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Sample records for non-ideal flow patterns

  1. Growth and decay of acceleration waves in non-ideal gas flow with radiative heat transfer

    NASA Astrophysics Data System (ADS)

    Singh, Lal; Singh, Raghwendra; Ram, Subedar

    2012-09-01

    The present paper is concerned with the study of the propagation of acceleration waves along the characteristic path in a non-ideal gas flow with effect of radiative heat transfer. It is shown that a linear solution in the characteristic plane can exhibit non-linear behavior in the physical plane. It is also investigated as to how the radiative heat transfer under the optically thin limit will affect the formation of shock in planer, cylindrical and spherically symmetric flows. We conclude that there exists critical amplitude such that any compressive waves with initial amplitude greater than the critical one terminate into shock waves while an initial amplitude less than the critical one results in the decay of the disturbance. The critical time for shock formation has been computed. In this paper we also compare/contrast the nature of solution in ideal and non ideal gas flows.

  2. Reactive flow modeling of small scale detonation failure experiments for a baseline non-ideal explosive

    NASA Astrophysics Data System (ADS)

    Kittell, David E.; Cummock, Nick R.; Son, Steven F.

    2016-08-01

    Small scale characterization experiments using only 1-5 g of a baseline ammonium nitrate plus fuel oil (ANFO) explosive are discussed and simulated using an ignition and growth reactive flow model. There exists a strong need for the small scale characterization of non-ideal explosives in order to adequately survey the wide parameter space in sample composition, density, and microstructure of these materials. However, it is largely unknown in the scientific community whether any useful or meaningful result may be obtained from detonation failure, and whether a minimum sample size or level of confinement exists for the experiments. In this work, it is shown that the parameters of an ignition and growth rate law may be calibrated using the small scale data, which is obtained from a 35 GHz microwave interferometer. Calibration is feasible when the samples are heavily confined and overdriven; this conclusion is supported with detailed simulation output, including pressure and reaction contours inside the ANFO samples. The resulting shock wave velocity is most likely a combined chemical-mechanical response, and simulations of these experiments require an accurate unreacted equation of state (EOS) in addition to the calibrated reaction rate. Other experiments are proposed to gain further insight into the detonation failure data, as well as to help discriminate between the role of the EOS and reaction rate in predicting the measured outcome.

  3. A reactive flow model with coupled reaction kinetics for detonation and combustion in non-ideal explosives

    SciTech Connect

    Miller, P.J.

    1996-07-01

    A new reactive flow model for highly non-ideal explosives and propellants is presented. These compositions, which contain large amounts of metal, upon explosion have reaction kinetics that are characteristic of both fast detonation and slow metal combustion chemistry. A reaction model for these systems was incorporated into the two-dimensional, finite element, Lagrangian hydrodynamic code, DYNA2D. A description of how to determine the model parameters is given. The use of the model and variations are applied to AP, Al, and nitramine underwater explosive and propellant systems.

  4. Mechanisms for non-ideal flow in low-power arc-heated supersonic nozzles

    NASA Astrophysics Data System (ADS)

    Wu, Cheng-Kang; Pan, Wen-Xia; Meng, Xian; Wang, Hai-Xing

    2015-08-01

    The flow in a low-powered arc gas heater combined with a supersonic nozzle of throat diameter less than 1 mm is quite complicated and difficult to describe in quantitative detail. Experiments on arc-heated supersonic jet thrusters of monatomic gases argon and helium have been carried out and their performance measured. The flow characteristics are analyzed with the help of numerical simulation. Results show that the viscous effect is the most important factor causing the large difference between ideal and real performance. A large outer section of the exit flow is slow-moving. This is especially pronounced in helium, where 70 % of the exit area of the nozzle might be in subsonic flow. Friction forces can be much larger than the net thrust, reaching several times higher in helium, resulting in very low efficiencies. Other factors causing the differences between ideal and real flow include: complex flow in the throat region, electric arc extending to the nozzle expansion section, heat transfer to the inlet gas and from the hot plasma, and environmental pressure in the vacuum chamber. It is recognized that the ordinary concepts of supersonic nozzle flow must be greatly modified when dealing with such complicated situations. The general concepts presented in this paper could be helpful in guiding the design and operation of this equipment.

  5. Advanced development of diagnostics for non-ideal blast flows. Technical report 1 Apr 89-1 Jun 91

    SciTech Connect

    Modarress, D.; Hoeft, T.

    1992-07-01

    Investigations of non-ideal airblast are performed at the Ernst Mach Institute in a shock tube that simulates a radiation-induced thermal layer. Visualization techniques were adequate for overall study of the flow, but did not provide the detailed data for validation of computer codes. Under this contract three tasks were performed to provide needed data. The first task was to develop a software package for analysis of interferogram fringes. This package translates fringes shift due to the presence of helium into densities over the image area. This package was installed at EMI. The second task was to evaluate and test techniques for direct time-varying measurement of gas species concentration. Absorption spectroscopy of NO2 was selected to be used, but had corrosion problems and was abandoned. As a replacement, filtered Rayleigh scattering from Freon gas was identified. The third task was to fabricate and install a multi-location laser Doppler velocimeter system for the shock tube. This unit was installed in the shock tube and preliminary velocity measurements of flow over a rough surface were made.

  6. Tandem pulsed acousto-optics: obtaining the tagged light fraction from modulated non-ideal speckle patterns

    NASA Astrophysics Data System (ADS)

    Resink, S. G.; Steenbergen, W.

    2016-01-01

    Recently we presented novel methods for acousto-optic (AO) imaging of biological tissues, taking (1) the mean square difference of speckle patterns (subtraction method) or (2) the contrast of the summation of speckle patterns (summation method) acquired from nanosecond pulses of coherent light, fired at different ultrasound phases. In this study we relate the two methods both analytically and experimentally. We experimentally show that these two methods are nearly identical provided that the maximum achievable speckle contrast is determined correctly. We show with simulations that after correction the outcome is independent of experimental detection parameters. This makes the AO methods in this study reliable, allowing quantifying speckle observations in terms of the ultrasonically tagged fractions of light. The use of tandem nanosecond pulses in one burst of ultrasound overcomes the challenge of tissue dynamics.

  7. Measuring explosive non-ideality

    SciTech Connect

    Souers, P C

    1999-02-17

    The sonic reaction zone length may be measured by four methods: (1) size effect, (2) detonation front curvature, (3) crystal interface velocity and (4) in-situ gauges. The amount of data decreases exponentially from (1) to (4) with there being almost no gauge data for prompt detonation at steady state. The ease and clarity of obtaining the reaction zone length increases from (1) to (4). The method of getting the reaction zone length, , is described for the four methods. A measure of non-ideality is proposed: the reaction zone length divided by the cylinder radius. N = /R{sub o}. N = 0 for true ideality. It also decreases with increasing radius as it should. For N < 0.10, an equilibrium EOS like the JWL may be used. For N > 0.10, a time-dependent description is essential. The crystal experiment, which measures the particle velocity of an explosive-transparent material interface, is presently rising in importance. We examine the data from three experiments and apply: (1) an impedance correction that transfers the explosive C-J particle velocity to the corresponding value for the interface, and (2) multiplies the interface time by 3/4 to simulate the explosive speed of sound. The result is a reaction zone length comparable to those obtained by other means. A few explosives have reaction zones so small that the change of slope in the particle velocity is easily seen.

  8. Experimental and Numerical Investigation of Two Dimensional CO2 Adsorption/Desorption in Packed Sorption Beds under Non-Ideal Flows

    NASA Technical Reports Server (NTRS)

    Mohamadinejad, H.; Knox, J. C.; Smith, J. E.; Croomes, Scott (Technical Monitor)

    2001-01-01

    The experimental results of CO2 adsorption and desorption in a packed column indicated that the concentration wave front at the center of the packed column differs from those which are close to the wall of column filled with adsorbent material even though the ratio of column diameter to the particle size is greater than 20. The comparison of the experimental results with one dimensional model of packed column shows that in order to simulate the average breakthrough in a packed column a two dimensional (radial and axial) model of packed column is needed. In this paper the mathematical model of a non-slip flow through a packed column with 2 inches in diameter and 18 inches in length filled with 5A zeolite pellets is presented. The comparison of experimental results of CO2 absorption and desorption for the mixed and central breakthrough of the packed column with numerical results is also presented.

  9. Non-Ideal Behavior in Solvent Extraction

    SciTech Connect

    Peter Zalupski

    2011-09-01

    This report presents a summary of the work performed to meet FCR&D level 3 milestone M31SW050801, 'Complete the year-end report summarizing FY11 experimental and modeling activities.' This work was carried out under the auspices of the Non-Ideality in Solvent Extraction Systems FCR&D work package. The report summarizes our initial considerations of potential influences that non-ideal chemistry may impose on computational prediction of outcomes in solvent extraction systems. The report is packaged into three separate test cases where a robustness of the prediction by SXFIT program is under scrutiny. The computational exercises presented here emphasize the importance of accurate representation of both an aqueous and organic mixtures when modeling liquid-liquid distribution systems. Case No.1 demonstrates that non-ideal behavior of HDEHP in aliphatic diluents, such as n-dodecane, interferes with the computation. Cases No.2 and No.3 focus on the chemical complexity of aqueous electrolyte mixtures. Both exercises stress the need for an improved thermodynamic model of an aqueous environment present in the europium distribution experiments. Our efforts for year 2 of this project will focus on the improvements of aqueous and non-aqueous solution models using fundamental physical properties of mixtures acquired experimentally in our laboratories.

  10. Modeling of non-ideal aluminized explosives

    SciTech Connect

    Fried, L E; Howard, W M; Souers, P C

    1999-06-01

    We have implemented a Wood-Kirkwood kinetic detonation model based on multi-species equations of state and multiple reaction rate laws. Finite rate laws are used for the slowest chemical reactions, while other reactions are given infinite rates and are kept in constant thermodynamic equilibrium. Within the context of WK theory, we study the chemical interaction between Al and HMX detonation products in non-ideal explosives. We develop a kinetic rate law for the combustion of Al in a condensed detonation that depends on the pressure and the detonation product gases. We use a Murnaghan form for the equation of state of the solid and liquid Al and Al{sub 2}O{sub 3}. We find that we can replicate experimental detonation velocities for HMX/Al composites to within a few percent for a wide range of aluminum content. We discuss the uncertainties in our model and the implications of our results on the modeling of other non-ideal explosives.

  11. Non-ideal solution thermodynamics of cytoplasm.

    PubMed

    Ross-Rodriguez, Lisa U; Elliott, Janet A W; McGann, Locksley E

    2012-10-01

    Quantitative description of the non-ideal solution thermodynamics of the cytoplasm of a living mammalian cell is critically necessary in mathematical modeling of cryobiology and desiccation and other fields where the passive osmotic response of a cell plays a role. In the solution thermodynamics osmotic virial equation, the quadratic correction to the linear ideal, dilute solution theory is described by the second osmotic virial coefficient. Herein we report, for the first time, intracellular solution second osmotic virial coefficients for four cell types [TF-1 hematopoietic stem cells, human umbilical vein endothelial cells (HUVEC), porcine hepatocytes, and porcine chondrocytes] and further report second osmotic virial coefficients indistinguishable from zero (for the concentration range studied) for human hepatocytes and mouse oocytes. PMID:23840923

  12. Examples for Non-Ideal Solution Thermodynamics Study

    ERIC Educational Resources Information Center

    David, Carl W.

    2004-01-01

    A mathematical model of a non-ideal solution is presented, where it is shown how and where the non-ideality manifests itself in the standard thermodynamics tableau. Examples related to the non-ideal solution thermodynamics study are also included.

  13. Effect of solution non-ideality on erythrocyte volume regulation.

    PubMed

    Levin, R L; Cravalho, E G; Huggins, C E

    1977-03-01

    A non-ideal, hydrated, non-dilute pseudo-binary salt-protein-water solution model of the erythrocyte intracellular solution is presented to describe the osmotic behavior of human erythrocytes. Existing experimental activity data for salts and proteins in aqueous solutions are used to formulate van Laar type expressions for the solvent and solute activity coefficients. Reasonable estimates can therefore be made of the non-ideality of the erythrocyte intracellular solution over a wide range of osmolalities. Solution non-ideality is shown to affect significantly the degree of solute polarization within the erythrocyte intracellular solution during freezing. However, the non-ideality has very little effect upon the amount of water retained within erythrocytes cooled at sub-zero temperatures. PMID:16250333

  14. Detonation shock dynamics calibration for non-ideal HE: ANFO

    SciTech Connect

    Short, Mark; Salyer, Terry R; Aslam, Tariq D; Kiyanda, Charles B; Morris, John S; Zimmerley, Tony

    2009-01-01

    Linear D{sub n}-{kappa} detonation shock dynamics (DSD) filling forms are obtained for four ammonium nitrate-fuel oil (ANFO) mixtures involving variations in the ammonium nitrate prill properties and ANFO stoichiometries. The detonation of ammonium nitrate-fuel oil (ANFO) mixtures is considered to be highly nonideal involving long reaction zones ({approx} several cms), low detonation energies and large failure diameters ({approx} 10s-100s cms). A number of experimental programs have been undertaken to understand ANFO detonation properties as a function of the AN properties [1]-[7]. Given the highly heterogeneous nature of ANFO mixtures (typical high explosive (HE) grade AN prills are porous with a range of diameters) a predictive reactive flow simulation of ANFO detonation will present significant challenges. At Los Alamos, a simulation capability has been developed for predicting the propagation of detonation in non-ideal HE and the work conducted on surrounding materials via a combination of a detonation shock dynamics (DSD) approach and a modified programmed burn method known as the pseudo-reaction-zone (or PRZ) method that accounts for the long detonation reaction zone. In the following, linear D{sub n}-{kappa} DSD fitting forms are obtained for four ammonium nitrate-fuel oil mixtures involving variation in the ammonium nitrate prill properties and ANFO stoichiometries. A detonation shock dynamics calibration for ANFO consisting of regular porous HE grade AN in a 94/6 wt.% AN to FO mix has been obtained in [7].

  15. NICIL: Non-Ideal magnetohydrodynamics Coefficients and Ionisation Library

    NASA Astrophysics Data System (ADS)

    Wurster, James

    2016-08-01

    NICIL (Non-Ideal magnetohydrodynamics Coefficients and Ionisation Library) calculates the ionization values and the coefficients of the non-ideal magnetohydrodynamics terms of Ohmic resistivity, the Hall effect, and ambipolar diffusion. Written as a standalone Fortran90 module that can be implemented in existing codes, NICIL is fully parameterizable, allowing the user to choose which processes to include and decide the values of the free parameters. The module includes both cosmic ray and thermal ionization; the former includes two ion species and three species of dust grains (positively charged, negatively charged and neutral), and the latter includes five elements which can be doubly ionized.

  16. Detonation Failure in Ideal and Non-Ideal Explosives

    NASA Astrophysics Data System (ADS)

    Haskins, Peter J.; Cook, Malcolm D.

    2007-12-01

    In this paper we revisit and extend the classic treatment of detonation failure developed by Eyring et al. [1]. We recently published a development of this theory [2] in which a pressure dependant rate law was substituted for the Arrhenius temperature dependant law originally considered. Here we show that by assuming a 2-component rate law based upon a temperature dependant ignition phase and a pressure dependant growth phase we are able to rationalise the very different failure characteristics (critical diameter and velocity decrement at failure) of ideal and non-ideal explosives.

  17. Kinetic modeling of non-ideal explosives with CHEETAH

    SciTech Connect

    Fried, L E; Howard, W M; Souers, P C

    1998-08-06

    We report an implementation of the Wood-Kirkwood kinetic detonation model based on multi-species equations of state and multiple reaction rate laws. Finite rate laws are used for the slowest chemical reactions. Other reactions are given infinite rates and are kept in constant thermodynamic equilibrium. We model a wide range of ideal and non-ideal composite energetic materials. We find that we can replicate experimental detonation velocities to within a few per cent, while obtaining good agreement with estimated reaction zone lengths. The detonation velocity as a function of charge radius is also correctly reproduced.

  18. Can non-ideal magnetohydrodynamics solve the magnetic braking catastrophe?

    NASA Astrophysics Data System (ADS)

    Wurster, James; Price, Daniel J.; Bate, Matthew R.

    2016-03-01

    We investigate whether or not the low ionization fractions in molecular cloud cores can solve the `magnetic braking catastrophe', where magnetic fields prevent the formation of circumstellar discs around young stars. We perform three-dimensional smoothed particle non-ideal magnetohydrodynamics (MHD) simulations of the gravitational collapse of one solar mass molecular cloud cores, incorporating the effects of ambipolar diffusion, Ohmic resistivity and the Hall effect alongside a self-consistent calculation of the ionization chemistry assuming 0.1 μm grains. When including only ambipolar diffusion or Ohmic resistivity, discs do not form in the presence of strong magnetic fields, similar to the cases using ideal MHD. With the Hall effect included, disc formation depends on the direction of the magnetic field with respect to the rotation vector of the gas cloud. When the vectors are aligned, strong magnetic braking occurs and no disc is formed. When the vectors are anti-aligned, a disc with radius of 13 au can form even in strong magnetic when all three non-ideal terms are present, and a disc of 38 au can form when only the Hall effect is present; in both cases, a counter-rotating envelope forms around the first hydrostatic core. For weaker, anti-aligned fields, the Hall effect produces massive discs comparable to those produced in the absence of magnetic fields, suggesting that planet formation via gravitational instability may depend on the sign of the magnetic field in the precursor molecular cloud core.

  19. Zonal flow as pattern formation

    NASA Astrophysics Data System (ADS)

    Parker, Jeffrey B.; Krommes, John A.

    2013-10-01

    Zonal flows are well known to arise spontaneously out of turbulence. We show that for statistically averaged equations of the stochastically forced generalized Hasegawa-Mima model, steady-state zonal flows, and inhomogeneous turbulence fit into the framework of pattern formation. There are many implications. First, the wavelength of the zonal flows is not unique. Indeed, in an idealized, infinite system, any wavelength within a certain continuous band corresponds to a solution. Second, of these wavelengths, only those within a smaller subband are linearly stable. Unstable wavelengths must evolve to reach a stable wavelength; this process manifests as merging jets.

  20. Zonal flow as pattern formation

    SciTech Connect

    Parker, Jeffrey B.; Krommes, John A.

    2013-10-15

    Zonal flows are well known to arise spontaneously out of turbulence. We show that for statistically averaged equations of the stochastically forced generalized Hasegawa-Mima model, steady-state zonal flows, and inhomogeneous turbulence fit into the framework of pattern formation. There are many implications. First, the wavelength of the zonal flows is not unique. Indeed, in an idealized, infinite system, any wavelength within a certain continuous band corresponds to a solution. Second, of these wavelengths, only those within a smaller subband are linearly stable. Unstable wavelengths must evolve to reach a stable wavelength; this process manifests as merging jets.

  1. High Order Filter Methods for the Non-ideal Compressible MHD Equations

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Sjoegreen, Bjoern

    2003-01-01

    The generalization of a class of low-dissipative high order filter finite difference methods for long time wave propagation of shock/turbulence/combustion compressible viscous gas dynamic flows to compressible MHD equations for structured curvilinear grids has been achieved. The new scheme is shown to provide a natural and efficient way for the minimization of the divergence of the magnetic field numerical error. Standard divergence cleaning is not required by the present filter approach. For certain non-ideal MHD test cases, divergence free preservation of the magnetic fields has been achieved.

  2. Detonation properties of the non-ideal explosive PBXW-123

    SciTech Connect

    Wilson, W.H.; Forbes, J.W.; Gustavson, P.K.; Lemar, E.R.; Sutherland, G.T.

    1996-05-01

    Detonation stability and wave curvature in PBXW-123, an aluminized, non-ideal explosive, have been studied. Reaction failed very slowly in unconfined 75 mm, 100 mm, and 126 mm dia. samples. Peak output pressure was still {approximately}28kb after a run distance of 548 mm in a 126 mm dia. charge. Confinement had a significant effect on reaction stability. Detonation velocity was steady at {approximately}5.5mm/{mu}s in 76 mm dia. samples confined in brass tubes. Reaction wavefront curvature was measured in unconfined and confined samples; detonation wavefront radius of curvature was {approximately}140mm at the centerline in the confined charge. {copyright} {ital 1996 American Institute of Physics.}

  3. Non-ideal detonation behaviour of PBX 9502

    NASA Astrophysics Data System (ADS)

    Schoch, Stefan; Nikiforakis, Nikos

    2009-06-01

    Numerical experiments are performed investigating the non-ideal detonation behaviour of PBX 9502 in two setups. In the first setup we consider a three-dimensional rate stick experiment. A booster charge initiates a reaction front leading to a curved detonation wave. The numerical results are compared to theory and experimental evidence. The effects of weak and strong confinement are discussed. The second setup considers the so called ``hockey puck experiment.'' Experimental results show the appearance of a dead zone due to the effect of the geometry. This is captured by the numerical results, which also reveal that the initially spherical detonation is diffracted leading to local detonation failure. The numerical simulations are performed by solving a mathematical model for a three-phase medium based on the Euler equations. The numerical results are obtained using high-resolution shock-capturing methods combined with adaptive mesh refinement.

  4. Surface wave propagation in non-ideal plasmas

    NASA Astrophysics Data System (ADS)

    Pandey, B. P.; Dwivedi, C. B.

    2015-03-01

    The properties of surface waves in a partially ionized, compressible magnetized plasma slab are investigated in this work. The waves are affected by the non-ideal magnetohydrodynamic (MHD) effects which causes finite drift of the magnetic field in the medium. When the magnetic field drift is ignored, the characteristics of the wave propagation in a partially ionized plasma fluid is similar to the fully ionized ideal MHD except now the propagation properties depend on the fractional ionization as well as on the compressibility of the medium. The phase velocity of the sausage and kink waves increases marginally (by a few per cent) due to the compressibility of the medium in both ideal as well as Hall-diffusion-dominated regimes. However, unlike ideal regime, only waves below certain cut-off frequency can propagate in the medium in Hall dominated regime. This cut-off for a thin slab has a weak dependence on the plasma beta whereas for thick slab no such dependence exists. More importantly, since the cut-off is introduced by the Hall diffusion, the fractional ionization of the medium is more important than the plasma compressibility in determining such a cut-off. Therefore, for both compressible as well incompressible medium, the surface modes of shorter wavelength are permitted with increasing ionization in the medium. We discuss the relevance of these results in the context of solar photosphere-chromosphere.

  5. Detonation Failure in Ideal and Non-Ideal Explosives

    NASA Astrophysics Data System (ADS)

    Haskins, P. J.; Cook, M. D.

    2007-06-01

    In this paper we revisit and extend the classic treatment of detonation failure developed by Eyring et. al. [1]. We recently published a development of this theory [2] in which a pressure dependant rate law was substituted for the Arrhenius temperature dependant law originally considered. Here we show that by assuming a 2-component rate law based upon a temperature dependant ignition phase and a pressure dependant growth phase we are able to rationalise the very different failure characteristics (critical diameter and velocity decrement at failure) of ideal and non-ideal explosives. [1] Eyring, H., Powell, R.E., Duffy, G.H., and Parlin, R.B., ``The stability of detonation,'' Chem. Rev. 45, 69-181 (1949). [2] Haskins, P.J., Cook, M.D., and Wood, A.D., ``On the dependence of critical diameter and velocity decrement at failure on the burn law,'' in proceedings of the 33rd International Pyrotechnics Seminar, Fort Collins, Co, USA, 385-391 (2006).

  6. Suicide intervention and non-ideal Kantian theory.

    PubMed

    Cholbi, Michael J

    2002-01-01

    Philosophical discussions of the morality of suicide have tended to focus on its justifiability from an agent's point of view rather than on the justifiability of attempts by others to intervene so as to preserve it. This paper addresses questions of suicide intervention within a broadly Kantian perspective. In such a perspective, a chief task is to determine the motives underlying most suicidal behaviour. Kant wrongly characterizes this motive as one of self-love or the pursuit of happiness. Psychiatric and scientifc evidence suggests that suicide is instead motivated by nihilistic disenchantment with the possibility of happiness which, at its apex, results in the loss of the individual's conception of her practical identity. Because of this, methods of intervention that appeal to agents' happiness, while morally benign, will prove ineffective in forestalling suicide. At the same time, more aggressive methods violate the Kantian concern for autonomy. This apparent dilemma can be resolved by seeing suicide intervention as an action undertaken in non-ideal circumstances, where otherwise unjustified manipulation, coercion, or paternalism are morally permitted. PMID:12747359

  7. On controlling nonlinear dissipation in high order filter methods for ideal and non-ideal MHD

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Sjogreen, B.

    2004-01-01

    The newly developed adaptive numerical dissipation control in spatially high order filter schemes for the compressible Euler and Navier-Stokes equations has been recently extended to the ideal and non-ideal magnetohydrodynamics (MHD) equations. These filter schemes are applicable to complex unsteady MHD high-speed shock/shear/turbulence problems. They also provide a natural and efficient way for the minimization of Div(B) numerical error. The adaptive numerical dissipation mechanism consists of automatic detection of different flow features as distinct sensors to signal the appropriate type and amount of numerical dissipation/filter where needed and leave the rest of the region free from numerical dissipation contamination. The numerical dissipation considered consists of high order linear dissipation for the suppression of high frequency oscillation and the nonlinear dissipative portion of high-resolution shock-capturing methods for discontinuity capturing. The applicable nonlinear dissipative portion of high-resolution shock-capturing methods is very general. The objective of this paper is to investigate the performance of three commonly used types of nonlinear numerical dissipation for both the ideal and non-ideal MHD.

  8. Magnetically stimulated fluid flow patterns

    ScienceCinema

    Martin, Jim; Solis, Kyle

    2014-08-06

    Sandia National Laboratories' Jim Martin and Kyle Solis explain research on the effects of magnetic fields on fluid flows and how they stimulate vigorous flows. Fluid flow is a necessary phenomenon in everything from reactors to cooling engines in cars.

  9. Magnetically stimulated fluid flow patterns

    SciTech Connect

    Martin, Jim; Solis, Kyle

    2014-03-06

    Sandia National Laboratories' Jim Martin and Kyle Solis explain research on the effects of magnetic fields on fluid flows and how they stimulate vigorous flows. Fluid flow is a necessary phenomenon in everything from reactors to cooling engines in cars.

  10. Nonlinear filtering and limiting in high order methods for ideal and non-ideal MHD

    NASA Technical Reports Server (NTRS)

    Yee,H. C.; Sjogreen, B.

    2004-01-01

    The various filtering mechanisms and base scheme options of the newly developed adaptive numerical dissipation control in spatially high order filter schemes for the ideal and non-ideal magnetohydrodynamics (MHD) equations are investigated. These filter schemes are applicable to complex unsteady MHD high-speed shock/shear/turbulence problems. They also provide a natural and efficient way for the minimization of Div(B) numerical error. The type of spatial base scheme to be used in conjunction with our filter idea is very general. For example, spectral, compact and non-compact spatially central finite difference schemes are possible candidates. The adaptive numerical dissipation mechanism consists of automatic detection of different flow features as distinct sensors to signal the appropriate type and amount of numerical dissipation/filter where needed and to leave the rest of the region free from numerical dissipation contamination. The numerical dissipation considered consists of high order linear dissipation for the suppression of high frequency oscillation and the nonlinear dissipative portion of high-resolution shock-capturing methods for discontinuity capturing. The applicable nonlinear dissipative portion of high-resolution shock-capturing methods is also very general. The objective of this paper is to investigate the performance of using compact and non-compact central base schemes in conjunction with three commonly used types of nonlinear numerical dissipation for both the ideal and non-ideal MHD. This extended abstract shows the performance of three nonlinear filters in conjunction with a sixth-order non-compact spatial central base scheme. In the final paper, the high order compact spatial central base scheme will be illustrated and compared with the non-compact base scheme. The reason for the investigation of the high order compact spatial central base scheme over the non-compact base scheme is to evaluate if additional accuracy can be gained in regions of

  11. Adaptive Numerical Dissipation Control in High Order Schemes for Multi-D Non-Ideal MHD

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Sjoegreen, B.

    2005-01-01

    The required type and amount of numerical dissipation/filter to accurately resolve all relevant multiscales of complex MHD unsteady high-speed shock/shear/turbulence/combustion problems are not only physical problem dependent, but also vary from one flow region to another. In addition, proper and efficient control of the divergence of the magnetic field (Div(B)) numerical error for high order shock-capturing methods poses extra requirements for the considered type of CPU intensive computations. The goal is to extend our adaptive numerical dissipation control in high order filter schemes and our new divergence-free methods for ideal MHD to non-ideal MHD that include viscosity and resistivity. The key idea consists of automatic detection of different flow features as distinct sensors to signal the appropriate type and amount of numerical dissipation/filter where needed and leave the rest of the region free from numerical dissipation contamination. These scheme-independent detectors are capable of distinguishing shocks/shears, flame sheets, turbulent fluctuations and spurious high-frequency oscillations. The detection algorithm is based on an artificial compression method (ACM) (for shocks/shears), and redundant multiresolution wavelets (WAV) (for the above types of flow feature). These filters also provide a natural and efficient way for the minimization of Div(B) numerical error.

  12. A Unified Theory of Non-Ideal Gas Lattice Boltzmann Models

    NASA Technical Reports Server (NTRS)

    Luo, Li-Shi

    1998-01-01

    A non-ideal gas lattice Boltzmann model is directly derived, in an a priori fashion, from the Enskog equation for dense gases. The model is rigorously obtained by a systematic procedure to discretize the Enskog equation (in the presence of an external force) in both phase space and time. The lattice Boltzmann model derived here is thermodynamically consistent and is free of the defects which exist in previous lattice Boltzmann models for non-ideal gases. The existing lattice Boltzmann models for non-ideal gases are analyzed and compared with the model derived here.

  13. Set-valued solutions for non-ideal detonation

    NASA Astrophysics Data System (ADS)

    Semenko, R.; Faria, L. M.; Kasimov, A. R.; Ermolaev, B. S.

    2016-03-01

    The existence and structure of a steady-state gaseous detonation propagating in a packed bed of solid inert particles are analyzed in the one-dimensional approximation by taking into consideration frictional and heat losses between the gas and the particles. A new formulation of the governing equations is introduced that eliminates the difficulties with numerical integration across the sonic singularity in the reactive Euler equations. With the new algorithm, we find that when the sonic point disappears from the flow, there exists a one-parameter family of solutions parameterized by either pressure or temperature at the end of the reaction zone. These solutions (termed "set-valued" here) correspond to a continuous spectrum of the eigenvalue problem that determines the detonation velocity as a function of a loss factor.

  14. Using NMR to Determine the Boiling Point Diagram for a Non-Ideal Solution

    ERIC Educational Resources Information Center

    Allen, Fritz S.; And Others

    1975-01-01

    Describes an experiment that enables the student to concentrate on the fundamentals of the non-ideal liquid-vapor equilibrium. Presents typical student data and suggests features which might be added to the experiment. (GS)

  15. Unraveling Flow Patterns through Nonlinear Manifold Learning

    PubMed Central

    Tauro, Flavia; Grimaldi, Salvatore; Porfiri, Maurizio

    2014-01-01

    From climatology to biofluidics, the characterization of complex flows relies on computationally expensive kinematic and kinetic measurements. In addition, such big data are difficult to handle in real time, thereby hampering advancements in the area of flow control and distributed sensing. Here, we propose a novel framework for unsupervised characterization of flow patterns through nonlinear manifold learning. Specifically, we apply the isometric feature mapping (Isomap) to experimental video data of the wake past a circular cylinder from steady to turbulent flows. Without direct velocity measurements, we show that manifold topology is intrinsically related to flow regime and that Isomap global coordinates can unravel salient flow features. PMID:24614890

  16. Adaptive Numerical Dissipative Control in High Order Schemes for Multi-D Non-Ideal MHD

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Sjoegreen, B.

    2004-01-01

    The goal is to extend our adaptive numerical dissipation control in high order filter schemes and our new divergence-free methods for ideal MHD to non-ideal MHD that include viscosity and resistivity. The key idea consists of automatic detection of different flow features as distinct sensors to signal the appropriate type and amount of numerical dissipation/filter where needed and leave the rest of the region free of numerical dissipation contamination. These scheme-independent detectors are capable of distinguishing shocks/shears, flame sheets, turbulent fluctuations and spurious high-frequency oscillations. The detection algorithm is based on an artificial compression method (ACM) (for shocks/shears), and redundant multi-resolution wavelets (WAV) (for the above types of flow feature). These filter approaches also provide a natural and efficient way for the minimization of Div(B) numerical error. The filter scheme consists of spatially sixth order or higher non-dissipative spatial difference operators as the base scheme for the inviscid flux derivatives. If necessary, a small amount of high order linear dissipation is used to remove spurious high frequency oscillations. For example, an eighth-order centered linear dissipation (AD8) might be included in conjunction with a spatially sixth-order base scheme. The inviscid difference operator is applied twice for the viscous flux derivatives. After the completion of a full time step of the base scheme step, the solution is adaptively filtered by the product of a 'flow detector' and the 'nonlinear dissipative portion' of a high-resolution shock-capturing scheme. In addition, the scheme independent wavelet flow detector can be used in conjunction with spatially compact, spectral or spectral element type of base schemes. The ACM and wavelet filter schemes using the dissipative portion of a second-order shock-capturing scheme with sixth-order spatial central base scheme for both the inviscid and viscous MHD flux

  17. Precipitation patterns during channel flow

    NASA Astrophysics Data System (ADS)

    Jamtveit, B.; Hawkins, C.; Benning, L. G.; Meier, D.; Hammer, O.; Angheluta, L.

    2013-12-01

    Mineral precipitation during channelized fluid flow is widespread in a wide variety of geological systems. It is also a common and costly phenomenon in many industrial processes that involve fluid flow in pipelines. It is often referred to as scale formation and encountered in a large number of industries, including paper production, chemical manufacturing, cement operations, food processing, as well as non-renewable (i.e. oil and gas) and renewable (i.e. geothermal) energy production. We have studied the incipient stages of growth of amorphous silica on steel plates emplaced into the central areas of the ca. 1 meter in diameter sized pipelines used at the hydrothermal power plant at Hellisheidi, Iceland (with a capacity of ca 300 MW electricity and 100 MW hot water). Silica precipitation takes place over a period of ca. 2 months at approximately 120°C and a flow rate around 1 m/s. The growth produces asymmetric ca. 1mm high dendritic structures ';leaning' towards the incoming fluid flow. A novel phase-field model combined with the lattice Boltzmann method is introduced to study how the growth morphologies vary under different hydrodynamic conditions, including non-laminar systems with turbulent mixing. The model accurately predicts the observed morphologies and is directly relevant for understanding the more general problem of precipitation influenced by turbulent mixing during flow in channels with rough walls and even for porous flow. Reference: Hawkins, C., Angheluta, L., Hammer, Ø., and Jamtveit, B., Precipitation dendrites in channel flow. Europhysics Letters, 102, 54001

  18. Propagation of a cylindrical shock wave in a mixture of a non-ideal gas and small solid particles under the action of monochromatic radiation

    NASA Astrophysics Data System (ADS)

    Sahu, Praveen Kumar; Nath, Gorakh

    2016-07-01

    Cylindrical shock wave in a dusty gas is discussed under the action of monochromatic radiation into stellar atmosphere with a constant intensity on unit area. The gas is assumed to be grey and opaque and shock to be transparent. The dusty gas is assumed to be a mixture of non-ideal gas and small solid particles. To obtain some essential features of the shock propagation, small solid particles are taken as pseudo-fluid and it is assumed that the equilibrium flow condition is maintained in the flow-field. The effects of variation of the parameters of the non-idealness of the gas, the mass concentration of solid particles in the mixture, the ratio of the density of solid particles to the initial density of the gas and the radiation parameter are investigated. It is shown that an increase in the parameters of the non-idealness of the gas and the radiation parameter have decaying effect on the shock waves; whereas with an increase in the ratio of the density of solid particles to the initial density of the gas the shock strength increases. It is found that an increase in the parameter non-idealness of the gas and the ratio of the density of solid particles to the initial density of the gas have opposite behaviour on fluid velocity, pressure and shock strength. Also, it is shown that an increase in the radiation parameter has effect to decrease the flow variables and the shock strength.

  19. Structure characterisation method for ideal and non-ideal twisted plywoods.

    PubMed

    Aguilar Gutierrez, Oscar F; Rey, Alejandro D

    2014-12-21

    The twisted plywood architecture, known as the Bouligand structure, is a ubiquitous biological and synthetic fibrous composite structure, analogous to that of cholesteric liquid crystals. Twisted plywoods can show ideal or non-ideal structures and are formed via equilibrium or non-equilibrium liquid crystal self-assembly processes. A key to the structure characterisation of plywood films is the specification of the local and global helix vector h(x) and pitch p(x) of the cholesteric order. Previous extensive work demonstrated that oblique cuts of the plywood give rise to arc-patterns that depend both on the unknown incision angle α and the unknown pitch p(x), thus making the precise 3D cholesteric reconstruction ambiguous. In this paper we present an efficient method based on geometric modelling and new visualization software that determines unambiguously the cholesteric pitch under spatially homogeneous and heterogeneous conditions. The method is applied to films that display two-pitch and spatially non-homogenous structures, as sometimes observed under equilibrium and non-equilibrium self-assembly. The method can be extended to other biological materials such as cornea-like, cylindrical, and various cuticle plywoods. PMID:25342518

  20. A Thermodynamically-Consistent Non-Ideal Stochastic Hard-Sphere Fluid

    SciTech Connect

    Donev, A; Alder, B J; Garcia, A L

    2009-08-03

    A grid-free variant of the Direct Simulation Monte Carlo (DSMC) method is proposed, named the Isotropic DSMC (I-DSMC) method, that is suitable for simulating collision-dominated dense fluid flows. The I-DSMC algorithm eliminates all grid artifacts from the traditional DSMC algorithm and is Galilean invariant and microscopically isotropic. The stochastic collision rules in I-DSMC are modified to introduce a non-ideal structure factor that gives consistent compressibility, as first proposed in [Phys. Rev. Lett. 101:075902 (2008)]. The resulting Stochastic Hard Sphere Dynamics (SHSD) fluid is empirically shown to be thermodynamically identical to a deterministic Hamiltonian system of penetrable spheres interacting with a linear core pair potential, well-described by the hypernetted chain (HNC) approximation. We develop a kinetic theory for the SHSD fluid to obtain estimates for the transport coefficients that are in excellent agreement with particle simulations over a wide range of densities and collision rates. The fluctuating hydrodynamic behavior of the SHSD fluid is verified by comparing its dynamic structure factor against theory based on the Landau-Lifshitz Navier-Stokes equations. We also study the Brownian motion of a nano-particle suspended in an SHSD fluid and find a long-time power-law tail in its velocity autocorrelation function consistent with hydrodynamic theory and molecular dynamics calculations.

  1. GenePattern flow cytometry suite

    PubMed Central

    2013-01-01

    Background Traditional flow cytometry data analysis is largely based on interactive and time consuming analysis of series two dimensional representations of up to 20 dimensional data. Recent technological advances have increased the amount of data generated by the technology and outpaced the development of data analysis approaches. While there are advanced tools available, including many R/BioConductor packages, these are only accessible programmatically and therefore out of reach for most experimentalists. GenePattern is a powerful genomic analysis platform with over 200 tools for analysis of gene expression, proteomics, and other data. A web-based interface provides easy access to these tools and allows the creation of automated analysis pipelines enabling reproducible research. Results In order to bring advanced flow cytometry data analysis tools to experimentalists without programmatic skills, we developed the GenePattern Flow Cytometry Suite. It contains 34 open source GenePattern flow cytometry modules covering methods from basic processing of flow cytometry standard (i.e., FCS) files to advanced algorithms for automated identification of cell populations, normalization and quality assessment. Internally, these modules leverage from functionality developed in R/BioConductor. Using the GenePattern web-based interface, they can be connected to build analytical pipelines. Conclusions GenePattern Flow Cytometry Suite brings advanced flow cytometry data analysis capabilities to users with minimal computer skills. Functionality previously available only to skilled bioinformaticians is now easily accessible from a web browser. PMID:23822732

  2. Patterns in simulated turbulent channel flow

    NASA Technical Reports Server (NTRS)

    Stretch, D.

    1990-01-01

    The surface stress is a key diagnostic in wall bounded turbulent flows. Large fluctuations in the stress are believed to be associated with intermittent 'bursting' events during which a large proportion of the turbulence production takes place. If this is so, then a detailed investigation of the structure of the surface stress and its spatial relationship to events within the flow could have wide application in drag reduction and other aspects of flow control. The initial phase of this project, therefore, concentrated on the surface stress field. The first objective is to carry out a statistical analysis of the instantaneous surface stress in a simulated turbulent channel flow, including comparison with multipoint experimental data from a zero pressure gradient turbulent boundary layer. The second objective is to apply a simple pattern recognition procedure to educe the characteristic spatial structure of various flow diagnostics. The final objective is to extend the pattern recognition analysis to examine the whole three dimensional structure of the flow.

  3. Flow Pattern Characterization for a Centrifugal Impeller

    NASA Astrophysics Data System (ADS)

    Benavides, Efrén M.

    2014-08-01

    This paper proposes a model for characterizing the flow pattern of a centrifugal impeller attending to the severity of the reverse flow. The model assumes 1) a definition of an escaping particle as the one that flows in every operational point from the trailing edge towards the leading edge of the impeller blades, and 2) a characterization of flow where an operational point is said to have a theoretical flow pattern if it is not possible to establish a fully-reversed escaping particle on it. Therefore, the first part of the article is focused on defining an escaping particle for a centrifugal compressor. The model locates over the map of a centrifugal impeller the line that splits the map in two regions: the region on the right hand side, where a theoretical flow pattern can exist, and the region on the left, where a theoretical flow pattern cannot exist. Therefore, the locus of this line marks a frontier where the expected performance of the impeller cannot be sustained as high as expected. The second part of the article uses a high-performance commercial centrifugal impeller wheel for contrasting the model. A qualitative characterization of the surge line, conclusions and discussions are presented.

  4. Graft compliance and anastomotic flow patterns.

    PubMed

    Wang, L C; Guo, G X; Tu, R; Hwang, N H

    1990-01-01

    The oscillatory flow patterns at the venous anastomosis of a hemodialysis angioaccess loop graft system were studied using two new compliant vascular prostheses: a longitudinally compliant polytetrafluoroethylene-composite (Baxter Ultraflex PTFE-Plus) graft (BA) and a radially compliant ultrafine polyester fiber (TORAY-UFPF) graft (TR). A non-compliant Gore-Tex polytetrafluoroethylene graft was used as the control. The experimental grafts were 8 mm inside diameter x 25 cm long. Flow experiments were done in a transparent, elastic bench-top flow model; fabrication was based on silicone rubber casts obtained from femoral-to-femoral arteriovenous loop grafts surgically implanted in dogs. The loop graft constructed in the dog model was made to mimic the branchial-to-cephalic angioaccess loop graft commonly used in hemodialysis patients. The flow model was connected to a pulse generator, an adjustable arterial afterload, and a venous afterload. Under identical input conditions, the pressure and flow waveforms were monitored simultaneously at the proximal and distal ends of both the arterial and venous anastomoses. For each graft studied, the anastomotic flow field was visualized using laser illuminated hydrogen bubbles as tracers. At pulse rates of 60 and 90 beats/min, graft flow rates were 2.2 and 2.5 L/min, respectively. Among the grafts studied, measurable differences in pressure and flow wave attenuation and their respective phase lags resulted in characteristically dissimilar flow patterns at the venous anastomosis. Growth of the separation zone at the toe of the anastomosis, and the pattern of retrograde flow in the distal vein are visibly different in all three grafts. PMID:2340213

  5. Effect of fluid-colloid interactions on the mobility of a thermophoretic microswimmer in non-ideal fluids.

    PubMed

    Fedosov, Dmitry A; Sengupta, Ankush; Gompper, Gerhard

    2015-09-01

    Janus colloids propelled by light, e.g., thermophoretic particles, offer promising prospects as artificial microswimmers. However, their swimming behavior and its dependence on fluid properties and fluid-colloid interactions remain poorly understood. Here, we investigate the behavior of a thermophoretic Janus colloid in its own temperature gradient using numerical simulations. The dissipative particle dynamics method with energy conservation is used to investigate the behavior in non-ideal and ideal-gas like fluids for different fluid-colloid interactions, boundary conditions, and temperature-controlling strategies. The fluid-colloid interactions appear to have a strong effect on the colloid behavior, since they directly affect heat exchange between the colloid surface and the fluid. The simulation results show that a reduction of the heat exchange at the fluid-colloid interface leads to an enhancement of colloid's thermophoretic mobility. The colloid behavior is found to be different in non-ideal and ideal fluids, suggesting that fluid compressibility plays a significant role. The flow field around the colloid surface is found to be dominated by a source-dipole, in agreement with the recent theoretical and simulation predictions. Finally, different temperature-control strategies do not appear to have a strong effect on the colloid's swimming velocity. PMID:26223678

  6. Flow Pattern Phenomena in Two-Phase Flow in Microchannels

    NASA Astrophysics Data System (ADS)

    Keska, Jerry K.; Simon, William E.

    2004-02-01

    Space transportation systems require high-performance thermal protection and fluid management techniques for systems ranging from cryogenic fluid management devices to primary structures and propulsion systems exposed to extremely high temperatures, as well as for other space systems such as cooling or environment control for advanced space suits and integrated circuits. Although considerable developmental effort is being expended to bring potentially applicable technologies to a readiness level for practical use, new and innovative methods are still needed. One such method is the concept of Advanced Micro Cooling Modules (AMCMs), which are essentially compact two-phase heat exchangers constructed of microchannels and designed to remove large amounts of heat rapidly from critical systems by incorporating phase transition. The development of AMCMs requires fundamental technological advancement in many areas, including: (1) development of measurement methods/systems for flow-pattern measurement/identification for two-phase mixtures in microchannels; (2) development of a phenomenological model for two-phase flow which includes the quantitative measure of flow patterns; and (3) database development for multiphase heat transfer/fluid dynamics flows in microchannels. This paper focuses on the results of experimental research in the phenomena of two-phase flow in microchannels. The work encompasses both an experimental and an analytical approach to incorporating flow patterns for air-water mixtures flowing in a microchannel, which are necessary tools for the optimal design of AMCMs. Specifically, the following topics are addressed: (1) design and construction of a sensitive test system for two-phase flow in microchannels, one which measures ac and dc components of in-situ physical mixture parameters including spatial concentration using concomitant methods; (2) data acquisition and analysis in the amplitude, time, and frequency domains; and (3) analysis of results

  7. Flow-separation patterns on symmetric forebodies

    NASA Technical Reports Server (NTRS)

    Keener, Earl R.

    1986-01-01

    Flow-visualization studies of ogival, parabolic, and conical forebodies were made in a comprehensive investigation of the various types of flow patterns. Schlieren, vapor-screen, oil-flow, and sublimation flow-visualization tests were conducted over an angle-of-attack range from 0 deg. to 88 deg., over a Reynolds-number range from 0.3X10(6) to 2.0X10(6) (based on base diameter), and over a Mach number range from 0.1 to 2. The principal effects of angle of attack, Reynolds number, and Mach number on the occurrence of vortices, the position of vortex shedding, the principal surface-flow-separation patterns, the magnitude of surface-flow angles, and the extent of laminar and turbulent flow for symmetric, asymmetric, and wake-like flow-separation regimes are presented. It was found that the two-dimensional cylinder analogy was helpful in a qualitative sense in analyzing both the surface-flow patterns and the external flow field. The oil-flow studies showed three types of primary separation patterns at the higher Reynolds numbers owing to the influence of boundary-layer transition. The effect of angle of attack and Reynolds number is to change the axial location of the onset and extent of the primary transitional and turbulent separation regions. Crossflow inflectional-instability vortices were observed on the windward surface at angles of attack from 5 deg. to 55 deg. Their effect is to promote early transition. At low angles of attack, near 10 deg., an unexpected laminar-separation bubble occurs over the forward half of the forebody. At high angles of attack, at which vortex asymmetry occurs, the results support the proposition that the principal cause of vortex asymmetry is the hydrodynamic instability of the inviscid flow field. On the other hand, boundary-layer asymmetries also occur, especially at transitional Reynolds numbers. The position of asymmetric vortex shedding moves forward with increasing angle of attack and with increasing Reynolds number, and moves

  8. Quenching in a non-ideal mechanical system and the Averaging Method

    NASA Astrophysics Data System (ADS)

    Dantas, Márcio José Horta; Balthazar, José Manoel; Felix, Jorge Luiz Palacios

    2012-11-01

    In this paper, for the first time, a quenching result in a non-ideal system is rigorously obtained. In order to do this a new mechanical hypothesis is assumed, it means that the moment of inertia of the rotating parts of the energy source is big. From this is possible to use the Averaging Method.

  9. The J-S model versus a non-ideal MHD theory

    NASA Astrophysics Data System (ADS)

    Franchi, Franca; Lazzari, Barbara; Nibbi, Roberta

    2015-07-01

    A new non-ideal electromagnetic interpretation of the J-S type viscoelastic model for polymeric fluids is given and a generalized resisto-elastic magnetohydrodynamic scenario for collisionless plasmas is proposed. The influence of the new theory on the incompressible transverse Alfvén waves is thoroughly investigated.

  10. The Representation of Highly Non-Ideal Phase Equilibria Using Computer Graphics.

    ERIC Educational Resources Information Center

    Charos, Georgios N.; And Others

    1986-01-01

    Previous work focused on use of computer graphics in teaching thermodynamic phase equilibria for classes I and II. Extends this work to include the considerably more non-ideal phase behavior shown by classes III, IV, and V. Student and instructor response has been overwhelmingly positive about the approach. (JN)

  11. Magnetogasdynamics shock waves in a rotational axisymmetric non-ideal gas with increasing energy and conductive and radiative heat-fluxes

    NASA Astrophysics Data System (ADS)

    Nath, Gorakh

    2016-07-01

    Self-similar solutions are obtained for one-dimensional adiabatic flow behind a magnetogasdynamics cylindrical shock wave propagating in a rotational axisymmetric non ideal gas with increasing energy and conductive and radiative heat fluxes in presence of an azimuthal magnetic field. The fluid velocities and the azimuthal magnetic field in the ambient medium are assume to be varying and obeying power laws. In order to find the similarity solutions the angular velocity of the ambient medium is taken to be decreasing as the distance from the axis increases. The heat conduction is expressed in terms of Fourier's law and the radiation is considered to be the diffusion type for an optically thick grey gas model. The thermal conductivity and the absorption coefficient are assumed to vary with temperature and density. The effects of the presence of radiation and conduction, the non-idealness of the gas and the magnetic field on the shock propagation and the flow behind the shock are investigated.

  12. Evolutionary behavior of weak shocks in a non-ideal gas

    NASA Astrophysics Data System (ADS)

    Arora, Rajan; Siddiqui, Mohd Junaid

    2013-03-01

    Except some empirical methods, which have been developed in the past, no analytical method exists to describe the evolutionary behavior of a shock wave without limiting its strength. In this paper, we have derived a system of transport equations for the shock strength and the induced continuity. We generate a completely intrinsic description of plane, cylindrical, and spherical shock waves of weak strength, propagating into a non-ideal gas. It is shown that for a weak shock, the disturbance evolves like an acceleration wave at the leading order. For a weak shock, we may assume that [InlineEquation not available: see fulltext.]. We have considered a case when the effect of the first order-induced discontinuity or the disturbances that overtook the shock from behind are strong, i.e., [ p x ] = O(1). The evolutionary behavior of the weak shocks in a non-ideal gas is described using the truncation approximation.

  13. 3-D Simulations of Plasma Wakefield Acceleration with Non-Idealized Plasmas and Beams

    SciTech Connect

    Deng, S.; Katsouleas, T.; Lee, S.; Muggli, P.; Mori, W.B.; Hemker, R.; Ren, C.; Huang, C.; Dodd, E.; Blue, B.E.; Clayton, C.E.; Joshi, C.; Wang, S.; Decker, F.J.; Hogan, M.J.; Iverson, R.H.; O'Connell, C.; Raimondi, P.; Walz, D.; /SLAC

    2005-09-27

    3-D Particle-in-cell OSIRIS simulations of the current E-162 Plasma Wakefield Accelerator Experiment are presented in which a number of non-ideal conditions are modeled simultaneously. These include tilts on the beam in both planes, asymmetric beam emittance, beam energy spread and plasma inhomogeneities both longitudinally and transverse to the beam axis. The relative importance of the non-ideal conditions is discussed and a worst case estimate of the effect of these on energy gain is obtained. The simulation output is then propagated through the downstream optics, drift spaces and apertures leading to the experimental diagnostics to provide insight into the differences between actual beam conditions and what is measured. The work represents a milestone in the level of detail of simulation comparisons to plasma experiments.

  14. Shallow flows over surfaces of patterned wettability

    NASA Astrophysics Data System (ADS)

    Grivel, Morgane; Jeon, David; Gharib, Morteza

    2014-11-01

    Our previous work showed that surfaces with spatially patterned wetting properties induce passive displacements of shallow flows. Polycarbonate plates were patterned with hydrophobic and hydrophilic stripes, and a thin, rectangular water jet impinged on the patterned surface. We reported development of intriguing roller structures at the hydrophobic-hydrophilic interfaces. In our present work, we study the effect of varying the stripes' width, spacing, and orientation on the dynamics of these roller structures. Specifically, we are interested in the vortex generation and air entrainment by the rollers. We report quantitative results to this effect. We will also discuss potential uses of this technique for modifying contact line dynamics and bow waves near ships. This work is supported by the Office of Naval Research (Grant # ONR-N00014-11-1-0031) and by NSF-GRFP.

  15. The know unknowns: Detailed simulations and low-order modeling to characterize facility-induced non-idealities in chemical-kinetics experiments

    NASA Astrophysics Data System (ADS)

    Ihme, Matthias

    2013-11-01

    Experimental investigations to study chemical-kinetics processes, reaction-rates or ignition properties are frequently accompanied by facility-induced non-idealities. Examples are turbulence and thermo-viscous boundary layers in rapid compression machines, temperature fluctuations and mixture inhomogeneities in flow-reactors, or shock-bifurcations and pressure drifts in shock-tubes. Although experimental investigations are carefully conducted to mitigate these effects, they are difficult to quantify experimentally. Simulations can assist in identifying these non-idealities and in guiding experimental instrumentation to improve measurement accuracies. This presentation discusses three different modeling approaches to characterize facility-effects in rapid compression machines, flow reactors, and shock-tubes. After providing an overview about these facilities and describing the underlying models, examples are presented to illustrate effects of turbulence, mixture-inhomogeneities, heat-losses, and thermal stratification on the ignition dynamics in these facilities. Diagnostics is developed to assess the sensitivity of the induction chemistry and to quantify reliable operating regimes that are not contaminated by these non-ideal processes.

  16. Exciton-like electromagnetic excitations in non-ideal microcavity supercrystals

    PubMed Central

    Rumyantsev, Vladimir; Fedorov, Stanislav; Gumennyk, Kostyantyn; Sychanova, Marina; Kavokin, Alexey

    2014-01-01

    We study localized photonic excitations in a quasi-two-dimensional non-ideal binary microcavity lattice with use of the virtual crystal approximation. The effect of point defects (vacancies) on the excitation spectrum is investigated by numerical modelling. We obtain the dispersion and the energy gap of the electromagnetic excitations which may be considered as Frenkel exciton-like quasiparticles and analyze the dependence of their density of states on the defect concentrations in a microcavity supercrystal. PMID:25374150

  17. Flow patterns measurements with PIV laser method

    NASA Astrophysics Data System (ADS)

    Podlinski, Janusz; Kocik, Marek; Dors, Miroslaw; Metel, Emilia; Mizeraczyk, Jerzy

    2007-03-01

    In this paper a Particle Image Velocimetry (PIV) measurement technique and it's application for the flow patterns measurements in our experiments is presented. Present PIV system consist of double Nd:YAG laser with pulse energy of 50 mJ, optics for transmission and formation a laser beam, two CCD cameras (Kodak MegaPlus ES-1.0 and FlowSense M2), Dantec processor PIV 1100 and PC computer with FlowManager software. The maximum measured area is 0.5 m2 and flow velocity in the range of 0-300 m/s. So far, the PIV measurements were carried out in hydrodynamic and transonic ducts, corona discharge reactors, electrostatic precipitator models and a microwave torch discharge reactor in The Szewalski Institute of Fluid Flow Machinery, Polish Academy of Sciences in Gdansk. The PIV system was used also for the measurements of the velocity fields round the hull of the ship model in The Ship Design and Research Centre in Gdansk.

  18. Characteristic flow patterns generated by macrozoobenthic structures

    NASA Astrophysics Data System (ADS)

    Friedrichs, M.; Graf, G.

    2009-02-01

    A laboratory flume channel, equipped with an acoustic Doppler flow sensor and a bottom scanning laser, was used for detailed, non-intrusive flow measurements (at 2 cm s - 1 and 10 cm s - 1 ) around solitary biogenic structures, combined with high-resolution mapping of the structure shape and position. The structures were replicates of typical macrozoobenthic species commonly found in the Mecklenburg Bight and with a presumed influence on both, the near-bed current regime and sediment transport dynamics: a worm tube, a snail shell, a mussel, a sand mound, a pit, and a cross-stream track furrow. The flow was considerably altered locally by the different protruding structures (worm tube, snail, mussel and mound). They reduced the horizontal approach velocity by 72% to 79% in the wake zone at about 1-2 cm height, and the flow was deflected around the structures with vertical and lateral velocities of up to 10% and 20% of the free-stream velocity respectively in a region adjacent to the structures. The resulting flow separation (at flow Reynolds number of about 4000 and 20,000 respectively) divided an outer deflection region from an inner region with characteristic vortices and the wake region. All protruding structures showed this general pattern, but also produced individual characteristics. Conversely, the depressions (track and pit) only had a weak influence on the local boundary layer flow, combined with a considerable flow reduction within their cavities (between 29% and 53% of the free-stream velocity). A longitudinal vortex formed, below which a stagnant space was found. The average height affected by the structure-related mass flow rate deficit for the two velocities was 1.6 cm and 1.3 cm respectively (80% of height and 64%) for the protruding structures and 0.6 cm and 0.9 cm (90% and 127% of depth) for the depressions. Marine benthic soft-bottom macrozoobenthos species are expected to benefit from the flow modifications they induce, particularly in terms of

  19. Treatment of non-ideality in the SPACCIM multiphase model - Part 1: Model development

    NASA Astrophysics Data System (ADS)

    Rusumdar, A. J.; Wolke, R.; Tilgner, A.; Herrmann, H.

    2016-01-01

    Ambient tropospheric deliquesced particles generally comprise a complex mixture of electrolytes, organic compounds, and water. Dynamic modeling of physical and chemical processes in this complex matrix is challenging. Thus, up-to-date multiphase chemistry models generally do not consider non-ideal solution effects. Therefore, the present study was aimed at presenting further development of the SPACCIM (Spectral Aerosol Cloud Chemistry Interaction Model) through treatment of solution non-ideality, which has not been considered before. The present paper firstly describes the model developments including (i) the implementation of solution non-ideality in aqueous-phase reaction kinetics in the SPACCIM framework, (ii) the advancements in the coupling scheme of microphysics and multiphase chemistry and (iii) the required adjustments of the numerical schemes, especially in the sparse linear solver and the calculation of the Jacobian. Secondly, results of sensitivity investigations are outlined, aiming at the evaluation of different activity coefficient modules and the examination of the contributions of different intermolecular forces to the overall activity coefficients. Finally, first results obtained with the new model framework are presented. The SPACCIM parcel model was developed and, so far, applied for the description of aerosol-cloud interactions. To advance SPACCIM also for modeling physical and chemical processes in deliquesced particles, the solution non-ideality has to be taken into account by utilizing activities in reaction terms instead of aqueous concentrations. The main goal of the extended approach was to provide appropriate activity coefficients for solved species. Therefore, an activity coefficient module was incorporated into the kinetic model framework of SPACCIM. Based on an intercomparison of different activity coefficient models and the comparison with experimental data, the AIOMFAC approach was implemented and extended by additional interaction

  20. Treatment of non-ideality in the multiphase model SPACCIM - Part 1: Model development

    NASA Astrophysics Data System (ADS)

    Rusumdar, A. J.; Wolke, R.; Tilgner, A.; Herrmann, H.

    2015-06-01

    Ambient tropospheric deliquesced particles generally comprise a complex mixture of electrolytes, organic compounds, and water. Dynamic modeling of physical and chemical processes in this complex matrix is challenging. Thus, up-to-date multiphase chemistry models do generally not consider non-ideal solution effects. Therefore, the present study was aimed at the further development of the SPACCIM model to treat both complex multiphase chemistry and phase transfer processes considering newly non-ideality properties of concentrated aerosol solutions. The present paper describes firstly, the performed model development including (i) the kinetic implementation of the non-ideality in the SPACCIM framework, (ii) the advancements in the coupling scheme of microphysics and multiphase chemistry and (iii) the required adjustments of the numerical schemes, especially in the sparse linear solver and the calculation of the Jacobian. Secondly, results of performed sensitivity investigations are outlined aiming at the evaluation of different activity coefficient modules and the examination of the contributions of different intermolecular forces to the overall activity coefficients. Finally, first results obtained with the new model framework are presented. The main product of the performed model development is the new kinetic model approach SPACCIM-SpactMod, which utilizes activities in reaction terms instead of aqueous concentrations. Based on an intercomparison of different activity coefficient models and the comparison with experimental data, AIOMFAC was selected as base model and extended by additional interaction parameters from literature for mixed organic-inorganic systems. Moreover, the performance and the capability of the applied activity coefficient module were evaluated by means of water activity measurements, literature data and results of other thermodynamic equilibrium models. Comprehensive comparison studies showed that the SpactMod (SPACCIM activity coefficient

  1. Numerical modelling of underwater detonation of non-ideal condensed-phase explosives

    NASA Astrophysics Data System (ADS)

    Schoch, Stefan; Nikiforakis, Nikolaos

    2015-01-01

    The interest in underwater detonation tests originated from the military, since the expansion and subsequent collapse of the explosive bubble can cause considerable damage to surrounding structures or vessels. In military applications, the explosive is typically represented as a pre-burned material under high pressure, a reasonable assumption due to the short reaction zone lengths, and complete detonation of the unreacted explosive. Hence, numerical simulations of underwater detonation tests have been primarily concerned with the prediction of target loading and the damage incurred rather than the accurate modelling of the underwater detonation process. The mining industry in contrast has adopted the underwater detonation test as a means to experimentally characterise the energy output of their highly non-ideal explosives depending on explosive type and charge configuration. This characterisation requires a good understanding of how the charge shape, pond topography, charge depth, and additional charge confinement affect the energy release, some of which can be successfully quantified with the support of accurate numerical simulations. In this work, we propose a numerical framework which is able to capture the non-ideal explosive behaviour and in addition is capable of capturing both length scales: the reaction zone and the pond domain. The length scale problem is overcome with adaptive mesh refinement, which, along with the explosive model, is validated against experimental data of various TNT underwater detonations. The variety of detonation and bubble behaviour observed in non-ideal detonations is demonstrated in a parameter study over the reactivity of TNT. A representative underwater mining test containing an ammonium-nitrate fuel-oil ratestick charge is carried out to demonstrate that the presented method can be readily applied alongside experimental underwater detonation tests.

  2. Non-ideal Effects in Streaming Bi-Dust Acoustic Instability

    SciTech Connect

    Puerta, J.; Castro, E.; Martin, P.; Arias, H.

    2006-12-04

    Streaming dust acoustic instabilities in the presence of a dust beam in a weakly non-ideal dusty plasma have been studied considering a new form for the state equation with two kind of grains. Fluctuating charging effects are not considered in this work. Homogeneous dust-acoustic waves (DAWS) are studied for a perturbed plasma in a very low frequency regime, where dusty plasmas support new kind of waves and instabilities due to the dust collective dynamics. In this analysis a fluid model is used and electrons and ions are determined by their Boltzmann factors in order to find an adequate dispersion relation, which has several parameters depending of the state equation constants. In this paper we use the state equation structured by Ree and Hoover using Pade approximant for a hard-sphere gas in the form P = nT 1 + nb{sub 0} (1 + a{sub 1}b{sub 0}n + a{sub 2}b{sub 0}{sup 2}n{sup 2}/1 - b{sub 1}b{sub 0}n + b{sub 2}b{sub 0}{sup 2}n{sup 2}) is applied, where b0 is calculated by the second virial term for the hard-core model. This type of equation is more accurate than other expressions and easier to manipulate. Comparisons between the ideal and non ideal cases is performed. Constants a1, a2, b1, b2, are calculated with the Pade method. The onset of the instability and also the growth rates are studied in function of relevant parameters of the system as the radius of the grains and their densities. In our analysis the instability region for non ideal plasma is compared with that of the ideal ones.

  3. Non-Ideal Detonation Properties of Ammonium Nitrate and Activated Carbon Mixtures

    NASA Astrophysics Data System (ADS)

    Miyake, Atsumi; Echigoya, Hiroshi; Kobayashi, Hidefumi; Ogawa, Terushige; Katoh, Katsumi; Kubota, Shiro; Wada, Yuji; Ogata, Yuji

    To obtain a better understanding of detonation properties of ammonium nitrate (AN) and activated carbon (AC) mixtures, steel tube tests with several diameters were carried out for various compositions of powdered AN and AC mixtures and the influence of the charge diameter on the detonation velocity was investigated. The results showed that the detonation velocity increased with the increase of the charge diameter. The experimentally observed values were far below the theoretically predicted values made by the thermodynamic CHEETAH code and they showed so-called non-ideal detonation. The extrapolated detonation velocity of stoichiometric composition to the infinite diameter showed a good agreement with the theoretical value.

  4. Dynamics of the non-ideal autoparametric system with MR damper

    NASA Astrophysics Data System (ADS)

    Sado, Danuta

    2012-11-01

    The nonlinear response of a three degree of freedom autoparametric system with a double pendulum, including the magneto-rheological (MR) damper when the excitation comes from a DC motor which works with limited power supply, has been examined. The non-ideal source of power adds one degree of freedom which makes the system have four degrees of freedom. The influence of damping force in MR damper on the phenomenon of energy transfer has been studied. Near the internal and external resonance region, except periodic vibration also chaotic vibration has been observed.

  5. Quantification of non-ideal explosion violence with a shock tube

    SciTech Connect

    Jackson, Scott I; Hill, Larry G

    2009-01-01

    There is significant interest in quantifying the blast violence associated with various nonideal explosions. Such data is essential to evaluate the damage potential of both explosive cookoff and terrorist explosive scenarios. We present a technique designed to measure the source energy associated with a non-ideal, asymmetrical, and three-dimensional explosion. A tube is used to confine and focus energy from a blast event into a one-dimensional, quasi-planar shock front. During propagation along the length of the tube, the wave is allowed to shocksteepen into a more ideal form. Pressure transducers then measure the shock overpressure as a function of the distance from the source. One-dimensional blast scaling theory allows calculation of the source energy from this data. This small-scale test method addresses cost and noise concerns as well as boosting and symmetry issues associated with large-scale, three-dimensional, blast arena tests. Results from both ideal explosives and non-ideal explosives are discussed.

  6. Performance of active feedforward control systems in non-ideal, synthesized diffuse sound fields.

    PubMed

    Misol, Malte; Bloch, Christian; Monner, Hans Peter; Sinapius, Michael

    2014-04-01

    The acoustic performance of passive or active panel structures is usually tested in sound transmission loss facilities. A reverberant sending room, equipped with one or a number of independent sound sources, is used to generate a diffuse sound field excitation which acts as a disturbance source on the structure under investigation. The spatial correlation and coherence of such a synthesized non-ideal diffuse-sound-field excitation, however, might deviate significantly from the ideal case. This has consequences for the operation of an active feedforward control system which heavily relies on the acquisition of coherent disturbance source information. This work, therefore, evaluates the spatial correlation and coherence of ideal and non-ideal diffuse sound fields and considers the implications on the performance of a feedforward control system. The system under consideration is an aircraft-typical double panel system, equipped with an active sidewall panel (lining), which is realized in a transmission loss facility. Experimental results for different numbers of sound sources in the reverberation room are compared to simulation results of a comparable generic double panel system excited by an ideal diffuse sound field. It is shown that the number of statistically independent noise sources acting on the primary structure of the double panel system depends not only on the type of diffuse sound field but also on the sample lengths of the processed signals. The experimental results show that the number of reference sensors required for a defined control performance exhibits an inverse relationship to control filter length. PMID:25234987

  7. A study of grout flow pattern analysis

    SciTech Connect

    Lee, S. Y.; Hyun, S.

    2013-01-10

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

  8. Comparison of non-ideal solution theories for multi-solute solutions in cryobiology and tabulation of required coefficients.

    PubMed

    Zielinski, Michal W; McGann, Locksley E; Nychka, John A; Elliott, Janet A W

    2014-10-01

    Thermodynamic solution theories allow the prediction of chemical potentials in solutions of known composition. In cryobiology, such models are a critical component of many mathematical models that are used to simulate the biophysical processes occurring in cells and tissues during cryopreservation. A number of solution theories, both thermodynamically ideal and non-ideal, have been proposed for use with cryobiological solutions. In this work, we have evaluated two non-ideal solution theories for predicting water chemical potential (i.e. osmolality) in multi-solute solutions relevant to cryobiology: the Elliott et al. form of the multi-solute osmotic virial equation, and the Kleinhans and Mazur freezing point summation model. These two solution theories require fitting to only single-solute data, although they can make predictions in multi-solute solutions. The predictions of these non-ideal solution theories were compared to predictions made using ideal dilute assumptions and to available literature multi-solute experimental osmometric data. A single, consistent set of literature single-solute solution data was used to fit for the required solute-specific coefficients for each of the non-ideal models. Our results indicate that the two non-ideal solution theories have similar overall performance, and both give more accurate predictions than ideal models. These results can be used to select between the non-ideal models for a specific multi-solute solution, and the updated coefficients provided in this work can be used to make the desired predictions. PMID:25158101

  9. Enabling R&D for accurate simulation of non-ideal explosives.

    SciTech Connect

    Aidun, John Bahram; Thompson, Aidan Patrick; Schmitt, Robert Gerard

    2010-09-01

    We implemented two numerical simulation capabilities essential to reliably predicting the effect of non-ideal explosives (NXs). To begin to be able to treat the multiple, competing, multi-step reaction paths and slower kinetics of NXs, Sandia's CTH shock physics code was extended to include the TIGER thermochemical equilibrium solver as an in-line routine. To facilitate efficient exploration of reaction pathways that need to be identified for the CTH simulations, we implemented in Sandia's LAMMPS molecular dynamics code the MSST method, which is a reactive molecular dynamics technique for simulating steady shock wave response. Our preliminary demonstrations of these two capabilities serve several purposes: (i) they demonstrate proof-of-principle for our approach; (ii) they provide illustration of the applicability of the new functionality; and (iii) they begin to characterize the use of the new functionality and identify where improvements will be needed for the ultimate capability to meet national security needs. Next steps are discussed.

  10. Non-ideal assembly of the driving unit affecting shape of load-displacement curves

    NASA Astrophysics Data System (ADS)

    Huang, Hu; Zhao, Hongwei

    2015-03-01

    The results of nanoindentation testing strongly rely on load-displacement curves, but an abnormal load-displacement curve with obvious inflection in the unloading portion was commonly observed in previously published papers and the reason is not clear. In this paper, possible reasons involved in a custom-made indentation instrument, such as sensors, control and assembly issues, are analyzed and discussed step by step. Experimental results indicate that non-ideal assembly of the precision driving unit strongly affects the shape of the load-displacement curve and its affecting mechanism is studied by theoretical analysis and finite element simulations. This paper reveals the reason leading to the abnormal load-displacement curve, which is helpful for debugging of indentation instruments and can enhance comparability of indentation results.

  11. Role of spectral non-idealities in the design of solar thermophotovoltaics.

    PubMed

    Lenert, Andrej; Nam, Youngsuk; Bierman, David M; Wang, Evelyn N

    2014-10-20

    To bridge the gap between theoretically predicted and experimentally demonstrated efficiencies of solar thermophotovoltaics (STPVs), we consider the impact of spectral non-idealities on the efficiency and the optimal design of STPVs over a range of PV bandgaps (0.45-0.80 eV) and optical concentrations (1-3,000x). On the emitter side, we show that suppressing or recycling sub-bandgap radiation is critical. On the absorber side, the relative importance of high solar absorptance versus low thermal emittance depends on the energy balance. Both results are well-described using dimensionless parameters weighting the relative power density above and below the cutoff wavelength. This framework can be used as a guide for materials selection and targeted spectral engineering in STPVs. PMID:25607318

  12. Unsaturated Zone Flow Patterns and Analysis

    SciTech Connect

    C. Ahlers

    2001-10-17

    This Analysis/Model Report (AMR) documents the development of an expected-case model for unsaturated zone (UZ) flow and transport that will be described in terms of the representativeness of models of the natural system. The expected-case model will provide an evaluation of the effectiveness of the natural barriers, assess the impact of conservatism in the Total System Performance Assessment (TSPA), and support the development of further models and analyses for public confidence building. The present models used in ''Total System Performance Assessment for the Site Recommendation'' (Civilian Radioactive Waste Management System Management and Operating Contractor (CRWMS M&O) 2000 [1532461]) underestimate the natural-barrier performance because of conservative assumptions and parameters and do not adequately address uncertainty and alternative models. The development of an expected case model for the UZ natural barrier addresses issues regarding flow-pattern analysis and modeling that had previously been treated conservatively. This is in line with the Repository Safety Strategy (RSS) philosophy of treating conservatively those aspects of the UZ flow and transport system that are not important for achieving regulatory dose (CRWMS M&O 2000 [153246], Section 1.1.1). The development of an expected case model for the UZ also provides defense-in-depth in areas requiring further analysis of uncertainty and alternative models. In general, the value of the conservative case is to provide a more easily defensible TSPA for behavior of UZ flow and transport processes at Yucca Mountain. This AMR has been prepared in accordance with the ''Technical Work Plan for Unsaturated Zone (UZ) Flow and Transport Process Model Report'' (Bechtel SAIC Company (BSC) 2001 [155051], Section 1.3 - Work Package 4301213UMG). The work scope is to examine the data and current models of flow and transport in the Yucca Mountain UZ to identify models and analyses where conservatism may be reduced and

  13. Solute/solvent interaction corrections account for non-ideal freezing point depression.

    PubMed

    Zimmerman, R J; Chao, H; Fullerton, G D; Cameron, I L

    1993-02-01

    A new highly accurate curve-fitting technique for looking at freezing-point depression data was proposed by Fullerton et al. (Biochem. Cell Biol., in press). The method involve plotting mass solvent to mass solute ratio (Mw/M(s)) vs. 1/delta T (i.e. the inverse change in freezing point). A measured molecular weight and a solute/solvent interaction parameter (called I value) are inferred from the resultant linear plot. The accuracy of the molecular weight method was first demonstrated with the monomers of ethylene glycol, glycerol, propanol, mannitol, glucose and sucrose to show a mean molecular weight error of 0.02% with root mean square (RMS) error 0.9%. The RMS error (0.9%) is our best estimate of the molecular weight measurement accuracy for the method applied to a monomer. This error is consistent with the experimental precision (approximately 1%) which implies no systematic error. Non-ideality is described with a single constant, I. Polyethylene glycol (PEG) polymers of increasing length (vendor designation 200 to 10,000 Da) were analyzed to show monotonically increasing non-ideality (I values of 0.12 to 3.67) with increasing molecular weight. The measured molecular weights agreed with the end-point titration value for the three smallest polymers (where the number of polymeric units was less than or equal to 7). The method underestimates the vendor molecular weights for longer polymers. This disagreement is assigned to segmental motion (internal entropy) of longer, more flexible, PEG molecules. PMID:8482791

  14. Kinetic Modeling of Slow Energy Release in Non-Ideal Carbon Rich Explosives

    SciTech Connect

    Vitello, P; Fried, L; Glaesemann, K; Souers, C

    2006-06-20

    We present here the first self-consistent kinetic based model for long time-scale energy release in detonation waves in the non-ideal explosive LX-17. Non-ideal, insensitive carbon rich explosives, such as those based on TATB, are believed to have significant late-time slow release in energy. One proposed source of this energy is diffusion-limited growth of carbon clusters. In this paper we consider the late-time energy release problem in detonation waves using the thermochemical code CHEETAH linked to a multidimensional ALE hydrodynamics model. The linked CHEETAH-ALE model dimensional treats slowly reacting chemical species using kinetic rate laws, with chemical equilibrium assumed for species coupled via fast time-scale reactions. In the model presented here we include separate rate equations for the transformation of the un-reacted explosive to product gases and for the growth of a small particulate form of condensed graphite to a large particulate form. The small particulate graphite is assumed to be in chemical equilibrium with the gaseous species allowing for coupling between the instantaneous thermodynamic state and the production of graphite clusters. For the explosive burn rate a pressure dependent rate law was used. Low pressure freezing of the gas species mass fractions was also included to account for regions where the kinetic coupling rates become longer than the hydrodynamic time-scales. The model rate parameters were calibrated using cylinder and rate-stick experimental data. Excellent long time agreement and size effect results were achieved.

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

    PubMed Central

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

    2014-01-01

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

  16. A generic model of real-world non-ideal behaviour of FES-induced muscle contractions: simulation tool.

    PubMed

    Lynch, Cheryl L; Graham, Geoff M; Popovic, Milos R

    2011-08-01

    Functional electrical stimulation (FES) applications are frequently evaluated in simulation prior to testing in human subjects. Such simulations are usually based on the typical muscle responses to electrical stimulation, which may result in an overly optimistic assessment of likely real-world performance. We propose a novel method for simulating FES applications that includes non-ideal muscle behaviour during electrical stimulation resulting from muscle fatigue, spasms and tremors. A 'non-idealities' block that can be incorporated into existing FES simulations and provides a realistic estimate of real-world performance is described. An implementation example is included, showing how the non-idealities block can be incorporated into a simulation of electrically stimulated knee extension against gravity for both a proportional-integral-derivative controller and a sliding mode controller. The results presented in this paper illustrate that the real-world performance of a FES system may be vastly different from the performance obtained in simulation using nominal muscle models. We believe that our non-idealities block should be included in future simulations that involve muscle response to FES, as this tool will provide neural engineers with a realistic simulation of the real-world performance of FES systems. This simulation strategy will help engineers and organizations save time and money by preventing premature human testing. The non-idealities block will become available free of charge at www.toronto-fes.ca in late 2011. PMID:21757801

  17. A generic model of real-world non-ideal behaviour of FES-induced muscle contractions: simulation tool

    NASA Astrophysics Data System (ADS)

    Lynch, Cheryl L.; Graham, Geoff M.; Popovic, Milos R.

    2011-08-01

    Functional electrical stimulation (FES) applications are frequently evaluated in simulation prior to testing in human subjects. Such simulations are usually based on the typical muscle responses to electrical stimulation, which may result in an overly optimistic assessment of likely real-world performance. We propose a novel method for simulating FES applications that includes non-ideal muscle behaviour during electrical stimulation resulting from muscle fatigue, spasms and tremors. A 'non-idealities' block that can be incorporated into existing FES simulations and provides a realistic estimate of real-world performance is described. An implementation example is included, showing how the non-idealities block can be incorporated into a simulation of electrically stimulated knee extension against gravity for both a proportional-integral-derivative controller and a sliding mode controller. The results presented in this paper illustrate that the real-world performance of a FES system may be vastly different from the performance obtained in simulation using nominal muscle models. We believe that our non-idealities block should be included in future simulations that involve muscle response to FES, as this tool will provide neural engineers with a realistic simulation of the real-world performance of FES systems. This simulation strategy will help engineers and organizations save time and money by preventing premature human testing. The non-idealities block will become available free of charge at www.toronto-fes.ca in late 2011.

  18. A non-ideal portal frame energy harvester controlled using a pendulum

    NASA Astrophysics Data System (ADS)

    Iliuk, I.; Balthazar, J. M.; Tusset, A. M.; Piqueira, J. R. C.; Rodrigues de Pontes, B.; Felix, J. L. P.; Bueno, Á. M.

    2013-09-01

    A model of energy harvester based on a simple portal frame structure is presented. The system is considered to be non-ideal system (NIS) due to interaction with the energy source, a DC motor with limited power supply and the system structure. The nonlinearities present in the piezoelectric material are considered in the piezoelectric coupling mathematical model. The system is a bi-stable Duffing oscillator presenting a chaotic behavior. Analyzing the average power variation, and bifurcation diagrams, the value of the control variable that optimizes power or average value that stabilizes the chaotic system in the periodic orbit is determined. The control sensitivity is determined to parametric errors in the damping and stiffness parameters of the portal frame. The proposed passive control technique uses a simple pendulum to tuned to the vibration of the structure to improve the energy harvesting. The results show that with the implementation of the control strategy it is possible to eliminate the need for active or semi active control, usually more complex. The control also provides a way to regulate the energy captured to a desired operating frequency.

  19. Non-ideal magnetohydrodynamic simulations of the two-stage fragmentation model for cluster formation

    SciTech Connect

    Bailey, Nicole D.; Basu, Shantanu E-mail: basu@uwo.ca

    2014-01-01

    We model molecular cloud fragmentation with thin-disk, non-ideal magnetohydrodynamic simulations that include ambipolar diffusion and partial ionization that transitions from primarily ultraviolet-dominated to cosmic-ray-dominated regimes. These simulations are used to determine the conditions required for star clusters to form through a two-stage fragmentation scenario. Recent linear analyses have shown that the fragmentation length scales and timescales can undergo a dramatic drop across the column density boundary that separates the ultraviolet- and cosmic-ray-dominated ionization regimes. As found in earlier studies, the absence of an ionization drop and regular perturbations leads to a single-stage fragmentation on pc scales in transcritical clouds, so that the nonlinear evolution yields the same fragment sizes as predicted by linear theory. However, we find that a combination of initial transcritical mass-to-flux ratio, evolution through a column density regime in which the ionization drop takes place, and regular small perturbations to the mass-to-flux ratio is sufficient to cause a second stage of fragmentation during the nonlinear evolution. Cores of size ∼0.1 pc are formed within an initial fragment of ∼pc size. Regular perturbations to the mass-to-flux ratio also accelerate the onset of runaway collapse.

  20. THE SMALL-SCALE DYNAMO AND NON-IDEAL MAGNETOHYDRODYNAMICS IN PRIMORDIAL STAR FORMATION

    SciTech Connect

    Schober, Jennifer; Federrath, Christoph; Glover, Simon; Klessen, Ralf S.; Schleicher, Dominik; Banerjee, Robi E-mail: christoph.federrath@monash.edu E-mail: klessen@uni-heidelberg.de E-mail: banerjee@hs.uni-hamburg.de

    2012-08-01

    We study the amplification of magnetic fields during the formation of primordial halos. The turbulence generated by gravitational infall motions during the formation of the first stars and galaxies can amplify magnetic fields very efficiently and on short timescales up to dynamically significant values. Using the Kazantsev theory, which describes the so-called small-scale dynamo-a magnetohydrodynamical process converting kinetic energy from turbulence into magnetic energy-we can then calculate the growth rate of the small-scale magnetic field. Our calculations are based on a detailed chemical network and we include non-ideal magnetohydrodynamical effects such as ambipolar diffusion and Ohmic dissipation. We follow the evolution of the magnetic field up to larger scales until saturation occurs on the Jeans scale. Assuming a weak magnetic seed field generated by the Biermann battery process, both Burgers and Kolmogorov turbulence lead to saturation within a rather small density range. Such fields are likely to become relevant after the formation of a protostellar disk and, thus, could influence the formation of the first stars and galaxies in the universe.

  1. Nanoscale Fluid Flows in the Vicinity of Patterned Surfaces

    NASA Astrophysics Data System (ADS)

    Cieplak, Marek; Koplik, Joel; Banavar, Jayanth R.

    2006-03-01

    Molecular dynamics simulations of dense and rarefied fluids comprising small chain molecules in chemically patterned nanochannels predict a novel switching from Poiseuille to plug flow along the channel. We also demonstrate behavior akin to the lotus effect for a nanodrop on a chemically patterned substrate. Our results show that one can control and exploit the behavior of fluids at the nanoscale using chemical patterning.

  2. Pattern formation in flowing electrorheological fluids.

    PubMed

    von Pfeil, Karl; Graham, Michael D; Klingenberg, Daniel J; Morris, Jeffrey F

    2002-05-01

    A two-fluid continuum model is developed to describe mass transport in electro- and magnetorheological suspensions. The particle flux is related to the field-induced stresses. Solutions of the resulting mass balance show column formation in the absence of flow, and stripe formation when a suspension is subjected simultaneously to an applied electric field and shear flow. PMID:12005727

  3. The transition of flow patterns through critical stagnation points in two-dimensional groundwater flow

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A flow pattern is characterized by aquifer features and the number, type, and distribution of stagnation points (locations where the discharge is zero). This article identifies a condition for transition of flow patterns in two-dimensional groundwater flow obeying Darcy's law by examining changes in...

  4. Turbulent jet patterns in accelerating flows

    NASA Technical Reports Server (NTRS)

    Lipshitz, A.; Greber, I.

    1981-01-01

    Results of flow visualization experiments, and a semi-empirical model of a single turbulent jet injected perpendicularly to a different density cross flow are presented. The model is based on integral conservation equations, including the pressure terms appropriate to accelerating flow. It uses an entrainment correlation obtained from previous experiments of a jet in a cross stream. The results show trajectories and spreading rates, and are typified by a set of three parameters: momentum ratio, Froude number and density ratio. Agreement between test and calculated results is encouraging, but tend to be poorer with increasing momentum ratio.

  5. Patterns and instability of grannular flow

    SciTech Connect

    Ecke, Robert E; Borzsonyi, Tamas; Mcelwaine, Jim N

    2009-01-01

    Dense granular flows are often observed to become unstable and form inhomogeneous structures in nature or industry. Although recently significant advances have been made in understanding simple flows, instabilities are often not understood in detail. We present experimental and numerical results that show the formation of longitudinal stripes. These arise from instability of the uniform flowing state of granular media on a rough inclined plane. The form of the stripes depends critically on the mean density of the flow with a robust form of stripes at high density that consists of fast sliding plug-like regions (stripes) on top of highly agitated boiling material -- a configuration reminiscent of the Leidenfrost effect when a droplet of liquid lifted by its vapor is hovering above a hot surface.

  6. Non-ideal effects of MOS capacitor in a switched capacitor waveform recorder ASIC

    NASA Astrophysics Data System (ADS)

    Zhang, Hong-Yan; Deng, Zhi; Liu, Yi-Nong

    2016-07-01

    SCAs (Switched Capacitor Arrays) have a wide range of uses, especially in high energy physics, nuclear science and astrophysics experiments. This paper presents a method of using a MOS capacitor as a sampling capacitor to gain larger capacitance with small capacitor area in SCA design. It studies the non-ideal effects of the MOS capacitor and comes up with ways to reduce these adverse effects. A prototype SCA ASIC which uses a MOS capacitor to store the samples has been designed and tested to verify this method. The SCA integrates 32 channels and each has 64 cells and a readout amplifier. The stored voltage is converted to a pair of differential currents (±4 mA max) and multiplexed to the output. All the functionalities have been verified. The power consumption is less than 2 mW/ch. The INL of all the cells in one channel are better than 0.39%. The equivalent input noise of the SCA has been tested to be 2.2 mV with 625 kHz full-scale sine wave as input, sampling at 40 MSPS (Mega-samples per Second) and reading out at 5 MHz. The effective resolution is 8.8 bits considering 1 V dynamic range. The maximum sampling rate reaches up to 50 MSPS and readout rate of 15 MHz to keep noise smaller than 2.5 mV. The test results validate the feasibility of the MOS capacitor. Supported by National Natural Science Foundation of China (11375100), Strategic Pioneer Program on Space Sciences, Chinese Academy of Sciences (XDA04060606-06) and State Key Laboratory of Particle Detection and Electronics

  7. Non-Ideal Properties of Gallium Nitride Based Light-Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Shan, Qifeng

    The spectacular development of gallium nitride (GaN) based light-emitting diodes (LEDs) in recent years foreshadows a new era for lighting. There are still several non-ideal properties of GaN based LEDs that hinder their widespread applications. This dissertation studies these non-ideal properties including the large reverse leakage current, large subthreshold forward leakage current, an undesired parasitic cyan luminescence and high-concentration deep levels in GaInN blue LEDs. This dissertation also studies the thermal properties of GaInN LEDs. Chapter 1 gives a brief introduction of non-ideal properties of GaN based LEDs. The leakage current of GaN based LEDs, defects in epitaxially grown GaN devices, and doping problems of p-type GaN materials are discussed. The transient junction temperature measurement technique for GaN based LEDs is introduced. The leakage current of an LED includes the subthreshold forward leakage current and the reverse leakage current. The leakage current of GaN based LEDs affects the reliability, electrostatic discharge resilience, and sub-threshold power consumption. In Chapter 2, the reverse leakage current of a GaInN LED is analyzed by temperaturedependent current-voltage measurements. At low temperature, the reverse leakage current is attributed to the variable-range-hopping conduction. At high temperature, the reverse leakage current is attributed to a thermally-assisted multi-step tunneling. The thermal activation energies (95 meV ~ 162 meV), extracted from the Arrhenius plot for the reverse current in the high-temperature range, indicate a thermally activated tunneling process. Additional room-temperature capacitance-voltage (C-V) measurements are performed to obtain information on the depletion width and doping concentration of the LED. The average internal electric field is estimated by the C-V measurements. The strong internal electric field enhances the thermal emission of electrons in the

  8. Non-Ideal Properties of Gallium Nitride Based Light-Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Shan, Qifeng

    The spectacular development of gallium nitride (GaN) based light-emitting diodes (LEDs) in recent years foreshadows a new era for lighting. There are still several non-ideal properties of GaN based LEDs that hinder their widespread applications. This dissertation studies these non-ideal properties including the large reverse leakage current, large subthreshold forward leakage current, an undesired parasitic cyan luminescence and high-concentration deep levels in GaInN blue LEDs. This dissertation also studies the thermal properties of GaInN LEDs. Chapter 1 gives a brief introduction of non-ideal properties of GaN based LEDs. The leakage current of GaN based LEDs, defects in epitaxially grown GaN devices, and doping problems of p-type GaN materials are discussed. The transient junction temperature measurement technique for GaN based LEDs is introduced. The leakage current of an LED includes the subthreshold forward leakage current and the reverse leakage current. The leakage current of GaN based LEDs affects the reliability, electrostatic discharge resilience, and sub-threshold power consumption. In Chapter 2, the reverse leakage current of a GaInN LED is analyzed by temperaturedependent current-voltage measurements. At low temperature, the reverse leakage current is attributed to the variable-range-hopping conduction. At high temperature, the reverse leakage current is attributed to a thermally-assisted multi-step tunneling. The thermal activation energies (95 meV ~ 162 meV), extracted from the Arrhenius plot for the reverse current in the high-temperature range, indicate a thermally activated tunneling process. Additional room-temperature capacitance-voltage (C-V) measurements are performed to obtain information on the depletion width and doping concentration of the LED. The average internal electric field is estimated by the C-V measurements. The strong internal electric field enhances the thermal emission of electrons in the

  9. Development of a flow visualization apparatus. [to study convection flow patterns

    NASA Technical Reports Server (NTRS)

    Spradley, L. W.

    1975-01-01

    The use of an optical flow visualization device for studying convection flow patterns was investigated. The investigation considered use of a shadowgraph, schlieren and other means for visualizing the flow. A laboratory model was set up to provide data on the proper optics and photography procedures to best visualize the flow. A preliminary design of a flow visualization system is provided as a result of the study. Recommendations are given for a flight test program utilizing the flow visualization apparatus.

  10. Deriving Process-Driven Collaborative Editing Pattern from Collaborative Learning Flow Patterns

    ERIC Educational Resources Information Center

    Marjanovic, Olivera; Skaf-Molli, Hala; Molli, Pascal; Godart, Claude

    2007-01-01

    Collaborative Learning Flow Patterns (CLFPs) have recently emerged as a new method to formulate best practices in structuring the flow of activities within various collaborative learning scenarios. The term "learning flow" is used to describe coordination and sequencing of learning tasks. This paper adopts the existing concept of CLFP and argues…

  11. Study of flow patterns in fume hood enclosures

    SciTech Connect

    Pathanjali, C.; Rahman, M.M.

    1996-12-31

    A three-dimensional model for flow inside a fume hood enclosure was developed and numerical computations were carried out to explore the flow pattern and possible path of contaminant transport under different operating conditions of the hood. Equations for the conservation of mass and momentum were solved for different flow rate and opening conditions in the hood. The face velocity was maintained constant at its rated value of 0.4 m/s. The flow was assumed to enter through the front window opening (positive x-direction) and leave the cupboard through an opening on the top of the hood (positive z-direction). The flow was assumed to be fully turbulent. The {kappa}-{var_epsilon} model was used for the prediction of turbulence. The flow pattern for different sash openings were studied. The flow patterns around an object located at the bottom of the hood was studied for different locations of the object. In addition, the effect of a person standing in front of the hood on the flow pattern was investigated. It was found that air entering the hood proceeds directly to the back wall, impinges it and turns upward toward the top wall and exits through the outlet. The flow finds its way around any object forming a recirculating region at its trailing surface. With an increase in the sash opening, the velocity becomes higher and the fluid traces the path to the outlet more quickly. The volume occupied by recirculating flow decreases with increase in sash opening. The computed flow patterns will be very useful to design experiments with optimum sash opening providing adequate disposal of contaminants with minimum use of conditioned air from inside the room.

  12. Flow Interference between a Circular (Upstream) and a Square Cylinder: Flow Pattern Identification

    NASA Astrophysics Data System (ADS)

    Mohan, Jayalakshmi; R, Ajith Kumar; Kumar, Nithin S.

    2014-11-01

    In this paper, flow interference between an upstream circular cylinder and a square cylinder of equal size is studied in tandem arrangement. The main objective of this invesigation is to identify the possible flow patterns at different spacing ratios, L/B where L is the centre-to-centre distance between the cylinders and B is the characteristic dimension of the bodies. All the experiments are conducted in a water channel and the test Reynolds number is 2100 (based on B). L/B is varied from 1.0 to 5.0. The flow visualization experiments are videographed and then analyzed frame-by-frame to capture the finer details of the flow patterns. Flow over single square and circular cylinders is analyzed first. Then, flow interference between two circular cylinders is investigated. Subsequently, flow over a circular-square configuration is investigated. No such studies are reported so far. Different flow patterns are observed for the circular-square configuration. Additionally, the time of persistence of each flow pattern have been recorded over a sufficiently long period of time to see the most dominant flow pattern. The schedule of occurrence of flow patterns have also been studied during this investigation. This study is very much relevant in the context of possible interference effects occuring in engineering structures such as buildings, heat exchanger tubes etc.

  13. Flow Interference between a Square (Upstream) and a Circular Cylinder: Flow Pattern Identification

    NASA Astrophysics Data System (ADS)

    Kumar, Nithin S.; R, Ajith Kumar; Mohan, Jayalakshmi

    2014-11-01

    In this paper, flow interference between an upstream square cylinder and a circular cylinder of equal size is studied in tandem arrangement. The main objective of this invesigation is to identify the possible flow patterns at different spacing ratios, L/B where L is the centre-to-centre distance between the cylinders and B is the characteristic dimension of the bodies. All the experiments are conducted in a water channel and the test Reynolds number is 2100 (based on B). L/B is varied from 1.0 to 5.0. The flow visualization experiments are videographed and then analyzed frame-by-frame to capture the finer details of the flow patterns. Flow over single square and circular cylinders is analyzed first. Then, flow interference between two square cylinders is investigated. Subsequently, flow over a square-circular configuration is investigated. No such systematic studies are reported so far. Different flow patterns are observed for the square-circular configuration. Additionally, the time of persistence of each flow pattern have been recorded over a sufficiently long period of time to see the most dominant flow pattern. The schedule of occurrence of flow patterns have also been studied during this investigation. This study bears considerable practical relevance in the context of possible interference effects occurring in engineering structures such as buildings, bridges etc.

  14. MEANS FOR VISUALIZING FLUID FLOW PATTERNS

    DOEpatents

    Lynch, F.E.; Palmer, L.D.; Poppendick, H.F.; Winn, G.M.

    1961-05-16

    An apparatus is given for determining both the absolute and relative velocities of a phosphorescent fluid flowing through a transparent conduit. The apparatus includes a source for exciting a narrow trsnsverse band of the fluid to phosphorescence, detecting means such as a camera located downstream from the exciting source to record the shape of the phosphorescent band as it passes, and a timer to measure the time elapsed between operation of the exciting source and operation of the camera.

  15. Flow Patterns Around a Complex Building

    SciTech Connect

    Calhoun, R; Chan, S; Lee, R; Leone, J, Shinn, J; Stevens, D

    1999-09-24

    The authors compare the results of a computer simulated flow field around building 170 (B170) at Lawrence Livermore National Laboratory (LLNL) with field measurements. In order to aid in the setup of the field experiments, the simulations were performed first. B170 was chosen because of its architectural complexity and because a relatively simple fetch exists upwind (a field lies southwest of the site). Figure 1 shows a computational model of the building which retains the major architectural features of the real building (e.g., courtyard, alcoves, and a multi-level roof). Several important characteristics of the cases presented here are: (1) the flow was assumed neutral and no heat flux was imposed at the ground, representing cloudy or morning conditions, (2) a simple canopy parameterization was used to model the effect of a large row of eucalyptus trees which is located to the northeast of the building, (3) the wind directions studied were 200, 225, 250 degrees measured clockwise from true north (the prevailing winds at LLNL are from the southwest in the summer), (4) the incoming wind profile was modeled as logarithmic with a maximum of about 3 meters per second. In addition, note that the building is rotated counterclockwise by 25 degrees with respect to the east/west axis. For convenience, the flow is modeled in a coordinate system that has been rotated with the building.

  16. Pattern formation induced by a differential Poiseuille flow

    NASA Astrophysics Data System (ADS)

    Stucchi, L.; Vasquez, D. A.

    2014-12-01

    Differential advection, where a reactant is advected while another one is immobilized, leads to instabilities in reaction-advection-diffusion systems. In particular, a homogeneous steady state looses stability for strong enough flows, leading to chemical patterns moving in the direction of the flow. In this paper we study the effects of differential advection due to a two-dimensional Poiseuille flow. We carry out a linear stability analysis on a homogeneous state using an activator-inhibitor reaction. We find that shear dispersion induced by the Poiseuille flow may lead to instabilities at slower flow rates. We find that contrary to the one-dimensional system, the instability depends on which substance is advected. We find a critical average flow speed for instability depending on tube size. Numerical solutions of the nonlinear reaction-advection-diffusion result in patterns of constant shape propagating along the tube.

  17. Flow pattern and heat transfer behavior of boiling two-phase flow in inclined pipes

    NASA Astrophysics Data System (ADS)

    Liu, Dezhang; Ning, Ouyang

    1992-09-01

    Movable Electrical Conducting Probe (MECP), a kind of simple and reliable measuring transducer, used for predicting full-flow-path flow pattern in a boiling vapor/liquid two-phase flow is introduced in this paper. When the test pipe is set at different inclination angles, several kinds of flow patterns, such as bubble, slug, churn, intermittent, and annular flows, may be observed in accordance with the locations of MECP. By means of flow pattern analysis, flow field numerical calculations have been carried out, and heat transfer coefficient correlations along full-flow-path derived. The results show that heat transfer performance of boiling two-phase flow could be significantly augmented as expected in some flow pattern zones. The results of the investigation, measuring techniques and conclusions contained in this paper would be a useful reference in foundational research for prediction of flow pattern and heat transfer behavior in boiling two-phase flow, as well as for turbine vane liquid-cooling design.

  18. Patterns of Flows in an Intermediate Prominence Observed by Hinode

    NASA Astrophysics Data System (ADS)

    Ahn, Kwangsu; Chae, Jongchul; Cao, Wenda; Goode, Philip R.

    2010-09-01

    The investigation of plasma flows in filaments/prominences gives us clues to understanding their magnetic structures. We studied the patterns of flows in an intermediate prominence observed by Hinode/SOT. By examining a time series of Hα images and Ca II H images, we have found horizontal flows in the spine and vertical flows in the barb. Both of these flows have a characteristic speed of 10-20 km s-1. The horizontal flows displayed counterstreaming. Our detailed investigation revealed that most of the moving fragments in fact reversed direction at the end point of the spine near a footpoint close to the associated active region. These returning flows may be one possible explanation of the well-known counterstreaming flows in prominences. In contrast, we have found vertical flows—downward and upward—in the barb. Most of the horizontal flows in the spine seem to switch into vertical flows when they approach the barb, and vice versa. We propose that the net force resulting from a small deviation from magnetohydrostatic equilibrium, where magnetic fields are predominantly horizontal, may drive these patterns of flow. In the prominence studied here, the supposed magnetohydrostatic configuration is characterized by magnetic field lines sagging with angles of 13° and 39° in the spine and the barb, respectively.

  19. Instability patterns in a miscible core annular flow

    NASA Astrophysics Data System (ADS)

    D'Olce, Marguerite; Martin, Jerome; Rakotomalala, Nicole; Salin, Dominique; Talon, Laurent

    2006-11-01

    Laboratoire FAST, batiment 502, campus universitaire, 91405 Orsay Cedex (France). Experiments are performed with two miscible fluids of equal density but different viscosities. The fluids are injected co-currently and concentrically into a cylindrical pipe. The so-obtained base state is an axisymmetric parallel flow, for which the ratio of the flow rates of the two fluids monitors the relative amount (and so the radius) of the fluids. Depending on this relative amount and on the total flow rate of the fluids, unstable axisymmetric patterns such as mushrooms and pearls are observed. We delineate the diagram of occurrence of the two patterns and characterize the instabilities.

  20. Scale invariance of subsurface flow patterns and its limitation

    NASA Astrophysics Data System (ADS)

    Hergarten, S.; Winkler, G.; Birk, S.

    2016-05-01

    Preferential flow patterns in the subsurface are of great importance for the availability and the quality of water resources. However, knowledge of their spatial structure is still behind their importance, so that understanding the nature of preferential flow patterns is a major issue in subsurface hydrology. Comparing the statistics of river catchment sizes and spring discharges, we found that the morphology of preferential subsurface flow patterns is probably scale invariant and similar to that of dendritic river networks. This result is not limited to karstic aquifers where the occurrence of dendritic structures has been known at least qualitatively for a long time. The scale invariance even seems to be independent of the lithology of the aquifer. However, scale invariance of river patterns seems to be only limited by the continental scale, while scale invariance of subsurface flow patterns breaks down at much smaller scales. The upper limit of scale invariance in subsurface flow patterns is highly variable. We found a range from thousands of square kilometers for limestone aquifers down to less than 1 km2 in the weathered zone and debris accumulations of crystalline rocks.

  1. NICIL: A Stand Alone Library to Self-Consistently Calculate Non-Ideal Magnetohydrodynamic Coefficients in Molecular Cloud Cores

    NASA Astrophysics Data System (ADS)

    Wurster, James

    2016-09-01

    In this paper, we introduce Nicil: Non-Ideal magnetohydrodynamics Coefficients and Ionisation Library. Nicil is a stand-alone Fortran90 module that calculates the ionisation values and the coefficients of the non-ideal magnetohydrodynamics terms of Ohmic resistivity, the Hall effect, and ambipolar diffusion. The module is fully parameterised such that the user can decide which processes to include and decide upon the values of the free parameters, making this a versatile and customisable code. The module includes both cosmic ray and thermal ionisation; the former includes two ion species and three species of dust grains (positively charged, negatively charged, and neutral), and the latter includes five elements which can be doubly ionised. We demonstrate tests of the module, and then describe how to implement it into an existing numerical code.

  2. Non ideal behavior of AZO/ZnO/ZnPc/Au hybrid p-n junction diode

    NASA Astrophysics Data System (ADS)

    Singh, Budhi; Ghosh, Subhasis

    2015-06-01

    Temperature dependence current density-voltage characteristic of AZO/ZnO/ZnPc/Au inorganic/organic hybrid p-n junction diode have been used to investigate the non ideal behavior of AZO/ZnO/ZnPc/Au hybrid p-n junction diode. The diode shows high ideality factor of 3.0 at 300 K which increases with decreasing temperature and cannot be explained by the standard Shockley theory of the p-n junction diode.

  3. Flow Patterns During Friction Stir Welding

    NASA Technical Reports Server (NTRS)

    Guerra, M.; Schmidt, C.; McClure, J. C.; Murr, L. E.; Nunes, A. C.; Munafo, Paul M. (Technical Monitor)

    2002-01-01

    Friction Stir Welding is a relatively new technique for welding that uses a cylindrical pin or nib inserted along the weld seam. The nib (usually threaded) and the shoulder in which it is mounted are rapidly rotated and advanced along the seam. Extreme deformation takes place leaving a fine equiaxed structure in the weld region., The flow of metal during Friction Stir Welding is investigated using a faying surface tracer and a nib frozen in place during welding. It is shown that material is transported by two processes. The first is a wiping of material from the advancing front side of the nib onto a zone of material that rotates and advances with the nib. The material undergoes a helical motion within the rotational zone that both rotates and advances and descends in the wash of the threads on the nib and rises on the outer part of the rotational zone. After one or more rotations, this material is sloughed off in its wake of the nib, primarily on the advancing side. The second process is an entrainment of material from the front retreating side of the nib that fills in between the sloughed off pieces from the advancing side.

  4. Flow patterns in free liquid film caused by thermocapillary effect

    NASA Astrophysics Data System (ADS)

    Ueno, Ichiro; Fei, Linhao; Kowata, Yosuke; Kaneko, Toshihiro; Pettit, Donald

    2015-11-01

    The basic flow patterns realized in a thin free liquid film driven by the thermocapillary effect are focused. Spetial attention is paied to the effect of the volume ratio of the liquid film to the hole sustaining the film on the flow patterns. We prepare a thin liquid film of less than 0 . 5 mm in thickness in order to stably realize the film under normal gravity. Liquid has in general negative temperature coefficient of it surface tension; that is, the fluid is driven to the colder to hotter regions by the non-uniform surface-tension distribution. In the case of thin free liquid film, however, it is found that a unique flow pattern is induced. One of the present authors, DRP, carried out a series of experiments under microgravity condition in the International Space Station (ISS) in 2003. He prepared a ring made of metal, and formed a thin film of water inside the ring. Once he added a non-uniform temperature distribution to the film by placing a heated iron at one end of the ring, a net flow toward the heated iron was realized. In order to understand flow patterns, we focus on the flow structures of the thermocapillary convection in a cross section normal to the end walls as well as the surface temperature distributions.

  5. Flow patterns and morphology of a prograding river delta

    NASA Astrophysics Data System (ADS)

    Shaw, John B.; Mohrig, David; Wagner, R. Wayne

    2016-02-01

    The transition of flow between laterally confined channels and the unchannelized delta front controls the morphodynamic evolution of river deltas but has rarely been measured at the field scale. We quantify flow patterns and bathymetry that define the evolution of the subaqueous delta front on the Wax Lake Delta, a rapidly prograding delta in coastal Louisiana. A significant portion of flow (˜59%) departs the channel network over lateral channel margins as opposed to the downstream channel tips. Bathymetric surveys and remotely sensed estimates of flow direction allow spatial changes in flow velocity to be quantified and patterns of erosion and deposition to be estimated. Shallowing along channel margins produces spatial acceleration and erosion. Lateral spreading, deceleration, and deposition occur within three to eight channel widths outside of the channel margins. In interdistributary bays, the shape of each flow path is constrained by "nourishment boundaries" that separate the outflows from neighboring channels. Deposit elevation decreases with a basinward slope of 2.4 × 10-4 with distance from a channel margin along any flow path, regardless of the channel or location that flow departed the network. Bathymetric depressions called "interdistributary troughs" form along nourishment boundaries where flow paths are the longest and deposit elevation is correspondingly low. We conclude that the deposit morphology exerts a strong control on bathymetric evolution and that interaction between neighboring channels and even neighboring deltas can influence delta front morphology.

  6. Optical Imaging of Flow Pattern and Phantom

    NASA Technical Reports Server (NTRS)

    Galland, Pierre A.; Liang, X.; Wang, L.; Ho, P. P.; Alfano, R. R.; Breisacher, K.

    1999-01-01

    Time-resolved optical imaging technique has been used to image the spatial distribution of small droplets and jet sprays in a highly scattering environment. The snake and ballistic components of the transmitted pulse are less scattered, and contain direct information about the sample to facilitate image formation as opposed to the diffusive components which are due to multiple collisions as a light pulse propagates through a scattering medium. In a time-gated imaging scheme, these early-arriving, image-bearing components of the incident pulse are selected by opening a gate for an ultrashort period of time and a shadowgram image is detected. Using a single shot cooled CCD camera system, the formation of water droplets is monitored as a function of time. Picosecond time-gated image of drop in scattering cells, spray droplets as a function of let speed and gas pressure, and model calcification samples consisted of calcium carbonate particles of irregular shapes ranging in size from 0. 1 to 1.5 mm affixed to a microscope slide have been measured. Formation produced by an impinging jet will be further monitored using a CCD with 1 kHz framing illuminated with pulsed light. The desired image resolution of the fuel droplets is on the 20 pm scale using early light through a highly scattering medium. A 10(exp -6)m displacement from a jet spray with a flow speed of 100 m/sec introduced by the ns grating pulse used in the imaging is negligible. Early ballistic/snake light imaging offers nondestructive and noninvasive method to observe the spatial distribution of hidden objects inside a highly scattering environment for space, biomedical, and materials applications. In this paper, the techniques we will present are time-resolved K-F transillumination imaging and time-gated scattered light imaging. With a large dynamic range and high resolution, time-gated early light imaging has the potential for improving rocket/aircraft design by determining jets shape and particle sizes

  7. 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.

  8. Patterns of 3D flow in a rotating cylinder array

    NASA Astrophysics Data System (ADS)

    Craig, Anna; Dabiri, John; Koseff, Jeffrey

    2015-11-01

    Experimental data are presented for large arrays of rotating, finite-height cylinders, which show that the three-dimensional flows are strongly dependent on the geometric and rotational configurations of the array. Two geometric configurations of the cylinders, each with two rotational configurations, were examined for a total of four arrays. 2D PIV was conducted in multiple intersecting horizontal and vertical sheets at a location far downstream of the leading edge of the array in order to build up a picture of the 3D developed flow patterns. It was found that the rotation of the cylinders drives the formation of streamwise and transverse flow patterns between cylinders. These horizontal flow patterns, by conservation of mass, drive vertical flows through the top of the array. As the array of rotating cylinders may provide insight into the flow kinematics of an array of vertical axis wind turbines, this planform flux is of particular interest as it would bring down into the array high kinetic energy fluid from above the array, thus increasing the energy resource available to turbines far downstream of the leading edge of the array.

  9. Effect of the mitral valve on diastolic flow patterns

    NASA Astrophysics Data System (ADS)

    Seo, Jung Hee; Vedula, Vijay; Abraham, Theodore; Lardo, Albert C.; Dawoud, Fady; Luo, Hongchang; Mittal, Rajat

    2014-12-01

    The leaflets of the mitral valve interact with the mitral jet and significantly impact diastolic flow patterns, but the effect of mitral valve morphology and kinematics on diastolic flow and its implications for left ventricular function have not been clearly delineated. In the present study, we employ computational hemodynamic simulations to understand the effect of mitral valve leaflets on diastolic flow. A computational model of the left ventricle is constructed based on a high-resolution contrast computed-tomography scan, and a physiological inspired model of the mitral valve leaflets is synthesized from morphological and echocardiographic data. Simulations are performed with a diode type valve model as well as the physiological mitral valve model in order to delineate the effect of mitral-valve leaflets on the intraventricular flow. The study suggests that a normal physiological mitral valve promotes the formation of a circulatory (or "looped") flow pattern in the ventricle. The mitral valve leaflets also increase the strength of the apical flow, thereby enhancing apical washout and mixing of ventricular blood. The implications of these findings on ventricular function as well as ventricular flow models are discussed.

  10. Effect of the mitral valve on diastolic flow patterns

    SciTech Connect

    Seo, Jung Hee; Vedula, Vijay; Mittal, Rajat; Abraham, Theodore; Dawoud, Fady; Luo, Hongchang; Lardo, Albert C.

    2014-12-15

    The leaflets of the mitral valve interact with the mitral jet and significantly impact diastolic flow patterns, but the effect of mitral valve morphology and kinematics on diastolic flow and its implications for left ventricular function have not been clearly delineated. In the present study, we employ computational hemodynamic simulations to understand the effect of mitral valve leaflets on diastolic flow. A computational model of the left ventricle is constructed based on a high-resolution contrast computed-tomography scan, and a physiological inspired model of the mitral valve leaflets is synthesized from morphological and echocardiographic data. Simulations are performed with a diode type valve model as well as the physiological mitral valve model in order to delineate the effect of mitral-valve leaflets on the intraventricular flow. The study suggests that a normal physiological mitral valve promotes the formation of a circulatory (or “looped”) flow pattern in the ventricle. The mitral valve leaflets also increase the strength of the apical flow, thereby enhancing apical washout and mixing of ventricular blood. The implications of these findings on ventricular function as well as ventricular flow models are discussed.

  11. Urban Infrastructure, Channel-Floodplain Morphology and Flood Flow Patterns

    NASA Astrophysics Data System (ADS)

    Miller, A. J.; Smith, J. A.; Nelson, C. B.

    2006-12-01

    The relationship between the channel and the floodplain in urban settings is heavily influenced by (1) altered watershed hydrologic response and frequency distribution of flows, (2) channel enlargement resulting from altered hydrology under conditions of limited sediment supply, (3) direct modification of channels and floodplains for purposes of erosion mitigation, flood protection, commercial development and creation of public amenities, (4) valley constrictions and flow obstructions associated with bridges, culverts, road embankments and other types of floodplain encroachment causing fragmentation or longitudinal segmentation of the riparian corridor. Field observation of inundation patterns associated with recurring floods in the Baltimore metropolitan area is used in combination with 2-dimensional hydraulic modeling to simulate patterns of floodplain inundation and to explore the relationships between magnitude and shape of the flood hydrograph, morphology of the urban channel-floodplain system, and the frequency and extent of floodplain inundation. Case studies include a July 2004 flood associated with a 300-year 2-hour rainfall in a small (14.2 km2) urban watershed, as well as several other events caused by summer thunderstorms with shorter recurrence intervals that generated an extraordinary flood response. The influence of urban infrastructure on flood inundation and flow patterns is expressed in terms of altered (and hysteretic) stage-discharge relationships, stepped flood profiles, rapid longitudinal attenuation of flood waves, and transient flow reversals at confluences and constrictions. Given the current level of interest in restoration measures these patterns merit consideration in planning future development and mitigation efforts.

  12. Observations on traffic flow patterns and traffic engineering practice

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Gao, Lixin

    2002-07-01

    Border Gateway Protocol allows ASs to apply diverse routing policies for selecting routes and propagating reachability information to other ASs. This enables network operators to configure routing policies so as to control traffic flows between ASs. However, BGP is not designed for the inter-AS traffic engineering. This makes it difficult to implement effective routing policies to address network performance and utilization problems. Network operators usually tweak routing policies to influence the inter-domain traffic among the available links. This can lead to undesirable traffic flow patterns across the Internet and degrade the Internet traffic performance. In this paper, we show several observations on Internet traffic flow patterns and derive routing policies that give rise to the traffic flow patterns. Our results show that an AS can reach as much as 20% of the prefixes via a peer link even though there is a path via a customer link. In addition, an AS can reach as much as 80% of the prefixes via a provider link even though there is a path via a peer link. Second, we analyze the cause of the prevalence of these traffic patterns. Our analysis shows that an AS typically does not receive the potential route from its customers or peers. Third, we find that alternate routes have with lower propagation delay than the chosen routes for some prefixes. This shows that some traffic engineering practices might adversely affect Internet performance.

  13. Anisotropic Peridotite Rheology and Regional Upper Mantle Flow Patterns

    NASA Astrophysics Data System (ADS)

    Blackman, D. K.; Boyce, D.; Dawson, P.; Castelnau, O.

    2014-12-01

    We investigate the rheologic impact of strong lattice preferred orientation (LPO), such as develops due to plate-driven shear, on the pattern of upper mantle flow near plate boundaries. We use finite element models to simulate a regional system of mantle flow, that includes LPO evolution in olivine polycrystal aggregates tracked along flow paths and anisotropic viscosity tensors based on the LPO. Our first, loosely coupled approach begins with a flow field based on a scalar viscosity. The results are postprocessed to compute LPO by integration along streamlines, and an anisotropic viscosity tensor field is derived from LPO. A new flow field is then computed based on the viscosity tensor field. For this case, the predicted flow field differed in a modest but geologically relevant way from the isotropic case. In preparation for incorporating the LPO and effective viscosity calculation directly into the flow code, we have been testing this step separately to assess the sensitivity of the computed tensor to specified deformation parameters. New work explores a power law stress:strain rate relation for the LPO development, upon which the aggregate's effective viscosity tensor depends. The pattern and amplitude of predicted deviation from isotropic viscosity are stronger than for the previously assumed linear stress:strain rate case, as expected. Initial runs that employ the power law viscosity tensor in updated flow calculations are underway at the time of this writing. In addition to the stress exponent for LPO and the resulting viscosity tensor, flow model parameters that notably impact the predictions include the specified stiffening as asthenosphere cools to lithospheric temperatures and mesh resolution within the axial and the base of lithosphere regions. We will present results for subaxial oceanic spreading center flow and report the outcomes of model parameter testing.

  14. Mapping algorithm for freeform construction using non-ideal light sources

    NASA Astrophysics Data System (ADS)

    Li, Chen; Michaelis, D.; Schreiber, P.; Dick, L.; Bräuer, A.

    2015-09-01

    Using conventional mapping algorithms for the construction of illumination freeform optics' arbitrary target pattern can be obtained for idealized sources, e.g. collimated light or point sources. Each freeform surface element generates an image point at the target and the light intensity of an image point is corresponding to the area of the freeform surface element who generates the image point. For sources with a pronounced extension and ray divergence, e.g. an LED with a small source-freeform-distance, the image points are blurred and the blurred patterns might be different between different points. Besides, due to Fresnel losses and vignetting, the relationship between light intensity of image points and area of freeform surface elements becomes complicated. These individual light distributions of each freeform element are taken into account in a mapping algorithm. To this end the method of steepest decent procedures are used to adapt the mapping goal. A structured target pattern for a optics system with an ideal source is computed applying corresponding linear optimization matrices. Special weighting factor and smoothing factor are included in the procedures to achieve certain edge conditions and to ensure the manufacturability of the freefrom surface. The corresponding linear optimization matrices, which are the lighting distribution patterns of each of the freeform surface elements, are gained by conventional raytracing with a realistic source. Nontrivial source geometries, like LED-irregularities due to bonding or source fine structures, and a complex ray divergence behavior can be easily considered. Additionally, Fresnel losses, vignetting and even stray light are taken into account. After optimization iterations, with a realistic source, the initial mapping goal can be achieved by the optics system providing a structured target pattern with an ideal source. The algorithm is applied to several design examples. A few simple tasks are presented to discussed

  15. Flow-driven instabilities during pattern formation of Dictyostelium discoideum

    NASA Astrophysics Data System (ADS)

    Gholami, A.; Steinbock, O.; Zykov, V.; Bodenschatz, E.

    2015-06-01

    The slime mold Dictyostelium discoideum is a well known model system for the study of biological pattern formation. In the natural environment, aggregating populations of starving Dictyostelium discoideum cells may experience fluid flows that can profoundly change the underlying wave generation process. Here we study the effect of advection on the pattern formation in a colony of homogeneously distributed Dictyostelium discoideum cells described by the standard Martiel-Goldbeter model. The external flow advects the signaling molecule cyclic adenosine monophosphate (cAMP) downstream, while the chemotactic cells attached to the solid substrate are not transported with the flow. The evolution of small perturbations in cAMP concentrations is studied analytically in the linear regime and by corresponding numerical simulations. We show that flow can significantly influence the dynamics of the system and lead to a flow-driven instability that initiate downstream traveling cAMP waves. We also show that boundary conditions have a significant effect on the observed patterns and can lead to a new kind of instability.

  16. Chemical solver to compute molecule and grain abundances and non-ideal MHD resistivities in prestellar core-collapse calculations

    NASA Astrophysics Data System (ADS)

    Marchand, P.; Masson, J.; Chabrier, G.; Hennebelle, P.; Commerçon, B.; Vaytet, N.

    2016-07-01

    We develop a detailed chemical network relevant to calculate the conditions that are characteristic of prestellar core collapse. We solve the system of time-dependent differential equations to calculate the equilibrium abundances of molecules and dust grains, with a size distribution given by size-bins for these latter. These abundances are used to compute the different non-ideal magneto-hydrodynamics resistivities (ambipolar, Ohmic and Hall), needed to carry out simulations of protostellar collapse. For the first time in this context, we take into account the evaporation of the grains, the thermal ionisation of potassium, sodium, and hydrogen at high temperature, and the thermionic emission of grains in the chemical network, and we explore the impact of various cosmic ray ionisation rates. All these processes significantly affect the non-ideal magneto-hydrodynamics resistivities, which will modify the dynamics of the collapse. Ambipolar diffusion and Hall effect dominate at low densities, up to nH = 1012 cm-3, after which Ohmic diffusion takes over. We find that the time-scale needed to reach chemical equilibrium is always shorter than the typical dynamical (free fall) one. This allows us to build a large, multi-dimensional multi-species equilibrium abundance table over a large temperature, density and ionisation rate ranges. This table, which we make accessible to the community, is used during first and second prestellar core collapse calculations to compute the non-ideal magneto-hydrodynamics resistivities, yielding a consistent dynamical-chemical description of this process. The multi-dimensional multi-species equilibrium abundance table and a copy of the code are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/592/A18

  17. Subcutaneous blood flow in early male pattern baldness

    SciTech Connect

    Klemp, P.; Peters, K.; Hansted, B.

    1989-05-01

    The subcutaneous blood flow (SBF) was measured by the /sup 133/Xe washout method in the scalp of 14 patients with early male pattern baldness. Control experiments were performed in 14 normal haired men matched for age. The SBF in the scalp of the normal individuals was about 10 times higher than previously reported SBF values in other anatomical regions. In patients with early male pattern baldness, SBF was 2.6 times lower than the values found in the normal individuals (13.7 +/- 9.6 vs 35.7 +/- 10.5 ml/100 g/min-1). This difference was statistically significant (p much less than 0.001). A reduced nutritive blood flow to the hair follicles might be a significant event in the pathogenesis of early male pattern baldness.

  18. Flow-pattern evolution of the last British Ice Sheet

    NASA Astrophysics Data System (ADS)

    Hughes, Anna L. C.; Clark, Chris D.; Jordan, Colm J.

    2014-04-01

    We present a 10-stage reconstruction of the evolution in ice-flow patterns of the last British Ice Sheet from build-up to demise derived from geomorphological evidence. 100 flowsets identified in the subglacial bedform record (drumlins, mega-scale glacial lineations, and ribbed moraine) are combined with ancillary evidence (erratic-transport paths, absolute dates and a semi-independently reconstructed retreat pattern) to define flow patterns, ice divides and ice-sheet margins during build-up, maximum glaciation and retreat. Overprinting and cross-cutting of landform assemblages are used to define the relative chronology of flow patterns and a tentative absolute chronology is presented based on a collation of available dates for ice advance and retreat. The ice-flow configuration of the last British Ice Sheet was not static. Some ice divides were remarkably stable, persisting through multiple stages of the ice-sheet evolution, whereas others were transient features existing for a short time and/or shifting in position 10s km. The 10 reconstructed stages of ice-sheet geometry capture two main modes of operation; first as an integrated ice sheet with a broadly N-S orientated ice divide, and second as a multi-domed ice sheet orientated parallel with the shelf edge. A thick integrated ice sheet developed as ice expanded out of source areas in Scotland to envelop southerly ice caps in northern England and Wales, and connect with the Irish Ice Sheet to the west and the Scandinavian Ice Sheet across the North Sea. Following break-up of ice over the North Sea, ice streaming probably drove mass loss and ice-sheet thinning to create a more complex divide structure, where ice-flow patterns were largely controlled by the form of the underlying topography. Ice surface lowering occurred before separation of, and retreat to, multiple ice centres centred over high ground. We consider this 10-stage reconstruction of the evolution in ice-sheet configuration to be the simplest palaeo

  19. MODFLOW 2. 0: A program for predicting moderator flow patterns

    SciTech Connect

    Peterson, P.F. . Dept. of Nuclear Engineering); Paik, I.K. )

    1991-07-01

    Sudden changes in the temperature of flowing liquids can result in transient buoyancy forces which strongly impact the flow hydrodynamics via flow stratification. These effects have been studied for the case of potential flow of stratified liquids to line sinks, but not for moderator flow in SRS reactors. Standard codes, such as TRAC and COMMIX, do not have the capability to capture the stratification effect, due to strong numerical diffusion which smears away the hot/cold fluid interface. A related problem with standard codes is the inability to track plumes injected into the liquid flow, again due to numerical diffusion. The combined effects of buoyant stratification and plume dispersion have been identified as being important in operation the Supplementary Safety System which injects neutron-poison ink into SRS reactors to provide safe shutdown in the event of safety rod failure. The MODFLOW code discussed here provides transient moderator flow pattern information with stratification effects, and tracks the location of ink plumes in the reactor. The code, written in Fortran, is compiled for Macintosh II computers, and includes subroutines for interactive control and graphical output. Removing the graphics capabilities, the code can also be compiled on other computers. With graphics, in addition to the capability to perform safety related computations, MODFLOW also provides an easy tool for becoming familiar with flow distributions in SRS reactors.

  20. Pattern formation in crystal growth under parabolic shear flow.

    PubMed

    Ueno, K

    2003-08-01

    Morphological instability of the solid-liquid interface occurring in a crystal growing from an undercooled thin liquid bounded on one side by a free surface and flowing down inclined plane, is investigated by a linear stability analysis under shear flow. It is found that restoring forces due to gravity and surface tension is an important factor for stabilization of the solid-liquid interface on long length scales. This is a stabilizing effect different from the Gibbs-Thomson effect. A particular long wavelength mode of about 1 cm of wavy pattern, observed on the surface of icicles covered with a thin layer of flowing water is obtained from the dispersion relation, including the effect of flow and restoring forces. PMID:14524982

  1. Pattern formation and three-dimensional instability in rotating flows

    NASA Astrophysics Data System (ADS)

    Christensen, Erik A.; Aubry, Nadine; Sorensen, Jens N.

    1997-03-01

    A fluid flow enclosed in a cylindrical container where fluid motion is created by the rotation of one end wall as a centrifugal fan is studied. Direct numerical simulations and spatio-temporal analysis have been performed in the early transition scenario, which includes a steady-unsteady transition and a breakdown of axisymmetric to three-dimensional flow behavior. In the early unsteady regime of the flow, the central vortex undergoes a vertical beating motion, accompanied by axisymmetric spikes formation on the edge of the breakdown bubble. As traveling waves, the spikes move along the central vortex core toward the rotating end-wall. As the Reynolds number is increased further, the flow undergoes a three-dimensional instability. The influence of the latter on the previous patterns is studied.

  2. Rimming flows and pattern formation inside rapidly rotating cylinder

    NASA Astrophysics Data System (ADS)

    Polezhaev, Denis; Dyakova, Veronika; Kozlov, Victor

    2014-11-01

    The dynamics of fluid and granular medium in a rotating horizontal cylinder is experimentally studied. In a rapidly rotating cylinder liquid and granular medium coat the cylindrical wall under centrifugal force. In the cavity frame gravity field performs rotation and produces oscillatory fluid flow which is responsible for the series of novel effects of pattern formation, namely, axial segregation of heavy particles and pattern formation in the form of sand regular hills extended along the axis of rotation. At least two types of axial segregation are found: a) patterns of spatial period of the same order of magnitude as fluid layer thickness which induced by steady flows generated by inertial waves; b) fine patterns which manifests Gortler - Taylor vortices developing as a consequence of centrifugal instability of viscous boundary layer near the cylindrical wall. Under gravity, intensive fluid shear flow induces partial fluidization of annular layer of granular medium. The oscillatory motion is followed by onset of regular ripples extended along the axis of rotation. The work is supported by Russian Scientific Foundation (project 14-11-00476).

  3. 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.

  4. Time-Dependence and Pattern Formation in Flowing Granular Media.

    NASA Astrophysics Data System (ADS)

    Baxter, George William, III

    1990-01-01

    We study the time dependence and pattern formation of gravity driven flows of granular media in three experiments. In three dimensional flows of sand, the normal stress on the wall of a conical hopper is measured. There is no evidence of characteristic time scales predicted by a linear stability analysis of a current continuum theory of granular media. Instead, the signal is characterized by a power law power spectrum, and the time variation of the normal stress obeys a scaling law consistent with fractional Brownian motion with H ~ 0.2. As one of the best examples to date of fractional Brownian motion in a physical experiment, this provides a unique opportunity for a study of the theory's application. In digital subtraction radiography studies of sand flow through a thin (nearly two dimensional) wedge, density waves are found. The formation and motion of these depends on the geometry of the wedge and the roughness of the sand grains. The waves form in rough sand but not in smooth sand of the same approximate size, demonstrating that grain structure has a dramatic effect on the flow. Also, the position of stagnant regions along the sides of the wedge is found to scale as a power law of the wedge angle. Neither the density waves nor the position of the stagnant regions are predicted by current theories. Finally, a cellular automata model is proposed to model the two dimensional flow of ellipsoidal grains (such as grass seed) through a wedge. By including particle shape and orientation as degrees of freedom, this model is able to capture many features of real physical flows. In sum, these experiments demonstrate that flows of even simple materials like sand or grass seed contain time dependent patterns that are not predicted by current theoretical models. This demonstrates the need to include particle structure and orientation. Finally, the cellular automata model shows that even relatively simple models which include these added degrees of freedom can reproduce the

  5. Qualitative Changes in Flow Pattern in the Coating Flow inside a Rotating Cylinder.

    NASA Astrophysics Data System (ADS)

    Thoroddsen, S. T.

    1996-11-01

    We describe experimental work on the flow patterns in coating flow inside a partially-filled circular cylinder, which is rotated about its horizontally placed axis of symmetry. A prominent front forms at the bottom of the cylinder, associated with a recirculating region. This front is initially straight along the span. For a limited range of parameters, the front develops robust spanwise undulations, named shark teeth (S. T. Thoroddsen & L. Mahadevan, ``Experimental study of coating flows in a partially-filled horizontally rotating cylinder''), Experiments in Fluids (in press).. An intricate three-dimensional flow field is associated with these patterns. We study here the qualitative changes in the flow field associated with the transition of these shark teeth into waves traveling spanwise along the front. The wavelength and speed of these waves is investigated.

  6. Mantle Flow Pattern and Dynamic Topography beneath the Eastern US

    NASA Astrophysics Data System (ADS)

    Liu, S.; King, S. D.; Adam, C. M.; Long, M. D.; Benoit, M. H.; Kirby, E.

    2015-12-01

    The complex tectonic history of the eastern US over the past billion years includes episodes of subduction and rifting associated with two complete cycles of supercontinent assembly and breakup. Both the previous global tomography models (S40RTS, SAVANI, TX2011, GyPSuM, SMEAN) and the analysis of the shear-wave splitting from the broadband seismic stations find a distinct coast-to-inland differentiation pattern in the lithosphere and upper mantle. The Mid-Atlantic Geophysical Integrative Collaboration (MAGIC) includes a dense linear seismic array from the Atlantic coast of Virginia to the western boarder of Ohio, crossing several different tectonic zones. To derive the regional mantle flow pattern along with its surface expression such as dynamic topography and aid the interpretation of the seismic observations, we are building a new geodynamic model based on ASPECT (Advanced Solver for Problems in Earth CovecTion) that uses buoyancy derived from seismic tomography along with realistic lithosphere and sub-lithosphere structure. At present, we use S40RTS and SAVANI tomography models together with the temperature-dependent viscosity to compute the mantle flow and dynamic topography. Beneath the eastern US, the upper mantle flow in our model is primarily parallel to the trend of the Appalachian belt, which is broadly consistent with the direction of the local shear-wave splitting. The dynamic topography results exhibit a coast-to-inland magnitude differentiation along the MAGIC seismic deployment. The numerical tests also show that both the magnitude and pattern of the dynamic topography are quite sensitive to the density perturbation and rigidity of the lithosphere/sub-lithosphere. Our future work involves using other tomography and viscosity models to obtain the mantle flow pattern as well as the resulting dynamic topography and geoid.

  7. Advanced Numerical Imaging Procedure Accounting for Non-Ideal Effects in GPR Scenarios

    NASA Astrophysics Data System (ADS)

    Comite, Davide; Galli, Alessandro; Catapano, Ilaria; Soldovieri, Francesco

    2015-04-01

    The capability to provide fast and reliable imaging of targets and interfaces in non-accessible probed scenarios is a topic of great scientific interest, and many investigations have shown that Ground Penetrating Radar (GPR) can provide an efficient technique to conduct this kind of analysis in various applications of geophysical nature and civil engineering. In these cases, the development of an efficient and accurate imaging procedure is strongly dependent on the capability of accounting for the incident field that activates the scattering phenomenon. In this frame, based on a suitable implementation of an electromagnetic (EM) CAD tool (CST Microwave Studio), it has been possible to accurately and efficiently model the radiation pattern of real antennas in environments typically considered in GPR surveys [1]. A typical scenario of our interest is constituted by targets hidden in a ground medium, described by certain EM parameters and probed by a movable GPR using interfacial antennas [2]. The transmitting and receiving antennas considered here are Vivaldi ones, but a wide variety of other antennas can be modeled and designed, similar to those ones available in commercial GPR systems. Hence, an advanced version of a well-known microwave tomography approach (MTA) [3] has been implemented, both in the canonical 2D scalar case and in the more realistic 3D vectorial one. Such an approach is able to account for the real distribution of the radiated and scattered EM fields. Comparisons of results obtained by means of a 'conventional' implementation of the MTA, where the antennas are modeled as ideal line sources, and by means of our 'advanced' approach, which instead takes into account the radiation features of the chosen antenna type, have been carried out and discussed. Since the antenna radiation patterns are modified by the probed environment, whose EM features and the possible stratified structure usually are not exactly known, the imaging capabilities of the MTA

  8. Animating streamlines with repeated asymmetric patterns for steady flow visualization

    NASA Astrophysics Data System (ADS)

    Yeh, Chih-Kuo; Liu, Zhanping; Lee, Tong-Yee

    2012-01-01

    Animation provides intuitive cueing for revealing essential spatial-temporal features of data in scientific visualization. This paper explores the design of Repeated Asymmetric Patterns (RAPs) in animating evenly-spaced color-mapped streamlines for dense accurate visualization of complex steady flows. We present a smooth cyclic variable-speed RAP animation model that performs velocity (magnitude) integral luminance transition on streamlines. This model is extended with inter-streamline synchronization in luminance varying along the tangential direction to emulate orthogonal advancing waves from a geometry-based flow representation, and then with evenly-spaced hue differing in the orthogonal direction to construct tangential flow streaks. To weave these two mutually dual sets of patterns, we propose an energy-decreasing strategy that adopts an iterative yet efficient procedure for determining the luminance phase and hue of each streamline in HSL color space. We also employ adaptive luminance interleaving in the direction perpendicular to the flow to increase the contrast between streamlines.

  9. Graphical User Interface Development for Representing Air Flow Patterns

    NASA Technical Reports Server (NTRS)

    Chaudhary, Nilika

    2004-01-01

    In the Turbine Branch, scientists carry out experimental and computational work to advance the efficiency and diminish the noise production of jet engine turbines. One way to do this is by decreasing the heat that the turbine blades receive. Most of the experimental work is carried out by taking a single turbine blade and analyzing the air flow patterns around it, because this data indicates the sections of the turbine blade that are getting too hot. Since the cost of doing turbine blade air flow experiments is very high, researchers try to do computational work that fits the experimental data. The goal of computational fluid dynamics is for scientists to find a numerical way to predict the complex flow patterns around different turbine blades without physically having to perform tests or costly experiments. When visualizing flow patterns, scientists need a way to represent the flow conditions around a turbine blade. A researcher will assign specific zones that surround the turbine blade. In a two-dimensional view, the zones are usually quadrilaterals. The next step is to assign boundary conditions which define how the flow enters or exits one side of a zone. way of setting up computational zones and grids, visualizing flow patterns, and storing all the flow conditions in a file on the computer for future computation. Such a program is necessary because the only method for creating flow pattern graphs is by hand, which is tedious and time-consuming. By using a computer program to create the zones and grids, the graph would be faster to make and easier to edit. Basically, the user would run a program that is an editable graph. The user could click and drag with the mouse to form various zones and grids, then edit the locations of these grids, add flow and boundary conditions, and finally save the graph for future use and analysis. My goal this summer is to create a graphical user interface (GUI) that incorporates all of these elements. I am writing the program in

  10. Experimental and Numerical Investigation of Adsorption/Desorption in Packed Sorption Beds Under Ideal and Non-Ideal Flows

    NASA Technical Reports Server (NTRS)

    Mohamadinejad, H.; Knox, J. C.; Smith, James E.

    1999-01-01

    The importance of the wall effect on packed beds in the adsorption and desorption of carbon dioxide, nitrogen, and water on molecular sieve 5A of 0.127 cm in radius is examined experimentally and with one-dimensional computer simulations. Experimental results are presented for a 22.5-cm long by 4.5-cm diameter cylindrical column with concentration measurements taken at various radial locations. The set of partial differential equations are solved using finite differences and Newman's method. Comparison of test data with the axial-dispersed, non-isothermal, linear driving force model suggests that a two-dimensional model (submitted to Separation Science and Technology) is required for accurate simulation of the average column breakthrough concentration. Additional comparisons of test data with the model provided information on the interactive effects of carrier gas coadsorption with CO2, as well as CO2-H2O interactions.

  11. Pockmark Current Flow Patterns in Belfast Bay, Maine

    NASA Astrophysics Data System (ADS)

    Fandel, C. L.; Lippmann, T. C.; Foster, D. L.; Irish, J. D.; Brothers, L.

    2012-12-01

    Pockmarks are large, circular or elongate depressions in the seafloor that are globally distributed in a wide range of geologic settings including shallow, estuarine environments like Belfast Bay, Maine. The primary mechanism of pockmark formation in Belfast Bay is attributed to episodic methane venting of shallow, natural gas in the area. Recent models suggest pockmarks may be further maintained by the reduction or prevention of fine-grained sediment deposition due to inner-pockmark upwelling events induced by near-bed current flow and flow separation over the depressions. Fluid dynamics around these features may be similar to flow around dimples or cavities. In 2011, we tested this hypothesis by deploying two ADCP moorings at the rim and center of two pockmarks in Belfast Bay, Maine over a two day period. The sampled pockmarks consist of a circular, shallow (33 m) pockmark and a more elongated, deeper (42 m) pockmark, each with a length-to-depth ratio of 2.8. Time-varying current profiles indicate a complex rotational structure with depth, often exceeding 180°. Multiple upwelling and downwelling events extend throughout the water column with vertical velocities reaching up to 0.02 m/s. The shallow pockmark shows greater temporal and spatial variability in rotational structure that may be attributed to the converging tidal flows entering Belfast Bay. Current flow patterns in the deep pockmark are more directionally consistent with the tide and exhibit greater spatial alignment in the upper water column between the rim and center of the pockmark. Both pockmarks exhibit a counter-clockwise rotational pattern on the rising tide as current flow rotates nearly 100° from surface and into the pockmark. As the tide ebbs, a sub-division of flow is observed with a southerly-directed flow in the upper two-thirds of the water column and a northeasterly-directed flow within 10 m of the bottom. This circulation pattern resembles open cavity (L/D < 6) flow explained by

  12. IMPACT OF NON-IDEAL SORPTION ON LOW-CONCENTRATION TAILING BEHAVIOR FOR ATRAZINE TRANSPORT IN TWO NATURAL POROUS MEDIA

    PubMed Central

    Kempf, A.

    2011-01-01

    The impact of nonideal sorption on atrazine transport was investigated for two sandy porous media with 0.38 and 0.03% organic-carbon contents. In contrast to prior investigations, effluent atrazine concentrations were monitored over a range of five orders of magnitude to examine long-term elution behavior. As characterized by batch experiments, atrazine experienced nonlinear sorption for both media. The results of the column experiments showed that atrazine exhibited extensive elution tailing (delayed approach to relative concentration of zero). This non-ideal transport was more pronounced for the medium with higher organic-carbon content. A mathematical model incorporating nonlinear, rate-limited sorption/desorption described by a continuous distribution function was used to successfully simulate atrazine transport. PMID:19699507

  13. Method and apparatus for improving resolution in spectrometers processing output steps from non-ideal signal sources

    DOEpatents

    Warburton, William K.; Momayezi, Michael

    2006-06-20

    A method and apparatus for processing step-like output signals (primary signals) generated by non-ideal, for example, nominally single-pole ("N-1P ") devices. An exemplary method includes creating a set of secondary signals by directing the primary signal along a plurality of signal paths to a signal summation point, summing the secondary signals reaching the signal summation point after propagating along the signal paths to provide a summed signal, performing a filtering or delaying operation in at least one of said signal paths so that the secondary signals reaching said summing point have a defined time correlation with respect to one another, applying a set of weighting coefficients to the secondary signals propagating along said signal paths, and performing a capturing operation after any filtering or delaying operations so as to provide a weighted signal sum value as a measure of the integrated area QgT of the input signal.

  14. How does tidal flow affect pattern formation in mussel beds?

    PubMed

    Sherratt, Jonathan A; Mackenzie, Julia J

    2016-10-01

    In the Wadden Sea, mussel beds self-organise into spatial patterns consisting of bands parallel to the shore. A leading explanation for this phenomenon is that mussel aggregation reduces losses from dislodgement and predation, because of the adherence of mussels to one another. Previous mathematical modelling has shown that this can lead to spatial patterning when it is coupled to the advection from the open sea of algae-the main food source for mussels in the Wadden Sea. A complicating factor in this process is that the advection of algae will actually oscillate with the tidal flow. This has been excluded from previous modelling studies, and the present paper concerns the implications of this oscillation for pattern formation. The authors initially consider piecewise constant ("square-tooth") oscillations in advection, which enables analytical investigation of the conditions for pattern formation. They then build on this to study the more realistic case of sinusoidal oscillations. Their analysis shows that future research on the details of pattern formation in mussel beds will require an in-depth understanding of how the tides affect long-range inhibition among mussels. PMID:27343625

  15. Role of non-ideality for the ion transport in porous media: Derivation of the macroscopic equations using upscaling

    NASA Astrophysics Data System (ADS)

    Allaire, Grégoire; Brizzi, Robert; Dufrêche, Jean-François; Mikelić, Andro; Piatnitski, Andrey

    2014-07-01

    This paper is devoted to the homogenization (or upscaling) of a system of partial differential equations describing the non-ideal transport of a N-component electrolyte in a dilute Newtonian solvent through a rigid porous medium. Realistic non-ideal effects are taken into account by an approach based on the mean spherical approximation (MSA) model which takes into account finite size ions and screening effects. We first consider equilibrium solutions in the absence of external forces. In such a case, the velocity and diffusive fluxes vanish and the equilibrium electrostatic potential is the solution of a variant of the Poisson-Boltzmann equation coupled with algebraic equations. Contrary to the ideal case, this nonlinear equation has no monotone structure. However, based on invariant region estimates for the Poisson-Boltzmann equation and for small characteristic value of the solute packing fraction, we prove existence of at least one solution. To our knowledge this existence result is new at this level of generality. When the motion is governed by a small static electric field and a small hydrodynamic force, we generalize O'Brien's argument to deduce a linearized model. Our second main result is the rigorous homogenization of these linearized equations and the proof that the effective tensor satisfies Onsager properties, namely is symmetric positive definite. We eventually make numerical comparisons with the ideal case. Our numerical results show that the MSA model confirms qualitatively the conclusions obtained using the ideal model but there are quantitative differences arising that can be important at high charge or high concentrations.

  16. Improving optical fiber current sensor accuracy using artificial neural networks to compensate temperature and minor non-ideal effects

    NASA Astrophysics Data System (ADS)

    Zimmermann, Antonio C.; Besen, Marcio; Encinas, Leonardo S.; Nicolodi, Rosane

    2011-05-01

    This article presents a practical signal processing methodology, based on Artificial Neural Networks - ANN, to process the measurement signals of typical Fiber Optic Current Sensors - FOCS, achieving higher accuracy from temperature and non-linearity compensation. The proposed idea resolve FOCS primary problems, mainly when it is difficult to determine all errors sources present in the physical phenomenon or the measurement equation becomes too nonlinear to be applied in a wide measurement range. The great benefit of ANN is to get a transfer function for the measurement system taking in account all unknowns, even those from unwanted and unknowing effects, providing a compensated output after the ANN training session. Then, the ANN training is treated like a black box, based on experimental data, where the transfer function of the measurement system, its unknowns and non-idealities are processed and compensated at once, given a fast and robust alternative to the FOCS theoretical method. A real FOCS system was built and the signals acquired from the photo-detectors are processed by the Faraday's Laws formulas and the ANN method, giving measurement results for both signal processing strategies. The coil temperature measurements are also included in the ANN signal processing. To compare these results, a current measuring instrument standard is used together with a metrological calibration procedure. Preliminary results from a variable temperature experiment shows the higher accuracy, better them 0.2% of maximum error, of the ANN methodology, resulting in a quick and robust method to hands with FOCS difficulties on of non-idealities compensation.

  17. Electrohydrodynamic flow and colloidal patterning near inhomogeneities on electrodes.

    PubMed

    Ristenpart, W D; Jiang, P; Slowik, M A; Punckt, C; Saville, D A; Aksay, I A

    2008-11-01

    Current density inhomogeneities on electrodes (of physical, chemical, or optical origin) induce long-range electrohydrodynamic fluid motion directed toward the regions of higher current density. Here, we analyze the flow and its implications for the orderly arrangement of colloidal particles as effected by this flow on patterned electrodes. A scaling analysis indicates that the flow velocity is proportional to the product of the applied voltage and the difference in current density between adjacent regions on the electrode. Exact analytical solutions for the streamlines are derived for the case of a spatially periodic perturbation in current density along the electrode. Particularly simple asymptotic expressions are obtained in the limits of thin double layers and either large or small perturbation wavelengths. Calculations of the streamlines are in good agreement with particle velocimetry experiments near a mechanically generated inhomogeneity (a "scratch") that generates a current density larger than that of the unmodified electrode. We demonstrate that proper placement of scratches on an electrode yields desired patterns of colloidal particles. PMID:18828610

  18. Patterns, Instabilities, Colors, and Flows in Vertical Foam Films

    NASA Astrophysics Data System (ADS)

    Yilixiati, Subinuer; Wojcik, Ewelina; Zhang, Yiran; Pearsall, Collin; Sharma, Vivek

    2015-03-01

    Foams find use in many applications in daily life, industry and biology. Examples include beverages, firefighting foam, cosmetics, foams for oil recovery and foams formed by pollutants. Foams are collection of bubbles separated by thin liquid films that are stabilized against drainage by the presence of surfactant molecules. Drainage kinetics and stability of the foam are strongly influenced by surfactant type, addition of particles, proteins and polymers. In this study, we utilize the thin film interference colors as markers for identifying patterns, instabilities and flows within vertical foam films. We experimentally study the emergence of thickness fluctuations near the borders and within thinning films, and study how buoyancy, capillarity and gravity driven instabilities and flows, are affected by variation in bulk and interfacial physicochemical properties dependent on the choice of constituents.

  19. Simulation of Flow Patterns Within the Human Respiratory System

    NASA Astrophysics Data System (ADS)

    Quatember, Bernhard; Mayr, Martin; Recheis, Wolfgang

    2008-09-01

    A nonlinear simulation model of the respiratory system is presented here. It describes the flow patterns as well as the specific gas mixing and distribution processes that occur in the tracheobronchial tree. The model is based on the commonly used morphometric scheme of E. Weibel. It consists of a "pressure-flow submodel" and a "gas mixing submodel. The former is a lumped parameter model consisting of 24 lumped components. The second type, the "gas mixing submodel," enables the simulation of the mixing processes in the trachea and in the larger bronchi (up to the 10th generation). Several simulation studies that are based on it have been carried out; they deal with both the physiological conditions and the specific pathological changes that occur in the small airways during the early stages of chronic obstructive bronchitis.

  20. Multiple convection patterns and thermohaline flow in an idealized OGCM

    SciTech Connect

    Rahmstorf, S.

    1995-12-01

    This paper investigates how multiple steady states arise in an ocean general circulation model, caused by the fact that many different convection patterns can be stable under the same surface boundary conditions. Two alternative boundary conditions are used in the experiments: classical mixed boundary conditions and a diffusive atmospheric heat balance combined with fixed salt fluxes. In both cases, transitions between different quasi-steady convection patterns can be triggered by briefly adding fresh water at convection sites. Either a large-scale freshwater anomaly is used to completely erase the previous convection pattern or a {open_quotes}surgical{close_quotes} anomaly is added to single grid points to turn off convection there. Under classical mixed-boundary conditions, different convection sites can lead to different overturning rates of deep water. The dynamics of the convection-driven flow is analyzed in some detail. With an energy balance atmosphere, in contrast, the overturning rate is very robust, apparently regulated by a negative thermal feedback. In spite of this, different convection patterns are associated with very different climatic states, since the heat transport of the deep circulation depends strongly on where convection takes place. It is suggested that considerable climate variability in the North Atlantic could be caused by changes in high-latitude convection.

  1. Analysis of breathing air flow patterns in thermal imaging.

    PubMed

    Fei, Jin; Pavlidis, Ioannis

    2006-01-01

    We introduce a novel methodology to characterize breathing patterns based on thermal infrared imaging. We have retrofitted a Mid-Wave Infra-Red (MWIR) imaging system with a narrow band-pass filter in the CO(2) absorption band (4130 - 4427 nm). We use this system to record the radiation information from within the breathing flow region. Based on this information we compute the mean dynamic thermal signal of breath. The breath signal is quasi-periodic due to the interleaving of high and low intensities corresponding to expirations and inspirations respectively. We sample the signal at a constant rate and then filter the high frequency noise due to tracking instability. We detect the breathing cycles through zero cross thresholding, which is insensitive to noise around the zero line. We normalize the breathing cycles and align them at the transition point from inhalation to exhalation. Then, we compute the mean breathing cycle. We use the first eight (8) harmonic components of the mean cycle to characterize the breathing pattern. The harmonic analysis highlights the intra-individual similarity of breathing patterns. Our method opens the way for desktop, unobtrusive monitoring of human respiration and may find widespread applications in clinical studies of chronic ailments. It also brings up the intriguing possibility of using breathing patterns as a novel biometric. PMID:17945610

  2. Preferential accumulation of bubbles in Couette-Taylor flow patterns

    NASA Astrophysics Data System (ADS)

    Climent, Eric; Simonnet, Marie; Magnaudet, Jacques

    2007-08-01

    We investigate the migration of bubbles in several flow patterns occurring within the gap between a rotating inner cylinder and a concentric fixed outer cylinder. The time-dependent evolution of the two-phase flow is predicted through three-dimensional Euler-Lagrange simulations. Lagrangian tracking of spherical bubbles is coupled with direct numerical simulation of the Navier-Stokes equations. We assume that bubbles do not influence the background flow (one-way coupling simulations). The force balance on each bubble takes into account buoyancy, added-mass, viscous drag, and shear-induced lift forces. For increasing velocities of the rotating inner cylinder, the flow in the fluid gap evolves from the purely azimuthal steady Couette flow to Taylor toroidal vortices and eventually a wavy vortex flow. The migration of bubbles is highly dependent on the balance between buoyancy and centripetal forces (mostly due to the centripetal pressure gradient) directed toward the inner cylinder and the vortex cores. Depending on the rotation rate of the inner cylinder, bubbles tend to accumulate alternatively along the inner wall, inside the core of Taylor vortices or at particular locations within the wavy vortices. A stability analysis of the fixed points associated with bubble trajectories provides a clear understanding of their migration and preferential accumulation. The location of the accumulation points is parameterized by two dimensionless parameters expressing the balance of buoyancy, centripetal attraction toward the inner rotating cylinder, and entrapment in Taylor vortices. A complete phase diagram summarizing the various regimes of bubble migration is built. Several experimental conditions considered by Djéridi, Gabillet, and Billard [Phys. Fluids 16, 128 (2004)] are reproduced; the numerical results reveal a very good agreement with the experiments. When the rotation rate is increased further, the numerical results indicate the formation of oscillating bubble

  3. Effects of tumors on inhaled pharmacologic drugs: I. Flow patterns.

    PubMed

    Martonen, T B; Guan, X

    2001-01-01

    Lung carcinomas are now the most common form of cancer. Clinical data suggest that tumors are found preferentially in upper airways, perhaps specifically at carina within bifurcations. The disease can be treated by aerosolized pharmacologic drugs. To enhance their efficacies site-specific drugs must be deposited selectively. Since inhaled particles are transported by air, flow patterns will naturally affect their trajectories. Therefore, in Part I of a systematic investigation, we focused on tumor-induced effects on airstreams, in Part II (the following article [p. 245]), particle trajectories were determined. To facilitate the targeted delivery of inhaled drugs, we simulated bifurcations with tumors on carinas using a commercial computational fluid dynamics (CFD) software package (FIDAP) with a Cray T90 supercomputer and studied effects of tumor sizes and ventilatory parameters on localized flow patterns. Critical tumor sizes existed; e.g., tumors had dominant effects when r/R > or = 0.8 for bifurcation 3-4 and r/R > or = 0.6 for bifurcation 7-8 (r = tumor radius and R = airway radius). The findings suggest that computer modeling is a means to integrate alterations to airway structures caused by diseases into aerosol therapy protocols. PMID:11894843

  4. Flow Pattern relative to the Substorm Current Wedge

    NASA Astrophysics Data System (ADS)

    Chu, X.; McPherron, R. L.; Hsu, T.

    2013-12-01

    Magnetospheric substorms play a key role in the coupling of the solar wind and the magnetosphere. The Substorm Current Wedge (SCW) is a key element in the present physical model of substorms. It is widely accepted that the SCW is created by earthward busty flows, but the generation mechanism is still unknown. Previous studies suggest pressure gradients and magnetic vortices are possible candidates. Due to the sparse coverage of satellites in space, these studies were strongly dependent on the assumption that the satellites were in the generation region of the field-aligned currents (FAC) forming the SCW. In this work, we take advantage of an inversion technique that determines the parameters describing the SCW and perform a statistical study on the plasma and magnetic field parameters of the flow pattern relative to the SCW. The inversion technique finds the location and the intensity of the SCW from midlatitude magnetic data. The technique has been validated using auroral observations, Equivalent Ionospheric Currents (EIC), SYM-H index from SuperMAG, and magnetic perturbations at geosynchronous orbit by the GOES satellite. A database of substorm events has been created using midlatitude positive bays, which are the ground signature of the SCW at lower latitudes. The inversion technique is applied to each event in the database to determine the location of the origin of the SCW. The inversion results are also used to find conjunction events with space observations from VAP (RBSP), THEMIS and GOES. The plasma and magnetic field parameters such as the pressure gradient and magnetic vorticity are then categorized as a function of their location relative to the origin of the SCW. How the distribution/pattern of the pressure gradient and vorticity are related to the properties of the SCW (locations and intensity of the FAC), and flows (entropy, velocity and density) will be determined.

  5. Permutation blocking path integral Monte Carlo: a highly efficient approach to the simulation of strongly degenerate non-ideal fermions

    NASA Astrophysics Data System (ADS)

    Dornheim, Tobias; Groth, Simon; Filinov, Alexey; Bonitz, Michael

    2015-07-01

    Correlated fermions are of high interest in condensed matter (Fermi liquids, Wigner molecules), cold atomic gases and dense plasmas. Here we propose a novel approach to path integral Monte Carlo (PIMC) simulations of strongly degenerate non-ideal fermions at finite temperature by combining a fourth-order factorization of the density matrix with antisymmetric propagators, i.e., determinants, between all imaginary time slices. To efficiently run through the modified configuration space, we introduce a modification of the widely used continuous space worm algorithm, which allows for an efficient sampling at arbitrary system parameters. We demonstrate how the application of determinants achieves an effective blocking of permutations with opposite signs, leading to a significant relieve of the fermion sign problem. To benchmark the capability of our method regarding the simulation of degenerate fermions, we consider multiple electrons in a quantum dot and compare our results with other ab initio techniques, where they are available. The present permutation blocking PIMC approach allows us to obtain accurate results even for N = 20 electrons at low temperature and arbitrary coupling, where no other ab initio results have been reported, so far.

  6. Non-ideal effect in 4H-SiC bipolar junction transistor with double Gaussian-doped base

    NASA Astrophysics Data System (ADS)

    Yuan, Lei; Zhang, Yu-Ming; Song, Qing-Wen; Tang, Xiao-Yan; Zhang, Yi-Men

    2015-06-01

    The non-ideal effect of 4H-SiC bipolar junction transistor (BJT) with a double Gaussian-doped base is characterized and simulated in this paper. By adding a specific interface model between SiC and SiO2, the simulation results are in good agreement with the experiment data. An obvious early effect is found from the output characteristic. As the temperature rises, the early voltage increases, while the current gain gradually decreases, which is totally different from the scenario of silicon BJT. With the same effective Gummel number in the base region, the double Gaussian-doped base structure can realize higher current gain than the single base BJT due to the built-in electric field, whereas the early effect will be more salient. Besides, the emitter current crowding effect is also analyzed. Due to the low sheet resistance in the first highly-doped base epilayer, the 4H-BJT with a double base has more uniform emitter current density across the base-emitter junction, leading to better thermal stability. Project supported by the National Natural Science Foundation of China (Grant Nos. 60876061 and 61234006), the Natural Science Foundation of Shaanxi Province, China (Grant No. 2013JQ8012), and the Doctoral Fund of the Ministry of Education of China (Grant Nos. 20130203120017 and 20110203110010).

  7. Method And Aparatus For Improving Resolution In Spectrometers Processing Output Steps From Non-Ideal Signal Sources

    DOEpatents

    Warburton, William K.; Momayezi, Michael

    2003-07-01

    A method and apparatus for processing step-like output signals generated by non-ideal, nominally single-pole ("N-1P") devices responding to possibly time-varying, pulse-like input signals of finite duration, wherein the goal is to recover the integrated areas of the input signals. Particular applications include processing step-like signals generated by detector systems in response to absorbed radiation or particles and, more particularly, to digitally processing such step-like signals in high resolution, high rate gamma ray (.gamma.-ray) spectrometers with resistive feedback preamplifiers connected to large volume germanium detectors. Superconducting bolometers can be similarly treated. The method comprises attaching a set of one or more filters to the device's (e.g., preamplifier's) output, capturing a correlated multiple output sample from the filter set in response to a detected event, and forming a weighted sum of the sample values to accurately recover the total area (e.g., charge) of the detected event.

  8. Dissolution Patterns and Mixing Dynamics in Unstable Reactive Flow

    NASA Astrophysics Data System (ADS)

    Hidalgo, Juan J.; Dentz, Marco; Cabeza, Yoar; Carrera, Jesus

    2015-04-01

    We study the fundamental problem of mixing and chemical reactions under a Rayleigh-Bénard-type hydrodynamic instability in a two miscible fluids system. The dense fluid mixture, which is generated at the fluids interface, leads to the onset of a convective instability. At the same time, a fast chemical dissolution reaction produces a characteristic porosity pattern that follows the regions of maximum mixing. Contrary to intuition, the dissolution pattern does not map out the finger geometry of the unstable flow. Instead, it displays a dome-like, hierarchical structure that reflects the positions of the ascending fluid interface. We find that this behavior is caused by stagnation points along the deformed interface, which act as mixing and reaction hotspots due to a strong compression of the interfacial boundary layer. We develop a model for mixing and reaction around the stagnation points of the deformed fluids interface that captures the evolution of the global scalar dissipation and reaction rates and predicts their independence of the Rayleigh number.

  9. Pattern formation in granular binary mixtures under shear flow

    NASA Astrophysics Data System (ADS)

    Gao, Xin; Narteau, Clement; Rozier, Olivier

    2013-04-01

    We study numerically the formation and evolution of bed forms using a binary granular mixture. The two types of particles may have different dynamic properties and angle of repose. We associate these changes to two different grain sizes, the so-called coarse and thin particles. Our computation are based on a real-space cellular automaton that combines a model of sediment transport with a lattice-gas cellular automaton. Thus, we implement the permanent feedbacks between fluid flow and topography. Keeping constant the strength of the flow, we explore a parameter-space by varying the size of the coarse particles and their proportion within the bed. As a result of avalanches and sediment transport, we systematically find regions of segregation and stratification. In a vast majority of cases, we also observe the formation of an armoring layer mainly composed of coarse particles. Its depth is mainly controlled by the proportion of coarse grains and not by the size of these larger particles. When there is a larger proportion of thin particles, transverse dunes develop on the top of the armoring layer. As this proportion decreases, we may observe barchans or even no clear bed forms. We conclude that the main control parameter for dune pattern formation is the thin sediment availability. Finally, we discuss the processes responsible for the formation of the armoring layer and show how it controls the overall sediment transport.

  10. Statistical analysis on the signals monitoring multiphase flow patterns in pipeline-riser system

    NASA Astrophysics Data System (ADS)

    Ye, Jing; Guo, Liejin

    2013-07-01

    The signals monitoring petroleum transmission pipeline in offshore oil industry usually contain abundant information about the multiphase flow on flow assurance which includes the avoidance of most undesirable flow pattern. Therefore, extracting reliable features form these signals to analyze is an alternative way to examine the potential risks to oil platform. This paper is focused on characterizing multiphase flow patterns in pipeline-riser system that is often appeared in offshore oil industry and finding an objective criterion to describe the transition of flow patterns. Statistical analysis on pressure signal at the riser top is proposed, instead of normal prediction method based on inlet and outlet flow conditions which could not be easily determined during most situations. Besides, machine learning method (least square supported vector machine) is also performed to classify automatically the different flow patterns. The experiment results from a small-scale loop show that the proposed method is effective for analyzing the multiphase flow pattern.

  11. Assessing the non-ideality of the CO2-CS2 system at molecular level: A Raman scattering study

    NASA Astrophysics Data System (ADS)

    Besnard, M.; Cabaço, M. I.; Coutinho, J. A. P.; Danten, Y.

    2013-09-01

    The dense phase of CO2-CS2 mixtures has been analysed by Raman spectroscopy as a function of the CO2 concentration (0.02-0.95 mole fractions) by varying the pressure (0.5 MPa up to 7.7 MPa) at constant temperature (313 K). The polarised and depolarised spectra of the induced (ν2, ν3) modes of CS2 and of the ν1-2ν2 Fermi resonance dyad of both CO2 and CS2 have been measured. Upon dilution with CO2, the evolution of the spectroscopic observables of all these modes displays a "plateau-like" region in the CO2 mole fraction 0.3-0.7 never previously observed in CO2-organic liquids mixtures. The bandshape and intensity of the induced modes of CS2 are similar to those of pure CS2 up to equimolar concentration, after which variations occur. The preservation of the local ordering from pure CS2 to equimolar concentration together with the non-linear evolution of the spectroscopic observables allows inferring that two solvation regimes exist with a transition occurring in the plateau domain. In the first regime, corresponding to CS2 concentrated mixtures, the liquid phase is segregated with dominant CS2 clusters, whereas, in the second one, CO2 monomers and dimers and CO2-CS2 hetero-dimers coexist dynamically on a picosecond time-scale. It is demonstrated that the subtle interplay between attractive and repulsive interactions which provides a molecular interpretation of the non-ideality of the CO2-CS2 mixture allows rationalizing the volume expansion and the existence of the plateau-like region observed in the pressure-composition diagram previously ascribed to the proximity of an upper critical solution temperature at lower temperatures.

  12. Effects of parent vessel geometry on intraaneurysmal flow patterns

    NASA Astrophysics Data System (ADS)

    Castro, Marcelo A.; Putman, Christopher M.; Cebral, Juan R.

    2006-03-01

    This study shows the influence of the upstream parent artery geometry on intra-aneurysmal hemodynamics of cerebral aneurysms. Patient-specific models of four cerebral aneurysms at four typical locations were constructed from 3D rotational angiography images. Two geometrical models were constructed for each patient, one with the native parent vessel geometry and another with the parent vessel truncated approximately 1cm upstream from the aneurysm. For one aneurysm, two images were used to construct a model as realistic and large as possible - down to the carotid bifurcation - which was cut at seven different locations. Corresponding finite element grids were generated and computational fluid dynamics simulations were carried out under pulsatile flow conditions. It was found that truncated models tended to underestimate the wall shear stress in the aneurysm and to shift the impaction zone to the neck when compared with the native geometry. In one aneurysm the parent vessel included a tortuous segment close to the neck that strongly influenced the flow pattern entering the aneurysm. Thus, including longer portions of the parent vessel beyond this segment did not have a substantial effect. Depending on the dominant geometrical features the length of the parent artery needed for an accurate representation of the intraaneurysmal hemodynamics may vary among individuals. In conclusion, failure to properly model the inflow stream determined by the upstream parent artery can significantly influence the results of intra-aneurysmal hemodynamic models. The upstream portion of the parent vessel of cerebral aneurysms should be included in order to accurately represent the intraaneurysmal hemodynamics.

  13. Pattern formation in granular binary mixtures under shear flow

    NASA Astrophysics Data System (ADS)

    Gao, X.; Narteau, C.; Rozier, O.

    2012-12-01

    Polydisperse granular materials are ubiquitous in the field of geomorphology. Nevertheless, it remains a challenge to address the impact of segregation, stratification and mixing on landscape dynamics and sediment transport. Here, we study numerically the formation and evolution of bed forms using a binary granular mixture. The two types of particles may have different dynamic properties and angle of repose. We associate these changes to two different grain sizes, the so-called coarse and thin particles. Our computation are based on a real-space cellular automaton that combines a model of sediment transport with a lattice-gas cellular automaton. Thus, we implement the permanent feedbacks between fluid flow and topography. Keeping constant the strength of the flow, we explore a parameter-space by varying the size of the coarse particles and their proportion within the bed. As a result of avalanches and sediment transport, we systematically find regions of segregation and stratification. In a vast majority of cases, we also observe the formation of an armoring layer mainly composed of coarse particles. Its depth is mainly controlled by the proportion of coarse grains and not by the size of these larger particles. When there is a larger proportion of thin particles, transverse dunes develop on the top of the armoring layer. As this proportion decreases, we may observe barchans or even no clear bed forms. Not surprisingly, we conclude that the main control parameter for dune pattern formation is the thin sediment availability. Finally, we discuss the processes responsible for the formation of the armoring layer and show how it controls the overall sediment transport.

  14. Temporal Patterns in Bivalve Excurrent Flow Under Varying Ambient Flow Conditions

    NASA Astrophysics Data System (ADS)

    Delavan, S. K.; Webster, D. R.

    2008-11-01

    The predator-prey relationship between blue crabs (Callinectes sapidus) and bivalve clams (Mercenaria mercenaria) is mediated by the transport of metabolites released by the prey (clams) and transported downstream as a passive scalar. This study focuses on how the prey behavior contributes to the information available within the odorant plume. Clams may modify factors such as excurrent flux, flow unsteadiness, and siphon height and diameter. A Particle Image Velocimetry (PIV) system has been used to quantify the temporal patterns in the excurrent jet of the bivalve siphon under varying ambient flow conditions. According to a spectral analysis of siphon excurrent velocity time records, there is a low frequency periodic component that could contribute to the mixing of clam metabolites through the generation of persistent jet vorticies. Also, fractal analysis of the velocity time records shows that as the ambient velocity increases the excurrent velocity becomes more correlated and less random. These results suggest that for high ambient flow a low frequency periodicity may be sufficient to promote the mixing and dilution of metabolites. In contrast, for low ambient flow more random siphon excurrent velocity may be required to reduce the amount of information available to predators in the downstream odorant plume.

  15. Testing research for oil-gas-water flow pattern in Daqing oilfield

    NASA Astrophysics Data System (ADS)

    Liu, Xiaoyan; Mao, Qianjun; Liu, Lijun; Xu, Ying; Chen, Wei

    2013-07-01

    During the period of the high water cut later stage, it is significant for decreasing energy consumption of gathering system to research oil-gas-water flow pattern. At the moment, the studies on oil-gas-water flow pattern are mainly focused on the temperature range of crude oil freezing point. A experimental system is designed, constructed and operated in oilfields in horizontal pipeline., which is used for experimental investigation and analysis of oil-gas-water flow pattern under freezing point in horizontal pipeline. According to the crude oil condition, the results show that oil-gas-water flow pattern includes four types that are oil contact wave flow, oil-oil particle dispersion flow, oil lamellar flow, oil puddle slugging flow.

  16. Subsurface flow and vegetation patterns in tidal environments

    NASA Astrophysics Data System (ADS)

    Ursino, Nadia; Silvestri, Sonia; Marani, Marco

    2004-05-01

    Tidal environments are characterized by a complex interplay of hydrological, geomorphic, and biological processes, and their understanding and modeling thus require the explicit description of both their biotic and abiotic components. In particular, the presence and spatial distribution of salt marsh vegetation (a key factor in the stabilization of the surface soil) have been suggested to be related to topographic factors and to soil moisture patterns, but a general, process-based comprehension of this relationship has not yet been achieved. The present paper describes a finite element model of saturated-unsaturated subsurface flow in a schematic salt marsh, driven by tidal fluctuations and evapotranspiration. The conditions leading to the establishment of preferentially aerated subsurface zones are studied, and inferences regarding the development and spatial distribution of salt marsh vegetation are drawn, with important implications for the overall ecogeomorphological dynamics of tidal environments. Our results show that subsurface water flow in the marsh induces complex water table dynamics, even when the tidal forcing has a simple sinusoidal form. The definition of a space-dependent aeration time is then proposed to characterize root aeration. The model shows that salt marsh subsurface flow depends on the distance from the nearest creek or channel and that the subsurface water movement near tidal creeks is both vertical and horizontal, while farther from creeks, it is primarily vertical. Moreover, the study shows that if the soil saturated conductivity is relatively low (10-6 m s-1, values quite common in salt marsh areas), a persistently unsaturated zone is present below the soil surface even after the tide has flooded the marsh; this provides evidence of the presence of an aerated layer allowing a prolonged presence of oxygen for aerobic root respiration. The results further show that plant transpiration increases the extent and persistence of the aerated

  17. Dynamic thermal-hydraulic modeling and stack flow pattern analysis for all-vanadium redox flow battery

    NASA Astrophysics Data System (ADS)

    Wei, Zhongbao; Zhao, Jiyun; Skyllas-Kazacos, Maria; Xiong, Binyu

    2014-08-01

    The present study focuses on dynamic thermal-hydraulic modeling for the all-vanadium flow battery and investigations on the impact of stack flow patterns on battery performance. The inhomogeneity of flow rate distribution and reversible entropic heat are included in the thermal-hydraulic model. The electrolyte temperature in tanks is modeled with the finite element modeling (FEM) technique considering the possible non-uniform distribution of electrolyte temperature. Results show that the established model predicts electrolyte temperature accurately under various ambient temperatures and current densities. Significant temperature gradients exist in the battery system at extremely low flow rates, while the electrolyte temperature tends to be the same in different components under relatively high flow rates. Three stack flow patterns including flow without distribution channels and two cases of flow with distribution channels are compared to investigate their effects on battery performance. It is found that the flow rates are not uniformly distributed in cells especially when the stack is not well designed, while adding distribution channels alleviates the inhomogeneous phenomenon. By comparing the three flow patterns, it is found that the serpentine-parallel pattern is preferable and effectively controls the uniformity of flow rates, pressure drop and electrolyte temperature all at expected levels.

  18. Dissolution patterns and mixing dynamics in unstable reactive flow

    NASA Astrophysics Data System (ADS)

    Hidalgo, Juan J.; Dentz, Marco; Cabeza, Yoar; Carrera, Jesus

    2015-08-01

    We study the fundamental problem of mixing and chemical reactions under a Rayleigh-Taylor-type hydrodynamic instability in a miscible two-fluid system. The dense fluid mixture, which is generated at the fluid-fluid interface, leads to the onset of a convective fingering instability and triggers a fast chemical dissolution reaction. Contrary to intuition, the dissolution pattern does not map out the finger geometry. Instead, it displays a dome-like, hierarchical structure that follows the path of the ascending fluid interface and the regions of maximum mixing. These mixing and reaction hot spots coincide with the flow stagnation points, at which the interfacial mixing layer is compressed and deformed. We show that the deformation of the boundary layer around the stagnation points controls the evolution of the global scalar dissipation and reaction rates and shapes the structure of the reacted zones. The persistent compression of the mixing layer explains the independence of the mixing rate from the Rayleigh number when convection dominates.

  19. Patterns in groundwater chemistry resulting from groundwater flow

    NASA Astrophysics Data System (ADS)

    Stuyfzand, Pieter J.

    Groundwater flow influences hydrochemical patterns because flow reduces mixing by diffusion, carries the chemical imprints of biological and anthropogenic changes in the recharge area, and leaches the aquifer system. Global patterns are mainly dictated by differences in the flux of meteoric water passing through the subsoil. Within individual hydrosomes (water bodies with a specific origin), the following prograde evolution lines (facies sequence) normally develop in the direction of groundwater flow: from strong to no fluctuations in water quality, from polluted to unpolluted, from acidic to basic, from oxic to anoxic-methanogenic, from no to significant base exchange, and from fresh to brackish. This is demonstrated for fresh coastal-dune groundwater in the Netherlands. In this hydrosome, the leaching of calcium carbonate as much as 15m and of adsorbed marine cations (Na+, K+, and Mg2+) as much as 2500m in the flow direction is shown to correspond with about 5000yr of flushing since the beach barrier with dunes developed. Recharge focus areas in the dunes are evidenced by groundwater displaying a lower prograde quality evolution than the surrounding dune groundwater. Artificially recharged Rhine River water in the dunes provides distinct hydrochemical patterns, which display groundwater flow, mixing, and groundwater ages. Résumé Les écoulements souterrains influencent les différents types hydrochimiques, parce que l'écoulement réduit le mélange par diffusion, porte les marques chimiques de changements biologiques et anthropiques dans la zone d'alimentation et lessive le système aquifère. Ces types dans leur ensemble sont surtout déterminés par des différences dans le flux d'eau météorique traversant le sous-sol. Dans les "hydrosomes" (masses d'eau d'origine déterminée), les lignes marquant une évolution prograde (séquence de faciès) se développent normalement dans la direction de l'écoulement souterrain : depuis des fluctuations fortes de la

  20. Magnetoactive Sponges for Dynamic Control of Microfluidic Flow Patterns in Microphysiological Systems

    PubMed Central

    Yen, Ringo; Chan, Hon Fai; Leong, Kam W; Truskey, George A; Zhao, Xuanhe

    2014-01-01

    We developed a microfluidic flow-control system capable of dynamically generating various flow patterns on demand. The flow-control system is based on novel magnetoactive sponges embedded in microfluidic flow channels. Applying a non-uniform magnetic field compresses the magnetoactive sponge, significantly reducing porosity and hydraulic conductivity. Tuning the applied magnetic field can dynamically vary the flow rate in the microfluidic channel. Pulsatile and physiological flow patterns with frequency between 1 and 3 Hz, flow rates between 0.5 and 10 μL/min and duration over 3 weeks have been achieved. Smooth muscle cells in engineered blood vessels perfused for 7 days aligned perpendicular to the flow direction under pulsatile but not steady flow, similar to the in vivo orientation. Owing to its various advantages over traditional flow-control methods, the new system potentially has important applications in microfluidic-based microphysiological systems to simulate the physiological nature of blood flow. PMID:24310854

  1. Magnetic characterization of non-ideal single-domain monoclinic pyrrhotite and its demagnetization under hydrostatic pressure up to 2 GPa with implications for impact demagnetization

    NASA Astrophysics Data System (ADS)

    Bezaeva, Natalia S.; Chareev, Dmitriy A.; Rochette, Pierre; Kars, Myriam; Gattacceca, Jérôme; Feinberg, Joshua M.; Sadykov, Ravil A.; Kuzina, Dilyara M.; Axenov, Sergey N.

    2016-08-01

    Here we present a comprehensive magnetic characterization of synthesized non-ideal single-domain (SD) monoclinic pyrrhotite (Fe7S8). The samples were in the form of a powder and a powder dispersed in epoxy. "Non-ideal" refers to a powder fraction of predominantly SD size with a minor contribution of small pseudo-single-domain grains; such non-ideal SD pyrrhotite was found to be a remanence carrier in several types of meteorites (carbonaceous chondrites, SNC…), which justifies the usage of synthetic compositions as analogous to natural samples. Data were collected from 5 to 633 K and include low-field magnetic susceptibility (χ0), thermomagnetic curves, major hysteresis loops, back-field remanence demagnetization curves, first-order reversal curves (FORCs), alternating field and pressure demagnetization of saturation isothermal remanent magnetization (SIRM), low temperature data (such as zero-field-cooled and field-cooled remanence datasets together with room temperature SIRM cooling-warming cycles) as well as XRD and Mössbauer spectra. The characteristic Besnus transition is observed at ∼33 K. FORC diagrams indicate interacting SD grains. The application of hydrostatic pressure up to 2 GPa using nonmagnetic high-pressure cells resulted in the demagnetization of the sample by 32-38%. Repeated cycling from 1.8 GPa to atmospheric pressure and back resulted in a total remanence decrease of 44% (after 3 cycles). Pressure demagnetization experiments have important implications for meteorite paleomagnetism and suggest that some published paleointensities of meteorites with non-ideal SD monoclinic pyrrhotite as remanence carrier may be lower limits because shock demagnetization was not accounted for.

  2. Patterning process exploration of metal 1 layer in 7nm node with 3D patterning flow simulations

    NASA Astrophysics Data System (ADS)

    Gao, Weimin; Ciofi, Ivan; Saad, Yves; Matagne, Philippe; Bachmann, Michael; Oulmane, Mohamed; Gillijns, Werner; Lucas, Kevin; Demmerle, Wolfgang; Schmoeller, Thomas

    2015-03-01

    In 7mn node (N7), the logic design requires the critical poly pitch (CPP) of 42-45nm and metal 1 (M1) pitch of 28- 32nm. Such high pattern density pushes the 193 immersion lithography solution toward its limit and also brings extremely complex patterning scenarios. The N7 M1 layer may require a self-aligned quadruple patterning (SAQP) with triple litho-etch (LE3) block process. Therefore, the whole patterning process flow requires multiple exposure+etch+deposition processes and each step introduces a particular impact on the pattern profiles and the topography. In this study, we have successfully integrated a simulation tool that enables emulation of the whole patterning flow with realistic process-dependent 3D profile and topology. We use this tool to study the patterning process variations of N7 M1 layer including the overlay control, the critical dimension uniformity (CDU) budget and the lithographic process window (PW). The resulting 3D pattern structure can be used to optimize the process flow, verify design rules, extract parasitics, and most importantly, simulate the electric field and identify hot spots for dielectric reliability. As an example application, we will report extractions of maximum electric field at M1 tipto- tip which is one of the most critical patterning locations and we will demonstrate the potential of this approach for investigating the impact of process variations on dielectric reliability. We will also present simulations of an alternative M1 patterning flow, with a single exposure block using extreme ultraviolet lithography (EUVL) and analyze its advantages compared to the LE3 block approach.

  3. Analysis of Viking infrared thermal mapping data of Mars. The effects of non-ideal surfaces on the derived thermal properties of Mars

    NASA Technical Reports Server (NTRS)

    Muhleman, D. O.; Jakosky, B. M.

    1979-01-01

    The thermal interia of the surface of Mars varies spatially by a factor of eight. This is attributable to changes in the average particle size of the fine material, the surface elevation, the atmospheric opacity due to dust, and the fraction of the surface covered by rocks and fine material. The effects of these non-ideal properties on the surface temperatures and derived thermal inertias are modeled, along with the the effects of slopes, CO2 condensed onto the surface, and layering of fine material upon solid rock. The non-ideal models are capable of producing thermal behavior similar to that observed by the Viking Infrared Thermal Mapper, including a morning delay in the post-dawn temperature rise and an enhanced cooling in the afternoon relative to any ideal, homogeneous model. The enhanced afternoon cooling observed at the Viking-1 landing site is reproduced by the non-ideal models while that atop Arsia Mons volcano is not, but may be attributed to the observing geometry.

  4. Application of holographic interferometry to flow pattern visualization in a RTCVD reactor

    SciTech Connect

    Rainova, Yu.P.; Antonenko, K.I.; Pezoldt, J.; Eichhorn, G.

    1996-12-01

    This paper presents the development of an experimental technique for the reception of holographic interferograms of H{sub 2} and Ar flows in a RTCVD reactor with a complex geometry. The obtained holographic patterns were analyzed for the reconstruction of the gas flow in the RTCVD reactor. The fringe patterns showing the gas density distributions were recalculated into temperature distributions. Experimental results were compared with the predicted flow field.

  5. Flow patterns of magma in dikes, Makhtesh Ramon, Israel

    SciTech Connect

    Baer, G.; Reches, Z.

    1987-06-01

    Directions of magma flow were measured in a system of radial dikes in Makhtesh Ramon, Israel. The flow directions were determined from field observations of segments, fingers, grooves, and groove molds of the dikes. The study indicates that the mean axis of magma flow is subhorizontal toward the north, in agreement with the direction of divergence of the radial dike system. Two modes of flow were observed: (1) regular, bedding-parallel flow in the well-stratified rock units and (2) irregular, meandering flow in the massive rock units. It is suggested that corrugated dike walls in well-stratified host rocks cause magma channelization, and random or self-generated restrictions in massive host rocks cause the apparent meanders. Furthermore, the major lithologic boundaries in the host units strongly affect segmentation of the dikes.

  6. OPTIMIZATION OF COAL PARTICLE FLOW PATTERNS IN LOW NOX BURNERS

    SciTech Connect

    Jost O.L. Wendt; Gregory E. Ogden; Jennifer Sinclair; Caner Yurteri

    2001-08-20

    The proposed research is directed at evaluating the effect of flame aerodynamics on NO{sub x} emissions from coal fired burners in a systematic manner. This fundamental research includes both experimental and modeling efforts being performed at the University of Arizona in collaboration with Purdue University. The objective of this effort is to develop rational design tools for optimizing low NO{sub x} burners to the kinetic emissions limit (below 0.2 lb./MMBTU). Experimental studies include both cold and hot flow evaluations of the following parameters: flame holder geometry, secondary air swirl, primary and secondary inlet air velocity, coal concentration in the primary air and coal particle size distribution. Hot flow experiments will also evaluate the effect of wall temperature on burner performance. Cold flow studies will be conducted with surrogate particles as well as pulverized coal. The cold flow furnace will be similar in size and geometry to the hot-flow furnace but will be designed to use a laser Doppler velocimeter/phase Doppler particle size analyzer. The results of these studies will be used to predict particle trajectories in the hot-flow furnace as well as to estimate the effect of flame holder geometry on furnace flow field. The hot-flow experiments will be conducted in a novel near-flame down-flow pulverized coal furnace. The furnace will be equipped with externally heated walls. Both reactors will be sized to minimize wall effects on particle flow fields. The cold-flow results will be compared with Fluent computation fluid dynamics model predictions and correlated with the hot-flow results with the overall goal of providing insight for novel low NO{sub x} burner geometry's.

  7. Longitudinal cerebral blood flow and amyloid deposition: an emerging pattern?

    PubMed Central

    Sojkova, Jitka; Beason-Held, Lori; Zhou, Yun; An, Yang; Kraut, Michael A; Ye, Weigo; Ferrucci, Luigi; Mathis, Chester A; Klunk, William E; Wong, Dean F; Resnick, Susan M

    2008-01-01

    Although cerebral amyloid deposition may precede cognitive impairment by decades, the relationship between amyloid deposition and longitudinal change in neuronal function has not been studied. The aim of this paper is to determine whether nondemented individuals with high and low amyloid burden show different patterns of longitudinal regional cerebral blood flow (rCBF) changes in the years preceding measurement of amyloid deposition. Methods Twenty-eight nondemented participants (mean (SD) age at [11C] PIB 82.5(4.8) yrs; 6 mildly impaired) from the Baltimore Longitudinal Study of Aging underwent yearly resting-state [15O]H2O PET scans for up to 8 years. [11C]PIB images of amyloid deposition were acquired on average 10.8(0.8) years after the first CBF scan. [11C]PIB distribution volume ratios (DVR) of regions of interest were estimated by fitting a reference tissue model to the measured time activity curves. Based on mean cortical DVR, participants were divided into high and low [11C]PIB retention groups. Differences in longitudinal rCBF changes between high and low [11C]PIB groups were investigated by voxel-based analysis. Results Longitudinal rCBF changes differed significantly between high (n=10) and low (n=18) [11C]PIB groups (p<=0.001). Greater longitudinal decreases in rCBF in the high [11C]PIB group were seen in right anterior/mid cingulate, right supramarginal gyrus, left thalamus and midbrain bilaterally relative to the low group. Greater increases in rCBF over time in the high [11C]PIB group were found in left medial and inferior frontal gyri, right precuneus, left inferior parietal lobule, and the left postcentral gyrus. Conclusion In this group of nondemented older adults, those with high [11C]PIB show greater longitudinal declines in rCBF in certain areas, representing regions with greater decrements in neuronal function. Greater longitudinal increases in rCBF are also observed in those with higher amyloid load and may represent an attempt to preserve

  8. Flow pattern changes influenced by variation of viscosities of a heterogeneous gas-liquid mixture flow in a vertical channel

    SciTech Connect

    Keska, Jerry K.; Hincapie, Juan; Jones, Richard

    2011-02-15

    In the steady-state flow of a heterogeneous mixture such as an air-liquid mixture, the velocity and void fraction are space- and time-dependent parameters. These parameters are the most fundamental in the analysis and description of a multiphase flow. The determination of flow patterns in an objective way is extremely critical, since this is directly related to sudden changes in spatial and temporal changes of the random like characteristic of concentration. Flow patterns can be described by concentration signals in time, amplitude, and frequency domains. Despite the vital importance and countless attempts to solve or incorporate the flow pattern phenomena into multiphase models, it has still been a very challenging topic in the scientific community since the 1940's and has not yet reached a satisfactory solution. This paper reports the experimental results of the impact of fluid viscosity on flow patterns for two-phase flow. Two-phase flow was created in laboratory equipment using air and liquid as phase medium. The liquid properties were changed by using variable concentrations of glycerol in water mixture which generated a wide-range of dynamic viscosities ranging from 1 to 1060 MPa s. The in situ spatial concentration vs. liquid viscosity and airflow velocity of two-phase flow in a vertical ID=50.8 mm pipe were measured using two concomitant computer-aided measurement systems. After acquiring data, the in situ special concentration signals were analyzed in time (spatial concentration and RMS of spatial concentration vs. time), amplitude (PDF and CPDF), and frequency (PSD and CPSD) domains that documented broad flow pattern changes caused by the fluid viscosity and air velocity changes. (author)

  9. Hyporheic flow patterns in relation to large river floodplain attributes

    EPA Science Inventory

    Field-calibrated models of hyporheic flow have emphasized low-order headwater systems. In many cases, however, hyporheic flow in large lowland river floodplains may be an important contributor to ecosystem services such as maintenance of water quality and habitat. In this study, ...

  10. Effect of diastolic flow patterns on the function of the left ventricle

    NASA Astrophysics Data System (ADS)

    Seo, Jung Hee; Mittal, Rajat

    2013-11-01

    Direct numerical simulations are used to study the effect of intraventricular flow patterns on the pumping efficiency and the blood mixing and transport characteristics of the left ventricle. The simulations employ a geometric model of the left ventricle which is derived from contrast computed tomography. A variety of diastolic flow conditions are generated for a fixed ejection fraction in order to delineate the effect of flow patterns on ventricular performance. The simulations indicate that the effect of intraventricular blood flow pattern on the pumping power is physiologically insignificant. However, diastolic flow patterns have a noticeable effect on the blood mixing as well as the residence time of blood cells in the ventricle. The implications of these findings on ventricular function are discussed.

  11. Flow pattern and mass transfer characteristics of valve tray in absorption process

    NASA Astrophysics Data System (ADS)

    Nurkhamidah, Siti; Altway, Ali; Wulansari, Ayu Savitri; Khanifah, Evi Fitriyah

    2015-12-01

    The flow pattern characteristics of valve tray in absorption process which is expressed in pressure drop and the number of equivalent tank in series (N) has an important role to know the efficiency and performance of a process. This study has been done in the absorption column by using water and air as liquid and gas phase, respectively. To observe pressure drop and flow pattern in the column, flow rate of liquid and air has been variated. Flow pattern has been determined by using pulse method and using NaCl as tracer. The experiment results show that the column pressure drop is mainly influenced by the liquid height on the tray. When the water flow rate is high, liquid height on the tray is higher so that the column pressure drops increases. Flow pattern characteristic of fluid on valve tray is affected by water and air flowrates. For high water flow rate, the residence time distribution (RTD) curve is sharper and the number of N is greater and the flow pattern tends to a plug flow. However, the number of N decreases when the air flowrate increases. The liquid-side mass transfer coefficient (kLa') is shown by the following empirical relationship kLa' = 2,607QL0,202Qv0,456.

  12. Flow regime and deposition pattern of evaporating binary mixture droplet suspended with particles.

    PubMed

    Zhong, Xin; Duan, Fei

    2016-02-01

    The flow regimes and the deposition pattern have been investigated by changing the ethanol concentration in a water-based binary mixture droplet suspended with alumina nanoparticles. To visualize the flow patterns, Particle Image Velocimetry (PIV) has been applied in the binary liquid droplet containing the fluorescent microspheres. Three distinct flow regimes have been revealed in the evaporation. In Regime I, the vortices and chaotic flows are found to carry the particles to the liquid-vapor interface and to promote the formation of particle aggregation. The aggregates move inwards in Regime II as induced by the Marangoni flow along the droplet free surface. Regime III is dominated by the drying of the left water and the capillary flow driving particles radially outward is observed. The relative weightings of Regimes I and II, which are enhanced with an increasing load of ethanol, determine the motion of the nanoparticles and the formation of the final drying pattern. PMID:26920521

  13. Variability of sap flow on forest hillslopes: patterns and controls

    NASA Astrophysics Data System (ADS)

    Hassler, Sibylle; Blume, Theresa

    2013-04-01

    Sap flow in trees is an essential variable in integrated studies of hydrologic fluxes. It gives indication of transpiration rates for single trees and, with a suitable method of upscaling, for whole stands. This information is relevant for hydrologic and climate models, especially for the prediction of change in water fluxes in the soil-plant-atmosphere continuum under climate change. To this end, we do not only need knowledge concerning the response of sapflow to atmospheric forcing but also an understanding of the main controls on its spatial variability. Our study site consists of several subcatchments of the Attert basin in Luxembourg underlain by schists of the Ardennes massif. Within these subcatchments we measure sap flow in more than 20 trees on a range of forested hillslopes covered by a variety of temperate deciduous tree species such as beech, oak, hornbeam and maple as well as conifers such as firs. Our sap flow sensors are based on the heat pulse velocity method and consist of three needles, one needle acting as the heating device and the other two holding three thermistors each, enabling us to simultaneously measure sap flow velocity at three different depths within the tree. In close proximity to the trees we collect additional data on soil moisture, matric potential and groundwater levels. First results show that the sensor design seems promising for an upscaling of the measured sap flow velocities to sap flow at the tree level. The maximum depth of actively used sapwood as well as the decrease in sap flow velocity with increasing depth in the tree can be determined by way of the three thermistors. Marked differences in sap flow velocity profiles are visible between the different species, resulting in differences in sap flow for trees of similar diameter. We examine the range of tree sap flow values and variation due to species, size class, slope position and exposition and finally relate them to the dynamics of soil moisture conditions with the

  14. Parametric study of flow patterns behind the standing accretion shock wave for core-collapse supernovae

    SciTech Connect

    Iwakami, Wakana; Nagakura, Hiroki; Yamada, Shoichi

    2014-05-10

    In this study, we conduct three-dimensional hydrodynamic simulations systematically to investigate the flow patterns behind the accretion shock waves that are commonly formed in the post-bounce phase of core-collapse supernovae. Adding small perturbations to spherically symmetric, steady, shocked accretion flows, we compute the subsequent evolutions to find what flow pattern emerges as a consequence of hydrodynamical instabilities such as convection and standing accretion shock instability for different neutrino luminosities and mass accretion rates. Depending on these two controlling parameters, various flow patterns are indeed realized. We classify them into three basic patterns and two intermediate ones; the former includes sloshing motion (SL), spiral motion (SP), and multiple buoyant bubble formation (BB); the latter consists of spiral motion with buoyant-bubble formation (SPB) and spiral motion with pulsationally changing rotational velocities (SPP). Although the post-shock flow is highly chaotic, there is a clear trend in the pattern realization. The sloshing and spiral motions tend to be dominant for high accretion rates and low neutrino luminosities, and multiple buoyant bubbles prevail for low accretion rates and high neutrino luminosities. It is interesting that the dominant pattern is not always identical between the semi-nonlinear and nonlinear phases near the critical luminosity; the intermediate cases are realized in the latter case. Running several simulations with different random perturbations, we confirm that the realization of flow pattern is robust in most cases.

  15. Children's Brain Responses to Optic Flow Vary by Pattern Type and Motion Speed.

    PubMed

    Gilmore, Rick O; Thomas, Amanda L; Fesi, Jeremy

    2016-01-01

    Structured patterns of global visual motion called optic flow provide crucial information about an observer's speed and direction of self-motion and about the geometry of the environment. Brain and behavioral responses to optic flow undergo considerable postnatal maturation, but relatively little brain imaging evidence describes the time course of development in motion processing systems in early to middle childhood, a time when psychophysical data suggest that there are changes in sensitivity. To fill this gap, electroencephalographic (EEG) responses were recorded in 4- to 8-year-old children who viewed three time-varying optic flow patterns (translation, rotation, and radial expansion/contraction) at three different speeds (2, 4, and 8 deg/s). Modulations of global motion coherence evoked coherent EEG responses at the first harmonic that differed by flow pattern and responses at the third harmonic and dot update rate that varied by speed. Pattern-related responses clustered over right lateral channels while speed-related responses clustered over midline channels. Both children and adults show widespread responses to modulations of motion coherence at the second harmonic that are not selective for pattern or speed. The results suggest that the developing brain segregates the processing of optic flow pattern from speed and that an adult-like pattern of neural responses to optic flow has begun to emerge by early to middle childhood. PMID:27326860

  16. Children's Brain Responses to Optic Flow Vary by Pattern Type and Motion Speed

    PubMed Central

    Thomas, Amanda L.; Fesi, Jeremy

    2016-01-01

    Structured patterns of global visual motion called optic flow provide crucial information about an observer's speed and direction of self-motion and about the geometry of the environment. Brain and behavioral responses to optic flow undergo considerable postnatal maturation, but relatively little brain imaging evidence describes the time course of development in motion processing systems in early to middle childhood, a time when psychophysical data suggest that there are changes in sensitivity. To fill this gap, electroencephalographic (EEG) responses were recorded in 4- to 8-year-old children who viewed three time-varying optic flow patterns (translation, rotation, and radial expansion/contraction) at three different speeds (2, 4, and 8 deg/s). Modulations of global motion coherence evoked coherent EEG responses at the first harmonic that differed by flow pattern and responses at the third harmonic and dot update rate that varied by speed. Pattern-related responses clustered over right lateral channels while speed-related responses clustered over midline channels. Both children and adults show widespread responses to modulations of motion coherence at the second harmonic that are not selective for pattern or speed. The results suggest that the developing brain segregates the processing of optic flow pattern from speed and that an adult-like pattern of neural responses to optic flow has begun to emerge by early to middle childhood. PMID:27326860

  17. Remarks on the derivation of the governing equations for the dynamics of a nonlinear beam to a non ideal shaft coupling

    SciTech Connect

    Fenili, André; Lopes Rebello da Fonseca Brasil, Reyolando Manoel

    2014-12-10

    We derive nonlinear governing equations without assuming that the beam is inextensible. The derivation couples the equations that govern a weak electric motor, which is used to rotate the base of the beam, to those that govern the motion of the beam. The system is considered non-ideal in the sense that the response of the motor to an applied voltage and the motion of the beam must be obtained interactively. The moment that the motor exerts on the base of the beam cannot be determined without solving for the motion of the beam.

  18. Magnetic field induced flow pattern reversal in a ferrofluidic Taylor-Couette system

    NASA Astrophysics Data System (ADS)

    Altmeyer, Sebastian; Do, Younghae; Lai, Ying-Cheng

    2015-12-01

    We investigate the dynamics of ferrofluidic wavy vortex flows in the counter-rotating Taylor-Couette system, with a focus on wavy flows with a mixture of the dominant azimuthal modes. Without external magnetic field flows are stable and pro-grade with respect to the rotation of the inner cylinder. More complex behaviors can arise when an axial or a transverse magnetic field is applied. Depending on the direction and strength of the field, multi-stable wavy states and bifurcations can occur. We uncover the phenomenon of flow pattern reversal as the strength of the magnetic field is increased through a critical value. In between the regimes of pro-grade and retrograde flow rotations, standing waves with zero angular velocities can emerge. A striking finding is that, under a transverse magnetic field, a second reversal in the flow pattern direction can occur, where the flow pattern evolves into pro-grade rotation again from a retrograde state. Flow reversal is relevant to intriguing phenomena in nature such as geomagnetic reversal. Our results suggest that, in ferrofluids, flow pattern reversal can be induced by varying a magnetic field in a controlled manner, which can be realized in laboratory experiments with potential applications in the development of modern fluid devices.

  19. Magnetic field induced flow pattern reversal in a ferrofluidic Taylor-Couette system

    PubMed Central

    Altmeyer, Sebastian; Do, Younghae; Lai, Ying-Cheng

    2015-01-01

    We investigate the dynamics of ferrofluidic wavy vortex flows in the counter-rotating Taylor-Couette system, with a focus on wavy flows with a mixture of the dominant azimuthal modes. Without external magnetic field flows are stable and pro-grade with respect to the rotation of the inner cylinder. More complex behaviors can arise when an axial or a transverse magnetic field is applied. Depending on the direction and strength of the field, multi-stable wavy states and bifurcations can occur. We uncover the phenomenon of flow pattern reversal as the strength of the magnetic field is increased through a critical value. In between the regimes of pro-grade and retrograde flow rotations, standing waves with zero angular velocities can emerge. A striking finding is that, under a transverse magnetic field, a second reversal in the flow pattern direction can occur, where the flow pattern evolves into pro-grade rotation again from a retrograde state. Flow reversal is relevant to intriguing phenomena in nature such as geomagnetic reversal. Our results suggest that, in ferrofluids, flow pattern reversal can be induced by varying a magnetic field in a controlled manner, which can be realized in laboratory experiments with potential applications in the development of modern fluid devices. PMID:26687638

  20. Magnetic field induced flow pattern reversal in a ferrofluidic Taylor-Couette system.

    PubMed

    Altmeyer, Sebastian; Do, Younghae; Lai, Ying-Cheng

    2015-01-01

    We investigate the dynamics of ferrofluidic wavy vortex flows in the counter-rotating Taylor-Couette system, with a focus on wavy flows with a mixture of the dominant azimuthal modes. Without external magnetic field flows are stable and pro-grade with respect to the rotation of the inner cylinder. More complex behaviors can arise when an axial or a transverse magnetic field is applied. Depending on the direction and strength of the field, multi-stable wavy states and bifurcations can occur. We uncover the phenomenon of flow pattern reversal as the strength of the magnetic field is increased through a critical value. In between the regimes of pro-grade and retrograde flow rotations, standing waves with zero angular velocities can emerge. A striking finding is that, under a transverse magnetic field, a second reversal in the flow pattern direction can occur, where the flow pattern evolves into pro-grade rotation again from a retrograde state. Flow reversal is relevant to intriguing phenomena in nature such as geomagnetic reversal. Our results suggest that, in ferrofluids, flow pattern reversal can be induced by varying a magnetic field in a controlled manner, which can be realized in laboratory experiments with potential applications in the development of modern fluid devices. PMID:26687638

  1. Sequential Learning and Recognition of Comprehensive Behavioral Patterns Based on Flow of People

    NASA Astrophysics Data System (ADS)

    Gibo, Tatsuya; Aoki, Shigeki; Miyamoto, Takao; Iwata, Motoi; Shiozaki, Akira

    Recently, surveillance cameras have been set up everywhere, for example, in streets and public places, in order to detect irregular situations. In the existing surveillance systems, as only a handful of surveillance agents watch a large number of images acquired from surveillance cameras, there is a possibility that they may miss important scenes such as accidents or abnormal incidents. Therefore, we propose a method for sequential learning and the recognition of comprehensive behavioral patterns in crowded places. First, we comprehensively extract a flow of people from input images by using optical flow. Second, we extract behavioral patterns on the basis of change-point detection of the flow of people. Finally, in order to recognize an observed behavioral pattern, we draw a comparison between the behavioral pattern and previous behavioral patterns in the database. We verify the effectiveness of our approach by placing a surveillance camera on a campus.

  2. Surface Patterning: Controlling Fluid Flow Through Dolphin and Shark Skin Biomimicry

    NASA Astrophysics Data System (ADS)

    Gamble, Lawren; Lang, Amy; Bradshaw, Michael; McVay, Eric

    2013-11-01

    Dolphin skin is characterized by circumferential ridges, perpendicular to fluid flow, present from the crest of the head until the tail fluke. When observing a cross section of skin, the ridges have a sinusoidal pattern. Sinusoidal grooves have been proven to induce vortices in the cavities that can help control flow separation which can reduce pressure drag. Shark skin, however, is patterned with flexible scales that bristle up to 50 degrees with reversed flow. Both dolphin ridges and shark scales are thought to help control fluid flow and increase swimming efficiency by delaying the separation of the boundary layer. This study investigates how flow characteristics can be altered with bio-inspired surface patterning. A NACA 4412 hydrofoil was entirely patterned with transverse sinusoidal grooves, inspired by dolphin skin but scaled so the cavities on the model have the same Reynolds number as the cavities on a swimming shark. Static tests were conducted at a Reynolds number of approximately 100,000 and at varying angles of attack. The results were compared to the smooth hydrofoil case. The flow data was quantified using Digital Particle Image Velocimetry (DPIV). The results of this study demonstrated that the patterned hydrofoil experienced greater separation than the smooth hydrofoil. It is hypothesize that this could be remediated if the pattern was placed only after the maximum thickness of the hydrofoil. Funding through NSF REU grant 1062611 is gratefully acknowledged.

  3. MotionFlow: Visual Abstraction and Aggregation of Sequential Patterns in Human Motion Tracking Data.

    PubMed

    Jang, Sujin; Elmqvist, Niklas; Ramani, Karthik

    2016-01-01

    Pattern analysis of human motions, which is useful in many research areas, requires understanding and comparison of different styles of motion patterns. However, working with human motion tracking data to support such analysis poses great challenges. In this paper, we propose MotionFlow, a visual analytics system that provides an effective overview of various motion patterns based on an interactive flow visualization. This visualization formulates a motion sequence as transitions between static poses, and aggregates these sequences into a tree diagram to construct a set of motion patterns. The system also allows the users to directly reflect the context of data and their perception of pose similarities in generating representative pose states. We provide local and global controls over the partition-based clustering process. To support the users in organizing unstructured motion data into pattern groups, we designed a set of interactions that enables searching for similar motion sequences from the data, detailed exploration of data subsets, and creating and modifying the group of motion patterns. To evaluate the usability of MotionFlow, we conducted a user study with six researchers with expertise in gesture-based interaction design. They used MotionFlow to explore and organize unstructured motion tracking data. Results show that the researchers were able to easily learn how to use MotionFlow, and the system effectively supported their pattern analysis activities, including leveraging their perception and domain knowledge. PMID:26529685

  4. Measurement of Flow Patterns and Dispersion in the Human Airways

    NASA Astrophysics Data System (ADS)

    Fresconi, Frank E.; Prasad, Ajay K.

    2006-03-01

    A detailed knowledge of the flow and dispersion within the human respiratory tract is desirable for numerous reasons. Both risk assessments of exposure to toxic particles in the environment and the design of medical delivery systems targeting both lung-specific conditions (asthma, cystic fibrosis, and chronic obstructive pulmonary disease (COPD)) and system-wide ailments (diabetes, cancer, hormone replacement) would profit from such an understanding. The present work features experimental efforts aimed at elucidating the fluid mechanics of the lung. Particle image velocimetry (PIV) and laser induced fluorescence (LIF) measurements of oscillatory flows were undertaken in anatomically accurate models (single and multi-generational) of the conductive region of the lung. PIV results captured primary and secondary velocity fields. LIF was used to determine the amount of convective dispersion across an individual generation of the lung.

  5. Tracking the flow of hippocampal computation: Pattern separation, pattern completion, and attractor dynamics.

    PubMed

    Knierim, James J; Neunuebel, Joshua P

    2016-03-01

    Classic computational theories of the mnemonic functions of the hippocampus ascribe the processes of pattern separation to the dentate gyrus (DG) and pattern completion to the CA3 region. Until the last decade, the large majority of single-unit studies of the hippocampus in behaving animals were from the CA1 region. The lack of data from the DG, CA3, and the entorhinal inputs to the hippocampus severely hampered the ability to test these theories with neurophysiological techniques. The past ten years have seen a major increase in the recordings from the CA3 region and the medial entorhinal cortex (MEC), with an increasing (but still limited) number of experiments from the lateral entorhinal cortex (LEC) and DG. This paper reviews a series of studies in a local-global cue mismatch (double-rotation) experiment in which recordings were made from cells in the anterior thalamus, MEC, LEC, DG, CA3, and CA1 regions. Compared to the standard cue environment, the change in the DG representation of the cue-mismatch environment was greater than the changes in its entorhinal inputs, providing support for the theory of pattern separation in the DG. In contrast, the change in the CA3 representation of the cue-mismatch environment was less than the changes in its entorhinal and DG inputs, providing support for a pattern completion/error correction function of CA3. The results are interpreted in terms of continuous attractor network models of the hippocampus and the relationship of these models to pattern separation and pattern completion theories. Whereas DG may perform an automatic pattern separation function, the attractor dynamics of CA3 allow it to perform a pattern separation or pattern completion function, depending on the nature of its inputs and the relative strength of the internal attractor dynamics. PMID:26514299

  6. Vapor Flow Patterns During a Start-Up Transient in Heat Pipes

    NASA Technical Reports Server (NTRS)

    Issacci, F.; Ghoniem, N, M.; Catton, I.

    1996-01-01

    The vapor flow patterns in heat pipes are examined during the start-up transient phase. The vapor core is modelled as a channel flow using a two dimensional compressible flow model. A nonlinear filtering technique is used as a post process to eliminate the non-physical oscillations of the flow variables. For high-input heat flux, multiple shock reflections are observed in the evaporation region. The reflections cause a reverse flow in the evaporation and circulations in the adiabatic region. Furthermore, each shock reflection causes a significant increase in the local pressure and a large pressure drop along the heat pipe.

  7. Numerical analysis of respiratory flow patterns within human upper airway

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Liu, Yingxi; Sun, Xiuzhen; Yu, Shen; Gao, Fei

    2009-12-01

    A computational fluid dynamics (CFD) approach is used to study the respiratory airflow dynamics within a human upper airway. The airway model which consists of the airway from nasal cavity, pharynx, larynx and trachea to triple bifurcation is built based on the CT images of a healthy volunteer and the Weibel model. The flow characteristics of the whole upper airway are quantitatively described at any time level of respiratory cycle. Simulation results of respiratory flow show good agreement with the clinical measures, experimental and computational results in the literature. The air mainly passes through the floor of the nasal cavity in the common, middle and inferior nasal meatus. The higher airway resistance and wall shear stresses are distributed on the posterior nasal valve. Although the airways of pharynx, larynx and bronchi experience low shear stresses, it is notable that relatively high shear stresses are distributed on the wall of epiglottis and bronchial bifurcations. Besides, two-dimensional fluid-structure interaction models of normal and abnormal airways are built to discuss the flow-induced deformation in various anatomy models. The result shows that the wall deformation in normal airway is relatively small.

  8. OPTIMIZATION OF COAL PARTICLE FLOW PATTERNS IN LOW NOX BURNERS

    SciTech Connect

    Jost O.L. Wendt; Gregory E. Ogden; Jennifer Sinclair; Stephanus Budilarto

    2001-09-04

    It is well understood that the stability of axial diffusion flames is dependent on the mixing behavior of the fuel and combustion air streams. Combustion aerodynamic texts typically describe flame stability and transitions from laminar diffusion flames to fully developed turbulent flames as a function of increasing jet velocity. Turbulent diffusion flame stability is greatly influenced by recirculation eddies that transport hot combustion gases back to the burner nozzle. This recirculation enhances mixing and heats the incoming gas streams. Models describing these recirculation eddies utilize conservation of momentum and mass assumptions. Increasing the mass flow rate of either fuel or combustion air increases both the jet velocity and momentum for a fixed burner configuration. Thus, differentiating between gas velocity and momentum is important when evaluating flame stability under various operating conditions. The research efforts described herein are part of an ongoing project directed at evaluating the effect of flame aerodynamics on NO{sub x} emissions from coal fired burners in a systematic manner. This research includes both experimental and modeling efforts being performed at the University of Arizona in collaboration with Purdue University. The objective of this effort is to develop rational design tools for optimizing low NO{sub x} burners. Experimental studies include both cold-and hot-flow evaluations of the following parameters: primary and secondary inlet air velocity, coal concentration in the primary air, coal particle size distribution and flame holder geometry. Hot-flow experiments will also evaluate the effect of wall temperature on burner performance.

  9. Patterned Periodic Nanofilter Array for Continuous-Flow Bimolecular Separation

    NASA Astrophysics Data System (ADS)

    Fu, Jianping; Han, Jongyoon

    2006-03-01

    We present an experimental study on sieving process of small biomolecules (i.e., proteins and small DNAs) in one- and two-dimensional periodic arrays of nanofilter. The nanofilters served as artificial sieves with precise pore size characterization and showed exceptional size selectivity and separation efficiency from the periodicity of the environment. A kinetic model is developed to explain the electrophoretic drift of charged molecules across periodically modulated free energy landscapes. Further experimental evidence shows the crossover from Ogston-like sieving to entropic trapping mechanism depending on nanofilter thickness and on electric field strength. We also demonstrate continuous-flow biomolecule separation with a device containing of two-dimensional periodic nanofilter arrays. The interaction between migrating molecules and the two-dimensional physical landscapes cause molecules of different sizes to follow radically different paths leading to separation. Continuous-flow fractionations of small DNA molecules (50bp-766bp) as well as SDS-protein complexes (11kDa-200kDa) were achieved in about 5 minutes with a resolution of 10%. By virtue of its gel-free and continuous-flow operation, this device suggests himself a key component to an integrated biomolecule sample preparation and analysis microsystem.

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

    PubMed

    Liepsch, D W

    1990-01-01

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

  11. Liquid-liquid extraction based on a new flow pattern: Two-fluid Taylor-Couette flow

    NASA Astrophysics Data System (ADS)

    Baier, Gretchen

    The exploitation of flow instabilities that can occur in rotating flows is investigated as a new approach to liquid extraction. Two immiscible liquids are radially stratified by centrifugal force in the annulus between corotating coaxial cylinders. The inner cylinder is rotated above a critical speed to form Taylor vortices in one or both of the fluids. This flow pattern produces a relatively small amount interfacial surface area that is of highly active for interphase mass transfer. Continuous processing is also possible with the addition of countercurrent axial flow. The present study includes: (1)A review of aqueous- aqueous and reversed micelle extraction techniques, the commercially available centrifugal extractors, and one fluid Taylor-Couette flow and its variations. (2)A theoretical analysis to predict the onset of the two- fluid Taylor-Couette instability in the presence of countercurrent axial flow. (3)Theoretical predictions for interphase mass transfer using penetration theory and computational fluid dynamics. (4)The demonstration of two-fluid Taylor-Couette flow with countercurrent axial flow in the laboratory, including: (1) fluid mechanics studies to determine the onset of vortices, and (2) mass transfer studies to characterize intraphase and interphase mass transfer. The agreement between the experiments and theory is good for both the fluid mechanics and the mass transfer. Furthermore, the extraction performance is quite promising with the mass transfer coefficient approximately proportional to the vortex strength. Even higher extraction efficiencies should be obtainable with even larger relative rotation rates or cylinder modification to promote vortex formation. Besides two-fluid Taylor-Couette flow, other instabilities can also occur. With low viscosity fluids at low rotation rates, the ``barber pole'' pattern is observed experimentally and is believed to be a lingering gravitational effect. At high countercurrent axial flowrates, the linear

  12. Direct numerical simulation of two-phase flow: Effective rheology and flow patterns of particle suspensions

    NASA Astrophysics Data System (ADS)

    Deubelbeiss, Y.; Kaus, B. J. P.; Connolly, J. A. D.

    2010-02-01

    We analyze the mechanical behavior of a two-phase system consisting of rigid grains and an interconnected pore fluid. For this purpose we use 2D direct numerical simulations on the spatial scale of individual grains for Newtonian and non-Newtonian fluid rheology. By using the stress-strain rate relation we derive scaling laws for effective viscosity of two-phase particle suspensions. We demonstrate that the effective rheology of the assemblage is non-Newtonian only if the fluid has a non-Newtonian rheology. At small fluid fraction, inter-granular strain rates are up to 3 orders of magnitude higher than the applied background strain rate. We suggest that this effect explains the experimentally observed change at higher strain rates in rheology, from Newtonian to non-Newtonian aggregate rheology. To establish the conditions at which the fluid-solid aggregate deforms coherently as a consequence of Rayleigh-Taylor instabilities we studied flow patterns of particle suspensions and characterized them as a function of fluid fraction, viscosity, density, shape and size of the grains. From initial conditions with homogeneously distributed grains and interstitial fluid above a layer of pure fluid, our results show that the Rayleigh-Taylor instability dominates for moderate to large fluid fractions. At large fluid fractions, we observed a transition to a Stokes suspension mode, in which grains do not interact but sink independently. An analytical expression is derived that predicts the transition from Rayleigh-Taylor instability to Stokes suspension mode. The transition is a function of fluid fraction, radius of the grains, height of the interface and initial amplitude. Systematic numerical simulations are in good agreement with the analytical predictions.

  13. Robust phase retrieval for high resolution edge illumination x-ray phase-contrast computed tomography in non-ideal environments.

    PubMed

    Zamir, Anna; Endrizzi, Marco; Hagen, Charlotte K; Vittoria, Fabio A; Urbani, Luca; De Coppi, Paolo; Olivo, Alessandro

    2016-01-01

    Edge illumination x-ray phase contrast tomography is a recently developed imaging technique which enables three-dimensional visualisation of low-absorbing materials. Dedicated phase retrieval algorithms can provide separate computed tomography (CT) maps of sample absorption, refraction and scattering properties. In this paper we propose a novel "modified local retrieval" method which is capable of accurately retrieving sample properties in a range of realistic, non-ideal imaging environments. These include system misalignment, defects in the used optical elements and system geometry variations over time due to vibrations or temperature fluctuations. System instabilities were analysed, modelled and incorporated into a simulation study. As a result, an additional modification was introduced to the retrieval procedure to account for changes in the imaging system over time, as well as local variations over the field of view. The performance of the proposed method was evaluated in comparison to a previously used "global retrieval" method by applying both approaches to experimental CT data of a rat's heart acquired in a non-ideal environment. The use of the proposed method resulted in the removal of major artefacts, leading to a significant improvement in image quality. This method will therefore enable acquiring high-resolution, reliable CT data of large samples in realistic settings. PMID:27502296

  14. Robust phase retrieval for high resolution edge illumination x-ray phase-contrast computed tomography in non-ideal environments

    NASA Astrophysics Data System (ADS)

    Zamir, Anna; Endrizzi, Marco; Hagen, Charlotte K.; Vittoria, Fabio A.; Urbani, Luca; de Coppi, Paolo; Olivo, Alessandro

    2016-08-01

    Edge illumination x-ray phase contrast tomography is a recently developed imaging technique which enables three-dimensional visualisation of low-absorbing materials. Dedicated phase retrieval algorithms can provide separate computed tomography (CT) maps of sample absorption, refraction and scattering properties. In this paper we propose a novel “modified local retrieval” method which is capable of accurately retrieving sample properties in a range of realistic, non-ideal imaging environments. These include system misalignment, defects in the used optical elements and system geometry variations over time due to vibrations or temperature fluctuations. System instabilities were analysed, modelled and incorporated into a simulation study. As a result, an additional modification was introduced to the retrieval procedure to account for changes in the imaging system over time, as well as local variations over the field of view. The performance of the proposed method was evaluated in comparison to a previously used “global retrieval” method by applying both approaches to experimental CT data of a rat’s heart acquired in a non-ideal environment. The use of the proposed method resulted in the removal of major artefacts, leading to a significant improvement in image quality. This method will therefore enable acquiring high-resolution, reliable CT data of large samples in realistic settings.

  15. Robust phase retrieval for high resolution edge illumination x-ray phase-contrast computed tomography in non-ideal environments

    PubMed Central

    Zamir, Anna; Endrizzi, Marco; Hagen, Charlotte K.; Vittoria, Fabio A.; Urbani, Luca; De Coppi, Paolo; Olivo, Alessandro

    2016-01-01

    Edge illumination x-ray phase contrast tomography is a recently developed imaging technique which enables three-dimensional visualisation of low-absorbing materials. Dedicated phase retrieval algorithms can provide separate computed tomography (CT) maps of sample absorption, refraction and scattering properties. In this paper we propose a novel “modified local retrieval” method which is capable of accurately retrieving sample properties in a range of realistic, non-ideal imaging environments. These include system misalignment, defects in the used optical elements and system geometry variations over time due to vibrations or temperature fluctuations. System instabilities were analysed, modelled and incorporated into a simulation study. As a result, an additional modification was introduced to the retrieval procedure to account for changes in the imaging system over time, as well as local variations over the field of view. The performance of the proposed method was evaluated in comparison to a previously used “global retrieval” method by applying both approaches to experimental CT data of a rat’s heart acquired in a non-ideal environment. The use of the proposed method resulted in the removal of major artefacts, leading to a significant improvement in image quality. This method will therefore enable acquiring high-resolution, reliable CT data of large samples in realistic settings. PMID:27502296

  16. Uncertainty estimation of non-ideal analog switches using programmable Josephson voltage standards for mutual inductance measurement in the joule balance

    NASA Astrophysics Data System (ADS)

    Wang, Gang; Zhang, Zhonghua; Li, Zhengkun; Xu, Jinxin; You, Qiang

    2016-02-01

    Measurement of the mutual inductance is one of the key techniques in the joule balance to determine the Planck constant h, where a standard-square-wave compensation method was proposed to accurately measure the dc value of the mutual inductance. With this method, analog switches are used to compose an analog-switch signal generator to synthesize the excitation and compensation voltages. However, the accuracy of the compensation voltage is influenced by the non-ideal behaviors of analog-switches. In this paper, the effect from these non-ideal switches is analyzed in detail and evaluated with the equivalent circuits. A programmable Josephson voltage standard (PJVS) is used to generate a reference compensation voltage to measure the time integration of the voltage waveform generated by the analog-switch signal generator. Moreover, the effect is also evaluated experimentally by comparing the difference between the mutual inductance measured with the analog-switch signal generator and the value determined by the PJVS-analog-switch generator alternately in the same mutual inductance measurement system. The result shows that the impact of analog switches is 1.97  ×  10-7 with an uncertainty of 1.83  ×  10-7 (k  =  1) and confirms that the analog switch method can be used regularly instead of the PJVS in the mutual inductance measurement for the joule balance experiment.

  17. Reconstructing Flow Patterns from Tsunami Deposits with No Visible Sedimentary Structure

    NASA Astrophysics Data System (ADS)

    Kain, C. L.; Chague-Goff, C.; Goff, J. R.; Wassmer, P.; Gomez, C. A.; Hart, D. E.

    2014-12-01

    High energy coastal events, such as tsunamis, commonly leave sediment deposits in the landscape that may be preserved in the geological record. A set of anomalous sand and silt layers intercalated between soil units was identified alongside an estuary in Okains Bay, Banks Peninsula, New Zealand. Okains Bay, comprised of a coastal plain of Holocene progradational dune ridges, was flooded by tsunamis in 1868 and 1960. Previous research has assessed the relationship between tsunami flow patterns and sediment deposits for recent events, and we aim to extend this application to older deposits where flow patterns were not recorded and sedimentary structures are not visually apparent. A multi-proxy approach was used to investigate the sediment deposits at twelve sites along a 2 km length of the estuary margin and map inundation patterns. Measurements of Magnetic Fabric (MF: Anisotropy of Magnetic Susceptibility) were used to determine the flow direction during deposition, alongside stratigraphy and particle size analyses to assess wave energy. Flow direction results were overlaid on a digital elevation model of the study site to interpret flow patterns. Deposits became thinner and particle size decreased with distance from the coast, indicating waning flow energy with distance inland. MF results indicate that inundation occurred via the estuary channel, with primary flow directions oriented perpendicular or sub-perpendicular to the channel at each site. On a smaller scale, results showed evidence of current reversal at some sites, with flow directed alternately away from and towards the estuary channel. This is consistent with uprush and backwash patterns observed in tsunami wave sequences. Topographic control of flow patterns is also evident from the data. This research demonstrates a method for investigating older, structurally-degraded deposits and has implications for the reconstruction of paleotsunami inundation from their sedimentary deposits.

  18. Patterns and Processes in Southwestern shrublands and grasslands: role of vegetation, soil- geomorphology, and overland flow

    NASA Astrophysics Data System (ADS)

    Bedford, D. R.; Small, E. E.; E, T. G.

    2007-12-01

    Pattern of variable soil properties have been linked to vegetation as well as soil-landform characteristics and processes. It has been long hypothesized that patterns of infiltration and overland flow play key roles in arid and semi-arid region ecohydrology. Specifically, the process of redistribution of water and sediments have been linked to vegetation related feedbacks that enable persistence of vegetation in water limited environments. Yet, the processes of redistribution, such as through runoff and surface ponding, have been poorly described or documented. We have documented that the spatial pattern of soil properties is dependant on the vegetation pattern as well as the type of, and in some cases location within a, landform. These patterns are likely due to feedbacks between vegetation and the surface processes that affect soil properties and therefore water availability. In this paper, we present observations and numerical simulation that show how patterns of overland flow and infiltration are affected by vegetation-topography related patterns of soil properties. We have developed a numerical model that works on 10 cm grid cells that can inform on the processes of infiltration and overland flow over continuously varying soil properties. We use this model to show how the patterns of soil properties affect runoff, as well as the conditions under which redistribution via runon and ponding can occur. Furthermore, we show using data from a central New Mexico grassland and shrubland, and an eastern Mojave Desert shrubland how climatic differences can affect the patterns of infiltration and runoff.

  19. Experimental and numerical study of patterns in laryngeal flow

    NASA Astrophysics Data System (ADS)

    Chisari, N. E.; Artana, G.; Sciamarella, D.

    2009-05-01

    Unsteady airflow is investigated in a channel with a geometry approximating that of the human larynx. The laryngeal flow is simulated by solving the Navier-Stokes equations for an incompressible two-dimensional viscous fluid, and visualized using the Schlieren technique in an experimental setup consisting of a rigid replica of the larynx, with and without ventricular bands. This study shows the spontaneous formation of vortex couples in several regions of the laryngeal profile, and at different stages of the evolution of the starting glottal jet.

  20. Fractal patterns in turbulent flow for laden particles

    NASA Astrophysics Data System (ADS)

    Farhan, M.; Nicolleau, F. C. G. A.; Nowakowski, A. F.; Angilella, J.-R.

    2011-12-01

    We use Kinematic Simulation as a particular kind of synthetic turbulence model to study the preferential accumulation of laden particles with inertia and gravity. Particles are released as a unifrom cloud in the periodic simulation box. We allow particles to settle in synthetic flow and after some times particles concentrate in a particular sub-domain. We study the dimensional properties of these attractors as functions of drift parameter and Stokes number. The attractor's topology varies from curve(D = 1) to fractal plane.

  1. Flow-driven pattern formation in the calcium-oxalate system

    NASA Astrophysics Data System (ADS)

    Bohner, Bíborka; Endrődi, Balázs; Horváth, Dezső; Tóth, Ágota

    2016-04-01

    The precipitation reaction of calcium oxalate is studied experimentally in the presence of spatial gradients by controlled flow of calcium into oxalate solution. The density difference between the reactants leads to strong convection in the form of a gravity current that drives the spatiotemporal pattern formation. The phase diagram of the system is constructed, the evolving precipitate patterns are analyzed and quantitatively characterized by their diameters and the average height of the gravity flow. The compact structures of calcium oxalate monohydrate produced at low flow rates are replaced by the thermodynamically unstable calcium oxalate dihydrate favored in the presence of a strong gravity current.

  2. Flow-driven pattern formation in the calcium-oxalate system.

    PubMed

    Bohner, Bíborka; Endrődi, Balázs; Horváth, Dezső; Tóth, Ágota

    2016-04-28

    The precipitation reaction of calcium oxalate is studied experimentally in the presence of spatial gradients by controlled flow of calcium into oxalate solution. The density difference between the reactants leads to strong convection in the form of a gravity current that drives the spatiotemporal pattern formation. The phase diagram of the system is constructed, the evolving precipitate patterns are analyzed and quantitatively characterized by their diameters and the average height of the gravity flow. The compact structures of calcium oxalate monohydrate produced at low flow rates are replaced by the thermodynamically unstable calcium oxalate dihydrate favored in the presence of a strong gravity current. PMID:27131554

  3. Solid oxide fuel cell having compound cross flow gas patterns

    DOEpatents

    Fraioli, Anthony V.

    1985-01-01

    A core construction for a fuel cell is disclosed having both parallel and cross flow passageways for the fuel and the oxidant gases. Each core passageway is defined by electrolyte and interconnect walls. Each electrolyte wall consists of cathode and anode materials sandwiching an electrolyte material. Each interconnect wall is formed as a sheet of inert support material having therein spaced small plugs of interconnect material, where cathode and anode materials are formed as layers on opposite sides of each sheet and are electrically connected together by the interconnect material plugs. Each interconnect wall in a wavy shape is connected along spaced generally parallel line-like contact areas between corresponding spaced pairs of generally parallel electrolyte walls, operable to define one tier of generally parallel flow passageways for the fuel and oxidant gases. Alternate tiers are arranged to have the passageways disposed normal to one another. Solid mechanical connection of the interconnect walls of adjacent tiers to the opposite sides of the common electrolyte wall therebetween is only at spaced point-like contact areas, 90 where the previously mentioned line-like contact areas cross one another.

  4. The structure of (linearly) stable double diffusive flow patterns in a laterally heated stratified liquid

    NASA Astrophysics Data System (ADS)

    Kranenborg, E. Jurjen; Dijkstra, Henk A.

    1995-03-01

    Layered double diffusive flow patterns in a laterally heated stably stratified liquid are considered in a configuration which allows for steady states to exist. For the heat/salt system, these flows are characterized by the thermal and solutal Rayleigh numbers RaT and RaS, or equivalently by RaT and the buoyancy ratio Rρ. The bifurcation structure of steady patterns with respect to RaT is computed for two cases: fixed RaS and fixed Rρ. For the first case, results in N. Tsitverblit and E. Kit [Phys. Fluids A 5, 1062 (1993)], are computed and extended, and it is shown that many of the previously found flow patterns are unstable; only in a small interval of RaT, multiple (linearly) stable steady states exist. For the second case, the physical relevance of the unstable steady states with respect to the evolution of the flow toward a stable steady state is demonstrated.

  5. The effect of evaporator operating parameters on the flow patterns inside horizontal pipes

    NASA Astrophysics Data System (ADS)

    Tong, Lige; Li, Haiyan; Wang, Li; Sun, Xinxing; Xie, Yunfei

    2011-08-01

    A general and simple model for simulating the steady state behaviors of air-to-refrigerant fin-and-tube evaporator is introduced with the focus on the detailed flow patterns inside the tubes. In order to simulate the heat transfer between air and the working fluid, the evaporator is divided into a number of control volumes. Empirical correlations from literature were also adopted to estimate the void fraction, the internal and external heat transfer coefficients, and the pressure drops. Simulations were performed to study the effects of varying inlet air temperature, refrigerant mass flow rate and evaporation pressure on the flow patterns inside the horizontal pipe of the evaporator. The simulation results indicate that the proposed model can be used to predict flow patterns well. The predicted results of the model agree well with experimental results, the difference is within ±3% for the cooling capacity, and is within ±0.2% for refrigerant evaporation temperature.

  6. Permeability and effective slip in confined flows transverse to wall slippage patterns

    NASA Astrophysics Data System (ADS)

    Kumar, Avinash; Datta, Subhra; Kalyanasundaram, Dinesh

    2016-08-01

    The pressure-driven Stokes flow through a plane channel with arbitrary wall separation having a continuous pattern of sinusoidally varying slippage of arbitrary wavelength and amplitude on one/both walls is modelled semi-analytically. The patterning direction is transverse to the flow. In the special situations of thin and thick channels, respectively, the predictions of the model are found to be consistent with lubrication theory and results from the literature pertaining to free shear flow. For the same pattern-averaged slip length, the hydraulic permeability relative to a channel with no-slip walls increases as the pattern wave-number, amplitude, and channel size are decreased. Unlike discontinuous wall patterns of stick-slip zones studied elsewhere in the literature, the effective slip length of a sinusoidally patterned wall in a confined flow continues to scale with both channel size and the pattern-averaged slip length even in the limit of thin channel size to pattern wavelength ratio. As a consequence, for sufficiently small channel sizes, the permeability of a channel with sinusoidal wall slip patterns will always exceed that of an otherwise similar channel with discontinuous patterns on corresponding walls. For a channel with one no-slip wall and one patterned wall, the permeability relative to that of an unpatterned reference channel of same pattern-averaged slip length exhibits non-monotonic behaviour with channel size, with a minimum appearing at intermediate channel sizes. Approximate closed-form estimates for finding the location and size of this minimum are provided in the limit of large and small pattern wavelengths. For example, if the pattern wavelength is much larger than the channel thickness, exact results from lubrication theory indicate that a worst case permeability penalty relative to the reference channel of ˜23% arises when the average slip of the patterned wall is ˜2.7 times the channel size. The results from the current study should

  7. Discharge characteristics and hydrodynamics behaviors of atmospheric plasma jets produced in various gas flow patterns

    NASA Astrophysics Data System (ADS)

    Setsuhara, Yuichi; Uchida, Giichiro; Nakajima, Atsushi; Takenaka, Kosuke; Koga, Kazunori; Shiratani, Masaharu

    2015-09-01

    Atmospheric nonequilibrium plasma jets have been widely employed in biomedical applications. For biomedical applications, it is an important issue to understand the complicated mechanism of interaction of the plasma jet with liquid. In this study, we present analysis of the discharge characteristics of a plasma jet impinging onto the liquid surface under various gas flow patterns such as laminar and turbulence flows. For this purpose, we analyzed gas flow patters by using a Schlieren gas-flow imaging system in detail The plasma jet impinging into the liquid surface expands along the liquid surface. The diameter of the expanded plasma increases with gas flow rate, which is well explained by an increase in the diameter of the laminar gas-flow channel. When the gas flow rate is further increased, the gas flow mode transits from laminar to turbulence in the gas flow channel, which leads to the shortening of the plasm-jet length. Our experiment demonstrated that the gas flow patterns strongly affect the discharge characteristics in the plasma-jet system. This study was partly supported by a Grant-in-Aid for Scientific Research on Innovative Areas ``Plasma Medical Innovation'' (24108003) from the Ministry of Education, Culture, Sports, Science and Technology, Japan (MEXT).

  8. Localized electric field induced transition and miniaturization of two-phase flow patterns inside microchannels.

    PubMed

    Sharma, Abhinav; Tiwari, Vijeet; Kumar, Vineet; Mandal, Tapas Kumar; Bandyopadhyay, Dipankar

    2014-10-01

    Strategic application of external electrostatic field on a pressure-driven two-phase flow inside a microchannel can transform the stratified or slug flow patterns into droplets. The localized electrohydrodynamic stress at the interface of the immiscible liquids can engender a liquid-dielectrophoretic deformation, which disrupts the balance of the viscous, capillary, and inertial forces of a pressure-driven flow to engender such flow morphologies. Interestingly, the size, shape, and frequency of the droplets can be tuned by varying the field intensity, location of the electric field, surface properties of the channel or fluids, viscosity ratio of the fluids, and the flow ratio of the phases. Higher field intensity with lower interfacial tension is found to facilitate the oil droplet formation with a higher throughput inside the hydrophilic microchannels. The method is successful in breaking down the regular pressure-driven flow patterns even when the fluid inlets are exchanged in the microchannel. The simulations identify the conditions to develop interesting flow morphologies, such as (i) an array of miniaturized spherical or hemispherical or elongated oil drops in continuous water phase, (ii) "oil-in-water" microemulsion with varying size and shape of oil droplets. The results reported can be of significance in improving the efficiency of multiphase microreactors where the flow patterns composed of droplets are preferred because of the availability of higher interfacial area for reactions or heat and mass exchange. PMID:25044128

  9. Effect of viscoelasticity on the flow pattern and the volumetric flow rate in electroosmotic flows through a microchannel.

    PubMed

    Park, H M; Lee, W M

    2008-07-01

    Many lab-on-a-chip based microsystems process biofluids such as blood and DNA solutions. These fluids are viscoelastic and show extraordinary flow behaviors, not existing in Newtonian fluids. Adopting appropriate constitutive equations these exotic flow behaviors can be modeled and predicted reasonably using various numerical methods. In the present paper, we investigate viscoelastic electroosmotic flows through a rectangular straight microchannel with and without pressure gradient. It is shown that the volumetric flow rates of viscoelastic fluids are significantly different from those of Newtonian fluids under the same external electric field and pressure gradient. Moreover, when pressure gradient is imposed on the microchannel there appear appreciable secondary flows in the viscoelastic fluids, which is never possible for Newtonian laminar flows through straight microchannels. The retarded or enhanced volumetric flow rates and secondary flows affect dispersion of solutes in the microchannel nontrivially. PMID:18584093

  10. A study of gas flow pattern, undercutting and torch modification in variable polarity plasma arc welding

    NASA Technical Reports Server (NTRS)

    Mcclure, John C.; Hou, Haihui Ron

    1994-01-01

    A study on the plasma and shield gas flow patterns in variable polarity plasma arc (VPPA) welding was undertaken by shadowgraph techniques. Visualization of gas flow under different welding conditions was obtained. Undercutting is often present with aluminum welds. The effects of torch alignment, shield gas flow rate and gas contamination on undercutting were investigated and suggestions made to minimize the defect. A modified shield cup for the welding torch was fabricated which consumes much less shield gas while maintaining the weld quality. The current torch was modified with a trailer flow for Al-Li welding, in which hot cracking is a critical problem. The modification shows improved weldablility on these alloys.

  11. A numerical analysis of the aortic blood flow pattern during pulsed cardiopulmonary bypass.

    PubMed

    Gramigna, V; Caruso, M V; Rossi, M; Serraino, G F; Renzulli, A; Fragomeni, G

    2015-01-01

    In the modern era, stroke remains a main cause of morbidity after cardiac surgery despite continuing improvements in the cardiopulmonary bypass (CPB) techniques. The aim of the current work was to numerically investigate the blood flow in aorta and epiaortic vessels during standard and pulsed CPB, obtained with the intra-aortic balloon pump (IABP). A multi-scale model, realized coupling a 3D computational fluid dynamics study with a 0D model, was developed and validated with in vivo data. The presence of IABP improved the flow pattern directed towards the epiaortic vessels with a mean flow increase of 6.3% and reduced flow vorticity. PMID:24962383

  12. Analyzing Unsatirated Flow Patterns in Fractured Rock Using an Integrated Modeling Approach

    SciTech Connect

    Y.S. Wu; G. Lu; K. Zhang; L. Pan; G.S. Bodvarsson

    2006-08-03

    Characterizing percolation patterns in unsaturated fractured rock has posed a greater challenge to modeling investigations than comparable saturated zone studies, because of the heterogeneous nature of unsaturated media and the great number of variables impacting unsaturated flow. This paper presents an integrated modeling methodology for quantitatively characterizing percolation patterns in the unsaturated zone of Yucca Mountain, Nevada, a proposed underground repository site for storing high-level radioactive waste. The modeling approach integrates a wide variety of moisture, pneumatic, thermal, and isotopic geochemical field data into a comprehensive three-dimensional numerical model for modeling analyses. It takes into account the coupled processes of fluid and heat flow and chemical isotopic transport in Yucca Mountain's highly heterogeneous, unsaturated fractured tuffs. Modeling results are examined against different types of field-measured data and then used to evaluate different hydrogeological conceptualizations and their results of flow patterns in the unsaturated zone. In particular, this model provides a much clearer understanding of percolation patterns and flow behavior through the unsaturated zone, both crucial issues in assessing repository performance. The integrated approach for quantifying Yucca Mountain's flow system is demonstrated to provide a practical modeling tool for characterizing flow and transport processes in complex subsurface systems.

  13. Analyzing unsaturated flow patterns in fractured rock using an integrated modeling approach

    NASA Astrophysics Data System (ADS)

    Wu, Yu-Shu; Lu, Guoping; Zhang, Keni; Pan, Lehua; Bodvarsson, Gudmundur S.

    2007-05-01

    Characterizing percolation patterns in unsaturated fractured rock has posed a greater challenge to modeling investigations than comparable saturated zone studies due to the heterogeneous nature of unsaturated media and the great number of variables impacting unsaturated flow. An integrated modeling methodology has been developed for quantitatively characterizing percolation patterns in the unsaturated zone of Yucca Mountain, Nevada (USA), a proposed underground repository site for storing high-level radioactive waste. The approach integrates moisture, pneumatic, thermal, and isotopic geochemical field data into a comprehensive three-dimensional numerical model for analyses. It takes into account the coupled processes of fluid and heat flow and chemical isotopic transport in Yucca Mountain’s highly heterogeneous, unsaturated fractured tuffs. Modeling results are examined against different types of field-measured data and then used to evaluate different hydrogeological conceptualizations through analyzing flow patterns in the unsaturated zone. In particular, this model provides clearer understanding of percolation patterns and flow behavior through the unsaturated zone, both crucial issues in assessing repository performance. The integrated approach for quantifying Yucca Mountain’s flow system is demonstrated to provide a practical modeling tool for characterizing flow and transport processes in complex subsurface systems.

  14. Lower limits of spin detection efficiency for two-parameter two-qubit (TPTQ) states with non-ideal ferromagnetic detectors

    NASA Astrophysics Data System (ADS)

    Majd, Nayereh; Ghasemi, Zahra

    2016-07-01

    We have investigated a TPTQ state as an input state of a non-ideal ferromagnetic detectors. Minimal spin polarization required to demonstrate spin entanglement according to entanglement witness and CHSH inequality with respect to (w.r.t.) their two free parameters have been found, and we have numerically shown that the entanglement witness is less stringent than the direct tests of Bell's inequality in the form of CHSH in the entangled limits of its free parameters. In addition, the lower limits of spin detection efficiency fulfilling secure cryptographic key against eavesdropping have been derived. Finally, we have considered TPTQ state as an output of spin decoherence channel and the region of ballistic transmission time w.r.t. spin relaxation time and spin dephasing time has been found.

  15. Depth distribution of preferential flow patterns in a sandy loam soil as affected by tillage

    NASA Astrophysics Data System (ADS)

    Petersen, C. T.; Hansen, S.; Jensen, H. E.

    Dye-tracer studies using the anionic dye Brilliant Blue FCF were conducted on a structured sandy loam soil (Typic Agrudalf). 25 mm of dye solution was applied to the surface of 11 1.6 x 1.6 m field plots, some of which had been subjected to conventional seed bed preparation (harrowing) while others had been rotovated to either 5 or 15 cm depth before sowing. The soil was excavated to about 160 cm depth one or two days after dye application. Flow patterns and structural features appearing on vertical or horizontal cross sections were examined and photographed. The flow patterns were digitized, and depth functions for the number of activated flow pathways and the degree of dye coverage were calculated. Dye was found below 100 cm depth on 26 out of 33 vertical cross sections made in conventionally tilled plots showing that preferential flow was a prevailing phenomenon. The depth-averaged number of stained flow pathways in the 25-100 cm layer was significantly smaller in a plot rotovated to 5 cm depth than in a conventionally tilled plot, both under relatively dry initial soil conditions and when the entire soil profiles were initially at field capacity. There were no examples of dye penetration below 25 cm depth one month after deep rotovation. Distinct horizontal structures in flow patterns appearing at 20-40 cm depth coupled with changes in flow domains indicated soil layering with abrupt changes in soil structure and hydraulic properties.

  16. Experimental investigation on the heat transfer characteristics and flow pattern in vertical narrow channels heated from one side

    NASA Astrophysics Data System (ADS)

    Huang, Lihao; Li, Gang; Tao, Leren

    2016-07-01

    Experimental investigation for the flow boiling of water in a vertical rectangular channel was conducted to reveal the boiling heat transfer mechanism and flow patterns map aspects. The onset of nucleate boiling went upward with the increasing of the working fluid mass flow rate or the decreasing of the inlet working fluid temperature. As the vapour quality was increased, the local heat transfer coefficient increased first, then decreased, followed by various flow patterns. The test data from other researchers had a similar pattern transition for the bubble-slug flow and the slug-annular flow. Flow pattern transition model analysis was performed to make the comparison with current test data. The slug-annular and churn-annular transition models showed a close trend with current data except that the vapor phase superficial velocity of flow pattern transition was much higher than that of experimental data.

  17. Analyzing flow patterns in unsaturated fractured rock of YuccaMountain using an integrated modeling approach

    SciTech Connect

    Wu, Yu-Shu; Lu, Guoping; Zhang, Keni; Pan, Lehua; Bodvarsson,Gudmundur S.

    2003-11-03

    This paper presents a series of modeling investigations to characterize percolation patterns in the unsaturated zone of Yucca Mountain, Nevada, a proposed underground repository site for storing high-level radioactive waste. The investigations are conducted using a modeling approach that integrates a wide variety of moisture, pneumatic, thermal, and isotopic geochemical field data into a comprehensive three-dimensional numerical model through model calibration. This integrated modeling approach, based on a dual-continuum formulation, takes into account the coupled processes of fluid and heat flow and chemical isotopic transport in Yucca Mountain's highly heterogeneous, unsaturated fractured tuffs. In particular, the model results are examined against different types of field-measured data and used to evaluate different hydrogeological conceptual models and their effects on flow patterns in the unsaturated zone. The objective of this work to provide understanding of percolation patterns and flow behavior through the unsaturated zone, which is a crucial issue in assessing repository performance.

  18. Comparison of visualized turbine endwall secondary flows and measured heat transfer patterns

    NASA Astrophysics Data System (ADS)

    Gaugler, R. E.; Russell, L. M.

    1983-03-01

    Various flow visualization techniques were used to define the secondary flows near the endwall in a large heat transfer data. A comparison of the visualized flow patterns and the measured Stanton number distribution was made for cases where the inlet Reynolds number and exit Mach number were matched. Flows were visualized by using neutrally buoyant helium-filled soap bubbles, by using smoke from oil soaked cigars, and by a few techniques using permanent marker pen ink dots and synthetic wintergreen oil. Details of the horseshoe vortex and secondary flows can be directly compared with heat transfer distribution. Near the cascade entrance there is an obvious correlation between the two sets of data, but well into the passage the effect of secondary flow is not as obvious.

  19. Comparison of visualized turbine endwall secondary flows and measured heat transfer patterns

    NASA Astrophysics Data System (ADS)

    Gaugler, R. E.; Russell, L. M.

    1984-01-01

    Various flow visualization techniques were used to define the seondary flows near the endwall in a large heat transfer data. A comparison of the visualized flow patterns and the measured Stanton number distribution was made for cases where the inlet Reynolds number and exit Mach number were matched. Flows were visualized by using neutrally buoyant helium-filled soap bubbles, by using smoke from oil soaked cigars, and by a few techniques using permanent marker pen ink dots and synthetic wintergreen oil. Details of the horseshoe vortex and secondary flows can be directly compared with heat transfer distribution. Near the cascade entrance there is an obvious correlation between the two sets of data, but well into the passage the effect of secondary flow is not as obvious. Previously announced in STAR as N83-14435

  20. Comparison of visualized turbine endwall secondary flows and measured heat transfer patterns

    NASA Technical Reports Server (NTRS)

    Gaugler, R. E.; Russell, L. M.

    1983-01-01

    Various flow visualization techniques were used to define the secondary flows near the endwall in a large heat transfer data. A comparison of the visualized flow patterns and the measured Stanton number distribution was made for cases where the inlet Reynolds number and exit Mach number were matched. Flows were visualized by using neutrally buoyant helium-filled soap bubbles, by using smoke from oil soaked cigars, and by a few techniques using permanent marker pen ink dots and synthetic wintergreen oil. Details of the horseshoe vortex and secondary flows can be directly compared with heat transfer distribution. Near the cascade entrance there is an obvious correlation between the two sets of data, but well into the passage the effect of secondary flow is not as obvious.

  1. The internal flow pattern analysis of a tidal power turbine operating on bidirectional generation-pumping

    NASA Astrophysics Data System (ADS)

    Y Luo, Y.; Xiao, Y. X.; Wang, Z. W.

    2013-12-01

    Using tidal energy can reduce environment pollution, save conventional energy and improve energy structure, hence it presents great advantage and is developing potential. Influenced by flood tide and low tide, a fully functional tidal power station needs to experience six operating modes, including bidirectional generation, pumping and sluice; the internal unsteady flow pattern and dynamic characters are very complicated. Based on a bidirectional tidal generator unit, three-dimensional unsteady flows in the flow path were calculated for four typical operating conditions with the pressure pulsation characteristics analyzed. According to the numerical results, the internal flow characteristics in the flow path were discussed. The influence of gravity to the hydraulic performance and flow characteristics were analysed. The results provide a theoretical analysis method of the hydraulic optimization design of the same type unit as well as a direction for stable operation and optimal scheduling of existing tidal power unit.

  2. Constraining Paleo-Hydrologic Flow Fields from Iron Oxide Cementation Patterns

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Chan, M. A.

    2013-12-01

    Fine-grained sandstone in Mesozoic sedimentary red beds of the Colorado Plateau (southwestern United States) contain iron oxides cements (e.g., hematite and goethite) that display spectacular pattern formation, including evenly spaced nodule formation and banding with nested scales spanning about two to three orders of magnitude (Fig. 1). These nodules are commonly referred to as concretions, which are cemented mineral masses. The size of concretions typically ranges from millimeters to centimeters, while the spacing of bands ranges from millimeters to sub-meters. Spatial transition of one pattern to another or one pattern superimposed on another is also observed. Such patterns may embed important information about paleo-environments of sediment diagenesis, especially regarding the fluid migration and geochemical conditions involved. Field evidence indicates that the formation of iron oxide bands in sandstone seems closely related to groundwater flows. Here we show that such patterns can autonomously emerge from a previously unrecognized Ostwald ripening mechanism and they capture rich information regarding ancient chemical and hydrologic environments. Using a linear stability analysis, we demonstrate that the pattern transition from nodules to bands results from symmetry breaking triggered by groundwater advection. Nodules tend to develop under nearly stagnant hydrologic conditions, while repetitive bands tend to form in the presence of persistent water flows. The banding is formed perpendicularly to the flow direction, and the flow rate is expected to be proportional to the square of banding spacing. Therefore, careful mapping of cementation patterns and banding spacing over rock outcrops will allow us to reconstruct a detail map of water flow field for a sandstone aquifer. Concretion nodules formed in Jurassic Navajo Sandstone have been proposed as a terrestrial analogue to hematite spherules detected by the rover Opportunity at the Meridiani Planum site on the

  3. Photodirecting Marangoni Flow to Pattern Thin Polymer Films: Decoupling Viscosity and Diffusivity

    NASA Astrophysics Data System (ADS)

    Kim, Chae Bin; Jones, Amanda; Janes, Dustin; Arshad, Talha; Bonnecaze, Roger; Ellison, Christopher

    The Marangoni effect causes liquids to flow towards localized regions of higher surface tension. In thin polymer films, this effect could offer a practically useful route to manufacture topographically patterned surfaces. In this presentation, we report a photochemical strategy to harness Marangoni flow as a versatile patterning method along with comparisons to a theoretical model that reveals the underlying physics of this process. The model agrees well with experiments with no adjustable parameters. It further indicates that higher aspect ratio features are favored by large surface tension gradients, low diffusivities and low viscosities. However, as described by the Rouse model, low viscosities are generally correlated with high diffusivities; diffusivity is also an important factor in the timescale by which the spatial surface tension patterns decay. This coupling between diffusivity and viscosity could critically limit feature aspect ratio for any given surface tension pattern. A potential strategy that decouples diffusivity and viscosity of the film components will be presented.

  4. Evaluation of groundwater flow patterns around a dual-screened groundwater circulation well.

    PubMed

    Johnson, Richard L; Simon, Michelle A

    2007-08-15

    Dual-screened groundwater circulation wells (GCWs) can be used to remove contaminant mass and to mix reagents in situ. GCWs are so named because they force water in a circular pattern between injection and extraction screens. The radial extent, flux and direction of the effective flow of this circulation cell are difficult to measure or predict. The objective of this study is to develop a robust protocol for assessing GCW performance. To accomplish this, groundwater flow patterns surrounding a GCW are assessed using a suite of tools and data, including: hydraulic head, in situ flow velocity, measured hydraulic conductivity data from core samples, chemical tracer tests, contaminant distribution data, and numerical flow and transport models. The hydraulic head data show patterns that are consistent with pumping on a dual-screened well, however, many of the observed changes are smaller than expected. In situ thermal perturbation flow sensors successfully measured horizontal flow, but vertical flow could not be determined with sufficient accuracy to be useful in mapping flow patterns. Two types of chemical tracer tests were utilized at the site and showed that much of the flow occurs within a few meters of the GCW. Flow patterns were also assessed based on changes in contaminant (trichloroethylene, TCE) concentrations over time. The TCE data clearly showed treated water moving away from the GCW at shallow and intermediate depths, but the circulation of that water back to the well, except very close to the well, was less clear. Detailed vertical and horizontal hydraulic conductivities were measured on 0.3 m-long sections from a continuous core from the GCW installation borehole. The measured vertical and horizontal hydraulic conductivity data were used to construct numerical flow and transport models, the results of which were compared to the head, velocity and concentration data. Taken together, the field data and modeling present a fairly consistent picture of flow

  5. An Active Region Model for Capturing Fractal Flow Patterns inUnsaturated Soils: Model Development

    SciTech Connect

    Liu, Hui-Hai; Zhang, R.; Bodvarsson, Gudmundur S.

    2005-06-11

    Preferential flow commonly observed in unsaturated soils allows rapid movement of solute from the soil surface or vadose zone to the groundwater, bypassing a significant volume of unsaturated soil and increasing the risk of groundwater contamination. A variety of evidence indicates that complex preferential patterns observed from fields are fractals. In this study, we developed a relatively simple active region model to incorporate the fractal flow pattern into the continuum approach. In the model, the flow domain is divided into active and inactive regions. Flow occurs preferentially in the active region (characterized by fractals), and inactive region is simply bypassed. A new constitutive relationship (the portion of the active region as a function of saturation) was derived. The validity of the proposed model is demonstrated by the consistency between field observations and the new constitutive relationship.

  6. Two-phase Flow Patterns in High Temperature Generator of Absorption Chiller / Heater

    NASA Astrophysics Data System (ADS)

    Furukawa, Masahiro; Kanuma, Hitoshi; Sekoguchi, Kotohiko; Takeishi, Masayuki

    There is a lack of information about vapor-liquid two-phase flow patterns determined using void signals in high temperature generator of absorption chiller/heater. Sensing void fraction has been hampered because lithium bromide aqueous solution of strong alkalinity is employed as working fluid at high temperature and high level of vacuum. New void sensor applicable to such difficult conditions was developed. The void Fractions at 48 locations in a high temperature generator were measured simultaneously in both cooling and heating operations. Analysis of void signals detected reveals that the most violent boiling occurs at the upper part of rear plate of combustion chamber and the first line of vertical tubes located in the flue. The flow patterns are strongly affected by the system pressure difference between the cooling and heating operations: there appear bubbly, slug and froth flows in the cooling operation, but only bubbly flow in the heating operation.

  7. Differentiation of abnormal blood flow patterns in coronary arteries based on Doppler catheter recordings.

    PubMed

    Denardo, S J; Yock, P G; Hargrave, V K; Srebro, J P; Ports, T A; Talbot, L

    1991-09-01

    Abnormal arterial blood flow patterns have been implicated as etiologic factors in thrombosis and atherosclerosis. Intravascular pulsed Doppler ultrasound techniques with fast-Fourier transform analysis offer the opportunity to measure these abnormalities. The authors hypothesized that statistical analysis of radial-directed beam spectra could be used to distinguish disturbed from non-disturbed flow and that analysis of conventional axial-directed beam spectra could then be used to distinguish laminar high-shear from laminar low-shear flow. They developed a scaled-up in-vitro model of coronary flow consisting of a glycerol/H2O test fluid flowing through an acrylic cylinder at Reynolds numbers spanning the typical physiologic range within the coronary arteries. A scaled-up Doppler catheter with the capacity for 90 degrees reflection of the beam was placed centrally. Disturbed flow was created by introducing a flow screen, and altered shear rates were produced by changing the Reynolds number. For the radial-directed beam studies, the coefficients of variation of the Doppler spectra for the disturbed flow states were significantly greater than for the nondisturbed flow states (p less than 0.01). For the axial-directed beam studies, the coefficients of variation of the Doppler spectra for the laminar high-shear flow states were significantly greater than for the laminar low-shear flow states (p less than 0.01). They conclude that abnormal blood flow patterns can be differentiated by the selective use of radial-directed and axial-directed Doppler catheter recordings. PMID:1928812

  8. Flow pattern in the vicinity of self-propelling hot Janus particles.

    PubMed

    Bickel, Thomas; Majee, Arghya; Würger, Alois

    2013-07-01

    We study the temperature field and the resulting flow pattern in the vicinity of a heated metal-capped Janus particle. If its thickness exceeds about 10 nm, the cap forms an isotherm and the flow pattern comprises a quadrupolar term that decays with the square of the inverse distance ~r(-2). For much thinner caps the velocity varies as ~r(-3). These findings could be relevant for collective effects in dense suspensions and for the circular tracer motion observed recently in the vicinity of a tethered Janus particle. PMID:23944457

  9. Flow pattern in the vicinity of self-propelling hot Janus particles

    NASA Astrophysics Data System (ADS)

    Bickel, Thomas; Majee, Arghya; Würger, Alois

    2013-07-01

    We study the temperature field and the resulting flow pattern in the vicinity of a heated metal-capped Janus particle. If its thickness exceeds about 10 nm, the cap forms an isotherm and the flow pattern comprises a quadrupolar term that decays with the square of the inverse distance ˜r-2. For much thinner caps the velocity varies as ˜r-3. These findings could be relevant for collective effects in dense suspensions and for the circular tracer motion observed recently in the vicinity of a tethered Janus particle.

  10. An Integrated Modeling Analysis of Unsaturated Flow Patterns inFractured Rock

    SciTech Connect

    Wu, Yu-Shu; Lu, Guoping; Zhang, Keni; Pan, Lehua; Bodvarsson,Gudmundur S.

    2005-03-21

    Characterizing percolation patterns in unsaturated zones hasposed a greater challenge to numerical modeling investigations thancomparable saturated zone studies, because of the heterogeneous nature ofunsaturated media as well as the great number of variables impactingunsaturated zone flow. This paper presents an integrated modelingmethodology for quantitatively characterizing percolation patterns in theunsaturated zone of Yucca Mountain, Nevada, a proposed undergroundrepository site for storing high-level radioactive waste. It takes intoaccount the multiple coupled processes of air, water, heat flow andchemical isotopic transport in Yucca Mountain s highly heterogeneous,unsaturated fractured tuffs. The modeling approach integrates a widevariety of moisture, pneumatic, thermal, and isotopic geochemical fielddata into a comprehensive three-dimensional numerical model for modelinganalyses. Modeling results are examined against different types offield-measured data and then used to evaluate different hydrogeologicalconceptual models and their results of flow patterns in the unsaturatedzone. In particular, this integration model provides a much clearerunderstanding of percolation patterns and flow behavior through theunsaturated zone, both crucial issues in assessing repositoryperformance. The integrated approach for quantifying Yucca Mountain sflow system is also demonstrated to provide a comprehensive modeling toolfor characterizing flow and transport processes in complex subsurfacesystems.

  11. A herringbone bedform pattern of possible Taylor-Görtler type flow origin seen in sonographs

    USGS Publications Warehouse

    Toimil, Lawrence J.; Reimnitz, Erk

    1979-01-01

    Side-scan sonar records collected in a shallow arctic lagoon (2–2.5 m depth) reveal a herringbone pattern of current-aligned linear reflectors with branching diagonals. The major longitudinal reflectors have no detectable relief (<20 cm), are spaced 5–10 m apart, and may represent current-aligned helical cell boundaries preserved in the silty fine sand of the lagoon floor. The pattern suggests a three-dimensional flow regime of the Taylor-Görtler type.

  12. Pattern recognition analysis of anterior cingulate cortex blood flow to classify depression polarity†

    PubMed Central

    Almeida, J. R. C.; Mourao-Miranda, J.; Aizenstein, H. J.; Versace, A.; Kozel, F. A.; Lu, H.; Marquand, A.; LaBarbara, E. J.; Brammer, M.; Trivedi, M.; Kupfer, D. J.; Phillips, M. L.

    2013-01-01

    Differentiating bipolar from recurrent unipolar depression is a major clinical challenge. In 18 healthy females and 36 females in a depressive episode - 18 with bipolar disorder type I, 18 with recurrent unipolar depression - we applied pattern recognition analysis using subdivisions of anterior cingulate cortex (ACC) blood flow at rest, measured with arterial spin labelling. Subgenual ACC blood flow classified unipolar v. bipolar depression with 81% accuracy (83% sensitivity, 78% specificity). PMID:23969484

  13. Probabilistic and Other Neural Nets in Multi-Hole Probe Calibration and Flow Angularity Pattern Recognition

    NASA Technical Reports Server (NTRS)

    Baskaran, Subbiah; Ramachandran, Narayanan; Noever, David

    1998-01-01

    The use of probabilistic (PNN) and multilayer feed forward (MLFNN) neural networks are investigated for calibration of multi-hole pressure probes and the prediction of associated flow angularity patterns in test flow fields. Both types of networks are studied in detail for their calibration and prediction characteristics. The current formalism can be applied to any multi-hole probe, however the test results for the most commonly used five-hole Cone and Prism probe types alone are reported in this article.

  14. Simulation and visualization of flow pattern in microarrays for liquid phase oligonucleotide and peptide synthesis.

    PubMed

    O-Charoen, Sirimon; Srivannavit, Onnop; Gulari, Erdogan

    2007-01-01

    Microfluidic microarrays have been developed for economical and rapid parallel synthesis of oligonucleotide and peptide libraries. For a synthesis system to be reproducible and uniform, it is crucial to have a uniform reagent delivery throughout the system. Computational fluid dynamics (CFD) is used to model and simulate the microfluidic microarrays to study geometrical effects on flow patterns. By proper design geometry, flow uniformity could be obtained in every microreactor in the microarrays. PMID:17480053

  15. SIMULATION AND VISUALIZATION OF FLOW PATTERN IN MICROARRAYS FOR LIQUID PHASE OLIGONUCLEOTIDE AND PEPTIDE SYNTHESIS

    PubMed Central

    O-Charoen, Sirimon; Srivannavit, Onnop; Gulari, Erdogan

    2008-01-01

    Microfluidic microarrays have been developed for economical and rapid parallel synthesis of oligonucleotide and peptide libraries. For a synthesis system to be reproducible and uniform, it is crucial to have a uniform reagent delivery throughout the system. Computational fluid dynamics (CFD) is used to model and simulate the microfluidic microarrays to study geometrical effects on flow patterns. By proper design geometry, flow uniformity could be obtained in every microreactor in the microarrays. PMID:17480053

  16. Distribution Pattern of Terrestrial Heat Flow in Bohai Bay Basin, North China

    NASA Astrophysics Data System (ADS)

    Wang, L.; Gong, Y.; Liu, S.; Li, C.; Li, H.

    2004-12-01

    New temperature data from wells in Bohai bay basin increasing associated with the enhancement of oil and gas exploration there provides more reliable information about studying on Terrestrial heat flow pattern. Based on the data from 88 systematic continuous temperature logging curves and more than 1000 well test temperature data, along with the corresponding thermo-physical parameters of rock samples, here we determined 53 heat flow data and estimated other 172 according to thermal resistance method, then the distribution Pattern of heat flow in Bohai Bay basin is presented. Heat flow in Bohai bay basin is relatively large than those in the surrounding mountain areas. For instance, heat flow of Yanshan, north of the basin, is only low as 25 ~ 54 mW/m2, and less than 50 mW/m2 for Taihang mountain to the west, the average heat flow of Luxi Uplift is about 54 mW/m2. Crustal thickness of regions outside the basin to the west and north approximating to 36~44km, apparently is larger than that of basin, which maybe accounts for the high heat flow in Bohai bay basin. Those regions of relatively thin crust within the basin are of middle-high heat flow. Heat flow in such depressions as the Lower Liaohe, Bozhong, Jiyang and Yongqing area northeast of Jizhong Depression, together with Bohai offshore, for example, are all larger than 64 mW/m2, and even high as 70 mW/m2 for some regions with mantle upwelling. Low heat flow appears in those areas with relatively thick crust. For instance, heat flow in Linqing Depression, southwest margin of Jizhong Depression and southern Huanghua Depression, are all less than 64 mW/m2, even less than 60 mW/m2 for those areas with mantle downwelling. Heat flow pattern in Bohai Bay basin is negative correlation with crustal thickness, for those regions with relatively crustal thinning, heat derived from the deep earth is more due to the large lithospheric extension, resulting in the high heat flow; while for those with crustal thickening, heat

  17. Flow regime patterns and their controlling factors in the Ebro basin (Spain)

    NASA Astrophysics Data System (ADS)

    Bejarano, M. Dolores; Marchamalo, Miguel; García de Jalón, Diego; González del Tánago, Marta

    2010-05-01

    SummaryNatural intra-annual flow fluctuations vary between rivers, being a determining factor for aquatic insects, fish and riparian communities which are adapted to the habitat conditions and different flows throughout the seasons. Moreover, restoration of seasonal flow patterns plays an important role in achieving good ecological status of rivers, through the preservation and/or recovery of components and processes of natural river ecosystems. In this work we: (a) classify fluvial segments in the Ebro basin (North-Eastern Spain) according to the intra-annual variability of flows under natural conditions using statistical cluster analysis of monthly mean flow data; (b) characterise the resulting flow typologies according to several ecologically important hydrological variables; (c) analyse the relationships between flow regimes of fluvial segments and physical variables from their catchments; and finally (d) predict the most probable natural flow regime using logistic models based on the most determinant physical characteristics. Fifteen natural flow typologies were described in the Ebro basin, which were characterised in terms of flow fluctuation through the year as well as timing, flow ratio and duration of the maximum and minimum flows. Precipitation, biogeography and geology of catchments showed the highest correlations with flow regimes. Basin size, mean elevation and slope were also correlated. The logistic model we developed had a prediction success of 72% in the Ebro basin. The definition of the natural hydrological conditions (to which the biological communities are tailored), even when flow data are not available, is an important support in the management of river ecosystems. It is especially suitable for setting goals in aquatic ecosystem conservation or restoration projects.

  18. Zonal Flow as Pattern Formation: Merging Jets and the Ultimate Jet Length Scale

    SciTech Connect

    Jeffrey B. Parker and John A. Krommes

    2013-01-30

    Zonal flows are well known to arise spontaneously out of turbulence. It is shown that for statisti- cally averaged equations of quasigeostrophic turbulence on a beta plane, zonal flows and inhomoge- neous turbulence fit into the framework of pattern formation. There are many implications. First, the zonal flow wavelength is not unique. Indeed, in an idealized, infinite system, any wavelength within a certain continuous band corresponds to a solution. Second, of these wavelengths, only those within a smaller subband are linearly stable. Unstable wavelengths must evolve to reach a stable wavelength; this process manifests as merging jets.

  19. Modality transition-based network from multivariate time series for characterizing horizontal oil-water flow patterns

    NASA Astrophysics Data System (ADS)

    Ding, Mei-Shuang; Jin, Ning-De; Gao, Zhong-Ke

    2015-11-01

    The simultaneous flow of oil and water through a horizontal pipe is a common occurrence during petroleum industrial processes. Characterizing the flow behavior underlying horizontal oil-water flows is a challenging problem of significant importance. In order to solve this problem, we carry out experiment to measure multivariate signals from different flow patterns and then propose a novel modality transition-based network to analyze the multivariate signals. The results suggest that the local betweenness centrality and weighted shortest path of the constructed network can characterize the transitions of flow conditions and further allow quantitatively distinguishing and uncovering the dynamic flow behavior underlying different horizontal oil-water flow patterns.

  20. Interactions of double patterning technology with wafer processing, OPC and design flows

    NASA Astrophysics Data System (ADS)

    Lucas, Kevin; Cork, Chris; Miloslavsky, Alex; Luk-Pat, Gerry; Barnes, Levi; Hapli, John; Lewellen, John; Rollins, Greg; Wiaux, Vincent; Verhaegen, Staf

    2008-03-01

    Double patterning technology (DPT) is one of the main options for printing logic devices with half-pitch less than 45nm; and flash and DRAM memory devices with half-pitch less than 40nm. DPT methods decompose the original design intent into two individual masking layers which are each patterned using single exposures and existing 193nm lithography tools. The results of the individual patterning layers combine to re-create the design intent pattern on the wafer. In this paper we study interactions of DPT with lithography, masks synthesis and physical design flows. Double exposure and etch patterning steps create complexity for both process and design flows. DPT decomposition is a critical software step which will be performed in physical design and also in mask synthesis. Decomposition includes cutting (splitting) of original design intent polygons into multiple polygons where required; and coloring of the resulting polygons. We evaluate the ability to meet key physical design goals such as: reduce circuit area; minimize rework; ensure DPT compliance; guarantee patterning robustness on individual layer targets; ensure symmetric wafer results; and create uniform wafer density for the individual patterning layers.

  1. Computational Representation of Collaborative Learning Flow Patterns Using IMS Learning Design

    ERIC Educational Resources Information Center

    Hernandez-Leo, Davinia; Asensio-Perez, Juan I.; Dimitriadis, Yannis

    2005-01-01

    The identification and integration of reusable and customizable CSCL (Computer Supported Collaborative Learning) may benefit from the capture of best practices in collaborative learning structuring. The authors have proposed CLFPs (Collaborative Learning Flow Patterns) as a way of collecting these best practices. To facilitate the process of CLFPs…

  2. Simultaneous imaging of blood flow and hemoglobin concentration change in skin tissue using NIR speckle patterns

    NASA Astrophysics Data System (ADS)

    Aizu, Yoshihisa; Hirata, Tatsuya; Maeda, Takaaki; Nishidate, Izumi; Yokoi, Naomichi

    2009-07-01

    We propose a method for imaging simultaneously blood flow and hemoglobin concentration change in skin tissue using speckle patterns acquired at two wavelengths of 780 and 830 nm. Experimental results demonstrate that the method is useful for time-varying analysis of blood circulation in human forearm skin tissue from one set of sequential speckle images.

  3. Fractal regional myocardial blood flows pattern according to metabolism, not vascular anatomy.

    PubMed

    Yipintsoi, Tada; Kroll, Keith; Bassingthwaighte, James B

    2016-02-01

    Regional myocardial blood flows are markedly heterogeneous. Fractal analysis shows strong near-neighbor correlation. In experiments to distinguish control by vascular anatomy vs. local vasomotion, coronary flows were increased in open-chest dogs by stimulating myocardial metabolism (catecholamines + atropine) with and without adenosine. During control states mean left ventricular (LV) myocardial blood flows (microspheres) were 0.5-1 ml·g(-1)·min(-1) and increased to 2-3 ml·g(-1)·min(-1) with catecholamine infusion and to ∼4 ml·g(-1)·min(-1) with adenosine (Ado). Flow heterogeneity was similar in all states: relative dispersion (RD = SD/mean) was ∼25%, using LV pieces 0.1-0.2% of total. During catecholamine infusion local flows increased in proportion to the mean flows in 45% of the LV, "tracking" closely (increased proportionately to mean flow), while ∼40% trended toward the mean. Near-neighbor regional flows remained strongly spatially correlated, with fractal dimension D near 1.2 (Hurst coefficient 0.8). The spatial patterns remain similar at varied levels of metabolic stimulation inferring metabolic dominance. In contrast, adenosine vasodilation increased flows eightfold times control while destroying correlation with the control state. The Ado-induced spatial patterns differed from control but were self-consistent, inferring that with full vasodilation the relaxed arterial anatomy dominates the distribution. We conclude that vascular anatomy governs flow distributions during adenosine vasodilation but that metabolic vasoregulation dominates in normal physiological states. PMID:26589329

  4. Application of the Colloidal Borescope to Determine a Complex Groundwater Flow Pattern

    SciTech Connect

    Narbutovskih, Susan M.; McDonald, John P.; Schalla, Ronald; Sweeney, Mark D.; M.N. Sara and L.G. Everett

    2002-10-01

    Pacific Northwest National Laboratory made in situ flow measurements in groundwater monitoring wells at the U.S. Department of Energy (DOE) Hanford Site to determine the flow direction in an aquifer with a flat water table. Given the total errors in water level elevations, flow directions based on the potentiometric surface are ambiguous at best. The colloidal borescope was used because it allows direct, real time observation of mobile colloidal particles in the open interval of a water well and thus, avoids the use of water level data. The results characterize a complex groundwater flow pattern under several buried waste storage tank farms. The aquifer, artificially high due to large volume liquid discharges to the soil column from Hanford's nuclear production era, is currently receding to original conditions. The aquifer lies in unconsolidated gravel beds overlying an impermeable basalt surface that has a plucked, flood-scoured, scabland structure. The current aquifer thickness is similar to the relief on the basalt basement. Thus the groundwater must flow around the impermeable basalt structures producing a complicated flow pattern under the waste storage unit. The original monitoring network was designed for northwest flow when the water table was held artificially high. Proper locations for new wells are dependent on our knowledge of the flow direction. The results of the colloidal borescope investigation agree with the southerly direction indicated from hydrographs, contaminant trends, other direct flow data and the general concept of a receding aquifer draining off the southern limb of a basalt anticline. Flow in the aquifer is diverted by irregular local structural highs of very low permeability basalt.

  5. Detection and Interpretation of Patterns of Motion in Mesoscale Atmospheric Flows

    NASA Astrophysics Data System (ADS)

    Ludwig, F. L.; Street, R. L.; Chen, Y.

    2002-12-01

    An objective analysis scheme was used to generate three dimensional flow fields from data collected during the October 2000 Vertical Transport and Mixing eXperiment (VTMX) in the Salt Lake Valley. The original observations and the examined flow fields have been analyzed using an Empirical Orthogonal Function (EOF) approach to detect recurring patterns of motion. The observations were used to identify relative strengths of valley flow, slope flow and canyon winds. For the 10 locations chosen, 2 EOFs accounted for about 75 percent of the variance. The results have been interpreted in terms of diurnal variations of the thermal flows in the Valley. The gridded winds from the objective analyses were also analyzed using EOFs to determine the nature of variations about the general flow over a 5 by 5 grid, with 1 km spacing. Three EOFs accounted for about half the variance. We are currently interpreting the results. The preferred patterns appear to be fairly regular, and include cases of undulation in the flow, enhanced shear, and patterns similar to singular points in a flow. We will examine how the statistics of intensity for these features varies with scale, by smoothing our analyses and reapplying the EOFs at different scales. We also intend to apply the same methods to numerical simulations of the same meteorological conditions in order to evaluate the simulations, and, we hope, to extend the analysis to smaller scales than can be derived from the observations. This work was supported by the U.S. Department of Energy, under the auspices of the Atmospheric Sciences Program of the Office of Biological and Environmental Research. We are grateful to the many VTMX participants who provided their data. They include those from Argonne, Livermore, Los Alamos and Pacific Northwest National Labs, from Arizona State and Utah Universities, NCAR, NOAA and others.

  6. Video camera observation for assessing overland flow patterns during rainfall events

    NASA Astrophysics Data System (ADS)

    Silasari, Rasmiaditya; Oismüller, Markus; Blöschl, Günter

    2015-04-01

    Physically based hydrological models have been widely used in various studies to model overland flow propagation in cases such as flood inundation and dam break flow. The capability of such models to simulate the formation of overland flow by spatial and temporal discretization of the empirical equations makes it possible for hydrologists to trace the overland flow generation both spatially and temporally across surface and subsurface domains. As the upscaling methods transforming hydrological process spatial patterns from the small obrseved scale to the larger catchment scale are still being progressively developed, the physically based hydrological models become a convenient tool to assess the patterns and their behaviors crucial in determining the upscaling process. Related studies in the past had successfully used these models as well as utilizing field observation data for model verification. The common observation data used for this verification are overland flow discharge during natural rainfall events and camera observations during synthetic events (staged field experiments) while the use of camera observations during natural events are hardly discussed in publications. This study advances in exploring the potential of video camera observations of overland flow generation during natural rainfall events to support the physically based hydrological model verification and the assessment of overland flow spatial patterns. The study is conducted within a 64ha catchment located at Petzenkirchen, Lower Austria, known as HOAL (Hydrological Open Air Laboratory). The catchment land covers are dominated by arable land (87%) with small portions (13%) of forest, pasture and paved surfaces. A 600m stream is running at southeast of the catchment flowing southward and equipped with flumes and pressure transducers measuring water level in minutely basis from various inlets along the stream (i.e. drainages, surface runoffs, springs) to be calculated into flow discharge. A

  7. Classification of gas-liquid flow patterns by the norm entropy of wavelet decomposed pressure fluctuations across a bluff body

    NASA Astrophysics Data System (ADS)

    Sun, Zhiqiang; Chen, Yanping; Gong, Hui

    2012-12-01

    Identification of gas-liquid flow patterns remains one of the paramount needs in multiphase flow metering. It is hardly possible to realize accurate measurement and control of parameters in a gas-liquid flow system without a clear understanding of its flow pattern. Here we explore the characterization of gas-liquid flow patterns using the norm entropy extracted from the wavelet decomposed pressure fluctuations across a bluff body. Experiments on air-water two-phase flow at ambient temperature and atmospheric pressure are carried out in the bubble, plug, slug and annular flow patterns. On the basis of the experimental results, two original flow-pattern maps are constructed: one is coordinated with the average norm entropy versus the total mass flow rate, and the other is the average norm entropy versus the volumetric void fraction. Verification tests demonstrate that the overall identification rates of the flow-pattern maps developed exceed 95%. This approach provides an effective and simple solution to the classification of gas-liquid flow patterns.

  8. Pattern formation in multiphase flow through porous media: continuum models and phase diagrams

    NASA Astrophysics Data System (ADS)

    Cueto-Felgueroso, L.; Juanes, R.

    2009-12-01

    Carbon capture and geologic storage, dissociation of methane hydrates in permafrost, infiltration of water in soil, and enhanced oil recovery, are some relevant examples of multiphase flow in porous media. While flow instabilities and pattern formation play a central role in these processes, our ability to describe them using mathematical models has been hampered by the lack of a macroscopic theory that explains the patterns observed in experimental and field conditions. We propose a new approach —phase-field modeling— to advance our fundamental understanding of multiphase porous media flow. The basic tenet, with origins in the mathematical description of solidification processes, is that the energy of the system is a function of the inhomogeneous distribution of fluid phases in the pore space, and should account for the presence of macroscopic interfaces. We present numerical simulations and compare our predictions with experimental observations. Numerical simulation of viscous fingering in a Hele-Shaw cell using the proposed phase-field modeling approach

  9. Non-parametric linear regression of discrete Fourier transform convoluted chromatographic peak responses under non-ideal conditions of internal standard method.

    PubMed

    Korany, Mohamed A; Maher, Hadir M; Galal, Shereen M; Fahmy, Ossama T; Ragab, Marwa A A

    2010-11-15

    This manuscript discusses the application of chemometrics to the handling of HPLC response data using the internal standard method (ISM). This was performed on a model mixture containing terbutaline sulphate, guaiphenesin, bromhexine HCl, sodium benzoate and propylparaben as an internal standard. Derivative treatment of chromatographic response data of analyte and internal standard was followed by convolution of the resulting derivative curves using 8-points sin x(i) polynomials (discrete Fourier functions). The response of each analyte signal, its corresponding derivative and convoluted derivative data were divided by that of the internal standard to obtain the corresponding ratio data. This was found beneficial in eliminating different types of interferences. It was successfully applied to handle some of the most common chromatographic problems and non-ideal conditions, namely: overlapping chromatographic peaks and very low analyte concentrations. For example, a significant change in the correlation coefficient of sodium benzoate, in case of overlapping peaks, went from 0.9975 to 0.9998 on applying normal conventional peak area and first derivative under Fourier functions methods, respectively. Also a significant improvement in the precision and accuracy for the determination of synthetic mixtures and dosage forms in non-ideal cases was achieved. For example, in the case of overlapping peaks guaiphenesin mean recovery% and RSD% went from 91.57, 9.83 to 100.04, 0.78 on applying normal conventional peak area and first derivative under Fourier functions methods, respectively. This work also compares the application of Theil's method, a non-parametric regression method, in handling the response ratio data, with the least squares parametric regression method, which is considered the de facto standard method used for regression. Theil's method was found to be superior to the method of least squares as it assumes that errors could occur in both x- and y-directions and

  10. Analysis of spatial flow patterns across the Indian subcontinent via multi-basin hydrological modelling

    NASA Astrophysics Data System (ADS)

    Pechlivanidis, Ilias; Arheimer, Berit

    2016-04-01

    In here, we use examples from the recent HYPE hydrological model set-up across 6010 subbasins for the Indian subcontinent, named India-HYPE v1.0 (Pechlivanidis and Arheimer, 2015), and demonstrate the potential of multi-basin modelling for process understanding and comparative hydrology. We analyse the flow characteristics in all modelled 6010 subbasins and group them based on similarities in 12 flow signatures to gain insights in spatial patterns of flow generating processes. We applied a k-means clustering approach within the 12-dimensional space (consisting of the 12 calculated flow signatures) to categorise the subbasins based on their combined similarity in flow signatures. To highlight the hydrological insights gained during model identification, we conducted the clustering analysis on two different steps of the model calibration and explored the sensitivity of calibration on the spatial patterns of flow signatures. Analysis resulted into six different classes of varying size with different distribution in signatures. Although the classes are geographically distinct, their flow response is dependent on the physiographic and climatic characteristics at the regional scale. Factors including for instance the dominance of snow/ice processes, volume in precipitation and evaporation rates affect the catchment functioning and hence drive the clustering. Catchments in the Himalayan region and the Western Ghats respond similarly and are characterised by high mean annual specific runoff values and variable flow regime. Response of the catchments in the tropical zone is characterised by high peaks, while catchments in the dry regions show very strong flow variability and respond quickly to rainfall. Finally, model parameterisation can affect the spatial pattern of clusters in terms of catchment functioning. In particular, clusters after calibration seem to have a consistent spatial structure; this also justifies the validity of parameter regionalisation approaches based