Science.gov

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 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.

  3. 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

  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 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

  1. 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

  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. 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.

  11. 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

  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. 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.

  12. 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.

  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

    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.

  19. 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.

  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. 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.

  4. 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.

  5. 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.

  6. 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.

  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. 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.

  5. 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.

  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. 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.

  10. 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.

  11. 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.

  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 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.

  20. 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.

  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. 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

  7. 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).

  8. 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.

  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. 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.

  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. 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.

  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. 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.

  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. 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.

  6. 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.

  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. 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.

  16. 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.

  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. 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.

  7. 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.

  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

  11. Microbial field pilot study

    SciTech Connect

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

    1993-05-01

    A multi-well microbially enhanced oil recovery field pilot has been performed in the Southeast Vassar Vertz Sand Unit in Payne County, Oklahoma. The primary emphasis of the experiment was preferential plugging of high permeability zones for the purpose of improving waterflood sweep efficiency. Studies were performed to determine reservoir chemistry, ecology, and indigenous bacteria populations. Growth experiments were used to select a nutrient system compatible with the reservoir that encouraged growth of a group of indigenous nitrate-using bacteria and inhibit growth of sulfate-reducing bacteria. A specific field pilot area behind an active line drive waterflood was selected. Surface facilities were designed and installed. Injection protocols of bulk nutrient materials were prepared to facilitate uniform distribution of nutrients within the pilot area. By the end of December, 1991, 82.5 tons (75.0 tonnes) of nutrients had been injected in the field. A tracer test identified significant heterogeneity in the SEVVSU and made it necessary to monitor additional production wells in the field. The tracer tests and changes in production behavior indicate the additional production wells monitored during the field trial were also affected. Eighty two and one half barrels (13.1 m[sup 3]) of tertiary oil have been recovered. Microbial activity has increased CO[sub 2] content as indicated by increased alkalinity. A temporary rise in sulfide concentration was experienced. These indicate an active microbial community was generated in the field by the nutrient injection. Pilot area interwell pressure interference test results showed that significant permeability reduction occurred. The interwell permeabilities in the pilot area between the injector and the three pilot production wells were made more uniform which indicates a successful preferential plugging enhanced oil recovery project.

  12. Analysis on the design and property of flow field plates of innovative direct methanol fuel cell.

    PubMed

    Chang, Ho; Kao, Mu-Jung; Chen, Chih-Hao; Kuo, Chin-Guo; Lee, Kuang-Ying

    2014-10-01

    The paper uses technology of lithography process to etch flow fields on single side of a printed circuit board (PCB), and combines flow field plate with collector plate to make innovative anode flow field plates and cathode flow field plates required in direct methanol fuel cell (DMFC), and meanwhile makes membrane electrode assembly (MEA) and methanol fuel plate. The flow field plates are designed to be in the form of serpentine flow field. The paper measured the assembled DMFC to achieve the overall efficiency of DMFC under the conditions of different screw torques and different concentration, flow rate and temperature of methanol. Experimental results show that when the flow field width of flow field plate is 1 mm, the screw torque is 16 kgf/cm, and the concentration, flow rate and temperature of methanol-water are 1 M, 180 ml/h and 50 degrees C respectively, the prepared DMFC can have better power density of 5.5 mW/cm2, 5.4 mW/cm2, 11.2 mW/cm2 and 11.8 mW/cm2. Besides, the volume of the DMFC designed and assembled by the study is smaller than the generally existing DMFC by 40%. PMID:25942924

  13. Field-Flow Fractionation of Carbon Nanotubes and Related Materials

    SciTech Connect

    John P. Selegue

    2011-11-17

    During the grant period, we carried out FFF studies of carbonaceous soot, single-walled and multi-walled carbon nanotubes, carbon nano-onions and polyoxometallates. FFF alone does not provide enough information to fully characterize samples, so our suite of characterization techniques grew to include light scattering (especially Photon Correlation Spectroscopy), scanning and transmission electron microscopy, thermogravimetric analysis and spectroscopic methods. We developed convenient techniques to deposit and examine minute FFF fractions by electron microscopy. In collaboration with Arthur Cammers (University of Kentucky), we used Flow Field-Flow Fractionation (Fl-FFF) to monitor the solution-phase growth of keplerates, a class of polyoxometallate (POM) nanoparticles. We monitored the evolution of Mo-POM nanostructures over the course of weeks by by using flow field-flow fractionation and corroborated the nanoparticle structures by using transmission electron microscopy (TEM). Total molybdenum in the solution and precipitate phases was monitored by using inductively coupled plasma analyses, and total Mo-POM concentration by following the UV-visible spectra of the solution phase. We observe crystallization-driven formation of (Mo132) keplerate and solution phase-driven evolution of structurally related nanoscopic species (3-60 nm). FFF analyses of other classes of materials were less successful. Attempts to analyze platelets of layered materials, including exfoliated graphite (graphene) and TaS2 and MoS2, were disappointing. We were not able to optimize flow conditions for the layered materials. The metal sulfides react with the aqueous carrier liquid and settle out of suspension quickly because of their high density.

  14. Hierarchical streamline bundles for visualizing 2D flow fields.

    SciTech Connect

    Shene, Ching-Kuang; Wang, Chaoli; Yu, Hongfeng; Chen, Jacqueline H.

    2010-08-01

    We present hierarchical streamline bundles, a new approach to simplifying and visualizing 2D flow fields. Our method first densely seeds a flow field and produces a large number of streamlines that capture important flow features such as critical points. Then, we group spatially neighboring and geometrically similar streamlines to construct a hierarchy from which we extract streamline bundles at different levels of detail. Streamline bundles highlight multiscale flow features and patterns through a clustered yet non-cluttered display. This selective visualization strategy effectively accentuates visual foci and therefore is able to convey the desired insight into the flow fields. The hierarchical streamline bundles we have introduced offer a new way to characterize and visualize the flow structure and patterns in multiscale fashion. Streamline bundles highlight critical points clearly and concisely. Exploring the hierarchy allows a complete visualization of important flow features. Thanks to selective streamline display and flexible LOD refinement, our multiresolution technique is scalable and is promising for viewing large and complex flow fields. In the future, we would like to seek a cost-effective way to generate streamlines without enforcing the dense seeding condition. We will also extend this approach to handle real-world 3D complex flow fields.

  15. An experimental study of the flow of gas along synthetic faults of varying orientation to the stress field: Implications for performance assessment of radioactive waste disposal

    NASA Astrophysics Data System (ADS)

    Cuss, Robert J.; Harrington, Jon F.; Noy, David J.; Sathar, Shanvas; Norris, Simon

    2015-05-01

    Critical stress theory states that fault transmissivity is strongly dependent upon orientation with respect to the stress tensor. This paper describes an experimental study aimed at verifying critical stress theory using a bespoke angled shear rig designed to examine the relationship between gas flows along a kaolinite-filled synthetic fault as a function of fault dip. A total of 22 gas injection experiments were conducted on faults oriented 0°, 15°, 30°, and 45° to horizontal; both with and without active shear. Gas flow was seen to be complex; repeat gas injection testing showed a consistent gas entry pressure but considerably different, nonrepeatable, gas peak or breakthrough pressure. Gas flow occurred along discrete, dilatant pathways. The physics governing the pressure at which these features formed was repeatable; however, permeability was dependent on the number, distribution, and geometry of the resultant pathways. The nonrepeatable gas response suggests that the number of pathways was dependent on very subtle variations in gouge properties. No fault orientations were seen to exhibit nonflow characteristics, although critical stress theory predicted that two of the investigated fault angles should be effective seals. However, a small variation in gas entry pressure was seen with fault angle as a result of varying normal and shear stress acting on the gouge material. Shear was seen to enhance gas movement by reducing gas entry pressure and increased permeability once gas became mobile. Therefore, in kaolinite gouge-filled faults, shear is not an effective self-sealing mechanism to gas flow.

  16. Flow damping due to stochastization of the magnetic field

    PubMed Central

    Ida, K.; Yoshinuma, M.; Tsuchiya, H.; Kobayashi, T.; Suzuki, C.; Yokoyama, M.; Shimizu, A.; Nagaoka, K.; Inagaki, S.; Itoh, K.; Akiyama, T.; Emoto, M.; Evans, T.; Dinklage, A.; Du, X.; Fujii, K.; Goto, M.; Goto, T.; Hasuo, M.; Hidalgo, C.; Ichiguchi, K.; Ishizawa, A.; Jakubowski, M.; Kamiya, K.; Kasahara, H.; Kawamura, G.; Kato, D.; Kobayashi, M.; Morita, S.; Mukai, K.; Murakami, I.; Murakami, S.; Narushima, Y.; Nunami, M.; Ohdach, S.; Ohno, N.; Osakabe, M.; Pablant, N.; Sakakibara, S.; Seki, T.; Shimozuma, T.; Shoji, M.; Sudo, S.; Tanaka, K.; Tokuzawa, T.; Todo, Y.; Wang, H.; Yamada, H.; Takeiri, Y.; Mutoh, T.; Imagawa, S.; Mito, T.; Nagayama, Y.; Watanabe, K. Y.; Ashikawa, N.; Chikaraishi, H.; Ejiri, A.; Furukawa, M.; Fujita, T.; Hamaguchi, S.; Igami, H.; Isobe, M.; Masuzaki, S.; Morisaki, T.; Motojima, G.; Nagasaki, K.; Nakano, H.; Oya, Y.; Suzuki, Y.; Sakamoto, R.; Sakamoto, M.; Sanpei, A.; Takahashi, H.; Tokitani, M.; Ueda, Y.; Yoshimura, Y.; Yamamoto, S.; Nishimura, K.; Sugama, H.; Yamamoto, T.; Idei, H.; Isayama, A.; Kitajima, S.; Masamune, S.; Shinohara, K.; Bawankar, P. S.; Bernard, E.; von Berkel, M.; Funaba, H.; Huang, X. L.; Ii, T.; Ido, T.; Ikeda, K.; Kamio, S.; Kumazawa, R.; Moon, C.; Muto, S.; Miyazawa, J.; Ming, T.; Nakamura, Y.; Nishimura, S.; Ogawa, K.; Ozaki, T.; Oishi, T.; Ohno, M.; Pandya, S.; Seki, R.; Sano, R.; Saito, K.; Sakaue, H.; Takemura, Y.; Tsumori, K.; Tamura, N.; Tanaka, H.; Toi, K.; Wieland, B.; Yamada, I.; Yasuhara, R.; Zhang, H.; Kaneko, O.; Komori, A.

    2015-01-01

    The driving and damping mechanism of plasma flow is an important issue because flow shear has a significant impact on turbulence in a plasma, which determines the transport in the magnetized plasma. Here we report clear evidence of the flow damping due to stochastization of the magnetic field. Abrupt damping of the toroidal flow associated with a transition from a nested magnetic flux surface to a stochastic magnetic field is observed when the magnetic shear at the rational surface decreases to 0.5 in the large helical device. This flow damping and resulting profile flattening are much stronger than expected from the Rechester–Rosenbluth model. The toroidal flow shear shows a linear decay, while the ion temperature gradient shows an exponential decay. This observation suggests that the flow damping is due to the change in the non-diffusive term of momentum transport. PMID:25569268

  17. The 3D Flow Field Around an Embedded Planet

    NASA Astrophysics Data System (ADS)

    Fung, Jeffrey; Artymowicz, Pawel; Wu, Yanqin

    2015-10-01

    3D modifications to the well-studied 2D flow topology around an embedded planet have the potential to resolve long-standing problems in planet formation theory. We present a detailed analysis of the 3D isothermal flow field around a 5 Earth-mass planet on a fixed circular orbit, simulated using our graphics processing unit hydrodynamics code PEnGUIn. We find that, overall, the horseshoe region has a columnar structure extending vertically much beyond the Hill sphere of the planet. This columnar structure is only broken for some of the widest horseshoe streamlines, along which high altitude fluid descends rapidly into the planet’s Bondi sphere, performs one horseshoe turn, and exits the Bondi sphere radially in the midplane. A portion of this flow exits the horseshoe region altogether, which we refer to as the “transient” horseshoe flow. The flow continues as it rolls up into a pair of up-down symmetric horizontal vortex lines shed into the wake of the planet. This flow, unique to 3D, affects both planet accretion and migration. It prevents the planet from sustaining a hydrostatic atmosphere due to its intrusion into the Bondi sphere, and leads to a significant corotation torque on the planet, unanticipated by 2D analysis. In the reported simulation, starting with a {{Σ }}˜ {r}-3/2 radial surface density profile, this torque is positive and partially cancels with the negative differential Lindblad torque, resulting in a factor of three slower planet migration rate. Finally, we report 3D effects can be suppressed by a sufficiently large disk viscosity, leading to results similar to 2D.

  18. The applicability of Brillouin scattering to flow field diagnostics

    NASA Technical Reports Server (NTRS)

    Laiosa, J.; Lederman, S.

    1979-01-01

    To fill the void between turbulence theory and experiment; particularly in the flow fields consisting of monatomic gases, for example in wind tunnels, means of measuring fluctuating quantities are needed. In the area of density fluctuation measurement, the optical method of Brillouin scattering was suggested. This was based on the theory, that the Brillouin scattered intensity is proportional to a function of density. In this investigation the potential of this method as a diagnostic tool was studied. Here the density fluctuations in gases were sought. Continuous wave lasers and interferometers were used as the primary illuminating source and scattered light filters respectively.

  19. DNS studies of bubbly flows

    NASA Astrophysics Data System (ADS)

    Tryggvason, Gretar; Esmaeeli, Asghar; Biswas, Souvik

    2004-11-01

    Recent stuies of bubbly flows, using direct numerical simulations, are discussed. The goal of this study is to examine the collective behavior of many bubbles as the rise Reynolds number is increased and and a single bubble rises unsteadily, as well as to examine the motion of bubbles in channels. A front-tracking/finite volume method is used to fully resolve all flow scales, including the bubbles and the flow around them. Two cases are simulated, for one the bubbles remain nearly spherical and for the other case the bubbles are deformable and wobble. The wobbly bubbles remains relatively uniformly distributed and are not susceptible to the streaming instability found by Bunner and Tryggvason (2003) for deformable bubbles at lower rise Reynolds numbers. The more spherical bubbles, on the other hand, form transients ``rafts'' somewhat similar to those seen in potential flow simulation of many bubbles. For channel flow we compare results from direct numerical simulations of bubbly flow with prediction of the steady-state two-fluid model of Antal, Lahey, and Flaherty (1991). The simulations are done assuming a two-dimensional system and the model coefficients are adjusted slightly to match the data for upflow. The results generally agree reasonably well, even though the simulated void fraction is considerably higher than the one assumed in the derivation of the model. Research supported by DOE.

  20. Bleed Hole Flow Phenomena Studied

    NASA Technical Reports Server (NTRS)

    1997-01-01

    Boundary-layer bleed is an invaluable tool for controlling the airflow in supersonic aircraft engine inlets. Incoming air is decelerated to subsonic speeds prior to entering the compressor via a series of oblique shocks. The low momentum flow in the boundary layer interacts with these shocks, growing in thickness and, under some conditions, leading to flow separation. To remedy this, bleed holes are strategically located to remove mass from the boundary layer, reducing its thickness and helping to maintain uniform flow to the compressor. The bleed requirements for any inlet design are unique and must be validated by extensive wind tunnel testing to optimize performance and efficiency. To accelerate this process and reduce cost, researchers at the NASA Lewis Research Center initiated an experimental program to study the flow phenomena associated with bleed holes. Knowledge of these flow properties will be incorporated into computational fluid dynamics (CFD) models that will aid engine inlet designers in optimizing bleed configurations before any hardware is fabricated. This ongoing investigation is currently examining two hole geometries, 90 and 20 (both with 5-mm diameters), and various flow features.

  1. Gradient isolator for flow field of fuel cell assembly

    DOEpatents

    Ernst, W.D.

    1999-06-15

    Isolator(s) include isolating material and optionally gasketing material strategically positioned within a fuel cell assembly. The isolating material is disposed between a solid electrolyte and a metal flow field plate. Reactant fluid carried by flow field plate channel(s) forms a generally transverse electrochemical gradient. The isolator(s) serve to isolate electrochemically a portion of the flow field plate, for example, transversely outward from the channel(s), from the electrochemical gradient. Further, the isolator(s) serve to protect a portion of the solid electrolyte from metallic ions. 4 figs.

  2. Gradient isolator for flow field of fuel cell assembly

    DOEpatents

    Ernst, William D.

    1999-01-01

    Isolator(s) include isolating material and optionally gasketing material strategically positioned within a fuel cell assembly. The isolating material is disposed between a solid electrolyte and a metal flow field plate. Reactant fluid carried by flow field plate channel(s) forms a generally transverse electrochemical gradient. The isolator(s) serve to isolate electrochemically a portion of the flow field plate, for example, transversely outward from the channel(s), from the electrochemical gradient. Further, the isolator(s) serve to protect a portion of the solid electrolyte from metallic ions.

  3. Binary stellar winds. [flow and magnetic field interactions

    NASA Technical Reports Server (NTRS)

    Siscoe, G. L.; Heinemann, M. A.

    1974-01-01

    Stellar winds from a binary star will interact with each other along a contact discontinuity. We discuss qualitatively the geometry of the flow and field resulting from this interaction in the simplest case where the stars and winds are identical. We consider the shape of the critical surface (defined as the surface where the flow speed is equal to the sound speed) as a function of stellar separation and the role of shock waves in the flow field. The effect of stellar spin and magnetic sectors on the field configuration is given. The relative roles of mass loss and magnetic torque in the evolution of orbital parameters are discussed.

  4. Binary stellar winds. [flow and magnetic field geometry

    NASA Technical Reports Server (NTRS)

    Siscoe, G. L.; Heinemann, M. A.

    1974-01-01

    Stellar winds from a binary star pair will interact with each other along a contact discontinuity. We discuss qualitatively the geometry of the flow and field resulting from this interaction in the simplest case where the stars and winds are identical. We consider the shape of the critical surface (defined as the surface where the flow speed is equal to the sound speed) as a function of stellar separation and the role of shock waves in the flow field. The effect of stellar spin and magnetic sectors on the field configuration is given. The relative roles of mass loss and magnetic torque in the evolution of orbital parameters is discussed.

  5. Horizontal flow fields observed in Hinode G-band images. II. Flow fields in the final stages of sunspot decay

    NASA Astrophysics Data System (ADS)

    Verma, M.; Balthasar, H.; Deng, N.; Liu, C.; Shimizu, T.; Wang, H.; Denker, C.

    2012-02-01

    Context. Generation and dissipation of magnetic fields is a fundamental physical process on the Sun. In comparison to flux emergence and the initial stages of sunspot formation, the demise of sunspots still lacks a comprehensive description. Aims: The evolution of sunspots is most commonly discussed in terms of their intensity and magnetic field. Here, we present additional information about the three-dimensional flow field in the vicinity of sunspots towards the end of their existence. Methods: We present a subset of multi-wavelengths observations obtained with the Japanese Hinode mission, the Solar Dynamics Observatory (SDO), and the Vacuum Tower Telescope (VTT) at Observatorio del Teide, Tenerife, Spain during the time period 2010 November 18-23. Horizontal proper motions were derived from G-band and Ca ii H images, whereas line-of-sight velocities were extracted from VTT echelle Hα λ656.28 nm spectra and Fe i λ630.25 nm spectral data of the Hinode/Spectro-Polarimeter, which also provided three-dimensional magnetic field information. The Helioseismic and Magnetic Imager on board SDO provided continuum images and line-of-sight magnetograms, in addition to the high-resolution observations for the entire disk passage of the active region. Results: We perform a quantitative study of photospheric and chromospheric flow fields in and around decaying sunspots. In one of the trailing sunspots of active region NOAA 11126, we observe moat flow and moving magnetic features (MMFs), even after its penumbra had decayed. We also detect a superpenumbral structure around this pore. We find that MMFs follow well-defined, radial paths from the spot all the way to the border of a supergranular cell surrounding the spot. In contrast, flux emergence near the other sunspot prevents the establishment of similar well ordered flow patterns, which could be discerned around a tiny pore of merely 2 Mm diameter. After the disappearance of the sunspots/pores, a coherent patch of abnormal

  6. Modulating patterns of two-phase flow with electric fields

    PubMed Central

    Liu, Dingsheng; Hakimi, Bejan; Volny, Michael; Rolfs, Joelle; Anand, Robbyn K.; Turecek, Frantisek; Chiu, Daniel T.

    2014-01-01

    This paper describes the use of electro-hydrodynamic actuation to control the transition between three major flow patterns of an aqueous-oil Newtonian flow in a microchannel: droplets, beads-on-a-string (BOAS), and multi-stream laminar flow. We observed interesting transitional flow patterns between droplets and BOAS as the electric field was modulated. The ability to control flow patterns of a two-phase fluid in a microchannel adds to the microfluidic tool box and improves our understanding of this interesting fluid behavior. PMID:25379091

  7. Influence of Local Flow Field on Flow Accelerated Corrosion Downstream from an Orifice

    NASA Astrophysics Data System (ADS)

    Utanohara, Yoichi; Nagaya, Yukinori; Nakamura, Akira; Murase, Michio

    Flow accelerated corrosion (FAC) rate downstream from an orifice was measured in a high-temperature water test loop to evaluate the effects of flow field on FAC. Orifice flow was also measured using laser Doppler velocimetry (LDV) and simulated by steady RANS simulation and large eddy simulation (LES). The LDV measurements indicated the flow structure did not depend on the flow velocity in the range of Re = 2.3×104 to 1.2×105. Flow fields predicted by RANS and LES agreed well with LDV data. Measured FAC rate was higher downstream than upstream from the orifice and the maximum appeared at 2D (D: pipe diameter) downstream. The shape of the profile of the root mean square (RMS) wall shear stress predicted by LES had relatively good agreement with the shape of the profile of FAC rate. This result indicates that the effects of flow field on FAC can be evaluated using the calculated wall shear stress.

  8. A novel potential/viscous flow coupling technique for computing helicopter flow fields

    NASA Technical Reports Server (NTRS)

    Summa, J. Michael; Strash, Daniel J.; Yoo, Sungyul

    1990-01-01

    Because of the complexity of helicopter flow field, a zonal method of analysis of computational aerodynamics is required. Here, a new procedure for coupling potential and viscous flow is proposed. An overlapping, velocity coupling technique is to be developed with the unique feature that the potential flow surface singularity strengths are obtained directly from the Navier-Stokes at a smoother inner fluid boundary. The closed-loop iteration method proceeds until the velocity field is converged. This coupling should provide the means of more accurate viscous computations of the near-body and rotor flow fields with resultant improved analysis of such important performance parameters as helicopter fuselage drag and rotor airloads.

  9. Flow field of a unitary Fermi gas for the scissors mode

    NASA Astrophysics Data System (ADS)

    Lu, Zhen-Bang; Chen, Ji-Sheng; Li, Jia-Rong

    2014-08-01

    The scissors mode plays a crucial role in the study of the unitary Fermi gas. In this paper, we simulate the scissors mode by solving the hydrodynamic equations with appropriate initial conditions, and then extract the flow field of the gas. The flow fields in different regimes are found to be essentially different. The characteristic differences in the flow patterns between the superfluid and the normal viscous fluid are presented. Irrotational flow signals superfluidity, while rotational one indicates normal hydrodynamical behavior. These different characteristics can be visualized by the velocity portraits of the flow, which provide an intuitive way to discriminate the states of the Fermi gas.

  10. Evaluation of lateral flow assay as a field test for investigation of brucellosis outbreak in an organized buffalo farm: A pilot study

    PubMed Central

    Shome, R.; Filia, G.; Padmashree, B. S.; Krithiga, N.; Sahay, Swati; Triveni, K.; Shome, B. R.; Mahajan, V.; Singh, Amarjit; Rahman, H.

    2015-01-01

    Aim: The aim was to evaluate lateral flow assay (LFA) as a field test for investigation of brucellosis outbreak in organized buffalo farm. Materials and Methods: A total of 153 serum samples were tested to detect the presence of brucella antibodies by LFA and three other serological tests i.e. rose bengal plate test (RBPT), protein G based indirect enzyme-linked immunoassay (iELISA), and competitive ELISA (cELISA). The performances of LFA and other serological tests were evaluated using OIE complaint cELISA as the gold standard. Results: Serological tests revealed 50% of the animals were seropositive for Brucella antibodies and correlated with clinical history of abortions, infertility, and productive failures. The newly developed assay showed 87.1% and 92.6% sensitivity and specificity, which was even higher than the specificity of RBPT. Conclusions: The investigation proved the potential usefulness of LFA for field diagnosis of brucellosis in the regions where laboratory facilities are limited. PMID:27047121

  11. Investigation of Spherical-Wave-Initiated Flow Fields Around Bodies

    NASA Technical Reports Server (NTRS)

    McFarland, Donald R.

    1959-01-01

    Measurements of the velocity flow fields and vortex movements have been made about various simple blunt models undergoing spherical blast waves with a positive overpressure of 4 pounds per square inch. A bullet-optical method was used to determine flow velocities and is applied to velocity fields in which the gradients are largely normal to the free-stream direction. The velocity flow fields are shown at various flow times following passage of the blast front for different models. Vortex movements with time are compared for square-bar models of various aspect ratios. Corner sharpness had no discernible effect on the overall disturbed velocity fields or vortex movements for the square-box models used.

  12. Flow field induced particle accumulation inside droplets in rectangular channels.

    PubMed

    Hein, Michael; Moskopp, Michael; Seemann, Ralf

    2015-07-01

    Particle concentration is a basic operation needed to perform washing steps or to improve subsequent analysis in many (bio)-chemical assays. In this article we present field free, hydrodynamic accumulation of particles and cells in droplets flowing within rectangular micro-channels. Depending on droplet velocity, particles either accumulate at the rear of the droplet or are dispersed over the entire droplet cross-section. We show that the observed particle accumulation behavior can be understood by a coupling of particle sedimentation to the internal flow field of the droplet. The changing accumulation patterns are explained by a qualitative change of the internal flow field. The topological change of the internal flow field, however, is explained by the evolution of the droplet shape with increasing droplet velocity altering the friction with the channel walls. In addition, we demonstrate that accumulated particles can be concentrated, removing excess dispersed phase by splitting the droplet at a simple channel junction. PMID:26032835

  13. Synthetic Jet Flow Field Database for CFD Validation

    NASA Technical Reports Server (NTRS)

    Yao, Chung-Sheng; Chen, Fang Jenq; Neuhart, Dan; Harris, Jerome

    2004-01-01

    An oscillatory zero net mass flow jet was generated by a cavity-pumping device, namely a synthetic jet actuator. This basic oscillating jet flow field was selected as the first of the three test cases for the Langley workshop on CFD Validation of Synthetic Jets and Turbulent Separation Control. The purpose of this workshop was to assess the current CFD capabilities to predict unsteady flow fields of synthetic jets and separation control. This paper describes the characteristics and flow field database of a synthetic jet in a quiescent fluid. In this experiment, Particle Image Velocimetry (PIV), Laser Doppler Velocimetry (LDV), and hot-wire anemometry were used to measure the jet velocity field. In addition, the actuator operating parameters including diaphragm displacement, internal cavity pressure, and internal cavity temperature were also documented to provide boundary conditions for CFD modeling.

  14. On Hammershock Propagation in a Supersonic Flow Field

    NASA Technical Reports Server (NTRS)

    Porro, A. Robert

    2002-01-01

    A wind tunnel test program was conducted to acquire flow-field data during a supersonic propulsion system compressor stall and inlet unstart sequence. The propulsion system consisted of a mixed-compression, two-dimensional bifurcated inlet coupled to a General Electric J85-13 turbojet engine. The propulsion system was mounted beneath a large flat plate that simulated an underwing propulsion pod installation. Transient flow-field pitot pressure and wing simulator surface static pressure data were acquired during multiple compressor stall and inlet unstart events at a free-stream Mach number of 2.20. The experimental results obtained in this investigation indicate that a supersonic propulsion system compressor stall-inlet unstart transient event adversely affects the surrounding local flow field. The data show that the stall-unstart event affects the surrounding flow field on a millisecond time scale and causes a three-dimensional expanding wave front called a hammershock to propagate outward from the inlet. The flow nearest the wing simulator separates from the surface during the transient event. At the end of the transient event, a distinct process occurs wherein the affected flow field recovers to free-stream conditions and the wing simulator boundary layer reattaches to the flow surface.

  15. Dynamic Pressure Probes Developed for Supersonic Flow-Field Measurements

    NASA Technical Reports Server (NTRS)

    Porro, A. Robert

    2001-01-01

    A series of dynamic flow-field pressure probes were developed for use in large-scale supersonic wind tunnels at the NASA Glenn Research Center. These flow-field probes include pitot and static pressure probes that can capture fast-acting flow-field pressure transients occurring on a millisecond timescale. The pitot and static probes can be used to determine local Mach number time histories during a transient event. The flow-field pressure probe contains four major components: 1) Static pressure aerodynamic tip; 2) Pressure-sensing cartridge assembly; 3) Pitot pressure aerodynamic tip; 4) Mounting stem. This modular design allows for a variety of probe tips to be used for a specific application. Here, the focus is on flow-field pressure measurements in supersonic flows, so we developed a cone-cylinder static pressure tip and a pitot pressure tip. Alternatively, probe tips optimized for subsonic and transonic flows could be used with this design. The pressure-sensing cartridge assembly allows the simultaneous measurement of steady-state and transient pressure which allows continuous calibration of the dynamic pressure transducer.

  16. Synchrotron microimaging technique for measuring the velocity fields of real blood flows

    SciTech Connect

    Lee, Sang-Joon; Kim, Guk Bae

    2005-03-15

    Angiography and Doppler methods used for diagnosing vascular diseases give information on the shape of blood vessels and pointwise blood speed but do not provide detailed information on the flow fields inside the blood vessels. In this study, we developed a method for visualizing blood flow by using coherent synchrotron x rays. This method, which does not require the addition of any contrast agent or tracer particles, visualizes the flow pattern of blood by enhancing the diffraction and interference characteristics of the blood cells. This was achieved by optimizing the sample- (blood) to-detector (charge-coupled device camera) distance and the sample thickness. The proposed method was used to extract quantitative velocity field information from blood flowing inside an opaque microchannel by applying a two-frame particle image velocimetry algorithm to enhanced x-ray images of the blood flow. The measured velocity field data showed a flow structure typical of flow in a macrochannel.

  17. Particle and flow field holography: A critical survey

    NASA Technical Reports Server (NTRS)

    Trolinger, James D.

    1987-01-01

    A brief background is provided for the fields of particle and flow visualization holography. A summary of methods currently in use is given, followed by a discussion of more recent and unique applications. The problem of data reduction is discussed. A state of the art summary is then provided with a prognosis of the future of the field. Particle and flow visualization holography are characterized as powerful tools currently in wide use and with significant untapped potential.

  18. Space shuttle orbiter flow visualization study. [water tunnel study of vortex flow during atmospheric entry

    NASA Technical Reports Server (NTRS)

    Lorincz, D. J.

    1980-01-01

    The vortex flows generated at subsonic speed during the final portion of atmospheric reentry were defined using a 0.01 scale model of the orbiter in a diagnostic water tunnel. Flow visualization photographs were obtained over an angle-of-attack range to 40 deg and sideslip angles up to 10 deg. The vortex flow field development, vortex path, and vortex breakdown characteristics were determined as a function of angle-of-attack at zero sideslip. Vortex flows were found to develop on the highly swept glove, on the wing, and on the upper surface of the fuselage. No significant asymmetries were observed at zero sideslip in the water tunnel tests. The sensitivity of the upper surface vortex flow fields to variations in sideslip angle was also studied. The vortex formed on the glove remained very stable in position above the wing up through the 10 deg of sideslip tested. There was a change in the vortex lifts under sideslip due to effective change in leading-edge sweep angles. Asymmetric flow separation occurred on the upper surface of the fuselage at small sideslip angles. The influence of vortex flow fields in sideslip on the lateral/ directional characteristics of the orbiter is discussed.

  19. Flow field stratigraphy surrounding Sekmet Mons Volcano, Kawelu Planitia, Venus

    NASA Astrophysics Data System (ADS)

    Zimbelman, James R.

    2003-05-01

    Detailed mapping has revealed several stratigraphic components among lobate plains in the vicinity of Sekmet Mons volcano (44.5°N. lat., 240.5° long.), located on the northern lowland plains of Kawelu Planitia on Venus. Volcanic effusion events produced discrete lobate plains throughout the area. Superposition of flow margins between adjacent lobate plains components indicate that the effusive activity generally progressed from southwest to northeast across the Sekmet Mons area, leading to a cumulative total of 1.5 million km2 covered by adjacent lobate plains components. Source areas for the effusion responsible for the lobate plains components occur primarily along fracture zones or from concentrations of low volcanic domes (``shield fields'') instead of from single constructs. Magellan radar backscatter values from a mixture of both radar bright and radar dark flow components within the flow fields are well below values typical of clinkery a'a lava flows on Earth, but they are consistent with values from terrestrial pahoehoe flows. Detailed mapping of Strenia Fluctus (centered on 41.5° N. lat., 251.0° long.), one of the latest lobate plains units in the area, does not show a systematic trend among effusive centers that contributed to the generation of this flow field. Instead, the Strenia Fluctus flow field is a complex mixture of flows that emanated from a shield field along Mist Chasma and that flowed down a very gentle (>0.1°) regional slope to the east. A 4-km-diameter cone north of Strenia Fluctus was the source of a flow complex traceable for more than 200 km over a slope of only 0.03°. Individual flows within Strenia Fluctus are composed of intermixed lobes, similar to relationships observed on the distal portion of the 75-km-long Carrizozo basalt flow in New Mexico, which also displays abundant inflation features and a predominant pahoehoe surface texture. If the Venusian lobate plains consist of pahoehoe flows comparable to the Carrizozo flow

  20. The electromagnetic force field, fluid flow field and temperature profiles in levitated metal droplets

    NASA Technical Reports Server (NTRS)

    El-Kaddah, N.; Szekely, J.

    1982-01-01

    A mathematical representation was developed for the electromagnetic force field, the flow field, the temperature field (and for transport controlled kinetics), in a levitation melted metal droplet. The technique of mutual inductances was employed for the calculation of the electromagnetic force field, while the turbulent Navier - Stokes equations and the turbulent convective transport equations were used to represent the fluid flow field, the temperature field and the concentration field. The governing differential equations, written in spherical coordinates, were solved numerically. The computed results were in good agreement with measurements, regarding the lifting force, and the average temperature of the specimen and carburization rates, which were transport controlled.

  1. Transport of Magnetic Field by a Turbulent Flow of Liquid Sodium

    SciTech Connect

    Volk, R.; Odier, Ph.; Pinton, J.-F.; Ravelet, F.; Monchaux, R.; Chiffaudel, A.; Daviaud, F.; Berhanu, M.; Fauve, S.; Mordant, N.; Petrelis, F.

    2006-08-18

    We study the effect of a turbulent flow of liquid sodium generated in the von Karman geometry, on the localized field of a magnet placed close to the frontier of the flow. We observe that the field can be transported by the flow on distances larger than its integral length scale. In the most turbulent configurations, the mean value of the field advected at large distance vanishes. However, the rms value of the fluctuations increases linearly with the magnetic Reynolds number. The advected field is strongly intermittent.

  2. The effect of swirling number on the flow field of downshot flame furnace

    SciTech Connect

    Zhijun, Z.; Zili, Z.; Xiang, Z.; Xinyu, C.; Junhu, Z.; Zhengyu, H.; Jianzhong, L.; Kefa, C.

    2000-07-01

    The cold model test is adopted to study the flow field of downshot flame furnace with swirling burners in this paper. The flow field is measured with tri-hole probe. The ribbon method and fireworks tracer technology are adopted to find out the flow field distribution qualitatively. The results show that the momentum ratio of arch air and side-wall air is not the most important factor which determines the flow field when swirling burners are adopted. The effect of swirling number of arch air on the flow field is notable, and the jet will decline like normal swirling jet. Under general swirling number, the momentum ratio of arch air and side-wall air should be large enough.

  3. Gene flow in maize fields with different local pollen densities

    NASA Astrophysics Data System (ADS)

    Goggi, A. Susana; Lopez-Sanchez, Higinio; Caragea, Petrutza; Westgate, Mark; Arritt, Raymond; Clark, Craig A.

    2007-08-01

    The development of maize ( Zea mays L.) varieties as factories of pharmaceutical and industrial compounds has renewed interest in controlling pollen dispersal. The objective of this study was to compare gene flow into maize fields of different local pollen densities under the same environmental conditions. Two fields of approximately 36 ha were planted with a nontransgenic, white hybrid, in Ankeny, Iowa, USA. In the center of both fields, a 1-ha plot of a yellow-seeded stacked RR/Bt transgenic hybrid was planted as a pollen source. Before flowering, the white receiver maize of one field was detasseled in a 4:1 ratio to reduce the local pollen density (RPD). The percentage of outcross in the field with RPD was 42.2%, 6.3%, and 1.3% at 1, 10, and 35 m from the central plot, respectively. The percentage of outcross in the white maize with normal pollen density (NPD) was 30.1%, 2.7%, and 0.4%, respectively, at these distances. At distances greater than 100 m, the outcross frequency decreased below 0.1 and 0.03% in the field with RPD and NPD, respectively. A statistical model was used to compare pollen dispersal based on observed outcross percentages. The likelihood ratio test confirmed that the models of outcrossing in the two fields were significantly different ( P is practically 0). Results indicated that when local pollen is low, the incoming pollen has a competitive advantage and the level of outcross is significantly greater than when the local pollen is abundant.

  4. On the flow field around a Savonius rotor

    NASA Astrophysics Data System (ADS)

    Bergeles, G.; Athanassiadis, N.

    A model of a two-bucket Savonius rotor windmill was constructed and tested in a wind tunnel. The flow field around the rotor was examined visually and also quantitatively with the use of a hot wire. The flow visualization revealed an upstream influence on the flow field up to 3 rotor diameters away and a strong downwash downstream. Hot wire measurements showed a large velocity deficit behind the rotor and a quick velocity recovery downstream due to strong mixing; the latter was associated with high levels of turbulence. Energy spectra revealed that all turbulence was concentrated in a single harmonic corresponding to twice the rotational speed of the rotor.

  5. The sound field of a rotating monopole in a plug flow

    NASA Astrophysics Data System (ADS)

    Belyaev, I. V.

    2016-07-01

    A theoretical study is performed on the sound field generated by a rotating point monopole in a jet flow, the mixing layer of which is simulated by a velocity discontinuity. Its sound in the far field is compared to the sound field generated by a rotating monopole in a uniform flow in the absence of a velocity discontinuity, which makes it possible to estimate the size of the sound refraction effect.

  6. Magnetic Field Suppression of Flow in Semiconductor Melt

    NASA Technical Reports Server (NTRS)

    Fedoseyev, A. I.; Kansa, E. J.; Marin, C.; Volz, M. P.; Ostrogorsky, A. G.

    2000-01-01

    One of the most promising approaches for the reduction of convection during the crystal growth of conductive melts (semiconductor crystals) is the application of magnetic fields. Current technology allows the experimentation with very intense static fields (up to 80 KGauss) for which nearly convection free results are expected from simple scaling analysis in stabilized systems (vertical Bridgman method with axial magnetic field). However, controversial experimental results were obtained. The computational methods are, therefore, a fundamental tool in the understanding of the phenomena accounting during the solidification of semiconductor materials. Moreover, effects like the bending of the isomagnetic lines, different aspect ratios and misalignments between the direction of the gravity and magnetic field vectors can not be analyzed with analytical methods. The earliest numerical results showed controversial conclusions and are not able to explain the experimental results. Although the generated flows are extremely low, the computational task is a complicated because of the thin boundary layers. That is one of the reasons for the discrepancy in the results that numerical studies reported. Modeling of these magnetically damped crystal growth experiments requires advanced numerical methods. We used, for comparison, three different approaches to obtain the solution of the problem of thermal convection flows: (1) Spectral method in spectral superelement implementation, (2) Finite element method with regularization for boundary layers, (3) Multiquadric method, a novel method with global radial basis functions, that is proven to have exponential convergence. The results obtained by these three methods are presented for a wide region of Rayleigh and Hartman numbers. Comparison and discussion of accuracy, efficiency, reliability and agreement with experimental results will be presented as well.

  7. Identification of the Temperature Field in Pulsatile Impinging Flow

    NASA Astrophysics Data System (ADS)

    Vít, Tomáš; Lédl, Vít

    2010-09-01

    The presented paper shows the possibility of using holographic interferometry and hot-wire anemometry in the research of heat transfer from impingement pulsatile flow. The intensity of heat transfer in the case of impingement flow is often measured with glue-on heat flux sensors, or by indirect methods such as naphthalene sublimation. All these methods have a response time too long for measuring instant values of the heat transfer coefficient on a surface cooled/heated by impingement pulsatile flow. This shortcoming should be overcome by using CTA glue-on probes or, preferably, by using optical methods such as holographic interferometry. It is necessary to employ a special holographic setup with double sensitivity instead of the commonly used Mach-Zehnder type of holographic interferometer in order to attain the parameters sufficient for the studied case. This setup is not light efficient like the Mach-Zehnder type but has double sensitivity. The results from the holographic interferometry experiments will be compared with the temperature field achieved by methods of hot-wire anemometry.

  8. Numerical Simulations of Canted Nozzle and Scarfed Nozzle Flow Fields

    NASA Astrophysics Data System (ADS)

    Javed, Afroz; Chakraborty, Debasis

    2016-06-01

    Computational fluid dynamics (CFD) techniques are used for the analysis of issues concerning non-conventional (canted and scarfed) nozzle flow fields. Numerical simulations are carried out for the quality of flow in terms of axisymmetric nature at the inlet of canted nozzles of a rocket motor. Two different nozzle geometries are examined. The analysis of these simulation results shows that the flow field at the entry of the nozzles is non axisymmetric at the start of the motor. With time this asymmetry diminishes, also the flow becomes symmetric before the nozzle throat, indicating no misalignment of thrust vector with the nozzle axis. The qualitative flow fields at the inlet of the nozzles are used in selecting the geometry with lesser flow asymmetry. Further CFD methodology is used to analyse flow field of a scarfed nozzle for the evaluation of thrust developed and its direction. This work demonstrates the capability of the CFD based methods for the nozzle analysis problems which were earlier solved only approximately by making simplifying assumptions and semi empirical methods.

  9. Observation of airplane flow fields by natural condensation effects

    NASA Technical Reports Server (NTRS)

    Campbell, James F.; Chambers, Joseph R.; Rumsey, Christopher L.

    1988-01-01

    In-flight condensation patterns can illustrate a variety of airplane flow fields, such as attached and separated flows, vortex flows, and expansion and shock waves. These patterns are a unique source of flow visualization that has not been utilized previously. Condensation patterns at full-scale Reynolds number can provide useful information for researchers experimenting in subscale tunnels. It is also shown that computed values of relative humidity in the local flow field provide an inexpensive way to analyze the qualitative features of the condensation pattern, although a more complete theoretical modeling is necessary to obtain details of the condensation process. Furthermore, the analysis revealed that relative humidity is more sensitive to changes in local static temperature than to changes in pressure.

  10. Transverse Flow of Gluon Fields in Heavy Ion Collision

    NASA Astrophysics Data System (ADS)

    Chen, Guangyao; Fries, Rainer J.

    2014-09-01

    We describe the dynamics of initial gluon fields in heavy ion collision using a formal recursive solution of the Yang Mills equations and solving for the energy momentum tensor analytically in a boost-invariant setup. We generalize the original McLerran-Venugopalan (MV) model in order to allow for realistic nuclear profiles. This leads to a transverse flow of gluon fields. This flow pattern is inherited by the quark gluon plasma fluid after thermalization. Its most interesting aspect is a rapidity-odd flow component. We show that this rapidity-odd flow does not break boost invariance and that it emerges naturally from the Yang Mills equations. It leads to directed flow of particles and introduces angular momentum to the system.

  11. Factors affecting measurement of channel thickness in asymmetrical flow field-flow fractionation.

    PubMed

    Dou, Haiyang; Jung, Euo Chang; Lee, Seungho

    2015-05-01

    Asymmetrical flow field-flow fractionation (AF4) has been considered to be a useful tool for simultaneous separation and characterization of polydisperse macromolecules or colloidal nanoparticles. AF4 analysis requires the knowledge of the channel thickness (w), which is usually measured by injecting a standard with known diffusion coefficient (D) or hydrodynamic diameter (dh). An accurate w determination is a challenge due to its uncertainties arising from the membrane's compressibility, which may vary with experimental condition. In the present study, influence of factors including the size and type of the standard on the measurement of w was systematically investigated. The results revealed that steric effect and the particles-membrane interaction by van der Waals or electrostatic force may result in an error in w measurement. PMID:25817708

  12. A simple and feasible process for using multi-stage high-precision DTMs, field surveys and rainfall data to study debris flow occurrence factors of Shenmu area, Taiwan

    NASA Astrophysics Data System (ADS)

    Lo, W.-C.; Lin, B.-S.; Ho, H.-C.; Keck, J.; Yin, H.-Y.; Shan, H.-Y.

    2012-11-01

    The occurrence of typhoon Herb in 1996 caused massive landslides in the Shenmu area of Taiwan. Many people died and stream and river beds were covered by meters of debris. Debris flows almost always take place in the Shenmu area during the flood season, especially in the catchment areas around Tsushui river and Aiyuzih river. Anthropogenic and natural factors that cause debris flow occurrences are complex and numerous. The precise conditions of initiation are difficult to be identified, but three factors are generally considered to be the most important ones, i.e. rainfall characteristics, geologic conditions and topography. This study proposes a simple and feasible process that combines remote sensing technology and multi-stage high-precision DTMs from aerial orthoimages and airborne LiDAR with field surveys to establish a connection between three major occurrence factors that trigger debris flows in the Shenmu area.

  13. Field-flow fractionation of chromosomes

    SciTech Connect

    Giddings, J.C.

    1991-09-01

    The work done on this project is divided into two principal areas. The first involves the application of sedimentation/steric FFF to metaphase chromosomes in an attempt to fractionate the chromosomes according to their size. The preparation of chromosomes from a number of organisms was attempted; procedures were finally worked out in collaboration with Los Alamos National Laboratory for the preparation of metaphase chromosomes from Chinese hamster cells. After extensive experimental work was done to identify suitable operating conditions, the partial fractionation of the Chinese hamster chromosomes was achieved. In the second component of the project, flow FFF was applied to the separation of DNA fragments. Figures are provided that show considerable success in the separation of plasmid digests and in the separation of single from double stranded DNA under 10{sup 4} base pairs. Preliminary work was done on DNA fragments having a size greater than 10{sup 4} base pairs. This work has served to establish the inversion point for DNA.

  14. Stability Analysis of Flow Induced by the Traveling Magnetic Field

    NASA Technical Reports Server (NTRS)

    Mazuruk, Konstantin

    2003-01-01

    Re-circulating flow in molten metal columns can be conveniently induced by the axisymmetric traveling magnetic field. A number of applications can benefit from this technique, such as mixing under microgravity environment, or crysta1 growth from metallic melts. For small magnetic field excitations, the flow is laminar and stationary. As the imposed field increases, a more complex flow will set up in the cylindrical column. Conditions for stable laminar flow are of importance for practical applications. In this work, a linear stability analysis is performed in order to determine the onset of the bifurcation in the system. Here the analysis is restricted to the axisymmetric modes and the low-frequency regime.

  15. Stability Analysis of Flow Induced by the Traveling Magnetic Field

    NASA Technical Reports Server (NTRS)

    Mazuruk, Konstantin

    2003-01-01

    Re-circulating flow in molten metal columns can be conveniently induced by the axisymmetric traveling magnetic field. A number of applications can benefit from this technique, such as mixing under microgravity environment, or.crysta1 growth from metallic melts. For small magnetic field excitations, the flow is laminar and stationary. As the imposed field increases, a more complex flow will set up in the cylindrical column. Conditions for stable laminar flow are of importance for practical applications. In this work, a linear stability analysis is performed in order to determine the onset of the bifurcation in the system. Here the analysis is restricted to the axisymmetric modes and the low-frequency regime.

  16. Effect of blood flow parameters on flow patterns at arterial bifurcations--studies in models.

    PubMed

    Liepsch, D W

    1990-01-01

    Atherosclerotic lesions are found primarily at arterial bends and bifurcations. Flow disturbances at these anatomic sites play a major role in atherogenesis. How hemodynamic factors such as vessel geometry, the pulsatile nature of blood flow, vessel wall elasticity and the non-Newtonian flow behavior of blood influence the flow field at these sites must be clarified. We have performed fundamental studies using a birefringent solution in a simplified rigid 90 degree T-bifurcation and pulsatile flow. The velocity distribution was measured with a laser Doppler anemometer. Flow in an elastic abdominal aorta model has been visualized using magnetic resonance imaging. In both flow studies, zones with negative velocity were found. These model measurements demonstrate that no flow parameter can be neglected. Further detailed studies are necessary to examine the interaction between fluid dynamic and cellular surface properties. PMID:2404201

  17. Ellipsoid flowed around by a harmonic vector field

    NASA Astrophysics Data System (ADS)

    Savchenko, A. O.; Savchenko, O. Ya.

    2012-03-01

    We consider the screening of an external magnetic field in which a superconducting ellipsoid is inserted and a change in the velocity distribution in an ideal liquid flowing around an ellipsoid inserted in it. In both cases, the solution is given by a harmonic vector field parallel to the surface near the ellipsoid.

  18. Debris flow study in Malaysia

    NASA Astrophysics Data System (ADS)

    Bahrin Jaafar, Kamal

    2016-04-01

    The phenomenon of debris flow occurs in Malaysia occasionally. The topography of Peningsular Malysia is characterized by the central mountain ranges running from south to north. Several parts of hilly areas with steep slopes, combined with high saturation of soil strata that deliberately increase the pore water pressure underneath the hill slope. As a tropical country Malaysia has very high intensity rainfall which is triggered the landslide. In the study area where the debris flow are bound to occur, there are a few factors that contribute to this phenomenon such as high rainfall intensity, very steep slope which an inclination more than 35 degree and sandy clay soil type which is easily change to liquidity soil. This paper will discuss the study of rainfall, mechanism, modeling and design of mitigation measure to avoid repeated failure in future in same area.

  19. An Empirical Method for Fast Prediction of Rarefied Flow Field around a Vertical Plate

    NASA Astrophysics Data System (ADS)

    He, Tao; Wang, Jiang-Feng

    2016-06-01

    Numerical study is conducted to investigate the effects of free-stream Knudsen (Kn) number on rarefied flow field around a vertical plate employing an unstructured DSMC method, and an empirical method for fast prediction of flow-field structure at different Kn numbers in a given inflow velocity is proposed. First, the flow at a velocity 7500m/s is simulated using a perfect-gas model with free-stream Kn changing from 0.035 to 13.36. The flow-field characteristics in these cases with varying Kn numbers are analyzed and a linear-expansion phenomenon as a function of the square of Kn is discovered. An empirical method is proposed for fast flow-field prediction at different Kn based on the least-square-fitting method. Further, the effects of chemical reactions on flow field are investigated to verify the applicability of the empirical method in the real gas conditions. Three of the cases in perfect-gas flow are simulated again by introducing five-species air chemical module. The flow properties with and without chemical reactions are compared. In the end, the variation of chemical-reaction flow field as a function of Kn is analyzed and it is shown that the empirical method are also suitable when considering chemical reactions.

  20. Convective Flow Induced by Localized Traveling Magnetic Fields

    NASA Technical Reports Server (NTRS)

    Mazuruk, Konstantin; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    An axisymmetric traveling magnetic field induces a meridional base flow in a cylindrical zone of an electrically conducting liquid. This remotely induced flow can be conveniently controlled, in magnitude and direction, and can have benefits for crystal growth applications. In particular, it can be used to offset natural convection. For long vertical cylinders, non-uniform and localized in the propagating direction, magnetic fields are required for this purpose. Here we investigate a particular form of this field, namely that induced by a set of a few electric current coils. An order of magnitude reduction of buoyancy convection is theoretically demonstrated for a vertical Bridgman crystal growth configuration.

  1. Magnetic field-aligned electric potentials in nonideal plasma flows

    NASA Technical Reports Server (NTRS)

    Schindler, K.; Hesse, M.; Birn, J.

    1991-01-01

    The electric field component parallel to the magnetic field arising from plasma flows which violate the frozen-in field condition of ideal magnetohydrodynamics is discussed. The quantity of interest is the potential U = integral E parallel ds where the integral is extended along field lines. It is shown that U can be directly related to magnetic field properties, expressed by Euler potentials, even when time-dependence is included. These results are applicable to earth's magnetosphere, to solar flares, to aligned-rotator models of compact objects, and to galactic rotation. On the basis of order-of-magnitude estimates, these results support the view that parallel electric fields associated with nonideal plasma flows might play an important role in cosmic particle acceleration.

  2. Swan falls instream flow study

    SciTech Connect

    Anglin, D.R.; Cummings, T.R.; Ecklund, A.E.

    1992-10-01

    The purpose of the Swan Falls Instream Flow Study was to define the relationship between streamflows and instream habitat for resident fish species and to assess the relative impact of several different hydrographs on resident fish habitat. Specific objectives included the following: (1) Conduct a literature search to compile life history, distribution, and habitat requirements for species of interest. Physical and hydrologic characteristics of the Snake River were also compiled. (2) Determine physical habitat versus discharge relationships and conduct habitat time series analysis for each species/lifestage using the Instream Flow Incremental Methodology (IFIM) developed by the U.S. Fish and Wildlife Service. (3) Examine the impacts on resident fish habitat of proposed hydrographs, including Swan Falls Agreement flows, relative to current conditions. (4) Characterize water quality conditions, including water temperature and dissolved oxygen, in the vicinity of the study area and determine the implications of those conditions for the resident species of interest. (5) Determine streamflows necessary to protect and maintain resident fish habitat in the study area.

  3. Basic studies of microstructure of combusting turbulent flows

    NASA Astrophysics Data System (ADS)

    Hussain, Fazle

    1991-03-01

    The goal is to develop a state-of-the-art measurement technique, Holographic Particle Displacement Velocimetry (HPV), which can provide instantaneous velocities everywhere in the flow field simultaneously. Another goal is to use the power of supercomputers to simulate 3D flows with heat release to study the physics of combusting turbulent flows. Computations suffer from limited flow times and Reynolds number but can provide flow properties in more detail than possible by any existing experimental techniques. Moreover, numerical simulations can provide quantities almost impossible to measure experimentally. This article discusses efforts to develop the holographic particle displacement velocimetry system and results of direct numerical numerical simulations of combusting flows.

  4. Numerical Simulation of Flow Field Within Parallel Plate Plastometer

    NASA Technical Reports Server (NTRS)

    Antar, Basil N.

    2002-01-01

    Parallel Plate Plastometer (PPP) is a device commonly used for measuring the viscosity of high polymers at low rates of shear in the range 10(exp 4) to 10(exp 9) poises. This device is being validated for use in measuring the viscosity of liquid glasses at high temperatures having similar ranges for the viscosity values. PPP instrument consists of two similar parallel plates, both in the range of 1 inch in diameter with the upper plate being movable while the lower one is kept stationary. Load is applied to the upper plate by means of a beam connected to shaft attached to the upper plate. The viscosity of the fluid is deduced from measuring the variation of the plate separation, h, as a function of time when a specified fixed load is applied on the beam. Operating plate speeds measured with the PPP is usually in the range of 10.3 cm/s or lower. The flow field within the PPP can be simulated using the equations of motion of fluid flow for this configuration. With flow speeds in the range quoted above the flow field between the two plates is certainly incompressible and laminar. Such flows can be easily simulated using numerical modeling with computational fluid dynamics (CFD) codes. We present below the mathematical model used to simulate this flow field and also the solutions obtained for the flow using a commercially available finite element CFD code.

  5. Field observations of a debris flow event in the Dolomites

    NASA Astrophysics Data System (ADS)

    Berti, Matteo; Genevois, Rinaldo; Simoni, Alessandro; Tecca, Pia Rosella

    1999-09-01

    A debris flow event occurred in June 1997 in the Dolomites (Eastern Alps, Italy). The phenomenon was directly observed in the field and recorded by a video camera near its initiation area. The debris flow originated shortly after an intense rainstorm (25 mm in 30 min) whose runoff mobilised the loose coarse debris that filled the bottom of the channel in its upper part. The analysis of the steep headwater basin indicates a very short concentration time (9-14 min) that fits the quick hydrological response observed in the field. The debris flow mobilisation was not contemporaneous with the arrival of the peak water discharge in the initiation area probably due to the time required for the saturation of the highly conductive channel-bed material. Channel cross-section measurements taken along the flow channel indicate debris flow peak velocity and discharge ranging from 3.1 to 9.0 m/s and from 23 to 71 m 3/s, respectively. Samples collected immediately after deposition were used to determine the water content and bulk density of the material. Channel scouring, fines enrichment and transported volume increase testify erosion and entrainment of material along the flow channel. Field estimates of the rheological properties based on open channel flow of Bingham fluid indicate a yield strength of 5000±400 Pa and relatively low viscosity (60-326 Pa s), probably due to a high percentage of fines (approx. 30%).

  6. Laboratory observation of magnetic field growth driven by shear flow

    SciTech Connect

    Intrator, T. P. Feng, Y.; Sears, J.; Weber, T.; Dorf, L.; Sun, X.

    2014-04-15

    Two magnetic flux ropes that collide and bounce have been characterized in the laboratory. We find screw pinch profiles that include ion flow v{sub i}, magnetic field B, current density J, and plasma pressure. The electron flow v{sub e} can be inferred, allowing the evaluation of the Hall J×B term in a two fluid magnetohydrodynamic Ohm's Law. Flux ropes that are initially cylindrical are mutually attracted and compress each other, which distorts the cylindrical symmetry. Magnetic field is created via the ∇×v{sub e}×B induction term in Ohm's Law where in-plane (perpendicular) shear of parallel flow (along the flux rope) is the dominant feature, along with some dissipation and magnetic reconnection. We predict and measure the growth of a quadrupole out-of-plane magnetic field δB{sub z}. This is a simple and coherent example of a shear flow driven dynamo. There is some similarity with two dimensional reconnection scenarios, which induce a current sheet and thus out-of-plane flow in the third dimension, despite the customary picture that considers flows only in the reconnection plane. These data illustrate a general and deterministic mechanism for large scale sheared flows to acquire smaller scale magnetic features, disordered structure, and possibly turbulence.

  7. Electromagnetic Field Penetration Studies

    NASA Technical Reports Server (NTRS)

    Deshpande, M.D.

    2000-01-01

    A numerical method is presented to determine electromagnetic shielding effectiveness of rectangular enclosure with apertures on its wall used for input and output connections, control panels, visual-access windows, ventilation panels, etc. Expressing EM fields in terms of cavity Green's function inside the enclosure and the free space Green's function outside the enclosure, integral equations with aperture tangential electric fields as unknown variables are obtained by enforcing the continuity of tangential electric and magnetic fields across the apertures. Using the Method of Moments, the integral equations are solved for unknown aperture fields. From these aperture fields, the EM field inside a rectangular enclosure due to external electromagnetic sources are determined. Numerical results on electric field shielding of a rectangular cavity with a thin rectangular slot obtained using the present method are compared with the results obtained using simple transmission line technique for code validation. The present technique is applied to determine field penetration inside a Boeing-757 by approximating its passenger cabin as a rectangular cavity filled with a homogeneous medium and its passenger windows by rectangular apertures. Preliminary results for, two windows, one on each side of fuselage were considered. Numerical results for Boeing-757 at frequencies 26 MHz, 171-175 MHz, and 428-432 MHz are presented.

  8. Fuel cell with metal screen flow-field

    DOEpatents

    Wilson, Mahlon S.; Zawodzinski, Christine

    2001-01-01

    A polymer electrolyte membrane (PEM) fuel cell is provided with electrodes supplied with a reactant on each side of a catalyzed membrane assembly (CMA). The fuel cell includes a metal mesh defining a rectangular flow-field pattern having an inlet at a first corner and an outlet at a second corner located on a diagonal from the first corner, wherein all flow paths from the inlet to the outlet through the square flow field pattern are equivalent to uniformly distribute the reactant over the CMA. In a preferred form of metal mesh, a square weave screen forms the flow-field pattern. In a particular characterization of the present invention, a bipolar plate electrically connects adjacent fuel cells, where the bipolar plate includes a thin metal foil having an anode side and a cathode side; a first metal mesh on the anode side of the thin metal foil; and a second metal mesh on the cathode side of the thin metal foil. In another characterization of the present invention, a cooling plate assembly cools adjacent fuel cells, where the cooling plate assembly includes an anode electrode and a cathode electrode formed of thin conducting foils; and a metal mesh flow field therebetween for distributing cooling water flow over the electrodes to remove heat generated by the fuel cells.

  9. Fuel cell with metal screen flow-field

    DOEpatents

    Wilson, M.S.; Zawodzinski, C.

    1998-08-25

    A polymer electrolyte membrane (PEM) fuel cell is provided with electrodes supplied with a reactant on each side of a catalyzed membrane assembly (CMA). The fuel cell includes a metal mesh defining a rectangular flow-field pattern having an inlet at a first corner and an outlet at a second corner located on a diagonal from the first corner, wherein all flow paths from the inlet to the outlet through the square flow field pattern are equivalent to uniformly distribute the reactant over the CMA. In a preferred form of metal mesh, a square weave screen forms the flow-field pattern. In a particular characterization of the present invention, a bipolar plate electrically connects adjacent fuel cells, where the bipolar plate includes a thin metal foil having an anode side and a cathode side; a first metal mesh on the anode side of the thin metal foil; and a second metal mesh on the cathode side of the thin metal foil. In another characterization of the present invention, a cooling plate assembly cools adjacent fuel cells, where the cooling plate assembly includes an anode electrode and a cathode electrode formed of thin conducting foils; and a metal mesh flow field there between for distributing cooling water flow over the electrodes to remove heat generated by the fuel cells. 11 figs.

  10. Fuel cell with metal screen flow-field

    DOEpatents

    Wilson, Mahlon S.; Zawodzinski, Christine

    1998-01-01

    A polymer electrolyte membrane (PEM) fuel cell is provided with electrodes supplied with a reactant on each side of a catalyzed membrane assembly (CMA). The fuel cell includes a metal mesh defining a rectangular flow-field pattern having an inlet at a first corner and an outlet at a second corner located on a diagonal from the first corner, wherein all flow paths from the inlet to the outlet through the square flow field pattern are equivalent to uniformly distribute the reactant over the CMA. In a preferred form of metal mesh, a square weave screen forms the flow-field pattern. In a particular characterization of the present invention, a bipolar plate electrically connects adjacent fuel cells, where the bipolar plate includes a thin metal foil having an anode side and a cathode side; a first metal mesh on the anode side of the thin metal foil; and a second metal mesh on the cathode side of the thin metal foil. In another characterization of the present invention, a cooling plate assembly cools adjacent fuel cells, where the cooling plate assembly includes an anode electrode and a cathode electrode formed of thin conducting foils; and a metal mesh flow field therebetween for distributing cooling water flow over the electrodes to remove heat generated by the fuel cells.

  11. Electrotaxis of oral squamous cell carcinoma cells in a multiple-electric-field chip with uniform flow field

    PubMed Central

    Tsai, Hsieh-Fu; Peng, Shih-Wei; Wu, Chun-Ying; Chang, Hui-Fang; Cheng, Ji-Yen

    2012-01-01

    We report a new design of microfluidic chip (Multiple electric Field with Uniform Flow chip, MFUF chip) to create multiple electric field strengths (EFSs) while providing a uniform flow field simultaneously. MFUF chip was fabricated from poly-methyl methacrylates (PMMA) substrates by using CO2 laser micromachining. A microfluidic network with interconnecting segments was utilized to de-couple the flow field and the electric field (EF). Using our special design, different EFSs were obtained in channel segments that had an identical cross-section and therefore a uniform flow field. Four electric fields with EFS ratio of 7.9:2.8:1:0 were obtained with flow velocity variation of only 7.8% CV (coefficient of variation). Possible biological effect of shear force can therefore be avoided. Cell behavior under three EFSs and the control condition, where there is no EF, was observed in a single experiment. We validated MFUF chip performance using lung adenocarcinoma cell lines and then used the chip to study the electrotaxis of HSC-3, an oral squamous cell carcinoma cell line. The MFUF chip has high throughput capability for studying the EF-induced cell behavior under various EFSs, including the control condition (EFS = 0). PMID:24009650

  12. Near field flow structure of isothermal swirling flows and reacting non-premixed swirling flames

    SciTech Connect

    Olivani, Andrea; Solero, Giulio; Cozzi, Fabio; Coghe, Aldo

    2007-04-15

    Two confined lean non-premixed swirl-stabilized flame typologies were investigated in order to achieve detailed information on the thermal and aerodynamic field in the close vicinity of the burner throat and provide correlation with the exhaust emissions. Previous finding indicated the generation of a partially premixed flame with radial fuel injection and a purely diffusive flame with co-axial injection in a swirling co-flow. In the present work, the experimental study is reported which has been conducted on a straight exit laboratory burner with no quarl cone, fuelled by natural gas and air, and fired vertically upwards with the flame stabilized at the end of two concentric pipes with the annulus supplying swirled air and the central pipe delivering the fuel. Two fuel injection typologies, co-axial and radial (i.e., transverse), leading to different mixing mechanisms, have been characterized through different techniques: particle image velocimetry (PIV) and laser Doppler velocimetry (LDV) for a comprehensive analysis of the velocity field, still photography for the detection of flame front and main visible features, and thermocouples for the temperature distribution. Isothermal flow conditions have been included in the experimental investigation to provide a basic picture of the flow field and to comprehend the modifications induced by the combustion process. The results indicated that, although the global mixing process and the main flame structure are governed by the swirl motion imparted to the air stream, the two different fuel injection methodologies play an important role on mixture formation and flame stabilization in the primary mixing zone. Particularly, it has been found that, in case of axial injection, the turbulent interaction between the central fuel jet and the backflow generated by the swirl can induce an intermittent fuel penetration in the recirculated hot products and the formation of a central sooting luminous plume, a phenomenon totally

  13. Patterns in the sky: Natural visualization of aircraft flow fields

    NASA Technical Reports Server (NTRS)

    Campbell, James F.; Chambers, Joseph R.

    1994-01-01

    The objective of the current publication is to present the collection of flight photographs to illustrate the types of flow patterns that were visualized and to present qualitative correlations with computational and wind tunnel results. Initially in section 2, the condensation process is discussed, including a review of relative humidity, vapor pressure, and factors which determine the presence of visible condensate. Next, outputs from computer code calculations are postprocessed by using water-vapor relationships to determine if computed values of relative humidity in the local flow field correlate with the qualitative features of the in-flight condensation patterns. The photographs are then presented in section 3 by flow type and subsequently in section 4 by aircraft type to demonstrate the variety of condensed flow fields that was visualized for a wide range of aircraft and flight maneuvers.

  14. Flow effects in long-range dipolar field MRI

    NASA Astrophysics Data System (ADS)

    Loureiro de Sousa, Paulo; Gounot, Daniel; Grucker, Daniel

    2003-06-01

    Incoherent spin motion, such as diffusion, can lead to significant signal loss in multiple spin echoes (MSE) experiments, sometimes to its complete extinction. Coherent spin motion, such as laminar flow, can also modify the magnetization in MSE imaging and yield additional contrast. Our experimental results indicate that MSE is flow-sensitive. Our theoretical analysis and experimental results show how the effect of the distant dipolar field can be annihilated by flow. This effect can be quantified by directly solving the nonlinear Bloch equation, taking into account the deformation of the dipolar field by motion. Unexpected results have been observed, such as a recovery of the dipolar interaction due to flow in the "magic angle" condition.

  15. The mantle flow field beneath western North America.

    PubMed

    Silver, P G; Holt, W E

    2002-02-01

    Although motions at the surface of tectonic plates are well determined, the accompanying horizontal mantle flow is not. We have combined observations of surface deformation and upper mantle seismic anisotropy to estimate this flow field for western North America. We find that the mantle velocity is 5.5 +/- 1.5 centimeters per year due east in a hot spot reference frame, nearly opposite to the direction of North American plate motion (west-southwest). The flow is only weakly coupled to the motion of the surface plate, producing a small drag force. This flow field is probably due to heterogeneity in mantle density associated with the former Farallon oceanic plate beneath North America. PMID:11834831

  16. Field-effect Flow Control in Polymer Microchannel Networks

    NASA Technical Reports Server (NTRS)

    Sniadecki, Nathan; Lee, Cheng S.; Beamesderfer, Mike; DeVoe, Don L.

    2003-01-01

    A new Bio-MEMS electroosmotic flow (EOF) modulator for plastic microchannel networks has been developed. The EOF modulator uses field-effect flow control (FEFC) to adjust the zeta potential at the Parylene C microchannel wall. By setting a differential EOF pumping rate in two of the three microchannels at a T-intersection with EOF modulators, the induced pressure at the intersection generated pumping in the third, field-free microchannel. The EOF modulators are able to change the magnitude and direction of the pressure pumping by inducing either a negative or positive pressure at the intersection. The flow velocity is tracked by neutralized fluorescent microbeads in the microchannels. The proof-of-concept of the EOF modulator described here may be applied to complex plastic ,microchannel networks where individual microchannel flow rates are addressable by localized induced-pressure pumping.

  17. A conservative approach for flow field calculations on multiple grids

    NASA Technical Reports Server (NTRS)

    Kathong, Monchai; Tiwari, Surendra N.

    1988-01-01

    In the computation of flow fields about complex configurations, it is very difficult to construct body-fitted coordinate systems. An alternative approach is to use several grids at once, each of which is generated independently. This procedure is called the multiple grids or zonal grids approach and its applications are investigated in this study. The method follows the conservative approach and provides conservation of fluxes at grid interfaces. The Euler equations are solved numerically on such grids for various configurations. The numerical scheme used is the finite-volume technique with a three-state Runge-Kutta time integration. The code is vectorized and programmed to run on the CDC VPS-32 computer. Some steady state solutions of the Euler equations are presented and discussed.

  18. Results of a study of Mach number and Reynolds number effects on the lee side vortex flow field characteristics of an ogive-cylinder-frustum-cylinder at angles of attack to 25 degrees. Volume 2: Appendix

    NASA Technical Reports Server (NTRS)

    Foley, J. E.

    1972-01-01

    A listing of the data reduction computer program output for the analysis of the lee side vortex flow about an ogive-cylinder-frustum-cylinder is presented. A computed local flow property for the flow field location array at a specific body station and freestream condition is listed. Significant local flow properties are computed. The local circulation strengths in the radial and circumferential directions are analyzed.

  19. Influence of pressure distribution on flow field temperature reconstruction.

    PubMed

    Chen, Yun-yun; Song, Yang; Li, Zhen-hua; He, An-zhi

    2011-05-20

    This research proposes an issue that has previously been omitted in flow field temperature reconstruction by optical computerized tomography (OCT). To prove that it is not reasonable to always assume an isobaric process occurs when OCT is adopted to obtain the temperature distributions of flow fields, a propane-air flame and an argon arc plasma are chosen as two practical examples for experiment. In addition, the measurement of the refractive index is achieved by moiré deflection tomography. The results indicate that the influence of pressure distribution on temperature reconstruction is a universal phenomenon for various flow fields. Hence, the condition that can be introduced to estimate when an isobaric process can no longer be assumed is presented. In addition, an equation is offered to describe the temperature reconstruction imprecision that is caused by using the supposed pressure instead of the practical pressure. PMID:21614105

  20. Heat-flow mapping at the Geysers Geothermal Field

    SciTech Connect

    Thomas, R.P.

    1986-10-31

    Pertinent data were compiled for 187 temperature-gradient holes in the vicinity of The Geysers Geothermal field. Terrain-correction techniques were applied to most of the temperature-gradient data, and a temperature-gradient map was constructed. Cutting samples from 16, deep, production wells were analyzed for thermal conductivity. From these samples, the mean thermal conductivities were determined for serpentinized ultramafic rock, greenstone, and graywacke. Then, a heat flow map was made. The temperature-gradient and heat-flow maps show that The Geysers Geothermal field is part of a very large, northwesterly-trending, thermal anomaly; the commercially productive portion of the field may be 100 km/sup 2/ in area. The rate that heat energy flows through the surface by thermal conduction is estimated at 1.79 x 10/sup 9/MJ per year. The net heat energy loss from commercial production for 1983 is estimated at 180.14 x 10/sup 9/MJ.

  1. Experimental Investigation on Liquid Metal Flow Distribution in Insulating Manifold under Uniform Magnetic Field

    NASA Astrophysics Data System (ADS)

    Miura, Masato; Ueki, Yoshitaka; Yokomine, Takehiko; Kunugi, Tomoaki

    2012-11-01

    Magnetohydrodynamics (MHD) problem which is caused by interaction between electrical conducting fluid flow and the magnetic field is one of the biggest problem in the liquid metal blanket of the fusion reactor. In the liquid metal blanket concept, it is necessary to distribute liquid metal flows uniformly in the manifold because imbalance of flow rates should affect the heat transfer performance directly, which leads to safety problem. While the manifold is insulated electrically as well as the flow duct, the 3D-MHD effect on the flowing liquid metal in the manifold is more apparent than that in straight duct. With reference to the flow distribution in this concept, the liquid metal flow in the electrical insulating manifold under the uniform transverse magnetic field is investigated experimentally. In this study, GaInSn is selected as working fluid. The experimental system includes the electrical magnet and the manifold test section which is made of acrylic resin for perfectly electrical insulation. The liquid metal flows in a non-symmetric 180°-turn with manifold, which consists of one upward channel and two downward channels. The flow rates in each channel are measured by electromagnetic flow meters for several combinations Reynolds number and Hartman number. The effects of magnetic field on the uniformity of flow distribution are cleared.

  2. Flow field measurements in the cell culture unit

    NASA Technical Reports Server (NTRS)

    Walker, Stephen; Wilder, Mike; Dimanlig, Arsenio; Jagger, Justin; Searby, Nancy

    2002-01-01

    The cell culture unit (CCU) is being designed to support cell growth for long-duration life science experiments on the International Space Station (ISS). The CCU is a perfused loop system that provides a fluid environment for controlled cell growth experiments within cell specimen chambers (CSCs), and is intended to accommodate diverse cell specimen types. Many of the functional requirements depend on the fluid flow field within the CSC (e.g., feeding and gas management). A design goal of the CCU is to match, within experimental limits, all environmental conditions, other than the effects of gravity on the cells, whether the hardware is in microgravity ( micro g), normal Earth gravity, or up to 2g on the ISS centrifuge. In order to achieve this goal, two steps are being taken. The first step is to characterize the environmental conditions of current 1g cell biology experiments being performed in laboratories using ground-based hardware. The second step is to ensure that the design of the CCU allows the fluid flow conditions found in 1g to be replicated from microgravity up to 2g. The techniques that are being used to take these steps include flow visualization, particle image velocimetry (PIV), and computational fluid dynamics (CFD). Flow visualization using the injection of dye has been used to gain a global perspective of the characteristics of the CSC flow field. To characterize laboratory cell culture conditions, PIV is being used to determine the flow field parameters of cell suspension cultures grown in Erlenmeyer flasks on orbital shakers. These measured parameters will be compared to PIV measurements in the CSCs to ensure that the flow field that cells encounter in CSCs is within the bounds determined for typical laboratory experiments. Using CFD, a detailed simulation is being developed to predict the flow field within the CSC for a wide variety of flow conditions, including microgravity environments. Results from all these measurements and analyses of the

  3. Numerical analysis of the flow fields in a RQL gas turbine combustor

    NASA Astrophysics Data System (ADS)

    Cline, Michael C.; Micklow, Gerald J.; Yang, S. L.; Nguyen, H. L.

    1992-06-01

    The KIVA-2 code was modified to allow calculation of the flow field in a Richburn/Quick quench/Lean burn (RQL) staged gas turbine combustor including the airblast fuel nozzle. The results illustrate the complicated flow field present in RQL combustors. In particular the thermal protection requirements of the quick-quench mixer used in this study may be similar to those of the rich-burn combustor despite the presence of the cool dilution jet. Variation of the mass flow split between the fuel nozzle air passages has a significant effect on the flow as well as the level of the NO emissions. In addition, the slanted dilution slots form a counter-rotating flow field. From the results obtained to date, it appears that the modified KIVA-2 code can be used to study the effects of various RQL combustor design and operating conditions.

  4. Simulation of the flow field of a ram accelerator

    NASA Astrophysics Data System (ADS)

    Soetrisno, Moeljo; Imlay, Scott T.

    1991-06-01

    An effort is made to achieve a more complete numerical model than heretofore available for analysis and performance prediction regarding ram-accelerator projectiles, using the finite-rate chemistry code HANA. Results are presented from such analyses of a ram accelerator projectile operating in both the thermally-choked mode and the transdetonative mode. The flow field about the projectile, the complex oblique shock system, and the flow properties in the combusting region are detailed. The code uses a novel diagonal implicit solution algorithm which eliminates the expense of inverting the large block matrices arising in chemically reacting flows.

  5. Turbulence in Flowing Soap Films: Velocity, Vorticity, and Thickness Fields

    SciTech Connect

    Rivera, M.; Vorobieff, P.; Ecke, R.E.

    1998-08-01

    We report experimental measurements of the velocity, vorticity, and thickness fields of turbulent flowing soap films using a modified particle-image velocimetry technique. These data yield the turbulent energy and enstrophy of the two-dimensional flows with microscale Reynolds numbers of about 100 and demonstrate the effects of compressibility arising from variations in film thickness. Despite the compressibility of the flow, real-space correlations of velocity, vorticity, and enstrophy flux are consistent with theoretical predictions for two-dimensional turbulence. {copyright} {ital 1998} {ital The American Physical Society }

  6. Analysis of supersonic combustion flow fields with embedded subsonic regions

    NASA Technical Reports Server (NTRS)

    Dash, S.; Delguidice, P.

    1972-01-01

    The viscous characteristic analysis for supersonic chemically reacting flows was extended to include provisions for analyzing embedded subsonic regions. The numerical method developed to analyze this mixed subsonic-supersonic flow fields is described. The boundary conditions are discussed related to the supersonic-subsonic and subsonic-supersonic transition, as well as a heuristic description of several other numerical schemes for analyzing this problem. An analysis of shock waves generated either by pressure mismatch between the injected fluid and surrounding flow or by chemical heat release is also described.

  7. Determination of the functioning parameters in asymmetrical flow field-flow fractionation with an exponential channel.

    PubMed

    Déjardin, P

    2013-08-30

    The flow conditions in normal mode asymmetric flow field-flow fractionation are determined to approach the high retention limit with the requirement d≪l≪w, where d is the particle diameter, l the characteristic length of the sample exponential distribution and w the channel height. The optimal entrance velocity is determined from the solute characteristics, the channel geometry (exponential to rectangular) and the membrane properties, according to a model providing the velocity fields all over the cell length. In addition, a method is proposed for in situ determination of the channel height. PMID:23885667

  8. Turbulent Flow Field Measurements of Separate Flow Round and Chevron Nozzles with Pylon Interaction Using Particle Image Velocimetry

    NASA Technical Reports Server (NTRS)

    Doty, Michael J.; Henerson, Brenda S.; Kinzie, Kevin W.

    2004-01-01

    Particle Image Velocimetry (PIV) measurements for six separate flow bypass ratio five nozzle configurations have recently been obtained in the NASA Langley Jet Noise Laboratory. The six configurations include a baseline configuration with round core and fan nozzles, an eight-chevron core nozzle at two different clocking positions, and repeats of these configurations with a pylon included. One run condition representative of takeoff was investigated for all cases with the core nozzle pressure ratio set to 1.56 and the total temperature to 828 K. The fan nozzle pressure ratio was set to 1.75 with a total temperature of 350 K, and the freestream Mach number was M = 0.28. The unsteady flow field measurements provided by PIV complement recent computational, acoustic, and mean flow field studies performed at NASA Langley for the same nozzle configurations and run condition. The PIV baseline configuration measurements show good agreement with mean flow field data as well as existing PIV data acquired at NASA Glenn. Nonetheless, the baseline configuration turbulence profile indicates an asymmetric flow field, despite careful attention to concentricity. The presence of the pylon increases the upper shear layer turbulence levels while simultaneously decreasing the turbulence levels in the lower shear layer. In addition, a slightly shorter potential core length is observed with the addition of the pylon. Finally, comparisons of computational results with PIV measurements are favorable for mean flow, slightly over-predicted for Reynolds shear stress, and underpredicted for Reynolds normal stress components.

  9. A novel approach to improve operation and performance in flow field-flow fractionation.

    PubMed

    Johann, Christoph; Elsenberg, Stephan; Roesch, Ulrich; Rambaldi, Diana C; Zattoni, Andrea; Reschiglian, Pierluigi

    2011-07-01

    A new system design and setup are proposed for the combined use of asymmetrical flow field-flow fractionation (AF4) and hollow-fiber flow field-flow fractionation (HF5) within the same instrumentation. To this purpose, three innovations are presented: (a) a new flow control scheme where focusing flow rates are measured in real time allowing to adjust the flow rate ratio as desired; (b) a new HF5 channel design consisting of two sets of ferrule, gasket and cap nut used to mount the fiber inside a tube. This design provides a mechanism for effective and straightforward sealing of the fiber; (c) a new AF4 channel design with only two fluid connections on the upper plate. Only one pump is needed to deliver the necessary flow rates. In the focusing/relaxation step the two parts of the focusing flow and a bypass flow flushing the detectors are created with two splits of the flow from the pump. In the elution mode the cross-flow is measured and controlled with a flow controller device. This leads to reduced pressure pulsations in the channel and improves signal to noise ratio in the detectors. Experimental results of the separation of bovine serum albumin (BSA) and of a mix of four proteins demonstrate a significant improvement in the HF5 separation performance, in terms of efficiency, resolution, and run-to-run reproducibility compared to what has been reported in the literature. Separation performance in HF5 mode is shown to be comparable to the performance in AF4 mode using a channel with two connections in the upper plate. PMID:21227436

  10. Field Effect Flow Control in a Polymer T-Intersection Microfluidic Network

    NASA Technical Reports Server (NTRS)

    Sniadecki, Nathan J.; Chang, Richard; Beamesderfer, Mike; Lee, Cheng S.; DeVoe, Don L.

    2003-01-01

    We present a study of induced pressure pumping in a polymer microchannel due to differential electroosmotic flow @OF) rates via field-effect flow control (FEFC). The experimental results demonstrate that the induced pressure pumping is dependent on the distance of the FEFC gate from the cathodic gate. A proposed flow model based on a linearly-decaying zeta potential profile is found to successfully predict experimental trends.

  11. Paper-Based Flow Fractionation System Applicable to Preconcentration and Field-Flow Separation.

    PubMed

    Hong, Seokbin; Kwak, Rhokyun; Kim, Wonjung

    2016-02-01

    We present a novel paper-based flow fractionation system for preconcentration and field-flow separation. In this passive fluidic device, a straight channel is divided into multiple daughter channels, each of which is connected with an expanded region. The hydrodynamic resistance of the straight channel is predominant compared with those of expanded regions, so we can create steady flows through the straight and daughter channels. While the expanded regions absorb a great amount of water via capillarity, the steady flow continues for 10 min without external pumping devices. By controlling the relative hydrodynamic resistances of the daughter channels, we successfully divide the flow with flow rate ratios of up to 30. Combining this bifurcation system with ion concentration polarization (ICP), we develop a continuous-flow preconcentrator on a paper platform, which can preconcentrate a fluorescent dye up to 33-fold. In addition, we construct a field-flow separation system to divide two different dyes depending on their electric polarities. Our flow fractionation systems on a paper-based platform would make a breakthrough for point-of-care diagnostics with specific functions including preconcentration and separation. PMID:26713779

  12. Pollen- and Seed-Mediated Transgene Flow in Commercial Cotton Seed Production Fields

    PubMed Central

    Heuberger, Shannon; Ellers-Kirk, Christa; Tabashnik, Bruce E.; Carrière, Yves

    2010-01-01

    Background Characterizing the spatial patterns of gene flow from transgenic crops is challenging, making it difficult to design containment strategies for markets that regulate the adventitious presence of transgenes. Insecticidal Bacillus thuringiensis (Bt) cotton is planted on millions of hectares annually and is a potential source of transgene flow. Methodology/Principal Findings Here we monitored 15 non-Bt cotton (Gossypium hirsutum, L.) seed production fields (some transgenic for herbicide resistance, some not) for gene flow of the Bt cotton cry1Ac transgene. We investigated seed-mediated gene flow, which yields adventitious Bt cotton plants, and pollen-mediated gene flow, which generates outcrossed seeds. A spatially-explicit statistical analysis was used to quantify the effects of nearby Bt and non-Bt cotton fields at various spatial scales, along with the effects of pollinator abundance and adventitious Bt plants in fields, on pollen-mediated gene flow. Adventitious Bt cotton plants, resulting from seed bags and planting error, comprised over 15% of plants sampled from the edges of three seed production fields. In contrast, pollen-mediated gene flow affected less than 1% of the seed sampled from field edges. Variation in outcrossing was better explained by the area of Bt cotton fields within 750 m of the seed production fields than by the area of Bt cotton within larger or smaller spatial scales. Variation in outcrossing was also positively associated with the abundance of honey bees. Conclusions/Significance A comparison of statistical methods showed that our spatially-explicit analysis was more powerful for understanding the effects of surrounding fields than customary models based on distance. Given the low rates of pollen-mediated gene flow observed in this study, we conclude that careful planting and screening of seeds could be more important than field spacing for limiting gene flow. PMID:21152426

  13. Characterization of Three-Stream Jet Flow Fields

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda S.; Wernet, Mark P.

    2016-01-01

    Flow-field measurements were conducted on single-, dual- and three-stream jets using two-component and stereo Particle Image Velocimetry (PIV). The flow-field measurements complimented previous acoustic measurements. The exhaust system consisted of externally-plugged, externally-mixed, convergent nozzles. The study used bypass-to-core area ratios equal to 1.0 and 2.5 and tertiary-to-core area ratios equal to 0.6 and 1.0. Axisymmetric and offset tertiary nozzles were investigated for heated and unheated high-subsonic conditions. Centerline velocity decay rates for the single-, dual- and three-stream axisymmetric jets compared well when axial distance was normalized by an equivalent diameter based on the nozzle system total exit area. The tertiary stream had a greater impact on the mean axial velocity for the small bypass-to-core area ratio nozzles than for large bypass-to-core area ratio nozzles. Normalized turbulence intensities were similar for the single-, dual-, and three-stream unheated jets due to the small difference (10 percent) in the core and bypass velocities for the dual-stream jets and the low tertiary velocity (50 percent of the core stream) for the three-stream jets. For heated jet conditions where the bypass velocity was 65 percent of the core velocity, additional regions of high turbulence intensity occurred near the plug tip which were not present for the unheated jets. Offsetting the tertiary stream moved the peak turbulence intensity levels upstream relative to those for all axisymmetric jets investigated.

  14. Characterization of Three-Stream Jet Flow Fields

    NASA Technical Reports Server (NTRS)

    Henderson, Brenda S.; Wernet, Mark P.

    2016-01-01

    Flow-field measurements were conducted on single-, dual- and three-stream jets using two-component and stereo Particle Image Velocimetry (PIV). The flow-field measurements complimented previous acoustic measurements. The exhaust system consisted of externally-plugged, externally-mixed, convergent nozzles. The study used bypass-to-core area ratios equal to 1.0 and 2.5 and tertiary-to-core area ratios equal to 0.6 and 1.0. Axisymmetric and offset tertiary nozzles were investigated for heated and unheated high-subsonic conditions. Centerline velocity decay rates for the single-, dual- and three-stream axisymmetric jets compared well when axial distance was normalized by an equivalent diameter based on the nozzle system total exit area. The tertiary stream had a greater impact on the mean axial velocity for the small bypass-to-core area ratio nozzles than for large bypass-to-core area ratio nozzles. Normalized turbulence intensities were similar for the single-, dual-, and three-stream unheated jets due to the small difference (10%) in the core and bypass velocities for the dual-stream jets and the low tertiary velocity (50% of the core stream) for the three-stream jets. For heated jet conditions where the bypass velocity was 65% of the core velocity, additional regions of high turbulence intensity occurred near the plug tip which were not present for the unheated jets. Offsetting the tertiary stream moved the peak turbulence intensity levels upstream relative to those for all axisymmetric jets investigated.

  15. Penn State axial flow turbine facility: Performance and nozzle flow field

    NASA Technical Reports Server (NTRS)

    Lakshminarayana, B.; Zaccaria, M.; Itoh, S.

    1991-01-01

    The objective is to gain a thorough understanding of the flow field in a turbine stage including three-dimensional inviscid and viscid effects, unsteady flow field, rotor-stator interaction effects, unsteady blade pressures, shear stress, and velocity field in rotor passages. The performance of the turbine facility at the design condition is measured and compared with the design distribution. The data on the nozzle vane static pressure and wake characteristics are presented and interpreted. The wakes are found to be highly three-dimensional, with substantial radial inward velocity at most spanwise locations.

  16. Direct numerical simulations of magnetic field effects on turbulent flow in a square duct

    NASA Astrophysics Data System (ADS)

    Chaudhary, R.; Vanka, S. P.; Thomas, B. G.

    2010-07-01

    Magnetic fields are crucial in controlling flows in various physical processes of industrial significance. One such process is the continuous casting of steel, where different magnetic field configurations are used to control the turbulent flow of steel in the mold in order to minimize defects in the cast steel. The present study has been undertaken to understand the effects of a magnetic field on mean velocities and turbulence parameters in turbulent molten metal flow through a square duct. The coupled Navier-Stokes magnetohydrodynamic equations have been solved using a three-dimensional fractional-step numerical procedure. The Reynolds number was kept low in order to resolve all the scales in the flow without using a subgrid scale turbulence model. Computations were performed with three different grid resolutions, the finest grid having 8.4×106 cells. Because liquid metals have low magnetic Reynolds number, the induced magnetic field has been considered negligible and the electric potential method for magnetic field-flow coupling has been implemented. After validation of the computer code, computations of turbulent flow in a square duct with different Hartmann numbers were performed until complete laminarization of the flow. The time-dependent and time-averaged nature of the flow has been examined through distribution of mean velocities, turbulent fluctuations, vorticity, and turbulent kinetic energy budgets.

  17. Rapid Numerical Simulation of Viscous Axisymmetric Flow Fields

    NASA Technical Reports Server (NTRS)

    Tweedt, Daniel L.; Chima, Rodrick V.

    1995-01-01

    A two-dimensional Navier-Stokes code has been developed for rapid numerical simulation of axisymmetric flow fields, including flow fields with an azimuthal velocity component. The azimuthal-invariant Navier-Stokes equations in a cylindrical coordinate system are mapped to a general body-fitted coordinate system, with the streamwise viscous terms then neglected by applying the thin-layer approximation. Turbulence effects are modeled using an algebraic model, typically the Baldwin-Lomax turbulence model, although a modified Cebeci-Smith model can also be used. The equations are discretized using central finite differences and solved using a multistage Runge-Kutta algorithm with a spatially varying time step and implicit residual smoothing. Results are presented for calculations of supersonic flow over a waisted body-of-revolution, transonic flow through a normal shock wave in a straight circular duct of constant cross sectional area, swirling supersonic (inviscid) flow through a strong shock in a straight radial duct, and swirling subsonic flow in an annular-to-circular diffuser duct. Comparisons between computed and experimental results are in fair to good agreement, demonstrating that the viscous code can be a useful tool for practical engineering design and analysis work.

  18. Navier-Stokes computations of aft end flow fields

    NASA Astrophysics Data System (ADS)

    Weinberg, B. C.; McDonald, H.; Shamroth, S. J.

    1982-05-01

    A Navier-Stokes code to solve the aft end flow field of missile type configurations is presented. The consistently split linearized block implicit method of McDonald and Briley is employed in modified form to handle L-shaped domains with sharp reentrant corners. Appropriate boundary conditions are applied for the supersonic flow in particular at the outer boundary so that waves generated within the flow field are allowed to pass out of the computational domain without reflecting back into it. An adaptive grid option has been incorporated into the code and has been exercised by following the shear layer in a model backstep problem. Results are presented for the supersonic turbulent flow over a nozzle boattail configuration with and without jet exhaust and the results are compared with experiment. Calculations of the 2-D turbulent supersonic flow over a right angle back step with shear layer reattachment on a 20 deg ramp are also shown, and compared with experiments. The computation shows the qualitative physical behavior of the flows and there is generally good agreement with the experimental velocity profiles through most of the free shear layer and the ramp reattachment zone.

  19. Experimental characterization of rotating flow field in a model vortex burner

    SciTech Connect

    Shtork, S.I.; Cala, C.E.; Fernandes, E.C.

    2007-07-15

    Acoustic techniques, high speed filming and LDA were employed to characterize swirling jet flow in a model vortex burner. The isothermal flow conditions studied correspond to Re = 16,000 and swirl number S = 1, resulting in onset of the swirling jet breakdown. The breakdown zone exhibited distinct flow unsteadiness in the form of a precessing vortex core (PVC). Phase-averaged analysis of the LDA data was used to reveal an ''instantaneous'' flow field spatial distribution and to determine the precessing vortex characteristics. These results were compared against the time mean data to reveal the PVC's footprint in the time-averaged flow structure. In particular, this approach was shown to provide access to the precessing structure parameters making use of conventional flow field diagnostics. (author)

  20. Lava flow surface textures - SIR-B radar image texture, field observations, and terrain measurements

    NASA Technical Reports Server (NTRS)

    Gaddis, Lisa R.; Mouginis-Mark, Peter J.; Hayashi, Joan N.

    1990-01-01

    SIR-B images, field observations, and small-scale (cm) terrain measurements are used to study lave flow surface textures related to emplacement processes of a single Hawaiian lava flow. Although smooth pahoehoe textures are poorly characterized on the SIR-B data, rougher pahoehoe types and the a'a flow portion show image textures attributed to spatial variations in surface roughness. Field observations of six distinct lava flow textural units are described and used to interpret modes of emplacement. The radar smooth/rough boundary between pahoehoe and a'a occurs at a vertical relief of about 10 cm on this lava flow. While direct observation and measurement most readily yield information related to lava eruption and emplacement processes, analyses of remote sensing data such as those acquired by imaging radars and altimeters can provide a means of quantifying surface texture, identifying the size and distribution of flow components, and delineating textural unit boundaries.

  1. Computational analysis of hypersonic airbreathing aircraft flow fields

    NASA Technical Reports Server (NTRS)

    Dwoyer, Douglas L.; Kumar, Ajay

    1987-01-01

    The general problem of calculating the flow fields associated with hypersonic airbreathing aircraft is presented. Unique aspects of hypersonic aircraft aerodynamics are introduced and their demands on computational fluid dynamics are outlined. Example calculations associated with inlet/forebody integration and hypersonic nozzle design are presented to illustrate the nature of the problems considered.

  2. Design of vortex fluid amplifiers with asymmetrical flow fields.

    NASA Technical Reports Server (NTRS)

    Lawley, T. J.; Price, D. C.

    1972-01-01

    Variation of geometric parameters, including supply area, control area, chamber length, and outlet diameter, of a large scale, modular design vortex fluid amplifier with single supply and control jets, has confirmed and extended a previously published design method, developed for vortex amplifiers with symmetric flow fields. This allows application of the method to devices which are more representative of practical, production type components.

  3. Preservation of Blueschist Facies Minerals Along a Shear Zone By Fast Flowing CO2-Bearing Fluids - a Field Study from the Cycladic Blueschist Unit on Syros, Greece

    NASA Astrophysics Data System (ADS)

    Kleine, B. I.; Skelton, A.; Huet, B.; Pitcairn, I.

    2014-12-01

    Our study was undertaken at Fabrika Beach on the southeastern shore of Syros which belongs to the Greek Cycladic archipelago in the Aegean Sea. The island is situated within the Attic-Cycladic metamorphic core complex belt and is now located in the back-arc of the active Hellenic subduction zone. At Fabrika Beach, blueschist facies minerals are observed in haloes fringing a shear zone within greenschist facies rocks. The approximately vertical shear zone cuts a near horizontal layer of greenschist facies rocks. The blue haloes are ca. 1 m wide, and are seen on both sides of the shear zone. The haloes consist of a carbonated blueschist facies mineral assemblage. Based on petrological, geochemical and thermodynamic evidence we show that these haloes were preserved at greenschist facies conditions in response to fast flowing CO2-bearing fluid. Furthermore, we use a simple mass balance to calculate the fluid flux within the shear zone which would be required to cause the observed preservation of blueschist facies minerals. We constructed a simplified P-T vs. XCO2 pseudosection using PerPlex 6.6.6 to confirm that preservation of carbonated blueschist can occur at greenschist facies conditions in the presence of CO2-bearing fluid. The flux of CO2-bearing fluid along the shear zone was rapid with respect to the fluid flux in the surrounding rocks. Mass balance calculations reveal that the fluid flux within the shear zone was at least 100 - 2000 times larger than the fluid flux within the surrounding rocks. Mineral textures show greenschist facies minerals partially replacing blueschist minerals in the haloes supporting our interpretation that blueschist facies minerals were preserved during greenschist facies retrogression.

  4. Monodisperse granular flows in viscous dispersions in a centrifugal acceleration field

    NASA Astrophysics Data System (ADS)

    Cabrera, Miguel Angel; Wu, Wei

    2016-04-01

    Granular flows are encountered in geophysical flows and innumerable industrial applications with particulate materials. When mixed with a fluid, a complex network of interactions between the particle- and fluid-phase develops, resulting in a compound material with a yet unclear physical behaviour. In the study of granular suspensions mixed with a viscous dispersion, the scaling of the stress-strain characteristics of the fluid phase needs to account for the level of inertia developed in experiments. However, the required model dimensions and amount of material becomes a main limitation for their study. In recent years, centrifuge modelling has been presented as an alternative for the study of particle-fluid flows in a reduced scaled model in an augmented acceleration field. By formulating simple scaling principles proportional to the equivalent acceleration Ng in the model, the resultant flows share many similarities with field events. In this work we study the scaling principles of the fluid phase and its effects on the flow of granular suspensions. We focus on the dense flow of a monodisperse granular suspension mixed with a viscous fluid phase, flowing down an inclined plane and being driven by a centrifugal acceleration field. The scaled model allows the continuous monitoring of the flow heights, velocity fields, basal pressure and mass flow rates at different Ng levels. The experiments successfully identify the effects of scaling the plastic viscosity of the fluid phase, its relation with the deposition of particles over the inclined plane, and allows formulating a discussion on the suitability of simulating particle-fluid flows in a centrifugal acceleration field.

  5. Can core flows inferred from geomagnetic field models explain the Earth's dynamo?

    NASA Astrophysics Data System (ADS)

    Schaeffer, N.; Silva, E. Lora; Pais, M. A.

    2016-02-01

    We test the ability of large-scale velocity fields inferred from geomagnetic secular variation data to produce the global magnetic field of the Earth. Our kinematic dynamo calculations use quasi-geostrophic (QG) flows inverted from geomagnetic field models which, as such, incorporate flow structures that are Earth-like and may be important for the geodynamo. Furthermore, the QG hypothesis allows straightforward prolongation of the flow from the core surface to the bulk. As expected from previous studies, we check that a simple QG flow is not able to sustain the magnetic field against ohmic decay. Additional complexity is then introduced in the flow, inspired by the action of the Lorentz force. Indeed, on centennial timescales, the Lorentz force can balance the Coriolis force and strict quasi-geostrophy may not be the best ansatz. When our columnar flow is modified to account for the action of the Lorentz force, magnetic field is generated for Elsasser numbers larger than 0.25 and magnetic Reynolds numbers larger than 100. This suggests that our large-scale flow captures the relevant features for the generation of the Earth's magnetic field and that the invisible small-scale flow may not be directly involved in this process. Near the threshold, the resulting magnetic field is dominated by an axial dipole, with some reversed flux patches. Time dependence is also considered, derived from principal component analysis applied to the inverted flows. We find that time periods from 120 to 50 yr do not affect the mean growth rate of the kinematic dynamos. Finally, we note that the footprint of the inner core in the magnetic field generated deep in the bulk of the shell, although we did not include one in our computations.

  6. Dynamics of intrinsic axial flows in unsheared, uniform magnetic fields

    NASA Astrophysics Data System (ADS)

    Li, J. C.; Diamond, P. H.; Xu, X. Q.; Tynan, G. R.

    2016-05-01

    A simple model for the generation and amplification of intrinsic axial flow in a linear device, controlled shear decorrelation experiment, is proposed. This model proposes and builds upon a novel dynamical symmetry breaking mechanism, using a simple theory of drift wave turbulence in the presence of axial flow shear. This mechanism does not require complex magnetic field structure, such as shear, and thus is also applicable to intrinsic rotation generation in tokamaks at weak or zero magnetic shear, as well as to linear devices. This mechanism is essentially the self-amplification of the mean axial flow profile, i.e., a modulational instability. Hence, the flow development is a form of negative viscosity phenomenon. Unlike conventional mechanisms where the residual stress produces an intrinsic torque, in this dynamical symmetry breaking scheme, the residual stress induces a negative increment to the ambient turbulent viscosity. The axial flow shear is then amplified by this negative viscosity increment. The resulting mean axial flow profile is calculated and discussed by analogy with the problem of turbulent pipe flow. For tokamaks, the negative viscosity is not needed to generate intrinsic rotation. However, toroidal rotation profile gradient is enhanced by the negative increment in turbulent viscosity.

  7. High Speed Size Sorting of Subcellular Organelles by Flow Field-Flow Fractionation.

    PubMed

    Yang, Joon Seon; Lee, Ju Yong; Moon, Myeong Hee

    2015-06-16

    Separation/isolation of subcellular species, such as mitochondria, lysosomes, peroxisomes, Golgi apparatus, and others, from cells is important for gaining an understanding of the cellular functions performed by specific organelles. This study introduces a high speed, semipreparative scale, biocompatible size sorting method for the isolation of subcellular organelle species from homogenate mixtures of HEK 293T cells using flow field-flow fractionation (FlFFF). Separation of organelles was achieved using asymmetrical FlFFF (AF4) channel system at the steric/hyperlayer mode in which nuclei, lysosomes, mitochondria, and peroxisomes were separated in a decreasing order of hydrodynamic diameter without complicated preprocessing steps. Fractions in which organelles were not clearly separated were reinjected to AF4 for a finer separation using the normal mode, in which smaller sized species can be well fractionated by an increasing order of diameter. The subcellular species contained in collected AF4 fractions were examined with scanning electron microscopy to evaluate their size and morphology, Western blot analysis using organelle specific markers was used for organelle confirmation, and proteomic analysis was performed with nanoflow liquid chromatography-tandem mass spectrometry (nLC-ESI-MS/MS). Since FlFFF operates with biocompatible buffer solutions, it offers great flexibility in handling subcellular components without relying on a high concentration sucrose solution for centrifugation or affinity- or fluorescence tag-based sorting methods. Consequently, the current study provides an alternative, competitive method for the isolation/purification of subcellular organelle species in their intact states. PMID:26005782

  8. Recent Development in Hot Flow Anomaly Studies

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Wang, S.; Zong, Q.

    2013-05-01

    Hot flow anomalies (HFAs) are events observed near the bow shock that are characterized by greatly heated solar wind plasmas and substantial flow deflection from the Sun-Earth direction, with duration of a few minutes and scale size of the order of a few Re. HFAs are thought to be produced by the interaction of some very special interplanetary current sheets that satisfy several strict conditions with planetary bow shocks. When the current sheet (discontinuity) is connected to the bow shock and the motional electric fields point towards the discontinuity, ions reflected from the bow shock are trapped in the current sheet. The relative streaming energy of the original solar wind beam and the reflected beam is converted to the thermal energy. However, we found recently that HFAs can be generated spontaneously (in the absence of any current sheets) at quasi-parallel bow shocks where the interplanetary magnetic field lies nearly parallel to the shock normal. Statistical studies show that 60% of the HFAs are not associated with clear discontinuities. In addition, there are 13% of the HFAs with the motional electric fields on neither leading nor trailing edge pointing towards the discontinuity. These new results indicate that this phenomenon is still not well understood although it was discovered almost 30 years ago.

  9. Recent Development in Hot Flow Anomaly Studies

    NASA Astrophysics Data System (ADS)

    Zhang, H.; Wang, S.; Zong, Q.

    2013-12-01

    Hot flow anomalies (HFAs) are events observed near the bow shock that are characterized by greatly heated solar wind plasmas and substantial flow deflection from the Sun-Earth direction, with duration of a few minutes and scale size of the order of a few RE. HFAs are thought to be produced by the interaction of some very special interplanetary current sheets that satisfy several strict conditions with planetary bow shocks. When the current sheet (discontinuity) is connected to the bow shock and the motional electric fields point towards the discontinuity, ions reflected from the bow shock are trapped in the current sheet. The relative streaming energy of the original solar wind beam and the reflected beam is converted to the thermal energy. However, we found recently that HFAs can be generated spontaneously (in the absence of any current sheets) at quasi-parallel bow shocks where the interplanetary magnetic field lies nearly parallel to the shock normal. Statistical studies show that 60% of the HFAs are not associated with clear discontinuities. In addition, there are 13% of the HFAs with the motional electric fields on neither leading nor trailing edge pointing towards the discontinuity. These new results indicate that this phenomenon is still not well understood although it was discovered almost 30 years ago.

  10. A stochastic filtering technique for fluid flow velocity fields tracking.

    PubMed

    Cuzol, Anne; Mémin, Etienne

    2009-07-01

    In this paper, we present a method for the temporal tracking of fluid flow velocity fields. The technique we propose is formalized within a sequential Bayesian filtering framework. The filtering model combines an Itô diffusion process coming from a stochastic formulation of the vorticity-velocity form of the Navier-Stokes equation and discrete measurements extracted from the image sequence. In order to handle a state space of reasonable dimension, the motion field is represented as a combination of adapted basis functions, derived from a discretization of the vorticity map of the fluid flow velocity field. The resulting nonlinear filtering problem is solved with the particle filter algorithm in continuous time. An adaptive dimensional reduction method is applied to the filtering technique, relying on dynamical systems theory. The efficiency of the tracking method is demonstrated on synthetic and real-world sequences. PMID:19443925

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

    NASA Astrophysics Data System (ADS)

    Orlandini, Stefano; Moretti, Giovanni; Corticelli, Mauro A.; Santangelo, Paolo E.; Capra, Alessandro; Rivola, Riccardo; Albertson, John D.

    2012-10-01

    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 water were released at selected points on a warmer slope and individual overland flow patterns originating from each of these points were observed using a terrestrial laser scanner and a thermal imaging camera. Land microtopography was determined by using laser returns from the dry land surface, whereas overland flow patterns were determined by using either laser returns or infrared emissions from the wetted portions of the land surface. Planar overland flow dispersion is found to play an important role in the region lying immediately downslope of the point source, but attenuates rapidly as flow propagates downslope. In contrast, existing dispersive flow direction methods are found to provide a continued dispersion with distance downslope. Predicted propagation patterns, for all methods considered here, depend critically on the size h of grid cells involved. All methods are found to be poorly sensitive in extremely fine grids (h ≤ 2 cm), and to be poorly specific in coarse grids (h = 2 m). Satisfactory results are, however, obtained in grids having resolutions h that approach the average flow width (50 cm), with the best performances displayed by the MD8 method in the finest grids (5 ≤ h ≤ 20 cm), and by the MD∞, D∞, and D∞-LTD methods in the coarsest grids (20 cm < h ≤ 1 m).

  12. Laboratory and field trials of Coriolis mass flow metering for three-phase flow measurement

    NASA Astrophysics Data System (ADS)

    Zhou, Feibiao; Henry, Manus; Tombs, Michael

    2014-04-01

    A new three-phase flow metering technology is discussed in this paper, which combines Coriolis mass flow and water cut readings and without applying any phase separation [1]. The system has undergone formal laboratory trials at TUV NEL (National Engineering Laboratory), UK and at VNIIR (National Flow Laboratory), Kazan, Russia; a number of field trials have taken place in Russia. Laboratory trial results from the TUV NEL will be described in detail. For the 50mm (2") metering system, the total liquid flow rate ranged from 2.4 kg/s up to 11 kg/s, the water cut ranged from 0% to 100%, and the gas volume fraction (GVF) from 0 to 50%. In a formally observed trial, 75 test points were taken at a temperature of approximately 40 °C and with a skid inlet pressure of approximately 350 kPa. Over 95% of the test results fell within the desired specification, defined as follows: the total (oil + water) liquid mass flow error should fall within ± 2.5%, and the gas mass flow error within ± 5.0%. The oil mass flow error limit is ± 6.0% for water cuts less than 70%, while for water cuts between 70% and 95% the oil mass flow error limit is ± 15.0%. These results demonstrate the potential for using Coriolis mass flow metering combined with water cut metering for three-phase (oil/water/gas) measurement.

  13. Velocity-Field Measurements of an Axisymmetric Separated Flow Subjected to Amplitude-Modulated Excitation

    NASA Technical Reports Server (NTRS)

    Trosin, Barry James

    2007-01-01

    Active flow control was applied at the point of separation of an axisymmetric, backward-facing-step flow. The control was implemented by employing a Helmholtz resonator that was externally driven by an amplitude-modulated, acoustic disturbance from a speaker located upstream of the wind tunnel. The velocity field of the separating/reattaching flow region downstream of the step was characterized using hotwire velocity measurements with and without flow control. Conventional statistics of the data reveal that the separating/reattaching flow is affected by the imposed forcing. Triple decomposition along with conditional averaging was used to distinguish periodic disturbances from random turbulence in the fluctuating velocity component. A significant outcome of the present study is that it demonstrates that amplitude-modulated forcing of the separated flow alters the flow in the same manner as the more conventional method of periodic excitation.

  14. Transient simulation in interior flow field of lobe pump

    NASA Astrophysics Data System (ADS)

    Li, Y. B.; Sang, X. H.; Meng, Q. W.; Shen, H.; Jia, K.

    2013-12-01

    The subject of this paper is mainly focused on the development and control of the double folium and trifolium lobe pump profiles by using the principle of involute engagement and use CAD to get an accurate involute profile. We use the standard k-ε turbulence model and PISO algorithm based on CFD software FLUENT. The dynamic mesh and UDF technology is introduced to simulate the interior flow field inside a lobe pump, and the variation of interior flow field under the condition of the lobe rotating is analyzed. We also analyse the influence produced by the difference in lobes, and then reveal which lobe is best. The results show that dynamic variation of the interior flow field is easily obtained by dynamic mesh technology and the distribution of its pressure and velocity. Because of the small gaps existing between the rotors and pump case, the higher pressure area will flow into the lower area though the small gaps which cause the working area keep with higher pressure all the time. Both of the double folium and trifolium are existing the vortex during the rotting time and its position, size and shape changes all the time. The vortexes even disappear in a circle period and there are more vortexes in double folium lobe pump. The velocity and pressure pulsation of trifolium pump are lower than that of the double folium.

  15. Experimental studies of rotating exchange flow

    NASA Astrophysics Data System (ADS)

    Rabe, B.; Smeed, D. A.; Dalziel, S. B.; Lane-Serff, G. F.

    2007-02-01

    Ocean basins are connected by straits and passages, geometrically limiting important heat and salt exchanges which in turn influence the global thermohaline circulation and climate. Such exchange can be modeled in an idealized way by taking into consideration the density-driven two-layer flow along a strait under the influence of rotation. We use a laboratory model of a lock exchange between two reservoirs of different density through a flat-bottom channel with a horizontal narrows, set up on two different platforms: a 1 m diameter turntable, where density interface position was measured by dye attenuation, and the 14 m diameter turntable at Coriolis/LEGI (Grenoble, France), where correlation imaging velocimetry, a particle imaging technique, allowed us to obtain for the first time detailed measurements of the velocity fields in these flows. The influence of rotation is studied by varying a parameter, Bu, a type of Burger number given by the ratio of the Rossby radius to the channel width at the narrows. In addition, a two-layer version of the Miami Isopycnic Coordinate Model (MICOM) is used, to study the cases with low Burger number. Results from experiments by Dalziel [1988. Two-layer hydraulics: maximal exchange flows. Ph.D. Thesis, Department of Applied Mathematics and Theoretical Physics, University of Cambridge, see also ] are also included for comparison. Time-mean exchange fluxes for any Bu are in close agreement with the inviscid zero-potential vorticity theory of Dalziel [1990. Rotating two-layer sill flows. In: Pratt, L.J. (Ed.), The Physical Oceanography of Sea Straits. Kluwer Academic, Dordrecht, pp. 343-371] and Whitehead et al. [1974. Rotating hydraulics of strait and sill flows. Geophysical Fluid Dynamics 6, 101-125], who found that fluxes for Bu>1 mainly vary with channel width, similar to non-rotating flow, but for Bu<1 are only limited by the Rossby radius. We also show

  16. Decomposition of the swirling flow field downstream of Francis turbine runner

    NASA Astrophysics Data System (ADS)

    Rudolf, P.; Štefan, D.

    2012-11-01

    Practical application of proper orthogonal decomposition (POD) is presented. Spatio-temporal behaviour of the coherent vortical structures in the draft tube of hydraulic turbine is studied for two partial load operating points. POD enables to identify the eigen modes, which compose the flow field and rank the modes according to their energy. Swirling flow fields are decomposed, which provides information about their streamwise and crosswise development and the energy transfer among modes. Presented methodology also assigns frequencies to the particular modes, which helps to identify the spectral properties of the flow with concrete mode shapes. Thus POD offers a complementary view to current time domain simulations or measurements.

  17. Comparison of Orbiter PRCS Plume Flow Fields Using CFD and Modified Source Flow Codes

    NASA Technical Reports Server (NTRS)

    Rochelle, Wm. C.; Kinsey, Robin E.; Reid, Ethan A.; Stuart, Phillip C.; Lumpkin, Forrest E.

    1997-01-01

    The Space Shuttle Orbiter will use Reaction Control System (RCS) jets for docking with the planned International Space Station (ISS). During approach and backout maneuvers, plumes from these jets could cause high pressure, heating, and thermal loads on ISS components. The object of this paper is to present comparisons of RCS plume flow fields used to calculate these ISS environments. Because of the complexities of 3-D plumes with variable scarf-angle and multi-jet combinations, NASA/JSC developed a plume flow-field methodology for all of these Orbiter jets. The RCS Plume Model (RPM), which includes effects of scarfed nozzles and dual jets, was developed as a modified source-flow engineering tool to rapidly generate plume properties and impingement environments on ISS components. This paper presents flow-field properties from four PRCS jets: F3U low scarf-angle single jet, F3F high scarf-angle single jet, DTU zero scarf-angle dual jet, and F1F/F2F high scarf-angle dual jet. The RPM results compared well with plume flow fields using four CFD programs: General Aerodynamic Simulation Program (GASP), Cartesian (CART), Unified Solution Algorithm (USA), and Reacting and Multi-phase Program (RAMP). Good comparisons of predicted pressures are shown with STS 64 Shuttle Plume Impingement Flight Experiment (SPIFEX) data.

  18. [Effects of carrier liquid and flow rate on the separation in gravitational field-flow fractionation].

    PubMed

    Guo, Shuang; Zhu, Chenqi; Gao-Yang, Yaya; Qiu, Bailing; Wu, Di; Liang, Qihui; He, Jiayuan; Han, Nanyin

    2016-02-01

    Gravitational field-flow fractionation is the simplest field-flow fractionation technique in terms of principle and operation. The earth' s gravity is its external field. Different sized particles are injected into a thin channel and carried by carrier fluid. The different velocities of the carrier liquid in different places results in a size-based separation. A gravitational field-flow fractionation (GrFFF) instrument was designed and constructed. Two kinds of polystyrene (PS) particles with different sizes (20 µm and 6 µm) were chosen as model particles. In this work, the separation of the sample was achieved by changing the concentration of NaN3, the percentage of mixed surfactant in the carrier liquid and the flow rate of carrier liquid. Six levels were set for each factor. The effects of these three factors on the retention ratio (R) and plate height (H) of the PS particles were investigated. It was found that R increased and H decreased with increasing particle size. On the other hand, the R and H increased with increasing flow rate. The R and H also increased with increasing NaN3 concentration. The reason was that the electrostatic repulsive force between the particles and the glass channel wall increased. The force allowed the samples approach closer to the channel wall. The results showed that the resolution and retention time can be improved by adjusting the experimental conditions. These results can provide important values to the further applications of GrFFF technique. PMID:27382718

  19. Performance enhancement of iron-chromium redox flow batteries by employing interdigitated flow fields

    NASA Astrophysics Data System (ADS)

    Zeng, Y. K.; Zhou, X. L.; Zeng, L.; Yan, X. H.; Zhao, T. S.

    2016-09-01

    The catalyst for the negative electrode of iron-chromium redox flow batteries (ICRFBs) is commonly prepared by adding a small amount of Bi3+ ions in the electrolyte and synchronously electrodepositing metallic particles onto the electrode surface at the beginning of charge process. Achieving a uniform catalyst distribution in the porous electrode, which is closely related to the flow field design, is critically important to improve the ICRFB performance. In this work, the effects of flow field designs on catalyst electrodeposition and battery performance are investigated. It is found that compared to the serpentine flow field (SFF) design, the interdigitated flow field (IFF) forces the electrolyte through the porous electrode between the neighboring channels and enhances species transport during the processes of both the catalyst electrodeposition and iron/chromium redox reactions, thus enabling a more uniform catalyst distribution and higher mass transport limitation. It is further demonstrated that the energy efficiency of the ICRFB with the IFF reaches 80.7% at a high current density (320 mA cm-2), which is 8.2% higher than that of the ICRFB with the SFF. With such a high performance and intrinsically low-cost active materials, the ICRFB with the IFF offers a great promise for large-scale energy storage.

  20. Computational analysis of flow field around Ahmed car model passing underneath a flyover

    NASA Astrophysics Data System (ADS)

    Musa, Md Nor; Osman, Kahar; Hamat, Ab Malik A.

    2012-06-01

    A flow structure around a ground vehicle has been studied by many researchers using numerous methods, either computational or experimental. However, no analysis of flow field generated by a car passing under a flyover has been carried out. One of the famous simplified models of a car is the Ahmed body that has been established to investigate the influence of the flow structure on the drag. In this paper, we investigate a flow field around Ahmed body of a single cruising condition as the vehicle passes under a flyover, using a computational method with RANS equation. The main objective of this paper is to evaluate the turbulence kinetic energy and velocity magnitude developed within the wall boundary created by the flyover, to the air flow field that is generated by the Ahmed reference car. It was observed that the simulated airflow passes the vehicle was bounded by the wall of the flyover and consequently changes the pattern of the flow field. Understanding the characteristic of this flow field under a flyover is essential if one wants to maximize the recovery of the dissipated energy which, for example, can be used to power a small vertical-axis wind turbine to produce and store electrical energy for lighting under the flyover.

  1. Mechanism and kinetics of the loss of poorly soluble drugs from liposomal carriers studied by a novel flow field-flow fractionation-based drug release-/transfer-assay.

    PubMed

    Hinna, Askell Hvid; Hupfeld, Stefan; Kuntsche, Judith; Bauer-Brandl, Annette; Brandl, Martin

    2016-06-28

    Liposomes represent a versatile drug formulation approach e.g. for improving the water-solubility of poorly soluble drugs but also to achieve drug targeting and controlled release. For the latter applications it is essential that the drug remains associated with the liposomal carrier during transit in the vascular bed. A range of in vitro test methods has been suggested over the years for prediction of the release of drug from liposomal carriers. The majority of these fail to give a realistic prediction for poorly water-soluble drugs due to the intrinsic tendency of such compounds to remain associated with liposome bilayers even upon extensive dilution. Upon i.v. injection, in contrast, rapid drug loss often occurs due to drug transfer from the liposomal carriers to endogenous lipophilic sinks such as lipoproteins, plasma proteins or membranes of red blood cells and endothelial cells. Here we report on the application of a recently introduced in vitro predictive drug transfer assay based on incubation of the liposomal drug carrier with large multilamellar liposomes, the latter serving as a biomimetic model sink, using flow field-flow fractionation as a tool to separate the two types of liposomes. By quantifying the amount of drug remaining associated with the liposomal drug carrier as well as that transferred to the acceptor liposomes at distinct times of incubation, both the kinetics of drug transfer and release to the water phase could be established for the model drug p-THPP (5,10,15,20-tetrakis(4-hydroxyphenyl)21H,23H-porphine). p-THPP is structurally similar to temoporfin, a photosensitizer which is under clinical evaluation in a liposomal formulation. Mechanistic insights were gained by varying the donor-to-acceptor lipid mass ratio, size and lamellarity of the liposomes. Drug transfer kinetics from one liposome to another was found rate determining as compared to redistribution from the outermost to the inner concentric bilayers, such that the overall

  2. Numerical simulation of three-dimensional boattail afterbody flow fields

    NASA Technical Reports Server (NTRS)

    Deiwert, G. S.

    1980-01-01

    The thin shear layer approximations of the three-dimensional, compressible Navier-Stokes equations are solved for subsonic, transonic, and supersonic flow over axisymmetric boattail bodies at moderate angles of attack. The plume is modeled by a solid body configuration identical to those used in experimental tests. An implicit algorithm of second-order accuracy is used to solve the equations on the ILLIAC IV computer. The turbulence is expressed by an algebraic model applicable to three-dimensional flow fields with moderate separation. The computed results compare favorably with three different sets of experimental data reported by Reubush, Shrewsbury, and Benek, respectively

  3. Large perturbation flow field analysis and simulation for supersonic inlets

    NASA Technical Reports Server (NTRS)

    Varner, M. O.; Martindale, W. R.; Phares, W. J.; Kneile, K. R.; Adams, J. C., Jr.

    1984-01-01

    An analysis technique for simulation of supersonic mixed compression inlets with large flow field perturbations is presented. The approach is based upon a quasi-one-dimensional inviscid unsteady formulation which includes engineering models of unstart/restart, bleed, bypass, and geometry effects. Numerical solution of the governing time dependent equations of motion is accomplished through a shock capturing finite difference algorithm, of which five separate approaches are evaluated. Comparison with experimental supersonic wind tunnel data is presented to verify the present approach for a wide range of transient inlet flow conditions.

  4. Local Flow Field and Slip Length of Superhydrophobic Surfaces.

    PubMed

    Schäffel, David; Koynov, Kaloian; Vollmer, Doris; Butt, Hans-Jürgen; Schönecker, Clarissa

    2016-04-01

    While the global slippage of water past superhydrophobic surfaces has attracted wide interest, the local distribution of slip still remains unclear. Using fluorescence correlation spectroscopy, we performed detailed measurements of the local flow field and slip length for water in the Cassie state on a microstructured superhydrophobic surface. We revealed that the local slip length is finite, nonconstant, anisotropic, and sensitive to the presence of surfactants. In combination with numerical calculations of the flow, we can explain all these properties by the local hydrodynamics. PMID:27081981

  5. Numerical simulation of the flow field around a complete aircraft

    NASA Technical Reports Server (NTRS)

    Shang, J. S.; Scherr, S. J.

    1986-01-01

    The present effort represents a first attempt of numerical simulation of the flow field around a complete aircraft-like, lifting configuration utilizing the Reynolds averaged Navier-Stokes equations. The numerical solution generated for the experimental aircraft concept X24C-10D at a Mach number of 5.95 not only exhibited accurate prediction of detailed flow properties but also of the integrated aerodynamic coefficients. In addition, the present analysis demonstrated that a page structure of data collected into cyclic blocks is an efficient and viable means for processing the Navier-Stokes equations on the CRAY XMP-22 computer with external memory device.

  6. Local Flow Field and Slip Length of Superhydrophobic Surfaces

    NASA Astrophysics Data System (ADS)

    Schäffel, David; Koynov, Kaloian; Vollmer, Doris; Butt, Hans-Jürgen; Schönecker, Clarissa

    2016-04-01

    While the global slippage of water past superhydrophobic surfaces has attracted wide interest, the local distribution of slip still remains unclear. Using fluorescence correlation spectroscopy, we performed detailed measurements of the local flow field and slip length for water in the Cassie state on a microstructured superhydrophobic surface. We revealed that the local slip length is finite, nonconstant, anisotropic, and sensitive to the presence of surfactants. In combination with numerical calculations of the flow, we can explain all these properties by the local hydrodynamics.

  7. Three-dimensional flow field in a turbine nozzle passage

    NASA Technical Reports Server (NTRS)

    Zaccaria, M.; Ristic, D.; Lakshminarayana, B.

    1993-01-01

    Detailed measurements were taken in the nozzle of a low speed single stage axial flow turbine at two axial planes inside the nozzle and on the nozzle and endwall surfaces. Velocity, turbulence and angle measurements were taken at midchord with an LDV while a five hole probe was used to measure the pressure, velocities and angles just upstream of the trailing edge. Nozzle surface and endwall static pressures were also measured. These measurements were compared to measurements previously completed at two axial planes downstream of the nozzle. The results show that at midchord, the secondary flow seems to be weak and it is in the early stages of development. Just upstream of the trailing edge, the secondary flow is clearly visible. The radially inward flow near the suction surface augments the casing passage vortex, while counteracting the hub passage vortex. Traveling downstream, the casing passage vortex remains strong while at the hub, the radially inward flow of the suction surface boundary layer has reversed direction due to the rotating hub. The blade static pressures and the passage averaged velocities compare well with Katsanis' quasi-three-dimensional code. These and other data are presented, interpreted and synthesized to understand the nozzle flow field.

  8. Flow field-flow fractionation for the analysis of nanoparticles used in drug delivery.

    PubMed

    Zattoni, Andrea; Roda, Barbara; Borghi, Francesco; Marassi, Valentina; Reschiglian, Pierluigi

    2014-01-01

    Structured nanoparticles (NPs) with controlled size distribution and novel physicochemical features present fundamental advantages as drug delivery systems with respect to bulk drugs. NPs can transport and release drugs to target sites with high efficiency and limited side effects. Regulatory institutions such as the US Food and Drug Administration (FDA) and the European Commission have pointed out that major limitations to the real application of current nanotechnology lie in the lack of homogeneous, pure and well-characterized NPs, also because of the lack of well-assessed, robust routine methods for their quality control and characterization. Many properties of NPs are size-dependent, thus the particle size distribution (PSD) plays a fundamental role in determining the NP properties. At present, scanning and transmission electron microscopy (SEM, TEM) are among the most used techniques to size characterize NPs. Size-exclusion chromatography (SEC) is also applied to the size separation of complex NP samples. SEC selectivity is, however, quite limited for very large molar mass analytes such as NPs, and interactions with the stationary phase can alter NP morphology. Flow field-flow fractionation (F4) is increasingly used as a mature separation method to size sort and characterize NPs in native conditions. Moreover, the hyphenation with light scattering (LS) methods can enhance the accuracy of size analysis of complex samples. In this paper, the applications of F4-LS to NP analysis used as drug delivery systems for their size analysis, and the study of stability and drug release effects are reviewed. PMID:24012480

  9. Experiments and modeling of dilution jet flow fields

    NASA Technical Reports Server (NTRS)

    Holdeman, James D.

    1986-01-01

    Experimental and analytical results of the mixing of single, double, and opposed rows of jets with an isothermal or variable-temperature main stream in a straight duct are presented. This study was performed to investigate flow and geometric variations typical of the complex, three-dimensional flow field in the dilution zone of gas-turbine-engine combustion chambers. The principal results, shown experimentally and analytically, were the following: (1) variations in orifice size and spacing can have a significant effect on the temperature profiles; (2) similar distributions can be obtained, independent of orifice diameter, if momentum-flux ratio and orifice spacing are coupled; (3) a first-order approximation of the mixing of jets with a variable-temperature main stream can be obtained by superimposing the main-stream and jets-in-an-isothermal-crossflow profiles; (4) the penetration of jets issuing mixing is slower and is asymmetric with respect to the jet centerplanes, which shift laterally with increasing downstream distance; (5) double rows of jets give temperature distributions similar to those from a single row of equally spaced, equal-area circular holes; (6) for opposed rows of jets, with the orifice centerlines in line, the optimum ratio of orifice spacing to duct height is one-half the optimum value for single-side injection at the same momentum-flux ratiol and (7) for opposed rows of jets, with the orifice centerlines staggered, the optimum ratio of orifice spacing to duct height is twice the optimum value for single-side injection at the same momentum-flux ratio.

  10. Development of an algebraic stress/two-layer model for calculating thrust chamber flow fields

    NASA Technical Reports Server (NTRS)

    Chen, C. P.; Shang, H. M.; Huang, J.

    1993-01-01

    Following the consensus of a workshop in Turbulence Modeling 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.

  11. Development of an algebraic stress/two-layer model for calculating thrust chamber flow fields

    NASA Astrophysics Data System (ADS)

    Chen, C. P.; Shang, H. M.; Huang, J.

    1993-07-01

    Following the consensus of a workshop in Turbulence Modeling 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.

  12. Magnetic fields and the cluster cooling flow hypothesis

    NASA Astrophysics Data System (ADS)

    Garasi, Christopher Joseph

    2001-12-01

    Through the development of modern observations and computational techniques, the picture associated with clusters of galaxies has become more complex. Initially thought to be isothermal and hydrostatic, the X-ray emitting intracluster medium (ICM) is now viewed as a turbulent, magnetized environment. Mergers, ejecta from member galaxies, and jets from active galactic nuclei all serve to perturb the ICM. Magnetic field has been detected at all spatial scales within the ICM, with magnetic pressure close to equipartition with the gas pressure near some cluster cores. All of these phenomena have an impact on the ICM. Nearly thirty years ago a subset of clusters of galaxies referred to as ``cooling flows'' were identified through enhanced X-ray emission above the typical cluster sample. The radiative cooling time for these systems was found to be shorter than the cluster age. It was hypothesized that radiative cooling should bring the ICM out of hydrostatic balance, evolving into a steady-state radial inflow. Since direct observation of material inflow is not yet possible, estimates of the mass accretion rate have come from X-ray observations. The dominant mechanism governing the dynamics of these environments was assumed to be purely hydrodynamic. The role which magnetic fields play within the ICM has come into question due to magnetic field measurements within the cores of ``cooling flows.'' Previous attempts have been made to address the importance of magnetic fields within the ICM, however, the conclusions have been conflicting. We investigate the impact which magnetic fields have on a radiatively collapsing environment using one-dimensional numerical simulations. A hydrodynamic baseline is first established, and then followed by simulations invoking ideal magnetohydrodynamics (MHD) as well as magnetic dissipation. The results from the simulations indicate that hydrodynamics alone will not produce a solution which matches the observed characteristics of cooling

  13. [Analysis of Influence on Single Eythrocyte Injury Caused by Oscillating Boundary Flow Field].

    PubMed

    Yun, Zhong; Xiang, Chuang; Cai, Chao; Xu, Junrui

    2016-02-01

    The implantable axial blood pump, driven by external electromagnet, is studied recently. It oscillats when it is running because of the elastic implanted environment and driving force disequilibrium, etc. In this paper, a model of single erythrocyte in vibrated flow field was built to simulate the deformation and force of the erythrocyte. By using the mechanical injury principle of blood in blood pump, we studied the injury of a single erythrocyte resulted from oscillating boundary flow field. The research results indicated that the shape of the erythrocyte, force and velocity field nearby, which are affected by oscillating boundary flow field, all cause injury to the erythrocyte. All the researches shown in the present paper are expected to provide theoretical foundation for lightening hemolysis by the blood pump. PMID:27382744

  14. Field Observations of Canopy Flows over Complex Terrain

    NASA Astrophysics Data System (ADS)

    Grant, Eleanor R.; Ross, Andrew N.; Gardiner, Barry A.; Mobbs, Stephen D.

    2015-08-01

    The investigation of airflow over and within forests in complex terrain has been, until recently, limited to a handful of modelling and laboratory studies. Here, we present an observational dataset of airflow measurements inside and above a forest situated on a ridge on the Isle of Arran, Scotland. The spatial coverage of the observations all the way across the ridge makes this a unique dataset. Two case studies of across-ridge flow under near-neutral conditions are presented and compared with recent idealized two-dimensional modelling studies. Changes in the canopy profiles of both mean wind and turbulent quantities across the ridge are broadly consistent with these idealized studies. Flow separation over the lee slope is seen as a ubiquitous feature of the flow. The three-dimensional nature of the terrain and the heterogeneous forest canopy does however lead to significant variations in the flow separation across the ridge, particularly over the less steep western slope. Furthermore, strong directional shear with height in regions of flow separation has a significant impact on the Reynolds stress terms and other turbulent statistics. Also observed is a decrease in the variability of the wind speed over the summit and lee slope, which has not been seen in previous studies. This dataset should provide a valuable resource for validating models of canopy flow over real, complex terrain.

  15. Numerical computation of space shuttle orbiter flow field

    NASA Technical Reports Server (NTRS)

    Tannehill, John C.

    1988-01-01

    A new parabolized Navier-Stokes (PNS) code has been developed to compute the hypersonic, viscous chemically reacting flow fields around 3-D bodies. The flow medium is assumed to be a multicomponent mixture of thermally perfect but calorically imperfect gases. The new PNS code solves the gas dynamic and species conservation equations in a coupled manner using a noniterative, implicit, approximately factored, finite difference algorithm. The space-marching method is made well-posed by special treatment of the streamwise pressure gradient term. The code has been used to compute hypersonic laminar flow of chemically reacting air over cones at angle of attack. The results of the computations are compared with the results of reacting boundary-layer computations and show excellent agreement.

  16. Elevator mode convection in flows with strong magnetic fields

    SciTech Connect

    Liu, Li; Zikanov, Oleg

    2015-04-15

    Instability modes in the form of axially uniform vertical jets, also called “elevator modes,” are known to be the solutions of thermal convection problems for vertically unbounded systems. Typically, their relevance to the actual flow state is limited by three-dimensional breakdown caused by rapid growth of secondary instabilities. We consider a flow of a liquid metal in a vertical duct with a heated wall and strong transverse magnetic field and find elevator modes that are stable and, thus, not just relevant, but a dominant feature of the flow. We then explore the hypothesis suggested by recent experimental data that an analogous instability to modes of slow axial variation develops in finite-length ducts, where it causes large-amplitude fluctuations of temperature. The implications for liquid metal blankets for tokamak fusion reactors that potentially invalidate some of the currently pursued design concepts are discussed.

  17. The Flow Field on Hydrofoils with Leading Edge Protuberances

    NASA Astrophysics Data System (ADS)

    Custodio, Derrick; Henoch, Charles; Johari, Hamid

    2009-11-01

    The exceptional mobility of the humpback whale has been linked to the use of its unique pectoral flippers. Biologists speculate that the flippers leading edge protuberances are a form of passive flow control. Force measurements on 2D hydrofoils with spanwise uniform leading edge protuberances, resembling those seen on the humpback whale flipper, were taken in a water tunnel and have revealed performance modifications when compared to a baseline NACA 63(4)-021 hydrofoil model. Qualitative flow visualization techniques and Particle Image Velocimetry (PIV) flow field measurements on the modified hydrofoils have shown that streamwise vortices originating from the shoulders of the protuberances are the likely cause of performance changes. Varying levels of interaction among adjacent streamwise vortices have been observed as a function of angle of attack and chord location. The circulation of these vortices as a function of angle of attack and spatial location was measured and an analysis of the vortex interactions will be presented.

  18. Elevator mode convection in flows with strong magnetic fields

    NASA Astrophysics Data System (ADS)

    Liu, Li; Zikanov, Oleg

    2015-04-01

    Instability modes in the form of axially uniform vertical jets, also called "elevator modes," are known to be the solutions of thermal convection problems for vertically unbounded systems. Typically, their relevance to the actual flow state is limited by three-dimensional breakdown caused by rapid growth of secondary instabilities. We consider a flow of a liquid metal in a vertical duct with a heated wall and strong transverse magnetic field and find elevator modes that are stable and, thus, not just relevant, but a dominant feature of the flow. We then explore the hypothesis suggested by recent experimental data that an analogous instability to modes of slow axial variation develops in finite-length ducts, where it causes large-amplitude fluctuations of temperature. The implications for liquid metal blankets for tokamak fusion reactors that potentially invalidate some of the currently pursued design concepts are discussed.

  19. Longitudinal Dispersivity in a Radial Diverging Flow Field

    NASA Astrophysics Data System (ADS)

    Seaman, J. C.; Wilson, M.; Bertsch, P. M.; Aburime, S. A.

    2005-12-01

    Hydrodynamic dispersion is an important factor controlling contaminant migration in the subsurface environment. However, few comprehensive data sets exist for evaluating the impact of travel distance and site heterogeneity on solute dispersion under non-uniform flow conditions. In addition, anionic tracers are often used to estimate physical transport parameters based on an erroneous assumption of conservative (i.e., non-reactive) behavior. Therefore, a series of field experiments using tritiated water and several other commonly used hydrologic tracers (Br, Cl, FBAs) were conducted in the water-table aquifer on the U.S. Department of Energy's Savannah River Site (Aiken, SC) to evaluate solute transport processes in a diverging radial flow field. For each experiment, tracer-free groundwater was injected for approximately 24 hours at a fixed rate of 56.7 L/min (15 gpm) to establish a forced radial gradient prior to the introduction of a tracer pulse. After the tracer pulse, the forced gradient was maintained throughout the experiment using non-labeled groundwater. Tracer migration was monitored using a set of six sampling wells radially spaced at approximate distances of 1.5, 3, and 4.5 meters from a central injection well. Each sampling well was further divided into three discrete sampling depths that were monitored continuously throughout the course of the tracer experiment. At various time intervals, discrete groundwater samples were collected from all 18 sampling ports for tritium analysis. Longitudinal dispersivity for tritium breakthrough at each sampling location was estimated using analytical approximations of the convection dispersion equation (CDE) for radial flow assuming an instantaneous Dirac pulse and a pulse of known duration. The results were also compared to dispersivity values derived from fitting the tracer data to analytical solutions derived from assuming uniform flow conditions. Tremendous variation in dispersivity values and tracer arrival

  20. Flow and temperature field measurements of thermal convection in a small vertical gap using liquid crystals

    NASA Astrophysics Data System (ADS)

    Heiland, Hans Georg; Wozniak, Günter; Wozniak, Klaus

    2007-07-01

    Thermal convection in a small vertical gap is studied experimentally applying digital particle image velocimetry/thermometry. This optical method enables the simultaneous measurement of two-dimensional flow and temperature fields in a liquid. The principle is based on seeding the liquid flow medium with thermochromic liquid crystal particles. The temperature is measured by the crystal particles which change their reflected colour as function of temperature. The flow velocity is measured by using the same particles as flow tracers. The investigation shall contribute to the understanding of the fluid mechanical behaviour of biological liquids within micro reactor systems. However, the problem is also of fundamental interest as far as heat and mass transfer is concerned. Measured temperature and flow velocity fields are presented and discussed.

  1. PIV measurements of coolant flow field in a diesel engine cylinder head

    NASA Astrophysics Data System (ADS)

    Ma, Hongwei; Zhang, Zhenyang; Xue, Cheng; Huang, Yunlong

    2015-04-01

    This paper presents experimental measurements of coolant flow field in the water jacket of a diesel engine cylinder head. The test was conducted at three different flow rates using a 2-D PIV system. Appropriate tracing particles were selected and delivery device was designed and manufactured before the test. The flow parameters, such as velocity, vorticity and turbulence, were used to analyze the flow field. The effects of vortex which was located between the intake valve and the exhaust valve were discussed. The experimental results showed an asymmetric distribution of velocity in the water jacket. This led to an asymmetric thermal distribution, which would shorten the service life of the cylinder head. The structure optimization to the water jacket of cylinder head was proposed in this paper. The experimental system, especially the 2-D PIV system, is a great help to study the coolant flow structure and analyze cooling mechanism in the diesel engine cylinder head.

  2. A high-performance flow-field structured iron-chromium redox flow battery

    NASA Astrophysics Data System (ADS)

    Zeng, Y. K.; Zhou, X. L.; An, L.; Wei, L.; Zhao, T. S.

    2016-08-01

    Unlike conventional iron-chromium redox flow batteries (ICRFBs) with a flow-through cell structure, in this work a high-performance ICRFB featuring a flow-field cell structure is developed. It is found that the present flow-field structured ICRFB reaches an energy efficiency of 76.3% with a current density of 120 mA cm-2 at 25 °C. The energy efficiency can be as high as 79.6% with an elevated current density of 200 mA cm-2 at 65 °C, a record performance of the ICRFB in the existing literature. In addition, it is demonstrated that the energy efficiency of the battery is stable during the cycle test, and that the capacity decay rate of the battery is 0.6% per cycle. More excitingly, the high performance of the flow-field structured battery significantly lowers the capital cost at 137.6 kWh-1, which is 28.2% lower than that of the conventional ICRFB for 8-h energy storage.

  3. Studies of two phase flow

    NASA Technical Reports Server (NTRS)

    Witte, Larry C.

    1994-01-01

    The development of instrumentation for the support of research in two-phase flow in simulated microgravity conditions was performed. The funds were expended in the development of a technique for characterizing the motion and size distribution of small liquid droplets dispersed in a flowing gas. Phenomena like this occur in both microgravity and normal earth gravity situations inside of conduits that are carrying liquid-vapor mixtures at high flow rates. Some effort to develop a conductance probe for the measurement of liquid film thickness was also expended.

  4. Inverse Simulation of Field Infiltration Experiment Counting Preferential Flow

    NASA Astrophysics Data System (ADS)

    Zumr, David; Snehota, Michal; Nemcova, Renata; Dohnal, Michal; Cislerova, Milena

    2010-05-01

    The field tension and ponded infiltration experiments were conducted to monitor and describe irregularities of moisture propagation and to estimate the soil hydraulic properties (Distric Cambisol, Korkusova Hut, Sumava). On these soils the preferential pathways have been observed in several scales with the use of dye tracers, MRI and CT imaging. Preferential behavior was detected also during laboratory infiltration experiments. The flow irregularities are credited to variable air entrapment at the beginning of infiltrations. The field infiltration experiment was carried out in a shallow pit for a period of one day. The upper boundary condition was controlled by the tension disk infiltrometer, the propagation of a water front was monitored by two tensiometers installed in two depths below the infiltration disk. The propagation of saline solution front during ponded infiltration was visualized with high resolution electrical resistivity tomography (ERT). Infiltration experiments were monitored with TDR probes, tensiometers and ERT. Zones of preferential flow were determined through analyses of photographs taken during laboratory dye tracer infiltration experiments performed on undisturbed soil samples. Connectivity, volumetric ratio and spatial development of preferential pathways were evaluated as the necessary information for numerical simulations of flow using dual-permeability approach. 2D axisymetric numerical simulations were conducted to evaluate the results of the experiment. The parameter estimator PEST coupled with the simulation code S2D_DUAL (Vogel et al., 2000) were employed. Two different approaches were used: 1. Single-domain approach based on Richards' equation. 2. Dual-permeability approach based on two interacting water flow domains (matrix and preferential domains), each governed by one Richards' equation. Concerning the existence of preferential flow on investigated soil, the dual-permeability model gives a better picture of the flow regime. The

  5. A phase-field model of unsaturated flow

    NASA Astrophysics Data System (ADS)

    Juanes, R.; Cueto-Felgueroso, L.

    2009-12-01

    In gravity-driven infiltration into initially dry, homogeneous soil, the resulting pattern often takes the form of preferential flow paths (fingers), which have been consistently observed in laboratory and field experiments for nearly half a century. Despite the frequent occurrence of gravity fingers in unsaturated media, the explanation, modeling and prediction of fingered flows with continuum (macroscopic) mathematical models has remained elusive. In this paper, we present a new continuum mathematical model of infiltration. The inspiration for the new model is the flow of thin films (like water down a plane), which also displays fingering instability. The key idea is very simple: the macroscopic equations must reflect the presence of a macroscopic interface---the wetting front. We then cast the model in the rigorous framework of phase-field models and nonlocal thermodynamics. The new model is appealing. It is a simple extension of Richards' equation, with a new term (a fourth-order derivative in space) but without any new parameters. It reproduces the two key features of unsaturated flow: a nonmonotonic saturation profile, and gravity fingering. It explains why, when, and how, fingers form. It shows excellent quantitative agreement with experiments in terms of tip saturation, tip velocity and finger width. The most attractive aspect is, however, that the new model offers a starting point for fundamentally new formulations of multiphase flow in porous media. Saturation maps from a numerical simulation of the proposed model show that the flow dynamics and the distinctive saturation overshoot at the tip of the fingers agree with experimental observations.

  6. Unsteady Simulation of a Landing-Gear Flow Field

    NASA Technical Reports Server (NTRS)

    Li, Fei; Khorrami, Mehdi R.; Malik, Mujeeb R.

    2002-01-01

    This paper presents results of an unsteady Reynolds-averaged Navier-Stokes simulation of a landing-gear flow field. The geometry of the four-wheel landing gear assembly consists of several of the fine details including the oleo-strut, two diagonal struts, a door, yokes/pin and a flat-plate simulating the wing surface. The computational results, obtained by using 13.3 million grid points, are presented with an emphasis on the characteristics of the unsteadiness ensuing from different parts of the landing-gear assembly, including vortex shedding patterns and frequencies of dominant oscillations. The results show that the presence of the diagonal struts and the door significantly influence the flow field. Owing to the induced asymmetry, vortices are shed only from one of the rear wheels and not the other. Present computations also capture streamwise vortices originating from the upstream corners of the door.

  7. The laser measurement technology of combustion flow field

    NASA Astrophysics Data System (ADS)

    Wang, Mingdong; Wang, Guangyu; Qu, Dongsheng

    2014-07-01

    The parameters of combustion flow field such as temperature, velocity, pressure and mole-fraction are of significant value in engineering application. The laser spectroscopy technology which has the non-contact and non- interference properties has become the most important method and it has more advantages than conventionally contacting measurement. Planar laser induced fluorescence (PLIF/LIF) is provided with high sensibility and resolution. Filtered Rayleigh scattering (FRS) is a good measurement method for complex flow field .Tunable diode laser absorption spectroscopy (TDLAS) is prosperity on development and application. This article introduced the theoretical foundation, technical principle, system structure, merits and shortages. It is helpful for researchers to know about the latest development tendency and do the related research.

  8. The flow field in a rotating detonation-wave engine

    NASA Astrophysics Data System (ADS)

    Kailasanath, Kazhikathra; Schwer, Douglas

    2011-11-01

    Rotating detonation-wave engines (RDE) are a form of continuous detonation-wave engine. They potentially provide further gains than an intermittent or pulsed detonation-wave engine (PDE). However, significantly less work has been on this concept when compared to the PDE. In this talk, we present the detailed flow field in an idealized RDE, primarily consisting of two concentric cylinders. A premixed detonable mixture is injected into the annulus between the two concentric cylinders. Once a detonation is initiated, it keeps travelling around in the annulus as long as there is fresh detonable mixture ahead of it. Hence, the injection process is critically important to the stability and performance of the RDE. Furthermore, we show that the flow field is quite complex consisting of multiple shock waves and the outflow is primarily axial, although the detonation-wave is travelling around circumferentially. Sponsored by the NRL 6.1 Computational Physics Task Area.

  9. Fuel cell with interdigitated porous flow-field

    DOEpatents

    Wilson, Mahlon S.

    1997-01-01

    A polymer electrolyte membrane (PEM) fuel cell is formed with an improved system for distributing gaseous reactants to the membrane surface. A PEM fuel cell has an ionic transport membrane with opposed catalytic surfaces formed thereon and separates gaseous reactants that undergo reactions at the catalytic surfaces of the membrane. The fuel cell may also include a thin gas diffusion layer having first and second sides with a first side contacting at least one of the catalytic surfaces. A macroporous flow-field with interdigitated inlet and outlet reactant channels contacts the second side of the thin gas diffusion layer for distributing one of the gaseous reactants over the thin gas diffusion layer for transport to an adjacent one of the catalytic surfaces of the membrane. The porous flow field may be formed from a hydrophilic material and provides uniform support across the backside of the electrode assembly to facilitate the use of thin backing layers.

  10. Fuel cell with interdigitated porous flow-field

    DOEpatents

    Wilson, M.S.

    1997-06-24

    A polymer electrolyte membrane (PEM) fuel cell is formed with an improved system for distributing gaseous reactants to the membrane surface. A PEM fuel cell has an ionic transport membrane with opposed catalytic surfaces formed thereon and separates gaseous reactants that undergo reactions at the catalytic surfaces of the membrane. The fuel cell may also include a thin gas diffusion layer having first and second sides with a first side contacting at least one of the catalytic surfaces. A macroporous flow-field with interdigitated inlet and outlet reactant channels contacts the second side of the thin gas diffusion layer for distributing one of the gaseous reactants over the thin gas diffusion layer for transport to an adjacent one of the catalytic surfaces of the membrane. The porous flow field may be formed from a hydrophilic material and provides uniform support across the backside of the electrode assembly to facilitate the use of thin backing layers. 9 figs.

  11. Effect of far-field flow on a columnar crystal in the convective undercooled melt

    NASA Astrophysics Data System (ADS)

    Ji, Xiao-Jian; Chen, Ming-Wen; Xu, Xiao-Hua; Wang, Zi-Dong

    2015-01-01

    The growth behavior of a columnar crystal in the convective undercooled melt affected by the far-field uniform flow is studied and the asymptotic solution for the interface evolution of the columnar crystal is derived by means of the asymptotic expansion method. The results obtained reveal that the far-field flow induces a significant change of the temperature around the columnar crystal and the convective flow caused by the far-field flow accelerates the growth velocity of the interface of the growing columnar crystal in the upstream direction and inhibits its growth velocity in the downstream direction. Our results are similar to the experimental data and numerical simulations. Project supported by the Overseas Distinguished Scholar Program by the Ministry of Education of China (Grant No. MS2010BJKJ005), the National Natural Science Foundation of China (Grant No. 10972030), and the Science and Technology Support Project of Jiangxi, China (Grant No. 20112BBE50006).

  12. Changes in mobile phase ion distribution when combining pressurized flow and electric field.

    PubMed

    Eriksson, Björn O; Dahl, Magnus; Andersson, Magnus B O; Blomberg, Lars G

    2004-10-01

    The distribution of ions in a capillary with both pressurized flow and an electric field has been studied. We have earlier reported that the overall concentration of ions increase in a capillary with high electric field and a pressurized flow. Now we describe how the ions are distributed in the capillary both along the capillary length and in the radial direction as a result of the parabolic flow profile. We have combined current measurements with finite element techniques in order to get better understanding of the system. We have found that the concentration of the ions that because of the electric mobility moves towards the flow primarily increases at the beginning of the electric field and close to the capillary wall. In view of the results we have proposed an alterative explanation of earlier published results concerning voltage-induced variation in capacity factors. PMID:15472979

  13. Trajectory of microscale entities in a microdevice for field-flow fractionation based on dielectrophoresis

    NASA Astrophysics Data System (ADS)

    Mathew, Bobby; Alazzam, Anas; Khashan, Saud A.; El-Khasawneh, Bashar S.

    2015-06-01

    This article deals with the development of a two-dimensional dynamic model for tracking the path of cells subjected to dielectrophoresis, in a continuous flow microfluidic device, for purposes of field-flow fractionation. The nonuniform electric field exists between the top and bottom surface of the microchannel; the top electrode runs over the entire length of the microchannel while the bottom surface of the same holds multiple finite sized electrodes of opposite polarity. The model consists of two governing equations with each describing the movement of the cell in one of the two dimensions of interest. The equations governing of the cell trajectories as well as that of the electric potential inside the microchannel are solved using finite difference method. The model is subsequently used for parametric study; the parameters considered include cell radii, actuation voltage, microchannel height and volumetric flow rate. The model is particularly useful in the design of microfluidic device employing dielectrophoresis for field flow fractionation.

  14. Flow-induced Crystallization of Long Chain Aliphatic Polyamides under a Complex Flow Field

    NASA Astrophysics Data System (ADS)

    Dong, Xia; Gao, Yunyun; Wang, Lili; Wang, Dujin

    The present work deals with the flow-induced multiple orientations and crystallization structure of polymer melts under a complex flow field. This complex flow field is characteristic of the consistent coupling of extensional ``pulse'' and closely followed shear flow in a narrow channel. Utilizing an ingenious combination of an advanced micro-injection device and long chain aliphatic polyamides, the flow-induced crystallization morphology was well preserved for ex-situ synchrotron micro-focused wide angle X-ray scattering as well as small angle X-ray scattering. The experimental results clearly indicate that the effect of extensional pulse on the polymer melt is restrained and further diminished due to either the transverse tumble of fountain flow or the rapid retraction of stretched high molecular weight tails. However, the residual shish-kebab structures in the core layer of the far-end of channel suggest that the effect of extensional pulse should be considered in the small-scaled geometries or under the high strain rate condition. The authors thank the financial support from MOST (2013BAE02B02, 2014CB643600) and NSFC(21574140).

  15. Flow visualization and flow field measurements of a 1/12 scale tilt rotor aircraft in hover

    NASA Technical Reports Server (NTRS)

    Coffen, Charles D.; George, Albert R.; Hardinge, Hal; Stevenson, Ryan

    1991-01-01

    The results are given of flow visualization studies and inflow velocity field measurements performed on a 1/12 scale model of the XV-15 tilt rotor aircraft in the hover mode. The complex recirculating flow due to the rotor-wake-body interactions characteristic of tilt rotors was studied visually using neutrally buoyant soap bubbles and quantitatively using hot wire anemometry. Still and video photography were used to record the flow patterns. Analysis of the photos and video provided information on the physical dimensions of the recirculating fountain flow and on details of the flow including the relative unsteadiness and turbulence characteristics of the flow. Recirculating flows were also observed along the length of the fuselage. Hot wire anemometry results indicate that the wing under the rotor acts to obstruct the inflow causing a deficit in the inflow velocities over the inboard region of the model. Hot wire anemometry also shows that the turbulence intensities in the inflow are much higher in the recirculating fountain reingestion zone.

  16. Theoretical analysis of magnetic field interactions with aortic blood flow

    SciTech Connect

    Kinouchi, Y.; Yamaguchi, H.; Tenforde, T.S.

    1996-04-01

    The flow of blood in the presence of a magnetic field gives rise to induced voltages in the major arteries of the central circulatory system. Under certain simplifying conditions, such as the assumption that the length of major arteries (e.g., the aorta) is infinite and that the vessel walls are not electrically conductive, the distribution of induced voltages and currents within these blood vessels can be calculated with reasonable precision. However, the propagation of magnetically induced voltages and currents from the aorta into neighboring tissue structures such as the sinuatrial node of the heart has not been previously determined by any experimental or theoretical technique. In the analysis presented in this paper, a solution of the complete Navier-Stokes equation was obtained by the finite element technique for blood flow through the ascending and descending aortic vessels in the presence of a uniform static magnetic field. Spatial distributions of the magnetically induced voltage and current were obtained for the aortic vessel and surrounding tissues under the assumption that the wall of the aorta is electrically conductive. Results are presented for the calculated values of magnetically induced voltages and current densities in the aorta and surrounding tissue structures, including the sinuatrial node, and for their field-strength dependence. In addition, an analysis is presented of magnetohydrodynamic interactions that lead to a small reduction of blood volume flow at high field levels above approximately 10 tesla (T). Quantitative results are presented on the offsetting effects of oppositely directed blood flows in the ascending and descending aortic segments, and a quantitative estimate is made of the effects of assuming an infinite vs. a finite length of the aortic vessel in calculating the magnetically induced voltage and current density distribution in tissue.

  17. Design method for the flow field and drag of bodies of revolution in incompressible flow

    SciTech Connect

    Wolfe, W.P.; Oberkampf, W.L.

    1982-01-01

    A design method has been developed for determining the flow field, pressure distribution, boundary layer separation point, and drag of bodies of revolution at zero angle of attack in incompressible flow. The approach taken is the classical coupling of potential and boundary solutions to obtain the flow field about the body. The potential solution is obtained by modeling the body with an axial distribution of source/sink elements whose strengths vary linearly along their length. The laminar and turbulent boundary layer solutions are obtained from conventional solutions of the momentum integral equation. An approximate method is used to estimate the boundary layer transition point on the body. An empirical base pressure correlation is used to determine the base drag. Body surface pressure distributions and drag predictions are compared with experimental measurements.

  18. Effects of inlet distortion on the flow field in a transonic compressor rotor

    SciTech Connect

    Hah, C.; Rabe, D.C.; Sullivan, T.J.; Wadia, A.R.

    1998-04-01

    The effects of circumferential distortions in inlet total pressure on the flow field in a low-aspect-ratio, high-speed, high-pressure-ratio, transonic compressor rotor are investigated in this paper. The flow field was studied experimentally and numerically with and without inlet total pressure distortion. Total pressure distortion was created by screens mounted upstream from the rotor inlet. Circumferential distortions of eight periods per revolution were investigated at two different rotor speeds. The unsteady blade surface pressures were measured with miniature pressure transducers mounted in the blade. The flow fields with and without inlet total pressure distortion were analyzed numerically by solving steady and unsteady forms of the Reynolds-averaged Navier-Stokes equations. Steady three-dimensional viscous flow calculations were performed for the flow without inlet distortion while unsteady three-dimensional viscous flow calculations were used for the flow with inlet distortion. For the time-accurate calculation, circumferential and radial variations of the inlet total pressure were used as a time-dependent inflow boundary condition. A second-order implicit scheme was used for the time integration. The experimental measurements and the numerical analysis are highly complementary for this study because of the extreme complexity of the flow field. The current investigation shows that inlet flow distortions travel through the rotor blade passage and are convected into the following stator. At a high rotor speed where the flow is transonic, the passage shock was found to oscillate by as much as 20% of the blade chord, and very strong interactions between the unsteady passage shock and the blade boundary layer were observed. This interaction increases the effective blockage of the passage, resulting in an increased aerodynamic loss and a reduced stall margin.

  19. Flow field and near and far sound field of a subsonic jet

    NASA Astrophysics Data System (ADS)

    Zaman, K. B. M. Q.

    1986-04-01

    Flow and sound field data are presented for a 2°54 cm diameter air jet at a Mach number of 0·50 and a Reynolds number of 3×10 5. Distributions of mean velocity, turbulence intensities, Reynolds stress, spectral components of turbulence as well as of the near field pressure, together with essential characteristics of the far field sound are reported. This detailed set of data for one particular flow, erstwhile unavailable in the literature, is expected to help promote and calibrate subsonic jet noise theories. "Source locations" in terms of the turbulence maxima, coupling between the entrainment dynamics and the near pressure field, the sound radiation paths, and the balance in mass, momentum and sound energy fluxes are discussed. The results suggest that the large scale coherent structures of the jet govern the "source locations" by controlling the turbulence and also strongly influence the near field pressure fluctuations.

  20. Flow fields in soap films: Relating viscosity and film thickness

    NASA Astrophysics Data System (ADS)

    Prasad, V.; Weeks, Eric R.

    2009-08-01

    We follow the diffusive motion of colloidal particles in soap films with varying h/d , where h is the thickness of the film and d is the diameter of the particles. The hydrodynamics of these films are determined by looking at the correlated motion of pairs of particles as a function of separation R . The Trapeznikov approximation [A. A. Trapeznikov, Proceedings of the 2nd International Congress on Surface Activity (Butterworths, London, 1957), p. 242] is used to model soap films as an effective two-dimensional (2D) fluid in contact with bulk air phases. The flow fields determined from correlated particle motions show excellent agreement with what is expected for the theory of 2D fluids for all our films where 0.6≤h/d≤14.3 , with the 2D shear viscosity matching that predicted by Trapeznikov. However, the parameters of these flow fields change markedly for thick films (h/d>7±3) . Our results indicate that three-dimensional effects become important for these thicker films, despite the flow fields still having a 2D character.

  1. Online Learner's "Flow" Experience: An Empirical Study

    ERIC Educational Resources Information Center

    Shin, Namin

    2006-01-01

    This study is concerned with online learners' "low" experiences. On the basis of Csikszentmihalyi's theory of flow, flow was conceptualised as a complex, multimentional, reflective construct composing of "enjoyment", "telepresence", "focused attention", "engagement" and "time distortion" on the part of learners. A flow model was put forward with…

  2. Flow field around Vorticella: Mixing with a reciprocal stroke

    NASA Astrophysics Data System (ADS)

    Pepper, Rachel E.; Roper, Marcus; Stone, Howard A.

    2008-11-01

    Vorticella is a stalked protozoan. It has an extremely fast biological spring, whose contraction is among the fastest biological motions relative to size. Though the Vorticella body is typically only 30 μm across, the contracting spring accelerates it up to speeds of centimeters per second. Vorticella live in an aqueous environment attached to a solid substrate and use their spring to retract their body towards the substrate. The function of the rapid retraction is not known. Many hypothesize that it stirs the surrounding liquid and exposes the Vorticella to fresh nutrients. We evaluate this hypothesis by modeling the Vorticella as a sphere moving normal to a wall, with a stroke that moves towards the wall at high Reynolds number, and away from the wall at low Reynolds number. We approximate the flow during contraction as potential flow, while the flow during re-extension is considered Stokes flow. The analytical results are compared to the flow field obtained with a finite element (Comsol Multiphysics) simulation of the full Navier-Stokes equations.

  3. Metrology of confined flows using wide field nanoparticle velocimetry

    PubMed Central

    Ranchon, Hubert; Picot, Vincent; Bancaud, Aurélien

    2015-01-01

    The manipulation of fluids in micro/nanofabricated systems opens new avenues to engineer the transport of matter at the molecular level. Yet the number of methods for the in situ characterization of fluid flows in shallow channels is limited. Here we establish a simple method called nanoparticle velocimetry distribution analysis (NVDA) that relies on wide field microscopy to measure the flow rate and channel height based on the fitting of particle velocity distributions along and across the flow direction. NVDA is validated by simulations, showing errors in velocity and height determination of less than 1% and 8% respectively, as well as with experiments, in which we monitor the behavior of 200 nm nanoparticles conveyed in channels of ~1.8 μm in height. We then show the relevance of this assay for the characterization of flows in bulging channels, and prove its suitability to characterize the concentration of particles across the channel height in the context of visco-elastic focusing. Our method for rapid and quantitative flow characterization has therefore a broad spectrum of applications in micro/nanofluidics, and a strong potential for the optimization of Lab-on-Chips modules in which engineering of confined transport is necessary. PMID:25974654

  4. Calculations of inlet distortion induced compressor flow field instability

    NASA Technical Reports Server (NTRS)

    Chue, R.; Greitzer, E. M.; Tan, C. S.; Hynes, T. P.; Longley, J. P.

    1989-01-01

    Calculations of the onset of flow instability are carried out for low-speed multistage axial compressors operating with asymmetric inlet flow. The modeling of the fluid dynamic interaction between the spoiled and unspoiled sectors of the compressor is the most important feature of the calculation procedure. The calculations show that annulus average slope of the compressor pressure rise characteristic equal to zero is a useful approximate stability criterion for situations where the dynamics of the compressor flow field do not couple strongly to the compression system or the structure of the imposed distortion is not similar to that of the eigenmodes of the flow in the compressor annulus. This criterion is employed to investigate the relationship between the present model and the 'parallel compressor' model. Calculations are also presented for cases when compressor and compressor system are closely coupled, and situations in which the compressor is subjected to a rotating distortion. These first-of-a-kind computations, and the accompanying description of the physical mechanisms, show that the stability of the flow in the compressor can be adversely affected if the temporal or spatial structure of the distortion is such that resonant type responses can be evoked either from the compressor or from compressor/compression system interactions.

  5. Light field optical flow for refractive surface reconstruction

    NASA Astrophysics Data System (ADS)

    Iffa, Emishaw; Wetzstein, Gordon; Heidrich, Wolfgang

    2012-10-01

    This paper discusses a method to reconstruct a transparent ow surface from single camera shot with the aid of a Micro-lens array. An intentionally prepared high frequency background which is placed behind the refractive flow is captured and a curl-free optical flow algorithm is applied between pairs of images taken by different micro-lenses. The computed raw optical ow vector is a blend of motion parallax and background deformation vector due to the underlying flow. Subtracting the motion parallax, which is obtained by calibration, from the total op- optical flow vector yields the background deformation vector. The deflection vectors on each images are used to reconstruct the flow profile. A synthetic data set of fuel injection was used to evaluate the accuracy of the proposed algorithm and good agreement was achieved between the test and reconstructed data. Finally, real light field data of hot air created by a lighter flame is used to reconstruct and show a hot air plume surface.

  6. Determining 3D Flow Fields via Multi-camera Light Field Imaging

    PubMed Central

    Truscott, Tadd T.; Belden, Jesse; Nielson, Joseph R.; Daily, David J.; Thomson, Scott L.

    2013-01-01

    In the field of fluid mechanics, the resolution of computational schemes has outpaced experimental methods and widened the gap between predicted and observed phenomena in fluid flows. Thus, a need exists for an accessible method capable of resolving three-dimensional (3D) data sets for a range of problems. We present a novel technique for performing quantitative 3D imaging of many types of flow fields. The 3D technique enables investigation of complicated velocity fields and bubbly flows. Measurements of these types present a variety of challenges to the instrument. For instance, optically dense bubbly multiphase flows cannot be readily imaged by traditional, non-invasive flow measurement techniques due to the bubbles occluding optical access to the interior regions of the volume of interest. By using Light Field Imaging we are able to reparameterize images captured by an array of cameras to reconstruct a 3D volumetric map for every time instance, despite partial occlusions in the volume. The technique makes use of an algorithm known as synthetic aperture (SA) refocusing, whereby a 3D focal stack is generated by combining images from several cameras post-capture 1. Light Field Imaging allows for the capture of angular as well as spatial information about the light rays, and hence enables 3D scene reconstruction. Quantitative information can then be extracted from the 3D reconstructions using a variety of processing algorithms. In particular, we have developed measurement methods based on Light Field Imaging for performing 3D particle image velocimetry (PIV), extracting bubbles in a 3D field and tracking the boundary of a flickering flame. We present the fundamentals of the Light Field Imaging methodology in the context of our setup for performing 3DPIV of the airflow passing over a set of synthetic vocal folds, and show representative results from application of the technique to a bubble-entraining plunging jet. PMID:23486112

  7. Kinetic simulation of rarefied and weakly ionized hypersonic flow fields

    NASA Astrophysics Data System (ADS)

    Farbar, Erin D.

    When a vehicle enters the Earth's atmosphere at the very large velocities associated with Lunar and Mars return, a strong bow shock is formed in front of the vehicle. The shock heats the air to very high temperatures, causing collisions that are sufficiently energetic to produce ionized particles. As a result, a weakly ionized plasma is formed in the region between the bow shock and the vehicle surface. The presence of this plasma impedes the transport of radio frequency waves to the vehicle, causing the phenomenon known as "communications black out". The plasma also interacts with the neutral particles in the flow field, and contributes to the heat flux at the vehicle surface. Since it is difficult to characterize these flow fields using flight or ground based experiments, computational tools play an important role in the design of reentry vehicles. It is important to include the physical phenomena associated with the presence of the plasma in the computational analysis of the flow fields about these vehicles. Physical models for the plasma phenomena are investigated using a state of the art, Direct Simulation Monte Carlo (DSMC) code. Models for collisions between charged particles, plasma chemistry, and the self-induced electric field that currently exist in the literature are implemented. Using these baseline models, steady state flow field solutions are computed for the FIRE II reentry vehicle at two different trajectory points. The accuracy of each baseline plasma model is assessed in a systematic fashion, using one flight condition of the FIRE II vehicle as the test case. Experimental collision cross section data is implemented to model collisions of electrons with neutral particles. Theoretical and experimental reaction cross section data are implemented to model chemical reactions that involve electron impact, and an associative ionization reaction. One-dimensional Particle-In-Cell (PIC) routines are developed and coupled to the DSMC code, to assess the

  8. Quantitative assessment of flow and electric fields for electrophoretic focusing at a converging channel entrance with interfacial electrode

    PubMed Central

    Keebaugh, Michael W.; Mahanti, Prasun; Hayes, Mark A.

    2013-01-01

    The electric field and flow field gradients near an electrified converging channel are amenable to separating and focusing specific classes of electrokinetic material, but the detailed local electric field and flow dynamics in this region have not been thoroughly investigated. Finite elemental analysis was used to develop a model of a buffer reservoir connected to a smaller channel to simulate the electrophoretic and flow velocities (which correspond directly to the respective electric and flow fields) at a converging entrance. A detailed PTV (Particle Tracking Velocimetry) study using charged fluorescent microspheres was performed to assess the model validity both in the absence and presence of an applied electric field. The predicted flow velocity gradient from the model agreed with the PTV data when no electric field was present. Once the additional forces that act on the large particles required for tracing (dielectrophoresis) were included, the model accurately described the velocity of the charged particles in electric fields. PMID:22806456

  9. The morphology and evolution of the Stromboli 2002-2003 lava flow field--An example of a basaltic flow field emplaced on a steep slope

    USGS Publications Warehouse

    Lodato, Luigi; Harris, A.; Spampinato, L.; Calvari, Sonia; Dehn, J.; Patrick, M.

    2007-01-01

    The use of a hand-held thermal camera during the 2002–2003 Stromboli effusive eruption proved essential in tracking the development of flow field structures and in measuring related eruption parameters, such as the number of active vents and flow lengths. The steep underlying slope on which the flow field was emplaced resulted in a characteristic flow field morphology. This comprised a proximal shield, where flow stacking and inflation caused piling up of lava on the relatively flat ground of the vent zone, that fed a medial–distal lava flow field. This zone was characterized by the formation of lava tubes and tumuli forming a complex network of tumuli and flows linked by tubes. Most of the flow field was emplaced on extremely steep slopes and this had two effects. It caused flows to slide, as well as flow, and flow fronts to fail frequently, persistent flow front crumbling resulted in the production of an extensive debris field. Channel-fed flows were also characterized by development of excavated debris levees in this zone (Calvari et al. 2005). Collapse of lava flow fronts and inflation of the upper proximal lava shield made volume calculation very difficult. Comparison of the final field volume with that expecta by integrating the lava effusion rates through time suggests a loss of ~70% erupted lava by flow front crumbling and accumulation as debris flows below sea level. Derived relationships between effusion rate, flow length, and number of active vents showed systematic and correlated variations with time where spreading of volume between numerous flows caused an otherwise good correlation between effusion rate, flow length to break down. Observations collected during this eruption are useful in helping to understand lava flow processes on steep slopes, as well as in interpreting old lava–debris sequences found in other steep-sided volcanoes subject to effusive activity.

  10. An experimental investigation of the flow field of a rectangular wall jet

    NASA Technical Reports Server (NTRS)

    Horne, C.; Karamcheti, K.

    1979-01-01

    The structure of a laminar, rectangular wall jet developing from an initially parabolic velocity profile was investigated with measurements of the mean and fluctuating velocity field, and with Schlieren flow visualization. The effects on mean and fluctuating velocity fields of changes in the jet Reynolds number over the range of from 0 to 4800, and of various wall lengths ranging from 0 to 312 jet widths were studied. For a given wall length and Reynolds number, disturbances in the flow field were regular and periodic, and of a constant frequency in a large region of the flow field. Small, self-excited disturbances at the nozzle exit were observed to grow exponentially with downstream distance, and roll up to form a convecting array of discrete vortices. For certain values of wall length and jet speed, discrete audible tones were detected, and appeared to be associated with an enhancement of the regularity and stability of the vortex array.

  11. Origin of north Queensland Cenozoic volcanism: Relationships to long lava flow basaltic fields, Australia

    NASA Astrophysics Data System (ADS)

    Sutherland, F. L.

    1998-11-01

    A plume model proposed for north Queensland late Cenozoic volcanism and long lava flow distribution combines basalt ages with recent seismic studies of Australia's mantle, regional stress fields, and plate motion. Several basalt fields overlie mantle "thermal" anomalies, and other fields outside these anomalies can be traced to them through past lithospheric motion. Elsewhere, anomalies close to Australia's eastern rift margin show little volcanism, probably due to gravity-enhanced compression. Since final collision of north Queensland with New Guinea, areas of basaltic volcanism have developed over 10 Myr, and episodes appear to migrate southward from 15° to 20°S. Long lava flows increase southward as area/volume of fields increases, but topography, vent distributions, and uplifts play a role. This is attributed to magmatic plume activation within a tensional zone, as lithosphere moves over mantle thermal anomalies. The plume model predicts peak magmatism under the McBride field, coincident with the Undara long lava flow and that long lava flow fields will erupt for another 5-10 Myr. Queensland's movement over a major N-S thermal system imparts a consistent isotopic signature to its northern younger basalts, distinct to basalts from older or more southern thermal systems. Australia's motion toward this northern thermal system will give north Queensland fields continued vigorous volcanism, in contrast to the Victorian field which is leaving its southern thermal system.

  12. Direct Measurement of the Flow Field around Swimming Microorganisms

    NASA Astrophysics Data System (ADS)

    Drescher, Knut; Goldstein, Raymond E.; Michel, Nicolas; Polin, Marco; Tuval, Idan

    2010-10-01

    Swimming microorganisms create flows that influence their mutual interactions and modify the rheology of their suspensions. While extensively studied theoretically, these flows have not been measured in detail around any freely-swimming microorganism. We report such measurements for the microphytes Volvox carteri and Chlamydomonas reinhardtii. The minute (˜0.3%) density excess of V. carteri over water leads to a strongly dominant Stokeslet contribution, with the widely-assumed stresslet flow only a correction to the subleading source dipole term. This implies that suspensions of V. carteri have features similar to suspensions of sedimenting particles. The flow in the region around C. reinhardtii where significant hydrodynamic interaction is likely to occur differs qualitatively from a puller stresslet, and can be described by a simple three-Stokeslet model.

  13. Direct measurement of the flow field around swimming microorganisms

    NASA Astrophysics Data System (ADS)

    Polin, Marco; Drescher, Knut; Goldstein, Raymond E.; Michel, Nicolas; Tuval, Idan

    2010-11-01

    Swimming microorganisms create flows that influence their mutual interactions and modify the rheology of their suspensions. While extensively studied theoretically, these flows have not been measured in detail around any freely-swimming microorganism. We report such measurements for the microphytes Volvox carteri and Chlamydomonas reinhardtii. The minute (˜0.3%) density excess of V. carteri over water leads to a strongly dominant Stokeslet contribution, with the widely-assumed stresslet flow only a correction to the subleading source dipole term. This implies that suspensions of V. carteri have features similar to suspensions of sedimenting particles. The flow in the region around C. reinhardtii where significant hydrodynamic interaction is likely to occur differs qualitatively from a "puller" stresslet, and can be described by a simple three-Stokeslet model.

  14. Modeling field scale unsaturated flow and transport processes

    SciTech Connect

    Gelhar, L.W.; Celia, M.A.; McLaughlin, D.

    1994-08-01

    The scales of concern in subsurface transport of contaminants from low-level radioactive waste disposal facilities are in the range of 1 to 1,000 m. Natural geologic materials generally show very substantial spatial variability in hydraulic properties over this range of scales. Such heterogeneity can significantly influence the migration of contaminants. It is also envisioned that complex earth structures will be constructed to isolate the waste and minimize infiltration of water into the facility. The flow of water and gases through such facilities must also be a concern. A stochastic theory describing unsaturated flow and contamination transport in naturally heterogeneous soils has been enhanced by adopting a more realistic characterization of soil variability. The enhanced theory is used to predict field-scale effective properties and variances of tension and moisture content. Applications illustrate the important effects of small-scale heterogeneity on large-scale anisotropy and hysteresis and demonstrate the feasibility of simulating two-dimensional flow systems at time and space scales of interest in radioactive waste disposal investigations. Numerical algorithms for predicting field scale unsaturated flow and contaminant transport have been improved by requiring them to respect fundamental physical principles such as mass conservation. These algorithms are able to provide realistic simulations of systems with very dry initial conditions and high degrees of heterogeneity. Numerical simulation of the movement of water and air in unsaturated soils has demonstrated the importance of air pathways for contaminant transport. The stochastic flow and transport theory has been used to develop a systematic approach to performance assessment and site characterization. Hypothesis-testing techniques have been used to determine whether model predictions are consistent with observed data.

  15. Quantifying uranium complexation by groundwater dissolved organic carbon using asymmetrical flow field-flow fractionation

    NASA Astrophysics Data System (ADS)

    Ranville, James F.; Hendry, M. Jim; Reszat, Thorsten N.; Xie, Qianli; Honeyman, Bruce D.

    2007-05-01

    The long-term mobility of actinides in groundwaters is important for siting nuclear waste facilities and managing waste-rock piles at uranium mines. Dissolved organic carbon (DOC) may influence the mobility of uranium, but few field-based studies have been undertaken to examine this in typical groundwaters. In addition, few techniques are available to isolate DOC and directly quantify the metals complexed to it. Determination of U-organic matter association constants from analysis of field-collected samples compliments laboratory measurements, and these constants are needed for accurate transport calculations. The partitioning of U to DOC in a clay-rich aquitard was investigated in 10 groundwater samples collected between 2 and 30 m depths at one test site. A positive correlation was observed between the DOC (4-132 mg/L) and U concentrations (20-603 μg/L). The association of U and DOC was examined directly using on-line coupling of Asymmetrical Flow Field-Flow Fractionation (AsFlFFF) with UV absorbance (UVA) and inductively coupled plasma-mass spectrometer (ICP-MS) detectors. This method has the advantages of utilizing very small sample volumes (20-50 μL) as well as giving molecular weight information on U-organic matter complexes. AsFlFFF-UVA results showed that 47-98% of the DOC (4-136 mg C/L) was recovered in the AsFlFFF analysis, of which 25-64% occurred in the resolvable peak. This peak corresponded to a weight-average molecular weight of about 900-1400 Daltons (Da). In all cases, AsFlFFF-ICP-MS suggested that ≤ 2% of the U, likely present as U(VI), was complexed with the DOC. This result was in good agreement with the U speciation modeling performed on the sample taken from the 2.3 m depth, which predicted approximately 3% DOC-complexed U. This good agreement suggests that the AsFlFFF-ICP-MS method may be very useful for determining U-organic matter association in small volume samples. Because the pH (7.0-8.1) and carbonate concentrations of these waters

  16. Generation of electromagnetic emission during the injection of dense supersonic plasma flows into arched magnetic field

    NASA Astrophysics Data System (ADS)

    Mansfeld, Dmitry; Golubev, Sergey; Viktorov, Mikhail; Vodopyanov, Alexander; Yushkov, George

    2015-11-01

    Interaction of dense supersonic plasma flows with an inhomogeneous arched magnetic field is one of the key problems in near-Earth and space plasma physics. In this work a new experimental approach is suggested to study interaction of supersonic (ion Mach number up to 2.7) dense (up to 1015cm-3) plasma flows with inhomogeneous magnetic field (an arched magnetic trap with a field strength up to 3.3 T) which opens wide opportunities to model space plasma processes in laboratory conditions. Fully ionized plasma flows with density from 1013cm-3 to 1015cm-3 are created by plasma generator on the basis of pulsed vacuum arc discharge and injected into open magnetic trap across magnetic field lines. The filling of the arched magnetic trap with plasma and further magnetic field lines break by dense plasma flow was accompanied by pulsed electromagnetic emission at electron cyclotron frequency range, which can generated by electrons in the place of intensive deceleration of plasma flow in magnetic field. Grant of Ministry of Education 14.Z50.31.0007.

  17. Interface evolution of a particle in a supersaturated solution affected by a far-field uniform flow

    NASA Astrophysics Data System (ADS)

    Chen, Ming-Wen; Wang, Zi-Dong

    2013-09-01

    The effect of far-field uniform flow on the morphological evolution of a spherical particle in a supersaturated solution affected by a far-field uniform flow is studied by using the matched asymptotic expansion method. The analytical solution for the interface shape, concentration field, and interface velocity of the particle growth shows that the convection induced by the far-field uniform flow facilitates the growth of the spherical particle, the upstream flow imposed on the particle enhances the growth velocity of the interface when the flow comes in, the downstream flow lowers the growth velocity of the surface when the flow goes out, and the interface morphology evolves into a peach-like shape.

  18. An Experimental Investigation of Steady and Unsteady Flow Field in an Axial Flow Turbine

    NASA Technical Reports Server (NTRS)

    Zaccaria, M.; Lakshminarayana, B.

    1997-01-01

    Measurements were made in a large scale single stage turbine facility. Within the nozzle passage measurements were made using a five hole probe, a two-component Laser Doppler Velocimeter (LDV), and a single sensor hot wire probe. These measurements showed weak secondary flows at midchord, and two secondary flow loss cores at the nozzle exit. The casing vortex loss core was the larger of the two. At the exit radial inward flow was found over the entire passage, and was more pronounced in the wake. Nozzle wake decay was found to be more rapid than for an isolated vane row due to the rotor's presence. The midspan rotor flow field was measured using a two-component LDV. Measurements were made from upstream of the rotor to a chord behind the rotor. The distortion of the nozzle wake as it passed through the rotor blade row was determined. The unsteadiness in the rotor flow field was determined. The decay of the rotor wake was also characterized.

  19. Hybrid laminar flow control study

    NASA Technical Reports Server (NTRS)

    1982-01-01

    Hybrid laminar flow control (HLFC) in which leading edge suction is used in conjunction with wing pressure distribution tailoring to postpone boundary layer transition and reduce friction drag was examined. Airfoil design characteristics required for laminar flow control (LFC) were determined. The aerodynamic design of the HLFC wing for a 178 passenger commercial turbofan transport was developed, and a drag was estimated. Systems changes required to install HLFC were defined, and weights and fuel economy were estimated. The potential for 9% fuel reduction for a 3926-km (2120-nmi) mission is identified.

  20. Flow downstream of the heliospheric terminal shock - Magnetic field kinematics

    NASA Technical Reports Server (NTRS)

    Nerney, S.; Suess, S. T.; Schmahl, E. J.

    1991-01-01

    A kinematic model of the interplanetary magnetic field in the heliosheath beyond the solar wind terminal shock is presented in order to evaluate the possible importance of MHD effects in that region of space. The need for this evaluation arises because the interplanetary magnetic field is compressed across the terminal shock and further amplified by the decreasing flow speed beyond the shock. Streamlines which approach the stagnation point before turning in the downstream direction lead to the strongest effects due to the extreme slowing of the solar wind and consequent compression of the embedded magnetic field. The magnetic volume force therefore cannot be neglected on streamlines that approach the heliopause in the upstream direction, where the volume containing them is a large fraction of the overall of the heliosheath in the upstream direction. The increase in the magnetic pressure may act to bring the upstream terminal shock significantly closer to the sun, potentially reconciling a conflict between models and observations.

  1. Online recognition of the multiphase flow regime and study of slug flow in pipeline

    NASA Astrophysics Data System (ADS)

    Liejin, Guo; Bofeng, Bai; Liang, Zhao; Xin, Wang; Hanyang, Gu

    2009-02-01

    single sensor performance. Among various flow patterns of gas-liquid flow, slug flow occurs frequently in the petroleum, chemical, civil and nuclear industries. In the offshore oil and gas field, the maximum slug length and its statistical distribution are very important for the design of separator and downstream processing facility at steady state operations. However transient conditions may be encountered in the production, such as operational upsets, start-up, shut-down, pigging and blowdown, which are key operational and safety issues related to oil field development. So it is necessary to have an understanding the flow parameters under transient conditions. In this paper, the evolution of slug length along a horizontal pipe in gas-liquid flow is also studied in details and then an experimental study of flowrate transients in slug flow is provided. Also, the special gas-liquid flow phenomena easily encountered in the life span of offshore oil fields, called severe slugging, is studied experimentally and some results are presented.

  2. Two-dimensional modeling of preferential water flow and pesticide transport from a tile-drained field

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Preferential flow through soil macropores in tile-drained soils can significantly increase the risk of pollution of surface water bodies by agricultural chemicals such as pesticides. While many field studies have shown the importance of preferential flow in tile-drained fields, few have included det...

  3. Analytical and experimental investigation of flow fields of annular jets with and without swirling flow

    NASA Technical Reports Server (NTRS)

    Simonson, M. R.; Smith, E. G.; Uhl, W. R.

    1974-01-01

    Analytical and experimental studies were performed to define the flowfield of annular jets, with and, without swirling flow. The analytical model treated configurations with variations of flow angularities, radius ratio, and swirl distributions. Swirl distributions characteristic of stator vanes and rotor blade rows, where the total pressure and swirl distributions are related were incorporated in the mathematical model. The experimental studies included tests of eleven nozzle models, both with and, without swirling exhaust flow. Flowfield surveys were obtained and used for comparison with the analytical model. This comparison of experimental and analytical studies served as the basis for evaluation of several empirical constants as required for application of the analysis to the general flow configuration. The analytical model developed during these studies is applicable to the evaluation of the flowfield and overall performance of the exhaust of statorless lift fan systems that contain various levels of exhaust swirl.

  4. Improved Flow-Field Structures for Direct Methanol Fuel Cells

    SciTech Connect

    Gurau, Bogdan

    2013-05-31

    The direct methanol fuel cell (DMFC) is ideal if high energy-density liquid fuels are required. Liquid fuels have advantages over compressed hydrogen including higher energy density and ease of handling. Although state-of-the-art DMFCs exhibit manageable degradation rates, excessive fuel crossover diminishes system energy and power density. Although use of dilute methanol mitigates crossover, the concomitant lowering of the gross fuel energy density (GFED) demands a complex balance-of-plant (BOP) that includes higher flow rates, external exhaust recirculation, etc. An alternative approach is redesign of the fuel delivery system to accommodate concentrated methanol. NuVant Systems Inc. (NuVant) will maximize the GFED by design and assembly of a DMFC that uses near neat methanol. The approach is to tune the diffusion of highly concentrated methanol (to the anode catalytic layer) to the back-diffusion of water formed at the cathode (i.e. in situ generation of dilute methanol at the anode layer). Crossover will be minimized without compromising the GFED by innovative integration of the anode flow-field and the diffusion layer. The integrated flow-field-diffusion-layers (IFDLs) will widen the current and potential DMFC operating ranges and enable the use of cathodes optimized for hydrogen-air fuel cells.

  5. Different elution modes and field programming in gravitational field-flow fractionation. III. Field programming by flow-rate gradient generated by a programmable pump.

    PubMed

    Plocková, J; Chmelík, J

    2001-05-25

    Gravitational field-flow fractionation (GFFF) utilizes the Earth's gravitational field as an external force that causes the settlement of particles towards the channel accumulation wall. Hydrodynamic lift forces oppose this action by elevating particles away from the channel accumulation wall. These two counteracting forces enable modulation of the resulting force field acting on particles in GFFF. In this work, force-field programming based on modulating the magnitude of hydrodynamic lift forces was implemented via changes of flow-rate, which was accomplished by a programmable pump. Several flow-rate gradients (step gradients, linear gradients, parabolic, and combined gradients) were tested and evaluated as tools for optimization of the separation of a silica gel particle mixture. The influence of increasing amount of sample injected on the peak resolution under flow-rate gradient conditions was also investigated. This is the first time that flow-rate gradients have been implemented for programming of the resulting force field acting on particles in GFFF. PMID:11407583

  6. Method of electric field flow fractionation wherein the polarity of the electric field is periodically reversed

    DOEpatents

    Stevens, Fred J.

    1992-01-01

    A novel method of electric field flow fractionation for separating solute molecules from a carrier solution is disclosed. The method of the invention utilizes an electric field that is periodically reversed in polarity, in a time-dependent, wave-like manner. The parameters of the waveform, including amplitude, frequency and wave shape may be varied to optimize separation of solute species. The waveform may further include discontinuities to enhance separation.

  7. Acoustically Generated Flow and Temperature Fields in a Rectangular Cavity

    NASA Astrophysics Data System (ADS)

    Farouk, Bakhtier; Oran, Elaine

    1998-11-01

    Flows induced by a vibrating transducer in a gas-filled two-dimensional cavity are investigated by solving the two-dimensional compressible Navier-Stokes equations. The transducer (driver) is located along the left vertical wall of the cavity whereas the right rigid wall acts as an acoustic reflector. Both the left and right vertical walls of the cavity are considered to be conducting (isothermal) walls. The top and the bottom walls are insulated. The frequency of the driver was varied between 10 and 500 kHz. The length of the cavity was adjusted such that standing waves are formed within the cavity, which in turn create well defined vortical flows (acoustic streaming. The characteristics of the two-dimensional acoustically generated flows are studied systematically by varying the frequency and amplitude of the motion of the transducer and the aspect ratio of the cavity. The result exhibit organized flow structures within the cavity and the existence of lateral temperature gradients. Such acoustically induced temperature gradients are essential in the operation of thermoacoustic engines and refrigerators. The effect of cooling or heating the reflector wall on the acoustically generated flows are also investigated. Long time solutions of the governing equations exhibit the existence of pseudo-steady oscillatory flow conditions.

  8. Effect of asymmetrical flow field-flow fractionation channel geometry on separation efficiency.

    PubMed

    Ahn, Ji Yeon; Kim, Ki Hun; Lee, Ju Yong; Williams, P Stephen; Moon, Myeong Hee

    2010-06-11

    The separation efficiencies of three different asymmetrical flow field-flow fractionation (AF4) channel designs were evaluated using polystyrene latex standards. Channel breadth was held constant for one channel (rectangular profile), and was reduced either linearly (trapezoidal profile) or exponentially (exponential profile) along the length for the other two. The effective void volumes of the three channel types were designed to be equivalent. Theoretically, under certain flow conditions, the mean channel flow velocity of the exponential channel could be arranged to remain constant along the channel length, thereby improving separation in AF4. Particle separation obtained with the exponential channel was compared with particle separation obtained with the trapezoidal and rectangular channels. We demonstrated that at a certain flow rate condition (outflow/inflow rate=0.2), the exponential channel design indeed provided better performance with respect to the separation of polystyrene nanoparticles in terms of reducing band broadening. While the trapezoidal channel exhibited a little poorer performance than the exponential, the strongly decreasing mean flow velocity in the rectangular channel resulted in serious band broadening, a delay in retention time, and even failure of larger particles to elute. PMID:20439106

  9. Measurements of Turbulent Flow Field in Separate Flow Nozzles with Enhanced Mixing Devices - Test Report

    NASA Technical Reports Server (NTRS)

    Bridges, James

    2002-01-01

    As part of the Advanced Subsonic Technology Program, a series of experiments was conducted at NASA Glenn Research Center on the effect of mixing enhancement devices on the aeroacoustic performance of separate flow nozzles. Initial acoustic evaluations of the devices showed that they reduced jet noise significantly, while creating very little thrust loss. The explanation for the improvement required that turbulence measurements, namely single point mean and RMS statistics and two-point spatial correlations, be made to determine the change in the turbulence caused by the mixing enhancement devices that lead to the noise reduction. These measurements were made in the summer of 2000 in a test program called Separate Nozzle Flow Test 2000 (SFNT2K) supported by the Aeropropulsion Research Program at NASA Glenn Research Center. Given the hot high-speed flows representative of a contemporary bypass ratio 5 turbofan engine, unsteady flow field measurements required the use of an optical measurement method. To achieve the spatial correlations, the Particle Image Velocimetry technique was employed, acquiring high-density velocity maps of the flows from which the required statistics could be derived. This was the first successful use of this technique for such flows, and shows the utility of this technique for future experimental programs. The extensive statistics obtained were likewise unique and give great insight into the turbulence which produces noise and how the turbulence can be modified to reduce jet noise.

  10. Ground Based Studies of Thermocapillary Flows in Levitated Drops

    NASA Technical Reports Server (NTRS)

    Sadhal, Satwindar Singh; Trinh, Eugene H.

    1996-01-01

    Ground-based experiments together with analytical studies are presently being conducted for levitated drops. Both acoustic and electrostatic techniques are being employed to achieve levitation of drops in a gaseous environment. The scientific effort is principally on the thermal and the fluid phenomena associated with the local heating of levitated drops, both at 1-g and at low-g. In particular, the thermocapillary flow associated with local spot heating is being studied. Fairly stable acoustic levitation of drops has been achieved with some exceptions when random rotational motion of the drop persists. The flow visualization has been carried out by light scattering from smoke particles for the exterior flow and fluorescent tracer particles in the drop. The results indicate a lack of axial symmetry in the internal flow even though the apparatus and the heating are symmetric. The theoretical studies for the past year have included fundamental analyses of acoustically levitated spherical drops. The flow associated with a particle near the velocity antinode is being investigated by the singular perturbation technique. As a first step towards understanding the effect of the particle displacement from the antinode, the flow field about the node has been calculated for the first time. The effect of the acoustic field on the interior of a liquid drop has also been investigated. The results predict that the internal flow field is very weak.

  11. Velocity measurement and flow field simulation of a sit-type water closet

    NASA Astrophysics Data System (ADS)

    Cheng, Wei-Seng; Jhang, Chao-Yu

    2012-06-01

    Evacuation of a sit-type water closet is driven by siphon effect established inside its water passage when flushed. However, the flow condition in the passage of a water closet is still unclear. It is clear that we have a fundamental understanding of the flow phenomenon before we know how to enhance siphon effect. This research studies the flow phenomenon in the passage imbedded in a sit-type water closet by using both experimental measurement and numerical simulation. Particle-tracing technique by using a high speed camera is used to measure velocity of particles flowing with the water flow in a full scale model. These velocity values of particles are transformed to estimate the mean velocity of the water flow in the passage of the model throughout the time span of a flush. This velocity profile in time compares reasonably well in trend with literature data and is used to validate the results of subsequent numerical simulations. Numerical simulations of the transient flushed-flow based on in-compressible, viscous, turbulent and two-phase assumptions are performed. Simulation result agrees reasonably well with measurement data and can provide detail information of the transient flow field. Numerical simulation reveals that a clear circulation center exists in the flow and when siphon effect takes place water flow will reach its highest velocity value.

  12. FlowSim/FlowRisk: A code system for studying risk associated with material process flows

    SciTech Connect

    Kaufman, A.M.

    1993-10-01

    The need to study and assess life-cycle risks of Pu release by nuclear warheads during peace time lead to the development of a code suite which could model day to day operations involving nuclear weapons and calculate the associated risk involved in these proceedings. The life-cycle study called LIONSHARE is described in Reference 1. The code that models the flow is called FlowSim. The code that evaluates the associated risk is called FlowRisk. We shall concentrate here on the methodology used by FlowSim in modeling material flows. FlowRisk, mainly a postprocessor of FlowSim runs, will be dealt with in less detail.

  13. Simultaneous solution for core magnetic field and fluid flow beneath an electrically conducting mantle

    NASA Technical Reports Server (NTRS)

    Voorhies, Coerte V.; Nishihama, Masahiro

    1993-01-01

    The effects of laterally homogeneous mantle electrical conductivity were included in steady, frozen-flux core surface flow estimation along with refinements in method and weighting. The refined method allows simultaneous solution for both the initial radial geomagnetic field component at the core-mantle boundary (CMB) and the sub-adjacent fluid motion; it also features Gauss' method for solving the non-linear inverse problem associated with steady motional induction. The tradeoff between spatial complexity of the derived flows and misfit to the weighted Definitive Geomagnetic Reference Field models (DGRF's) is studied for various mantle conductivity profiles. For simple flow and a fixed initial geomagnetic condition, a fairly high deep-mantle conductivity performs better than either insulating or weakly conducting profiles; however, a thin, very high conductivity layer at the base of the mantle performs almost as well. Simultaneous solution for both initial geomagnetic field and flow reduces the misfit per degree of freedom even more than does changing the mantle conductivity profile. Moreover, when both core field and flow are estimated, the performance of the solutions and the derived flows become insensitive to the conductivity profile.

  14. Simultaneous solution for core magnetic field and fluid flow beneath an electrically conducting mantle

    NASA Technical Reports Server (NTRS)

    Voorhies, Goerte V.; Nishihama, Masahiro

    1994-01-01

    The effects of laterally homogeneous mantle electrical conductivity have been included in steady, frozen-flux core surface flow estimation along with refinements in method and weighting. The refined method allows simultaneous solution for both the initial radial geomagnetic field component at the core-mantle boundary and the subadjacent fluid motion; it also features Gauss' method for solving the nonlinear inverse problem associated with steady motional induction. The trade-off between spatial complexity of the derived flows and misfit to the weighted Definitive Geomagnetic Reference Field models is studied for various mantle conductivity profiles. For simple flow and a fixed initial geomagnetic condition a fairly high deep-mantle conductivity performs better than either insulating or weakly conducting profiles; however, a thin, very high conductivity layer at the base of the mantle performs almost as well. Simultaneous solution for both initial geomagnetic field and fluid flow reduces the misfit per degree of freedom even more than does changing the mantle conductivity profile. Moreover, when both core field and flow are estimated, the performance of the solutions and the derived flows become insensitive to the conductivity profile.

  15. Simultaneous solution for core magnetic field and fluid flow beneath an electrically conducting mantle

    NASA Astrophysics Data System (ADS)

    Voorhies, Goerte V.; Nishihama, Masahiro

    1994-04-01

    The effects of laterally homogeneous mantle electrical conductivity have been included in steady, frozen-flux core surface flow estimation along with refinements in method and weighting. The refined method allows simultaneous solution for both the initial radial geomagnetic field component at the core-mantle boundary and the subadjacent fluid motion; it also features Gauss' method for solving the nonlinear inverse problem associated with steady motional induction. The trade-off between spatial complexity of the derived flows and misfit to the weighted Definitive Geomagnetic Reference Field models is studied for various mantle conductivity profiles. For simple flow and a fixed initial geomagnetic condition a fairly high deep-mantle conductivity performs better than either insulating or weakly conducting profiles; however, a thin, very high conductivity layer at the base of the mantle performs almost as well. Simultaneous solution for both initial geomagnetic field and fluid flow reduces the misfit per degree of freedom even more than does changing the mantle conductivity profile. Moreover, when both core field and flow are estimated, the performance of the solutions and the derived flows become insensitive to the conductivity profile.

  16. An analysis of the flow field in the region of the ASRM field joints

    NASA Technical Reports Server (NTRS)

    Dill, Richard A.; Whitesides, Harold R.

    1992-01-01

    The flow field in the region of a solid rocket motor field joint is very important since fluid dynamic and mechanical propellant stresses can couple to cause a motor failure at a joint. Presented here is an examination of the flow field in the region of the Advanced Solid Rocket Motor (ASRM) field joints. The analyses were performed as a first step in assessing the design of the ASRM forward and aft field joints in order to assure the proper operation of the motor prior to further development of test firing. The analyses presented here were performed by employing a two-dimensional axisymmetric assumption. Fluent/BFC, a three dimensional full Navier-Stokes flow field code, was used to make the numerical calculations. This code utilizes a staggered grid formulation along with the SIMPLER numerical algorithm. Wall functions are used to determine the character of the laminar sublayer, and a standard kappa-epsilon turbulence model is used to close the fluid dynamic equations. The analyses performed to this date verify that the ASRM field joint design operates properly. The fluid dynamic stresses at the field joints are small due to the inherent design of the field joints. A problem observed in some other solid rocket motors is that large fluid dynamic stresses are generated at the motor joint on the downstream propellant grain due to forward facing step geometries. The design of the ASRM field joints are such that this is not a problem as shown by the analyses. Also, the analyses of the inhibitor stub left protruding into the port flow from normal propellant burn back show that more information is necessary to complete these analyses. These analyses were performed as parametric analyses in relation to the height of the inhibitor stub left protruding into the motor port. A better estimate of the amount of the inhibitor stub remaining at later burn times must be determined since the height which the inhibitor stub protrudes into the port flow drastically affects the fluid

  17. An analysis of the flow field in the region of the ASRM field joints

    NASA Astrophysics Data System (ADS)

    Dill, Richard A.; Whitesides, Harold R.

    1992-07-01

    The flow field in the region of a solid rocket motor field joint is very important since fluid dynamic and mechanical propellant stresses can couple to cause a motor failure at a joint. Presented here is an examination of the flow field in the region of the Advanced Solid Rocket Motor (ASRM) field joints. The analyses were performed as a first step in assessing the design of the ASRM forward and aft field joints in order to assure the proper operation of the motor prior to further development of test firing. The analyses presented here were performed by employing a two-dimensional axisymmetric assumption. Fluent/BFC, a three dimensional full Navier-Stokes flow field code, was used to make the numerical calculations. This code utilizes a staggered grid formulation along with the SIMPLER numerical algorithm. Wall functions are used to determine the character of the laminar sublayer, and a standard kappa-epsilon turbulence model is used to close the fluid dynamic equations. The analyses performed to this date verify that the ASRM field joint design operates properly. The fluid dynamic stresses at the field joints are small due to the inherent design of the field joints. A problem observed in some other solid rocket motors is that large fluid dynamic stresses are generated at the motor joint on the downstream propellant grain due to forward facing step geometries. The design of the ASRM field joints are such that this is not a problem as shown by the analyses. Also, the analyses of the inhibitor stub left protruding into the port flow from normal propellant burn back show that more information is necessary to complete these analyses. These analyses were performed as parametric analyses in relation to the height of the inhibitor stub left protruding into the motor port. A better estimate of the amount of the inhibitor stub remaining at later burn times must be determined since the height which the inhibitor stub protrudes into the port flow drastically affects the fluid

  18. A study of grout flow pattern analysis

    SciTech Connect

    Lee, S. Y.; Hyun, S.

    2013-01-10

    A new disposal unit, designated as Salt Disposal Unit no. 6 (SDU6), is being designed for support of site accelerated closure goals and salt nuclear waste projections identified in the new Liquid Waste System plan. The unit is cylindrical disposal vault of 380 ft diameter and 43 ft in height, and it has about 30 million gallons of capacity. Primary objective was to develop the computational model and to perform the evaluations for the flow patterns of grout material in SDU6 as function of elevation of grout discharge port, and slurry rheology. A Bingham plastic model was basically used to represent the grout flow behavior. A two-phase modeling approach was taken to achieve the objective. This approach assumes that the air-grout interface determines the shape of the accumulation mound. The results of this study were used to develop the design guidelines for the discharge ports of the Saltstone feed materials in the SDU6 facility. The focusing areas of the modeling study are to estimate the domain size of the grout materials radially spread on the facility floor under the baseline modeling conditions, to perform the sensitivity analysis with respect to the baseline design and operating conditions such as elevation of discharge port, discharge pipe diameter, and grout properties, and to determine the changes in grout density as it is related to grout drop height. An axi-symmetric two-phase modeling method was used for computational efficiency. Based on the nominal design and operating conditions, a transient computational approach was taken to compute flow fields mainly driven by pumping inertia and natural gravity. Detailed solution methodology and analysis results are discussed here.

  19. The 3-dimensional radio mapping experiment /SBH/ on ISEE-C. [interplanetary magnetic field structure for solar wind flow studies using type 3 bursts

    NASA Technical Reports Server (NTRS)

    Knoll, R.; Epstein, G.; Hoang, S.; Huntzinger, G.; Steinberg, J. L.; Fainberg, J.; Grena, F.; Stone, R. G.; Mosier, S. R.

    1978-01-01

    The SBH experiment on ISEE-C will provide maps of the large scale structure of the interplanetary magnetic field from ten solar radii altitude to the earth orbit, in and out of the ecliptic. The SBH instrument will track type III solar radio bursts at 24 frequencies in the range 30 kHz-2 MHz thus providing the positions of 24 points along the line of force which guides the electrons producing the radio radiation. The antennas are two dipoles: one (90 m long) in the spin plane, the other (15 m long) along the spin axis. The receiver was designed for high sensitivity (0.3 microV in 3 kHz BW), high intermodulation rejection (80 dB/1 microV input for order 2 products), large dynamic range (70 dB), high selectivity (-30-dB response 6.5 kHz away from the center frequency of 10.7 MHz for the 3 kHz BW channels), and high reliability (expected orbital life: 3 years).

  20. Mean-field description of plastic flow in amorphous solids

    NASA Astrophysics Data System (ADS)

    Lin, Jie; Wyart, Matthieu

    Failure and flow of amorphous materials are central to various phenomena including earthquakes and landslides. There is accumulating evidence that the yielding transition between a flowing and an arrested phase is a critical phenomenon, but the associated exponents are not understood, even at a mean-field level where the validity of popular models is debated. Here we solve a mean-field model that captures the broad distribution of the mechanical noise generated by plasticity, whose behavior is related to biased Lévy flights near an absorbing boundary. We compute the exponent θ characterizing the density of shear transformation P (x) ~xθ , where x is the stress increment beyond which they yield. We find that after an isotropic thermal quench, θ = 1 / 2 . However, θ depends continuously on the applied shear stress, this dependence is not monotonic, and its value at the yield stress is not universal. The model rationalizes previously unexplained observations, and captures reasonably well the value of exponents in three dimensions. These results support that it is the true mean-field model that applies in large dimension, and raise fundamental questions on the nature of the yielding transition.

  1. Mean-Field Description of Plastic Flow in Amorphous Solids

    NASA Astrophysics Data System (ADS)

    Lin, Jie; Wyart, Matthieu

    2016-01-01

    Failure and flow of amorphous materials are central to various phenomena including earthquakes and landslides. There is accumulating evidence that the yielding transition between a flowing and an arrested phase is a critical phenomenon, but the associated exponents are not understood, even at a mean-field level where the validity of popular models is debated. Here, we solve a mean-field model that captures the broad distribution of the mechanical noise generated by plasticity, whose behavior is related to biased Lévy flights near an absorbing boundary. We compute the exponent θ characterizing the density of shear transformation P (x )˜xθ, where x is the stress increment beyond which they yield. We find that after an isotropic thermal quench, θ =1 /2 . However, θ depends continuously on the applied shear stress; this dependence is not monotonic, and its value at the yield stress is not universal. The model rationalizes previously unexplained observations and captures reasonably well the value of exponents in three dimensions. Values of exponents in four dimensions are accurately predicted. These results support the fact that it is the true mean-field model that applies in large dimensions, and they raise fundamental questions about the nature of the yielding transition.

  2. The Development of a Full Field Three-Dimensional Microscale Flow Measurement Technique for Application to Near Contact Line Flows

    NASA Technical Reports Server (NTRS)

    He, Qun; Hallinan, Kevin

    1996-01-01

    The goal of this paper is to present details of the development of a new three-dimensional velocity field measurement technique which can be used to provide more insight into the dynamics of thin evaporating liquid films (not limited to just low heat inputs for the heat transfer) and which also could prove useful for the study of spreading and wetting phenomena and other microscale flows.

  3. Experimental Analyses of Flow Field Structures around Clustered Linear Aerospike Nozzles

    NASA Astrophysics Data System (ADS)

    Taniguchi, Mashio; Mori, Hideo; Nishihira, Ryutaro; Niimi, Tomohide

    2005-05-01

    An aerospike nozzle has been expected as a candidate for an engine of a reusable space shuttle to respond to growing demand for rocket-launching and its cost reduction. In this study, the flow field structures in any cross sections around clustered linear aerospike nozzles are visualized and analyzed, using laser induced fluorescence (LIF) of NO seeded in the carrier gas N2. Since flow field structures are affected mainly by pressure ratio (Ps/Pa, Ps: the source pressure in a reservoir, Pa: the ambient pressure in the vacuum chamber), the clustered linear aerospike nozzle is set inside a vacuum chamber to carry out the experiments in the wide range of pressure ratios from 75 to 200. Flow fields are visualized in several cross-sections, demonstrating the complicated three-dimensional flow field structures. Pressure sensitive paint (PSP) of PtTFPP bound by poly-IBM-co-TFEM is also applied to measurement of the complicated pressure distribution on the spike surface, and to verification of contribution of a truncation plane to the thrust. Finally, to examine the effect of the sidewalls attached to the aerospike nozzle, the flow fields around the nozzle with the sidewalls are compared with those without sidewalls.

  4. Results of a study of Mach number and Reynolds number effects on the lee side vortex flow field characteristics of an ogive-cylinder-frustum-cylinder at angles of attack to 25 degrees, volume 1

    NASA Technical Reports Server (NTRS)

    Foley, J. E.

    1972-01-01

    An experimental program was conducted to survey the lee side vortex flow field about an ogive-cylinder-frustum-cylinder at angles of attack to 25 degrees for two Reynolds numbers at Mach number 0.8, and one Reynolds number at Mach number 1.96. The data were obtained using miniature 5-port conical pressure probes calibrated for angle of attack and roll angle over a Mach number range of 0.6 to 3.0. The results are presented here as local flow field properties and circulation strengths for various body stations.

  5. Planetary geomorphology field studies: Washington and Alaska

    NASA Technical Reports Server (NTRS)

    Malin, M. C.

    1984-01-01

    Field studies of terrestrial landforms and the processes that shape them provide new directions to the study of planetary features. Investigations discussed address principally mudflow phenomena and drainage development. At the Valley of 10,000 Smokes (Katmai, AK) and Mount St. Helens, WA, studies of the development of erosional landforms (in particular, drainage) on fresh, new surfaces permitted analysis of the result of competition between geomorphic processes. Of specific interest is the development of stream pattern as a function of the competition between perennial seepage overland flow (from glacial or groundwater sources), ephemeral overland flow (from pluvial or seasonal melt sources), and ephemeral/perennial groundwater sapping, as a function of time since initial resurfacing, material properties, and seasonal/annual environmental conditions.

  6. The significance of late-stage processes in lava flow emplacement: squeeze-ups in the 2001 Etna flow field

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

    The general processes associated with the formation and activity of ephemeral boccas in lava flow fields are well documented (e.g. Pinkerton & Sparks 1976; Polacci & Papale 1997). The importance of studying such behaviour is illustrated by observations of the emplacement of a basaltic andesite flow at Parícutin during the 1940s. Following a pause in advance of one month, this 8 km long flow was reactivated by the resumption of supply from the vent, which forced the rapid drainage of stagnant material in the flow front region. The material extruded during drainage was in a highly plastic state (Krauskopf 1948), and its displacement allowed hot fluid lava from the vent to be transported in a tube to the original flow front, from where it covered an area of 350,000 m2 in one night (Luhr & Simkin 1993). Determining when a flow has stopped advancing, and cannot be drained in such a manner, is therefore highly important in hazard assessment and flow modelling, and our ability to do this may be improved through the examination of relatively small-scale secondary extrusions and boccas. The 2001 flank eruption of Mt. Etna, Sicily, resulted in the emplacement of a 7 km long compound `a`ā flow field over a period of 23 days. During emplacement, many ephemeral boccas were observed in the flow field, which were active for between two and at least nine days. The longer-lived examples initially fed well-established flows that channelled fresh material from the main vent. With time, as activity waned, the nature of the extruded material changed. The latest stages of development of all boccas involved the very slow extrusion of material that was either draining from higher parts of the flow or being forced out of the flow interior as changing local flow conditions pressurised parts of the flow that had been stagnant for some time. Here we describe this late-stage activity of the ephemeral boccas, which resulted in the formation of ‘squeeze-ups' of lava with a markedly different

  7. CFD-based aero-optical analysis of flow fields over two-dimensional cavities with active flow control

    NASA Astrophysics Data System (ADS)

    Tan, Yan

    Prediction and control of optical wave front distortions and aberrations in a high energy laser beam due to interaction with an unsteady highly non-uniform flow field is of great importance in the development of directed energy weapon systems for Unmanned Air Vehicles (UAV). The unsteady shear layer over the weapons bay cavity is the primary cause of this distortion of the optical wave front. The large scale vortical structure of the shear layer over the cavity can be significantly reduced by employing an active flow control technique combined with passive flow control. This dissertation explores various active and passive control methods to suppress the cavity oscillations and thereby improve the aero-optics of cavity flow. In active flow control technique, a steady or a pulsed jet is applied at the sharp leading edge of cavities of different aspect ratios L/D (=2, 4, 15), where L and D are the width and the depth of a cavity respectively. In the passive flow control approach, the sharp leading or trailing edge of the cavity is modified into a round edge of different radii. Both of these active and passive flow control approaches are studied independently and in combination. Numerical simulations are performed, with and without active flow control for subsonic free stream flow past two-dimensional sharp and round leading or trailing edge cavities using Unsteady Reynolds-Averaged Navier-Stokes (URANS) equations with a two-equation Shear Stress Transport (SST) turbulence model or a hybrid SST/Large Eddy Simulation (LES) model. Aero-optical analysis is developed and applied to all the simulation cases. Index of refraction and Optical Path Difference (OPD) are compared for flow fields without and with active flow control. Root-Mean-Square (RMS) value of OPD is calculated and compared with the experimental data, where available. The effect of steady and pulsed blowing on buffet loading on the downstream face of the cavity is also computed. Using the numerical

  8. Behavior of nanoparticle clouds around a magnetized microsphere under magnetic and flow fields

    NASA Astrophysics Data System (ADS)

    Magnet, C.; Kuzhir, P.; Bossis, G.; Meunier, A.; Nave, S.; Zubarev, A.; Lomenech, C.; Bashtovoi, V.

    2014-03-01

    When a micron-sized magnetizable particle is introduced into a suspension of nanosized magnetic particles, the nanoparticles accumulate around the microparticle and form thick anisotropic clouds extended in the direction of the applied magnetic field. This phenomenon promotes colloidal stabilization of bimodal magnetic suspensions and allows efficient magnetic separation of nanoparticles used in bioanalysis and water purification. In the present work, the size and shape of nanoparticle clouds under the simultaneous action of an external uniform magnetic field and the flow have been studied in detail. In experiments, a dilute suspension of iron oxide nanoclusters (of a mean diameter of 60 nm) was pushed through a thin slit channel with the nickel microspheres (of a mean diameter of 50 μm) attached to the channel wall. The behavior of nanocluster clouds was observed in the steady state using an optical microscope. In the presence of strong enough flow, the size of the clouds monotonically decreases with increasing flow speed in both longitudinal and transverse magnetic fields. This is qualitatively explained by enhancement of hydrodynamic forces washing the nanoclusters away from the clouds. In the longitudinal field, the flow induces asymmetry of the front and the back clouds. To explain the flow and the field effects on the clouds, we have developed a simple model based on the balance of the stresses and particle fluxes on the cloud surface. This model, applied to the case of the magnetic field parallel to the flow, captures reasonably well the flow effect on the size and shape of the cloud and reveals that the only dimensionless parameter governing the cloud size is the ratio of hydrodynamic-to-magnetic forces—the Mason number. At strong magnetic interactions considered in the present work (dipolar coupling parameter α ≥2), the Brownian motion seems not to affect the cloud behavior.

  9. Verifying a Simplified Fuel Oil Flow Field Measurement Protocol

    SciTech Connect

    Henderson, H.; Dentz, J.; Doty, C.

    2013-07-01

    The Better Buildings program is a U.S. Department of Energy program funding energy efficiency retrofits in buildings nationwide. The program is in need of an inexpensive method for measuring fuel oil consumption that can be used in evaluating the impact that retrofits have in existing properties with oil heat. This project developed and verified a fuel oil flow field measurement protocol that is cost effective and can be performed with little training for use by the Better Buildings program as well as other programs and researchers.

  10. The numerical calculation of inviscid plume flow fields

    NASA Technical Reports Server (NTRS)

    Salas, M. D.

    1974-01-01

    A numerical method is presented for the computation of inviscid, axisymmetric, underexpanded plumes. The numerical techniques developed by Moretti (1969, 1971, 1972) are used in conjunction with Abbett's (1970) theory for locating the Mach disk. Abbett's theory and three other prediction methods are compared to experimental results. Results are presented for jets exhausting into static ambients and supersonic free stream. Detailed results from a flow field with multiple Mach disks are also presented. Finally, some problems associated with the computation of very small Mach disks are discussed.

  11. Real gas flow fields about three dimensional configurations

    NASA Technical Reports Server (NTRS)

    Balakrishnan, A.; Lombard, C. K.; Davy, W. C.

    1983-01-01

    Real gas, inviscid supersonic flow fields over a three-dimensional configuration are determined using a factored implicit algorithm. Air in chemical equilibrium is considered and its local thermodynamic properties are computed by an equilibrium composition method. Numerical solutions are presented for both real and ideal gases at three different Mach numbers and at two different altitudes. Selected results are illustrated by contour plots and are also tabulated for future reference. Results obtained compare well with existing tabulated numerical solutions and hence validate the solution technique.

  12. [Flow field test on the tangential section of polypropylene tubular membrane module annular gap in rotating linear tangential flow].

    PubMed

    Wang, Chengduan; Chen, Wenmei; Li, Jianming; Jiang, Guangming

    2002-07-01

    A new type of polypropylene tubular membrane apparatus of rotating cross flow was designed to study experimentally the flow field characteristics of the tangential section of the membrane annular gap. The authors designed rotary linear tangential flow tubular membrane separator and its test system for the first time. Through the system, the flow field of rotary linear tangential flow with the advanced Particle Image Velocimetry (PIV) was tested for the first time. A lot of streamlines and vorticity maps of the tangential section of separator in different operation conditions were obtained. The velocity distribution characteristics were analyzed quantitatively: 1. At non-vortex area, no matter how the operation parameters change, the velocity near to rotary tangential flow entrance was higher than the velocity far from entrance at the same radial coordinates. At vortex area, generally the flow velocity of inner vortex was lower than the outer vortex. At the vortex center, the velocity was lowest, the tangential velocity were equal to zero generally. At the vortex center zone, the tangential velocity was less than the axial velocity. 2. Under test operations, the tangential velocity and axial velocity of vortices borders are 1-2 times of average axial velocity of membrane module annular gap. The maximum tangential velocity and axial velocity of ellipse vortices were 2-6 times of average axial velocity of membrane module annular gap. 3. The vortices that are formed on the tangential section, there existed mass transfer between inner and outer parts of fluid. Much fluid of outer vortices got into the inner ones, which was able to prevent membrane tube from particles blocking up very soon. PMID:12371104

  13. Phase-locked flow field analysis in a synthetic human larynx model

    NASA Astrophysics Data System (ADS)

    Lodermeyer, Alexander; Becker, Stefan; Döllinger, Michael; Kniesburges, Stefan

    2015-04-01

    The fluid flow within a human larynx plays an essential role in the fluid-structure-acoustic interaction during voice production. This study addresses the flow field downstream of aerodynamically driven, synthetic vocal folds. In order to quantitatively investigate the supraglottal formation of the flow field within one oscillation cycle of the vocal folds, a phase-locked PIV technique is introduced. The pseudo-time-resolved measurement results were averaged for each phase angle. When including a supraglottal channel, the jet was deflected from the centerline of the supraglottal channel and changed the direction of deflection in different cycles. The result is a bistable flow field. Therefore, a sorting method based on the mean cyclic supraglottal pressure difference was introduced. For both states of the flow field, a recirculation area was detected, interacting with the arising glottal jet in every oscillation cycle. This interaction could be identified as the major cause for supraglottal jet deflection, and the sense of rotation of the recirculation area defined the direction of deflection. The asymmetric structure of the flow field was caused by the geometric boundary condition, i.e., due to the present supraglottal channel. An additional key factor was found to be the contact between the two vocal folds in each oscillation cycle which interrupted the jet flow periodically. Removing the supraglottal channel resulted in a symmetric jet location. When avoiding vocal fold contact, the bistable behavior vanished and the jet was steadily deflected to one lateral side. In the present study, it cannot be confirmed that the Coanda effect is responsible for the deflection.

  14. Pressure losses and flow field distortion induced by tip clearance of centrifugal and axial compressors

    NASA Astrophysics Data System (ADS)

    Senoo, Yasutoshi

    1987-03-01

    The flow field near the tip of compressor rotor blades is distorted by leakage through the tip clearance and the performance of the compressor is deteriorated. The literature regarding the tip clearance of compressor blades consists of computational fluid mechanics and experimental studies on the flow field and the pressure loss. Empirical equations expressing the pressure loss and the efficiency drop are varied. They relate to the lift coefficient in different ways, depending upon the ways of understanding the mechanics of pressure losses. These methods are examined and compared. Also, a brief discussion is made on the optimum value of the tip clearance.

  15. Computation of the flow field in an annular gas turbine combustor

    NASA Technical Reports Server (NTRS)

    Cline, Michael C.; Deur, John M.; Micklow, Gerald J.; Harper, Michael R.; Kundu, Krishna P.

    1993-01-01

    The KIVA-II code was modified to calculate the 3D flow field in a typical annular gas turbine combustor. The airblast fuel nozzle, cooling baffle, cooling slots, primary and dilution jets, and effusion cooling (bleed) pads were accounted for in this calculation. The turbulence and combustion were modeled using the k-epsilon model and laminar Arrhenius kinetics, respectively. The fuel was modeled as an evaporating liquid spray. The results illustrate the complicated flow fields present in such combustors. From the results obtained to date it appears that the modified KIVA-II code can be used to study the effects of different annular combustor designs and operating conditions.

  16. The applications of optical computerized tomography (OCT) in cold and hot complex flow fields

    NASA Astrophysics Data System (ADS)

    Chen, Yun-Yun; Chen, Li-zhu; Gu, Fang

    2014-11-01

    Optical computerized tomography (OCT), as a branch of computerized tomography (CT) techniques, has been widely used to display and diagnose a variety of complex flow fields, due to its characteristics of real-time, stable, non-contact and can supply 3-D distributions. In practical applications, we found some different phenomenon when they are adopted in clod and hot complex flow fields. In this paper, the cold and hot flow field's OCT diagnosis is analyzed and compared. The results show that 1) OCT can directly reflect the spatial distribution of the measured flow field's refractive index, for both the cold and the hot complex flow fields; 2) OCT can reflect the boundary or structure of the cold flow fields, but could not well done for the hot flow fields. The involved results will help us to make better use of OCT methods to diagnose various cold or hot complex flow fields.

  17. Flow field measurements for cylindrical configurations in a hypersonic wind tunnel: Windward and leeward flow fields

    NASA Technical Reports Server (NTRS)

    Bertin, J. J.; Lamb, J. P.; Center, K. R.; Graumann, B. W.

    1971-01-01

    Windward and leeward measurements were made for a variety of simulated infinite cylinders exposed to hypersonic streams over an angle of attack from 30 deg to 90 deg. For the range of conditions included in the study, the following conclusions are made: (1) Swept cylinder theory provides a reasonable correlation of the measured laminar heat transfer rates from the plane of symmetry. (2) The boundary layer transition criteria in the plane of symmetry are a function of the transverse curvature. (3) Relaminarization of the circumferential boundary layer for a right circular cylinder was observed at the highest Reynolds number tested. (4) The effect of leeside geometry on the average heat transfer rate can be correlated with a single geometric parameter which is dependent on the location of separation. (5) The relationship of leeward heating to angle of attack is virtually linear for each cross section. (6) No systematic effect of free stream Reynolds number was observed.

  18. Time-resolved mixing and flow-field measurements during droplet formation in a flow-focusing junction

    NASA Astrophysics Data System (ADS)

    Carrier, Odile; Gökhan Ergin, F.; Li, Huai-Zhi; Watz, Bo B.; Funfschilling, Denis

    2015-08-01

    Highly monodispersed emulsions can be produced in microfluidic flow-focusing junctions (Anna et al 2003 Appl. Phys. Lett. 82 364-6, Baroud et al 2010 Lab Chip 10 2032-45). This is the reason why many industrial processes in the medical industry among others are based on droplet manipulation and involve at some point a step of dripping within a junction. However, only a few studies have focused on the flow field inside and outside the droplet, even though it is a necessary step for understanding the physical mechanism involved and for modeling the droplet formation process. Water-in-oil emulsions are produced in flow-focusing junctions of square cross sections. The fluids constituting the emulsion are (i) a 5.0 mPa·s silicon oil for the oil phase and (ii) distilled water containing 2.0 wt% of sodium dodecyl sulfate surfactant for the aqueous phase. Time-resolved shadow particle images are acquired using a microscale particle image velocimetry (µPIV) system and flow fields are calculated using an adaptive PIV algorithm in combination with dynamic masking. Inside the microchannel and in the permanent regime, the droplet has an internal circulation that has been well established by Sarrazin et al (AICHE J. 52 4061-70). But during the formation of a droplet in a flow-focusing junction, the flow field is not so well known, and the circulation in the finger flows forward along the sides and returns along the center. The mechanism can be described in terms of four distinct steps: droplet growth, necking, rupture, and recoil. The liquid expelled from the neck just before rupture is also well observed. The flow field and mixing are measured in detail during a complete cycle of formation of a main droplet and satellite droplets using high-speed imaging. This allows us to develop a better understanding of the different forces that are present and of the physical mechanism of droplet formation.

  19. Large Eddy Simulations of Double-Ruler Electromagnetic Field Effect on Transient Flow During Continuous Casting

    NASA Astrophysics Data System (ADS)

    Singh, Ramnik; Thomas, Brian G.; Vanka, Surya P.

    2014-06-01

    Transient flow during nominally steady conditions is responsible for many intermittent defects during the continuous casting of steel. The double-ruler electromagnetic field configuration, or "FC-Mold EMBr," is popular in commercial slab casting as it provides independent control of the applied static field near the jet and free surface regions of the mold. In the current study, transient flow in a typical commercial caster is simulated in the absence and in the presence of a double-ruler magnetic field, with rulers of equal strengths. Large eddy simulations with the in-house code CU-FLOW resolve the important transient behavior, using grids of over five million cells with a fast parallel solver. In the absence of a magnetic field, a double-roll pattern is observed, with transient unbalanced behavior, high surface velocities (~0.5 m/s), surface vortex formation, and very large surface-level fluctuations (~±12 mm). Applying the magnetic field suppresses the unbalanced behavior, producing a more complex mold flow pattern, but with much lower surface velocities (~0.1 m/s), and a flat surface level with small level fluctuations (<±1 mm). Nail board measurements taken at this commercial caster, in the absence of the field, matched reasonably well with the calculated results, both quantitatively and qualitatively.

  20. Magnetic Field Effect on the Stability of Flow Induced by a Rotating Magnetic Field

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Volz, M. P.; Gillies, D. C.

    1999-01-01

    A linear stability analysis has been performed for the flow induced by a rotating magnetic field in a cylindrical column filled with electrically conducting fluid. The first transition is time- independent and results in the generation of Taylor vortices. The critical value of the magnetic Taylor number has been examined as a function of the strength of the transverse rotating magnetic field, the strength of an axial static magnetic field, and thermal buoyancy. Increasing the transverse field increases the critical magnetic Taylor number and decreases the aspect ratio of the Taylor vortices at the onset of instability. An increase in the axial magnetic field also increases the critical magnetic Taylor number but increases the aspect ratio of the Taylor vortices. Thermal buoyancy is found to have only a negligible effect on the onset of instability.

  1. Magnetic Field Effect on the Stability of Flow Induced by a Rotating Magnetic Field

    NASA Technical Reports Server (NTRS)

    Mazuruk, K.; Gillies, D. C.; Volz, M. P.

    1999-01-01

    A linear stability analysis has been performed for the flow induced by a rotating magnetic field in a cylindrical column filled with electrically conducting fluid. The first transition is time-independent and results in the generation of Taylor vortices. The critical value of the magnetic Taylor number has been examined as a function of the strength of the transverse rotating magnetic field, the strength of an axial static magnetic field, and thermal buoyancy. Increasing the transverse field increases the critical magnetic Taylor number and decreases the aspect ratio of the Taylor vortices at the onset of instability. An increase in the axial magnetic field also increases the critical magnetic Taylor number but increases the aspect ratio of the Taylor vortices. Thermal buoyancy is found to have only a negligible effect on the onset of instability.

  2. Field test of a biological assumption of instream flow models

    SciTech Connect

    Cada, G.F.; Sale, M.J.; Cushman, R.M.; Loar, J.M.

    1983-01-01

    Hydraulic-rating methods are an attractive means of deriving instream flow recommendations at many small hydropower sites because they represent a compromise between relatively inexpensive, low-resolution, discharge methods and the costly, complex, habitat evaluation models. Like the other methods, however, they rely on certain biological assumptions about the relationship between aquatic biota and streamflow characteristics. One such assumption is that benthic production available as food for fishes is proportional to stream bottom area. Wetted perimeter is an easily measured physical parameter which represents bottom area and that is a function of discharge. Therefore, wetted perimeter should reflect the benthic food resource available to support stream fishes under varying flows. As part of a larger effort to compare a number of existing instream flow assessment methods in southern Appalachian trout streams, we examined the validity of the benthos/wetted perimeter relationship at four field sites. Benthos samples were taken at permanent riffle transects over a variety of discharges and were used to relate observed benthos densities to the fluctuations in wetted perimeter and streamflow in these systems. For most of the sites and taxa examined, benthic densities did not show a consistent relationship with discharge/wetted perimeter dynamics. Our analysis indicates that simple physical habitat descriptors obtained from hydraulic-rating models do not provide sufficient information on the response of benthic organisms to decreased discharges. Consequently, these methods may not be sufficient to protect aquatic resources in water-use conflicts.

  3. Investigation of a supersonic cruise fighter model flow field

    NASA Technical Reports Server (NTRS)

    Reubush, D. E.; Bare, E. A.

    1985-01-01

    An investigation was conducted in the Langley 16-Foot Transonic Tunnel to survey the flow field around a model of a supersonic cruise fighter configuration. Local values of angle of attack, side flow, Mach number, and total pressure ratio were measured with a single multi-holed probe in three survey areas on a model previously used for nacelle/nozzle integration investigations. The investigation was conducted at Mach numbers of 0.6, 0.9, and 1.2, and at angles of attack from 0 deg to 10 deg. The purpose of the investigation was to provide a base of experimental data with which theoretically determined data can be compared. To that end the data are presented in tables as well as graphically, and a complete description of the model geometry is included as fuselage cross sections and wing span stations. Measured local angles of attack were generally greater than free stream angle of attack above the wing and generally smaller below. There were large spanwise local angle-of-attack and side flow gradients above the wing at the higher free stream angles of attack.

  4. Online Coupling of Flow-Field Flow Fractionation and Single Particle Inductively Coupled Plasma-Mass Spectrometry: Characterization of Nanoparticle Surface Coating Thickness and Aggregation State

    EPA Science Inventory

    Surface coating thickness and aggregation state have strong influence on the environmental fate, transport, and toxicity of engineered nanomaterials. In this study, flow-field flow fractionation coupled on-line with single particle inductively coupled plasma-mass spectrometry i...

  5. TAS: A Transonic Aircraft/Store flow field prediction code

    NASA Technical Reports Server (NTRS)

    Thompson, D. S.

    1983-01-01

    A numerical procedure has been developed that has the capability to predict the transonic flow field around an aircraft with an arbitrarily located, separated store. The TAS code, the product of a joint General Dynamics/NASA ARC/AFWAL research and development program, will serve as the basis for a comprehensive predictive method for aircraft with arbitrary store loadings. This report described the numerical procedures employed to simulate the flow field around a configuration of this type. The validity of TAS code predictions is established by comparison with existing experimental data. In addition, future areas of development of the code are outlined. A brief description of code utilization is also given in the Appendix. The aircraft/store configuration is simulated using a mesh embedding approach. The computational domain is discretized by three meshes: (1) a planform-oriented wing/body fine mesh, (2) a cylindrical store mesh, and (3) a global Cartesian crude mesh. This embedded mesh scheme enables simulation of stores with fins of arbitrary angular orientation.

  6. ASRM Multi-Port Igniter Flow Field Analysis

    NASA Technical Reports Server (NTRS)

    Kania, Lee; Dumas, Catherine; Doran, Denise

    1993-01-01

    The Advanced Solid Rocket Motor (ASRM) program was initiated by NASA in response to the need for a new generation rocket motor capable of providing increased thrust levels over the existing Redesigned Solid Rocket Motor (RSRM) and thus augment the lifting capacity of the space shuttle orbiter. To achieve these higher thrust levels and improve motor reliability, advanced motor design concepts were employed. In the head end of the motor, for instance, the propellent cast has been changed from the conventional annular configuration to a 'multi-slot' configuration in order to increase the burn surface area and guarantee rapid motor ignition. In addition, the igniter itself has been redesigned and currently features 12 exhaust ports in order to channel hot igniter combustion gases into the circumferential propellent slots. Due to the close proximity of the igniter ports to the propellent surfaces, new concerns over possible propellent deformation and erosive burning have arisen. The following documents the effort undertaken using computational fluid dynamics to perform a flow field analysis in the top end of the ASRM motor to determine flow field properties necessary to permit a subsequent propellent fin deformation analysis due to pressure loading and an assessment of the extent of erosive burning.

  7. Control of Flowing Liquid Films by Electrostatic Fields in Space

    NASA Technical Reports Server (NTRS)

    Griffing, E. M.; Bankoff, S. G.; Schluter, R. A.; Miksis, M. J.

    1999-01-01

    The interaction of a spacially varying electric field and a flowing thin liquid film is investigated experimentally for the design of a proposed light weight space radiator. Electrodes are utilized to create a negative pressure at the bottom of a fluid film and suppress leaks if a micrometeorite punctures the radiator surface. Experimental pressure profiles under a vertical falling film, which passes under a finite electrode, show that fields of sufficient strength can be used safely in such a device. Leak stopping experiments demonstrate that leaks can be stopped with an electric field in earth gravity. A new type of electrohydrodynamic instability causes waves in the fluid film to develop into 3D cones and touch the electrode at a critical voltage. Methods previously used to calculate critical voltages for non moving films are shown to be inappropriate for this situation. The instability determines a maximum field which may be utilized in design, so the possible dependence of critical voltage on electrode length, height above the film, and fluid Reynolds number is discussed.

  8. Fast wave power flow along SOL field lines in NSTX

    NASA Astrophysics Data System (ADS)

    Perkins, R. J.; Bell, R. E.; Diallo, A.; Gerhardt, S.; Hosea, J. C.; Jaworski, M. A.; Leblanc, B. P.; Kramer, G. J.; Phillips, C. K.; Roquemore, L.; Taylor, G.; Wilson, J. R.; Ahn, J.-W.; Gray, T. K.; Green, D. L.; McLean, A.; Maingi, R.; Ryan, P. M.; Jaeger, E. F.; Sabbagh, S.

    2012-10-01

    On NSTX, a major loss of high-harmonic fast wave (HHFW) power can occur along open field lines passing in front of the antenna over the width of the scrape-off layer (SOL). Up to 60% of the RF power can be lost and at least partially deposited in bright spirals on the divertor floor and ceiling [1,2]. The flow of HHFW power from the antenna region to the divertor is mostly aligned along the SOL magnetic field [3], which explains the pattern of heat deposition as measured with infrared (IR) cameras. By tracing field lines from the divertor back to the midplane, the IR data can be used to estimate the profile of HHFW power coupled to SOL field lines. We hypothesize that surface waves are being excited in the SOL, and these results should benchmark advanced simulations of the RF power deposition in the SOL (e.g., [4]). Minimizing this loss is critical optimal high-power long-pulse ICRF heating on ITER while guarding against excessive divertor erosion.[4pt] [1] J.C. Hosea et al., AIP Conf Proceedings 1187 (2009) 105. [0pt] [2] G. Taylor et al., Phys. Plasmas 17 (2010) 056114. [0pt] [3] R.J. Perkins et al., to appear in Phys. Rev. Lett. [0pt] [4] D.L. Green et al., Phys. Rev. Lett. 107 (2011) 145001.

  9. An empirically derived model of field-scale gene flow in winter wheat

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The potential introduction of wheat (Triticum aestivum L.) cultivars with transgenic traits has generated increased interest in pollen-mediated gene flow (PMGF). The objectives of this study were to estimate wheat PMGF between commercial fields across multiple years and locations, and to compare est...

  10. Flows for non-smooth vector fields with subexponentially integrable divergence

    NASA Astrophysics Data System (ADS)

    Clop, Albert; Jiang, Renjin; Mateu, Joan; Orobitg, Joan

    2016-07-01

    In this paper, we study flows associated to Sobolev vector fields with subexponentially integrable divergence. Our approach is based on the transport equation following DiPerna-Lions [17]. A key ingredient is to use a quantitative estimate of solutions to the Cauchy problem of transport equation to obtain the regularity of density functions.

  11. A water tunnel flow visualization study of the F-15

    NASA Technical Reports Server (NTRS)

    Lorincz, D. J.

    1978-01-01

    Water tunnel studies were performed to qualitatively define the flow field of the F-15 aircraft. Two lengthened forebodies, one with a modified cross-sectional shape, were tested in addition to the basic forebody. Particular emphasis was placed on defining vortex flows generated at high angles of attack. The flow visualization tests were conducted in the Northrop diagnostic water tunnel using a 1/48-scale model of the F-15. Flow visualization pictures were obtained over an angle-of-attack range to 55 deg and sideslip angles up to 10 deg. The basic aircraft configuration was investigated in detail to determine the vortex flow field development, vortex path, and vortex breakdown characteristics as a function of angle of attack and sideslip. Additional tests showed that the wing upper surface vortex flow fields were sensitive to variations in inlet mass flow ratio and inlet cowl deflection angle. Asymmetries in the vortex systems generated by each of the three forebodies were observed in the water tunnel at zero sideslip and high angles of attack.

  12. Modelling field-data of preferential flow in paddy soil induced by earthworm burrows.

    PubMed

    Sander, Till; Gerke, Horst H

    2009-02-16

    Dye tracer studies revealed that earthworm burrows in the compacted plough pan of a Chinese paddy rice field can serve as preferential flow paths. It is, however, unclear whether the observed bypass of the compacted soil horizon might be explained by differences in hydraulic properties between the plough pan, the worm burrows with a surrounding denser drilosphere and the un-compacted subsoil, or by lower-permeable macropore walls. The objective is to separately analyse effects of the individual flow domains and to identify possible limiting factors (bottlenecks) in the flow system for better soil drainage management. Hydraulic properties are inversely estimated from in situ measurements of pressure heads and evaporation by using HYDRUS_1D code. Field data of 2D pressure head progression after dye tracer infiltration in the vicinity of worm burrows are simulated using HYDRUS_2D. The axisymmetric 2D flow model considers a highly permeable cylindrical macropore region in the centre of the flow domain, assuming Darcy's law is valid. The match between simulated and measured pressure head fields improved after including a lower-permeable drilosphere pore domain. Scenario simulations show that the inflow into the 'bypass-flow' domain are reduced by the homogenized topsoil (i.e., after puddling) and limited if the macropore domain is relatively shallow. The results suggest that basic structural features may in this concept be considered as one possibility to describe observed preferential flow patterns. The separate consideration of soil structural effects may help developing and improving management strategies for manipulation of preferential flow in soils of paddy fields. PMID:19064301

  13. Novel Applications of Magnetic Fields for Fluid Flow Control and for Simulating Variable Gravity Conditions

    NASA Technical Reports Server (NTRS)

    Ramachandran, N.

    2005-01-01

    Static and dynamic magnetic fields have been used to control convection in many materials processing applications. In most of the applications, convection control (damping or enhancement) is achieved through the Lorentz force that can be tailored to counteract/assist dominant system flows. This technique has been successfully applied to liquids that are electrically conducting, such as high temperature melts of semiconductors, metals and alloys, etc. In liquids with low electrical conductivity such as ionic solutions of salts in water, the Lorentz force is weak and hence not very effective and alternate ways of flow control are necessary. If the salt in solution is paramagnetic then the variation of magnetic susceptibility with temperature and/or concentration can be used for flow control. For thermal buoyancy driven flows this can be accomplished in a temperature range below the Curie point of the salt. The magnetic force is proportional to the magnetic susceptibility and the product of the magnetic field and its gradient. By suitably positioning the experiment cell in the magnet, system flows can be assisted or countered, as desired. A similar approach can be extended to diamagnetic substances and fluids but the required magnetic force is considerably larger than that required for paramagnetic substances. The presentation will provide an overview of work to date on a NASA fluid physics sponsored project that aims to test the hypothesis of convective flow control using strong magnetic fields in protein crystal growth. The objective is to understand the nature of the various forces that come into play, delineate causative factors for fluid flow and to quantify them through experiments, analysis, and numerical modeling. The seminar will report specifically on the experimental results using paramagnetic salts and solutions in magnetic fields and compare them to analytical predictions. Applications of the concept to protein crystallization studies will be discussed

  14. Field and wind tunnel modeling of an idealized street canyon flow

    NASA Astrophysics Data System (ADS)

    Blackman, K.; Perret, L.; Savory, E.; Piquet, T.

    2015-04-01

    The present work examines the flow field in a simple street canyon that has been modeled at full-scale and at 1:200 scale in a wind tunnel. It relies on the detailed analysis of statistics of both flows including two-point correlation coefficients, an approach not commonly done for canyon flows. Comparison between the field and wind tunnel study has demonstrated good agreement for the mean velocity and turbulence statistics, which are typically within 20%. However, significant differences in the along-canyon mean and turbulent components have been observed and are shown to be a result of the changing of the ambient wind direction and low frequency motion present in the field. As the wind direction changes over time the result is a channeling of flow along the canyon axis. This phenomenon cannot be accurately reproduced by the wind tunnel model, which produces nominally 2D flow. The turbulence dynamics were investigated through two-point spatial correlation of the streamwise, spanwise and vertical components, which show agreement to within 15-30% between the field and wind tunnel results. From estimation of boundary layer log-law parameters it has been shown that using a single point reference velocity measurement at 10 m height to estimate the boundary layer log-law parameters is unreliable in the present case.

  15. Instantaneous velocity field imaging instrument for supersonic reacting flows

    NASA Technical Reports Server (NTRS)

    Allen, M. G.; Davis, S. J.; Kessler, W. J.; Legner, H. H.; Mcmanus, K. R.; Mulhall, P. A.; Parker, T. E.; Sonnenfroh, D. M.

    1993-01-01

    The technical tasks conducted to develop and demonstrate a new gas velocity measurement technique for high enthalpy reacting flows is described. The technique is based on Doppler-shifted Planar Laser-induced Fluorescence (PLIF) imaging of the OH radical. The imaging approach permits, in principle, single-shot measurements of the 2-D distribution of a single velocity component in the measurement plane, and is thus a technique of choice for applications in high enthalpy transient flow facilities. In contrast to previous work in this area, the present program demonstrated an approach which modified the diagnostic technique to function under the constraints of practical flow conditions of engineering interest, rather than vice-versa. In order to accomplish the experimental demonstrations, the state-of-the-art in PLIF diagnostic techniques was advanced in several ways. Each of these tasks is described in detail and is intended to serve as a reference in supporting the transition of this new capability to the fielded PLIF instruments now installed at several national test facilities. Among the new results of general interest in LlF-based flow diagnostics, a detailed set of the first measurements of the collisional broadening and shifting behavior of OH (1,0) band transitions in H7-air combustion environments is included. Such measurements are critical in the design of a successful strategy for PLIF velocity imaging; they also relate to accurate concentration and temperature measurements, particularly in compressible flow regimes. Furthermore, the results shed new light on the fundamental relationship between broadening and energy transfer collisions in OH A(sup 2)Sigma(+)v(sup ') = 1. The first single-pulse, spectrally-resolved measurements of the output of common pulsed dye lasers were also produced during the course of this effort. As with the OH broadening measurements, these data are a significant aspect of a successful velocity imaging strategy, and also have

  16. Algebraic structure of general electromagnetic fields and energy flow

    SciTech Connect

    Hacyan, Shahen

    2011-08-15

    Highlights: > Algebraic structure of general electromagnetic fields in stationary spacetime. > Eigenvalues and eigenvectors of the electomagnetic field tensor. > Energy-momentum in terms of eigenvectors and Killing vector. > Explicit form of reference frame with vanishing Poynting vector. > Application of formalism to Bessel beams. - Abstract: The algebraic structures of a general electromagnetic field and its energy-momentum tensor in a stationary space-time are analyzed. The explicit form of the reference frame in which the energy of the field appears at rest is obtained in terms of the eigenvectors of the electromagnetic tensor and the existing Killing vector. The case of a stationary electromagnetic field is also studied and a comparison is made with the standard short-wave approximation. The results can be applied to the general case of a structured light beams, in flat or curved spaces. Bessel beams are worked out as example.

  17. Experimental study of periodic flow effects on spanwise vortex

    NASA Astrophysics Data System (ADS)

    Garcia Molina, Cruz Daniel; Lopez Sanchez, Erick Javier; Ruiz Chavarria, Gerardo; Medina Ovando, Abraham

    2014-11-01

    We present an experimental study about the spanwise vortex produced in a flow going out of a channel in shallow waters. This vortex travels in front of the dipole. The velocity field measurement was done using the PIV technique, and DPIVsoft (https://www.irphe.fr/ ~meunier/) was used for data processing. In this case the flow has a periodic forcing to simulate ocean tides. The experiment was conducted in a channel with variable width and the measurements were made using three different values of the aspect ratio width-depth. We present results of the position, circulation of this spanwise vortex and the flow inversion effect. The change of flow direction modify the intensity of the vortex, but it does not destroy it. The vertical components of the velocity field contributes particle transport. G. Ruiz Chavarria, E. J. Lopez Sanchez and C. D. Garcia Molina acknowledge DGAPA-UNAM by support under project IN 116312 (Vorticidad y ondas no lineales en fluidos).

  18. The flow field investigations of no load conditions in axial flow fixed-blade turbine

    NASA Astrophysics Data System (ADS)

    Yang, J.; Gao, L.; Wang, Z. W.; Zhou, X. Z.; Xu, H. X.

    2014-03-01

    During the start-up process, the strong instabilities happened at no load operation in a low head axial flow fixed-blade turbine, with strong pressure pulsation and vibration. The rated speed can not reach until guide vane opening to some extent, and stable operation could not be maintained under the rated speed at some head, which had a negative impact on the grid-connected operation of the unit. In order to find the reason of this phenomenon, the unsteady flow field of the whole flow passage at no load conditions was carried out to analyze the detailed fluid field characteristics including the pressure pulsation and force imposed on the runner under three typical heads. The main hydraulic cause of no load conditions instability was described. It is recommended that the power station should try to reduce the no-load running time and go into the high load operation as soon as possible when connected to grid at the rated head. Following the recommendations, the plant operation practice proved the unstable degree of the unit was reduced greatly during start up and connect to the power grid.

  19. Hot accretion flow with ordered magnetic field, outflow, and saturated conduction

    NASA Astrophysics Data System (ADS)

    Faghei, Kazem

    2013-05-01

    The importance of thermal conduction on hot accretion flow is confirmed by observations of hot gas that surrounds Sgr A∗ and a few other nearby galactic nuclei. On the other hand, the existence of outflow in accretion flows is confirmed by observations and magnetohydrodynamic (MHD) simulations. In this research, we study the influence of both thermal conduction and outflow on hot accretion flows with ordered magnetic field. Since the inner regions of hot accretion flows are, in many cases, collisionless with an electron mean free path due to Coulomb collision larger than the radius, we use a saturated form of thermal conduction, as is appropriate for weakly collisional systems. We also consider the influence of outflow on accretion flow as a sink for mass, and the radial and the angular momentum, and energy taken away from or deposited into the inflow by outflow. The magnetic field is assumed to have a toroidal component and a vertical component as well as a stochastic component. We use a radially self-similar method to solve the integrated equations that govern the behavior of such accretion flows. The solutions show that with an ordered magnetic field, both the surface density and the sound speed decrease, while the radial and angular velocities increase. We found that a hot accretion flow with thermal conduction rotates more quickly and accretes more slowly than that without thermal conduction. Moreover, thermal conduction reduces the influences of the ordered magnetic field on the angular velocities and the sound speed. The study of this model with the magnitude of outflow parameters implies that the gas temperature decreases due to mass, angular momentum, and energy loss. This property of outflow decreases for high thermal conduction.

  20. Magnetic field distribution in the plasma flow generated by a plasma focus discharge

    SciTech Connect

    Mitrofanov, K. N.; Krauz, V. I. Myalton, V. V.; Velikhov, E. P.; Vinogradov, V. P.; Vinogradova, Yu. V.

    2014-11-15

    The magnetic field in the plasma jet propagating from the plasma pinch region along the axis of the chamber in a megajoule PF-3 plasma focus facility is studied. The dynamics of plasma with a trapped magnetic flow is analyzed. The spatial sizes of the plasma jet region in which the magnetic field concentrates are determined in the radial and axial directions. The magnetic field configuration in the plasma jet is investigated: the radial distribution of the azimuthal component of the magnetic field inside the jet is determined. It is shown that the magnetic induction vector at a given point in space can change its direction during the plasma flight. Conclusions regarding the symmetry of the plasma flow propagation relative to the chamber axis are drawn.

  1. Time-resolved PIV measurements of the flow field in a stenosed, compliant arterial model

    NASA Astrophysics Data System (ADS)

    Geoghegan, P. H.; Buchmann, N. A.; Soria, J.; Jermy, M. C.

    2013-05-01

    Compliant (flexible) structures play an important role in several biological flows including the lungs, heart and arteries. Coronary heart disease is caused by a constriction in the artery due to a build-up of atherosclerotic plaque. This plaque is also of major concern in the carotid artery which supplies blood to the brain. Blood flow within these arteries is strongly influenced by the movement of the wall. To study these problems experimentally in vitro, especially using flow visualisation techniques, can be expensive due to the high-intensity and high-repetition rate light sources required. In this work, time-resolved particle image velocimetry using a relatively low-cost light-emitting diode illumination system was applied to the study of a compliant flow phantom representing a stenosed (constricted) carotid artery experiencing a physiologically realistic flow wave. Dynamic similarity between in vivo and in vitro conditions was ensured in phantom construction by matching the distensibility and the elastic wave propagation wavelength and in the fluid system through matching Reynolds ( Re) and Womersley number ( α) with a maximum, minimum and mean Re of 939, 379 and 632, respectively, and a α of 4.54. The stenosis had a symmetric constriction of 50 % by diameter (75 % by area). Once the flow rate reached a critical value, Kelvin-Helmholtz instabilities were observed to occur in the shear layer between the main jet exiting the stenosis and a reverse flow region that occurred at a radial distance of 0.34 D from the axis of symmetry in the region on interest 0-2.5 D longitudinally downstream from the stenosis exit. The instability had an axis-symmetric nature, but as peak flow rate was approached this symmetry breaks down producing instability in the flow field. The characteristics of the vortex train were sensitive not only to the instantaneous flow rate, but also to whether the flow was accelerating or decelerating globally.

  2. Two-phase flow numerical simulation of infiltration and groundwater drainage in a rice field

    NASA Astrophysics Data System (ADS)

    Lugomela, G. V.

    Farming of rice normally uses a substantially larger amount of water than other cereal grain crops mainly due to the traditional flooding of rice fields. Flooding of the fields result in a seepage flow condition whereby infiltration occurs at a potential rate. The potential infiltration rate obstructs the free movement of pore-air through the ground surface and gradually compresses the pore-air between the infiltrating wetting front and the groundwater table under which subsurface drains are installed. The Galerkin finite element method (FEM) simulation of two-phase flow of air and water in the porous media of the rice field shows that the subsequent increase in the pore-air pressure makes the pore-air act as a link phase which transfers the effects of the processes taking place in the wetting front above and the saturated zone below the groundwater table. This phenomenon is clearly demonstrated when the results of the two-phase flow simulation are compared to the corresponding single-phase flow simulation which neglects the effect of the pore-air. It is concluded that the ‘ponding’ which appears in rice fields can partly be explained by the resistance offered by the pore-air to the percolation process. The study demonstrates that flooding of rice fields during most of its growth time is not necessary rather it is enough to keep the ground surface just saturated and the rest of the water can be saved.

  3. Computational flow study of the continuous flow ventricular assist device, prototype number 3 blood pump.

    PubMed

    Anderson, J B; Wood, H G; Allaire, P E; Bearnson, G; Khanwilkar, P

    2000-05-01

    A computational fluid dynamics study of blood flow in the continuous flow ventricular assist device, Prototype No. 3 (CFVAD3), which consists of a 4 blade shrouded impeller fully supported in magnetic bearings, was performed. This study focused on the regions within the pump where return flow occurs to the pump inlet, and where potentially damaging shear stresses and flow stagnation might occur: the impeller blade passages and the narrow gap clearance regions between the impeller-rotor and pump housing. Two separate geometry models define the spacing between the pump housing and the impeller's hub and shroud, and a third geometry model defines the pump's impeller and curved blades. The flow fields in these regions were calculated for various operating conditions of the pump. Pump performance curves were calculated, which compare well with experimentally obtained data. For all pump operating conditions, the flow rates within the gap regions were predicted to be toward the inlet of the pump, thus recirculating a portion of the impeller flow. Two smaller gap clearance regions were numerically examined to reduce the recirculation and to improve pump efficiency. The computational and geometry models will be used in future studies of a smaller pump to determine increased pump efficiency and the risk of hemolysis due to shear stress, and to insure the washing of blood through the clearance regions to prevent thrombosis. PMID:10848679

  4. Nanoparticle separation with a miniaturized asymmetrical flow field-flow fractionation cartridge

    PubMed Central

    Müller, David; Cattaneo, Stefano; Meier, Florian; Welz, Roland; de Mello, Andrew J.

    2015-01-01

    Asymmetrical Flow Field-Flow Fractionation (AF4) is a separation technique applicable to particles over a wide size range. Despite the many advantages of AF4, its adoption in routine particle analysis is somewhat limited by the large footprint of currently available separation cartridges, extended analysis times and significant solvent consumption. To address these issues, we describe the fabrication and characterization of miniaturized AF4 cartridges. Key features of the down-scaled platform include simplified cartridge and reagent handling, reduced analysis costs and higher throughput capacities. The separation performance of the miniaturized cartridge is assessed using certified gold and silver nanoparticle standards. Analysis of gold nanoparticle populations indicates shorter analysis times and increased sensitivity compared to conventional AF4 separation schemes. Moreover, nanoparticulate titanium dioxide populations exhibiting broad size distributions are analyzed in a rapid and efficient manner. Finally, the repeatability and reproducibility of the miniaturized platform are investigated with respect to analysis time and separation efficiency. PMID:26258119

  5. Hollow-Fiber Flow Field-Flow Fractionation for Mass Spectrometry: From Proteins to Whole Bacteria

    NASA Astrophysics Data System (ADS)

    Reschiglian, Pierluigi; Zattoni, Andrea; Rambaldi, Diana Cristina; Roda, Aldo; Hee Moon, Myeong

    Mass spectrometry (MS) provides analyte identification over a wide molar-mass range. However, particularly in the case of complex matrices, this ability is often enhanced by the use of pre-MS separation steps. A separation, prototype technique for the "gentle" fractionation of large/ultralarge analytes, from proteins to whole cells, is here described to reduce complexity and maintain native characteristics of the sample before MS analysis. It is based on flow field-flow fractionation, and it employs a micro-volume fractionation channel made of a ca. 20 cm hollow-fiber membrane of sub-millimeter section. The key advantages of this technique lie in the low volume and low-cost of the channel, which makes it suitable to a disposable usage. Fractionation performance and instrumental simplicity make it an interesting methodology for in-batch or on-line pre-MS treatment of such samples.

  6. Nanoparticle separation with a miniaturized asymmetrical flow field-flow fractionation cartridge.

    PubMed

    Müller, David; Cattaneo, Stefano; Meier, Florian; Welz, Roland; de Mello, Andrew J

    2015-01-01

    Asymmetrical Flow Field-Flow Fractionation (AF4) is a separation technique applicable to particles over a wide size range. Despite the many advantages of AF4, its adoption in routine particle analysis is somewhat limited by the large footprint of currently available separation cartridges, extended analysis times and significant solvent consumption. To address these issues, we describe the fabrication and characterization of miniaturized AF4 cartridges. Key features of the down-scaled platform include simplified cartridge and reagent handling, reduced analysis costs and higher throughput capacities. The separation performance of the miniaturized cartridge is assessed using certified gold and silver nanoparticle standards. Analysis of gold nanoparticle populations indicates shorter analysis times and increased sensitivity compared to conventional AF4 separation schemes. Moreover, nanoparticulate titanium dioxide populations exhibiting broad size distributions are analyzed in a rapid and efficient manner. Finally, the repeatability and reproducibility of the miniaturized platform are investigated with respect to analysis time and separation efficiency. PMID:26258119

  7. Nanoparticle separation with a miniaturized asymmetrical flow field-flow fractionation cartridge

    NASA Astrophysics Data System (ADS)

    Müller, David; Cattaneo, Stefano; Meier, Florian; Welz, Roland; deMello, Andrew

    2015-07-01

    Asymmetrical Flow Field-Flow Fractionation (AF4) is a separation technique applicable to particles over a wide size range. Despite the many advantages of AF4, its adoption in routine particle analysis is somewhat limited by the large footprint of currently available separation cartridges, extended analysis times and significant solvent consumption. To address these issues, we describe the fabrication and characterization of miniaturized AF4 cartridges. Key features of the scale-down platform include simplified cartridge and reagent handling, reduced analysis costs and higher throughput capacities. The separation performance of the miniaturized cartridge is assessed using certified gold and silver nanoparticle standards. Analysis of gold nanoparticle populations indicates shorter analysis times and increased sensitivity compared to conventional AF4 separation schemes. Moreover, nanoparticulate titanium dioxide populations exhibiting broad size distributions are analyzed in a rapid and efficient manner. Finally, the repeatability and reproducibility of the miniaturized platform are investigated with respect to analysis time and separation efficiency.

  8. Generation of electromagnetic emission during the injection of dense supersonic plasma flows into arched magnetic field

    NASA Astrophysics Data System (ADS)

    Viktorov, Mikhail; Golubev, Sergey; Mansfeld, Dmitry; Vodopyanov, Alexander

    2016-04-01

    Interaction of dense supersonic plasma flows with an inhomogeneous arched magnetic field is one of the key problems in near-Earth and space plasma physics. It can influence on the energetic electron population formation in magnetosphere of the Earth, movement of plasma flows in magnetospheres of planets, energy release during magnetic reconnection, generation of electromagnetic radiation and particle precipitation during solar flares eruption. Laboratory study of this interaction is of big interest to determine the physical mechanisms of processes in space plasmas and their detailed investigation under reproducible conditions. In this work a new experimental approach is suggested to study interaction of supersonic (ion Mach number up to 2.7) dense (up to 1015 cm‑3) plasma flows with inhomogeneous magnetic field (an arched magnetic trap with a field strength up to 3.3 T) which opens wide opportunities to model space plasma processes in laboratory conditions. Fully ionized plasma flows with density from 1013 cm‑3 to 1015 cm‑3 are created by plasma generator on the basis of pulsed vacuum arc discharge. Then plasma is injected in an arched open magnetic trap along or across magnetic field lines. The filling of the arched magnetic trap with dense plasma and further magnetic field lines break by dense plasma flow were experimentally demonstrated. The process of plasma deceleration during the injection of plasma flow across the magnetic field lines was experimentally demonstrated. Pulsed plasma microwave emission at the electron cyclotron frequency range was observed. It was shown that frequency spectrum of plasma emission is determined by position of deceleration region in the magnetic field of the magnetic arc, and is affected by plasma density. Frequency spectrum shifts to higher frequencies with increasing of arc current (plasma density) because the deceleration region of plasma flow moves into higher magnetic field. The observed emission can be related to the

  9. Adaptive hydrological flow field modeling based on water body extraction and surface information

    NASA Astrophysics Data System (ADS)

    Puttinaovarat, Supattra; Horkaew, Paramate; Khaimook, Kanit; Polnigongit, Weerapong

    2015-01-01

    Hydrological flow characteristic is one of the prime indicators for assessing flood. It plays a major part in determining drainage capability of the affected basin and also in the subsequent simulation and rainfall-runoff prediction. Thus far, flow directions were typically derived from terrain data which for flat landscapes are obscured by other man-made structures, hence undermining the practical potential. In the absence (or diminutive) of terrain slopes, water passages have a more pronounced effect on flow directions than elevations. This paper, therefore, presents detailed analyses and implementation of hydrological flow modeling from satellite and topographic images. Herein, gradual assignment based on support vector machine was applied to modified normalized difference water index and a digital surface model, in order to ensure reliable water labeling while suppressing modality-inherited artifacts and noise. Gradient vector flow was subsequently employed to reconstruct the flow field. Experiments comparing the proposed scheme with conventional water boundary delineation and flow reconstruction were presented. Respective assessments revealed its advantage over the generic stream burning. Specifically, it could extract water body from studied areas with 98.70% precision, 99.83% recall, 98.76% accuracy, and 99.26% F-measure. The correlations between resultant flows and those obtained from the stream burning were as high as 0.80±0.04 (p≤0.01 in all resolutions).

  10. Flow dynamics at a river confluence on Mississippi River: field measurement and large eddy simulation

    NASA Astrophysics Data System (ADS)

    Le, Trung; Khosronejad, Ali; Bartelt, Nicole; Woldeamlak, Solomon; Peterson, Bonnie; Dewall, Petronella; Sotiropoulos, Fotis; Saint Anthony Falls Laboratory, University of Minnesota Team; Minnesota Department of Transportation Team

    2015-11-01

    We study the dynamics of a river confluence on Mississippi River branch in the city of Minneapolis, Minnesota, United States. Field measurements by Acoustic Doppler Current Profiler using on-board GPS tracking were carried out for five campaigns in the summer of 2014 and 2015 to collect both river bed elevation data and flow fields. Large Eddy Simulation is carried out to simulate the flow field with the total of 100 million grid points for the domain length of 3.2 km. The simulation results agree well with field measurements at measured cross-sections. The results show the existence of wake mode on the mixing interface of two branches near the upstream junction corner. The mutual interaction between the shear layers emanating from the river banks leading to the formation of large scale energetic structures that leads to ``switching'' side of the flow coherent structures. Our result here is a feasibility study for the use of eddy-resolving simulations in predicting complex flow dynamics in medium-size natural rivers. This work is funded by Minnesota Dept. Transportation and Minnesota Institute of Supercomputing.

  11. (Studies in quantum field theory)

    SciTech Connect

    Not Available

    1990-01-01

    During the period 4/1/89--3/31/90 the theoretical physics group supported by Department of Energy Contract No. AC02-78ER04915.A015 and consisting of Professors Bender and Shrauner, Associate Professor Papanicolaou, Assistant Professor Ogilvie, and Senior Research Associate Visser has made progress in many areas of theoretical and mathematical physics. Professors Bender and Shrauner, Associate Professor Papanicolaou, Assistant Professor Ogilvie, and Research Associate Visser are currently conducting research in many areas of high energy theoretical and mathematical physics. These areas include: strong-coupling approximation; classical solutions of non-Abelian gauge theories; mean-field approximation in quantum field theory; path integral and coherent state representations in quantum field theory; lattice gauge calculations; the nature of perturbation theory in large order; quark condensation in QCD; chiral symmetry breaking; the 1/N expansion in quantum field theory; effective potential and action in quantum field theories, including OCD; studies of the early universe and inflation, and quantum gravity.

  12. Numerical Study of Unsteady Flow in Centrifugal Cold Compressor

    NASA Astrophysics Data System (ADS)

    Zhang, Ning; Zhang, Peng; Wu, Jihao; Li, Qing

    In helium refrigeration system, high-speed centrifugal cold compressor is utilized to pumped gaseous helium from saturated liquid helium tank at low temperature and low pressure for producing superfluid helium or sub-cooled helium. Stall and surge are common unsteady flow phenomena in centrifugal cold compressors which severely limit operation range and impact efficiency reliability. In order to obtain the installed range of cold compressor, unsteady flow in the case of low mass flow or high pressure ratio is investigated by the CFD. From the results of the numerical analysis, it can be deduced that the pressure ratio increases with the decrease in reduced mass flow. With the decrease of the reduced mass flow, backflow and vortex are intensified near the shroud of impeller. The unsteady flow will not only increase the flow loss, but also damage the compressor. It provided a numerical foundation of analyzing the effect of unsteady flow field and reducing the flow loss, and it is helpful for the further study and able to instruct the designing.

  13. Numerical simulation of supersonic and hypersonic inlet flow fields

    NASA Technical Reports Server (NTRS)

    Mcrae, D. Scott; Kontinos, Dean A.

    1995-01-01

    This report summarizes the research performed by North Carolina State University and NASA Ames Research Center under Cooperative Agreement NCA2-719, 'Numerical Simulation of Supersonic and Hypersonic Inlet Flow Fields". Four distinct rotated upwind schemes were developed and investigated to determine accuracy and practicality. The scheme found to have the best combination of attributes, including reduction to grid alignment with no rotation, was the cell centered non-orthogonal (CCNO) scheme. In 2D, the CCNO scheme improved rotation when flux interpolation was extended to second order. In 3D, improvements were less dramatic in all cases, with second order flux interpolation showing the least improvement over grid aligned upwinding. The reduction in improvement is attributed to uncertainty in determining optimum rotation angle and difficulty in performing accurate and efficient interpolation of the angle in 3D. The CCNO rotational technique will prove very useful for increasing accuracy when second order interpolation is not appropriate and will materially improve inlet flow solutions.

  14. Application of strand meshes to complex aerodynamic flow fields

    NASA Astrophysics Data System (ADS)

    Katz, Aaron; Wissink, Andrew M.; Sankaran, Venkateswaran; Meakin, Robert L.; Chan, William M.

    2011-07-01

    We explore a new approach for viscous computational fluid dynamics calculations for external aerodynamics around geometrically complex bodies that incorporates nearly automatic mesh generation and efficient flow solution methods. A prismatic-like grid using "strands" is grown a short distance from the body surface to capture the viscous boundary layer, and adaptive Cartesian grids are used throughout the rest of the domain. The approach presents several advantages over established methods: nearly automatic grid generation from triangular or quadrilateral surface tessellations, very low memory overhead, automatic mesh adaptivity for time-dependent problems, and fast and efficient solvers from structured data in both the strand and Cartesian grids.The approach is evaluated for complex geometries and flow fields. We investigate the effects of strand length and strand vector smoothing to understand the effects on computed solutions. Results of three applications using the strand-adaptive Cartesian approach are given, including a NACA wing, isolated V-22 (TRAM) rotor in hover, and the DLR-F6 wing-body transport. The results from these cases show that the strand approach can successfully resolve near-body and off-body features as well as or better than established methods.

  15. Gravitational field-flow fractionation of human hemopoietic stem cells.

    PubMed

    Roda, Barbara; Reschiglian, Pierluigi; Alviano, Francesco; Lanzoni, Giacomo; Bagnara, Gian Paolo; Ricci, Francesca; Buzzi, Marina; Tazzari, Pier Luigi; Pagliaro, Pasqualepaolo; Michelini, Elisa; Roda, Aldo

    2009-12-25

    New cell sorting methodologies, which are simple, fast, non-invasive, and able to isolate homogeneous cell populations, are needed for applications ranging from gene expression analysis to cell-based therapy. In particular, in the forefront of stem cell isolation, progenitor cells have to be separated under mild experimental conditions from complex heterogeneous mixtures prepared from human tissues. Most of the methodologies now employed make use of immunological markers. However, it is widely acknowledged that specific markers for pluripotent stem cells are not as yet available, and cell labelling may interfere with the differentiation process. This work presents for the first time gravitational field-flow fractionation (GrFFF), as a tool for tag-less, direct selection of human hematopoietic stem and progenitor cells from cell samples obtained by peripheral blood aphaeresis. These cells are responsible to repopulate the hemopoietic system and they are used in transplantation therapies. Blood aphaeresis sample were injected into a GrFFF system and collected fractions were characterized by flow cytometry for CD34 and CD45 expression, and then tested for viability and multi-differentiation potential. The developed GrFFF method allowed obtaining high enrichment levels of viable, multi-potent hematopoietic stem cells in specific fraction and it showed to fulfil major requirements of analytical performance, such as selectivity and reproducibility of the fractionation process and high sample recovery. PMID:19647835

  16. The Interaction of Focused Attention with Flow-field Sensitivity

    NASA Technical Reports Server (NTRS)

    Stoffregen, T.

    1984-01-01

    Two studies were performed to determine whether a subject's response to naturalistic optical flow specifying egomotion would be affected by a concurrent attention task. In the first study subjects stood in a moving room in which various areas of the optical flow generated by room movement were visible. Subjects responded to room motion with strong compensatory sway when the entire room was visible. When the side walls of the room were completely obscured by stationary screens, leaving only the front wall visible, sway was significantly reduced, though it remained greater than in an eyes-closed control. In Exp. 2 subjects were presented with either the full room (large sway response) or the room with only the front wall visible (moderate response), each in combination with either a hard or easy verbal addition task. Preliminary results show that swaying in the fully visible room and in the room with only the front wall visible increased when combined with either the hard or easy tasks. These preliminary results suggest that at the least the pick-up of optical flow specifying egomotion is not affected by concurrent attentional activity.

  17. Large Eddy Simulation of Transonic Flow Field in NASA Rotor 37

    NASA Technical Reports Server (NTRS)

    Hah, Chunill

    2009-01-01

    The current paper reports on numerical investigations on the flow characteristics in a transonic axial compressor, NASA Rotor 37. The flow field was used previously as a CFD blind test case conducted by American Society of Mechanical Engineers in 1994. Since the CFD blind-test exercise, many numerical studies on the flow field in the NASA Rotor 37 have been reported. Although steady improvements have been reported in both numerical procedure and turbulence closure, it is believed that all the important aspects of the flow field have not been fully explained with numerical studies based on the Reynolds Averaged Navier-Stokes (RANS) solution. Experimental data show large dip in total pressure distribution near the hub at downstream of the rotor at 100% rotor speed. Most original numerical solutions from the blind test exercise did not predict this total pressure deficit correctly. This total pressure deficit at the rotor exit was attributed to a hub corner flow separation by the author. Several subsequent numerical studies with different turbulence closure model also calculated this dip in total pressure rise. Also, several studies attributed this total pressure deficit to a small leakage flow coming from the hub in the test article. As the experimental study cannot be repea