Science.gov

Sample records for non-ideal flow patterns

  1. SU2: the Open-Source Software for Non-ideal Compressible Flows

    NASA Astrophysics Data System (ADS)

    Pini, M.; Vitale, S.; Colonna, P.; Gori, G.; Guardone, A.; Economon, T.; Alonso, J. J.; Palacios, F.

    2017-03-01

    The capabilities of the open-source SU2 software suite for the numerical simulation of viscous flows over unstructured grid are extended to non-ideal compressible-fluid dynamics (NICFD). A built-in thermodynamic library is incorporated to account for the non-ideal thermodynamic characteristics of fluid flows evolving in the close proximity of the liquid-vapour saturation curve and critical point. The numerical methods, namely the Approximate Riemann Solvers (ARS), viscous fluxes and boundary conditions are generalised to non-ideal fluid properties. Quantities of interest for turbomachinery cascades, as loss coefficients and flow angles, can be automatically determined and used for design optimization. A variety of test cases are carried out to assess the performance of the solver. At first, numerical methods are verified against analytical solution of reference NICFD test cases, including steady shock reflection and unsteady shock tube. Then, non-ideal gas effects in planar nozzles and past turbine cascades, typically encountered in Organic Rankine Cycle applications, are investigated and debated. The obtained results demonstrate that SU2 is highly suited for the analysis and the automatic design of internal flow devices operating in the non-ideal compressible-fluid regime.

  2. A Bayesian study of uncertainty in ultrasonic flow meters under non-ideal flow conditions

    NASA Astrophysics Data System (ADS)

    Belligoli, Z.; Dwight, R. P.; Kok, G. J. P.; Lucas, P.

    2017-08-01

    This paper presents an approach for updating the epistemic uncertainty of ultrasonic flow meter measurements under non-ideal flow conditions. Instead of re-calibrating the instrument to correct its behavior in these difficult working conditions, a Bayesian calibration of a computer model of the real process is used. The numerical model is based on computational fluid dynamics (CFD) and a surrogate model is constructed from a limited number of CFD calculations using kriging. The computer model predicts the flow rate dependent on certain parameters including the bulk Reynolds number—which carries information about the true speed of the flow, and is measured only approximately by an ultrasonic flow meter. Bayesian calibration is applied, and the posterior of the true speed can be derived from the marginal posterior of the Reynolds number. This pdf has a smaller uncertainty with respect to the observed data used to fit the model on the condition that sufficiently informative data are available. If this is the case, the proposed approach is capable of reducing not only the uncertainty but also the error associated with the flow meter measurements in non-ideal conditions.

  3. Non-Ideal Compressible-Fluid Dynamics of Fast-Response Pressure Probes for Unsteady Flow Measurements in Turbomachinery

    NASA Astrophysics Data System (ADS)

    Gori, G.; Molesini, P.; Persico, G.; Guardone, A.

    2017-03-01

    The dynamic response of pressure probes for unsteady flow measurements in turbomachinery is investigated numerically for fluids operating in non-ideal thermodynamic conditions, which are relevant for e.g. Organic Rankine Cycles (ORC) and super-critical CO2 applications. The step response of a fast-response pressure probe is investigated numerically in order to assess the expected time response when operating in the non-ideal fluid regime. Numerical simulations are carried out exploiting the Non-Ideal Compressible Fluid-Dynamics (NICFD) solver embedded in the open-source fluid dynamics code SU2. The computational framework is assessed against available experimental data for air in dilute conditions. Then, polytropic ideal gas (PIG), i.e. constant specific heats, and Peng-Robinson Stryjek-Vera (PRSV) models are applied to simulate the flow field within the probe operating with siloxane fluid octamethyltrisiloxane (MDM). The step responses are found to depend mainly on the speed of sound of the working fluid, indicating that molecular complexity plays a major role in determining the promptness of the measurement devices. According to the PRSV model, non-ideal effects can increase the step response time with respect to the acoustic theory predictions. The fundamental derivative of gas-dynamic is confirmed to be the driving parameter for evaluating non-ideal thermodynamic effects related to the dynamic calibration of fast-response aerodynamic pressure probes.

  4. 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.

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

    SciTech Connect

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

    2016-08-14

    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.

  6. 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.

  7. Divergence Free High Order Filter Methods for Multiscale Non-ideal MHD Flows

    NASA Technical Reports Server (NTRS)

    Yee, H. C.; Sjoegreen, Bjoern

    2003-01-01

    Low-dissipative high order filter finite difference methods for long time wave propagation of shock/turbulence/combustion compressible viscous MHD flows has been constructed. Several variants of the filter approach that cater to different flow types are proposed. These filters provide a natural and efficient way for the minimization of the divergence of the magnetic field (Delta . B) numerical error in the sense that no standard divergence cleaning is required. For certain 2-D MHD test problems, divergence free preservation of the magnetic fields of these filter schemes has been achieved.

  8. 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.

  9. Kinetics of osmotic water flow across cell membranes in non-ideal solutions during freezing and thawing.

    PubMed

    Weng, Lindong; Li, Weizhong; Zuo, Jianguo

    2010-10-01

    Cryopreservation requires quantitatively analytical models to simulate the biophysical responses of biomaterials during cryopreservation. The Mazur model and other improved ones, such as Karlsson model concerning solutions containing cryoprotectants (CPA), are somehow precluded by some minor points, particularly, the assumption of ideal solutions. To avoid the ideal solution assumption, in this study a new method is developed to simulate water transport across cell membranes in non-ideal solutions during cooling and thawing. The comparison between osmolalities calculated by the linear freezing-point depression used in this new method and other non-ideal ones is conducted and a good agreement is achieved. In addition, in an ideal case, besides a theoretical agreement, this new approach has been validated by its numerical simulation results. Comparisons between this new approach and the traditional ones with an ideal solution assumption have been conducted based on a spherical hypothetical cell. The main results are (1) the predicted non-ideal intracellular water content is larger than the ideal results; (2) the concentration of CPA solutions is directly proportional to the deviation between the non-ideal and ideal curves. In the end, this study presents a direct description of the degree of subcooling of the protoplasm during dynamic cooling. This study demonstrates that our experimental data-based method is a valid one with clear physical interpretations, convenient expressions and a more extensive application room than traditional ones. Copyright © 2010 Elsevier Inc. All rights reserved.

  10. Similarity solution for the flow behind a shock wave in a non-ideal gas with heat conduction and radiation heat-flux in magnetogasdynamics

    NASA Astrophysics Data System (ADS)

    Nath, G.; Vishwakarma, J. P.

    2014-05-01

    The propagation of a spherical (or cylindrical) shock wave in a non-ideal gas with heat conduction and radiation heat-flux, in the presence of a spacially decreasing azimuthal magnetic field, driven out by a moving piston is investigated. The heat conduction is expressed in terms of Fourier's law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient αR are assumed to vary with temperature and density. The gas is assumed to have infinite electrical conductivity and to obey a simplified van der Waals equation of state. The shock wave moves with variable velocity and the total energy of the wave is non-constant. Similarity solutions are obtained for the flow-field behind the shock and the effects of variation of the heat transfer parameters, the parameter of the non-idealness of the gas, both, decreases the compressibility of the gas and hence there is a decrease in the shock strength. Further, it is investigated that with an increase in the parameters of radiative and conductive heat transfer the tendency of formation of maxima in the distributions of heat flux, density and isothermal speed of sound decreases. The pressure and density vanish at the inner surface (piston) and hence a vacuum is form at the center of symmetry. The shock waves in conducting non-ideal gas with conductive and radiative heat fluxes can be important for description of shocks in supernova explosions, in the study of central part of star burst galaxies, nuclear explosion, chemical detonation, rupture of a pressurized vessels, in the analysis of data from exploding wire experiments, and cylindrically symmetric hypersonic flow problems associated with meteors or reentry vehicles, etc. The findings of the present works provided a clear picture of whether and how the non-idealness parameter, conductive and radiative heat transfer parameters and the magnetic field affect the flow behind the shock

  11. Steady non-ideal detonations

    NASA Astrophysics Data System (ADS)

    Sharpe, Gary

    2009-06-01

    Theories for determining the velocity of detonation (VoD) in highly non-ideal explosives, e.g. commercial explosives used in mining, are discussed. Such explosives have critical charge diameters of several centimetres. An analysis of the interaction between detonations and confining materials along the explosive-confiner interface reveals there a two main types of interaction. In the first (denoted here by case 1) the detonation drives an oblique shock into the confiner. For the second (case 2), a wave propagates in the confiner ahead of the detonation in the explosive. Shock polar interactions are examined for commercial explosives and rocks, which shows that a significant proportion of problems are case 2 in mining. For case 1, numerical simulations show that for a given explosive model there is a unique relationship (valid for all charge diameters and confinements) between the VoD and the curvature of the detonation shock at the charge axis. This relationship is shown to be well predicted by a quasi-one-dimensional type analysis. A simple detonation shock dynamics method which uses this relationships predicts well the VoD even in highly non-ideal cases, provided the explosive is sufficiently confined (usually the case in mining), but which is inaccurate in the limit of an unconfined charge. Preliminary results of a novel variational method for solving the unconfined situation are also discussed. Numerical simulations are performed to investigate the coupling mechanisms in case 2 situations, including the influence on diameter effects. It is shown that, in agreement with an approximate theory, the detonation is driven up to VoDs above the confiner's sound speed, and the wave in the confiner weakly pre-compresses the explosive ahead of the detonation front.

  12. 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.

  13. Steady Non-Ideal Detonation

    NASA Astrophysics Data System (ADS)

    Sharpe, G. J.; Luheshi, M. Y.; Braithwaite, M.; Falle, S. A. E. G.

    2009-12-01

    Highly non-ideal explosives, such as commercial ammonium nitrate based explosives used in mining and blasting, have critical charge diameters of several centimetres and relatively low detonation speeds. Shock polar match analyses between these explosives and confining inert materials give two main types of interactions. For the first type (denoted here by case I), the detonation drives an oblique shock into the confiner. For the second type (case II), a wave propagates in the confiner ahead of the detonation wave in the explosive. In case I, numerical simulations show that for a given explosive model there is a unique relationship (valid for all charge diameters and confinements) between the velocity of detonation (VoD) and the curvature of the detonation shock at the charge axis. This relationship is shown to be well predicted by a quasi-one-dimensional analysis. A simple detonation shock dynamics method which uses this relationship predicts the VoD provided the explosive is sufficiently confined (usually the case in mining), but is inaccurate in the limit of an unconfined charge. For commercial explosives confined by rocks, a significant proportion of problems are case II. Numerical simulations are performed to investigate the coupling mechanisms in these situations. It is found that, in agreement with an approximate theory, the detonation is driven up to VoDs near the confiner's sound speed, and the wave in the confiner weakly pre-compresses the explosive ahead of the detonation front.

  14. Flux and Field Line Conservation in 3-D Non-Ideal MHD Flows: Remarks About Criteria for 3-D Reconnection Without Magnetic Neutral Points and Their Application to the Heliospheric Interface

    NASA Astrophysics Data System (ADS)

    Nickeler, D. H.; Fahr, H.-J.

    2006-05-01

    In this paper, we address the issue of finding velocity fields which conserve magnetic flux or at least magnetic fieldline connectivity. We start from the basic principles of flux and line conservation and present and discuss the criterion, given by Newcomb (1958), Stern (1966), and Vasyliunas (1972). In addition, we find a new formulation of the line-conserving velocity field by solving the system of partial differential equations which corresponds to Newcomb's criterion for line conservation. This velocity field is given by a correlation between the non-idealness, described by a generalized form of the Ohm's law and a general transporting velocity, which is fieldline conserving. Our considerations give additional insights into the discussion on violations of the frozen-in field concept which started recently with the papers by Baranov and Fahr (2003a,b). These authors analyzed a generalized form of Ohm's law, which is valid for the heliosphere and claimed that the transport velocity for the magnetic flux may be different from the plasma velocity. We can show that the non-idealness given in the paper by Baranov and Fahr could not change the magnetic topology and can therefore not be responsible for magnetic reconnection. But we found that it is in general not clear if the flux-conserving velocity field is identical to the plasma flow or to any species velocity field.

  15. 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.

  16. Supersonic flow of non-ideal fluids in nozzles: An application of similitude theory and lessons for ORC turbine design and flexible use considering system performance

    NASA Astrophysics Data System (ADS)

    White, M.; Sayma, A. I.; Markides, C. N.

    2017-03-01

    A significant improvement in the economy-of-scale of small-scale organic Rankine cycle (ORC) systems can arise from the appropriate design of components that can be manufactured in large volumes and implemented flexibly into a wide range of systems and potential applications. This, in turn, requires accurate predictions of component performance that can capture variations in the cycle conditions, parameters or changes to the working fluid. In this paper previous work investigating a modified similitude theory used to predict the performance of subsonic ORC turbines is extended to analyse the supersonic flow of organic fluids within 2D converging-diverging nozzles. Two nozzles are developed using a minimum length method of characteristics design model coupled to REFPROP. These are designed for R245fa and Toluene as working fluids with nozzle exit Mach numbers of 1.4 and 1.7 respectively. First, the nozzle performance is confirmed using CFD simulations, and then further CFD simulations are performed to evaluate the performance of the same nozzles over a range of different inlet conditions and with different working fluids. The CFD simulations are compared to predictions made using the original and modified similitude theories, and also to predictions made by conserving the Prandtl-Meyer function for the different operating conditions. The results indicate that whilst the modified similitude model does not accurately predict nozzle performance, conserving the Prandtl-Meyer function allows to predict the nozzle outlet Mach number to within 2% providing there is not a significant change in the polytropic index. Finally, the effect of working fluid replacement on the ORC system is discussed, and preliminary results demonstrate the possibility of matching a particular turbine to a heat source through optimal working fluid selection.

  17. Modeling of non-ideal aluminized explosives

    NASA Astrophysics Data System (ADS)

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

    2000-04-01

    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 Al2O3. 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 ???

  18. 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.

  19. Modeling of Non-Ideal Aluminized Detonations

    NASA Astrophysics Data System (ADS)

    Howard, W. Michael; Fried, Laurence E.; Souers, P. Clark

    1999-06-01

    We have implemented a Wood-Kirkwood (WK) 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 burning of Al in condensed detonation that depends on the surface properties of the Al grains and the detonation product gases. Moreover, we use an exp-6 equation of state for the product fluids that reproduces a wide range experimental shock hugoniot and static compression data. We use a Murnaghan form for the equation of state of the solid and liquid Al and Al_2O_3. We find that we can replicate experimental detonation velocities to within a few per cent 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. This work was performed under the auspices of the U. S. Department of Energy under Contract No. W-7405-ENG-48.

  20. 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.

  1. Non-ideal Solution Thermodynamics of Cytoplasm

    PubMed Central

    Ross-Rodriguez, Lisa U.; McGann, Locksley E.

    2012-01-01

    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

  2. Kinetic modeling of non-ideal explosives

    SciTech Connect

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

    1999-03-01

    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. We model a wide range of ideal and non-ideal composite energetic materials. In addition, we develop an exp-6 equation of state for the product fluids that reproduces a wide range experimental shock Hugoniot and static compression data. For unreacted solids, including solid and liquid Al and Al{sub 2}O{sub 3}, we use a Murnaghan form for the equation of state. We find that we can replicate experimental detonation velocities to within a few per cent for a wide range of explosives, while obtaining good agreement with estimated reaction zone lengths. The detonation velocity as a function of charge radius is also correctly reproduced.

  3. Non-ideal compressible-fluid effects in oblique shock waves

    NASA Astrophysics Data System (ADS)

    Gori, G.; Vimercati, D.; Guardone, A.

    2017-03-01

    The non-monotone dependence of the speed of sound along adiabatic transformations is demonstrated to result in the admissibility of non-ideal increase of the flow Mach number across oblique shock waves, for pre-shock states in close proximity of the liquid-vapour saturation curve. This non-ideal behaviour is primarily associated with a less-than-unity value of the fundamental derivative of gasdynamics and, therefore, non-ideal shock waves are expected to be observed in flows of fluids with moderate molecular complexity. The simple yet qualitatively sound van der Waals model is used to confirm the present findings and to provide exemplary non-ideal shock waves.

  4. Patterning flows and polymers

    NASA Astrophysics Data System (ADS)

    Stroock, Abraham Duncan

    This thesis presents the use of patterned surfaces for controlling fluid dynamics on a sub-millimeter scale, and for fabricating a new class of polymeric materials. In chapters 1--4, chemical and mechanical structures were used to control the form of flows of fluids in microchannels. This work was done in the context of the development of microfluidic technology for performing chemical tasks in portable, integrated devices. Chapter 1 reviews this work for an audience of chemists who are potential users of these techniques in the development of micro-analytical and micro-synthetic devices. Appendix 1 contains a more general review of microfluidics. Chapter 2 presents experimental results on the use of patterned surface charge density to create new electroosmotic (EO) flows in microchannels; the chapter includes a successful model of the observed flows. In Chapter 3, patterns of topography on the wall of a microchannel were used to generate recirculation in pressure-driven flows. The design and characterization of an efficient mixer based on these flows is presented. A theoretical treatment of these flows is given in Appendix 2. The experimental methods used for the work with both EO and pressure-driven flows are presented in Chapter 4. In Chapter 5, a pattern of asymmetrical grooves in a heated plate was used to perturb Marangoni-Benard (M-B) convection, a dynamic system that spontaneously forms patterned flows. The interaction of the imposed pattern and the inherent pattern of the M-B convection led to a net flow in the plane of convecting layer of fluid. The direction of this flow depended on the orientation of the asymmetrical grooves, the temperature difference across the layer, and the thickness of the layer. A phenomenological model is presented to explain this ratchet effect in which local recirculation was coupled into a global flow. In Chapter 6, surfaces patterned by microcontact printing were used as a workbench on which to build molecularly thin polymer

  5. Evolution of weak shock waves in non-ideal magnetogasdynamics

    NASA Astrophysics Data System (ADS)

    Nath, Triloki; Gupta, R. K.; Singh, L. P.

    2017-04-01

    The aim of this paper is to analyze the main features of weakly non-linear waves propagating in a compressible, inviscid, non-ideal gas with infinite electrical conductivity modelled by van der Waals equation of state permeated by transverse magnetic field. An asymptotic approach is used to derive the evolution equation, which characterizes the wave phenomena in a high frequency domain. The growth equation of an acceleration wave is derived as a special case. Further, we also discuss the propagation of disturbances in the form of sawtooth profile. The effect of magnetic field and van der Waals parameter on the decay of sawtooth profile is presented. A remarkable difference between planar and nonplanar flows in magnetic case and nonmagnetic case has been drawn. Also the variation in velocity profile between planar and nonplanar flows has been discussed.

  6. Non-ideal axicon-generated Bessel beam application for intra-volume glass modification.

    PubMed

    Dudutis, Juozas; GeČys, Paulius; RaČiukaitis, Gediminas

    2016-12-12

    The extended focal depth of Bessel beams is a very attracting property for glass cutting applications. However, Bessel beam generation with a non-ideal conical lens induces beam pattern distortions. We present our novel results on bulk modifications of soda-lime glass using a non-ideal axicon-generated Bessel beam. Modelling of the Bessel beam pattern and experimental measurements indicated ellipticity of the central core diameter. That resulted in the formation of cracks in a transverse direction inside the bulk of glass. Furthermore, we demonstrate the possibility to control the transverse crack propagation direction, which is crucial in the case of glass cutting applications.

  7. 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].

  8. Non-Ideal Compressible Fluid Dynamics: A Challenge for Theory

    NASA Astrophysics Data System (ADS)

    Kluwick, A.

    2017-03-01

    The possibility that compression as well as rarefaction shocks may form in single phase vapours was envisaged first by Bethe (1942). However calculations based on the Van der Waals equation of state indicated that the latter type of shock is possible only if the specific heat at constant volume cv divided by the universal gas constant R is larger than about 17.5 which he considered too large to be satisfied by real fluids. This conclusion was contested by Thompson (1971) who showed that the type of shock capable of forming in arbitrary fluids is determined by the sign of the thermodynamic quantity to which he referred to as fundamental derivative of gas dynamics. Here v, p, s and c denote the specific volume, the pressure, the entropy and the speed of sound. Thompson and co-workers also showed that the required condition for the existence of rarefaction shocks, that Γ may take on negative values, is indeed satisfied for a number of hydrocarbon and fluorocarbon vapours. This finding spawned a burst of theoretical studies elaborating on the unusual and often counterintuitive behaviour of shocks with rarefaction shocks present. These produced both results of theoretical character but also results suggesting the practical importance of Non-Ideal Compressible Fluid Dynamics in general. The present paper addresses some of the challenges encountered in connection with the theoretical treatment of the associated flow behaviour. Weakly nonlinear acoustic waves of finite amplitude serve as a starting point. Here mixed rather than strictly positive nonlinearity generates a wealth of phenomena not possible in perfect gases. Examples of steady flows where these non-classical effects play a decisive role (and which may be useful also for future experimental work) are quasi one-dimensional nozzle flows and transonic two-dimensional flows past corners. The study of viscous effects concentrates on laminar flows of boundary layer type. Here non-classical phenomena are caused by the

  9. 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.

  10. Determination of performance of non-ideal aluminized explosives.

    PubMed

    Keshavarz, Mohammad Hossein; Mofrad, Reza Teimuri; Poor, Karim Esmail; Shokrollahi, Arash; Zali, Abbas; Yousefi, Mohammad Hassan

    2006-09-01

    Non-ideal explosives can have Chapman-Jouguet (C-J) detonation pressure significantly different from those expected from existing thermodynamic computer codes, which usually allows finding the parameters of ideal detonation of individual high explosives with good accuracy. A simple method is introduced by which detonation pressure of non-ideal aluminized explosives with general formula C(a)H(b)N(c)O(d)Al(e) can be predicted only from a, b, c, d and e at any loading density without using any assumed detonation products and experimental data. Calculated detonation pressures show good agreement with experimental values with respect to computed results obtained by complicated computer code. It is shown here how loading density and atomic composition can be integrated into an empirical formula for predicting detonation pressure of proposed aluminized explosives.

  11. Influence of non-ideality on condensation to aerosol

    NASA Astrophysics Data System (ADS)

    Compernolle, S.; Ceulemans, K.; Müller, J.-F.

    2009-02-01

    Secondary organic aerosol (SOA) is a complex mixture of water and organic molecules. Its composition is determined by the presence of semi-volatile or non-volatile compounds, their saturation vapor pressure and activity coefficient. The activity coefficient is a non-ideality effect and is a complex function of SOA composition. In a previous publication, the detailed chemical mechanism (DCM) for α-pinene oxidation and subsequent aerosol formation BOREAM was presented. In this work, we investigate with this DCM the impact of non-ideality by simulating smog chamber experiments for α-pinene degradation and aerosol formation and taking the activity coefficient into account of all molecules in the aerosol phase. Several versions of the UNIFAC method are tested for this purpose, and missing parameters for e.g. hydroperoxides and nitrates are inferred from fittings to activity coefficient data generated using the SPARC model. Alternative approaches to deal with these missing parameters are also tested, as well as an activity coefficient calculation method based on Hansen solubility parameters (HSP). It turns out that for most experiments, non-ideality has only a limited impact on the interaction between the organic molecules, and therefore on SOA yields and composition, when water uptake is ignored. The reason is that often, the activity coefficient is on average close to 1 and, specifically for high-VOC experiments, partitioning is not very sensitive on the activity coefficient because the equilibrium is shifted strongly towards condensation. Still, for ozonolysis experiments with low amounts of volatile organic carbon (low-VOC), the UNIFAC parameterization of Raatikainen et al. leads to significantly higher SOA yields (by up to a factor 1.6) compared to the ideal case and to other parameterizations. Water uptake is model dependent, in the order: ideal > UNIFAC-Raatikainen > UNIFAC-Peng > UNIFAC-Hansen ≍ UNIFAC-Magnussen ≍ UNIFAC-Ming. In the absence of salt

  12. 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.

  13. Cylindrical shock waves in rotational axisymmetric non-ideal dusty gas with increasing energy under the action of monochromatic radiation

    NASA Astrophysics Data System (ADS)

    Sahu, P. K.

    2017-08-01

    The propagation of a cylindrical shock wave in a rotational axisymmetric non-ideal dusty gas under the action of monochromatic radiation with increasing energy, which has variable azimuthal and axial components of fluid velocity, is investigated. The dusty gas is assumed to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. Similarity solutions are obtained as well as the effects of the variation of the radiation parameters, the parameter of 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 piston velocity index are worked out in detail. The total energy of the shock wave is varying and increases with time. It is observed that the radiation parameter and the piston velocity index have opposite behaviour on the flow variables as well as the shock strength.

  14. Stochastic Flux-Freezing for Non-Ideal Hydromagnetic Plasmas

    NASA Astrophysics Data System (ADS)

    Eyink, Gregory

    2009-11-01

    Non-ideal (viscous and resistive) magnetohydrodynamic plasmas are shown to possess stochastic versions of ideal flux-freezing laws. The magnetic field at a point is equal to the average of an infinite ensemble of field-lines advected to that point by the plasma velocity perturbed with a random white-noise (stochastic Lundquist formula). This implies a stochastic Alfv'en theorem, valid for any value of the magnetic Prandtl number. At unit Prandtl number there is also a random version of the generalized Kelvin theorem derived by Bekenstein-Oron for ideal MHD. These stochastic conservation laws are not only consequences of the non-ideal MHD equations, but are in fact equivalent to those equations. Similar results hold for Hall magnetohydrodynamics and the two-fluid plasma model. We argue that flux-conservation remains stochastic for turbulent MHD plasmas in the limit of infinite Reynolds numbers. Infinitely-many field lines are advected to each point by turbulent Richardson diffusion. The reconnection speed for pairs of field lines is the relative velocity of the turbulent fluid at their initial locations. Small-scale turbulent dynamo effect is rigorously related to angular correlation of the individual field vectors before reconnection.

  15. 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.

  16. (Air flow patterns within buildings)

    SciTech Connect

    Harrje, D.T.

    1990-10-15

    As Annex 20 enters the final year, deliverables in the form of reports, guidelines, and data formats are nearing completion. The Reporting Guidelines for the Measurement of Air Flows and Related Factors in Buildings will be published by the AIVC next month and was presented to the research community at the 11th AIVC Conference. Measurement guidelines and state-of-the-art equipment descriptions are part of a comprehensive manual, Measurement Techniques Related to Air Flow Patterns Within Buildings -- An Application Guide, in the final stages of preparation in Part 2 of Annex 20, together with reports on how to estimate the effects of flow through large openings, as well as contaminant movements in buildings. The Measurement Manual will include the latest information from the AIVC. The next AIVC Conference, in Ottawa, September 1991, will feature more than 12 presentations of Annex 20 results, including the information from Part 1 which has focused on the detailed air flow patterns in a variety of single-room configurations. Both complex modelling (including CFD) and detailed measurements have been completed, and it is now desirable that added tests be made in the next months by the University of Illinois, BERL, representing the US in Part 1 for the first time.

  17. 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.

  18. Model of non-ideal detonation of condensed high explosives

    NASA Astrophysics Data System (ADS)

    Smirnov, E. B.; Kostitsin, O. V.; Koval, A. V.; Akhlyustin, I. A.

    2016-11-01

    The Zeldovich-Neumann-Doering theory of ideal detonation allows one to describe adequately the detonation of charges with near-critical diameter. For smaller diameters, detonation velocity can differ significantly from an ideal value expected based on equilibrium chemical thermodynamics. This difference is quite evident when using non-ideal explosives; in certain cases, this value can be up to one third of ideal detonation velocity. Numerical simulation of these systems is a very labor-consuming process because one needs to compute the states inside the chemical reaction zone, as well as to obtain data on the equation of state of high-explosive detonation products mixture and on the velocity of chemical reaction; however, these characteristics are poorly studied today. For practical purposes, one can use the detonation shock dynamics model based on interrelation between local velocity of the front and its local curvature. This interrelation depends on both the equation of state of explosion products, and the reaction velocity; but the explicit definition of these characteristics is not needed. In this paper, experimental results are analyzed. They demonstrate interrelation between the local curvature of detonation front and the detonation velocity. Equation of detonation front shape is found. This equation allows us to predict detonation velocity and shape of detonation wave front in arbitrary geometry by integrating ordinary differential equation for the front shape with a boundary condition at the charge edge. The results confirm that the model of detonation shock dynamics can be used to describe detonation processes in non-ideal explosives.

  19. Propagation of exponential shock wave in an axisymmetric rotating non-ideal dusty gas

    NASA Astrophysics Data System (ADS)

    Nath, G.

    2016-09-01

    One-dimensional unsteady isothermal and adiabatic flow behind a strong exponential shock wave propagating in a rotational axisymmetric mixture of non-ideal gas and small solid particles, which has variable azimuthal and axial fluid velocities, is analyzed. The shock wave is driven out by a piston moving with time according to exponential law. The azimuthal and axial components of the fluid velocity in the ambient medium are assumed to be varying and obeying exponential laws. In the present work, small solid particles are considered as pseudo-fluid with the assumption that the equilibrium flow-conditions are maintained in the flow-field, and the viscous-stress and heat conduction of the mixture are negligible. Solutions are obtained in both the cases, when the flow between the shock and the piston is isothermal or adiabatic by taking into account the components of vorticity vector and compressibility. It is found that the assumption of zero temperature gradient brings a profound change in the density, axial component of vorticity vector and compressibility distributions as compared to that of the adiabatic case. To investigate the behavior of the flow variables and the influence on the shock wave propagation by the parameter of non-idealness of the gas overline{b} in the mixture as well as by the mass concentration of solid particles in the mixture Kp and by the ratio of the density of solid particles to the initial density of the gas G1 are worked out in detail. It is interesting to note that the shock strength increases with an increase in G1 ; whereas it decreases with an increase in overline{b} . Also, a comparison between the solutions in the cases of isothermal and adiabatic flows is made.

  20. Inspiratory flow pattern in humans.

    PubMed

    Lafortuna, C L; Minetti, A E; Mognoni, P

    1984-10-01

    The theoretical estimation of the mechanical work of breathing during inspiration at rest is based on the common assumption that the inspiratory airflow wave is a sine function of time. Different analytical studies have pointed out that from an energetic point of view a rectangular wave is more economical than a sine wave. Visual inspection of inspiratory flow waves recorded during exercise in humans and various animals suggests that a trend toward a rectangular flow wave may be a possible systematic response of the respiratory system. To test this hypothesis, the harmonic content of inspiratory flow waves that were recorded in six healthy subjects at rest, during exercise hyperventilation, and during a maximum voluntary ventilation (MVV) maneuver were evaluated by a Fourier analysis, and the results were compared with those obtained on sinusoidal and rectangular models. The dynamic work inherent in the experimental waves and in the sine-wave model was practically the same at rest; during exercise hyperventilation and MVV, the experimental wave was approximately 16-20% more economical than the sinusoidal one. It was concluded that even though at rest the sinusoidal model is a reasonably good approximation of inspiratory flow, during exercise and MVV, a physiological controller is probably operating in humans that can select a more economical inspiratory pattern. Other peculiarities of airflow wave during hyperventilation and some optimization criteria are also discussed.

  1. Mutual optical intensity propagation through non-ideal mirrors.

    PubMed

    Meng, Xiangyu; Shi, Xianbo; Wang, Yong; Reininger, Ruben; Assoufid, Lahsen; Tai, Renzhong

    2017-09-01

    The mutual optical intensity (MOI) model is extended to include the propagation of partially coherent radiation through non-ideal mirrors. The propagation of the MOI from the incident to the exit plane of the mirror is realised by local ray tracing. The effects of figure errors can be expressed as phase shifts obtained by either the phase projection approach or the direct path length method. Using the MOI model, the effects of figure errors are studied for diffraction-limited cases using elliptical cylinder mirrors. Figure errors with low spatial frequencies can vary the intensity distribution, redistribute the local coherence function and distort the wavefront, but have no effect on the global degree of coherence. The MOI model is benchmarked against HYBRID and the multi-electron Synchrotron Radiation Workshop (SRW) code. The results show that the MOI model gives accurate results under different coherence conditions of the beam. Other than intensity profiles, the MOI model can also provide the wavefront and the local coherence function at any location along the beamline. The capability of tuning the trade-off between accuracy and efficiency makes the MOI model an ideal tool for beamline design and optimization.

  2. Mutual optical intensity propagation through non-ideal mirrors

    DOE PAGES

    Meng, Xiangyu; Shi, Xianbo; Wang, Yong; ...

    2017-08-18

    The mutual optical intensity (MOI) model is extended to include the propagation of partially coherent radiation through non-ideal mirrors. The propagation of the MOI from the incident to the exit plane of the mirror is realised by local ray tracing. The effects of figure errors can be expressed as phase shifts obtained by either the phase projection approach or the direct path length method. Using the MOI model, the effects of figure errors are studied for diffraction-limited cases using elliptical cylinder mirrors. Figure errors with low spatial frequencies can vary the intensity distribution, redistribute the local coherence function and distortmore » the wavefront, but have no effect on the global degree of coherence. The MOI model is benchmarked againstHYBRIDand the multi-electronSynchrotron Radiation Workshop(SRW) code. The results show that the MOI model gives accurate results under different coherence conditions of the beam. Other than intensity profiles, the MOI model can also provide the wavefront and the local coherence function at any location along the beamline. The capability of tuning the trade-off between accuracy and efficiency makes the MOI model an ideal tool for beamline design and optimization.« less

  3. 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.

  4. 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.

  5. Non-ideal effects on the stability and transport of magnetized plasmas

    NASA Astrophysics Data System (ADS)

    Ferraro, Nathaniel Mandrachia

    Magnetohydrodynamics (MHD), a fluid model of the low-frequency behavior of magnetized plasma, provides the most successful framework for understanding the equilibrium and large-scale stability of magnetically confined plasma. The success of this model is due in large part to its simplicity relative to more complete models. Much of this simplicity comes at the expense of the omission of non-ideal effects, which include dissipation, two-fluid and finite Larmor radius effects, micro-turbulence, and wave-particle interactions, among others. Often, the inclusion of these effects leads to important and unexpected phenomena. However, incorporating some of these effects, which may occur on vastly disparate spatial and temporal scales, introduces significant mathematical complexity and makes obtaining numerical solutions substantially more difficult. This dissertation investigates methods for numerically solving fluid models that have been extended to include some of these non-ideal effects, and to use these methods together with analytic theory to explore non- ideal effects on the steady-states and stability of magnetized plasmas. An overview of the two-fluid model of a magnetized plasma is given. This overview includes discussion of various methods of closing the fluid equations, and the physical effects included (or excluded) by each method. A method for the solution of a generic set of collisional two-fluid equations is described, and results from an implementation of this method, the numerical code M3D- C 1 , are presented. The importance of two-fluid effects and gyroviscosity on the linear growth rate of three instabilities--the gravitational instability, the magnetorotational instability, and the magnetothermal instability--is demonstrated analytically. It is shown that gyroviscosity, in particular, may play an important role in the stability threshold of these instabilities. Toroidal axisymmetric steady-states of the two-fluid model are obtained using M3D- C 1 for

  6. Effects of non-ideal boundary conditions on natural frequencies of fluid conveying micro-beams

    SciTech Connect

    Atci, Duygu Çömen; Özkaya, Erdoğan

    2016-06-08

    In this study, vibrations of fluid conveying micro-beams under non-ideal boundary conditions are investigated. Non-ideal boundary conditions are modeled as a linear combination of ideal clamped and ideal simply supported boundary conditions. The weighting factor k is presented as a rate of non-ideal boundary condition. Non-ideal clamped and non-ideal simply supported beams are both considered to see the effects of the boundary conditions. Hamilton’s principle is used to obtain equations of motion of the system and the method of multiple scales which is one of the perturbation techniques is applied to the equation. Approximate solutions of the linear and nonlinear equations of motion are obtained and the effects of non-ideal boundary conditions on natural frequencies are presented.

  7. Magnetically stimulated fluid flow patterns

    ScienceCinema

    Martin, Jim; Solis, Kyle

    2016-07-12

    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.

  8. 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.

  9. Laboratory astrophysics and non-ideal equations of state: the next challenges for astrophysical MHD simulations

    NASA Astrophysics Data System (ADS)

    Carver, Robert L.; Cunningham, Andrew J.; Frank, Adam; Hartigan, Patrick; Coker, Robert; Wilde, B. H.; Foster, John; Rosen, Paula

    2010-12-01

    Laboratory astrophysics holds great promise not only as a highly effective validation tool for astrophysical magneto-hydrodynamics (MHD) codes but it also presents a unique challenge for these codes. The high-density plasmas found in these experiments are not well modeled by the ideal equations of state (EOS) found in most astrophysical simulation codes. To solve this problem, we replaced the ideal EOS scheme in an existing MHD code, AstroBEAR, with a non-ideal EOS method and validated our implementation with van der Waals shock tube tests. The improved code is also able to model flows that contain more than one material, as required in laboratory experiments. Simulations of jet experiments performed at the OMEGA Laser reproduce the morphology of the jet much better than when the code used a single material and an ideal EOS.

  10. Influence of probe geometry on measurement results of non-ideal thermal conductivity sensors

    NASA Astrophysics Data System (ADS)

    Tiefenbacher, Patrick; Kömle, Norbert I.; Macher, Wolfgang; Kargl, Günter

    2016-09-01

    The thermal properties of the surface and subsurface layers of planets and planetary objects yield important information that allows us to better understand the thermal evolution of the body itself and its interactions with the environment. Various planetary bodies of our Solar System are covered by so-called regolith, a granular and porous material. On such planetary bodies the dominant heat transfer mechanism is heat conduction via IR radiation and contact points between particles. In this case the energy balance is mainly controlled by the effective thermal conductivity of the top surface layers, which can be directly measured by thermal conductivity probes. A traditionally used method for measuring the thermal conductivity of solid materials is the needle-probe method. Such probes consist of thin steel needles with an embedded heating wire and temperature sensors. For the evaluation of the thermal conductivity of a specific material the temperature change with time is determined by heating a resistance wire with a well-defined electrical current flowing through it and simultaneously measuring the temperature increase inside the probe over a certain time. For thin needle probes with a large length-to-diameter ratio it is mathematically easy to derive the thermal conductivity, while this is not so straightforward for more rugged probes with a larger diameter and thus a smaller length-to-diameter ratio. Due to the geometry of the standard thin needle probes they are mechanically weak and subject to bending when driven into a soil. Therefore, using them for planetary missions can be problematic. In this paper the thermal conductivity values determined by measurements with two non-ideal, ruggedized thermal conductivity sensors, which only differ in length, are compared to each other. Since the theory describing the temperature response of non-ideal sensors is highly complicated, those sensors were calibrated with an ideal reference sensor in various solid and

  11. 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

  12. 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

  13. Simple equations to simulate closed-loop recycling liquid-liquid chromatography: Ideal and non-ideal recycling models.

    PubMed

    Kostanyan, Artak E

    2015-12-04

    The ideal (the column outlet is directly connected to the column inlet) and non-ideal (includes the effects of extra-column dispersion) recycling equilibrium-cell models are used to simulate closed-loop recycling counter-current chromatography (CLR CCC). Simple chromatogram equations for the individual cycles and equations describing the transport and broadening of single peaks and complex chromatograms inside the recycling closed-loop column for ideal and non-ideal recycling models are presented. The extra-column dispersion is included in the theoretical analysis, by replacing the recycling system (connecting lines, pump and valving) by a cascade of Nec perfectly mixed cells. To evaluate extra-column contribution to band broadening, two limiting regimes of recycling are analyzed: plug-flow, Nec→∞, and maximum extra-column dispersion, Nec=1. Comparative analysis of ideal and non-ideal models has shown that when the volume of the recycling system is less than one percent of the column volume, the influence of the extra-column processes on the CLR CCC separation may be neglected.

  14. 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.

  15. Unraveling flow patterns through nonlinear manifold learning.

    PubMed

    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.

  16. Numerical simulation of vehicular traffic for non-ideal drivers.

    NASA Astrophysics Data System (ADS)

    Domínguez, Laura; Amador, Carlos

    2004-03-01

    Numerical simulations of vehicular traffic based on cellular automatae have provided a description of the more relevant experimentally observed properties of the system. Rules for drivers behaviour, though, are highly idealized. In this work we have included rules to mimic the different personalities of drivers: lane changers, passers, over-cautious drivers, tail-gaters, etc. Also we have adopted rules specific to the behaviour of drivers in Mexico City. The whole space of parameters is studied and conclusions are drawn for the effect of this variability on overall vehicular flow. As a further application of the model we study the effect of "shoulder of the road" drivers (who pass congested traffic and return to the main road afterwards) on overall vehicular flow.

  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. 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.

  19. 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.

  20. 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)

  1. 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)

  2. 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

  3. 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.

  4. Photoelastic modulator non-idealities in magneto-optical polarization measurements

    NASA Astrophysics Data System (ADS)

    Vandendriessche, Stefaan; Verbiest, Thierry

    2013-09-01

    Modifying and detecting the polarization of light is increasingly important in many contexts such as Faraday isolators and electro-optical modulators. In order to control the polarization of light, it is necessary to know the polarization characteristics of the materials used in the applications. To be able to (magneto-)optically characterize novel materials, we designed a setup using a single photoelastic modulator (PEM) to simultaneously detect natural and magnetic circular dichroism and circular birefringence over a large spectral range. We then theoretically analyzed and experimentally characterized the effect of non-idealities in the PEM on the setup and the resulting data. Our results demonstrate an influence of PEM non-idealities on the measured signals, resulting in non-negligible mixing of circular birefringence and circular dichroism signals. Our measurements of the wavelength dependence of these non-idealities reveal larger non-idealities towards shorter wavelengths. These results illustrate the necessity to take PEM non-idealities into account when working with PEMs, especially at shorter wavelengths or when dealing with signals spanning different orders of magnitude. PEM non-idealities, while frequently neglected in experimental setup design and theoretical derivations, are expected to be more complicated and possibly exert a larger influence on obtained results for experimental setups with multiple PEMs.

  5. Magnetogasdynamic spherical shock wave in a non-ideal gas under gravitational field with conductive and radiative heat fluxes

    NASA Astrophysics Data System (ADS)

    Nath, G.; Vishwakarma, J. P.

    2016-11-01

    Similarity solutions are obtained for the flow behind a spherical shock wave in a non-ideal gas under gravitational field with conductive and radiative heat fluxes, in the presence of a spatially decreasing azimuthal magnetic field. The shock wave is driven by a piston moving with time according to power law. The radiation is considered to be of the diffusion type for an optically thick grey gas model and the heat conduction is expressed in terms of Fourier's law for heat conduction. Similarity solutions exist only when the surrounding medium is of constant density. The gas is assumed to have infinite electrical conductivity and to obey a simplified van der Waals equation of state. It is shown that an increase of the gravitational parameter or the Alfven-Mach number or the parameter of the non-idealness of the gas decreases the compressibility of the gas in the flow-field behind the shock, and hence there is a decrease in the shock strength. The pressure and density vanish at the inner surface (piston) and hence a vacuum is formed at the center of symmetry. The shock waves in conducting non-ideal gas under gravitational field with conductive and radiative heat fluxes can be important for description of shocks in supernova explosions, in the study of a flare produced shock in the solar wind, central part of star burst galaxies, nuclear explosion etc. The solutions obtained can be used to interpret measurements carried out by space craft in the solar wind and in neighborhood of the Earth's magnetosphere.

  6. 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.

  7. Patterns and dynamics in transitional shear flows

    NASA Astrophysics Data System (ADS)

    Tuckerman, Laurette

    2009-11-01

    One of the greatest mysteries in fluid dynamics is surely transition to turbulence. The classic shear flows -- channel, plane Couette and pipe flow -- while linearly stable, undergo sudden transition to 3D turbulence. In recent years, transition has been attacked with an arsenal of weapons from dynamical systems theory, such as low-dimensional chaos, unstable periodic orbits, heteroclinic connections, fractal basin boundaries. At the same time, 3D physical mechanisms such as streamwise vorticity and streaks have supplanted the 2D picture of linear instability long promoted by Squire's theorem. A striking recent discovery by experimentalists at CEA-Saclay is that large-aspect-ratio plane Couette flow near transition actually takes the form of a steady pattern of wide turbulent and laminar bands, with a fixed angle and wavelength. We have been able to reproduce these remarkable flows in numerical simulations of the Navier-Stokes equations. Simulations display a rich variety of variants of these patterns, including spatio-temporal intermittency, branching and travelling states, and localized states analogous to spots. Because similar patterns have since also been observed in Taylor-Couette, channel and pipe flow, it appears that they are inevitable intermediate states on the route from turbulent to laminar flow in large aspect-ratio shear flows. In addition to their intrinsic interest, these patterns provide clues to the transition to turbulence.

  8. 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.

  9. 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

  10. 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.

  11. Medical ethics and more: ideal theories, non-ideal theories and conscientious objection.

    PubMed

    Luna, Florencia

    2015-01-01

    Doing 'good medical ethics' requires acknowledgment that it is often practised in non-ideal circumstances! In this article I present the distinction between ideal theory (IT) and non-ideal theory (NIT). I show how IT may not be the best solution to tackle problems in non-ideal contexts. I sketch a NIT framework as a useful tool for bioethics and medical ethics and explain how NITs can contribute to policy design in non-ideal circumstances. Different NITs can coexist and be evaluated vis-à-vis the IT. Additionally, I address what an individual doctor ought to do in this non-ideal context with the view that knowledge of NITs can facilitate the decision-making process. NITs help conceptualise problems faced in the context of non-compliance and scarcity in a better and more realistic way. Deciding which policy is optimal in such contexts may influence physicians' decisions regarding their patients. Thus, this analysis-usually identified only with policy making-may also be relevant to medical ethics. Finally, I recognise that this is merely a first step in an unexplored but fundamental theoretical area and that more work needs to be done. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  12. The impact of non-ideal magnetohydrodynamics on binary star formation

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    We investigate the effect of non-ideal magnetohydrodynamics (MHD) on the formation of binary stars using a suite of three-dimensional smoothed particle magnetohydrodynamics simulations of the gravitational collapse of 1 M⊙, rotating, perturbed molecular-cloud cores. Alongside the role of Ohmic resistivity, ambipolar diffusion and the Hall effect, we also examine the effects of magnetic field strength, orientation and amplitude of the density perturbation. When modelling sub-critical cores, ideal MHD models do not collapse whereas non-ideal MHD models collapse to form single protostars. In supercritical ideal MHD models, increasing the magnetic field strength or decreasing the initial-density perturbation amplitude decreases the initial binary separation. Strong magnetic fields initially perpendicular to the rotation axis suppress the formation of binaries and yield discs with magnetic fields ∼10 times stronger than if the magnetic field was initially aligned with the rotation axis. When non-ideal MHD is included, the resulting discs are larger and more massive, and the binary forms on a wider orbit. Small differences in the supercritical cores caused by non-ideal MHD effects are amplified by the binary interaction near periastron. Overall, the non-ideal effects have only a small impact on binary formation and early evolution, with the initial conditions playing the dominant role.

  13. 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

  14. Simple correlation for predicting detonation velocity of ideal and non-ideal explosives.

    PubMed

    Keshavarz, Mohammad Hossein

    2009-07-30

    This paper describes a simple method for prediction of detonation velocity of ideal and non-ideal explosives. A non-ideal aluminized and nitrated explosive can have Chapman-Jouguet detonation velocity significantly different from that expected from existing thermodynamic computer codes for equilibrium and steady-state calculations. Detonation velocity of explosives with general formula C(a)H(b)N(c)O(d)Al(e) can be predicted only from values of a, b, c, d, e and a specific structural parameter without using any assumed detonation products, heat of formation and experimental data. Predicted detonation velocities by this procedure for ideal and non-ideal explosives show good agreement with respect to experimental values as compared to computed results of BKWR and BKWS equations of state.

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

    PubMed

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

    2015-09-07

    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.

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

    NASA Astrophysics Data System (ADS)

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

    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.

  17. Blood flow patterns underlie developmental heart defects.

    PubMed

    Midgett, Madeline; Thornburg, Kent; Rugonyi, Sandra

    2017-03-01

    Although cardiac malformations at birth are typically associated with genetic anomalies, blood flow dynamics also play a crucial role in heart formation. However, the relationship between blood flow patterns in the early embryo and later cardiovascular malformation has not been determined. We used the chicken embryo model to quantify the extent to which anomalous blood flow patterns predict cardiac defects that resemble those in humans and found that restricting either the inflow to the heart or the outflow led to reproducible abnormalities with a dose-response type relationship between blood flow stimuli and the expression of cardiac phenotypes. Constricting the outflow tract by 10-35% led predominantly to ventricular septal defects, whereas constricting by 35-60% most often led to double outlet right ventricle. Ligation of the vitelline vein caused mostly pharyngeal arch artery malformations. We show that both cardiac inflow reduction and graded outflow constriction strongly influence the development of specific and persistent abnormal cardiac structure and function. Moreover, the hemodynamic-associated cardiac defects recapitulate those caused by genetic disorders. Thus our data demonstrate the importance of investigating embryonic blood flow conditions to understand the root causes of congenital heart disease as a prerequisite to future prevention and treatment.NEW & NOTEWORTHY Congenital heart defects result from genetic anomalies, teratogen exposure, and altered blood flow during embryonic development. We show here a novel "dose-response" type relationship between the level of blood flow alteration and manifestation of specific cardiac phenotypes. We speculate that abnormal blood flow may frequently underlie congenital heart defects. Copyright © 2017 the American Physiological Society.

  18. Heterogeneity in a Low-Permeability Formation or Non-Ideal Testing Conditions?

    NASA Astrophysics Data System (ADS)

    Mishra, S.; Deeds, N. E.; Pickens, J. F.; Distinguin, M.; Delay, J.

    2005-12-01

    Hydraulic testing in packer-isolated wellbore intervals in low-permeability formations is often complicated by non-ideal conditions such as thermal expansion of fluid in the test interval, packer squeeze and borehole closure. Such processes lead to fluid accumulation and pressurization within the wellbore during shut-in, and can exert significant effects on the measured borehole pressure response. Unless these conditions are taken into account during test interpretation, it is possible to make inappropriate conclusions regarding formation heterogeneity (e.g., lateral permeability variations) and/or static pressure levels. We have developed a lumped parameter modeling approach by treating the combined effect of these processes as the equivalent of an additional volume of fluid accumulating within the test interval (in addition to the nominal test-interval volume at the time of shut-in). We postulate that the rate of fluid accumulation can be treated in a simple manner as a constant value for the duration of the test. Thus, the fluid accumulation problem can be recast as the equivalent of a constant injection rate into the packed-off volume within the borehole. We show how this surrogate injection rate can be estimated from the measured pressure data by exploiting the analogy between the pressure response during borehole storage dominated conditions and that of a line-source well with an exponentially varying flow rate. Shut-in test sequences (i.e., shut-in period prior to initiation of a pressure pulse test and shut-in period(s) during pulse test(s)) can then be analyzed as effective constant-rate injection periods. The methodology is demonstrated using data from a recent series of hydraulic tests conducted in support of site characterization activities by ANDRA, the French radioactive waste management agency. In many of these tests, the measured pressure response was fitted to a 2-zone radially composite system model. Although the fit was visually excellent, static

  19. 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.

  20. 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)

  1. The dual-color photon counting histogram with non-ideal photodetectors.

    PubMed

    Hillesheim, Lindsey N; Müller, Joachim D

    2005-11-01

    Dual-color photon counting histogram (PCH) analysis utilizes the photon counts in two detection channels to distinguish species by differences in brightness and color. Here we modify the existing dual-color PCH theory, which assumes ideal detectors, to include the non-ideal nature of the detector. Specifically, we address the effects of deadtime and afterpulsing. Both effects modify the shape of the dual-color PCH and thus potentially lead to incorrect values for the brightness and number of molecules if an ideal model is assumed. We use the modified theory to predict the effects of detector non-idealities on dual-color PCH as a function of concentration and brightness. In addition, we introduce a method based on moment analysis to determine the error in brightness due to non-ideal detector effects. We verify our theory experimentally by measuring a dye solution as a function of concentration and brightness. We determine the deadtime and afterpulse probability of our detectors and show that both effects play an important role in the analysis of dual-color PCH experiments. We demonstrate that resolving a mixture of CFP and YFP requires taking non-ideal detector effects into account. These corrections are also crucial for cellular measurements, as shown for GFP and RFP in mammalian cells.

  2. The Dual-Color Photon Counting Histogram with Non-Ideal Photodetectors

    PubMed Central

    Hillesheim, Lindsey N.; Müller, Joachim D.

    2005-01-01

    Dual-color photon counting histogram (PCH) analysis utilizes the photon counts in two detection channels to distinguish species by differences in brightness and color. Here we modify the existing dual-color PCH theory, which assumes ideal detectors, to include the non-ideal nature of the detector. Specifically, we address the effects of deadtime and afterpulsing. Both effects modify the shape of the dual-color PCH and thus potentially lead to incorrect values for the brightness and number of molecules if an ideal model is assumed. We use the modified theory to predict the effects of detector non-idealities on dual-color PCH as a function of concentration and brightness. In addition, we introduce a method based on moment analysis to determine the error in brightness due to non-ideal detector effects. We verify our theory experimentally by measuring a dye solution as a function of concentration and brightness. We determine the deadtime and afterpulse probability of our detectors and show that both effects play an important role in the analysis of dual-color PCH experiments. We demonstrate that resolving a mixture of CFP and YFP requires taking non-ideal detector effects into account. These corrections are also crucial for cellular measurements, as shown for GFP and RFP in mammalian cells. PMID:16126829

  3. Elastic fingering patterns in confined lifting flows.

    PubMed

    Fontana, João V; Miranda, José A

    2016-09-01

    The elastic fingering phenomenon occurs when two confined fluids are brought into contact, and due to a chemical reaction, the interface separating them becomes elastic. We study elastic fingering pattern formation in Newtonian fluids flowing in a lifting (time-dependent gap) Hele-Shaw cell. Using a mode-coupling approach, nonlinear effects induced by the interplay between viscous and elastic forces are investigated and the weakly nonlinear behavior of the fluid-fluid interfacial patterns is analyzed. Our results indicate that the existence of the elastic interface allows the development of unexpected morphological behaviors in such Newtonian fluid flow systems. More specifically, we show that depending on the values of the governing physical parameters, the observed elastic fingering structures are characterized by the occurrence of either finger tip splitting or side branching. The impact of the elastic interface on finger-competition events is also discussed.

  4. Micromechanics of emergent patterns in plastic flows.

    PubMed

    Biswas, Santidan; Grant, Martin; Samajdar, Indradev; Haldar, Arunansu; Sain, Anirban

    2013-01-01

    Crystalline solids undergo plastic deformation and subsequently flow when subjected to stresses beyond their elastic limit. In nature most crystalline solids exist in polycrystalline form. Simulating plastic flows in polycrystalline solids has wide ranging applications, from material processing to understanding intermittency of earthquake dynamics. Using phase field crystal (PFC) model we show that in sheared polycrystalline solids the atomic displacement field shows spatio-temporal heterogeneity spanning over several orders of length and time scales, similar to that in amorphous solids. The displacement field also exhibits localized quadrupolar patterns, characteristic of two dislocations of the opposite sign approaching each other. This is a signature of crystallinity at microscopic scale. Polycrystals being halfway between single crystals and amorphous solids, in terms of the degree of structural order, descriptions of solid mechanics at two widely different scales, namely continuum plastic flow and discrete dislocation dynamics turns out to be necessary here.

  5. Using Capillary Flows to Pattern Lines

    NASA Astrophysics Data System (ADS)

    Vyawahare, Saurabh; Craig, Kate; Scherer, Axel

    2006-03-01

    One can appreciate how capillary forces cause unexpected patterns and shapes by looking at a soap bubble. Pattern formation by surface tension is seen in ring patterns of coffee stains, fingering patterns in Hele-Shaw cells, ordering of two dimensional micro-sphere crystals, combing of DNA and skeleton formation in marine creatures called radiolarians. Though comman, problems involving the understanding and control of the self-assembly mechanism need to be resolved before using capillary forces as a practical lithographic tool. Here, we report capillary flows create line patterns in evaporating liquids between closely spaced parallel plates. The widths of these lines range from a few microns to a few nanometers. Deliberate patterning of such lines requires pinning of the contact line and the presence of foaming surfactants. The position and type of line can be controlled with artificial pinning points and varying solutes respectively, and large-scale photolithography can be used to guide and control the definition of nanostructures. We provide ``proof of principle'' demonstrations of this method's application by creating lines of colloidal quantum dots and micro-spheres. This represents the first step in using capillary phenomena to create controlled, self--assembling, one-dimensional wire-like structures

  6. 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

  7. Ultrasonic density measurement cell design and simulation of non-ideal effects.

    PubMed

    Higuti, Ricardo Tokio; Buiochi, Flávio; Adamowski, Júlio Cezar; de Espinosa, Francisco Montero

    2006-07-01

    This paper presents a theoretical analysis of a density measurement cell using an unidimensional model composed by acoustic and electroacoustic transmission lines in order to simulate non-ideal effects. The model is implemented using matrix operations, and is used to design the cell considering its geometry, materials used in sensor assembly, range of liquid sample properties and signal analysis techniques. The sensor performance in non-ideal conditions is studied, considering the thicknesses of adhesive and metallization layers, and the effect of residue of liquid sample which can impregnate on the sample chamber surfaces. These layers are taken into account in the model, and their effects are compensated to reduce the error on density measurement. The results show the contribution of residue layer thickness to density error and its behavior when two signal analysis methods are used.

  8. Non-ideal feedforward torque control of wind turbines: Impacts on annual energy production & gross earnings

    NASA Astrophysics Data System (ADS)

    Hackl, Christoph; Schechner, Korbinian

    2016-09-01

    We discuss non-ideal torque control in wind turbine systems. Most high-level controllers generate a reference torque which is then send to the underlying electrical drive system (generator+inverter) of the wind turbine system to steer the turbine/generator to its optimal operation point (depending on the wind speed). The energy production heavily depends on the mechanical power (i.e. the product of rotational speed and generator torque). However, since torque sensors in the MW range are not available or extremely expensive, the underlying torque control system is implemented as feedforward control and, therefore, is inherently sensitive to parameter variations/uncertainties. Based on real wind data and a wind turbine system model, we discuss causes and impacts of non-ideal feedforward torque control on the energy production and the annual gross earnings.

  9. 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.

  10. Patterns and flow in frictional fluid dynamics

    PubMed Central

    Sandnes, B.; Flekkøy, E.G.; Knudsen, H.A.; Måløy, K.J.; See, H.

    2011-01-01

    Pattern-forming processes in simple fluids and suspensions have been studied extensively, and the basic displacement structures, similar to viscous fingers and fractals in capillary dominated flows, have been identified. However, the fundamental displacement morphologies in frictional fluids and granular mixtures have not been mapped out. Here we consider Coulomb friction and compressibility in the fluid dynamics, and discover surprising responses including highly intermittent flow and a transition to quasi-continuodynamics. Moreover, by varying the injection rate over several orders of magnitude, we characterize new dynamic modes ranging from stick-slip bubbles at low rate to destabilized viscous fingers at high rate. We classify the fluid dynamics into frictional and viscous regimes, and present a unified description of emerging morphologies in granular mixtures in the form of extended phase diagrams. PMID:21505444

  11. On the main flow pattern in hydrocyclones

    SciTech Connect

    Hwang, C.C.; Shen, H.Q.; Zhu, G.; Khonsari, M.M. . Dept. of Mechanical Engineering)

    1993-03-01

    A theoretical model is developed for the prediction of the main flow pattern in hydrocyclones. The model regards the main body of the cyclone as inviscid and includes provisions for the fluid underflow in cyclones. The governing equations are solved analytically in closed form. To verify the results, a laboratory-scale conically-shaped hydrocyclone was designed, built, and tested. Experimental measurements for axial and tangential velocities are presented with a series of test solely devoted to the effect of underflow. The theoretical and experimental results are shown to be in good agreement. It is concluded that such an inviscid model gives an adequate representation of the main flow field in a cyclone.

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

    PubMed

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

    2014-11-06

    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.

  13. Profiles of neutral lines emitted from weakly non-ideal helium plasmas produced in flashlamps

    SciTech Connect

    Vitel, Yves; El Bezzari, Mohammed; D'yachkov, Lev G.; Kurilenkov, Yuri K.

    1999-04-01

    High pressure helium arcs are created in linear flashlamps. Plasma diagnostics taking into account non-ideality effects, give on axis electron densities in the range 2 10{sup 17}-1.7 10{sup 18} cm{sup -3} and temperatures included between 20000 and 30000 K. In these conditions of dense plasmas, profiles of emitted neutral lines are recorded and compared with other experimental values and theoretical calculations.

  14. Beyond the second virial coefficient: Sedimentation equilibrium in highly non-ideal solutions.

    PubMed

    Rivas, Germán; Minton, Allen P

    2011-05-01

    The general theory of sedimentation equilibrium (SE), applicable to mixtures of interacting sedimentable solutes at arbitrary concentration, is summarized. Practical techniques for the acquisition of SE data suitable for analysis are described. Experimental measurements and analyses of SE in concentrated protein solutions are reviewed. The method of non-ideal tracer sedimentation equilibrium (NITSE) is described. Experimental studies using NITSE to detect and quantitatively characterize intermolecular interactions in mixtures of dilute tracer species and concentrated proteins or polymers are reviewed.

  15. 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

  16. Assessing the Damaging Potential of Non-Ideal Explosives Based Upon Ammonium Nitrate Fertilizer

    DTIC Science & Technology

    1996-08-01

    fertilizer modified by grinding and the addition of a solid fuel to convert them into explosives. On April 19th 1995, a similar massive bomb this time...allegedly based upon a mixture of prilled agricultural ammonium nitrate fertilizer and fuel oil (ANFO) was used in Oklahoma City to devastate the...Federal building with severe loss of life. Explosives based upon fertilizer are classified as non-ideal. They neither react in the same way as ideal

  17. Effects of non-ideal boundary conditions on the vibrations of a slightly curved micro beam

    NASA Astrophysics Data System (ADS)

    Sarı, Gözde; Pakdemirli, Mehmet

    2012-11-01

    Response of a slightly curved resonant microbeam having non-ideal boundary conditions is investigated. Non-ideal boundary conditions are formulated using perturbation theory. These non-ideal conditions allow for small deflection at the right end of the microbeam. The curvature is taken as a sinusoidal function of the spatial variable. The initial displacement is due to the geometry of the microbeam itself. They are produced intentionally to be curved or made curved by buckling straight beams through compressive axial loads. The model accounts for mid-plane stretching, an applied axial load and an AC harmonic force. The ends of the curved microbeam are on immovable simple supports. Immovable end conditions introduce integral type nonlinearity. The integro-differential equations of motion are solved analytically by means of direct application of the method of multiple scales (a perturbation method). The amplitude and phase modulation equations are derived for the case of primary resonances. The effect of curvature on the vibrations of the microbeam is examined. It is found that the effect of curvature is of softening type. The frequencies and mode shapes obtained are compared with the ideal boundary conditions case and the differences between them are contrasted on frequency response curves.

  18. How important is non-ideal physics in simulations of sub-Eddington accretion on to spinning black holes?

    NASA Astrophysics Data System (ADS)

    Foucart, Francois; Chandra, Mani; Gammie, Charles F.; Quataert, Eliot; Tchekhovskoy, Alexander

    2017-09-01

    Black holes with accretion rates well below the Eddington rate are expected to be surrounded by low-density, hot, geometrically thick accretion discs. This includes the two black holes being imaged at subhorizon resolution by the Event Horizon Telescope. In these discs, the mean free path for Coulomb interactions between charged particles is large, and the accreting matter is a nearly collisionless plasma. Despite this, numerical simulations have so far modelled these accretion flows using ideal magnetohydrodynamics. Here, we present the first global, general relativistic, 3D simulations of accretion flows on to a Kerr black hole including the non-ideal effects most likely to affect the dynamics of the disc: the anisotropy between the pressure parallel and perpendicular to the magnetic field, and the heat flux along magnetic field lines. We show that for both standard and magnetically arrested discs, the pressure anisotropy is comparable to the magnetic pressure, while the heat flux remains dynamically unimportant. Despite this large pressure anisotropy, however, the time-averaged structure of the accretion flow is strikingly similar to that found in simulations treating the plasma as an ideal fluid. We argue that these similarities are largely due to the interchangeability of the viscous and magnetic shear stresses as long as the magnetic pressure is small compared to the gas pressure, and to the subdominant role of pressure/viscous effects in magnetically arrested discs. We conclude by highlighting outstanding questions in modelling the dynamics of low-collisionality accretion flows.

  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. Patterns and stability of a whirlpool flow

    NASA Astrophysics Data System (ADS)

    Carrión, Luis; Herrada, Miguel A.; Shtern, Vladimir N.; María López-Herrera, José

    2017-04-01

    This numerical study reveals stable multi-eddy patterns of a steady axisymmetric air-water flow driven by the rotating bottom disk in a vertical sealed cylindrical container. As rotation strength Re increases, eddies emerge, coalesce, separate, and disappear in both air and water. The topological scenario varies with water volume fraction H w according to the results obtained for H w = 0.3, 0.5, and 0.8. Interesting features are: (a) zipper-like chains of air and water eddies forming as the interface bends and (b) bubble-ring air eddies existing in the Re ranges specified in the paper. The stability analysis, performed with the help of a novel efficient technique for two-fluid flows, shows that these multi-eddy motions are stable. The shear-layer instability develops as the interface approaches either the top or bottom of the container and some eddies vanish. The physical reasoning behind the eddy formation and the flow instability is provided. The results are of fundamental interest and can have applications in bioreactors.

  1. 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

  2. Oil-flow separation patterns on an ogive forebody

    NASA Technical Reports Server (NTRS)

    Keener, E. R.

    1981-01-01

    Oil flow patterns on a symmetric tangent ogive forebody having a fineness ratio of 3.5 are presented for angles of attack up to 88 deg at a transitional Reynolds number of 8 million (based on base diameter) and a Mach number of 0.25. Results show typical surface flow separation patterns, the magnitude of surface flow angles, and the extent of laminar and turbulent flow for symmetric, asymmetric, and wakelike flow regimes.

  3. 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.

  4. NON-IDEAL MHD EFFECTS AND MAGNETIC BRAKING CATASTROPHE IN PROTOSTELLAR DISK FORMATION

    SciTech Connect

    Li Zhiyun; Krasnopolsky, Ruben; Shang Hsien

    2011-09-10

    Dense, star-forming cores of molecular clouds are observed to be significantly magnetized. A realistic magnetic field of moderate strength has been shown to suppress, through catastrophic magnetic braking, the formation of a rotationally supported disk (RSD) during the protostellar accretion phase of low-mass star formation in the ideal MHD limit. We address, through two-dimensional (axisymmetric) simulations, the question of whether realistic levels of non-ideal effects, computed with a simplified chemical network including dust grains, can weaken the magnetic braking enough to enable an RSD to form. We find that ambipolar diffusion (AD), the dominant non-ideal MHD effect over most of the density range relevant to disk formation, does not enable disk formation, at least in two dimensions. The reason is that AD allows the magnetic flux that would be dragged into the central stellar object in the ideal MHD limit to pile up instead in a small circumstellar region, where the magnetic field strength (and thus the braking efficiency) is greatly enhanced. We also find that, on the scale of tens of AU or more, a realistic level of Ohmic dissipation does not weaken the magnetic braking enough for an RSD to form, either by itself or in combination with AD. The Hall effect, the least explored of these three non-ideal MHD effects, can spin up the material close to the central object to a significant, supersonic rotation speed, even when the core is initially non-rotating, although the spun-up material remains too sub-Keplerian to form an RSD. The problem of catastrophic magnetic braking that prevents disk formation in dense cores magnetized to realistic levels remains unresolved. Possible resolutions of this problem are discussed.

  5. 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.

  6. Pattern palette for complex fluid flows

    NASA Astrophysics Data System (ADS)

    Sandnes, B.

    2012-04-01

    From landslides to oil and gas recovery to the squeeze of a toothpaste tube, flowing complex fluids are everywhere around us in nature and engineering. That is not to say, though, that they are always well understood. The dissipative interactions, through friction and inelastic collisions, often give rise to nonlinear dynamics and complexity manifested in pattern formation on large scales. The images displayed on this poster illustrate the diverse morphologies found in multiphase flows involving wet granular material: Air is injected into a generic mixture of granular material and fluid contained in a 500 µm gap between two parallel glass plates. At low injection rates, friction between the grains - glass beads averaging 100 µm in diameter - dominates the rheology, producing "stick-slip bubbles" and labyrinthine frictional fingering. A transition to various other morphologies, including "corals" and viscous fingers, emerges for increasing injection rate. At sufficiently high granular packing fractions, the material behaves like a deformable, porous solid, and the air rips through in sudden fractures.

  7. Air flow patterns in the operating theatre.

    PubMed

    Howorth, F H

    1980-04-01

    Bacteria-carrying particles and exhaled anaesthetic gases are the two contaminants found in the air flow patterns of operating rooms. Their origin, direction and speed were illustrated by a motion picture using Schlieren photography and smoke tracers. Compared with a conventionally well air conditioned operating theatre, it was shown that a downward flow of clean air reduced the number of bacteria-carrying particles at the wound site by sixty times. The Exflow method of achieving this without the restriction of any side panels or floor obstruction was described. The total body exhaust worn by the surgical team was shown to reduce the bacteria count by a further eleven times. Clinical results show that when both these systems are used together, patient infection was reduced from 9 per cent to between 0.3 per cent and 0.5 per cent, even when no pre-operative antibiotics were used. Anaesthetic gas pollution was measured and shown to be generally 1000 p.p.m. at the head of the patient, in induction, operating and recovery rooms, also in dental and labour rooms. A high volume low pressure active scavenging system was described together with its various attachments including one specially for paediatric scavenging. Results showed a reduction of nitrous oxide pollution to between zero and 3 p.p.m. The economy and cost effectiveness of both these pollution control systems was shown to be good due to the removal of health hazards from patients and theatre staff.

  8. 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.

  9. 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.

  10. A mechanistic view of the non-ideal osmotic and motional behavior of intracellular water.

    PubMed

    Cameron, I L; Kanal, K M; Keener, C R; Fullerton, G D

    1997-02-01

    It is commonly assumed that essentially all of the water in cells has the same ideal motional and colligative properties as does water in bulk liquid state. This assumption is used in studies of volume regulation, transmembrane movement of solutes and electrical potentials, solute and solution motion, solute solubility and other phenomena. To get at the extent and the source of non-ideally behaved water (an operational term dependent on the measurement method), we studied the motional and colligative properties of water in cells, in solutions of amino acids and glycine peptides whose surface characteristics are known, and in solution of bovine serum albumin, hemoglobin and some synthetic polypeptides. Solutions of individual amino acids with progressively larger hydrophobic side chains showed one perturbed water molecule (structured-slowed in motion) per nine square angstroms of hydrophobic surface area. Water molecules adjacent to hydrophobic surfaces form pentagonal structural arrays, as shown by X-ray diffraction studies, that are reported to be disrupted by heat, electric field, hydrostatic pressure and phosphorylation state. Hydrophilic amino acids demonstrated water destructuring (increased motion) that was attributed to dielectric realignment of dipolar water molecules in the electric field between charge groups. In solutions of proteins, several methods indicate the equivalent of 2-8 layers of structured water molecules extending beyond the protein surface, and we have recently demonstrated that induced protein conformational change modifies the extent of non-ideally behaved water. Water self-diffusion rate as measured in three different cell types was about half that of bulk water, indicating that most of the water in these cells was slower in motion than bulk water. In different cell types the extent of osmotically perturbed water ranged from less that half to almost all of the intracellular water. The assumption that essentially all intracellular water

  11. Characterization in bi-parameter space of a non-ideal oscillator

    NASA Astrophysics Data System (ADS)

    de Souza, S. L. T.; Batista, A. M.; Baptista, M. S.; Caldas, I. L.; Balthazar, J. M.

    2017-01-01

    We investigate the dynamical behavior of a non-ideal Duffing oscillator, a system composed of a mass-spring-pendulum driven by a DC motor with limited power supply. To identify new features on Duffing oscillator parameter space due to the limited power supply, we provide an extensive numerical characterization in the bi-parameter space by using Lyapunov exponents. Following this procedure, we identify remarkable new organized distribution of periodic windows, the ones known as Arnold tongues and also shrimp-shaped structures. In addition, we also identify intertwined basins of attraction for coexisting multiple attractors connected with tongues.

  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. 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.

  14. Atomic force microscopy analysis of nanoparticles in non-ideal conditions

    PubMed Central

    2011-01-01

    Nanoparticles are often measured using atomic force microscopy or other scanning probe microscopy methods. For isolated nanoparticles on flat substrates, this is a relatively easy task. However, in real situations, we often need to analyze nanoparticles on rough substrates or nanoparticles that are not isolated. In this article, we present a simple model for realistic simulations of nanoparticle deposition and we employ this model for modeling nanoparticles on rough substrates. Different modeling conditions (coverage, relaxation after deposition) and convolution with different tip shapes are used to obtain a wide spectrum of virtual AFM nanoparticle images similar to those known from practice. Statistical parameters of nanoparticles are then analyzed using different data processing algorithms in order to show their systematic errors and to estimate uncertainties for atomic force microscopy analysis of nanoparticles under non-ideal conditions. It is shown that the elimination of user influence on the data processing algorithm is a key step for obtaining accurate results while analyzing nanoparticles measured in non-ideal conditions. PMID:21878120

  15. Compensation of non-ideal beam splitter polarization distortion effect in Michelson interferometer

    NASA Astrophysics Data System (ADS)

    Liu, Yeng-Cheng; Lo, Yu-Lung; Liao, Chia-Chi

    2016-02-01

    A composite optical structure consisting of two quarter-wave plates and a single half-wave plate is proposed for compensating for the polarization distortion induced by a non-ideal beam splitter in a Michelson interferometer. In the proposed approach, the optimal orientations of the optical components within the polarization compensator are determined using a genetic algorithm (GA) such that the beam splitter can be treated as a free-space medium and modeled using a unit Mueller matrix accordingly. Two implementations of the proposed polarization controller are presented. In the first case, the compensator is placed in the output arm of Michelson interferometer such that the state of polarization of the interfered output light is equal to that of the input light. However, in this configuration, the polarization effects induced by the beam splitter in the two arms of the interferometer structure cannot be separately addressed. Consequently, in the second case, compensator structures are placed in the Michelson interferometer for compensation on both the scanning and reference beams. The practical feasibility of the proposed approach is introduced by considering a Mueller polarization-sensitive (PS) optical coherence tomography (OCT) structure with three polarization controllers in the input, reference and sample arms, respectively. In general, the results presented in this study show that the proposed polarization controller provides an effective and experimentally-straightforward means of compensating for the polarization distortion effects induced by the non-ideal beam splitters in Michelson interferometers and Mueller PS-OCT structures.

  16. Cable dynamics under non-ideal support excitations: Nonlinear dynamic interactions and asymptotic modelling

    NASA Astrophysics Data System (ADS)

    Guo, Tieding; Kang, Houjun; Wang, Lianhua; Zhao, Yueyu

    2016-12-01

    Cable dynamics under ideal longitudinal support motions/excitations assumes that the support's mass, stiffness and mechanical energy are infinite. However, for many long/slender support structures, their finite mass and stiffness should be taken into account and the cable-support dynamic interactions should be modelled and evaluated. These moving supports are non-ideal support excitations, deserving a proper coupling analysis. For systems with a large support/cable mass ratio, using the multiple scale method and asymptotic approximations, a cable-support coupled reduced model, with both cable's geometric nonlinearity and cable-support coupling nonlinearity included, is established asymptotically and validated numerically in this paper. Based upon the reduced model, cable's nonlinear responses under non-ideal support excitations(and also the coupled responses) are found, with stability and bifurcation characteristics determined. By finding the modifications caused by the support/cable mass ratio, boundary damping, and internal detuning, full investigations into coupling-induced dynamic effects on the cable are conducted. Finally, the approximate analytical results based on the reduced model are verified by numerical results from the original full model.

  17. 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.

  18. Adaptive tracking control for active suspension systems with non-ideal actuators

    NASA Astrophysics Data System (ADS)

    Pan, Huihui; Sun, Weichao; Jing, Xingjian; Gao, Huijun; Yao, Jianyong

    2017-07-01

    As a critical component of transportation vehicles, active suspension systems are instrumental in the improvement of ride comfort and maneuverability. However, practical active suspensions commonly suffer from parameter uncertainties (e.g., the variations of payload mass and suspension component parameters), external disturbances and especially the unknown non-ideal actuators (i.e., dead-zone and hysteresis nonlinearities), which always significantly deteriorate the control performance in practice. To overcome these issues, this paper synthesizes an adaptive tracking control strategy for vehicle suspension systems to achieve suspension performance improvements. The proposed control algorithm is formulated by developing a unified framework of non-ideal actuators rather than a separate way, which is a simple yet effective approach to remove the unexpected nonlinear effects. From the perspective of practical implementation, the advantages of the presented controller for active suspensions include that the assumptions on the measurable actuator outputs, the prior knowledge of nonlinear actuator parameters and the uncertain parameters within a known compact set are not required. Furthermore, the stability of the closed-loop suspension system is theoretically guaranteed by rigorous mathematical analysis. Finally, the effectiveness of the presented adaptive control scheme is confirmed using comparative numerical simulation validations.

  19. A Novel Calibration-Minimum Method for Prediction of Mole Fraction in Non-Ideal Mixture.

    PubMed

    Shibayama, Shojiro; Kaneko, Hiromasa; Funatsu, Kimito

    2017-04-01

    This article proposes a novel concentration prediction model that requires little training data and is useful for rapid process understanding. Process analytical technology is currently popular, especially in the pharmaceutical industry, for enhancement of process understanding and process control. A calibration-free method, iterative optimization technology (IOT), was proposed to predict pure component concentrations, because calibration methods such as partial least squares, require a large number of training samples, leading to high costs. However, IOT cannot be applied to concentration prediction in non-ideal mixtures because its basic equation is derived from the Beer-Lambert law, which cannot be applied to non-ideal mixtures. We proposed a novel method that realizes prediction of pure component concentrations in mixtures from a small number of training samples, assuming that spectral changes arising from molecular interactions can be expressed as a function of concentration. The proposed method is named IOT with virtual molecular interaction spectra (IOT-VIS) because the method takes spectral change as a virtual spectrum x nonlin,i into account. It was confirmed through the two case studies that the predictive accuracy of IOT-VIS was the highest among existing IOT methods.

  20. 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.

  1. Effect of initial densities in the lattice Boltzmann model for non-ideal fluid with curved interface

    NASA Astrophysics Data System (ADS)

    Gong, Jiaming; Oshima, Nobuyuki

    2017-06-01

    The effect of initial densities in a free energy based two-phase-flow lattice Boltzmann method for non-ideal fluids with a curved interface was investigated in the present work. To investigate this effect, the initial densities in the liquid and gas phases coming from the saturation points and the equilibrium state were adopted in the simulation of a static droplet in an open and a closed system. For the purpose of simplicity and easier comparison, the closed system is fabricated by the implementation of the periodic boundary condition at the inlet and outlet of a gas channel, and the open system is fabricated by the implementation of a constant flux boundary condition at the inlet and a free-out boundary condition at the outlet of the same gas channel. By comparing the simulation results from the two types of initial densities in the open and closed systems, it is proven that the commonly used saturation initial densities setting is the reason for droplet mass and volume variation which occurred in the simulation, particularly in the open system with a constant flux boundary condition. Such problems are believed to come from the curvature effect of the surface tension and can be greatly reduced by adopting the initial densities in the two phases from equilibrium state.

  2. Analytical and Experimental Performance Evaluation of BLE Neighbor Discovery Process Including Non-Idealities of Real Chipsets

    PubMed Central

    Perez-Diaz de Cerio, David; Hernández, Ángela; Valenzuela, Jose Luis; Valdovinos, Antonio

    2017-01-01

    The purpose of this paper is to evaluate from a real perspective the performance of Bluetooth Low Energy (BLE) as a technology that enables fast and reliable discovery of a large number of users/devices in a short period of time. The BLE standard specifies a wide range of configurable parameter values that determine the discovery process and need to be set according to the particular application requirements. Many previous works have been addressed to investigate the discovery process through analytical and simulation models, according to the ideal specification of the standard. However, measurements show that additional scanning gaps appear in the scanning process, which reduce the discovery capabilities. These gaps have been identified in all of the analyzed devices and respond to both regular patterns and variable events associated with the decoding process. We have demonstrated that these non-idealities, which are not taken into account in other studies, have a severe impact on the discovery process performance. Extensive performance evaluation for a varying number of devices and feasible parameter combinations has been done by comparing simulations and experimental measurements. This work also includes a simple mathematical model that closely matches both the standard implementation and the different chipset peculiarities for any possible parameter value specified in the standard and for any number of simultaneous advertising devices under scanner coverage. PMID:28273801

  3. Analytical and Experimental Performance Evaluation of BLE Neighbor Discovery Process Including Non-Idealities of Real Chipsets.

    PubMed

    Perez-Diaz de Cerio, David; Hernández, Ángela; Valenzuela, Jose Luis; Valdovinos, Antonio

    2017-03-03

    The purpose of this paper is to evaluate from a real perspective the performance of Bluetooth Low Energy (BLE) as a technology that enables fast and reliable discovery of a large number of users/devices in a short period of time. The BLE standard specifies a wide range of configurable parameter values that determine the discovery process and need to be set according to the particular application requirements. Many previous works have been addressed to investigate the discovery process through analytical and simulation models, according to the ideal specification of the standard. However, measurements show that additional scanning gaps appear in the scanning process, which reduce the discovery capabilities. These gaps have been identified in all of the analyzed devices and respond to both regular patterns and variable events associated with the decoding process. We have demonstrated that these non-idealities, which are not taken into account in other studies, have a severe impact on the discovery process performance. Extensive performance evaluation for a varying number of devices and feasible parameter combinations has been done by comparing simulations and experimental measurements. This work also includes a simple mathematical model that closely matches both the standard implementation and the different chipset peculiarities for any possible parameter value specified in the standard and for any number of simultaneous advertising devices under scanner coverage.

  4. Redundant imprinting of information in non-ideal environments: Quantum Darwinism via a noisy channel

    NASA Astrophysics Data System (ADS)

    Zwolak, Michael; Quan, Haitao; Zurek, Wojciech

    2011-03-01

    Quantum Darwinism provides an information-theoretic framework for the emergence of the classical world from the quantum substrate. It recognizes that we - the observers - acquire our information about the ``systems of interest'' indirectly from their imprints on the environment. Objectivity, a key property of the classical world, arises via the proliferation of redundant information into the environment where many observers can then intercept it and independently determine the state of the system. While causing a system to decohere, environments that remain nearly invariant under the Hamiltonian dynamics, such as very mixed states, have a diminished ability to transmit information about the system, yet can still acquire redundant information about the system [1,2]. Our results show that Quantum Darwinism is robust with respect to non-ideal initial states of the environment. This research is supported by the U.S. Department of Energy through the LANL/LDRD Program.

  5. 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.

  6. Non-ideal mixing behaviour of hydrogen bonding in mixtures of protic ionic liquids.

    PubMed

    Fumino, Koichi; Bonsa, Anne-Marie; Golub, Benjamin; Paschek, Dietmar; Ludwig, Ralf

    2015-02-02

    Ionic liquids (ILs) attract interest in science and technology as a result of their unique properties. Binary and ternary mixtures of ILs significantly increase the number of possible cation/anion combinations, resulting in targeted physical and chemical properties. In this work, we study the mixing behaviour of two protic ILs: triethyl ammonium methylsulfonate [Et3 NH][CH3 SO3 ] and triethylammonium triflate [Et3 NH][CF3 SO3 ]. We find a characteristic deviation from ideal mixing by means of low-frequency infrared spectroscopy. By using molecular dynamics simulations, we explain this behaviour as being the result of different strengths of anion/cation hydrogen bonding. This non-ideality of non-random H-bond mixing is also reflected in macroscopic properties such as the viscosity. Mixing suitable ILs may, thus, result in new ILs with targeted physical properties.

  7. Building a numerical relativistic non-ideal magnetohydrodynamics code for astrophysical applications

    NASA Astrophysics Data System (ADS)

    Aranguren, S. Miranda; Aloy, M. A.; Aloy, Carmen.

    2014-08-01

    Including resistive effects in relativistic magnetized plasmas is a challenging task, that a number of authors have recently tackled employing different methods. From the numerical point of view, the difficulty in including non-ideal terms arises from the fact that, in the limit of very high plasma conductivity (i.e., close to the ideal MHD limit), the system of governing equations becomes stiff, and the standard explicit integrating methods produce instabilities that destroy the numerical solution. To deal with such a difficulty, we have extended the relativistic MHD code MR-GENESIS, to include a number of Implicit Explicit Runge-Kutta (IMEX-RK) numerical methods. To validate the implementation of the IMEX-RK schemes, two standard tests are presented in one and two spatial dimensions, covering different conductivity regimes.

  8. Flow in geothermal wells. Part IV. Transition criteria for two-phase flow patterns

    SciTech Connect

    Bilicki, Z.; Kestin, J.

    1980-12-01

    Detailed considerations justifying the criteria for transitions between flow patterns are presented. The following are covered: transition from bubble to plug (or slug) flow, transition from plug flow to froth flow, transition from froth to annular mist flow, and model comparisons. (MHR)

  9. 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.

  10. Numerical modeling of photon recycling and luminescence coupling in non-ideal multijunction solar cell

    NASA Astrophysics Data System (ADS)

    Yuan, Mengyang; Lyu, Zheng; Jia, Jieyang; Chen, Yusi; Liu, Yi; Huo, Yijie; Miao, Yu; Harris, James

    2016-03-01

    For solar cells composed of direct bandgap semiconductors such as GaAs, the performance can be significantly improved by utilizing photon recycling and luminescence coupling effects. Accurate modeling with those effects may offer insightful guidance in designing such devices. Previous research has demonstrated different numerical models on photon recycling and luminescent coupling. However, most of those works are based on complicated theoretical derivation and idealized assumptions, which made them hard to implement. In addition, very few works provide method to model both photon recycling and luminescent coupling effects. In this paper, we demonstrate an easy-to-implement but accurate numerical model to simulate those effects in multijunction solar cells. Our numerical model can be incorporated into commonly used equivalent circuit model with high accuracy. The simulation results were compared with experimental data and exhibit good consistency. Our numerical simulation is based on a self-consistent optical-electrical model that includes non-ideal losses in both the single junction and the tandem device. Based on the numerical analysis, we modified the two-diode circuit model by introducing additional current-control-current sources to represent the effects of both photon recycling and luminescence coupling. The effects of photon recycling on the diode equation have been investigated based on detailed-balanced model, accounting for internal optical losses. We also showed the practical limit of performance enhancement of photon recycling and luminescent coupling effects. This work will potentially facilitate the accurate simulation of solar cell with non-ideal effects, and provide more efficient tools for multijunction solar cell design and optimization.

  11. 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.

  12. Gas liquid flow at microgravity conditions - Flow patterns and their transitions

    NASA Astrophysics Data System (ADS)

    Dukler, A. E.; Fabre, J. A.; McQuillen, J. B.; Vernon, R.

    The prediction of flow patterns during gas-liquid flow in conduits is central to the modern approach for modeling two phase flow and heat transfer. The mechanisms of transition are reasonably well understood for flow in pipes on earth where it has been shown that body forces largely control the behavior observed. This work explores the patterns which exist under conditions of microgravity when these body forces are suppressed. Data are presented which were obtained for air-water flow in tubes during drop tower experiments and Learjet trajectories. Preliminary models to explain the observed flow pattern map are evolved.

  13. Gas liquid flow at microgravity conditions - Flow patterns and their transitions

    NASA Technical Reports Server (NTRS)

    Dukler, A. E.; Fabre, J. A.; Mcquillen, J. B.; Vernon, R.

    1987-01-01

    The prediction of flow patterns during gas-liquid flow in conduits is central to the modern approach for modeling two phase flow and heat transfer. The mechanisms of transition are reasonably well understood for flow in pipes on earth where it has been shown that body forces largely control the behavior observed. This work explores the patterns which exist under conditions of microgravity when these body forces are suppressed. Data are presented which were obtained for air-water flow in tubes during drop tower experiments and Learjet trajectories. Preliminary models to explain the observed flow pattern map are evolved.

  14. Patterns in flowing sand: understanding the physics of granular flow.

    PubMed

    Börzsönyi, Tamás; Ecke, Robert E; McElwaine, Jim N

    2009-10-23

    Dense granular flows are often unstable and form inhomogeneous structures. Although significant advances have been recently made in understanding simple flows, instabilities of such flows are often not understood. We present experimental and numerical results that show the formation of longitudinal stripes that 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 pluglike 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.

  15. 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.

  16. Non-Ideality in Solvent Extraction Systems: PNNL FY 2014 Status Report

    SciTech Connect

    Levitskaia, Tatiana G.; Chatterjee, Sayandev; Pence, Natasha K.

    2014-09-30

    The overall objective of this project is to develop predictive modeling capabilities for advanced fuel cycle separation processes by gaining a fundamental quantitative understanding of non-ideality effects and speciation in relevant aqueous and organic solutions. Aqueous solutions containing actinides and lanthanides encountered during nuclear fuel reprocessing have high ionic strength and do not behave as ideal solutions. Activity coefficients must be calculated to take into account the deviation from ideality and predict their behavior. In FY 2012-2013, a convenient method for determining activity effects in aqueous electrolyte solutions was developed. Our initial experiments demonstrated that water activity and osmotic coefficients of the electrolyte solutions can be accurately measured by the combination of two techniques, a Water Activity Meter and Vapor Pressure Osmometry (VPO). The water activity measurements have been conducted for binary lanthanide solutions in wide concentration range for all lanthanides (La-Lu with the exception of Pm). The osmotic coefficients and Pitzer parameters for each binary system were obtained by the least squares fitting of the water activity data. However, application of Pitzer model for the quantitative evaluation of the activity effects in the multicomponent mixtures is difficult due to the large number of the required interaction parameters. In FY 2014, the applicability of the Bromley model for the determination of the Ln(NO3)3 activity coefficients was evaluated. The new Bromley parameters for the binary Ln(NO3)3 electrolytes were obtained based on the available literature and our experimental data. This allowed for the accurate prediction of the Ln(NO3)3 activity coefficients for the binary Ln(NO3)3 electrolytes. This model was then successfully implemented for the determination of the Ln(NO3)3 activity coefficients in the ternary Nd(NO3)3/HNO3/H2O, Eu(NO3)3/HNO3/H2O, and Eu(NO3)3/NaNO3/H2O systems. The main achievement

  17. Effect of compositional heterogeneity on dissolution of non-ideal LNAPL mixtures.

    PubMed

    Vasudevan, M; Johnston, C D; Bastow, T P; Lekmine, G; Rayner, J L; Nambi, I M; Suresh Kumar, G; Ravi Krishna, R; Davis, G B

    2016-11-01

    The extent of dissolution of petroleum hydrocarbon fuels into groundwater depends greatly on fuel composition. Petroleum fuels can consist of thousands of compounds creating different interactions within the non-aqueous phase liquid (NAPL), thereby affecting the relative dissolution of the components and hence a groundwater plume's composition over long periods. Laboratory experiments were conducted to study the variability in the effective solubilities and activity coefficients for common constituents of gasoline fuels (benzene, toluene, p-xylene and 1,2,4-trimethylbenzene) (BTX) in matrices with an extreme range of molar volumes and chemical affinities. Four synthetic mixtures were investigated comprising BTX with the bulk of the NAPL mixtures made up of either, ethylbenzene (an aromatic like BTX with similar molar volume); 1,3,5-trimethylbenzene (an aromatic with a greater molar volume); n-hexane (an aliphatic with a low molar volume); and n-decane (an aliphatic with a high molar volume). Equilibrium solubility values for the constituents were under-predicted by Raoult's law by up to 30% (higher experimental concentrations) for the mixture with n-hexane as a filler and over-predicted by up to 12% (lower experimental concentrations) for the aromatic mixtures with ethylbenzene and 1,3,5-trimethylbenzene as fillers. Application of PP-LFER (poly-parameter linear free energy relationship) model for non-ideal mixtures also resulted in poor correlation between experimentally measured and predicted concentrations, indicating that differences in chemical affinities can be the major cause of deviation from ideal behavior. Synthetic mixtures were compared with the dissolution behavior of fresh and naturally weathered unleaded gasoline. The presence of lighter aliphatic components in the gasoline had a profound effect on estimating effective solubility due to chemical affinity differences (estimated at 0.0055 per percentage increase in the molar proportion of aliphatic) as

  18. Effect of compositional heterogeneity on dissolution of non-ideal LNAPL mixtures

    NASA Astrophysics Data System (ADS)

    Vasudevan, M.; Johnston, C. D.; Bastow, T. P.; Lekmine, G.; Rayner, J. L.; Nambi, I. M.; Suresh Kumar, G.; Ravi Krishna, R.; Davis, G. B.

    2016-11-01

    The extent of dissolution of petroleum hydrocarbon fuels into groundwater depends greatly on fuel composition. Petroleum fuels can consist of thousands of compounds creating different interactions within the non-aqueous phase liquid (NAPL), thereby affecting the relative dissolution of the components and hence a groundwater plume's composition over long periods. Laboratory experiments were conducted to study the variability in the effective solubilities and activity coefficients for common constituents of gasoline fuels (benzene, toluene, p-xylene and 1,2,4-trimethylbenzene) (BTX) in matrices with an extreme range of molar volumes and chemical affinities. Four synthetic mixtures were investigated comprising BTX with the bulk of the NAPL mixtures made up of either, ethylbenzene (an aromatic like BTX with similar molar volume); 1,3,5-trimethylbenzene (an aromatic with a greater molar volume); n-hexane (an aliphatic with a low molar volume); and n-decane (an aliphatic with a high molar volume). Equilibrium solubility values for the constituents were under-predicted by Raoult's law by up to 30% (higher experimental concentrations) for the mixture with n-hexane as a filler and over-predicted by up to 12% (lower experimental concentrations) for the aromatic mixtures with ethylbenzene and 1,3,5-trimethylbenzene as fillers. Application of PP-LFER (poly-parameter linear free energy relationship) model for non-ideal mixtures also resulted in poor correlation between experimentally measured and predicted concentrations, indicating that differences in chemical affinities can be the major cause of deviation from ideal behavior. Synthetic mixtures were compared with the dissolution behavior of fresh and naturally weathered unleaded gasoline. The presence of lighter aliphatic components in the gasoline had a profound effect on estimating effective solubility due to chemical affinity differences (estimated at 0.0055 per percentage increase in the molar proportion of aliphatic) as

  19. 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.

  20. Mathematical study of non-ideal electrostatic correlations in equilibrium electrolytes

    NASA Astrophysics Data System (ADS)

    Ern, Alexandre; Joubaud, Rémi; Lelièvre, Tony

    2012-06-01

    We undertake the mathematical analysis of a model describing equilibrium binary electrolytes surrounded by charged solid walls. The problem is formulated in terms of the electrostatic potential and the ionic concentrations which have prescribed spatial mean values. The free energy of the system is decomposed as the difference of the internal energy and entropy functionals. The entropy functional is the sum of an ideal entropy and an excess entropy, the latter taking into account non-ideality due to electrostatic correlations at low ionic concentrations and steric exclusion effects at high ionic concentrations. We derive sufficient conditions to achieve convexity of the entropy functional, yielding a convex-concave free energy functional. Our main result is the existence and uniqueness of the saddle point of the free energy functional and its characterization as a solution of the original model problem. The proof hinges on positive uniform lower bounds for the ionic concentrations and uniform upper bounds for the ionic concentrations and the electrostatic potential. Some numerical experiments are presented in the case where the excess entropy is evaluated using the mean spherical approximation.

  1. 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.

  2. Effect of non-ideal clamping shape on the resonance frequencies of silicon nanocantilevers.

    PubMed

    Guillon, Samuel; Saya, Daisuke; Mazenq, Laurent; Perisanu, Sorin; Vincent, Pascal; Lazarus, Arnaud; Thomas, Olivier; Nicu, Liviu

    2011-06-17

    In this paper, we investigate the effects of non-ideal clamping shapes on the dynamic behavior of silicon nanocantilevers. We fabricated silicon nanocantilevers using silicon on insulator (SOI) wafers by employing stepper ultraviolet (UV) lithography, which permits a resolution of under 100 nm. The nanocantilevers were driven by electrostatic force inside a scanning electron microscope (SEM). Both lateral and out-of-plane resonance frequencies were visually detected with the SEM. Next, we discuss overhanging of the cantilever support and curvature at the clamping point in the silicon nanocantilevers, which generally arises in the fabrication process. We found that the fundamental out-of-plane frequency of a realistically clamped cantilever is always lower than that for a perfectly clamped cantilever, and depends on the cantilever width and the geometry of the clamping point structure. Using simulation with the finite-elements method, we demonstrate that this discrepancy is attributed to the particular geometry of the clamping point (non-zero joining curvatures and a flexible overhanging) that is obtained in the fabrication process. The influence of the material orthotropy is also investigated and is shown to be negligible.

  3. Spectral Analysis of Non-ideal MRI Modes: The Effect of Hall Diffusion

    NASA Astrophysics Data System (ADS)

    Mohandas, Gopakumar; Pessah, Martin E.

    2017-03-01

    The effect of magnetic field diffusion on the stability of accretion disks is a problem that has attracted considerable interest of late. In particular, the Hall effect has the potential to bring about remarkable changes in the dynamical behavior of disks that are without parallel. In this paper, we conduct a systematic examination of the linear eigenmodes in a weakly magnetized differentially rotating gas with a special focus on Hall diffusion. We first develop a geometrical representation of the eigenmodes and provide a detailed quantitative description of the polarization properties of the oscillatory modes under the combined influence of the Coriolis and Hall effects. We also analyze the effects of magnetic diffusion on the structure of the unstable modes and derive analytical expressions for the kinetic and magnetic stresses and energy densities associated with the non-ideal magnetorotational instability (MRI). Our analysis explicitly demonstrates that, if the dissipative effects are relatively weak, the kinetic stresses and energies make up the dominant contribution to the total stress and energy density when the equilibrium angular momentum and magnetic field vectors are anti-parallel. This is in sharp contrast to what is observed in the case of the ideal or dissipative MRI. We conduct shearing box simulations and find very good agreement with the results derived from linear theory. Because the modes under consideration are also exact solutions of the nonlinear equations, the unconventional nature of the kinetic and magnetic stresses may have significant implications for the nonlinear evolution in some regions of protoplanetary disks.

  4. Non-ideal effects in bending response of soft substrates covered with biomimetic scales.

    PubMed

    Ghosh, Ranajay; Ebrahimi, Hamid; Vaziri, Ashkan

    2017-08-01

    Biomimetic scales are known to substantially alter the mechanics response of the underlying substrate engendering complex nonlinearities that can manifest even in small deformations due to scales interaction. This interaction is typically modeled using a-priori homogenization with an enforced periodicity of engagement. Such a framework is fairly useful especially when dealing with the structural length scale which is at least one order of magnitude greater than the scales themselves since individual tracking of a large number of scales become insurmountable. On the other hand, this scheme makes several assumptions whose validity has not yet been investigated including infinite length of the substrate and rigidity of the scales. The validity of these assumptions and the accuracy and limitations of associated analytical models are investigated. Finite element based numerical studies were carried out to identify the critical role of edge effects and other non-ideal behavior such as violation of periodicity and nonlinear constitutive response on scale rotation. Our investigation shows that several important quantities show a strong saturation characteristic which justify many of the simplifying assumptions whereas others need much greater care. Copyright © 2017 Elsevier Ltd. All rights reserved.

  5. Two- phase flow patterns and heat transfer in parallel microchannels

    NASA Astrophysics Data System (ADS)

    Mosyak, A.; Segal, Z.; Pogrebnyak, E.; Hetsroni, G.

    2002-11-01

    Microchannel heat sinks with two-phase flow can satisfy the increasing heat removal requirements of modern micro electronic devices. One of the important aspects associated with two- phase flows in microchannels is to study the bubble behavior. However, in the literature most of the reports present data of only a single channel. This does not account for flow mixing and hydrodynamic instability that occurs in parallel microchannels, connected by common inlet and outlet collectors. In the present study, experiments were performed for air- water and steam- water flow in parallel triangular microchannels with a base of 200 300 µ m. The experimental study is based on systematic measurements of temperature and flow pattern by infrared radiometry and high-speed digital video imaging. In air-water flow, different flow patterns were observed simultaneously in the various microchannels at a fixed values of water and gas flow rates. In steam-water flow, instability in uniformly heated microchannels was observed. This work develops a practical modeling approach for two-phase microchannel heat sinks and considers discrepancy between flow patterns of air- water and steam- water flow in microchannels.

  6. Flow pattern visualization in a mimic anaerobic digester using CFD.

    PubMed

    Vesvikar, Mehul S; Al-Dahhan, Muthanna

    2005-03-20

    Three-dimensional steady-state computational fluid dynamics (CFD) simulations were performed in mimic anaerobic digesters to visualize their flow pattern and obtain hydrodynamic parameters. The mixing in the digester was provided by sparging gas at three different flow rates. The gas phase was simulated with air and the liquid phase with water. The CFD results were first evaluated using experimental data obtained by computer automated radioactive particle tracking (CARPT). The simulation results in terms of overall flow pattern, location of circulation cells and stagnant regions, trends of liquid velocity profiles, and volume of dead zones agree reasonably well with the experimental data. CFD simulations were also performed on different digester configurations. The effects of changing draft tube size, clearance, and shape of the tank bottoms were calculated to evaluate the effect of digester design on its flow pattern. Changing the draft tube clearance and height had no influence on the flow pattern or dead regions volume. However, increasing the draft tube diameter or incorporating a conical bottom design helped in reducing the volume of the dead zones as compared to a flat-bottom digester. The simulations showed that the gas flow rate sparged by a single point (0.5 cm diameter) sparger does not have an appreciable effect on the flow pattern of the digesters at the range of gas flow rates used.

  7. Disruption of intracardiac flow patterns in the newborn infant.

    PubMed

    Groves, Alan M; Durighel, Giuliana; Finnemore, Anna; Tusor, Nora; Merchant, Nazakat; Razavi, Reza; Hajnal, Jo V; Edwards, A David

    2012-04-01

    Consistent patterns of rotational intracardiac flow have been demonstrated in the healthy adult human heart. Intracardiac rotational flow patterns are hypothesized to assist in the maintenance of kinetic energy of inflowing blood, augmenting cardiac function. Newborn cardiac function is known to be suboptimal secondary to decreased receptor number and sympathetic innervation, increased afterload, and increased reliance on atrial contraction to support ventricular filling. Patterns of intracardiac flow in the newborn have not previously been examined. Whereas 5 of the 13 infants studied showed significant evidence of rotational flow within the right atrium, 8 infants showed little or no rotational flow. Presence or absence of rotational flow was not related to gestational age, birth weight, postnatal age, atrial size, or image quality. Despite absence of intra-atrial rotational flow, atrioventricular valve flow into the left and right ventricles later in the cardiac cycle could be seen, suggesting that visualization techniques were adequate. While further study is required to assess its exact consequences on cardiac mechanics and energetics, disruption to intracardiac flow patterns could be another contributor to the multifactorial sequence that produces newborn circulatory failure. We studied 13 newborn infants, using three-dimensional (3D) cardiac magnetic resonance phase-contrast imaging (spatial resolution 0.84 mm, temporal resolution 22.6 ms) performed without sedation/anesthesia.

  8. 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.

  9. 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.

  10. 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.

  11. Design flow automation for variable-shaped beam pattern generators

    NASA Astrophysics Data System (ADS)

    Bloecker, Martin; Ballhorn, Gerd

    2002-07-01

    Raster scan pattern generators have been used in the photomask industry for many years. Methods and software tools for data preparation for these pattern generators are well established and have been integrated into design flows with a high degree of automation. But the growing requirements for pattern fidelity have lead to the introduction of 50 kV variable shaped beam pattern generators. Due to their different writing strategy these tools use proprietary data formats and in turn require an optimized data preparation. As a result the existing design flow has to be adopted to account for these requirements. Due to the fact that cycle times have grown severely over the last years the automation of this adopted design flow will not only enhance the design flow quality by avoiding errors during manual operations but will also help to reduce turn-around times. We developed and implemented an automated design flow for a variable shaped beam pattern generator which had to fulfill two conflicting requirements: Well established automated tools originally developed for raster scan pattern generators had to be retained with only slight modifications to avoid the (re)implementation and the concurrent usage of two systems while on the other hand data generation especially during fracturing had to be optimized for a variable shaped beam pattern generator.

  12. Global simulations of protoplanetary disks with net magnetic flux. I. Non-ideal MHD case

    NASA Astrophysics Data System (ADS)

    Béthune, William; Lesur, Geoffroy; Ferreira, Jonathan

    2017-04-01

    Context. The planet-forming region of protoplanetary disks is cold, dense, and therefore weakly ionized. For this reason, magnetohydrodynamic (MHD) turbulence is thought to be mostly absent, and another mechanism has to be found to explain gas accretion. It has been proposed that magnetized winds, launched from the ionized disk surface, could drive accretion in the presence of a large-scale magnetic field. Aims: The efficiency and the impact of these surface winds on the disk structure is still highly uncertain. We present the first global simulations of a weakly ionized disk that exhibits large-scale magnetized winds. We also study the impact of self-organization, which was previously demonstrated only in non-stratified models. Methods: We perform numerical simulations of stratified disks with the PLUTO code. We compute the ionization fraction dynamically, and account for all three non-ideal MHD effects: ohmic and ambipolar diffusions, and the Hall drift. Simplified heating and cooling due to non-thermal radiation is also taken into account in the disk atmosphere. Results: We find that disks can be accreting or not, depending on the configuration of the large-scale magnetic field. Magnetothermal winds, driven both by magnetic acceleration and heating of the atmosphere, are obtained in the accreting case. In some cases, these winds are asymmetric, ejecting predominantly on one side of the disk. The wind mass loss rate depends primarily on the average ratio of magnetic to thermal pressure in the disk midplane. The non-accreting case is characterized by a meridional circulation, with accretion layers at the disk surface and decretion in the midplane. Finally, we observe self-organization, resulting in axisymmetric rings of density and associated pressure "bumps". The underlying mechanism and its impact on observable structures are discussed.

  13. Non-ideal interactions in calcic amphiboles and their bearing on amphibole-plagioclase thermometry

    NASA Astrophysics Data System (ADS)

    Holland, Tim; Blundy, Jon

    1994-05-01

    Amphibole thermodynamics are approximated with the symmetric formalism (regular solution model for within-site non-ideality and a reciprocal solution model for cross-site-terms) in order to formulate improved thermometers for amphibole-plagioclase assemblages. This approximation provides a convenient framework with which to account for composition-dependence of the ideal (mixing-on-sites) equilibrium constants for the equilibria: A) edenite+4quartz=tremolite+albite B) edenite+albite=richterite+anorthite For A and B all possible within-site and cross-site interactions among the species □-K-Na-Ca-Mg-Fe2+-Fe3+-Al-Si on the A, M4, M1, M3, M2 and T1 amphibole crystallographic sites were examined. Of the 36 possible interaction energy terms, application of the symmetric formalism results in a dramatic simplification to eight independent parameters. Plagioclase nonideality is modelled using Darken's quadratic formalism. We have supplemented an experimental data set of 92 amphibole-plagioclase pairs with 215 natural pairs from igneous and metamorphic rocks in which the pressure and temperature of equilibration are well constrained. Regression of the combined dataset yields values for the eight interaction parameters as well as for apparent enthalpy, entropy and volume changes for each reaction. These parameters are used to formulate two new thermometers, which perform well (±40°C) in the range 400 1000°C and 1 15 kbar over a broad range of bulk compositions, including tschermakitic amphiboles from garnet amphibolites which caused problems for the simple thermometer of Blundy and Holland (1990). For silica-saturated rocks both thermometers may be applied: in silica-undersaturated rocks or magmas thermometer B alone can be applied. An improved procedure for estimation of ferric iron in calcic amphiboles is presented in the appendix.

  14. 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

  15. 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

  16. Velocity-vorticity patterns in turbulent flow

    SciTech Connect

    Pelz, R.B.; Yakhot, V.; Orszag, S.A.; Shtilman, L.; Levich, E.

    1985-06-10

    Direct numerical simulation of the Navier-Stokes equations is used for the investigation of local helicity fluctuations in plane Poiseuille (channel) and Taylor-Green vortex flows. It is shown that in regions of high dissipation, the cosine of the angle between velocity and vorticity is evenly distributed; in regions of low dissipation, the velocity and vorticity vectors have a tendency to align. It is also shown that near the central part of the channel, velocity and vorticity vectors have a strong tendency to be aligned, while in the buffer region, all angles are nearly equally probable.

  17. 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.

  18. Pattern formation induced by a differential shear flow

    NASA Astrophysics Data System (ADS)

    Stucchi, L.; Vasquez, Desiderio A.

    2013-02-01

    Fluid flow advecting one substance while others are immobilized can generate an instability in a homogeneous steady state of a reaction-diffusion-advection system. This differential-flow instability leads to the formation of steady spatial patterns in a moving reference frame. We study the effects of shear flow on this instability by considering two layers of fluid moving independently from each other, but allowing the substances to diffuse along and across the layers. We find that shear flow can generate instabilities even if the average flow velocity is zero for both substances. These instabilities are strongly dependent on which substance is advected by the shear flow. We explain these effects using the results of Taylor dispersion, where an effective diffusivity is enhanced by shear flow.

  19. Basic cerebrospinal fluid flow patterns in ventricular catheters prototypes.

    PubMed

    Galarza, Marcelo; Giménez, Ángel; Valero, José; Pellicer, Olga; Martínez-Lage, Juan F; Amigó, José M

    2015-06-01

    A previous study by computational fluid dynamics (CFD) of the three-dimensional (3-D) flow in ventricular catheters (VC) disclosed that most of the total fluid mass flows through the catheter's most proximal holes in commercially available VC. The aim of the present study is to investigate basic flow patterns in VC prototypes. The general procedure for the development of a CFD model calls for transforming the physical dimensions of the system to be studied into a virtual wire-frame model which provides the coordinates for the virtual space of a CFD mesh, in this case, a VC. The incompressible Navier-Stokes equations, a system of strongly coupled, nonlinear, partial differential conservation equations governing the motion of the flow field, are then solved numerically. New designs of VC, e.g., with novel hole configurations, can then be readily modeled, and the corresponding flow pattern computed in an automated way. Specially modified VCs were used for benchmark experimental testing. Three distinct types of flow pattern in prototype models of VC were obtained by varying specific parameters of the catheter design, like the number of holes in the drainage segments and the distance between them. Specifically, we show how to equalize and reverse the flow pattern through the different VC drainage segments by choosing appropriate parameters. The flow pattern in prototype catheters is determined by the number of holes, the hole diameter, the ratio hole/segment, and the distance between hole segments. The application of basic design principles of VC may help to develop new catheters with better flow circulation, thus reducing the possibility of becoming occluded.

  20. 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.

  1. Relating Segregation Patterns and Symmetries in Chaotic Granular Flow

    NASA Astrophysics Data System (ADS)

    Cisar, Stephen; Meier, Steven; Lueptow, Richard; Ottino, Julio

    2006-11-01

    Segregation patterns formed by time-periodic flow of polydisperse granular material (varying in particle size) in quasi-two-dimensional (quasi-2D) tumblers capture the symmetries of Poincar'e sections, stroboscopic maps of the underlying flow, derived from a continuum model. The similarities are striking despite the fact that the model contains no information about particle properties. We study this phenomenon experimentally by using mixtures of bidisperse granular material in which the concentration of small particles is varied in quasi-2D tumblers with square and pentagonal cross-sections. Experimental segregation patterns can be connected to the dynamics of the underlying flow by an analysis of periodic points. Patterns vary with small particle concentration based on the location of both elliptic points that characterize islands of regular flow and hyperbolic points that characterize regions of chaotic flow seen in Poincar'e sections. The calculation of the eigenvectors and unstable manifolds of hyperbolic points shows that lobes of segregated small particles stretch from hyperbolic points toward corners of the tumbler, demonstrating the connection between regions of chaotic flow and the shape of the segregation patterns. Furthermore, unstable manifolds map the shape of lobes of segregated particles. Funded by DOE, Office of Basic Energy Sciences and NSF.

  2. Self-similar solution of cylindrical shock wave propagation in a rotational axisymmetric mixture of a non-ideal gas and small solid particles

    NASA Astrophysics Data System (ADS)

    Nath, Gorakh

    Similarity solutions are obtained for one-dimensional isothermal and adiabatic unsteady flow behind a strong cylindrical shock wave propagating in a rotational axisymmetric dusty gas, which has a variable azimuthal fluid velocity together with a variable axial fluid velocity. The experimental studies and astrophysical observations show that the outer atmosphere of the planets rotates due to rotation of the planets. Macroscopic motion with supersonic speed occurs in an interplanetary atmosphere and shock waves are generated. Thus rotation of planets or stars significantly affect the process taking place in their outer layers, therefore question connected with the explosions in rotating gas atmospheres are of definite astrophysical interest. The shock is assumed to be driven out by a moving piston and the dusty gas to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It is assumed that the equilibrium flow-condition is maintained and variable energy input is continuously supplied by the piston. The shock Mach number is not infinite, but has a finite value. The azimuthal and axial component of the fluid velocity in the ambient medium are assume to be vary and obey power laws, and the density of the ambient medium is assumed to be constant. In order to obtain the similarity solutions the angular velocity of the ambient medium is assume to be decreasing as the distance from the axis increases. Effects of the variation of the parameter of non-idealness of the gas in the mixture, the mass concentration of solid particles and the ratio of the density of solid particles to the initial density of the gas are investigated.

  3. 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

  4. 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

  5. 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.

  6. Accounting for thermodynamic non-ideality in the Guinier region of small-angle scattering data of proteins.

    PubMed

    Scott, David J

    2016-12-01

    Hydrodynamic studies of the solution properties of proteins and other biological macromolecules are often hard to interpret when the sample is present at a reasonably concentrated solution. The reason for this is that solutions exhibit deviations from ideal behaviour which is manifested as thermodynamic non-ideality. The range of concentrations at which this behaviour typically is exhibited is as low as 1-2 mg/ml, well within the range of concentrations used for their analysis by techniques such as small-angle scattering. Here we discuss thermodynamic non-ideality used previously used in the context of light scattering and sedimentation equilibrium analytical ultracentrifugation and apply it to the Guinier region of small-angle scattering data. The results show that there is a complementarity between the radially averaged structure factor derived from small-angle X-ray scattering/small-angle neutron scattering studies and the second virial coefficient derived from sedimentation equilibrium analytical ultracentrifugation experiments.

  7. 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.

  8. Pattern Dynamics in Taylor Vortex Flow with Double Hourglass Geometry

    NASA Astrophysics Data System (ADS)

    Wiener, Richard; Olsen, Thomas

    2005-11-01

    In previous investigations ootnotetextWiener et al., Phys. Rev. E 55, 5489 (1997) & Phys. Rev. Lett. 83, 2340 (1999) we have demonstrated experimentally that Taylor vortex flow in an hourglass geometry undergoes a period-doubling cascade to chaotic pattern dynamics that can be controlled by proportional feedback with small perturbations. The hourglass geometry creates a spatial ramp in the Reynolds number. This results in a region of supercritical vortex flow between regions of subcritical structureless flow that provide the pattern with soft boundaries that allow for persistent dynamics. For a range of reduced Reynolds numbers, the Taylor vortex pattern exhibits persistent dynamics consisting of drifting and stretching vortices punctuated with phase slips. Each phase slip corresponds to the generation of a new vortex pair. We are currently investigating the phase dynamics of Tayor vortex flow with a double hourglass geometry which consists of two regions of supercritical flow in which phase slips occur, separated by a narrow region of subcritical flow. Initial results indicate that at some reduced Reynolds numbers there is synchronization between the vortex dynamics in the two regions, both in the temporal occurrence of the phase slips as well as the drift directions of the vortices.

  9. Exact analytical solutions of the forward non-ideal diode equation with series and shunt parasitic resistances

    NASA Astrophysics Data System (ADS)

    Ortiz-Conde, Adelmo; García Sánchez, Francisco J.; Muci, Juan

    2000-10-01

    Exact closed form solutions based on the Lambert W-function are presented to express the forward current-voltage characteristics of non-ideal single-exponential diodes containing all possible combinations of series and shunt parasitic resistances. It is shown that these expressions could be useful for carrying out highly accurate computations at speeds almost as fast as those possible when using less precise approximate solutions based on common elementary functions.

  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. Deposition patterns and dispersion in reactive channel flows

    NASA Astrophysics Data System (ADS)

    Angheluta, L.; Hawkins, C.; Jamtveit, B.

    2015-12-01

    Flow of natural fluids is often associated with dispersion of dissolved chemical species and their surface deposition either by precipitation kinetics or aggregation. For most industrial or practical flows, this wall deposition has a detrimental effect that hiders transport by clogging or alters the fluid container; therefore it is important to gain a better understanding of transport in reactive flows and the range of deposition patterns developed. This talk has two main aims. Firstly, it is to present a combined theoretical and numerical approach to explore the diverse yet generic wall morphologies that develop in channel flows either due to precipitation kinetics or aggregation of spherical particles. These deposition patterns range from dendrites to needles and fan-like structures growing against the mean flow direction, and depend strongly on flow perturbations and dispersion properties. The second goal is to revisit classical Taylor's theory of dispersion in turbulent pipe flows and to show that, in fully developed turbulence, it predicts a nontrivial connection between longitudinal dispersion and the turbulent energy spectrum that we can also test and observe in numerical simulations.

  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. 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.

  14. Turbulent patterns in wall-bounded flows: A Turing instability?

    NASA Astrophysics Data System (ADS)

    Manneville, Paul

    2012-06-01

    In their way to/from turbulence, plane wall-bounded flows display an interesting transitional regime where laminar and turbulent oblique bands alternate, the origin of which is still mysterious. In line with Barkley's recent work about the pipe flow transition involving reaction-diffusion concepts, we consider plane Couette flow in the same perspective and transform Waleffe's classical four-variable model of self-sustaining process into a reaction-diffusion model. We show that, upon fulfillment of a condition on the relative diffusivities of its variables, the featureless turbulent regime becomes unstable against patterning as the result of a Turing instability. A reduced two-variable model helps us to delineate the appropriate region of parameter space. An intrinsic status is therefore given to the pattern's wavelength for the first time. Virtues and limitations of the model are discussed, calling for a microscopic support of the phenomenological approach.

  15. 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.

  16. Flow pattern and pressure drop of vertical upward gas-liquid flow in sinusoidal wavy channels

    SciTech Connect

    Nilpueng, Kitti; Wongwises, Somchai

    2006-06-15

    Flow patterns and pressure drop of upward liquid single-phase flow and air-water two-phase flow in sinusoidal wavy channels are experimentally studied. The test section is formed by a sinusoidal wavy wall of 1.00 m length with a wave length of 67.20mm, an amplitude of 5.76mm. Different phase shifts between the side walls of the wavy channel of 0{sup o}, 90{sup o} and 180{sup o} are investigated. The flow phenomena, which are bubbly flow, slug flow, churn flow, and dispersed bubbly flow are observed and recorded by high-speed camera. When the phase shifts are increased, the onset of the transition from the bubbly flow to the churn flow shifts to a higher value of superficial air velocity, and the regions of the slug flow and the churn flow are smaller. In other words, the regions of the bubbly flow and the dispersed bubbly flow are larger as the phase shift increases. The slug flow pattern is only found in the test sections with phase shifts of 0{sup o} and 90{sup o}. Recirculating gas bubbles are always found in the troughs of the corrugations. The recirculating is higher when the phase shifts are larger. The relationship between the two-phase multipliers calculated from the measured pressure drops, and the Martinelli parameter is compared with the Lockhart-Martinelli correlation. The correlation in the case of turbulent-turbulent condition is shown to fit the data very well for the phase shift of 0{sup o} but shows greater deviation when the phase shifts are higher. (author)

  17. 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.

  18. 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.

  19. Propagation of a spherical shock wave in mixture of non-ideal gas and small solid particles under gravitational field with conductive and radiative heat fluxes

    NASA Astrophysics Data System (ADS)

    Nath, Gorakh

    Self-similar solutions are obtained for one-dimensional unsteady adiabatic flow behind a spherical shock wave propagating in a dusty gas with conductive and radiative heat fluxes under a gravitational field. The shock is assumed to be driven out by a moving piston and the dusty gas to be a mixture of non-ideal (or perfect) gas and small solid particles, in which solid particles are continuously distributed. It is assumed that the equilibrium flow-conditions are maintained and variable energy input is continuously supplied by the piston. The heat conduction is express in terms of Fourier’s law and the radiation is considered to be of 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 medium is assumed to be under a gravitational field due to heavy nucleus at the origin (Roche Model). The unsteady model of Roche consists of a dusty gas distributed with spherical symmetry around a nucleus having large mass It is assumed that the gravitational effect of the mixture itself can be neglected compared with the attraction of the heavy nucleus. The density of the ambient medium is taken to be constant. Our analysis reveals that after inclusion of gravitational field effect surprisingly the shock strength increases and remarkable difference can be found in the distribution of flow variables. The effects of the variation of the heat transfer parameters, the gravitational parameter and non-idealness of the gas in the mixture are investigated. Also, the effects of an increase in (i) the mass concentration of solid particles in the mixture and (ii) the ratio of the density of solid particles to the initial density of the gas on the flow variables are investigated. It is found that the shock strength is increased with an increase in the value of gravitational parameter. Further, it is investigated that the presence of gravitational field increases the

  20. Using pattern matching to increase performance in hotspot fixing flows

    NASA Astrophysics Data System (ADS)

    Falch, Bradley J.; Baek, Seung-Hee; Tsai, John; Ji, Mingchao; Zhu, Jun

    2017-03-01

    As feature sizes and pitches continue to decrease, more complex correction algorithms are needed to solve increasingly difficult geometric configurations. Usage of these more complex algorithms results in unacceptably long time-to-mask when applied to an entire design. In many cases, the more complex algorithms are only required in a small percentage of areas of the entire design, and these areas are not always known prior to tapeout. Hotspot fixing (HSF) flows are increasingly used to fix these hotspot areas to minimize errors and decrease time-to-mask. These flows involve "recorrecting" a design, using the previous correction output as the input to the HSF flow. This input file contains a hierarchy that was optimized for the original correction. Hotspot areas are frequently smaller than the original correction areas and frequently repeat in unique cell outputs of the original correction, so the optimal hierarchy for a HSF fix flow may be very different from the original correction. A new hierarchy, optimized for HSF, is difficult to form from the corrected output. This paper describes the usage of pattern-matching to regain hierarchical compression for identical hotspot areas that are not repeating cells in the original correction. Using this pattern-matching HSF flow, turnaround time for the hotspot fixing can be more than 50X faster than re-using the original correction's hierarchy for complex HSF methods. These significant gains can be achieved in spite of the additional complexity it can add to the flow. In the case where simpler/faster HSF correction methods are used, significant turnaround time gains can still be made by using this pattern matching technique. Hotspot fixing methodologies are increasingly deployed during tapeouts as a means to optimize the tradeoffs between complex, highly accurate correction methods and faster methods that are sufficient for most pattern areas.1 However, pattern database hierarchies may not be optimum for these hotspot

  1. Flow Patterns in the Dog Descending Aorta under a Steady Flow Condition Simulating Mid-Systole

    NASA Astrophysics Data System (ADS)

    Endo, Shunsuke; Goldsmith, Harry Leonardo; Karino, Takeshi

    Hemodynamic factors are suspected to be involved in the localized pathogenesis and development of atherosclerotic lesions in the human thoracico-abdominal aorta. Hence, we studied the detailed flow patterns and the distributions of fluid velocity and wall shear stress there under the condition of a steady flow using five transparent aortic trees prepared from dogs as models of the human descending aorta and by means of flow visualization and high-speed cinemicrographic techniques. It was found that in all the cases the flow in the descending aorta was not fully developed to the extent to provide a parabolic velocity profile. Flow was disturbed at each junction, and most complex secondary and adverse flows formed at the branching site of the left renal artery adjacent to the lateral and posterior walls of the descending aorta. Furthermore, there was considerable interaction between the secondary and adverse flows formed at the branching sites of the four major arteries that stemmed off the descending aorta.

  2. 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

  3. The steady-state flow pattern past gravitating bodies

    NASA Astrophysics Data System (ADS)

    Ormel, C. W.

    2013-02-01

    Gravitating bodies significantly alter the flow pattern (density and velocity) of the gas that attempts to stream past. Still, small protoplanets in the Mars-super-Earth range can only bind limited amounts of nebular gas; until the so-called critical core mass has been reached (˜1-10 M⊕) this gas is in near hydrostatic equilibrium with the nebula. Here we aim for a general description of the flow pattern surrounding these low-mass, embedded planets. Using various simplifying assumptions (subsonic, 2D, inviscid flow, etc.), we reduce the problem to a partial differential equation that we solve numerically as well as approximate analytically. It is found that the boundary between the atmosphere and the nebula gas strongly depends on the value of the disc headwind (deviation from Keplerian rotation). With increasing headwind the atmosphere decreases in size and also becomes more asymmetrical. Using the derived flow pattern for the gas, trajectories of small solid particles, which experience both gas drag and gravitational forces, are integrated numerically. Accretion rates for small particles (dust) are found to be low, as they closely follow the streamlines, which curl away from the planet. However, pebble-size particles achieve large accretion rates, in agreement with previous numerical and analytical works.

  4. 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).

  5. Wettability control on multiphase flow in patterned microfluidics

    NASA Astrophysics Data System (ADS)

    Juanes, R.; Zhao, B.; MacMinn, C. W.

    2016-12-01

    Multiphase flow in porous media is important in many natural and industrial processes, including geologic CO2 sequestration, enhanced oil recovery, and water infiltration into soil. Although it is well known that the wetting properties of porous media can vary drastically depending on the type of media and pore fluids, the effect of wettability on multiphase flow continues to challenge our microscopic and macroscopic descriptions. Here, we study the impact of wettability on viscously unfavorable fluid-fluid displacement in disordered media by means of high-resolution imaging in microfluidic flow cells patterned with vertical posts. By systematically varying the wettability of the flow cell over a wide range of contact angles, we find that increasing the substrate's affinity to the injected fluid results in more efficient displacement of the defending fluid up to a critical wetting transition, beyond which the trend is reversed. We identify the pore-scale mechanisms—cooperative pore filling (increasing displacement efficiency) and corner flow (decreasing displacement efficiency)—responsible for this macroscale behavior, and show that they rely on the inherent 3D nature of interfacial flows, even in quasi-2D media. Our results demonstrate the powerful control of wettability on multiphase flow in porous media, and show that the markedly different invasion protocols that emerge—from pore-filling to post-bridging—are determined by physical mechanisms that are missing from current pore-scale and continuum-scale descriptions.

  6. Wettability control on multiphase flow in patterned microfluidics

    PubMed Central

    Zhao, Benzhong; Juanes, Ruben

    2016-01-01

    Multiphase flow in porous media is important in many natural and industrial processes, including geologic CO2 sequestration, enhanced oil recovery, and water infiltration into soil. Although it is well known that the wetting properties of porous media can vary drastically depending on the type of media and pore fluids, the effect of wettability on multiphase flow continues to challenge our microscopic and macroscopic descriptions. Here, we study the impact of wettability on viscously unfavorable fluid–fluid displacement in disordered media by means of high-resolution imaging in microfluidic flow cells patterned with vertical posts. By systematically varying the wettability of the flow cell over a wide range of contact angles, we find that increasing the substrate’s affinity to the invading fluid results in more efficient displacement of the defending fluid up to a critical wetting transition, beyond which the trend is reversed. We identify the pore-scale mechanisms—cooperative pore filling (increasing displacement efficiency) and corner flow (decreasing displacement efficiency)—responsible for this macroscale behavior, and show that they rely on the inherent 3D nature of interfacial flows, even in quasi-2D media. Our results demonstrate the powerful control of wettability on multiphase flow in porous media, and show that the markedly different invasion protocols that emerge—from pore filling to postbridging—are determined by physical mechanisms that are missing from current pore-scale and continuum-scale descriptions. PMID:27559089

  7. Wettability control on multiphase flow in patterned microfluidics

    NASA Astrophysics Data System (ADS)

    Juanes, Ruben; Zhao, Benzhong; MacMinn, Christopher

    2016-11-01

    Multiphase flow in porous media is important in many natural and industrial processes, including geologic CO2 sequestration, enhanced oil recovery, and water infiltration into soil. Although it is well known that the wetting properties of porous media can vary drastically depending on the type of media and pore fluids, the effect of wettability on multiphase flow continues to challenge our microscopic and macroscopic descriptions. Here, we study the impact of wettability on viscously unfavorable fluid-fluid displacement in disordered media by means of high-resolution imaging in microfluidic flow cells patterned with vertical posts. By systematically varying the wettability of the flow cell over a wide range of contact angles, we find that increasing the substrate's affinity to the injected fluid results in more efficient displacement of the defending fluid up to a critical wetting transition, beyond which the trend is reversed. We identify the pore-scale mechanisms-cooperative pore filling (increasing displacement efficiency) and corner flow (decreasing displacement efficiency)-responsible for this macroscale behavior, and show that they rely on the inherent 3D nature of interfacial flows, even in quasi-2D media. Our results demonstrate the powerful control of wettability on multiphase flow in porous media, and show that the markedly different invasion protocols that emerge-from pore-filling to post-bridging-are determined by physical mechanisms that are missing from current pore-scale and continuum-scale descriptions.

  8. Pattern formation and mixing in three-dimensional film flow

    NASA Astrophysics Data System (ADS)

    Heining, C.; Pollak, T.; Aksel, N.

    2012-04-01

    The effect of inertia on gravity-driven free surface flow over different three-dimensional periodic corrugations is considered analytically, numerically and experimentally. In the case of high bottom amplitudes, compared to the film thickness, the results predict complex free surface structures especially in cases where the topography is not fully flooded by the liquid film. The investigation of the flow field shows a rich variety of pattern formation phenomena depending on the interplay between the geometry of the topography and the inertia of the film. Finally, we show how the complex topographical structure enhances the laminar mixing within the film.

  9. 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

  10. Binary Collision Density in a Non-Ideal Gas as a Function of Particle Density, Collision Diameter, and Temperature

    NASA Astrophysics Data System (ADS)

    Mohazzabi, Pirooz

    2017-09-01

    Using molecular dynamics simulations, binary collision density in a dense non-ideal gas with Lennard-Jones interactions is investigated. It is shown that the functional form of the dependence of collision density on particle density and collision diameter remains the same as that for an ideal gas. The temperature dependence of the collision density, however, has a very different form at low temperatures, where it decreases as temperature increases. But at higher temperatures the functional form becomes the same as that for an ideal gas.

  11. Evoluton of polygonal fracture patterns in lava flows.

    PubMed

    Aydin, A; Degraff, J M

    1988-01-29

    Cooling-induced fractures, also known as columnar joints, divide basaltic lava flows into prismatic columns with polygonal cross sections. The regularity and symmetry of the fracture patterns have long fascinated naturalists. In view of the recent selection of two candidate nuclear waste sites in areas where polygonally fractured volcanic rocks are located, a better understanding of the fracture patterns is required. Field data indicate that the tetragonal networks at flow surfaces evolve systematically to hexagonal networks as the joints grow inward during solidification of lava. This evolution occurs by the gradual change of most orthogonal intersections to nonorthogonal intersections of about 120 degrees. The surface features and intersection geometries of columnar joints show that joint segments at any given level form sequentially yet harmoniously.

  12. 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.

  13. DC parameter extraction of equivalent circuit model in InGaAsSb heterojunction bipolar transistors including non-ideal effects in the base region

    NASA Astrophysics Data System (ADS)

    Chang, Yang-Hua; Cheng, Zong-Tai

    2011-07-01

    This paper presents the DC parameter extraction of the equivalent circuit model in an InP-InGaAsSb double heterojunction bipolar transistor (HBT). The non-ideal collector current is modeled by a non-ideal doping distribution in the base region. Then several consequent non-ideal effects, which have always been neglected in typical HBTs, are studied using Medici device simulator. Moreover, the associated DC parameters of VBIC model are extracted accordingly. The equivalent circuit model is in good agreement with the measured data in I C- V CE characteristics.

  14. Microscopic Current Flow Patterns in Nanoscale Quantum Point Contacts

    NASA Astrophysics Data System (ADS)

    Sai, Na; Bushong, Neil; Hatcher, Ryan; di Ventra, Massimiliano

    2006-03-01

    Transport in nanoscale conductors has been studied extensively mainly using the stationary scattering approach. However, the dynamical nature of transport, and in particular, the flow patterns of the microscopic current through a nanoscale junction, have remained poorly understood. We apply a novel time-dependent transport approach [1], which combines closed and finite geometries with time-dependent density functional theory,to study current flow patterns in nanoscale quantum point contacts [2]. The results of both atomistic and jellium calculations show that surface charges form dynamically at the junction-electrode interfaces in both abrupt and adiabatic junctions. The curr ent exhibits some characteristics of a classical hydrodynamic liquid but also displays unique patterns arising from the interaction with the surface charges. We also investigate the effect of the flow velocity, charge density, and lattice structures on the electron dynamics. If time permits we also discuss the effects of the viscosity of the electron liquid [3]. Work supported by DOE (DE-FG02-05ER46204). [1] M. Di Ventra and T.N. Todorov, J. Phys. Cond. Matt. 16, 8025 (2004). [2] N. Bushong, N. Sai and, M. Di Ventra, Nano Lett. (in press). [3] N. Sai, M. Zwolak, G. Vignale, and M. Di Ventra, Phys. Rev. Lett. 94, 186810 (2005 ).

  15. 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.

  16. 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

  17. 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

  18. 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

  19. Analysis of VOD-Diameter Data Using an Analytical Two-Dimensional Non-Ideal Detonation Model

    NASA Astrophysics Data System (ADS)

    Kirby, I. J.; Chan, S. K.

    2006-07-01

    An analytical two-dimensional detonation model is described that has successfully determined the ignition and growth behaviour of a highly non-ideal explosive from experimental VOD-diameter data. The model is based on a first order approximation of two-dimensional cylindrically symmetric steady state ZND detonation theory. A new ignition and growth model describes the kinetics. Previous analytical methods for analysing highly non-ideal explosives have used quasi-one dimensional models that determine the curvature of the shock front on the axis, and then require empirical relationships to determine the charge diameter. Consistency checks suggest that the inaccuracies introduced by the first order approximations and assumptions of the model cause overall errors of less than 10%. The model was verified by a series of experiments on an emulsion explosive. Data on detonation velocity, particle velocity and shock front curvature, as a function of charge diameter, were measured in these experiments. It is shown that three parameters defining the ignition and growth are both necessary and sufficient to match the theory to the experimental VOD-diameter data, and correctly predict the shock front curvature. The fourth parameter is required to adequately match the theory to the particle velocity profiles.

  20. Analysis of VOD-diameter data using an analytical two-dimensional non-ideal detonation model

    NASA Astrophysics Data System (ADS)

    Chan, Sek; Kirby, Ian

    2005-07-01

    An analytical two-dimensional detonation model is described that has successfully used experimental VOD-diameter data to determine the ignition and growth behaviour of a highly non-ideal explosive. The model is based on a first order approximation of two-dimensional cylindrically symmetric steady state ZND detonation theory. A new ignition and growth model describes the kinetics. Previous analytical methods for analysing highly non-ideal explosives have used quasi-one dimensional models that determine the curvature of the shock front on the axis, and then require empirical relationships to determine the charge diameter. Consistency checks, and comparison with a hydrocode, suggest that the inaccuracies introduced by the first order approximations and assumptions of the model cause overall errors of less than 10%. The model was verified by a series of experiments on an emulsion explosive. Data on detonation velocity, particle velocity and shock front curvature, as a function of charge diameter, were measured in these experiments. It is shown that three parameters defining the ignition and growth are both necessary and sufficient for matching to the experimental VOD-diameter data. The model uses these parameters to predict the shock front and particle velocity profiles, both of which agree with the experimental data to within the estimated errors.

  1. Scale invariance of subsurface flow patterns and its limitation

    NASA Astrophysics Data System (ADS)

    Hergarten, Stefan; Winkler, Gerfried; Birk, Steffen

    2015-04-01

    The morphology of river networks at the Earth's surface has been addressed in numerous studies. Numerical simulations of fluvial erosion processes and concepts of optimization have provided a rather comprehensive understanding about the scale invariance of river networks. Less is known about the structure of preferential flow patterns in the subsurface because these are only accessible by indirect measurements in most cases. As preferential flow patterns are crucial for all transport processes in the subsurface, unraveling their structure is a major challenge in subsurface hydrology. Transferring the idea of optimization from surface flow to subsurface flow it was recently suggested that preferential subsurface flow patterns should also have a dendritic, scale-invariant structure similar to that of river networks. In this study we analyzed the mean discharges of serval thousand springs with respect to scale invariance. For this purpose we reanalyzed a data set comprising about 17,000 springs from Spain already published in the literature and three new data sets from the Eastern Alps in Austria. We found that the probability density f(Q) of the discharge distribution can be described by a power law with an exponential cutoff, f(Q) ≈ Q-τe- QQc. The scaling exponent τ was found to be about 1.6, which is slightly larger than the exponent τ = 1.5 of river networks. In contrast to rivers, the distributions of the spring discharges are characterized by a significant cutoff at large discharges. This cutoff strongly depends on the lithology of the aquifers, while the scaling exponent τ ˜ 1.6 seems to be universal. The highest cutoff was found for limestones being one of the primary host rocks for karstic aquifers. We found Qc ˜ 6000 l/s for the limestones in the data set from Spain, suggesting a scale-invariant subsurface flow pattern up to catchment sizes of several thousand square kilometers. At the other edge, we found a cutoff at catchment sizes in the order of

  2. Flow pattern changes improve roller cone bit performance

    SciTech Connect

    Huffstutler, A.D.

    1996-05-06

    Improving the flow pattern through and around roller cone bits has increased penetration rate and footage while dropping the cost per foot drilled. These changes to the flow area around the bit help clean the bit and borehole more efficiently. By eliminating the protruding nozzle bosses, increasing nozzle bore size, narrowing the width of the bit arm segments, and providing a convex spherical dome, flow trajectories have been improved. These altered flow trajectories have eliminated hydraulic dead spots commonly found around current roller cone rock bit configurations. Nozzles are directed significantly more inward, toward the well bore bottom and away from the edge of the borehole. The flow impacts the bottom of the hole where it is needed most. Further performance enhancement features include an angled ramp on the shirt-tail portion of the arm to aid in lifting the cuttings upward, away from the cones and the bearing seals. Changing contours of the bit arms in the nozzle and bearing areas also improves cleaning and prevents cuttings from packing off in the bearing seal area.

  3. Development of radial optic flow pattern sensitivity at different speeds.

    PubMed

    Joshi, Mahesh Raj; Falkenberg, Helle K

    2015-05-01

    The development of sensitivity to radial optic flow discrimination was investigated by measuring motion coherence thresholds (MCTs) in school-aged children at two speeds. A total of 119 child observers aged 6-16years and 24 young adult observers (23.66+/-2.74years) participated. In a 2AFC task observers identified the direction of motion of a 5° radial (expanding vs. contracting) optic flow pattern containing 100 dots with 75% Michelson contrast moving at 1.6°/s and 5.5°/s and. The direction of each dot was drawn from a Gaussian distribution whose standard deviation was either low (similar directions) or high (different directions). Adult observers also identified the direction of motion for translational (rightward vs. leftward) and rotational (clockwise vs. anticlockwise) patterns. Motion coherence thresholds to radial optic flow improved gradually with age (linear regression, p<0.05), with different rates of development at the two speeds. Even at 16years MCTs were higher than that for adults (independent t-tests, p<0.05). Both children and adults had higher sensitivity at 5.5°/s compared to 1.6°/s (paired t-tests, p<0.05). Sensitivity to radial optic flow is still immature at 16years of age, indicating late maturation of higher cortical areas. Differences in sensitivity and rate of development of radial optic flow at the different speeds, suggest that different motion processing mechanisms are involved in processing slow and fast speeds.

  4. Regular patterns in the information flow of local dephasing channels

    NASA Astrophysics Data System (ADS)

    Giraldi, Filippo

    2017-02-01

    Consider local dephasing processes of a qubit that interacts with a structured reservoir of frequency modes or a thermal bath, with Ohmic-like spectral density (SD). It is known that non-Markovian evolution appears uniquely above a temperature-dependent critical value of the Ohmicity parameter and non-Markovianity can be induced by properly engineering the external environment. In the same scenario, we find regular patterns in the flow of quantum information: Alternate directions appear in correspondence with periodic intervals of the Ohmicity parameter α0. The information flows back into the system over long times at zero temperature for 2 +4 n <α0<4 +4 n , where n =0 ,1 ,2 ,..., and at nonvanishing temperatures for 3 +4 n <α0<5 +4 n . Under special conditions, backflow of information appears also for nonvanishing, even natural values of the Ohmicity parameter, at zero temperature, and for odd natural values at nonvanishing temperatures. Otherwise, the long-time information flows into the environment. In the transition from vanishing to arbitrary nonvanishing temperature, the long-time backflow of information is stable for 3 +4 n <α0<4 +4 n , while it is reversed for 2 +4 n <α0<3 +4 n and 4 +4 n <α0<5 +4 n . The patterns in the information flow are not altered if the low-frequency Ohmic-like profiles of the SDs are perturbed with additional factors that consist in arbitrary powers of logarithmic forms. Consequently, the flow of information can be controlled, directed, and reversed over long times by engineering a wide variety of reservoirs that includes and continuously departs from the Ohmic-like structure at low frequencies. Non-Markovianity and recoherence appear according to the same rules along with the backflow of information.

  5. Pattern centric OPC flow: a special RET flow with fast turn-around-time

    NASA Astrophysics Data System (ADS)

    Wang, Tom; Wu, Joanne; Liu, Qingwei; Zhang, Gary; Wang, Benny; Su, Bo; Cheng, Guojie

    2008-03-01

    Low K1 photolithography process increases the complexity of RET applications in IC designs. As technology node shrinks, pattern density is much denser along with much smaller geometry dimensions. Model-based OPC (Optical Proximity Correction) and post-OPC verification require more complex models and through process window compensated approaches, which significantly increase computational burden. Both lithographical challenges and computational complexity associated with 45nm process and below create a need for advanced capabilities on commercial OPC tools. To answer those challenges, hardware-accelerated OPC solution made a debut to solve runtime bottleneck issues, but they came in with very expensive price tags. As today, there are no explorations on the linkage between design styles and layout pattern OPC reusability. This paper introduces a new OPC flow with pattern-centric approach to leverage OPC knowledge of repeated design cells and patterns to achieve fast full chip OPC convergence, shorter cycle time, better OPC quality, and eventually lead to high manufacturing yields. In this paper, the main concepts of pattern-based OPC flow are demonstrated in 65nm customer memory designs. Pattern-based OPC is a natural extension of Anchor's pattern-centric approaches in DFM (Design for Manufacturing) domain.

  6. Stochastic Modeling of Buoyancy driven Gas Flow Pattern: Can Continuum Models describe Channelized Gas Flow?

    NASA Astrophysics Data System (ADS)

    Geistlinger, H. W.; Samani, S.

    2010-12-01

    The injection of gases into the subsurface has become an important research topic in groundwater remediation technology, e.g. air sparging, and in CCS-technology, e.g. CO2-sequestration into saline aquifers. In both cases risk assessment is based on 2-phase flow modeling assuming that the stochastic gas flow patterns can be described by the continuum approach. As Cinar et al. (2009) have stated: “The fundamental understanding of drainage, as it applies to CO2 sequestration process, is limited primarily by the lack of well characterized experiments that allow a detailed classification of the microscopic flow regimes”. In case of air sparging the two important flow regimes are capillary fingering and viscous fingering. Using pore scale network modeling Ewing and Berkowitz (1998) were able to describe the transition from capillary fingering (= incoherent channelized flow) to viscous fingering (= coherent channelized flow). In order to investigate the stability of buoyancy-driven gas flow and the transition between coherent channelized flow and incoherent channelized flow we conducted high-resolution optical bench scale experiments. Our main results, which are in strong contradiction to the commonly used continuum models (CM) are: (1) Capillary trapping can already occur during injection and at the front of the plume (Lazik and Geistlinger, 2008) (2) Gas clusters or bubbles can be mobile (incoherent gas flow) and immobile (capillary trapping), and (3) Incoherent gas flow can not be described by a generalized Darcy law (Geistlinger et al., 2006, 2009). Glass et al. (2000) conducted CO2-gas injection experiments. Based on their experimental results they also questioned the validity of CM to describe coherent and incoherent gas flow and the validity of homogeneous stability analysis to predict channel width, channel number and channel velocity in heterogeneous porous media. Despite these findings there is an ongoing controversial discussion in the literature about

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

    PubMed

    Sherratt, Jonathan A; Mackenzie, Julia J

    2016-10-07

    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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. 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.

  9. Transport of nonaparticles flowing past a patterned substrate

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Koplik, Joel

    2011-11-01

    We consider the defection of suspended particle trajectories due to flow past a patterned surface using complimentary Langevin numerical simulations and theoretical analyses based on the Fokker-Planck equation. The intended application is to vector particle separation in a nanofluidic channel. The simulations of flow past an alternating periodic striped pattern of attractive and repelling regions generally show that particles are deflected away from the imposed flow direction, to a degree that depends on the particle's size and the details of the substrate interaction. Both van der Waals and Coulomb interactions are studied, and in the latter case we explore the effects of the spatial distribution of bounding surface charge. Theoretically, both exactly in two dimensions and within the Fick-Jacobs approximation in three, we show that the effect of a periodic potential on the particle motion is always to impede the mean transport velocity in the orthogonal direction and deflect the trajectory, or equivalently reduce the effective diffusivity. Upper and lower bounds are found for the deflection angle, and explicit estimates are obtained in the limit of a weakly varying interaction. Supported by the NSF.

  10. Fluid flow patterns in porous media with partially ordered microstructure

    NASA Astrophysics Data System (ADS)

    Mirsaeidi, A.; Thompson, K. E.

    2014-12-01

    Natural granular porous media found in geosciences applications are disordered at the pore scale, which contributes to the interesting behavior that they exhibit including hydrodynamic dispersion, capillary pressure and wetting behavior, and various types of fingering. Many standard equations and models that have been developed for transport in porous media are based on the assumption of uniform disorder, randomly distributed parameters, and isotropic behavior. However, factors that cause partial ordering (e.g., settling of oblong grains, alignment of elongated particles, or packing structures near a boundary) can lead to anomalous flow behavior relative to the base case, when in turn requires different ways to understand and describe transport. In this work we examine the packing structure and fluid flow patterns in packings of equilateral cylindrical particles that are packed in a tube. The detailed packing structures are obtained experimentally from microCT experiments, and the flow patterns are simulated by numerical solution of the Stokes equations using the finite element method. This research is of interest in chemical engineering because this type of packing is used in catalytic reactors. However, the structures are also interesting from both a fundamental perspective and as prototypes for partially ordered natural materials because the packings undergo a transition from fully disordered internally to highly structured at the wall, and therefore provide insight into differences caused by the ordering.

  11. Two-phase flow patterns in adiabatic and diabatic corrugated plate gaps

    NASA Astrophysics Data System (ADS)

    Polzin, A.-E.; Kabelac, S.; de Vries, B.

    2016-09-01

    Correlations for two-phase heat transfer and pressure drop can be improved considerably, when they are adapted to specific flow patterns. As plate heat exchangers find increasing application as evaporators and condensers, there is a need for flow pattern maps for corrugated plate gaps. This contribution presents experimental results on flow pattern investigations for such a plate heat exchanger background, using an adiabatic visualisation setup as well as a diabatic setup. Three characteristic flow patterns were observed in the considered range of two-phase flow: bubbly flow, film flow and slug flow. The occurrence of these flow patterns is a function of mass flux, void fraction, fluid properties and plate geometry. Two different plate geometries having a corrugation angle of 27° and 63°, respectively and two different fluids (water/air and R365mfc liquid/vapor) have been analysed. A flow pattern map using the momentum flux is presented.

  12. 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

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

    NASA Astrophysics Data System (ADS)

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

    Understanding and controlling the drainage kinetics of thin films is an important problem that underlies the stability, lifetime and rheology of foams and emulsions. We follow the drainage kinetics of vertical foam films using imaging and color science. Interference between light reflected from two surfactant-laden surfaces that are 100 nm - 10 micron apart leads to thickness-dependent iridescent colors in the visible region. Below 50 nm the thin films appear as black. In this study, we utilize the thin film interference colors as markers for identifying patterns, instabilities and flows within vertical foam films. We study the emergence of thickness fluctuations near the borders (i.e. marginal regeneration) and within thinning films. Finally, we elucidate how buoyancy, capillarity, convection and gravity-driven instabilities and flows, are affected by the choice and concentration of constituents. We find fascinating examples of two-dimensional hydrodynamics and unexplained, if not unprecedented, drainage kinetics.

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

    NASA Astrophysics Data System (ADS)

    Yilixiati, Subinuer; Wojcik, Ewelina; Zhang, Yiran; Shah, Krupa; Sharma, Vivek

    2015-11-01

    Understanding and controlling the drainage kinetics of thin films is an important problem that underlies the stability, lifetime and rheology of foams and emulsions. We follow the drainage kinetics of vertical foam films using imaging and color science. Interference between light reflected from two surfactant-laden surfaces that are 100 nm - 10 micron apart leads to thickness-dependent iridescent colors in the visible region. Below 50 nm the thin films appear as black. In this study, we utilize the thin film interference colors as markers for identifying patterns, instabilities and flows within vertical foam films. We study the emergence of thickness fluctuations near the borders (i.e. marginal regeneration) and within thinning films. Finally, we elucidate how buoyancy, capillarity, convection and gravity-driven instabilities and flows, are affected by the choice and concentration of constituents. We find fascinating examples of two-dimensional hydrodynamics and unexplained, if not unprecedented, drainage kinetics.

  15. Pattern formation during mixing and segregation of flowing granular materials

    NASA Astrophysics Data System (ADS)

    Metcalfe, Guy; Shattuck, Mark

    1996-02-01

    Powder mixing plays an important role in a number of industries ranging from pharmaceuticals and food to ceramics and mining. Avalanches provide a mechanism for the stretching and folding needed to mix granular solids. However, unlike fluids, when particles dissimilar in size, density, or shape flow, they can spontaneously demix or segregate. Using magnetic resonance imaging, we track the transport of granular solids in a slowly rotating tube both with and without segregation effects. Compared with experiments in a 2-dimensional rotating disk partially filled with colored particles, the mixing kinematics and the granular pattern formation in a tube are changed by an axial flow instability. From simple physical principles we argue how size and density segregation mechanisms can be made to cancel, allowing good mixing of dissimilar particles, and we show experiments verifying this. Further experiments isolate the axial transport in the slowly rotating tube. Axial transport can appear faster with segregation than without.

  16. 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.

  17. Flow-induced polymer translocation through narrow and patterned channels.

    PubMed

    Nikoubashman, Arash; Likos, Christos N

    2010-08-21

    We consider linear and branched polymers driven through narrow and patterned channels by imposing a Poiseuille flow on the ambient solvent. We establish, by means of scaling arguments, that the translocation probability of dendrimers through the pore is independent of the number of monomers and that it takes place above a viscosity-dependent critical external current. When the channel walls are smooth, the translocation times of linear and branched polymers with the same monomer number are very similar. However, for walls that are decorated with attractive patches, dramatic differences show up: whereas a dendrimer successively docks at the patches and "walks" from one to the next, being carried away by the solvent flow, linear chains spread themselves along the channel wall without achieving translocation within simulation times. Our findings are relevant for, e.g., drug delivery through dendritic carrier molecules in capillary arterioles.

  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. Gene flow pattern among Aedes aegypti populations in Mexico.

    PubMed

    de Lourdes Muñoz, Maria; Mercado-Curiel, Ricardo F; Diaz-Badillo, Alvaro; Pérez Ramirez, Gerardo; Black, William C

    2013-03-01

    Patterns of gene flow vary greatly among Aedes aegypti populations throughout Mexico. The populations are panmictic along the Pacific coast, isolated by distance in northeast Mexico, and exhibit moderate gene flow across the Yucatan peninsula. Nine Ae. aegypti collections from 6 cities in Oaxaca, Mexico, were taken to examine the local patterns of gene flow. Genetic variation was examined in a 387-bp region of the nicotinamide adenine dinucleotide dehydrogenase subunit 4 mitochondrial gene (ND4) using single-strand conformation polymorphism analysis, and 3 haplotypes were detected. Cluster analysis on the linearized FST genetic distances failed to group collections in geographic proximity. Regression analysis of linear or road distances on linearized F(ST) indicated that proximal collections were as diverse as distant collections across an approximately 800-km range. The geographical distribution of the Mexican mosquito haplotype frequencies was determined for the ND4 sequences from 524 individuals from Oaxaca (this study) and 2,043 individuals from our previous studies. Herein, we report on yet another pattern dominated by genetic drift among 9 Ae. aegypti collections from 6 cities in Oaxaca, Mexico, and compare it to those reported in other regions of Mexico. Molecular analysis of variance showed that there was as much genetic variation among collections 4 km apart as there was among all collections. The numbers of haplotypes and the amount of genetic diversity among the collections from Oaxaca were much lower than detected in previous studies in other regions of Mexico and may reflect the effects of control efforts or adaptations to the altitudinal limits (1,500 m) of the species in Mexico. The geographical distribution of mosquito haplotypes in Mexico is also reported. Furthermore, based on the distribution of the mosquito haplotypes in America, we suggest that mosquito dispersion is very efficient, most likely due to commercial transportation.

  20. Pattern formation in granular and granular-fluid flows

    NASA Astrophysics Data System (ADS)

    Duong, Nhat-Hang P.

    Particles and suspensions of particles in fluids are regularly used in many engineering disciplines such as catalysis and reaction engineering, environmental engineering, pharmaceutical engineering, etc. A few issues that are commonly encountered include ensuring homogeneity in pharmaceutical suspensions, predicting particle transport in atmospheric and effluent streams, and manufacturing uniform composite materials. Yet the fundamental study of particle motions in granular media or in highly concentrated granular suspensions has received little attention. Relevant issues of research interest include development of adaptive models that permit wide ranges of particle concentrations, improvement of analyses that allow physical interpretation of particle motions in any medium, of scales ranging from particle size to system size, and accurate validation of theoretical with experimental data. Given the above shortcomings, this dissertation will focus on investigating basic transport behavior of particles in fluids and developing predictive models for granular media and granular suspensions. Emphasis will be given to combining experiments with computations through examples of pattern forming phenomena in a granular medium and a dense granular-fluid system. The background motivation and the objectives of this dissertation are stated in the opening chapter 1. The next three chapters address these objectives in detail. First, chapter 2 presents experimental evidence, descriptions, and characteristics of novel patterns in a dense granular suspension. This is followed by chapter 3 in which a mean-field continuum model is derived to further elucidate the reported patterning phenomena. Chapter 4 uncovers several novel granular patterns experimentally and is concluded with a coarse-grained phenomenological model for granular surface flows. Lastly, chapter 5 closes the dissertation with conclusions and possible future directions. This work provides additional understanding and

  1. 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.

  2. Shared solvation of sodium ions in alcohol-water solutions explains the non-ideality of free energy of solvation.

    PubMed

    Lange, Kathrin M; Bergmann, Ulf; Hodeck, Kai F; Könnecke, René; Schade, Ulrich; Aziz, Emad F

    2011-09-14

    In order to explain the discrepancies between theories and experiments regarding the non-ideality in the free energy of solvation, here we present a microscopic picture of sodium ions dissolved in water-alcohol mixed solvents. We used X-ray absorption spectroscopy to probe the K-edge of sodium ions in mixed solvents of water and alcohols (methanol, ethanol) and in the respective pure solvents. In the mixed solvents a shared solvation of the sodium ions is observed. We find that specifically the water component plays a key role in stabilizing the solvation shell in mixed solvents, which was revealed by a selective photochemical process occurring only in the pure alcohol solvents. This journal is © the Owner Societies 2011

  3. 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.

  4. 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.

  5. Flow Patterns at the Interface Between Free Flow and Sediment Bed

    NASA Astrophysics Data System (ADS)

    Leonardi, Alessandro; Zanello, Francesca; Pokrajac, Dubravka; Roman, Federico; Armenio, Vincenzo

    2017-04-01

    Bedload transport phenomena in rivers and reservoirs are driven by the flow pattern that develops at the interface between free flow and sediment bed. This is a very difficult area to investigate, due to heterogeneous flow which is often restricted to small length scales and hard to resolve with measuring instruments. Yet its interpretation is of prime interest for the understanding of the mass and momentum exchange between the free flow and the sediment. When dealing with the sediment transport triggering mechanism, most studies focus on the flow that develops above the bed, while the characteristics of the flow inside the bed are usually extrapolated from above or simply neglected. This approach yields an incomplete picture of what happens at the interface. Motivated by this, we propose a study where a free-surface flow tops a permeable bed composed of layers of equally-sized spherical beads. The physics of this configuration, originally analyzed with an experimental setup at the University of Aberdeen, was only partially understood, due to the difficulties in measuring velocity and pressure inside the pores. With a Large-Eddy Simulation (LES) we resolve the velocity and pressure fields in both the free flow and inside the porous bed. The no-slip boundary along the beads' surface is imposed using immersed boundaries, which also allows to compute the force exerted by the flow. We observe the development of momentum exchange between free flow and the porous bed, which activates turbulence penetrations that affect the pores closer to the surface of the permeable bed, and has two important consequences. First, the streamwise velocity in these pores is lower than that in the lower layers, a fact that challenges the usual assumption of a monotonically decreasing velocity profile within the bed. Secondly, the turbulence penetration generates an extra fluctuating component in the sphere lift forces whose role for the initiation of their movement is still not clear.

  6. Decoding complex flow-field patterns in visual working memory.

    PubMed

    Christophel, Thomas B; Haynes, John-Dylan

    2014-05-01

    There has been a long history of research on visual working memory. Whereas early studies have focused on the role of lateral prefrontal cortex in the storage of sensory information, this has been challenged by research in humans that has directly assessed the encoding of perceptual contents, pointing towards a role of visual and parietal regions during storage. In a previous study we used pattern classification to investigate the storage of complex visual color patterns across delay periods. This revealed coding of such contents in early visual and parietal brain regions. Here we aim to investigate whether the involvement of visual and parietal cortex is also observable for other types of complex, visuo-spatial pattern stimuli. Specifically, we used a combination of fMRI and multivariate classification to investigate the retention of complex flow-field stimuli defined by the spatial patterning of motion trajectories of random dots. Subjects were trained to memorize the precise spatial layout of these stimuli and to retain this information during an extended delay. We used a multivariate decoding approach to identify brain regions where spatial patterns of activity encoded the memorized stimuli. Content-specific memory signals were observable in motion sensitive visual area MT+ and in posterior parietal cortex that might encode spatial information in a modality independent manner. Interestingly, we also found information about the memorized visual stimulus in somatosensory cortex, suggesting a potential crossmodal contribution to memory. Our findings thus indicate that working memory storage of visual percepts might be distributed across unimodal, multimodal and even crossmodal brain regions. Copyright © 2014 Elsevier Inc. All rights reserved.

  7. 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.

  8. Regional characteristics of extreme drought patterns in stream flow records

    NASA Astrophysics Data System (ADS)

    Nasrollahi, N.; Ahmadi, M.; Alaeipour, A.

    2010-12-01

    Global warming has shown dramatic effects on natural systems in some parts of the world. Middle East is one of the locations that is affected by the severe changes in the climate conditions. In this study, the regional characteristics of severe seasonal droughts have been studied by analyzing the extreme value properties of the annual maximum series of river stream flows in the last 30 years. The study region is Karun River located in south western Iran. Karun River is Iran's most effluent, and the only navigable river which is 720 km long. It rises in the Zard Kuh Mountains and continues toward the Persian Gulf. There are a number of dams on the Karun River, with the purpose of generating hydroelectric power and flood control. The area is divided into 10 catchments with daily stream flow records. To investigate the drought periods, the threshold level is defined by percentiles from the flow duration curve. Two different regionalization tools are compared, L-moment diagrams and empirical orthogonal functions. The L-moment and EOF diagrams provided virtually the same conclusions with regard to clustering of catchments, and large scale trends were found in the data which confirms a regional pattern.

  9. Flow pattern analysis of the Baylor total artificial heart.

    PubMed

    Meier, D; Wernicke, J T; Orime, Y; Takatani, S; Tasai, K; Damm, G; Naito, K; Mizuguchi, K; Makinouchi, K; Glueck, J

    1994-12-01

    To obtain an optimal design of the left blood chamber of the total artificial heart (TAH), flow visualization studies were performed. Information on velocities in critical areas of the left chamber was gathered using sectional pulsed laser light. The flow patterns on the entire pumping duration were photographed frame by frame. The inflow port, the opposite of the inflow and outflow of the pump (bottom area), and the diaphragm/housing junction were the focal areas. The pump conditions, such as chamber pressure, preload and afterload pressure, pumping rate and roller screw, and displacement were recorded. Major stagnations and a low washout effect were observed in the bottom region. The closing of the inflow valve was irregular. In order to solve this problem, the inflow valve angle was changed 20 degrees. A comparison study showed a better valve closing characteristic, and no stagnation areas were observed with this new valve angle. Various velocity profiles confirmed the results. The valve closing characteristics is described in relationship to back flow.

  10. Mixing dynamics and pattern formation around flow stagnation points

    NASA Astrophysics Data System (ADS)

    Hidalgo, Juan J.; Dentz, Marco

    2016-04-01

    We study the mixing of two reactive fluids in the presence of convective instabilities. Such system is characterized by the formation of unique porosity patterns and mixing dynamics linked to the evolution of vortices and stagnation points. Around them, the fluid-fluid interface is stretched and compressed, which enhances mixing and triggers chemical reactions, and the system can be analyzed using fluid deformation model. We consider velocity fields generated by a double gyre synthetic velocity field and Rayleigh-Bénard and Rayleigh-Taylor instabilities. The different flow structures can be visualized by the strain rate and the finite time Lyapunov exponents. We show that the mixing enhancement given by the scalar dissipation rate is controlled by the equilibrium between interface compression and diffusion, which depends on the velocity field configuration. Furthermore, we establish a quantitative relation between the mixing rate and the evolution of the potential energy of the fluid when convection is driven by density instabilities.

  11. Iridescent Patterns and Flows in Vertical Foam Films

    NASA Astrophysics Data System (ADS)

    Wojcik, Ewelina; Yilixiati, Subinuer; Abbott-Klostermann, Will; Sharma, Vivek

    2015-03-01

    Liquid foams consist of bubbles separated by thin films. Individual films consist of two surfactant-laden surfaces that are ~ 5 nm - 10 micron apart. Sandwiched between these interfacial layers is a fluid that drains primarily under the influence of gravitational, viscous and interfacial forces, including disjoining pressure. Understanding and controlling the drainage kinetics of thin films is an important problem that underlies the stability, lifetime and rheology of foams and emulsions. We experimentally follow the drainage kinetics of foam films using imaging & color science. Interference between light reflected from two surfactant-laden surfaces that are ~ 100 nm - 10 micron apart leads to thickness-dependent iridescent colors in the visible region. Below 50 nm the thin films appear as black. We find fascinating examples of two-dimensional hydrodynamics and unexplained, if not unprecedented, drainage kinetics. In particular, we study the origin of marginal regeneration, i. e. the complex flow patterns that originate near the borders of foam films.

  12. Impact of fracture network geometry on free convective flow patterns

    NASA Astrophysics Data System (ADS)

    Vujević, Katharina; Graf, Thomas; Simmons, Craig T.; Werner, Adrian D.

    2014-09-01

    The effect of fracture network geometry on free convection in fractured rock is studied using numerical simulations. We examine the structural properties of fracture networks that control the onset and strength of free convection and the patterns of density-dependent flow. Applicability of the equivalent porous medium approach (EPM) is also tested, and recommendations are given, for which situations the EPM approach is valid. To date, the structural properties of fracture networks that determine free convective flow are examined only in few, predominantly simplified regular fracture networks. We consider fracture networks containing continuous, discontinuous, orthogonal and/or inclined discrete fractures embedded in a low-permeability rock matrix. The results indicate that bulk permeability is not adequate to infer the occurrence and magnitude of free convection in fractured rock. Fracture networks can inhibit or promote convection depending on the fracture network geometry. Continuous fracture circuits are the crucial geometrical feature of fracture networks, because large continuous fracture circuits with a large vertical extent promote convection. The likelihood of continuous fracture circuits and thus of free convection increases with increasing fracture density and fracture length, but individual fracture locations may result in great deviances in strength of convection between statistically equivalent fracture networks such that prediction remains subject to large uncertainty.

  13. 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.

  14. Measurement and prediction of two-phase flow patterns for new refrigerants inside horizontal tubes

    SciTech Connect

    Kattan, N.; Favrat, D.; Thome, J.R.

    1995-12-31

    Two-phase flow pattern data were obtained with 12-mm-bore sight glasses for five refrigerants: R-123, R-134a, R-502, R-402A, and R-404A. The existing flow pattern maps of Taitel and Dukler (1976) and Hashizume (1983) poorly represented the data, while, with the exception of mist flows, the VDI map identified the flow patterns successfully. Methods used in horizontal flow boiling correlations to determine the threshold between all wet wall and partially wet wall flows were shown to be unreliable.

  15. Gas-particle partitioning of atmospheric aerosols: interplay of physical state, non-ideal mixing and morphology.

    PubMed

    Shiraiwa, Manabu; Zuend, Andreas; Bertram, Allan K; Seinfeld, John H

    2013-07-21

    Atmospheric aerosols, comprising organic compounds and inorganic salts, play a key role in air quality and climate. Mounting evidence exists that these particles frequently exhibit phase separation into predominantly organic and aqueous electrolyte-rich phases. As well, the presence of amorphous semi-solid or glassy particle phases has been established. Using the canonical system of ammonium sulfate mixed with organics from the ozone oxidation of α-pinene, we illustrate theoretically the interplay of physical state, non-ideality, and particle morphology affecting aerosol mass concentration and the characteristic timescale of gas-particle mass transfer. Phase separation can significantly affect overall particle mass and chemical composition. Semi-solid or glassy phases can kinetically inhibit the partitioning of semivolatile components and hygroscopic growth, in contrast to the traditional assumption that organic compounds exist in quasi-instantaneous gas-particle equilibrium. These effects have significant implications for the interpretation of laboratory data and the development of improved atmospheric air quality and climate models.

  16. The dynamic behavior of a cantilever beam coupled to a non-ideal unbalanced motor through numerical and experimental analysis

    NASA Astrophysics Data System (ADS)

    Gonçalves, P. J. P.; Silveira, M.; Pontes Junior, B. R.; Balthazar, J. M.

    2014-09-01

    An excitation force that is not influenced by the system state is said to be an ideal energy source. In real situations, a direct and feedback coupling between the excitation source and the system must always exist at a certain level. This manifestation of the law of conservation of energy is known as the Sommerfeld effect. In the case of obtaining a mathematical model for such a system, additional equations are usually necessary to describe the vibration sources with limited power and its coupling with the mechanical system. In this work, a cantilever beam and a non-ideal DC motor fixed to its free end are analyzed. The motor has an unbalanced mass that provides excitation to the system which is proportional to the current applied to the motor. During the coast up operation of the motor, if the drive power is increased slowly, making the excitation frequency pass through the first natural frequency of the beam, the DC motor speed will remain the same until it suddenly jumps to a much higher value (simultaneously its amplitude jumps to a much lower value) upon exceeding a critical input power. It was found that the Sommerfeld effect depends on some system parameters and the motor operational procedures. These parameters are explored to avoid the resonance capture in the Sommerfeld effect. Numerical simulations and experimental tests are used to help gather insight of this dynamic behavior.

  17. 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.

  18. 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.

  19. 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.

  20. 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.

  1. 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

  2. Experimental investigation of two-phase flow patterns in minichannels at horizontal orientation

    NASA Astrophysics Data System (ADS)

    Saljoshi, P. S.; Autee, A. T.

    2017-09-01

    Two-phase flow is the simplest case of multiphase flow in which two phases are present for a pure component. The mini channel is considered as diameter below 3.0-0.2 mm and conventional channel is considered diameter above 3.0 mm. An experiment was conducted to study the adiabatic two-phase flow patterns in the circular test section with inner diameter of 1.1, 1.63, 2.0, 2.43 and 3.0 mm for horizontal orientation using air and water as a fluid. Different types of flow patterns found in the experiment. The parameters that affect most of these patterns and their transitions are channel size, phase superficial velocities (air and liquid) and surface tension. The superficial velocity of liquid and gas ranges from 0.01 to 66.70 and 0.01 to 3 m/s respectively. Two-phase flow pattern photos were recorded using a high speed CMOS camera. In this experiment different flow patterns were identified for different tube diameters that confirm the diameter effect on flow patterns in two-phase flows. Stratified flow was not observed for tube diameters less than 3.0 mm. Similarly, wavy-annular flow pattern was not observed in 1.6 and 1.0 mm diameter tubes due to the surface-tension effect and decrease in tube diameter. Buoyancy effects were clearly visible in 2.43 and 3.0 mm diameter tubes flow pattern. It has also observed that as the test-section diameter decreases the transition lines shift towards the higher gas and liquid velocity. However, the result of flow pattern lines in the present study has good agreement with the some of the existing flow patterns maps.

  3. Flow patterns and transition characteristics for steam condensation in silicon microchannels

    NASA Astrophysics Data System (ADS)

    Ma, Xuehu; Fan, Xiaoguang; Lan, Zhong; Hao, Tingting

    2011-07-01

    This study investigated the two-phase flow patterns and transition characteristics for steam condensation in silicon microchannels with different cross-sectional geometries. Novel experimental techniques were developed to determine the local heat transfer rate and steam quality by testing the temperature profile of a copper cooler. Flow regime maps for different microchannels during condensation were established in terms of steam mass flux and steam quality. Meanwhile, the correlation for the flow pattern transition was obtained using different geometrical and dimensionless parameters for steam condensation in microchannels. To better understand the flow mechanisms in microchannels, the condensation flow patterns, such as annular flow, droplet flow, injection flow and intermittent flow, were captured and analyzed. The local heat transfer rate showed the nonlinear variations along the axial direction during condensation. The experimental results indicate that the flow patterns and transition characteristics strongly depend on the geometries of microchannels. With the increasing steam mass flux and steam quality, the annular/droplet flow expands and spans over a larger region in the microchannels; otherwise the intermittent flow occupies the microchannels. The dimensionless fitting data also reveal that the effect of surface tension and vapor inertia dominates gravity and viscous force at the specified flow pattern transitional position.

  4. Pressure drop, flow pattern and local water volume fraction measurements of oil-water flow in pipes

    NASA Astrophysics Data System (ADS)

    Kumara, W. A. S.; Halvorsen, B. M.; Melaaen, M. C.

    2009-11-01

    Oil-water flow in horizontal and slightly inclined pipes was investigated. The experimental activities were performed using the multiphase flow loop at Telemark University College, Porsgrunn, Norway. The experiments were conducted in a 15 m long, 56 mm diameter, inclinable steel pipe using Exxsol D60 oil (density of 790 kg m-3 and viscosity of 1.64 mPa s) and water (density of 996 kg m-3 and viscosity of 1.00 mPa s) as test fluids. The test pipe inclination was changed in the range from 5° upward to 5° downward. Mixture velocity and inlet water cut vary up to 1.50 m s-1 and 0.975, respectively. The time-averaged cross-sectional distributions of oil and water were measured with a single-beam gamma densitometer. The pressure drop along the test section of the pipe was also measured. The characterization of flow patterns and identification of their boundaries are achieved via visual observations and by analysis of local water volume fraction measurements. The observed flow patterns were presented in terms of flow pattern maps for different pipe inclinations. In inclined flows, dispersions appear at lower mixture velocities compared to the horizontal flows. Smoothly stratified flows observed in the horizontal pipe disappeared in upwardly inclined pipes and new flow patterns, plug flow and stratified wavy flow were observed. The water-in-oil dispersed flow regime slightly shrinks as the pipe inclination increases. In inclined flows, the dispersed oil-in-water flow regime extended to lower mixture velocities and lower inlet water cuts. The present experimental data were compared with the results of a flow-pattern-dependent prediction model, which uses the area-averaged steady-state two-fluid model for stratified flow and the homogeneous model for dispersed flow. The two-fluid model was able to predict the pressure drop and water hold-up for stratified flow. The homogeneous model was not able to predict the pressure profile of dispersed oil-water flow at higher water

  5. A study of oil-water flow patterns in horizontal pipes

    SciTech Connect

    Trallero, J.L.; Intevep, S.A.; Sarica, C.; Brill, J.P.

    1996-12-31

    Oil-water flow pattern transitions in horizontal pipes have been studied both experimentally and theoretically. A new state-of-the-art, oil-water test facility was designed, constructed and operated. A transparent test section (5.013-cm inside diameter x 15.54-m long) can be inclined at any angle, to study both upward and downward flow simultaneously. Mineral oil and water were the working fluids ({mu}{sub o}/{mu}{sub w} = 29.6, {rho}{sub o}/{rho}{sub w} = 0.85 and {sigma} = 36 dynes/cm @ 25.6{degrees}C). Only horizontal flow tests were conducted. A new classification for oil-water flow patterns based on published and acquired data is proposed. Six flow patterns were identified and classified into two categories: Segregated flow and Dispersed flow. Stratified flow and stratified flow with some mixing at the interface (ST & MI) are segregated flow patterns. The dispersed flow can be either water dominated or oil dominated. A dispersion of oil in water over a water layer and an emulsion of oil in water are water dominated flow patterns. An emulsion of water in oil and a dual dispersion are oil dominant flow patterns. Conductance probe data and high speed photographs were found to be adequate flow pattern identification tools while wall pressure fluctuations are not. Pressure drop decreases when the transition to dispersed flow is crossed. Slippage is only relevant for segregated flow patterns. The oil-water flow pattern transitions for light oils are predicted using the two-fluid model and a balance between gravity and turbulent fluctuations normal to the axial flow direction. Linear and non-linear analyses reveal that the stratified/non-stratified transition must be addressed with the complete two-fluid model. Stratified flow is predicted by the viscous Kelvin-Helmholtz analysis while inviscid Kelvin-Helmholtz theory predicted the ST & MI flow pattern. Both the viscous Kelvin-Helmholtz analysis and structural stability criterion are satisfied simultaneously.

  6. Dynamics of High Sound-Speed Metal Confiners Driven By Non-Ideal High-Explosive Detonation

    SciTech Connect

    Short, Mark; Jackson, Scott I.

    2015-01-23

    Here, the results of 14 tests examining the behavior of aluminum (Al) conifners driven by non-ideal ANFO detonation in a cylinder test configuration are presented. In each test, the measured detonation phase velocity is slower than the aluminum sound speed. Thus, in the detonation reference frame, the ow in the Al is both shockless and subsonic. The tests involve: 3-inch inner diameter (ID) cylinders with Al wall thicknesses of 1/4, 3/8, 1/2, 1 and 2 inches; a 4-inch ID cylinder with a 1/2-inch Al wall thickness; and 6-inch ID cylinders with Al wall thicknesses of 1/2, 1 and 2 inches. The ANFO detonation velocity is seen to increase with increasing wall thickness for both the 3- and 6-inch ID tests, with no limiting velocity reached for the wall thicknesses used. The motion of the outer Al wall due to precursor elastic waves in the Al running ahead of the detonation is also measured at various axial locations along the cylinders. It is found that the magnitude of the outer wall motion due to the precursor elastic waves is small, while the associated wall motion is unsteady and decays in amplitude as the elastic disturbances move further ahead of the detonation front. The variations in the expansion history of the main outer wall motion of the cylinders are presented for increasing wall thickness at fixed ID, and for increasing cylinder inner diameter at a fixed wall thickness. Finally, we also explore the existence of a geometric similarity scaling of the wall expansion history for three geometrically scaled tests (3- and 6-inch ID cylinders with 1/4- and 1/2-inch walls respectively, 3- and 6-inch ID cylinders with 1/2- and 1-inch walls and 3- and 6-inch ID cylinders with 1- and 2-inch walls respectively). We find that the wall velocity histories for each of the three scaled tests, when plotted directly against time relative to start of main motion of the wall, are similar over a certain range of wall velocities without any geometric based rescaling in time. The

  7. Dynamics of High Sound-Speed Metal Confiners Driven By Non-Ideal High-Explosive Detonation

    DOE PAGES

    Short, Mark; Jackson, Scott I.

    2015-01-23

    Here, the results of 14 tests examining the behavior of aluminum (Al) conifners driven by non-ideal ANFO detonation in a cylinder test configuration are presented. In each test, the measured detonation phase velocity is slower than the aluminum sound speed. Thus, in the detonation reference frame, the ow in the Al is both shockless and subsonic. The tests involve: 3-inch inner diameter (ID) cylinders with Al wall thicknesses of 1/4, 3/8, 1/2, 1 and 2 inches; a 4-inch ID cylinder with a 1/2-inch Al wall thickness; and 6-inch ID cylinders with Al wall thicknesses of 1/2, 1 and 2 inches.more » The ANFO detonation velocity is seen to increase with increasing wall thickness for both the 3- and 6-inch ID tests, with no limiting velocity reached for the wall thicknesses used. The motion of the outer Al wall due to precursor elastic waves in the Al running ahead of the detonation is also measured at various axial locations along the cylinders. It is found that the magnitude of the outer wall motion due to the precursor elastic waves is small, while the associated wall motion is unsteady and decays in amplitude as the elastic disturbances move further ahead of the detonation front. The variations in the expansion history of the main outer wall motion of the cylinders are presented for increasing wall thickness at fixed ID, and for increasing cylinder inner diameter at a fixed wall thickness. Finally, we also explore the existence of a geometric similarity scaling of the wall expansion history for three geometrically scaled tests (3- and 6-inch ID cylinders with 1/4- and 1/2-inch walls respectively, 3- and 6-inch ID cylinders with 1/2- and 1-inch walls and 3- and 6-inch ID cylinders with 1- and 2-inch walls respectively). We find that the wall velocity histories for each of the three scaled tests, when plotted directly against time relative to start of main motion of the wall, are similar over a certain range of wall velocities without any geometric based rescaling in time

  8. Intra-aneurysmal flow patterns: illustrative comparison among digital subtraction angiography, optical flow, and computational fluid dynamics.

    PubMed

    Brina, O; Ouared, R; Bonnefous, O; van Nijnatten, F; Bouillot, P; Bijlenga, P; Schaller, K; Lovblad, K-O; Grünhagen, T; Ruijters, D; Pereira, V Mendes

    2014-12-01

    Digital subtraction angiography is the gold standard vascular imaging and it is used for all endovascular treatment of intracranial anerysms. Optical flow imaging has been described as a potential method to evaluate cerebral hemodynamics through DSA. In this study, we aimed to compare the flow patterns measured during angiography, by using an optical flow method, with those measured by using computational fluid dynamics in intracranial aneurysms. A consecutive series of 21 patients harboring unruptured saccular intracranial aneurysms who underwent diagnostic angiography before treatment was considered. High-frame-rate digital subtraction angiography was performed to obtain an intra-aneurysmal velocity field by following the cardiac-modulated contrast wave through the vascular structures by using optical flow principles. Additionally, computational fluid dynamics modeling was performed for every case by using patient-specific inlet-boundary conditions measured with the optical flow method from both DSA and 3D rotational angiography datasets. Three independent observers compared qualitatively both the inflow direction and the apparent recirculation in regular DSA, optical flow images, and computational fluid dynamics flow patterns for each patient; κ statistics were estimated. We included 21 patients. In 14 of these 21, the flow patterns were conclusive and matching between the optical flow images and computational fluid dynamics within the same projection view (κ = .91). However, in only 8 of these 14 patients the optical flow images were conclusive and matching regular DSA images (observer κ = 0.87). In 7 of the 21 patients, the flow patterns in the optical flow images were inconclusive, possibly due to improper projection angles. The DSA-based optical flow technique was considered qualitatively consistent with computational fluid dynamics outcomes in evaluating intra-aneurysmal inflow direction and apparent recirculation. Moreover, the optical flow technique

  9. 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.

  10. 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)

  11. Polynomial analysis of placental flow patterns in growth-retarded fetuses.

    PubMed

    Hütter, W; Grab, D; Sterzik, K; Terinde, R; Wolf, A

    1993-01-01

    Correct interpretation of conspicuous blood flow velocity waveforms cannot rely solely on the evaluation of uteroplacental vascular Doppler flow patterns by means of angle-independent indices such as the resistance or pulsatility index. In addition to the degree of pulsatility, the waveform shape between the systolic and diastolic peak values is of considerable consequence. A subdivision of the total flow waveform into orthogonal polynomial components allows both pulsatility evaluation and notching to be registered, providing a higher sensitivity in identification of pathological vascular resistance. Accurate recording and assessment of the flow waveform is therefore an important qualitative criterion for the classification of Doppler flow patterns in pregnancies with reduced uteroplacental perfusion.

  12. Interventional physiology. Part XVI: normal coronary flow velocity patterns: considerations of artifacts, arrhythmias, and anomalies.

    PubMed

    Tron, C; Donohue, T J; Kern, M J

    1995-04-01

    During normal flow velocity recording, various physiologic or technical problems may appear which can produce confusing flow signals. This section of Interventional Physiology reviews the patterns of normal coronary flow velocity and examines several artifacts and other features encountered in clinical practice. Recognition of these variations will help the interventional cardiologist to differentiate between physiologic and pathologic events.

  13. 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.

  14. 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

  15. 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, ...

  16. Patterns of the turbulent Taylor-Couette flow

    NASA Astrophysics Data System (ADS)

    Prigent, Arnaud; Talioua, Abdessamad; Mutabazi, Innocent

    2016-11-01

    We are interested in the study of the transition to turbulence in the Taylor-Couette flow, the flow between two independently rotating coaxial cylinders. Once the geometry is fixed, the flow is controlled by the inner and outer Reynolds numbers and present a large variety of flow regimes. In counter-rotation, the transition is characterized by a succession of more or less turbulent flow regimes: intermittency with turbulent spots, spiral turbulence, featureless turbulence. For larger values of the inner Reynolds number, turbulent Taylor roll re-emerge from the featureless turbulence and remain for very large values of the Reynolds numbers. Bifurcations between different turbulent rolls states are even observed in the ultimate turbulence regime. Nevertheless the transition from the featureless turbulence to the turbulent rolls still requires a detailed study and the mechanism which causes and sustains turbulent spots or turbulent spirals remains unknown. In this study we present new experimental information on the organization of the flow for the different regimes with turbulence. The experiments are conducted in a Taylor-Couette flow with η = 0 . 8 . Stereo-Particle Image Velocimetry measurements and visualizations of the different flow regimes are realized and discussed. This work was supported by the ANR TRANSFLOW - ANR-13-BS09-0025.

  17. 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, ...

  18. Abnormal cerebral blood flow patterns in preterm infants with a large patent ductus arteriosus.

    PubMed

    Martin, C G; Snider, A R; Katz, S M; Peabody, J L; Brady, J P

    1982-10-01

    To determine whether there are significant alterations in cerebral blood flow patterns in infants with a patent ductus arteriosus and whether these alterations correlate with alterations in aortic blood flow, we performed range-gated pulsed-Doppler examinations of the aorta and cerebral arteries in 20 infants. Ten infants had a PDA and ten control infants did not. We analyzed these flow patterns quantitatively by calculating the pulsatility index (peak systolic frequency minus trough diastolic frequency)/peak systolic frequency. In the ten control infants and in three infants with a small PDA, there was no significant diastolic flow in the descending aorta; flow in the cerebral arteries was antegrade throughout systole and diastole (PI = 0.75 +/- 0.03 for control infants and 0.73 +/- 0.07 for small PDA infants). In seven infants with a large PDA, there was retrograde diastolic flow in the descending aorta. This pattern was not seen after PDA closure. In the cerebral arteries of the seven infants with a large PDA, diastolic flow was retrograde in three and decreased or absent in four, and PI was significantly higher (PI = 0.96 +/- 0.06. P less than 0.001 vs controls). After PDA closure, cerebral diastolic flow was antegrade in all seven infants (PI = 0.74 +/- 0.04). We conclude that a large PDA can cause abnormal flow patterns in the descending aorta and cerebral arteries. These flow patterns may predispose these infants to CNS ischemia or intraventricular hemorrhage.

  19. Effect of reverse flow on the pattern of wall shear stress near arterial branches.

    PubMed

    Kazakidi, A; Plata, A M; Sherwin, S J; Weinberg, P D

    2011-11-07

    Atherosclerotic lesions have a patchy distribution within arteries that suggests a controlling influence of haemodynamic stresses on their development. The distribution near aortic branches varies with age and species, perhaps reflecting differences in these stresses. Our previous work, which assumed steady flow, revealed a dependence of wall shear stress (WSS) patterns on Reynolds number and side-branch flow rate. Here, we examine effects of pulsatile flow. Flow and WSS patterns were computed by applying high-order unstructured spectral/hp element methods to the Newtonian incompressible Navier-Stokes equations in a geometrically simplified model of an aorto-intercostal junction. The effect of pulsatile but non-reversing side-branch flow was small; the aortic WSS pattern resembled that obtained under steady flow conditions, with high WSS upstream and downstream of the branch. When flow in the side branch or in the aortic near-wall region reversed during part of the cycle, significantly different instantaneous patterns were generated, with low WSS appearing upstream and downstream. Time-averaged WSS was similar to the steady flow case, reflecting the short duration of these events, but patterns of the oscillatory shear index for reversing aortic near-wall flow were profoundly altered. Effects of reverse flow may help explain the different distributions of lesions.

  20. Effect of reverse flow on the pattern of wall shear stress near arterial branches

    PubMed Central

    Kazakidi, A.; Plata, A. M.; Sherwin, S. J.; Weinberg, P. D.

    2011-01-01

    Atherosclerotic lesions have a patchy distribution within arteries that suggests a controlling influence of haemodynamic stresses on their development. The distribution near aortic branches varies with age and species, perhaps reflecting differences in these stresses. Our previous work, which assumed steady flow, revealed a dependence of wall shear stress (WSS) patterns on Reynolds number and side-branch flow rate. Here, we examine effects of pulsatile flow. Flow and WSS patterns were computed by applying high-order unstructured spectral/hp element methods to the Newtonian incompressible Navier–Stokes equations in a geometrically simplified model of an aorto-intercostal junction. The effect of pulsatile but non-reversing side-branch flow was small; the aortic WSS pattern resembled that obtained under steady flow conditions, with high WSS upstream and downstream of the branch. When flow in the side branch or in the aortic near-wall region reversed during part of the cycle, significantly different instantaneous patterns were generated, with low WSS appearing upstream and downstream. Time-averaged WSS was similar to the steady flow case, reflecting the short duration of these events, but patterns of the oscillatory shear index for reversing aortic near-wall flow were profoundly altered. Effects of reverse flow may help explain the different distributions of lesions. PMID:21508011

  1. Gas-liquid pipe flow under microgravity conditions: influence of tube diameter on flow patterns and pressure drops

    NASA Astrophysics Data System (ADS)

    Colin, C.; Fabre, J.

    1995-08-01

    Gas-liquid flow experiments have been performed in small tubes of 19 mm, 10 mm and 6 mm diameter, during parabolic flights, for a range of superficial liquid velocities from 0.1 to 2 m/s and superficial gas velocities from 0.05 m/s to 10 m/s. Results are compared to those previously obtained by Colin et al., /1/, in a 40 mm i.d. tube. The flow patterns identified are: bubbly flow, slug flow and a pattern halfway between slug and annular flows. The main difference between the experiments in small tubes and the previous ones, concerns the transition between bubbly flow and slug flow, the role of coalescence and the wall friction factor. Coalescence is shown to play a major role in the transition from bubbly to slug flow. In particular at small Reynolds number coalescence seems to be partly inhibited. Single-phase flow correlations for wall shear stress underestimate the wall friction factor in the intermediate range of Reynolds number between laminar and turbulent flow.

  2. Experimental investigation on flow patterns of RP-3 kerosene under sub-critical and supercritical pressures

    NASA Astrophysics Data System (ADS)

    Wang, Ning; Zhou, Jin; Pan, Yu; Wang, Hui

    2014-02-01

    Active cooling with endothermic hydrocarbon fuel is proved to be one of the most promising approaches to solve the thermal problem for hypersonic aircraft such as scramjet. The flow patterns of two-phase flow inside the cooling channels have a great influence on the heat transfer characteristics. In this study, phase transition processes of RP-3 kerosene flowing inside a square quartz-glass tube were experimentally investigated. Three distinct phase transition phenomena (liquid-gas two phase flow under sub-critical pressures, critical opalescence under critical pressure, and corrugation under supercritical pressures) were identified. The conventional flow patterns of liquid-gas two phase flow, namely bubble flow, slug flow, churn flow and annular flow are observed under sub-critical pressures. Dense bubble flow and dispersed flow are recognized when pressure is increased towards the critical pressure whilst slug flow, churn flow and annular flow disappear. Under critical pressure, the opalescence phenomenon is observed. Under supercritical pressures, no conventional phase transition characteristics, such as bubbles are observed. But some kind of corrugation appears when RP-3 transfers from liquid to supercritical. The refraction index variation caused by sharp density gradient near the critical temperature is thought to be responsible for this corrugation.

  3. Profound spatial heterogeneity of coronary reserve. Discordance between patterns of resting and maximal myocardial blood flow.

    PubMed

    Austin, R E; Aldea, G S; Coggins, D L; Flynn, A E; Hoffman, J I

    1990-08-01

    We examined the ability of individual regions of the canine left ventricle to increase blood flow relative to baseline rates of perfusion. Regional coronary flow was measured by injecting radioactive microspheres over 90 seconds in seven anesthetized mongrel dogs. Preliminary experiments demonstrated a correlation between the regional distributions of blood flow during asphyxia and pharmacological vasodilatation with adenosine (mean r = 0.75; 192 regions in each of two dogs), both of which resulted in increased coronary flow. Subsequent experiments, during which coronary perfusion pressure was held constant at 80 mm Hg, examined the pattern of blood flow in 384 regions (mean weight, 106 mg) of the left ventricular free wall during resting flow and during maximal coronary flow effected by intracoronary adenosine infusion. We found that resting and maximal flow patterns were completely uncorrelated to each other in a given dog (mean r = 0.06, p = NS; n = 3 dogs). Furthermore, regional coronary reserve, defined as the ratio of maximal to resting flow, ranged from 1.75 (i.e., resting flow was 57% of maximum) to 21.9 (resting flow was 4.5% of maximum). Thus, coronary reserve is spatially heterogeneous and determined by two distinct perfusion patterns: the resting (control) pattern and the maximal perfusion pattern. Normal hearts, therefore, contain small regions that may be relatively more vulnerable to ischemia. This may explain the patchy nature of infarction with hypoxia and at reduced perfusion pressures as well as the difficulty of using global parameters to predict regional ischemia. Despite the wide dispersion of coronary reserve, we found, by autocorrelation analysis, that reserve in neighboring regions (even when separated by a distance of several tissue samples) was significantly correlated. This also applied to patterns of resting myocardial flow. Thus, both resting coronary blood flow and reserve appear to be locally continuous and may define functional

  4. 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.

  5. 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.

  6. Echocardiographic and hemodynamic determinants of right coronary artery flow reserve and phasic flow pattern in advanced non-ischemic cardiomyopathy

    PubMed Central

    Graziosi, Pedro; Ianni, Barbara; Ribeiro, Expedito; Perin, Marco; Beck, Leonardo; Meneghetti, Claudio; Mady, Charles; Filho, Eulogio Martinez; Ramires, Jose AF

    2007-01-01

    Background In patients with advanced non-ischemic cardiomyopathy (NIC), right-sided cardiac disturbances has prognostic implications. Right coronary artery (RCA) flow pattern and flow reserve (CFR) are not well known in this setting. The purpose of this study was to assess, in human advanced NIC, the RCA phasic flow pattern and CFR, also under right-sided cardiac disturbances, and compare with left coronary circulation. As well as to investigate any correlation between the cardiac structural, mechanical and hemodynamic parameters with RCA phasic flow pattern or CFR. Methods Twenty four patients with dilated severe NIC were evaluated non-invasively, even by echocardiography, and also by cardiac catheterization, inclusive with Swan-Ganz catheter. Intracoronary Doppler (Flowire) data was obtained in RCA and left anterior descendent coronary artery (LAD) before and after adenosine. Resting RCA phasic pattern (diastolic/systolic) was compared between subgroups with and without pulmonary hypertension, and with and without right ventricular (RV) dysfunction; and also with LAD. RCA-CFR was compared with LAD, as well as in those subgroups. Pearson's correlation analysis was accomplished among echocardiographic (including LV fractional shortening, mass index, end systolic wall stress) more hemodynamic parameters with RCA phasic flow pattern or RCA-CFR. Results LV fractional shortening and end diastolic diameter were 15.3 ± 3.5 % and 69.4 ± 12.2 mm. Resting RCA phasic pattern had no difference comparing subgroups with vs. without pulmonary hypertension (1.45 vs. 1.29, p = NS) either with vs. without RV dysfunction (1.47 vs. 1.23, p = NS); RCA vs. LAD was 1.35 vs. 2.85 (p < 0.001). It had no significant correlation among any cardiac mechanical or hemodynamic parameter with RCA-CFR or RCA flow pattern. RCA-CFR had no difference compared with LAD (3.38 vs. 3.34, p = NS), as well as in pulmonary hypertension (3.09 vs. 3.10, p = NS) either in RV dysfunction (3.06 vs. 3.22, p

  7. 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

  8. 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.

  9. 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.

  10. Two-phase flow patterns characteristics analysis based on image and conductance sensors

    NASA Astrophysics Data System (ADS)

    Wang, Zhenya; Jin, Ningde; Wang, Chun; Wang, Jinxiang

    2008-10-01

    In order to study the temporal and spatial evolution characteristics of gas-liquid two-phase flow pattern, the two-phase flow monitoring system composed of high-speed dynamic camera and Vertical Multi-Electrode Array conductance sensor (VMEA) was utilized to shoot dynamic images and acquire the conductance fluctuating signals of 5 typical vertical gas-liquid two-phase flow patterns in a 125mm i.d. upward pipe. Gray level co-occurrence matrix (GLCM) was used to extract four time-varying characteristic parameter indices which represented different flow image texture structures and also Lempel-Ziv complexity of them were calculated. Then the transition of flow structure and flow property were comprehensively analyzed, combining the result derived from image information with recurrence plots (RPs) and Lempel-Ziv complexity of conductance fluctuating signals. The study showed that the line texture structure of RPs enabled to indicate flow pattern characteristics; the flow image texture structure characteristic parameters sequence described the variance of flow structure and dynamical complexity of different flow patterns.

  11. Effect of Groove Pattern of Chemical Mechanical Polishing Pad on Slurry Flow Behavior

    NASA Astrophysics Data System (ADS)

    Yamazaki, Tsutomu; Doi, Toshiro K.; Uneda, Michio; Kurokawa, Syuhei; Ohnishi, Osamu; Seshimo, Kiyoshi; Aida, Hideo

    2012-05-01

    In chemical mechanical polishing (CMP), the slurry flow behavior on the polishing pad is very important both for improving polishing effectiveness and for reducing the slurry consumption. In this study, we aim to evaluate two types of CMP pad that have unique special groove patterns, slurry outflow and inflow pads, for controlling the slurry flow behavior. We describe the effect of the groove patterns on the slurry flow behavior observed using images recorded using a high-speed digital camera. The results of the study indicate several advantages of the proposed pads over the conventional pads from the viewpoint of slurry flow behavior.

  12. Infant-specific gaze patterns in response to radial optic flow

    PubMed Central

    Shirai, Nobu; Imura, Tomoko

    2016-01-01

    The focus of a radial optic flow is a valid visual cue used to perceive and control the heading direction of animals. Gaze patterns in response to the focus of radial optic flow were measured in human infants (N = 100, 4–18 months) and in adults (N = 20) using an eye-tracking technique. Overall, although the adults showed an advantage in detecting the focus of an expansion flow (representing forward locomotion) against that of a contraction flow (representing backward locomotion), infants younger than 1 year showed an advantage in detecting the focus of a contraction flow. Infants aged between 13 and 18 months showed no significant advantage in detecting the focus in either the expansion or in the contraction flow. The uniqueness of the gaze patterns in response to the focus of radial optic flow in infants shows that the visual information necessary to perceive heading direction potentially differs between younger and mature individuals. PMID:27708361

  13. The Dakota aquifer near Pueblo, Colorado; faults and flow patterns

    USGS Publications Warehouse

    Banta, E.R.

    1985-01-01

    The Dakota Sandstone and the underlying Purgatoire Formation consisting of the Glencairn Shale and Lytle Sandstone Members form a board outcrop at the southeastern margin of the Canon City Embankment. The two formations form the Dakota aquifer, which supplies water to many domestic, stock, and irrigation wells in addition to a few municipal wells in the 12-township study area. Five large faults and several small faults, all apparently of high angle, are found in the study area. Analysis of water levels and water quality shows that parts of some of these faults restrict the flow of groundwater in the Dakota aquifer. Lithology of the rocks, particularly in the Dakota Sandstone and in the Glencairn Shale Member, is extremely variable. The lithology appears to affect the flow regime, possibly by determining how a particular segment of a fault affects flow. (USGS)

  14. 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.

  15. 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.

  16. Boundary layer flow visualisation patterns on a riblet surface

    NASA Astrophysics Data System (ADS)

    Clark, D. G.

    Boundary layer flow visualization methods, developed at Queen Mary and Westfield College, have been applied to a riblet surface. The results reveal cellular crossflows developing in the grooves between the riblets. These local flor regimes appear to have little direct effect on the flow in the wall layers immediately adjacent to them. Qualitatively, the behavior of the wall layers appears to be that which would be expected if a virtual surface existed at a level slightly above the riblet tops, but a tendency for the origin of longitudinal eddy pairs to become anchored to the top of a riblet is noted.

  17. Pattern formation by particles settling in viscous flows

    NASA Technical Reports Server (NTRS)

    Smith, L. A.; Spiegel, E. A.

    1985-01-01

    Results are reported of several simulations of the motions of small objects in two-dimensional cellular flows performed to study the evolution of the distributions of particle flows over time in processes such as sedimentation. Stream functions are defined in the form of a Hamiltonian system for the particle motions, with inertial and particle acceleration being neglected. Conditions are found for which the particles will become trapped in an oscillatory motion or the particle orbits attain an oscillary motion. Various simulation images are provided to illustrate the usefulness of the technique for modeling fractal swarms.

  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. Observations of spatial flow patterns at the coral colony scale on a shallow reef flat

    NASA Astrophysics Data System (ADS)

    Hench, James L.; Rosman, Johanna H.

    2013-03-01

    Although small-scale spatial flow variability can affect both larger-scale circulation patterns and biological processes on coral reefs, there are few direct measurements of spatial flow patterns across horizontal scales <100 m. Here flow patterns on a shallow reef flat were measured at scales from a single colony to several adjacent colonies using an array of acoustic Doppler velocimeters on a diver-operated traverse. We observed recirculation zones immediately behind colonies, reduced currents and elevated dissipation rates in turbulent wakes up to 2 colony diameters downstream and enhanced Reynolds stresses in shear layers around wake peripheries. Flow acceleration zones were observed above and between colonies. Coherent flow structures varied with incident flow speeds; recirculation zones were stronger and wakes were more turbulent in faster flows. Low-frequency (<0.03 Hz) flow variations, for which water excursions were large compared with the colony diameters (Keulegan-Carpenter number, KC >1), had similar spatial patterns to wakes, while higher-frequency variations (0.05-0.1 Hz, KC < 1) had no observable spatial structure. On the reef flat, both drag and inertial forces exerted by coral colonies could have significant effects on flow, but within different frequency ranges; drag dominates for low-frequency flow variations and inertial forces dominate for higher-frequency variations, including the wave band. Our scaling analyses suggest that spatial flow patterns at colony and patch scales could have important implications for both physical and biological processes at larger reef scales through their effects on forces exerted on the flow, turbulent mixing, and dispersion.

  1. Flow-Induced Control of Pattern Formation in Chemical Systems

    NASA Astrophysics Data System (ADS)

    Berenstein, Igal; Beta, Carsten

    Since Alan Turing's seminal paper in 1952, the study of spatio-temporal patterns that arise in systems of reacting and diffusing components has grown into an immense and vibrant realm of scientific research. This field includes not only chemical systems but spans many areas of science as diverse as cell and developmental biology, ecology, geosciences, or semiconductor physics. For several decades research in this field has concentrated on the vast variety of patterns that can emerge in reaction-diffusion systems and on the underlying instabilities. In the 1990s, stimulated by the pioneering work of Ott, Grebogi and Yorke, control of pattern formation arose as a new topical focus and gradually developed into an entire new field of research. On the one hand, research interests concentrated on control and suppression of undesired dynamical states, in particular on control of chaos. On the other hand, the design and engineering of particular space-time patterns became a major focus in this field that motivates ongoing scientific effort until today...

  2. 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.

  3. Umbilical blood flow patterns directly after birth before delayed cord clamping.

    PubMed

    Boere, I; Roest, A A W; Wallace, E; Ten Harkel, A D J; Haak, M C; Morley, C J; Hooper, S B; te Pas, A B

    2015-03-01

    Delayed umbilical cord clamping (DCC) affects the cardiopulmonary transition and blood volume in neonates immediately after birth. However, little is known of blood flow in the umbilical vessels immediately after birth during DCC. The objective is to describe the duration and patterns of blood flow through the umbilical vessels during DCC. Arterial and venous umbilical blood flow was measured during DCC using Doppler ultrasound in uncomplicated term vaginal deliveries. Immediately after birth, the probe was placed in the middle of the umbilical cord, pattern and duration of flow in vein and arteries were evaluated until cord clamping. Thirty infants were studied. Venous flow: In 10% no flow was present, in 57% flow stopped at 4:34 (3:03-7:31) (median (IQR) min:sec) after birth, before the cord was clamped. In 33%, flow continued until cord clamping at 5:13 (2:56-9:15) min:sec. Initially, venous flow was intermittent, increasing markedly during large breaths or stopping and reversing during crying, but then became continuous. Arterial flow: In 17% no flow was present, in 40% flow stopped at 4:22 (2:29-7:17) min:sec, while cord pulsations were still palpable. In 43% flow continued until the cord was clamped at 5:16 (3:32-10:10) min:sec. Arterial flow was pulsatile, unidirectional towards placenta or bidirectional to/from placenta. In 40% flow became continuous towards placenta later on. During delayed umbilical cord clamping, venous and arterial umbilical flow occurs for longer than previously described. Net placental transfusion is probably the result of several factors of which breathing could play a major role. Umbilical flow is unrelated to cessation of pulsations. Published by the BMJ Publishing Group Limited. For permission to use (where not already granted under a licence) please go to http://group.bmj.com/group/rights-licensing/permissions.

  4. 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.

  5. 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.

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

    NASA Astrophysics Data System (ADS)

    Faulkner, Barton R.; Renée Brooks, J.; Forshay, Kenneth J.; Cline, Steven P.

    2012-07-01

    SummaryField-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, we used a network of shallow monitoring wells, Light Detection and Ranging (LiDAR), and continuous monitoring to parameterize and calibrate stochastic three-dimensional ground water models for a 9.7 km2 (2400 acres) area along a naturally-meandering section of the Willamette River floodplain in Oregon. This large river floodplain is representative of other similar systems. Steady-state simulations were done representing the wet winter and dry summer seasons. During the dry season, hyporheic flow was oriented along the floodplain elevation gradient and median steady-state residence times in small islands and bars were on the order of months. In the larger islands steady-state residence times were on the order of years. In the wet season, flow was oriented laterally away from the river and quickly intercepted and returned to the surface water system in alcoves and cutoffs connected to the river, and recharge due to infiltration of precipitation prevented hyporheic flow through older island areas. In the younger islands, median steady-state residence times ranged from about 6.1 × 101 to 1.6 × 102 days. In the model domain overall, the steady-state dry season median pathline length was about 8.2 × 102 with a maximum length of about 5.7 × 103 m. For the wet season, the median was about 2.0 × 102 m with a maximum length of about 3.5 × 103 m. Wet season hyporheic water penetrated deeper into the lower permeability geologic units by an order of magnitude, as compared to the dry season. This was likely due to the absence of precipitation infiltration during the dry season. We used particle tracking in order to characterize residence time distributions for hyporheic water. We found two

  7. 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.

  8. Flow patterns around old sunspots and flare activity.

    NASA Astrophysics Data System (ADS)

    Kalman, B.

    1997-11-01

    New magnetic flux emerges significantly more probably in already existing solar active regions. Based on the the Debrecen Observatory photographic observations, several active regions are collected, where at least one large, X-class flare was recorded, and emergence of new activity, birth and quick motion of new umbrae was observed in the vicinity of old spots, the new activity emerged in the center of the old active region. Newly emerging magnetic flux in older sunspot groups can be distinguished by its quicker and generally westward proper motions. Umbrae of the new activity do not coalesce with older umbrae of the same polarity, but both elastic and inelastic collisions between them can be observed. Spots of the emerging new activity can flow around old unipolar spots (presumably shallower structures, ``ω-loops") westward, like a hydrodynamic flow around a cylinder, forming a wake behind it. Collision of different polarities in the wake can lead to large flares. The presence of old spots disturbs the normal emergence of the new activity, so motions of the new spots are distorted by the flow, the new emerging ``{OMEGA}-loop" can be stuck between the umbrae of the old, tight dipole, the orientation of the new dipole can be distorted by as much as 180° . The general direction of the flow around the old spots seems to depend on the latitude, the angle between the motion axis and the E-W direction grows with the latitude. The intensive flare activity seems to be connected strongly with the newly emerging magnetic flux; interacting of differently oriented dipoles and the difference of the orientation of the emerging new dipole from the ordinary Hale-Nicholson orientation is also significant. Simply large gradients of magnetic fields (δ-configuration) are not enough, dynamical processes (emergence of new flux, shearing or colliding motions of umbrae of different magnetic polarity) must also be present for large flares.

  9. 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.

  10. 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.

  11. Analysis of the polishing slurry flow of chemical mechanical polishing by polishing pad with phyllotactic pattern

    NASA Astrophysics Data System (ADS)

    Lv, Yushan; Zhang, Tian; Wang, Jun; Li, Nan; Duan, Min; Xing, Xue-Ling

    2010-12-01

    In order to make the polishing slurry distribution more uniform over the polishing region, a new kind of polishing pad, which has sunflower seed pattern, has been designed based on the phyllotaxis theory of biology, and the boundary conditions of polishing slurry flow have been established. By the help of computational fluid dynamics software (FLUENT), the flow state of the polishing slurry is simulated and the effects of the phyllotactic parameters of polishing pad on the flow field of polishing slurry are analyzed. The results show that when the polishing slurry is imported from the center of phyllotaxis polishing pad, the slurry flows along the counterclockwise and clockwise spiral grooves of phyllotatic pattern, which make fluid flow divergence around, and the flow field becomes more uniform.

  12. 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.

  13. Pattern formation in diffusive excitable systems under magnetic flow effects

    NASA Astrophysics Data System (ADS)

    Mvogo, Alain; Takembo, Clovis N.; Ekobena Fouda, H. P.; Kofané, Timoléon C.

    2017-07-01

    We study the spatiotemporal formation of patterns in a diffusive FitzHugh-Nagumo network where the effect of electromagnetic induction has been introduced in the standard mathematical model by using magnetic flux, and the modulation of magnetic flux on membrane potential is realized by using memristor coupling. We use the multi-scale expansion to show that the system equations can be reduced to a single differential-difference nonlinear equation. The linear stability analysis is performed and discussed with emphasis on the impact of magnetic flux. It is observed that the effect of memristor coupling importantly modifies the features of modulational instability. Our analytical results are supported by the numerical experiments, which reveal that the improved model can lead to nonlinear quasi-periodic spatiotemporal patterns with some features of synchronization. It is observed also the generation of pulses and rhythmics behaviors like breathing or swimming which are important in brain researches.

  14. Continuous flow chemistry: a discovery tool for new chemical reactivity patterns.

    PubMed

    Hartwig, Jan; Metternich, Jan B; Nikbin, Nikzad; Kirschning, Andreas; Ley, Steven V

    2014-06-14

    Continuous flow chemistry as a process intensification tool is well known. However, its ability to enable chemists to perform reactions which are not possible in batch is less well studied or understood. Here we present an example, where a new reactivity pattern and extended reaction scope has been achieved by transferring a reaction from batch mode to flow. This new reactivity can be explained by suppressing back mixing and precise control of temperature in a flow reactor set up.

  15. Scaling analysis of gas-liquid two-phase flow pattern in microgravity

    NASA Technical Reports Server (NTRS)

    Lee, Jinho

    1993-01-01

    A scaling analysis of gas-liquid two-phase flow pattern in microgravity, based on the dominant physical mechanism, was carried out with the goal of predicting the gas-liquid two-phase flow regime in a pipe under conditions of microgravity. The results demonstrated the effect of inlet geometry on the flow regime transition. A comparison of the predictions with existing experimental data showed good agreement.

  16. 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.

  17. 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.

  18. Modelling unsaturated flow patterns in green roof substrates

    NASA Astrophysics Data System (ADS)

    Palla, Anna; Gnecco, Ilaria; Lanza, Luca G.

    2010-05-01

    The aim of this research is to examine the unsaturated flow within the green roof substrates realized with high conductivity and coarse grained porous media. In order to base our research on experimental evidences, a monitoring program was carried out at University of Genova (Italy). The green roof experimental site was obtained by retrofitting an existing single-layer vegetated roof built in the sixties into a modern technological system fully equipped with sensors for on-site meteorological, hygrometric and flow rate measurements. The drainage and growing substrates are volcanic material mined, blended and graded by Europomice Srl (Grosseto, Italy). These graded porous media are employed in green roof systems for their low bulk density, high porosity and high hydraulic conductivity. The site is equipped with a meteorological station (for rain data, air temperature and humidity, solar radiation and air pressure), four TDR probes for continuous water content monitoring along a vertical profile and a suitable hydraulic device for continuous outflow monitoring. The SWMS - 2D model that solves the Richards' equation for two-dimensional saturated -unsaturated water flow was used to simulate the hydrologic response of the experimental green roof. The model was calibrated and validated using rain events recorded at the experimental site in a one-year monitoring campaign. The calibration and validation events are selected in order to include events representative of the four seasonal conditions characterized by different antecedent dry weather periods and consequently different initial soil water content distributions. The calibration and validation strategy involved comparing predicted and measured outflow hydrographs. The mechanistic model, here employed to describe the variably saturated flow within the thin stratigraphy of a green roof, is based on a single porosity approach and is demonstrated to suitably describe both the outflow hydrograph and the water content

  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. 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.

  1. On non-linear dynamics and control designs applied to the ideal and non-ideal variants of the Fitzhugh Nagumo (FN) mathematical model

    NASA Astrophysics Data System (ADS)

    Chavarette, Fábio Roberto; Balthazar, José Manoel; Peruzzi, Nelson José; Rafikov, Marat

    2009-03-01

    The Fitzhugh-Nagumo (FH) mathematical model is considered a simplification of the Hodgkin-Huxley (HH) model. This paper analyzes the non-linear dynamics of the Fitzhugh-Nagumo (FN) mathematical model, and still presents some modifications in the governing equations of the system in order to transform it into a non-ideal one (taking into account that an energy source has limited power supply). We also developed an optimal linear control design and used Sinhas's theory for the membrane's action potential in order to stabilize the variation of this potential.

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

    DOEpatents

    Fraioli, A.V.

    1983-10-12

    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.

  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. Comparison of flow-controlled calcium and barium carbonate precipitation patterns

    NASA Astrophysics Data System (ADS)

    Schuszter, G.; De Wit, A.

    2016-12-01

    Various precipitation patterns can be obtained in flow conditions when injecting a solution of sodium carbonate in a confined geometry initially filled with a solution of either barium or calcium chloride. We compare here the barium and calcium carbonate precipitate structures as a function of initial concentrations and injection flow rate. We show that, in some part of the parameter space, the patterns are similar and feature comparable properties indicating that barium and calcium behave similarly in the related flow-controlled precipitation conditions. For other values of parameters though, the precipitate structures are different indicating that the cohesive and microscopic properties of barium versus calcium carbonate are then important in shaping the pattern in flow conditions.

  5. 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).

  6. Luminal flow patterns dictate arterial drug deposition in stent-based delivery

    PubMed Central

    Kolachalama, Vijaya B.; Tzafriri, Abraham R.; Arifin, Davis Y.; Edelman, Elazer R.

    2010-01-01

    Endovascular stents reside in a dynamic flow environment and yet the impact of flow on arterial drug deposition after stent-based delivery is only now emerging. We employed computational fluid dynamic modeling tools to investigate the influence of luminal flow patterns on arterial drug deposition and distribution. Flow imposes recirculation zones distal and proximal to the stent strut that extend the coverage of tissue absorption of eluted drug and induce asymmetry in tissue drug distribution. Our analysis now explains how the disparity in sizes of the two recirculation zones and the asymmetry in drug distribution are determined by a complex interplay of local flow and strut geometry. When temporal periodicity was introduced as a model of pulsatile flow, the net luminal flow served as an index of flow-mediated spatio-temporal tissue drug uptake. Dynamically changing luminal flow patterns are intrinsic to the coronary arterial tree. Coronary drug eluting stents should be appropriately considered where luminal flow, strut design and pulsatility have direct effects on tissue drug uptake after local delivery. PMID:18926864

  7. Blood flow patterns during incremental and steady-state aerobic exercise.

    PubMed

    Coovert, Daniel; Evans, LeVisa D; Jarrett, Steven; Lima, Carla; Lima, Natalia; Gurovich, Alvaro N

    2017-05-30

    Endothelial shear stress (ESS) is a physiological stimulus for vascular homeostasis, highly dependent on blood flow patterns. Exercise-induced ESS might be beneficial on vascular health. However, it is unclear what type of ESS aerobic exercise (AX) produces. The aims of this study are to characterize exercise-induced blood flow patterns during incremental and steady-state AX. We expect blood flow pattern during exercise will be intensity-dependent and bidirectional. Six college-aged students (2 males and 4 females) were recruited to perform 2 exercise tests on cycleergometer. First, an 8-12-min incremental test (Test 1) where oxygen uptake (VO2), heart rate (HR), blood pressure (BP), and blood lactate (La) were measured at rest and after each 2-min step. Then, at least 48-hr. after the first test, a 3-step steady state exercise test (Test 2) was performed measuring VO2, HR, BP, and La. The three steps were performed at the following exercise intensities according to La: 0-2 mmol/L, 2-4 mmol/L, and 4-6 mmol/L. During both tests, blood flow patterns were determined by high-definition ultrasound and Doppler on the brachial artery. These measurements allowed to determine blood flow velocities and directions during exercise. On Test 1 VO2, HR, BP, La, and antegrade blood flow velocity significantly increased in an intensity-dependent manner (repeated measures ANOVA, p<0.05). Retrograde blood flow velocity did not significantly change during Test 1. On Test 2 all the previous variables significantly increased in an intensity-dependent manner (repeated measures ANOVA, p<0.05). These results support the hypothesis that exercise induced ESS might be increased in an intensity-dependent way and blood flow patterns during incremental and steady-state exercises include both antegrade and retrograde blood flows.

  8. Retention time and flow patterns in Lake Marion, South Carolina, 1984

    USGS Publications Warehouse

    Patterson, G.G.; Harvey, R.M.

    1995-01-01

    In 1984, six dye tracer tests were made on Lake Marion to determine flow patterns and retention times under conditions of high and low flow. During the high-flow tests, with an average inflow of about 29,000 cubic feet per second, the approximate travel time through the lake for the peak tracer concentration was 14 days. The retention time was about 20 days. During the low-flow tests, with an average inflow of about 9,000 cubic feet per second, the approximate travel time was 41 days, and the retention time was about 60 days. The primary factors controlling movement of water in the lake are lake inflow and outflow. The tracer cloud moved consistently downstream, slowing as the lake widened. Flow patterns in most of the coves, and in some areas along the northeastern shore, are influenced more by tributary inflow than by factors attributable to water from the main body of the lake.

  9. 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. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Designing Optimal Flow Patterns for Fall Chinook Salmon in a Central Valley, California River

    SciTech Connect

    Jager, H.I.

    2003-01-01

    Widespread declines in stocks of Pacific salmon in the genus Oncorhynchus highlight the need for research to find new and effective management strategies for recovery. Two recovery objectives are (1) to ensure that recruitment is adequate to rebuild self-sustaining populations and (2) to maintain phenotypic diversity. This study seeks to understand how seasonal flow patterns in a flow-regulated California river might be managed to attain each of these recovery objectives, specifically for the fall and late-fall runs of chinook salmon O. tshawytscha. We ask two questions: (1) Does the optimal pattern of seasonal flows change as the amount of water available is constrained by droughts or diversions of flows? and (2) How do optimal flow regimes designed for the two conservation objectives differ? We coupled simulated annealing with a recruitment model to find flow regimes that maximize either the number of smolt out-migrant ‘‘recruits’’ (MR) or the variation in spawning times among recruits (MV). Optimal flow regimes identified for both the MR and MV objectives changed as we increased the annual quantity of water available, allocating higher flows during the spring and fall seasons. Flow regimes that optimized the MR and MV objectives were different. For example, the MV flow regime with unlimited annual flow provided a pulse of high flow 2 weeks before the peak spawning date of the minority late-fall run. Simulated recruits produced by MV flow regimes were fewer in number—and had parents that spawned later and over a wider range of dates—than recruits produced by MR flow regimes. Although these results have not been verified by empirical studies, they demonstrate the potential for managing species with special conservation status by combining state-of-the-art numerical optimization methods with mechanistic ecological models.

  11. Transition from time-dependent to stationary flow patterns in the Taylor-Dean system

    NASA Astrophysics Data System (ADS)

    Mutabazi, Innocent; Andereck, C. David

    1991-11-01

    The flow between two horizontal coaxial cylinders with a partially filled gap, the Taylor-Dean system, is investigated for the case in which the outer cylinder rotates while the inner cylinder remains at rest. The initial instability is to a mixed state of both traveling inclined rolls and laminar base flow. At a larger rotation rate, the entire flow becomes time dependent. At a still larger rotation rate, the flow undergoes a subcritical transition to a stationary roll pattern, a process previously observed only in binary fluid mixtures.

  12. 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.

  13. Effects of rainfall patterns and land cover on the subsurface flow generation of sloping Ferralsols in southern China.

    PubMed

    Duan, Jian; Yang, Jie; Tang, Chongjun; Chen, Lihua; Liu, Yaojun; Wang, Lingyun

    2017-01-01

    Rainfall patterns and land cover are two important factors that affect the runoff generation process. To determine the surface and subsurface flows associated with different rainfall patterns on sloping Ferralsols under different land cover types, observational data related to surface and subsurface flows from 5 m × 15 m plots were collected from 2010 to 2012. The experiment was conducted to assess three land cover types (grass, litter cover and bare land) in the Jiangxi Provincial Soil and Water Conservation Ecological Park. During the study period, 114 natural rainfall events produced subsurface flow and were divided into four groups using k-means clustering according to rainfall duration, rainfall depth and maximum 30-min rainfall intensity. The results showed that the total runoff and surface flow values were highest for bare land under all four rainfall patterns and lowest for the covered plots. However, covered plots generated higher subsurface flow values than bare land. Moreover, the surface and subsurface flows associated with the three land cover types differed significantly under different rainfall patterns. Rainfall patterns with low intensities and long durations created more subsurface flow in the grass and litter cover types, whereas rainfall patterns with high intensities and short durations resulted in greater surface flow over bare land. Rainfall pattern I had the highest surface and subsurface flow values for the grass cover and litter cover types. The highest surface flow value and lowest subsurface flow value for bare land occurred under rainfall pattern IV. Rainfall pattern II generated the highest subsurface flow value for bare land. Therefore, grass or litter cover are able to convert more surface flow into subsurface flow under different rainfall patterns. The rainfall patterns studied had greater effects on subsurface flow than on total runoff and surface flow for covered surfaces, as well as a greater effect on surface flows associated

  14. Effects of non-idealities and quantization of the center of mass motion on symmetric and asymmetric collective states in a collective state atomic interferometer

    NASA Astrophysics Data System (ADS)

    Sarkar, Resham; Kim, May E.; Fang, Renpeng; Tu, Yanfei; Shahriar, Selim M.

    2015-09-01

    We investigate the behavior of an ensemble of ? non-interacting, identical atoms excited by a laser. In general, the ?-th atom sees a Rabi frequency ?, an initial position dependent laser phase ?, and a motion induced Doppler shift of ?. When ? or ? is distinct for each atom, the system evolves into a superposition of ? intercoupled states, of which there are ? symmetric and ? asymmetric collective states. For a collective state atomic interferometer (COSAIN), we recently proposed, it is important to understand the behavior of all the collective states under various conditions. In this paper, we show how to formulate the properties of these states under various non-idealities, and use this formulation to understand the dynamics thereof. We also consider the effect of treating the center of mass degree of freedom of the atoms quantum mechanically on the description of the collective states, illustrating that it is indeed possible to construct a generalized collective state, as needed for the COSAIN, when each atom is assumed to be in a localized wave packet. The analysis presented in this paper is important for understanding the dynamics of the COSAIN, and will help advance the analysis and optimization of spin squeezing in the presence of practically unavoidable non-idealities as well as in the domain where the center of mass motion of the atoms is quantized.

  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. 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.

  18. Finite element and analytical solutions for van der Pauw and four-point probe correction factors when multiple non-ideal measurement conditions coexist

    NASA Astrophysics Data System (ADS)

    Reveil, Mardochee; Sorg, Victoria C.; Cheng, Emily R.; Ezzyat, Taha; Clancy, Paulette; Thompson, Michael O.

    2017-09-01

    This paper presents an extensive collection of calculated correction factors that account for the combined effects of a wide range of non-ideal conditions often encountered in realistic four-point probe and van der Pauw experiments. In this context, "non-ideal conditions" refer to conditions that deviate from the assumptions on sample and probe characteristics made in the development of these two techniques. We examine the combined effects of contact size and sample thickness on van der Pauw measurements. In the four-point probe configuration, we examine the combined effects of varying the sample's lateral dimensions, probe placement, and sample thickness. We derive an analytical expression to calculate correction factors that account, simultaneously, for finite sample size and asymmetric probe placement in four-point probe experiments. We provide experimental validation of the analytical solution via four-point probe measurements on a thin film rectangular sample with arbitrary probe placement. The finite sample size effect is very significant in four-point probe measurements (especially for a narrow sample) and asymmetric probe placement only worsens such effects. The contribution of conduction in multilayer samples is also studied and found to be substantial; hence, we provide a map of the necessary correction factors. This library of correction factors will enable the design of resistivity measurements with improved accuracy and reproducibility over a wide range of experimental conditions.

  19. Patterning of cell-instructive hydrogels by hydrodynamic flow focusing.

    PubMed

    Cosson, Steffen; Allazetta, Simone; Lutolf, Matthias P

    2013-06-07

    Microfluidic gradient systems offer a very precise means to probe the response of cells to graded biomolecular signals in vitro, for example to model how morphogen proteins affect cell fate during developmental processes. However, existing gradient makers are designed for non-physiological plastic or glass cell culture substrates that are often limited in maintaining the phenotype and function of difficult-to-culture mammalian cell types, such as stem cells. To address this bottleneck, we combine hydrogel engineering and microfluidics to generate tethered protein gradients on the surface of biomimetic poly(ethylene glycol) (PEG) hydrogels. Here we used software-assisted hydrodynamic flow focusing for exposing and rapidly capturing tagged proteins to gels in a step-wise fashion, resulting in immobilized gradients of virtually any desired shape and composition. To render our strategy amenable for high-throughput screening of multifactorial artificial cellular microenvironments, a dedicated microfluidic chip was devised for parallelization and multiplexing, yielding arrays of orthogonally overlapping gradients of up to 4 × 4 proteins. To illustrate the power of the platform for stem cell biology, we assessed how gradients of tethered leukemia inhibitory factor (LIF) influence embryonic stem cell (ESC) behavior. ESC responded to LIF gradients in a binary manner, maintaining the pluripotency marker Rex1/Zfp42 and forming self-renewing colonies above a threshold concentration of 85 ng cm(-2). Our concept should be broadly applicable to probe how complex signaling microenvironments influence stem cell fate in culture.

  20. RADIAL FLOW PATTERN OF A SLOW CORONAL MASS EJECTION

    SciTech Connect

    Feng, Li; Gan, Weiqun; Inhester, Bernd

    2015-06-01

    Height–time plots of the leading edge of coronal mass ejections (CMEs) have often been used to study CME kinematics. We propose a new method to analyze the CME kinematics in more detail by determining the radial mass transport process throughout the entire CME. Thus, our method is able to estimate not only the speed of the CME front but also the radial flow speed inside the CME. We have applied this method to a slow CME with an average leading edge speed of about 480 km s{sup −1}. In the Lagrangian frame, the speeds of the individual CME mass elements stay almost constant within 2 and 15 R{sub S}, the range over which we analyzed the CME. Hence, we have no evidence of net radial forces acting on parts of the CME in this range or of a pile up of mass ahead of the CME. We find evidence that the leading edge trajectory obtained by tie-pointing may gradually lag behind the Lagrangian front-side trajectories derived from our analysis. Our results also allow a much more precise estimate of the CME energy. Compared with conventional estimates using the CME total mass and leading edge motion, we find that the latter may overestimate the kinetic energy and the gravitational potential energy.

  1. Forecasting Flows from Target Pattern Instability in Rayleigh-Benard Convection

    NASA Astrophysics Data System (ADS)

    Suri, Balachandra; Perkins, Adam; Schatz, Michael

    2011-11-01

    Using lab experiments combined with numerical simulations, we study systematically how the initial instability of an ordered pattern gradually evolves to a state of spatio-temporal complexity. The experiments begin from a reference pattern of axisymmetric convection rolls (a target pattern) that is reproducibly imposed using an optical technique for actuating fluid flow. For sufficiently large Rayleigh numbers, the axisymmetric pattern loses stability to patterns where the target's bull's-eye shifts off-center. We analyze an experimental ensemble of unstable patterns with nearby initial conditions to extract the spatial structure of the dominant modes and corresponding growth rates. We then test the extent to which a Boussinesq numerical model, in combination with a state estimation algorithm (Local Ensemble Transform Kalman Filter (LETKF)), can be used to predict the subsequent evolution of the experimentally observed patterns.

  2. Classification of annular bed flow patterns and investigation on their influence on the bottom spray fluid bed coating process.

    PubMed

    Wang, Li Kun; Heng, Paul Wan Sia; Liew, Celine Valeria

    2010-05-01

    This study aims to classify annular bed flow patterns in the bottom spray fluid bed coating process, study their influence on coat uniformity and investigate the feasibility of developing real-time annular bed flow pattern detection as a PAT tool. High-speed imaging and particle image velocimetry were used to visualize annular bed flow. Color coating and subsequent tristimulus colorimetry were employed to determine influence of annular bed flow pattern on coat uniformity. Feasibility of monitoring annular bed flow pattern through an observation window was tested using miniaturized particle velocity field and time series particle velocity orientation information. Three types of annular bed flow patterns were identified. Plug flow gave the best coat uniformity followed by global and localized fluidization. Plug flow may be advantageous for high spray-rate conditions, large-scale coating and prevention of particle segregation. Plug flow could be differentiated from the other flow patterns through a simulated observation window. Annular bed flow patterns were classified and found to influence particle coat uniformity noticeably. Availability of annular bed flow information for large-scale coaters would enable adjustments for process optimization. This study highlights the potential of monitoring annular bed flow pattern as a PAT tool.

  3. 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.

  4. A new splitting scheme to the discrete Boltzmann equation for non-ideal gases on non-uniform meshes

    NASA Astrophysics Data System (ADS)

    Patel, Saumil; Lee, Taehun

    2016-12-01

    We present a novel numerical procedure for solving the discrete Boltzmann equations (DBE) on non-uniform meshes. Our scheme is based on the Strang splitting method where we seek to investigate two-phase flow applications. In this note, we investigate the onset of parasitic currents which arise in many computational two-phase algorithms. To the best of our knowledge, the results presented in this work show, for the first time, a spectral element discontinuous Galerkin (SEDG) discretization of a discrete Boltzmann equation which successfully eliminates parasitic currents on non-uniform meshes. With the hope that this technique can be used for applications in complex geometries, calculations are performed on non-uniform mesh distributions by using high-order (spectral), body-fitting quadrilateral elements. Validation and verification of our work is carried out by comparing results against the classical 2D Young-Laplace law problem for a static drop.

  5. Velocity bias induced by flow patterns around ADCPs and associated deployment platforms

    USGS Publications Warehouse

    Mueller, David S.

    2015-01-01

    Velocity measurements near the Acoustic Doppler Current Profiler (ADCP) are important for mapping surface currents, measuring velocity and discharge in shallow streams, and providing accurate estimates of discharge in the top unmeasured portion of the water column. Improvements to ADCP performance permit measurement of velocities much closer (5 cm) to the transducer than has been possible in the past (25 cm). Velocity profiles collected by the U.S. Geological Survey (USGS) with a 1200 kHz Rio Grande Zedhead ADCP in 2002 showed a negative bias in measured velocities near the transducers. On the basis of these results, the USGS initiated a study combining field, laboratory, and numerical modeling data to assess the effect of flow patterns caused by flow around the ADCP and deployment platforms on velocities measured near the transducers. This ongoing study has shown that the negative bias observed in the field is due to the flow pattern around the ADCP. The flow pattern around an ADCP violates the basic assumption of flow homogeneity required for an accurate three-dimensional velocity solution. Results, to date (2014), have indicated velocity biases within the measurable profile, due to flow disturbance, for the TRDI 1200 kHz Rio Grande Zedhead and the SonTek RiverSurveyor M9 ADCPs. The flow speed past the ADCP, the mount and the deployment platform have also been shown to play an important role in the magnitude and extent of the velocity bias.

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

    NASA Technical Reports Server (NTRS)

    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

  7. 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.

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

    NASA Technical Reports Server (NTRS)

    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

  9. Hemodynamics in the Left Atrium and Its Effect on Ventricular Flow Patterns.

    PubMed

    Vedula, Vijay; George, Richard; Younes, Laurent; Mittal, Rajat

    2015-11-01

    In the present study, we investigate the hemodynamics inside left atrium (LA) and understand its impact on the development of ventricular flow patterns. We construct the heart model using dynamic-computed tomographic images and perform simulations using an immersed boundary method based flow solver. We show that the atrial hemodynamics is characterized by a circulatory flow generated by the left pulmonary veins (LPVs) and a direct stream from the right pulmonary veins (RPVs). The complex interaction of the vortex rings formed from each of the PVs leads to vortex breakup and annihilation, thereby producing a regularized flow at the mitral annulus. A comparison of the ventricular flow velocities between the physiological and a simplified pipe-based atrium model shows that the overall differences are limited to about 10% of the peak mitral flow velocity. The implications of this finding on the functional morphology of the left heart as well the computational and experimental modeling of ventricular hemodynamics are discussed.

  10. 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.

  11. 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.

  12. Decompositions of injection patterns for nodal flow allocation in renewable electricity networks

    NASA Astrophysics Data System (ADS)

    Schäfer, Mirko; Tranberg, Bo; Hempel, Sabrina; Schramm, Stefan; Greiner, Martin

    2017-08-01

    The large-scale integration of fluctuating renewable power generation represents a challenge to the technical and economical design of a sustainable future electricity system. In this context, the increasing significance of long-range power transmission calls for innovative methods to understand the emerging complex flow patterns and to integrate price signals about the respective infrastructure needs into the energy market design. We introduce a decomposition method of injection patterns. Contrary to standard flow tracing approaches, it provides nodal allocations of link flows and costs in electricity networks by decomposing the network injection pattern into market-inspired elementary import/export building blocks. We apply the new approach to a simplified data-driven model of a European electricity grid with a high share of renewable wind and solar power generation.

  13. Recognition and tracking of convective flow patterns using Wollaston shearing interferometry

    NASA Astrophysics Data System (ADS)

    Zaussinger, F.; Krebs, A.; Travnikov, V.; Egbers, Ch.

    2017-09-01

    The GeoFlow experiment on the ISS is designed to study convective flows in a spherical gap under microgravity conditions. The main challenge, however, is the visualization of the fluid flow especially under the safety requirements of the Columbus module. The Wollaston shearing interferometry unit of the Fluid Science Laboratory works by optical means alone and is therefore utilized as measurement device for temperature fluctuations. The resulting interferograms in terms of fringe patterns are the base for the presented advanced post-processing techniques. They are used to identify convective patterns, to track these structures and to reconstruct the inaccessible three-dimensional temperature field. A comparison between experimentally gained results and numerically calculated interferograms is given, too. We show that convective patterns are automatically recognized and tracked accurately in experimental images by means of the generalized structure tensor. Furthermore, generic numerical simulations are used to deduce the internal temperature distribution by comparison with interferograms from the experiment.

  14. Flow-driven instabilities during aggregation and pattern formation of Dictyostelium Discoideum: Experiments and modeling

    NASA Astrophysics Data System (ADS)

    Gholami, Azam; Steinbock, Oliver; Zykov, Vladimir; Bodenschatz, Eberhard

    2013-03-01

    We report the first experimental verification of the Differential Flow Induced Chemical Instability (DIFICI) in a signaling chemotactic biological population, where a differential flow induces traveling waves in the signaling pattern. The traveling wave speed was observed to be proportional to the flow velocity while the wave period was 7 min, which is comparable to that of starved Dictyostelium cells. Analysis and numerical simulations of the Goldbeter model show that the resulting DIFICI wave patterns appear in the oscillatory regime. In the experiments, we observe that the DIFICI wave pattern disappears after 4-5 h of starvation. We extrapolated the Goldbeter model to the experimental situation. This suggests that the dynamics switches from the oscillatory to the excitable regime as the DIFICI waves disappear in the experiment.

  15. 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.

  16. 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.

  17. 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.

  18. Impact of vegetation die-off on spatial flow patterns over a tidal marsh

    NASA Astrophysics Data System (ADS)

    Temmerman, Stijn; Moonen, Pieter; Schoelynck, Jonas; Govers, Gerard; Bouma, Tjeerd J.

    2012-02-01

    Large-scale die-off of tidal marsh vegetation, caused by global change, is expected to change flow patterns over tidal wetlands, and hence to affect valuable wetland functions such as reduction of shoreline erosion, attenuation of storm surges, and sedimentation in response to sea level rise. This study quantified for the first time the effects of large-scale (4 ha) artificial vegetation removal, as proxy of die-off, on the spatial flow patterns through a tidal marsh channel and over the surrounding marsh platform. After vegetation removal, the flow velocities measured on the platform increased by a factor of 2 to 4, while the channel flow velocities decreased by almost a factor of 3. This was associated with a change in flow directions on the platform, from perpendicular to the channel edges when vegetation was present, to a tendency of more parallel flow to the channel edges when vegetation was absent. Comparison with hydrodynamic model simulations explains that the vegetation-induced friction causes both flow reduction on the vegetated platform and flow acceleration towards the non-vegetated channels. Our findings imply that large-scale vegetation die-off would not only result in decreased platform sedimentation rates, but also in sediment infilling of the channels, which together would lead to further worsening of plant growth conditions and a potentially runaway feedback to permanent vegetation loss.

  19. 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

  20. Using soil moisture and spatial yield patterns to identify subsurface flow pathways.

    PubMed

    Gish, T J; Walthall, C L; Daughtry, C S T; Kung, K-J S

    2005-01-01

    Subsurface soil water dynamics can influence crop growth and the fate of surface-applied fertilizers and pesticides. Recently, a method was proposed using only ground-penetrating radar (GPR) and digital elevation maps (DEMs) to identify locations where subsurface water converged into discrete pathways. For this study, the GPR protocol for identifying horizontal subsurface flow pathways was extended to a 3.2-ha field, uncertainty is discussed, and soil moisture and yield patterns are presented as confirming evidence of the extent of the subsurface flow pathways. Observed soil water contents supported the existence of discrete preferential funnel flow processes occurring near the GPR-identified preferential flow pathways. Soil moisture also played a critical role in the formation of corn (Zea mays L.) grain yield patterns with yield spatial patterns being similar for mild and severe drought conditions. A buffer zone protocol was introduced that allowed the impact of subsurface flow pathways on corn grain yield to be quantified. Results indicate that when a GPR-identified subsurface clay layer was within 2 m of the soil surface, there was a beneficial impact on yield during a drought year. Furthermore, the buffer zone analysis demonstrated that corn grain yields decreased as the horizontal distance from the GPR-identified subsurface flow pathways increased during a drought year. Averaged real-time soil moisture contents at 0.1 m also decreased with increasing distance from the GPR-identified flow pathways. This research suggests that subsurface flow pathways exist and influence soil moisture and corn grain yield patterns.

  1. 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.

  2. Chaotic Flow Patterns from a Deep Plutonic Environment: a Case Study on Natural Magma Mixing

    NASA Astrophysics Data System (ADS)

    De Campos, Cristina P.

    2015-07-01

    This work focuses on the mixing between basalt and granite in a deep plutonic environment. The description of mixing patterns and measurements of fractal dimensions, and the evaluation of geochemical data from a Cambro-Ordovician granitic pluton are summarized and discussed. Different morphologic domains within the pluton reveal concentric fragmented and/or folded layers of granite in a gabbro/granite mixed matrix. This stands in contrast to two predominantly regular gabbroic regions. These regular regions are separated by tightly stretched filament areas, in which mixing is enhanced. Sharp and gradational contacts between granitic and gabbroic domains depict the interplay among frozen flows (mingling) and convection-enhanced diffusion processes (mixing). Measurements of fractal dimensions at different scales and analysis of normalized concentration variance for major elements point towards magma mixing: the compositional variability and flow patterns of the studied pluton have been greatly controlled by a natural chaotic mixing process between a granitic and a basaltic end-member. During the mixing process, coeval fractional crystallization no doubt contributed to increasing the complexity of the system. However, since flow, and therefore mixing, stops with temperature decrease, flow patterns must have retained the predominant morphology and composition of the moment at which both contrasting magmas came together and froze. Flow patterns have been preserved. With further temperature decrease, fractional crystallization took over and hybrid rocks were generated from the fractionation of magmas previously mixed in different proportions.

  3. Breathing pattern characterization in chronic heart failure patients using the respiratory flow signal.

    PubMed

    Garde, A; Sörnmo, L; Jané, R; Giraldo, B F

    2010-12-01

    This study proposes a method for the characterization of respiratory patterns in chronic heart failure (CHF) patients with periodic breathing (PB) and nonperiodic breathing (nPB), using the flow signal. Autoregressive modeling of the envelope of the respiratory flow signal is the starting point for the pattern characterization. Spectral parameters extracted from the discriminant frequency band (DB) are used to characterize the respiratory patterns. For each classification problem, the most discriminant parameter subset is selected using the leave-one-out cross-validation technique. The power in the right DB provides an accuracy of 84.6% when classifying PB vs. nPB patterns in CHF patients, whereas the power of the DB provides an accuracy of 85.5% when classifying the whole group of CHF patients vs. healthy subjects, and 85.2% when classifying nPB patients vs. healthy subjects.

  4. Experimental surface flow patterns and flow-field phenomena of a delta-wing space-shuttle orbiter

    NASA Technical Reports Server (NTRS)

    Cleary, J. W.

    1972-01-01

    Composite photographs of the surface flow and shadowgraphs of the shock wave pattern are presented that depict the hypersonic flow field of a typical delta wing space shuttle orbiter. Results from a wind tunnel test in air are given in side, oblique, and projected plan views for angles of attack from 0 to 60 deg. The tests were conducted at a Mach number of 7.4 and for Reynolds numbers based on body length of 6,000,000 and 9,000,000. The interrelationship is shown for the intersecting bow and wing leading edge waves with the surface flow for angles of attack for which: (1) the leading edge wave is attached, and (2) the leading edge wave is detached.

  5. 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.

  6. Pattern formation and flow control of fine particles by laser-scanning micromanipulation.

    PubMed

    Sasaki, K; Koshioka, M; Misawa, H; Kitamura, N; Masuhara, H

    1991-10-01

    A novel micromanipulation technique is proposed for aligning fine particles on micrometer-scale spatial patterns and for moving the particles continuously along the formed patterns. This technique is based on the repetitive scanning of a focused trapping laser beam. The velocity of the particle flow can be controlled by scan speed and laser power. The origin of the driving force is considered theoretically and experimentally.

  7. Vector projectile imaging: time-resolved dynamic visualization of complex flow patterns.

    PubMed

    Yiu, Billy Y S; Lai, Simon S M; Yu, Alfred C H

    2014-09-01

    Achieving non-invasive, accurate and time-resolved imaging of vascular flow with spatiotemporal fluctuations is well acknowledged to be an ongoing challenge. In this article, we present a new ultrasound-based framework called vector projectile imaging (VPI) that can dynamically render complex flow patterns over an imaging view at millisecond time resolution. VPI is founded on three principles: (i) high-frame-rate broad-view data acquisition (based on steered plane wave firings); (ii) flow vector estimation derived from multi-angle Doppler analysis (coupled with data regularization and least-squares fitting); (iii) dynamic visualization of color-encoded vector projectiles (with flow speckles displayed as adjunct). Calibration results indicated that by using three transmit angles and three receive angles (-10°, 0°, +10° for both), VPI can consistently compute flow vectors in a multi-vessel phantom with three tubes positioned at different depths (1.5, 4, 6 cm), oriented at different angles (-10°, 0°, +10°) and of different sizes (dilated diameter: 2.2, 4.4 and 6.3 mm; steady flow rate: 2.5 mL/s). The practical merit of VPI was further illustrated through an anthropomorphic flow phantom investigation that considered both healthy and stenosed carotid bifurcation geometries. For the healthy bifurcation with 1.2-Hz carotid flow pulses, VPI was able to render multi-directional and spatiotemporally varying flow patterns (using a nominal frame rate of 416 fps or 2.4-ms time resolution). In the case of stenosed bifurcations (50% eccentric narrowing), VPI enabled dynamic visualization of flow jet and recirculation zones. These findings suggest that VPI holds promise as a new tool for complex flow analysis. Copyright © 2014 World Federation for Ultrasound in Medicine & Biology. Published by Elsevier Inc. All rights reserved.

  8. Modelling flow pattern transitions for steady upward gas-liquid flow in vertical tubes. [Bubble, slug, churn and dispersed-annular; also existence regions and transitions

    SciTech Connect

    Taitel, Y.; Bornea, D.; Dukler, A.E.

    1980-05-01

    Models for predicting flow patterns in steady upward gas-liquid flow in vertical tubes (such as production-well tubing) delineate the transition boundaries between each of the four basic flow patterns for gas-liquid flow in vertical tubes: bubble, slug, churn, and dispersed-annular. Model results suggest that churn flow is the development region for the slug pattern and that bubble flow can exist in small pipes only at high liquid rates, where turbulent dispersion forces are high. Each transition depends on the flow-rate pair, fluid properties, and pipe size, but the nature of the dependence is different for each transition because of differing control mechanisms. The theoretical predictions are in reasonably good agreement with a variety of published flow maps based on experimental data.

  9. Identification of microfluidic two-phase flow patterns in lab-on-chip devices.

    PubMed

    Yang, Zhaochu; Dong, Tao; Halvorsen, Einar

    2014-01-01

    This work describes a capacitive sensor for identification of microfluidic two-phase flow in lab-on-chip devices. With interdigital electrodes and thin insulation layer utilized, this sensor is capable of being integrated with the microsystems easily. Transducing principle and design considerations are presented with respect to the microfluidic gas/liquid flow patterns. Numerical simulation results verify the operational principle. And the factors affecting the performance of the sensor are discussed. Besides, a feasible process flow for the fabrication is also proposed.

  10. 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.

  11. Using a 3-dimensional laser anemometer to determine mean streamline patterns in a turbulent flow

    NASA Technical Reports Server (NTRS)

    Orloff, K. L.; Snyder, P. K.

    1984-01-01

    The determination of mean streamline patterns by moving the test point in the direction of the measured velocity is shown to produce cumulative errors that are unacceptable. A two-dimensional algorithm that minimizes these errors is presented and is analytically validated using simple potential flows. The algorithm is extended to three-dimensional flows and is again validated analytically. Finally, as an example of a typical application of the algorithm, mean streamlines are measured in a complex, turbulent flow with a three-dimensional laser anemometer.

  12. Fluid flow and pattern selection in dendritic growth - Ground based in situ observation

    NASA Astrophysics Data System (ADS)

    Huang, Tao; Liu, Shan; Lu, Deyang; Zhou, Yaohe; Cheng, Gongshan

    1989-02-01

    Model experiments on fluid flow and pattern selection have been done by creating flow in liquid regions close to the growth fronts in dendritic growth of SCN-aceton dilute alloys. The kinetics and morphology of dendritic growth were measured as a function of thermal gradient, growth velocity, and flow velocity. The present paper provides the first study of convection effects on constrained dendritic and cellular growth which focuses on the tip morphology and develops a boundary layer analysis. All of the problems addressed have application to the interpretation of the experimental phenomena arising from solidification and fluid dynamics on earth and in a space laboratory.

  13. A potential role for isothermal calorimetry in studies of the effects of thermodynamic non-ideality in enzyme-catalyzed reactions.

    PubMed

    Lonhienne, Thierry G A; Winzor, Donald J

    2004-01-01

    Attention is drawn to the feasibility of using isothermal calorimetry for the characterization of enzyme reactions under conditions bearing greater relevance to the crowded biological environment, where kinetic parameters are likely to differ significantly from those obtained by classical enzyme kinetic studies in dilute solution. An outline of the application of isothermal calorimetry to the determination of enzyme kinetic parameters is followed by considerations of the nature and consequences of crowding effects in enzyme catalysis. Some of those effects of thermodynamic non-ideality are then illustrated by means of experimental results from calorimetric studies of the effect of molecular crowding on the kinetics of catalysis by rabbit muscle pyruvate kinase. This review concludes with a discussion of the potential of isothermal calorimetry for the experimental determination of kinetic parameters for enzymes either in biological environments or at least in media that should provide reasonable approximations of the crowded conditions encountered in vivo.

  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

    2016-10-01

    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. A simple evaluation procedure of the TAN calibration and the influence of non-ideal calibration elements on VNA S-parameter measurements

    NASA Astrophysics Data System (ADS)

    Stumper, U.

    2007-06-01

    For the 7-term general TAN (Through-Attenuator-Network) self-calibration method of a four-sampler vector network analyser (VNA), and for all derived calibration methods like TLN, TRL, TRM, TAR, or TMN, it is shown that a very simple evaluation procedure of the seven error terms is possible, even if the Through connection is replaced by a reflectionless network with known transmission. Expressions for the deviations of the measured S-parameters of two-port test objects (d.u.t.s) from the true values, which are caused by deviations of the modeled S-parameters of non-ideal calibration elements ("standards") from their true values, are also presented. Additionally, it is shown that a TAN calibration is also possible in case of unequal reflections of the Network.

  16. Swash zone boundary conditions derived from optical remote sensing of swash zone flow patterns

    NASA Astrophysics Data System (ADS)

    Power, H. E.; Holman, R. A.; Baldock, T. E.

    2011-06-01

    Optical remote sensing is used to measure flow patterns in the swash zone. Timestack images are analyzed to measure the asymmetry and the relative duration of the inflow into the swash zone. This varies significantly between individual swashes, contrary to the classical analytical swash model for runup induced by bores, which predicts a similar flow pattern for all events. For swash forced by breaking bores, the gradient of the x-t locus of flow reversal varies over a wide range and flow reversal can occur simultaneously across the whole swash zone. This variation of the gradient of the locus of flow reversal in x-t space can be parameterized in terms of a single free variable in recent solutions to the nonlinear shallow water equations, which fully defines the swash boundary inflow condition. Consistent with the theory, the horizontal runup, the swash period, and the swash similarity parameter were observed to be independent of the swash inflow conditions but the flow asymmetry is not. Only a weak correlation was observed between the swash boundary condition and the Iribarren number and beach slope. Conversely, the analysis suggests that the degree of swash-swash interaction does influence the swash boundary condition and the resulting internal flow kinematics. The variation in inflow conditions is expected to influence the magnitudes of the velocity moments within the swash zone and therefore sediment transport rates.

  17. Modeling of debris flow depositional patterns according to the catchments and sediment source areas characteristics

    NASA Astrophysics Data System (ADS)

    Tiranti, Davide; Deangeli, Chiara

    2015-03-01

    A method to predict the most probable flow rheology in Alpine debris flows is presented. The methods classifies outcropping rock masses in catchments on the basis of the type of resulting unconsolidated deposits. The grain size distribution of the debris material and the depositional style of past debris flow events are related to the dominant flow processes: viscoplastic and frictional/collisional. Three catchments in the upper Susa Valley (Western Alps), characterized by different lithologies, were selected for numerical analysis carried out with a Cellular Automata code with viscoplastic and frictional/collisional rheologies. The obtained numerical results are in good agreement with in site evidences in terms of depositional patterns, confirming the possibility of choosing the rheology of the debris flow based on the source material within the catchment.

  18. Distillation-based Droplet Modeling of Non-Ideal Oxygenated Gasoline Blends: Investigating the Role of Droplet Evaporation on PM Emissions

    DOE PAGES

    Burke, Stephen C.; Ratcliff, Matthew; McCormick, Robert; ...

    2017-03-28

    In some studies, a relationship has been observed between increasing ethanol content in gasoline and increased particulate matter (PM) emissions from vehicles equipped with spark ignition engines. The fundamental cause of the PM increase seen for moderate ethanol concentrations is not well understood. Ethanol features a greater heat of vaporization (HOV) than gasoline and also influences vaporization by altering the liquid and vapor composition throughout the distillation process. A droplet vaporization model was developed to explore ethanol's effect on the evaporation of aromatic compounds known to be PM precursors. The evolving droplet composition is modeled as a distillation process, withmore » non-ideal interactions between oxygenates and hydrocarbons accounted for using UNIFAC group contribution theory. Predicted composition and distillation curves were validated by experiments. Detailed hydrocarbon analysis was applied to fuel samples and to distillate fractions, and used as input for the initial droplet composition. With composition calculated throughout the distillation, the changing HOV and other physical properties can be found using reference data. The droplet can thus be modeled in terms of energy transfer, which in turn provides the transient mass transfer, droplet temperature, and droplet diameter. Model predictions suggest that non-ideal vapor-liquid equilibrium along with an increase in HOV can alter the droplet composition evolution. Results predict that the presence of ethanol causes enrichment of the higher boiling fractions (T90+) in the aromatic components as well as lengthens the droplet lifetime. A simulation of the evaporation process in a transient environment as experienced within an engine cylinder predicts a decrease in mixing time of the heaviest fractions of the fuel prior to spark initiation, possibly explaining observations linking ethanol to PM.« less

  19. 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.

  20. 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.

  1. Flow patterns of larval fish: undulatory swimming in the intermediate flow regime.

    PubMed

    Müller, Ulrike K; van den Boogaart, Jos G M; van Leeuwen, Johan L

    2008-01-01

    Fish larvae, like many adult fish, swim by undulating their body. However, their body size and swimming speeds put them in the intermediate flow regime, where viscous and inertial forces both play an important role in the interaction between fish and water. To study the influence of the relatively high viscous forces compared with adult fish, we mapped the flow around swimming zebrafish (Danio rerio) larvae using two-dimensional digital particle image velocimetry (2D-DPIV) in the horizontal and transverse plane of the fish. Fish larvae initiate a swimming bout by bending their body into a C shape. During this initial tail-beat cycle, larvae shed two vortex pairs in the horizontal plane of their wake, one during the preparatory and one during the subsequent propulsive stroke. When they swim ;cyclically' (mean swimming speed does not change significantly between tail beats), fish larvae generate a wide drag wake along their head and anterior body. The flow along the posterior body is dominated by the undulating body movements that cause jet flows into the concave bends of the body wave. Patches of elevated vorticity form around the jets, and travel posteriorly along with the body wave, until they are ultimately shed at the tail near the moment of stroke reversal. Behind the larva, two vortex pairs are formed per tail-beat cycle (the tail beating once left-to-right and then right-to-left) in the horizontal plane of the larval wake. By combining transverse and horizontal cross sections of the wake, we inferred that the wake behind a cyclically swimming zebrafish larva contains two diverging rows of vortex rings to the left and right of the mean path of motion, resembling the wake of steadily swimming adult eels. When the fish larva slows down at the end of a swimming bout, it gradually reduces its tail-beat frequency and amplitude, while the separated boundary layer and drag wake of the anterior body extend posteriorly to envelope the entire larva. This drag wake is

  2. Effect of atrial fibrillation on pulmonary venous flow patterns: transoesophageal pulsed Doppler echocardiographic study.

    PubMed

    Ren, W D; Visentin, P; Nicolosi, G L; Canterin, F A; Dall'Aglio, V; Lestuzzi, C; Mimo, R; Pavan, D; Sparacino, L; Cervesato, E

    1993-10-01

    The effect of atrial fibrillation on pulmonary venous flow patterns is still not well known. Twenty-four patients in atrial fibrillation and 21 patients in sinus rhythm were studied by transoesophageal echocardiography. In ninety-five percent (20/21) of sinus rhythm patients, the early systolic wave due to atrial relaxation or reverse wave due to atrial contraction could be distinguished on pulsed Doppler tracings by transoesophageal echocardiography. However, there was no early systolic wave and/or reverse at the end of diastole in any atrial fibrillation patients. In atrial fibrillation patients without mitral regurgitation (n = 14), the onset of systolic flow was delayed (165 +/- 38 vs 50 +/- 46 ms, P < 0.05), and systolic peak velocities, time-velocity integrals and systolic fractions were reduced (31 +/- 13 vs 54 +/- 17 cm.s-1, P < 0.05; 5 +/- 2 vs 13 +/- 6 cm, P < 0.05 and 36 +/- 8 vs 61 +/- 15%, P < 0.05, respectively) as compared to those in sinus rhythm. Significant mitral regurgitation (n = 10) reduced systolic velocity parameters considerably in atrial fibrillation patients but the diastolic flow parameters were not significantly different between sinus rhythm and atrial fibrillation patients. Stepwise multiple regression analysis identified atrial fibrillation as an important independent predictor for changes in systolic flow parameters. The R-R interval is also an important factor for diastolic flow parameters. Thus, the present study demonstrates that atrial fibrillation significantly modifies pulmonary venous flow pattern and is an important factor for systolic flow parameters. Significant mitral regurgitation can further modify systolic flow pattern in atrial fibrillation patients.

  3. 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.

  4. Closed-loop control of flow separation using instantaneous trajectory patterns

    NASA Astrophysics Data System (ADS)

    Spohn, Andreas; Parezanović, Vladimir; Kaiser, Eurika; Cordier, Laurent; Noack, Bernd

    2014-11-01

    A new sensor technique based on visualized instantaneous trajectory patterns is tested to control flow separation. A smooth ramp mounted inside the test section of a water tunnel produces canonical separation conditions. Pulsed hydrogen bubbles furnish instantaneous trajectory patterns of the underlying dynamical system. The evolution of these patterns feeds machine learning algorithms to determine actions that reduce the separated flow region. Compared to periodic forcing the results show even with less actuator action, a major impact on the separated flow. The controlled flow states contain strongly reduced recirculation zones which remain robust even under adverse conditions. Additionally, the visualization of instantaneous trajectory patterns is shown to have some promising options: The Lagrangian coherent structures (LCS) of the controlled dynamical system can be deduced in-time without determination and integration of the instantaneous velocity fields. Additionally, classical procedures to reduce the data dimensionality, as for example the principal component analysis (PCA) and its variants, can be applied directly to the visualizations in order to feed the controller. Funding of the ANR program SepaCoDe and the ANR Chair of Excellence TUCOROM is gratefully acknowledged.

  5. Flow patterns in the ductus arteriosus during open fetal myelomeningocele repair.

    PubMed

    Howley, Lisa; Wood, Cristina; Patel, Sonali S; Zaretsky, Michael V; Crombleholme, Timothy; Cuneo, Bettina

    2015-06-01

    The objective of this study is to perform a longitudinal evaluation of blood flow patterns in the ductus arteriosus (DA) during the perioperative period in fetal myelomeningocele (MMC) surgical patients. Serial fetal echocardiograms were reviewed in 10 MMC cases where mothers received indomethacin and intravenous and inhaled anesthesia. One-way analysis of variance was utilized to evaluate for differences in peak systolic velocity, end-diastolic velocity (EDV), time-averaged mean velocity (TAMV), and Pulsatility Index (PI) throughout the monitoring period. Regression analysis was performed to evaluate the relationship between PI and maternal hemodynamics and medications. The DA TAMV and EDV increased between baseline and inhaled anesthesia and decreased between inhaled anesthesia and postoperative day 2. PI decreased to a nadir during inhaled anesthesia and then increased through postoperative day 2. Three distinct ductal flow patterns, characterizing degree of ductal constriction, were observed. Two fetuses exhibited a severely constricted ductal flow pattern with concurrent moderate tricuspid insufficiency and right ventricular dysfunction during inhaled anesthesia. Abnormal DA flow patterns culminating in significant DA constriction occurred during fetal MMC repair. Limiting maternal exposure to indomethacin, supplemental oxygen, and inhaled anesthesia may reduce the incidence and severity of DA constriction and perhaps reduce fetal cardiac dysfunction during open fetal surgery. © 2015 John Wiley & Sons, Ltd.

  6. Flow pattern, void fraction and pressure drop of two-phase air-water flow in a horizontal circular micro-channel

    SciTech Connect

    Saisorn, Sira; Wongwises, Somchai

    2008-01-15

    Adiabatic two-phase air-water flow characteristics, including the two-phase flow pattern as well as the void fraction and two-phase frictional pressure drop, in a circular micro-channel are experimentally studied. A fused silica channel, 320 mm long, with an inside diameter of 0.53 mm is used as the test section. The test runs are done at superficial velocity of gas and liquid ranging between 0.37-16 and 0.005-3.04 m/s, respectively. The flow pattern map is developed from the observed flow patterns i.e. slug flow, throat-annular flow, churn flow and annular-rivulet flow. The flow pattern map is compared with those of other researchers obtained from different working fluids. The present single-phase experiments also show that there are no significant differences in the data from the use of air or nitrogen gas, and water or de-ionized water. The void fraction data obtained by image analysis tends to correspond with the homogeneous flow model. The two-phase pressure drops are also used to calculate the frictional multiplier. The multiplier data show a dependence on flow pattern as well as mass flux. A new correlation of two-phase frictional multiplier is also proposed for practical application. (author)

  7. Left Atrial Ligation Alters Intracardiac Flow Patterns and the Biomechanical Landscape in the Chick Embryo

    PubMed Central

    Kowalski, William J.; Teslovich, Nikola C.; Menon, Prahlad G.; Tinney, Joseph P.; Keller, Bradley B.; Pekkan, Kerem

    2014-01-01

    Background Hypoplastic left heart syndrome (HLHS) is a major human congenital heart defect that results in single ventricle physiology and high mortality. Clinical data indicate that intracardiac blood flow patterns during cardiac morphogenesis are a significant etiology. We used the left atrial ligation (LAL) model in the chick embryo to test the hypothesis that LAL immediately alters intracardiac flow streams and the biomechanical environment, preceding morphologic and structural defects observed in HLHS. Results Using fluorescent dye injections, we found that intracardiac flow patterns from the right common cardinal vein, right vitelline vein, and left vitelline vein were altered immediately following LAL. Furthermore, we quantified a significant ventral shift of the right common cardinal and right vitelline vein flow streams. We developed an in silico model of LAL, which revealed that wall shear stress was reduced at the left atrioventricular canal and left side of the common ventricle. Conclusions Our results demonstrate that intracardiac flow patterns change immediately following LAL, supporting the role of hemodynamics in the progression of HLHS. Sites of reduced WSS revealed by computational modeling are commonly affected in HLHS, suggesting that changes in the biomechanical environment may lead to abnormal growth and remodeling of left heart structures. PMID:24868595

  8. Circular flow patterns induced by ciliary activity in reconstituted human bronchial epithelium

    NASA Astrophysics Data System (ADS)

    Viallat, Annie; Khelloufi, Kamel; Gras, Delphine; Chanez, Pascal; Aix Marseille Univ., CNRS, CINaM, Marseille, France Team; Aix Marseille Univ., CNRS, Inserm, LAI, Marseille, France Team

    2016-11-01

    Mucociliary clearance is the transport at the surface of airways of a complex fluid layer, the mucus, moved by the beats of microscopic cilia present on epithelial ciliated cells. We explored the coupling between the spatial organisation and the activity of cilia and the transport of surface fluids on reconstituted cultures of human bronchial epithelium at air-liquid interface, obtained by human biopsies. We reveal the existence of stable local circular surface flow patterns of mucus or Newtonian fluid at the epithelium surface. We find a power law over more than 3 orders of magnitude showing that the average ciliated cell density controls the size of these flow patterns, and, therefore the distance over which mucus can be transported. We show that these circular flow patterns result from the radial linear increase of the local propelling forces (due to ciliary beats) on each flow domain. This linear increase of local forces is induced by a fine self-regulation of both cilia density and orientation of ciliary beats. Local flow domains grow and merge during ciliogenesis to provide macroscopic mucus transport. This is possible only when the viscoelastic mucus continuously exerts a shear stress on beating cilia, revealing a mechanosensitive function of cilia. M. K. Khelloufi thanks the society MedBioMed for financial support. This work was supported by the ANR MUCOCIL project, Grant ANR-13-BSV5-0015 of the French Agence Nationale de la Recherche.

  9. The shock-vortex interaction patterns affected by vortex flow regime and vortex models

    NASA Astrophysics Data System (ADS)

    Chang, Keun-Shik; Barik, Hrushikesh; Chang, Se-Myong

    2009-08-01

    We have used a third-order essentially non-oscillatory method to obtain numerical shadowgraphs for investigation of shock-vortex interaction patterns. To search different interaction patterns, we have tested two vortex models (the composite vortex model and the Taylor vortex model) and as many as 47 parametric data sets. By shock-vortex interaction, the impinging shock is deformed to a S-shape with leading and lagging parts of the shock. The vortex flow is locally accelerated by the leading shock and locally decelerated by the lagging shock, having a severely elongated vortex core with two vertices. When the leading shock escapes the vortex, implosion effect creates a high pressure in the vertex area where the flow had been most expanded. This compressed region spreads in time with two frontal waves, an induced expansion wave and an induced compression wave. They are subsonic waves when the shock-vortex interaction is weak but become supersonic waves for strong interactions. Under a intermediate interaction, however, an induced shock wave is first developed where flow speed is supersonic but is dissipated where the incoming flow is subsonic. We have identified three different interaction patterns that depend on the vortex flow regime characterized by the shock-vortex interaction.

  10. Simulating Regional Groundwater Flow Patterns in South Florida Using Density-Dependent Numerical Models

    NASA Astrophysics Data System (ADS)

    England, S. M.; Stevens, G. T.

    2008-05-01

    Aquifer Storage and Recovery (ASR) is the storage of fresh water in an aquifer via injection during times when water is available, and recovery of the water from the same aquifer via pumping during times when it is needed. ASR is one of the proposed alternatives recommended by the Comprehensive Everglades Restoration Plan (CERP) to help with water supply, storage, and distribution of water in South Florida. To evaluate the numerous design considerations and the variation in aquifer response resulting from CERP ASR, regional density- dependent numerical modeling of the Floridan Aquifer System (FAS) in the southern half of Florida is in progress. This modeling incorporates use of two density-dependent numerical codes, SEAWAT and WASH123D, and the synthesis of regional knowledge of the FAS in terms of geologic parameters, groundwater flow patterns, and salinity influences. Several challenges have been discovered in replicating the existing regional groundwater flow patterns, most notably, that in south-central Florida the simulated heads are considerably lower than observed values. Recent model studies of several factors that could affect south Florida regional flow patterns indicate that the inclusion of preferential flow as well as the effects of temperature on groundwater density yield results that are more consistent with observed values. Future work will focus on the investigation of field data to support the application of preferential flow and the addition of groundwater injection and withdrawal including existing and proposed ASR projects.

  11. Laminar-turbulent patterning in wall-bounded shear flows: a Galerkin model

    NASA Astrophysics Data System (ADS)

    Seshasayanan, K.; Manneville, P.

    2015-06-01

    On its way to turbulence, plane Couette flow-the flow between counter-translating parallel plates-displays a puzzling steady oblique laminar-turbulent pattern. We approach this problem via Galerkin modelling of the Navier-Stokes equations. The wall-normal dependence of the hydrodynamic field is treated by means of expansions on functional bases fitting the boundary conditions exactly. This yields a set of partial differential equations for spatiotemporal dynamics in the plane of the flow. Truncating this set beyond the lowest nontrivial order is numerically shown to produce the expected pattern, therefore improving over what was obtained at the cruder effective wall-normal resolution. Perspectives opened by this approach are discussed.

  12. Flow patterns of natural convection in an air-filled vertical cavity

    NASA Astrophysics Data System (ADS)

    Wakitani, Shunichi

    1998-08-01

    Flow patterns of two-dimensional natural convection in a vertical air-filled tall cavity with differentially heated sidewalls are investigated. Numerical simulations based on a finite difference method are carried out for a wide range of Rayleigh numbers and aspect ratios from the onset of the steady multicellular flow, through the reverse transition to the unicellular pattern, to the unsteady multicellular flow. For aspect ratios (height/width) from 10 to 24, the various cellular structures characterized by the number of secondary cells are clarified from the simulations by means of gradually increasing Rayleigh number to 106. Unsteady multicellular solutions are found in some region of Rayleigh numbers less than those at which the reverse transition has occurred.

  13. Flow patterns and velocity distributions in the human vertebrobasilar arterial system. Laboratory investigation.

    PubMed

    Kobayashi, Nobuaki; Karino, Takeshi

    2010-10-01

    The authors conducted a study to elucidate the relationship between the flow patterns and the formation of aneurysms at the bifurcation of the basilar artery (BA). Six isolated, transparent vertebrobasilar arterial systems were prepared from humans postmortem, and flow patterns and velocity distributions were studied in detail using flow visualization and cinemicrographic techniques. The authors found that if the diameters of 2 vertebral arteries (VAs) were nearly equal and they formed a symmetrical inverted Y-shaped junction with the BA, the BA flow was also symmetrical. The fluid elements that flowed into the BA from 2 VAs traveled almost parallel to the vessel wall of the BA without mixing with each other, and then they flowed out through ipsilateral superior cerebellar and posterior cerebral arteries. In contrast to this, if the diameters of 2 VAs were very different or the BA was badly bent, the BA flow was disturbed as a result of the formation of swirling and secondary flows. The approaching velocity profile at the BA's terminal bifurcation was flattened if the inverted Y-junction was symmetrical, and it was sharpened if the junction was asymmetrical. Thus, in the latter case, fluid elements impinged on the vessel wall around the flow divider of the bifurcation with much larger velocities and, hence, larger kinetic energy, compared with the case of a symmetrical inverted Y-junction, exerting high fluid pressures, wall shear stresses, and wall tensions on the vessel wall there. The symmetrical structure of the inverted Y-junction in a normal vertebrobasilar arterial system provides a flattened approaching velocity profile at the terminal bifurcation of the BA, lowering the hemodynamic stresses (pressure, tension, and shear stress) exerted on the wall of the bifurcation. This may account for the relatively low incidence of aneurysm formation at this site.

  14. Two-dimensional distribution of microbial activity and flow patterns within naturally fractured chalk.

    PubMed

    Arnon, Shai; Ronen, Zeev; Adar, Eilon; Yakirevich, Alexander; Nativ, Ronit

    2005-10-01

    The two-dimensional distribution of flow patterns and their dynamic change due to microbial activity were investigated in naturally fractured chalk cores. Long-term biodegradation experiments were conducted in two cores ( approximately 20 cm diameter, 31 and 44 cm long), intersected by a natural fracture. 2,4,6-tribromophenol (TBP) was used as a model contaminant and as the sole carbon source for aerobic microbial activity. The transmissivity of the fractures was continuously reduced due to biomass accumulation in the fracture concurrent with TBP biodegradation. From multi-tracer experiments conducted prior to and following the microbial activity, it was found that biomass accumulation causes redistribution of the preferential flow channels. Zones of slow flow near the fracture inlet were clogged, thus further diverting the flow through zones of fast flow, which were also partially clogged. Quantitative evaluation of biodegradation and bacterial counts supported the results of the multi-tracer tests, indicating that most of the bacterial activity occurs close to the inlet. The changing flow patterns, which control the nutrient supply, resulted in variations in the concentrations of the chemical constituents (TBP, bromide and oxygen), used as indicators of biodegradation.

  15. Simulation of tidal flow and circulation patterns in the Loxahatchee River Estuary, southeastern Florida

    USGS Publications Warehouse

    Russell, G.M.; Goodwin, C.R.

    1987-01-01

    Results of a two-dimensional, vertically averaged, computer simulation model of the Loxahatchee River estuary show that under typical low freshwater inflow and vertically well mixed conditions, water circulation is dominated by freshwater inflow rather than by tidal influence. The model can simulate tidal flow and circulation in the Loxahatchee River estuary under typical low freshwater inflow and vertically well mixed conditions, but is limited, however, to low-flow and well mixed conditions. Computed patterns of residual water transport show a consistent seaward flow from the northwest fork through the central embayment and out Jupiter Inlet to the Atlantic Ocean. A large residual seaward flow was computed from the North Intracoastal Waterway to the inlet channel. Although the tide produces large flood and ebb flows in the estuary, tide-induced residual transport rates are low in comparison with freshwater-induced residual transport. Model investigations of partly mixed or stratified conditions in the estuary need to await development of systems capable of simulating three-dimensional flow patterns. (Author 's abstract)

  16. Streaming driven by sessile microbubbles: Explaining flow patterns and frequency response

    NASA Astrophysics Data System (ADS)

    Rallabandi, Bhargav; Wang, Cheng; Guo, Lin; Hilgenfeldt, Sascha

    2013-11-01

    Ultrasound excitation of bubbles drives powerful steady streaming flows which have found widespread applications in microfluidics, where bubbles are typically of semicircular cross section and attached to walls of the device (sessile). While bubble-driven streaming in bulk fluid is well understood, this practically relevant case presents additional complexity introduced by the wall and contact lines. We develop an asymptotic theory that takes into account the presence of the wall as well as the oscillation dynamics of the bubble, providing a complete description of the streaming flow as a function only of the driving frequency, the bubble size, and the physical properties of the fluid. We show that the coupling between different bubble oscillation modes sustains the experimentally observed streaming flow vortex pattern over a broad range of frequencies, greatly exceeding the widths of individual mode resonances. Above a threshold frequency, we predict, and observe in experiment, reversal of the flow direction. Our analytical theory can be used to guide the design of microfluidic devices, both in situations where robust flow patterns insensitive to parameter changes are desired (e.g. lab-on-a-chip sorters), and in cases where intentional modulation of the flow field appearance is key (e.g. efficient mixers). Current address: Department of Mechanical and Aerospace Engineering, Missouri University of Science and Technology.

  17. An artificial intelligence based improved classification of two-phase flow patterns with feature extracted from acquired images.

    PubMed

    Shanthi, C; Pappa, N

    2017-02-13

    Flow pattern recognition is necessary to select design equations for finding operating details of the process and to perform computational simulations. Visual image processing can be used to automate the interpretation of patterns in two-phase flow. In this paper, an attempt has been made to improve the classification accuracy of the flow pattern of gas/ liquid two- phase flow using fuzzy logic and Support Vector Machine (SVM) with Principal Component Analysis (PCA). The videos of six different types of flow patterns namely, annular flow, bubble flow, churn flow, plug flow, slug flow and stratified flow are recorded for a period and converted to 2D images for processing. The textural and shape features extracted using image processing are applied as inputs to various classification schemes namely fuzzy logic, SVM and SVM with PCA in order to identify the type of flow pattern. The results obtained are compared and it is observed that SVM with features reduced using PCA gives the better classification accuracy and computationally less intensive than other two existing schemes. This study results cover industrial application needs including oil and gas and any other gas-liquid two-phase flows.

  18. Code requirements document: MODFLOW 2. 1: A program for predicting moderator flow patterns

    SciTech Connect

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

    1992-03-01

    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 of 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.

  19. Code requirements document: MODFLOW 2.1: A program for predicting moderator flow patterns

    SciTech Connect

    Peterson, P.F.; Paik, I.K.

    1992-03-01

    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 of 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. MODFLOW 2.0: A program for predicting moderator flow patterns

    SciTech Connect

    Peterson, P.F.; 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.

  1. Relationship between Oral Flow Patterns, Nasal Obstruction, and Respiratory Events during Sleep

    PubMed Central

    Suzuki, Masaaki; Furukawa, Taiji; Sugimoto, Akira; Katada, Koji; Kotani, Ryosuke; Yoshizawa, Takayuki

    2015-01-01

    Study Objectives: Sleep breathing patterns are altered by nasal obstruction and respiratory events. This study aimed to describe the relationships between specific sleep oral flow (OF) patterns, nasal airway obstruction, and respiratory events. Methods: Nasal flow and OF were measured simultaneously by polysomnography in 85 adults during sleep. OF was measured 2 cm in front of the lips using a pressure sensor. Results: OF could be classified into three patterns: postrespiratory event OF (postevent OF), during-respiratory event OF (during-event OF), and spontaneous arousal-related OF (SpAr-related OF). Postevent OFs begin at the end of airflow reduction, are preceded by respiratory arousal, and are accompanied by postapneic hyperventilation; during-event OFs occur during nasal flow reduction; and SpAr-related OFs to OF begin during stable breathing, and are preceded by spontaneous arousal but are rarely accompanied by apnea/hypopnea. Multivariate regression showed that nasal obstruction was predictive of SpAr-related OF. The relative frequency of SpAr-related OF events was negatively correlated with the apnea-hypopnea index. The fraction of SpAr-related OF duration relative to total OF duration was significantly greater in patients with nasal obstruction than in those without. Conclusions: SpAr-related OF was associated with nasal obstruction, but not respiratory events. This pattern thus functions as a “nasal obstruction bypass”, mainly in normal subjects and patients with mild sleep disordered breathing (SDB). By contrast, the other two types were related to respiratory events and were typical patterns seen in patients with moderate and severe SDB. Citation: Suzuki M, Furukawa T, Sugimoto A, Katada K, Kotani R, Yoshizawa T. Relationship between oral flow patterns, nasal obstruction, and respiratory events during sleep. J Clin Sleep Med 2015;11(8):855–860. PMID:25766699

  2. Flow pattern, pressure drop and void fraction of two-phase gas-liquid flow in an inclined narrow annular channel

    SciTech Connect

    Wongwises, Somchai; Pipathattakul, Manop

    2006-03-01

    Two-phase flow pattern, pressure drop and void fraction in horizontal and inclined upward air-water two-phase flow in a mini-gap annular channel are experimentally studied. A concentric annular test section at the length of 880mm with an outer diameter of 12.5mm and inner diameter of 8mm is used in the experiments. The flow phenomena, which are plug flow, slug flow, annular flow, annular/slug flow, bubbly/plug flow, bubbly/slug-plug flow, churn flow, dispersed bubbly flow and slug/bubbly flow, are observed and recorded by high-speed camera. A slug flow pattern is found only in the horizontal channel while slug/bubbly flow patterns are observed only in inclined channels. When the inclination angle is increased, the onset of transition from the plug flow region to the slug flow region (for the horizontal channel) and from the plug flow region to slug/bubbly flow region (for inclined channels) shift to a lower value of superficial air velocity. Small shifts are found for the transition line between the dispersed bubbly flow and the bubbly/plug flow, the bubbly/plug flow and the bubbly/slug-plug flow, and the bubbly/plug flow and the plug flow. The rest of the transition lines shift to a higher value of superficial air velocity. Considering the effect of flow pattern on the pressure drop in the horizontal tube at low liquid velocity, the occurrence of slug flow stops the rise of pressure drop for a short while, before rising again after the air velocity has increased. However, the pressure does not rise abruptly in the tubes with {theta}=30{sup o} and 60{sup o} when the slug/bubbly flow occurs. At low gas and liquid velocity, the pressure drop increases, when the inclination angles changes from horizontal to 30{sup o} and 60{sup o}. Void fraction increases with increasing gas velocity and decreases with increasing liquid velocity. After increasing the inclination angle from horizontal to {theta}=30{sup o} and 60{sup o}, the void fraction appears to be similar, with a

  3. Simulated Flow Pattern in Massive Pulmonary Embolism: Significance for Selective Intrapulmonary Thrombolysis

    SciTech Connect

    Schmitz-Rode, Thomas; Kilbinger, Markus; Guenther, Rolf W.

    1998-05-15

    Purpose: The flow pattern in the central pulmonary arteries proximal to large pulmonary emboli was studied experimentally. The currents to which thrombolytic agents are exposed when administered via an intrapulmonary catheter were visualized in order to explain the lack of benefit of local versus systemic administration. Methods: By illumination of suspended microspheres, the flow pattern proximal to an obstructing embolus was visualized in an in vitro pulmonary arterial flow model. In six dogs massive pulmonary embolism was created. A pigtail catheter was positioned in the pulmonary artery immediately proximal to the central edge of the occluding embolus. To allow visualization of the local flow pattern, a small amount of contrast material (4 ml) was injected through the catheter at a high flow rate (25 ml/sec). The course of the radiopaque spot that emerged from the catheter tip within 160 msec was monitored with digital subtraction angiography at a frame rate of 12.5 frames/sec. In two dogs, the study was repeated after embolus fragmentation with the same catheter position. Results: The flow model study revealed formation of a vortex proximal to the occluding embolus. In vivo experiments showed that the radiopaque spot was whirled by the vortex proximal to the embolus and made only evanescent contact with the edge of the embolus. Regardless of the embolus location, the contrast spot was washed into the non-occluded ipsilateral and contralateral pulmonary arteries within 0.40-0.64 sec. After embolus fragmentation, the contrast spot was carried completely into the formerly occluded artery. Conclusion: Flow studies explain why thrombolytic agents administered via a catheter positioned adjacent to the embolus may have no more effect than systemically administered agents. An enhanced local effect is precluded by the rapid washout into the non-occluded pulmonary arteries and subsequent systemic dilution. These results support the practice of direct intrathrombic

  4. Coal Particle Flow Patterns for O2 Enriched, Low NOx Burners

    SciTech Connect

    Jennifer Sinclair Curtis

    2005-08-01

    This project involved a systematic investigation examining the effect of near-flame burner aerodynamics on standoff distance and stability of turbulent diffusion flames and the resultant NO{sub x} emissions from actual pulverized coal diffusion flames. Specifically, the scope of the project was to understand how changes in near-flame aerodynamics and transport air oxygen partial pressure can influence flame attachment and coal ignition, two properties essential to proper operation of low NO{sub x} burners. Results from this investigation utilized a new 2M tall, 0.5m in diameter combustor designed to evaluate near-flame combustion aerodynamics in terms of transport air oxygen partial pressure (Po{sub 2}), coal fines content, primary fuel and secondary air velocities, and furnace wall temperature furnish insight into fundamental processes that occur during combustion of pulverized coal in practical systems. Complementary cold flow studies were conducted in a geometrically similar chamber to analyze the detailed motion of the gas and particles using laser Doppler velocimetry. This final technical report summarizes the key findings from our investigation into coal particle flow patterns in burners. Specifically, we focused on the effects of oxygen enrichment, the effect of fines, and the effect of the nozzle velocity ratio on the resulting flow patterns. In the cold flow studies, detailed measurements using laser Doppler velocimetry (LDV) were made to determine the details of the flow. In the hot flow studies, observations of flame stability and measurements of NO{sub x} were made to determine the effects of the flow patterns on burner operation.

  5. Dual-RiverSonde measurements of two-dimensional river flow patterns

    USGS Publications Warehouse

    Teague, C.C.; Barrick, D.E.; Lilleboe, P.M.; Cheng, R.T.; Stumpner, P.; Burau, J.R.

    2008-01-01

    Two-dimensional river flow patterns have been measured using a pair of RiverSondes in two experiments in the Sacramento-San Joaquin River Delta system of central California during April and October 2007. An experiment was conducted at Walnut Grove, California in order to explore the use of dual RiverSondes to measure flow patterns at a location which is important in the study of juvenile fish migration. The data available during the first experiment were limited by low wind, so a second experiment was conducted at Threemile Slough where wind conditions and surface turbulence historically have resulted in abundant data. Both experiments included ADCP near-surface velocity measurements from either manned or unmanned boats. Both experiments showed good comparisons between the RiverSonde and ADCP measurements. The flow conditions at both locations are dominated by tidal effects, with partial flow reversal at Walnut Grove and complete flow reversal at Threemile Slough. Both systems showed complex flow patterns during the flow reversals. Quantitative comparisons between the RiverSondes and an ADCP on a manned boat at Walnut Grove showed mean differences of 4.5 cm/s in the u (eastward) and 7.6 cm/s in the v (northward) components, and RMS differences of 14.7 cm/s in the u component and 21.0 cm/s in the v component. Quantitative comparisons between the RiverSondes and ADCPs on autonomous survey vessels at Threemile Slough showed mean differences of 0.007 cm/s in the u component and 0.5 cm/s in the v component, and RMS differences of 7.9 cm/s in the u component and 13.5 cm/s in the v component after obvious outliers were removed. ?? 2008 IEEE.

  6. Variable heat-flow patterns and hydrothermal processes near the Mid-Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Lucazeau, Francis

    2014-05-01

    Oceanic heat-flow is commonly affected by water circulation. The primary mechanism was identified by Lister (1972) near the Juan de Fuca ridge (NE Pacific) and attributed to hydrothermal flow within the oceanic basement: sea-water recharges at certain seamounts, flows within the high-permeability basement below the sediments and discharges at other seamounts. As a result, the heat-flow measured at the ocean bottom is significantly lower than expected for a conductively cooling lithosphere, as long as the fluid is not in equilibrium with the host rock. But this is not the only mechanism for low heat-flow values in the oceanic lithosphere: near the Mid-Atlantic ridge, Langseth et al (1992) have identified the process of sea-water drawdown into the sediments. Here we present results from a recent heat-flow survey (OCEANOGRAFLU, June 2013) on the Mid-Atlantic Ridge flanks at about 35°N, close to the Oceanographer fracture zone, where we have observed similar evidences that sea-water can flow directly into the surficial sediments. Where the heat-flow is lower than the conductive cooling values, the temperature-depth profiles are systematically non-linear, showing sigmoid shapes or negative gradients, and the sediment porewaters have compositions close to that of sea-water. No clear evidence for basement recharge or discharge is observed, which differs significantly from the results of a previous study 400 km North, where the heat-flow pattern was more consistent with water flowing into the oceanic basement rather than into the sediment (Lucazeau et al, 2006). We will present the relevant observations and examine the possible causes for the different processes affecting the heat-flow in the Mid-Atlantic Ridge flanks.

  7. Cerebral blood flow response pattern during balloon test occlusion of the internal carotid artery

    SciTech Connect

    Witt, J.P.; Yonas, H.; Jungreis, C.

    1994-05-01

    To evaluate the risk of temporary or permanent internal carotid artery occlusion. In 156 patients intraarterial balloon test occlusion in combination with a stable xenon-enhanced CT cerebral blood flow study was performed before radiologic or surgical treatment. All 156 patients passed the clinical balloon test occlusion and underwent a xenon study in combination with a second balloon test. Quantitative flow data were analyzed for absolute changes as well as changes in symmetry. Fourteen patients exhibited reduced flow values between 20 and 30 mL/100 g per minute, an absolute decrease in flow, and significant asymmetry in the middle cerebral artery territory during balloon test occlusion. These patients would be considered at high risk for cerebral infarction if internal carotid artery occlusion were to be performed. With one exception they belonged to a group (class I) of 61 patients who showed bilateral or ipsilateral flow decrease and significant asymmetry with lower flow on the side of occlusion. The other 95 patients, who showed a variety of cerebral blood flow response patterns including ipsilateral or bilateral flow increase, were at moderate (class II) or low (class III) stroke risk. In contrast to these findings, exclusively qualitative flow analysis failed to identify the patients at high risk: a threshold with an asymmetry index of 10% revealed only 16% specificity whereas an asymmetry index of 45% showed only 61% sensitivity for detection of low flow areas (<30 mL/100 g per minute). For achieving a minimal hemodynamic related-stroke rate associated with permanent clinical internal carotid artery occlusion we suggest integration of a thorough analysis of quantitative cerebral blood flow data before and during balloon test occlusion. 68 refs., 5 figs., 2 tabs.

  8. Patterns and age distribution of ground-water flow to streams

    USGS Publications Warehouse

    Modica, E.; Reilly, T.E.; Pollock, D.W.

    1997-01-01

    Simulations of ground-water flow in a generic aquifer system were made to characterize the topology of ground-water flow in the stream subsystem and to evaluate its relation to deeper ground-water flow. The flow models are patterned after hydraulic characteristics of aquifers of the Atlantic Coastal Plain and are based on numerical solutions to three-dimensional, steady-state, unconfined flow. The models were used to evaluate the effects of aquifer horizontal-to-vertical hydraulic conductivity ratios, aquifer thickness, and areal recharge rates on flow in the stream subsystem. A particle tracker was used to determine flow paths in a stream subsystem, to establish the relation between ground-water seepage to points along a simulated stream and its source area of flow, and to determine ground-water residence time in stream subsystems. In a geometrically simple aquifer system with accretion, the source area of flow to streams resembles an elongated ellipse that tapers in the downgradient direction. Increased recharge causes an expansion of the stream subsystem. The source area of flow to the stream expands predominantly toward the stream headwaters. Baseflow gain is also increased along the reach of the stream. A thin aquifer restricts ground-water flow and causes the source area of flow to expand near stream headwaters and also shifts the start-of-flow to the drainage basin divide. Increased aquifer anisotropy causes a lateral expansion of the source area of flow to streams. Ground-water seepage to the stream channel originates both from near- and far-recharge locations. The range in the lengths of flow paths that terminate at a point on a stream increase in the downstream direction. Consequently, the age distribution of ground water that seeps into the stream is skewed progressively older with distance downstream. Base flow ia an integration of ground water with varying age and potentially different water quality, depending on the source within the drainage basin

  9. Flow structures and particle deposition patterns in double-bifurcation airway models. Part 1. Air flow fields

    NASA Astrophysics Data System (ADS)

    Comer, J. K.; Kleinstreuer, C.; Zhang, Z.

    2001-05-01

    The understanding and quantitative assessment of air flow fields and local micron-particle wall concentrations in tracheobronchial airways are very important for estimating the health risks of inhaled particulate pollutants, developing algebraic transfer functions of global lung deposition models used in dose-response analyses, and/or determining proper drug-aerosol delivery to target sites in the lung. In this paper (Part 1) the theory, model geometries, and air flow results are provided. In a companion paper (Part 2, Comer et al. 2001), the history of particle deposition patterns and comparisons with measured data sets are reported. Decoupling of the naturally dilute particle suspension makes it feasible to present the results in two parts.

  10. Complex Flow Separation Pattern on Transonic Fan Airfoils Revealed by Flow Visualization

    NASA Technical Reports Server (NTRS)

    Lepicovsky, Jan

    2001-01-01

    Modern turbofan engines employ a highly loaded fan stage with transonic or low-supersonic velocities in the blade-tip region. The fan blades are often prone to flutter at off-design conditions. Flutter is a highly undesirable and dangerous self-excited mode of blade oscillations that can result in high-cycle fatigue blade failure. The origins of blade flutter are not fully understood yet. The latest view is that the blade oscillations are triggered by high-frequency changes in the extent of the partially separated area on the airfoil suction side. There is a lack of experimental data describing the separated flow characteristics of modern airfoils for transonic fans.

  11. Consistency of groundwater flow patterns in mountainous topography: Implications for valley bottom water replenishment and for defining groundwater flow boundaries

    NASA Astrophysics Data System (ADS)

    Welch, L. A.; Allen, D. M.

    2012-05-01

    Topographic influences on groundwater flow processes that contribute to baseflow and mountain block recharge (MBR) are conceptually investigated using three-dimensional numerical models of saturated groundwater flow. Model domains for conceptual and real topographies are developed as "mountain groundwatershed units" (MGUs) to represent regional-scale watershed systems. Results indicate regularity in groundwater flow patterns that reflect consistency of prominent topographic features, providing a basis for conceptualizing three-dimensional groundwater flow. Baseflow is generated mainly from recharge within the watershed area. MBR is produced primarily from recharge that is focused across triangular facets near the mountain front (˜73%-97% of total MBR), with additional contributions originating within the watershed (up to ˜27% of MBR). MBR contributions originating from recharge near the highest-elevation watershed boundaries are minimal but are greater for topography with less stream incision. With orographic influences, more MBR originates within the watershed. MBR rates are relatively consistent between models because of similarities in mountain front topography, while baseflow is variable. Gains and losses to systems via cross-watershed groundwater flux, generated because of topographic differences between adjacent watersheds, cause baseflow to vary by up to ˜10% but do not significantly influence MBR. In data-sparse regions such as mountains, a basic numerical modeling approach, using the MGU concept with topography data and mapped watershed boundaries, can be used to develop site-specific conceptual models to constrain water budgets, to delineate recharge areas, and to guide further investigation and data collection.

  12. A study of the Marangoni flow and particle deposition patterns in an evaporating octane droplet

    NASA Astrophysics Data System (ADS)

    Hu, Hua; Larson, Ronald

    2004-03-01

    We investigate flow behavior in an evaporating octane droplet experimentally and theoretically. In the experiments, we for the first time observed a strong recirculatory flow, which we attribute to a Marangoni effect driven by a temperature gradient along the droplet surface due to thermal cooling. A micro-PIV technique is used to map the velocity field in the droplet, including the strong recirculation. An approximated analytical solution of the Marangoni flow is developed using the lubrication assumption and is confirmed to be accurate by an FEM analysis for the flow in the evaporating droplet. The experimental results are compared with the theoretical results and good agreement is found. Finally, the particle deposition patterns on the substrate formed at various Marangoni numbers are discussed.

  13. [An evaluation of the pulmonary venous flow pattern by transesophageal and transthoracic Doppler echocardiography in a normal subject].

    PubMed

    Cottini, E; Giacone, G; Cosentino, M; Rando, G; Vintaloro, G; De Roberto, S

    1994-10-01

    Transesophageal echocardiographic studies have permitted a pulmonary venous flow velocity pattern to be identified which is comparable to that recorder using invasive methods. The pattern consists of 4 stages: an anterograde systolic flow with an early (S1) and late (S2) peak velocity, a diastolic anterograde flow (D) and a retrograde flow liked to atrial contraction (Ar). The aim of this study was to evaluate the pattern of pulmonary venous flow velocity using transesophageal and transthoracic colour Doppler echocardiography in normal subjects in an attempt to: 1) determine normal values derived from the pulmonary venous flow pattern which may contribute to future studies; 2) find correlations between the pattern of pulmonary venous flow and a number of physiological, hemodynamic and echocardiographic parameters which take account of the morphological variations of this flow pattern within a normal range; 3) demonstrate the possibility of being able to carry out study using transthoracic colour Doppler echocardiography. The study was carried out in 38 normal subjects aged between 15 and 76 years old (mean 45 +/- 15) who underwent transthoracic and transesophageal colour-Doppler echocardiography. The following parameters were measured: left atrium diameter, diameters and telediastolic and telesystolic volumes of the left ventricle, ejection fraction and systolic percentage shortening of the left ventricle, peak velocity of the mitral flow pattern and the pulmonary venous flow pattern. The results obtained show that: 1) the pattern of pulmonary venous flow alters with ageing causing the prevalence of systolic over diastolic peak velocity; 2) the pulmonary venous flow parameters which appear to be most significant in hemodynamic terms are the peak velocities of the early systolic flow and anterograde diastolic flow and the ratios S1/S2 and S2/D; 3) the echocardiographic parameters most closely correlated with the peak velocity of pulmonary venous flow are the

  14. Flow patterns at the stenosed carotid bifurcation: effect of concentric versus eccentric stenosis.

    PubMed

    Steinman, D A; Poepping, T L; Tambasco, M; Rankin, R N; Holdsworth, D W

    2000-04-01

    Carotid stenosis severity is a commonly used indicator for assessing risk of stroke. However, the majority of individuals with severe carotid artery disease never suffer a stroke, and strokes can occur even with only mild or moderate stenosis. This suggests local factors (other than stenosis severity) at or near the carotid artery bifurcation may be important in determining stroke risk. In this paper we investigate the effect of stenosis geometry on flow patterns in the stenosed carotid bifurcation, using concentrically and eccentrically stenosed anthropomorphic carotid bifurcation models having identical stenosis severity. Computational simulations and experimental flow visualizations both demonstrate marked differences in flow patterns of concentric and eccentric stenosis models for moderately and severely stenosed cases, respectively. In particular, we identify post-stenotic recirculation zone size and location, and spatial extent of elevated wall shear stress as key factors differing between the two geometries. As these are also rotid plaque more vulnerable to cerebral embolus prokey biophysical factors promoting thrombogenesis, we propose that the stenosed carotid bifurcation geometry--or the induced flow patterns themselves--may provide more specific indicators for those plaques that are vulnerable to enhanced thromboembolic potential, and hence, increased risk of ischemic stroke.

  15. Small-scale flow patterns at the vertical sidewalls of the thermally driven rotating annulus

    NASA Astrophysics Data System (ADS)

    von Larcher, Thomas; Viazzo, Stephane; Randriamampianina, Anthony; Harlander, Uwe

    2017-04-01

    We report on small-scale instabilities in the thermally driven rotating annulus filled with a liquid of moderate Prandtl number. Our study is based on numerical computations and accompanying laboratory experiments. The computations were performed independently with two different flow solvers, that is the finite volume flow solver EULAG and a higher order finite difference compact scheme (HOC). We found small-scale flow patterns at both vertical sidewalls of the annulus, the cooled inner sidewall and the heated outer one. Obviously, these small-scale instabilities are localized and connected to the large-scale baroclinic wave field. While the existence of small-scale flow structures at the inner sidewall is already described in recent publications, e.g., [1], [2], the occurrence of short wavelength waves at the outer sidewall has not been reported yet. Here, we focus on characterising the dynamics of the small-scale patterns at the outer sidewall. Physical mechanisms that might trigger these patterns are discussed. References: [1] Jacoby, T.N.L., Read, P.L., Williams, P.D. & Young, R.M.B., 2011, Generation of inertia-gravity waves in the rotating, thermal annulus by a localised boundary layer instability. Geophys. Astrophys. Fluid Dyn., 105, 161-181. [2] Randriamampianina, A. & Crespo del Arco, E., 2015, Inertia-gravity waves in a liquid-filled, differentially heated, rotating annulus. J. Fluid Mech., 782, 144-177.

  16. Cryptic Species? Patterns of Maternal and Paternal Gene Flow in Eight Neotropical Bats

    PubMed Central

    Clare, Elizabeth L.

    2011-01-01

    Levels of sequence divergence at mitochondrial loci are frequently used in phylogeographic analysis and species delimitation though single marker systems cannot assess bi-parental gene flow. In this investigation I compare the phylogeographic patterns revealed through the maternally inherited mitochondrial COI region and the paternally inherited 7th intron region of the Dby gene on the Y-chromosome in eight common Neotropical bat species. These species are diverse and include members of two families from the feeding guilds of sanguivores, nectarivores, frugivores, carnivores and insectivores. In each case, the currently recognized taxon is comprised of distinct, substantially divergent intraspecific mitochondrial lineages suggesting cryptic species complexes. In Chrotopterus auritus, and Saccopteryx bilineata I observed congruent patterns of divergence in both genetic regions suggesting a cessation of gene flow between intraspecific groups. This evidence supports the existence of cryptic species complexes which meet the criteria of the genetic species concept. In Glossophaga soricina two intraspecific groups with largely sympatric South American ranges show evidence for incomplete lineage sorting or frequent hybridization while a third group with a Central American distribution appears to diverge congruently at both loci suggesting speciation. Within Desmodus rotundus and Trachops cirrhosus the paternally inherited region was monomorphic and thus does not support or refute the potential for cryptic speciation. In Uroderma bilobatum, Micronycteris megalotis and Platyrrhinus helleri the gene regions show conflicting patterns of divergence and I cannot exclude ongoing gene flow between intraspecific groups. This analysis provides a comprehensive comparison across taxa and employs both maternally and paternally inherited gene regions to validate patterns of gene flow. I present evidence for previously unrecognized species meeting the criteria of the genetic species

  17. Classification of pulmonary system diseases patterns using flow-volume curve.

    PubMed

    Arabalibeik, Hossein; Jafari, Samaneh; Agin, Khosro

    2011-01-01

    Spirometry is the most common pulmonary function test. It provides useful information for early detection of respiratory system abnormalities. While decision support systems use normally calculated parameters such as FEV1, FVC, and FEV1% to diagnose the pattern of respiratory system diseases, expert physicians pay close attention to the pattern of the flow-volume curve as well. Fisher discriminant analysis shows that coefficients of a simple polynomial function fitted to the curve, can capture the information about the disease patterns much better than the familiar single point parameters. A neural network then can classify the abnormality pattern as restrictive, obstructive, mixed, or normal. Using the data from 205 adult volunteers, total accuracy, sensitivity and specificity for four categories are 97.6%, 97.5% and 98.8% respectively.

  18. Spatial and temporal patterns of debris flow deposition in the Oregon Coast Range, USA

    USGS Publications Warehouse

    May, Christine L.; Gresswell, Robert E.

    2004-01-01

    Patterns of debris-flow occurrence were investigated in 125 headwater basins in the Oregon Coast Range. Time since the previous debris-flows was established using dendrochronology, and recurrence interval estimates ranged from 98 to 357 years. Tributary basins with larger drainage areas had a greater abundance of potential landslide source areas and a greater frequency of scouring events compared to smaller basins. The flux rate of material delivered to the confluence with a larger river influenced the development of small-scale debris-flow fans. Fans at the mouths of tributary basins with smaller drainage areas had a higher likelihood of being eroded by the mainstem river in the interval between debris-flows, compared to bigger basins that had larger, more persistent fans. Valley floor width of the receiving channel also influenced fan development because it limited the space available to accommodate fan formation. Of 63 recent debris-flows, 52% delivered sediment and wood directly to the mainstem river, 30% were deposited on an existing fan before reaching the mainstem, and 18% were deposited within the confines of the tributary valley before reaching the confluence. Spatial variation in the location of past and present depositional surfaces indicated that sequential debris-flow deposits did not consistently form in the same place. Instead of being spatially deterministic, results of this study suggest that temporally variable and stochastic factors may be important for predicting the runout length of debris-flows.

  19. Assessment of the debris-flow susceptibility in tropical mountains using clast distribution patterns

    NASA Astrophysics Data System (ADS)

    de Carvalho Faria Lima Lopes, Laís; de Almeida Prado Bacellar, Luís; Amorim Castro, Paulo de Tarso

    2016-12-01

    Channel morphometric parameters and clast distribution patterns in selected basins of the Ferriferous Quadrangle tropical mountains, Brazil, were analyzed in order to assess susceptibility to debris flows. Median bed surface clast size (D50) in the main stream channel of these basins shows a coarsening downstream trend with drainage areas of up to 6 km2, which is attributed to debris flow dominated-channels by some authors. The composition and roundness of the bed load, clast sand, and the presence of allochthonous large boulders throughout the channels also suggest the occurrence of past debris flow in the region. Luminescence Optically Stimulated (LOE) dating points out that debris flow could have occurred as a consequence of climate changes in the Late Pleistocene and Holocene and it can now be triggered by deforestation or extreme rainfall events. There has not been any record of past debris flow in the study area, or in other mountainous regions of Brazil where debris flows have recently occurred. Thus, the adopted approach can be useful to assess debris flow susceptibility in this and other similar areas.

  20. Local adaptation, patterns of selection, and gene flow in the Californian serpentine sunflower (Helianthus exilis).

    PubMed

    Sambatti, Julianno B M; Rice, Kevin J

    2006-04-01

    The traditional view of the species as the fundamental unit of evolution has been challenged by observations that in heterogeneous environments, gene flow may be too restricted to overcome the effects of local selection. Whether a species evolves as a cohesive unit depends critically on the dynamic balance between homogenizing gene flow among populations and potentially disruptive local adaptation. To examine this evolutionary balance between "global" gene flow and local selection, we studied northern Californian populations of Helianthus exilis, the serpentine sunflower, within a mosaic of contrasting serpentine and nonserpentine areas that differ considerably in soil chemistry and water availability. Local adaptation to riparian and serpentine habitats was studied in Helianthus exilis along with an analysis of gene flow patterns among populations within these habitats. Local adaptation was assessed in H. exilis during 2002 and 2003 using reciprocal transplant experiments at multiple locations within serpentine and riparian habitats. Effects of competition and germination date on the expression of local adaptation were also examined within the reciprocal transplant experiments. Local adaptation was detected in both years at the local site level and at the level of habitat. The analysis of the transplanted populations indicated that the patterns of selection differed considerably between riparian and serpentine sites. Differential survivorship occurred in serpentine habitats, whereas selection on reproductive output predominated in riparian habitats. Local adaptation was expressed only in the absence of competition. Local adaptation in terms of survivorship was most strongly expressed in treatments with delayed seed germination. Microsatellite markers were used to quantify population genetic parameters and examine the patterns of gene flow among sampled populations. Analysis of molecular markers revealed a system of population patches that freely exchange genes

  1. Complex blood flow patterns in an idealized left ventricle: A numerical study

    NASA Astrophysics Data System (ADS)

    Tagliabue, Anna; Dedè, Luca; Quarteroni, Alfio

    2017-09-01

    In this paper, we study the blood flow dynamics in a three-dimensional (3D) idealized left ventricle of the human heart whose deformation is driven by muscle contraction and relaxation in coordination with the action of the mitral and aortic valves. We propose a simplified but realistic mathematical treatment of the valves function based on mixed time-varying boundary conditions (BCs) for the Navier-Stokes equations modeling the flow. These switchings in time BCs, from natural to essential and vice versa, model either the open or the closed configurations of the valves. At the numerical level, these BCs are enforced by means of the extended Nitsche's method (Tagliabue et al., Int. J. Numer. Methods Fluids, 2017). Numerical results for the 3D idealized left ventricle obtained by means of Isogeometric Analysis are presented, discussed in terms of both instantaneous and phase-averaged quantities of interest and validated against those available in the literature, both experimental and computational. The complex blood flow patterns are analysed to describe the characteristic fluid properties, to show the transitional nature of the flow, and to highlight its main features inside the left ventricle. The sensitivity of the intraventricular flow patterns to the mitral valve properties is also investigated.

  2. The impact of traffic-flow patterns on air quality in urban street canyons.

    PubMed

    Thaker, Prashant; Gokhale, Sharad

    2016-01-01

    We investigated the effect of different urban traffic-flow patterns on pollutant dispersion in different winds in a real asymmetric street canyon. Free-flow traffic causes more turbulence in the canyon facilitating more dispersion and a reduction in pedestrian level concentration. The comparison of with and without a vehicle-induced-turbulence revealed that when winds were perpendicular, the free-flow traffic reduced the concentration by 73% on the windward side with a minor increase of 17% on the leeward side, whereas for parallel winds, it reduced the concentration by 51% and 29%. The congested-flow traffic increased the concentrations on the leeward side by 47% when winds were perpendicular posing a higher risk to health, whereas reduced it by 17-42% for parallel winds. The urban air quality and public health can, therefore, be improved by improving the traffic-flow patterns in street canyons as vehicle-induced turbulence has been shown to contribute significantly to dispersion.

  3. Intraventricular flow patterns and stasis in the LVAD-assisted heart.

    PubMed

    Wong, K; Samaroo, G; Ling, I; Dembitsky, W; Adamson, R; del Álamo, J C; May-Newman, K

    2014-04-11

    Left ventricular assist device (LVAD) support disrupts the natural blood flow path through the heart, introducing flow patterns associated with thrombosis, especially in the presence of medical devices. The aim of this study was to quantitatively evaluate the flow patterns in the left ventricle (LV) of the LVAD-assisted heart, with a focus on alterations in vortex development and stasis. Particle image velocimetry of a LVAD-supported LV model was performed in a mock circulatory loop. In the Pre-LVAD flow condition, a vortex ring initiating from the LV base migrated toward the apex during diastole and remained in the LV by the end of ejection. During LVAD support, vortex formation was relatively unchanged although vortex circulation and kinetic energy increased with LVAD speed, particularly in systole. However, as pulsatility decreased and aortic valve opening ceased, a region of fluid stasis formed near the left ventricular outflow tract. These findings suggest that LVAD support does not substantially alter vortex dynamics unless cardiac function is minimal. The altered blood flow introduced by the LVAD results in stasis adjacent to the LV outflow tract, which increases the risk of thrombus formation in the heart.

  4. Analysing the impact of urban areas patterns on the mean annual flow of 43 urbanized catchments

    NASA Astrophysics Data System (ADS)

    Salavati, B.; Oudin, L.; Furusho, C.; Ribstein, P.

    2015-06-01

    It is often argued that urban areas play a significant role in catchment hydrology, but previous studies reported disparate results of urbanization impacts on stream flow. This might stem either from the difficulty to quantify the historical flow changes attributed to urbanization only (and not climate variability) or from the inability to decipher what type of urban planning is more critical for flows. In this study, we applied a hydrological model on 43 urban catchments in the United States to quantify the flow changes attributable to urbanization. Then, we tried to relate these flow changes to the changes of urban/impervious areas of the catchments. We argue that these spatial changes of urban areas can be more precisely characterized by landscape metrics, which enable analysing the patterns of historical urban growth. Landscape metrics combine the richness (the number) and evenness (the spatial distribution) of patch types represented on the landscape. Urbanization patterns within the framework of patch analysis have been widely studied but, to our knowledge, previous research works had not linked them to catchments hydrological behaviours. Our results showed that the catchments with larger impervious areas and larger mean patch areas are likely to have larger increase of runoff yield.

  5. Pattern Formation in Diffusion Flames Embedded in von Karman Swirling Flows

    NASA Technical Reports Server (NTRS)

    Nayagam, Vedha

    2006-01-01

    Pattern formation is observed in nature in many so-called excitable systems that can support wave propagation. It is well-known in the field of combustion that premixed flames can exhibit patterns through differential diffusion mechanism between heat and mass. However, in the case of diffusion flames where fuel and oxidizer are separated initially there have been only a few observations of pattern formation. It is generally perceived that since diffusion flames do not possess an inherent propagation speed they are static and do not form patterns. But in diffusion flames close to their extinction local quenching can occur and produce flame edges which can propagate along stoichiometric surfaces. Recently, we reported experimental observations of rotating spiral flame edges during near-limit combustion of a downward-facing polymethylmethacrylate disk spinning in quiescent air. These spiral flames, though short-lived, exhibited many similarities to patterns commonly found in quiescent excitable media including compound tip meandering motion. Flame disks that grow or shrink with time depending on the rotational speed and in-depth heat loss history of the fuel disk have also been reported. One of the limitations of studying flame patterns with solid fuels is that steady-state conditions cannot be achieved in air at normal atmospheric pressure for experimentally reasonable fuel thickness. As a means to reproduce the flame patterns observed earlier with solid fuels, but under steady-state conditions, we have designed and built a rotating, porous-disk burner through which gaseous fuels can be injected and burned as diffusion flames. The rotating porous disk generates a flow of air toward the disk by a viscous pumping action, generating what is called the von K rm n boundary layer which is of constant thickness over the entire burner disk. In this note we present a map of the various dynamic flame patterns observed during the combustion of methane in air as a function of

  6. 4D flow MRI assessment of right atrial flow patterns in the normal heart – influence of caval vein arrangement and implications for the patent foramen ovale

    PubMed Central

    Parikh, Jehill D.; Kakarla, Jayant; Keavney, Bernard; O’Sullivan, John J.; Ford, Gary A.; Blamire, Andrew M.; Hollingsworth, Kieren G.

    2017-01-01

    Aim To investigate atrial flow patterns in the normal adult heart, to explore whether caval vein arrangement and patency of the foramen ovale (PFO) may be associated with flow pattern. Materials and Methods Time-resolved, three-dimensional velocity encoded magnetic resonance imaging (4D flow) was employed to assess atrial flow patterns in thirteen healthy subjects (6 male, 40 years, range 25–50) and thirteen subjects (6 male, 40 years, range 21–50) with cryptogenic stroke and patent foramen ovale (CS-PFO). Right atrial flow was defined as vortical, helico-vortical, helical and multiple vortices. Time-averaged and peak systolic and diastolic flows in the caval and pulmonary veins and their anatomical arrangement were compared. Results A spectrum of right atrial flow was observed across the four defined categories. The right atrial flow patterns were strongly associated with the relative position of the caval veins. Right atrial flow patterns other than vortical were more common (p = 0.015) and the separation between the superior and inferior vena cava greater (10±5mm versus 3±3mm, p = 0.002) in the CS-PFO group. In the left atrium all subjects except one had counter-clockwise vortical flow. Vortex size varied and was associated with left lower pulmonary vein flow (systolic r = 0.61, p = 0.001, diastolic r = 0.63 p = 0.002). A diastolic vortex was less common and time-averaged left atrial velocity was greater in the CS-PFO group (17±2cm/sec versus 15±1, p = 0.048). One CS-PFO subject demonstrated vortical retrograde flow in the descending aortic arch; all other subjects had laminar descending aortic flow. Conclusion Right atrial flow patterns in the normal heart are heterogeneous and are associated with the relative position of the caval veins. Patterns, other than ‘typical’ vortical flow, are more prevalent in the right atrium of those with cryptogenic stroke in the context of PFO. Left atrial flow patterns are more homogenous in normal hearts and show a

  7. Propagation of a spherical shock wave in mixture of non-ideal gas and small solid particles under the influence of gravitational field with conductive and radiative heat fluxes

    NASA Astrophysics Data System (ADS)

    Nath, G.

    2016-01-01

    Self-similar solutions are obtained for one-dimensional unsteady adiabatic flow behind a spherical shock wave propagating in a dusty gas with conductive and radiative heat fluxes under the influence of a gravitational field. The shock is assumed to be driven out by a moving piston and the dusty gas to be a mixture of non-ideal gas and small solid particles, in which solid particles are uniformly distributed. It is assumed that the equilibrium flow-conditions are maintained and variable energy input is continuously supplied by the piston. The heat conduction is expressed in terms of Fourier's law and the radiation is considered to be of the diffusion type for an optically thick grey gas model. The thermal conductivity K and the absorption coefficient αR are assumed to vary with temperature and density. The medium is assumed to be under the influence of a gravitational field due to central mass ( bar{m} ) at the origin (Roche Model). It is assumed that the gravitational effect of the mixture itself can be neglected compared with the attraction of the central mass. The initial density of the ambient medium is taken to be always constant. The effects of the variation of the gravitational parameter and nonidealness of the gas in the mixture are investigated. Also, the effects of an increase in (i) the mass concentration of solid particles in the mixture and (ii) the ratio of the density of solid particles to the initial density of the gas on the flow variables are investigated. It is shown that due to an increase in the gravitational parameter the compressibility of the medium at any point in the flow-field behind the shock decreases and all other flow variables and the shock strength are increased. Further, it is found that the presence of gravitational field increases the compressibility of the medium, due to which it is compressed and therefore the distance between the piston and the shock surface is reduced. The shock waves in dusty gas under the influence of a

  8. Flow-driven control of calcium carbonate precipitation patterns in a confined geometry.

    PubMed

    Schuszter, Gábor; Brau, Fabian; De Wit, A

    2016-09-14

    Upon injection of an aqueous solution of carbonate into a solution of calcium ions in the confined geometry of a Hele-Shaw cell, various calcium carbonate precipitation patterns are observed. We discuss here the properties of these precipitation structures as a function of the injection flow rate and concentrations of the reactants. We show that such flow-controlled conditions can be used to influence the total amount and the spatial distribution of the solid phase produced as well as the reaction efficiency defined here as the amount of product formed for a given initial concentration of the injected solution.

  9. Analogs in the wintertime 500 mb height field. [recurrent flow patterns

    NASA Technical Reports Server (NTRS)

    Gutzler, D. S.; Shukla, J.

    1984-01-01

    Lorenz (1969) has considered the possibility that an atmospheric circulation pattern might recur, taking into account the definition of a pair of analogous flows or 'analogs'. The present investigation is concerned with a search of time series of Northern Hemisphere wintertime geopotential heights for possible analogs. Attention is given to data and analysis procedure, analog quality, and error growth rates. The obtained results imply that the found analogs are not a useful tool for forecasting the evolution of the midlatitude flow on time scales of several days. It is pointed out, however, that the negative results should not be extended to other applications of analog forecasting.

  10. Analogs in the wintertime 500 mb height field. [recurrent flow patterns

    NASA Technical Reports Server (NTRS)

    Gutzler, D. S.; Shukla, J.

    1984-01-01

    Lorenz (1969) has considered the possibility that an atmospheric circulation pattern might recur, taking into account the definition of a pair of analogous flows or 'analogs'. The present investigation is concerned with a search of time series of Northern Hemisphere wintertime geopotential heights for possible analogs. Attention is given to data and analysis procedure, analog quality, and error growth rates. The obtained results imply that the found analogs are not a useful tool for forecasting the evolution of the midlatitude flow on time scales of several days. It is pointed out, however, that the negative results should not be extended to other applications of analog forecasting.

  11. 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

  12. Fingering patterns in the lifting flow of a confined miscible ferrofluid.

    PubMed

    Chen, Ching-Yao; Wu, S-Y; Miranda, José A

    2007-03-01

    Miscible flow displacements of a ferrofluid droplet subjected to various magnetic field configurations and confined in a time-dependent gap Hele-Shaw cell are examined through highly accurate numerical simulations. The interplay between lifting, miscibility, and applied magnetic fields resulted in complex interfacial pattern formation. By varying the symmetry properties of the applied magnetic fields and by considering the action of Korteweg stresses, a number of interesting droplet morphologies are identified and characterized. The possibility of controlling the degree of fluid mixing and the ultimate shape of the emerging patterns by appropriately adjusting the strength of the applied magnetic fields is also discussed.

  13. Preliminary simulated tidal flow and circulation patterns in Hillsborough Bay, Florida

    USGS Publications Warehouse

    Goodwin, Carl R.

    1980-01-01

    The effect of channel dredging and island construction on tidal flow and circulation in Hillsborough Bay, Fla., due to the Tampa Harbor Deepening Project is being investigated using a two-dimensional, finite-difference numerical model. Preliminary model results are presented as a series of maps showing tidal flood, tidal ebb, and circulation patterns in the bay for predredging and postdredging conditions. Complex circulation patterns occur near the bay mouth in an area where there is (1) a change in thalweg alinement of the bay, (2) an intersection of three major ship channels, and (3) submergent and emergent dredged material located adjacent to each of the channels. (USGS)

  14. Groundwater flow pattern and related environmental phenomena in complex geologic setting based on integrated model construction

    NASA Astrophysics Data System (ADS)

    Tóth, Ádám; Havril, Tímea; Simon, Szilvia; Galsa, Attila; Monteiro Santos, Fernando A.; Müller, Imre; Mádl-Szőnyi, Judit

    2016-08-01

    Groundwater flow, driven, controlled and determined by topography, geology and climate, is responsible for several natural surface manifestations and affected by anthropogenic processes. Therefore, flowing groundwater can be regarded as an environmental agent. Numerical simulation of groundwater flow could reveal the flow pattern and explain the observed features. In complex geologic framework, where the geologic-hydrogeologic knowledge is limited, the groundwater flow model could not be constructed based solely on borehole data, but geophysical information could aid the model building. The integrated model construction was presented via the case study of the Tihany Peninsula, Hungary, with the aims of understanding the background and occurrence of groundwater-related environmental phenomena, such as wetlands, surface water-groundwater interaction, slope instability, and revealing the potential effect of anthropogenic activity and climate change. The hydrogeologic model was prepared on the basis of the compiled archive geophysical database and the results of recently performed geophysical measurements complemented with geologic-hydrogeologic data. Derivation of different electrostratigraphic units, revealing fracturing and detecting tectonic elements was achieved by systematically combined electromagnetic geophysical methods. The deduced information can be used as model input for groundwater flow simulation concerning hydrostratigraphy, geometry and boundary conditions. The results of numerical modelling were interpreted on the basis of gravity-driven regional groundwater flow concept and validated by field mapping of groundwater-related phenomena. The 3D model clarified the hydraulic behaviour of the formations, revealed the subsurface hydraulic connection between groundwater and wetlands and displayed the groundwater discharge pattern, as well. The position of wetlands, their vegetation type, discharge features and induced landslides were explained as

  15. Analysis of flow patterns in a patient-specific aortic dissection model.

    PubMed

    Cheng, Z; Tan, F P P; Riga, C V; Bicknell, C D; Hamady, M S; Gibbs, R G J; Wood, N B; Xu, X Y

    2010-05-01

    Aortic dissection is the most common acute catastrophic event affecting the thoracic aorta. The majority of patients presenting with an uncomplicated type B dissection are treated medically, but 25% of these patients develop subsequent aneurysmal dilatation of the thoracic aorta. This study aimed at gaining more detailed knowledge of the flow phenomena associated with this condition. Morphological features and flow patterns in a dissected aortic segment of a presurgery type B dissection patient were analyzed based on computed tomography images acquired from the patient. Computational simulations of blood flow in the patient-specific model were performed by employing a correlation-based transitional version of Menter's hybrid k-epsilon/k-omega shear stress transport turbulence model implemented in ANSYS CFX 11. Our results show that the dissected aorta is dominated by locally highly disturbed, and possibly turbulent, flow with strong recirculation. A significant proportion (about 80%) of the aortic flow enters the false lumen, which may further increase the dilatation of the aorta. High values of wall shear stress have been found around the tear on the true lumen wall, perhaps increasing the likelihood of expanding the tear. Turbulence intensity in the tear region reaches a maximum of 70% at midsystolic deceleration phase. Incorporating the non-Newtonian behavior of blood into the same transitional flow model has yielded a slightly lower peak wall shear stress and higher maximum turbulence intensity without causing discernible changes to the distribution patterns. Comparisons between the laminar and turbulent flow simulations show a qualitatively similar distribution of wall shear stress but a significantly higher magnitude with the transitional turbulence model.

  16. Computational modeling of lava domes using particle dynamics to investigate the effect of conduit flow mechanics on flow patterns

    NASA Astrophysics Data System (ADS)

    Husain, Taha Murtuza

    Large (1--4 x 106 m3) to major (> 4 x 106 m3) dome collapses for andesitic lava domes such as Soufriere Hills Volcano, Montserrat are observed for elevated magma discharge rates (6--13 m3/s). The gas rich magma pulses lead to pressure build up in the lava dome that result in structural failure of the over steepened canyon-like walls which may lead to rockfall or pyroclastic flow. This indicates that dome collapse intimately related to magma extrusion rate. Variation in magma extrusion rate for open-system magma chambers is observed to follow alternating periods of high and low activity. Periodic behavior of magma exhibits a rich diversity in the nature of its eruptive history due to variation in magma chamber size, total crystal content, linear crystal growth rate and magma replenishment rate. Distinguished patterns of growth were observed at different magma flow rates ranging from endogenous to exogenous dome growth for magma with varying strengths. Determining the key parameters that control the transition in flow pattern of the magma during its lava dome building eruption is the main focus. This dissertation examines the mechanical effects on the morphology of the evolving lava dome on the extrusion of magma from a central vent using a 2D particle dynamics model. The particle dynamics model is coupled with a conduit flow model that incorporates the kinetics of crystallization and rheological stiffening to investigate important mechanisms during lava dome building eruptions. Chapter I of this dissertation explores lava dome growth and failure mechanics using a two-dimensional particle-dynamics model. The model follows the evolution of fractured lava, with solidification driven by degassing induced crystallization of magma. The particle-dynamics model emulates the natural development of dome growth and rearrangement of the lava dome which is difficult in mesh-based analyses due to mesh entanglement effects. The deformable talus evolves naturally as a frictional

  17. Gravitational gradients and blood flow patterns in specialized arboreal (Ahaetulla nasuta) and terrestrial (Crotalus adamanteus) snakes.

    PubMed

    Young, B A; Wassersug, R J; Pinder, A

    1997-01-01

    Blood pressure and blood flow patterns were recorded from the carotid artery and aortae of a thick-bodied terrestrial snake (Crotalus adamanteus) and a thin-bodied arboreal species (Ahaetulla nasuta) anesthetized with ketamine hydrochloride. Hemodynamic stress induced by rotation resulted in pronounced changes in the blood flow patterns and pressure in C. adamanteus: rotation of A. nasuta produced changes of a similar type, but of a much lower magnitude. The markedly different responses of these two species, the baroreceptor reflexes of which were disrupted, suggest that morphological factors--such as differential gross cardiac displacement, or variation in the interaortic foramen--in addition to physiological factors, are important in determining a snake's ability to withstand hemodynamic stress.

  18. Electrode configurations inside an electrostatic precipitator and their impact on collection efficiency and flow pattern

    NASA Astrophysics Data System (ADS)

    Ning, Zhiyuan; Cheng, Lu; Shen, Xinjun; Li, Shuran; Yan, Keping

    2016-06-01

    Electrostatic precipitator (ESP) units have wide application in lots industries processes as gas filtration devices. Regarding their high efficiency, further improvement is still required. Wide ESP (plate-to-plate distance greater than 400 mm) is one of a promising way to improve existing ESP due to its ability to reduce equipment investment significantly. However, its large-scale application has been limited because it may potentially lead to collection efficiency reduction. This article focuses on the study of two major effects when several different electrode configurations are applied. The electrohydrodynamic (EHD) flow pattern inside ESP and particle collection efficiency were investigated by using particle image velocimetry (PIV) and electrical low pressure impactor (ELPI) respectively. Results suggested that the collection efficiency of wide ESP is rather complicated and highly related to inner gas flow pattern.

  19. Effects of refraction by means flow velocity gradients on the standing wave pattern in three-dimensional, rectangular waveguides

    NASA Technical Reports Server (NTRS)

    Hersh, A. S.

    1979-01-01

    The influence of a mean vortical flow on the connection between the standing wave pattern in a rectangular three dimensional waveguide and the corresponding duct axial impedance was determined analytically. The solution was derived using a perturbation scheme valid for low mean flow Mach numbers and plane wave sound frequencies. The results show that deviations of the standing wave pattern due to refraction by the mean flow gradients are small.

  20. Architectural adaptation and protein expression patterns of Salmonella enterica serovar Enteritidis biofilms under laminar flow conditions.

    PubMed

    Mangalappalli-Illathu, Anil K; Lawrence, John R; Swerhone, George D W; Korber, Darren R

    2008-03-31

    Salmonella enterica serovar Enteritidis is a significant biofilm-forming pathogen. The influence of a 10-fold difference in nutrient laminar flow velocity on the dynamics of Salmonella Enteritidis biofilm formation and protein expression profiles were compared in order to ascertain how flow velocity influenced biofilm structure and function. Low-flow (0.007 cm s(-1)) biofilms consisted of diffusely-arranged microcolonies which grew until merging by approximately 72 h. High-flow (0.07 cm s(-1)) biofilms were significantly thicker (36+/-3 microm (arithmetic mean+/-standard error; n=225) versus 16+/-2 microm for low-flow biofilms at 120 h) and consisted of large bacterial mounds interspersed by water channels. Lectin-binding analysis of biofilm exopolymers revealed a significantly higher (P<0.05) proportion of N-acetylgalactosamine (GalNAc) in low-flow biofilms (55.2%), relative to only 1.2% in high-flow biofilms. Alternatively, the proportions of alpha-L-fucose and N-acetylglucosamine (GlcNAc2)-N-acetylneuraminic acid (NeuNAc) polymer-conjugates were significantly higher (P<0.05) in high-flow biofilms (69.1% and 29.6%, respectively) than low-flow biofilms (33.1% and 11.7%, respectively). Despite an apparent flow rate-based physiologic effect on biofilm structure and exopolymer composition, no major shift in whole-cell protein expression patterns was seen between 168 h-old low-flow and high-flow biofilms, and notably did not include any response involving the stress response proteins, DnaK, SodB, and Tpx. Proteins involved in degradation and energy metabolism (PduA, GapA, GpmA, Pgk, and RpiA), RNA and protein biosynthesis (Tsf, TufA, and RpoZ), cell processes (Crr, MalE, and PtsH), and adaptation (GrcA), and some hypothetical proteins (YcbL and YnaF) became up-regulated in both biofilm systems relative to a 168 h-old planktonic cell control. Our results indicate that Salmonella Enteritidis biofilms altered their structure and extracellular glycoconjugate composition

  1. Analysing flow patterns in degraded peat soils using TiO2 dye

    NASA Astrophysics Data System (ADS)

    Liu, Haojie; Lennartz, Bernd

    2014-05-01

    Dye tracing is a valuable method for studying the flow patterns in soils. However, limited information is available on water flow and solute transport pathways in dark colored peat soils because the frequently used Brilliant Blue FCF dye does not visibly stain the soil. In this study, we were aiming at testing the suitability of Titanium dioxide (TiO2) as a dye tracer for dark peat soils. The objectives were to quantify the physical properties of different degraded peat soils and visualize the flow patterns. Soil samples were collected from two low-lying fen sites, where the top soil was highly degraded, while lower horizons were less decomposed. Dye tracer experiments were conducted at both sites by applying a TiO2 suspension (10 g/l) with a pulse of 40 mm. Soil profiles were prepared for photo documentation the following day. It was found that the physical and hydraulic properties of peat were significantly influenced by the degree of peat decomposition and degradation. Higher decomposed and degraded peat soils had a higher bulk density, lower organic matter content and lower porosity. Moreover, higher decomposition and degradation resulted in a lower saturated hydraulic conductivity as long as investigated samples originated from the same site. In addition, degraded peat soils showed less anisotropy than un-degraded peat. It turned out that TiO2 is a suitable dye tracer to visualize the flow paths in peat soils. Although dye patterns differed within the same plot and between different plots, most of the flow patterns indicated a preferential flow situation. The distribution of TiO2 in the soil profile, as analyzed from 5 by 5 cm grid cells, compared to the distribution of bromide, which was applied along with the dye confirming the suitability of the dye tracer. Un-decomposed plant structures, such as wood branches and leaves, were identified as the major preferential flow path in un-degraded peat. For degraded peat, bio-pores, such as root and earthworm

  2. Pattern formation in the flow between two horizontal coaxial cylinders with a partially filled gap

    NASA Astrophysics Data System (ADS)

    Mutabazi, Innocent; Hegseth, John J.; Andereck, C. David; Wesfreid, Jose E.

    1988-11-01

    Flow between two horizontal coaxial cylinders with a partially filled gap is subject to several types of centrifugal instabilities which lead to the formation of a variety of spatial patterns. An experimental investigation has shown that there are five distinct branches of primary instabilities occurring in the system and that four codimension-2 points are easily reached. Theoretical predictions are in qualitative agreement with the observations.

  3. Film flows and self-organized patterns of 2D-localized structures

    SciTech Connect

    Frenkel, A.L.

    1996-12-31

    Films flowing down an inclined plane are considered. An unconventional perturbation approach is discussed. It yields the most general evolution equation for film thickness and the least restrictive conditions for its validity. Results of numerical simulations of the dissipative-dispersive evolution equation indicate that novel, more complex type of spatiotemporal patterns can exist for strange attractors of nonequilibrium systems. It is suggested that real-life experiments satisfying the validity conditions of this theory are possible.

  4. PROCESS FLOW FOR CLASSIFICATION AND CLUSTERING OF FRUIT FLY GENE EXPRESSION PATTERNS

    PubMed Central

    Heffel, Andreas; Stadler, Peter F.; Prohaska, Sonja J.; Kauer, Gerhard; Kuska, Jens-Peer

    2009-01-01

    The rapidly growing collection of fruit fly embryo images makes automated Image Segmentation and classification an indispensable requirement for a large-scale analysis of in situ hybridization (ISH) – gene expression patterns (GEP). We present here such an automated process flow for Segmenting, Classification, and Clustering large-scale sets of Drosophila melanogaster GEP that is capable of dealing with most of the complications implicated in the images. PMID:20046820

  5. Patterns of steady axisymmetric supersonic compression flows with a Mach disk

    NASA Astrophysics Data System (ADS)

    Gounko, Yu. P.

    2017-05-01

    Results of a numerical simulation of steady axisymmetric supersonic flows in convergent conical ducts and in overexpanded jets are presented. The characteristic feature of these compression flows is the formation of an initial longitudinally curved shock wave with intensity increasing downstream and toward the flow axis, which is finalized by the generation of a central Mach disk. Computations have demonstrated patterns of an irregular interaction of these shocks followed by the formation of a triple-shock configuration, including a reflected shock and a shear layer with entropy varying across the layer. The formation of triple-shock configurations is analogous to the configurations known for the steady inviscid two-dimensional flows where the irregular reflection of a wedge-generated shock from a wall with Mach stem formation occurs. Either a single triple-shock Mach configuration occurs or a triple-shock configuration corresponding to the von Neumann paradox condition is formed at the considered flow Mach numbers and initial angles of deflection to the axis of the flow behind the longitudinally curved shock wave.

  6. Patterns of steady axisymmetric supersonic compression flows with a Mach disk

    NASA Astrophysics Data System (ADS)

    Gounko, Yu. P.

    2016-11-01

    Results of a numerical simulation of steady axisymmetric supersonic flows in convergent conical ducts and in overexpanded jets are presented. The characteristic feature of these compression flows is the formation of an initial longitudinally curved shock wave with intensity increasing downstream and toward the flow axis, which is finalized by the generation of a central Mach disk. Computations have demonstrated patterns of an irregular interaction of these shocks followed by the formation of a triple-shock configuration, including a reflected shock and a shear layer with entropy varying across the layer. The formation of triple-shock configurations is analogous to the configurations known for the steady inviscid two-dimensional flows where the irregular reflection of a wedge-generated shock from a wall with Mach stem formation occurs. Either a single triple-shock Mach configuration occurs or a triple-shock configuration corresponding to the von Neumann paradox condition is formed at the considered flow Mach numbers and initial angles of deflection to the axis of the flow behind the longitudinally curved shock wave.

  7. Two-dimensional surface river flow patterns measured with paired RiverSondes

    USGS Publications Warehouse

    Teague, C.C.; Barrick, D.E.; Lilleboe, P.M.; Cheng, R.T.

    2008-01-01

    Two RiverSondes were operated simultaneously in close proximity in order to provide a two-dimensional map of river surface velocity. The initial test was carried out at Threemile Slough in central California. The two radars were installed about 135 m apart on the same bank of the channel. Each radar used a 3-yagi antenna array and determined signal directions using direction finding. The slough is approximately 200 m wide, and each radar processed data out to about 300 m, with a range resolution of 15 m and an angular resolution of 1 degree. Overlapping radial vector data from the two radars were combined to produce total current vectors at a grid spacing of 10 m, with updates every 5 minutes. The river flow in the region, which has a maximum velocity of about 0.8 m/s, is tidally driven with flow reversals every 6 hours, and complex flow patterns were seen during flow reversal. The system performed well with minimal mutual interference. The ability to provide continuous, non-contact two-dimensional river surface flow measurements will be useful in several unique settings, such as studies of flow at river junctions where impacts to juvenile fish migration are significant. Additional field experiments are planned this year on the Sacramento River. ?? 2007 IEEE.

  8. Two-dimensional surface river flow patterns measured with paired RiverSondes

    USGS Publications Warehouse

    Teague, C.C.; Barrick, D.E.; Lilleboe, P.M.; Cheng, R.T.

    2007-01-01

    Two RiverSondes were operated simultaneously in close proximity in order to provide a two-dimensional map of river surface velocity. The initial test was carried out at Threemile Slough in central California. The two radars were installed about 135 m apart on the same bank of the channel. Each radar used a 3-yagi antenna array and determined signal directions using direction finding. The slough is approximately 200 m wide, and each radar processed data out to about 300 m, with a range resolution of 15 m and an angular resolution of 1 degree. Overlapping radial vector data from the two radars were combined to produce total current vectors at a grid spacing of 10 m, with updates every 5 minutes. The river flow in the region, which has a maximum velocity of about 0.8 m/s, is tidally driven with flow reversals every 6 hours, and complex flow patterns were seen during flow reversal. The system performed well with minimal mutual interference. The ability to provide continuous, non-contact two-dimensional river surface flow measurements will be useful in several unique settings, such as studies of flow at river junctions where impacts to juvenile fish migration are significant. Additional field experiments are planned this year on the Sacramento River. ?? 2007 IEEE.

  9. Effect of Static Deformation on Basic Flow Patterns in Thermocapillary-Driven Free Liquid Film

    NASA Astrophysics Data System (ADS)

    Fei, Linhao; Ikebukuro, Koichi; Katsuta, Takeshi; Kaneko, Toshihiro; Ueno, Ichiro; Pettit, Donald R.

    2016-11-01

    A series of terrestrial, parabolic-flight and on-orbit experiments on thermocapillary-driven flows in free liquid films are carried out. We focus on the basic flow patterns induced in the film formed in a rectangular hole by varying the film volume in order to make a comparison with the results of the fluid physics experiments under microgravity conditions conducted by one of the authors, Pettit, on the International Space Station. The free liquid film is formed in a rectangular hole of O(0.1 mm) in thickness under a designated temperature difference between the end walls. The temperature dependence of the surface tension results in a non-uniform surface tension distribution over the free surfaces. A liquid generally has a negative temperature coefficient of surface tension; i.e., the fluid over a free surface is driven from a higher-temperature region to a lower-temperature region. In the case of a thin free liquid film with two free surfaces, however, an unusual flow pattern is realized. That is, the fluid seems to be driven toward the heated region from a colder region. In order to understand the physical mechanism of this behavior in the free liquid film, a series of on-orbit and ground experiments were conducted. We indicate several flow patterns in the film and corresponding film profiles as well as the surface temperature distribution. We also try to illustrate the cross-sectional flow structures in the thin free liquid film with two free surfaces.

  10. Effect of Static Deformation on Basic Flow Patterns in Thermocapillary-Driven Free Liquid Film

    NASA Astrophysics Data System (ADS)

    Fei, Linhao; Ikebukuro, Koichi; Katsuta, Takeshi; Kaneko, Toshihiro; Ueno, Ichiro; Pettit, Donald R.

    2017-02-01

    A series of terrestrial, parabolic-flight and on-orbit experiments on thermocapillary-driven flows in free liquid films are carried out. We focus on the basic flow patterns induced in the film formed in a rectangular hole by varying the film volume in order to make a comparison with the results of the fluid physics experiments under microgravity conditions conducted by one of the authors, Pettit, on the International Space Station. The free liquid film is formed in a rectangular hole of O(0.1 mm) in thickness under a designated temperature difference between the end walls. The temperature dependence of the surface tension results in a non-uniform surface tension distribution over the free surfaces. A liquid generally has a negative temperature coefficient of surface tension; i.e., the fluid over a free surface is driven from a higher-temperature region to a lower-temperature region. In the case of a thin free liquid film with two free surfaces, however, an unusual flow pattern is realized. That is, the fluid seems to be driven toward the heated region from a colder region. In order to understand the physical mechanism of this behavior in the free liquid film, a series of on-orbit and ground experiments were conducted. We indicate several flow patterns in the film and corresponding film profiles as well as the surface temperature distribution. We also try to illustrate the cross-sectional flow structures in the thin free liquid film with two free surfaces.

  11. Impact of non-idealities in gas-tracer tests on the estimation of reaeration, respiration, and photosynthesis rates in streams.

    PubMed

    Knapp, Julia L A; Osenbrück, Karsten; Cirpka, Olaf A

    2015-10-15

    Estimating respiration and photosynthesis rates in streams usually requires good knowledge of reaeration at the given locations. For this purpose, gas-tracer tests can be conducted, and reaeration rate coefficients are determined from the decrease in gas concentration along the river stretch. The typical procedure for analysis of such tests is based on simplifying assumptions, as it neglects dispersion altogether and does not consider possible fluctuations and trends in the input signal. We mathematically derive the influence of these non-idealities on estimated reaeration rates and how they are propagated onto the evaluation of aerobic respiration and photosynthesis rates from oxygen monitoring. We apply the approach to field data obtained from a gas-tracer test using propane in a second-order stream in Southwest Germany. We calculate the reaeration rate coefficients accounting for dispersion as well as trends and uncertainty in the input signals and compare them to the standard approach. We show that neglecting dispersion significantly underestimates reaeration, and results between sections cannot be compared if trends in the input signal of the gas tracer are disregarded. Using time series of dissolved oxygen and the various estimates of reaeration, we infer respiration and photosynthesis rates for the same stream section, demonstrating that the bias and uncertainty of reaeration using the different approaches significantly affects the calculation of metabolic rates.

  12. Generalized quantum efficiency analysis for non-ideal solar cells: Case of Cu{sub 2}ZnSnSe{sub 4}

    SciTech Connect

    Hages, Charles J.; Carter, Nathaniel J.; Agrawal, Rakesh

    2016-01-07

    Detailed quantum efficiency (QE) analysis of a nanoparticle-based Cu{sub 2}ZnSnSe{sub 4} (CZTSe) solar cell has been conducted to understand photogenerated carrier collection in the device. Specifically, voltage-dependent analysis has been considered to characterize both diffusion limitations and recombination limitations to carrier collection. Application of a generalized QE model and corresponding experimental and analytical procedures are presented to account for non-ideal device behavior, with specific consideration of photogenerated charge trapping, finite absorber thickness, back-surface recombination, and recombination of photogenerated carriers via interface, space-charge-region limited, and/or band tail limited recombination mechanisms. Analysis of diffusion limited collection results in extraction of the minority carrier diffusion length, mobility, back surface recombination velocity, and absorption coefficient. Additionally, forward bias QE measurements afford analysis of the dominant recombination mechanism for photogenerated carriers. For the analyzed CZTSe device, diffusion limitations are not expected to play a significant role in carrier collection in forward bias. However, voltage-dependent carrier collection, previously identified to contribute to open-circuit voltage limitations, is attributed to high recombination rates via band tail states/potential fluctuations in forward bias. A consideration of the assumptions commonly applied to diffusion length, band gap, and band tail extraction is also discussed.

  13. Two-phase flow pattern recognition in a varying section based on void fraction and pressure measurements

    NASA Astrophysics Data System (ADS)

    de Kerret, F.; Benito, I.; Béguin, C.; Pelletier, D.; Etienne, S.

    2016-11-01

    In a hydroelectric turbine, the air injected during operation has an impact on the yield of the machine leading to important losses of energy. To understand those losses and be able to reduce them, a first step is to understand the pattern of the two-phase flows and describe their characteristics in the turbine. Those two-phase flows can be bubbly, intermittent, or annular, with different types of intermittent flow possible. Two-phase flow patterns are well defined in classical geometries such as cylinders with reliable descriptions available [5]. But, there is a critical lack of knowledge for flow patterns in other geometries. In our present work we take interest into a geometry that is a pipe with periodical changes of the section and realize a flow pattern map. To realize this map, we measure the pressure variations and void fraction fluctuations while changing the flow rates of water and air in our test section. We then use our physical understanding of the phenomena to analyze data and identify different flow patterns, characterize them, and build a new flow pattern map.

  14. Design of a High Viscosity Couette Flow Facility for Patterned Surface Drag Measurements

    NASA Astrophysics Data System (ADS)

    Johnson, Tyler; Lang, Amy

    2009-11-01

    Direct drag measurements can be difficult to obtain with low viscosity fluids such as air or water. In this facility, mineral oil is used as the working fluid to increase the shear stress across the surface of experimental models. A mounted conveyor creates a flow within a plexiglass tank. The experimental model of a flat or patterned surface is suspended above a moving belt. Within the gap between the model and moving belt a Couette flow with a linear velocity profile is created. PIV measurements are used to determine the exact velocities and the Reynolds numbers for each experiment. The model is suspended by bars that connect to the pillow block housing of each bearing. Drag is measured by a force gauge connected to linear roller bearings that slide along steel rods. The patterned surfaces, initially consisting of 2-D cavities, are embedded in a plexiglass plate so as to keep the total surface area constant for each experiment. First, the drag across a flat plate is measured and compared to theoretical values for laminar Couette flow. The drag for patterned surfaces is then measured and compared to a flat plate.

  15. Affinity flow fractionation of cells via transient interactions with asymmetric molecular patterns

    NASA Astrophysics Data System (ADS)

    Bose, Suman; Singh, Rishi; Hanewich-Hollatz, Mikhail; Shen, Chong; Lee, Chia-Hua; Dorfman, David M.; Karp, Jeffrey M.; Karnik, Rohit

    2013-07-01

    Flow fractionation of cells using physical fields to achieve lateral displacement finds wide applications, but its extension to surface molecule-specific separation requires labeling. Here we demonstrate affinity flow fractionation (AFF) where weak, short-range interactions with asymmetric molecular patterns laterally displace cells in a continuous, label-free process. We show that AFF can directly draw neutrophils out of a continuously flowing stream of blood with an unprecedented 400,000-fold depletion of red blood cells, with the sorted cells being highly viable, unactivated, and functionally intact. The lack of background erythrocytes enabled the use of AFF for direct enumeration of neutrophils by a downstream detector, which could distinguish the activation state of neutrophils in blood. The compatibility of AFF with capillary microfluidics and its ability to directly separate cells with high purity and minimal sample preparation will facilitate the design of simple and portable devices for point-of-care diagnostics and quick, cost-effective laboratory analysis.

  16. Blood flow patterns in an anatomically realistic coronary vessel: influence of three different reconstruction methods.

    PubMed

    Berthier, B; Bouzerar, R; Legallais, C

    2002-10-01

    Many clinical studies suggest that local blood flow patterns are involved in the location and development of atherosclerosis. In coronary diseases, this assumption should be corroborated by quantitative information on local hemodynamic parameters such as pressure, velocity or wall shear stress. Nowadays, computational fluid dynamics (CFD) algorithms coupled to realistic 3-D reconstructions of such vessels make these data accessible. Nevertheless, they should be carefully analysed to avoid misinterpretations when the physiological parameters are not all considered. As an example, we propose here to compare the flow patterns calculated in a coronary vessel reconstructed by three different methods. In the three cases, the vessel trajectory respected the physiology. In the simplest reconstruction, the coronary was modelled by a tube of constant diameter while in the most complex one, the cross-sections corresponded to the reality. We showed that local pressures, wall shear rates and velocity profiles were severely affected by the geometrical modifications. In the constant cross-section vessel, the flow resembled to that of Poiseuille in a straight tube. On the contrary, velocity and shear rate exhibited sudden local variations in the more realistic vessels. As an example, velocity could be multiplied by 5 as compared to Poiseuille's flow and area of very low wall shear rates appeared. The results obtained with the most complex model clearly outlined that, in addition to a proper description of the vessel trajectory, the section area changes should be carefully taken into account, confirming assumptions already highlighted before the rise of commercially available and efficient CFD softwares.

  17. Pressure-flow characteristics of normal and disordered esophageal motor patterns.

    PubMed

    Singendonk, Maartje M J; Kritas, Stamatiki; Cock, Charles; Ferris, Lara F; McCall, Lisa; Rommel, Nathalie; van Wijk, Michiel P; Benninga, Marc A; Moore, David; Omari, Taher I

    2015-03-01

    To perform pressure-flow analysis (PFA) in a cohort of pediatric patients who were referred for diagnostic manometric investigation. PFA was performed using purpose designed Matlab-based software. The pressure-flow index (PFI), a composite measure of bolus pressurization relative to flow and the impedance ratio, a measure of the extent of bolus clearance failure were calculated. Tracings of 76 pediatric patients (32 males; 9.1 ± 0.7 years) and 25 healthy adult controls (7 males; 36.1 ± 2.2 years) were analyzed. Patients mostly had normal motility (50%) or a category 4 disorder and usually weak peristalsis (31.5%) according to the Chicago Classification. PFA of healthy controls defined reference ranges for PFI ≤142 and impedance ratio ≤0.49. Pediatric patients with pressure-flow (PF) characteristics within these limits had normal motility (62%), most patients with PF characteristics outside these limits also had an abnormal Chicago Classification (61%). Patients with high PFI and disordered motor patterns all had esophagogastric junction outflow obstruction. Disordered PF characteristics are associated with disordered esophageal motor patterns. By defining the degree of over-pressurization and/or extent of clearance failure, PFA may be a useful adjunct to esophageal pressure topography-based classification. Copyright © 2015 Elsevier Inc. All rights reserved.

  18. Analysis of fluid flow and wall shear stress patterns inside partially filled agitated culture well plates.

    PubMed

    Salek, M Mehdi; Sattari, Pooria; Martinuzzi, Robert J

    2012-03-01

    The appearance of highly resistant bacterial biofilms in both community and hospitals environments is a major challenge in modern clinical medicine. The biofilm structural morphology, believed to be an important factor affecting the behavioral properties of these "super bugs", is strongly influenced by the local hydrodynamics over the microcolonies. Despite the common use of agitated well plates in the biology community, they have been used rather blindly without knowing the flow characteristics and influence of the rotational speed and fluid volume in these containers. The main purpose of this study is to characterize the flow in these high-throughput devices to link local hydrodynamics to observed behavior in cell cultures. In this work, the flow and wall shear stress distribution in six-well culture plates under planar orbital translation is simulated using Computational Fluid Dynamics (CFD). Free surface, flow pattern and wall shear stress for two shaker speeds (100 and 200 rpm) and two volumes of fluid (2 and 4 mL) were investigated. Measurements with a non-intrusive optical shear stress sensor and High Frame-rate Particle Imaging Velocimetry (HFPIV) are used to validate CFD predictions. An analytical model to predict the free surface shape is proposed. Results show a complex three-dimensional flow pattern, varying in both time and space. The distribution of wall shear stress in these culture plates has been related to the topology of flow. This understanding helps explain observed endothelial cell orientation and bacterial biofilm distributions observed in culture dishes. The results suggest that the mean surface stress field is insufficient to capture the underlying dynamics mitigating biological processes.

  19. Patterns and rates of ground-water flow on Long Island, New York

    USGS Publications Warehouse

    Buxton, Herbert T.; Modica, Edward

    1992-01-01

    Increased ground-water contamination from human activities on Long Island has prompted studies to define the pattern and rate of ground-water movement. A two-dimensional, fine-mesh, finite-element model consisting of 11,969 nodes and 22,880 elements was constructed to represent ground-water flow along a north-south section through central Long Island. The model represents average hydrologic conditions within a corridor approximately 15 miles wide. The model solves discrete approximations of both the potential and stream functions. The resulting flownet depicts flow paths and defines the vertical distribution of flow within the section. Ground-water flow rates decrease with depth. Sixty-two percent of the water flows no deeper than the upper glacial (water-table) aquifer, 38 percent enters the underlying Magothy aquifer, and only 3.1 percent enters the Lloyd aquifer. The limiting streamlines for flow to the Magothy and Lloyd aquifers indicate that aquifer recharge areas are narrow east-west bands through the center of the island. The recharge area of the Magothy aquifer is only 5.4 miles wide; that of the Lloyd aquifer is less than 0.5 miles. The distribution of ground-water traveltime and a flownet are calculated from model results; both are useful in the investigation of contaminant transport or the chemical evolution of ground water within the flow system. A major discontinuity in traveltime occurs across the streamline which separates the flow subsystems of the two confined aquifers. Water that reaches the Lloyd aquifer attains traveltimes as high as 10,000 years, whereas water that has not penetrated deeper than the Magothy aquifer attains traveltimes of only 2,000 years. The finite-element approach used in this study is particularly suited to ground-water systems that have complex hydrostratigraphy and cross-sectional symmetry.

  20. Invasion Patterns During Two-phase Flow In Deformable Porous Media

    NASA Astrophysics Data System (ADS)

    Eriksen, Fredrik K.; Toussaint, Renaud; Jørgen Måløy, Knut; Grude Flekkøy, Eirik

    2016-04-01

    We will present our experimental study of the viscous fingering and fracturing patterns that occur when air at constant overpressure invades a circular Hele-Shaw cell containing a liquid-saturated deformable porous medium [1] - i.e. during the flow of two non-miscible fluids in a confined granular medium at high enough rate to deform it. The resulting patterns are characterized in terms of growth rate, average finger thickness as function of radius and time, and fractal properties. Based on experiments with various injection pressures, we identify and compare typical pattern characteristics when there is no deformation, compaction, and/or decompaction of the porous medium. This is achieved by preparing monolayers of glass beads in cells with various boundary conditions, ranging from a rigid disordered porous medium to a deformable granular medium with either a semi-permeable or a free outer boundary. We show that the patterns formed have characteristic features depending on the boundary conditions. For example, the average finger thickness is found to be constant with radius in the non-deformable system, while in the deformable ones there is a larger initial thickness decreasing to the non-deformable value. Then, depending on whether the outer boundary is semi-permeable or free there is a further decrease or increase in the average finger thickness. When estimated from the flow patterns, the box-counting fractal dimensions Db= 1.59±0.06 are not found to change significantly with boundary conditions, but by using a method to locally estimate fractal dimensions, we see a transition in behavior with radius for patterns in deformable systems; In the deformable system with a free boundary, it seems to be a transition in universality class as the local fractal dimensions decrease towards the outer rim, where fingers are opening up like fractures in a paste. In addition, we show a collapse of mass N plotted as function of radius r for the patterns at different snapshots

  1. Invasion patterns during two-phase flow in deformable porous media

    NASA Astrophysics Data System (ADS)

    Eriksen, Fredrik; Toussaint, Renaud; Måløy, Knut Jørgen; Flekkøy, Eirik

    2015-10-01

    We study the formation of viscous fingering and fracturing patterns that occur when air at constant overpressure invades a circular Hele-Shaw cell containing a liquid-saturated deformable porous medium -- i.e. during the flow of two non-miscible fluids in a confined granular medium at high enough rate to deform it. The resulting patterns are characterized in terms of growth rate, average finger thickness as function of radius and time, and fractal properties. Based on experiments with various injection pressures, we identify and compare typical pattern characteristics when there is no deformation, compaction, and/or decompaction of the porous medium. This is achieved by preparing monolayers of glass beads in cells with various boundary conditions, ranging from a rigid disordered porous medium to a deformable granular medium with either a semi-permeable or a free outer boundary. We show that the patterns formed have characteristic features depending on the boundary conditions. For example, the average finger thickness is found to be constant with radius in the non-deformable system, while in the deformable ones there is a larger initial thickness decreasing to the non-deformable value. Then, depending on whether the outer boundary is semi-permeable or free there is a further decrease or increase in the average finger thickness. When estimated from the flow patterns, the box-counting fractal dimensions are not found to change significantly with boundary conditions, but by using a method to locally estimate fractal dimensions, we see a transition in behavior with radius for patterns in deformable systems; In the deformable system with a free boundary, it seems to be a transition in universality class as the local fractal dimensions decrease towards the outer rim, where fingers are opening up like fractures in a paste.

  2. Flow-pattern analysis of artificial heart valves using high-speed camera and PIV technique

    NASA Astrophysics Data System (ADS)

    Lee, Dong Hyuk; Seo, Soo W.; Min, Byong Goo

    1995-05-01

    Artificial heart valve is one of the most important artificial organs which have been implanted to many patients. The most serious problems related to the artificial heart valve prothesis are thrombosis and hemolysis. In vivo experiment to test against this problem is complex and hard work. Nowadays the request for in vitro artificial heart valve testing system is increasing. Several papers have announced us that the flow pattern of artificial heart valve is highly correlated with thrombosis and hemolysis. LDA is a usual method to get flow pattern, which is difficult to operate, is expensive and has narrow measure region. PIV (Particle Image Velocimetry) can solve these problems. Because the flow speed of valve is too high to catch particles by CCD camera and high-speed camera (Hyspeed; Holland-Photonics) was used. The estimated max flow speed was 5 m/sec and max trackable length is 0.5 cm, so the shutter speed was determined as 1000 frames per sec. Several image processing techniques (blurring, segmentation, morphology, etc.) were used for the preprocessing. Particle tracking algorithm and 2D interpolation technique which were necessary in making gridrized velocity profile, were applied to this PIV program. By using Single- Pulse Multi-Frame particle tracking algorithm, some problems of PIV can be solved. To eliminate particles which penetrate the sheeted plane and to determine the direction of particle paths are these. 1D relaxation formula is modified to interpolate 2D field. Parachute artificial heart valve which was developed by Scoul National University and Bjork-Shiely valve was testified. For each valve, different flow pattern, velocity profile, wall shear stress, turbulence intensity profile and mean velocity were obtained. Those parameters were compared with the result of in vivo experiment. In this experiment we can conclude wall shear stress is not high enough to generate hemolysis and higher turbulence intensity to make more hemolysis. For further

  3. Linking fault pattern with groundwater flow in crystalline rocks at the Grimsel Test Site (Switzerland)

    NASA Astrophysics Data System (ADS)

    Schneeberger, Raphael; Berger, Alfons; Mäder, Urs K.; Niklaus Waber, H.; Kober, Florian; Herwegh, Marco

    2017-04-01

    Water flow across crystalline bedrock is of major interest for deep-seated geothermal energy projects as well as for underground disposal of radioactive waste. In crystalline rocks enhanced fluid flow is related to zones of increased permeability, i.e. to fractures that are associated to fault zones. The flow regime around the Grimsel Test Site (GTS, Central Aar massif) was assessed by establishing a 3D fault zone pattern on a local scale in the GTS underground facility (deca-meter scale) and on a regional scale at the surface (km-scale). The study reveals the existence of a dense fault zone network consisting of several km long and few tens of cm to meter wide, sub-vertically oriented major faults that are connected by tens to hundreds of meters long minor bridging faults. This geometrical information was used as input for the generation of a 3D fault zone network model. The faults originate from ductile shear zones that were reactivated as brittle faults under retrograde conditions during exhumation. Embrittlement and associated dilatancy along the faults provide the pathways for today's groundwater flow. Detection of the actual 3D flow paths is, however, challenging since flow seem to be not planar but rather tube-like. Two strategies are applied to constrain the 3D geometry of the flow tubes: (i) Characterization of the groundwater infiltrating into the GTS (location, yield, hydraulic head, and chemical composition) and (ii) stress modelling on the base of the 3D structural model to unravel potential domains of enhanced fluid flow such as fault plane intersections and domains of dilatancy. At the Grimsel Test Site, hydraulic and structural data demonstrate that the groundwater flow is head-driven from the surface towards the GTS located some 450 m below the surface. The residence time of the groundwater in this surface-near section is >60 years as evidenced by absence of detectable tritium. However, hydraulic heads obtained from interval pressure measurements

  4. Flow patterns and heat convection in a rectangular water bolus for use in superficial hyperthermia.

    PubMed

    Birkelund, Yngve; Jacobsen, Svein; Arunachalam, Kavitha; Maccarini, Paolo; Stauffer, Paul R

    2009-07-07

    This paper investigates both numerically and experimentally the spatio-temporal effects of water flow in a custom-made water bolus used for superficial hyperthermia generated by a 915-MHz, 4 x 3 microwave applicator array. Similar hyperthermia models referenced in the literature use a constant water temperature and uniform heat flux to describe conduction and convection energy exchange within the heating apparatus available to cool the tissue surface. The results presented in this paper show that the spatially varying flow pattern and rate are vital factors for the overall heat control applicability of the 5 mm thick bolus under study. Regions with low flow rates and low heat convection clearly put restrictions on the maximum microwave energy possible within the limits of skin temperature rise under the bolus. Our analysis is illustrated by experimental flow front studies using a contrast liquid set-up monitored by high definition video and complemented by numerical analysis of liquid flow and heat exchange within the rectangular water bolus loaded by malignant tissue. Important factors for the improvement of future bolus designs are also discussed in terms of diameter and configuration of the water input and output tubing network.

  5. Flow patterns and heat convection in a rectangular water bolus for use in superficial hyperthermia

    NASA Astrophysics Data System (ADS)

    Birkelund, Yngve; Jacobsen, Svein; Arunachalam, Kavitha; Maccarini, Paolo; Stauffer, Paul R.

    2009-07-01

    This paper investigates both numerically and experimentally the spatio-temporal effects of water flow in a custom-made water bolus used for superficial hyperthermia generated by a 915-MHz, 4 × 3 microwave applicator array. Similar hyperthermia models referenced in the literature use a constant water temperature and uniform heat flux to describe conduction and convection energy exchange within the heating apparatus available to cool the tissue surface. The results presented in this paper show that the spatially varying flow pattern and rate are vital factors for the overall heat control applicability of the 5 mm thick bolus under study. Regions with low flow rates and low heat convection clearly put restrictions on the maximum microwave energy possible within the limits of skin temperature rise under the bolus. Our analysis is illustrated by experimental flow front studies using a contrast liquid set-up monitored by high definition video and complemented by numerical analysis of liquid flow and heat exchange within the rectangular water bolus loaded by malignant tissue. Important factors for the improvement of future bolus designs are also discussed in terms of diameter and configuration of the water input and output tubing network.

  6. Flow patterns and heat convection in a rectangular water bolus for use in superficial hyperthermia

    PubMed Central

    Birkelund, Yngve; Jacobsen, Svein; Arunachalam, Kavitha; Maccarini, Paolo; Stauffer, Paul R

    2009-01-01

    This paper investigates both numerically and experimentally the spatio-temporal effects of water flow in a custom made water bolus used for superficial hyperthermia generated by a 915-MHz, 4 × 3 microwave applicator array. Similar hyperthermia models referenced in the literature use a constant water temperature and uniform heat flux to describe conduction and convection energy exchange within the heating apparatus available to cool the tissue surface. The results presented in this paper show that the spatially varying flow pattern and rate are vital factors for the overall heat control applicability of the 5 mm thick bolus under study. Regions with low flow rates and low heat convection clearly put restrictions on the maximum microwave energy possible within the limits of skin temperature rise under the bolus. Our analysis is illustrated by experimental flow front studies using a contrast liquid setup monitored by high definition video and complemented by numerical analysis of liquid flow and heat exchange within the rectangular water bolus loaded by malignant tissue. Important factors for improvement of future bolus designs are also discussed in terms of diameter and configuration of the water input and output tubing network. PMID:19494426

  7. Pattern formation of Dictystelium discoideum in the presence of laminar flow and cAMP pulses

    NASA Astrophysics Data System (ADS)

    Gholami, Azam; Steinbock, Oliver; Zykov, Vladimir; Bodenschatz, Eberhard

    2014-03-01

    Dictyostelium discoideum (D.d) amobae undergo starvation-induced multicellular development in which single cells aggregate chemotactically towards cAMP signals emitted periodically from an aggregation center. We are investigating spatiotemporal pattern formation of D.d. cells under the presence of a laminar flow. Starved cells are loaded into a straight millifluidic device with an external flow and cell response to the signaling molecule cAMP is monitored indirectly using dark-field microscopy. The observed contraction waves develop simultaneously over the entire channel, are propagating only in flow direction, and have curved wave fronts resembling the parabolic flow profile. The wave dynamics analysis shows that the wave velocity is locked to the flow velocity and yields a wave period of T0 6 min, which matches the typical oscillation period of extracellular cAMP in spatial homogeneous, well-stirred systems. We apply a small cAMP perturbation at the inlet region of the channel and observe the spatiotemporal response of the cells as the pulse is propagating down the channel. The results show that D.d. cells are in the oscillatory regime and the system can be forced within resonance tongue. We compared our results with analytical and numerical analysis of Goldbeter model.

  8. Effects of aeration patterns on the flow field in wastewater aeration tanks.

    PubMed

    Gresch, Markus; Armbruster, Martin; Braun, Daniel; Gujer, Willi

    2011-01-01

    Due to the high energy input of aeration, the spatial distribution of air diffusers largely determines the flow field in aeration tanks. This has consequences on the efficiency of the aeration system, the performance of the aeration tank and on tank operation and control. This paper deals with these effects applying both Computational Fluid Dynamics (CFD) enhanced with a biokinetic model and full scale validation using velocity and reactive tracer measurements with high temporal and spatial resolution. It is shown that small changes in the diffuser arrangement drastically change the overall flow field. Using different aeration patterns in the same tank may lead to large scale instabilities in the flow field that lower plant performance and produce strong variations in concentration signals impeding their use for plant control. CFD is a valuable tool to analyze the interaction of flow field and aeration and their effects on plant performance and operation. But, in complex flow situations experimental validation is needed and strongly suggested. Copyright © 2010 Elsevier Ltd. All rights reserved.

  9. Fluid flow pattern in upflow reactors of anerobic treatment of beet sugar factory wastewater

    SciTech Connect

    Heertjes, P.M.; Kuijvenhaven, L.J.; Van Der Meer, R.R.

    1982-01-01

    Residence-time-distribution experiments for the fluid in a 30-m cubed pilot plant and a 200-m cubed prototype upflow reactor were performed by means of continuous injection of an LiCl solution as a tracer in the influent of the reactor and measurement of the response of this stimulus on several locations in the reactor and in the effluent. In a similar way as described in an article published earlier, models have been developed by use of the measured data of the fluid flow pattern which consisted of regions of ideal mixing, plug flow, dead space, and short circuiting. It appeared that the fluid flow patterns in the two reactors were to a large extent analogous. For the pilot plant, three-mixer models appeared to be appropriate while for the prototype reactor two-mixer models have been found. This difference was a result of the difference in the heights of the sludge beds in the reactor: 2-3 m in the pilot plant and only 0.4 m in the prototype reactor, a result of too small an amount of sludge. Another difference was that, due to a large amount of mud in the prototype reactor, a region of dead space occurred in the models for the fluid flow pattern in this reactor. The dimensions of the prototype reactor have been chosen according to several recommendations obtained from work with the pilot plant, (e.g., scale-up should be done by increasing the cross section of the reactor; one influent point should be applied per 5 m squared bottom surface). The results presented here clearly show the value of these recommendations. (Refs. 7).

  10. A landscape lake flow pattern design approach based on automated CFD simulation and parallel multiple objective optimization.

    PubMed

    Guo, Hao; Tian, Yimei; Shen, Hailiang; Wang, Yi; Kang, Mengxin

    A design approach for determining the optimal flow pattern in a landscape lake is proposed based on FLUENT simulation, multiple objective optimization, and parallel computing. This paper formulates the design into a multi-objective optimization problem, with lake circulation effects and operation cost as two objectives, and solves the optimization problem with non-dominated sorting genetic algorithm II. The lake flow pattern is modelled in FLUENT. The parallelization aims at multiple FLUENT instance runs, which is different from the FLUENT internal parallel solver. This approach: (1) proposes lake flow pattern metrics, i.e. weighted average water flow velocity, water volume percentage of low flow velocity, and variance of flow velocity, (2) defines user defined functions for boundary setting, objective and constraints calculation, and (3) parallels the execution of multiple FLUENT instances runs to significantly reduce the optimization wall-clock time. The proposed approach is demonstrated through a case study for Meijiang Lake in Tianjin, China.

  11. Modeling of heavy-gas effects on airfoil flows

    NASA Technical Reports Server (NTRS)

    Drela, Mark

    1992-01-01

    Thermodynamic models were constructed for a calorically imperfect gas and for a non-ideal gas. These were incorporated into a quasi one dimensional flow solver to develop an understanding of the differences in flow behavior between the new models and the perfect gas model. The models were also incorporated into a two dimensional flow solver to investigate their effects on transonic airfoil flows. Specifically, the calculations simulated airfoil testing in a proposed high Reynolds number heavy gas test facility. The results indicate that the non-idealities caused significant differences in the flow field, but that matching of an appropriate non-dimensional parameter led to flows similar to those in air.

  12. Pulmonary venous flow and mitral inflow velocity pattern in uncomplicated obesity: evidence for late diastolic dysfunction.

    PubMed

    Mureddu, G F; Celentano, A; Pasanisi, F; Greco, R; Rocco, A; Contaldo, F; de Simone, G

    2000-03-01

    Active left ventricular relaxation, assessed by Doppler isovolumic relaxation time, is impaired in obesity. There is little information on left ventricular passive properties during filling. To evaluate left ventricular late diastolic stiffness in obesity, Doppler echocardiographic interrogation of mitral inflow tract and pulmonary vein flow velocities were obtained from 47 normotensive, young obese subjects (11 males, 36 females) and 43 normotensive, young normal-weight volunteers (13 males, 30 females) of comparable age. After controlling the effect of blood pressure and left ventricular mass, isovolumic relaxation time was prolonged in obese subjects (p < 0.0001 vs normal-weight controls). No difference was found in transmitral peak early and late flow velocities. Obese subjects exhibited prolonged pulmonary vein reverse flow velocity during atrial contraction (p < 0.004), and a higher difference or ratio between duration of pulmonary reverse flow and duration of transmitral forward late flow (6 +/- 31 vs -20 +/- 39 ms or 1.06 +/- 0.3 vs 0.84 +/- 0.3, p < 0.002 and p < 0.001, respectively). These differences were also confirmed after controlling blood pressure and left ventricular mass. Non-invasively estimated left ventricular end-diastolic pressure was higher in obese subjects than in controls (p < 0.002). At multivariate analysis a higher body mass index was the sole predictor of prolonged difference between duration of pulmonary reverse flow and duration of transmitral forward late flow (beta = 0.38, p < 0.001). Obesity is associated with prolonged left ventricular active relaxation and abnormalities of filling pressure not detectable by the sole mitral inflow velocity pattern. These latter abnormalities are consistent with the presence of early increased left ventricular passive stiffness.

  13. A probabilistic approach to quantifying spatial patterns of flow regimes and network-scale connectivity

    NASA Astrophysics Data System (ADS)

    Garbin, Silvia; Alessi Celegon, Elisa; Fanton, Pietro; Botter, Gianluca

    2017-04-01

    The temporal variability of river flow regime is a key feature structuring and controlling fluvial ecological communities and ecosystem processes. In particular, streamflow variability induced by climate/landscape heterogeneities or other anthropogenic factors significantly affects the connectivity between streams with notable implication for river fragmentation. Hydrologic connectivity is a fundamental property that guarantees species persistence and ecosystem integrity in riverine systems. In riverine landscapes, most ecological transitions are flow-dependent and the structure of flow regimes may affect ecological functions of endemic biota (i.e., fish spawning or grazing of invertebrate species). Therefore, minimum flow thresholds must be guaranteed to support specific ecosystem services, like fish migration, aquatic biodiversity and habitat suitability. In this contribution, we present a probabilistic approach aiming at a spatially-explicit, quantitative assessment of hydrologic connectivity at the network-scale as derived from river flow variability. Dynamics of daily streamflows are estimated based on catchment-scale climatic and morphological features, integrating a stochastic, physically based approach that accounts for the stochasticity of rainfall with a water balance model and a geomorphic recession flow model. The non-exceedance probability of ecologically meaningful flow thresholds is used to evaluate the fragmentation of individual stream reaches, and the ensuing network-scale connectivity metrics. A multi-dimensional Poisson Process for the stochastic generation of rainfall is used to evaluate the impact of climate signature on reach-scale and catchment-scale connectivity. The analysis shows that streamflow patterns and network-scale connectivity are influenced by the topology of the river network and the spatial variability of climatic properties (rainfall, evapotranspiration). The framework offers a robust basis for the prediction of the impact of

  14. Heat flow and seismicity patterns in the vicinity of the eastern Snake River Plain, Idaho

    SciTech Connect

    Blackwell, D.D. Kelley, S.A.; Steele, J.L. . Dept. of Geological Sciences)

    1993-04-01

    New heat flow data and thermal modeling are used to calculate crustal temperatures in and adjacent to the eastern Snake River Plain (SRP). The estimated crustal temperature are then used to investigate the relationship between crustal strength and the observed parabolic pattern of seismicity around the SRP. Heat flow below the SRP aquifer in deep wells on the Idaho National Engineering Laboratory (INEL) site near the northern margin of the SRP is 107 [plus minus] 15 mWm[sup [minus]2]. Heat flow values from deep wells on both the northern and southern margins of the eastern SRP average 100 [plus minus] 15 mWm[sup [minus]2]. 2-D finite-difference thermal models were developed to fit seismic and heat flow data in the vicinity of the SRP. The models have a shallow silicic magma chamber that is as wide as the SRP. The silicic chamber is underlain by mafic heat sources in the middle to lower crust and in the upper mantle. The heat flow data are best fit by models with deep heat sources that are wider than the SRP. These results are consistent with the presence of young basaltic centers that have been observed outside the SRP. The temperature from the authors thermal models were used to calculate strength envelopes for the crust in the SRP/Basin and Range region. The weakest part of the crust is along the edge of the Basin and Range, where it is heated by the SRP; thus the boundary to the two provinces may be a zone of weak coupling. Their modeling indicates that it is difficult to explain the earthquake pattern in the vicinity of the SRP as a thermomechanical effect related to the passage of the Yellowstone hot spot.

  15. A clinical study on velocity patterns of pulmonary venous flow in canine heartworm disease.

    PubMed

    Shibata, T; Wakao, Y; Takahashi, M

    2000-02-01

    In this study, we evaluated methods of determining the velocity patterns of pulmonary venous flow (PVF) in dogs and then investigated the relationship of the patterns to cardiac functions in heartworm disease (HD) by transthoracic echocardiography (TTE). The results revealed that there was a good correlation between PVF patterns determined by transesophageal echocardiography (TEE) and TTE in animals lying on their left sides. The measurement of S and D wave velocities (PVS and PVD) by TTE was shown to allow clinical determination of the velocity patterns of PVF in dogs. The HD groups showed significant increases in PVS and PVD, and S and D wave time-velocity integrals (S-TVI and D-TVI) of the right cranial lobe PVF, when compared with the normal group, as determined by TTE (P<0.05). In contrast, the HD groups produced significant decreases in PVD and D-TVI of the right caudal lobe PVF compared with the normal group (P<0.05), and a significant increase in the ratio of S-TVI to (S-TVI + D-TVI) (P<0.05). It is, therefore, suggested that measurement of the velocity patterns of the right cranial and caudal lobe PVF could be one method of assessing the stages of obstructive lesions in the pulmonary artery.

  16. Non-ideal diffusion effects, short-range ordering, and unsteady-state effects strongly influence Brownian aggregation rates in concentrated dispersions of interacting spheres.

    PubMed

    Kelkar, Aniruddha V; Franses, Elias I; Corti, David S

    2015-08-21

    Brownian aggregation rates are determined for concentrated dispersions of interacting particles with Brownian dynamics (BD) simulations and various theoretical models. Using simulation results as benchmarks, the predictions of the classical Fuchs-Smoluchowski (FS) model are shown to be quite inaccurate for concentrated dispersions. A new aggregation model is presented which provides significantly improved predictions. This model is developed on the basis of the fundamental measure theory (FMT) which is a rigorous "liquid-state" dynamic density-functional theory (DDFT) approach. It provides a major improvement of the FS model by considering short-range ordering, non-ideal diffusion, and unsteady-state effects. These were recently shown by the authors to play important roles in Brownian aggregation of hard spheres at high concentrations. Two types of interparticle interaction potentials are examined, the purely attractive van der Waals potential and the DLVO potential which includes van der Waals attraction and electrostatic double layer repulsion. For dispersions of particles with purely attractive interactions, the FS model underpredicts the aggregation rates by up to 1000 fold. In the presence of strong interparticle repulsive forces, its predictions are in fair agreement with the BD simulation results for dilute systems with particle volume fractions ϕ < < 0.1. In contrast, the predictions of the new FM-DDFT based model compare favorably with the BD simulation results, in both cases, up to ϕ = 0.3. A new quantitative measure for colloidal dispersion stability, different from the classical FS stability ratio, is proposed on the basis of aggregation half-times. Hence, a better mechanistic understanding of Brownian aggregation is obtained for concentrated dispersions of particles with either attractive or repulsive interactions, or both.

  17. Apatite-Melt Partitioning at 1 Bar: An Assessment of Apatite-Melt Exchange Equilibria Resulting from Non-Ideal Mixing of F and Cl in Apatite

    NASA Technical Reports Server (NTRS)

    McCubbin, F. M.; Ustunisik, G.; Vander Kaaden, K. E.

    2016-01-01

    The mineral apatite [Ca5(PO4)3(F,Cl,OH)] is present in a wide range of planetary materials. Due to the presence of volatiles within its crystal structure (X-site), many recent studies have attempted to use apatite to constrain the volatile contents of planetary magmas and mantle sources. In order to use the volatile contents of apatite to precisely determine the abundances of volatiles in coexisting silicate melt or fluids, thermodynamic models for the apatite solid solution and for the apatite components in multi-component silicate melts and fluids are required. Although some thermodynamic models for apatite have been developed, they are incomplete. Furthermore, no mixing model is available for all of the apatite components in silicate melts or fluids, especially for F and Cl components. Several experimental studies have investigated the apatite-melt and apatite-fluid partitioning behavior of F, Cl, and OH in terrestrial and planetary systems, which have determined that apatite-melt partitioning of volatiles are best described as exchange equilibria similar to Fe-Mg partitioning between olivine and silicate melt. However, McCubbin et al. recently reported that the exchange coefficients may vary in portions of apatite compositional space where F, Cl, and OH do not mix ideally in apatite. In particular, solution calorimetry data of apatite compositions along the F-Cl join exhibit substantial excess enthalpies of mixing. In the present study, we conducted apatite-melt partitioning experiments in evacuated, sealed silica-glass tubes at approximately 1 bar and 950-1050 degrees Centigrade on a synthetic Martian basalt composition equivalent to the basaltic shergottite Queen Alexandria Range (QUE) 94201. These experiments were conducted dry, at low pressure, to assess the effects of temperature and apatite composition on the partitioning behavior of F and Cl between apatite and basaltic melt along the F-Cl apatite binary join, where there is non-ideal mixing of F and Cl

  18. Application of chaos theory in identification of two-phase flow patterns and transitions in a small, horizontal, rectangular channel

    SciTech Connect

    Cai, Y.; Wambsganss, M.W.; Jendrzejczyk, J.A.

    1996-02-01

    Various measurement tools of chaos theory were applied to analyze two-phase pressure signals with the objective to identify and interpret flow pattern transitions for two-phase flows in a small, horizontal rectangular channel. These measurement tools included power spectral density function, autocorrelation function, pseudo-phase-plane trajectory, Lyapunov exponents, and fractal dimensions. It was demonstrated that the randomlike pressure fluctuations characteristic of two-phase flow in small rectangular channels are chaotic in nature. As such, they are governed by a high-order deterministic system. The correlation dimension is potentially a new approach for identification of certain two-phase flow patterns and transitions.

  19. Gas–liquid two-phase flow patterns in rectangular polymeric microchannels: effect of surface wetting properties

    PubMed Central

    Huh, D; Kuo, C-H; Grotberg, J B

    2010-01-01

    Here we map gas–liquid two-phase flow regimes observed in polymeric microchannels with different wetting properties. We utilized video and confocal microscopy to examine two-phase flow patterns produced by parallel injection of air and water through a Y-shaped junction into a rectangular microchannel made of poly(dimethylsiloxane) (PDMS). We observed seven flow regimes in microchannels with hydrophobic walls, whereas only two flow patterns were identified in hydrophilic microchannels. Our study demonstrates that surface wettability has a profound influence on the spatial distribution of air and water moving in microchannels. PMID:20126421

  20. Patterning of ultrathin polymethylmethacrylate films by in-situ photodirecting of the Marangoni flow

    NASA Astrophysics Data System (ADS)

    Elashnikov, Roman; Fitl, Premysl; Svorcik, Vaclav; Lyutakov, Oleksiy

    2017-02-01

    Laser heating and Marangoni flow result in the formation of surface structures with different geometries and shape on thin polymer films. By laser beam irradiation combined with a sample movement the solid polymethylmethacrylate (PMMA) films are heated and undergo phase transition which leads to a material flow. Since the laser beam has a non-linear distribution of energy, the PMMA film is heated inhomogeneously and a surface tension gradient in a lateral direction is introduced. During this procedure additional phenomena such as "reversible" or cyclic polymer flow also take place. The careful choice of experimental conditions enables the preparation of patterns with sophisticated geometries and with hierarchical pattern organization. Depending on initial PMMA film thickness and speed of the sample movement line arrays are created, which can subsequently be transformed into the crimped lines or system of circular holes. In addition, the introduction of a constant acceleration in the sample movement or a laser beam distortion enables the preparation of regularly crimped lines, ordered hexagonal holes or overlapped plates.

  1. Common patterns of energy flow and biomass distribution on weighted food webs

    NASA Astrophysics Data System (ADS)

    Zhang, Jiang; Feng, Yuanjing

    2014-07-01

    Weights of edges and nodes on food webs which are available from the empirical data hide much information about energy flows and biomass distributions in ecosystem. We define a set of variables related to weights for each species i, including the throughflow Ti, the total biomass Xi, and the dissipated flow Di (output to the environment) to uncover the following common patterns in 19 empirical weighted food webs: (1) DGBD distributions (Discrete version of a Generalized Beta Distribution), a kind of deformed Zipf's law, of energy flow and storage biomass; (2) The allometric scaling law Ti∝Xiα, which can be viewed as the counterpart of the Kleiber's 3/4 law at the population level; (3) The dissipation law Di∝Tiβ; and (4) The gravity law, including univariate version f∝( and bivariate approvement f∝Tiγ1Tjγ2. These patterns are very common and significant in all collected webs, as a result, some remarkable regularities are hidden in weights.

  2. Two-dimensional intraventricular flow pattern visualization using the image-based computational fluid dynamics.

    PubMed

    Doost, Siamak N; Zhong, Liang; Su, Boyang; Morsi, Yosry S

    2017-04-01

    The image-based computational fluid dynamics (IB-CFD) technique, as the combination of medical images and the CFD method, is utilized in this research to analyze the left ventricle (LV) hemodynamics. The research primarily aims to propose a semi-automated technique utilizing some freely available and commercial software packages in order to simulate the LV hemodynamics using the IB-CFD technique. In this research, moreover, two different physiological time-resolved 2D models of a patient-specific LV with two different types of aortic and mitral valves, including the orifice-type valves and integrated with rigid leaflets, are adopted to visualize the process of developing intraventricular vortex formation and propagation. The blood flow pattern over the whole cardiac cycle of two models is also compared to investigate the effect of utilizing different valve types in the process of the intraventricular vortex formation. Numerical findings indicate that the model with integrated valves can predict more complex intraventricular flow that can match better the physiological flow pattern in comparison to the orifice-type model.

  3. Effect of compressibility and non-uniformity in flow on the scattering pattern of acoustic cloak.

    PubMed

    Ryoo, Hyeonbin; Jeon, Wonju

    2017-05-18

    During the last decade, most of acoustic cloak research has been done within a theoretical framework in which the medium is at rest. However, such an acoustic cloak cannot preserve its unique properties or functions to make an object acoustically invisible in the presence of flow. In this study, we propose a theoretical framework to accurately investigate the effect of compressibility and non-uniformity in flow on the scattering pattern of acoustic cloak. In the formulation, the wave operator is coupled with the non-uniform velocity vector, and the equivalent source terms due to mean flow are divided into the compressibility effect and the non-uniformity effect with their own physical meanings. Numerical simulation shows the difference in far-field directivity between previous and present formulations. The polarity of the equivalent sources in the present formulation shows hexapole and skewed quadrupole patterns for non-uniformity and compressibility effects, respectively, and their magnitudes increase with power laws of Mach number as the Mach number increases. As an application, we make use of the present formulation for predicting the acoustic scattering from newly designed convective cloaks. The simulation results show better performance compared to the existing convective cloak.

  4. Baleen wear reveals intraoral water flow patterns of mysticete filter feeding.

    PubMed

    Werth, Alexander J; Straley, Janice M; Shadwick, Robert E

    2016-04-01

    A survey of macroscopic and microscopic wear patterns in the baleen of eight whale species (Cetacea: Mysticeti) discloses structural, functional, and life history properties of this neomorphic keratinous tissue, including evidence of intraoral water flow patterns involved in filter feeding. All baleen demonstrates wear, particularly on its medial and ventral edges, as flat outer layers of cortical keratin erode to reveal horn tubes, also of keratin, which emerge as hair-like fringes. This study quantified five additional categories of specific wear: pitting of plates, scratching of plates, scuffing of fringes, shortening of fringes, and reorientation of fringes (including fringes directed between plates to the exterior of the mouth). Blue whale baleen showed the most pitting and sei whale baleen the most scratching; gray whale baleen had the most fringe wear. The location of worn baleen within the mouth suggests that direct contact with the tongue is not responsible for most wear, and that flowing water as well as abrasive prey or sediment carried by the flowing water likely causes pitting and scratching of plates as well as fringe fraying, scuffing, shortening, and reorientation. Baleen also has elevated vertical and horizontal ridges that are unrelated to wear; these are probably related to growth and may allow for age determination.

  5. A D-Shaped Bileaflet Bioprosthesis which Replicates Physiological Left Ventricular Flow Patterns

    PubMed Central

    Tan, Sean Guo-Dong; Kim, Sangho; Hon, Jimmy Kim Fatt; Leo, Hwa Liang

    2016-01-01

    Prior studies have shown that in a healthy heart, there exist a large asymmetric vortex structure that aids in establishing a steady flow field in the left ventricle. However, the implantation of existing artificial heart valves at the mitral position is found to have a negative effect on this physiological flow pattern. In light of this, a novel D-shaped bileaflet porcine bioprosthesis (GD valve) has been designed based on the native geometry mitral valve, with the hypothesis that biomimicry in valve design can restore physiological left ventricle flow patterns after valve implantation. An in-vitro experiment using two dimensional particle velocimetry imaging was carried out to determine the hemodynamic performance of the new bileaflet design and then compared to that of the well-established St. Jude Epic valve which functioned as a control in the experiment. Although both valves were found to have similar Reynolds shear stress and Turbulent Kinetic Energy levels, the novel D-shape valve was found to have lower turbulence intensity and greater mean kinetic energy conservation. PMID:27258099

  6. Flow uncertainty from hurricane rain forecasted patterns obtained using a modified multivariable radar tracking technique

    NASA Astrophysics Data System (ADS)

    Corzo P, G. A.; Marquez, O.

    2012-04-01

    Different cities around Central and North American countries suffer from lack of spatial data as well as from hurricane induced floods. This paper extends a technique to project radar information into neighbor regions where the radar doesn't reach. To be able to use the precipitation patterns obtained from these projections in a flood forecasting system, it is required to know the uncertainty of such patterns. This is even more important when the region is prone to hurricanes. The hurricanes are highly dynamic and complex phenomena that commonly spread its influence in cyclic patterns. This work explores the use of projected spatial patterns of the hurricane Arlene (Category 2) from day 29 to 30 June in the basin of the Santa Catarina River in Mexico. The tracking is done by displacing the precipitation patterns in space using a data driven model (e.g. Neural Netwok). The decay of mass in the projection of hurricane event was calculated with a multivariable mixture of experts' model, using the cumulative change in mass of the whole radar information at previous time steps. A comparative