates by traditional means; however, once a model is calibrated using both infiltration and temperature data

  16. A field study of air flow and turbulent features of advection fog

    NASA Technical Reports Server (NTRS)

    Connell, J. D.

    1979-01-01

    The setup and initial operation of a set of specialized meteorological data collection hardware are described. To study the life cycle of advection fogs at a lake test site, turbulence levels in the fog are identified, and correlated with the temperature gradients and mean wind profiles. A meteorological tower was instrumented to allow multiple-level measurements of wind and temperature on a continuous basis. Additional instrumentation was: (1)hydrothermograph, (2)microbarograph, (3)transmissometers, and (4)a boundary layer profiler. Two types of fogs were identified, and important differences in the turbulence scales were noted.

  17. A numerical study of mixing enhancement in supersonic reacting flow fields

    NASA Astrophysics Data System (ADS)

    Drummond, J. Philip; Mukunda, H. S.

    Work has been underway for a number of years at the NASA Langley Research Center to develop a supersonic combustion ramjet or scramjet that is capable of propelling a vehicle at hypersonic speeds in the atmosphere or beyond. A recent part of that research has been directed toward the optimization of the scramjet combustor, and in particular the efficiency of fuel-air mixing and reaction in the engine. A supersonic, spatially developing and reacting mixing layer serves as an excellent physical model for the mixing and reaction processes that take place in a scramjet combustor, This paper describes a study of fuel-air mixing and reaction in a supersonic mixing layer and discusses several techniques that were applied for enhancing the mixing processes and the overall combustion efficiency in the layer. Based on the results of this study, an alternate fuel injector configuration was computationally designed, and that configuration significantly increased the amount of fuel-air mixing and combustion over a given combustor length that was achieved.

  18. A combined field and modeling study of groundwater flow in a tidal marsh

    NASA Astrophysics Data System (ADS)

    Xia, Y. Q.; Li, H. L.

    2012-03-01

    Bald mud beaches were found among the mangrove marshes in Dongzhaigang National Nature Reserve, Hainan, China. To investigate the possible reasons for this phenomenon, the intertidal zones of a mangrove transect and a bald beach transect with similar topography and tidal actions were selected for comparison study. Along both transects, observed water table variations were significant in the high and low intertidal zones and negligible in the middle intertidal zones. Despite the same tidal actions and above-mentioned similarities, observed groundwater salinity was significantly smaller along the mangrove transect (average 23.0 ppt) than along the bald beach transect (average 28.5 ppt). These observations invite one hypothesis: the hydraulic structure of tidal marsh and freshwater availability may be the main hydrogeological factors critical to mangrove development. Two-dimensional numerical simulations corroborated the speculation and gave results in line with the observed water table. The two transects investigated were found to have a mud-sand two-layered structure: a surface zone of low-permeability mud and an underlying high-permeability zone that outcrops at the high and low tide lines. The freshwater recharge from inland is considerable along the mangrove transect but negligible along the bald beach transect. The high-permeability zone may provide opportunity for the plants in the mangrove marsh to uptake freshwater and oxygen through their roots extending downward into the high-permeability zone, which may help limit the buildup of salt in the root zone caused by evapotranspiration and enhance salt removal, which may further increase the production of marsh grasses and influence their spatial distribution. The bald beach is most probably due to the lack of enough freshwater for generating a brackish beach soil condition essential to mangrove growth. It is also indicated that seawater infiltrated the high-permeability zone through its outcrop near the high

  19. Flow field mapping in data rack model

    NASA Astrophysics Data System (ADS)

    Manoch, L.; Matěcha, J.; Pohan, P.

    2013-04-01

    The main objective of this study was to map the flow field inside the data rack model, fitted with three 1U server models. The server model is based on the common four-processor 1U server. The main dimensions of the data rack model geometry are taken fully from the real geometry. Only the model was simplified with respect to the greatest possibility in the experimental measurements. The flow field mapping was carried out both experimentally and numerically. PIV (Particle Image Velocimetry) method was used for the experimental flow field mapping, when the flow field has been mapped for defined regions within the 2D/3D data rack model. Ansys CFX and OpenFOAM software were used for the numerical solution. Boundary conditions for numerical model were based on data obtained from experimental measurement of velocity profile at the output of the server mockup. This velocity profile was used as the input boundary condition in the calculation. In order to achieve greater consistency of the numerical model with experimental data, the numerical model was modified with regard to the results of experimental measurements. Results from the experimental and numerical measurements were compared and the areas of disparateness were identified. In further steps the obtained proven numerical model will be utilized for the real geometry of data racks and data.

  20. Graphics and Flow Visualization of Computer Generated Flow Fields

    NASA Technical Reports Server (NTRS)

    Kathong, M.; Tiwari, S. N.

    1987-01-01

    Flow field variables are visualized using color representations described on surfaces that are interpolated from computational grids and transformed to digital images. Techniques for displaying two and three dimensional flow field solutions are addressed. The transformations and the use of an interactive graphics program for CFD flow field solutions, called PLOT3D, which runs on the color graphics IRIS workstation are described. An overview of the IRIS workstation is also described.

  1. Field-aligned magnetohydrodynamic bow shock flows in the switch-on regime. Parameter study of the flow around a cylinder and results for the axi-symmetrical flow over a sphere

    NASA Astrophysics Data System (ADS)

    de Sterck, H.; Poedts, S.

    1999-03-01

    A parameter study is undertaken for steady symmetrical planar field-aligned MHD bow shock flows around a perfectly conducting cylinder. For sets of values of the inflow plasma beta and Alfvénic Mach number (MA) which allow for switch-on shocks, a numerical solution is obtained which exhibits a complex bow shock shape and topology with multiple shock fronts and a dimpled leading front. For parameter values outside the switch-on domain, a classical single-front bow shock flow is obtained. These results show that the beta and MA parameter regime for which the complex bow shock topology occurs, corresponds closely to the parameter regime for which switch-on shocks are possible. The axi-symmetrical field-aligned bow shock flow over a perfectly conducting sphere is then calculated for one set of values for beta and MA in the switch-on domain, resulting in a complex bow shock topology similar to the topology of the flow around a cylinder. These complex shock shapes and topologies may be encountered in low-beta space plasmas. Fast coronal mass ejections moving away from the sun in the low-beta inner corona may induce preceding shock fronts with upstream parameters in the switch-on domain. Planetary and cometary bow shocks may have upstream parameters in the switch-on domain when the impinging solar wind occasionally becomes low-beta . The simulation results may be important for phenomena in the Earth's magnetosheath.

  2. A preliminary study on the feedback of heat transfer on groundwater flow in a Karst geothermal field

    NASA Astrophysics Data System (ADS)

    Kong, Y.; Pang, Z.; Hu, S.; Pang, J.; Shao, H.; Kolditz, O.

    2014-12-01

    In deep sedimentary basins, groundwater movement can significantly alter the heat flow pattern. At the same time, heat flux induced temperature change can reversely determine the flow regime through density dependent convection process. In Karst aquifers, the heterogeneity in the carbonate rocks makes the identification of this feedback much more complex. In this work, a preliminary study has been made on this feedback in Xiongxian geothermal field. The Karst aquifer in our site has an average thickness of about 1000 m, and is overlaid by over 400 m of quaternary clay, and subsequently 600 m of Neogene sandstone. Geothermal energy has been exploited in the site for space heating. During the heating period from Nov 15th to Mar 15th every year, hot water was extracted from the aquifer and re-injected after the heat extraction. A detailed temperature logging has been carried out in the field, both before and after the heating period, with the consideration that temperature distribution will be affected by the re-injection of cold water. The vertical distribution of temperature in the cap rock shows a constant positive gradient over depth. The heat flux at different locations has been calculated respectively. It is found to decline from southwest to northeast, with the highest value of 113.9 mW/m2 to the lowest of 80.6 mW/m2. This pattern can be well explained by the tectonic features. More interestingly, two inflection points appear on the temperature profile of the Karst layer, revealing strong influence from the cold re-injection water. Also, a 3℃ temperature difference was observed in the June and October measurement, which is related to the reservoir recovery. Currently, a 3D numerical model is being constructed, using the open-source software OpenGeoSys. Heat transport process is coupled with density dependent flow in a monolithic approach, to simulate both heat conduction and groundwater convection. This model will help to quantify the feedback from heat

  3. An experimental study into the influence of aquatic plant motion characteristics on the generation of a fluvial turbulent flow field

    NASA Astrophysics Data System (ADS)

    Hardy, R. J.; Marjoribanks, T.; Parsons, D. R.; Thomas, R. E.

    2015-12-01

    Aquatic vegetation has a determining effect on flow and consequently sediment transport as it generates both skin friction and form drag. The measurement of flow above the vegetation canopy has received much attention and there is now a good process understanding of mean and turbulent flow, although, much of this research has focused on rigid vegetation with relatively simple morphology. However, vegetation immersed in a flow experiences several forces (buoyancy; drag; virtual mass; Basset; and Saffman) which are counteracted by the properties of the vegetation (flexural rigidity; modulus of elasticity; the plant area exposed to the flow and; the packing density of the stems). The ratio of these forces determines the plant motion characteristics which are generally classified as either i) erect with no movement; ii) gently swaying; iii) strong, coherent swaying or; iv) prone. Here we report on an investigation into the influence of plant motion on the turbulence structure in the mixing zone as vortices in this region have been shown to account for the majority of the momentum transport between the canopy and the open flow. We report on a series of flume experiments where flow over a canopy of surrogate aquatic vegetation was measured using PIV at a spatial resolution of ~1mm2 and at a temporal resolution of 100 Hz. This provided whole flow field measurements for all three components of flow over the vegetation canopy. Plant motion characteristics were altered by modifying the flow Reynolds number through both velocity and depth. The influences of plant stem length were also assessed. The measured flows were analysed by standard Reynolds decomposition approaches and Eulerian and Lagrangian coherent flow structure identification methods. Kelvin-Helmholtz and Görtler-type vortices were identified within the canopy shear layer that are generated close to the canopy top and evolve downstream into span-wise roller vortices, which expand with both distance and time. When

  4. Flow field of flexible flapping wings

    NASA Astrophysics Data System (ADS)

    Sallstrom, Erik

    The agility and maneuverability of natural fliers would be desirable to incorporate into engineered micro air vehicles (MAVs). However, there is still much for engineers to learn about flapping flight in order to understand how such vehicles can be built for efficient flying. The goal of this study is to develop a methodology for capturing high quality flow field data around flexible flapping wings in a hover environment and to interpret it to gain a better understanding of how aerodynamic forces are generated. The flow field data was captured using particle image velocimetry (PIV) and required that measurements be taken around a repeatable flapping motion to obtain phase-averaged data that could be studied throughout the flapping cycle. Therefore, the study includes the development of flapping devices with a simple repeatable single degree of freedom flapping motion. The acquired flow field data has been examined qualitatively and quantitatively to investigate the mechanisms behind force production in hovering flight and to relate it to observations in previous research. Specifically, the flow fields have been investigated around a rigid wing and several carbon fiber reinforced flexible membrane wings. Throughout the whole study the wings were actuated with either a sinusoidal or a semi-linear flapping motion. The semi-linear flapping motion holds the commanded angular velocity nearly constant through half of each half-stroke while the sinusoidal motion is always either accelerating or decelerating. The flow fields were investigated by examining vorticity and vortex structures, using the Q criterion as the definition for the latter, in two and three dimensions. The measurements were combined with wing deflection measurements to demonstrate some of the key links in how the fluid-structure interactions generated aerodynamic forces. The flow fields were also used to calculate the forces generated by the flapping wings using momentum balance methods which yielded

  5. Field emission microplasma actuation for microchannel flows

    NASA Astrophysics Data System (ADS)

    Sashank Tholeti, Siva; Shivkumar, Gayathri; Alexeenko, Alina A.

    2016-06-01

    Microplasmas offer attractive flow control methodology for gas transport in microsystems where large viscous losses make conventional pumping methods highly inefficient. We study microscale flow actuation by dielectric-barrier discharge (DBD) with field emission (FE) of electrons, which allows lowering the operational voltage from kV to a few hundred volts and below. A feasibility study of FE-DBD for flow actuation is performed using 2D particle-in-cell method with Monte Carlo collisions (PIC/MCC) at 10 MHz in nitrogen at atmospheric pressure. The free diffusion dominated, high velocity field emission electrons create a large positive space charge and a body force on the order of 106 N m‑3. The body force and Joule heat decrease with increase in dielectric thickness and electrode thickness. The body force also decreases at lower pressures. The plasma body force distribution along with the Joule heating is then used in the Navier–Stokes simulations to quantify the flow actuation in a microchannel. Theoretical analysis and simulations for plasma actuated planar Poiseuille flow show that the gain in flow rate is inversely proportional to Reynolds number. This theoretical analysis is in good agreement with the simulations for a microchannel with closely placed actuators under incompressible conditions. Flow rate of FE-DBD driven 2D microchannel is around 100 ml min‑1 mm‑1 for an input power of 64 μW mm‑1. The gas temperature rises by 1500 K due to the Joule heating, indicating FE-DBD’s potential for microcombustion, micropropulsion and chemical sensing in addition to microscale pumping and mixing applications.

  6. Granular temperature field of monodisperse granular flows

    NASA Astrophysics Data System (ADS)

    Gollin, Devis; Bowman, Elisabeth; Shepley, Paul

    2015-04-01

    For dry granular flows as well as solid-fluid mixtures such as debris avalanches, the momentum transfer is carried by frictional and collisional stresses. The latter may be described by the granular temperature, which provides a measure of the energy contained within the fluctuating nature of the granular motion. Thus, granular temperature can be used as a valuable means to infer the ability of a granular system to flow. Granular materials are known for the difficulties they pose in obtaining accurate microscale laboratory measurements. This is why many theories, such as the kinetic theory of granular gases, are primarily compared to numerical simulations. However, thanks to recent advancements in optical techniques along with high-speed recording systems, experimentalists are now able to obtain robust measurements of granular temperature. At present, the role of granular temperature in granular flows still entails conjecture. As a consequence, it is extremely important to provide experimental data against which theories and simulations can be judged. This investigation focuses on dry granular flows of sand and spherical beads performed on a simple inclined chute geometry. Fluctuation velocity, granular temperature and velocity patterns are obtained by means of particle image velocimetry (PIV). Flow behaviour is probed for different spatial (interrogation sizes) and temporal (frame rates) resolutions. Through the variation of these parameters an attempt to demonstrate the consistency of the degree of unsteadiness within the flow is made. In many studies a uniform stationary flow state is usually sought or preferably assumed for the simplicity it provides in the calculations. If one tries to measure microscale fields such as granular temperature, this assumption may be inappropriate. Thus, a proper definition of the flow regime should be made in order to estimate the correct flow properties. In addition, PIV analysis is compared against particle tracking velocimetry

  7. Analytical and experimental study of the acoustics and the flow field characteristics of cavitating self-resonating water jets

    SciTech Connect

    Chahine, G.L.; Genoux, P.F.; Johnson, V.E. Jr.; Frederick, G.S.

    1984-09-01

    Waterjet nozzles (STRATOJETS) have been developed which achieve passive structuring of cavitating submerged jets into discrete ring vortices, and which possess cavitation incipient numbers six times higher than obtained with conventional cavitating jet nozzles. In this study we developed analytical and numerical techniques and conducted experimental work to gain an understanding of the basic phenomena involved. The achievements are: (1) a thorough analysis of the acoustic dynamics of the feed pipe to the nozzle; (2) a theory for bubble ring growth and collapse; (3) a numerical model for jet simulation; (4) an experimental observation and analysis of candidate second-generation low-sigma STRATOJETS. From this study we can conclude that intensification of bubble ring collapse and design of highly resonant feed tubes can lead to improved drilling rates. The models here described are excellent tools to analyze the various parameters needed for STRATOJET optimizations. Further analysis is needed to introduce such important factors as viscosity, nozzle-jet interaction, and ring-target interaction, and to develop the jet simulation model to describe the important fine details of the flow field at the nozzle exit.

  8. Knowledge-based flow field zoning

    NASA Technical Reports Server (NTRS)

    Andrews, Alison E.

    1988-01-01

    Automation flow field zoning in two dimensions is an important step towards easing the three-dimensional grid generation bottleneck in computational fluid dynamics. A knowledge based approach works well, but certain aspects of flow field zoning make the use of such an approach challenging. A knowledge based flow field zoner, called EZGrid, was implemented and tested on representative two-dimensional aerodynamic configurations. Results are shown which illustrate the way in which EZGrid incorporates the effects of physics, shape description, position, and user bias in a flow field zoning.

  9. Flow-Field Surveys for Rectangular Nozzles

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.

    2012-01-01

    Flow field survey results for three rectangular nozzles are presented for a low subsonic condition obtained primarily by hot-wire anemometry. The three nozzles have aspect ratios of 2:1, 4:1 and 8:1. A fourth case included has 2:1 aspect ratio with chevrons added to the long edges. Data on mean velocity, turbulent normal and shear stresses as well as streamwise vorticity are presented covering a streamwise distance up to sixteen equivalent diameters from the nozzle exit. These detailed flow properties, including initial boundary layer characteristics, are usually difficult to measure in high speed flows and the primary objective of the study is to aid ongoing and future computational and noise modeling efforts.

  10. Interaction of bentonite colloids with Cs, Eu, Th and U in presence of humic acid: A flow field-flow fractionation study

    NASA Astrophysics Data System (ADS)

    Bouby, Muriel; Geckeis, Horst; Lützenkirchen, Johannes; Mihai, Silvia; Schäfer, Thorsten

    2011-07-01

    The interaction of Cs(I), Eu(III), Th(IV) and U(VI) with montmorillonite colloids was investigated in natural Grimsel Test Site groundwater over a 3 years period. The asymmetric flow field-flow fractionation combined with various detectors was applied to study size variations of colloids and to monitor colloid association of trace metals. The colloids suspended directly in the low ionic strength ( I), slightly alkaline granitic groundwater ( I = 10 -3 mol/L, pH 9.6) showed a gradual agglomeration with a size distribution shift from initially 10-200 nm to 50-400 nm within over 3 years. The Ca 2+ concentration of 2.1 × 10 -4 mol/L in the ground water is believed to be responsible for the slow agglomeration due to Ca 2+ ion exchange against Li + and Na + at the permanently charged basal clay planes. Furthermore, the Ca 2+ concentration lies close to the critical coagulation concentration (CCC) of 10 -3 mol L -1 for clay colloids. Slow destabilization may delimit clay colloid migration in this specific groundwater over long time scales. Eu(III) and Th(IV) are found predominantly bound to clay colloids, while U(VI) prevails as the UO 2(OH) 3- complex and Cs(I) remains mainly as aquo ion under our experimental conditions. Speciation calculations qualitatively represent the experimental data. A focus was set on the reversibility of metal ion-colloid binding. Addition of humic acid as a competing ligand induces rapid metal ion dissociation from clay colloids in the case of Eu(III) even after previous aging for about 3 years. Interestingly only partial dissociation occurs in the case of Th(IV). Experiments and calculations prove that the humate complexes dominate the speciation of all metal ions under given conditions. The partial irreversibility of clay bound Th(IV) is presently not understood but might play an important role for the colloid-mediated transport of polyvalent actinides over wide distances in natural groundwater.

  11. Improved visualization of flow field measurements

    NASA Technical Reports Server (NTRS)

    Miles, Jeffrey Hilton

    1991-01-01

    A capability is proposed that makes it feasible to apply to measured flow field data the visualization tools developed to display numerical solutions for computational fluid dynamic problems. The measurement monitor surface (MMS) methodology was used for the analysis of flow field measurements within a low-aspect-ratio transonic axial-flow fan rotor acquired with two-dimensional laser anemometry. It is shown that the MMS method may be utilized to generate input for the multidimensional processing and analytical tools developed for numerical flow field simulation data. Thus an experimenter utilizing an interactive graphics program could illustrate scalar quantities such as Mach number by profiles, contour lines, carpet plots, and surfaces employing various color intensities. Also, flow directionality can be shown by the display of vector fields and particle traces.

  12. SRMAFTE facility checkout model flow field analysis

    NASA Technical Reports Server (NTRS)

    Dill, Richard A.; Whitesides, Harold R.

    1992-01-01

    The Solid Rocket Motor Air Flow Equipment (SRMAFTE) facility was constructed for the purpose of evaluating the internal propellant, insulation, and nozzle configurations of solid propellant rocket motor designs. This makes the characterization of the facility internal flow field very important in assuring that no facility induced flow field features exist which would corrupt the model related measurements. In order to verify the design and operation of the facility, a three-dimensional computational flow field analysis was performed on the facility checkout model setup. The checkout model measurement data, one-dimensional and three-dimensional estimates were compared, and the design and proper operation of the facility was verified. The proper operation of the metering nozzles, adapter chamber transition, model nozzle, and diffuser were verified. The one-dimensional and three-dimensional flow field estimates along with the available measurement data are compared.

  13. Low magnetic fields for flow propagators in permeable rocks.

    PubMed

    Singer, Philip M; Leu, Gabriela; Fordham, Edmund J; Sen, Pabitra N

    2006-12-01

    Pulsed field gradient NMR flow propagators for water flow in Bentheimer sandstone are measured at low fields (1H resonance 2 MHz), using both unipolar and bipolar variants of the pulsed gradient method. We compare with propagators measured at high fields (1H resonance 85 MHz). We show that (i) measured flow propagators appear to be equivalent, in this rock, and (ii) the lower signal to noise ratio at low fields is not a serious limitation. By comparing different pulse sequences, we study the effects of the internal gradients on the propagator measurement at 2 MHz, which for certain rocks may persist even at low fields. PMID:16962343

  14. Field Flows of Dark Energy

    SciTech Connect

    Cahn, Robert N.; de Putter, Roland; Linder, Eric V.

    2008-07-08

    Scalar field dark energy evolving from a long radiation- or matter-dominated epoch has characteristic dynamics. While slow-roll approximations are invalid, a well defined field expansion captures the key aspects of the dark energy evolution during much of the matter-dominated epoch. Since this behavior is determined, it is not faithfully represented if priors for dynamical quantities are chosen at random. We demonstrate these features for both thawing and freezing fields, and for some modified gravity models, and unify several special cases in the literature.

  15. Numerical calculations of flow fields

    NASA Technical Reports Server (NTRS)

    Anderson, D. M.; Vogel, J. M.

    1972-01-01

    The solutions to the equations of motion for inviscid fluid flow around a pointed elliptic cone at incidence are presented. The numerical method used, MacCormack's second order preferential predictor-corrector finite difference approximation, is applied to the fluid flow equations derived in conservation-law form. The entropy boundary condition, hitherto unused for elliptic cone problems, is investigated and compared to reflection boundary condition solutions. The stagnation streamline movement of the inclined elliptic cone is noted and surface pressure coefficients are plotted. Also presented are solutions for an elliptic cone and a circular cone at zero incidence and a circular cone at a small angle of attack. Comparisons are made between these present solutions and previously published theory.

  16. Study on dynamics of the influence exerted by plasma on gas flow field in non-thermal atmospheric pressure plasma jet

    NASA Astrophysics Data System (ADS)

    Qaisrani, M. Hasnain; Xian, Yubin; Li, Congyun; Pei, Xuekai; Ghasemi, Maede; Lu, Xinpei

    2016-06-01

    In this paper, first, steady state of the plasma jet at different operating conditions is investigated through Schlieren photography with and without applying shielding gas. Second, the dynamic process for the plasma impacting on the gas flow field is studied. When the discharge is ignited, reduction in laminar flow occurs. However, when the gas flow rate is too low or too high, this phenomenon is not obvious. What is more, both frequency and voltage have significant impact on the effect of plasma on the gas flow, but the former is more significant. Shielding gas provides a curtain for plasma to propagate further. High speed camera along with Schlieren photography is utilized to study the impact of plasma on the gas flow when plasma is switched on and off. The transition of the gas flow from laminar to turbulent or vice versa happens right after the turbulent front. It is concluded that appearance and propagation of turbulence front is responsible for the transition of the flow state.

  17. Two-phase numerical study of the flow field formed in water pump sump: influence of air entrainment

    NASA Astrophysics Data System (ADS)

    Bayeul-Lainé, A. C.; Simonet, S.; Bois, G.; Issa, A.

    2012-11-01

    In a pump sump it is imperative that the amount of non-homogenous flow and entrained air be kept to a minimum. Free air-core vortex occurring at a water-intake pipe is an important problem encountered in hydraulic engineering. These vortices reduce pump performances, may have large effects on the operating conditions and lead to increase plant operating costs.This work is an extended study starting from 2006 in LML and published by ISSA and al. in 2008, 2009 and 2010. Several cases of sump configuration have been numerically investigated using two specific commercial codes and based on the initial geometry proposed by Constantinescu and Patel. Fluent and Star CCM+ codes are used in the previous studies. The results, obtained with a structured mesh, were strongly dependant on main geometrical sump configuration such as the suction pipe position, the submergence of the suction pipe on one hand and the turbulence model on the other hand. Part of the results showed a good agreement with experimental investigations already published. Experiments, conducted in order to select best positions of the suction pipe of a water-intake sump, gave qualitative results concerning flow disturbances in the pump-intake related to sump geometries and position of the pump intake. The purpose of this paper is to reproduce the flow pattern of experiments and to confirm the geometrical parameter that influences the flow structure in such a pump. The numerical model solves the Reynolds averaged Navier-Stokes (RANS) equations and VOF multiphase model. STAR CCM+ with an adapted mesh configuration using hexahedral mesh with prism layer near walls was used. Attempts have been made to calculate two phase unsteady flow for stronger mass flow rates and stronger submergence with low water level in order to be able to capture air entrainment. The results allow the knowledge of some limits of numerical models, of mass flow rates and of submergences for air entrainment. In the validation of this

  18. DECORRELATION TIMES OF PHOTOSPHERIC FIELDS AND FLOWS

    SciTech Connect

    Welsch, B. T.; Kusano, K.; Yamamoto, T. T.; Muglach, K.

    2012-03-10

    We use autocorrelation to investigate evolution in flow fields inferred by applying Fourier local correlation tracking (FLCT) to a sequence of high-resolution (0.''3), high-cadence ({approx_equal} 2 minute) line-of-sight magnetograms of NOAA active region (AR) 10930 recorded by the narrowband filter imager of the Solar Optical Telescope aboard the Hinode satellite over 2006 December 12 and 13. To baseline the timescales of flow evolution, we also autocorrelated the magnetograms, at several spatial binnings, to characterize the lifetimes of active region magnetic structures versus spatial scale. Autocorrelation of flow maps can be used to optimize tracking parameters, to understand tracking algorithms' susceptibility to noise, and to estimate flow lifetimes. Tracking parameters varied include: time interval {Delta}t between magnetogram pairs tracked, spatial binning applied to the magnetograms, and windowing parameter {sigma} used in FLCT. Flow structures vary over a range of spatial and temporal scales (including unresolved scales), so tracked flows represent a local average of the flow over a particular range of space and time. We define flow lifetime to be the flow decorrelation time, {tau}. For {Delta}t > {tau}, tracking results represent the average velocity over one or more flow lifetimes. We analyze lifetimes of flow components, divergences, and curls as functions of magnetic field strength and spatial scale. We find a significant trend of increasing lifetimes of flow components, divergences, and curls with field strength, consistent with Lorentz forces partially governing flows in the active photosphere, as well as strong trends of increasing flow lifetime and decreasing magnitudes with increases in both spatial scale and {Delta}t.

  19. Decorrelation Times of Photospheric Fields and Flows

    NASA Technical Reports Server (NTRS)

    Welsch, B. T.; Kusano, K.; Yamamoto, T. T.; Muglach, K.

    2012-01-01

    We use autocorrelation to investigate evolution in flow fields inferred by applying Fourier Local Correlation Tracking (FLCT) to a sequence of high-resolution (0.3 "), high-cadence (approx = 2 min) line-of-sight magnetograms of NOAA active region (AR) 10930 recorded by the Narrowband Filter Imager (NFI) of the Solar Optical Telescope (SOT) aboard the Hinode satellite over 12 - 13 December 2006. To baseline the timescales of flow evolution, we also autocorrelated the magnetograms, at several spatial binnings, to characterize the lifetimes of active region magnetic structures versus spatial scale. Autocorrelation of flow maps can be used to optimize tracking parameters, to understand tracking algorithms f susceptibility to noise, and to estimate flow lifetimes. Tracking parameters varied include: time interval Delta t between magnetogram pairs tracked, spatial binning applied to the magnetograms, and windowing parameter sigma used in FLCT. Flow structures vary over a range of spatial and temporal scales (including unresolved scales), so tracked flows represent a local average of the flow over a particular range of space and time. We define flow lifetime to be the flow decorrelation time, tau . For Delta t > tau, tracking results represent the average velocity over one or more flow lifetimes. We analyze lifetimes of flow components, divergences, and curls as functions of magnetic field strength and spatial scale. We find a significant trend of increasing lifetimes of flow components, divergences, and curls with field strength, consistent with Lorentz forces partially governing flows in the active photosphere, as well as strong trends of increasing flow lifetime and decreasing magnitudes with increases in both spatial scale and Delta t.

  20. Advancement of Shock-wave Induced Spraying Process through the Study of Gas and Particle Flow Fields

    NASA Astrophysics Data System (ADS)

    Karimi Esfahani, Mohammad

    This research advances the knowledge of the working principles of the Shock-wave Induced Spraying Process (SISP), a thermal spray material deposition technique. Pulses created by a fast acting valve pass through a heated line increasing energy content and interacting with metered batches of heated or non-heated powder introduced into the line. The powder is accelerated to high velocities before bonding to the substrate upon impact. Advantages over other cold spray processes include cost savings and a more effective transfer of thermal energy to the powder. The shock-wave occurring near the substrate in other cold spray processes is avoided. The SISP flow field is resolved by using a computational model. The two-dimensional model accounts for the valve, gas heater, a tapered nozzle at the tip of the device, and preheating of the powder. It is implemented with a commercial computational fluid dynamics code. Comparisons are made with one-dimensional predictions, and measurements of pressure and temperature. Particle flow predictions are validated using particle velocity and adhesion measurements. A flow region of both high temperature and velocity gas, favorable to material deposition, forms which is not present in comparable steady-state cold spray processes. Increasing gas pressure increases the gas speed, while increasing temperature increases speed and temperature of this region. Using helium results in greater energy levels but for shorter periods of time. This indicates the need for a powder feeder which places particles in the flow at correct instants and durations of time. The effects of particle flow parameters on system performance are examined. It is found that the device must be operated at very high main heater and powder heater temperatures: 900 °C and 700 °C respectively to achieve a coating with stainless steel using nitrogen as the driving gas. It is also shown that a heater length range of 0.9 m to 1.4 m results in the greatest likelihood of

  1. Experimental results for a hypersonic nozzle/afterbody flow field

    NASA Technical Reports Server (NTRS)

    Spaid, Frank W.; Keener, Earl R.; Hui, Frank C. L.

    1995-01-01

    This study was conducted to experimentally characterize the flow field created by the interaction of a single-expansion ramp-nozzle (SERN) flow with a hypersonic external stream. Data were obtained from a generic nozzle/afterbody model in the 3.5 Foot Hypersonic Wind Tunnel at the NASA Ames Research Center, in a cooperative experimental program involving Ames and McDonnell Douglas Aerospace. The model design and test planning were performed in close cooperation with members of the Ames computational fluid dynamics (CFD) team for the National Aerospace Plane (NASP) program. This paper presents experimental results consisting of oil-flow and shadow graph flow-visualization photographs, afterbody surface-pressure distributions, rake boundary-layer measurements, Preston-tube skin-friction measurements, and flow field surveys with five-hole and thermocouple probes. The probe data consist of impact pressure, flow direction, and total temperature profiles in the interaction flow field.

  2. Study on blood flow containing nanoparticles through porous arteries in presence of magnetic field using analytical methods

    NASA Astrophysics Data System (ADS)

    Ghasemi, Seiyed E.; Hatami, M.; Sarokolaie, A. Kalani; Ganji, D. D.

    2015-06-01

    In this paper, flow analysis for a third grade non-Newtonian blood in porous arteries in presence of magnetic field is simulated analytically and numerically. Blood is considered as the third grade non-Newtonian fluid containing nanoparticles. Collocation Method (CM) and Optimal Homotopy Asymptotic Method (OHAM) are used to solve the Partial Differential Equation (PDE) governing equation which a good agreement between them was observed in the results. The influences of the some physical parameters such as Brownian motion parameter, pressure gradient and thermophoresis parameter, etc. on temperature, velocity and nanoparticles concentration profiles are considered. For instance, increasing the thermophoresis parameter (Nt) caused an increase in temperature values in whole domain and an increase in nanoparticles concentration near the inner wall.

  3. Controlling flow direction in nanochannels by electric field strength

    NASA Astrophysics Data System (ADS)

    Gao, Xiang; Zhao, Tianshou; Li, Zhigang

    2015-08-01

    Molecular dynamics simulations are conducted to study the flow behavior of CsF solutions in nanochannels under external electric fields E . It is found that the channel surface energy greatly affects the flow behavior. In channels of high surface energy, water molecules, on average, move in the same direction as that of the electric field regardless of the strength of E . In low surface energy channels, however, water transports in the opposite direction to the electric field at weak E and the flow direction is changed when E becomes sufficiently large. The direction change of water flow is attributed to the coupled effects of different water-ion interactions, inhomogeneous water viscosity, and ion distribution changes caused by the electric field. The flow direction change observed in this work may be employed for flow control in complex micro- or nanofluidic systems.

  4. Use of computer graphics for visualization of flow fields

    NASA Technical Reports Server (NTRS)

    Watson, Val; Buning, Pieter; Choi, Diana; Bancroft, Gordon; Merritt, Fergus; Rogers, Stuart

    1987-01-01

    A high-performance graphics workstation has been combined with software developed for flow-field visualization to yield a highly effective tool for analysis of fluid-flow dynamics. After the flow fields are obtained from experimental measurements or computer simulations, the workstation permits one to interactively view the dynamics of the flow fields; e.g., the viewer can zoom into a region or rotate his viewing position about the region to study it in more detail. Several techniques for visualization of flow fields with this workstation are described in this paper and illustrated with a videotape available from the authors. The computer hardware and software required to create effective flow visualization displays are discussed. Additional software and hardware required to create videotapes or 16mm movies are also described. Limitations imposed by current workstation performance is addressed and future workstation performance is forecast.

  5. Numerical study of the SSME nozzle flow fields during transient operations: A comparison of the animated results with test

    NASA Technical Reports Server (NTRS)

    Wang, Ten-See; Dumas, Catherine

    1993-01-01

    A computational fluid dynamics (CFD) model has been applied to study the transient flow phenomena of the nozzle and exhaust plume of the Space Shuttle Main Engine (SSME), fired at sea level. The CFD model is a time accurate, pressure based, reactive flow solver. A six-species hydrogen/oxygen equilibrium chemistry is used to describe the chemical-thermodynamics. An adaptive upwinding scheme is employed for the spatial discretization, and a predictor, multiple corrector method is used for the temporal solution. Both engine start-up and shut-down processes were simulated. The elapse time is approximately five seconds for both cases. The computed results were animated and compared with the test. The images for the animation were created with PLOT3D and FAST and then animated with ABEKAS. The hysteresis effects, and the issues of free-shock separation, restricted-shock separation and the end-effects were addressed.

  6. Numerical study of the SSME nozzle flow fields during transient operations: A comparison of the animated results with test

    NASA Astrophysics Data System (ADS)

    Wang, Ten-See; Dumas, Catherine

    1993-07-01

    A computational fluid dynamics (CFD) model has been applied to study the transient flow phenomena of the nozzle and exhaust plume of the Space Shuttle Main Engine (SSME), fired at sea level. The CFD model is a time accurate, pressure based, reactive flow solver. A six-species hydrogen/oxygen equilibrium chemistry is used to describe the chemical-thermodynamics. An adaptive upwinding scheme is employed for the spatial discretization, and a predictor, multiple corrector method is used for the temporal solution. Both engine start-up and shut-down processes were simulated. The elapse time is approximately five seconds for both cases. The computed results were animated and compared with the test. The images for the animation were created with PLOT3D and FAST and then animated with ABEKAS. The hysteresis effects, and the issues of free-shock separation, restricted-shock separation and the end-effects were addressed.

  7. Flow field visualization about external axial corners

    NASA Technical Reports Server (NTRS)

    Talcott, N. A., Jr.

    1978-01-01

    An experimental investigation was conducted to visualize the flow field about external axial corners. The investigation was initiated to provide answers to questions about the inviscid flow pattern for continuing numerical investigations. Symmetrical and asymmetrical corner models were tested at a Reynolds number per meter of 60,700,000. Oil-flow and vapor-screen photographs were taken for both models at angle of attack and yaw. The paper presents the results of the investigation in the form of oil-flow photographs and the surrounding shock wave location obtained from the vapor screens.

  8. Geology of the Tyrrhenus Mons Lava Flow Field, Mars

    NASA Astrophysics Data System (ADS)

    Crown, David A.; Mest, Scott C.

    2014-11-01

    The ancient, eroded Martian volcano Tyrrhenus Mons exhibits a central caldera complex, layered flank deposits dissected by radial valleys, and a 1000+ km-long flow field extending to the southwest toward Hellas Planitia. Past studies suggested an early phase of volcanism dominated by large explosive eruptions followed by subsequent effusive activity at the summit and to the southwest. As part of a new geologic mapping study of northeast Hellas, we are examining the volcanic landforms and geologic evolution of the Tyrrhenus Mons flow field, including the timing and nature of fluvial activity and effects on volcanic units. New digital geologic mapping incorporates THEMIS IR (100 m/pixel) and CTX (5 m/pixel) images as well as constraints from MOLA topography.Mapping results to-date include delineation of the boundaries of the flow field, identification and mapping of volcanic and erosional channels within the flow field, and mapping and analysis of lava flow lobes. THEMIS IR and CTX images allow improved discrimination of the numerous flow lobes that are observed in the flow field, including refinement of the margins of previously known flows and identification of additional and smaller lobes. A prominent sinuous rille extending from Tyrrhenus Mons’ summit caldera is a major feature that supplied lava to the flow field. Smaller volcanic channels are common throughout the flow field; some occur in segments along crests of local topographic highs and may delineate lava tubes. In addition to volcanic channels, the flow field surface is characterized by several types of erosional channels, including wide troughs with scour marks, elongate sinuous channels, and discontinuous chains of elongate pits and troughs. High-resolution images reveal the widespread and significant effects of fluvial activity in the region, and further mapping studies will examine spatial and temporal interactions between volcanism and fluvial processes.

  9. Improved modeling techniques for turbomachinery flow fields

    SciTech Connect

    Lakshminarayana, B.; Fagan, J.R. Jr.

    1995-12-31

    This program has the objective of developing an improved methodology for modeling turbomachinery flow fields, including the prediction of losses and efficiency. Specifically, the program addresses the treatment of the mixing stress tensor terms attributed to deterministic flow field mechanisms required in steady-state Computational Fluid Dynamic (CFD) models for turbomachinery flow fields. These mixing stress tensors arise due to spatial and temporal fluctuations (in an absolute frame of reference) caused by rotor-stator interaction due to various blade rows and by blade-to-blade variation of flow properties. This will be accomplished in a cooperative program by Penn State University and the Allison Engine Company. These tasks include the acquisition of previously unavailable experimental data in a high-speed turbomachinery environment, the use of advanced techniques to analyze the data, and the development of a methodology to treat the deterministic component of the mixing stress tenor.

  10. Hypervelocity atmospheric flight: Real gas flow fields

    NASA Technical Reports Server (NTRS)

    Howe, John T.

    1990-01-01

    Flight in the atmosphere is examined from the viewpoint of including real gas phenomena in the flow field about a vehicle flying at hypervelocity. That is to say, the flow field is subject not only to compressible phenomena, but is dominated by energetic phenomena. There are several significant features of such a flow field. Spatially, its composition can vary by both chemical and elemental species. The equations which describe the flow field include equations of state and mass, species, elemental, and electric charge continuity; momentum; and energy equations. These are nonlinear, coupled, partial differential equations that were reduced to a relatively compact set of equations of a self-consistent manner (which allows mass addition at the surface at a rate comparable to the free-stream mass flux). The equations and their inputs allow for transport of these quantities relative to the mass-averaged behavior of the flow field. Thus transport of mass by chemical, thermal, pressure, and forced diffusion; transport of momentum by viscosity; and transport of energy by conduction, chemical considerations, viscosity, and radiative transfer are included. The last of these complicate the set of equations by making the energy equation a partial integrodifferential equation. Each phenomenon is considered and represented mathematically by one or more developments. The coefficients which pertain are both thermodynamically and chemically dependent. Solutions of the equations are presented and discussed in considerable detail, with emphasis on severe energetic flow fields. For hypervelocity flight in low-density environments where gaseous reactions proceed at finite rates, chemical nonequilibrium is considered and some illustrations are presented. Finally, flight where the flow field may be out of equilibrium, both chemically and thermodynamically, is presented briefly.

  11. Hypervelocity atmospheric flight: Real gas flow fields

    NASA Technical Reports Server (NTRS)

    Howe, John T.

    1989-01-01

    Flight in the atmosphere is examined from the viewpoint of including real gas phenomena in the flow field about a vehicle flying at hypervelocity. That is to say, the flow field is subject not only to compressible phenomena, but is dominated by energetic phenomena. There are several significant features of such a flow field. Spatially, its composition can vary by both chemical and elemental species. The equations which describe the flow field include equations of state and mass, species, elemental, and electric charge continuity; momentum; and energy equations. These are nonlinear, coupled, partial differential equations that have been reduced to a relatively compact set of equations in a self-consistent manner (which allows mass addition at the surface at a rate comparable to the free-stream mass flux). The equations and their inputs allow for transport of these quantities relative to the mass-average behavior of the flow field. Thus transport of mass by chemical, thermal, pressure, and forced diffusion; transport of momentum by viscosity; and transport of energy by conduction, chemical considerations, viscosity, and radiative transfer are included. The last of these complicate the set of equations by making the energy equations a partial integrodifferential equation. Each phenomenon is considered and represented mathematically by one or more developments. The coefficients which pertain are both thermodynamically and chemically dependent. Solutions of the equations are presented and discussed in considerable detail, with emphasis on severe energetic flow fields. Hypervelocity flight in low-density environments where gaseous reactions proceed at finite rates chemical nonequilibrium is considered, and some illustrations are presented. Finally, flight where the flow field may be out of equilibrium, both chemically and thermodynamically, is presented briefly.

  12. Impeller flow field measurement and analysis

    NASA Technical Reports Server (NTRS)

    Fagan, J. R.; Fleeter, S.

    1991-01-01

    A series of experiments are performed to investigate and quantify the three-dimensional mean flow field in centrifugal compressor flow passages and to evaluate contemporary internal flow models. The experiments include the acquisition and analysis of LDV data in the impeller passages of a low-speed moderate-scale research mixed-flow centrifugal compressor operating at its design point. Predictions from a viscous internal flow model are then correlated with these data. The LDV data show the traditional jet-wake structure observed in many centrifugal compressors, with the wake observed along the shroud 70 percent of the length from the pressure to suction surface. The viscous model predicts the major flow phenomena. However, the correlations of the viscous predictions with the LDV data were poor.

  13. Flow Field Around a Hovering Rotor

    NASA Technical Reports Server (NTRS)

    Tung, C.; Low, S.

    1997-01-01

    A lifting surface hover code developed by the Analytical Method Inc. (AMI) was used to compute the average and unsteady velocity flow field of an isolated rotor without ground effect. The predicted velocity field compares well with experimental data obtained by hot-wire anemometry and by Laser Doppler Velocimetry. A subroutine 'DOWNWASH' was written to predict the velocity field at any given point in the wake for a given blade position.

  14. Molecular characterization of solution styrene-butadiene rubber: thermal field-flow fractionation/multi-angle light scattering studies.

    PubMed

    Choi, You Jin; Kim, Sun Tae; Lee, Seung Hwa; Kim, A-Ju; Kwag, Gwanghoon; Lee, Seungho

    2013-11-01

    Solution styrene-butadiene rubber (SSBR) is mainly constituted of a random copolymer of styrene and butadiene. SSBR usually contains microgels, having ultrahigh molecular weight (M>10(7)g/mol), affecting rheological properties of the rubber. Thus, determinations of M and size distribution of these microgels are critical in performance evaluation and control for SSBR. We employ thermal field-flow fractionation (ThFFF), combined with online multi-angle light scattering (MALS), as most suited for characterization of solutions containing the microgels since they can be characterized in toto without removing the microgels from the solution. ThFFF-MALS was applied for characterization of linear and branched SBR materials from various commercial sources, and the results were compared to those from size-exclusion chromatography (SEC). ThFFF provides higher resolution than SEC for high molecular fractions and allowed gel content to be measured. The gel content was determined by subtracting the amount of sol from total injection mass, and was measured to be 10-15%. We infer from the characterization results that the microgel content may not be correlated to the microstructure, the styrene and vinyl content of butadiene but to the fraction of high molecular weight in SSBR. Finally, the macromolecular structure and the content of microgel (larger than about 100nm) were found to significantly affect various rheological parameters such as viscosity, mechanical and dynamic properties. PMID:24063984

  15. Images constructed from computed flow fields

    NASA Technical Reports Server (NTRS)

    Yates, Leslie A.

    1992-01-01

    A method for constructing interferograms, schlieren, and shadowgraphs from ideal- and real-gas, two- and three-dimensional computed flow fields is described. The computational grids can be structured or unstructured, and multiple grids are an option. The constructed images are compared to experimental images for several types of flow, including a ramp, a blunt-body, a nozzle, and a reacting flow. The constructed images simulate the features observed in the experimental images. They are sensitive to errors in the flow-field solutions and can be used to identify solution errors. In addition, techniques for obtaining phase shifts from experimental finite-fringe interferograms and for removing experimentally induced phase-shift errors are discussed. Both the constructed images and calculated phase shifts can be used for validation of computational fluid dynamics (CFD) codes.

  16. Space Station resource node flow field analysis

    NASA Technical Reports Server (NTRS)

    Kania, Lee; Kumar, Ganesh; Mcconnaughey, Paul

    1991-01-01

    An analysis of the flow field within the Space Station Freedom resource node with operational intermodule ventilation and temperature/humidity control ventilation systems has been conducted. The INS3D code, an incompressible, steady-state Navier-Stokes solver has been used to assess the design of the ventilation system via quantification of the level of fluid mixing and identification of 'dead air' regions and short-circuit ventilation. Numerical results indicate significant short-circuit ventilation in the forward and midsections of the node and insufficient fluid mixing is found to exist in the aft node section. These results as well as results from a solution grid dependence study are presented.

  17. Computational interferometric description of nested flow fields

    NASA Technical Reports Server (NTRS)

    Havener, A. George; Obergefell, L. A.

    1987-01-01

    Computer graphics and theoretical descriptions of density are used to obtain computer generated flow visualizations called computational interferograms. Computational interferograms are pictorially analogous to optical interferograms, and examples showing the fringe pattern for the flow about a sharp tip cone in a supersonic air stream are presented. To ascertain the effect of unsteady behavior, local density disturbances are added to the steady state flow field. This introduces irregularities to the computational interferogram like those seen in the optical interferograms. These theoretical disturbances can be varied in geometry, density description, translated with time, and strengthened or dissipated. The accuracy of computational interferometry relies on the accuracy of the theoretical density descriptions and therefore, it provides a way of verifying existing models of flow fields, especially those containing unsteady or turbulent behavior. In addition to being a unique method of flow visualization, computational interferometry can be used to develop and modify theories or numerical solutions to both simple and complex flow fields. The presented research is a general description of this process.

  18. Enhanced capture of magnetic microbeads using combination of reduced magnetic field strength and sequentially switched electroosmotic flow--a numerical study.

    PubMed

    Das, Debarun; Al-Rjoub, Marwan F; Banerjee, Rupak K

    2015-05-01

    Magnetophoretic immunoassay is a widely used technique in lab-on-chip systems for detection and isolation of target cells, pathogens, and biomolecules. In this method, target pathogens (antigens) bind to specific antibodies coated on magnetic microbeads (mMBs) which are then separated using an external magnetic field for further analysis. Better capture of mMB is important for improving the sensitivity and performance of magnetophoretic assay. The objective of this study was to develop a numerical model of magnetophoretic separation in electroosmotic flow (EOF) using magnetic field generated by a miniaturized magnet and to evaluate the capture efficiency (CE) of the mMBs. A finite-volume solver was used to compute the trajectory of mMBs under the coupled effects of EOF and external magnetic field. The effect of steady and time varying (switching) electric fields (150-450 V/cm) on the CE was studied under reduced magnetic field strength. During switching, the electric potential at the inlet and outlet of the microchannel was reversed or switched, causing reversal in flow direction. The CE was a function of the momentum of the mMB in EOF and the applied magnetic field strength. By switching the electric field, CE increased from 75% (for steady electric field) to 95% for lower electric fields (150-200 V/cm) and from 35% to 47.5% for higher electric fields (400-450 V/cm). The CE was lower at higher EOF electric fields because the momentum of the mMB overcame the external magnetic force. Switching allowed improved CE due to the reversal and decrease in EOF velocity and increase in mMB residence time under the reduced magnetic field strength. These improvements in CE, particularly at higher electric fields, made sequential switching of EOF an efficient separation technique of mMBs for use in high throughput magnetophoretic immunoassay devices. The reduced size of the magnet, along with the efficient mMB separation technique of switching can lead to the development

  19. Flow Transitions in a Rotating Magnetic Field

    NASA Technical Reports Server (NTRS)

    Volz, M. P.; Mazuruk, K.

    1996-01-01

    Critical Rayleigh numbers have been measured in a liquid metal cylinder of finite height in the presence of a rotating magnetic field. Several different stability regimes were observed, which were determined by the values of the Rayleigh and Hartmann numbers. For weak rotating magnetic fields and small Rayleigh numbers, the experimental observations can be explained by the existence of a single non-axisymmetric meridional roll rotating around the cylinder, driven by the azimuthal component of the magnetic field. The measured dependence of rotational velocity on magnetic field strength is consistent with the existence of laminar flow in this regime.

  20. Microgravity Geyser and Flow Field Prediction

    NASA Technical Reports Server (NTRS)

    Hochstein, J. I.; Marchetta, J. G.; Thornton, R. J.

    2006-01-01

    Modeling and prediction of flow fields and geyser formation in microgravity cryogenic propellant tanks was investigated. A computational simulation was used to reproduce the test matrix of experimental results performed by other investigators, as well as to model the flows in a larger tank. An underprediction of geyser height by the model led to a sensitivity study to determine if variations in surface tension coefficient, contact angle, or jet pipe turbulence significantly influence the simulations. It was determined that computational geyser height is not sensitive to slight variations in any of these items. An existing empirical correlation based on dimensionless parameters was re-examined in an effort to improve the accuracy of geyser prediction. This resulted in the proposal for a re-formulation of two dimensionless parameters used in the correlation; the non-dimensional geyser height and the Bond number. It was concluded that the new non-dimensional geyser height shows little promise. Although further data will be required to make a definite judgement, the reformulation of the Bond number provided correlations that are more accurate and appear to be more general than the previously established correlation.

  1. A validation study of a rapid field-based rating system for discriminating among flow permanence classes of headwater streams in South Carolina.

    PubMed

    Fritz, Ken M; Wenerick, William R; Kostich, Mitch S

    2013-11-01

    Rapid field-based protocols for classifying flow permanence of headwater streams are needed to inform timely regulatory decisions. Such an existing method was developed for and has been used in North Carolina since 1998. The method uses ordinal scoring of 26 geomorphology, hydrology, and biology attributes of streams. The attribute scores are summed and compared to threshold scores to assign a flow permanence class. Our study objective was to evaluate the method's ability to classify the flow permanence of forested stream reaches from Piedmont and Southeastern Plains ecoregions in South Carolina. Ephemeral reaches scored significantly lower than intermittent and perennial reaches, but scores from intermittent and perennial reaches did not differ. Scores collected in the dry and wet seasons were strongly correlated, indicating that the method was seasonally stable. Scores had positive nonlinear relationships with the maximum recorded wet duration and the proportion of the record that reaches were wet, but were not related to drying frequency. Scores of the presence of baseflow in the dry season were more important in flow permanence classification than those from the wet season. Other important attributes and parameters in discriminating flow classes were macrobenthos, rooted upland plants, bankfull width, drainage area, and ecoregion. Although the North Carolina method did not consistently differentiate intermittent from perennial reaches, the indicator-based approach is a strong foundation from which to build a protocol for South Carolina. Adding measures like bankfull width and drainage area, weighting by ecoregion, or shifting thresholds may be warranted modifications for South Carolina. PMID:24000112

  2. Unsteady fluid dynamic model for propeller induced flow fields

    NASA Technical Reports Server (NTRS)

    Katz, Joseph; Ashby, Dale L.; Yon, Steven

    1991-01-01

    A potential flow based three-dimensional panel method was modified to treat time dependent flow conditions in which the body's geometry may vary with time. The main objective of this effort was the study of a flow field due to a propeller rotating relative to a nonrotating body which is otherwise moving at a constant forward speed. Calculated surface pressure, thrust and torque coefficient data for a four-bladed marine propeller/body compared favorably with previously published experimental results.

  3. The use of asymmetrical flow field-flow fractionation with on-line detection in the study of drug retention within liposomal nanocarriers and drug transfer kinetics.

    PubMed

    Hinna, Askell Hvid; Hupfeld, Stefan; Kuntsche, Judith; Brandl, Martin

    2016-05-30

    Due to their solubilizing capabilities, liposomes (phospholipid vesicles) are suited for designing formulations for intravenous administration of drug compounds which are poorly water-soluble. Despite the good in-vitro stability of such formulations with minimal drug leakage, upon i.v. injection there is a risk of premature drug loss due to drug transfer to plasma proteins and cell membranes. Here we report on the refinement of a recently introduced simple in vitro predictive tool by Hinna and colleagues in 2014, which brings small drug loaded (donor) liposomes in contact with large acceptor liposomes, the latter serving as a model mimicking biological sinks in the body. The donor- and acceptor-liposomes were subsequently separated using asymmetrical flow field-flow fractionation (AF4), during which the sample is exposed to a large volume of eluent which corresponds to a dilution factor of approximately 600. The model drug content in the donor- and acceptor fraction was quantified by on-line UV/VIS extinction measurements with correction for turbidity and by off-line HPLC measurements of collected fractions. The refined method allowed for (near) baseline separation of donor and acceptor vesicles as well as reliable quantification of the drug content not only of the donor- but now also of the acceptor-liposomes due to their improved size-homogeneity, colloidal stability and reduced turbidity. This improvement over the previously reported approach allowed for simultaneous quantification of both drug transfer and drug release to the aqueous phase. By sampling at specific incubation times, the release and transfer kinetics of the model compound p-THPP (5,10,15,20-tetrakis(4-hydroxyphenyl)21H,23H-porphine) was determined. p-THPP is structurally closely related to the photosensitizer temoporfin, which is in clinical use and under evaluation in liposomal formulations. The transfer of p-THPP to the acceptor vesicles followed 1st order kinetics with a half-life of

  4. Effect of flow field on the performance of an all-vanadium redox flow battery

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Jayanti, S.

    2016-03-01

    A comparative study of the electrochemical energy conversion performance of a single-cell all-vanadium redox flow battery (VRFB) fitted with three flow fields has been carried out experimentally. The charge-discharge, polarization curve, Coulombic, voltage and round-trip efficiencies of a 100 cm2 active area VRFB fitted with serpentine, interdigitated and conventional flow fields have been obtained under nearly identical experimental conditions. The effect of electrolyte circulation rate has also been investigated for each flow field. Stable performance has been obtained for each flow field for at least 40 charge/discharge cycles. Ex-situ measurements of pressure drop have been carried out using water over a range of Reynolds numbers. Together, the results show that the cell fitted with the serpentine flow field gives the highest energy efficiency, primarily due to high voltaic efficiency and also the lowest pressure drop. The electrolyte flow rate is seen to have considerable effect on the performance; a high round-trip energy efficiency of about 80% has been obtained at the highest flow rate with the serpentine flow field. The data offer interesting insights into the effect of electrolyte circulation on the performance of VRFB.

  5. Improved modeling techniques for turbomachinery flow fields

    SciTech Connect

    Lakshminarayana, B.; Fagan, J.R. Jr.

    1995-10-01

    This program has the objective of developing an improved methodology for modeling turbomachinery flow fields, including the prediction of losses and efficiency. Specifically, the program addresses the treatment of the mixing stress tensor terms attributed to deterministic flow field mechanisms required in steady-state Computational Fluid Dynamic (CFD) models for turbo-machinery flow fields. These mixing stress tensors arise due to spatial and temporal fluctuations (in an absolute frame of reference) caused by rotor-stator interaction due to various blade rows and by blade-to-blade variation of flow properties. These tasks include the acquisition of previously unavailable experimental data in a high-speed turbomachinery environment, the use of advanced techniques to analyze the data, and the development of a methodology to treat the deterministic component of the mixing stress tensor. Penn State will lead the effort to make direct measurements of the momentum and thermal mixing stress tensors in high-speed multistage compressor flow field in the turbomachinery laboratory at Penn State. They will also process the data by both conventional and conditional spectrum analysis to derive momentum and thermal mixing stress tensors due to blade-to-blade periodic and aperiodic components, revolution periodic and aperiodic components arising from various blade rows and non-deterministic (which includes random components) correlations. The modeling results from this program will be publicly available and generally applicable to steady-state Navier-Stokes solvers used for turbomachinery component (compressor or turbine) flow field predictions. These models will lead to improved methodology, including loss and efficiency prediction, for the design of high-efficiency turbomachinery and drastically reduce the time required for the design and development cycle of turbomachinery.

  6. Biofilm responses to smooth flow fields and chemical gradients in novel microfluidic flow cells.

    PubMed

    Song, Jisun L; Au, Kelly H; Huynh, Kimberly T; Packman, Aaron I

    2014-03-01

    We present two novel microfluidic flow cells developed to provide reliable control of flow distributions and chemical gradients in biofilm studies. We developed a single-inlet microfluidic flow cell to support biofilm growth under a uniform velocity field, and a double-inlet flow cell to provide a very smooth transverse concentration gradient. Both flow cells consist of a layer of polydimethylsiloxane (PDMS) bonded to glass cover slips and were fabricated using the replica molding technique. We demonstrate the capabilities of the flow cells by quantifying flow patterns before and after growth of Pseudomonas aeruginosa biofilms through particle imaging velocimetry, and by evaluating concentration gradients within the double-inlet microfluidic flow cell. Biofilm growth substantially increased flow complexity by diverting flow around biomass, creating high- and low-velocity regions and surface friction. Under a glucose gradient in the double-inlet flow cell, P. aeruginosa biofilms grew in proportion to the local glucose concentration, producing distinct spatial patterns in biofilm biomass relative to the imposed glucose gradient. When biofilms were subjected to a ciprofloxacin gradient, spatial patterns of fractions of dead cells were also in proportion to the local antibiotic concentration. These results demonstrate that the microfluidic flow cells are suitable for quantifying flow complexities resulting from flow-biofilm interactions and investigating spatial patterns of biofilm growth under chemical gradients. These novel microfluidic flow cells will facilitate biofilm research that requires flow control and in situ imaging, particularly investigations of biofilm-environment interactions. PMID:24038055

  7. Biofilm responses to smooth flow fields and chemical gradients in novel microfluidic flow cells

    PubMed Central

    Song, Jisun L.; Au, Kelly H.; Huynh, Kimberly T.

    2013-01-01

    We present two novel microfluidic flow cells developed to provide reliable control of flow distributions and chemical gradients in biofilm studies. We developed a single-inlet microfluidic flow cell to support biofilm growth under a uniform velocity field, and a double-inlet flow cell to provide a very smooth transverse concentration gradient. Both flow cells consist of a layer of polydimethylsiloxane (PDMS) bonded to glass cover slips and were fabricated using the replica molding technique. We demonstrate the capabilities of the flow cells by quantifying flow patterns before and after growth of Pseudomonas aeruginosa biofilms through particle imaging velocimetry, and by evaluating concentration gradients within the double-inlet microfluidic flow cell. Biofilm growth substantially increased flow complexity by diverting flow around biomass, creating high- and low-velocity regions and surface friction. Under a glucose gradient in the double-inlet flow cell, P. aeruginosa biofilms grew in proportion to the local glucose concentration, producing distinct spatial patterns in biofilm biomass relative to the imposed glucose gradient. When biofilms were subjected to a ciprofloxacin gradient, spatial patterns of fractions of dead cells were also in proportion to the local antibiotic concentration. These results demonstrate that the microfluidic flow cells are suitable for quantifying flow complexities resulting from flow-biofilm interactions and investigating spatial patterns of biofilm growth under chemical gradients. These novel microfluidic flow cells will facilitate biofilm research that requires flow control and in situ imaging, particularly investigations of biofilm-environment interactions. PMID:24038055

  8. Micromodel foam flow study

    SciTech Connect

    Chambers, K.T.; Radke, C.J.

    1990-10-01

    Foams are often utilized as part of enhanced oil recovery techniques. This report presents the results of a micromodel foam flow study. Micromodels are valuable tools in uncovering capillary phenomena responsible for lamellae generation and coalescence during foam flow in porous media. Among the mechanisms observed are snap-off, weeping-flow breakup, and lamella division and leave behind. Coalescence mechanisms include dynamic capillary-pressure-induced lamella drainage and gas diffusion. These phenomena are sensitive to the mode of injection, the local capillary environment, and the geometry of the pore structure. An important consideration in presenting a tractable model of foam flow behavior is the ability to identify the pore-level mechanisms having the greatest impact on foam texture. The predominant mechanisms will vary depending upon the application for foam as an enhanced oil recovery (EOR) fluid. Both simultaneous gas and surfactant injection and surfactant alternating with gas injection (SAG) have been used to create foam for mobility control in EOR projects. The model developed is based on simultaneous gas and surfactant injection during steady-state conditions into a Berea sandstone core. The lamellae generation and coalescence mechanisms included in this model are snap-off, lamella division, and dynamic capillary-pressure-induced lamella drainage. This simplified steady-state model serves as a foundation for developing more complete rate expressions and for extending the population balance to handle transient foam flow behavior. 70 refs., 30 figs.

  9. Digital enhancement of flow field images

    NASA Technical Reports Server (NTRS)

    Kudlinski, Robert A.; Park, Stephen K.

    1988-01-01

    Most photographs of experimentally generated fluid flow fields have inherently poor photographic quality, specifically low contrast. Thus, there is a need to establish a process for quickly and accurately enhancing these photographs to provide improved versions for physical interpretation, analysis, and publication. A sequence of digital image processing techniques which have been demonstrated to effectively enhance such photographs is described.

  10. Flow fields of low pressure vent exhausts

    NASA Technical Reports Server (NTRS)

    Scialdone, John J.

    1989-01-01

    The flow field produced by low pressure gas vents are described based on experimental data obtained from tests in a large vacuum chamber. The gas density, pressure, and flux at any location in the flow field are calculated based on the vent plume description and the knowledge of the flow rate and velocity of the venting gas. The same parameters and the column densities along a specified line of sight traversing the plume are also obtained and shown by a computer-generated graphical representation. The fields obtained with a radially scanning Pitot probe within the exhausting gas are described by a power of the cosine function, the mass rate and the distance from the exit port. The field measurements were made for gas at pressures ranging from 2 to 50 torr venting from pipe fittings with diameters of 3/16 inch to 1-1/2 inches I.D. (4.76 mm to 38.1 mm). The N(2) mass flow rates ranged from 2E-4 to 3.7E-1 g/s.

  11. Flow fields of low pressure vent exhausts

    NASA Technical Reports Server (NTRS)

    Scialdone, John J.

    1990-01-01

    The flow field produced by low pressure gas vents are described based on experimental data obtained from tests in a large vacuum chamber. The gas density, pressure, and flux at any location in the flow field are calculated based on the vent plume description and the knowledge of the flow rate and velocity of the venting gas. The same parameters and the column densities along a specified line of sight traversing the plume are also obtained and shown by a computer generated graphical representation. The fields obtained with a radically scanning Pitot probe within the exhausting gas are described by a power of the cosine function, the mass rate, and the distance from the exit port. The field measurements were made for gas at pressures ranging from 2 to 50 torr venting from pipe fittings with diameters to 3/16 to 1-1/2 inches I.D. (4.76 to 38.1 mm). The N2 mass flow rates ranged from 2E-4 to 3.7E-1 g/s.

  12. The Impact of the Flow Field Heterogeneity and of the Injection Rate on the Effective Reaction Rates in Carbonates: a Study at the Pore Scale

    NASA Astrophysics Data System (ADS)

    Nunes, J. P. P.; Bijeljic, B.; Blunt, M. J.

    2015-12-01

    Carbonate rocks are notoriously difficult to characterize. Their abrupt facies variations give rise to drastic changes in the petrophysical properties of the reservoir. Such heterogeneity, when further associated with variations in rock mineralogy due to diagenetic processes, result in a challenging scenario to model from the pore to the field scale. Micro-CT imaging is one of the most promising technologies to characterize porous rocks. The understanding at the pore scale of reactive and non-reactive transport is being pushed forward by recent developments in both imaging capability - 3D images with resolution of a few microns - and in modeling techniques - flow simulations in giga-cell models. We will present a particle-based method capable of predicting the evolution of petrophysical properties of carbonate cores subjected to CO2 injection at reservoir conditions (i.e. high pressures and temperatures). Reactive flow is simulated directly on the voxels of high resolution micro-CT images of rocks. Reactants are tracked using a semi-analytical streamline tracing algorithm and rock-fluid interaction is controlled by the diffusive flux of particles from the pores to the grains. We study the impact of the flow field heterogeneity and of the injection rate on the sample-averaged (i.e. effective) reaction rate of calcite dissolution in three rocks of increasing complexity: a beadpack, an oolitic limestone and a bioclastic limestone. We show how decreases in the overall dissolution rate depend on both the complexity of the pore space and also on the flow rate. This occurs even in chemically homogenous rocks. Our results suggest that the large differences observed between laboratory and field scale rates could, in part, be explained by the inhomogeneity in the flow field at the pore scale and the consequent transport-limited flux of reactants at the solid surface. Our results give valuable insight into the processes governing carbonate dissolution and provide a starting

  13. Solid rocket motor aft field joint flow field analysis

    NASA Technical Reports Server (NTRS)

    Sabnis, Jayant S.; Gibeling, Edward J.; Mcdonald, Henry

    1987-01-01

    An efficient Navier-Stokes analysis was successfully applied to simulate the complex flow field in the vicinity of a slot in a solid rocket motor with segment joints. The capability of the computer code to resolve the flow near solid surfaces without using a wall function assumption was demonstrated. In view of the complex nature of the flow field in the vicinity of the slot, this approach is considered essential. The results obtained from these calculations provide valuable design information, which would otherwise be extremely difficult to obtain. The results of the axisymmetric calculations indicate the presence of a region of reversed axial flow at the aft-edge of the slot and show the over-pressure in the slot to be only about 10 psi. The results of the asymmetric calculations indicate that a pressure asymmetry more than two diameters downstream of the slot has no noticeable effect on the flow field in the slot. They also indicate that the circumferential pressure differential caused in the slot due to failure of a 15 deg section of the castable inhibitor will be approximately 1 psi.

  14. Nitrification cessation and recovery in an aerated saturated vertical subsurface flow treatment wetland: Field studies and microscale biofilm modeling.

    PubMed

    Murphy, Clodagh; Rajabzadeh, Amin R; Weber, Kela P; Nivala, Jaime; Wallace, Scott D; Cooper, David J

    2016-06-01

    In aerated treatment wetlands, oxygen availability is not a limiting factor in sustaining a high level of nitrification in wastewater treatment. In the case of an air blower failure, nitrification would cease, potentially causing adverse effects to the nitrifying bacteria. A field trial was completed investigating nitrification loss when aeration is switched off, and the system recovery rate after the aeration is switched back on. Loss of dissolved oxygen was observed to be more rapid than loss of nitrification. Nitrate was observed in the effluent long after the aeration was switched off (48h+). A complementary modeling study predicted nitrate diffusion out of biofilm over a 48h period. After two weeks of no aeration in the established system, nitrification recovered within two days, whereas nitrification establishment in a new system was previously observed to require 20-45days. These results suggest that once established resident nitrifying microbial communities are quite robust. PMID:26967335

  15. Numerical study of the ferrofluid flow and heat transfer through a rectangular duct in the presence of a non-uniform transverse magnetic field

    NASA Astrophysics Data System (ADS)

    Aminfar, H.; Mohammadpourfard, M.; Ahangar Zonouzi, S.

    2013-02-01

    This paper investigates numerically the hydro-thermal characteristics of a ferrofluid (water and 4 vol% Fe3O4) in a vertical rectangular duct which is exposed to a non-uniform transverse magnetic field generated by an electric current going through a wire located parallelly under the duct. The two phase mixture model and the control volume technique have been used to study the flow. The results show that applying the aforementioned magnetic field increases the Nusselt number and friction factor and also creates a pair of vortices that enhances heat transfer and prevents sedimentation of nano-particles. Furthermore, unlike the axial non-uniform magnetic field, the increase of the Nusselt number for the transverse magnetic field is considerable in all length along the duct and it is also concluded that with increasing the Reynolds number, the effect of the transverse non-uniform magnetic field on the Nusselt number is more than that of the axial non-uniform magnetic field.

  16. Holographic interferometric tomography for reconstructing flow fields

    NASA Technical Reports Server (NTRS)

    Cha, Soyoung S.

    1994-01-01

    Holographic interferometric tomography is a technique for instantaneously capturing and quantitatively reconstructing three-dimensional flow fields. It has a very useful application potential for high-speed aerodynamics. However, three major challenging tasks need to be accomplished before its practical applications. First, fluid flows are mostly unsteady or at least non repeatable. Consequently, a means for Instantaneously recording three-dimensional flow fields, that is, a simple holographic technique for simultaneously recording multi-directional projections, needs to be developed. Second, while holographic interferometry provides enormous data storage capabilities, expeditious data extraction from complicated interferograms is very important for timely near real-time applications. Third, unlike medical applications, flow tomography does not provide complete data sets but instead involves ill-posed reconstruction problems of incomplete projection and limited angular scanning. During this summer research period, new experimental techniques and corresponding hardware were developed and tested to address the above mentioned tasks. The first task was achieved by diffuser illumination. This concept allows instantaneous capture of many projections with a conventional setup for single-projection recording. For the second task, a phase-shifting technique was incorporated. This technique allows one to acquire multiple phase-stepped interferograms for a single projection and thus to extract phase information from intensity data almost at real-time. For the third task, the research that has been extensively conducted previously was utilized. In this research period, a complete experimental setup that provides the above three major capabilities was designed, built, and tested by integrating all the techniques. A simple laboratory experiment for simulating wind-tunnel testing was then conducted. A test flow was produced by employing a relatively simple device that generated

  17. Preliminary study of the effect of the turbulent flow field around complex surfaces on their acoustic characteristics

    NASA Technical Reports Server (NTRS)

    Olsen, W. A.; Boldman, D.

    1978-01-01

    Fundamental theories for noise generated by flow over surfaces exist for only a few simple configurations. The role of turbulence in noise generation by complex surfaces should be essentially the same as for simple configurations. Examination of simple-surface theories indicates that the spatial distributions of the mean velocity and turbulence properties are sufficient to define the noise emission. Measurements of these flow properties were made for a number of simple and complex surfaces. The configurations were selected because of their acoustic characteristics are quite different. The spatial distribution of the turbulent flow properties around the complex surfaces and approximate theory are used to locate and describe the noise sources, and to qualitatively explain the varied acoustic characteristics.

  18. Computation of flow pressure fields from magnetic resonance velocity mapping.

    PubMed

    Yang, G Z; Kilner, P J; Wood, N B; Underwood, S R; Firmin, D N

    1996-10-01

    Magnetic resonance phase velocity mapping has unrivalled capacities for acquiring in vivo multi-directional blood flow information. In this study, the authors set out to derive both spatial and temporal components of acceleration, and hence differences of pressure in a flow field using cine magnetic resonance velocity data. An efficient numerical algorithm based on the Navier-Stokes equations for incompressible Newtonian fluid was used. The computational approach was validated with in vitro flow phantoms. This work aims to contribute to a better understanding of cardiovascular dynamics and to serve as a basis for investigating pulsatile pressure/flow relationships associated with normal and impaired cardiovascular function. PMID:8892202

  19. Turbulence modelling of flow fields in thrust chambers

    NASA Astrophysics Data System (ADS)

    Chen, C. P.; Kim, Y. M.; Shang, H. M.

    1993-02-01

    Following the consensus of a workshop in Turbulence Modelling for Liquid Rocket Thrust Chambers, the current effort was undertaken to study the effects of second-order closure on the predictions of thermochemical flow fields. To reduce the instability and computational intensity of the full second-order Reynolds Stress Model, an Algebraic Stress Model (ASM) coupled with a two-layer near wall treatment was developed. Various test problems, including the compressible boundary layer with adiabatic and cooled walls, recirculating flows, swirling flows, and the entire SSME nozzle flow were studied to assess the performance of the current model. Detailed calculations for the SSME exit wall flow around the nozzle manifold were executed. As to the overall flow predictions, the ASM removes another assumption for appropriate comparison with experimental data to account for the non-isotropic turbulence effects.

  20. Turbulence modelling of flow fields in thrust chambers

    NASA Technical Reports Server (NTRS)

    Chen, C. P.; Kim, Y. M.; Shang, H. M.

    1993-01-01

    Following the consensus of a workshop in Turbulence Modelling for Liquid Rocket Thrust Chambers, the current effort was undertaken to study the effects of second-order closure on the predictions of thermochemical flow fields. To reduce the instability and computational intensity of the full second-order Reynolds Stress Model, an Algebraic Stress Model (ASM) coupled with a two-layer near wall treatment was developed. Various test problems, including the compressible boundary layer with adiabatic and cooled walls, recirculating flows, swirling flows, and the entire SSME nozzle flow were studied to assess the performance of the current model. Detailed calculations for the SSME exit wall flow around the nozzle manifold were executed. As to the overall flow predictions, the ASM removes another assumption for appropriate comparison with experimental data to account for the non-isotropic turbulence effects.

  1. Assessing early fitness consequences of exotic gene flow in the wild: a field study with Iberian pine relicts.

    PubMed

    Unger, Gregor M; Heuertz, Myriam; Vendramin, Giovanni G; Robledo-Arnuncio, Juan J

    2016-02-01

    Gene flow from plantations of nonlocal (genetically exotic) tree provenances into natural stands of the same species is probably a widespread phenomenon, but its effects remain largely unexamined. We investigated early fitness consequences of intraspecific exotic gene flow in the wild by assessing differences in survival among native, nonlocal, and F1 intraspecific hybrid seedlings naturally established within two native pine relicts (one of Pinus pinaster and the other of P. sylvestris) surrounded by nonlocal plantations. We obtained broad-scale temporally sequential genotypic samples of a cohort of recruits in each pine relict, from seeds before dispersal to established seedlings months after emergence, tracking temporal changes in the estimated proportion of each parental cross-type. Results show significant proportions of exotic male gametes before seed dispersal in the two pine relicts. Subsequently to seedling establishment, the frequency of exotic male gametes became nonsignificant in P. pinaster, and dropped by half in P. sylvestris. Exotic zygotic gene flow was significantly different from zero among early recruits for P. sylvestris, decreasing throughout seedling establishment. Seedling mortality resulted in small late sample sizes, and temporal differences in exotic gene flow estimates were not significant, so we could not reject the null hypothesis of invariant early viability across parental cross types in the wild. PMID:26834830

  2. Flow Field of a Human Cough

    NASA Astrophysics Data System (ADS)

    Hertzberg, Jean

    2005-11-01

    Cough generated infectious aerosols are of interest while developing strategies for the mitigation of disease risks ranging from the common cold to SARS. In this work, the velocity field of human cough was measured using particle image velocimetry (PIV). The project subjects (total 29) coughed into an enclosure seeded with stage fog for most measurements. Cough flow speed profiles, average widths of the cough jet, waveform, and maximum cough speeds were measured. Maximum cough speeds ranged from 1.5 m/s to 28.8 m/s. No correlation was found for maximum cough flow speeds to height or gender. The slow growth of the width of the cough flow suggests that a cough may penetrate farther into a room than a steady jet of similar volume. The velocity profile was found to scale with the square root of downstream distance.

  3. Effect of elongational flow on ferrofuids under a magnetic field.

    PubMed

    Altmeyer, S; Do, Younghae; Lopez, J M

    2013-07-01

    To set up a mathematical model for the flow of complex magnetic fluids, noninteracting magnetic particles with a small volume or an even point size are typically assumed. Real ferrofluids, however, consist of a suspension of particles with a finite size in an almost ellipsoid shape as well as with particle-particle interactions that tend to form chains of various lengths. To come close to the realistic situation for ferrofluids, we investigate the effect of elongational flow incorporated by the symmetric part of the velocity gradient field tensor, which could be scaled by a so-called transport coefficient λ(2). Based on the hybrid finite-difference and Galerkin scheme, we study the flow of a ferrofluid in the gap between two concentric rotating cylinders subjected to either a transverse or an axial magnetic field with the transport coefficient. Under the influence of a transverse magnetic field with λ(2)=0, we show that basic state and centrifugal unstable flows are modified and are inherently three-dimensional helical flows that are either left-winding or right-winding in the sense of the azimuthal mode-2, which is in contrast to the generic cases. That is, classical modulated rotating waves rotate, but these flows do not. We find that under elongational flow (λ(2)≠0), the flow structure from basic state and centrifugal instability flows is modified and their azimuthal vorticity is linearly changed. In addition, we also show that the bifurcation threshold of the supercritical centrifugal unstable flows under a magnetic field depends linearly on the transport coefficient, but it does not affect the general stabilization effect of any magnetic field. PMID:23944545

  4. Field Emission Microplasma Actuated Microchannel Flow

    NASA Astrophysics Data System (ADS)

    Tholeti, Siva Sashank; Shivkumar, Gayathri; Alexeenko, Alina

    2015-11-01

    Flow actuation by dielectric barrier discharges (DBD) involve no moving parts and provide high power density for flow enhancement, heating and mixing applications in microthrusters, micropumps and microcombustors. Conventional micro-DBDs require voltages ~ kV for flow enhancement of a few m/s for 500 μm high channel. However for gaps <10 microns, field emission lowers the breakdown voltage following modified Paschen curve. We consider a micropump concept that takes advantage of the field emission from a micro-DBD with dielectric thickness of 3 μm and a peak voltage of -325 V at 10 MHz. At 760 Torr, for electrode thickness of 1 μm, Knudsen number with respect to the e-nitrogen collisions is 0.1. So, kinetic approach of particle-in-cell method with Monte Carlo collisions is applied in nitrogen at 300 K to resolve electron (ne) and ion (ni) number densities. Body force, fb = eE(ni-ne) , where, e is electron charge and E is electric field. The major source of heating from plasma is Joule heating, J.E, where J is current density. At 760 Torr, for fb,avg = 1 mN/cubic mm and J.E = 8 W/cubic mm, micro-DBD induced a flow with a velocity of 4.1 m/s for a 64 mW/m power input for a channel height of 500 μm. The PIC/MCC plasma simulations are coupled to a CFD solver for analysis of the resulting flow actuation in microchannels at various Reynolds numbers. This work was supported by NSF ECCS Grant No. 1202095.

  5. Influence of protein formulation and carrier solution on asymmetrical flow field-flow fractionation: a case study of the plant-produced recombinant anthrax protective antigen pp-PA83.

    PubMed

    Palais, Caroline; Chichester, Jessica A; Manceva, Slobodanka; Yusibov, Vidadi; Arvinte, Tudor

    2015-02-01

    Asymmetrical flow field-flow fractionation (afFFF) was used to investigate the properties of a plant-produced anthrax toxin protective antigen, pp-PA83. The afFFF fractogram consisted of two main peaks with molar masses similar to the molecular mass of pp-PA83 monomer. afFFF carrier solutions strongly influenced the ratio and the intensity of the two main peaks. These differences indicate that conformation changes in the pp-PA83 molecule occurred during the afFFF analysis. Similar fractograms were obtained for different pp-PA83 formulations when the afFFF carrier solution and the protein formulation were the same (or very similar). The data show that in specific cases, afFFF could be used to study protein conformation and document the importance of studying the influence of the carrier solution on afFFF. PMID:25417936

  6. Paper-based flow fractionation system for preconcentration and field-flow fractionation.

    NASA Astrophysics Data System (ADS)

    Hong, Seokbin; Kwak, Rhokyun; Kim, Wonjung

    2015-11-01

    We present a novel paper-based flow fractionation system for preconcentration and field-flow fractionation. The paper fluidic system consisting of a straight channel connected with expansion regions can generate a fluid flow with a constant flow rate for 10 min without any external pumping devices. The flow bifurcates with a fraction ratio of up to 30 depending on the control parameters of the channel geometry. Utilizing this simple paper-based bifurcation system, we developed a continuous-flow preconcentrator and a field-flow fractionator on a paper platform. Our experimental results show that the continuous-flow preconcentrator can produce a 33-fold enrichment of the ion concentration and that the flow fractionation system successfully separates the charged dyes. Our study suggests simple, cheap ways to construct preconcentration and field-flow fractionation systems for paper-based microfluidic diagnostic devices. This work was supported by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIP) (NRF-2015R1A2A2A04006181).

  7. On the no-field method for void time determination in flow field-flow fractionation.

    PubMed

    Martin, Michel; Hoyos, Mauricio

    2011-07-01

    Elution time measurements of colloidal particles injected in a symmetrical flow field-flow fractionation (flow FFF) system when the inlet and outlet cross-flow connections are closed have been performed. This no-field method has been proposed earlier for void time (and void volume) determination in flow FFF Giddings et al. (1977). The elution times observed were much larger than expected on the basis of the channel geometrical volume and the flow rate. In order to explain these discrepancies, a flow model allowing the carrier liquid to flow through the porous walls toward the reservoirs located behind the porous elements and along these reservoirs was developed. The ratio between the observed elution time and expected one is found to depend only on a parameter which is a function of the effective permeability and thickness of the porous elements and of the channel thickness and length. The permeabilities of the frits used in the system were measured. Their values lead to predicted elution times in reasonable agreement with experimental ones, taking into account likely membrane protrusion inside the channel on system assembly. They comfort the basic feature of the flow model, in the no-field case. The carrier liquid mostly bypasses the channel to flow along the system mainly in the reservoir. It flows through the porous walls toward the reservoirs near channel inlet and again through the porous walls from the reservoirs to the channel near channel outlet before exiting the system. In order to estimate the extent of this bypassing process, it is desirable that the hydrodynamic characteristics of the permeable elements (permeability and thickness) are provided by flow FFF manufacturers. The model applies to symmetrical as well as asymmetrical flow FFF systems. PMID:21256498

  8. Flow Driven by an Archimedean Helical Permanent Magnetic Field. Part I: Flow Patterns and Their Transitions

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Wang, Xiaodong; Etay, Jacqueline; Na, Xianzhao; Zhang, Xinde; Fautrelle, Yves

    2016-04-01

    In this study, an Archimedean helical permanent magnetic field was constructed and its driving effects on liquid metal were examined. A magnetic stirrer was constructed using a series of arc-like magnets. The helical distribution of its magnetic field, which was confirmed via Gauss probe measurements and numerical simulations, can be considered a combination of rotating and traveling magnetic fields. The characteristics of the flow patterns, particularly the transitions between the meridian secondary flow (two vortices) and the global axial flow (one vortex), driven by this magnetic field were quantitatively measured using ultrasonic Doppler velocimetry. The transient and modulated flow behaviors will be presented in a companion article. The D/ H dimension ratio was used to characterize the transitions of these two flow patterns. The results demonstrated that the flow patterns depend on not only the intrinsic structure of the magnetic field, e.g., the helix lead angle, but also the performance parameters, e.g., the dimensional ratio of the liquid bulk. The notable opposing roles of these two flow patterns in the improvement of macrosegregations when imposing such magnetic fields near the solidifying front were qualitatively addressed.

  9. Microbial Field Pilot Study

    SciTech Connect

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Chisholm, J.L.

    1990-11-01

    This report covers progress made during the first year of the Microbial Field Pilot Study project. Information on reservoir ecology and characterization, facility and treatment design, core experiments, bacterial mobility, and mathematical modeling are addressed. To facilitate an understanding of the ecology of the target reservoir analyses of the fluids which support bacteriological growth and the microbiology of the reservoir were performed. A preliminary design of facilities for the operation of the field pilot test was prepared. In addition, procedures for facilities installation and for injection treatments are described. The Southeast Vassar Vertz Sand Unit (SEVVSU), the site of the proposed field pilot study, is described physically, historically, and geologically. The fields current status is presented and the ongoing reservoir simulation is discussed. Core flood experiments conducted during the last year were used to help define possible mechanisms involved in microbial enhanced oil recovery. Two possible mechanisms, relative permeability effects and changes in the capillary number, are discussed and related to four Berea core experiments' results. The experiments were conducted at reservoir temperature using SEVVSU oil, brine, and bacteria. The movement and activity of bacteria in porous media were investigated by monitoring the growth of bacteria in sandpack cores under no flow conditions. The rate of bacteria advancement through the cores was determined. A mathematical model of the MEOR process has been developed. The model is a three phase, seven species, one dimensional model. Finite difference methods are used for solution. Advection terms in balance equations are represented with a third- order upwind differencing scheme to reduce numerical dispersion and oscillations. The model is applied to a batch fermentation example. 52 refs., 26 figs., 21 tabs.

  10. Sultan - forced flow, high field test facility

    SciTech Connect

    Horvath, I.; Vecsey, G.; Weymuth, P.; Zellweger, J.

    1981-09-01

    Three European laboratories: CNEN (Frascati, I) ECN (Petten, NL) and SIN (Villigen, CH) decided to coordinate their development efforts and to install a common high field forced flow test facility at Villigen Switzerland. The test facility SULTAN (Supraleiter Testanlage) is presently under construction. As a first step, an 8T/1m bore solenoid with cryogenic periphery will be ready in 1981. The cryogenic system, data acquisition system and power supplies which are contributed by SIN are described. Experimental feasibilities, including cooling, and instrumentation are reviewed. Progress of components and facility construction is described. Planned extension of the background field up to 12T by insert coils is outlined. 5 refs.

  11. Aerodynamic Flow Field Measurements for Automotive Systems

    NASA Technical Reports Server (NTRS)

    Hepner, Timothy E.

    1999-01-01

    The design of a modern automotive air handling system is a complex task. The system is required to bring the interior of the vehicle to a comfortable level in as short a time as possible. A goal of the automotive industry is to predict the interior climate of an automobile using advanced computational fluid dynamic (CFD) methods. The development of these advanced prediction tools will enable better selection of engine and accessory components. The goal of this investigation was to predict methods used by the automotive industry. To accomplish this task three separate experiments were performed. The first was a laboratory setup where laser velocimeter (LV) flow field measurements were made in the heating and air conditioning unit of a Ford Windstar. The second involved flow field measurements in the engine compartment of a Ford Explorer, with the engine running idle. The third mapped the flow field exiting the center dashboard panel vent inside the Explorer, while the circulating fan operated at 14 volts. All three experiments utilized full-coincidence three-component LV systems. This enabled the mean and fluctuating velocities to be measured along with the Reynolds stress terms.

  12. Unsteady Flow Field in a Multistage Axial Flow Compressor

    NASA Technical Reports Server (NTRS)

    Suryavamshi, N.; Lakshminarayana, B.; Prato, J.

    1997-01-01

    The flow field in a multistage compressor is three-dimensional, unsteady, and turbulent with substantial viscous effects. Some of the specific phenomena that has eluded designers include the effects of rotor-stator and rotor-rotor interactions and the physics of mixing of velocity, pressure, temperature and velocity fields. An attempt was made, to resolve experimentally, the unsteady pressure and temperature fields downstream of the second stator of a multistage axial flow compressor which will provide information on rotor-stator interaction effects and the nature of the unsteadiness in an embedded stator of a three stage axial flow compressor. Detailed area traverse measurements using pneumatic five hole probe, thermocouple probe, semi-conductor total pressure probe (Kulite) and an aspirating probe downstream of the second stator were conducted at the peak efficiency operating condition. The unsteady data was then reduced through an ensemble averaging technique which splits the signal into deterministic and unresolved components. Auto and cross correlation techniques were used to correlate the deterministic total temperature and velocity components (acquired using a slanted hot-film probe at the same measurement locations) and the gradients, distributions and relative weights of each of the terms of the average passage equation were then determined. Based on these measurements it was observed that the stator wakes, hub leakage flow region, casing endwall suction surface corner region, and the casing endwall region away from the blade surfaces were the regions of highest losses in total pressure, lowest efficiency and highest levels of unresolved unsteadiness. The deterministic unsteadiness was found to be high in the hub and casing endwall regions as well as on the pressure side of the stator wake. The spectral distribution of hot-wire and kulite voltages shows that at least eight harmonics of all three rotor blade passing frequencies are present at this

  13. Microbial field pilot study

    SciTech Connect

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Chisholm, J.L.

    1992-03-01

    The objective of this project is to perform a microbial enhanced oil recovery field pilot in the Southeast Vassar Vertz Sand Unit (SEVVSU) in Payne County, Oklahoma. Indigenous, anaerobic, nitrate reducing bacteria will be stimulated to selectively plug flow paths which have been referentially swept by a prior waterflood. This will force future flood water to invade bypassed regions of the reservoir and increase sweep efficiency. This report covers progress made during the second year, January 1, 1990 to December 31, 1990, of the Microbial Field Pilot Study project. Information on reservoir ecology, surface facilities design, operation of the unit, core experiments, modeling of microbial processes, and reservoir characterization and simulation are presented in the report. To better understand the ecology of the target reservoir, additional analyses of the fluids which support bacteriological growth and the microbiology of the reservoir were performed. The results of the produced and injected water analysis show increasing sulfide concentrations with respect to time. In March of 1990 Mesa Limited Partnership sold their interest in the SEVVSU to Sullivan and Company. In April, Sullivan and Company assumed operation of the field. The facilities for the field operation of the pilot were refined and implementation was begun. Core flood experiments conducted during the last year were used to help define possible mechanisms involved in microbial enhanced oil recovery. The experiments were performed at SEVVSU temperature using fluids and inoculum from the unit. The model described in last year's report was further validated using results from a core flood experiment. The model was able to simulate the results of one of the core flood experiments with good quality.

  14. Microbial field pilot study

    SciTech Connect

    Knapp, R.M.; McInerney, M.J.; Menzie, D.E.; Chisholm, J.L.

    1992-03-01

    The objective of this project is to perform a microbial enhanced oil recovery field pilot in the Southeast Vassar Vertz Sand Unit (SEVVSU) in Payne County, Oklahoma. Indigenous, anaerobic, nitrate reducing bacteria will be stimulated to selectively plug flow paths which have been referentially swept by a prior waterflood. This will force future flood water to invade bypassed regions of the reservoir and increase sweep efficiency. This report covers progress made during the second year, January 1, 1990 to December 31, 1990, of the Microbial Field Pilot Study project. Information on reservoir ecology, surface facilities design, operation of the unit, core experiments, modeling of microbial processes, and reservoir characterization and simulation are presented in the report. To better understand the ecology of the target reservoir, additional analyses of the fluids which support bacteriological growth and the microbiology of the reservoir were performed. The results of the produced and injected water analysis show increasing sulfide concentrations with respect to time. In March of 1990 Mesa Limited Partnership sold their interest in the SEVVSU to Sullivan and Company. In April, Sullivan and Company assumed operation of the field. The facilities for the field operation of the pilot were refined and implementation was begun. Core flood experiments conducted during the last year were used to help define possible mechanisms involved in microbial enhanced oil recovery. The experiments were performed at SEVVSU temperature using fluids and inoculum from the unit. The model described in last year`s report was further validated using results from a core flood experiment. The model was able to simulate the results of one of the core flood experiments with good quality.

  15. Meeting in Florida: Using Asymmetric Flow Field-Flow Fractionation (AF4) to Determine C60 Colloidal Size Distributions

    EPA Science Inventory

    The study of nanomaterials in environmental systems requires robust and specific analytical methods. Analytical methods which discriminate based on particle size and molecular composition are not widely available. Asymmetric Flow Field-Flow Fractionation (AF4) is a separation...

  16. Transient rheological behavior of natural polysaccharide xanthan gum solutions in start-up shear flow fields: An experimental study using a strain-controlled rheometer

    NASA Astrophysics Data System (ADS)

    Lee, Ji-Seok; Kim, Yong-Seok; Song, Ki-Won

    2015-08-01

    The objective of the present study is to experimentally investigate the transient rheological behavior of concentrated xanthan gum solutions in start-up shear flow fields. Using a strain-controlled rheometer, a number of constant shear rates were suddenly imposed to aqueous xanthan gum solutions with different concentrations and the resultant shear stress responses were measured with time. The main findings obtained from this study can be summarized as follows: (1) For all shear rates imposed, however low it may be, the shear stress is rapidly increased with time (stress overshoot) upon inception of steady shear flow before passing through the maximum stress value and then gradually decreased with time (stress decay) until reaching a steady state flow. (2) As the imposed shear rate is increased, a more pronounced stress overshoot takes place and the maximum stress value becomes larger, whereas both times at which the maximum stress is observed and needed to reach a steady state flow are shortened. (3) The maximum shear stress is linearly increased with shear rate in a double logarithmic scale and becomes larger with increasing concentration at equal shear rates. In addition, the time at which the maximum stress occurs exhibits a linear relationship with the inverse of shear rate in a double logarithmic scale for all xanthan gum solutions, regardless of their concentrations. (4) The shear stress is sharply increased with an increase in strain until reaching the maximum stress at small range of deformations. The maximum stress is observed at similar strain values, irrespective of the imposed shear rates lower than 10 1/s. (5) The Bird-Leider model can be successfully used with regard to quantitatively predicting the transient behavior of concentrated xanthan gum solutions. However, this model has a fatal weakness in terms of describing a decrease in shear stress (stress decay).

  17. U.S.-MEXICO BORDER PROGRAM ARIZONA BORDER STUDY--STANDARD OPERATING PROCEDURE FOR FLOW AND CUSTODY OF FIELD DATA FORMS (UA-C-5.0)

    EPA Science Inventory

    The purpose of this SOP is to describe the flow of field data forms through the data processing system and to define who is responsible for the data at any time. It applies to field data forms collected and processed by Arizona NHEXAS. This procedure was followed to ensure cons...

  18. Directed Plasma Flow across Magnetic Field

    NASA Astrophysics Data System (ADS)

    Presura, R.; Stepanenko, Y.; Neff, S.; Sotnikov, V. I.

    2008-04-01

    The Hall effect plays a significant role in the penetration of plasma flows across magnetic field. For example, its effect may become dominant in the solar wind penetration into the magnetosphere, in the magnetic field advection in wire array z-pinch precursors, or in the arcing of magnetically insulated transmission lines. An experiment performed at the Nevada Terawatt Facility explored the penetration of plasma with large Hall parameter (˜10) across ambient magnetic field. The plasma was produced by ablation with the short pulse high intensity laser Leopard (0.35 ps, 10^17W/cm^2) and the magnetic field with the pulsed power generator Zebra (50 T). The expanding plasma assumed a jet configuration and propagated beyond a distance consistent with a diamagnetic bubble model. Without magnetic field, the plasma expansion was close to hemispherical. The ability to produce the plasma and the magnetic field with distinct generators allows a controlled, quasi-continuous variation of the Hall parameter and other plasma parameters making the experiments useful for benchmarking numerical simulations.

  19. Evaluation of flow field approximations for transonic compressor stages

    SciTech Connect

    Dorney, D.J.; Sharma, O.P.

    1997-07-01

    The flow through gas turbine compressors is often characterized by unsteady, transonic, and viscous phenomena. Accurately predicting the behavior of these complex multi-blade-row flows with unsteady rotor-stator interacting Navier-Stokes analyses can require enormous computer resources. In this investigation, several methods for predicting the flow field, losses, and performance quantities associated with axial compressor stages are presented. The methods studied include: (1) the unsteady fully coupled blade row technique, (2) the steady coupled blade row method, (3) the steady single blade row technique, and (4) the loosely coupled blade row method. The analyses have been evaluated in terms of accuracy and efficiency.

  20. Vibrational relaxation in hypersonic flow fields

    NASA Technical Reports Server (NTRS)

    Meador, Willard E.; Miner, Gilda A.; Heinbockel, John H.

    1993-01-01

    Mathematical formulations of vibrational relaxation are derived from first principles for application to fluid dynamic computations of hypersonic flow fields. Relaxation within and immediately behind shock waves is shown to be substantially faster than that described in current numerical codes. The result should be a significant reduction in nonequilibrium radiation overshoot in shock layers and in radiative heating of hypersonic vehicles; these results are precisely the trends needed to bring theoretical predictions more in line with flight data. Errors in existing formulations are identified and qualitative comparisons are made.

  1. Rectangular subsonic jet flow field measurements

    NASA Technical Reports Server (NTRS)

    Morrison, Gerald L.; Swan, David H.

    1990-01-01

    Flow field measurements of three subsonic rectangular cold air jets are presented. The three cases had aspect ratios of 1x2, 1x4 at a Mach number of 0.09 and an aspect ratio of 1x2 at a Mach number of 0.9. All measurements were made using a 3-D laser Doppler anemometer system. The data includes the mean velocity vector, all Reynolds stress tensor components, turbulent kinetic energy and velocity correlation coefficients. The data are presented in tabular and graphical form. No analysis of the measured data or comparison to other published data is made.

  2. Experimental studies of transonic flow field near a longitudinally slotted wind tunnel wall. Ph.D. Thesis - George Washington Univ., 1988

    NASA Technical Reports Server (NTRS)

    Everhart, Joel L.; Bobbitt, Percy J.

    1994-01-01

    The results of detailed parametric experiments are presented for the near-wall flow field of a longitudinally slotted transonic wind tunnel. Existing data are reevaluated and new data obtained in the Langley 6- by 19-inch Transonic Wind Tunnel are presented and analyzed. In the experiments, researchers systematically investigate many pertinent wall-geometry variables such as the wall openness and the number of slots along with the free stream Mach number and model angle of attack. Flow field surveys on the plane passing through the centerline of the slot were conducted and are presented. The effects of viscosity on the slot flow are considered in the analysis. The present experiments, combined with those of previous investigations, give a more complete physical characterization of the flow near and through the slotted wall of a transonic wind tunnel.

  3. Preliminary corrosion studies of P-91 in flowing lead-lithium with and without magnetic field for Indian lead-lithium ceramic breeder test blanket module

    NASA Astrophysics Data System (ADS)

    Sarada Sree, Atchutuni; Tanaji, Kamble; Poulami, Chakraborty; Fotedar, R. K.; Rajendra Kumar, E.; Suri, A. K.; Platacis, E.; Ziks, A.; Bucenieks, I.; Poznjaks, A.; Shisko, A.

    2014-08-01

    To study the corrosion of P-91 (9% chromium and 1% molybdenum) material with lead-lithium (Pb-Li) eutectic, two experiments were carried out in a forced convection loop, at eutectic temperature of 550 °C. The first experiment was carried out at a velocity of 15 cm s-1 for 1000 h and the second experiment, at a velocity of 30 cm s-1 for 2700 h. In both the experiments, P-91 sample coupons were exposed to Pb-Li flow in the presence and absence of magnetic field. Samples were analyzed using an optical microscope, scanning electron microscope (SEM) and electron probe micro-analyzer (EPMA). Micro-Vickers hardness testing was also carried out. Dissolution of elements into liquid metal is the main corrosion mechanism. Iron and chromium were selectively getting leached out from the near-surface region (˜4 µm) in the first experiment and molybdenum and manganese were also found leaching from a greater depth in the second experiment. The samples kept in the magnetic field showed a higher corrosion rate (˜320 µm/year) as compared with the corrosion rate (˜200 µm/year) of the samples kept in non-magnetic field regions. Hardness of the exposed samples was lower than the unexposed samples in both the experiments. Hardness was found to be low in the near-surface region for all the samples in both the experiments.

  4. Field-flow fractionation of chromosomes

    SciTech Connect

    Giddings, J.C.

    1993-04-01

    The first topic of this project involved the preparation, fractionation by sedimentation/steric Field Flow Fractionation (FFF), and modeling of metaphase chromosomes. After numerous unsuccessful attempts to prepare chromosomes, we have implemented a procedure (in collaboration with Los Alamos National Laboratory) to prepare metaphase chromosomes from Chinese hamster cells. Extensive experimentation was necessary to identify a suitable FFF channel surface to minimize chromosome adsorption and a carrier liquid to stabilize and disperse the chromosomes. Under suitable operating conditions, the Chinese hamster chromosomes were purified from cell debris and partially fractionated. The purified, preenriched chromosomes that can be prepared by sedimentation/steric FFF or produced continuously by continuous SPLITT fractionation provide an enriched feed material for subsequent flow cytometry. In the second project component, flow FFF permitted successful separations of single- from double-stranded circular DNA, double-stranded circular DNAs of various sizes, and linear double-stranded DNA fragments of various lengths. Diffusion coefficients extracted from retention data agreed well with literature data as well as predictions of major polymer theories. The capacity of FFF separations was evaluated to examine potential applications to long DNA chains.

  5. Theoretical and Experimental Studies of the Transonic Flow Field and Associated Boundary Conditions near a Longitudinally-Slotted Wind-Tunnel Wall. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Everhart, Joel Lee

    1988-01-01

    A theoretical examination of the slotted-wall flow field is conducted to determine the appropriate wall pressure drop (or boundary condition) equation. This analysis improves the understanding of the fluid physics of these types of flow fields and helps in evaluating the uncertainties and limitations existing in previous mathematical developments. It is shown that the resulting slotted-wall boundary condition contains contributions from the airfoil-induced streamline curvature and the non-linear, quadratic, slot crossflow in addition to an often neglected linear term which results from viscous shearing in the slot. Existing and newly acquired experimental data are examined in the light of this formulation and theoretical developments.

  6. Field methods for measuring concentrated flow erosion

    NASA Astrophysics Data System (ADS)

    Castillo, C.; Pérez, R.; James, M. R.; Quinton, J. N.; Taguas, E. V.; Gómez, J. A.

    2012-04-01

    techniques (3D) for measuring erosion from concentrated flow (pole, laser profilemeter, photo-reconstruction and terrestrial LiDAR) The comparison between two- and three-dimensional methods has showed the superiority of the 3D techniques for obtaining accurate cross sectional data. The results from commonly-used 2D methods can be subject to systematic errors in areal cross section that exceed magnitudes of 10 % on average. In particular, the pole simplified method has showed a clear tendency to understimate areas. Laser profilemeter results show that further research on calibrating optical devices for a variety of soil conditions must be carried out to improve its performance. For volume estimations, photo-reconstruction results provided an excellent approximation to terrestrial laser data and demonstrate that this new remote sensing technique has a promising application field in soil erosion studies. 2D approaches involved important errors even over short measurement distances. However, as well as accuracy, the cost and time requirements of a technique must be considered.

  7. Thermal effects of groundwater flow through subarctic fens - a case study based on field observation and numerical modeling

    SciTech Connect

    Sjoberg, Ylva; Coon, Ethan T.; Sannel, A. Britta K.; Pannetier, Romain; Harp, Dylan; Frampton, Andrew; Painter, Scott L; Lyon, Steve W

    2016-01-01

    Modeling and observation of ground temperature dynamics are the main tools for understand-ing current permafrost thermal regimes and projecting future thaw. Until recently, most studies on perma-frost have focused on vertical ground heat uxes. Groundwater can transport heat in both lateral andvertical directions but its in uence on ground temperatures at local scales in permafrost environments isnot well understood. In this study we combine eld observations from a subarctic fen in the sporadic per-mafrost zone with numerical simulations of coupled water and thermal uxes. At the Tavvavuoma studysite in northern Sweden, ground temperature pro les and groundwater levels were observed in boreholes.These observations were used to set up one- and two-dimensional simulations down to 2 m depth across agradient of permafrost conditions within and surrounding the fen. Two-dimensional scenarios representingthe fen under various hydraulic gradients were developed to quantify the in uence of groundwater ow onground temperature. Our observations suggest that lateral groundwater ow signi cantly affects groundtemperatures. This is corroborated by modeling results that show seasonal ground ice melts 1 month earlierwhen a lateral groundwater ux is present. Further, although the thermal regime may be dominated by ver-tically conducted heat uxes during most of the year, isolated high groundwater ow rate events such asthe spring freshet are potentially important for ground temperatures. As sporadic permafrost environmentsoften contain substantial portions of unfrozen ground with active groundwater ow paths, knowledge ofthis heat transport mechanism is important for understanding permafrost dynamics in these environments.

  8. Electric field evidence for tailward flow at substorm onset

    NASA Technical Reports Server (NTRS)

    Nishida, A.; Tulunay, Y. K.; Mozer, F. S.; Cattell, C. A.; Hones, E. W., Jr.; Birn, J.

    1983-01-01

    Electric field observations made near the neutral sheet of the magnetotail provide additional support for the view that reconnection occurs in the near-earth region of the tail. Southward turnings of the magnetic field that start at, or shortly after, substorm onsets are accompanied by enhancements in the dawn-to-dusk electric field, resulting in a tailward E x B drift velocity. Both the magnetic and the electric fields in the tailward-flowing plasma are nonuniform and vary with inferred spatial scales of several earth radii in the events examined in this paper. These nonuniformities may be the consequence of the tearing-mode process. The E x B flow was also towards the neutral sheet and away from midnight in the events studied.

  9. A validation study of a rapid field-based rating system for discriminating among flow permanence classes of headwater streams in South Carolina

    EPA Science Inventory

    Rapid field-based protocols for classifying flow permanence of headwater streams are needed to inform timely regulatory decisions. Such an existing method was developed for and has been used in North Carolina since 1997. The method uses ordinal scoring of 26 geomorphology, hydr...

  10. Fluctuating pressures in flow fields of jets

    NASA Technical Reports Server (NTRS)

    Schroeder, J. C.; Haviland, J. K.

    1976-01-01

    The powered lift configurations under present development for STOL aircraft are the externally blown flap (EBF), involving direct jet impingement on the aircraft flaps, and the upper surface blown (USB), where the jet flow is attached on the upper surface of the wing and directed downwards. Towards the goal of developing scaling laws to predict unsteady loads imposed on the structural components of these STOL aircraft from small model tests, the near field fluctuating pressure behavior for the simplified cases of a round free cold jet and the same jet impinging on a flat plate was investigated. Examples are given of coherences, phase lags (giving convection velocities), and overall fluctuating pressure levels measured. The fluctuating pressure levels measured on the flat plate are compared to surface fluctuating pressure levels measured on full-scale powered-lift configuration models.

  11. Rectangular subsonic jet flow field measurements

    NASA Technical Reports Server (NTRS)

    Morrison, Gerald L.; Swan, David H.

    1989-01-01

    Flow field measurements are presented of 3 subsonic rectangular cold air jets. The 3 cases presented had aspect ratios of 1 x 2, 1 x 4 at a Mach number of 0.09 and an aspect ratio of 1 x 2 at a Mach number of 0.9. All measurements were made using a 3-D laser Doppler anemoneter system. The presented data includes the mean velocity vector, all Reynolds stress tensor components, turbulent kinetic energy and velocity correlation coefficients. The data is presented in tabular and graphical form. No analysis of the measured data or comparison to other published data is made. All tabular data are available in ASCII format on MS-DOS compatible disks.

  12. Low thrust viscous nozzle flow fields prediction

    NASA Technical Reports Server (NTRS)

    Liaw, Goang-Shin

    1987-01-01

    An existing Navier-Stokes code (PARC2D) was used to compute the nozzle flow field. Grids were generated by the interactive grid generator codes TBGG and GENIE. All computations were made on the NASA/MSFC CRAY X-MP computer. Comparisons were made between the computations and MSFC in-house wall pressure measurements for CO2 flow through a conical nozzle having an area ratio of 40. Satisfactory agreements exist between the computations and measurements for different stagnation pressures of 29.4, 14.7, and 7.4 psia, at stagnation temperature of 1060 R. However, agreements did not match precisely near the nozzle exit. Several reasons for the lack of agreement are possible. The computational code assumes a constant gas gamma, whereas the gamma i.e. the specific heat ratio for CO2 varied from 1.22 in the plenum chamber to 1.38 at the nozzle exit. The computations also assumes adiabatic and no-slip walls. Both assumptions may not be correct. Finally, it is possible that condensation occurs during the nozzle expansion at the low stagnation pressure. The next phase of the work will incorporate variable gamma and slip wall boundary conditions in the computational code and develop a more accurate computer code.

  13. Interaction of multiple supersonic jets with a transonic flow field

    NASA Technical Reports Server (NTRS)

    Seginer, A.; Manela, J.

    1983-01-01

    The influence of multiple high pressure, supersonic, radial or tangential jets, that are injected from the circumference of the base plane of an axisymmetric body, on its longitudinal aerodynamic coefficients in transonic flow is studied experimentally. The interaction of the jets with the body flow field increases the pressures on the forebody, thus altering its lift and static stability characteristics. It is shown that, within the range of parameters studied. This interaction has a stabilizing effect on the body. The contribution to lift and stability is significant at small angles of attack and decreases nonlinearly at higher angles when the crossflow mechanism becomes dominant.

  14. Numerical study of corrosion of ferritic/martensitic steels in the flowing PbLi with and without a magnetic field

    NASA Astrophysics Data System (ADS)

    Smolentsev, Sergey; Saedi, Sheida; Malang, Siegfried; Abdou, Mohamed

    2013-01-01

    A computational suite called TRANSMAG has been developed to address corrosion of ferritic/martensitic steels and associated transport of corrosion products in the eutectic alloy PbLi as applied to blankets of a fusion power reactor. The computational approach is based on simultaneous solution of flow, energy and mass transfer equations with or without a magnetic field, assuming mass transfer controlled corrosion and uniform dissolution of iron in the flowing PbLi. First, the new tool is applied to solve an inverse mass transfer problem, where the saturation concentration of iron in PbLi at temperatures up to 550 °C is reconstructed from the experimental data on corrosion in turbulent flows without a magnetic field. As a result, a new correlation for the saturation concentration CS has been obtained in the form CS = e13.604-12975/T, where T is the temperature of PbLi in K and CS is in wppm. Second, the new correlation is used in the computations of corrosion in laminar flows in a rectangular duct in the presence of a strong transverse magnetic field. As shown, the mass loss increases with the magnetic field such that the corrosion rate in the presence of a magnetic field can be a few times higher compared to purely hydrodynamic flows. In addition, the corrosion behavior was found to be different between the side wall of the duct (parallel to the magnetic field) and the Hartmann wall (perpendicular to the magnetic field) due to formation of high-velocity jets at the side walls. The side walls experience a stronger corrosion attack demonstrating a mass loss up to 2-3 times higher compared to the Hartmann walls. Also, computations of the mass loss are performed to characterize the effect of the temperature (400-550 °C) and the flow velocity (0.1-1 m/s) on corrosion in the presence of a strong 5 T magnetic field prototypic to the outboard blanket conditions.

  15. Visual study of the effect of grazing flow on the oscillatory flow in a resonator orifice

    NASA Technical Reports Server (NTRS)

    Baumeister, K. J.; Rice, E. J.

    1975-01-01

    Grazing flow and oscillatory flow in an orifice were studied in a plexiglass flow channel with a single side branch Helmholtz resonator using water as the fluid medium. An oscillatory flow was applied to the resonatory cavity, and color dyes were injected in both the orifice and the grazing flow field to record the motion of the fluid. The flow regimes associated with linear and nonlinear (high sound pressure level) impedances with and without grazing flows were recorded by a high-speed motion-picture camera. Appreciable differences in the oscillatory flow field were seen in the various flow regimes. With high grazing flows, the outflow and inflow from the resonator cavity are found to be asymmetric. The visual study confirms that jet energy loss during flow into a resonator cavity is much larger than the loss for ejection from the cavity into the grazing flow. For inflow into the resonator cavity, the effective orifice area was significantly reduced.

  16. Computational Analysis of Flow Field Inside Coral Colony

    NASA Astrophysics Data System (ADS)

    Hossain, Md Monir; Staples, Anne

    2015-11-01

    Development of the flow field inside coral colonies is a key issue for understanding coral natural uptake, photosynthesis and wave dissipation capabilities. But most of the computations and experiments conducted earlier, measured the flow outside the coral reef canopies. Experimental studies are also constrained due to the limitation of measurement techniques and limited environmental conditions. Numerical simulations can be an answer to overcome these shortcomings. In this work, a detailed, three-dimensional simulation of flow around a single coral colony was developed to examine the interaction between coral geometry and hydrodynamics. To simplify grid generation and minimize computational cost, Immersed Boundary method (IBM) was implemented. The computation of IBM involves identification of the interface between the solid body and the fluid, establishment of the grid/interface relation and identification of the forcing points on the grid and distribution of the forcing function on the corresponding points. LES was chosen as the framework to capture the turbulent flow field without requiring extensive modeling. The results presented will give insight into internal coral colony flow fields and the interaction between coral and surrounding ocean hydrodynamics.

  17. Navier-Stokes Flow Field Analysis of Compressible Flow in a Pressure Relief Valve

    NASA Technical Reports Server (NTRS)

    Vu, Bruce T.; Wang, Ten-See; Shih, Ming-Hsin; Soni, Bharat K.

    1993-01-01

    The present study was motivated to analyze the complex flow field involving gaseous oxygen (GOX) flow in a relief valve (RV). The 9391 RV, pictured in Figure 1, was combined with the pilot valve to regulate the actuation pressure of the main valve system. During a high-pressure flow test at Marshall Space Flight Center (MSFC) the valve system developed a resonance chatter, which destroyed most of the valve body. Figures 2-4 show the valve body before and after accident. It was understood that the subject RV has never been operated at 5500 psia. In order to fully understand the flow behavior in the RV, a computational fluid dynamics (CFD) analysis is carried out to investigate the side load across the piston sleeve and the erosion patterns resulting from flow distribution around piston/nozzle interface.

  18. Navier-Stokes flow field analysis of compressible flow in a pressure relief valve

    NASA Astrophysics Data System (ADS)

    Vu, Bruce T.; Wang, Ten-See; Shih, Ming-Hsin; Soni, Bharat K.

    1993-07-01

    The present study was motivated to analyze the complex flow field involving gaseous oxygen (GOX) flow in a relief valve (RV). The 9391 RV, pictured in Figure 1, was combined with the pilot valve to regulate the actuation pressure of the main valve system. During a high-pressure flow test at Marshall Space Flight Center (MSFC) the valve system developed a resonance chatter, which destroyed most of the valve body. Figures 2-4 show the valve body before and after accident. It was understood that the subject RV has never been operated at 5500 psia. In order to fully understand the flow behavior in the RV, a computational fluid dynamics (CFD) analysis is carried out to investigate the side load across the piston sleeve and the erosion patterns resulting from flow distribution around piston/nozzle interface.

  19. Interdependence of centrifugal compressor blade geometry and relative flow field

    NASA Astrophysics Data System (ADS)

    Krain, H.

    1985-03-01

    The influence of the impeller blade geometry on the calculated relative flow field has been studied by means of an impeller design program available at DFVLR (Krain, 1984). Several geometrical parameters were varied, however, the meridional channel geometry was always kept constant. By this approach the blade wrap angle has been found to react significantly on the relative flow which is illustrated by comparing two designs with different wrap angles. Primarily in the hub/leading edge area a better boundary layer flow connected with a reduction of blade loading was obtained by increasing the wrap angle. But also in the shroud/pressure side area the increased blade looping attributed to an additional flow stabilization.

  20. Solar-Cycle Evolution of Subsurface Flows and Magnetic Field

    NASA Astrophysics Data System (ADS)

    Kosovichev, Alexander G.; Zhao, Junwei

    2016-05-01

    Local helioseismology and magnetic field measurements from the HMI instrument on SDO provide unique high-resolution data that allow us to investigate detailed dynamics of the upper convection zone and its relation to the magnetic field evolution during the first five years of the current solar cycle. This study is focused on the understanding the role of the near-surface shear layer (NSSL) in the dynamo process, generation, emergence and transport of the solar magnetic flux. The helioseismology data represent 3D flow maps in the depth range of 0-20 Mm, obtained uninterruptedly every 8 hours for almost the whole solar disk with the spatial sampling of two arcsec. We calculate the flow characteristics (such as divergence, vorticity and kinetic helicity) on different spatio-temporal scales from supergranulation to global-scale zonal and meridional flows. We investigate the multi-scale organization of the subsurface flows, including the inflows into active regions, the hemispheric `flip-flop’ asymmetry of variations of the meridional flows, the structure and dynamics of torsional oscillations, and compare the flow behavior with the evolution of the observed magnetic activity of the current cycle.

  1. Assessment of real-time PCR based methods for quantification of pollen-mediated gene flow from GM to conventional maize in a field study.

    PubMed

    Pla, Maria; La Paz, José-Luis; Peñas, Gisela; García, Nora; Palaudelmàs, Montserrat; Esteve, Teresa; Messeguer, Joaquima; Melé, Enric

    2006-04-01

    Maize is one of the main crops worldwide and an increasing number of genetically modified (GM) maize varieties are cultivated and commercialized in many countries in parallel to conventional crops. Given the labeling rules established e.g. in the European Union and the necessary coexistence between GM and non-GM crops, it is important to determine the extent of pollen dissemination from transgenic maize to other cultivars under field conditions. The most widely used methods for quantitative detection of GMO are based on real-time PCR, which implies the results are expressed in genome percentages (in contrast to seed or grain percentages). Our objective was to assess the accuracy of real-time PCR based assays to accurately quantify the contents of transgenic grains in non-GM fields in comparison with the real cross-fertilization rate as determined by phenotypical analysis. We performed this study in a region where both GM and conventional maize are normally cultivated and used the predominant transgenic maize Mon810 in combination with a conventional maize variety which displays the characteristic of white grains (therefore allowing cross-pollination quantification as percentage of yellow grains). Our results indicated an excellent correlation between real-time PCR results and number of cross-fertilized grains at Mon810 levels of 0.1-10%. In contrast, Mon810 percentage estimated by weight of grains produced less accurate results. Finally, we present and discuss the pattern of pollen-mediated gene flow from GM to conventional maize in an example case under field conditions. PMID:16604462

  2. TV News Flow Studies Revisited.

    ERIC Educational Resources Information Center

    Hjarvard, Stig

    1995-01-01

    Compares different theoretical approaches to the study of international news. Finds many comparative studies of the foreign news output of national broadcasters and few studies analyzing the actual flow of television news between actors at the wholesale level and the flow between wholesale and retail level. Suggests a better framework for the…

  3. 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.

  4. Channel Flow Cell Studies of the Inhibiting Action of Gypsum on the Dissolution Kinetics of Calcite: A Laboratory Approach with Implications for Field Monitoring.

    PubMed

    Wilkins, Shelley J.; Compton, Richard G.; Taylor, Mark A.; Viles, Heather A.

    2001-04-15

    The rate of dissolution of surface-treated calcite crystals in aqueous acidic solution has been studied using an adaptation of the channel flow cell method with microdisc electrode detection. Surface treatments of calcite with sulfuric acid lead to the nucleation of gypsum overgrowths, which reduce the rate of dissolution of calcite. Rate constants for untreated calcite and calcite pretreated with sulfuric acid conditions of 0.01 M for 1 h, 0.05 M for 5 h, and 0.1 M for 21 h are found to be 0.035, 0.018, 0.006, and 0.004 cm s(-1), respectively. Deterioration of calcite materials caused by acid deposition was investigated by field exposure of untreated and sulfate pretreated calcite rocks under urban conditions for 12 months. The rate constant for both pretreated and untreated calcite exposed to weathering is 0.003 cm s(-1). This suggests that calcite self-passivates the surface from further reaction when exposed to acid deposition. However, surface studies indicate that the surface undergoes erosion and dissolution before passivation. Pretreatment of the surface with sulfate protects the surface from acid deposition so it remains less reactive toward acid compared with untreated calcite. Copyright 2001 Academic Press. PMID:11401383

  5. Time-to-Passage Judgments in Nonconstant Optical Flow Fields

    NASA Technical Reports Server (NTRS)

    Kaiser, Mary K.; Hecht, Heiko

    1995-01-01

    The time until an approaching object will pass an observer (time to passage, or TTP) is optically specified by a global flow field even in the absence of local expansion or size cues. Kaiser and Mowafy have demonstrated that observers are in fact sensitive to this global flow information. The present studies investigate two factors that are usually ignored in work related to TTP: (1) non-constant motion functions and (2) concomitant eye rotation. Non-constant velocities violate an assumption of some TTP derivations, and eye rotations may complicate heading extraction. Such factors have practical significance, for example, in the case of a pilot accelerating an aircraft or executing a roll. In our studies, a flow field of constant-sized stars was presented monocularly on a large screen. TIP judgments had to be made on the basis of one target star. The flow field varied in its acceleration pattern and its roll component. Observers did not appear to utilize acceleration information. In particular, TTP with decelerating motion were consistently underestimated. TTP judgments were fairly robust with respect to roll, even when roll axis and track vector were decoupled. However, substantial decoupling between heading and track vector led to a decrement in performance, in both the presence and the absence of roll.

  6. A fundamental study of relation between the velocity fields far upstream of, at and far downstream of a a rotor disk in a shear flow

    NASA Astrophysics Data System (ADS)

    Johansson, B. C. A.

    1983-10-01

    For the analysis of wind turbine low, it would be of great value to find a general relation between the local velocity fields far upstream, at the rotor disk and far downstream of a rotor inducing large perturbations in a shear flow. When the velocity perturbations of a parallel flow are small, the induced velocity at the obstacle causing the perturbation (disk or lifting line) is half the induced velocity far downstream at the same streamline. For a rotor in uniform flow, the mean induced velocity at the disk is also half the mean induced velocity far downstream, even if the perturbation velocities are not small. A first step was taken towards obtaining the desired general relation. A numerical example is calculated, which shows that the ratio one half has no general validity. Results are applicable not only to wind turbines, also to propellers, and helicopter rotors.

  7. Numerical parameter studies of 3D melt flow and interface shape for directional solidification of silicon in a traveling magnetic field

    NASA Astrophysics Data System (ADS)

    Vizman, D.; Dadzis, K.; Friedrich, J.

    2013-10-01

    The role of various growth and process conditions (Lorentz force, temperature gradients in the melt and the crystal, steady-state crystallization velocity) in directional solidification of multicrystalline silicon in a traveling magnetic field is analyzed for a research-scale furnace (melt size of 22×22×11 cm3). The influence on the melt flow pattern, the typical melt flow velocity, the oscillation amplitude of the velocity and the temperature, the shape of the crystallization interface is determined using three-dimensional (3D) numerical calculations with the STHAMAS3D software and a local quasi steady-state model. It was found that both the interface shape and the melt flow are sensitive to the variation of the considered growth and process parameters.

  8. 3-D Flow Visualization with a Light-field Camera

    NASA Astrophysics Data System (ADS)

    Thurow, B.

    2012-12-01

    Light-field cameras have received attention recently due to their ability to acquire photographs that can be computationally refocused after they have been acquired. In this work, we describe the development of a light-field camera system for 3D visualization of turbulent flows. The camera developed in our lab, also known as a plenoptic camera, uses an array of microlenses mounted next to an image sensor to resolve both the position and angle of light rays incident upon the camera. For flow visualization, the flow field is seeded with small particles that follow the fluid's motion and are imaged using the camera and a pulsed light source. The tomographic MART algorithm is then applied to the light-field data in order to reconstruct a 3D volume of the instantaneous particle field. 3D, 3C velocity vectors are then determined from a pair of 3D particle fields using conventional cross-correlation algorithms. As an illustration of the concept, 3D/3C velocity measurements of a turbulent boundary layer produced on the wall of a conventional wind tunnel are presented. Future experiments are planned to use the camera to study the influence of wall permeability on the 3-D structure of the turbulent boundary layer.Schematic illustrating the concept of a plenoptic camera where each pixel represents both the position and angle of light rays entering the camera. This information can be used to computationally refocus an image after it has been acquired. Instantaneous 3D velocity field of a turbulent boundary layer determined using light-field data captured by a plenoptic camera.

  9. Magnetohydrodynamic channel flows with weak transverse magnetic fields.

    PubMed

    Rothmayer, A P

    2014-07-28

    Magnetohydrodynamic flow of an incompressible fluid through a plane channel with slowly varying walls and a magnetic field applied transverse to the channel is investigated in the high Reynolds number limit. It is found that the magnetic field can first influence the hydrodynamic flow when the Hartmann number reaches a sufficiently large value. The magnetic field is found to suppress the steady and unsteady viscous flow near the channel walls unless the wall shapes become large. PMID:24936018

  10. Basic studies of baroclinic flows

    NASA Technical Reports Server (NTRS)

    Miller, Tim L.; Chou, S.-H.; Leslie, Fred W.; Lu, H.-I.; Butler, K. A.

    1991-01-01

    Computations were completed of transition curves in the conventional annulus, including hysteresis effect. The model GEOSIM was used to compute the transition between axisymmetric flow and baroclinic wave flow in the conventional annulus experiments. Thorough testing and documentation of the GEOSIM code were also completed. The Spacelab 3 results from the Geophysical Fluid Flow Cell (GFFC) were reviewed and numerical modeling was performed of many of the cases with horizontal temperature gradients as well as heating from below, with different rates of rotation. A numerical study of the lower transition to axisymmetric flow in the baroclinic annulus was performed using GEOSIM.

  11. General flow field analysis methods for helicopter rotor aeroacoustics

    NASA Technical Reports Server (NTRS)

    Quackenbush, Todd R.; Lam, C. Gordon; Bliss, Donald B.

    1991-01-01

    Previous work in the analysis of rotor flow fields for aeroacoustic applications involved the preliminary development of an efficient and accurate Lagrangian simulation of the unsteady vorticity field in the vicinity of helicopter main rotor that could analyze a limited class of rotor/wake interactions. The capabilities of this analysis have subsequently been considerably enhanced to allow it to serve as the foundation for a general analysis of the rotor/wake interaction noise. This paper presents the details of these enhancements, which focus on the expansion of the reconstruction approach developed previously to handle arbitrary vortex wake interactions within three-dimensional regions located near or within the rotor disk. Also, the development of nearfield velocity corrections appropriate for the analysis of such interactions is described, as is a preliminary study of methods for using the new high-resolution flow field analysis for noise predictions. The results show that by employing this novel flow field reconstruction technique it is possible to employ full-span free wake analyses with temporal and spatial resolution suitable for acoustic applications while reducing the computation time required by one to two orders of magnitude relative to traditional methods.

  12. Flow-Field Surveys for Rectangular Nozzles. Supplement

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.

    2012-01-01

    Flow field survey results for three rectangular nozzles are presented for a low subsonic condition obtained primarily by hot-wire anemometry. The three nozzles have aspect ratios of 2:1, 4:1 and 8:1. A fourth case included has 2:1 aspect ratio with chevrons added to the long edges. Data on mean velocity, turbulent normal and shear stresses as well as streamwise vorticity are presented covering a streamwise distance up to sixteen equivalent diameters from the nozzle exit. These detailed flow properties, including initial boundary layer characteristics, are usually difficult to measure in high speed flows and the primary objective of the study is to aid ongoing and future computational and noise modeling efforts. This supplement contains data files, charts and source code.

  13. Transitional and weakly turbulent flow in a rotating magnetic field

    NASA Astrophysics Data System (ADS)

    Stiller, J.; Fraňa, K.; Cramer, A.

    2006-07-01

    The early stage of turbulent flow driven by a rotating magnetic field is studied via direct numerical simulations and electric potential measurements for the case of a cylindrical geometry. The numerical results show that the undisturbed flow remains stable up to the linear stability limit (Tac), whereas small perturbations may initiate a nonlinear transition at subcritical Taylor numbers. The observed instabilities occur randomly as isolated pairs of Taylor-Görtler vortices, which grow from spots to long tubes until they are dissipated in the lid boundary layers. At 7.5Tac, the flow is governed by large-scale three-dimensional fluctuations and may be characterized as weakly turbulent. Taylor-Görtler vortices provide the major turbulence mechanism, apart from oscillations of the rotation axis. As the vortices tend to align with the azimuthal direction, they result in a locally two-dimensional turbulence pattern.

  14. Testing flow-through air samplers for use in near-field vapour drift studies by measuring pyrimethanil in air after spraying.

    PubMed

    Geoghegan, Trudyanne S; Hageman, Kimberly J; Hewitt, Andrew J

    2014-03-01

    Pesticide volatilisation and subsequent vapour drift reduce a pesticide's efficiency and contribute to environmental contamination. High-volume air samplers (HVSs) are often used to measure pesticide concentrations in air but these samplers are expensive to purchase and require network electricity, limiting the number and type of sites where they can be deployed. The flow-through sampler (FTS) presents an opportunity to overcome these limitations. The FTS is a wind-driven passive sampler that has been developed to quantify organic contaminants in remote ecosystems. FTSs differ from other passive samplers in that they turn into the wind and use the wind to draw air through the sampling media. The main objective of this work was to evaluate the FTS in a near-field pesticide vapour drift study by comparing the concentrations of pyrimethanil in air measured using one HVS and three FTSs placed in the same location. Pyrimethanil was sprayed onto a vineyard as part of normal pest management procedures. Air samples were collected every eight hours for 48 h. The volume of air sampled by the FTSs was calculated using the measured relationship between ambient wind speed and the wind speed inside the sampler as determined with a separate wind tunnel study. The FTSs sampled 1.7 to 40.6 m(3) of air during each 8 h sampling period, depending on wind speed, whereas the mean volume sampled by the HVS was 128.7 m(3). Mean pyrimethanil concentrations ranged from 0.4 to 3.2 μg m(-3) of air. Inter-sampler reproducibility, as represented by percent relative standard deviation, for the three FTSs was ∼20%. The largest difference in FTS-derived versus HVS-derived pyrimethanil concentrations occurred during the lowest wind-speed period. During this period, it is likely that the FTS predominately acted like a traditional diffusion-based passive sampler. As indicated by both types of sampler, pyrimethanil concentrations in air changed by a factor of ∼2 during the two days after spaying

  15. Granular flows through vertical pipes controlled by an electric field

    NASA Astrophysics Data System (ADS)

    Chen, Wei; Hou, Meiying; Lu, Kunquan; Jiang, Zehui; Lam, Lui

    2001-12-01

    The flow of granular nickel particles moving down vertical pipes from a hopper in the presence of a local, horizontal ac electric field is studied experimentally. The flow is initiated by opening the bottom outlet of the pipe after the pipe is fully filled with particles from the hopper. The mass of particles flowing out of the pipe is measured as a function of time by an electronic balance. The time dependence of the steady-state flow rate Q, under each fixed voltage V, is obtained. Depending on the magnitude of V, two types of flow behaviors are observed. For low V (flow rates QA2 and, later in time, QB. The particles measured by QA2 originate from the pipe above the electrodes, and those by QB coming initially from the hopper. For high V (>=Vc), no interface exists and the whole region between the hopper and the electrodes are densely filled; only one constant flow rate QA2 is observed. (The precise meaning of QA2 and QB are defined in the text.) The steady-state flow rates QA2 and QB measured for each V, are plotted as a function of V. The flow rate QA2 is a monotonically decreasing function of V, which can be approximately fitted by a power law, with an exponent of -0.8, while QB is found to be voltage independent. These features result from a competition between the blocking effect of the electric-field region and the gravity-driven pushing effect from the hopper outlet. The local electric field is able to retard the downward movement of a dense column existing above it, but is ineffective in doing so when the column above is dilute in density.

  16. Relation between photospheric flow fields and the magnetic field distribution on the solar surface

    SciTech Connect

    Simon, G.W.; Title, A.M.; Topka, K.P.; Tarbell, T.D.; Shine, R.A.

    1988-04-01

    Using the technique of local correlation tracking on a 28 minute time sequence of white-light images of solar granulation, the horizontal flow field on the solar surface is measured. The time series was obtained by the Solar Optical Universal Polarimeter (SOUP) on Spacelab 2 (Space Shuttle flight 51-F) and is free from atmospheric blurring and distortion. The SOUP flow fields have been compared with carefully aligned magnetograms taken over a nine hour period at the Big Bear Solar Observatory before, during, and after the SOUP images. The flow field and the magnetic field agree in considerable detail: vectors which define the flow of the white-light intensity pattern (granulation) point toward magnetic field regions, magnetic fields surround flow cells, and magnetic features move along the flow arrows. The projected locations of free particles (corks) in the measured flow field congregate at the same locations where the magnetic field is observed. 31 references.

  17. Field measurement of basal forces generated by erosive debris flows

    USGS Publications Warehouse

    McCoy, S.W.; Tucker, G.E.; Kean, J.W.; Coe, J.A.

    2013-01-01

    It has been proposed that debris flows cut bedrock valleys in steeplands worldwide, but field measurements needed to constrain mechanistic models of this process remain sparse due to the difficulty of instrumenting natural flows. Here we present and analyze measurements made using an automated sensor network, erosion bolts, and a 15.24 cm by 15.24 cm force plate installed in the bedrock channel floor of a steep catchment. These measurements allow us to quantify the distribution of basal forces from natural debris‒flow events that incised bedrock. Over the 4 year monitoring period, 11 debris‒flow events scoured the bedrock channel floor. No clear water flows were observed. Measurements of erosion bolts at the beginning and end of the study indicated that the bedrock channel floor was lowered by 36 to 64 mm. The basal force during these erosive debris‒flow events had a large‒magnitude (up to 21 kN, which was approximately 50 times larger than the concurrent time‒averaged mean force), high‒frequency (greater than 1 Hz) fluctuating component. We interpret these fluctuations as flow particles impacting the bed. The resulting variability in force magnitude increased linearly with the time‒averaged mean basal force. Probability density functions of basal normal forces were consistent with a generalized Pareto distribution, rather than the exponential distribution that is commonly found in experimental and simulated monodispersed granular flows and which has a lower probability of large forces. When the bed sediment thickness covering the force plate was greater than ~ 20 times the median bed sediment grain size, no significant fluctuations about the time‒averaged mean force were measured, indicating that a thin layer of sediment (~ 5 cm in the monitored cases) can effectively shield the subjacent bed from erosive impacts. Coarse‒grained granular surges and water‒rich, intersurge flow had very similar basal force distributions despite

  18. Numerical study of flow turning phenomenon

    NASA Astrophysics Data System (ADS)

    Baum, J. D.; Levine, J. N.

    1986-01-01

    A research project is currently being conducted that is to provide an understanding of the physical mechanisms by which energy is exchanged between the mean and acoustic flowfields in resonant combustion chambers, giving particular attention to solid rocket motors. The present paper is concerned with progress which has been made toward the understanding of the 'flow turning' phenomenon. This term is used to describe the loss of acoustic energy by the acoustic field in the combustor resulting from the inflow of combustion products through the lateral boundary of a combustion chamber containing longitudinal acoustic waves. Attention is given to the modeling of flow turning, acoustic refraction, the numerical solution, numerical results, acoustic wave propagation with no mean flow, and a flow turning study. The discussed research verifies the existence of the flow turning loss phenomenon.

  19. Reconstruction of velocity fields in electromagnetic flow tomography.

    PubMed

    Lehtikangas, Ossi; Karhunen, Kimmo; Vauhkonen, Marko

    2016-06-28

    Electromagnetic flow meters (EMFMs) are the gold standard in measuring flow velocity in process industry. The flow meters can measure the mean flow velocity of conductive liquids and slurries. A drawback of this approach is that the velocity field cannot be determined. Asymmetric axial flows, often encountered in multiphase flows, pipe elbows and T-junctions, are problematic and can lead to serious systematic errors. Recently, electromagnetic flow tomography (EMFT) has been proposed for measuring velocity fields using several coils and a set of electrodes attached to the surface of the pipe. In this work, a velocity field reconstruction method for EMFT is proposed. The method uses a previously developed finite-element-based computational forward model for computing boundary voltages and a Bayesian framework for inverse problems. In the approach, the vz-component of the velocity field along the longitudinal axis of the pipe is estimated on the pipe cross section. Different asymmetric velocity fields encountered near pipe elbows, solids-in-water flows in inclined pipes and in stratified or multiphase flows are tested. The results suggest that the proposed reconstruction method could be used to estimate velocity fields in complicated pipe flows in which the conventional EMFMs have limited accuracy. This article is part of the themed issue 'Supersensing through industrial process tomography'. PMID:27185961

  20. Evaluation of flow direction methods against field observations of overland flow dispersion

    NASA Astrophysics Data System (ADS)

    Orlandini, S.; Moretti, G.; Corticelli, M. A.; Santangelo, P. E.; Capra, A.; Rivola, R.; Albertson, J. D.

    2012-12-01

    Despite the broad effort made in grid-based distributed catchment modeling to account for planar overland flow dispersion, actual dispersion experienced by overland flow along a natural slope has not been measured so far, and the ability of terrain analysis methods to reproduce this dispersion has not been evaluated. In the present study, the D8, D8-LTD, D∞ -LTD, D∞ , MD∞ , and MD8 flow direction methods are evaluated against field observations of overland flow dispersion obtained from novel experimental methods. Thin flows of cold (2--10oC) water were released at selected points on a warmer (15--30oC) slope and individual overland flow patterns originating from each of these points were observed using a terrestrial laser scanner and a thermal imaging camera. Prior to each experimental water release, a ScanStation C10 terrestrial laser scanner by Leica Geosystems was used to acquire a point cloud having average density of 25~points/cm2. This point cloud was used to generate alternative grid-based digital elevation models having resolution h ranging from 1~cm to 2~m. During the experiments, an Avio Advanced Thermo TVS-500EX camera by Nippon Avionics was used to monitor land surface temperature with resolution better than 0.05oC. The overland flow patterns were also found to be discernible in terrestrial laser scanner reflectance signal acquired immediately following the flow experiments. Overland flow patterns were determined by considering contrasted temperature and reflectance of the dry and wetted land surface portions. Predicted propagation patterns and observed flow patterns were compared by considering the fractions of flow released at the point source that propagates through the grid cells. Predictions of these quantities were directly provided by flow direction methods and by related flow accumulation algorithms. Suitable data for the comparison were derived from observed overland flow patterns by assuming a uniform distribution of flow along each

  1. Additional flow field studies of the GA(W)-1 airfoil with 30-percent chord Fowler flap including slot-gap variations and cove shape modifications

    NASA Technical Reports Server (NTRS)

    Wentz, W. H., Jr.; Ostowari, C.

    1983-01-01

    Experimental measurements were made to determine the effects of slot gap opening and flap cove shape on flap and airfoil flow fields. Test model was the GA(W)-1 airfoil with 0.30c Fowler flap deflected 35 degrees. Tests were conducted with optimum, wide and narrow gaps, and with three cove shapes. Three test angles were selected, corresponding to pre-stall and post-stall conditions. Reynolds number was 2,200,000 and Mach number was 0.13. Force, surface pressure, total pressure, and split-film turbulence measurements were made. Results were compared with theory for those parameters for which theoretical values were available.

  2. Computational and Experimental Flow Field Analyses of Separate Flow Chevron Nozzles and Pylon Interaction

    NASA Technical Reports Server (NTRS)

    Massey, Steven J.; Thomas, Russell H.; AbdolHamid, Khaled S.; Elmiligui, Alaa A.

    2003-01-01

    A computational and experimental flow field analyses of separate flow chevron nozzles is presented. The goal of this study is to identify important flow physics and modeling issues required to provide highly accurate flow field data which will later serve as input to the Jet3D acoustic prediction code. Four configurations are considered: a baseline round nozzle with and without a pylon, and a chevron core nozzle with and without a pylon. The flow is simulated by solving the asymptotically steady, compressible, Reynolds-averaged Navier-Stokes equations using an implicit, up-wind, flux-difference splitting finite volume scheme and standard two-equation kappa-epsilon turbulence model with a linear stress representation and the addition of a eddy viscosity dependence on total temperature gradient normalized by local turbulence length scale. The current CFD results are seen to be in excellent agreement with Jet Noise Lab data and show great improvement over previous computations which did not compensate for enhanced mixing due to high temperature gradients.

  3. Steady hydromagnetic flows in open magnetic fields. II - Global flows with static zones

    NASA Technical Reports Server (NTRS)

    Tsinganos, K.; Low, B. C.

    1989-01-01

    A theoretical study of an axisymmetric steady stellar wind with a static zone is presented, with emphasis on the situation where the global magnetic field is symmetrical about the stellar equator and is partially open. In this scenario, the wind escapes in open magnetic fluxes originating from a region at the star pole and a region at an equatorial belt of closed magnetic field in static equilibrium. The two-dimensional balance of the pressure gradient and the inertial, gravitational, and Lorentz forces in different parts of the flow are studied, along with the static interplay between external sources of energy (heating and/or cooling) distributed in the flow and the pressure distribution.

  4. The impact of hillslope groundwater dynamics and landscape functioning in event-flow generation: a field study in the Rietholzbach catchment, Switzerland

    NASA Astrophysics Data System (ADS)

    von Freyberg, Jana; Rao, P. Suresh C.; Radny, Dirk; Schirmer, Mario

    2015-08-01

    A reliable prediction of hydrograph responses in mountainous headwater catchments requires a mechanistic understanding of the coupled hydro-climatic processes in these regions. This study shows that only a small fraction of the total area in a pre-Alpine headwater catchment actively regulates streamflow responses to hydro-climatic forcing, which facilitates the application of a parsimonious framework for hydrograph time-series prediction. Based on landscape analysis and hydrometric data from the Upper Rietholzbach catchment (URHB, 0.94 km2, northeast Switzerland), a conceptual model was established. Here, the rainfall-event-driven contribution of surface runoff and subsurface flow (event flow) accounts for around 50 % of total river discharge. The event-flow hydrograph is generated from approximately 25 % of the entire area consisting of riparian zones (8 %) and adjacent hillslopes (17 %), each with characteristic streamflow-generating mechanisms. Baseflow generation is attributed to deep groundwater discharge from a fractured-rock aquifer covering ˜75 % of the catchment area. A minimalistic model, that represents event flow as depletion of two parallel linear reservoirs, verified the conceptual model of the URHB with adequate hydrograph simulations ( R 2 = 0.67, Nash-Sutcliffe efficiency (NSE) = 0.64). Hereby, the expansion of the event-flow contributing areas was found to be particularly significant during long and high-intensity rainfall events. These findings provide a generalized approach for the large-scale characterization of groundwater recharge and hydrological behavior of mountainous catchments with similar landscape properties.

  5. Holocene Flows of the Cima Volcanic Field, Mojave Desert, Part 2: Flow Rheology from Laboratory Measurements

    NASA Astrophysics Data System (ADS)

    Robertson, T.; Whittington, A. G.; Soldati, A.; Sehlke, A.; Beem, J. R.; Gomez, F. G.

    2014-12-01

    Lava flow morphology is often utilized as an indicator of rheological behavior during flow emplacement. Rheological behavior can be characterized by the viscosity and yield strength of lava, which in turn are dependent on physical and chemical properties including crystallinity, vesicularity, and bulk composition. We are studying the rheology of a basaltic lava flow from a monogenetic Holocene cinder cone in the Cima lava field (Mojave Desert, California). The flow is roughly 2.5 km long and up to 700m wide, with a well-developed central channel along much of its length. Samples were collected along seven different traverses across the flow, along with real-time kinematic (RTK) GPS profiles to allow levee heights and slopes to be measured. Surface textures change from pahoehoe ropes near the vent to predominantly jagged `a`a blocks over the majority of the flow, including all levees and the toe. Chemically the lava shows little variation, plotting on the trachybasalt-basanite boundary on the total alkali-silica diagram. Mineralogically the lava is dominated by plagioclase, clinopyroxene and olivine phenocrysts, with abundant flow-aligned plagioclase microcrystals. The total crystal fraction is ~50% near the vent, with higher percentages in the distal portion of the flow. Vesicularity varies between ~10 and more than ~60%. Levees are ~10-15m high with slopes typically ~25-35˚, suggesting a yield strength at final emplacement of ~150,000 Pa. The effective emplacement temperature and yield strength of lava samples will be determined using the parallel-plate technique. We will test the hypothesis that these physical and rheological properties of the lava during final emplacement correlate with spatial patterns in flow morphology, such as average slope and levee width, which have been determined using remote sensing observations (Beem et al. 2014).

  6. Left ventricular systolic intraventricular flow field assessment in hyperthyroidism patients using vector flow mapping.

    PubMed

    Zhou, Bin-Yu; Wang, Jing; Xie, Ming-Xing; Liu, Man-Wei; Lv, Qing

    2015-08-01

    Intraventricular hydrodynamics is considered an important component of cardiac function assessment. Vector flow mapping (VFM) is a novel flow visualization method to describe cardiac pathophysiological condition. This study examined use of new VFM and flow field for assessment of left ventricular (LV) systolic hemodynamics in patients with simple hyperthyroidism (HT). Thirty-seven simple HT patients were enrolled as HT group, and 38 gender- and age-matched healthy volunteers as control group. VFM model was used to analyze LV flow field at LV apical long-axis view. The following flow parameters were measured, including peak systolic velocity (Vs), peak systolic flow (Fs), total systolic negative flow (SQ) in LV basal, middle and apical level, velocity gradient from the apex to the aortic valve (ΔV), and velocity according to half distance (V1/2). The velocity vector in the LV cavity, stream line and vortex distribution in the two groups were observed. The results showed that there were no significant differences in the conventional parameters such as left ventricular ejection fraction (LVEF), left ventricular end-diastolic diameter (LVEDD) and left atrium diameter (LAD) between HT group and control group (P>0.05). Compared with the control group, a brighter flow and more vortexes were detected in HT group. Non-uniform distribution occurred in the LV flow field, and the stream lines were discontinuous in HT group. The values of Vs and Fs in three levels, SQ in middle and basal levels, ΔV and V1/2 were higher in HT group than in control group (P<0.01). ΔV was positively correlated with serum free thyroxin (FT4) (r=0.48, P<0.01). Stepwise multiple regression analysis showed that LVEDD, FT4, and body surface area (BSA) were the influence factors of ΔV. The unstable left ventricular systolic hydrodynamics increased in a compensatory manner in simple HT patients. The present study indicated that VFM may be used for early detection of abnormal ventricle contraction in

  7. Field theoretical approach for bio-membrane coupled with flow field

    NASA Astrophysics Data System (ADS)

    Oya, Y.; Kawakatsu, T.

    2013-02-01

    Shape deformation of bio-membranes in flow field is well known phenomenon in biological systems, for example red blood cell in blood vessel. To simulate such deformation with use of field theoretical approach, we derived the dynamical equation of phase field for shape of membrane and coupled the equation with Navier-Stokes equation for flow field. In 2-dimensional simulations, we found that a bio-membrane in a Poiseuille flow takes a parachute shape similar to the red blood cells.

  8. Pressure-field extraction on unstructured flow data using a Voronoi tessellation-based networking algorithm: a proof-of-principle study

    NASA Astrophysics Data System (ADS)

    Neeteson, Nathan J.; Rival, David E.

    2015-02-01

    A novel technique is described for pressure extraction from Lagrangian particle-tracking data. The technique uses a Poisson solver to extract the pressure field on a network of data nodes, which is constructed using the Voronoi tessellation and the Delaunay triangulation. The technique is demonstrated on two cases: synthetic Lagrangian data generated for the analytical case of Hill's spherical vortex, and the flow in the wake behind a NACA 0012 which was impulsively accelerated to . The experimental data were collected using four-camera, three-dimensional particle-tracking velocimetry. For both the analytical case and the experimental case, the dependence of pressure-field error or sensitivity on the normalized spatial particle density was found to follow similar power-law relationships. It was shown that in order to resolve the salient flow structures from experimental data, the required particle density was an order of magnitude greater than for the analytical case. Furthermore, additional sub-structures continued to be identified in the experimental data as the particle density was increased. The increased density requirements of the experimental data were assumed to be due to a combination of phase-averaging error and the presence of turbulent coherent structures in the flow. Additionally, the computational requirements of the technique were assessed. It was found that in the current implementation, the computational requirements are slightly nonlinear with respect to the number of particles. However, the technique will remain feasible even as advancements in particle-tracking techniques in the future increase the density of Lagrangian data.

  9. Doppler Global Velocimetry Measurements for Supersonic Flow Fields

    NASA Technical Reports Server (NTRS)

    Meyers, James F.

    2005-01-01

    The application of Doppler Global Velocimetry (DGV) to high-speed flows has its origins in the original development of the technology by Komine et al (1991). Komine used a small shop-air driven nozzle to generate a 200 m/s flow. This flow velocity was chosen since it produced a fairly large Doppler shift in the scattered light, resulting in a significant transmission loss as the light passed through the Iodine vapor. This proof-of-concept investigation showed that the technology was capable of measuring flow velocity within a measurement plane defined by a single-frequency laser light sheet. The effort also proved that velocity measurements could be made without resolving individual seed particles as required by other techniques such as Fringe- Type Laser Velocimetry and Particle Image Velocimetry. The promise of making planar velocity measurements with the possibility of using 0.1-micron condensation particles for seeding, Dibble et al (1989), resulted in the investigation of supersonic jet flow fields, Elliott et al (1993) and Smith and Northam (1995) - Mach 2.0 and 1.9 respectively. Meyers (1993) conducted a wind tunnel investigation above an inclined flat plate at Mach 2.5 and above a delta wing at Mach 2.8 and 4.6. Although these measurements were crude from an accuracy viewpoint, they did prove that the technology could be used to study supersonic flows using condensation as the scattering medium. Since then several research groups have studied the technology and developed solutions and methodologies to overcome most of the measurement accuracy limitations:

  10. Three Dimensional Viscous Flow Field in an Axial Flow Turbine Nozzle Passage

    NASA Technical Reports Server (NTRS)

    Ristic, D.; Lakshminarayana, B.

    1997-01-01

    The objective of this investigation is experimental and computational study of three dimensional viscous flow field in the nozzle passage of an axial flow turbine stage. The nozzle passage flow field has been measured using a two sensor hot-wire probe at various axial and radial stations. In addition, two component LDV measurements at one axial station (x/c(sum m) = 0.56) were performed to measure the velocity field. Static pressure measurements and flow visualization, using a fluorescent oil technique, were also performed to obtain the location of transition and the endwall limiting streamlines. A three dimensional boundary layer code, with a simple intermittency transition model, was used to predict the viscous layers along the blade and endwall surfaces. The boundary layers on the blade surface were found to be very thin and mostly laminar, except on the suction surface downstream of 70% axial chord. Strong radial pressure gradient, especially close to the suction surface, induces strong cross flow components in the trailing edge regions of the blade. On the end-walls the boundary layers were much thicker, especially near the suction corner of the casing surface, caused by secondary flow. The secondary flow region near the suction-casing surface corner indicates the presence of the passage vortex detached from the blade surface. The corner vortex is found to be very weak. The presence of a closely spaced rotor downstream (20% of the nozzle vane chord) introduces unsteadiness in the blade passage. The measured instantaneous velocity signal was filtered using FFT square window to remove the periodic unsteadiness introduced by the downstream rotor and fans. The filtering decreased the free stream turbulence level from 2.1% to 0.9% but had no influence on the computed turbulence length scale. The computation of the three dimensional boundary layers is found to be accurate on the nozzle passage blade surfaces, away from the end-walls and the secondary flow region. On