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Sample records for flow field study

  1. A Study of Coaxial Rotor Performance and Flow Field Characteristics

    DTIC Science & Technology

    2016-01-22

    A Study of Coaxial Rotor Performance and Flow Field Characteristics Natasha L. Barbely Aerospace Engineer NASA Ames Research Center Moffett Field...The pressure field generated by the two airfoils aided our interpretation of the more complex coaxial rotor system flow field. The pressure fields...velocity (ft/sec) Z vertical distance between rotors (ft) αS pitch angle (deg), negative pitch down κint coaxial rotor induced power interference

  2. Numerical simulation study on the flow field of porous hydrofoil

    NASA Astrophysics Data System (ADS)

    Yu, F. R.; Zhang, L. X.

    2012-11-01

    Because cavitation and cavitation erosion will caused significant impact to the security and stability of hydro turbine, so changing geometric structure to reduce the risk of cavitation is considered. Punching many holes on the hydrofoil is adopted. By using RNG κ - ɛ turbulence model and SIMPLEC algorithm, the flow field around hydrofoil and porous hydrofoil are simulated based computational fluid dynamics(CFD). The numerical simulation result-velocity and pressure field of hydrofoil with different geometry are compared and analysed. This study introduces geometry optimization ideas to researchers for improving cavitation phenomenon in water turbine.

  3. Experimental Study of Impinging Jets Flow-Fields

    DTIC Science & Technology

    2016-07-27

    the jet plumes and outwash flow . Lift plate surface pressure measurements have also been made. The unsteady flow , known to have significant large...contributed to the identification and measurement of the major features of the flow -field generated by the two parallel impinging model jets. These...and outwash flow . 3 Laser Doppler Velocimeter Measurements Highlights of the LDV measurements are presented in the next two figures

  4. Flow field studies using holographic interferometry at Langley

    NASA Astrophysics Data System (ADS)

    Burner, A. W.; Snow, W. L.; Goad, W. K.; Helms, V. T.; Gooderum, P. B.

    1982-09-01

    Some of the uses of holographic interferometry at Langley Research Center both for flow visualization and for density field determinations are described and tests in cryogenic flows at the Langley 0.3-Meter Transonic Cryogenic Tunnel are discussed. Experimental and theoretical fringe shift data are compared.

  5. A Field Study of Particle Orientations in Shear Flows

    NASA Astrophysics Data System (ADS)

    Nayak, A. R.; Twardowski, M.; Sullivan, J. M.; McFarland, M.; Stockley, N.; Nardelli, S.

    2016-02-01

    Oceanic waters are populated by a myriad of particles of various shapes and sizes which play a critical role in the propagation and scattering of light. Ocean optics theory and models (e.g., radiative transfer) inherently assume that the particles are randomly oriented in the water column. Increasingly, this critical assumption has been challenged by a handful of recent theoretical and experimental studies. Thus, it is imperative to thoroughly assess the prevalence of any non-random particle orientation by characterizing the biophysical interactions through in situ measurements in natural, undisturbed oceanic flows. To achieve this objective, a suite of optical and acoustic instruments were concurrently deployed during field measurements recently conducted at East Sound, WA. The platform consisted of the following instrumentation: (i) a submersible holographic microscopy system (HOLOCAM) capable of acquiring video images at 15 Hz, while maintaining adequate resolution to characterize particles ranging in size over three orders of magnitude, i.e. 1 micron to 5 mm; (ii) an acoustic Doppler velocimeter and a high resolution Doppler profiler to provide simultaneous measurements of the turbulence and shear in the water column, and (iii) an optical package consisting of several instruments at different orientations measuring polarized and unpolarized volume scattering functions and path attenuation. Over a span of 10 days, nearly 40 runs, each spanning 10-15 minutes were obtained by slowly profiling the platform with a free fall velocity of 4-10 cm/s through the water column under varying environmental conditions. In this presentation, we explore whether the local small scale flow structure plays an important role in preferentially orienting the particle field.

  6. A Study of Hybrid Computing Techniques for Transonic Flow Fields.

    DTIC Science & Technology

    1980-02-01

    e (2.8) ax rr x r ar r r where, with e = div q, 8uav 8u T = z L. -+xe T rTr- + Moc ax Kr rx ax 8r (Z.9) T = + T + e rr = r + r Supersonic Far Field...Since only the flow downstream of a sonic nozzle is really needed for testing purposes, the numerical computations should not be very difficult. In this... Nozzle Throat, J. Fluid Mech., 69 (1975), 97-108. (3)Richey, 0. K. and Adamson, T. C., Jr., Analysis of Unsteady Transonic Channel Flow with Shock Waves

  7. A study of the flow field surrounding interacting line fires

    Treesearch

    Trevor Maynard; Marko Princevac; David R. Weise

    2016-01-01

    The interaction of converging fires often leads to significant changes in fire behavior, including increased flame length, angle, and intensity. In this paper, the fluid mechanics of two adjacent line fires are studied both theoretically and experimentally. A simple potential flow model is used to explain the tilting of interacting flames towards each other, which...

  8. 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.

  9. 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

  10. 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.

  11. Study on performance and flow field of an undershot cross-flow water turbine comprising different number of blades

    NASA Astrophysics Data System (ADS)

    Nishi, Yasuyuki; Hatano, Kentaro; Inagaki, Terumi

    2017-10-01

    Recently, small hydroelectric generators have gained attention as a further development in water turbine technology for ultra low head drops in open channels. The authors have evaluated the application of cross-flow water turbines in open channels as an undershot type after removing the casings and guide vanes to substantially simplify these water turbines. However, because undershot cross-flow water turbines are designed on the basis of cross-flow water turbine runners used in typical pipelines, it remains unclear whether the number of blades has an effect on the performance or flow fields. Thus, in this research, experiments and numerical analyses are employed to study the performance and flow fields of undershot cross-flow water turbines with varying number of blades. The findings show that the turbine output and torque are lower, the fluctuation is significantly higher, and the turbine efficiency is higher for runners with 8 blades as opposed to those with 24 blades.

  12. In situ visualization study of CO 2 gas bubble behavior in DMFC anode flow fields

    NASA Astrophysics Data System (ADS)

    Yang, H.; Zhao, T. S.; Ye, Q.

    This paper reports on a visual study of the CO 2 bubble behavior in the anode flow field of an in-house fabricated transparent Direct Methanol Fuel Cell (DMFC), which consisted of a membrane electrode assembly (MEA) with an active area of 4.0 × 4.0 cm 2, two bipolar plates with a single serpentine channel, and a transparent enclosure. The study reveals that at low current densities, small discrete bubbles appeared in the anode flow field. At moderate current densities, a number of gas slugs formed, in addition to small discrete bubbles. And at high current densities, the flow field was predominated by rather long gas slugs. The experiments also indicate that the cell orientation had a significant effect on the cell performance, especially at low methanol flow rates; for the present flow field design the best cell performance could be achieved when the cell was orientated vertically. It has been shown that higher methanol solution flow rates reduced the average length and the number of gas slugs in the flow field, but led to an increased methanol crossover. In particular, the effect of methanol solution flow rates on the cell performance became more pronounced at low temperatures. The effect of temperature on the bubble behavior and the cell performance was also examined. Furthermore, for the present flow field consisting of a single serpentine channel, the channel-blocking phenomenon caused by CO 2 gas slugs was never encountered under all the test conditions in this work.

  13. 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.

  14. Experimental Study on Flow Field behind Backward-Facing Step Using Detonation-Driven Shock Tunnel

    NASA Astrophysics Data System (ADS)

    Kim, Tae-Hwan; Obara, Tetsuro; Ohyagi, Shigeharu; Yoshikawa, Masato

    As a research to develop a SCRAM-jet engine is actively conducted, a necessity to produce a high-enthalpy flow in a laboratory is increasing. In order to develop the SCRAM-jet engine, stabilized combustion in a supersonic flow-field should be attained, in which a duration time of flow is extremely short. Therefore, a mixing process of breathed air and fuel, which is injected into supersonic flow-fields is one of the most important problem. Since, the flow inside SCRAM-jet engine has high-enthalpy, an experimental facility is required to produce such high-enthalpy flow-field. In this study, a detonation-driven shock tunnel was built and was used to produce high-enthalpy flow. At first, a performance of this facility was investigated in order to obtain a Tayloring condition. Furthermore, SCRAM-jet combustor model equipped backward-facing step was installed at test section and flow-fields were visualized using color-schlieren technique. The fuel was injected perpendicular to the flow of Mach number three behind step. The height of backward-facing step and injection pressure were changed to investigate effects of the step on a mixing characteristic between air and fuel. The schlieren photograph and pressure histories show that the fuel was ignited behind step and the height of step is important factor to ignite a fuel in a supersonic flow-field.

  15. Numerical study of soap-film flow by nonuniform alternating electric fields

    NASA Astrophysics Data System (ADS)

    Nasiri, M.; Shirsavar, R.; Mollaei, S.; Ramos, A.

    2017-02-01

    Fluid flow of suspended liquid films induced by non-uniform alternating electric fields has been reported. The electric fields were generated by two rod-like electrodes perpendicular to the fluid surface. The observed fluid flow was explained qualitatively by considering a charge induction mechanism, where the electric field actuates on the charge induced on the film surface. In this paper we perform a numerical study of this fluid flow taking into account the charge induction mechanism. The numerical results are compared with experiments and good agreement is found. Finally, we propose the application of the device as a new kind of two dimensional fluid pump.

  16. Numerical study of soap-film flow by nonuniform alternating electric fields.

    PubMed

    Nasiri, M; Shirsavar, R; Mollaei, S; Ramos, A

    2017-02-01

    Fluid flow of suspended liquid films induced by non-uniform alternating electric fields has been reported. The electric fields were generated by two rod-like electrodes perpendicular to the fluid surface. The observed fluid flow was explained qualitatively by considering a charge induction mechanism, where the electric field actuates on the charge induced on the film surface. In this paper we perform a numerical study of this fluid flow taking into account the charge induction mechanism. The numerical results are compared with experiments and good agreement is found. Finally, we propose the application of the device as a new kind of two dimensional fluid pump.

  17. 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.

  18. Field implementation of Particle Image Velocimetry (PIV) for studying flow dynamics at river confluences

    NASA Astrophysics Data System (ADS)

    Lewis, Q. W.; Rhoads, B. L.

    2014-12-01

    The complex hydrodynamics of river confluences have been the focus of numerous investigations over the past several decades. Confluences are locations in river systems characterized by complex patterns of turbulent flow structure, especially within the mixing interface that develops between the two flows. To date, most field investigations of flow structure at stream confluences have been based on point measurements of velocity time series (e.g using ADVs) or on time-averaged data with high spatial resolution, but poor temporal resolution (e.g. using ADCPs). Past approaches have failed to capture the spatial and temporal density of velocity measurements needed to adequately characterize complex turbulent flow structures. In contrast, Particle Image Velocimetry (PIV) has been used successfully in laboratory studies to define in considerable detail the characteristics of turbulent structures. This study uses field-based PIV to characterize surficial flow structure within a small stream confluence. Landscape mulch served as seeding material for the PIV. Particle motion was recorded at a high frame rate using a small action camera mounted above the surface of the flow. Near-surface 3D velocities of flow were measured with an acoustic Doppler velocimeter (ADV) to evaluate velocity data generated by the PIV analysis. Results show that field-based PIV captures nicely complex patterns of fluid motion at the surface of the flow, revealing the two-dimensional characteristics of coherent flow structures. Velocities resulting from the PIV analysis match measured velocities most closely where the flow is least complex and where seeding material remains uniformly distributed throughout the flow. Overall the method appears promising for qualitatively assessing flow structure and for quantifying the size, duration, and vorticity of turbulent structures. Field-based PIV is a valuable technique that can be used along with traditional velocity measurements to more completely and

  19. Whole-Field Measurements of Turbulent Flow for the Study of Aero-optical Effects

    DTIC Science & Technology

    2007-11-02

    Aerooptical phenomena associated with the propagation of optical beams and imaging through turbulent index-of-refraction fields have been investigated...Using simultaneous imaging of optical -beam distortion and the turbulent index-or-refraction field, we have documented near-field behavior, following...of TECHNOLOGY Pasadena, California 91125 Whole-field measurements of turbulent flow for the study of aero- optical effects Paul E. Dimotakis Air

  20. Equivariant mean field flow

    NASA Astrophysics Data System (ADS)

    Castéras, Jean-baptiste

    2013-12-01

    We consider a gradient flow associated to the mean field equation on (M,g), a compact Riemannian surface without boundary. We prove that this flow exists for all time. Moreover, letting G be a group of isometry acting on (M,g), we obtain the convergence of the flow to a solution of the mean field equation under suitable hypothesis on the orbits of points of M under the action of G.

  1. The study of turbulence in MHD flow generated by rotating and traveling magnetic fields

    NASA Astrophysics Data System (ADS)

    Kolesnichenko, Ilya; Pavlinov, Alexander; Golbraikh, Ephim; Frick, Peter; Kapusta, Arkadii; Mikhailovich, Boris

    2015-05-01

    We consider a problem of spectral analysis of signals from electromagnetic sensors operating in a turbulent MHD flow generated by rotating and traveling magnetic fields, which create a strong electromagnetic noise. Using a wavelet-based technique for cross-correlation signal analysis and filtration, we show that at frequencies lower than the frequency of the applied magnetic field, the spectral properties of the velocity field can be clearly seen in spite of the fact that the measured fields are much weaker than the driving rotating (or traveling) magnetic field. On the basis of the proposed method, spectra of turbulent velocity fields, measured in the experiment, were studied.

  2. Experimental studies of zonal flow and field in compact helical system plasmaa)

    NASA Astrophysics Data System (ADS)

    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.; Nagashima, Y.; Itoh, S.-I.; Diamond, P. H.

    2008-05-01

    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.

  3. 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.

  4. Kamoamoa Flow Field Animation

    NASA Image and Video Library

    2012-02-06

    This frame from an animation, which depicts the growth of the Kamoamoa Flow Field, Kilauea Volcano, Hawaii, was generated from a sequence of ten multispectral images acquired between September 3 and 17, 1995.

  5. 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)

  6. 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.

  7. Flow routing in mangrove forests: A field study in Trang province, Thailand

    NASA Astrophysics Data System (ADS)

    Horstman, Erik M.; Dohmen-Janssen, C. Marjolein; Hulscher, Suzanne J. M. H.

    2013-12-01

    Flow routing in mangrove forests has great implications for the transport and distribution of sediments and nutrients and hence for mangroves' development and persistence. Whereas previous studies were limited to the creeks, supposedly feeding the surrounding mangroves, this study demonstrates the contribution of biogeophysical impacts on flow routing through estuarine mangroves. We present the results of a field campaign covering three pristine mangrove sites in two estuaries in Trang province, Thailand. The sites range from a mangrove forest elevated above mean sea level with steep cliffs and incised by tidal creeks, to smoothly inclining mangroves fronted by extensive mudflats and showing a clear vegetation zonation starting below mean sea level. It is shown how flow routing through estuarine mangroves is impacted by biogeophysical factors; elevation, exposure and vegetation. Within the higher elevated mangroves, creek flow prevails when water levels remain below a dense vegetation layer at the mangrove fringe bordering the estuary. Sheet flow prevails when this threshold is exceeded and direct water exchange takes place. The low-lying sites do not feature creeks and tidal flows are typically sheet flows, being susceptible to forcing by river discharges. With decreasing water depths and/or increasing vegetation densities, the effects of this forcing are reduced and flow velocities follow the vegetation induced cross-shore water level gradients. Flow velocities within the creeks are up to an order of magnitude greater than those within the vegetation, where velocities decrease progressively with increasing vegetation densities. Particular vegetation and elevation characteristics cause irregular velocity variations along the vertical, within the vegetation as well as in the creeks. Tentative tidal flux calculations demonstrate the significant contribution of creek flow to the total tidal prism in higher elevated mangroves. By explicitly quantifying and mapping

  8. Flow field study in the T-313 wind-tunnel test section for M = 7

    NASA Astrophysics Data System (ADS)

    Zapryagaev, V. I.; Mazhul, I. I.; Maksimov, A. I.

    2013-06-01

    Results of a numerical and experimental study of flow-field characteristics in the test section of the T-313 supersonic blow-down wind tunnel of ITAM SB RAS at Mach number M = 7 are reported. The distributions of local Mach numbers, stagnation temperatures, static pressures, angles of flow deflection from the test-section axis were analyzed. For comparison, distributions of Mach numbers across the flow at several stations at M = 5 and 6 are reported as well. We show that, in the T-313 wind tunnel, two-dimensional nozzle inserts can be used to perform experiments at M = 7.

  9. Feasibility study of red blood cell debulking by magnetic field-flow fractionation with step-programmed flow

    PubMed Central

    Moore, Lee R.; Williams, P. Stephen; Nehl, Franziska; Abe, Koji; Chalmers, Jeffrey J.; Zborowski, Maciej

    2013-01-01

    Emerging applications of rare cell separation and analysis, such as separation of mature red blood cells from hematopoietic cell cultures require efficient methods of red blood cell (RBC) debulking. We have tested the feasibility of magnetic RBC separation as an alternative to centrifugal separation using an approach based on the mechanism of magnetic field-flow fractionation (MgFFF). A specially designed permanent magnet assembly generated a quadrupole field having a maximum field of 1.68 T at the magnet pole tips, zero field at the aperture axis, and a nearly constant radial field gradient of 1.75 T/mm (with a negligible angular component) inside a cylindrical aperture of 1.9 mm (diameter) and 76 mm (length). The cell samples included high-spin hemoglobin RBCs obtained by chemical conversion of hemoglobin to methemoglobin (met RBC) or by exposure to anoxic conditions (deoxy RBC), low-spin hemoglobin obtained by exposure of RBC suspension to ambient air (oxy RBC), and mixtures of deoxy RBC and cells from a KG-1a white blood cell (WBC) line. The observation that met RBCs did not elute from the channel at the lower flow rate of 0.05 mL/min applied for 15 min but quickly eluted at the subsequent higher flow rate of 2.0 mL/min was in agreement with FFF theory. The well-defined experimental conditions (precise field and flow characteristics) and a well-established FFF theory verified by studies with model cell systems provided us with a strong basis for making predictions about potential practical applications of the magnetic RBC separation. PMID:24141316

  10. Feasibility study of red blood cell debulking by magnetic field-flow fractionation with step-programmed flow.

    PubMed

    Moore, Lee R; Williams, P Stephen; Nehl, Franziska; Abe, Koji; Chalmers, Jeffrey J; Zborowski, Maciej

    2014-02-01

    Emerging applications of rare cell separation and analysis, such as separation of mature red blood cells from hematopoietic cell cultures, require efficient methods of red blood cell (RBC) debulking. We have tested the feasibility of magnetic RBC separation as an alternative to centrifugal separation using an approach based on the mechanism of magnetic field-flow fractionation (MgFFF). A specially designed permanent magnet assembly generated a quadrupole field having a maximum field of 1.68 T at the magnet pole tips, zero field at the aperture axis, and a nearly constant radial field gradient of 1.75 T/mm (with a negligible angular component) inside a cylindrical aperture of 1.9 mm (diameter) and 76 mm (length). The cell samples included high-spin hemoglobin RBCs obtained by chemical conversion of hemoglobin to methemoglobin (met RBC) or by exposure to anoxic conditions (deoxy RBC), low-spin hemoglobin obtained by exposure of RBC suspension to ambient air (oxy RBC), and mixtures of deoxy RBC and cells from a KG-1a white blood cell (WBC) line. The observation that met RBCs did not elute from the channel at the lower flow rate of 0.05 mL/min applied for 15 min but quickly eluted at the subsequent higher flow rate of 2.0 mL/min was in agreement with FFF theory. The well-defined experimental conditions (precise field and flow characteristics) and a well-established FFF theory verified by studies with model cell systems provided us with a strong basis for making predictions about potential practical applications of the magnetic RBC separation.

  11. 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.

  12. 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.

  13. 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.

  14. Studies and Vorticity Effects by the Euler Equations with Emphasis on Supersonic Flow Fields.

    DTIC Science & Technology

    1983-10-01

    to see if the Euler equations will predict the fi loads in highly vortical flow fields for cruciform missiles . Body-alone and wing ...flow fields for cruciform missiles . Body-alone and wing -body flow :* fields were measured in the Bumblebee Program at a position where a tail might be...application of a supersonic marching Euler code to complete configurations , such as a wing -body- tail combination, further investigation

  15. 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.

  16. Numerical Study of Two-Phase Flow Field in a Simplified Swirl Cup Combustor (Preprint)

    DTIC Science & Technology

    2007-09-24

    Article 3 . DATES COVERED (From - To) 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Numerical Study of Two-Phase Flow Field in a Simplified Swirl Cup...swirl provides a recirculation zone which enhances mixing and flame stability. Some high-performance aircraft engines such as in GE/SNECMA CFM56 ...downstream of a GE/SNECMA CFM56 engine combustor swirl cup in which the primary and secondary swirlers provide co-axial, counter-swirling airstreams

  17. 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

    2011-07-08

    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.

  18. Study of Flow-Field Interactions in a Transonic Compressor using DPIV

    NASA Astrophysics Data System (ADS)

    Estevadeordal, Jordi; Gogineni, Sivaram; Goss, Larry; Copenhaver, William; Gorrell, Steve; Koch, Peter

    1999-11-01

    The unsteadiness and spatial structures in a high-through-flow, axial-flow transonic compressor are captured using Digital Particle Image Velocimetry (DPIV). The measurements are made using both single-color and two-color DPIV systems. A special optical probe was designed for laser delivery through the inlet guide vanes (IGVs). Viewing windows on the compressor housing allow optical access. Submicron sized smoke particles are used for seeding the compressor flow and the DPIV system is synchronized with the blade passage. The interactions between the coherent structures from the IGVs with the rotor blades and the bow shock are studied for various configurations. The coherent structures interactions with the potential field of the leading edge of the blades and the shock as a function of the blade position are analyzed for a full blade passage through the wake. Comparisons are made with unsteady numerical simulations.

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

    USDA-ARS?s Scientific Manuscript database

    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...

  20. 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

  1. 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).

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

    NASA Astrophysics Data System (ADS)

    Anderson, W. W.; Chamecki, M.; Kocurek, G.; Mohrig, D. C.

    2013-12-01

    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 which 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 has 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, Ls, and vortex spacing, Lambda_x -- and show that Ls = m Lambda_x, where m is approximately 8 in the different sections considered (for turbulent mixing layers, 7 < m < 10, Rogers and Moser, 1994: Phys. Fluids A, 6, 903-922). These results guide discussion on the statistics of aerodynamic drag across the dunes; probability density functions of time-series of aerodynamic drag for the dunes are shown to exhibit skewness and variance much greater than values reported for turbulent boundary layer flow over an homogeneous roughness distribution. Thus, we propose that

  3. Flow field study in a bulb turbine runner using LDV and endoscopic S-PIV measurements

    NASA Astrophysics Data System (ADS)

    Lemay, S.; Fraser, R.; Ciocan, G. D.; Aeschlimann, V.; Deschênes, C.

    2014-03-01

    The flow in the inter-blade channels of a bulb turbine was measured using two different techniques. The first involved a classical laser Doppler velocimetry (LDV) setup whereas the second integrated endoscopic cameras to a stereoscopic particle image velocimetry (S-PIV) system. This paper presents results from both measurement campaigns and also provides some key conclusions based on the two datasets. Before getting into the thick of the data though, the technical aspect of both measurement configurations is addressed. A quick overview of the LDV setup is presented, but the main focus is on the novelties and challenges brought by the use of endoscopic cameras to achieve S-PIV measurements between the runner blades. Endoscopic PIV systems have already led to successful measurements of flow fields in a few studies concerning turbomachinery, especially in aerodynamics. However, to the author's knowledge, the realisation of such measurements in a hydraulic turbine is a first. After this outline of the techniques used, the results and conclusions are shown. First, the influence of the guide vanes wakes on the runner flow is described. The size, localisation, strength and dissipation of those structures are inferred from the information coming from both measurement techniques. Then, a flow imbalance is assessed circumferentially. On another subject, the blade tip vortices are identified and characterized using the LDV data. The size, position and direction of rotation of those structures are all extracted from the measured flow field. Finally, the PIV data allows the identification of yet another vortex located near the suction side of the blades and originating from the corner between the leading edge and the hub when operating the bulb turbine at part load.

  4. 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

  5. Air flow and pollution in a real, heterogeneous urban street canyon: A field and laboratory study

    NASA Astrophysics Data System (ADS)

    Karra, Styliani; Malki-Epshtein, Liora; Neophytou, Marina K.-A.

    2017-09-01

    observed throughout the modelled street. The real-field observations and the laboratory measurements were compared. Overall, we found that lower variability in the background wind does not necessarily ensure a better agreement between the airflow velocity measured in the field and in the lab. In fact, it was observed that in certain cross sections, the airflow was more affected by the particular complex architectural features such as building extrusions and balconies, which were not represented in the simplified physical model tested in the laboratory, than by the real wind field variability. For wind speed comparisons the most favourable agreement (36.6% of the compared values were within a factor of 2) was found in the case of lowest wind variability and in the section with the most simple geometry where the physical lab model was most similar to the real street. For wind direction comparisons the most favourable agreement (45.5% of the compared values was within ±45°) was found in the case with higher wind variability but in the cross-sections with more homogeneous geometrical features. Street canyons are often simplified in research and are often modelled as homogenous symmetrical canyons under steady flow, for practical purposes; our study as a whole demonstrates that natural variability and heterogeneity play a large role in how pollution disperses throughout the street, and therefore further detail in models is vital to understand real world conditions.

  6. 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.

  7. 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.

  8. Analytical study on the influence of nonequilibrium ionization for current flow pattern and flow field of MPD arcjets

    NASA Astrophysics Data System (ADS)

    Kimura, Itsuro; Shoji, Tsunetake

    1990-07-01

    The effect of non-equilibrium ionization on a one-dimensional supersonic self-field MPD flow, which starts from the point of Mach number 1, is analyzed taking ionization and recombination rate-equations and electron energy equation into consideration. It was observed generally that for given inlet boundary conditions and a total discharge current, the solution exists in a limited region of propellant flow rate and the required electrode becomes longer for lower propellant flow rate, as in the cases of frozen or thermal-equilibrium flow. Based on the calculated results with argon or hydrogen propellant, it was shown that a remarkable deviation from ionization equilibrium appears in the course of plasma acceleration, when the propellant flow rate is near the lower limit, and that for molecular species hydrogen, current concentration on the inlet part, observed in the case of argon, is removed by the influence of dissociation process.

  9. Fracture propagation and fluid flow in fractured reservoirs: field studies and numerical models

    NASA Astrophysics Data System (ADS)

    Brenner, S. L.

    2005-05-01

    In fractured reservoirs (e.g., for petroleum or geothermal water), fluid flow is largely controlled by the permeability of the fracture network. Together with shear fractures (faults), hydrofractures (extension fractures generated by internal fluid pressure, including mineral veins and joints) contribute considerably to the permeability in fractured reservoirs. The permeability of an individual fracture is proportional to the cube of its aperture. But for fluid flow to occur between two sites in a reservoir, there must be at least one interconnected cluster of fractures that links these sites, that is, the percolation threshold must be reached. Field observations show that in heterogeneous and anisotropic, e.g., layered, rocks many hydrofractures become arrested or offset at layer contacts (become stratabound) and do not form interconnected networks. Here I present results from field studies in layered sedimentary rocks from the Bristol Channel Basin, UK. The Lower Jurassic sections exposed near Kilve, Somerset Coast (Southwest England), and around Nash Point, Glamorgan Coast (South Wales) consist of limestone and shale layers dissected by normal faults (Kilve) or strike-slip faults (Nash Point). Whereas joints occur throughout the study areas, calcite veins occur almost exclusively in the cores and damage zones of the faults. These observations indicate that geothermal water was transported along the then-active faults into the host rocks. Furthermore, there is evidence that the veins were injected as hydrofractures from the fault planes into the limestone layers next to the faults. The most important factors that contribute to hydrofracture arrest or offset are discontinuities, stiffness (Young's modulus) changes between layers, and stress barriers - layers where the local stress field is unfavorable to the propagation of a hydrofracture. Using numerical models I explore the conditions for hydrofracture propagation and conclude that mechanical layering largely

  10. 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.

  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. 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.

  13. 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.

  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).

  15. 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

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. PC-based visual stimuli for behavioural and electrophysiological studies of optic flow field detection.

    PubMed

    Johnson, Aaron P; Horseman, B Geoff; Macauley, Martin W S; Barnes, W Jon P

    2002-02-15

    A PC-based visual-stimulus-generation package for behavioural and electrophysiological studies of responses to optic flow is described. Developed for studies of crab vision, the package is particularly well suited for use with animals that have very large fields of view, i.e. +/-120 degrees. Programs, written in the Borland Delphi language, use the OpenGL graphics library to create realistic representations of motion in a three dimensional environment. Large-field stimuli include simulations of self-motion (rotation and translation, separately or in combination) relative to a square-wave grating or other, user-selected, background. The package also includes representations of approaching and receding objects, and rotating spiral patterns for the investigation of neural responses to looming/anti-looming. Additionally, the package provides local motion stimuli, translating or rotating targets presented at many points in the receptive field, which can be used to derive response maps of large-field motion-sensitive interneurones. In all these stimuli, inconsistencies in animation timing that have hitherto hindered the use of standard PCs running Microsoft Windows for such applications have been minimised by using an improved real-time clock to control the animation cycle.

  2. Study on Flow Field Characteristics of Nozzle Water Jet in Hydraulic cutting

    NASA Astrophysics Data System (ADS)

    Liao, Wen-tao; Deng, Xiao-yu

    2017-08-01

    Based on the theory of hydrodynamics, a mathematical model of nozzle water jet flow field in hydraulic cutting is established. By numerical simulation, the effects of nozzle convergence angle, nozzle outlet diameter and cylindrical section length on water jet flow impact is obtained, and the influence of three factors on the nozzle water jet flow field is analyzed. The optimal nozzle parameters are obtained by simulation as follows: convergence angle is 13 °, cylindrical section length is 8 mm and nozzle outlet diameter is 2 mm. Under this optimal nozzle parameters, hydraulic cutting has the best comprehensive effect.

  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. Numerical Study on the Optimization of Flow and Temputre Field in the Desulphurization Spray Tower

    NASA Astrophysics Data System (ADS)

    Zeng, F.; Yin, L. Q.; Chen, Q.; Wang, Y.

    The CFD software Fluent and Gambit had been introduced for the simulation of the flow and temperature fields of the wet flue gas desulphurization. Standard k-ɛ turbulence model and the particle path model described the motion of the flue gas and the liquid droplets. The problems of the desulphurization spray tower were found the flue gas stuck tower wall, the distribution of the flow-fields was not an ideal state and the temperature of the export was higher by numerical simulation. Aiming at these problems it was optimized design by numerical simulation. The simulation results indicate that the angle of the flue gas entrance was down to 15° and installed the flue gas distributor in area of atomization down the spray layers, the flue gas following along the tower wall was overcome. At the same time the gas temperature of the export was lower than before the modification. The study results supplied the basis of the optimization of the structure of desulphurization spray tower.

  5. Field studies of transport and dispersion of atmospheric tracers in nocturnal drainage flows

    Treesearch

    Paul H. Gudiksen; Gilbert J. Ferber; Malcolm M. Fowler; Wynn L. Eberhard; Michael A. Fosberg; William R. Knuth

    1984-01-01

    A series of tracer experiments were carried out as part of the Atmospheric Studies in Complex Terrain (ASCOT) program to evaluate pollutant transport and dispersion characteristics of nocturnal drainage flows within a valley in northern California. The results indicate that the degree of interaction of the drainage flows with the larger scale regional flows are...

  6. 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

  7. 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.

  8. 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.

  9. Simulation study of overtaking in pedestrian flow using floor field cellular automaton model

    NASA Astrophysics Data System (ADS)

    Fu, Zhijian; Xia, Liang; Yang, Hongtai; Liu, Xiaobo; Ma, Jian; Luo, Lin; Yang, Lizhong; Chen, Junmin

    Properties of pedestrian may change along the moving path, for example, as a result of fatigue or injury, which has never been properly investigated in the past research. The paper attempts to study tactical overtaking in pedestrian flow. That is difficult to be modeled using a microscopic discrete model because of the complexity of the detailed overtaking behavior, and crossing/overlaps of pedestrian routes. Thus, a multi-velocity floor field cellular automaton model explaining the detailed psychical process of overtaking decision was proposed. Pedestrian can be either in normal state or in tactical overtaking state. Without tactical decision, pedestrians in normal state are driven by the floor field. Pedestrians make their tactical overtaking decisions by evaluating the walking environment around the overtaking route (the average velocity and density around the route, visual field of pedestrian) and obstructing conditions (the distance and velocity difference between the overtaking pedestrian and the obstructing pedestrian). The effects of tactical overtaking ratio, free velocity dispersion, and visual range on fundamental diagram, conflict density, and successful overtaking ratio were explored. Besides, the sensitivity analysis of the route factor relative intensity was performed.

  10. Numerical and experimental study of unsteady flow field and vibration in radial inflow turbines

    SciTech Connect

    Kreuz-Ihli, T.; Filsinger, D.; Schulz, A.; Wittig, S.

    2000-04-01

    The blades of turbocharger impellers are exposed to unsteady aerodynamic forces, which cause blade vibrations and may lead to failures. An indispensable requirement for a safe design of radial inflow turbines is a detailed knowledge of the exciting forces. Up to now, only a few investigations relating to unsteady aerodynamic forces in radial turbines have been presented. To give a detailed insight into the complex phenomena, a comprehensive research project was initiated at the Institut fuer Thermische Stroemungsmaschinen, at the University of Karlsruhe. A turbocharger test rig was installed in the high-pressure, high-temperature laboratory of the institute. The present paper gives a description of the test rig design and the measuring techniques. The flow field in a vaneless radial inflow turbine was analyzed using laser-Doppler anemometry. First results of unsteady flow field investigations in the turbine scroll and unsteady phase-resolved measurements of the flow field in the turbine rotor will be discussed. Moreover, results from finite element calculations analyzing frequencies and mode shapes are presented. As vibrations in turbines of turbochargers are assumed to be predominantly excited by unsteady aerodynamic forces, a method to predict the actual transient flow in a radial turbine utilizing the commercial Navier-Stokes solver TASCflow3d was developed. Results of the unsteady calculations are presented and comparisons with the measured unsteady flow field are made. As a major result, the excitation effect of the tongue region in a vaneless radial inflow turbine can be demonstrated.

  11. 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.

  12. 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.

  13. 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

  14. 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.

  15. 3-D Flow Field Diagnostics and Validation Studies using Stereoscopic Tracking Velocimetry

    NASA Technical Reports Server (NTRS)

    Cha, Soyoung Stephen; Ramachandran, Narayanan; Whitaker, Ann F. (Technical Monitor)

    2002-01-01

    The measurement of 3-D three-component velocity fields is of great importance in both ground and space experiments for understanding materials processing and fluid physics. Here, we present the investigation results of stereoscopic tracking velocimetry (STV) for measuring 3-D velocity fields. The effort includes diagnostic technology development, experimental velocity measurement, and comparison with analytical and numerical computation. The advantages of STV stems from the system simplicity for building compact hardware and in software efficiency for continual near-real-time process monitoring. It also has illumination flexibility for observing volumetric flow fields from arbitrary directions. STV is based on stereoscopic CCD observations of particles seeded in a flow. Neural networks are used for data analysis. The developed diagnostic tool is tested with a simple directional solidification apparatus using Succinonitrile. The 3-D velocity field in the liquid phase is measured and compared with results from detailed numerical computations. Our theoretical, numerical, and experimental effort has shown STV to be a viable candidate for reliably quantifying the 3-D flow field in materials processing and fluids experiments.

  16. The Effect of Inlet Cannula Length on the Intraventricular Flow Field An In Vitro Flow Visualization Study Using the Evaheart LVAD.

    PubMed

    May-Newman, Karen; Moon, Juyeun; Ramesh, Varsha; Montes, Ricardo; Campos, Josue; Herold, Brian; Isingoma, Paul; Motomura, Tadashi; Benkowski, Robert

    2017-03-20

    LVAD inflow cannula malposition is a significant risk for pump thrombosis. Thrombus development is influenced by altered flow dynamics, such as stasis or high shear that promote coagulation. The goal of this study was to measure the intraventricular flow field surrounding the apical inflow cannula of the Evaheart centrifugal LVAD, and assess flow stasis, vortex structures and pulsatility for a range of cannula insertion depths and support conditions. Experimental studies were performed using a mock loop with a customized silicone left ventricle (LV) and the Evaheart LVAD. A transparent inflow cannula was positioned at 1cm, 2cm, or 3cm insertion depth into the LV and the velocity field in the LV midplane was measured for two levels of LVAD support: 1800rpm and 2300rpm. The LV velocity field exhibits a diastolic vortex ring whose size, path and strength are affected by the flow conditions and cannula position. During diastole, the large clockwise midplane vortex grows, but its circulation and kinetic energy are reduced with cannula insertion depth. The counter-clockwise vortex is smaller and exhibits more complex behavior, reflecting a flow split at 3cm. Overall, the 1cm cannula insertion depth produces the flow pattern that exhibits the least apical flow stasis and greatest pulsatility and should correlate to a lower risk of thrombus formation.

  17. 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

  18. 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.

  19. A Preliminary Field Study of Turbulent Flow Over and Inside a Forest Edge.

    DTIC Science & Technology

    2014-09-26

    Edge, Turbulent flow, Turbulence sensors, 3-D wind sensors, miccometeorology, Forest Canopy, Hot -films. 20 AgerRAC? (CeNtO perOe Oti...characterizes the flow regime in a forest canopy 44 are a dual triple-split hot -film probe and a tri-diagonal hot -film probe with a wind octant...electronic sensor (WOES). e calibration of the triple-split hot -films has bee completed and the probe is ready for field applications. The response of WOES

  20. A field study of colloid transport in surface and subsurface flows

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Tang, Xiang-Yu; Xian, Qing-Song; Weisbrod, Noam; Yang, Jae E.; Wang, Hong-Lan

    2016-11-01

    Colloids have been recognized to enhance the migration of strongly-sorbing contaminants. However, few field investigations have examined combined colloid transport via surface runoff and subsurface flows. In a headwater catchment of the upper Yangtze River, a 6 m (L) by 4 m (W) sloping (6°) farmland plot was built by cement walls to form no-flow side boundaries. The plot was monitored in the summer of 2014 for the release and transport of natural colloids via surface runoff and subsurface flows (i.e., the interflow from the soil-mudrock interface and fracture flow from the mudrock-sandstone interface) in response to rain events. The water sources of the subsurface flows were apportioned to individual rain events using a two end-member model (i.e., mobile pre-event soil water extracted by a suction-cup sampler vs. rainwater (event water)) based on δ18O measurements. For rain events with high preceding soil moisture, mobile pre-event soil water was the main contributor (generally >60%) to the fracture flow. The colloid concentration in the surface runoff was 1-2 orders of magnitude higher than that in the subsurface flows. The lowest colloid concentration was found in the subsurface interflow, which was probably the result of pore-scale colloid straining mechanisms. The rainfall intensity and its temporal variation govern the dynamics of the colloid concentrations in both surface runoff and subsurface flows. The duration of the antecedent dry period affected not only the relative contributions of the rainwater and the mobile pre-event soil water to the subsurface flows but also the peak colloid concentration, particularly in the fracture flow. The <10 μm fine colloid size fraction accounted for more than 80% of the total suspended particles in the surface runoff, while the colloid size distributions of both the interflow and the fracture flow shifted towards larger diameters. These results highlight the need to avoid the application of strongly

  1. Influence of flow velocity on flow field's optical tomography diagnosis

    NASA Astrophysics Data System (ADS)

    Chen, Yun-yun; Yu, Yang; Zhong, Xia; Zhang, Ying-ying

    2017-01-01

    The effect of flow velocity is usually neglected when optical computerized tomography (OCT) methods are chosen to measure the temperature distribution of the flow fields up to now. In this paper, two sets of experiment are supplied to verify the effect of flow velocity on flow field's moiré tomography. Specifically speaking, the temperature results with the assumption that it is an isobaric process (omit the effect of flow velocity) in the measured flame flow fields, manifest that the isobaric supposition is not suitable for all the flames. And then, a condition, which can be adopted to judge that when the effect of flow velocity on its temperature reconstruction can not be neglected any more, is proposed. This study would provide some reference to the temperature diagnosis by the optical methods which are based on the measurement of the refractive index.

  2. 3D numerical study of a feed jet in a rotating flow-field

    NASA Astrophysics Data System (ADS)

    Jiang, D. J.; Zeng, S.

    2016-09-01

    A contribution of a feed drive in the total counter-current flow in a gas centrifuge for isotope separation is an important problem in optimization of its separation performance. A 3D model is used to simulate flow structures of a feed jet in a rotating flow-field. By using a CFD code, the details of a feed jet are obtained under the axial feed jet boundary condition. It is demonstrated that because of the vacuum regime in the region near the axis of rotation, the results of numerical simulation of a CFD code bring errors. The 3D DSMC simulation is a feasible method to overcome this problem in the future.

  3. 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.

  4. 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.

  5. 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

  6. The structure of the vorticity field in turbulent channel flow. Part 2: Study of ensemble-averaged fields

    NASA Technical Reports Server (NTRS)

    Kim, J.; Moin, P.

    1984-01-01

    Several conditional sampling techniques are applied to a data base generated by large-eddy simulation of turbulent channel flow. It is shown that the bursting process is associated with well-organized horseshoe vortices inclined at about 45 deg. to the wall. These vortical structures are identified by examining the vortex lines of three-dimensional, ensemble averaged vorticity fields. Two distinct horseshoe-shaped vortices corresponding to the sweep and ejection events are detected. These vortices are associated with high Reynolds shear stress and hence make a significant contribution to turbulent energy production. The dependency of the ensemble averaged vortical structures on the detection criteria, and the question of whether this ensemble-averaged structure is an artifact of the ensemble averaging process are examined. The ensemble-averaged pattern of these vortical structures that emerge from the analysis could provide the basis for a hypothetical model of the organized structures of wall-bounded shear flows.

  7. The structure of the vorticity field in turbulent channel flow. II - Study of ensemble-averaged fields

    NASA Technical Reports Server (NTRS)

    Kim, J.; Moin, P.

    1986-01-01

    Several conditional sampling techniques are applied to a data base generated by large-eddy simulation of turbulent channel flow. It is shown that the bursting process is associated with well-organized horseshoe vortices inclined at about 45 deg to the wall. These vortical structures are identified by examining the vortex lines of three-dimensional, ensemble averaged vorticity fields. Two distinct horseshoe-shaped vortices corresponding to the sweep and ejection events are detected. These vortices are associated with high Reynolds shear stress and hence make a significant contribution to turbulent energy production. The dependency of the ensemble averaged vortical structures on the detection criteria, and the question of whether this ensemble-averaged structure is an artifact of the ensemble averaging process are examined. The ensemble-averaged pattern of these vortical structures that emerge from the analysis could provide the basis for a hypothetical model of the organized structures of wall-bounded shear flows.

  8. 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.

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

    DTIC Science & Technology

    2008-10-01

    ground) are presented in Figures 11 through 15. These results were obtained using the code OVERFLOW 2 [14, 15] with the Spalart - Allmaras ...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. Notation 1 CT = thrust coefficient IGE = in ground effect OGE = out of

  10. 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

  11. 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

  12. 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.

  13. 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.

  14. 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

  15. 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.

  16. Experimental study on the flow field behind a backward-facing step using a detonation-driven shock tunnel

    NASA Astrophysics Data System (ADS)

    Kim, T.-H.; Yoshikawa, M.; Obara, T.; Ohyagi, S.

    2006-03-01

    The supersonic combustion RAM jet (SCRAM jet) engine is expected to be used in next-generation space planes and hypersonic airliners. To develop the engine, stabilized combustion in a supersonic flow field must be attained even though the residence time of flow is extremely short. A mixing process for breathed air and fuel injected into the supersonic flow field is therefore one of the most important design problems. Because the flow inside the SCRAM jet engine has high enthalpy, an experimental facility is required to produce the high-enthalpy flow field. In this study, a detonation-driven shock tunnel was built to produce a high-enthalpy flow, and a model SCRAM jet engine equipped with a backward-facing step was installed in the test section of the facility to visualize flow fields using a color schlieren technique and high-speed video camera. The fuel was injected perpendicularly to a Mach 3 flow behind the backward-facing step. The height of the step, the injection distance and injection pressure were varied to investigate the effects of the step on air/fuel mixing characteristics. The results show that the recirculation region increases as the fuel injection pressure increases. For injection behind the backward-facing step, mixing efficiency is much higher than with a flat plate. Also, the injection position has a significant influence on the size of the recirculation region generated behind the backward-facing step. The schlieren photograph and pressure histories measured on the bottom wall of the SCRAM jet engine model show that the fuel was ignited behind the step.

  17. Molecular dynamics study of nanoconfined water flow driven by rotating electric fields under realistic experimental conditions.

    PubMed

    De Luca, Sergio; Todd, B D; Hansen, J S; Daivis, Peter J

    2014-03-25

    In our recent work, J. Chem. Phys. 2013, 138, 154712, we demonstrated the feasibility of unidirectional pumping of water, exploiting translational-rotational momentum coupling using nonequilibrium molecular dynamics simulations. Flow can be sustained when the fluid is driven out of equilibrium by an external spatially uniform rotating electric field and confined between two planar surfaces exposing different degrees of hydrophobicity. The permanent dipole moment of water follows the rotating field, thus inducing the molecules to spin, and the torque exerted by the field is continuously injected into the fluid, enabling a steady conversion of spin angular momentum into linear momentum. The translational-rotational coupling is a sensitive function of the rotating electric field parameters. In this work, we have found that there exists a small energy dissipation region attainable when the frequency of the rotating electric field matches the inverse of the dielectric relaxation time of water and when its amplitude lies in a range just before dielectric saturation effects take place. In this region, that is, when the frequency lies in a small window of the microwave region around ∼20 GHz and amplitude ∼0.03 V Å(-1), the translational-rotational coupling is most effective, yielding fluid velocities of magnitudes of ∼2 ms(-1) with only moderate fluid heating. In this work, we also confine water to a realistic nanochannel made of graphene giving a hydrophobic surface on one side and β-cristobalite giving a hydrophilic surface on the other, reproducing slip-and-stick velocity boundary conditions, respectively. This enables us to demonstrate that in a realistic environment, the coupling can be effectively exploited to achieve noncontact pumping of water at the nanoscale. A quantitative comparison between nonequilibrium molecular dynamics and analytical solutions of the extended Navier-Stokes equations, including an external rotating electric field has been performed

  18. 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.

  19. Experimental study of the flow of ferrofluid in a porous media under a magnetic field

    NASA Astrophysics Data System (ADS)

    Khurana, Muskaan

    This research presents results from a laboratory-scale experimental setup that was designed to visualize the behavior of ferrofluid percolation through a porous media. Ferrofluids are colloidal suspensions made of magnetic particles of a few nanometers and stabilized in carrier liquids like water or mineral oil. Ferrofluids get magnetized and align themselves in the direction of a magnetic field when a field gradient is applied. With the help of this experiment we investigate the viability of controlling fluid flow in porous medium by a magnetic field in vicinity. The experiments show that ferrofluids can be used as a transporting media to push the higher viscosity fluid out of the porous media when magnetic forces are acting on it. The magnetic force produces stronger attractive forces on the ferrofluid around the magnet which results in a predictable arrangement which is in- dependent of the heterogeneity of the medium. When capillary or viscous forces are predominant during the 2-dimensional drainage of immiscible fluids in a permeable medium, the injected fluid forms very thin finger like structure which then retains the fluid being displaced in them. No fingers due to varying viscosities are observed during displacement by ferrofluids in the medium. Displacement visualization experiments in an oil saturated porous medium shows that ferrofluids obtain a rectangular shaped final configuration around the magnet, irrespective of the initial arrangement and flow path. The aim of this research is to control the instabilities that occur during the displacement of a fluid with the help of ferrofluid and magnetic field in vicinity. While the applications of ferrofluids are promising in the field of engineering, the results obtained are particularly relevant to the laboratory scale experiments where the weakening of magnetic strength due to increasing distance is a smaller limitation. Ferrofluids may find an immediate application in areas like enhancing oil recovery, in

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Flow field studies of a new series of turbulent premixed stratified flames

    SciTech Connect

    Seffrin, F.; Fuest, F.; Dreizler, A.; Geyer, D.

    2010-02-15

    This paper presents a new burner design for lean premixed stratified combustion for experiments to validate models for numerical simulations. The burner demonstrates combustion phenomena relevant to technological applications, where flames are often turbulent, lean premixed, and stratified. The generic burner was designed for high Reynolds number flows and can stabilize a variety of different lean premixed flames. The burner's design and its versatile operational conditions are introduced. Shear, stratification, and fuel type are parametrically varied to provide a sound database of related flow configurations. Reacting and corresponding non-reacting configurations are examined. Experimental setups and the results of laser Doppler velocimetry (LDV) and particle image velocimetry (PIV) are presented and discussed. LDV measurements provide radial profiles of mean axial velocity, mean radial velocity, and turbulent kinetic energy as well as integral time scales. High-speed PIV is introduced as a novel technique to determine integral time and length scales and provide 2D 2-component velocity fields and related quantities, such as vorticity. (author)

  6. 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.

  7. Evolving Dynamics of the Supergranular Flow Field

    NASA Astrophysics Data System (ADS)

    De Rosa, M. L.; Lisle, J. P.; Toomre, J.

    2000-05-01

    We study several large (45-degree square) fields of supergranules for as long as they remain visible on the solar disk (about 6 days) to characterize the dynamics of the supergranular flow field and its interaction with surrounding photospheric magnetic field elements. These flow fields are determined by applying correlation tracking methods to time series of mesogranules seen in full-disk SOI-MDI velocity images. We have shown previously that mesogranules observed in this way are systematically advected by the larger scale supergranular flow field in which they are embedded. Applying correlation tracking methods to such time series yields the positions of the supergranular outflows quite well, even for locations close to disk center. These long-duration datasets contain several instances where individual supergranules are recognizable for time scales as long as 50 hours, though most cells persist for about 25 hours that is often quoted as a supergranular lifetime. Many supergranule merging and splitting events are observed, as well as other evolving flow patterns such as lanes of converging and diverging fluid. By comparing the flow fields with the corresponding images of magnetic fields, we confirm the result that small-scale photospheric magnetic field elements are quickly advected to the intercellular lanes to form a network between the supergranular outflows. In addition, we characterize the influence of larger-scale regions of magnetic flux, such as active regions, on the flow fields. Furthermore, we have measured even larger-scale flows by following the motions of the supergranules, but these flow fields contain a high noise component and are somewhat difficult to interpret. This research was supported by NASA through grants NAG 5-8133 and NAG 5-7996, and by NSF through grant ATM-9731676.

  8. Laboratory and Field Studies of Fracture Flow and Its Extension in Underground Settings

    NASA Astrophysics Data System (ADS)

    Wang, J. S.; Hudson, J. A.

    2012-12-01

    Basic studies of fracture flow, such as the cubic law, were widely cited for over four decades and used in understanding processes in fractured media. We evaluate the fracture flow law implications and its extensions. The understanding of fluid flow through fractured rocks is important for progress in the many existing and proposed engineering projects dedicated to the support of mankind. Moreover, the characterization of this understanding is crucial during the use of the supporting computer modeling—which is becoming evermore ambitious and ubiquitous. The calculations and resultant outputs need to be validated, both in order to ensure appropriate engineering decisions and because there is increasing emphasis on the use of the Earth's resources, their sustainability and more accountability of engineers' decisions. Within this context, there remain many unknowns: how do we establish the geometrical and hydro-geological properties of fractures in a specific rock mass?; how do we establish the link between the hydro-geological fracture properties and other variables such as the in situ stress state?; and how do we validate the results at the full scale? Concurrently with the laboratory and numerical studies of fracture flows, we have made progresses in developing underground research laboratories (URLs) in both hard and soft rocks, in housing large halls for particle detections at great depths, and in testing the energy and resource recovery capacities and the waste disposal potentials through borehole complexes. In addition to existing worldwide networks for radioactive wastes, we initiate comparisons of different underground laboratories and facilities, including also physics laboratories and borehole complexes. The 2011-2012 findings of a Commission for the International Society for Rock Mechanics on URL Networking are summarized. Side drifts of roadway tunnels, dedicated facilities with tunneling and shafting to reach desired depths, and levels in active and

  9. Particle and flow field holography

    NASA Astrophysics Data System (ADS)

    Trolinger, J. D.

    1985-01-01

    The current status of particle field and flow field holography is examined, and the methods based on the principles of either class of imagery are described. Special consideration is given to the automated data reduction technology. Current applications of flow diagnostics, which can provide thousands of holograms during a one-day experiment, include NASA applications in wind tunnel holography, in a Laser Doppler Velocimeter, in holographic movies, and in an optical device for recording crystal growth at zero gravity, to be used in the Space Lab 3 shuttle mission scheduled for May 1985. Military applications of the flow diagnostics include the use of holographic tomography for visualizing flow fields around airborne structures, in wind tunnels, and in the analyses of rocket exhausts and gun ranges. The information provided by the particle sizing holography, concerning the size, shape, number, and velocity of particles and the records of the particle break-up phenomenon, can be used in various military field oriented and airborne applications and in meteorology and environment protection science.

  10. 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.

  11. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  12. 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.

  13. Numerical study of electric potential formation in a weakly ionized plasma flowing supersonically through open magnetic field lines

    NASA Astrophysics Data System (ADS)

    Laosunthara, Ampan; Takeda, Jun; Akatsuka, Hiroshi

    2017-01-01

    We investigate the mechanism of space potential formation due to a diverging magnetic field on a rarefied weakly ionized plasma flowing supersonically by performing a hybrid simulation. Ions and neutrals are treated by the particle-based direct simulation Monte Carlo method, while electrons are treated as a fluid to save time and memory. We apply an electron continuity equation in order to treat the electron velocity independently of the ion velocity. We find the number density of ions (and electrons) distributed along the magnetic field. We also find electron rotation along the flowing direction. Since we remove the current-free condition assumed in our previous study, we find that the longitudinal variation in the space potential agrees reasonably well with our previous experimental results.

  14. 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.

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

    PubMed

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

    2014-01-01

    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. 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 between high

  16. 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

  17. A new analytical approach based on asymmetrical flow field-flow fractionation coupled to ultraviolet spectrometry and light scattering detection for SWCNT aqueous dispersion studies.

    PubMed

    Gigault, Julien; Grassl, Bruno; Lespes, Gaëtane

    2012-02-21

    This work demonstrates the potential of asymmetrical flow field-flow fractionation (A4F) coupled to Ultraviolet spectrometry (UV) and multi-angle light scattering (MALS) for the study of single-walled carbon nanotube (SWCNT) dispersion in aqueous solutions containing a surfactant. The results indicate that this technique is a powerful analytical tool that is able to evaluate SWCNT dispersion states in aqueous media and, more importantly, determine the presence or absence of aggregates, the numbers and sizes of different SWCNT populations and the SWCNT size distribution. Dynamic light scattering was employed to complete and demonstrate the relevance of the data that were obtained via A4F-UV-MALS. Two different anionic surfactants that are used to disperse SWCNTs were then studied. The dispersing powers of the surfactants were experimentally evaluated based on their structural organizations. This study demonstrates that surfactant concentration and sonication energy are key parameters that control the SWCNT dispersion state and SWCNT structural integrity therein.

  18. Neural Action Fields for Optic Flow Based Navigation: A Simulation Study of the Fly Lobula Plate Network

    PubMed Central

    Borst, Alexander; Weber, Franz

    2011-01-01

    Optic flow based navigation is a fundamental way of visual course control described in many different species including man. In the fly, an essential part of optic flow analysis is performed in the lobula plate, a retinotopic map of motion in the environment. There, the so-called lobula plate tangential cells possess large receptive fields with different preferred directions in different parts of the visual field. Previous studies demonstrated an extensive connectivity between different tangential cells, providing, in principle, the structural basis for their large and complex receptive fields. We present a network simulation of the tangential cells, comprising most of the neurons studied so far (22 on each hemisphere) with all the known connectivity between them. On their dendrite, model neurons receive input from a retinotopic array of Reichardt-type motion detectors. Model neurons exhibit receptive fields much like their natural counterparts, demonstrating that the connectivity between the lobula plate tangential cells indeed can account for their complex receptive field structure. We describe the tuning of a model neuron to particular types of ego-motion (rotation as well as translation around/along a given body axis) by its ‘action field’. As we show for model neurons of the vertical system (VS-cells), each of them displays a different type of action field, i.e., responds maximally when the fly is rotating around a particular body axis. However, the tuning width of the rotational action fields is relatively broad, comparable to the one with dendritic input only. The additional intra-lobula-plate connectivity mainly reduces their translational action field amplitude, i.e., their sensitivity to translational movements along any body axis of the fly. PMID:21305019

  19. 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.

  20. 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.

  1. 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.

  2. 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.

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

    SciTech Connect

    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 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. 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.

  4. 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.

  5. 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.

  6. 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 %.

  7. 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. Published by Oxford University Press on behalf of the British Occupational Hygiene Society 2015.

  8. 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

  9. 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.

  10. Groundwater flow and mixing in a wetland-stream system: Field study and numerical modeling

    NASA Astrophysics Data System (ADS)

    Karan, Sachin; Engesgaard, Peter; Looms, Majken C.; Laier, Troels; Kazmierczak, Jolanta

    2013-04-01

    SummaryWe combined electrical resistivity tomography (ERT) on land and in a stream with zone-based hydraulic conductivities (from multi-level slug testing) to investigate the local geological heterogeneity of the deposits in a wetland-stream system. The detailed geology was incorporated into a numerical steady-state groundwater model that was calibrated against average head observations. The model results were tested against groundwater fluxes determined from streambed temperature measurements. Discharge varied up to one order of magnitude across the stream and the model was successful in capturing this variability. Water quality analyses from multi-level sampling underneath the streambed and in the wetland showed a stratification in groundwater composition with an aerobic shallow zone with oxygen and nitrate (top ˜3 m) overlying a reduced, anoxic zone. While NO3- concentrations up to 58 mg L-1 were found in the top of the aquifer and immediately underneath the streambed no NO3- was detected deeper within the aquifer. An inverse relationship between NO3- and SO42- suggests that pyrite oxidation takes place in the deeper parts of the aquifer. Simulated flow path lines showed very different origins for deeper groundwater samples. No nitrate reduction is believed to occur in the shallow zone, where oxygen is present, and the residence time is on the order of 1 year. Nitrate reduction can, however, occur in the deeper parts, which are oxygen-free, and where the residence time is on the order of 7 years. A simulation with a homogeneous model did not match the observations nearly as well as a heterogeneous model based on ERT and a spatially distributed hydraulic conductivity. Furthermore, the origin of the sampled groundwater could not have been predicted from groundwater hydraulic head and the groundwater chemistry alone. The presented approach of integrating such methods in groundwater-surface water exchange studies, proved efficient to obtain information of the

  11. 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.

  12. Size separations of starch of different botanical origin studied by asymmetrical-flow field-flow fractionation and multiangle light scattering.

    PubMed

    Wahlund, Karl-Gustav; Leeman, Mats; Santacruz, Stalin

    2011-02-01

    Asymmetrical-flow field-flow fractionation combined with multiangle light scattering and refractive index detection has been revealed to be a powerful tool for starch characterization. It is based on size separation according to the hydrodynamic diameter of the starch components. Starch from a wide range of different botanical sources were studied, including normal starch and high-amylose and high-amylopectin starch. The starch was dissolved by heat treatment at elevated pressure in a laboratory autoclave. This gave clear solutions with no granular residues. Amylose retrogradation was prevented by using freshly dissolved samples. Programmed cross flow starting at 1.0 mL min(-1) and decreasing exponentially with a half-life of 4 min was utilised. The starches showed two size populations representing mainly amylose and mainly amylopectin with an overlapping region where amylose and amylopectin were possibly co-eluted. Most of the first population had molar masses below 10(6) g mol(-1), and most of the second size population had molar masses above 10(7) g mol(-1). Large differences were found in the relative amounts of the two populations, the molar mass, and hydrodynamic diameters, depending on the plant source and its varieties.

  13. 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.

  14. Flow Field Classification Using Critical Point Matching

    NASA Astrophysics Data System (ADS)

    Krueger, Paul S.; Williams, Sheila; Hahsler, Michael; Olinick, Eli V.

    2016-11-01

    Classification of flow fields according to topological similarities can help reveal features of the flow generation and evolution for bluff body flows, and characterize different swimming maneuvers in aquatic locomotion, to name a few. Rigorous classification can be challenging, however, especially when complex flows are distorted by measurement uncertainties or variable flow generating conditions. The present work uses critical points of the velocity field to characterize the global flow topology. Flow fields are compared by finding a best match of critical points in two flow fields based on topological and location characteristics of the critical points together with general point set distance measures. The similarity between the flow fields is quantified based on the matched critical points. Applying clustering algorithms to a set of flow fields with quantified similarity can then be used to group flows with similar characteristics. This approach has been applied to generic 2D flow fields constructed using potential flow results and is able to correctly identify similar flow fields even after large distortions (up to 20% of the vortex separation) have been applied to the flows. Support of NSF Grant Nos. 1115139 and 1557698, and the Lyle School of Engineering is gratefully acknowledged.

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

    DOE PAGES

    Sjöberg, Ylva; Coon, Ethan; K. Sannel, A. Britta; ...

    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

  16. 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.

  17. Variation of flow field around twin cylinders with and without the outer perforated cylinder — Numerical study

    NASA Astrophysics Data System (ADS)

    Srinivasan, Chandrasekaran; Madhavi, N.

    2016-10-01

    Presence of the outer perforated cylinder reduces the direct wave impact on the inner cylinder, which has been testified by many researchers. However, the force reduction mechanism, which is complicated due to the wave-porous structure interaction, needs to be addressed in detail. The present study explains the mechanism with the aid of the computational fluid dynamics (CFD) tool STAR CCM+. This package is chosen for its capabilities to simulate viscous and turbulence effects caused by passage of waves. For the present study, flow fields around the twin cylinders with different orientations are examined with and without the outer perforated cover. Mechanism contributing to the reduction of force on the existing structure is explained in physical terms, and force reduction is quantified. The present study has direct application in the retrofitting application of offshore members.

  18. 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.

  19. Motion field and optical flow: Qualitative properties

    NASA Astrophysics Data System (ADS)

    Verri, Alessandro; Poggio, Tomaso

    1986-12-01

    The optical flow, a 2-D field that can be associated with the variation of the image brightness pattern, and the 2-D motion field, the projection on the image plane of the 3-D velocity field of a moving scene, are in general different, unless very special conditions are satisfied. The optical flow, therefore, is ill suited for computing structure from motion, and for reconstructing the 3-D velocity field, problems that require an accurate estimate of the 2-D motion field. A different use of the optical flow is suggested. Stable field and the 3-D structure of the scene, and they can usually be obtained from the optical flow. The smoothed optical flow and 2-D motion field, interpreted as vector fields tangent to flows of planar dynamical systems, may have the same qualitative properties from the point of view of the theory of structural stability of dynamical systems.

  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. 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.

  2. 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.

  3. Field study of air change and flow rate in six automobiles.

    PubMed

    Knibbs, L D; de Dear, R J; Atkinson, S E

    2009-08-01

    For many people, a relatively large proportion of daily exposure to a multitude of pollutants may occur inside an automobile. A key determinant of exposure is the amount of outdoor air entering the cabin (i.e. air change or flow rate). We have quantified this parameter in six passenger vehicles ranging in age from 18 years to <1 year, at three vehicle speeds and under four different ventilation settings. Average infiltration into the cabin with all operable air entry pathways closed was between 1 and 33.1 air changes per hour (ACH) at a vehicle speed of 60 km/h, and between 2.6 and 47.3 ACH at 110 km/h, with these results representing the most (2005 Volkswagen Golf) and least air-tight (1989 Mazda 121) vehicles, respectively. Average infiltration into stationary vehicles parked outdoors varied between approximately 0 and 1.4 ACH and was moderately related to wind speed. Measurements were also performed under an air recirculation setting with low fan speed, while airflow rate measurements were conducted under two non-recirculate ventilation settings with low and high fan speeds. The windows were closed in all cases, and over 200 measurements were performed. The results can be applied to estimate pollutant exposure inside vehicles. There is increasing recognition of the often disproportionately large contribution of in-vehicle pollutant exposures to overall measures. This has highlighted the need for accurate and representative quantification of determinant factors to facilitate exposure estimation and mitigation. The ventilation rate in a vehicle cabin is a key parameter affecting the transfer of pollutants from outdoors to the cabin interior, and vice-versa. New data regarding this variable are presented here, and the results indicate substantial variability in outdoor air infiltration into vehicles of differing age. The efficacy of simple measures to reduce outdoor air infiltration into 'leaky' vehicles to increase occupant protection would be a worthwhile avenue

  4. 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

  5. Computational studies of the effects of acoustics and chemistry on the flow field in an axisymmetric ramjet combustor

    NASA Astrophysics Data System (ADS)

    Kailasanath, K.; Gardner, J. H.; Oran, E. S.; Boris, J. P.

    1986-10-01

    A potentially important source of large pressure oscillations in compact ramjets is a combustion instability induced by the interaction of large-scale vortex structures with acoustic modes in the combustion chamber. To study these interactions numerical simulations were performed using the Flux Corrected Transport technique. The highlights are presented of the work to date on the chemical-acoustic-vortex interactions in an idealized axisymmetric ramjet combustor. The results of a number of cold flow calculations are presented in which the length of the combustion chamber and the acoustic forcing function were systematically varied. These simulations indicate a strong coupling between the acoustic modes and the frequency of formation of large vortical structures near the entrance to the combustion chamber. They also show the presence of a low frequency oscillation which does not directly depend on the acoustics of the combustor but depends on the acoustics of the inlet. The effects of energy release from chemical reactions on the flow field in the combustor and the low frequecy oscillations are discussed.

  6. 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

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Studies on fluid dynamics of the flow field and gas transfer in orbitally shaken tubes.

    PubMed

    Zhu, Li-Kuan; Song, Bo-Yan; Wang, Zhen-Long; Monteil, Dominique T; Shen, Xiao; Hacker, David L; De Jesus, Maria; Wurm, Florian M

    2017-01-01

    Orbitally shaken cylindrical bioreactors [OrbShake bioreactors (OSRs)] without an impeller or sparger are increasingly being used for the suspension cultivation of mammalian cells. Among small volume OSRs, 50-mL tubes with a ventilated cap (OSR50), originally derived from standard laboratory centrifuge tubes with a conical bottom, have found many applications including high-throughput screening for the optimization of cell cultivation conditions. To better understand the fluid dynamics and gas transfer rates at the liquid surface in OSR50, we established a three-dimensional simulation model of the unsteady liquid forms (waves) in this vessel. The studies verified that the operating conditions have a large effect on the interfacial surface. The volumetric mass transfer coefficient (kL a) was determined experimentally and from simulations under various working conditions. We also determined the liquid-phase mass transfer coefficient (kL ) and the specific interfacial area (a) under different conditions to demonstrate that the value of a affected the gas transfer rate more than did the value of kL . High oxygen transfer rates, sufficient for supporting the high-density culture of mammalian cells, were found. Finally, the average axial velocity of the liquid was identified to be an important parameter for maintaining cells in suspension. Overall these studies provide valuable insights into the preferable operating conditions for the OSR50, such as those needed for cell cultures requiring high oxygen levels. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 33:192-200, 2017. © 2016 American Institute of Chemical Engineers.

  13. Laboratory Experiments and Modeling for Interpreting Field Studies of Secondary Organic Aerosol Formation Using an Oxidation Flow Reactor

    SciTech Connect

    Jimenez, Jose-Luis

    2016-02-01

    This grant was originally funded for deployment of a suite of aerosol instrumentation by our group in collaboration with other research groups and DOE/ARM to the Ganges Valley in India (GVAX) to study aerosols sources and processing. Much of the first year of this grant was focused on preparations for GVAX. That campaign was cancelled due to political reasons and with the consultation with our program manager, the research of this grant was refocused to study the applications of oxidation flow reactors (OFRs) for investigating secondary organic aerosol (SOA) formation and organic aerosol (OA) processing in the field and laboratory through a series of laboratory and modeling studies. We developed a gas-phase photochemical model of an OFR which was used to 1) explore the sensitivities of key output variables (e.g., OH exposure, O3, HO2/OH) to controlling factors (e.g., water vapor, external reactivity, UV irradiation), 2) develop simplified OH exposure estimation equations, 3) investigate under what conditions non-OH chemistry may be important, and 4) help guide design of future experiments to avoid conditions with undesired chemistry for a wide range of conditions applicable to the ambient, laboratory, and source studies. Uncertainties in the model were quantified and modeled OH exposure was compared to tracer decay measurements of OH exposure in the lab and field. Laboratory studies using OFRs were conducted to explore aerosol yields and composition from anthropogenic and biogenic VOC as well as crude oil evaporates. Various aspects of the modeling and laboratory results and tools were applied to interpretation of ambient and source measurements using OFR. Additionally, novel measurement methods were used to study gas/particle partitioning. The research conducted was highly successful and details of the key results are summarized in this report through narrative text, figures, and a complete list of publications acknowledging this grant.

  14. 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

  15. 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

  16. 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

  17. 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.

  18. Microbial field pilot study

    SciTech Connect

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

    1991-12-06

    The objective of this project is to perform a microbial enhanced oil recovery field pilot test 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 preferentially swept by a prior waterflood. This will force future flood water to invade bypassed regions of the reservoir and increase sweep efficiency. During this quarter an additional tracer study was performed in the field to determine pre-treatment flow paths and the first nutrients were injected. 2 figs.

  19. Io: Heat flow from dark volcanic fields

    NASA Astrophysics Data System (ADS)

    Veeder, Glenn J.; Davies, Ashley Gerard; Matson, Dennis L.; Johnson, Torrence V.

    2009-11-01

    Dark flow fields on the jovian satellite Io are evidence of current or recent volcanic activity. We have examined the darkest volcanic fields and quantified their thermal emission in order to assess their contribution to Io's total heat flow. Loki Patera, the largest single source of heat flow on Io, is a convenient point of reference. We find that dark volcanic fields are more common in the hemisphere opposite Loki Patera and this large scale concentration is manifested as a maximum in the longitudinal distribution (near ˜200 °W), consistent with USGS global geologic mapping results. In spite of their relatively cool temperatures, dark volcanic fields contribute almost as much to Io's heat flow as Loki Patera itself because of their larger areal extent. As a group, dark volcanic fields provide an asymmetric component of ˜5% of Io's global heat flow or ˜5 × 10 12 W.

  20. 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.

  1. Lattice-based flow field modeling.

    PubMed

    Wei, Xiaoming; Zhao, Ye; Fan, Zhe; Li, Wei; Qiu, Feng; Yoakum-Stover, Suzanne; Kaufman, Arie E

    2004-01-01

    We present an approach for simulating the natural dynamics that emerge from the interaction between a flow field and immersed objects. We model the flow field using the Lattice Boltzmann Model (LBM) with boundary conditions appropriate for moving objects and accelerate the computation on commodity graphics hardware (GPU) to achieve real-time performance. The boundary conditions mediate the exchange of momentum between the flow field and the moving objects resulting in forces exerted by the flow on the objects as well as the back-coupling on the flow. We demonstrate our approach using soap bubbles and a feather. The soap bubbles illustrate Fresnel reflection, reveal the dynamics of the unseen flow field in which they travel, and display spherical harmonics in their undulations. Our simulation allows the user to directly interact with the flow field to influence the dynamics in real time. The free feather flutters and gyrates in response to lift and drag forces created by its motion relative to the flow. Vortices are created as the free feather falls in an otherwise quiescent flow.

  2. 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.

  3. 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.

  4. Simulating unsaturated flow fields based on saturationmeasurements

    SciTech Connect

    Kitterod, Nils-Otto; Finsterle, Stefan

    2003-12-15

    Large amounts of de-icing chemicals are applied at the airport of Oslo, Norway. These chemicals pose a potential hazard to the groundwater because the airport is located on a delta deposit over an unconfined aquifer. Under normal flow conditions, most of the chemicals degrade in the vadose zone, but during periods of intensive infiltration, the residence time of contaminants in the unsaturated zone may be too short for sufficient degradation. To assess the potential for groundwater contamination and to design remedial actions, it is essential to quantify flow velocities in the vadose zone. The main purpose of this study is to evaluate theoretical possibilities of using measurements of liquid saturation in combination with inverse modeling for the estimation of unsaturated flow velocities. The main stratigraphic units and their geometry were identified from ground penetrating radar (GPR) measurements and borehole logs. These observations are included as a priori information in the inverse modeling. The liquid saturation measurements reveal the smaller-scale heterogeneities within each stratigraphic unit. The relatively low sensitivity of flow velocities to the observable saturation limits the direct inference of hydraulic parameters. However, even an approximate estimate of flow velocities is valuable as long as the estimate is qualified by an uncertainty measure. A method referred to as simulation by Empirical Orthogonal Functions (EOF) was adapted for uncertainty propagation analyses. The EOF method is conditional in the sense that statistical moments are reproduced independent of second-order stationarity. This implies that unlikely parameter combinations are discarded from the uncertainty propagation analysis. Simple forward simulations performed with the most likely parameter set are qualitatively consistent with the apparent fast flow of contaminants from an accidental spill. A field tracer test performed close to the airport will be used as an independent

  5. 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.

  6. 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.

  7. 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.

  8. Io: Heat Flow from Dark Volcanic Fields

    NASA Astrophysics Data System (ADS)

    Veeder, G. J.; Matson, D. L.; Davies, A. G.; Johnson, T. V.

    2008-03-01

    We focus on the heat flow contribution from dark volcanic fields on Io. These are concentrated in the anti-Loki hemisphere. We use the areas and estimated effective temperatures of dark flucti to derive their total power.

  9. 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.

  10. 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.

  11. Internal corner flow fields. [calculations for super/hypersonic inlets

    NASA Technical Reports Server (NTRS)

    Marconi, F.

    1979-01-01

    A computational procedure has been developed to predict the inviscid super/hypersonic flow field of conical internal corners. The prediction of internal corner flow fields can be important in the design of supersonic 'box' type inlets. The computational procedure utilizes a second order finite difference marching technique to asymptote to the conical corner flow solution of Euler's equations. These flow fields are dominated by complex shock interactions. All discontinuities, shocks and slip surfaces are fitted with the appropriate jump conditions. The 'triple' points (the interaction of two shocks and a slip surface) are also computed exactly. Computed results are compared with experimental data and the computational results of other investigators. In addition, the sensitivity of these flow fields to a number of geometric parameters is studied, and the impact of these flows on inlet performance is assessed.

  12. 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.

  13. Field Detection of Chemical Assimilation in A Basaltic Lava Flow

    NASA Technical Reports Server (NTRS)

    Young, K. E.; Bleacher, J. E.; Needham, D. H.; Evans, C. A.; Whelley, P. L.; Scheidt, S. P.; Williams, D. A.; Rogers, A. D.; Glotch, T.

    2017-01-01

    Lava channels are features seen throughout the inner Solar System, including on Earth, the Moon, and Mars. Flow emplacement is therefore a crucial process in the shaping of planetary surfaces. Many studies, including some completed by members of this team at the December 1974 lava flow, have investigated the dynamics of lava flow emplacement, both on Earth and on the Moon and how pre-flow terrain can impact final channel morphology, but far fewer have focused on how the compositional characteristics of the substrate over which a flow was em-placed influenced its final flow morphology. Within the length of one flow, it is common for flows to change in morphology, a quality linked to rheology (a function of multiple factors including viscosi-ty, temperature, composition, etc.). The relationship between rheology and temperature has been well-studied but less is known about the relationship between an older flow's chemistry and how the interaction between this flow and the new flow might affect lava rheology and therefore emplacement dynamics. Lava erosion. Through visual observations of active terrestrial flows, mechanical erosion by flowing lava has been well-documented. Lava erosion by which flow composition is altered as the active lava melts and assimilates the pre-flow terrain over which it moves is also hypothesized to affect channel formation. However, there is only one previous field study that geochemically documents the process in recent basaltic flow systems.

  14. A comprehensive study on the atom flow in the cross-field discharge of a Hall thruster

    NASA Astrophysics Data System (ADS)

    Mazouffre, S.; Bourgeois, G.; Garrigues, L.; Pawelec, E.

    2011-03-01

    The flow properties of Xe atoms were investigated in the 1 kW class PPS100-ML Hall effect thruster by means of Doppler-shifted laser-induced fluorescence spectroscopy in the near infrared. Fluorescence spectra of the 6s\\,[1/2]_2^o resonant level and the 6s\\,[3/2]_2^o metastable level have been acquired inside and outside the thruster channel under several operating conditions. Analytical treatment and modelling of the measured lineshapes indicate the atom axial velocity increases inside the channel to a value well above the sound speed before decreasing quickly in the near-field plume. Numerical simulations performed with a fluid/kinetic hybrid approach allow us to explain the shape of the velocity profile. Atomic flow acceleration originates in the combination of three processes, namely the selective ionization of slow atoms, the flow expansion and the creation of fast neutrals on BN-SiO2 walls owing to recombination of ions. Deceleration results from the invasion of the atomic jet by slow and relatively cold atoms from the residual background gas and from the cathode. In addition, it is shown that charge-exchange collisions have a non-negligible impact on the atom velocity in spite of the low background pressure in test chambers.

  15. 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.

  16. Inviscid Flow Field Effects: Experimental results

    NASA Astrophysics Data System (ADS)

    Otten, L. J., III; Gilbert, K. G.

    1980-04-01

    The aero-optical distortions due to invisid flow effects over airborne laser turrets is investigated. Optical path differences across laser turret apertures are estimated from two data sources. The first is a theoretical study of main flow effects for a spherical turret assembly for a Mach number (M) of 0.6. The second source is an actual wind tunnel density field measurement on a 0.3 scale laser turret/fairing assembly, with M = 0.75. A range of azimuthal angles from 0 to 90 deg was considered, while the elevation angle was always 0 deg (i.e., in the plane of the flow). The calculated optical path differences for these two markedly different geometries are of the same order. Scaling of results to sea level conditions and an aperture diameter of 50 cm indicated up to 0.0007 cm of phase variation across the aperture for certain forward look angles and a focal length of F = -11.1 km. These values are second order for a 10.6 micron system.

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

    SciTech Connect

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

    2016-06-15

    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.

  18. Flow-synchronous field motion refrigeration

    DOEpatents

    Hassen, Charles N.

    2017-08-22

    An improved method to manage the flow of heat in an active regenerator in a magnetocaloric or an electrocaloric heat-pump refrigeration system, in which heat exchange fluid moves synchronously with the motion of a magnetic or electric field. Only a portion of the length of the active regenerator bed is introduced to or removed from the field at one time, and the heat exchange fluid flows from the cold side toward the hot side while the magnetic or electric field moves along the active regenerator bed.

  19. 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.

  20. 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.

  1. 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

  2. Flow Fields Over Unsteady Three Dimensional Dunes

    NASA Astrophysics Data System (ADS)

    Hardy, R. J.; Reesink, A.; Parsons, D. R.; Ashworth, P. J.; Best, J.

    2013-12-01

    The flow field over dunes has been extensively measured in laboratory conditions and there is general understanding on the nature of the flow over dunes formed under equilibrium flow conditions. However, fluvial systems typically experience unsteady flow and therefore the sediment-water interface is constantly responding and reorganizing to these unsteady flows, over a range of both spatial and temporal scales. This is primarily through adjustment of bed forms (including ripples, dunes and bar forms) which then subsequently alter the flow field. This paper investigates, through the application of a numerical model, the influence of these roughness elements on the overall flow and the increase in flow resistance. A series of experiments were undertaken in a flume, 16m long and 2m wide, where a fine sand (D50 of 239μm) mobile bed was water worked under a range of unsteady hydraulic conditions to generate a series of quasi-equilibrium three dimensional bed forms. During the experiments flow was measured with acoustic Doppler velocimeters, (aDv's). On four occasions the flume was drained and the bed topography measured with terrestrial LiDAR to create digital elevation models. This data provide the necessary boundary conditions and validation data for a Large Eddy Simulation (LES) model, which provided a three dimensional time dependent prediction of flow over the four static beds. The numerical predicted flow is analyzed through a series of approaches, and included: i) standard Reynolds decomposition to the flow fields; ii) Eulerian coherent structure detection methods based on the invariants of the velocity gradient tensor; iii) Lagrangian coherent structure identification methods based upon direct Lyapunov exponents (DLE). The results show that superimposed bed forms can cause changes in the nature of the classical separated flow region in particularly the number of locations where vortices are shed and the point of flow reattachment, which may be important for

  3. 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.

  4. Numerical Temperature And Fluid-Flow Modelling For The Topographic Effects On Hydrothermal Circulation; A case study in Lucy Strike Vent Field

    NASA Astrophysics Data System (ADS)

    Erçetin, Engin; Düşünür Doǧan, Doǧa

    2017-04-01

    The aim of the study is to present a numerical temperature and fluid-flow modelling for the topographic effects on hydrothermal circulation. Bathymetry can create a major disturbance on fluid flow pattern. ANSYS Fluent Computational fluid dynamics software is used for simulations. Coupled fluid flow and temperature quations are solved using a 2-Dimensional control volume finite difference approach. Darcy's law is assumed to hold, the fluid is considered to be anormal Boussinesq incompressible fluid neglecting inertial effects. Several topographic models were simulated and both temperature and fluid flow calculations obtained for this study. The preliminary simulations examine the effect of a ingle bathymetric high on a single plume and the secondary study of simulations investigates the effect of multiple bathymetric highs on multiple plume. The simulations were also performed for the slow spreading Lucky Strike segment along the Mid-Atlantic Ridge (MAR), one of the best studied regions along the MAR, where a 3.4 km deep magma chamber extending 6 km along-axis is found at its center. The Lucky Strike segment displays a transitional morphology between that of the FAMOUS - North FAMOUS segments, which are characterized by well-developed axial valleys typical of slow-spreading segments, and that of the Menez Gwen segment, characterized by an axial high at the segment center. Lucky Strike Segment hosts a central volcano and active vent field located at the segment center and thus constitutes an excellent case study to simulate the effects of bathymetry on fluid flow. Results demonstrate that bathymetric relief has an important influence on hydrothermal flow. Subsurface pressure alterations can be formed by bathymetric highs, for this reason, bathymetric relief ought to be considered while simulating hydrothermal circulation systems. Results of this study suggest the dominant effect of bathymetric highs on fluid flow pattern and Darcy velocities will be presented

  5. 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.

  6. Experimental and computational studies on the flow fields in aortic aneurysms associated with deployment of AAA stent-grafts

    NASA Astrophysics Data System (ADS)

    Zhang, Xiwen; Yao, Zhaohui; Zhang, Yan; Xu, Shangdong

    2007-10-01

    Pulsatile flow fields in rigid abdominal aortic aneurysm (AAA) models were investigated numerically, and the simulation results are found in good agreement with particle image velocimetry (PIV) measurements. There are one or more vortexes in the AAA bulge, and a fairly high wall shear stress exists at the distal end, and thus the AAA is in danger of rupture. Medical treatment consists of inserting a vascular stent-graft in the AAA, which would decrease the blood impact to the inner walls and reduce wall shear stress so that the rupture could be prevented. A new computational model, based on porous medium model, was developed and results are documented. Therapeutic effect of the stent-graft was verified numerically with the new model.

  7. Dynamics of Deformable Active Particles under External Flow Field

    NASA Astrophysics Data System (ADS)

    Tarama, Mitsusuke

    2017-10-01

    In most practical situations, active particles are affected by their environment, for example, by a chemical concentration gradient, light intensity, gravity, or confinement. In particular, the effect of an external flow field is important for particles swimming in a solvent fluid. For deformable active particles such as self-propelled liquid droplets and active vesicles, as well as microorganisms such as euglenas and neutrophils, a general description has been developed by focusing on shape deformation. In this review, we present our recent studies concerning the dynamics of a single active deformable particle under an external flow field. First, a set of model equations of active deformable particles including the effect of a general external flow is introduced. Then, the dynamics under two specific flow profiles is discussed: a linear shear flow, as the simplest example, and a swirl flow. In the latter case, the scattering dynamics of the active deformable particles by the swirl flow is also considered.

  8. Interaction of unsteady separated flow over multi-bodies moving relatively in the same flow field

    NASA Astrophysics Data System (ADS)

    Zhou, Sheng; Zheng, Xin-qian; Hou, An-ping; Lu, Ya-jun

    2005-12-01

    Unsteady separated flow is one of research frontiers in current aerodynamic. Great accomplishments have been acquired; however, most studies are on single body in a stream, such as studies on unsteady separated flows over airfoils. There are typical cases in the nature and engineering applications, in which several interacting bodies with relative motions are within the same flow field. These interacting unsteady separated flow fields not only are closely related to the phenomena of noise and flutter induced by flows, but also have strong influences on aerodynamic performances. With axial flow compressors as background, the present paper carried out studies on 'interaction of unsteady separated flow over multi-bodies moving relatively in the same flow field'. Experiment investigations carried out in the stationary annular cascade wind tunnel and the single-stage low-speed axial flow compressor experimental facility as well as relevant CFD simulations demonstrate that under properly organized interactions between all unsteady components, the time-space structure of unsteady separated flow field can be remarkably improved and the time-averaged aerodynamic performances be significantly enhanced accordingly. The maximum reduction of the loss coefficient reached 27.4% and 76.5% in the stationary annular cascade wind tunnel and the CFD simulation for single-stage axial flow compressor, respectively.

  9. 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.

  10. Low thrust viscous nozzle flow fields prediction

    NASA Technical Reports Server (NTRS)

    Liaw, G. S.; Mo, J. D.

    1991-01-01

    A Navier-Stokes code was developed for low thrust viscous nozzle flow field prediction. An implicit finite volume in an arbitrary curvilinear coordinate system lower-upper (LU) scheme is used to solve the governing Navier-Stokes equations and species transportation equations. Sample calculations of carbon dioxide nozzle flow are presented to verify the validity and efficiency of this code. The computer results are in reasonable agreement with the experimental data.

  11. Flow Field Measurement of Mixing Driven by Buoyancy

    NASA Technical Reports Server (NTRS)

    Batur, C.; Zhong, H.

    2003-01-01

    Mixing driven by buoyancy-induced flows inside a cavity consists of stretching and folding of an interface. Measurement of the flow field using particle imaging velocimetry shows that during stretching the flow field has a single elliptic point, thus dominated by a single vortex. However, global bifurcation that results in folding introduces a hyperbolic point whereby the flow field degenerates to multiple vortex interactions. The short-lived coherent structure observed during mixing which results in the Rayleigh- Taylor morphology is attributed to vortex interactions. The mixing characteristics of non-homogeneous fluids driven by buoyancy are important towards understanding transport phenomenon in a microgravity environment. Mixing consists of stretching and folding of an interface due to a flow field whose intensity depends on the body force. For miscible liquids, the characteristic of the flow field determines whether mass transport is governed by diffusion or bulk stirring which induces mixing. For technologically important processes, transport of mass is governed by the coupling of the body force to scalar gradients such as concentration and or temperature' 2 3 . In order to lend insight into these classes of problems we consider a model experimental system to study mixing driven by buoyancy-induced flows. The characteristics of mixing is addressed from detail measurements of the flow field using particle imaging velocimetry (PIV), and its corresponding interface dynamics using image processing techniques.

  12. Improved visualization of flow field measurements

    NASA Technical Reports Server (NTRS)

    Miles, Jeffrey Hilton

    1991-01-01

    A capability was developed that makes it possible 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) procedure was applied to the analysis of flow field measurements within a low aspect ratio transonic axial flow fan rotor obtained with 2-D laser anemometry. The procedure generates input for the visualization tools developed to display numerical solutions for computational fluid dynamics problems. The relative Mach number contour plots obtained by this method resemble the conventional contour plots obtained by more traditional methods. The results show that the MMS procedure can be used to generate input for the multidimensional processing and analysis tools developed for data from numerical flow field simulations. They show that an experimenter can apply the MMS procedure to his data and then use an interactive graphics program to display scalar quantities like the Mach number by profiles, carpet plots, contour lines, and surfaces using various colors. Also, flow directionality can be shown by display of vector fields and particle traces.

  13. 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.

  14. Flow field interactions between two tandem cyclists

    NASA Astrophysics Data System (ADS)

    Barry, Nathan; Burton, David; Sheridan, John; Thompson, Mark; Brown, Nicholas A. T.

    2016-12-01

    Aerodynamic drag is the primary resistive force acting on cyclists at racing speeds. Many events involve cyclists travelling in very close proximity. Previous studies have shown that interactions result in significant drag reductions for inline cyclists. However, the interaction between cyclist leg position (pedalling) and the vortical flow structures that contribute significantly to the drag on an isolated cyclist has not previously been quantified or described for tandem cyclists of varying separation. To this end, scale model cyclists were constructed for testing in a water channel for inline tandem configurations. Particle image velocimetry was used to capture time-averaged velocity fields around two tandem cyclists. Perhaps surprisingly, the wake of a trailing cyclist maintains strong similarity to the characteristic wake of a single cyclist despite a significant disturbance to the upstream flow. Together with streamwise velocity measurements through the wake and upstream of the trailing cyclist, this work supports previous findings, which showed that the trailing cyclist drag reduction is primarily due to upstream sheltering effects reducing the stagnation pressure on forward-facing surfaces.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. 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.

  2. 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.

  3. Numerical simulation of scramjet inlet flow fields

    NASA Technical Reports Server (NTRS)

    Kumar, Ajay

    1986-01-01

    A computer program was developed to analyze supersonic combustion ramjet (scramjet) inlet flow fields. The program solves the three-dimensional Euler or Reynolds averaged Navier-Stokes equations in full conservation form by either the fully explicit or explicit-implicit, predictor-corrector method of MacCormack. Turbulence is modeled by an algebraic eddy-viscosity model. The analysis allows inclusion of end effects which can significantly affect the inlet flow field. Detailed laminar and turbulent flow results are presented for a symmetric-wedge corner, and comparisons are made with the available experimental results to allow assessment of the program. Results are then presented for two inlet configurations for which experimental results exist at the NASA Langley Research Center.

  4. 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. Copyright © 2013 Elsevier B.V. All rights reserved.

  5. 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.

  6. The Flow Field Inside Ventricle Assist Device

    NASA Astrophysics Data System (ADS)

    Einav, Shmuel; Rosenfeld, Moshe; Avrahami, Idit

    2000-11-01

    The evaluation of innovative ventricle assist devices (VAD), is of major importance. A New Left Heart Assist Device, with an improved energy converter unit, has been investigated both numerically and experimentally. For this purpose, an experimental Continuous Digital Particle Imagining Velocimetry (CDPIV) is combined with a computational fluid dynamics (CFD) analysis. These tools complement each other to result into a comprehensive description of the complex 3D, viscous and time-dependent flow field inside the artificial ventricle. A 3D numerical model was constructed to simulate the VAD pump and a time-depended CFD analysis with moving walls was performed to predict the flow behaviour in the VAD during the cardiac cycle. A commercial finite element package was used to solve the Navier-Stokes equations (FIDAP, Fluent Inc., Evanston). In the experimental analysis, an optically clear elastic model of the VAD was placed inside a 2D CDPIV system. The CDPIV system is capable of sampling 15 velocity vector fields per second based on image-pairs intervals lower than 0.5 millisecond. Continuous sequences of experimental images, followed by their calculated velocity transient fields, are given as animated presentation of the distensible VAD. These results are used for validating the CFD simulations. Once validated, the CFD results provide a detailed 3D and time dependent description of the flow field, allowing the identification of stagnation or high shear stress regions.

  7. 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

  8. 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.

  9. Flow Cytometry Total Cell Counts: A Field Study Assessing Microbiological Water Quality and Growth in Unchlorinated Drinking Water Distribution Systems

    PubMed Central

    Liu, G.; Van der Mark, E. J.; Verberk, J. Q. J. C.; Van Dijk, J. C.

    2013-01-01

    The objective of this study was to evaluate the application of flow cytometry total cell counts (TCCs) as a parameter to assess microbial growth in drinking water distribution systems and to determine the relationships between different parameters describing the biostability of treated water. A one-year sampling program was carried out in two distribution systems in The Netherlands. Results demonstrated that, in both systems, the biomass differences measured by ATP were not significant. TCC differences were also not significant in treatment plant 1, but decreased slightly in treatment plant 2. TCC values were found to be higher at temperatures above 15°C than at temperatures below 15°C. The correlation study of parameters describing biostability found no relationship among TCC, heterotrophic plate counts, and Aeromonas. Also no relationship was found between TCC and ATP. Some correlation was found between the subgroup of high nucleic acid content bacteria and ATP (R 2 = 0.63). Overall, the results demonstrated that TCC is a valuable parameter to assess the drinking water biological quality and regrowth; it can directly and sensitively quantify biomass, detect small changes, and can be used to determine the subgroup of active HNA bacteria that are related to ATP. PMID:23819117

  10. Flow cytometry total cell counts: a field study assessing microbiological water quality and growth in unchlorinated drinking water distribution systems.

    PubMed

    Liu, G; Van der Mark, E J; Verberk, J Q J C; Van Dijk, J C

    2013-01-01

    The objective of this study was to evaluate the application of flow cytometry total cell counts (TCCs) as a parameter to assess microbial growth in drinking water distribution systems and to determine the relationships between different parameters describing the biostability of treated water. A one-year sampling program was carried out in two distribution systems in The Netherlands. Results demonstrated that, in both systems, the biomass differences measured by ATP were not significant. TCC differences were also not significant in treatment plant 1, but decreased slightly in treatment plant 2. TCC values were found to be higher at temperatures above 15°C than at temperatures below 15°C. The correlation study of parameters describing biostability found no relationship among TCC, heterotrophic plate counts, and Aeromonas. Also no relationship was found between TCC and ATP. Some correlation was found between the subgroup of high nucleic acid content bacteria and ATP (R (2) = 0.63). Overall, the results demonstrated that TCC is a valuable parameter to assess the drinking water biological quality and regrowth; it can directly and sensitively quantify biomass, detect small changes, and can be used to determine the subgroup of active HNA bacteria that are related to ATP.

  11. 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.

  12. 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.

  13. 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.

  14. 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).

  15. 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.

  16. 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.

  17. 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

  18. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  19. Magnitude-frequency relationships of debris flows — A case study based on field surveys and tree-ring records

    NASA Astrophysics Data System (ADS)

    Stoffel, Markus

    2010-03-01

    Debris-flow activity in a watershed is usually defined in terms of magnitude and frequency. While magnitude-frequency (M-F) relations have long formed the basis for risk assessment and engineering design in hydrology and fluvial hydraulics, only fragmentary and insufficiently specified data for debris flows exists. This paper reconstructs M-F relationships of 62 debris flows for an aggradational cone of a small (< 5 km 2), high elevation watershed in the Swiss Alps since A.D. 1863. The frequency of debris flows is obtained from tree-ring records. The magnitude of individual events is given as S, M, L, XL, and derived from volumetric data of deposits, grain size distributions of boulders, and a series of surrogates (snout elevations, tree survival, lateral spread of surges). Class S and M debris flows (< 5 × 10 3 m 3) encompass a typical size of events and have mean recurrence intervals of 5.4 (SD: 3.2) and 7.4 years (SD: 6.7), respectively. Class XL events (10 4-5 ×10 4 m 3) are, in contrast, only identified three times over the past 150 years, and major erosional activity on the cone was restricted to two of these events in 1948 and 1993. A comparison of results with hydrometeorological records shows that class L and XL events are typically triggered by advective storms (rainfall > 50 mm) in August and September, when the active layer of the rock glacier in the source area of debris flows is largest. Over the past ˜ 150 years, climate has exerted control on material released from the source area and prevented triggering of class XL events before 1922. With the projected climatic change, permafrost degradation and the potential increase in storm intensity are likely to produce " class XXL" events in the future with volumes surpassing 5 × 10 4 m 3 at the level of the debris-flow cone.

  20. Situational awareness and information flow in prehospital emergency medical care from the perspective of paramedic field supervisors: a scenario-based study.

    PubMed

    Norri-Sederholm, Teija; Paakkonen, Heikki; Kurola, Jouni; Saranto, Kaija

    2015-01-16

    In prehospital emergency medical services, one of the key factors in the successful delivery of appropriate care is the efficient management and supervision of the area's emergency medical services units. Paramedic field supervisors have an important role in this task. One of the key factors in the daily work of paramedic field supervisors is ensuring that they have enough of the right type of information when co-operating with other authorities and making decisions. However, a gap in information sharing still exists especially due to information overload. The aim of this study was to find out what type of critical information paramedic field supervisors need during multi-authority missions in order to manage their emergency medical services area successfully. The study also investigated both the flow of information, and interactions with the paramedic field supervisors and the differences that occur depending on the incident type. Ten paramedic field supervisors from four Finnish rescue departments participated in the study in January-March 2012. The data were collected using semi-structured interviews based on three progressive real-life scenarios and a questionnaire. Data were analysed using deductive content analysis. Data management and analysis were performed using Atlas.ti 7 software. Five critical information categories were formulated: Incident data, Mission status, Area status, Safety at work, and Tactics. Each category's importance varied depending on the incident and on whether it was about information needed or information delivered by the paramedic field supervisors. The main communication equipment used to receive information was the authority radio network (TETRA). However, when delivering information, mobile phones and TETRA were of equal importance. Paramedic field supervisors needed more information relating to area status. Paramedic field supervisors communicate actively with EMS units and other authorities such as Emergency Medical Dispatch

  1. Social Studies Flow Chart.

    ERIC Educational Resources Information Center

    New York State Education Dept., Albany. Bureau of General Education Curriculum Development.

    The flow chart outlines the division of content within social studies courses for each grade (K-12) in New York State public schools. It is strictly an outline of content; it does not reflect emphasis on concept development or use of the inductive mode which are stressed in state teacher's guides. In kindergarten and grade one, social studies…

  2. 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.

  3. 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...

  4. 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...

  5. Flow Driven by an Archimedean Helical Permanent Magnetic Field. Part II: Transient and Modulated Flow Behaviors

    NASA Astrophysics Data System (ADS)

    Wang, Bo; Wang, Xiaodong; Fautrelle, Yves; Etay, Jacqueline; Na, Xianzhao; Baltaretu, Florin

    2016-12-01

    The present study considers the transient and modulated flow behaviors of liquid metal driven by a helical permanent magnetic field. The transient process, in which the fluid at rest experiences an increase in the angular velocity, is observed both in secondary and global axial flow with duration time less than 1 second. The flow fields are measured quantitatively to reveal the evolution of the transient flow, and the transient process is due to the variation of the electromagnetic force. Besides, the modulated flow behaviors of global axial flow, which is significantly different from that of secondary flow, is expected to avoid flow-induced macrosegregation in solidification process if the modulated time is suitable because its direction reversed periodically with the modulated helical stirrer. In addition, an optimal modulation frequency, under which the magnetic field could efficiently stir the solute at the solidification front, exists both in secondary and global axial flow (0.1 Hz and 0.625 Hz, respectively). Future investigations will focus on additional metallic alloy solidification experiments.

  6. 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.

  7. Mean-flow measurements of the flow field diffusing bend

    NASA Technical Reports Server (NTRS)

    Mcmillan, O. J.

    1982-01-01

    Time-average measurements of the low-speed turbulent flow in a diffusing bend are presented. The experimental geometry consists of parallel top and bottom walls and curved diverging side walls. The turning of the center line of this channel is 40 deg, the area ratio is 1.5 and the ratios of height and center-line length to throat width are 1.5 and 3, respectively. The diffusing bend is preceded and followed by straight constant area sections. The inlet boundary layers on the parallel walls are artificially thickened and occupy about 30% of the channel height; those on the side walls develop naturally and are about half as thick. The free-stream speed at the inlet was approximately 30 m/sec for all the measurements. Inlet boundary layer mean velocity and turbulence intensity profiles are presented, as are data for wall static pressures, and at six cross sections, surveys of the velocity-vector and static-pressure fields. The dominant feature of the flow field is a pair of counter-rotating streamwise vortices formed by the cross-stream pressure gradient in the bend on which an overall deceleration is superimposed.

  8. Three dimensional flow field inside the passage of a low speed axial flow compressor rotor

    NASA Technical Reports Server (NTRS)

    Pouagare, M.; Murthy, K. N. S.; Lakshminarayana, B.

    1982-01-01

    Measurements of the subsonic flow in the rotor passage of a single stage axial flow compressor were made to study the nature of the flow field and to verify the existing numerical codes. The velocity and pressure fields were measured across the entire rotor passage at six axial locations and at five radial locations. A five-hole probe, rotating with the rotor, was used to measure the three components of velocity, the static and the total pressure. The experimental results are compared with the predictions from Katsanis and McNally's computer program. The agreement between the two is good for most of the cases.

  9. Flow field simulation for a corncob incinerator

    SciTech Connect

    Wu, C.H.

    1999-02-01

    This article utilizes the standard k-{epsilon} turbulent model to simulate a corncob incinerator using the PISO algorithm with computational fluid dynamics (CFD). The flow patterns of the incinerator equipped with secondary air inlets are predicted and compared for the various geometrical layouts. It is demonstrated that a wider recirculation zone can be found while the inclined angles of inlets increased, so a longer residence time and higher combustion efficiency will be expected. The longer distance between primary and secondary inlets will facilitate the formation of recirculation zone in this bigger space. The more the number of the secondary air inlets, the less the resident air in the top recirculation zone near the exit of the furnace. By using the CFD technique, the flow field of the incinerator can be understood more precisely, and it can serve as an excellent design tool. Furthermore, the computational program can be composed with FORTRAN and set up on a PC, and can easily be analyzed to get the flow field of the corncob incinerator.

  10. 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.

  11. 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.

  12. 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.

  13. Experimental Smoke and Electromagnetic Analog Study of Induced Flow Field About a Model Rotor in Steady Flight Within Ground Effect

    NASA Technical Reports Server (NTRS)

    Gray, Robin B.

    1960-01-01

    Hovering and steady low-speed forward-flight tests were run on a 4-foot-diameter rotor at a ground height of 1 rotor radius. The two blades had a 2 to 1 taper ratio and were mounted in a see-saw hub. The solidity ratio was 0.05. Measurements were made of the rotor rpm, collective pitch, and forward-flight velocity. Smoke was introduced into the tip vortex and the resulting vortex pattern was photographed from two positions. Using the data obtained from these photographs, wire models of the tip vortex configurations were constructed and the distribution of the normal component of induced velocity at the blade feathering axis that is associated with these tip vortex configurations was experimentally determined at 450 increments in azimuth position from this electromagnetic analog. Three steady-state conditions were analyzed. The first was hovering flight; the second, a flight velocity just under the wake "tuck under" speed; and the third, a flight velocity just above this speed. These corresponded to advance ratios of 0, 0.022, and 0.030 (or ratios of forward velocity to calculated hovering induced velocity of approximately 0, 0.48, and 0.65), respectively, for the model test rotor. Cross sections of the wake at 450 intervals in azimuth angle as determined from the path of the tip vortex are presented graphically for all three cases. The nondimensional normal component of the induced velocity that is associated with the tip vortex as determined by an electromagnetic analog at 450 increments in azimuth position and at the blade feathering axis is presented graphically. It is shown that the mean value of this component of the induced velocity is appreciably less after tuck-under than before. It is concluded that this method yields results of engineering accuracy and is a very useful means of studying vortex fields.

  14. Effective contaminant detection networks in uncertain groundwater flow fields.

    PubMed

    Hudak, P F

    2001-01-01

    A mass transport simulation model tested seven contaminant detection-monitoring networks under a 40 degrees range of groundwater flow directions. Each monitoring network contained five wells located 40 m from a rectangular landfill. The 40-m distance (lag) was measured in different directions, depending upon the strategy used to design a particular monitoring network. Lagging the wells parallel to the central flow path was more effective than alternative design strategies. Other strategies allowed higher percentages of leaks to migrate between monitoring wells. Results of this study suggest that centrally lagged groundwater monitoring networks perform most effectively in uncertain groundwater-flow fields.

  15. Neutron tomography of axisymmetric flow fields in porous media

    NASA Astrophysics Data System (ADS)

    Gilbert, A. J.; Deinert, M. R.

    2013-04-01

    A significant problem in the study of fluid transport in porous media is the ability to visualize the structure of the flow field when moisture contents vary rapidly in space and time. Here we present a method for determining the radial and vertical saturation profiles within axisymmetric preferential flow fields using neutron radiography. Flow fields such as these are surprisingly common in nature and determining the three-dimensional structure of their wetting front region has proven difficult. In this work, the moisture profiles are determined using a simple algorithm for algebraic computed tomography, which gives the three-dimensional structure of the moisture profile with a temporal resolution that is limited only by the desired noise level. The algorithm presented can be translated to radiography done using X-rays or light and is applicable to any rotationally symmetric object.

  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. 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.

  18. Pulsatile Flow Studies in Atherosclerotic Carotid Bifurcation

    NASA Astrophysics Data System (ADS)

    Bale-Glickman, Jocelyn; Selby, Kathy; Saloner, David; Savas, Omer

    2002-11-01

    Particle image velocimetry and flow visualization techniques are used to study flow in models of atherosclerotic carotid bifurcations. The models exactly replicate the interior geometry of plaque excised from patients. The input flow is a physiological waveform derived from Doppler Ultrasound scans done on the patients before surgery. The systolic and diastolic Reynolds numbers are 200 and 900 respectively. The complex internal geometry of the diseased artery combined with the pulsatile input flows give exceedingly complex flow patterns. These flow patterns include internal jets, three-dimensional shear layers, stagnation lines, and multiple recirculation and separation regions. Ensemble averaged and instantaneous flow fields are compared. Wall shear stresses at the stenoses are estimated to be on the order of 10 PA. The physiological input flows are also compared to flows when the waveform is sinusoidal.

  19. Several examples where turbulence models fail in inlet flow field analysis

    NASA Technical Reports Server (NTRS)

    Anderson, Bernhard H.

    1993-01-01

    Computational uncertainties in turbulence modeling for three dimensional inlet flow fields include flows approaching separation, strength of secondary flow field, three dimensional flow predictions of vortex liftoff, and influence of vortex-boundary layer interactions; computational uncertainties in vortex generator modeling include representation of generator vorticity field and the relationship between generator and vorticity field. The objectives of the inlet flow field studies presented in this document are to advance the understanding, prediction, and control of intake distortion and to study the basic interactions that influence this design problem.

  20. Several examples where turbulence models fail in inlet flow field analysis

    NASA Astrophysics Data System (ADS)

    Anderson, Bernhard H.

    Computational uncertainties in turbulence modeling for three dimensional inlet flow fields include flows approaching separation, strength of secondary flow field, three dimensional flow predictions of vortex liftoff, and influence of vortex-boundary layer interactions; computational uncertainties in vortex generator modeling include representation of generator vorticity field and the relationship between generator and vorticity field. The objectives of the inlet flow field studies presented in this document are to advance the understanding, prediction, and control of intake distortion and to study the basic interactions that influence this design problem.

  1. 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.

  2. 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.

  3. 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.

  4. A study of the local pressure field in turbulent shear flow and its relation to aerodynamic noise generation

    NASA Technical Reports Server (NTRS)

    Jones, B. G.; Planchon, H. P., Jr.

    1973-01-01

    Work during the period of this report has been in three areas: (1) pressure transducer error analysis, (2) fluctuating velocity and pressure measurements in the NASA Lewis 6-inch diameter quiet jet facility, and (3) measurement analysis. A theory was developed and experimentally verified to quantify the pressure transducer velocity interference error. The theory and supporting experimental evidence show that the errors are a function of the velocity field's turbulent structure. It is shown that near the mixing layer center the errors are negligible. Turbulent velocity and pressure measurements were made in the NASA Lewis quiet jet facility. Some preliminary results are included.

  5. Electrohydrodynamic flow caused by field-enhanced dissociation solely

    NASA Astrophysics Data System (ADS)

    Vasilkov, S. A.; Chirkov, V. A.; Stishkov, Yu. K.

    2017-06-01

    Electrohydrodynamic (EHD) flows emerge in dielectric liquids under the action of the Coulomb force and underlie energy-efficient techniques for heat and mass transfer. The key issue in the phenomena is the way how the net charge is created. One of the most promising, yet poorly studied charge formation mechanisms is the field-enhanced dissociation (or the Wien effect). So the paper studies an EHD flow caused solely by the effect by virtue of both experiment and computer simulation. To preclude the competing mechanism of charge formation—the injection—a new EHD system of a special design was examined. Its main feature is the use of solid insulation to create the region of the strong electric field far from the electrode metal surfaces. The experimental study used the particle image velocimetry technique to observe velocity distributions, whereas the computations were based on the complete set of electrohydrodynamic equations employing the commercial software package COMSOL Multiphysics. Spatial distributions of key quantities (including the ion concentrations, the total space charge density, and the velocity) and the acting forces were obtained in the computer simulation and were analyzed. The experimental flow structure was observed for a number of voltages up to 30 kV. The comparison of the numerical and experimental results yielded a good quantitative agreement for strong electric fields though some overshoot was observed for weak ones. The results allow concluding on the applicability of the Onsager theory of the field-enhanced dissociation in the context of EHD flows.

  6. 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.

  7. Propagation of experimental uncertainties from the tunnel to the body coordinate system in 3-D LDV flow field studies

    NASA Technical Reports Server (NTRS)

    Neuhart, Dan H.

    1994-01-01

    An analysis of experimental laser Doppler velocimetry (LDV) data uncertainties that propagate from measurements in the tunnel coordinate system to results in the model system are provided. Calculations of uncertainties as functions of the variables that comprise the final result requires assessment of the contribution each variable makes. Such an analysis enables and necessitates the experimentalists to identify and address the contributing error sources in the experimental measurement system. This provides an opportunity to improve the quality of data derived from experimental systems. This is especially important in experiments where small changes in test conditions are expected to produce small, detectable changes in results. In addition, the need for high-quality experimental data for CFD method validation demands a thorough assessment of experimental uncertainty. Transforming from one Cartesian coordinate system to another by three sequential rotations, equations were developed to transform the variables initially obtained in the original coordinates into variables in the final coordinate system. Based on the transformation equations, propagation equations for errors in the experimentally-derived flow quantities were derived for a model at angle of attack. Experimental uncertainties were then propagated from the tunnel coordinate system into the model system.

  8. Field testing, gene flow assessment and pre-commercial studies on transgenic Solanum tuberosum spp. tuberosum (cv. Spunta) selected for PVY resistance in Argentina.

    PubMed

    Bravo-Almonacid, Fernando; Rudoy, Valeria; Welin, Bjorn; Segretin, María Eugenia; Bedogni, María Cecilia; Stolowicz, Fabiana; Criscuolo, Marcelo; Foti, Marcelo; Gomez, Maximiliano; López, Mariana; Serino, Germán; Cabral, Silvia; Dos Santos, Cristina; Huarte, Marcelo; Mentaberry, Alejandro

    2012-10-01

    Solanum tuberosum ssp. tuberosum (cv. Spunta) was transformed with a chimeric transgene containing the Potato virus Y (PVY) coat protein (CP) sequence. Screening for PVY resistance under greenhouse conditions yielded over 100 independent candidate lines. Successive field testing of selected lines allowed the identification of two genetically stable PVY-resistant lines, SY230 and SY233, which were further evaluated in field trials at different potato-producing regions in Argentina. In total, more than 2,000 individuals from each line were tested along a 6-year period. While no or negligible PVY infection was observed in the transgenic lines, infection rates of control plants were consistently high and reached levels of up to 70-80%. Parallel field studies were performed in virus-free environments to assess the agronomical performance of the selected lines. Tubers collected from these assays exhibited agronomical traits and biochemical compositions indistinguishable from those of the non-transformed Spunta cultivar. In addition, an interspecific out-crossing trial to determine the magnitude of possible natural gene flow between transgenic line SY233 and its wild relative Solanum chacoense was performed. This trial yielded negative results, suggesting an extremely low probability for such an event to occur.

  9. Particle image velocimetry: study of the flow field within an Erlenmeyer flask on an orbital shaker table

    NASA Astrophysics Data System (ADS)

    Walker, S. M.

    2003-04-01

    Cell growth experiments are used to determine the effects that various environmental factors have on the development and life cycles of cells. For current earth-based testing, the experiments are conducted in Erlenmeyer flasks on orbital shaker tables. This method has been used for several decades and serves as teh baseline-testing configuration. In the future, cell growth experiments will be conducted on the International Space Station (ISS), which will permit long duration testing of the effects of gravity on the development and life cycle of cells. Particle Image Velocimetry (PIV) has been used to measure the 3D velocity field within the flasks. The high-resolution PIV data have been used to calcluate accelerations and shear stresses that the cells typically encounter during testing. The PIV data will be used to verify that the fluid environment during testing on the ISS is comparable to that encountered during earth-based testing.

  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. Low thrust viscous nozzle flow fields prediction

    NASA Astrophysics Data System (ADS)

    Liaw, Goang-Shin

    1987-12-01

    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.

  14. 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.

  15. Asymmetrical flow field-flow fractionation of white wine chromophoric colloidal matter.

    PubMed

    Coelho, Christian; Parot, Jérémie; Gonsior, Michael; Nikolantonaki, Maria; Schmitt-Kopplin, Philippe; Parlanti, Edith; Gougeon, Régis D

    2017-04-01

    Two analytical separation methods-size-exclusion chromatography and asymmetrical flow field-flow fractionation-were implemented to evaluate the integrity of the colloidal composition of Chardonnay white wine and the impact of pressing and fermentations on the final macromolecular composition. Wine chromophoric colloidal matter, representing UV-visible-absorbing wine macromolecules, was evaluated by optical and structural measurements combined with the description of elution profiles obtained by both separative techniques. The objective of this study was to apply these two types of fractionation on a typical Chardonnay white wine produced in Burgundy and to evaluate how each of them impacted the determination of the macromolecular chromophoric content of wine. UV-visible and fluorescence measurements of collected fractions were successfully applied. An additional proteomic study revealed that grape and microorganism proteins largely impacted the composition of chromophoric colloidal matter of Chardonnay wines. Asymmetrical flow field-flow fractionation appeared to be more reliable and less invasive with respect to the native chemical environment of chromophoric wine macromolecules, and hence is recommended as a tool to fractionate chromophoric colloidal matter in white wines. Graphical Abstract An innovative macromolecular separation method based on Asymmetrical Flow Field-Flow Fractionation was developed to better control colloidal dynamics across Chardonnay white winemaking.

  16. Computational Analysis of Flow Field Inside Coral Colony

    NASA Astrophysics Data System (ADS)

    Hossain, Md Monir; Staples, Anne

    2015-11-01

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

  17. Development of the 1990 Kalapana Flow Field, Kilauea Volcano, Hawaii

    USGS Publications Warehouse

    Mattox, T.N.; Heliker, C.; Kauahikaua, J.; Hon, K.

    1993-01-01

    The 1990 Kalapana flow field is a complex patchwork of tube-fed pahoehoe flows erupted from the Kupaianaha vent at a low effusion rate (approximately 3.5 m3/s). These flows accumulated over an 11-month period on the coastal plain of Kilauea Volcano, where the pre-eruption slope angle was less than 2??. the composite field thickened by the addition of new flows to its surface, as well as by inflation of these flows and flows emplaced earlier. Two major flow types were identified during the development of the flow field: large primary flows and smaller breakouts that extruded from inflated primary flows. Primary flows advanced more quickly and covered new land at a much higher rate than breakouts. The cumulative area covered by breakouts exceeded that of primary flows, although breakouts frequently covered areas already buried by recent flows. Lava tubes established within primary flows were longer-lived than those formed within breakouts and were often reoccupied by lava after a brief hiatus in supply; tubes within breakouts were never reoccupied once the supply was interrupted. During intervals of steady supply from the vent, the daily areal coverage by lava in Kalapana was constant, whereas the forward advance of the flows was sporadic. This implies that planimetric area, rather than flow length, provides the best indicator of effusion rate for pahoehoe flow fields that form on lowangle slopes. ?? 1993 Springer-Verlag.

  18. 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.

  19. 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.

  20. 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.

  1. Drop Breakup in Fixed Bed Flows as Model Stochastic Flow Fields

    NASA Technical Reports Server (NTRS)

    Shaqfeh, Eric S. G.; Mosler, Alisa B.; Patel, Prateek

    1999-01-01

    We examine drop breakup in a class of stochastic flow fields as a model for the flow through fixed fiber beds and to elucidate the general mechanisms whereby drops breakup in disordered, Lagrangian unsteady flows. Our study consists of two parallel streams of investigation. First, large scale numerical simulations of drop breakup in a class of anisotropic Gaussian fields will be presented. These fields are generated spectrally and have been shown in a previous publication to be exact representations of the flow in a dilute disordered bed of fibers if close interactions between the fibers and the drops are dynamically unimportant. In these simulations the drop shape is represented by second and third order small deformation theories which have been shown to be excellent for the prediction of drop breakup in steady strong flows. We show via these simulations that the mechanisms of drop breakup in these flows are quite different than in steady flows. The predominant mechanism of breakup appears to be very short lived twist breakups. Moreover, the occurrence of breakup events is poorly predicted by either the strength of the local flow in which the drop finds itself at breakup, or the degree of deformation that the drop achieves prior to breakup. It is suggested that a correlation function of both is necessary to be predictive of breakup events. In the second part of our research experiments are presented where the drop deformation and breakup in PDMS/polyisobutylene emulsions is considered. We consider very dilute emulsions such that coalescence is unimportant. The flows considered are simple shear and the flow through fixed fiber beds. Turbidity, small angle light scattering, dichroism and microscopy are used to interrogate the drop deformation process in both flows. It is demonstrated that breakup at very low capillary numbers occurs in both flows but larger drop deformation occurs in the fixed bed flow. Moreover, it is witnessed that breakup in the bed occurs

  2. Lava flow superposition: the reactivation of flow units in compound flow fields

    NASA Astrophysics Data System (ADS)

    Applegarth, Jane; Pinkerton, Harry; James, Mike; Calvari, Sonia

    2010-05-01

    Long-lived basaltic eruptions often produce compound `a`ā lava flow fields that are constructed of many juxtaposed and superposed flow units. We have examined the processes that result from superposition when the underlying flows are sufficiently young to have immature crusts and deformable cores. It has previously been recognised that the time elapsed between the emplacement of two units determines the fate of the underlying flow[1], because it controls the rheological contrast between the units. If the time interval is long, the underlying flow is able to cool, degas and develop a rigid crust, so that it shows no significant response to loading, and the two units are easily discernable stratigraphically. If the interval is short, the underlying flow has little time to cool, so the two units may merge and cool as a single unit, forming a ‘multiple' flow[1]. In this case, the individual units are more difficult to distinguish post-eruption. The effects of superposition in intermediate cases, when underlying flows have immature roofs, are less well understood, and have received relatively little attention in the literature, possibly due to the scarcity of observations. However, the lateral and vertical coalescence of lava tubes has been described on Mt. Etna, Sicily[2], suggesting that earlier tubes can be reactivated and lengthened as a result of superposition. Through our recent analysis of images taken by INGV Catania during the 2001 eruption of Mt. Etna (Sicily), we have observed that the emplacement of new surface flows can reactivate underlying units by squeezing the still-hot flow core away from the site of loading. We have identified three different styles of reactivation that took place during that eruption, which depend on the time interval separating the emplacement of the two flows, and hence the rheological contrast between them. For relatively long time intervals (> 2 days), hence high rheological contrasts, superposition can cause an overpressure

  3. 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...

  4. 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...

  5. Flow Web: a graph based user interface for 3D flow field exploration

    NASA Astrophysics Data System (ADS)

    Xu, Lijie; Shen, Han-Wei

    2010-01-01

    While there have been intensive efforts in developing better 3D flow visualization techniques, little attention has been paid to the design of better user interfaces and more effective data exploration work flow. In this paper, we propose a novel graph-based user interface called Flow Web to enable more systematic explorations of 3D flow data. The Flow Web is a node-link graph that is constructed to highlight the essential flow structures where a node represents a region in the field and a link connects two nodes if there exist particles traveling between the regions. The direction of an edge implies the flow path, and the weight of an edge indicates the number of particles traveling through the connected nodes. Hierarchical flow webs are created by splitting or merging nodes and edges to allow for easy understanding of the underlying flow structures. To draw the Flow Web, we adopt force based graph drawing algorithms to minimize edge crossings, and use a hierarchical layout to facilitate the study of flow patterns step by step. The Flow Web also supports user queries to the properties of nodes and links. Examples of the queries for node properties include the degrees, complexity, and some associated physical attributes such as velocity magnitude. Queries for edges include weights, flow path lengths, existence of circles and so on. It is also possible to combine multiple queries using operators such as and , or, not. The FlowWeb supports several types of user interactions. For instance, the user can select nodes from the subgraph returned by a query and inspect the nodes with more details at different levels of detail. There are multiple advantages of using the graph-based user interface. One is that the user can identify regions of interest much more easily since, unlike inspecting 3D regions, there is very little occlusion. It is also much more convenient for the user to query statistical information about the nodes and links at different levels of detail. With

  6. DEM simulation of granular flows in a centrifugal acceleration field

    NASA Astrophysics Data System (ADS)

    Cabrera, Miguel Angel; Peng, Chong; Wu, Wei

    2017-04-01

    The main purpose of mass-flow experimental models is abstracting distinctive features of natural granular flows, and allow its systematic study in the laboratory. In this process, particle size, space, time, and stress scales must be considered for the proper representation of specific phenomena [5]. One of the most challenging tasks in small scale models, is matching the range of stresses and strains among the particle and fluid media observed in a field event. Centrifuge modelling offers an alternative to upscale all gravity-driven processes, and it has been recently employed in the simulation of granular flows [1, 2, 3, 6, 7]. Centrifuge scaling principles are presented in Ref. [4], collecting a wide spectrum of static and dynamic models. However, for the case of kinematic processes, the non-uniformity of the centrifugal acceleration field plays a major role (i.e., Coriolis and inertial effects). In this work, we discuss a general formulation for the centrifugal acceleration field, implemented in a discrete element model framework (DEM), and validated with centrifuge experimental results. Conventional DEM simulations relate the volumetric forces as a function of the gravitational force Gp = mpg. However, in the local coordinate system of a rotating centrifuge model, the cylindrical centrifugal acceleration field needs to be included. In this rotating system, the centrifugal acceleration of a particle depends on the rotating speed of the centrifuge, as well as the position and speed of the particle in the rotating model. Therefore, we obtain the formulation of centrifugal acceleration field by coordinate transformation. The numerical model is validated with a series of centrifuge experiments of monodispersed glass beads, flowing down an inclined plane at different acceleration levels and slope angles. Further discussion leads to the numerical parameterization necessary for simulating equivalent granular flows under an augmented acceleration field. The premise of

  7. Time-to-passage judgments in nonconstant optical flow fields.

    PubMed

    Kaiser, M K; Hecht, H

    1995-08-01

    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 (1993) 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 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. TTP 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, TTPs 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.

  8. 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.

  9. Mean-field dynamo action in renovating shearing flows.

    PubMed

    Kolekar, Sanved; Subramanian, Kandaswamy; Sridhar, S

    2012-08-01

    We study mean-field dynamo action in renovating flows with finite and nonzero correlation time (τ) in the presence of shear. Previous results obtained when shear was absent are generalized to the case with shear. The question of whether the mean magnetic field can grow in the presence of shear and nonhelical turbulence, as seen in numerical simulations, is examined. We show in a general manner that, if the motions are strictly nonhelical, then such mean-field dynamo action is not possible. This result is not limited to low (fluid or magnetic) Reynolds numbers nor does it use any closure approximation; it only assumes that the flow renovates itself after each time interval τ. Specifying to a particular form of the renovating flow with helicity, we recover the standard dispersion relation of the α(2)Ω dynamo, in the small τ or large wavelength limit. Thus mean fields grow even in the presence of rapidly growing fluctuations, surprisingly, in a manner predicted by the standard quasilinear closure, even though such a closure is not strictly justified. Our work also suggests the possibility of obtaining mean-field dynamo growth in the presence of helicity fluctuations, although having a coherent helicity will be more efficient.

  10. Development of flow/steric field-flow fractionation as a routine process control method

    SciTech Connect

    Barman, B.N.

    1988-08-30

    Researchers studied the feasibility of using the Flow/Steric Field-Flow Fractionation (Flow/StFFF) method for the characterization of particulate materials with diameters in the 1-100 micrometers range. Studies on the optimization of the method for the separation and characterization of different size particulate samples, as well as on the role of the crossflow field and channel flowrate on the separation and resolution, were performed with a number of spherical polystyrene divinylbenzene latex standards and included in the report. Applicability of the method as a fast and reliable practical tool for industrial process control, particularly for grinding operations, was examined by analyzing a number of samples obtained by grinding. Examples of materials considered include coal, limestone and glass.

  11. Supersonic Flow Control by Magnetic Field

    DTIC Science & Technology

    2005-12-01

    control over supersonic flows in supersonic intakes . Experimental and numerical investigations focuses on the basic aspects of MHD interaction taking into...transport, shock-waves dynamics, boundary layers on the intake walls, massive flow separation within the scram-jet flow pass. Recent results of...that a global change of intake flow structure might be achieved with local ( in time and space ) MHD impact. Other aspect is supposed to be

  12. Numerical computations of Orbiter flow fields and heating rates

    NASA Technical Reports Server (NTRS)

    Goodrich, W. D.; Li, C. P.; Houston, C. K.; Chiu, P.; Olmedo, L.

    1976-01-01

    Numerical computations of flow fields around an analytical description of the Space Shuttle Orbiter windward surface, including the root of the wing leading edge, are presented to illustrate the sensitivity of these calculations to several flow field modeling assumptions. Results of parametric flow field and boundary layer computations using the axisymmetric analogue concept to obtain three-dimensional heating rates, in conjunction with exact three-dimensional inviscid floe field solutions and two-dimensional boundary layer analysis - show the sensitivity of boundary layer edge conditions and heating rates to considerations of the inviscid flow field entropy layer, equilibrium air versus chemically and vibrationally frozen flow, and nonsimilar terms in the boundary layer computations. A cursory comparison between flow field predictions obtained from these methods and current Orbiter design methods has established a benchmark for selecting and adjusting these and future design methodologies.

  13. 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.

  14. Flow field around a sphere colliding against a wall.

    NASA Astrophysics Data System (ADS)

    Zenit, R.; Hunt, M. L.

    1998-11-01

    This study investigates the flow field and the fluid agitation generated by particle collisions. The motion of a particle towards a wall, or towards another particle, will result in a collision if the Reynolds number of the flow is large. As the particle approaches the wall, the fluid in the gap between the particle and the wall will be displaced. When the particle touches the wall and rebounds, the direction of the flow will reverse. This process produces a considerable agitation in the fluid phase. To study this process an immersed pendulum experiment was built to produce controlled collisions of particles. A fine string is attached to a particle, which is positioned at rest from some initial angle. Once released, the particle accelerates towards a wall, or to another suspended particle, resulting in a collision. The fluid is seeded with neutrally buoyant micro-spheres, which illuminated by a laser sheet serve as flow tracers. The motion of the particles and tracers is recorded using a high speed digital camera. The images are digitally processed to calculate displacements and velocities for different times before and after the collision. Flow fields are obtained for different impact velocities, particle diameters and solid-fluid density ratios, as well as for particle-wall and particle-particle collisions. Preliminary results show that for the flow conditions tested, the rebound of the particle is dependent on the shape of the wake behind the particle at the moment of collision, and not only on the flow in the gap between the particle and the wall. The amount of collision-generated agitation appears to increase with impact velocity and density ratio.

  15. Mantle flow field in the southern Ryukyu subduction system

    NASA Astrophysics Data System (ADS)

    Lin, S.; Kuo, B.

    2012-12-01

    The Okinawa trough in the Ryukyu subduction system is the only active back arc basin formed within a continental lithosphere. Recent shear-wave splitting measurements show variable fast directions along the trough suggesting complex three-dimensional flow field in the mantle wedge. In this study we use numerical subduction models to explore the effects of plate thickness variations caused by non-uniform lithospheric stretching on the dynamics in the southern Ryukyu subduction system. We calculate orientations of infinite strain axes as a proxy for olivine lattice preferred orientations and orientations of seismic anisotropy. Our models demonstrate that flow patterns may vary significantly with depth near the plate edge as a result of the along-arc variations in lithospheric thickness. The model results show that the toroidal circulation around the lateral slab edge predominates at greater depths. The thick neighboring lithosphere acts as an effective barrier of the lateral mass exchanges in the shallow portion of the mantle wedge. The wedge material is drawn in horizontally toward the plate edge from the central region of the subduction zone induced by pressure gradients, opposite to the inwards lateral flow at greater depths. Model predictions for the lattice preferred orientations of olivine aggregates agree reasonably well with the observed shear-wave splitting patterns. The results suggest that the depth-varying flow field near the subduction zone edge and the westward flow components in the shallow portion of the mantle wedge may contribute to complex patterns of seismic anisotropy and arc isotopic systematics.

  16. 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.

  17. Numerical study of juncture flows

    NASA Technical Reports Server (NTRS)

    Chen, Chung-Lung; Hung, Ching-Mao

    1991-01-01

    The present paper describes a computational study of laminar/turbulent and subsonic/supersonic horseshoe vortex systems generated by a cylindrical protuberance mounted on a flat plate. Various vortex structures are predicted and discussed. Low-speed laminar juncture flows are computed to determine the Reynolds number effect with the same incoming boundary-layer thickness. For a low subsonic laminar flow, the number of vortex arrays increases with the Reynolds number, in agreement with both experimental and numerical observations. Qualitative comparisons are made along with the computations, experimental observations, and analytical work. For incompressible flow, the relationships among pressure extrema, vorticity, and singular points in flow structure are discussed. A parametric study of the effect of the free-stream Mach number on the flow structure for laminar flow is conducted. The juncture flow when the incoming flow is turbulent and supersonic is computed.

  18. On the validity of modeling concepts for the simulation of groundwater flow in lowland peat areas - case study at the Zegveld experimental field

    NASA Astrophysics Data System (ADS)

    Trambauer, P.; Nonner, J.; Heijkers, J.; Uhlenbrook, S.

    2011-09-01

    The groundwater flow models currently used in the western part of The Netherlands and in other similar peaty areas are thought to be a too simplified representation of the hydrological reality. One of the reasons is that, due to the schematization of the subsoil, its heterogeneity cannot be represented adequately. Moreover, the applicability of Darcy's law in these types of soils has been questioned, but this law forms the basis of most groundwater flow models. With the purpose of assessing the typical heterogeneity of the subsoil and to verify the applicability of Darcy's law, geo-hydrological fieldwork was completed at an experimental field within a research area in the western part of The Netherlands. The assessments were carried out for the so-called Complex Confining Layer (CCL), which is the Holocene peaty to clayey layer overlying Pleistocene sandy deposits. Borehole drilling through the CCL with a hand auger was completed and revealed the typical heterogeneous character of this layer, showing a dominance of muddy, humified peat which is alternated with fresher peat and clay. Slug tests were carried out to study the applicability of Darcy's law, given that previous studies suggested its non-validity for humified peat soils due to a variable horizontal hydraulic conductivity Kh with head differences. For higher humification degrees, the experiments indeed suggested a variable Kh, but this appeared to be the result of the inappropriate use of steady-state formulae for transient experiments in peaty environments. The muddy peat sampled has a rather plastic nature, and the high compressibility of this material leads to transient behavior. However, using transient formulae, the slug tests conducted for different initial groundwater heads showed that there was hardly any evidence of a variation of the hydraulic conductivity with the applied head differences. Therefore, Darcy's law can be used for typical peat soils present in The Netherlands. The heterogeneity of

  19. 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.

  20. 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.

  1. Turbulent flow field predictions in sharply curved turn around ducts

    NASA Technical Reports Server (NTRS)

    Santi, L. M.

    1986-01-01

    In this investigation, two-dimensional turbulent flow of incompressible Newtonian fluids in sharply curved 180 deg turn around ducts is studied. Results of an approximate numerical flow field analysis utilizing an orthogonal, body-fitted, curvilinear coordinate system are compared to results based on a traditional cylindrical reference frame. Qualitative indication of general streamfield characteristics as well as quantitative benchmarks for the planning of future experimentation are provided. In addition, preliminary results of an augmented kappa-epsilon turbulence model analysis, which explicitly accounts for the effects of streamline curvature and pressure strain in internal turbulent flows, are presented. Specific model difficulties are discussed and comparisons with standard kappa-esilon model predictions are included.

  2. 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.

  3. The role of magnetic fields in cluster cooling flows

    NASA Technical Reports Server (NTRS)

    Soker, Noam; Sarazin, Craig L.

    1990-01-01

    An investigation is made of the dynamical effects of the intracluster magnetic field, whose radial inflow and shear can produce a dramatic increase in the field's strength while rendering it more radial, with cooling flows. It is found that field reconnection is the most likely dominant-loss mechanism, so that buoyancy effects are probably not important. Attention is given to the effect of the magnetic field on thermal instabilities. The most important observable effect of the magnetic field in cooling flows will probably be very strong Faraday rotation of the polarization of radio sources within or behind the cooling flow.

  4. Mixing, chemical reaction and flow field development in ducted rockets

    SciTech Connect

    Vanka, S.P.; Craig, R.R.; Stull, F.D.

    1984-09-01

    Calculations have been made of the three-dimensional mixing, chemical reaction, and flow field development in a typical ducted rocket configuration. The governing partial differential equations are numerically solved by an iterative finite-difference solution procedure. The physical models include the k approx. epsilon turbulence model, one-step reaction, and mixing controlled chemical reaction rate. Radiation is neglected. The mean flow structure, fuel dispersal patterns, and temperature field are presented in detail for a base configuration with 0.058 m (2 in.) dome height, 45/sup 0/ side arm inclination, and with gaseous ethylene injected from the dome plate at an eccentric location. In addition, the influences of the geometrical parameters such as dome height, inclination of the side arms, and location of the fuel injector are studied.

  5. 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

  6. Flow Field Evolution of a Decaying Sunspot

    NASA Astrophysics Data System (ADS)

    Deng, Na; Choudhary, Debi Prasad; Tritschler, Alexandra; Denker, Carsten; Liu, Chang; Wang, Haimin

    2007-12-01

    We study the evolution of the flows and horizontal proper motions in and around a decaying follower sunspot based on time sequences of two-dimensional spectroscopic observations in the visible and white-light imaging data obtained over 6 days from 2005 June 7 to 12. During this time period the sunspot decayed gradually to a pore. The spectroscopic observations were obtained with the Fabry-Pérot-based Visible-Light Imaging Magnetograph (VIM) in conjunction with the high-order adaptive optics (AO) system operated at the 65 cm vacuum reflector of the Big Bear Solar Observatory (BBSO). We apply local correlation tracking (LCT) to the speckle-reconstructed time sequences of white-light images around 600 nm to infer horizontal proper motions, while the Doppler shifts of the scanned Fe I line at 630.15 nm are used to calculate line-of-sight (LOS) velocities with subarcsecond resolution. We find that the dividing line between radial inward and outward proper motions in the inner and outer penumbra, respectively, survives the decay phase. In particular the moat flow is still detectable after the penumbra disappeared. Based on our observations, three major processes removed flux from the sunspot: (1) fragmentation of the umbra, (2) flux cancelation of moving magnetic features (MMFs; of the same polarity as the sunspot) that encounter the leading opposite polarity network and plages areas, and (3) flux transport by MMFs (of the same polarity as the sunspot) to the surrounding network and plage regions that have the same polarity as the sunspot.

  7. Reconstruction of velocity fields in electromagnetic flow tomography

    PubMed Central

    Lehtikangas, Ossi; Karhunen, Kimmo

    2016-01-01

    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

  8. 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'.

  9. Sound propagation through a real jet flow field with scattering due to interaction with turbulence

    NASA Technical Reports Server (NTRS)

    Maestrello, L.; Liu, C. H.; Ting, L.; Gunzburger, M.

    1974-01-01

    The sound propagation through a nonuniform turbulent jet flow field is studied by means of a system of linearized equations governing the acoustic variables. These equations depend on the fluctuating flow-field variables which are prescribed by experimental results. It is shown that the redistribution of the acoustic energy in the far field depends on space-time correlation of the turbulent velocities and on the mean flow variables and their gradients.

  10. Experimental design methodology applied to the study of channel dimensions on the elution of red blood cells in gravitational field flow fractionation.

    PubMed

    Rasouli, S; Assidjo, E; Chianéa, T; Cardot, P J

    2001-04-15

    Field flow fractionation (FFF) separation techniques have gained considerable success with micron-sized species. Living red blood cells (RBCs) of any origin have emerged as ideal models for cell separation development. Their elution mode is now described as "Lift-Hyperlayer". Certain separator dimension parameters are known to play a key role in the separation and band spreading process. Systematic studies of channel dimensions effects on RBC retention, band spreading, peak capacity and on a novel parameter described as "Particle Selectivity" were set up by means of a two-level factorial experimental design. From experimental results and statistical calculations it is confirmed that channel thickness plays a major role in retention ratio, peak variance, peak capacity and particle selectivity. Channel breadth strongly influences plate height, with lower impact on peak capacity and particle selectivity. Retention ratio, peak variance and peak capacity observed results are modulated by second-order interactions between channel dimensions. Preliminary rules for channel configurations are therefore set up and depend on separation goals. It is shown that a very polydisperse population is best disentangled in a thin and narrow channel whatever its length. If a mixture of many different micron-sized species is considered (each of limited polydispersities); a thick and broad channel should be preferred, with length modulating peak capacity to disentangle this polymodal mixture.

  11. Flow field design development using the segmented cell approach

    SciTech Connect

    Bender, G.; Ramsey, J. C.

    2002-01-01

    We report on fuel cell flow-field development employing two-dimensional computational fluid dynamics (2-D CFD). Simulation of the flow distribution of a parallel channel flow-field, with a simple one-channel manifold, predicted inhomogeneous performance distribution within the cell. Further modeling, focusing on modification of the inlet and outlet flow fields, was used to predict a more homogeneous flow distribution in the flow-field. Attempts were made to verify the theoretical predictions experimentally by application of the segmented cell system. Measurements of the current distribution and CO transient response supported the 2-D CFD predictions. However, the margin of error between predicted and experimental results was considered insufficient to be of practical use. Future work will involve the evaluation of 3-D CFD to achieve the appropriate level of accuracy.

  12. 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…

  13. 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…

  14. Static magnetic fields: animal studies.

    PubMed

    Saunders, Richard

    2005-01-01

    Various experimental studies carried out over the last 30-40 years have examined the effects of the chronic or acute exposure of laboratory animals to static magnetic fields. Many of the earlier studies have been adequately reviewed elsewhere; few adverse effects were identified. This review focuses on studies carried out more recently, mostly those using vertebrates, particularly mammals. Four main areas of investigation have been covered, viz., nervous system and behavioural studies, cardiovascular system responses, reproduction and development, and genotoxicity and cancer. Work on the role of the natural geomagnetic field in animal orientation and migration has been omitted. Generally, the acute responses found during exposure to static fields above about 4 T are consistent with those found in volunteer studies, namely the induction of flow potentials around the heart and the development of aversive/avoidance behaviour resulting from body movement in such fields. No consistently demonstrable effects of exposure to fields of approximately 1T and above have been seen on other behavioural or cardiovascular endpoints. In addition, no adverse effects of such fields on reproduction and development or on the growth and development of tumours have been firmly established. Overall, however, far too few animal studies have been carried out to reach any firm conclusions.

  15. 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.

  16. Mathematical modeling of flow field in ceramic candle filter

    NASA Astrophysics Data System (ADS)

    Seo, Taewon; Kim, Heuy-Dong; Choi, Joo-Hong; Chung, Jae Hwa

    1998-06-01

    Integrated gasification combined cycle (IGCC) is one of the candidates to achieve stringent environmental regulation among the clean coal technologies. Advancing the technology of the hot gas cleanup systems is the most critical component in the development of the IGCC. Thus the aim of this study is to understand the flow field in the ceramic filter and the influence of ceramic filter in removal of the particles contained in the hot gas flow. The numerical model based on the Reynolds stress turbulence model with the Darcy’s law in the porous region is adopted. It is found that the effect of the porosity in the flowfield is negligibly small while the effect of the filter length is significant. It is also found as the permeability decreases, the reattachment point due to the flow separation moves upstream. This is because the fluid is sucked into the filter region due to the pressure drop before the flow separation occurs. The particle follows well with the fluid stream and the particle is directly sucked into the filter due to the pressure drop even in the flow separation region.

  17. 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.

  18. Background field method in the gradient flow

    NASA Astrophysics Data System (ADS)

    Suzuki, Hiroshi

    2015-10-01

    In perturbative consideration of the Yang-Mills gradient flow, it is useful to introduce a gauge non-covariant term (“gauge-fixing term”) to the flow equation that gives rise to a Gaussian damping factor also for gauge degrees of freedom. In the present paper, we consider a modified form of the gauge-fixing term that manifestly preserves covariance under the background gauge transformation. It is shown that our gauge-fixing term does not affect gauge-invariant quantities as does the conventional gauge-fixing term. The formulation thus allows a background gauge covariant perturbative expansion of the flow equation that provides, in particular, a very efficient computational method of expansion coefficients in the small flow time expansion. The formulation can be generalized to systems containing fermions.

  19. Experimental Studies of Coaxial Jet Flows

    NASA Astrophysics Data System (ADS)

    Behrouzi, Parviz; McGuirk, James J.

    An experimental study was carried out to investigate the effect of coaxial nozzle operating conditions on near-field jet plume development. The study was conducted in a low speed water tunnel as well as in a high-speed airflow nozzle test facility. Laser Doppler Anemometry (LDA) and Laser Induced Fluorescence (LIF) techniques were employed to identify the flow structure as well as the mean velocity and turbulence structure of a coaxial nozzle under low speed flow conditions. Schlieren flow visualization, LDA and nozzle wall static pressure measurement surveys were performed in high speed flows. The effect of a nozzle shroud on jet development was studied and found very effective on suppression of the shock cells and on reduction of turbulence levels within the core region. The effect of the outer and inner Nozzle Pressure Ratios on shock cell structure and the nozzle internal wall pressure field were documented. LDA measurements in the water tunnel confirmed that the flow pattern produced of the Reynolds numbers and velocity ratios selected for this study was typical of practically occurring developing jet flow fields. Sufficient measured profiles of velocities, turbulence quantities and nozzle wall static pressures as well as jet plume images have been captured to serve as benchmark validation data for time-averaged turbulence-model-based RANS CFD predictions.

  20. Relationship Between Far Field Stresses, Fluid Flow and High-Pressure Deserpentinization in Subducting Slabs: a Case Study From the Almirez Ultramafic Massif

    NASA Astrophysics Data System (ADS)

    Dilissen, Nicole; Hidas, Károly; Garrido, Carlos J.; López Sánchez-Vizcaíno, Vicente; Kahl, Wolf-Achim; Padrón-Navarta, José Alberto; Jesús Román-Alpiste, Manuel

    2017-04-01

    Serpentinite dehydration during prograde metamorphism plays a crucial role in subduction dynamics. Observations from exhumed paleo-subduction metamorphic terranes suggest that the discharge of deserpentinization fluids from the subducting slab takes place along different pathways and mechanisms [e.g. 1-3]. Analysis of intermediate-depth focal solutions in active subduction zones indicates that slabs are subjected to different principal stress fields characterized primarily by downdip compression and downdip tension [4]. Although it is well known that far field stresses play a crucial role on fluid flow channeling, their potential impact on the kinetics of serpentinite dehydration and subsequent fluid escape in subducting slabs is still poorly understood. Here, we present a detailed structural and microstructural study to investigate the relationships between far field stresses, fluid flow and high-pressure deserpentinization in the Almirez ultramafic massif (Betic Cordillera, SE Spain) [1, 2]. This massif preserves the high-pressure breakdown of antigorite (Atg-) serpentinite to prograde chlorite (Chl-) harzburgite, which are separated by a sharp isograd [2, 5]. The Chl-harzburgite reaction products show either a granofels or spinifex-like texture indicating crystallization under different overstepping of the Atg-out reaction. The two different textural types of Chl-harzburgite occur below the Atg-out isograd as alternating, meter-wide lenses with either a granofels or spinifex texture. From field measurements, we infer that during antigorite dehydration the minimum compressive stress was subnormal to the dehydration front and the paleo-slab surface. This stress field is consistent with subduction zones with slabs under downdip compression at intermediate depths [4]. The detailed microstructural study —combining µ-CT and EBSD-SEM [6]— of Chl-harzburgite across a c. 15 m wide lens reveals that the SPO and CPO of olivines with contrasting textures are strongly

  1. Kinetic study of aggregation of milk protein and/or surfactant-stabilized oil-in-water emulsions by sedimentation field-flow fractionation.

    PubMed

    Kenta, Stella; Raikos, Vassilios; Vagena, Artemis; Sevastos, Dimitrios; Kapolos, John; Koliadima, Athanasia; Karaiskakis, George

    2013-08-30

    Milk proteins are able to facilitate the formation and stabilization of oil droplets in food emulsions. This study employed Sedimentation Field-Flow Fractionation (SdFFF) to monitor changes in particle size distribution of freshly prepared emulsions with varying weight contributions of sodium caseinate (SC) and whey protein concentrate (WPC). The effect of the addition of Tween 80 (T) on the initial droplet size was also investigated. The results indicated that emulsifying ability follows the order Tween 80>WPC>SC, with corresponding weight average droplet diameter of 0.319, 0.487 and 0.531μm respectively, when each of the above emulsifiers was used solely. The stability of sodium caseinate emulsions was studied at 30.5 and 80.0°C by measuring the particle size distribution for a period of 70h. Emulsions withstood the temperatures and exhibited an initial increase in particle size distribution caused by heat-induced droplet aggregation, followed by a decrease to approximately the initial droplet size. The rate of droplet aggregation depends on the severity of thermal processing, as revealed by the kinetics of particle aggregation during aging at different temperatures. Comparison of the experimental rate constants found from SdFFF, with those determined theoretically gives invaluable information about the oil droplet stability and the aggregation mechanism. Based on the proposed mechanistic scheme various physicochemical quantities, which are very important in explaining the stability of oil-in-water emulsions, were determined. Finally, the advantages of SdFFF in studying the aggregation of the oil-in-water droplets, in comparison with other methods used for the same purpose, are discussed. Copyright © 2013 Elsevier B.V. All rights reserved.

  2. 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).

  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. 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.

  5. [Lessons from Field Studies].

    PubMed

    Yoshimura, Takesumi

    2015-01-01

    During my academic career for more than 40 years, I was involved in 18 epidemiological field studies, partially or fully. Among these field studies, four (1. Medical services in remote rural areas in Okinawa, 2. Yusho episode, 3. JICA Onchocerciasis Control Project in Guatemala, and 4. Miyako cohort study in Fukuoka) are introduced in this paper, including the latest situation after the presentation. Through these field works experienced by the author, the following lessons were gained. 1. Strong human reliance between researchers and the targeted population is essential in carrying out epidemiological surveys successfully in the field. 2. Data obtained from the survey should be carefully examined and analyzed so that those data may reflect the real situation.

  6. 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%.

  7. Time resolved Schlieren imaging of DBD actuator flow fields

    NASA Astrophysics Data System (ADS)

    Nourgostar, Cyrus; Oksuz, Lutfi; Hershkowitz, Noah

    2009-10-01

    Schlieren imaging methods measure the first derivative of density in the direction of a knife-edge spatial filter. It has been used extensively in aerodynamic research to visualize the structure of flow fields. With a single barrier planer dielectric barrier discharge (DBD) actuator, Schlieren images clearly show the absence of significant vertical air flow normal to the surface, and no more than few millimeters thick induced boundary layer flow. A gated intensified CCD camera along with a Schlieren system can not only visualize the flow field induced by the actuator, but also temporarily resolve the images of the flow and plasma field. Our time resolved images with triangular applied voltage waveforms indicate that several separate discharge regimes occur during positive and negative going half cycles of single and double barrier DBD actuators. Time resolved Schlieren imaging of both single and double barrier DBDs with different applied waveforms, discharge parameters and electrode geometries reveal important information on the induced flow structure.

  8. A field study (Massachusetts, USA) of the factors controlling the depth of groundwater flow systems in crystalline fractured-rock terrain

    NASA Astrophysics Data System (ADS)

    Boutt, David F.; Diggins, Patrick; Mabee, Stephen

    2010-12-01

    Groundwater movement and availability in crystalline and metamorphosed rocks is dominated by the secondary porosity generated through fracturing. The distributions of fractures and fracture zones determine permeable pathways and the productivity of these rocks. Controls on how these distributions vary with depth in the shallow subsurface (<300 m) and their resulting influence on groundwater flow is not well understood. The results of a subsurface study in the Nashoba and Avalon terranes of eastern Massachusetts (USA), which is a region experiencing expanded use of the fractured bedrock as a potable-supply aquifer, are presented. The study logged the distribution of fractures in 17 boreholes, identified flowing fractures, and hydraulically characterized the rock mass intersecting the boreholes. Of all fractures encountered, 2.5% are hydraulically active. Boreholes show decreasing fracture frequency up to 300 m depth, with hydraulically active fractures showing a similar trend; this restricts topographically driven flow. Borehole temperature profiles corroborate this, with minimal hydrologically altered flow observed in the profiles below 100 m. Results from this study suggest that active flow systems in these geologic settings are shallow and that fracture permeability outside of the influence of large-scale structures will follow a decreasing trend with depth.

  9. Three-Dimensional Flow Fields and Bedform Migration in a Field-Scale Meandering Channel

    NASA Astrophysics Data System (ADS)

    Kozarek, J. L.; Palmsten, M. L.; Calantoni, J.; Khosronejad, A.; Sotiropoulos, F.

    2012-12-01

    The St. Anthony Falls Laboratory Outdoor StreamLab (OSL) at the University of Minnesota was constructed in 2008 as field-scale sand bed meandering stream channel within a vegetated floodplain. This state-of-the-art facility provides the unique opportunity to investigate physical, chemical, and biological stream and floodplain processes in a controlled outdoor environment with laboratory-quality measurement capabilities. The research presented here summarizes results from several experiments conducted in the OSL examining the effect of three-dimensional (3-D) flow fields on sediment transport and bedform development. Specifically, we examined bedform dimensions and flow fields in two scenarios 1) in the vicinity immobile rock structures, and 2) on the quasi-equilibrium bar that formed on the inner bank of a meander. A combination of methods were used for each study to determine the rate of scour hole formation, quasi-equilibrium bed elevation and variation in bed elevation, and bedform size and spacing. Bed topography data were collected at 1 cm resolution under live-bed conditions using a downward looking sonar probe attached to a mobile data acquisition (DAQ) cart. At each DAQ station, repeat scans were collected giving insight into the 3-dimensionality of bedforms in a meandering channel with and without rock structures. Supplementary data were collected at transects under two flow and sediment conditions (280 L/s and 6 kg/min and 199 L/s and 4 kg/min, for water and sediment, respectively) using an acoustic Doppler velocimeter (ADV) and a profiling ADV to measure 3-D flow fields and concurrent velocity and bed elevation data. These data were used in conjunction with data from optical remote sensing of bedform migration in the OSL to provide a validation dataset for a high-resolution 3-D hydro-morphodynamic model that is being used to simulate flow and sediment transport processes in meandering channels with embedded rock structures (Khosronejad et al. Adv. in

  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. 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:

  12. 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

  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. Field-flow fractionation of nucleic acids and proteins under large-scale gradient magnetic fields

    NASA Astrophysics Data System (ADS)

    Iwasaka, M.

    2007-05-01

    For the purpose of developing techniques for separating biological macromolecules, the present study reports a magnetic chromatography system employing high performance liquid chromatography and superconducting magnets of 14 and 5T. We observed chromatograms of catalase and albumin, which were eluded from columns that were exposed to magnetic fields of up to 14T with a maximum gradient of 90T/m. Without the magnetic fields, the chromatograms of the macromolecules showed a clear peak, while the chromatograms changed to have separated peaks for the same molecules after exposure to gradient magnetic fields. When the chromatocolumn was placed so the magnetic forces were opposite to the direction of flow, the albumin molecules separated into two groups. In addition, the chromatograms of catalase exposed to the magnetic fields indicated that the retention times of the two kinds of magnetically separated catalase were relatively changed if the column-field configuration was changed. Probably, the balance of paramagnetism in the heme and diamagnetism in the protein controlled the transport velocity under the influence of the gradient magnetic fields. In addition, the transport velocity of DNA molecules in the flow with a high gradient magnetic field was observed using a time-resolved spectrophotometric system.

  15. 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.

  16. A color video display technique for flow field surveys

    NASA Technical Reports Server (NTRS)

    Winkelmann, A. E.; Tsao, C. P.

    1982-01-01

    Color video display techniques for flow field surveys are presented. The following techniques were examined: traverse device, used for flow field surveys above and behind finite wing models; flow chart of data reduction for color video display technique; location of spanwise survey stations above and behind wing; hot wire data at first three survey stations on fully stalled wing; hot wire data at last three stations behind fully stalled wing; hot wire and pitch probe data; magnitude of velocity, yaw angle, pitch angle, and cross flow direction from 5 tube survey at X/C = 2.70 behind fully stalled wing.

  17. Simultaneous 3D Strain and Flow Fields Measurement of a Model Artery under Unsteady Flows

    NASA Astrophysics Data System (ADS)

    Toloui, Mostafa; Sheng, Jian

    2011-11-01

    Fluid-Structure Interaction imposes challenges in both aero-elasticity and biomedical studies. A simultaneous solid deformation and fluid flow measurement technique based on digital in-line holographic particle tracking velocimetry (PTV) has been developed. It allows us to measure concurrently 3D strain field of a deforming structure and the unsteady flow near it. To facilitate the measurement, both wall and flow are seeded with tracer particles distinguished by size. The motion of these tracers provides the 3D deformation of the wall and the 3D velocity distribution of the flow separately. A fully index matched facility including transparent artery and NaI solution is constructed to enable observations near the wall or through the complex geometry. An arterial model with the inner diameter of 9.5 mm and the thickness of 0.9 mm is manufactured from the cross-linked transparent PDMS at the mixing ratio of 1:10 and doped with mono-dispersed 19 μm polystyrene particles. A cinematic holographic PTV system is used to trace the 3D particle motion in the model and flow simultaneously. Preliminary study is performed within a sample volume of 15 × 15 × 75 mm with the spatial resolution of 7.4 μm in lateral and 10 μm in depth. Uncertainty and accuracy analysis will be reported. NSF Grant No: CBET-0844647.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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

  3. Inclination of magnetic fields and flows in sunspot penumbrae

    NASA Astrophysics Data System (ADS)

    Langhans, K.; Scharmer, G. B.; Kiselman, D.; Löfdahl, M. G.; Berger, T. E.

    2005-06-01

    An observational study of the inclination of magnetic fields and flows in sunspot penumbrae at a spatial resolution of 0.2 arcsec is presented. The analysis is based on longitudinal magnetograms and Dopplergrams obtained with the Swedish 1-m Solar Telescope on La Palma using the Lockheed Solar Optical Universal Polarimeter birefringent filter. Data from two sunspots observed at several heliocentric angles between 12 ° and 39 ° were analyzed. We find that the magnetic field at the level of the formation of the Fe i-line wing (630.25 nm) is in the form of coherent structures that extend radially over nearly the entire penumbra giving the impression of vertical sheet-like structures. The inclination of the field varies up to 45 ° over azimuthal distances close to the resolution limit of the magnetograms. Dark penumbral cores, and their extensions into the outer penumbra, are prominent features associated with the more horizontal component of the magnetic field. The inclination of this dark penumbral component - designated B - increases outwards from approximately 40 ° in the inner penumbra such that the field lines are nearly horizontal or even return to the solar surface already in the middle penumbra. The bright component of filaments - designated A - is associated with the more vertical component of the magnetic field and has an inclination with respect to the normal of about 35 ° in the inner penumbra, increasing to about 60 ° towards the outer boundary. The magnetogram signal is lower in the dark component B regions than in the bright component A regions of the penumbral filaments. The measured rapid azimuthal variation of the magnetogram signal is interpreted as being caused by combined fluctuations of inclination and magnetic field strength. The Dopplergrams show that the velocity field associated with penumbral component B is roughly aligned with the magnetic field while component A flows are more horizontal than the magnetic field. The observations give

  4. Pilot Field Test Study

    NASA Technical Reports Server (NTRS)

    Sherriff, Abigail

    2015-01-01

    The Field Test study is currently in full swing, preceded by the successful completion of the Pilot Field Test study that paved the way for collecting data on the astronauts in the medical tent in Kazakhstan. Abigail Sherriff worked alongside Logan Dobbe on one Field Test aspect to determine foot clearance over obstacles (5cm, 10cm, and 15cm) using APDM Inc. Internal Measurement Units (IMU) worn by the astronauts. They created a program to accurately calculate foot clearance using the accelerometer, magnetometer, and gyroscope data with the IMUs attached to the top of the shoes. To validate the functionality of their program, they completed a successful study on test subjects performing various tasks in an optical motion studio, considered a gold standard in biomechanics research. Future work will include further validation and expanding the program to include other analyses.

  5. Spatial variation of the magnetic field inside laminar flows of a perfect conductive fluid

    NASA Astrophysics Data System (ADS)

    Duka, Bejo; Boçi, Sonila

    2017-01-01

    The steady state of a perfect conductive fluid in laminar flow resulting from the ‘Hall effect’ is studied. Using the Maxwell equations, the spatial variation of the magnetic field in the steady state is calculated for three cases of different fluid flow geometries: flow between two infinite parallel planes, flow between two coaxial infinite-long cylinders and flow between two concentric spheres. According to our calculation of the three cases, the spatial variation of the magnetic field depends on the flow velocity. The magnetic field is strengthened in layers where the velocity is greater, but this dependency is negligible for non relativistic flows. Our approach in this study provides an example of how to receive interesting results using only basic knowledge of physics and mathematics.

  6. Evaluation of the intranasal flow field through computational fluid dynamics.

    PubMed

    Hildebrandt, Thomas; Goubergrits, Leonid; Heppt, Werner Johannes; Bessler, Stephan; Zachow, Stefan

    2013-04-01

    A reliable and comprehensive assessment of nasal breathing is problematic and still a common issue in rhinosurgery. Impairments of nasal breathing need an objective approach. In this regard, currently rhinomanometry is the only standard diagnostic tool available but has various limitations. However, in the last decade, computational fluid dynamics (CFD) has become a promising method in facing the challenge of qualifying nasal breathing. This article presents use of CFD with a symptom-free subject and a symptomatic patient. Thereby, certain flow field features and changes before and after surgery were investigated. Moreover, the study outlines suggestions for concrete rhinologic CFD applications. Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.

  7. Viscous and Interacting Flow Field Effects.

    DTIC Science & Technology

    1980-06-01

    supersonic causing a dramatic decrease in inmtx (see Fig 4). analysis, the frequency was predicted for six experi- Sepration will not occur at the spike...conditions at the solid wall have been discussed by the author [7]. The important fact is, that the flow close to the surface is strongly affected by the...without any solid theoretical foundation. It is there- fore of fundamental and practical importance to establish a basic theory of this damping

  8. Computational Methods for Complex Flow Fields.

    DTIC Science & Technology

    1986-06-28

    James J. Riley Joel H . Ferziger "Turbulent Flow Simulation - Future Needs" Micha Wolfshtein " Numerical Calculation of the Reynolds Stress and Turbulent...July 1983. Also in RECENT ADVANCES IN NUMERICAL METHODS IN FLUIDS, Vol. 3, Editor W.G. Habashi, Pineridge Press. 2. Usab, W.J., "Embedded Mesh Solutions...ridiaconal matrices applicable to approximane factorization methods . E:xlicit algcrit-s are also easier to adapz to multiProcessor arcr.itectures as the

  9. Partitioning of particle velocities in gas-solid turbulent flows into a continuous field and a spatially uncorrelated random distribution: theoretical formalism and numerical study

    NASA Astrophysics Data System (ADS)

    Février, Pierre; Simonin, Olivier; Squires, Kyle D.

    2005-06-01

    The velocity distribution of dilute suspensions of heavy particles in gas-solid turbulent flows is investigated. A statistical approach - the mesoscopic Eulerian formalism (MEF) - is developed in which an average conditioned on a realization of the turbulent carrier flow is introduced and enables a decomposition of the instantaneous particle velocity into two contributions. The first is a contribution from an underlying continuous turbulent velocity field shared by all the particles - the mesoscopic Eulerian particle velocity field (MEPVF) - that accounts for all particle-particle and fluid-particle two-point correlations. The second contribution corresponds to a distribution - the quasi-Brownian velocity distribution (QBVD) - that represents a random velocity component satisfying the molecular chaos assumption that is not spatially correlated and identified with each particle of the system. The MEF is used to investigate properties of statistically stationary particle-laden isotropic turbulence. The carrier flow is computed using direct numerical simulation (DNS) or large-eddy simulation (LES) with discrete particle tracking employed for the dispersed phase. Particle material densities are much larger than that of the fluid and the force of the fluid on the particle is assumed to reduce to the drag contribution. Computations are performed in the dilute regime for which the influences of inter-particle collisions and fluid-turbulence modulation are neglected. The simulations show that increases in particle inertia increase the contribution of the quasi-Brownian component to the particle velocity. The particle velocity field is correlated at larger length scales than the fluid, with the integral length scales of the MEPVF also increasing with particle inertia. Consistent with the previous work of Abrahamson (1975), the MEF shows that in the limiting case of large inertia, particle motion becomes stochastically equivalent to a Brownian motion with a random spatial

  10. 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.

  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. Hydrodynamic radius determination with asymmetrical flow field-flow fractionation using decaying cross-flows. Part II. Experimental evaluation.

    PubMed

    Magnusson, Emma; Håkansson, Andreas; Janiak, John; Bergenståhl, Björn; Nilsson, Lars

    2012-08-31

    In this study we investigate the effect of programmed cross-flows on the error in the hydrodynamic radii (r(h)) determination with asymmetrical flow field-flow fractionation (AsFlFFF). Three different standard polystyrene particles (nominal radii of 30 and 40 and 50 nm) are fractionated with exponentially and linearly decaying cross-flows with different decay rates. Hydrodynamic radii are calculated according to retention theory including steric effects. Rapid decay is expected to give rise to systematic deviations in r(h) determination. The error in r(h) was found to be small when decay rates with half-lives longer than 6 min were used, whereas steeper decays could give rise to errors as high as 16% of the particle size. The error is often explained in terms of secondary relaxation. However, comparisons show that experimental errors are significantly larger than what would be expected due to secondary relaxation, suggesting that other factors also have to be considered in order to fully understand deviations for rapidly decaying cross-flow.

  13. 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.

  14. Filtered Rayleigh Scattering Measurements in a Buoyant Flow Field

    DTIC Science & Technology

    2008-03-01

    John William Strutt , the third Baron of Rayleigh , or more commonly known as Lord Rayleigh , was the first to offer a correct explanation of the...FILTERED RAYLEIGH SCATTERING MEASUREMENTS IN A BUOYANT FLOW FIELD         THESIS       Steven Michael Meents, Captain, USAF...AFIT/GAE/ENY/08-M22 FILTERED RAYLEIGH SCATTERING MEASUREMENTS IN A BUOYANT FLOW FIELD THESIS Presented to the Faculty Department of Aeronautics

  15. Lava Flow Fields on Earth and Mars: Scales of Comparison

    NASA Astrophysics Data System (ADS)

    Gregg, T. K.; Bulmer, M. H.; Warner, N. H.

    2001-12-01

    Because an active lava flow has yet to be observed on Mars, and available data on surface composition is of limited scope (e.g., the SNC meteorites, or data collected by Sojourner) or resolution (e.g., the Mars Global Surveyor Thermal Emissions Spectrometer [MGS TES]), Martian eruption and emplacement parameters must be inferred from the resulting volcanic morphologies. A unique set of lava flow lobes to the southwest of Arsia Mons (and possibly genetically associated with that volcano) were initially identified using high-resolution ( ~50 m/pixel) Viking Orbiter (VO) images. These flows are characterized by a ridged surface texture, similar to that observed on folded evolved lava flows (e.g., andesites, dacites and rhyolites) on Earth, and relatively thick ( ~40 to 80 m) flow margins. Additional data collected by the Mars Orbiter Camera (MOC) and the Mars Orbiter Laser Altimeter (MOLA) reveal that these ridged flows are much more widespread than indicated by the VO images. MGS and VO datasets allow us to identify the location of these ridged flows, measure flow thickness and the wavelengths and amplitudes of the surface undulations. A large lava flow field ( ~67.5 km2) surrounding Sabancaya volcano, Peru, displays similar surface textures and flow thicknesses, and we have been investigating these andesitic to trachyandesitic lavas as potential analogs to the Martian flows. Using high-resolution GPS surveys-collected both along-flow and across-flow, we can quantify the surface topography of these flows with +/-1 cm horizontal and +/-2 cm vertical resolution. This resolution is approximately one order of magnitude better than will be obtained using global MOLA coverage of Mars. Quantitative comparison of the Sabancaya lava flows with those adjacent to Arsia Mons, combined with results from analytical and numerical modeling, suggest that the Sabancaya lavas are fundamentally different from the Martian flows. We therefore suggest that the Martian flows are either not

  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. Field studies courses open

    NASA Astrophysics Data System (ADS)

    Fourteen month-long courses combining applied academics with training in field research methodology are being offered this summer by the School for Field Studies. The courses, held in eight countries during May, June, July, and August, provide unique opportunities for participants to work as a team under primitive conditions.‘Our courses bind together the academic challenge of the research problem, the physical challenge of the site itself, and the interpersonal challenge of the expedition team in a dynamic way so that both cognitive and affective learning are accelerated,’ according to Jim Elder, the school's director.

  18. 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.

  19. SUPERSONIC AND HYPERSONIC INTERFERENCE FLOW FIELDS AND HEATING

    NASA Technical Reports Server (NTRS)

    Morris, D. J.

    1994-01-01

    on the surface, creating a small region with high stagnation heating. 5) Type V interference involves the interaction of two weak shocks of the same family. The interaction produces a shear layer, a supersonic jet, and a transmitted impinging shock. On a blunt body the shock interaction occurs near the upper sonic point. 6) Type VI interference involves the intersection of two weak shocks of the same family, which leads to an entirely supersonic flow field. This type of interference is important because it provides a means for predicting the onset of type V. Peak-heating correlations for laminar and turbulent shock-boundary-layer interactions are included in the programs for types I, II, V, and VI interference patterns. Heating correlations for laminar and turbulent reattaching shear layers obtained from separation studies are included in the program for type III interference. This program is written in FORTRAN IV for batch execution and has been implemented on a CDC 6000 Series computer. This program was developed in 1973.

  20. Biomat flow: fluorescent dye field experiments, pore-scale modeling of flow and transport properties, and field-scale flow models

    NASA Astrophysics Data System (ADS)

    Gerke, K.; Sidle, R. C.; Mallants, D.; Vasilyev, R.; Karsanina, M.; Skvortsova, E. B.; Korost, D. V.

    2013-12-01

    Recent studies highlight the important role that the upper litter layer in forest soils (biomat) plays in hillslope and catchment runoff generation. This biomat layer is a very loose material with high porosity and organic content. Direct sampling is usually problematic due to limited layer thickness. Conventional laboratory measurements can mobilize solids or even cause structure failure of the sample thus making measurements unreliable. It is also difficult to assess local variation in soil properties and transition zones using these methods; thus, they may not be applicable to biomat studies. However, if the physics of flow through this layer needs to be quantified and incorporated into a model, a detailed study of hydraulic properties is necessary. Herein we show the significance of biomat flow by staining experiments in the field, study its structure and transition to mineral soil layer using X-ray micro-tomography, assess hydraulic properties and structure differences using a pore-scale modeling approach, and, finally, use conventional variably-saturated flow modeling based on Richards equation to simulate flow in the hillslope. Using staining tracers we show that biomat flow in forested hillslopes can extend long distances (lateral displacement was about 1.2 times larger than for subsurface lateral flow) before infiltration occurs into deeper layers. The three-dimensional structure of an undisturbed sample (4 x 3 x 2.5 cm) of both biomat and deeper consolidated soil was obtained using an X-ray micro-tomography device with a resolution of 15 um. Local hydraulic properties (e.g., permeability and water retention curve) for numerous layers (e.g., transition zones, biomat, mineral soil) were calculated using Stokes flow FDM solution and pore-network modeling. Anisotropy, structure differences, and property fluctuations of different layers were quantified using local porosity analysis and correlation functions. Current results support the hypothesis that small

  1. Biomat flow: fluorescent dye field experiments, pore-scale modeling of flow and transport properties, and field-scale flow models

    NASA Astrophysics Data System (ADS)

    Gerke, K.; Sidle, R. C.; Mallants, D.; Vasilyev, R.; Karsanina, M.; Skvortsova, E. B.; Korost, D. V.

    2011-12-01

    Recent studies highlight the important role that the upper litter layer in forest soils (biomat) plays in hillslope and catchment runoff generation. This biomat layer is a very loose material with high porosity and organic content. Direct sampling is usually problematic due to limited layer thickness. Conventional laboratory measurements can mobilize solids or even cause structure failure of the sample thus making measurements unreliable. It is also difficult to assess local variation in soil properties and transition zones using these methods; thus, they may not be applicable to biomat studies. However, if the physics of flow through this layer needs to be quantified and incorporated into a model, a detailed study of hydraulic properties is necessary. Herein we show the significance of biomat flow by staining experiments in the field, study its structure and transition to mineral soil layer using X-ray micro-tomography, assess hydraulic properties and structure differences using a pore-scale modeling approach, and, finally, use conventional variably-saturated flow modeling based on Richards equation to simulate flow in the hillslope. Using staining tracers we show that biomat flow in forested hillslopes can extend long distances (lateral displacement was about 1.2 times larger than for subsurface lateral flow) before infiltration occurs into deeper layers. The three-dimensional structure of an undisturbed sample (4 x 3 x 2.5 cm) of both biomat and deeper consolidated soil was obtained using an X-ray micro-tomography device with a resolution of 15 um. Local hydraulic properties (e.g., permeability and water retention curve) for numerous layers (e.g., transition zones, biomat, mineral soil) were calculated using Stokes flow FDM solution and pore-network modeling. Anisotropy, structure differences, and property fluctuations of different layers were quantified using local porosity analysis and correlation functions. Current results support the hypothesis that small

  2. Flow field characteristics of an ornithopter

    NASA Astrophysics Data System (ADS)

    Juarez, Alfredo; Allen, James

    2007-11-01

    This paper details phase locked PIV measurements from a model Ornithopther flying in a wind tunnel at representative flight conditions. Testing over a range of Strouhal numbers, 0.1-0.3, shows that the unsteady wake is composed of coherent vortical structures that resemble vortex rings. A single ring is formed in the wake of each wing during one wing beat. Momentum balance from velocity field measurements are used to estimate the lift and drag of the ornithopter.

  3. Unsteady-flow-field predictions for oscillating cascades

    NASA Technical Reports Server (NTRS)

    Huff, Dennis L.

    1991-01-01

    The unsteady flow field around an oscillating cascade of flat plates with zero stagger was studied by using a time marching Euler code. This case had an exact solution based on linear theory and served as a model problem for studying pressure wave propagation in the numerical solution. The importance of using proper unsteady boundary conditions, grid resolution, and time step size was shown for a moderate reduced frequency. Results show that an approximate nonreflecting boundary condition based on linear theory does a good job of minimizing reflections from the inflow and outflow boundaries and allows the placement of the boundaries to be closer to the airfoils than when reflective boundaries are used. Stretching the boundary to dampen the unsteady waves is another way to minimize reflections. Grid clustering near the plates captures the unsteady flow field better than when uniform grids are used as long as the 'Courant Friedrichs Levy' (CFL) number is less than 1 for a sufficient portion of the grid. Finally, a solution based on an optimization of grid, CFL number, and boundary conditions shows good agreement with linear theory.

  4. 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.

  5. Generation of a Magnetic Field by Dynamo Action in a Turbulent Flow of Liquid Sodium

    SciTech Connect

    Monchaux, R.; Chiffaudel, A.; Daviaud, F.; Dubrulle, B.; Gasquet, C.; Marie, L.; Ravelet, F.; Berhanu, M.; Fauve, S.; Mordant, N.; Petrelis, F.; Bourgoin, M.; Moulin, M.; Odier, Ph.; Pinton, J.-F.; Volk, R.

    2007-01-26

    We report the observation of dynamo action in the von Karman sodium experiment, i.e., the generation of a magnetic field by a strongly turbulent swirling flow of liquid sodium. Both mean and fluctuating parts of the field are studied. The dynamo threshold corresponds to a magnetic Reynolds number R{sub m}{approx}30. A mean magnetic field of the order of 40 G is observed 30% above threshold at the flow lateral boundary. The rms fluctuations are larger than the corresponding mean value for two of the components. The scaling of the mean square magnetic field is compared to a prediction previously made for high Reynolds number flows.

  6. 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.

  7. Block Implicit Computation of Flow Field in Solid Rocket Ramjets

    NASA Astrophysics Data System (ADS)

    Ma, Zhibo; Zhu, Jianshi

    To compute the flow field in solid rocket ramjet (SRR) in which the chamber has a complex boundary, a block implicit algorithm (BIA) had been developed. The boundary conditions of three-dimensional steady-state Navier-Stokes (NS) equations were treated by modifying the discrete equations and the grids were generated through an algebraic way. These methods have been put into practice and proved to be valid and efficient in the computation of flow field in the chamber. The technique developed here applies to similar problems in porous medium flows. Keywords: rocket ramjet, numerical simulation, block implicit algorithm

  8. 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.

  9. Hydraulic well testing inversion for modeling fluid flow in fractured rocks using simulated annealing: a case study at Raymond field site, California

    NASA Astrophysics Data System (ADS)

    Nakao, Shinsuke; Najita, Julie; Karasaki, Kenzi

    2000-10-01

    Cluster variable aperture (CVA) simulated annealing (SA) is an inversion technique to construct fluid flow models in fractured rocks based on the transient pressure data from hydraulic tests. A two-dimensional fracture network system is represented as a filled regular lattice of fracture elements. The algorithm iteratively changes element apertures for a cluster of fracture elements in order to improve the match to observed pressure transients. This inversion technique has been applied to hydraulic data collected at the Raymond field site, CA to examine the spatial characteristics of the flow properties in a fractured rock mass. Two major conductive zones have been detected by various geophysical logs, geophysical imaging techniques and hydraulic tests; one occurring near a depth of 30 m and the other near a depth of 60 m. Our inversion results show that the practical range of spatial correlation for transmissivity distribution is estimated to be approximately 5 m in the upper zone and less than 2.5 m in the lower zones. From the televiewer and other fracture imaging logs it was surmised that the lower conductive zone is associated with an anomalous single open fracture as compared to the upper zone, which is an extensive fracture zone. This would explain the difference in the estimated practical range of the spatial correlation for transmissivity.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

    Javed, Afroz; Chakraborty, Debasis

    2017-10-01

    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.

  12. 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.

  13. 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.

  14. The structure of the vorticity field in homogeneous turbulent flows

    NASA Technical Reports Server (NTRS)

    Rogers, Michael M.; Moin, Parviz

    1987-01-01

    The structures of the vorticity fields in several homogeneous irrotational straining flows and a homogeneous turbulent shear flow were examined using a database generated by direct numerical simulation of the unsteady Navier-Stokes equations. In all cases, strong evidence was found for the presence of coherent vortical structures. The initially isotropic vorticity fields were rapidly affected by imposed mean strain and the rotational component of mean shear and developed accordingly. In the homogeneous turbulent shear-flow cases, the roll-up of mean vorticity into characteristic hairpin vortices was clearly observed, supporting the view that hairpin vortices are an important vortical structure in all turbulent shear flows; the absence of mean shear in the homogeneous irrotational straining flows precludes the presence of hairpin-like vortices.

  15. Kinematics and flow fields in 3D around swimming lamprey using light field PIV

    NASA Astrophysics Data System (ADS)

    Lehn, Andrea M.; Techet, Alexandra H.

    2016-11-01

    The fully time-resolved 3D kinematics and flow field velocities around freely swimming sea lamprey are derived using 3D light field imaging PIV. Lighthill's Elongated Body Theory (EBT) predicts that swimmers with anguilliform kinematics likened to lamprey, and similarly eels, will exhibit relatively poor propulsive efficiency. However, previous experimental studies of eel locomotion utilizing 2D PIV suggest disagreement with EBT estimates of wake properties; although, the thrust force generated by such swimmers has yet to be fully resolved using 3D measurements. A light field imaging array of multiple high-speed cameras is used to perform 3D synthetic aperture PIV around ammocoete sea lamprey (Petromyzon marinus). Fluid mechanics equations are used to determine thrust force generation, leading experimental studies closer to underpinning the physical mechanisms that enable aquatic locomotion of long, slender undulatory swimmers.

  16. Vapor Bubbles in Flow and Acoustic Fields

    NASA Technical Reports Server (NTRS)

    Prosperetti, Andrea; Hao, Yue

    2001-01-01

    The paper presents an order-of-magnitude analysis of the physical processes occurring during the pulsations of a vapor bubble subject to a sound field and shows several numerical examples relating to vapor bubbles in water with and without a translational velocity relative to the liquid. Finally, the growth and collapse of a bubble in a small tube under the action of a heat pulse is considered and it is pointed out that, in suitable conditions, a potentially useful pumping effect without mechanical moving parts can be achieved.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Microscopic and continuum descriptions of Janus motor fluid flow fields.

    PubMed

    Reigh, Shang Yik; Huang, Mu-Jie; Schofield, Jeremy; Kapral, Raymond

    2016-11-13

    Active media, whose constituents are able to move autonomously, display novel features that differ from those of equilibrium systems. In addition to naturally occurring active systems such as populations of swimming bacteria, active systems of synthetic self-propelled nanomotors have been developed. These synthetic systems are interesting because of their potential applications in a variety of fields. Janus particles, synthetic motors of spherical geometry with one hemisphere that catalyses the conversion of fuel to product and one non-catalytic hemisphere, can propel themselves in solution by self-diffusiophoresis. In this mechanism, the concentration gradient generated by the asymmetric catalytic activity leads to a force on the motor that induces fluid flows in the surrounding medium. These fluid flows are studied in detail through microscopic simulations of Janus motor motion and continuum theory. It is shown that continuum theory is able to capture many, but not all, features of the dynamics of the Janus motor and the velocity fields of the fluid.This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'. © 2016 The Author(s).

  4. Microscopic and continuum descriptions of Janus motor fluid flow fields

    NASA Astrophysics Data System (ADS)

    Reigh, Shang Yik; Huang, Mu-Jie; Schofield, Jeremy; Kapral, Raymond

    2016-11-01

    Active media, whose constituents are able to move autonomously, display novel features that differ from those of equilibrium systems. In addition to naturally occurring active systems such as populations of swimming bacteria, active systems of synthetic self-propelled nanomotors have been developed. These synthetic systems are interesting because of their potential applications in a variety of fields. Janus particles, synthetic motors of spherical geometry with one hemisphere that catalyses the conversion of fuel to product and one non-catalytic hemisphere, can propel themselves in solution by self-diffusiophoresis. In this mechanism, the concentration gradient generated by the asymmetric catalytic activity leads to a force on the motor that induces fluid flows in the surrounding medium. These fluid flows are studied in detail through microscopic simulations of Janus motor motion and continuum theory. It is shown that continuum theory is able to capture many, but not all, features of the dynamics of the Janus motor and the velocity fields of the fluid. This article is part of the themed issue 'Multiscale modelling at the physics-chemistry-biology interface'.

  5. 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.

  6. 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

  7. Sedimentation field flow fractionation monitoring of bimodal wheat starch amylolysis.

    PubMed

    Salesse, C; Battu, S; Begaud-Grimaud, G; Cledat, D; Cook-Moreau, J; Cardot, P J P

    2006-10-06

    Enzymatic starch granule hydrolysis is one of the most important reactions in many industrial processes. In this study, we investigated the capacity of sedimentation field flow fractionation (SdFFF) to monitor the amylolysis of a bimodal starch population: native wheat starch. Results demonstrated a correlation between fractogram changes and enzymatic hydrolysis. Furthermore, SdFFF was used to sort sub-populations which enhanced the study of granule size distribution changes occurring during amylolysis. These results show the interest in coupling SdFFF with particle size measurement methods to study complex starch size/density modifications associated to hydrolysis. These results suggested different applications such as the association of SdFFF with structural investigations to better understand the specific mechanisms of amylolysis or starch granule structure.

  8. Analysis of a solar collector field water flow network

    NASA Technical Reports Server (NTRS)

    Rohde, J. E.; Knoll, R. H.

    1976-01-01

    A number of methods are presented for minimizing the water flow variation in the solar collector field for the Solar Building Test Facility at the Langley Research Center. The solar collector field investigated consisted of collector panels connected in parallel between inlet and exit collector manifolds to form 12 rows. The rows were in turn connected in parallel between the main inlet and exit field manifolds to complete the field. The various solutions considered included various size manifolds, manifold area change, different locations for the inlets and exits to the manifolds, and orifices or flow control valves. Calculations showed that flow variations of less than 5 percent were obtainable both inside a row between solar collector panels and between various rows.

  9. Spatial statistics of magnetic field in two-dimensional chaotic flow in the resistive growth stage

    NASA Astrophysics Data System (ADS)

    Kolokolov, I. V.

    2017-03-01

    The correlation tensors of magnetic field in a two-dimensional chaotic flow of conducting fluid are studied. It is shown that there is a stage of resistive evolution where the field correlators grow exponentially with time. The two- and four-point field correlation tensors are computed explicitly in this stage in the framework of Batchelor-Kraichnan-Kazantsev model. They demonstrate strong temporal intermittency of the field fluctuations and high level of non-Gaussianity in spatial field distribution.

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

    NASA Astrophysics Data System (ADS)

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

    2014-04-01

    Two magnetic flux ropes that collide and bounce have been characterized in the laboratory. We find screw pinch profiles that include ion flow vi, magnetic field B, current density J, and plasma pressure. The electron flow ve 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 ∇×ve×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 δBz. 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.

  11. 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.

  12. 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.

  13. Selecting MODFLOW cell sizes for accurate flow fields.

    PubMed

    Haitjema, H; Kelson, V; de Lange, W

    2001-01-01

    Contaminant transport models often use a velocity field derived from a MODFLOW flow field. Consequently, the accuracy of MODFLOW in representing a ground water flow field determines in part the accuracy of the transport predictions, particularly when advective transport is dominant. We compared MODFLOW ground water flow rates and MODPATH particle traces (advective transport) for a variety of conceptual models and different grid spacings to exact or approximate analytic solutions. All of our numerical experiments concerned flow in a single confined or semiconfined aquifer. While MODFLOW appeared robust in terms of both local and global water balance, we found that ground water flow rates, particle traces, and associated ground water travel times are accurate only when sufficiently small cells are used. For instance, a minimum of four or five cells are required to accurately model total ground water inflow in tributaries or other narrow surface water bodies that end inside the model domain. Also, about 50 cells are needed to represent zones of differing transmissivities or an incorrect flow field and (locally) inaccurate ground water travel times may result. Finally, to adequately represent leakage through aquitards or through the bottom of surface water bodies it was found that the maximum allowable cell dimensions should not exceed a characteristic leakage length lambda, which is defined as the square root of the aquifer transmissivity times the resistance of the aquitard or stream bottom. In some cases a cell size of one-tenth of lambda is necessary to obtain accurate results.

  14. 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.

  15. 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.

  16. 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.

  17. Experimental Studies on the Effects of Thermal Bumps in the Flow-Field around a Flat Plate using a Hypersonic Wind Tunnel

    DTIC Science & Technology

    2012-07-01

    The main part is made of PEEK but the insert is still DURATEC 750. The density of  of PEEK is 1480 3kg m and maximum service temperature for...short term testing is 300 degree. The thermal conductivity of PEEK c is 0.24 W m K and the specific heat capacity of PEEK is 31.8 10 J kg K . These...2005). Effect of the laser repetition rate on the drag reduction rate was studied in supersonic flow by Sasoh et al. (Sasoh, Sekiya et al.) and Kim et

  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. 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

  20. 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.

  1. The mantle flow field beneath western North America.

    PubMed

    Silver, P G; Holt, W E

    2002-02-08

    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.

  2. 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.

  3. Investigation of flow fields within large scale hypersonic inlet models

    NASA Technical Reports Server (NTRS)

    Gnos, A. V.; Watson, E. C.; Seebaugh, W. R.; Sanator, R. J.; Decarlo, J. P.

    1973-01-01

    Analytical and experimental investigations were conducted to determine the internal flow characteristics in model passages representative of hypersonic inlets for use at Mach numbers to about 12. The passages were large enough to permit measurements to be made in both the core flow and boundary layers. The analytical techniques for designing the internal contours and predicting the internal flow-field development accounted for coupling between the boundary layers and inviscid flow fields by means of a displacement-thickness correction. Three large-scale inlet models, each having a different internal compression ratio, were designed to provide high internal performance with an approximately uniform static-pressure distribution at the throat station. The models were tested in the Ames 3.5-Foot Hypersonic Wind Tunnel at a nominal free-stream Mach number of 7.4 and a unit free-stream Reynolds number of 8.86 X one million per meter.

  4. 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.

  5. Different elution modes and field programming in gravitational field-flow fractionation. Effect of channel angle.

    PubMed

    Park, Mi Ri; Kang, Da Young; Chmelik, Josef; Kang, Namgoo; Kim, Jin Seog; Lee, Seungho

    2008-10-31

    Gravitational field-flow fractionation (GrFFF) has been shown to be useful for separation and characterization of various types of micrometer-sized particles. It has been recognized however that GrFFF is less versatile than other members of FFF because the external field (Earth's gravity) in GrFFF is relatively weak and is not tunable (constant), which makes the force acting on the particles constant. A few approaches have been suggested to control the force acting on particles in GrFFF. They include (1) changing the angle between the Earth's gravitational field and the longitudinal axis of the channel, and (2) the use of carrier liquid having different densities. In the hyperlayer mode of GrFFF, the hydrodynamic lift force (HLF) also act on particles. The existence of HLF allows other means of changing the force acting on the particles in GrFFF. They include (1) the flow rate programming, or (2) the use of channels having non-constant cross-section. In this study, with polystyrene latex beads used as model particles, the channel angle was varied to study its effect on elution parameters (such as selectivity, band broadening and resolution) in the steric or in the hyperlayer mode of GrFFF. In addition, the effects of the channel thickness and the flow rate on the elution parameters were also investigated. It was found that, in the steric mode, the resolution decreases as the flow rate increases due to increased zone broadening despite of the increase in the selectivity. At a constant volumetric flow rate, both the zone broadening and the selectivity increase as the channel thickness increases, resulting in the net increase in the resolution. It was also found that the retention time decreases as the channel angle increases in both up- and down-flow positions. The zone broadening tends to increase almost linearly with the channel angle, while no particular trends were found in selectivity. As a result, the resolution decreases as the channel angle increases.

  6. Propulsion efficiency and imposed flow fields of a copepod jump.

    PubMed

    Jiang, Houshuo; Kiørboe, Thomas

    2011-02-01

    Pelagic copepods jump to relocate, to attack prey and to escape predators. However, there is a price to be paid for these jumps in terms of their energy costs and the hydrodynamic signals they generate to rheotactic predators. Using observed kinematics of various types of jumps, we computed the imposed flow fields and associated energetics of jumps by means of computational fluid dynamics simulations by modeling the copepod as a self-propelled body. The computational fluid dynamics simulation was validated by particle image velocimetry data. The flow field generated by a repositioning jump quickly evolves into two counter-rotating viscous vortex rings that are near mirror image of one another, one in the wake and one around the body of the copepod; this near symmetrical flow may provide hydrodynamic camouflage because it contains no information about the position of the copepod prey within the flow structure. The flow field associated with an escape jump sequence also includes two dominant vortex structures: one leading wake vortex generated as a result of the first jump and one around the body, but between these two vortex structures is an elongated, long-lasting flow trail with flow velocity vectors pointing towards the copepod; such a flow field may inform the predator of the whereabouts of the escaping copepod prey. High Froude propulsion efficiency (0.94-0.98) was obtained for individual power stroke durations of all simulated jumps. This is unusual for small aquatic organisms but is caused by the rapidity and impulsiveness of the jump that allows only a low-cost viscous wake vortex to travel backwards.

  7. Colloidal transport and agglomeration in column studies for advanced run-off filtration facilities--particle size and time resolved monitoring of effluents with flow-field-flow-fractionation.

    PubMed

    Siepmann, R; von der Kammer, F; Förstner, U

    2004-01-01

    The efficiency of road run-off filtration facilities based on ion-exchange materials is reduced by pollutants which are transported bound to particles. To quantify the factors governing particle transport phenomena, a simplified model consisting of quartz sand-filled columns representing the filter/soil was set up. Suspensions of artificial clays, cold water-extracted natural clays, and real run-off were used as model effluents. Five experiments were performed: breakthrough of a natural soil suspension, remobilization of a natural soil suspension after ionic strength-drop, the same two experiments with a suspension of the artificial clay mineral Laponite, and the remobilization of run-off accumulated on a column at high ionic strength with an ionic strength down-gradient. Short-interval effluent fractions were analysed by flow-field-flow-fractionation (F4) to obtain the size distributions of the colloids present. The size distributions of subsequent fractions were then plotted in a staggered arrangement to give three-dimensional graphs that are time- and particle size-resolved. With this method the subsequent release of different agglomerate sizes formed on the column could be shown for the artificial clay mineral, questioning its use as a model colloid. The combined particle size- and time-resolved plots proved to be a powerful tool for monitoring colloidal solids in column effluents.

  8. Magnetic field generation from shear flow in flux ropes

    NASA Astrophysics Data System (ADS)

    Intrator, T. P.; Sears, J.; Gao, K.; Klarenbeek, J.; Yoo, C.

    2012-10-01

    In the Reconnection Scaling Experiment (RSX) we have measured out of plane quadrupole magnetic field structure in situations where magnetic reconnection was minimal. This quadrupole out of plane magnetic signature has historically been presumed to be the smoking gun harbinger of reconnection. On the other hand, we showed that when flux ropes bounced instead of merging and reconnecting, this signature could evolve. This can follow from sheared fluid flows in the context of a generalized Ohms Law. We reconstruct a shear flow model from experimental data for flux ropes that have been experimentally well characterized in RSX as screw pinch equilibria, including plasma ion and electron flow, with self consistent profiles for magnetic field, pressure, and current density. The data can account for the quadrupole field structure.

  9. 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.

  10. Acoustic tomographic imaging of temperature and flow fields in air

    NASA Astrophysics Data System (ADS)

    Barth, Manuela; Raabe, Armin

    2011-03-01

    Acoustic travel-time tomography is a remote sensing technique that uses the dependence of sound speed in air on temperature and wind speed along the sound propagation path. Travel-time measurements of acoustic signals between several sound sources and receivers travelling along different paths through a measuring area give information on the spatial distribution of temperature and flow fields within the area. After a separation of the two influences, distributions of temperature and flow can be reconstructed using inverse algorithms. As a remote sensing method, one advantage of acoustic travel-time tomography is its ability to measure temperature and flow field quantities without disturbing the area under investigation due to insertion of sensors. Furthermore, the two quantities—temperature and flow velocity—can be recorded simultaneously with this measurement method. In this paper, an acoustic tomographic measurement system is introduced which is capable of resolving three-dimensional distributions of temperature and flow fields in air within a certain volume (1.3 m × 1.0 m × 1.2 m) using 16 acoustic transmitter-receiver pairs. First, algorithms for the 3D reconstruction of distributions from line-integrated measurements are presented. Moreover, a measuring apparatus is introduced which is suited for educational purposes, for demonstration of the method as well as for indoor investigations. Example measurements within a low-speed wind tunnel with different incident flow situations (e.g. behind bluff bodies) using this system are shown. Visualizations of the flow illustrate the plausibility of the tomographically reconstructed flow structures. Furthermore, alternative individual measurement methods for temperature and flow speed provide comparable results.

  11. Visualization study of flow in axial flow inducer.

    NASA Technical Reports Server (NTRS)

    Lakshminarayana, B.

    1972-01-01

    A visualization study of the flow through a three ft dia model of a four bladed inducer, which is operated in air at a flow coefficient of 0.065, is reported in this paper. The flow near the blade surfaces, inside the rotating passages, downstream and upstream of the inducer is visualized by means of smoke, tufts, ammonia filament, and lampblack techniques. Flow is found to be highly three dimensional, with appreciable radial velocity throughout the entire passage. The secondary flows observed near the hub and annulus walls agree with qualitative predictions obtained from the inviscid secondary flow theory.

  12. Flow field measurements in the cell culture unit.

    PubMed

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

    2002-10-01

    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

  13. 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

  14. 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

  15. The behavior of a magnetic filament in flow under the influence of an external magnetic field

    NASA Astrophysics Data System (ADS)

    Lüsebrink, Daniel; Cerdà, Joan J.; Sánchez, Pedro A.; Kantorovich, Sofia S.; Sintes, Tomás

    2016-12-01

    We present an extensive numerical study of the behaviour of a filament made of ferromagnetic colloidal particles subjected to the simultaneous action of a fluid flow and a stationary external magnetic field perpendicular to the flow lines. We found that in the presence of a shear flow, the tumbling motion observed at zero field is strongly inhibited when the external magnetic field is applied. The field is able to stabilise the filament with a well defined degree of alignment that depends on the balance between hydrodynamic and magnetic torques. In addition, for a Poiseuille flow, it has been found that the initial position has a long lasting influence on the behaviour of the magnetic filament when the external field is applied.

  16. Turbulence, flow and transport: hints from reversed field pinch

    NASA Astrophysics Data System (ADS)

    Vianello, N.; Antoni, V.; Spada, E.; Spolaore, M.; Serianni, G.; Cavazzana, R.; Bergsåker, H.; Cecconello, M.; Drake, J. R.

    2006-04-01

    The interplay between sheared E × B flows and turbulence has been experimentally investigated in the edge region of the Extrap-T2R reversed field pinch experiment. Electrostatic fluctuations are found to rule the momentum balance equation representing the main driving term for sheared flows which counterbalances anomalous viscous damping. The driving role of electrostatic fluctuations is proved by the spatial structure of the Reynolds stress and by the time behaviour of the mean energy production term which supports the existence of an energy exchange from the small scales of turbulence to the larger scales of the mean flow.

  17. 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.

  18. 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 }

  19. 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.

  20. High-throughput flowing upstream sperm sorting in a retarding flow field for human semen analysis.

    PubMed

    Wu, Jen-Kuei; Chen, Peng-Chun; Lin, Yu-Nan; Wang, Chia-Woei; Pan, Li-Chern; Tseng, Fan-Gang

    2017-03-13

    In this paper, we propose a microfluidic device capable of generating a retarding flow field for the sorting and separation of human motile sperm in a high-throughput manner. The proposed sorting/separation process begins with a rapid flow field in a straight-flow zone to carry sperm into a sorting zone to maintain the sperm's mobility. The sorting zone consists of a diffuser-type sperm sorter to differentiate sperm with different motilities based on the flowing upstream nature of human sperm in a retarding flow field. The dead sperm will then be separated from the live ones by passing through a dumbbell flow field to the outlet for disposal. The proposed flowing upstream sperm sorter (FUSS) is designed to imitate the selection mechanism found in the female body when sperm swim into the uterus. The experimental results demonstrate the utility of this device with regard to throughput (approximately 200 000 sperm per minute and a maximum of 200 million cells per mL), efficiency (90% of selected sperm are mobile), and the ability to select sperm with high motility (∼20% of sperm with a velocity exceeding 120 μm s(-1)). The proposed device is suitable for intrauterine insemination as well as in vitro fertilization thanks to the highly efficient sorting process not interfering with the natural function and energy resource of human sperm.

  1. Laboratory Observation Of Magnetic Field Growth Driven By Shear Flow

    NASA Astrophysics Data System (ADS)

    Intrator, T.; Sun, X.; Dorf, L.; Sears, J.; Weber, T.; Lapenta, G.

    2012-12-01

    We have measured in the laboratory profiles of magnetic flux ropes, that include ion flow, magnetic field, current density, and plasma pressure. These data allow a complete screw pinch equilibrium with guide magnetic field to be reconstructed, and the electron flows to be inferred. We use this information to evaluate the Hall JxB term in a two fluid magnetohydrodynamic Ohms Law. The difference between ion and electron flows allows us to show experimentally and theoretically that the sheared electron flows can account for the generation of magnetic field. For example we show a measured quadrupole out of plane magnetic field B_z structure that occurs even in the absence of magnetic reconnection. This out of plane quadrupole pattern has historically been used as a signature of magnetic reconnection, especially with small to vanishing guide field. Recent theoretical analyses have pointed out that this presumption need not be true. *Supported by DOE Office of Fusion Energy Sciences under LANS contract DE-AC52-06NA25369, NASA Geospace NNHIOA044I, Basic

  2. 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

    2011-07-08

    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.

  3. 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.

  4. 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

  5. Experimental study of double-cavity flow

    NASA Astrophysics Data System (ADS)

    Tuerke, F.; Pastur, L. R.; Sciamarella, D.; Lusseyran, F.; Artana, G.

    2017-07-01

    The flow through two facing, identical cavities (double-cavity) is characterized experimentally, as the inflow velocity and the distance between the cavities is varied. Standard 2D2C particle image velocimetry measurements in the spanwise mid-plane provide information on the instantaneous and mean velocity flow fields. Laser Doppler velocimetry measurements at several points in the double-cavity domain reveal the global character of the streamwise fluctuating velocity spectra. The flow is characterized based on time series, recorded in the shear layer of one of the cavities, for a wide range of inflow velocities and intercavity distances. In a detailed spectral study, we show how the shear layer spectra get affected when the two cavities are brought closer together. Based on the experimental data, a temporal local linear stability analysis was carried out, which was able to explain why the frequency peaks for close intercavity distances broaden and move to higher Strouhal numbers.

  6. Human lymphocyte sorting by gravitational field-flow fractionation.

    PubMed

    Roda, Barbara; Reschiglian, Pierluigi; Zattoni, Andrea; Tazzari, Pier Luigi; Buzzi, Marina; Ricci, Francesca; Bontadini, Andrea

    2008-09-01

    Interest in biological studies on various cell types for many biomedical applications, from research to patient treatments, is constantly increasing. The ability to discriminate (sort) and/or quantify distinct subpopulations of cells has become increasingly important. For instance, not only detection but also the highest depletion of neoplastic cells from normal cells is an important requisite in the autologous transplantation of lymphocytes for blood cancer treatments. In this work, gravitational field-flow fractionation (GrFFF) is shown to be effective for sorting a heterogeneous mixture of human, living lymphocytes constituted of neoplastic B cells from a Burkitt lymphoma cell line and healthy T and B lymphocytes from blood samples. GrFFF does not require the use of fluorescent immunotags for sorting cells, and the sorted cells can be collected for their further characterization. Flow cytometry was used to assess the viability of the cells collected, and to evaluate the cell fractionation achieved. A low amount of neoplastic B lymphocytes (less than 2%) was found in a specific fraction obtained by GrFFF. The high depletion from neoplastic cells (more than 98%) was confirmed by a clonogenicity test.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. The effect of an electrostatic field on film flow down an inclined plane

    SciTech Connect

    Kim, H.; Bankoff, S.G. ); Miksis, M.J. )

    1992-10-01

    A study of the interaction of an electrostatic field with a thin liquid film flowing under gravity down an inclined plane is presented. First, the effect of the electric field on the stability of the film flow is examined. Next, several limits of the equations of motion are investigated analytically, and then compared with an explicit numerical calculation of the equations of motion. Also, applications of these calculations to a proposed electrostatic liquid film space radiator are discussed.

  14. 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.

  15. 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.

  16. Paleomagnetic study of Ar-Ar dated lava flows from Tancitaro Volcano and Tacambaro area, The Michoacan Guanajuato Volcanic Field (Western Mexico)

    NASA Astrophysics Data System (ADS)

    Maciel, R.; Gogichaishvili, A.; Garduño, V. H.; Ruiz Martinez, V. C.; Aguilar Reyes, B.; Morales Contreras, J.

    2009-05-01

    We sampled eleven fresh, apparently not altered outcrops out of 26 sites reported recently while 27 independent cooling units were collected at Tacambaro area belonging to the Michoacan Guanajuato Volcanic Field. All studied sites were dated by means of state-of-the-art 40Ar-39Ar geochronological method and span from 1.23 ± 0.2 ma to present. Low-field continuous susceptibility measurements performed in air show the presence of a single ferrimagnetic phase with Curie point compatible with Ti-poor titanomagnetite. The cooling and heating curves are reasonably reversible. Polished section observations under microscope also confirmed the presence of a near-magnetite phase associated with exsolved ilmenite of trellis or sometimes sandwich texture. In most samples a single and stable component of magnetization was observed upon thermal, alternating field or combined treatments. A secondary component, probably due to the lightning effects was present but was easily removed at very first steps of demagnetization. The mean direction is in agreement with the expected paleodirections for the late Pliocene, as derived from reference poles for the North American plate. Combining the available geochronologic data with the magnetic polarity, better constraints of the age of emplacement are achieved.

  17. Influence of magnetic field on chemically reactive blood flow through stenosed bifurcated arteries

    NASA Astrophysics Data System (ADS)

    Hossain, Khan Enaet; Haque, Md. Mohidul

    2017-06-01

    Dynamic response of mass transfer in chemically reactive blood flow through bifurcated arteries under the stenotic condition is numerically studied in the present of a uniform magnetic field. The blood flowing through the artery is assumed an incompressible, fully developed and Newtonian. The nonlinear unsteady flow phenomena are governed by the Navier-Stokes and concentration equations. All these equations together with the appropriate boundary conditions describing the present biomechanical problem are transformed by using a radial transformation and the numerical results are obtained using a finite difference technique. Effects of stenosed bifurcation and externally applied magnetic field on the blood flow with chemical reaction are discussed with the help of graph. All the flow characteristics are found to be affected by the presence of chemical reaction and exposure of magnetic field of different intensities. Finally some important findings of the problem are concluded in this work.

  18. 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.

  19. Analytical solutions for flow fields near continuous wall reactive barriers

    NASA Astrophysics Data System (ADS)

    Klammler, Harald; Hatfield, Kirk

    2008-05-01

    Permeable reactive barriers (PRBs) are widely applied for in-situ remediation of contaminant plumes transported by groundwater. Besides the goal of a sufficient contaminant remediation inside the reactive cell (residence time) the width of plume intercepted by a PRB is of critical concern. A 2-dimensional analytical approach is applied to determine the flow fields towards rectangular PRBs of the continuous wall (CW) configuration with and without impermeable side walls (but yet no funnel). The approach is based on the conformal mapping technique and assumes a homogeneous aquifer with a uniform ambient flow field. The hydraulic conductivity of the reactive material is furthermore assumed to exceed the conductivity of the aquifer by at least one order of magnitude as to neglect the hydraulic gradient across the reactor. The flow fields are analyzed regarding the widths and shapes of the respective capture zones as functions of the dimensions (aspect ratio) of the reactive cell and the ambient groundwater flow direction. Presented are an improved characterization of the advantages of impermeable side walls, a convenient approach to improved hydraulic design (including basic cost-optimization) and new concepts for monitoring CW PRBs. Water level data from a CW PRB at the Seneca Army Depot site, NY, are used for field demonstration.

  20. An Examination of the Resonant Acoustic Mixers Flow Field

    DTIC Science & Technology

    2013-12-01

    research. The most profound assumption that we make is that LESLIE3D is multiphase physics code designed for compressible fluid flows . At face value, this...AFRL-RW-EG-TR-2013-108 AN EXAMINATION OF THE RESONANT ACOUSTIC MIXER’S FLOW FIELD Douglas V. Nance AFRL/RWWC 101 W. Eglin Blvd...Simulation…………………………………………………………9 3.0 Results…………………………………………………………………………………….12 3.1 Flow Field Structure During the Mixing Process…………………………………13 3.2

  1. Adaptive flow-field measurements using digital holography

    NASA Astrophysics Data System (ADS)

    Czarske, Jürgen W.; Koukourakis, Nektarios; Fregin, Bob; König, Jörg; Büttner, Lars

    2017-02-01

    Variations of the optical detection path-length in image correlation based flow-field measurements result in strong errors in position allocation and thus lead to a strong enhancement of the measurement uncertainty of the velocity. In this contribution we use digital holography to measure the wavefront distortion induced by fluctuating phase boundary, employing spatially extended guide stars. The measured phase information is used to correct the influence of the phase boundary in the detection path employing a spatial light modulator. We analyze the potential of guide stars that are reflected by the phase boundary, i.e. the Fresnel reflex, and transmitted. Our results show, that the usage of wavefront shaping enables to strongly reduce the measurement uncertainty and to strongly improve the quality of image correlation based flow-field measurements. The approaches presented here are not limited to application in flow measurement, but could be useful for a variety of applications.

  2. On the validity of modeling concepts for (the simulation of) groundwater flow in lowland peat areas - case study at the Zegveld experimental field

    NASA Astrophysics Data System (ADS)

    Trambauer, P.; Nonner, J.; Heijkers, J.; Uhlenbrook, S.

    2011-02-01

    The groundwater flow models currently used in the western part of The Netherlands and in other similar peaty areas are thought to be a too simplified representation of the hydrological reality. One of the reasons is that due to the schematization of the subsoil, its heterogeneity cannot be represented adequately. Moreover, the applicability of Darcy's law in these types of soils has been questioned, but this law forms the basis of most groundwater flow models. With the purpose of assessing the typical heterogeneity of the subsoil and to verify the applicability of Darcy's law fieldwork was completed at a research site in the western part of The Netherlands. The assessments were carried for the so called Complex Confining Layer (CCL), which is the Holocene peaty to clayey layer overlying Pleistocene sandy deposits. Borehole drilling through the CCL with a hand auger was completed and revealed the typical heterogeneous character of this layer showing a dominance of muddy, humified peat which is alternated with fresher peat and clay. Slug tests were carried out to study the applicability of Darcy's law given that previous studies suggested the non validity for humified peat soils given by a variable hydraulic conductivity K with the hydraulic gradient. For higher humification degrees, the experiments indeed suggested a variable K, but this seems to be the result of the inappropriate use of steady-state formulae for transient experiments in peaty environments. The muddy peat sampled has a rather plastic nature, and the high compressibility of this material leads to transient behavior. However, using transient formulae, the slug tests conducted for different initial hydraulic heads showed that there was hardly any evidence of a variation of the hydraulic conductivity with the hydraulic gradient. Therefore, Darcy's law can be used for peat soils. The heterogeneity of the subsoil and the apparent applicability of Darcy's law were taking into account for the detailed

  3. 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.

  4. 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.

  5. Pulsatile Flow Studies in Atherosclerotic Carotid Bifurcations

    NASA Astrophysics Data System (ADS)

    Bale-Glickman, Jocelyn; Selby, Kathy; Saloner, David; Savas, Omer

    2001-11-01

    Particle image velocimetry and flow visualization techniques are used to study flows in models of atherosclerotic carotid bifurcations. The flow models exactly replicate the interior geometry of plaque excised from patients. The input flows are physiological wave forms derived from Doppler Ultrasound scans done on patients before surgery. The systolic and diastolic Reynolds numbers are 300 and 900. The complex internal geometry of the diseased artery combined with the pulsatile input flow results in exceedingly complex flow patterns. These flow patterns include internal jets, three-dimensional shear layers, stagnation lines, and multiple recirculation and separation regions. The physiological input flows are compared to flows when the wave form is sinusoidal.

  6. Analysis of plant ribosomes with asymmetric flow field-flow fractionation.

    PubMed

    Pitkänen, Leena; Tuomainen, Päivi; Eskelin, Katri

    2014-02-01

    Ribosome profiling is a technique used to separate ribosomal subunits, 80S ribosomes (monosomes), and polyribosomes (polysomes) from other RNA-protein complexes. It is traditionally performed in sucrose gradients. In this study, we used asymmetric flow field-flow fractionation (AsFlFFF) to characterize ribosome profiles of Nicotiana benthamiana plants. With the optimized running conditions, we were able to separate free molecules from ribosomal subunits and intact ribosomes. We used various chemical and enzymatic treatments to validate the positions of subunits, monosomes, and polysomes in the AsFlFFF fractograms. We also characterized the protein and RNA content of AsFlFFF fractions by gel electrophoresis and western blotting. The reverse transcription polymerase chain reaction (RT-PCR) analysis showed that ribosomes remained bound to messenger RNAs (mRNAs) during the analysis. Therefore, we conclude that AsFlFFF can be used for ribosome profiling to study the mRNAs that are being translated. It can also be used to study the protein composition of ribosomes that are active in translation at that particular moment.

  7. Numerical simulations on the flow fields of dynamic axial compression columns in chromatography processes

    NASA Astrophysics Data System (ADS)

    Chien Liang, Ru; Che Liu, Cheng; Tsai Liang, Ming; Chen, Jiann Lin

    2017-02-01

    Dynamic axial compression (DAC) columns are key elements in Simulated Moving Bed, which is a chromatography process in drug industry and chemical engineering. In this study, we apply the computational fluid dynamics (CFD) technique to analyze the flow fields in the DAC column and propose rules for distributor design based on mass conservation in fluid dynamics. Computer aided design (CAD) is used in constructing the numerical 3D modelling for the mesh system. The laminar flow fields with Darcy’s law to model the porous zone are governed by the Navier-Stokes equations and employed to describe the porous flow fields. Experimental works have been conducted as the benchmark for us to choose feasible porous parameters for CFD. Besides, numerical treatments are elaborated to avoid calculation divergence resulting from large source terms. Results show that CFD combined with CAD is a good approach to investigate detailed flow fields in DAC columns and the design for distributors is straightforward.

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

    SciTech Connect

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

    2016-05-15

    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.

  9. 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.

  10. On the flow field about an electrophoretic particle

    NASA Astrophysics Data System (ADS)

    Orsini, Gabriele; Tricoli, Vincenzo

    2012-10-01

    The flow field about an electrophoretic body is theoretically investigated by analytical methods. An effective boundary condition for the electric potential at particle surface is derived. This condition, which generalizes the one obtained by Levich [Physicochemical Hydrodynamics (Prentice-Hall, Englewood Cliffs, 1962), Chap. 9, p. 475], captures the effect of (convective and electromigratory) surface current in the Debye layer and is valid as far as it is legitimate to neglect ion-concentration gradient in the bulk liquid. Conditions for negligible concentration gradients are also presented and discussed. The effect of surface current determines a deviation from Morrison's "classical" theory, which predicts irrotational flow-field for any particle shape with electrophoretic velocity given by the well-known Smoluchowski formula and always directed along the applied electric field. It is shown here that in the presence of the above effect the irrotationality of the flow field is not preserved if the particle surface has non-uniform curvature. However, irrotational flow-field still subsists for a sphere and a cylinder and is analytically determined in terms of a new non-dimensional parameter, referred to as the electrophoretic number. The case of spheroidal objects is also examined in detail. In this case the flow field, though not strictly irrotational, is shown to be nearly approximated by an irrotational flow-field, which is also determined over wide ranges of electrophoretic number and spheroid aspect ratio. The quality of this approximation is expressed as a relative error on the Helmholtz-Smoluchowski condition and numerically evaluated both in longitudinal and transverse configuration. The limiting cases of spheroid degenerating into a needle and a disk are also addressed. In all above cases the respective mobilities deviate from Smoluchowski's formula and depend on the electrophoretic number. An important effect of surface ion-transport in the double layer is

  11. 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.

  12. Large eddy simulations of the flow field of a radially lobed nozzle

    NASA Astrophysics Data System (ADS)

    Amini, Noushin; Sekaran, Aarthi

    2016-11-01

    Lobed nozzles have been a studied over the past couple of decades due to their enhanced mixing capabilities. Despite experimental (Hu et al., 2000) and numerical studies (Cooper et al., 2005), the nature of the jet is yet to be fully understood. This numerical study intends to carry out a thorough analysis of the flow field within and downstream of a six lobed nozzle. The study aims to confirm vortical interaction mechanisms and establish the role of hydrodynamic instabilities in the mixing process. This was inspired by a prior study by the authors wherein the same flow was studied using hot-wire anemometry. Although this helped obtain a qualitative idea of the flow, the 2D data was incapable of visualizing streamwise structures and the flow within the nozzle. Previous numerical simulations have used RANS and to simulate a single lobe of the nozzle; these results show some deficiencies in predicting the potential core length. Previous simulations done by authors indicated that RANS models qualitatively capture the flow structures but do not accurately represent the values of key parameters in the flow field. The present study aims to perform a 3D LES study of the flow field within and downstream of the nozzle to follow the ensuing free jet and thus analyze various mechanisms.

  13. Delaunay Tessellation Field Estimator analysis of the PSCz local Universe: density field and cosmic flow

    NASA Astrophysics Data System (ADS)

    Romano-Díaz, Emilio; van de Weygaert, Rien

    2007-11-01

    We apply the Delaunay Tessellation Field Estimator (DTFE) to reconstruct and analyse the matter distribution and cosmic velocity flows in the local Universe on the basis of the PSCz galaxy survey. The prime objective of this study is the production of optimal resolution 3D maps of the volume-weighted velocity and density fields throughout the nearby universe, the basis for a detailed study of the structure and dynamics of the cosmic web at each level probed by underlying galaxy sample. Fully volume-covering 3D maps of the density and (volume-weighted) velocity fields in the cosmic vicinity, out to a distance of 150h-1Mpc, are presented. Based on the Voronoi and Delaunay tessellation defined by the spatial galaxy sample, DTFE involves the estimate of density values on the basis of the volume of the related Delaunay tetrahedra and the subsequent use of the Delaunay tessellation as natural multidimensional (linear) interpolation grid for the corresponding density and velocity fields throughout the sample volume. The linearized model of the spatial galaxy distribution and the corresponding peculiar velocities of the PSCz galaxy sample, produced by Branchini et al., forms the input sample for the DTFE study. The DTFE maps reproduce the high-density supercluster regions in optimal detail, both their internal structure as well as their elongated or flattened shape. The corresponding velocity flows trace the bulk and shear flows marking the region extending from the Pisces-Perseus supercluster, via the Local Superclusters, towards the Hydra-Centaurus and the Shapley concentration. The most outstanding and unique feature of the DTFE maps is the sharply defined radial outflow regions in and around underdense voids, marking the dynamical importance of voids in the local Universe. The maximum expansion rate of voids defines a sharp cut-off in the DTFE velocity divergence probability distribution function. We found that on the basis of this cut-off DTFE manages to consistently

  14. 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.

  15. Laboratory Observation of Magnetic Field Growth Driven by Shear Flow

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    We have measured in the laboratory profiles of magnetic flux ropes, that include ion flow, magnetic field, current density, and plasma pressure. The electron flows v_e can therefore be inferred, and we use this information to evaluate the Hall J × B term in a two fluid magnetohydrodynamic Ohm’s Law. Mutually attracted and compressed flux ropes break the cylindrical symmetry. This simple and coherent example of shear flow supports magnetic field growth corresponding to non vanishing curl × v_e × B. In the absence of magnetic reconnection we measure and predict a quadrupole out of plane magnetic field δBz, even though this has historically been invoked to be the signature of Hall magnetic reconnection. This provides a natural and general mechanism for large scale sheared flows to acquire smaller scale magnetic features, disordered structure, and possibly turbulence. *Supported by DOE Office of Fusion Energy Sciences under LANS contract DE-AC52-06NA25369, NASA Geospace NNHIOA044I, Basic

  16. Path planning in uncertain flow fields using ensemble method

    NASA Astrophysics Data System (ADS)

    Wang, Tong; Le Maître, Olivier P.; Hoteit, Ibrahim; Knio, Omar M.

    2016-10-01

    An ensemble-based approach is developed to conduct optimal path planning in unsteady ocean currents under uncertainty. We focus our attention on two-dimensional steady and unsteady uncertain flows, and adopt a sampling methodology that is well suited to operational forecasts, where an ensemble of deterministic predictions is used to model and quantify uncertainty. In an operational setting, much about dynamics, topography, and forcing of the ocean environment is uncertain. To address this uncertainty, the flow field is parametrized using a finite number of independent canonical random variables with known densities, and the ensemble is generated by sampling these variables. For each of the resulting realizations of the uncertain current field, we predict the path that minimizes the travel time by solving a boundary value problem (BVP), based on the Pontryagin maximum principle. A family of backward-in-time trajectories starting at the end position is used to generate suitable initial values for the BVP solver. This allows us to examine and analyze the performance of the sampling strategy and to develop insight into extensions dealing with general circulation ocean models. In particular, the ensemble method enables us to perform a statistical analysis of travel times and consequently develop a path planning approach that accounts for these statistics. The proposed methodology is tested for a number of scenarios. We first validate our algorithms by reproducing simple canonical solutions, and then demonstrate our approach in more complex flow fields, including idealized, steady and unsteady double-gyre flows.

  17. Constraints on the Observed Zonal Flows from the Magnetic Fields in Giant Planets

    NASA Astrophysics Data System (ADS)

    Liu, J. J.; Stevenson, D. J.

    2003-05-01

    The zonal winds on the surface of the giant planets are very strong ( 100m/s ) and stable (on a decadal time scale). Observations by the Galileo probe suggest that the zonal flow might be deep seated. However, the magnitude of the zonal flow must be reduced to a small value in the interior of the giant planets because the flow is defined relative to the magnetic field frame of reference (System III) and very large zonal flows can not be tolerated in a high conductivity region. The mechanisms for reducing the magnitude of the zonal flow and the coupling between the zonal flow and magnetic field are unclear. Here we use a coupled Navier-Stokes equation and the magnetic induction equation in steady state to study this. From Navier-Stokes, we find that the zonal flow vth can be expressed in three parts: vth(s,z) = a(s) + Bth2/4μ0ρ Ω s + F(grad(ρ ),Bth)/4μ0ρ Ω s, where a(s) is an arbitrary function of cylindrical radius (s) only, z is the coordinate parallel to the rotation axis, Bth is the toroidal field, μ 0 is the permeability of free space, ρ (s,z) is the density, Ω is the planetary rotation and F is a function of the density gradient (grad(ρ )) and the toroidal magnetic field. The first part is the geostrophic flow consistent with the Taylor-Proudman theorem. The second part is due to the tensile force that arises from the curvature of the toroidal field, and always leads a prograde flow. The third part comes from the density variation and meridional gradient of the toroidal field, and may lead to the prograde flow or the retrograde flow. Whether the flow observed on the surface could be reduced to small values in the interior will depend on the direction of the flow, the density gradient and also the structure of the toroidal magnetic field. It can also be shown that the magnitude of the generated toroidal magnetic field in the interior of the giant planets is very large and around 10 Tesla for consistency with the observed zonal flow on the surface of

  18. Baja California: Field Study

    ERIC Educational Resources Information Center

    Frey, John; Stewart, Jack

    1974-01-01

    Describes how to plan and execute an extended field trip which provides first hand observation of biological and cultural systems. Socialization of the participants was achieved through common planning and goal achievement. (BR)

  19. 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.

  20. [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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. Impact of carrier fluid composition on recovery of nanoparticles and proteins in flow field flow fractionation.

    PubMed

    Schachermeyer, Samantha; Ashby, Jonathan; Kwon, Minjung; Zhong, Wenwan

    2012-11-16

    Flow field flow fractionation (F4) is an invaluable separation tool for large analytes, including nanoparticles and biomolecule complexes. However, sample loss due to analyte-channel membrane interaction limits extensive usage of F4 at present, which could be strongly affected by the carrier fluid composition. This work studied the impacts of carrier fluid (CF) composition on nanoparticle (NP) recovery in F4, with focus on high ionic strength conditions. Successful analysis of NPs in a biomolecules-friendly environment could expand the applicability of F4 to the developing field of nanobiotechnology. Recovery of the unfunctionalized polystyrene NPs of 199, 102, and 45 nm in CFs with various pH (6.2, 7.4 and 8.2), increasing ionic strength (0-0.1M), and different types of co- and counter-ions, were investigated. Additionally, elution of the 85 nm carboxylate NPs and two proteins, human serum albumin (HSA) and immunoglobulin (IgG), at high ionic strengths (0-0.15M) was investigated. Our results suggested that (1) electrostatic repulsion between the negatively charged NPs and the regenerated cellulose membrane was the main force to avoid particle adsorption on the membrane; (2) larger particles experienced higher attractive force and thus were influenced more by variation in CF composition; and (3) buffers containing weak anions or NPs with weak anion as the surface functional groups provided higher tolerance to the increase in ionic strength, owing to more anions being trapped inside the NP porous structure. Protein adsorption onto the membrane was also briefly investigated in salted CFs, using HSA and IgG. We believe our findings could help to identify the basic carrier fluid composition for higher sample recovery in F4 analysis of nanoparticles in a protein-friendly environment, which will be useful for applying F4 in bioassays and in nanotoxicology studies. Copyright © 2012 Elsevier B.V. All rights reserved.

  6. Coupling gravitational and flow field-flow fractionation, and size-distribution analysis of whole yeast cells.

    PubMed

    Sanz, Ramsés; Puignou, Lluís; Galceran, Maria Teresa; Reschiglian, Pierluigi; Zattoni, Andrea; Melucci, Dora

    2004-08-01

    This work continues the project on field-flow fractionation characterisation of whole wine-making yeast cells reported in previous papers. When yeast cells are fractionated by gravitational field-flow fractionation and cell sizing of the collected fractions is achieved by the electrosensing zone technique (Coulter counter), it is shown that yeast cell retention depends on differences between physical indexes of yeast cells other than size. Scanning electron microscopy on collected fractions actually shows co-elution of yeast cells of different size and shape. Otherwise, the observed agreement between the particle size distribution analysis obtained by means of the Coulter counter and by flow field-flow fractionation, which employs a second mobile phase flow as applied field instead of Earth's gravity, indicates that yeast cell density can play a major role in the gravitational field-flow fractionation retention mechanism of yeast cells, in which flow field-flow fractionation retention is independent of particle density. Flow field-flow fractionation is then coupled off-line to gravitational field-flow fractionation for more accurate characterisation of the doubly-fractionated cells. Coupling gravitational and flow field-flow fractionation eventually furnishes more information on the multipolydispersity indexes of yeast cells, in particular on their shape and density polydispersity.

  7. Laser velocimetry in turbulent flow fields - Particle response

    NASA Technical Reports Server (NTRS)

    Bachalo, W. D.; Rudoff, R.; Houser, M. J.

    1987-01-01

    Measurements of the particle response in a decelerating flow and a highly turbulent two-phase flow were obtained. Simultaneous measurements of the particle size and velocity served to quantify the particle response to the prevailing flow field. In the case of a flow incident upon a cylinder, the particle lag for a range of size classes was recorded. Results were also obtained in the flow generated by an atomizer operating on the leeward side of a flat disk bluff body in a coflowing air stream. Measurements of the mean axial, mean radial, and rms velocities and angles of trajectories were obtained for representative particle size classes. The air velocity and turbulence intensity were inferred from the seed particles on the order of one micrometer in diameter. Particles 9 micrometers and larger showed significant differences with respect to the gas phase mean velocity and turbulence intensity even at low velocities. In two-phase flows, reliable measurements of the continuous phase velocity and turbulence parameters requires the simultaneous measurement of particle size as a means for rejecting readings from large particles from the velocity pdf's.

  8. Studying electric fields in dipolarization fronts

    NASA Astrophysics Data System (ADS)

    Balcerak, Ernie

    2014-11-01

    In Earth's magnetotail, sharp increases in the magnetic field known as dipolarization fronts are associated with high-speed plasma flows that connect Earth's ionosphere via electric currents. Some aspects of these dipolarization fronts have puzzled scientists; in particular, the dip in magnetic field that occurs just ahead of the dipolarization front layer is not well understood. Sun et al. analyze observations made using the Cluster satellites to elucidate the details of electric fields associated with dipolarization fronts. The study shows that a type of electric current known as a Hall current dominates in the dipolarization front region and in the region where the magnetic field dips, but this current flows in opposite directions in these two regions.

  9. Flow-field differences and electromagnetic-field properties of air and N2 inductively coupled plasmas

    NASA Astrophysics Data System (ADS)

    Yu, Minghao; Yamada, Kazuhiko; Takahashi, Yusuke; Liu, Kai; Zhao, Tong

    2016-12-01

    A numerical model for simulating air and nitrogen inductively coupled plasmas (ICPs) was developed considering thermochemical nonequilibrium and the third-order electron transport properties. A modified far-field electromagnetic model was introduced and tightly coupled with the flow field equations to describe the Joule heating and inductive discharge phenomena. In total, 11 species and 49 chemical reactions of air, which include 5 species and 8 chemical reactions of nitrogen, were employed to model the chemical reaction process. The internal energy transfers among translational, vibrational, rotational, and electronic energy modes of chemical species were taken into account to study thermal nonequilibrium effects. The low-Reynolds number Abe-Kondoh-Nagano k-ɛ turbulence model was employed to consider the turbulent heat transfer. In this study, the fundamental characteristics of an ICP flow, such as the weak ionization, high temperature but low velocity in the torch, and wide area of the plasma plume, were reproduced by the developed numerical model. The flow field differences between the air and nitrogen ICP flows inside the 10-kW ICP wind tunnel were made clear. The interactions between the electromagnetic and flow fields were also revealed for an inductive discharge.

  10. Flow of a Two-Dimensional Liquid Metal Jet in a Strong Magnetic Field

    NASA Astrophysics Data System (ADS)

    Molokov, S.; Reed, C. B.

    2002-01-01

    A combined effect of surface tension, gravity, inertia and a transverse nonuniform magnetic field on the steady, two-dimensional jet (or curtain) flow is studied with reference to liquid metal divertors of tokamaks and coating flows. Here main fundamental aspects of the flow are presented. More details on the assumptions, analysis and results are given in. Consider a steady flow of a viscous, electrically conducting, incompressible fluid in a jet pouring downward in the x-asterisk-direction (the direction of gravity) from a nozzle.

  11. 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.

  12. 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.

  13. 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.

  14. Reactive transport in stratified flow fields with idealized heterogeneity

    NASA Astrophysics Data System (ADS)

    Carleton, James N.; Montas, Hubert J.

    2009-06-01

    A two-dimensional equation governing the steady state spatial concentration distribution of a reactive constituent within a heterogeneous advective-dispersive flow field is solved analytically. The solution which is developed for the case of a single point source can be generalized to represent analogous situations with any number of separate point sources. A limiting case of special interest has a line source of constant concentration spanning the domain's upstream boundary. The work has relevance for improving understanding of reactive transport within various kinds of advection-dominated natural or engineered environments including rivers and streams, and bioreactors such as treatment wetlands. Simulations are used to examine quantitatively the impact that transverse dispersion (deviations from purely stochastic-convective flow) can have on mean concentration decline in the direction of flow. Results support the contention that transverse mixing serves to enhance the overall rate of reaction in such systems.

  15. 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.

  16. 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

  17. 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.

  18. 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.

  19. 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.

  20. Potential field cellular automata model for pedestrian flow.

    PubMed

    Zhang, Peng; Jian, Xiao-Xia; Wong, S C; Choi, Keechoo

    2012-02-01

    This paper proposes a cellular automata model of pedestrian flow that defines a cost potential field, which takes into account the costs of travel time and discomfort, for a pedestrian to move to an empty neighboring cell. The formulation is based on a reconstruction of the density distribution and the underlying physics, including the rule for resolving conflicts, which is comparable to that in the floor field cellular automaton model. However, we assume that each pedestrian is familiar with the surroundings, thereby minimizing his or her instantaneous cost. This, in turn, helps reduce the randomness in selecting a target cell, which improves the existing cellular automata modelings, together with the computational efficiency. In the presence of two pedestrian groups, which are distinguished by their destinations, the cost distribution for each group is magnified due to the strong interaction between the two groups. As a typical phenomenon, the formation of lanes in the counter flow is reproduced.

  1. 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.

  2. 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.

  3. Earth's field NMR flow meter: preliminary quantitative measurements.

    PubMed

    Fridjonsson, Einar O; Stanwix, Paul L; Johns, Michael L

    2014-08-01

    In this paper we demonstrate the use of Earth's field NMR (EF NMR) combined with a pre-polarising permanent magnet for measuring fast fluid velocities. This time of flight measurement protocol has a considerable history in the literature; here we demonstrate that it is quantitative when employing the Earth's magnetic field for signal detection. NMR signal intensities are measured as a function of flow rate (0-1m/s) and separation distance between the permanent magnet and the EF NMR signal detection. These data are quantitatively described by a flow model, ultimately featuring no free parameters, that accounts for NMR signal modulation due to residence time inside the pre-polarising magnet, between the pre-polarising magnet and the detection RF coil and inside the detection coil respectively. The methodology is subsequently demonstrated with a metallic pipe in the pre-polarising region.

  4. 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.

  5. 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.

  6. Hydrodynamic radius determination with asymmetrical flow field-flow fractionation using decaying cross-flows. Part I. A theoretical approach.

    PubMed

    Håkansson, Andreas; Magnusson, Emma; Bergenståhl, Björn; Nilsson, Lars

    2012-08-31

    Direct determination of hydrodynamic radius from retention time is an advantage of the field-flow fractionation techniques. However, this is not always completely straight forward since non-idealities exist and assumptions have been made in deriving the retention equations. In this study we investigate the effect on accuracy from two factors: (1) level of sophistication of the equations used to determine channel height from a calibration experiment and (2) the influence of secondary relaxation on the accuracy of hydrodynamic radius determination. A new improved technique for estimating the channel height from calibration experiments is suggested. It is concluded that severe systematic error can arise if the most common channel height equations are used and an alternative more rigorous approach is described. For secondary relaxation it is concluded that this effect increases with the cross-flow decay rate. The secondary relaxation effect is quantified for different conditions. This is part one of two. In the second part the determination of hydrodynamic radius are evaluated experimentally under similar conditions.

  7. 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.

  8. 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.

  9. Stochastic field modeling of cavitating flows in OpenFOAM

    NASA Astrophysics Data System (ADS)

    Ranft, Michael; Class, Andreas G.

    2013-11-01

    In analysis is presented for a fluidic diode with low/high pressure drop in forward/reverse flow direction. Accurate description of cavitation is needed due to the dominant effect of vapor bubbles on sound speed. The stochastic field method developed in represents the statistics of growing cavitation bubbles by a set of stochastic fields of vapor fraction which evolve according to the Rayleigh-Plesset equation and local instantaneous LES flow conditions. Cavitation may originate from nucleation sites in the core of turbulent vortices. In this work a RANS model is used instead of LES. Local turbulent pressure fluctuations are recovered based on kinetic energy k of turbulence and its Dissipation ɛ. In the Rayleigh-Plesset equation these fluctuations are represented by a Wiener process which is superimposed on the mean pressure. Usually a set of stochastic fields is introduced for each stochastic variable. Here two independent Wiener processes, both acting on the vapor-fraction stochastic fields, drive the evolution of vapor bubble growth, so that a single set of stochastic fields can be maintained. The proposed methodology is implemented in OpenFOAM and applied to verification cases including the fluidic diode. Funded by ANPS.

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

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.

    1986-01-01

    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 300,000. 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 promoote 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.

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

    NASA Technical Reports Server (NTRS)

    Zaman, K. B. M. Q.

    1986-01-01

    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 300,000. 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 promoote 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.

  12. Laser Velocimetry Measurements of Oscillating Airfoil Dynamic Stall Flow Field

    DTIC Science & Technology

    1991-06-01

    Velocimetry Measurements of Oscillating Airfoil Dynamic Stall Flow Field By M.S.Chandrasekharal Navy-NASA Joint Institute of Aeronautics and Fluid Mechanics ...tunnel of the Fluid Mechanics Laboratory(FML) angle information. The other could be used for the at NASA Ames Research Center (ARC). It is one of...were on throat is always kept choked so that no disturbances a different traverse mechanism , but this was driven as can propagate upstream into the

  13. 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.

  14. 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.

  15. Design and fabrication of novel anode flow-field for commercial size solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Canavar, Murat; Timurkutluk, Bora

    2017-04-01

    In this study, nickel based woven meshes are tested as not only anode current collecting meshes but also anode flow fields instead of the conventional gas channels fabricated by machining. For this purpose, short stacks with different anode flow fields are designed and built by using different number of meshes with various wire diameters and widths of opening. A short stack with classical machined flow channels is also constructed. Performance and impedance measurements of the short stacks with commercial size cells of 81 cm2 active area are performed and compared. The results reveal that it is possible to create solid oxide fuel cell anode flow fields with woven meshes and obtain acceptable power with a proper selection of the mesh number, type and orientation.

  16. Non-Newtonian flow of dilute ferrofluids in a uniform magnetic field.

    PubMed

    Weng, Huei Chu; Chen, Chieh-Li; Chen, Cha'o-Kuang

    2008-11-01

    Nonequilibrium magnetization states predict non-Newtonian ferrofluid properties. It is desirable to understand the corresponding flow fields and characteristics. In this study, we derive a magnetoviscosity expression coming from the effective-field method and describing the shear-thinning non-Newtonian behavior of dilute ferrofluids with finite magnetic anisotropy. A mathematical model is developed of non-Newtonian plane flow with respect to shear and pressure driving mechanisms in the presence of an applied stationary uniform magnetic field oriented in the direction perpendicular to vorticity. The results reveal that the non-Newtonian effect tends to increase the velocity and angular velocity but to reduce the magnetization strength. Moreover, an enhanced flow rate and reduced flow drag may be obtained. The maximum non-Newtonian effect is found at a ratio of the Néel relaxation time to the Brownian relaxation time of the order of 0.1.

  17. 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.

  18. Determining 3D flow fields via multi-camera light field imaging.

    PubMed

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

    2013-03-06

    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.

  19. Particle characterization in centrifugal fields. Comparison between ultracentrifugation and sedimentation field-flow fractionation.

    PubMed

    Li, J M; Caldwell, K D; Mächtle, W

    1990-09-26

    A ten-component mixture of polystyrene latex particles in the 67-1220 nm size range was subjected to analysis by analytical ultracentrifugation (AUC) and sedimentation field-flow fractionation (SdFFF) using programmed and constant fields. The AUC analysis of the mixture yielded diameter values in good agreement with data determined on the separate components; the relative amounts of each component in the mixture were likewise closely reproducing the sample's known composition. Diameters determined by SdFFF, either in a constant- or programmed-field mode, were in good agreement with the AUC for particles smaller than about 500 nm. For the sample's larger components, however, particularly the programmed mode showed diameter values smaller than expected. In addition, field programming resulted in incomplete recoveries of the larger particles, leading to more or less distorted mass distributions for the complex sample. The observed discrepancies, which are thought to result from events at the analytical wall in the FFF channel, suggested a protocol for accurate sizing, as opposed to fingerprinting, of samples with broad size distribution. By tracking sizes and amounts of the different components at different but constant field strengths, and retaining as analytically valid only those data recorded in a retention range from five to about thirty column volumes, it was possible to determine sizes and amounts in good agreement with known parameters for the sample. Unlike the AUC procedure, SdFFF produces fractions of a high degree of uniformity, which lend themselves to a secondary analysis, e.g. by electron microscopy, as shown in the study.

  20. 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.

  1. 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.

  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. Quantitative three-dimensional holographic interferometry for flow field analysis

    NASA Astrophysics Data System (ADS)

    Holden, C. M. E.; Parker, S. C. J.; Bryanston-Cross, P. J.

    Holographic interferometry offers the potential for quantitative, wholefield analysis of three-dimensional compressible flows. The technique is non-intrusive, does not require the introduction of seeding particles, and records the entire flow information within the pulse duration of a Q-switched ruby laser (~30ns). At present, however, holographic interferometry is mainly used qualitatively due to the practical restrictions of data recording, acquisition and processing. To address the potential of holographic flow analysis a prototype multi-channel interferometer has been designed and preliminary wind tunnel results have been obtained. The proposed configuration uses specular illumination which, unlike comparable diffuse systems, does not suffer from fringe localisation and speckle noise. Beam collimation and steering through the flow field is achieved in a single operation by the use of holographic optical elements (HOEs). The resulting design is compact, light efficient, has aberration compensation, and the recorded data are conducive to both tomographic analysis and direct comparison to computational fluid dynamics (CFD) predictions. Holograms have been recorded of simple two-dimensional and axisymmetric compressible flows, to compare the accuracy of holographic density measurements with data from conventional pressure sensors and CFD codes. Data extraction from the holograms, and the elimination of rigid body motion, was achieved using digital Fourier transform fringe analysis. The introduction of phase errors by image processing has been investigated by analysing simulated fringe patterns generated from a combination of experimental amplitude information and computer generated phase data.

  4. Flow field investigation in a bulb turbine diffuser

    NASA Astrophysics Data System (ADS)

    Pereira, M.; Duquesne, P.; Aeschlimann, V.; Deschênes, C.

    2017-04-01

    An important drop in turbine performances has been measured in a bulb turbine model operated at overload. Previous investigations have correlated the performance drop with diffuser losses, and particularly to the flow separation zone at the diffuser wall. The flow has been investigated in the transition part of the diffuser using two LDV measurement sections. The transition part is a diffuser section that transforms from a circular to a rectangular section. The two measurement sections are at the inlet and outlet of the diffuser transition part. The turbine has been operated at three operating points, which are representative of different flow patterns at the diffuser exit at overload. In addition to the average velocity field, the analysis is conducted based on a backflow occurrence function and on the swirl level. Results reveal a counter-rotating zone in the diffuser, which intensifies with the guide vanes opening. The guide vanes opening induces a modification of the flow phenomena: from a central backflow recirculation zone at the lowest flowrate to a backflow zone induced by flow separation at the wall at the highest flowrate.

  5. 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

  6. Autophagic subpopulation sorting by sedimentation field-flow fractionation.

    PubMed

    Naves, Thomas; Battu, Serge; Jauberteau, Marie-Odile; Cardot, Philippe J P; Ratinaud, Marie-Hélène; Verdier, Mireille

    2012-10-16

    The development of hypoxic areas often takes place in solid tumors and leads cells to undergo adaptive signalization like autophagy. This process is responsible for misfolded or aggregated proteins and nonfunctional organelle recycling, allowing cells to maintain their energetic status. However, it could constitute a double-edged pathway leading to both survival and cell death. So, in response to stress such as hypoxia, autophagic and apoptotic cells are often mixed. To specifically study and characterize autophagic cells and the process, we needed to develop a method able to (1) isolate autophagic subpopulation and (2) respect apoptotic and autophagic status. Sedimentation field-flow fractionation (SdFFF) was first used to monitor physical parameter changes due to the hypoxia mimetic CoCl(2) in the p53 mutated SKNBE2(c) human neuroblastoma cell line. Second, we showed that "hyperlayer" elution is able to prepare autophagic enriched populations, fraction (F3), overexpressing autophagic markers (i.e., LC3-II accumulation and punctiform organization of autophagosomes as well as cathepsin B overactivity). Conversely, the first eluted fraction exhibited apoptotic markers (caspase-3 activity and Bax increased expression). For the first time, SdFFF was employed as an analytical tool in order to discriminate apoptotic and autophagic cells, thus providing an enriched autophagic fraction consecutively to a hypoxic stress.

  7. Flow-field development during finger splitting at an exothermic chemical reaction front.

    PubMed

    Sebestíková, L; D'Hernoncourt, J; Hauser, M J B; Müller, S C; De Wit, A

    2007-02-01

    Fingertip splitting may be observed at chemical reaction fronts subject to buoyancy-induced Rayleigh-Taylor fingering, as investigated in ascending fronts of the iodate-arsenous acid reaction in vertical Hele-Shaw cells. We study the properties of the flow-field evolution during a tip-splitting event both experimentally and theoretically. Experimental particle-image velocimetry techniques show that the flow field associated to a finger displays a quadrupole of vortices. The evolution of the flow field and the reorganization of the vortices after a tip-splitting event are followed experimentally in detail. Numerical integration of a model reaction-diffusion-convection system for an exothermic reaction taking into account possible heat losses through the walls of the reactor shows that the nonlinear properties of the flow field are different whether the walls are insulating or conducting. In insulating systems, the flow field inside one finger features only one pair of vortices. A quadrupole of