Dynamic fluid connectivity during steady-state multiphase flow in a sandstone
NASA Astrophysics Data System (ADS)
Reynolds, Catriona A.; Menke, Hannah; Andrew, Matthew; Blunt, Martin J.; Krevor, Samuel
2017-08-01
The current conceptual picture of steady-state multiphase Darcy flow in porous media is that the fluid phases organize into separate flow pathways with stable interfaces. Here we demonstrate a previously unobserved type of steady-state flow behavior, which we term “dynamic connectivity,” using fast pore-scale X-ray imaging. We image the flow of N2 and brine through a permeable sandstone at subsurface reservoir conditions, and low capillary numbers, and at constant fluid saturation. At any instant, the network of pores filled with the nonwetting phase is not necessarily connected. Flow occurs along pathways that periodically reconnect, like cars controlled by traffic lights. This behavior is consistent with an energy balance, where some of the energy of the injected fluids is sporadically converted to create new interfaces.
Dynamic fluid connectivity during steady-state multiphase flow in a sandstone.
Reynolds, Catriona A; Menke, Hannah; Andrew, Matthew; Blunt, Martin J; Krevor, Samuel
2017-08-01
The current conceptual picture of steady-state multiphase Darcy flow in porous media is that the fluid phases organize into separate flow pathways with stable interfaces. Here we demonstrate a previously unobserved type of steady-state flow behavior, which we term "dynamic connectivity," using fast pore-scale X-ray imaging. We image the flow of N2 and brine through a permeable sandstone at subsurface reservoir conditions, and low capillary numbers, and at constant fluid saturation. At any instant, the network of pores filled with the nonwetting phase is not necessarily connected. Flow occurs along pathways that periodically reconnect, like cars controlled by traffic lights. This behavior is consistent with an energy balance, where some of the energy of the injected fluids is sporadically converted to create new interfaces.
Steady-State Flows in Two-Fluid Models of NSTX and DIII-D Plasmas
NASA Astrophysics Data System (ADS)
Ferraro, N. M.; Jardin, S. C.; Chen, J.
2009-05-01
Accurate axisymmetric steady-states of a comprehensive two-fluid model are calculated for plasmas in diverted NSTX and DIII-D geometries using the M3D-C^1 code [1]. It is found that gyroviscosity may have a significant effect on the flows in steady-state when a localized density source is present. The model implemented in M3D-C^1 self-consistently includes the effects of flows, anisotropic viscosity, anisotropic thermal conductivity, and resistivity. Results for ohmically driven plasmas are presented. New capabilities of M3D-C^1 allow the three-dimensional linear stability of axisymmetric equilibria to be calculated; these capabilities and preliminary stability results are discussed. Also discussed are recent and future extensions to M3D-C^1, including heuristic bootstrap current models, coupling to a physics-based transport model, and nonlinear non-axisymmetric capability. 3pt[1] S. C. Jardin, J. Breslau, N. Ferraro, J. Comput. Phys, 226 (2007) 2146
Numerical Studies of Two-Fluid Axisymmetric Steady-States with Flow in Ohmic NSTX-like Plasmas
NASA Astrophysics Data System (ADS)
Ferraro, Nathaniel; Jardin, Stephen
2008-11-01
Axisymmetric steady-states of the resistive two-fluid equations, including flow and gyroviscosity, are obtained by evolving these nonlinear equations from an initial ideal MHD equilibrium using the code M3D-C^1 [1], which has now been extended to toroidal geometry. Steady-states for high-β, inductively driven discharges in diverted NSTX geometries are studied. Excellent agreement with theoretical predictions of cross-surface Pfirsch-Schlüter flows in the axisymmetric steady-states is found. The dependence of flow velocities with resistivity is explored. It is found that in the two-fluid model, the statistical steady-state may be a fixed point, a limit cycle, or chaotic, depending on the parameters. Two-fluid terms lead to a preferred direction of toroidal rotation. The inclusion of gyroviscosity is observed to alter the character of the steady-state. The three-dimensional linear stability of simple equilibria in this two-fluid model are also explored using M3D-C^1 [2]. [1] N. Ferraro, S. Jardin. Phys. Plasmas 13:092101 (2006). [2] S. Jardin, N. Ferraro, J. Breslau, J. Chen, and M. Chance. Initial results for linear 3D Toroidal Two-Fluid stability using M3D-C1. APS DPP Conference, Dallas, TX (2008).
Steady State Transportation Cooling in Porous Media Under Local, Non-Thermal Equilibrium Fluid Flow
NASA Technical Reports Server (NTRS)
Rodriquez, Alvaro Che
2002-01-01
An analytical solution to the steady-state fluid temperature for 1-D (one dimensional) transpiration cooling has been derived. Transpiration cooling has potential use in the aerospace industry for protection against high heating environments for re-entry vehicles. Literature for analytical treatments of transpiration cooling has been largely confined to the assumption of thermal equilibrium between the porous matrix and fluid. In the present analysis, the fundamental fluid and matrix equations are coupled through a volumetric heat transfer coefficient and investigated in non-thermal equilibrium. The effects of varying the thermal conductivity of the solid matrix and the heat transfer coefficient are investigated. The results are also compared to existing experimental data.
Gaston, L.; Glut, B.; Bellet, M.; Chenot, J.L.
1995-12-31
This paper presents a two-dimensional lagrangian-eulerian finite element approach of non-steady state Navier-Stokes fluid flows with free surfaces, like those occurring during the mould filling stage in casting processes. The proposed model is based on a mixed velocity-pressure finite element formulation, including an augmented Lagrangian technique and an iterative solver of Uzawa type. Mesh updating is carried out through an arbitrary lagrangian-eulerian method in order to describe properly the free surface evolution. Heat transfer through the fluid flow is solved by a convection-diffusion splitting technique. The efficiency of the method is illustrated on an example of gravity casting.
Saeid Khalafvand, Seyed; Han, Hai-Chao
2015-06-01
It has been shown that arteries may buckle into tortuous shapes under lumen pressure, which in turn could alter blood flow. However, the mechanisms of artery instability under pulsatile flow have not been fully understood. The objective of this study was to simulate the buckling and post-buckling behaviors of the carotid artery under pulsatile flow using a fully coupled fluid-structure interaction (FSI) method. The artery wall was modeled as a nonlinear material with a two-fiber strain-energy function. FSI simulations were performed under steady-state flow and pulsatile flow conditions with a prescribed flow velocity profile at the inlet and different pressures at the outlet to determine the critical buckling pressure. Simulations were performed for normal (160 ml/min) and high (350 ml/min) flow rates and normal (1.5) and reduced (1.3) axial stretch ratios to determine the effects of flow rate and axial tension on stability. The results showed that an artery buckled when the lumen pressure exceeded a critical value. The critical mean buckling pressure at pulsatile flow was 17-23% smaller than at steady-state flow. For both steady-state and pulsatile flow, the high flow rate had very little effect (<5%) on the critical buckling pressure. The fluid and wall stresses were drastically altered at the location with maximum deflection. The maximum lumen shear stress occurred at the inner side of the bend and maximum tensile wall stresses occurred at the outer side. These findings improve our understanding of artery instability in vivo.
Steady-state flow of an incompressible viscoelastic polymer fluid between two coaxial cylinders
NASA Astrophysics Data System (ADS)
Blokhin, A. M.; Kruglova, E. A.; Semisalov, B. V.
2017-07-01
A boundary value problem for a quasi-linear equation determining the velocity profile of a flow of a polymer fluid in a pipe formed by two coaxial cylinders is considered. On the basis of methods of approximation without saturation, a computational algorithm of increased accuracy is developed, making it possible to solve the problem in a wide range of parameters, including record-low values of r 0, the radius of the inner cylinder.
Steady-state plasma production and fluid flow in ion beams with step-function density profiles
Lemons, D.S.; Jones, M.E.; Kadish, A.; Lee, H.; Newberger, B.S.
1985-06-01
The steady-state fluid equations for plasma production and transverse flow in an ion beam with a step-function density profile are solved exactly in both slab and cylindrical geometries. The beam edge is treated as both a neutral and a non-neutral sheath. In the former, the beam density falls from its value inside the beam to zero in a distance much greater than a Debye length, while in the latter the Debye length is much greater than the beam falloff distance. Physical solutions with plasma density profiles which decrease monotonically from the beam center are shown not to exist for negative ion beams with a non-neutral sheath.
NASA Astrophysics Data System (ADS)
Pantellini, Filippo; Griton, Léa
2016-10-01
The spatial structure of a steady state plasma flow is shaped by the standing modes with local phase velocity exactly opposite to the flow velocity. The general procedure of finding the wave vectors of all possible standing MHD modes in any given point of a stationary flow requires numerically solving an algebraic equation. We present the graphical procedure (already mentioned by some authors in the 1960's) along with the exact solution for the Alfvén mode and approximate analytic solutions for both fast and slow modes. The technique can be used to identify MHD modes in space and laboratory plasmas as well as in numerical simulations.
Morris, Paul D; Silva Soto, Daniel Alejandro; Feher, Jeroen F A; Rafiroiu, Dan; Lungu, Angela; Varma, Susheel; Lawford, Patricia V; Hose, D Rodney; Gunn, Julian P
2017-08-01
Fractional flow reserve (FFR)-guided percutaneous intervention is superior to standard assessment but remains underused. The authors have developed a novel "pseudotransient" analysis protocol for computing virtual fractional flow reserve (vFFR) based upon angiographic images and steady-state computational fluid dynamics. This protocol generates vFFR results in 189 s (cf >24 h for transient analysis) using a desktop PC, with <1% error relative to that of full-transient computational fluid dynamics analysis. Sensitivity analysis demonstrated that physiological lesion significance was influenced less by coronary or lesion anatomy (33%) and more by microvascular physiology (59%). If coronary microvascular resistance can be estimated, vFFR can be accurately computed in less time than it takes to make invasive measurements.
Calculations of two-fluid magnetohydrodynamic axisymmetric steady-states
NASA Astrophysics Data System (ADS)
Ferraro, N. M.; Jardin, S. C.
2009-11-01
M3D- C1 is an implicit, high-order finite element code for the solution of the time-dependent nonlinear two-fluid magnetohydrodynamic equations [S.C. Jardin, J. Breslau, N. Ferraro, A high-order implicit finite element method for integrating the two-fluid magnetohydrodynamic equations in two dimensions, J. Comp. Phys. 226 (2) (2007) 2146-2174]. This code has now been extended to allow computations in toroidal geometry. Improvements to the spatial integration and time-stepping algorithms are discussed. Steady-states of a resistive two-fluid model, self-consistently including flows, anisotropic viscosity (including gyroviscosity) and heat flux, are calculated for diverted plasmas in geometries typical of the National Spherical Torus Experiment (NSTX) [M. Ono et al., Exploration of spherical torus physics in the NSTX device, Nucl. Fusion 40 (3Y) (2000) 557-561]. These states are found by time-integrating the dynamical equations until the steady-state is reached, and are therefore stationary or statistically steady on both magnetohydrodynamic and transport time-scales. Resistively driven cross-surface flows are found to be in close agreement with Pfirsch-Schlüter theory. Poloidally varying toroidal flows are in agreement with comparable calculations [A.Y. Aydemir, Shear flows at the tokamak edge and their interaction with edge-localized modes, Phys. Plasmas 14]. New effects on core toroidal rotation due to gyroviscosity and a local particle source are observed.
Pressure updating methods for the steady-state fluid equations
NASA Technical Reports Server (NTRS)
Fiterman, A.; Turkel, E.; Vatsa, V.
1995-01-01
We consider the steady state equations for a compressible fluid. Since we wish to solve for a range of speeds we must consider the equations in conservation form. For transonic speeds these equations are of mixed type. Hence, the usual approach is to add time derivatives to the steady state equations and then march these equations in time. One then adds a time derivative of the density to the continuity equation, a derivative of the momentum to the momentum equation and a derivative of the total energy to the energy equation. This choice is dictated by the time consistent equations. However, since we are only interested in the steady state this is not necessary. Thus we shall consider the possibility of adding a time derivative of the pressure to the continuity equation and similar modifications for the energy equation. This can then be generalized to adding combinations of time derivatives to each equation since these vanish in the steady state. When using acceleration techniques such as residual smoothing, multigrid, etc. these are applied to the pressure rather than the density. Hence, the code duplicates the behavior of the incompressible equations for low speeds.
Jaynes' MaxEnt, Steady State Flow Systems and the Maximum Entropy Production Principle
NASA Astrophysics Data System (ADS)
Niven, Robert K.
2009-12-01
Jaynes' maximum entropy (MaxEnt) principle was recently used to give a conditional, local derivation of the "maximum entropy production" (MEP) principle, which states that a flow system with fixed flow(s) or gradient(s) will converge to a steady state of maximum production of thermodynamic entropy (R. K. Niven, Phys. Rev. E, 80(2) (2009) 021113). The analysis provides a steady state analog of the MaxEnt formulation of equilibrium thermodynamics, applicable to many complex flow systems at steady state. The present study examines the classification of physical systems, with emphasis on the choice of constraints in MaxEnt. The discussion clarifies the distinction between equilibrium, fluid flow, source/sink, flow/reactive and other systems, leading into an appraisal of the application of MaxEnt to steady state flow and reactive systems.
Measuring the steady state of pedestrian flow in bottleneck experiments
NASA Astrophysics Data System (ADS)
Liao, Weichen; Tordeux, Antoine; Seyfried, Armin; Chraibi, Mohcine; Drzycimski, Kevin; Zheng, Xiaoping; Zhao, Ying
2016-11-01
Experiments with pedestrians could depend strongly on initial conditions. Comparisons of the results of such experiments require to distinguish carefully between transient state and steady state. Thus a modified version of the Cumulative Sum Control Chart algorithm is proposed to robustly detect steady states from density and speed time series of bottleneck experiments. The threshold of the detection parameter in the algorithm is calibrated using an autoregressive model. Comparing the detected steady states with manually selected ones, the modified algorithm gives robust and reproducible results. For the applications, three groups of bottleneck experiments are analysed and the steady states are detected. The results reconfirm that the specific flow is constant as bottleneck width changes. Moreover, we proposed a criterion to judge the difference between the flows in all states and in steady states, which is the ratio of pedestrian number to bottleneck width. The critical value of the ratio is found to be approximately 115 persons/m. This conclusion applies not only for the analysis of existing bottleneck experiments but also for the design of new bottleneck experiments and the validation of evacuation models. Furthermore, the range of steady state in time series of pedestrian characteristics could be effectively controlled by adjusting the value of the ratio.
Multiple steady states in coupled flow tank reactors
NASA Astrophysics Data System (ADS)
Hunt, Katharine L. C.; Kottalam, J.; Hatlee, Michael D.; Ross, John
1992-05-01
Coupling between continuous-flow, stirred tank reactors (CSTR's), each having multiple steady states, can produce new steady states with different concentrations of the chemical species in each of the coupled tanks. In this work, we identify a kinetic potential ψ that governs the deterministic time evolution of coupled tank reactors, when the reaction mechanism permits a single-variable description of the states of the individual tanks; examples include the iodate-arsenous acid reaction, a cubic model suggested by Noyes, and two quintic models. Stable steady states correspond to minima of ψ, and unstable steady states to maxima or saddle points; marginally stable states typically correspond to saddle-node points. We illustrate the variation in ψ due to changes in the rate constant for external material intake (k0) and for exchange between tanks (kx). For fixed k0 values, we analyze the changes in numbers and types of steady states as kx increases from zero. We show that steady states disappear by pairwise coalescence; we also show that new steady states may appear with increasing kx, when the reaction mechanism is sufficiently complex. For fixed initial conditions, the steady state ultimately reached in a mixing experiment may depend on the exchange rate constant as a function of time, kx(t) : Adiabatic mixing is obtained in the limit of slow changes in kx(t) and instantaneous mixing in the limit as kx(t)→∞ while t remains small. Analyses based on the potential ψ predict the outcome of mixing experiments for arbitrary kx(t). We show by explicit counterexamples that a prior theory developed by Noyes does not correctly predict the instability points or the transitions between steady states of coupled tanks, to be expected in mixing experiments. We further show that the outcome of such experiments is not connected to the relative stability of steady states in individual tank reactors. We find that coupling may effectively stabilize the tanks. We provide
Efficient Steady-State Solution Techniques for Variably Saturated Groundwater Flow
NASA Astrophysics Data System (ADS)
Farthing, M. W.; Kees, C. E.; Coffey, T. S.; Kelley, C. T.; Miller, C. T.
2002-12-01
We consider the simulation of steady-state variably saturated groundwater flow using Richards' equation. The difficulties associated with solving Richards' equation numerically are well known. Most discretization approaches for Richards' equation lead to nonlinear systems that are large and difficult to solve. The solution of nonlinear systems for steady-state problems can be particularly challenging, since a good initial guess for the steady-state solution is often hard to obtain, and the resulting linear systems may be poorly scaled. Common approaches like modified Picard iteration or variations of Newton's method have their advantages but perform poorly with standard globalization techniques under certain conditions. Pseudo-transient continuation has been used in computational fluid dynamics for some time to obtain steady-state solutions for problems in which Newton's method with standard line-search strategies fails. It combines aspects of backward Euler time integration and Newton's method to select intermediate estimates of the steady-state solution. In this work, we examine the use of pseudo-transient continuation methods for Richards' equation. We evaluate their performance for steady-state problems in heterogeneous domains by comparing them with Newton's method using standard globalization techniques. We investigate the methods' performance with both direct and preconditioned Krylov iterative linear solvers. We then make recommendations for robust and efficient approaches to obtain steady-state solutions for Richards' equation under a variety of conditions.
Numerical computation of steady-state acoustic disturbances in flow
NASA Technical Reports Server (NTRS)
Watson, W. R.; Myers, M. K.
1992-01-01
Two time domain methods for computing two dimensional steady-state acoustic disturbances propagating through internal subsonic viscous flow fields in the presence of variable area are investigated. The first method solves the Navier-Stokes equations for the combined steady and acoustic field together and subtracts the steady flow to obtain the acoustic field. The second method solves a system of perturbation equations to obtain the acoustic disturbances, making use of a separate steady flow computation as input to the system. In each case the periodic steady-state acoustic fluctuations are obtained numerically on a supercomputer using a second order unsplit explicit MacCormack predictor-corrector method. Results show that the first method is not very effective for computing acoustic disturbances of even moderate amplitude. It appears that more accurate steady flow algorithms are required for this method to succeed. On the other hand, linear and nonlinear acoustic disturbances extracted from the perturbation approach are shown to exhibit expected behavior for the problems considered. It is also found that inflow boundary conditions for an equivalent uniform duct can be successfully applied to a nonuniform duct to obtain steady-state acoustic disturbances.
Numerical computation of steady-state acoustic disturbances in flow
NASA Technical Reports Server (NTRS)
Watson, W. R.; Myers, M. K.
1992-01-01
Two time domain methods for computing two dimensional steady-state acoustic disturbances propagating through internal subsonic viscous flow fields in the presence of variable area are investigated. The first method solves the Navier-Stokes equations for the combined steady and acoustic field together and subtracts the steady flow to obtain the acoustic field. The second method solves a system of perturbation equations to obtain the acoustic disturbances, making use of a separate steady flow computation as input to the system. In each case the periodic steady-state acoustic fluctuations are obtained numerically on a supercomputer using a second order unsplit explicit MacCormack predictor-corrector method. Results show that the first method is not very effective for computing acoustic disturbances of even moderate amplitude. It appears that more accurate steady flow algorithms are required for this method to succeed. On the other hand, linear and nonlinear acoustic disturbances extracted from the perturbation approach are shown to exhibit expected behavior for the problems considered. It is also found that inflow boundary conditions for an equivalent uniform duct can be successfully applied to a nonuniform duct to obtain steady-state acoustic disturbances.
Efficient steady-state solution techniques for variably saturated groundwater flow
NASA Astrophysics Data System (ADS)
Farthing, Matthew W.; Kees, Christopher E.; Coffey, Todd S.; Kelley, C. T.; Miller, Cass T.
We consider the simulation of steady-state variably saturated groundwater flow using Richards' equation (RE). The difficulties associated with solving RE numerically are well known. Most discretization approaches for RE lead to nonlinear systems that are large and difficult to solve. The solution of nonlinear systems for steady-state problems can be particularly challenging, since a good initial guess for the steady-state solution is often hard to obtain, and the resulting linear systems may be poorly scaled. Common approaches like Picard iteration or variations of Newton's method have their advantages but perform poorly with standard globalization techniques under certain conditions. Pseudo-transient continuation has been used in computational fluid dynamics for some time to obtain steady-state solutions for problems in which Newton's method with standard line-search strategies fails. Here, we examine the use of pseudo-transient continuation as well as Newton's method combined with standard globalization techniques for steady-state problems in heterogeneous domains. We investigate the methods' performance with direct and preconditioned Krylov iterative linear solvers. We then make recommendations for robust and efficient approaches to obtain steady-state solutions for RE under a range of conditions.
NASA Technical Reports Server (NTRS)
Hersh, A. S.; Walker, B.
1978-01-01
The effects of grazing flow on the steady state flow resistance and acoustic impedance of seven Feltmetal and three Rigimesh thin porous faced liners were studied. The steady-state flow resistance of the ten specimens was measured using standard fluid mechanical experimental techniques. The acoustic impedance was measured using the two microphone method. The principal findings of the study are that the effects of grazing flow were measured and found to be small; small differences were measured between steady-state and acoustic resistance, and a semi-empirical model was derived that correlated the steady-state resistance data of the seven Feltmetal liners and the face sheet reactance of both the Feltmetal and Rigimesh liners.
Zonal Flow Growth Rates: Modulational Instability vs Statistical Steady States.
NASA Astrophysics Data System (ADS)
Krommes, J. A.; Kolesnikov, R. A.
2002-11-01
The nonlinear growth rate of zonal flows has been the subject of various investigations. The calculations can be grouped into two major classes: those based on modulational instability of a fixed pump wave;(L. Chen et al., Phys. Plasmas 7), 3129 (2000); P. N. Guzdar et al., Phys. Rev. Lett. 87, 015001 (2001); C. N. Lashmore-Davies et al., Phys. Plasmas 8, 5121 (2001). and those employing statistical formalism to describe a self-consistent, energy-conserving steady state.(J. A. Krommes and C.--B. Kim, Phys. Rev. E 62), 8508 (2000), and references therein. The results from these two approaches do not necessarily agree either in their dependence on parameters like the plasma pressure β, on the threshold for instability, or even, in some cases, on the sign. The reasons for such disagreements are isolated, and it is shown to what extent the steady-state statistical approach can be reconciled with a generic modulational instability calculation. Generalizations of the statistical formalism to the multifield systems appropriate for finite β are described. Specific calculations based on model systems are used to illustrate the general arguments.
Models of steady state cooling flows in elliptical galaxies
NASA Technical Reports Server (NTRS)
Vedder, Peter W.; Trester, Jeffrey J.; Canizares, Claude R.
1988-01-01
A comprehensive set of steady state models for spherically symmetric cooling flows in early-type galaxies is presented. It is found that a reduction of the supernova (SN) rate in ellipticals produces a decrease in the X-ray luminosity of galactic cooling flows and a steepening of the surface brightness profile. The mean X-ray temperature of the cooling flow is not affected noticeably by a change in the SN rate. The external pressure around a galaxy does not markedly change the luminosity of the gas within the galaxy but does change the mean temperature of the gas. The presence of a dark matter halo in a galaxy only changes the mean X-ray temperature slightly. The addition of a distribution of mass sinks which remove material from the general accretion flow reduces L(X) very slightly, flattens the surface brightness profile, and reduces the central surface brightness level to values close to those actually observed. A reduction in the stellar mass-loss rate only slightly reduces the X-ray luminosity of the cooling flow and flattens the surface brightness by a small amount.
NASA Astrophysics Data System (ADS)
Tsakiroglou, C. D.; Avraam, D. G.; Payatakes, A. C.
2007-09-01
The water krw and oil kro relative permeability curves of a glass-etched planar pore network are estimated with history matching from transient displacement experiments performed at varying values of the capillary number, Ca, for two fluid systems: one of intermediate and one of strong wettability. The transient k,k are compared to corresponding ones measured with the steady-state method on the same porous medium [Avraam DG, Payatakes AC. Flow regimes and relative permeabilities during steady-state two-phase flow in porous media. J Fluid Mech 1995;293:207-36; Avraam DG, Payatakes AC. Generalized relative permeability coefficients during steady-state two-phase flow in porous media and correlation with the flow mechanisms. Transport Porous Med 1995;20:135-68; Avraam DG, Payatakes AC. Flow mechanisms, relative permeabilities, and coupling effects in steady-state two-phase flow through porous media. The case of strong wettability. Ind Eng Chem Res 1999;38:778-86.], and potential differences from them are interpreted in the light of the differences between the transient growth pattern, and the steady-state two-phase flow regime. For intermediate wettability, the transient kro and krw exceed the corresponding steady-state functions at low Ca values and have the tendency to become smaller than the steady-state ones at high Ca values. For strong wettability, the transient kro and krw are increasing functions of Ca, the transient kro is higher than the steady-state one, whereas the transient krw decreases substantially and becomes lower than the steady-state one at low Ca values. The dynamic capillary pressure estimated from transient experiments is a decreasing function of Ca in agreement with previous theoretical and experimental studies.
From arteries to boreholes: steady-state response of a poroelastic cylinder to fluid injection
NASA Astrophysics Data System (ADS)
Auton, L. C.; MacMinn, C. W.
2017-05-01
The radially outward flow of fluid into a porous medium occurs in many practical problems, from transport across vascular walls to the pressurization of boreholes. As the driving pressure becomes non-negligible relative to the stiffness of the solid structure, the poromechanical coupling between the fluid and the solid has an increasingly strong impact on the flow. For very large pressures or very soft materials, as is the case for hydraulic fracturing and arterial flows, this coupling can lead to large deformations and, hence, to strong deviations from a classical, linear-poroelastic response. Here, we study this problem by analysing the steady-state response of a poroelastic cylinder to fluid injection. We consider the qualitative and quantitative impacts of kinematic and constitutive nonlinearity, highlighting the strong impact of deformation-dependent permeability. We show that the wall thickness (thick versus thin) and the outer boundary condition (free versus constrained) play a central role in controlling the mechanics.
Existence of a steady state of a natural convective flow in a confined medium
NASA Astrophysics Data System (ADS)
Pignatel, J.-F.; Marcillat, J.
1983-04-01
Experimental results are presented from a study of convective flow in a parallelipiped-shaped cavity with walls maintained at different temperatures. Resistive heaters permitted varying the wall temperatures up to 150 C, and the container could be tilted from 0-90 deg. Air was used as the fluid medium, with Rayleigh numbers from 2000-1,000,000. The flows studied featured the appearances of both steady and unsteady instabilities. Attention was given to vertical movements and a two-dimensional numerical model was defined. Attempts were made to identify the limits of a steady state in terms of the Rayleigh number, the shape factors, and the tilt of the cavity.
Modeling of the blood rheology in steady-state shear flows
Apostolidis, Alex J.; Beris, Antony N.
2014-05-15
We undertake here a systematic study of the rheology of blood in steady-state shear flows. As blood is a complex fluid, the first question that we try to answer is whether, even in steady-state shear flows, we can model it as a rheologically simple fluid, i.e., we can describe its behavior through a constitutive model that involves only local kinematic quantities. Having answered that question positively, we then probe as to which non-Newtonian model best fits available shear stress vs shear-rate literature data. We show that under physiological conditions blood is typically viscoplastic, i.e., it exhibits a yield stress that acts as a minimum threshold for flow. We further show that the Casson model emerges naturally as the best approximation, at least for low and moderate shear-rates. We then develop systematically a parametric dependence of the rheological parameters entering the Casson model on key physiological quantities, such as the red blood cell volume fraction (hematocrit). For the yield stress, we base our description on its critical, percolation-originated nature. Thus, we first determine onset conditions, i.e., the critical threshold value that the hematocrit has to have in order for yield stress to appear. It is shown that this is a function of the concentration of a key red blood cell binding protein, fibrinogen. Then, we establish a parametric dependence as a function of the fibrinogen and the square of the difference of the hematocrit from its critical onset value. Similarly, we provide an expression for the Casson viscosity, in terms of the hematocrit and the temperature. A successful validation of the proposed formula is performed against additional experimental literature data. The proposed expression is anticipated to be useful not only for steady-state blood flow modeling but also as providing the starting point for transient shear, or more general flow modeling.
Giant Casimir effect in fluids in nonequilibrium steady states.
Kirkpatrick, T R; Ortiz de Zárate, J M; Sengers, J V
2013-06-07
In this Letter, we consider the fluctuation-induced force exerted between two plates separated by a distance L in a fluid with a temperature gradient. We predict that for a range of distances L, this nonequilibrium force is anomalously large compared to other Casimir forces. The physical reason is that correlations in a nonequilibrium fluid are generally of longer range than other correlations, even than those near an equilibrium critical point. This giant Casimir force is related to a divergent Burnett coefficient that characterizes an Onsager cross effect between the pressure and the temperature gradient. The predicted Casimir force should be detectable with currently available experimental techniques.
Vesicle dynamics in a confined Poiseuille flow: From steady state to chaos
NASA Astrophysics Data System (ADS)
Aouane, Othmane; Thiébaud, Marine; Benyoussef, Abdelilah; Wagner, Christian; Misbah, Chaouqi
2014-09-01
Red blood cells (RBCs) are the major component of blood, and the flow of blood is dictated by that of RBCs. We employ vesicles, which consist of closed bilayer membranes enclosing a fluid, as a model system to study the behavior of RBCs under a confined Poiseuille flow. We extensively explore two main parameters: (i) the degree of confinement of vesicles within the channel and (ii) the flow strength. Rich and complex dynamics for vesicles are revealed, ranging from steady-state shapes (in the form of parachute and slipper shapes) to chaotic dynamics of shape. Chaos occurs through a cascade of multiple periodic oscillations of the vesicle shape. We summarize our results in a phase diagram in the parameter plane (degree of confinement and flow strength). This finding highlights the level of complexity of a flowing vesicle in the small Reynolds number where the flow is laminar in the absence of vesicles and can be rendered turbulent due to elasticity of vesicles.
Steady-State Axial Temperature and Flow Velocity in Triga Channel.
ZEFRAN, BOJAN
2007-02-28
Version 00 TRISTAN-IJS is a computer program for calculating steady-state axial temperature distribution and flow velocity through a vertical coolant channel in low power TRIGA reactor core, cooled by natural circulation. It is designed for steady-state thermohydraulic analysis of TRIGA research reactors operating at a low power level of 1-2 MW.
Erpelding, Marion; Sinha, Santanu; Tallakstad, Ken Tore; Hansen, Alex; Flekkøy, Eirik Grude; Måløy, Knut Jørgen
2013-11-01
It is well known that the transient behavior during drainage or imbibition in multiphase flow in porous media strongly depends on the history and initial condition of the system. However, when the steady-state regime is reached and both drainage and imbibition take place at the pore level, the influence of the evolution history and initial preparation is an open question. Here, we present an extensive experimental and numerical work investigating the history dependence of simultaneous steady-state two-phase flow through porous media. Our experimental system consists of a Hele-Shaw cell filled with glass beads which we model numerically by a network of disordered pores transporting two immiscible fluids. From measurements of global pressure evolution, histograms of saturation, and cluster-size distributions, we find that when both phases are flowing through the porous medium, the steady state does not depend on the initial preparation of the system or on the way it has been reached.
Velocity dependence of biphasic flow structuration: steady-state and oscillating flow effects
NASA Astrophysics Data System (ADS)
Tore Tallakstad, Ken; Jankov, Mihailo; Løvoll, Grunde; Toussaint, Renaud; Jørgen Mâløy, Knut; Grude Flekkøy, Eirik; Schmittbuhl, Jean; Schäfer, Gerhard; Méheust, Yves; Arendt Knudsen, Henning
2010-05-01
We study various types of biphasic flows in quasi-two-dimensional transparent porous models. These flows imply a viscous wetting fluid, and a lowly viscous one. The models are transparent, allowing the displacement process and structure to be monitored in space and time. Three different aspects will be presented: 1. In stationary biphasic flows, we study the relationship between the macroscopic pressure drop (related to relative permeability) and the average flow rate, and how this arises from the cluster size distribution of the lowly viscous fluid [1]. 2. In drainage situations, we study how the geometry of the invader can be explained, and how it gives rise to apparent dynamic capillary effects. We show how these can be explained by viscous effects on evolving geometries of invading fluid [2]. 3. We study the impact of oscillating pressure fields superimposed to a background flow over the flow regimes patterns [3]. Steady-State Two-Phase Flow in Porous Media: Statistics and Transport Properties. First, in stationary flow with a control of the flux of both fluids, we show how the pressure drop depends on the flow rate. We will show that the dynamics is dominated by the interplay between a viscous pressure field from the wetting fluid and bubble transport of a less viscous, nonwetting phase. In contrast with more studied displacement front systems, steady-state flow is in equilibrium, statistically speaking. The corresponding theoretical simplicity allows us to explain a data collapse in the cluster size distribution of lowly viscous fluid in the system, as well as the relation |?P|∞√Ca--. This allows to explain so called relative permeability effects by the morphological changes of the cluster size distribution. Influence of viscous fingering on dynamic saturation-pressure curves in porous media. Next, we study drainage in such models, and investigate the relationship between the pressure field and the morphology of the invading fluid. This allows to model
Liu, H. H.
2010-09-15
Optimality principles have been used for investigating physical processes in different areas. This work attempts to apply an optimal principle (that water flow resistance is minimized on global scale) to steady-state unsaturated flow processes. Based on the calculus of variations, we show that under optimal conditions, hydraulic conductivity for steady-state unsaturated flow is proportional to a power function of the magnitude of water flux. This relationship is consistent with an intuitive expectation that for an optimal water flow system, locations where relatively large water fluxes occur should correspond to relatively small resistance (or large conductance). Similar results were also obtained for hydraulic structures in river basins and tree leaves, as reported in other studies. Consistence of this theoretical result with observed fingering-flow behavior in unsaturated soils and an existing model is also demonstrated.
Bifurcation analysis of steady-state flows in the lid-driven cavity
NASA Astrophysics Data System (ADS)
Nuriev, A. N.; Egorov, A. G.; Zaitseva, O. N.
2016-12-01
The paper is devoted to the study of the non-uniqueness issues of a steady-state flow in the square lid-driven cavity. A range 0\\lt {Re} \\lt 20000 of Reynolds numbers is considered in which a numerical bifurcation analysis is carried out. The analysis allows us to localize several branches of the steady-state solution and also to investigate their stability.
NASA Astrophysics Data System (ADS)
Gedeon, M.; Mallants, D.
2012-04-01
Radionuclide concentration predictions in aquifers play an important role in estimating impact of planned surface disposal of radioactive waste in Belgium, developed by the Belgian Agency for Radioactive Waste and Enriched Fissile Materials (ONDRAF), who also coordinates and leads the corresponding research. Long-term concentration predictions are based on a steady-state flow solution obtained by a cascade of multi-scale models from the catchment to the detailed (site) scale performed in MODFLOW. To test the concept and accuracy of the groundwater flow solution and conservativeness of the concentration predictions obtained therewith, a transient model, considered more realistic, was set up in a sub-domain of the intermediate scale steady-state model. Besides the modelling domain reduction, the transient model was and exact copy of the steady-state model, having the infiltration as the only time-varying parameter. The transient model was run for a twenty-year period, whereas the results were compared to the steady-state results based on infiltration value and observations averaged over the same period. The comparison of the steady-state and transient flow solutions includes the analyses of the goodness of fit, the parameter sensitivities, relative importance of the individual observations and one-percent sensitivity maps. The steady-state and transient flow solutions were subsequently translated into a site-scale transport model, used to predict the radionuclide concentrations in a hypothetical well in the aquifers. The translation of the flow solutions between the models of distinct scales was performed using the Local grid refinement method available in MODFLOW. In the site-scale models, MT3DMS transport simulations were performed to obtain respective concentration predictions in a hypothetical well, situated at 70 meters from the disposal tumuli. The equilibrium concentrations based on a constant source flux achieved using a steady-state solution were then
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.
Steady-state magnetohydrodynamic flow around an unmagnetized conducting sphere
Romanelli, N.; Gómez, D.; Bertucci, C.; Delva, M. E-mail: Magda.Delva@oeaw.ac.at
2014-07-01
The noncollisional interaction between conducting obstacles and magnetized plasma winds can be found in different scenarios, from the interaction occurring between regions inside galaxy clusters to the interaction between the solar wind and Mars, Venus, and active comets, or even the interaction between Titan and the Saturnian magnetospheric flow. These objects generate, through several current systems, perturbations in the streaming magnetic field leading to its draping around the obstacle's effective conducting surface. Recent observational results suggest that several properties associated with magnetic field draping, such as the location of the polarity reversal layer of the induced magnetotail, are affected by variations in the conditions of the streaming magnetic field. To improve our understanding of these phenomena, we perform a characterization of several magnetic field draping signatures by analytically solving an ideal problem in which a perfectly conducting magnetized plasma (with frozen-in magnetic field conditions) flows around a spherical body for various orientations of the streaming magnetic field. In particular, we compute the shift of the inverse polarity reversal layer as the orientation of the background magnetic field is changed.
Behavior of Drag Disc Turbine Transducers in Steady-State Two-Phase Flow
NASA Astrophysics Data System (ADS)
Solbrig, C. W.; Reimann, J.
1980-08-01
Many experiments being conducted to investigate the hypothesized loss-of-coolant accident (LOCA) in nuclear power plants involve the measurement of two-phase flow. This paper describes an experiment conducted to determine the behavior of a drag-disc turbine transducer (DTT) in a high pressure, high temperature, steam-water steady state environment. DTTs have been used extensively to measure mass flow rates in the Loss-of-Fluid-Test (LOFT) experiments. Drag discs and turbines have been used in many other safety related facilities. However, the performance of these instruments is highly dependent on flow regime and void fraction and this dependence makes data analysis difficult. Experiments conducted in separated flow are described in this paper. The results show the measured mass flow rates can be corrected if a three-beam gamma densitometer is available, if the calculated density ratio correction is less than three, and if the velocity measured by the turbine is greater than 2 m/ s. The results also suggest that the turbine and drag disc measure local mass average quantities averaged over the area of the DTT.
H.R. Barnard; C.B. Graham; W.J. van Verseveld; J.R. Brooks; B.J. Bond; J.J. McDonnell
2010-01-01
Mechanistic assessment of how transpiration influences subsurface flow is necessary to advance understanding of catchment hydrology. We conducted a 24-day, steady-state irrigation experiment to quantify the relationships among soil moisture, transpiration and hillslope subsurface flow. Our objectives were to: (1) examine the time lag between maximum transpiration and...
Programmable calculator uses equation to figure steady-state gas-pipeline flow
Holmberg, E.
1982-04-26
Because it is accurate and consistent over a wide range of variables, the Colebrook-White (C-W) formula serves as the basis for many methods of calculating turbulent flow in gas pipelines. Oilconsult reveals a simple way to adapt the C-W formula to calculate steady-state pipeline flow using the TI-59 programmable calculator.
Dust Devil Steady-State Structure from a Fluid Dynamics Perspective
NASA Astrophysics Data System (ADS)
Kurgansky, Michael V.; Lorenz, Ralph D.; Renno, Nilton O.; Takemi, Tetsuya; Gu, Zhaolin; Wei, Wei
2016-11-01
Simple analytical models for the flow structure of dust devils in steady state, and a "thermophysical" scaling theory that explains how these flow structures are maintained are reviewed. Then, results from high-resolution numerical simulations are used to provide insights into the structure of dust-devil-like vortices and study the impact of surface roughness on them. The article concludes with an overview of the influence of lofted dust on the flow structure of dust devils and a discussion of open questions.
NASA Astrophysics Data System (ADS)
Koroglu, Batikan; Mehl, Marco; Armstrong, Michael R.; Crowhurst, Jonathan C.; Weisz, David G.; Zaug, Joseph M.; Dai, Zurong; Radousky, Harry B.; Chernov, Alex; Ramon, Erick; Stavrou, Elissaios; Knight, Kim; Fabris, Andrea L.; Cappelli, Mark A.; Rose, Timothy P.
2017-09-01
We present the development of a steady state plasma flow reactor to investigate gas phase physical and chemical processes that occur at high temperature (1000 < T < 5000 K) and atmospheric pressure. The reactor consists of a glass tube that is attached to an inductively coupled argon plasma generator via an adaptor (ring flow injector). We have modeled the system using computational fluid dynamics simulations that are bounded by measured temperatures. In situ line-of-sight optical emission and absorption spectroscopy have been used to determine the structures and concentrations of molecules formed during rapid cooling of reactants after they pass through the plasma. Emission spectroscopy also enables us to determine the temperatures at which these dynamic processes occur. A sample collection probe inserted from the open end of the reactor is used to collect condensed materials and analyze them ex situ using electron microscopy. The preliminary results of two separate investigations involving the condensation of metal oxides and chemical kinetics of high-temperature gas reactions are discussed.
Saeid Khalafvand, Seyed; Han, Hai-Chao
2015-01-01
It has been shown that arteries may buckle into tortuous shapes under lumen pressure, which in turn could alter blood flow. However, the mechanisms of artery instability under pulsatile flow have not been fully understood. The objective of this study was to simulate the buckling and post-buckling behaviors of the carotid artery under pulsatile flow using a fully coupled fluid–structure interaction (FSI) method. The artery wall was modeled as a nonlinear material with a two-fiber strain-energy function. FSI simulations were performed under steady-state flow and pulsatile flow conditions with a prescribed flow velocity profile at the inlet and different pressures at the outlet to determine the critical buckling pressure. Simulations were performed for normal (160 ml/min) and high (350 ml/min) flow rates and normal (1.5) and reduced (1.3) axial stretch ratios to determine the effects of flow rate and axial tension on stability. The results showed that an artery buckled when the lumen pressure exceeded a critical value. The critical mean buckling pressure at pulsatile flow was 17–23% smaller than at steady-state flow. For both steady-state and pulsatile flow, the high flow rate had very little effect (<5%) on the critical buckling pressure. The fluid and wall stresses were drastically altered at the location with maximum deflection. The maximum lumen shear stress occurred at the inner side of the bend and maximum tensile wall stresses occurred at the outer side. These findings improve our understanding of artery instability in vivo. PMID:25761257
Minimization of a free-energy-like potential for non-equilibrium flow systems at steady state
Niven, Robert K.
2010-01-01
This study examines a new formulation of non-equilibrium thermodynamics, which gives a conditional derivation of the ‘maximum entropy production’ (MEP) principle for flow and/or chemical reaction systems at steady state. The analysis uses a dimensionless potential function ϕst for non-equilibrium systems, analogous to the free energy concept of equilibrium thermodynamics. Spontaneous reductions in ϕst arise from increases in the ‘flux entropy’ of the system—a measure of the variability of the fluxes—or in the local entropy production; conditionally, depending on the behaviour of the flux entropy, the formulation reduces to the MEP principle. The inferred steady state is also shown to exhibit high variability in its instantaneous fluxes and rates, consistent with the observed behaviour of turbulent fluid flow, heat convection and biological systems; one consequence is the coexistence of energy producers and consumers in ecological systems. The different paths for attaining steady state are also classified. PMID:20368250
On the Kaolinite Floc Size at the Steady State of Flocculation in a Turbulent Flow
Zhu, Zhongfan; Wang, Hongrui; Yu, Jingshan; Dou, Jie
2016-01-01
The flocculation of cohesive fine-grained sediment plays an important role in the transport characteristics of pollutants and nutrients absorbed on the surface of sediment in estuarine and coastal waters through the complex processes of sediment transport, deposition, resuspension and consolidation. Many laboratory experiments have been carried out to investigate the influence of different flow shear conditions on the floc size at the steady state of flocculation in the shear flow. Most of these experiments reported that the floc size decreases with increasing shear stresses and used a power law to express this dependence. In this study, we performed a Couette-flow experiment to measure the size of the kaolinite floc through sampling observation and an image analysis system at the steady state of flocculation under six flow shear conditions. The results show that the negative correlation of the floc size on the flow shear occurs only at high shear conditions, whereas at low shear conditions, the floc size increases with increasing turbulent shear stresses regardless of electrolyte conditions. Increasing electrolyte conditions and the initial particle concentration could lead to a larger steady-state floc size. PMID:26901652
On the Kaolinite Floc Size at the Steady State of Flocculation in a Turbulent Flow.
Zhu, Zhongfan; Wang, Hongrui; Yu, Jingshan; Dou, Jie
2016-01-01
The flocculation of cohesive fine-grained sediment plays an important role in the transport characteristics of pollutants and nutrients absorbed on the surface of sediment in estuarine and coastal waters through the complex processes of sediment transport, deposition, resuspension and consolidation. Many laboratory experiments have been carried out to investigate the influence of different flow shear conditions on the floc size at the steady state of flocculation in the shear flow. Most of these experiments reported that the floc size decreases with increasing shear stresses and used a power law to express this dependence. In this study, we performed a Couette-flow experiment to measure the size of the kaolinite floc through sampling observation and an image analysis system at the steady state of flocculation under six flow shear conditions. The results show that the negative correlation of the floc size on the flow shear occurs only at high shear conditions, whereas at low shear conditions, the floc size increases with increasing turbulent shear stresses regardless of electrolyte conditions. Increasing electrolyte conditions and the initial particle concentration could lead to a larger steady-state floc size.
LHe Flow Regime/Pressure Drop for D0 Solenoid at Steady State Conditions
Rucinski, R.; /Fermilab
1993-03-03
This paper describes in a note taking format what was learned from several sources on two phase liquid helium flow regimes and pressure drops as applied to the D-Zero solenoid upgrade project. Calculations to estimate the steady state conditions for the D-Zero solenoid at 5, 10 and 15 g/s are also presented. For the lower flow rates a stratified type regime can be expected with a pressure drop less than 0.5 psi. For the higher flow rate a more homogeneous flow regime can be expected with a pressure drop between 0.4 to 1.5 psi.
Steady-state and dynamic models of unified power flow controller (UPFC) for power system studies
Nabavi-Niaki, A.; Iravani, M.R.
1996-11-01
This paper provides comprehensive development procedures and final forms of mathematical models of unified power flow controller (UPFC) for steady-state, transient stability and eigenvalue studies. Based on the developed models, the impacts of control strategy, parameters and location of UPFC on power system operating conditions are discussed. The accuracy of the developed models is verified through comparing the study results with those obtained from detailed time-domain simulation using the Electromagnetic Transients Program (EMTP).
Blood flow patterns during incremental and steady-state aerobic exercise.
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.
Stress-Temperature Scaling for Steady-State Flow in Metallic Glasses
NASA Astrophysics Data System (ADS)
Guan, Pengfei; Chen, Mingwei; Egami, Takeshi
2010-05-01
Through computer simulation of steady-state flow in a Zr50Cu40Al10 metallic glass using a set of realistic potentials we find a simple scaling relationship between temperature and stress as they affect viscosity. The scaling relationship provides new insight into the microscopic mechanism of shear flow in the glassy state, in terms of the elastic energy of the applied stress modifying the local energy landscape. The results suggest that the plastic flow and mechanical failure in metallic glasses are consequences of stress-induced glass transition.
On the Stress-Temperature Scaling for Steady-State Flow in Metallic Glasses
Guan, Pengfei; Chen, Mingwei; Egami, T.
2010-01-01
Through computer simulation of steady-state flow in a Zr50Cu40Al10 metallic glass using a set of realistic potentials we found a simple scaling relationship between temperature and stress as they affect viscosity. The scaling relationship provides new insights for the microscopic mechanism of shear flow in the glassy state, in terms of the elastic energy of the applied stress modifying the local energy landscape. The results suggest that the plastic flow and mechanical failure in metallic glasses are consequences of stress-induced glass transition.
An analytical solution for the steady-state aerosol size distribution achieved in a steady-state, continuous flow chamber is derived, where particle growth is occurring by gas-to-particle conversion and particle loss is occurring by deposition to the walls of the chamber. The s...
An analytical solution for the steady-state aerosol size distribution achieved in a steady-state, continuous flow chamber is derived, where particle growth is occurring by gas-to-particle conversion and particle loss is occurring by deposition to the walls of the chamber. The s...
NASA Astrophysics Data System (ADS)
Brenner, Howard
2011-10-01
Linear irreversible thermodynamic principles are used to demonstrate, by counterexample, the existence of a fundamental incompleteness in the basic pre-constitutive mass, momentum, and energy equations governing fluid mechanics and transport phenomena in continua. The demonstration is effected by addressing the elementary case of steady-state heat conduction (and transport processes in general) occurring in quiescent fluids. The counterexample questions the universal assumption of equality of the four physically different velocities entering into the basic pre-constitutive mass, momentum, and energy conservation equations. Explicitly, it is argued that such equality is an implicit constitutive assumption rather than an established empirical fact of unquestioned authority. Such equality, if indeed true, would require formal proof of its validity, currently absent from the literature. In fact, our counterexample shows the assumption of equality to be false. As the current set of pre-constitutive conservation equations appearing in textbooks are regarded as applicable both to continua and noncontinua (e.g., rarefied gases), our elementary counterexample negating belief in the equality of all four velocities impacts on all aspects of fluid mechanics and transport processes, continua and noncontinua alike.
NASA Astrophysics Data System (ADS)
Rouvinskaya, Ekaterina; Korol, Alexey; Kurkina, Oxana; Kurkin, Andey; Talipova, Tatiana; Giniyatullin, Ayrat
2017-04-01
The process of long internal steady-state breather generation from sign-variable initial impulse in a three-layer fluid is studied numerically in the framework of full nonlinear (Euler) and weakly nonlinear (Gardner) hydrodynamic models. Such a wave can influence upon sediment transport, mixing of stratified layers of ocean water and also can lead to development of internal waves of anomalously large amplitudes. The comparison of results is carried out and effect of weak variation of water stratification on the generated internal wave field is studied. The influence of a constant flow on the nonlinear wave generation process is also studied. It is shown that in situations when existence of the solitary waves of the first mode is impossible, solitary waves of the second mode can appear with amplitudes comparable to the leading breather amplitude of the first mode. Keywords: internal waves; breathers; solitons; weakly nonlinear model; full nonlinear model; numerical modeling.
Simulates the Forced-Flow Chemical Vapor Infiltration in Steady State
Bessman, T. M.
1997-12-12
GTCVI is a finite volume model for steady-state simulation of forced-flow chemical vapor infiltration in either Cartesian or cylindrical coordinates. The model solves energy and momentum balances simultaneously over a given domain discretized into an array of finite volume elements. The species balances and deposition rates are determined after the energy and momentum balances converge. Density-dependent preform properties are included in the model. Transient average density, backpressure, temperature gradient, and average radial deposition rates can be summarized. Optimal infiltration conditions can be found by varying temperature, flow, and reactant concentration.
Network simulation of steady-state two-phase flow in consolidated porous media
Constantinides, G.N.; Payatakes, A.C.
1996-02-01
Multiphase flow in porous media is a complex process encountered in many fields of practical engineering interest, such as oil recovery from reservoir rocks, aquifer pollution by liquid wastes and soil reconstitution, and agricultural irrigation. A computer-aided simulator of steady-state two-phase flow in consolidated porous media is developed. The porous medium is modeled as a 3-D pore network of suitably shaped and randomly sized unit cells of the constricted-tube type. The problem of two-phase flow is solved using the network approach. The wetting phase saturation, the viscosity ratio, the capillary number, and the probability of coalescence between two colliding ganglia are changed systematically, where as the geometrical and topological characteristics of the porous medium and wettability (dynamic contact angles) are kept constant. In the range of the parameter values investigated, the flow behavior observed is ganglion population dynamics (intrinsically unsteady, but giving a time-averaged steady state). The mean ganglion size and fraction of the nonwetting phase in the form of stranded ganglia are studied as functions of the main dimensionless parameters. Fractional flows and relative permeabilities are determined and correlated with flow phenomena at pore level. Effects of the wetting phase saturation, the viscosity ratio, the capillary number, and the coalescence factor on relative permeabilities are examined.
Effect of grazing flow on steady-state resistance of isolated square-edged orifices
NASA Technical Reports Server (NTRS)
Rogers, T.
1976-01-01
Steady state diagnostic testing of an isolated orifice has shown the nature of the interaction between grazing and orifice flow causing the large increase in orifice resistance for both inflow and outflow. A simple inviscid interaction model is developed which uses thin aerofoil theory to account for pressure forces exerted at the interface between the orifice and grazing flow together with a one-dimensional discharge coefficient concept. The effect of grazing flow boundary layer thickness is also included in the model. Resistance measurements for each orifice tested, over a wide range of grazing flow speeds and flow rates, collapse into a single curve when plotted in terms of effective discharge coefficient against orifice to grazing velocity ratio. The correlation curves for inflow and outflow are different. Data for clustered orifices collapse in the same way as those for the single orifice. The effect of boundary layer thickness is compared with model predictions.
Steady-state response of a charcoal bed to radon in flowing air with water vapor
Blue, T.E.; Jarzemba, M.S.; Fentiman, A.W.
1995-06-01
Previously we have developed a mathematical model of radon adsorption in active air with water vapor on small U.S. Environmental Protection Agency charcoal canisters that are used for environmental measurements of radon. The purpose of this paper is to extend this mathematical model to describe the adsorption of radon by large charcoal beds with radon-laden air flowing through them. The resulting model equations are solved analytically to predict the steady-state adsorption of radon by such beds. 14 refs., 3 figs.
A population balance model for transient and steady-state foam flow in Boise sandstone
Kovscek, A.; Patzek, T.; Radke, C.
1995-07-01
An experimental and mechanistic-modeling study is reported for the transient flow of aqueous foam through 1.3-{mu}m{sup 2} (1.3-D) Boise sandstone at backpressures in excess of 5 MPa (700 psi) over a quality range from 0.80 to 0.99. Total superficial velocities range from as little as 0.42 to 2.20 m/day (1.4 ft/day to 7 ft/day). Sequential pressure taps and gamma-ray densitometry measure flow resistance and in-situ liquid saturations, respectively. We garner experimental pressure and saturation profiles in both the transient and steady states. Adoption of a mean-size foam-bubble conservation equation along with the traditional reservoir simulation equations allows mechanistic foam simulation. Since foam mobility depends heavily upon its texture, the bubble population balance is both useful and necessary as the role of foam texture must be incorporated into any model which seeks accurate prediction of flow properties. Our model employs capillary-pressure-dependent kinetic expressions for lamellae generation and coalescence and also a term for trapping of lamellae. Additionally, the effects of surfactant chemical transport are included. We find quantitative agreement between experimental and theoretical saturation and pressure profiles in both the transient and steady states.
Implicit unified gas-kinetic scheme for steady state solutions in all flow regimes
NASA Astrophysics Data System (ADS)
Zhu, Yajun; Zhong, Chengwen; Xu, Kun
2016-06-01
This paper presents an implicit unified gas-kinetic scheme (UGKS) for non-equilibrium steady state flow computation. The UGKS is a direct modeling method for flow simulation in all regimes with the updates of both macroscopic flow variables and microscopic gas distribution function. By solving the macroscopic equations implicitly, a predicted equilibrium state can be obtained first through iterations. With the newly predicted equilibrium state, the evolution equation of the gas distribution function and the corresponding collision term can be discretized in a fully implicit way for fast convergence through iterations as well. The lower-upper symmetric Gauss-Seidel (LU-SGS) factorization method is implemented to solve both macroscopic and microscopic equations, which improves the efficiency of the scheme. Since the UGKS is a direct modeling method and its physical solution depends on the mesh resolution and the local time step, a physical time step needs to be fixed before using an implicit iterative technique with a pseudo-time marching step. Therefore, the physical time step in the current implicit scheme is determined by the same way as that in the explicit UGKS for capturing the physical solution in all flow regimes, but the convergence to a steady state speeds up through the adoption of a numerical time step with large CFL number. Many numerical test cases in different flow regimes from low speed to hypersonic ones, such as the Couette flow, cavity flow, and the flow passing over a cylinder, are computed to validate the current implicit method. The overall efficiency of the implicit UGKS can be improved by one or two orders of magnitude in comparison with the explicit one.
NASA Astrophysics Data System (ADS)
Liakos, Anastasios; Malamataris, Nikolaos A.
2014-05-01
The topology and evolution of flow around a surface mounted cubical object in three dimensional channel flow is examined for low to moderate Reynolds numbers. Direct numerical simulations were performed via a home made parallel finite element code. The computational domain has been designed according to actual laboratory experiment conditions. Analysis of the results is performed using the three dimensional theory of separation. Our findings indicate that a tornado-like vortex by the side of the cube is present for all Reynolds numbers for which flow was simulated. A horseshoe vortex upstream from the cube was formed at Reynolds number approximately 1266. Pressure distributions are shown along with three dimensional images of the tornado-like vortex and the horseshoe vortex at selected Reynolds numbers. Finally, and in accordance to previous work, our results indicate that the upper limit for the Reynolds number for which steady state results are physically realizable is roughly 2000.
Steady-state simulation of ground-water flow in the Rush Springs Aquifer, western Oklahoma
Becker, M.F.
1998-01-01
A simplified steady-state ground-water flow model was prepared for the Rush Springs aquifer in western Oklahoma. A 3-kilometer square grid was established over the area containing two layers with 674 active nodes simulated in the model. The steady-state model simulation used a mean recharge rate of 3.05 x 10-4 feet per day and a hydraulic conductivity range from 0.8 to 10 feet per day. The error at each node in the model is defined as the difference between the measured and simulated water levels.The arithmetic mean error for 170 of the 674 active nodes was -0.11 feet, the absolute value mean error was 7.55 feet, and the standard deviation of the error was 10.21 feet. A net simulated recharge of 231 cubic feet per second is balanced by a discharge to drains and seeps of 190.6 cubic feet per second about 82 percent of the total recharge. Discharge to the main stem of the Washita River is about 41 cubic feet per second about 18 percent of the recharge.
Stable Laser-Driven Electron Beams from a Steady-State-Flow Gas Cell
Osterhoff, J.; Popp, A.; Karsch, S.; Major, Zs.; Marx, B.; Fuchs, M.; Hoerlein, R.; Gruener, F.; Habs, D.; Krausz, F.; Rowlands-Rees, T. P.; Hooker, S. M.
2009-01-22
Quasi-monoenergetic, laser-driven electron beams of up to {approx}200 MeV in energy have been generated from steady-state-flow gas cells [1]. These beams are emitted within a low-divergence cone of 2.1{+-}0.5 mrad FWHM and feature unparalleled shot-to-shot stability in energy (2.5% rms), pointing direction (1.4 mrad rms) and charge (16% rms) owing to a highly reproducible plasma-density profile within the laser-plasma-interaction volume. Laser-wakefield acceleration (LWFA) in gas cells of this type constitutes a simple and reliable source of relativistic electrons with well defined properties, which should allow for applications such as the production of extreme-ultraviolet undulator radiation in the near future.
Simultaneous confidence intervals for a steady-state leaky aquifer groundwater flow model
Christensen, S.; Cooley, R.L.
1996-01-01
Using the optimization method of Vecchia & Cooley (1987), nonlinear Scheffe??-type confidence intervals were calculated tor the parameters and the simulated heads of a steady-state groundwater flow model covering 450 km2 of a leaky aquifer. The nonlinear confidence intervals are compared to corresponding linear intervals. As suggested by the significant nonlinearity of the regression model, linear confidence intervals are often not accurate. The commonly made assumption that widths of linear confidence intervals always underestimate the actual (nonlinear widths was not correct for the head intervals. Results show that nonlinear effects can cause the nonlinear intervals to be offset from, and either larger or smaller than, the linear approximations. Prior information on some transmissivities helps reduce and stabilize the confidence intervals, with the most notable effects occurring for the parameters on which there is prior information and for head values in parameter zones for which there is prior information on the parameters.
Non-steady-state subduction and trench-parallel flow induced by overriding plate structure
NASA Astrophysics Data System (ADS)
Rodríguez-González, Juan; Billen, Magali I.; Negredo, Ana M.
2014-09-01
The direction of plate tectonic motion and the direction of mantle flow, as inferred from observations of seismic anisotropy measurements, show a good global correlation far from subduction zones. However, this correlation is poor near subduction zones, where below the slab seismic anisotropy is aligned parallel to the trench and above the slab has a complex pattern, which has not been fully explained. Here we present time-dependent three-dimensional (3D) fully-dynamic simulations of subduction to study the effect of overriding plate structure on the evolution of slab geometry and induced mantle flow. We find that along-strike variation in thermal thickness of the overriding plate causes increased hydrodynamic suction and shallower slab dip beneath the colder portion of the overriding plate; the variation in slab geometry drives strong trench-parallel flow beneath the slab and a complex flow pattern above the slab. This new mechanism for driving trench-parallel flow provides a good explanation for seismic anisotropy observations from the Middle and South America subduction zones, where both slab dip and overriding plate thermal state are strongly variable and correlated, and thus may be an important mechanism in other subduction zones. The location and strength of trench-parallel flow vary with the time-dependent evolution of the slab, suggesting that the global variability in seismic anisotropy observations in subduction zones is in part due to the non-steady-state behavior of these systems.
Two-lane traffic-flow model with an exact steady-state solution.
Kanai, Masahiro
2010-12-01
We propose a stochastic cellular-automaton model for two-lane traffic flow based on the misanthrope process in one dimension. The misanthrope process is a stochastic process allowing for an exact steady-state solution; hence, we have an exact flow-density diagram for two-lane traffic. In addition, we introduce two parameters that indicate, respectively, driver's driving-lane preference and passing-lane priority. Due to the additional parameters, the model shows a deviation of the density ratio for driving-lane use and a biased lane efficiency in flow. Then, a mean-field approach explicitly describes the asymmetric flow by the hop rates, the driving-lane preference, and the passing-lane priority. Meanwhile, the simulation results are in good agreement with an observational data, and we thus estimate these parameters. We conclude that the proposed model successfully produces two-lane traffic flow particularly with the driving-lane preference and the passing-lane priority.
In-cylinder air motion measurements by laser velocimetry under steady-state flow conditions
Coghe, A.; Gamma, F.; Mauri, M.; Brunello, G.; Calderini, F.; Antoni, L.F.D.
1985-01-01
A laser Doppler velocimeter (LDV) has been used to investigate the in-cylinder flow pattern produced by the helical inlet port of a model cylinder head, typical of those used in internal combustion engines. Measurements in a steady state flow rig were taken of the axial and tangential velocity components. The LDV results showed that the axial vortex formed behind the inlet port extends to more than one bore from the cylinder head and the tangential velocity profile is never that of a pure forced vortex. At lower lifts of the valve a smaller contra-rotating swirl was found together with the main swirl pattern, whereas at higher lifts a single swirl was established at the one bore position. Both the tangential and axial fluctuating velocity components were found more uniform than the mean values, with zones of higher turbulence around the flow reversal points. Flow visualization was also used to investigate the flow pattern in the whole cylinder, and hot-wire probes were employed to take advantage of their excellent frequency characteristics in deriving turbulence time scales.
Miyazawa, Hideyuki; Tanaka, Hajime
2007-07-01
It is a fundamental physical problem how a state is selected in a nonequilibrium steady state where the energy is continuously dissipated. This problem is common to phase transitions in liquids under shear flow and those in solids under deformation or electric current. In particular, soft matter often exhibits a strong nonlinear response to an external field, since its structural susceptibility to the external field is extremely large due to its softness and flexibility. Here we study the nucleation and growth process of the lamellar phase from the sponge phase under shear flow in a bilayer-forming surfactant system. We found an interesting shape selection of lamellar nuclei under shear flow between multilamellar vesicles (onions) and cylinders (leeks). These two types of behavior are separated sharply at a critical shear rate: a slight change of the shear rate is enough to switch one behavior to the other. We also found that, under a sufficiently strong shear flow, nucleated onions decrease their size with time, and eventually transform into leeks. This suggests that leeks may be the stable morphology under steady shear flow. However, the stability is limited only to the lamellar-sponge coexistence region. When a system enters into the lamellar phase region by further cooling, leeks lose their stability and break up into rather monodisperse onions, presumably via Rayleigh-like instability of a fluid tube. On the basis of these results, we draw a dynamic state diagram of smectic membrane organization under shear flow.
NASA Astrophysics Data System (ADS)
Liakos, Anastasios; Malamataris, Nikolaos
2014-11-01
The topology and evolution of flow around a surface mounted cubical object in three dimensional channel flow is examined for low to moderate Reynolds numbers. Direct numerical simulations were performed via a home made parallel finite element code. The computational domain has been designed according to actual laboratory experimental conditions. Analysis of the results is performed using the three dimensional theory of separation. Our findings indicate that a tornado-like vortex by the side of the cube is present for all Reynolds numbers for which flow was simulated. A horse-shoe vortex upstream from the cube was formed at Reynolds number approximately 1266. Pressure distributions are shown along with three dimensional images of the tornado-like vortex and the horseshoe vortex at selected Reynolds numbers. Finally, and in accordance to previous work, our results indicate that the upper limit for the Reynolds number for which steady state results are physically realizable is roughly 2000. Financial support of author NM from the Office of Naval Research Global (ONRG-VSP, N62909-13-1-V016) is acknowledged.
Structure development in confined polymer blends: steady-state shear flow and relaxation.
Vananroye, Anja; Van Puyvelde, Peter; Moldenaers, Paula
2006-02-28
In this work, the structure development in immiscible polymer blends in confined geometries is systematically investigated. Poly(dimethylsiloxane)/poly(isobutylene) blends with a droplet-matrix structure are subjected to simple shear flows. The confined environment is created by using a Linkam shearing cell in which the gap is systematically decreased to investigate the transition from "bulk" behavior toward "confined" behavior. Small-angle light scattering experiments in a confinement, which have not yet been reported in the literature, and also microscopy are used to observe the morphology development during steady-state shearing and relaxation. These experiments indicate that the size and relaxation of single droplets in a confined environment are still governed by the relations that describe the structure development in bulk situations. Yet, depending on the applied shear rates and blend concentrations, the droplets organize in superstructures such as pearl necklaces or extended superstrings in a single layer between the plates. These structures are stable under flow. To observe a single layer, a critical ratio of droplet size to gap spacing is required, but this ratio is clearly below the one already reported in the literature.
NASA Technical Reports Server (NTRS)
Schallhorn, Paul; Majumdar, Alok; Tiller, Bruce
2001-01-01
A general purpose, one dimensional fluid flow code is currently being interfaced with the thermal analysis program SINDA/G. The flow code, GFSSP, is capable of analyzing steady state and transient flow in a complex network. The flow code is capable of modeling several physical phenomena including compressibility effects, phase changes, body forces (such as gravity and centrifugal) and mixture thermodynamics for multiple species. The addition of GFSSP to SINDA/G provides a significant improvement in convective heat transfer modeling for SINDA/G. The interface development is conducted in multiple phases. This paper describes the first phase of the interface which allows for steady and quasisteady (unsteady solid, steady fluid) conjugate heat transfer modeling.
Volume of the steady-state space of financial flows in a monetary stock-flow-consistent model
NASA Astrophysics Data System (ADS)
Hazan, Aurélien
2017-05-01
We show that a steady-state stock-flow consistent macro-economic model can be represented as a Constraint Satisfaction Problem (CSP). The set of solutions is a polytope, which volume depends on the constraints applied and reveals the potential fragility of the economic circuit, with no need to study the dynamics. Several methods to compute the volume are compared, inspired by operations research methods and the analysis of metabolic networks, both exact and approximate. We also introduce a random transaction matrix, and study the particular case of linear flows with respect to money stocks.
Floc morphology and size distributions of cohesive sediment in steady-state flow.
Stone, M; Krishnappan, B G
2003-06-01
Fractal dimensions of particle populations of cohesive sediment were examined during deposition experiments in an annular flume at four conditions of steady-state flow (0.058, 0.123, 0.212 and 0.323Pa). Light microscopy and an image analysis system were used to determine area, longest axis and perimeter of suspended solids. Four fractal dimensions (D, D(1), D(2), D(k)) were calculated from the slopes of regression lines of the relevant variables on double log plots. The fractal dimension D, which relates the projected area (A) to the perimeter (P) of the particle (P proportional, variant A(D/2)), increased from 1.25+/-0.005 at a shear stress of 0.058Pa to a maximum of 1.36+/-0.003 at 0.121Pa then decreased to 1.34+/-0.001 at 0.323Pa. The change in D indicated that particle boundaries became more convoluted and the shape of larger particles was more irregular at higher levels of shear stress. At the highest shear stress, the observed decrease in D resulted from floc breakage due to increased particle collisions. The fractal dimension D(1), which relates the longest axis (l) to the perimeter of the particle (P proportional to l(D1)), increased from 1.00+/-0.006 at a shear stress of 0.058Pa to a maximum of 1.25+/-0.003 at 0.325Pa. The fractal dimension D(2), which relates the longest axis with the projected area of the particle (A proportional to l(D(2)), increased from 1.35+/-0.014 at a shear stress of 0.058Pa to a maximum of 1.81+/-0.005 at 0.323Pa. The observed increases in D(1) and D(2) indicate that particles became more elongated with increasing shear stress. Values of the fractal dimension D(k), resulting from the Korcak's empirical law for particle population, decreased from 3.68+/-0.002 at a shear stress of 0.058Pa to 1.33+/-0.001 at 0.323Pa and indicate that the particle size distribution changed from a population of similar sized particles at low shear to larger flocculated particles at higher levels of shear. The results show that small particle clusters
NASA Technical Reports Server (NTRS)
Le Roux, J. A.; Ptuskin, V. S.
1995-01-01
Realistic models of the outer heliosphere should consider that the interstellar cosmic-ray pressure becomes comparable to pressures in the solar wind at distances more than 100 AU from the Sun. The cosmic-ray pressure dynamically affects solar wind flow through deceleration. This effect, which occurs over a scale length of the order of the effective diffusion length at large radial distances, has important implications for cosmic-ray modulation and acceleration. As a first step toward solution of this nonlinear problem, a steady state numerical model was developed for a relatively cold spherical solar wind flow which encounters the confining isotropic pressure of the surrounding Galactic medium. This pressure is assumed to be dominated by energetic particles (Galactic cosmic rays). The system of equations, which are solved self-consistently, includes the relevant hydrodynamical equations for the solar wind flow and the spherical cosmic-ray transport equation. To avoid the closure parameter problem of the two-fluid model, the latter equation is solved for the energy-dependent cosmic-ray distribution function.
Simulating nonlinear steady-state traveling waves on the falling liquid film entrained by a gas flow
NASA Astrophysics Data System (ADS)
Tsvelodub, O. Yu
2016-10-01
The article is devoted to the simulation of nonlinear waves on a liquid film flowing under gravity in the known stress field at the interface. In the case of small Reynolds numbers the problem is reduced to the consideration of solutions of the nonlinear integral-differential equation for film thickness deviation from the undisturbed level. Weakly nonlinear steady-state traveling solutions of the equation with wave numbers in a vicinity of neutral wave numbers are constructed analytically. The nature of the wave branching from the undisturbed solution is investigated. Steady-state traveling solutions, whose wave numbers within the instability area are far from neutral wave numbers, are found numerically.
Ansari, A.F.; Gay, R.R.; Gitnick, B.J.
1981-07-01
A steady-state core flow distribution code (FIBWR) is described. The ability of the recommended models to predict various pressure drop components and void distribution is shown by comparison to the experimental data. Application of the FIBWR code to the Vermont Yankee Nuclear Power Station is shown by comparison to the plant measured data.
A hybrid multigrid technique for computing steady-state solutions to supersonic flows
NASA Technical Reports Server (NTRS)
Sanders, Richard
1992-01-01
Recently, Li and Sanders have introduced a class of finite difference schemes to approximate generally discontinuous solutions to hyperbolic systems of conservation laws. These equations have the form together with relevant boundary conditions. When modelling hypersonic spacecraft reentry, the differential equations above are frequently given by the compressible Euler equations coupled with a nonequilibrium chemistry model. For these applications, steady state solutions are often sought. Many tens (to hundreds) of super computer hours can be devoted to a single three space dimensional simulation. The primary difficulty is the inability to rapidly and reliably capture the steady state. In these notes, we demonstrate that a particular variant from the schemes presented can be combined with a particular multigrid approach to capture steady state solutions to the compressible Euler equations in one space dimension. We show that the rate of convergence to steady state coming from this multigrid implementation is vastly superior to the traditional approach of artificial time relaxation. Moreover, we demonstrate virtual grid independence. That is, the rate of convergence does not depend on the degree of spatial grid refinement.
Hill, M.C.; ,
1990-01-01
Parameters in numerical ground-water flow models have been successfully estimated using nonlinear-optimization methods such as the modified Gauss-Newton (GN) method and conjugate-direction methods. This paper investigates the relative efficiency of GN and three conjugate-direction parameter-estimation methods on two-dimensional, steady-state and transient ground-water flow test cases. The steady-state test cases are included to compare the performance of the algorithm with published examples. The three conjugate-direction methods are the Fletcher-Reeves (FR) and quasi-Newton (QN) regression methods, and combination Fletcher-Reeves quasi-Newton (FR-QN). All three are combined with Newton's method of calculating step size. The numerical ground-water flow model is described by McDonald and Harbaugh.
Pasch, James Jay
2017-02-07
A method of resolving a balanced condition that generates control parameters for start-up and steady state operating points and various component and cycle performances for a closed split flow recompression cycle system. The method provides for improved control of a Brayton cycle thermal to electrical power conversion system. The method may also be used for system design, operational simulation and/or parameter prediction.
NASA Astrophysics Data System (ADS)
Thomas, Herbert; Chapman, Randall; Garrison, George W.
1992-07-01
An axisymmetric, implicit, finite-difference algorithm is formulated for the steady-state performance prediction of arcjet and MPD-type thrusters subject to both self-induced and applied magnetic fields. The azimuthal momentum equation is included in the algorithm to accommodate the swirl flow induced by the applied magnetic field. Thermal nonequilibrium is taken into account with the ionization level calculated using Saha's equation evaluated at the electron temperature. In addition, viscous and Hall effects are considered.
Development of an Efficient Solution Scheme for Incompressible Steady- State Flow
1989-04-01
structures cost- effectively necessitates the evaluation of three-dimensional fluid/ structure interaction. Consequently, the level of detail required in...appropriately; (c) the model must consider multiple initial and boundary conditions; (d) the model must conserve mass both locally and globally and converge as...turbulence model to account for the effects of small, sub-grid scale eddies upon the large-scale flow. This should be done, however, only after the
Analysis of Transient and Steady State Neutral Flows in a Field Reversed Configuration Thruster
2011-05-03
stagnation temperature of 300 K. The carrier gas was molecular nitrogen in a ll cases except for one where neon was used. Transient evolution of gas flow...Navier-Stokes equations is CFD++ 8 developed by Metacomp Technologies, Inc. CFD++ is a flexible computational fluid dynamics software suite for the...intermolecular potential was assumed to be a variable hard sphere. Energy redistribution in molecular colli- sions between the internal and translational modes
Fractal dimension of cohesive sediment flocs at steady state under seven shear flow conditions
Zhu, Zhongfan; Yu, Jingshan; Wang, Hongrui; Dou, Jie; Wang, Cheng
2015-08-12
The morphological properties of kaolin flocs were investigated in a Couette-flow experiment at the steady state under seven shear flow conditions (shear rates of 5.36, 9.17, 14, 24, 31, 41 and 53 s^{-1}). These properties include a one-dimensional (1-D) fractal dimension (D_{1}), a two-dimensional (2-D) fractal dimension (D_{2}), a perimeter-based fractal dimension (D_{pf}) and an aspect ratio (AR). They were calculated based on the projected area (A), equivalent size, perimeter (P) and length (L) of the major axis of the floc determined through sample observation and an image analysis system. The parameter D_{2}, which characterizes the relationship between the projected area and the length of the major axis using a power function, A ∝ L^{D2}, increased from 1.73 ± 0.03, 1.72 ± 0.03, and 1.75 ± 0.04 in the low shear rate group (G = 5.36, 9.17, and 14 s^{-1}) to 1.92 ± 0.03, 1.82 ± 0.02, 1.85 ± 0.02, and 1.81 ± 0.02 in the high shear rate group (24, 31, 41 and 53 s^{-1}), respectively. The parameter D_{1} characterizes the relationship between the perimeter and length of the major axis by the function P ∝ L^{D1} and decreased from 1.52 ± 0.02, 1.48 ± 0.02, 1.55 ± 0.02, and 1.63 ± 0.02 in the low shear group (5.36, 9.17, 14 and 24 s^{-1}) to 1.45 ± 0.02, 1.39 ± 0.02, and 1.39 ± 0.02 in the high shear group (31, 41 and 53 s^{-1}), respectively. The results indicate that with increasing shear rates, the flocs become less elongated and that their boundary lines become tighter and more regular, caused by more breakages and possible restructurings of the flocs. The parameter D_{pf}, which is related to the perimeter and the projected area through the function , decreased as the shear rate increased almost linearly. The parameter AR, which is the ratio of the length of the major axis and equivalent diameter, decreased from 1.56, 1
Fractal dimension of cohesive sediment flocs at steady state under seven shear flow conditions
Zhu, Zhongfan; Yu, Jingshan; Wang, Hongrui; ...
2015-08-12
The morphological properties of kaolin flocs were investigated in a Couette-flow experiment at the steady state under seven shear flow conditions (shear rates of 5.36, 9.17, 14, 24, 31, 41 and 53 s-1). These properties include a one-dimensional (1-D) fractal dimension (D1), a two-dimensional (2-D) fractal dimension (D2), a perimeter-based fractal dimension (Dpf) and an aspect ratio (AR). They were calculated based on the projected area (A), equivalent size, perimeter (P) and length (L) of the major axis of the floc determined through sample observation and an image analysis system. The parameter D2, which characterizes the relationship between the projectedmore » area and the length of the major axis using a power function, A ∝ LD2, increased from 1.73 ± 0.03, 1.72 ± 0.03, and 1.75 ± 0.04 in the low shear rate group (G = 5.36, 9.17, and 14 s-1) to 1.92 ± 0.03, 1.82 ± 0.02, 1.85 ± 0.02, and 1.81 ± 0.02 in the high shear rate group (24, 31, 41 and 53 s-1), respectively. The parameter D1 characterizes the relationship between the perimeter and length of the major axis by the function P ∝ LD1 and decreased from 1.52 ± 0.02, 1.48 ± 0.02, 1.55 ± 0.02, and 1.63 ± 0.02 in the low shear group (5.36, 9.17, 14 and 24 s-1) to 1.45 ± 0.02, 1.39 ± 0.02, and 1.39 ± 0.02 in the high shear group (31, 41 and 53 s-1), respectively. The results indicate that with increasing shear rates, the flocs become less elongated and that their boundary lines become tighter and more regular, caused by more breakages and possible restructurings of the flocs. The parameter Dpf, which is related to the perimeter and the projected area through the function , decreased as the shear rate increased almost linearly. The parameter AR, which is the ratio of the length of the major axis and equivalent diameter, decreased from 1.56, 1.59, 1.53 and 1.51 in the low shear rate group to 1.43, 1.47 and 1.48 in the high shear rate group. These changes in Dpf and AR show that the flocs become
NASA Astrophysics Data System (ADS)
Guinot, Vincent; Cappelaere, Bernard
2009-04-01
This paper presents the analytical properties of the solutions of the sensitivity equations for steady-state, two-dimensional shallow water flow. These analytical properties are used to provide guidelines for model calibration and validation. The sensitivity of the water depth/level and that of the longitudinal unit discharge are shown to contain redundant information. Under subcritical conditions, the sensitivities of the flow variables are shown to obey an anisotropic elliptic equation. The main directions of the contour lines for water depth and the longitudinal unit discharge sensitivity are parallel and perpendicular to the flow, while they are diagonal to the flow for the transverse unit discharge sensitivity. Moreover, the sensitivity for all three variables extends farther in the transverse direction than in the longitudinal direction, the anisotropy ratio being a function of the sole Froude number. For supercritical flow, the sensitivity obeys an anisotropic hyperbolic equation. These findings are confirmed by application examples on idealized and real-world simulations. The sensitivities to the geometry, friction coefficient or model boundary conditions are shown to behave in different ways, thus providing different types of information for model calibration and validation.
Fractal Dimension of Cohesive Sediment Flocs at Steady State under Seven Shear Flow Conditions
Zhu, Zhongfan; Yu, Jingshan; Wang, Hongrui; Dou, Jie; Wang, Cheng
2015-08-01
The morphological properties of kaolin flocs were investigated in a Couetteflow experiment at the steady state under seven shear flow conditions (shear rates of 5.36, 9.17, 14, 24, 31, 41 and 53 s-1). These properties include a one-dimensional (1-D) fractal dimension (D1), a two-dimensional (2-D) fractal dimension (D2), a perimeter-based fractal dimension (Dpf) and an aspect ratio (AR). They were calculated based on the projected area (A), equivalent size, perimeter (P) and length (L) of the major axis of the floc determined through sample observation and an image analysis system. The parameter D2, which characterizes the relationship between the projected area and the length of the major axis using a power function, , increased from 1.73 ± 0.03, 1.72 ± 0.03, and 1.75 ± 0.04 in the low shear rate group (G = 5.36, 9.17, and 14 s-1) to 1.92 ± 0.03, 1.82 ± 0.02, 1.85 ± 0.02, and 1.81 ± 0.02 in the high shear rate group (24, 31, 41 and 53 s-1), respectively. The parameter D1 characterizes the relationship between the perimeter and length of the major axis by the function and decreased from 1.52 ± 0.02, 1.48 ± 0.02, 1.55 ± 0.02, and 1.63 ± 0.02 in the low shear group (5.36, 9.17, 14 and 24 s-1) to 1.45 ± 0.02, 1.39 ± 0.02, and 1.39 ± 0.02 in the high shear group (31, 41 and 53 s-1), respectively. The results indicate that with increasing shear rates, the flocs become less elongated and that their boundary lines become tighter and more regular, caused by more breakages and possible restructurings of the flocs. The parameter Dpf, which is related to the perimeter and the projected area through the function , decreased as the shear rate increased approximately linearly. The parameter AR, which is the ratio of the length of the major axis and equivalent diameter, decreased from 1.56, 1.59, 1.53 and 1.51 in the low shear rate group to 1.43, 1.47 and 1.48 in the high shear rate group. These changes in Dpf and AR show that the flocs become less convoluted and
Walter, Donald A.; Masterson, John P.
2003-01-01
The U.S. Geological Survey has developed several ground-water models in support of an investigation of ground-water contamination being conducted by the Army National Guard Bureau at Camp Edwards, Massachusetts Military Reservation on western Cape Cod, Massachusetts. Regional and subregional steady-state models and regional transient models were used to (1) improve understanding of the hydrologic system, (2) simulate advective transport of contaminants, (3) delineate recharge areas to municipal wells, and (4) evaluate how model discretization and time-varying recharge affect simulation results. A water-table mound dominates ground-water-flow patterns. Near the top of the mound, which is within Camp Edwards, hydraulic gradients are nearly vertically downward and horizontal gradients are small. In downgradient areas that are further from the top of the water-table mound, the ratio of horizontal to vertical gradients is larger and horizontal flow predominates. The steady-state regional model adequately simulates advective transport in some areas of the aquifer; however, simulation of ground-water flow in areas with local hydrologic boundaries, such as ponds, requires more finely discretized subregional models. Subregional models also are needed to delineate recharge areas to municipal wells that are inadequately represented in the regional model or are near other pumped wells. Long-term changes in recharge rates affect hydraulic heads in the aquifer and shift the position of the top of the water-table mound. Hydraulic-gradient directions do not change over time in downgradient areas, whereas they do change substantially with temporal changes in recharge near the top of the water-table mound. The assumption of steady-state hydraulic conditions is valid in downgradient area, where advective transport paths change little over time. In areas closer to the top of the water-table mound, advective transport paths change as a function of time, transient and steady-state paths
NASA Astrophysics Data System (ADS)
Brushlinskii, K. V.; Kozlov, A. N.; Konovalov, V. S.
2015-08-01
This paper continues the series of numerical investigations of self-ionizing gas flows in plasma accelerator channels with an azimuthal magnetic field. The mathematical model is based on the equations of dynamics of a three-component continuous medium consisting of atoms, ions, and electrons; the model is supplemented with the equation of ionization and recombination kinetics within the diffusion approximation with account for photoionization and photorecombination. It also takes into account heat exchange, which in this case is caused by radiative heat conductance. Upon a short history of the issue, the proposed model, numerical methods, and results for steady-state and pulsating flows are described.
Number of microstates and configurational entropy for steady-state two-phase flows in pore networks
NASA Astrophysics Data System (ADS)
Daras, T.; Valavanides, M. S.
2015-01-01
Steady-state two-phase flow in porous media is a process whereby a wetting phase displaces a non-wetting phase within a pore network. It is a stationary, off equilibrium process -in the sense that it is maintained in dynamic equilibrium on the expense of energy supplied to the system. The efficiency of the process depends on its spontaneity, measurable by the rate of global entropy production. The latter has been proposed to comprise two components: the rate of mechanical energy dissipation at constant temperature (a thermal entropy component, Q/T, in the continuum mechanics scale) and a configurational entropy production component (a Boltzmann-type statistical-entropy component, klnW), due to the existence of a canonical ensemble of flow configurations, physically admissible to the externally imposed macrostate stationary conditions. Here, the number of microstates, lnW, in steady-state two-phase flows in pore networks is estimated in three stages: Combinatorics are implemented to evaluate the number of identified microstates per physically admissible internal flow arrangement compatible with the imposed stationary flow conditions. Then, "Stirling's approximation limiting procedure" is applied to downscale the computational effort associated with the operations between large factorial numbers. Finally, the number of microstates is estimated by contriving a limiting procedure over the canonical ensemble of the physically admissible flow configurations. Counting the microstates is a prerequisite for estimating the process configurational entropy in order to implement the Maximum Entropy Production principle and justify the existence of optimum operating conditions.
Stopped-flow and steady-state study of the diphenolase activity of mushroom tyrosinase.
Rodríguez-López, J N; Fenoll, L G; García-Ruiz, P A; Varón, R; Tudela, J; Thorneley, R N; García-Cánovas, F
2000-08-29
The reaction of mushroom (Agaricus bisporus) tyrosinase with dioxygen in the presence of several o-diphenolic substrates has been studied by steady-state and transient-phase kinetics in order to elucidate the rate-limiting step and to provide new insights into the mechanism of oxidation of these substrates. A kinetic analysis has allowed for the first time the determination of individual rate constants for several of the partial reactions that comprise the catalytic cycle. Mushroom tyrosinase rapidly reacts with dioxygen with a second-order rate constant k(+8) = 2.3 x 10(7) M(-)(1) s(-)(1), which is similar to that reported for hemocyanins [(1.3 x 10(6))-(5.7 x 10(7)) M(-)(1) s(-)(1)]. Deoxytyrosinase binds dioxygen reversibly at the binuclear Cu(I) site with a dissociation constant K(D)(O)()2 = 46.6 microM, which is similar to the value (K(D)(O)()2 = 90 microM) reported for the binding of dioxygen to Octopus vulgaris deoxyhemocyanin [Salvato et al. (1998) Biochemistry 37, 14065-14077]. Transient and steady-state kinetics showed that o-diphenols such as 4-tert-butylcatechol react significantly faster with mettyrosinase (k(+2) = 9.02 x 10(6) M(-)(1) s(-)(1)) than with oxytyrosinase (k(+6) = 5.4 x 10(5) M(-)(1) s(-)(1)). This difference is interpreted in terms of differential steric and polar effects that modulate the access of o-diphenols to the active site for these two forms of the enzyme. The values of k(cat) for several o-diphenols are also consistent with steric and polar factors controlling the mobility, orientation, and thence the reactivity of substrates at the active site of tyrosinase.
Martoïa, F; Dumont, P J J; Orgéas, L; Belgacem, M N; Putaux, J-L
2016-02-14
In this study, we characterized and modeled the rheology of TEMPO-oxidized cellulose nanofibril (NFC) aqueous suspensions with electrostatically stabilized and unflocculated nanofibrous structures. These colloidal suspensions of slender and wavy nanofibers exhibited a yield stress and a shear thinning behavior at low and high shear rates, respectively. Both the shear yield stress and the consistency of these suspensions were power-law functions of the NFC volume fraction. We developed an original multiscale model for the prediction of the rheology of these suspensions. At the nanoscale, the suspensions were described as concentrated systems where NFCs interacted with the Newtonian suspending fluid through Brownian motion and long range fluid-NFC hydrodynamic interactions, as well as with each other through short range hydrodynamic and repulsive colloidal interaction forces. These forces were estimated using both the experimental results and 3D networks of NFCs that were numerically generated to mimic the nanostructures of NFC suspensions under shear flow. They were in good agreement with theoretical and measured forces for model colloidal systems. The model showed the primary role played by short range hydrodynamic and colloidal interactions on the rheology of NFC suspensions. At low shear rates, the origin of the yield stress of NFC suspensions was attributed to the combined contribution of repulsive colloidal interactions and the topology of the entangled NFC networks in the suspensions. At high shear rates, both concurrent colloidal and short (in some cases long) range hydrodynamic interactions could be at the origin of the shear thinning behavior of NFC suspensions.
NASA Astrophysics Data System (ADS)
Vollmayr-Lee, Katharina; Zippelius, Annette; Aspelmeier, Timo
2011-03-01
We study the dynamic structure factor of a granular fluid of hard spheres, driven into a stationary nonequilibrium state by balancing the energy loss due to inelastic collisions with the energy input due to driving. The driving is chosen to conserve momentum, so that fluctuating hydrodynamics predicts the existence of sound modes. We present results of computer simulations which are based on an event driven algorithm. The dynamic structure factor F (q , ω) is determined for volume fractions 0.05, 0.1 and 0.2 and coefficients of normal restitution 0.8 and 0.9. We observe sound waves, and compare our results for F (q , ω) with the predictions of generalized fluctuating hydrodynamics which takes into account that temperature fluctuations decay either diffusively or with a finite relaxation rate, depending on wave number and inelasticity. We determine the speed of sound and the transport coefficients and compare them to the results of kinetic theory. K.V.L. thanks the Institute of Theoretical Physics, University of Goettingen, for financial support and hospitality.
Shiomi, Masanori; Mori, Kenichiro; Osakada, Kozo
1995-12-31
Non-steady-state metal flow and temperature distribution in twin roll strip casting are simulated by the finite element method. In the present simulation, the viscoplastic finite element method is combined with that for heat conduction to calculate the metal flow and the temperature distribution during the casting process. The solid, mushy and liquid phases are assumed to be viscoplastic materials with individual flow stresses. In the temperature analysis, the latent heat due to solidification of the molten metal is taken into account by using the temperature recovery method. Since the metal flow and temperature distribution do not often attain to steady states, they are simulated by the stepwise calculation. To examine the accuracy of the calculated results, physical simulation of plane-strain twin roll strip casting is carried out by use of paraffin wax as a model material. The calculated profiles of the solid region agree qualitatively well with the experimental ones. Twin roll strip casting processes for stainless steel are also simulated. An optimum roll speed for obtaining a strip without a liquid zone under a minimum rolling load is obtained from the results of the simulation.
NASA Astrophysics Data System (ADS)
Kalatehjari, R.; Liou, T. S.
2016-12-01
Carrying out numerical simulations of fluid flow and solute transport in an interconnected discrete fracture network (DFN) is computationally demanding. However, the efficiency of simulation can be greatly enhanced if DFN can be properly converted into equivalent continuous porous medium (ECPM). In this study, a new upscaling algorithm using boundary element method (BEM) and volume averaging method is developed and used in steady-state flow field to convert DFN into ECPM. Considering a grid of favorable size in a low-permeable fractured rock, fractures are meshed by triangular elements. Initial head and velocity at boundary nodes of each fracture are achieved by applying boundary conditions. Assuming steady-state flow, a system of linear equations is then developed based on BEM to obtain head distribution in fracture planes by iterative calculation. The calculated head values at mesh nodes are then employed to find the velocity field. Finally, volume-averaged Darcy velocity and head gradient of the grid are applied to develop a system of linear equations for upscaling calculation. The minimum number of sufficient flow simulations to solve the over-determined system of linear equations is defined by evaluating the mass balance error. The solution is expressed in terms of heterogeneous and anisotropic block permeability tensors. A computer code was developed by Matlab to satisfy the calculation and visualization purposes. Benchmark examples were successfully verified to demonstrate the robustness of this method. In addition, a stochastic DFN model was analyzed to validate the functionality of the method in real case. To verify the results of this case, FracMan V7.5 was used to generate stochastic DFN model and flow simulations within the grid were solved by its internal MAFIC tool. A comparison of the results in terms of mass conservation and velocity field successfully verified the application of the proposed upscaling algorithm for low-permeability fractured rock.
A closed-form solution for steady-state coupled phloem/xylem flow using the Lambert-W function.
Hall, A J; Minchin, P E H
2013-12-01
A closed-form solution for steady-state coupled phloem/xylem flow is presented. This incorporates the basic Münch flow model of phloem transport, the cohesion model of xylem flow, and local variation in the xylem water potential and lateral water flow along the transport pathway. Use of the Lambert-W function allows this solution to be obtained under much more general and realistic conditions than has previously been possible. Variation in phloem resistance (i.e. viscosity) with solute concentration, and deviations from the Van't Hoff expression for osmotic potential are included. It is shown that the model predictions match those of the equilibrium solution of a numerical time-dependent model based upon the same mechanistic assumptions. The effect of xylem flow upon phloem flow can readily be calculated, which has not been possible in any previous analytical model. It is also shown how this new analytical solution can handle multiple sources and sinks within a complex architecture, and can describe competition between sinks. The model provides new insights into Münch flow by explicitly including interactions with xylem flow and water potential in the closed-form solution, and is expected to be useful as a component part of larger numerical models of entire plants.
On the validity of travel-time based nonlinear bioreactive transport models in steady-state flow
NASA Astrophysics Data System (ADS)
Sanz-Prat, Alicia; Lu, Chuanhe; Finkel, Michael; Cirpka, Olaf A.
2015-04-01
Travel-time based models simplify the description of reactive transport by replacing the spatial coordinates with the groundwater travel time, posing a quasi one-dimensional (1-D) problem and potentially rendering the determination of multidimensional parameter fields unnecessary. While the approach is exact for strictly advective transport in steady-state flow if the reactive properties of the porous medium are uniform, its validity is unclear when local-scale mixing affects the reactive behavior. We compare a two-dimensional (2-D), spatially explicit, bioreactive, advective-dispersive transport model, considered as "virtual truth", with three 1-D travel-time based models which differ in the conceptualization of longitudinal dispersion: (i) neglecting dispersive mixing altogether, (ii) introducing a local-scale longitudinal dispersivity constant in time and space, and (iii) using an effective longitudinal dispersivity that increases linearly with distance. The reactive system considers biodegradation of dissolved organic carbon, which is introduced into a hydraulically heterogeneous domain together with oxygen and nitrate. Aerobic and denitrifying bacteria use the energy of the microbial transformations for growth. We analyze six scenarios differing in the variance of log-hydraulic conductivity and in the inflow boundary conditions (constant versus time-varying concentration). The concentrations of the 1-D models are mapped to the 2-D domain by means of the kinematic (for case i), and mean groundwater age (for cases ii & iii), respectively. The comparison between concentrations of the "virtual truth" and the 1-D approaches indicates extremely good agreement when using an effective, linearly increasing longitudinal dispersivity in the majority of the scenarios, while the other two 1-D approaches reproduce at least the concentration tendencies well. At late times, all 1-D models give valid approximations of two-dimensional transport. We conclude that the
On the validity of travel-time based nonlinear bioreactive transport models in steady-state flow.
Sanz-Prat, Alicia; Lu, Chuanhe; Finkel, Michael; Cirpka, Olaf A
2015-01-01
Travel-time based models simplify the description of reactive transport by replacing the spatial coordinates with the groundwater travel time, posing a quasi one-dimensional (1-D) problem and potentially rendering the determination of multidimensional parameter fields unnecessary. While the approach is exact for strictly advective transport in steady-state flow if the reactive properties of the porous medium are uniform, its validity is unclear when local-scale mixing affects the reactive behavior. We compare a two-dimensional (2-D), spatially explicit, bioreactive, advective-dispersive transport model, considered as "virtual truth", with three 1-D travel-time based models which differ in the conceptualization of longitudinal dispersion: (i) neglecting dispersive mixing altogether, (ii) introducing a local-scale longitudinal dispersivity constant in time and space, and (iii) using an effective longitudinal dispersivity that increases linearly with distance. The reactive system considers biodegradation of dissolved organic carbon, which is introduced into a hydraulically heterogeneous domain together with oxygen and nitrate. Aerobic and denitrifying bacteria use the energy of the microbial transformations for growth. We analyze six scenarios differing in the variance of log-hydraulic conductivity and in the inflow boundary conditions (constant versus time-varying concentration). The concentrations of the 1-D models are mapped to the 2-D domain by means of the kinematic (for case i), and mean groundwater age (for cases ii & iii), respectively. The comparison between concentrations of the "virtual truth" and the 1-D approaches indicates extremely good agreement when using an effective, linearly increasing longitudinal dispersivity in the majority of the scenarios, while the other two 1-D approaches reproduce at least the concentration tendencies well. At late times, all 1-D models give valid approximations of two-dimensional transport. We conclude that the
Parameters of a Steady State Model for In-Cylinder Flow of an Internal Combustion Engine
NASA Astrophysics Data System (ADS)
Fortner, Elizabeth; Puzinauskas, Paul; Bolus, Nicholas
2013-11-01
Flow structures in an internal combustion engine are critical to engine performance and fuel consumption. Experiments are often conducted to explore how intake port geometry can be modified to induce desired tumble and swirl flow structures within the cylinder. To make these experiments cost-effective, they are often first conducted using a model cylinder on a steady flow bench prior to, or in lieu of, performing full unsteady engine tests. This research examines how model characteristics and experimental configuration choices affect results on these steady-flow tests. The experimental set-up uses DPIV to visualize the flow and a horizontally extracting swirl meter to measure the strength of the tumble structure. The configurations and characteristics examined included model geometry, seeding particle type and location of flow induction. The symmetric geometry experiment investigates how extraction affects the flow structures inside the cylinder. Three different seeding particles were used to see how particle properties affect DPIV results. Reversing the direction of flow through the system causes set-up challenges with removing leaks and introducing seeding particles, but is safer as it directs particles away from the flow bench. Deviation of results from the different test set-ups may indicate that cylinder model experiments need to be carefully designed to ensure high quality results accurate enough for use in designing full scale engine tests. Support from NSF REU Grant #1062611 is gratefully acknowledged.
The steady-state flow quality in a model of a non-return wind tunnel
NASA Technical Reports Server (NTRS)
Mort, K. W.; Eckert, W. T.; Kelly, M. W.
1972-01-01
The structural cost of non-return wind tunnels is significantly less than that of the more conventional closed-circuit wind tunnels. However, because of the effects of external winds, the flow quality of non-return wind tunnels is an area of concern at the low test speeds required for V/STOL testing. The flow quality required at these low speeds is discussed and alternatives to the traditional manner of specifying the flow quality requirements in terms of dynamic pressure and angularity are suggested. The development of a non-return wind tunnel configuration which has good flow quality at low as well as at high test speeds is described.
Parachute gore shape and flow visualization during transient and steady-state conditions.
NASA Technical Reports Server (NTRS)
Dereng, V. G.
1973-01-01
Single parachute gore segments were tested in an experimental wind tunnel having a unique 'V' splitter plate test section with a glass panel on the near side and a grid of orifices for smoke injection on the back panel. The parachute gore shape and flow patterns were viewed in cross section during the inflation process and also during changing flow conditions as would occur with rapid reduction of payload weight. Observations of flow during inflation revealed a transient internal counterflow and the formation and degeneration of several trailing vortices. Gore shapes observed compared well with those of free flight.
Brandt, Erik G
2013-07-01
The stochastic Eulerian-Lagrangian method (SELM) is used to simulate coarse-grained lipid membrane models under steady-state conditions and in shear flow. SELM is an immersed boundary method which combines the efficiency of particle-based simulations with the realistic solvent dynamics provided by fluctuating hydrodynamics. Membrane simulations in SELM are shown to give structural properties in accordance with equilibrium statistical mechanics and dynamic properties in agreement with previous simulations of highly detailed membrane models in explicit solvent. Simulations of sheared membranes are used to calculate surface shear viscosities and inter-monolayer friction coefficients. The membrane models are shown to be shear thinning under a wide range of applied shear rates.
A numerical program for steady-state flow of magma-gas mixtures through vertical eruptive conduits
Mastin, Larry G.; Ghiorso, Mark S.
2000-01-01
This report presents a model that calculates flow properties (pressure, vesicularity, and some 35 other parameters) as a function of vertical position within a volcanic conduit during a steady-state eruption. The model idealizes the magma-gas mixture as a single homogeneousfluid and calculates gas exsolution under the assumption of equilibrium conditions. These are the same assumptions on which classic conduit models (e.g. Wilson and Head, 1981) have been based. They are most appropriate when applied to eruptions of rapidly ascending magma (basaltic lava-fountain eruptions, and Plinian or sub-Plinian eruptions of intermediate or silicic magmas) that contains abundant nucleation sites (microlites, for example) for bubble growth.
The effect of grazing flow on the steady state resistance of square-edged orifices
NASA Technical Reports Server (NTRS)
Rogers, T.; Hersh, A. S.
1975-01-01
A simple inviscid interaction model has been developed which uses thin airfoil theory to account for pressure forces exerted at the interface between the orifice and grazing flow together with a one-dimensional discharge coefficient concept. The effect of grazing flow boundary layer thickness was also included in the model. Resistance measurements for a wide range of grazing flow speeds and orifice flow rates collapse into a single curve when plotted in terms of effective discharge coefficient versus orifice-to-grazing velocity ratio. The correlation curves for inflow and outflow are different. Data for clustered orifices collapse in the same way as the single orifice. The effect of boundary layer thickness is compared with model predictions. The effect of orifice length-diameter ratio is shown to be significant for inflow but negligible for outflow.
The steady-state flow quality of an open return wind tunnel model.
NASA Technical Reports Server (NTRS)
Mort, K. W.; Kelly, M. W.; Eckert, W. T.
1972-01-01
The structural cost of open return wind tunnels is significantly less than that of the more conventional closed return wind tunnels. However, because of the effects of external winds, the flow quality of open return wind tunnels is an area of concern at the low speeds required for V/STOL testing. The development of a configuration which has good flow quality at low as well as at high test speeds is described. The flow quality required at the low test speeds of interest for V/STOL aircraft is discussed and alternatives to the traditional manner of specifying the flow quality requirements in terms of dynamic pressure and angle of attack are suggested.
Steady state cooling flow models with gas loss for normal elliptical galaxies
NASA Technical Reports Server (NTRS)
Sarazin, Craig L.; Ashe, Gregory A.
1989-01-01
A grid of cooling flow models for the hot gas in normal elliptical galaxies is calculated, including the loss of gas due to inhomogeneous cooling. The loss process is modeled as a distributed sink for the gas with the rate of loss being proportional to the local cooling rate. The cooling flow models with gas loss have smaller sonic radii, smaller inflow rates in their central regions, lower densities, and higher temperatures than homogeneous models. The reduction in the amount of hot gas flowing into the center of the models brings the models into much better agreement with the observed X-ray surface brightness profiles of elliptical galaxies. However, there is a large dispersion in the observed X-ray luminosities of ellipticals, and this cannot be explained by variations in the efficiency of gas loss. The gas-loss models have X-ray surface brightness profiles which are much less centrally peaked than the no-gas-loss models.
Signal processing and statistical descriptive reanalysis of steady state chute-flow experiments
NASA Astrophysics Data System (ADS)
truong, hoan; eckert, nicolas; keylock, chris; naaim, mohamed; bellot, hervé
2014-05-01
An accurate knowledge of snow rheology is needed for the mitigation against avalanche hazard. Indeed snow avalanches have a significant impact on the livelihoods and economies of alpine communities. To do so, 60 small-scale in-situ flow experiments were performed with various slopes, temperatures and flow depths. The investigation of these data previously seemed to show the dense flow of dry snow may be composed of two layers; a sheared basal layer made of single snow grains and a less sheared upper layer made of large aggregates. These outcomes were mainly based on the mean velocity profile of the flow and on interpretation in terms of rheological behavior of granular materials and snow microstructure [Pierre G. Rognon et al., 2007]. Here, the main objective remains the same, but the rheological and physical viewpoints are put aside to extract as much information contained in the data as possible various using signal processing methods and descriptive statistics methods as the maximum overlap discrete wavelet transform (MODWT), transfer entropy (TE) and maximum cross-correlation (MCC). Specifically, we aim at the improving the velocity estimations as function of the depth particularly the velocity fluctuations around the mean profile to better document the behavior of dense dry snow flows during a steady and uniform chute regime. The data are composed of pairs of voltage signals (right and left), which makes that the velocity is known indirectly only. The MCC method is classically used to determine the time lag between both signals. Previously, the MCC method that showed the mean velocity profile may be fitted by a simple bilinear function [Pierre G. Rognon et al., 2007], but no interesting temporal dynamics could be highlighted. Hence, a new process method was developed to provide velocity series with much better temporal resolution. The process is mainly made of a MODWT-based denoising method and the choice of window size for correlation. The results prove to be
Stability of forced-convection subcooled boiling in steady-state and transient annular flow
Gehrke, V.; Bankoff, S.G.
1993-06-01
A semi-analytical model developed by Lee and Bankoff for OFI in round tubes is extended to annular or parallel-plate flows with unequal heat fluxes, and shown to compare well with data by Dougherty, et al. and by Whittle and Forgan. The model is a better fit in the high Peclet number range than the Saha-Zuber model, and is simple to use.
NASA Astrophysics Data System (ADS)
Koroglu, Batikan; Armstrong, Mike; Cappelli, Mark; Chernov, Alex; Crowhurst, Jonathan; Mehl, Marco; Radousky, Harry; Rose, Timothy; Zaug, Joe
2016-10-01
The high temperature chemistry of rapidly condensing matter is under investigation using a steady state inductively coupled plasma (ICP) flow reactor. The objective is to study chemical processes on cooling time scales similar to that of a low yield nuclear fireball. The reactor has a nested set of gas flow rings that provide flexibility in the control of hydrodynamic conditions and mixing of chemical components. Initial tests were run using two different aqueous solutions (ferric nitrate and uranyl nitrate). Chemical reactants passing through the plasma torch undergo non-linear cooling from 10,000K to 1,000K on time scales of <0.1 to 0.5s depending on flow conditions. Optical spectroscopy measurements were taken at different positions along the flow axis to observe the in situ spatial and temporal evolution of chemical species at different temperatures. The current data offer insights into the changes in oxide chemistry as a function of oxygen fugacity. The time resolved measurements will also serve as a validation target for the development of kinetic models that will be used to describe chemical fractionation during nuclear fireball condensation. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
NASA Astrophysics Data System (ADS)
Irsa, J.; Zhang, Y.
2012-09-01
We propose a novel direct method for estimating steady state hydrogeological model parameters and model state variables in an aquifer where boundary conditions are unknown. The method is adapted from a recently developed potential theory technique for solving general inverse/reconstruction problems. Unlike many inverse techniques used for groundwater model calibration, the new method is not based on fitting and optimizing an objective function, which usually requires forward simulation and iterative parameter updates. Instead, it directly incorporates noisy observed data (hydraulic heads and flow rates) at the measurement points in a single step, without solving a boundary value problem. The new method is computationally efficient and is robust to the presence of observation errors. It has been tested on two-dimensional groundwater flow problems with regular and irregular geometries, different heterogeneity patterns, variances of heterogeneity, and error magnitudes. In all cases, parameters (hydraulic conductivities) converge to the correct or expected values and are thus unique, based on which heads and flow fields are constructed directly via a set of analytical expressions. Accurate boundary conditions are then inferred from these fields. The accuracy of the direct method also improves with increasing amount of observed data, lower measurement errors, and grid refinement. Under natural flow (i.e., no pumping), the direct method yields an equivalent conductivity of the aquifer, suggesting that the method can be used as an inexpensive characterization tool with which both aquifer parameters and aquifer boundary conditions can be inferred.
A full-Bayesian approach to the inverse problem for steady-state groundwater flow and heat transport
NASA Astrophysics Data System (ADS)
Jiang, Yefang; Woodbury, Allan D.
2006-12-01
The full (hierarchal) Bayesian approach proposed by Woodbury & Ulrych and Jiang et al. is extended to the inverse problem for 2-D steady-state groundwater flow and heat transport. A stochastic conceptual framework for the heat flow and groundwater flow is adopted. A perturbation of both the groundwater flow and the advection-conduction heat transport equations leads to a linear formulation between heads, temperature and logarithm transmissivity [denoted as ln (T)]. A Bayesian updating procedure similar to that of Woodbury & Ulrych can then be performed. This new algorithm is examined against a generic example through simulations. The prior mean, variance and integral scales of ln (T) (hyperparameters) are treated as random variables and their pdfs are determined from maximum entropy considerations. It is also assumed that the statistical properties of the noise in the hydraulic head and temperature measurements are also uncertain. Uncertainties in all pertinent hyperparameters are removed by marginalization. It is found that the use of temperature measurements is showed to further improve the ln (T) estimates for the test case in comparison to the updated ln (T) field conditioned on ln (T) and head data; the addition of temperature data without hydraulic head data to the update also aids refinement of the ln (T) field compared to simply interpolating ln (T) data alone these results suggest that temperature measurements are a promising data source for site characterization for heterogeneous aquifer, which can be accomplished through the full-Bayesian methodology.
Steady-State Groundwater Flow Model for Great Neck, Long Island, New York
NASA Astrophysics Data System (ADS)
Chowdhury, S. H.; Klinger, D.; Sallemi, B. M.
2001-12-01
This paper describes a comprehensive groundwater flow model for the Great Neck section of Long Island, New York. The hydrogeology of this section of Long Island is dominated by a buried erosional valley consisting of sediments comparable to the North Shore Confining Unit. This formation cross-cuts, thus is in direct hydraulic connection with the Upper Glacial, North Shore Confining Unit, Raritan Clay, and Lloyd aquifers. The Magothy aquifer is present only in remote southern sections of the model area. In addition, various lenses of coarser material from the overlying Upper Glacial aquifer are dispersed throughout the area. Data collection consisted of gathering various parameter values from existing USGS reports. Hydraulic conductivity, porosity, estimated recharge values, evapotranspiration, well locations, and water level data have all been gathered from the USGS Office located in Coram, New York. Appropriate modeling protocol was followed throughout the modeling process. The computer code utilized for solving this numerical model is Visual MODFLOW as manufactured by Waterloo Hydrogeologic. Calibration and a complete sensitivity analysis were conducted. Modeled results indicate that the groundwater flow direction is consistent with what is viewed onsite. In addition, the model is consistent in returning favorable parameter results to historical data.
NASA Astrophysics Data System (ADS)
Rassi, Erik M.; Codd, Sarah L.; Seymour, Joseph D.
2011-01-01
Flow in porous media and the resultant hydrodynamics are important in fields including but not limited to the hydrology, chemical, medical and petroleum industries. The observation and understanding of the hydrodynamics in porous media are critical to the design and optimal utilization of porous media, such as those seen in trickle-bed reactors, medical filters, subsurface flows and carbon sequestration. Magnetic resonance (MR) provides for a non-invasive technique that can probe the hydrodynamics on pore and bulk scale lengths; many previous works have characterized fully saturated porous media, while rapid MR imaging (MRI) methods in particular have previously been applied to partially saturated flows. We present time- and ensemble-averaged MR measurements to observe the effects on a bead pack partially saturated with air under flowing water conditions. The 10 mm internal diameter bead pack was filled with 100 μm borosilicate glass beads. Air was injected into the bead pack as water flowed simultaneously through the sample at 25 ml h-1. The initial partially saturated state was characterized with MRI density maps, free induction decay (FID) experiments, propagators and velocity maps before the water flow rate was increased incrementally from 25 to 500 ml h-1. After the maximum flow rate of 500 ml h-1, the MRI density maps, FID experiments, propagators and velocity maps were repeated and compared to the data taken before the maximum flow rate. This work shows that a partially saturated single-phase flow has global flow dynamics that return to characteristic flow statistics once a steady-state high flow rate has been reached. This high flow rate pushed out a significant amount of the air in the bead pack and caused the return of a preferential flow pattern. Velocity maps indicated that local flow statistics were not the same for the before and after blow out conditions. It has been suggested and shown previously that a flow pattern can return to
NASA Technical Reports Server (NTRS)
Ciepluch, Carl C.
1948-01-01
An investigation was conducted in an altitude test chamber to determine the effects of inlet airflow distortion on the compressor steady-state and surge characteristics of a high-pressure ratio, axial-flow turbojet engine. Circumferential-type inlet flow distortions were investigated, which covered a range of distortion sector angles from 20 deg to 168 deg and distortion levels up to 22 percent. The presence of inlet airflow distortions at the compressor face resulted in a substantial increase in the local pressure ratio in the distorted region, primarily for the inlet stages. The local pressure ratio in the distorted region for the inlet stages increased as either the distortion sector angle decreased or the percent distortion increased. The average compressor-surge pressure ratio was much more sensitive to inlet airflow distortions at lower engine speeds than at engine speeds near rated. Hence, compressor-surge margin reduction due to inlet airflow distortion was quite severe at the lower engine speeds. Although the average compressor-surge pressure ratio was generally reduced with inlet flow distortion, local pressure ratios across the distorted sector of the compressor were obtained during surge and were significantly greater than the normal compressor-surge pressure ratio. This was a result of increased loading of the inlet stages in the distorted region.
Larsen, Poul S.; Riisgård, Hans Ulrik
2012-01-01
Summary To obtain precise and reliable laboratory clearance rate (filtration rate) measurements with the ‘flow-through chamber method’ (FTC) the design must ensure that only inflow water reaches the bivalve's inhalant aperture and that exit flow is fully mixed. As earlier recommended these prerequisites can be checked by a plot of clearance rate (CR) versus increasing through-flow (Fl) to reach a plateau, which is the true CR, but we also recommend to plot percent particles cleared versus reciprocal through-flow where the plateau becomes the straight line CR/Fl, and we emphasize that the percent of particles cleared is in itself neither a criterion for valid CR measurement, nor an indicator of appropriate ‘chamber geometry’ as hitherto adapted in many studies. For the ‘steady-state method’ (SS), the design must ensure that inflow water becomes fully mixed with the bivalve's excurrent flow to establish a uniform chamber concentration prevailing at its incurrent flow and at the chamber outlet. These prerequisites can be checked by a plot of CR versus increasing Fl, which should give the true CR at all through-flows. Theoretically, the experimental uncertainty of CR for a given accuracy of concentration measurements depends on the percent reduction in particle concentration (100×P) from inlet to outlet of the ideal ‘chamber geomety’. For FTC, it decreases with increasing values of P while for SS it first decreases but then increases again, suggesting the use of an intermediate value of P. In practice, the optimal value of P may depend on the given ‘chamber geometry’. The fundamental differences between the FTC and the SS methods and practical guidelines for their use are pointed out, and new data on CR for the blue mussel, Mytilus edulis, illustrate a design and use of the SS method which may be employed in e.g. long-term growth experiments at constant algal concentrations. PMID:23213362
Algorithms and a short description of the D1_Flow program for numerical modeling of one-dimensional steady-state flow in horizontally heterogeneous aquifers with uneven sloping bases are presented. The algorithms are based on the Dupuit-Forchheimer approximations. The program per...
NASA Astrophysics Data System (ADS)
Nwosu, Cajethan M.; Oti, Stephen E.; Ogbuka, Cosmas U.
2017-01-01
This paper presents transient and steady state performance analysis of power flow control in a 5.0 kW Doubly-Fed Induction Generator (DFIG) Variable Speed Wind Turbine (VSWT) under sub synchronous speed, super synchronous speed and synchronous speed modes of operation. Stator flux orientation is used for the control of the rotor-side converter (RSC) and DFIG whereas the grid (or stator) voltage orientation is the preferred choice for the control of the grid-side converter (GSC). In each of the three speeds modes, power is always supplied to the grid through the stator of the DFIG. The magnitude of net power (stator power plus rotor power) is less than stator power during the sub synchronous speed mode; it is greater than stator power during the super synchronous speed mode while it is equal to the stator power during the synchronous speed mode. In synchronous speed mode, the rotor power is zero indicating that power is neither supplied to the grid from the rotor nor supplied to the rotor from the grid; here the magnitude of net power is equal to stator power. The simulation results thus obtained in a MATLAB/SIMULINK environment laid credence to the controllability of power flow reversal in a DFIG-VSWT through back-to-back power electronic converter.
Williams, Kenneth A; Saini, Sunil; Wick, Timothy M
2002-01-01
Computational fluid dynamics (CFD) models to quantify momentum and mass transport under conditions of tissue growth will aid bioreactor design for development of tissue-engineered cartilage constructs. Fluent CFD models are used to calculate flow fields, shear stresses, and oxygen profiles around nonporous constructs simulating cartilage development in our concentric cylinder bioreactor. The shear stress distribution ranges from 1.5 to 12 dyn/cm(2) across the construct surfaces exposed to fluid flow and varies little with the relative number or placement of constructs in the bioreactor. Approximately 80% of the construct surface exposed to flow experiences shear stresses between 1.5 and 4 dyn/cm(2), validating the assumption that the concentric cylinder bioreactor provides a relatively homogeneous hydrodynamic environment for construct growth. Species mass transport modeling for oxygen demonstrates that fluid-phase oxygen transport to constructs is uniform. Some O(2) depletion near the down stream edge of constructs is noted with minimum pO(2) values near the constructs of 35 mmHg (23% O(2) saturation). These values are above oxygen concentrations in cartilage in vivo, suggesting that bioreactor oxygen concentrations likely do not affect chondrocyte growth. Scale-up studies demonstrate the utility and flexibility of CFD models to design and characterize bioreactors for growth of tissue-engineered cartilage.
Waddell, R.K.
1982-01-01
A two-dimensional, steady-state model of ground-water flow beneath the Nevada Test Site and vicinity has been developed using inverse techniques. The area is underlain by clastic and carbonate rocks of Precambrian and Paleozoic age and by volcanic rocks and alluvium of Tertiary and Quaternary age that have been juxtaposed by normal and strike-slip faulting. Aquifers are composed of carbonate and volcanic rocks and alluvium. Characteristics of the flow system are determined by distribution of low-conductivity rocks (barriers); by recharge originating in the Spring Mountains, Pahranagat, Timpahute, and Sheep Ranges, and in Pahute Mesa; and by underflow beneath Pahute Mesa from Gold Flat and Kawich Valley. Discharge areas (Ash Meadows, Oasis Valley, Alkali Flat, and Furnace Creek Ranch) are upgradient from barriers. Sensitivities of simulated hydraulic heads and fluxes to variations in model parameters were calculated to guide field studies and to help estimate errors in predictions from transport modeling. Hydraulic heads and fluxes are very sensitive to variations in the greater magnitude recharge/discharge terms. Transmissivity at a location may not be the most important transmissivity for determining flux there. Transmissivities and geometries of large barriers that impede flow from Pahute Mesa have major effects on fluxes elsewhere; as their transmissivities are decreased, flux beneath western Jackass Flats and Yucca Mountains is increased as water is diverted around the barriers. Fortymile Canyon is underlain by highly transmissive rocks that cause potentiometric contours to vee upgradient; increasing their transmissivity increases flow through them, and decreases it beneath Yucca Mountain. (USGS)
Ackerman, D.J.
1995-01-01
Quantitative estimates of ground-water flow directions and traveltimes for advective flow were developed for the regional aquifer system of the eastern Snake River Plain, Idaho. The work included: (1) descriptions of compartments in the aquifer that function as intermediate and regional flow systems, (2) descriptions of pathlines for flow originating at or near the water table, and (3) quantitative estimates of traveltimes for advective transport originating at or near the water table. A particle-tracking postprocessing program was used to compute pathlines on the basis of output from an existing three-dimensional steady-state flow model. The flow model uses 1980 conditions to approximate average annual conditions for 1950-80. The advective transport model required additional information about the nature of flow across model boundaries, aquifer thickness, and porosity. Porosity of two types of basalt strata has been reported for more than 1,500 individual cores from test holes, wells, and outcrops near the south side of the Idaho National Engineering Laboratory. The central 80 percent of samples had porosities of 0.08 to 0.25, the central 50 percent of samples, O. 11 to 0.21. Calibration of the model involved choosing a value for porosity that yielded the best solution. Two radiologic contaminants, iodine-129 and tritium, both introduced to the flow system about 40 years ago, are relatively conservative tracers. Iodine- 129 was considered to be more useful because of a lower analytical detection limit, longer half-life, and longer flow path. The calibration value for porosity was 0.21. Most flow in the aquifer is contained within a regional-scale compartment and follows paths that discharge to the Snake River downstream from Milner Dam. Two intermediate-scale compartments exist along the southeast side of the aquifer and near Mud Lake.One intermediate-scale compartment along the southeast side of the aquifer discharges to the Snake River near American Fails
NASA Technical Reports Server (NTRS)
Gartling, D. K.; Roache, P. J.
1978-01-01
The efficiency characteristics of finite element and finite difference approximations for the steady-state solution of the Navier-Stokes equations are examined. The finite element method discussed is a standard Galerkin formulation of the incompressible, steady-state Navier-Stokes equations. The finite difference formulation uses simple centered differences that are O(delta x-squared). Operation counts indicate that a rapidly converging Newton-Raphson-Kantorovitch iteration scheme is generally preferable over a Picard method. A split NOS Picard iterative algorithm for the finite difference method was most efficient.
Holtschlag, D.J.; Koschik, J.A.
2001-01-01
St. Clair and Detroit Rivers are connecting channels between Lake Huron and Lake Erie in the Great Lakes waterway, and form part of the boundary between the United States and Canada. St. Clair River, the upper connecting channel, drains 222,400 square miles and has an average flow of about 182,000 cubic feet per second. Water from St. Clair River combines with local inflows and discharges into Lake St. Clair before flowing into Detroit River. In some reaches of St. Clair and Detroit Rivers, islands and dikes split the flow into two to four branches. Even when the flow in a reach is known, proportions of flows within individual branches of a reach are uncertain. Simple linear regression equations, subject to a flow continuity constraint, are developed to provide estimators of these proportions and flows. The equations are based on 533 paired measurements of flow in 13 reaches forming 31 branches. The equations provide a means for computing the expected values and uncertainties of steady-state flows on the basis of flow conditions specified at the upstream boundaries of the waterway. In 7 upstream reaches, flow is considered fixed because it can be determined on the basis of flows specified at waterway boundaries and flow continuity. In these reaches, the uncertainties of flow proportions indicated by the regression equations can be used directly to determine the uncertainties of the corresponding flows. In the remaining 6 downstream reaches, flow is considered uncertain because these reaches do not receive flow from all the branches of an upstream reach, or they receive flow from some branches of more than one upstream reach. Monte Carlo simulation analysis is used to quantify this increase in uncertainty associated with the propagation of uncertainties from upstream reaches to downstream reaches. To eliminate the need for Monte Carlo simulations for routine calculations, polynomial regression equations are developed to approximate the variation in uncertainties as
NASA Astrophysics Data System (ADS)
Reynolds, C. A.; Menke, H. P.; Blunt, M. J.; Krevor, S. C.
2015-12-01
We observe a new type of non-wetting phase flow using time-resolved pore scale imaging. The traditional conceptual model of drainage involves a non-wetting phase invading a porous medium saturated with a wetting phase as either a fixed, connected flow path through the centres of pores or as discrete ganglia which move individually through the pore space, depending on the capillary number. We observe a new type of flow behaviour at low capillary number in which the flow of the non-wetting phase occurs through networks of persistent ganglia that occupy the large pores but continuously rearrange their connectivity (Figure 1). Disconnections and reconnections occur randomly to provide short-lived pseudo-steady state flow paths between pores. This process is distinctly different to the notion of flowing ganglia which coalesce and break-up. The size distribution of ganglia is dependent on capillary number. Experiments were performed by co-injecting N2and 25 wt% KI brine into a Bentheimer sandstone core (4mm diameter, 35mm length) at 50°C and 10 MPa. Drainage was performed at three flow rates (0.04, 0.3 and 1 ml/min) at a constant fractional flow of 0.5 and the variation in ganglia populations and connectivity observed. We obtained images of the pore space during steady state flow with a time resolution of 43 s over 1-2 hours. Experiments were performed at the Diamond Light Source synchrotron. Figure 1. The position of N2 in the pore space during steady state flow is summed over 40 time steps. White indicates that N2 occupies the space over >38 time steps and red <5 time steps.
Naehle, Claas P; Steinberg, Verena A; Schild, Hans; Mommertz, Gottfried
2015-05-01
Noninvasive measurement of peripheral muscle microperfusion could potentially improve diagnosis, management, and treatment of peripheral arterial disease (PAD) and thus improve patient care. Contrast-enhanced ultrasound (CEUS) as a noninvasive diagnostic tool allows quantification of muscle perfusion. Increasing data on bolus technique CEUS reflecting microperfusion are becoming available, but only limited data on steady-state CEUS for assessment of muscle microperfusion are available. Therefore, the aim of this study was to evaluate steady-state CEUS for assessment of peripheral muscle microperfusion in a PAD animal model. In a porcine animal model, peripheral muscle microperfusion was quantified by steady-state CEUS replenishment kinetics (mean transit time [mTT] and wash-in rate [WiR]) of the biceps femoris muscle during intravenous steady-state infusion of INN-sulfur hexafluoride (SonoVue; Bracco, Geneva, Switzerland). In addition, macroperfusion was quantified at the external femoral artery with a Doppler flow probe. Peripheral muscle microperfusion and Doppler flow measurements were performed bilaterally at rest and under adenosine stress (70 μg/kg body weight) before and after unilateral creation of a moderate external iliac artery stenosis. All measurements could be performed completely in 10 pigs. Compared with baseline measurements, peripheral muscle microperfusion decreased significantly during adenosine stress (rest vs adenosine stress: mTT, 7.8 ± 3.3 vs 21.2 ± 17.8 s, P = .0006; WiR, 58.4 ± 38.1 vs 25.3 ± 15.6 arbitrary units [a.u.]/s, P < .0001; Doppler flow, 122.3 ± 31.4 vs 83.6 ± 28.1 mL/min, P = .0067) and after stenosis creation (no stenosis vs stenosis: mTT, 8.1 ± 3.1 vs 29.2 ± 18.0 s, P = .0469; WiR, 53.0 ± 22.7 vs 13.6 ± 8.4 a.u./s, P = .0156; Doppler flow, 124.2 ± 41.8 vs 65.9 ± 40.0 mL/min, P = .0313). After stenosis creation, adenosine stress led to a further significant decrease of peripheral muscle microperfusion but had no
Yan, Tony Q; Orihuela, Carlos; Swanson, David
2008-02-01
This article discusses the chromatographic resolution of a racemic pharmaceutical intermediate. Preparative batch high performance liquid chromatography (HPLC), supercritical fluid chromatography (SFC), steady-state recycling (SSR), and simulated moving bed (SMB) were used to resolve a total of 12.2 kg of a racemic pharmaceutical intermediate. In this study, a first batch of 0.8 kg of racemate was separated on the preparative batch HPLC and SFC, and subsequently another 5.9 kg of racemate was separated on the SSR. Lastly, a third batch of 5.5 kg was separated on the SMB. The separation conditions and results of these techniques are discussed. The productivities and solvent costs of SFC versus HPLC are compared. The productivities and solvent costs of SMB, SSR, and HPLC are also compared. The analytical method development and process optimization of these processes are also discussed in this article.
NASA Astrophysics Data System (ADS)
Llebot, J. E.; Tremblay, A.-M. S.
1986-03-01
It is shown that calculations of fluctuations in fluids driven into a stationary state by a temperature gradient are independent of the thermodynamic representation even to nonlinear order in the temperature gradient. The contrast between this result and the conjecture of Garibay-Jiménez and García-Colin, Physica 130A (1985) 616, is clarified.
Kernodle, J.M.
1996-01-01
As part of a multidisciplinary regional aquifer-system analysis, a three-dimensional steady-state ground-water-flow model was constructed for the San Juan Basin in parts of New Mexico, Colorado, Arizona, and Utah. The model simulated ground- water flow in 12 hydrostratigraphic units representing all of the major sources of ground water from aquifers of Jurassic and younger age. Ten map reports in the U.S. Geological Survey Hydrologic Investigations Atlas 720 series were prepared in conjunction with this investigation. The units that were described in the atlases were the San Jose, Nacimiento, and Animas Formations; Ojo Alamo Sandstone; Kirtland Shale and Fruitland Formation; Pictured Cliffs Sandstone; Cliff House Sandstone; Menefee Formation; Point Lookout Sandstone; Gallup Sandstone; Dakota Sandstone; and Morrison Formation. Additional descriptions of the alluvial and landslide deposits, Chuska and Crevasse Canyon Sandstones, Lewis and Mancos Shales, Wanakah Formation, and Entrada Sandstone are included in this report. Much of the information in the HA-720 series was generated from digital computer data bases that were directly usable by the computer for compilation of input data for the model. In essence, the major components of the ground-water- flow model were described and documented in the series of hydrologic atlases. The primary finding resulting from the ground-water-flow simulation was that boundary conditions and internal geometry of the aquifers are the major controls of steady-state ground-water flow and hydraulic heads in the San Juan Basin. Another significant finding was that the computed steady-state ground- water flux is a very minor component (about 1 percent) of the total water budget of the basin.
NASA Astrophysics Data System (ADS)
Nœtinger, B.
2015-02-01
Modeling natural Discrete Fracture Networks (DFN) receives more and more attention in applied geosciences, from oil and gas industry, to geothermal recovery and aquifer management. The fractures may be either natural, or artificial in case of well stimulation. Accounting for the flow inside the fracture network, and accounting for the transfers between the matrix and the fractures, with the same level of accuracy is an important issue for calibrating the well architecture and for setting up optimal resources recovery strategies. Recently, we proposed an original method allowing to model transient pressure diffusion in the fracture network only [1]. The matrix was assumed to be impervious. A systematic approximation scheme was built, allowing to model the initial DFN by a set of N unknowns located at each identified intersection between fractures. The higher N, the higher the accuracy of the model. The main assumption was using a quasi steady state hypothesis, that states that the characteristic diffusion time over one single fracture is negligible compared with the characteristic time of the macroscopic problem, e.g. change of boundary conditions. In that context, the lowest order approximation N = 1 has the form of solving a transient problem in a resistor/capacitor network, a so-called pipe network. Its topology is the same as the network of geometrical intersections between fractures. In this paper, we generalize this approach in order to account for fluxes from matrix to fractures. The quasi steady state hypothesis at the fracture level is still kept. Then, we show that in the case of well separated time scales between matrix and fractures, the preceding model needs only to be slightly modified in order to incorporate these fluxes. The additional knowledge of the so-called matrix to fracture transfer function allows to modify the mass matrix that becomes a time convolution operator. This is reminiscent of existing space averaged transient dual porosity models.
Ackerman, Daniel J.; Rousseau, Joseph P.; Rattray, Gordon W.; Fisher, Jason C.
2010-01-01
Three-dimensional steady-state and transient models of groundwater flow and advective transport in the eastern Snake River Plain aquifer were developed by the U.S. Geological Survey in cooperation with the U.S. Department of Energy. The steady-state and transient flow models cover an area of 1,940 square miles that includes most of the 890 square miles of the Idaho National Laboratory (INL). A 50-year history of waste disposal at the INL has resulted in measurable concentrations of waste contaminants in the eastern Snake River Plain aquifer. Model results can be used in numerical simulations to evaluate the movement of contaminants in the aquifer. Saturated flow in the eastern Snake River Plain aquifer was simulated using the MODFLOW-2000 groundwater flow model. Steady-state flow was simulated to represent conditions in 1980 with average streamflow infiltration from 1966-80 for the Big Lost River, the major variable inflow to the system. The transient flow model simulates groundwater flow between 1980 and 1995, a period that included a 5-year wet cycle (1982-86) followed by an 8-year dry cycle (1987-94). Specified flows into or out of the active model grid define the conditions on all boundaries except the southwest (outflow) boundary, which is simulated with head-dependent flow. In the transient flow model, streamflow infiltration was the major stress, and was variable in time and location. The models were calibrated by adjusting aquifer hydraulic properties to match simulated and observed heads or head differences using the parameter-estimation program incorporated in MODFLOW-2000. Various summary, regression, and inferential statistics, in addition to comparisons of model properties and simulated head to measured properties and head, were used to evaluate the model calibration. Model parameters estimated for the steady-state calibration included hydraulic conductivity for seven of nine hydrogeologic zones and a global value of vertical anisotropy. Parameters
Trapp, Henry; Geiger, L.H.
1986-01-01
The sand-and-gravel aquifer is the only freshwater aquifer in southern Escambia County, Florida and is the source of public water supply for the area, including the City of Pensacola. The aquifer was simulated by a two-layer, digital model to provide hydrologic information for water resource planning. The lower layer represents the main-producing zone; the upper layer represents all of the aquifer above the main-producing zone including an unconfined zone and discontinuous perched, confined , and confining zones. The model was designed for steady-state simulation and predicts the response of the aquifer (changes in water levels) to groundwater pumping where steady-state conditions have been reached. Input to the model includes matrices representing constant-head nodes, starting head, transmissivity of layer 1, leakance between layers 1 and 2, lateral hydraulic conductivity of layer 2, and altitude of the base layer 2. The sources of water to the model are from recharge by infiltrated precipitation (estimated from base runoff), inflow across boundaries, and induced recharge from river leakance in periods of prolonged groundwater pumping. Model output includes final head and drawdown for each layer and total values for discharge and recharge in the model area. The model was calibrated for 1972 pumping and tested by simulating pumpages during 1939-40, 1958, and 1977. Sensitivity analyses showed water levels in both layers were most sensitive to changes in the recharge matrix and least sensitive to river leakage. Suggestions for further development of the model include subdivision and expansion of the grid, assignment of storage coefficients for transient simulations, more intensive study of the stream-aquifer relations, and consideration of the effects of infiltration basins on recharge. (Author 's abstract)
NASA Astrophysics Data System (ADS)
Fisher, J. C.; Ackerman, D. J.; Rousseau, J. P.; Rattray, G. W.
2009-12-01
Three-dimensional steady-state and transient models of groundwater flow and advective transport through the fractured basalts and interbedded sediments of the Eastern Snake River Plain (ESRP) aquifer were developed by the U.S. Geological Survey in cooperation with the U.S. Department of Energy. The model domain covers an area of 1,940 square miles that includes most of the Idaho National Laboratory (INL). A 50-year history of waste disposal at the INL has resulted in measurable concentrations of waste contaminants in the aquifer. Numerical models simulated 1980 steady-state conditions and transient flow for 1980-95. In the transient model, streamflow infiltration was the major stress. The models were calibrated using the parameter-estimation program incorporated in MODFLOW-2000. The steady-state model reasonably simulated the observed water-table altitude and gradients. Simulation of transient conditions reproduced changes in the flow system resulting from episodic infiltration from the Big Lost River. Analysis of simulations shows that flow is (1) dominantly horizontal through interflow zones in basalt, vertical anisotropy resulting from contrasts in hydraulic conductivity of different types of basalt and the interbedded sediments, (2) temporally variable due to streamflow infiltration from the Big Lost River, and (3) moving downward downgradient of the INL. Particle-tracking simulations were used to evaluate how simulated groundwater flow paths and travel times differ between the steady-state and transient flow models, and how well model-derived groundwater flow directions and velocities compare to independently-derived estimates. Particle tracking also was used to simulate the growth of tritium plumes originating at two INL facilities over a 16 year period under steady-state and transient flow conditions (1953-68). The shape, dimensions, and areal extent of these plumes were compared to a map of the plumes for 1968 from tritium releases beginning in 1952
Kernodle, J.M.; Scott, W.B.
1986-01-01
As part of the Southwest Alluvial Basins study, model was constructed to simulate the alluvial aquifer system underlying the Albuquerque-Belen Basin. The model was used to simulate the steady-state flow condition assumed to have existed prior to 1960. Until this time there apparently were no long-term groundwater level changes of a significant magnitude outside the immediate vicinity of Albuquerque. Therefore, the construction of a steady-state flow model of the aquifer system based on reported hydrologic data predating 1960 was justified. During construction of the steady-state model, simulated hydraulic conductivity values were adjusted, within acceptable physical limits, until a best fit between measured or reported and computed heads at 34 control wells was achieved. The modeled area was divided into six sub-areas, or zones, within each of which hydraulic conductivity was assumed to be uniform. The model consisted of six layers for each of which simulated transmissivity was proportional to the layer thickness. Adjustments to simulated hydraulic conductivity values in the different zones resulted in final values that ranged from a low of 0.25 ft/day in the west to 50 ft/day in the eastern part of the basin. The error of the simulation, defined as the absolute difference between the computed and the measured or reported water level at the corresponding point in the physical system being modeled, ranged from 0.6 ft to 36 ft, with an average of 14.6 ft for the 34 control wells. (Author 's abstract)
Tyree, Melvin T.; Christy, A. Lawrence; Ferrier, Jack M.
1974-01-01
A simple steady state iterative solution of Münch pressure-flow in unbranched sieve tubes containing only water and sucrose is derived. The iterative equations can be solved on a programmable desk calculator. Solutions are presented for steady state transport with specific mass transfer rates up to 1.5 × 10−5 mole second−1 centimeters−2 (= 18.5 grams hour−1 centimeters−2) over distances in excess of 50 meters. The calculations clearly indicate that a Münch pressure-flow system can operate over long distances provided (a) the sieve tube is surrounded by a semipermeable membrane; (b) sugars are actively loaded in one region and unloaded at another; (c) the sieve pores are unblocked so that the sieve tube hydraulic conductivity is high (around 4 centimeters2 second−1 bar−1); (d) the sugar concentration is kept high (around one molar in the source region); and (e) the average sap velocity is kept low (around 20-50 centimeters hour−1). The dimensions of sieve cells in several species of plants are reviewed and sieve tube hydraulic conductivities are calculated; the values range from 0.2 to 20 centimeters2 second−1 bar−1. For long distance pressure-flow to occur, the hydraulic conductivity of the sieve cell membranes must be about 5 × 10−7 centimeters second−1 bar−1 or greater. PMID:16658935
Tyree, M T; Christy, A L; Ferrier, J M
1974-10-01
A simple steady state iterative solution of Münch pressure-flow in unbranched sieve tubes containing only water and sucrose is derived. The iterative equations can be solved on a programmable desk calculator. Solutions are presented for steady state transport with specific mass transfer rates up to 1.5 x 10(-5) mole second(-1) centimeters(-2) (= 18.5 grams hour(-1) centimeters(-2)) over distances in excess of 50 meters. The calculations clearly indicate that a Münch pressure-flow system can operate over long distances provided (a) the sieve tube is surrounded by a semipermeable membrane; (b) sugars are actively loaded in one region and unloaded at another; (c) the sieve pores are unblocked so that the sieve tube hydraulic conductivity is high (around 4 centimeters(2) second(-1) bar(-1)); (d) the sugar concentration is kept high (around one molar in the source region); and (e) the average sap velocity is kept low (around 20-50 centimeters hour(-1)). The dimensions of sieve cells in several species of plants are reviewed and sieve tube hydraulic conductivities are calculated; the values range from 0.2 to 20 centimeters(2) second(-1) bar(-1). For long distance pressure-flow to occur, the hydraulic conductivity of the sieve cell membranes must be about 5 x 10(-7) centimeters second(-1) bar(-1) or greater.
Steady state thermal radiometers
NASA Technical Reports Server (NTRS)
Loose, J. D. (Inventor)
1974-01-01
A radiometer is described operating in a vacuum under steady state conditions. The front element is an aluminum sheet painted on the outer side with black or other absorptive material of selected characteristics. A thermocouple is bonded to the inner side of the aluminum sheet. That is backed by highly insulative layers of glass fiber and crinkled, aluminized Mylar polyester. Those layers are backed with a sturdy, polyester sheet, and the entire lamination is laced together by nylon cords. The device is highly reliable in that it does not drift out of calibration, and is significantly inexpensive.
Luvisetto, S; Schmehl, I; Cola, C; Azzone, G F
1991-11-15
1. The kinetics of acidification and realkalinization of the matrix after addition of nigericin to respiring and non-respiring mitochondria, recorded by intramitochondrial pH indicators such as neutral red and 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein (BCECF), is complementary to that recorded by extramitochondrial pH indicators. The extent of acidification decreases with the logarithm of the KCl concentration and is inhibited by Pi and ammonium ions. 2. Proton translocation during respiration has been compared with proton extraction from matrix bulk water. During oxygen pulses to EGTA-untreated mitochondria, BCECF records an extraction of protons from matrix bulk water of about 2-3 nmol H+/mg, reduced to 1-2 nmol H+/mg in EGTA-treated mitochondria. Since the amount of proton translocation required to achieve steady state is of the order of 6-7 nmol H+/mg, it appears that 75-90% of the protons are not extracted from matrix bulk water. Only a slight response is recorded by neutral red. 3. The effect of permeant cations and of uncouplers on the distribution of proton extraction between membrane and matrix bulk water has been studied in presteady state. During Sr2+ uptake, proton extrusion into cytosolic bulk water, as well as proton extraction from matrix bulk water, corresponds almost to 100% of the protons translocated by the redox proton pumps. In the absence of Sr2+, parallel to the disappearance of the proton extrusion in cytosolic bulk water, the proton extraction from matrix bulk water diminishes to about 20% of the proton translocation. 4. The mechanism by which divalent cation uptake and protonophoric uncouplers affect the distribution of proton extraction between matrix bulk water and membrane domains and the nature of the membrane domains are discussed.
Yan, Tony Q; Orihuela, Carlos; Preston, Jay P; Xia, Fang
2010-11-01
The use of phase appropriate technologies is critical for efficiently moving drug candidates forward in the early stages of drug discovery and development. Phase appropriate purification technology develops the analytical method and subsequently scales up the method and turns the sample around quickly (Kennedy et al., J Chromatogr A 2004; 1046:55). In this article, separation results and conditions from supercritical fluid chromatography (SFC), high-performance liquid chromatography (HPLC), and steady-state recycling (SSR) for the resolutions of three pharmaceutical intermediates in the early stage of the drug development are discussed. The first study used SFC and SSR to separate an impurity for a Good Manufacturing Practice (GMP) campaign. The analytical method development and scale-up conditions are discussed. Productivity, solvent usage, and sample solubility under SFC and SSR conditions are also compared. The second study compared SFC to batch HPLC in separating a diastereomer. Due to higher separation efficiency, SFC was able to resolute multiple peaks. The third study involved the addition of dichloromethane as a co-solvent in SFC purification--improving sample selectivity and solubility. From the separation results of these purifications, SFC and SSR are clearly phase appropriate technologies in the early drug development stage.
Zlotnik, V A; Zurbuchen, B R; Ptak, T
2001-01-01
Over the last decade the dipole-flow test (DFT) evolved from the general idea of using recirculatory flow to evaluate aquifer properties, to the development of prototype instrumentation and feasibility studies, to a reliable tool for characterization of aquifer heterogeneity. The DFT involves the interpretation of head in recirculatory flow between injection and extraction sections (chambers) in a single well isolated from each other by a multipacker system. In this study, the steady-state dipole flow test (DFT) has been used to characterize the statistics of horizontal hydraulic conductivity (Kr) of the highly permeable, heterogeneous, and thin aquifer at the Horkheimer Insel site, Germany. In previous studies, Kr estimates were based on the steady-state head difference between chambers. A new by-chamber interpretation is proposed that is based on drawdown within each individual chamber. This interpretation yields more detailed information on structure of heterogeneity of the aquifer without introducing complexity into the analysis. The DFT results indicate that Kr ranges from 49 to 6000 m/day (mean ln Kr [(m/s)] approximately -4, and variance of ln Kr [(m/s)] approximately 1-2). Descriptive statistics from the DFT compare well with those from previous field and laboratory tests (pumping, borehole flowmeter, and permeameter tests and grain-size analysis) at this site. It is shown that the role of confining boundaries in the DFT interpretation is negligible even in this case of a thin (< 4 m thick) aquifer. This study demonstrates the flexibility of the DFT and expands the potential application of this method to a wide range of hydrogeologic settings.
NASA Astrophysics Data System (ADS)
Lih, Shyh-Shiuh; Lee, Hyeong Jae; Bar-Cohen, Yoseph; Badescu, Mircea; Cervantes, William; Simonini, Alan
2017-04-01
One of the critical requirements for ensuring the safety of a steam pipe is to monitor the condensed water level under operation. For this objective, the authors initially developed methods and obtained preliminary test results based on the use of ultrasonic pulse-echo transducers and enhanced signal-processing tool; however, the methodology needed further development in order to obtain measurements in turbulent dynamic flow conditions. To improve the reliability of measurements taken in turbulent flow conditions, an experimental system was developed using multiple transducers driven by a multiplexer, and a data acquisition module capable of operating in any flow conditions. The system consists of a simulation testbed, which allows testing the performance over a range of flow rates and water levels and to observe flow conditions and patterns, as well as measure actual water level, flow velocities, wave conditions, etc. In this paper, we present the development details that include description of the testbed for simulating the flow of condensed water, the multiple transducers arrangement, the signal processing method, and the test results of both steady state and turbulent flow.
NASA Technical Reports Server (NTRS)
Yang, Cheng I.; Guo, Yan-Hu; Liu, C.- H.
1996-01-01
The analysis and design of a submarine propulsor requires the ability to predict the characteristics of both laminar and turbulent flows to a higher degree of accuracy. This report presents results of certain benchmark computations based on an upwind, high-resolution, finite-differencing Navier-Stokes solver. The purpose of the computations is to evaluate the ability, the accuracy and the performance of the solver in the simulation of detailed features of viscous flows. Features of interest include flow separation and reattachment, surface pressure and skin friction distributions. Those features are particularly relevant to the propulsor analysis. Test cases with a wide range of Reynolds numbers are selected; therefore, the effects of the convective and the diffusive terms of the solver can be evaluated separately. Test cases include flows over bluff bodies, such as circular cylinders and spheres, at various low Reynolds numbers, flows over a flat plate with and without turbulence effects, and turbulent flows over axisymmetric bodies with and without propulsor effects. Finally, to enhance the iterative solution procedure, a full approximation scheme V-cycle multigrid method is implemented. Preliminary results indicate that the method significantly reduces the computational effort.
NASA Astrophysics Data System (ADS)
Irvine, Dylan J.; Cartwright, Ian; Post, Vincent E. A.; Simmons, Craig T.; Banks, Eddie W.
2016-02-01
Steady state 1-D analytical solutions to estimate groundwater fluxes from temperature profiles are an attractive option because they are simple to apply, with no complex boundary or initial conditions. Steady state solutions have been applied to estimate both aquifer scale fluxes as well as to estimate groundwater discharge to streams. This study explores the sources of uncertainty in flux estimates from regional scale aquifers caused by sensor precision, aquifer heterogeneity, multidimensional flow and variations in surface temperature due to climate change. Synthetic temperature profiles were generated using 2-D groundwater flow and heat transport models with homogeneous and heterogeneous hydraulic and thermal properties. Temperature profiles were analyzed assuming temperature can be determined with a precision between 0.1°C and 0.001°C. Analysis of synthetic temperature profiles show that the Bredehoeft and Papadopulos (1965) method can provide good estimates of the mean vertical Darcy flux over the length of the temperature profile. Reliable flux estimates were obtained when the ratio of vertical to horizontal flux was as low as 0.1, and in heterogeneous media, providing that temperature at the upper boundary was constant in time. However, temporal increases in surface temperature led to over-estimation of fluxes. Overestimates increased with time since the onset of, and with the rate of surface warming. Overall, the Bredehoeft and Papadopulos (1965) method may be more robust for the conditions with constant temperature distributions than previously thought, but that transient methods that account for surface warming should be used to determine fluxes in shallow aquifers.
A novel model for smectic liquid crystals: Elastic anisotropy and response to a steady-state flow
NASA Astrophysics Data System (ADS)
Püschel-Schlotthauer, Sergej; Meiwes Turrión, Victor; Stieger, Tillmann; Grotjahn, Robin; Hall, Carol K.; Mazza, Marco G.; Schoen, Martin
2016-10-01
By means of a combination of equilibrium Monte Carlo and molecular dynamics simulations and nonequilibrium molecular dynamics we investigate the ordered, uniaxial phases (i.e., nematic and smectic A) of a model liquid crystal. We characterize equilibrium behavior through their diffusive behavior and elastic properties. As one approaches the equilibrium isotropic-nematic phase transition, diffusion becomes anisotropic in that self-diffusion D⊥ in the direction orthogonal to a molecule's long axis is more hindered than self-diffusion D∥ in the direction parallel to that axis. Close to nematic-smectic A phase transition the opposite is true, D∥ < D⊥. The Frank elastic constants K1, K2, and K3 for the respective splay, twist, and bend deformations of the director field n ̂ are no longer equal and exhibit a temperature dependence observed experimentally for cyanobiphenyls. Under nonequilibrium conditions, a pressure gradient applied to the smectic A phase generates Poiseuille-like or plug flow depending on whether the convective velocity is parallel or orthogonal to the plane of smectic layers. We find that in Poiseuille-like flow the viscosity of the smectic A phase is higher than in plug flow. This can be rationalized via the velocity-field component in the direction of the flow. In a sufficiently strong flow these smectic layers are not destroyed but significantly bent.
Noble, David J; Scoffings, Daniel; Ajithkumar, Thankamma; Williams, Michael V; Jefferies, Sarah J
2016-11-01
There is no consensus approach to covering skull base meningeal reflections-and cerebrospinal fluid (CSF) therein-of the posterior fossa cranial nerves (CNs VII-XII) when planning radiotherapy (RT) for medulloblastoma and ependymoma. We sought to determine whether MRI and specifically fast imaging employing steady-state acquisition (FIESTA) sequences can answer this anatomical question and guide RT planning. 96 posterior fossa FIESTA sequences were reviewed. Following exclusions, measurements were made on the following scans for each foramen respectively (left, right); internal acoustic meatus (IAM) (86, 84), jugular foramen (JF) (83, 85) and hypoglossal canal (HC) (42, 45). A protocol describes measurement procedure. Two observers measured distances for five cases and agreement was assessed. One observer measured all the remaining cases. IAM and JF measurement interobserver variability was compared. Mean measurement difference between observers was -0.275 mm (standard deviation 0.557). IAM and JF measurements were normally distributed. Mean IAM distance was 12.2 mm [95% confidence interval (CI) 8.8-15.6]; JF was 7.3 mm (95% CI 4.0-10.6). The HC was difficult to visualize on many images and data followed a bimodal distribution. Dural reflections of posterior fossa CNs are well demonstrated by FIESTA MRI. Measuring CSF extension into these structures is feasible and robust; mean CSF extension into IAM and JF was measured. We plan further work to assess coverage of these structures with photon and proton RT plans. Advances in knowledge: We have described CSF extension beyond the internal table of the skull into the IAM, JF and HC. Oncologists planning RT for patients with medulloblastoma and ependymoma may use these data to guide contouring.
NASA Astrophysics Data System (ADS)
Minakov, A.; Platonov, D.; Sentyabov, A.; Gavrilov, A.
2017-01-01
We performed numerical simulation of flow in a laboratory model of a Francis hydroturbine at three regimes, using two eddy-viscosity- (EVM) and a Reynolds stress (RSM) RANS models (realizable k-ɛ, k-ω SST, LRR) and detached-eddy-simulations (DES), as well as large-eddy simulations (LES). Comparison of calculation results with the experimental data was carried out. Unlike the linear EVMs, the RSM, DES, and LES reproduced well the mean velocity components, and pressure pulsations in the diffusor draft tube. Despite relatively coarse meshes and insufficient resolution of the near-wall region, LES, DES also reproduced well the intrinsic flow unsteadiness and the dominant flow structures and the associated pressure pulsations in the draft tube.
Ackerman, D.J.
1995-10-01
The regional aquifer system of the eastern Snake River Plain is an important component of the hydrologic system in eastern Idaho. The aquifer was thought to be the largest unified ground-water reservoir on the North American continent but is probably second to the Floridian aquifer in the southeastern United States. Flow in the aquifer is from major recharge areas in the northeastern part of the plain to discharge areas in the southwestern part. A comprehensive analysis of the occurrence and movement of water in the aquifer was presented by Garabedian. The analysis included a description of the recharge and discharge, the hydraulic properties, and a numerical model of the aquifer. The purposes of this report are to: (1) describe compartments in the aquifer that function as intermediate and regional flow systems, (2) describe pathlines for flow originating at or near the water table, and (3) quantify traveltimes for adjective transport originating at or near the water table. The model constructed for this study and described in this report will aid those concerned with the management and protection of the aquifer. The model will serve as a tool to further our understanding of the aquifer and will aid in assessing the needs for future flow and transport studies of the aquifer.
Droplet trapping and fast acoustic release in a multi-height device with steady-state flow.
Rambach, Richard W; Linder, Kevin; Heymann, Michael; Franke, Thomas
2017-10-11
We demonstrate a novel multilayer polydimethylsiloxane (PDMS) device for selective storage and release of single emulsion droplets. Drops are captured in a microchannel cavity and can be released on-demand through a triggered surface acoustic wave pulse. The surface acoustic wave (SAW) is excited by a tapered interdigital transducer (TIDT) deposited on a piezoelectric lithium niobate (LiNbO3) substrate and inverts the pressure difference across the cavity trap to push a drop out of the trap and back into the main flow channel. Droplet capture and release does not require a flow rate change, flow interruption, flow inversion or valve action and can be achieved in as fast as 20 ms. This allows both on-demand droplet capture for analysis and monitoring over arbitrary time scales, and continuous device operation with a high droplet rate of 620 drops per s. We hence decouple long-term droplet interrogation from other operations on the chip. This will ease integration with other microfluidic droplet operations and functional components.
NASA Astrophysics Data System (ADS)
Zhang, Da-Lin; Qiu, Sui-Zheng; Liu, Chang-Liang; Su, Guang-Hui
2008-08-01
The Molten Salt Reactor (MSR), one of the `Generation IV' concepts, is a liquid-fuel reactor, which is different from the conventional reactors using solid fissile materials due to the flow effect of fuel salt. The study on its neutronics considering the fuel salt flow, which is the base of the thermal-hydraulic calculation and safety analysis, must be done. In this paper, the theoretical model on neutronics under steady condition for a single-liquid-fueled MSR is conducted and calculated by numerical method. The neutronics model consists of two group neutron diffusion equations for fast and thermal neutron fluxes, and balance equations for six-group delayed neutron precursors considering the flow effect of fuel salt. The spatial discretization of the above models is based on the finite volume method, and the discretization equations are computed by the source iteration method. The distributions of neutron fluxes and the distributions of the delayed neutron precursors in the core are obtained. The numerical calculated results show that, the fuel salt flow has little effect on the distribution of fast and thermal neutron fluxes and the effective multiplication factor; however, it affects the distribution of the delayed neutron precursors significantly, especially the long-lived one. In addition, it could be found that the delayed neutron precursors influence the neutronics slightly under the steady condition. Supported by National Nature Science Foundation of China (10575079)
van der Hoven, Ben; van Pelt, Hans; Swart, Eleonore L; Bonthuis, Fred; Tilanus, Huug W; Bakker, Jan; Gommers, Diederik
2010-02-01
Plasma clearance of D-sorbitol, a nontoxic polyol, occurs predominantly in the liver and has been used to measure functional liver blood flow after bolus and steady- state intravenous administration. However, it is not known which of these two administration methods is superior. Therefore, plasma D-sorbitol clearance was studied in an animal model both after a bolus dose and under steady-state (SS) conditions and compared directly with liver blood flow, under normal conditions, and after the induction of endotoxin (LPS) sepsis. Adult male Wistar rats (526 +/- 38 g body wt; n = 27) were anesthetized and mechanically ventilated. Hemodynamics, hepatic arterial flow, and portal venous flow were measured. Two groups were studied, namely healthy animals that served as controls and a sepsis group that received 5 mg/kg LPS intravenously (Escherichia coli O127:B8). Each animal received either a SS infusion (0.1 mg/100 g body wt per min) or a bolus (3 mg/100 g body wt) of a 5% D-sorbitol solution intravenously in a randomized order. After the initial measurements and a 60-min pause time in between (T(1/2,sorbitol) = 9 min), a crossover was done. The hepatic clearance of D-sorbitol in the control group showed a good correlation between bolus and SS (Spearman's r = 0.7681, P = 0.0004), and both techniques correlated well with total liver blood flow (TLBF) (r = 0.7239, P = 0.0023 and r = 0.7226, P = 0.0023, respectively). Also in the sepsis group there was a good correlation between bolus and SS sorbitol clearance (r = 0.6655, P = 0.0182). In the sepsis group, only the SS clearance correlated with TLBF (r = 0.6434, P = 0.024). In conclusion, in normal and under septic conditions, hepatic clearance of D-sorbitol either by bolus or a SS infusion is comparable. In healthy animals, this also correlated well with TLBF but not in septic conditions. However, this is expected because of the changes in the liver microcirculation, shunting, and decreased hepatocyte function in sepsis.
Kuiper, Logan K.
1986-01-01
Two geostatistical approaches for the estimation of hydraulic conductivity and hydraulic head from hydraulic conductivity and hydraulic head measurements are developed for two-dimensional steady flow with sinks. For both approaches the field of the logarithm of hydraulic conductivity (log-conductivity) is represented as a random field. The first approach uses linearization of the discretized flow equations to allow the construction of the joint covariance matrix of the hydraulic head and log-conductivity measurements. It then uses maximum likelihood estimation to obtain these parameters and also a parameter associated with log-conductivity measurement error. Having found values for the parameters, it then uses kriging to form predictors for log-conductivity and hydraulic head from measured values of hydraulic conductivity and hydraulic head. The second approach uses kriging to form a parameter-dependent predictor for log-conductivity from measured hydraulic conductivity, and then uses this predicted log-conductivity placed into the discretized flow equations to compute hydraulic head. The parameters are determined by the minimization of the sum of the squares of the difference between the measured and computed hydraulic heads. A third approach simply allows the hydraulic conductivity field to be a step function with a different value for hydraulic conductivity assigned to each of several chosen regions in the two-dimensional aquifer. The three approaches are tested for hydraulic head prediction accuracy on two generated test problems, one of which is statistically generated, and also on a field problem. The third approach, despite its simplicity, performs as well or better than the other approaches.
NASA Astrophysics Data System (ADS)
Engdahl, N. B.; Bolster, D.
2015-12-01
Reactive transport problems are highly complex and contain a large number of factors that influence the temporal evolution of the system. Physical and chemical heterogeneity, mixing, and even the dimensionality of the system are all known to be important considerations but one important factor that has received comparatively little attention is the initial condition (IC). Oftentimes a single configuration for the IC is selected for a particular study and the other aspects of the problem are varied, but the sensitivity of the problem to perturbations in that IC is not addressed. This work specifically considers how minor changes to the IC affect a mixing limited reactive transport system. A relatively simple flow field is used to investigate changes in global reaction rates for a single, interface-mixing type transport problem. The IC is rotated to several different orientations for the simulations, each having identical reactant masses and initial particle distributions. Reactions are simulated using a Lagrangian, colocation based model that does not assume the reaction system is well mixed. The effects of the rotations on the mixing and reaction rates are variable, manifesting mostly as an increase in product formation relative to pure diffusion, but some configurations inhibit reactions at early times. The orientation of the interface relative to the directions of deformation and the velocity can be used to predict whether reactions rates will increase or decrease, relative to a deformation free flow. The same numerical experiments are then conducted in a transient, periodic shear flow, which exhibits similar results. Both sets of results have implications about how reaction rates should be upscaled and suggest that the configuration of the IC may be as important as proper characterization of the subsurface when considering reactions in complex systems.
NASA Astrophysics Data System (ADS)
Graham, Wendy D.; Tankersley, Claude D.
1994-05-01
Stochastic methods are used to analyze two-dimensional steady groundwater flow subject to spatially variable recharge and transmissivity. Approximate partial differential equations are developed for the covariances and cross-covariances between the random head, transmissivity and recharge fields. Closed-form solutions of these equations are obtained using Fourier transform techniques. The resulting covariances and cross-covariances can be incorporated into a Bayesian conditioning procedure which provides optimal estimates of the recharge, transmissivity and head fields given available measurements of any or all of these random fields. Results show that head measurements contain valuable information for estimating the random recharge field. However, when recharge is treated as a spatially variable random field, the value of head measurements for estimating the transmissivity field can be reduced considerably. In a companion paper, the method is applied to a case study of the Upper Floridan Aquifer in NE Florida.
NASA Astrophysics Data System (ADS)
Mather, B.; Moresi, L. N.; Cruden, A. R.
2014-12-01
Uncertainty of the lithospheric thermal regime greatly increases with depth. Measurements of temperature gradient and crustal rheology are concentrated in the upper crust, whereas the majority of the lithospheric measurements are approximated using empirical depth-dependent functions. We have applied a Monte Carlo approach to test the variation of crustal heat flow with temperature-dependent conductivity and the redistribution of heat-producing elements. The dense population of precision heat flow data in Victoria, Southeast Australia offers the ideal environment to test the variation of heat flow. A stochastically consistent anomalous zone of impossibly high Moho temperatures in the 3D model (> 900°C) correlates well with a zone of low teleseismic velocity and high electrical conductivity. This indicates that transient heat transfer has perturbed the thermal gradient and therefore a steady-state approach to 3D modelling is inappropriate in this zone. A spatial correlation between recent intraplate volcanic eruption points (< 5 Ma) and elevated Moho temperatures is a potential origin for additional latent heat in the crust.
Yobbi, D.K.
1989-01-01
A digital groundwater flow model was developed to approximate steady-state predevelopment flow conditions in the Upper Floridan aquifer of coastal west-central Florida. The aquifer is the major source of water and natural spring flow in the area. The aquifer was simulated as a one-layer system with constant vertical recharge and discharge rates. Calibrated transmissivities ranged from 8,640 sq ft/day in the northern part of the area to nearly 13,000,000 sq ft/day near large springs. Calibrated inflows were about 2,708 cu ft/sec; of this, about 2,565 cu ft/sec discharged as natural spring flow and 137 cu ft/sec discharged as upward leakage along the coast. The model was used to show how the system might respond to large manmade stresses. Withdrawal of 116 cu ft/sec from a hypothetical regional well field resulted in potentiometric-surface drawdowns ranging from 0.1 to 1.7 ft and declines of generally less than 0.2 ft along the coast. Total spring flow decreased 5%, and the effect on individual springs varied from 0.1 to 8.0%. Withdrawal of 62 cu ft/sec from the 4-sq-mi node at each spring resulted in six of seven springs to the south of the Chassahowitzka River contributing 50% of their flow to pumpage. Springs located north of the Chassahowitzka River contributed as much as 18% of their flow to pumpage. (USGS)
Mangan, M.; Mastin, L.; Sisson, T.
2004-01-01
In this paper we examine the consequences of bubble nucleation mechanism on eruptive degassing of rhyolite magma. We use the results of published high temperature and pressure decompression experiments as input to a modified version of CONFLOW, the numerical model of Mastin and Ghiorso [(2000) U.S.G.S. Open-File Rep. 00-209, 53 pp.] and Mastin [(2002) Geochem. Geophys. Geosyst. 3, 10.1029/2001GC000192] for steady, two-phase flow in vertical conduits. Synthesis of the available experimental data shows that heterogeneous nucleation is triggered at ??P 120-150 MPa, and leads to disequilibrium degassing at extreme H2O supersaturation. In this latter case, nucleation is an ongoing process controlled by changing supersaturation conditions. Exponential bubble size distributions are often produced with number densities of 106-109 bubbles/cm3. Our numerical analysis adopts an end-member approach that specifically compares equilibrium degassing with delayed, disequilibrium degassing characteristic of homogeneously-nucleating systems. The disequilibrium simulations show that delaying nucleation until ??P =150 MPa restricts degassing to within ???1500 m of the surface. Fragmentation occurs at similar porosity in both the disequilibrium and equilibrium modes (???80 vol%), but at the distinct depths of ???500 m and ???2300 m, respectively. The vesiculation delay leads to higher pressures at equivalent depths in the conduit, and the mass flux and exit pressure are each higher by a factor of ???2.0. Residual water contents in the melt reaching the vent are between 0.5 and 1.0 wt%, roughly twice that of the equilibrium model. ?? 2003 Elsevier B.V. All rights reserved.
NASA Astrophysics Data System (ADS)
Holt, W. E.; Fouch, M. J.; Flesch, L. M.; Klein, E. C.; West, J. D.
2010-12-01
500 km and perhaps more. Traction rates associated with the strain rate anomaly suggest inward-directed forcing, consistent with lithosphere coupling with mantle downwelling in the vicinity of the tomography anomaly. Whether this mantle flow is associated with an actual mantle drip [West et al., 2009] or with the sinking of a remnant section of the Juan de Fuca slab remains unresolved. Nevertheless, the contraction anomaly must constitute a transient feature, since the wider deformation field is purely extensional there. The loading mechanism of this elastic strain in the Great Basin region, as well as its release, may be related to the long-wavelength crustal velocity transients described by Wernicke et al. [2008] and Wernicke and Davis [2010].
NASA Astrophysics Data System (ADS)
Xu, Bing; Hu, Min; Zhang, Junhui
2015-09-01
The current research about the flow ripple of axial piston pump mainly focuses on the effect of the structure of parts on the flow ripple. Therein, the structure of parts are usually designed and optimized at rated working conditions. However, the pump usually has to work in large-scale and time-variant working conditions. Therefore, the flow ripple characteristics of pump and analysis for its test accuracy with respect to variant steady-state conditions and transient conditions in a wide range of operating parameters are focused in this paper. First, a simulation model has been constructed, which takes the kinematics of oil film within friction pairs into account for higher accuracy. Afterwards, a test bed which adopts Secondary Source Method is built to verify the model. The simulation and tests results show that the angular position of the piston, corresponding to the position where the peak flow ripple is produced, varies with the different pressure. The pulsating amplitude and pulsation rate of flow ripple increase with the rise of pressure and the variation rate of pressure. For the pump working at a constant speed, the flow pulsation rate decreases dramatically with the increasing speed when the speed is less than 27.78% of the maximum speed, subsequently presents a small decrease tendency with the speed further increasing. With the rise of the variation rate of speed, the pulsating amplitude and pulsation rate of flow ripple increase. As the swash plate angle augments, the pulsating amplitude of flow ripple increases, nevertheless the flow pulsation rate decreases. In contrast with the effect of the variation of pressure, the test accuracy of flow ripple is more sensitive to the variation of speed. It makes the test accuracy above 96.20% available for the pulsating amplitude of pressure deviating within a range of ±6% from the mean pressure. However, with a variation of speed deviating within a range of ±2% from the mean speed, the attainable test
Amatore, Christian; Da Mota, Nicolas; Sella, Catherine; Thouin, Laurent
2007-11-15
Integration of microelectrodes in microfluidic devices has attracted significant attention during the past years, in particular for analytical detections performed by direct or indirect electrochemical techniques. In contrast there is a lack of general theoretical treatments of the difficult diffusion-convection problems which are borne by such devices. In this context, we investigated the influence of the confining effect and hydrodynamic conditions on the steady-state amperometric responses monitored at a microband electrode embedded within a microchannel. Several convective-diffusive mass transport regimes were thus identified under laminar flow on the basis of numerical simulations performed as a function of geometrical and hydrodynamic parameters. A rationalization of these results has been proposed by establishing a zone diagram describing all the limiting and intermediate regimes. Concentration profiles generated by the electrode across the microchannel section were also simulated according to the experimental conditions. Their investigation allowed us to evaluate the thickness of the diffusive-convective layer probed by the electrode as well as the distance downstream from which the solution becomes again homogeneous across the whole microchannel section. Experimental checks of the theoretical principles delineated here have validated the present results. Experiments were performed at microband electrodes integrated in microchannels with aqueous solutions of ferrocene methanol under pressure-driven flow.
Kuniansky, E.L.
1990-01-01
A computer program based on the Galerkin finite-element method was developed to simulate two-dimensional steady-state ground-water flow in either isotropic or anisotropic confined aquifers. The program may also be used for unconfined aquifers of constant saturated thickness. Constant head, constant flux, and head-dependent flux boundary conditions can be specified in order to approximate a variety of natural conditions, such as a river or lake boundary, and pumping well. The computer program was developed for the preliminary simulation of ground-water flow in the Edwards-Trinity Regional aquifer system as part of the Regional Aquifer-Systems Analysis Program. Results of the program compare well to analytical solutions and simulations .from published finite-difference models. A concise discussion of the Galerkin method is presented along with a description of the program. Provided in the Supplemental Data section are a listing of the computer program, definitions of selected program variables, and several examples of data input and output used in verifying the accuracy of the program.
Arthur S. Rood
2004-11-01
A one-dimensional model for water flow and solute transport in the unsaturated zone under steady-state or transient flow conditions was developed from the principles of the mixing-cell model. The unsaturated zone is discretized into a series of independent mixing cells. Each cell may have unique hydrologic, lithologic, and sorptive properties. Ordinary differential equations (ODE) describe the material (water and solute) balance within each cell. Water flow equations are derived from the continuity equation assuming that unit-gradient conditions exist at all times in each cell. Pressure gradients are considered implicitly through model discretization. Unsaturated hydraulic conductivity and moisture contents are determined by the material-specific moisture characteristic curves. Solute transport processes included explicit treatment of advective processes, first-order chain decay, and linear sorption reactions. Dispersion is addressed through implicit and explicit dispersion. Implicit dispersion is an inherent feature of all mixing cell models and originates from the formulation of the problem in terms of mass balance around fully mixed volume elements. Expressions are provided that relate implicit dispersion to the physical dispersion of the system. The system of ODEs was solved using a forth-order Runge-Kutta algorithm coupled with adaptive step size control. Computer run times for transient flow and solute transport were typically several seconds on a 2-GHz Intel Pentium IV® desktop computer. The model was benchmarked against analytical solutions and finite-element approximations to the partial differential equations (PDE) describing unsaturated flow and transport. Differences between the maximum solute flux estimated by the mixing-cell model and the PDE models were typically less than 2%.
Liu, Xingrong; Van Natta, Kristine; Yeo, Helen; Vilenski, Olga; Weller, Paul E; Worboys, Philip D; Monshouwer, Mario
2009-04-01
The objective of the present study was to examine the accuracy of using unbound brain concentration determined by a brain homogenate method (C(ub)), cerebral spinal fluid concentration (C(CSF)), and unbound plasma concentration (C(up)) as a surrogate for brain interstitial fluid concentration determined by brain microdialysis (C(m)). Nine compounds-carbamazepine, citalopram, ganciclovir, metoclopramide, N-desmethylclozapine, quinidine, risperidone, 9-hydroxyrisperidone, and thiopental-were selected, and each was administered as an intravenous bolus (up to 5 mg/kg) followed by a constant intravenous infusion (1-9 mg/kg/h) for 6 h in rats. For eight of the nine compounds, the C(ub)s were within 3-fold of their C(m); thiopental had a C(m) 4-fold of its C(ub). The C(CSF)s of eight of the nine compounds were within 3-fold of their corresponding C(m); 9-hydroxyrisperidone showed a C(CSF) 5-fold of its C(m). The C(up)s of five of the nine compounds were within 3-fold of their C(m); four compounds (ganciclovir, metoclopramide, quinidine, and 9-hydroxyrisperidone) had C(up)s 6- to 14-fold of their C(m). In conclusion, the C(ub) and C(CSF) were within 3-fold of the C(m) for the majority of the compounds tested. The C(up)s were within 3-fold of C(m) for lipophilic non-P-glycoprotein (-P-gp) substrates and greater than 3-fold of C(m) for hydrophilic or P-gp substrates. The present study indicates that the brain homogenate and cerebral spinal fluid methods may be used as surrogate methods to predict brain interstitial fluid concentrations within 3-fold of error in drug discovery and development settings.
NASA Astrophysics Data System (ADS)
Flynn, M. R.; Ungarish, M.; Tan, A. W.
2012-02-01
We consider the propagation of a gravity current of density ρc at the bottom of a two-layer stratified ambient in a horizontal channel of height H, in the high-Reynolds number Boussinesq domain. The study emphasizes theoretical-analytical modeling, however, experimental and Navier-Stokes simulation data are also presented and their comparison with theory is discussed. The stratification parameters are S = (ρ1 - ρ2)/(ρc - ρ2) where ρ is the fluid density, and φ = h1R/H where h1R is the (unperturbed) ambient interface height. Here, 1 and 2 denote, respectively, the lower and upper layer and c denotes the gravity current. The reduced gravity is defined as g' = (ρc/ρ2 - 1)g. Rigorous results are obtained for the steady-state analogue of the classical problem of Benjamin [J. Fluid Mech. 31, 209 (1968)], 10.1017/S0022112068000133, in which the half-infinite gravity current has thickness h and speed U. We thereby demonstrate that the Froude number F= U/(g^' } h)^{1/2} is a function of a = h/H, S, and φ. In general, two solutions (or modes) may be realized. Issues of energy dissipation, sub- vs. supercriticality with respect to long internal waves and, more generally, the influence of upstream-propagating disturbances are discussed. For a gravity current released from a lock of height h0 and length x0, we derive an approximate shallow-water model and show that the motion is in this case governed by Ξ = H/h0, S, and φ. Although the shallow-water model neglects motion in the ambient layers and ignores the impact of propagation on stratification, the gravity current front speed in the slumping stage is in excellent agreement with measured data. Our theoretical solutions are consistent with previous results (in particular, Holyer and Huppert [J. Fluid Mech. 100, 739 (1980)] and Tan et al. [Environ. Fluid Mech. 11, 203 (2011)]), but have the advantages of being (i) derived without reliance on adjustable constants and ad hoc closures; (ii) applicable to a
Einstein's steady-state cosmology
NASA Astrophysics Data System (ADS)
O'Raifeartaigh, Cormac
2014-09-01
Last year, a team of Irish scientists discovered an unpublished manuscript by Einstein in which he attempted to construct a "steady-state" model of the universe. Cormac O'Raifeartaigh describes the excitement of finding this previously unknown work.
Arnold, L.R.
2010-01-01
The Lost Creek Designated Ground Water Basin (Lost Creek basin) is an important alluvial aquifer for irrigation, public supply, and domestic water uses in northeastern Colorado. Beginning in 2005, the U.S. Geological Survey, in cooperation with the Lost Creek Ground Water Management District and the Colorado Water Conservation Board, collected hydrologic data and constructed a steady-state numerical groundwater flow model of the Lost Creek basin. The model builds upon the work of previous investigators to provide an updated tool for simulating the potential effects of various hydrologic stresses on groundwater flow and evaluating possible aquifer-management strategies. As part of model development, the thickness and extent of regolith sediments in the basin were mapped, and data were collected concerning aquifer recharge beneath native grassland, nonirrigated agricultural fields, irrigated agricultural fields, and ephemeral stream channels. The thickness and extent of regolith in the Lost Creek basin indicate the presence of a 2- to 7-mile-wide buried paleovalley that extends along the Lost Creek basin from south to north, where it joins the alluvial valley of the South Platte River valley. Regolith that fills the paleovalley is as much as about 190 ft thick. Average annual recharge from infiltration of precipitation on native grassland and nonirrigated agricultural fields was estimated by using the chloride mass-balance method to range from 0.1 to 0.6 inch, which represents about 1-4 percent of long-term average precipitation. Average annual recharge from infiltration of ephemeral streamflow was estimated by using apparent downward velocities of chloride peaks to range from 5.7 to 8.2 inches. Average annual recharge beneath irrigated agricultural fields was estimated by using passive-wick lysimeters and a water-balance approach to range from 0 to 11.3 inches, depending on irrigation method, soil type, crop type, and the net quantity of irrigation water applied
NASA Astrophysics Data System (ADS)
Cowperthwaite, M.
1994-03-01
Methods of differential geometry and Bernoulli's equation, written as B=0, are used to develop a new approach for constructing an exact solution for axial flow in a classical, two-dimensional, ZND detonation wave in a polytropic explosive with an arbitrary rate of decomposition. This geometric approach is fundamentally different from the traditional approaches to this axial flow problem formulated by Wood and Kirkwood (WK) and Fickett and Davis (FD), and gives equations for the axial particle velocity (u), the sound speed (c), the pressure (p), and the density (ρ), that are expressed in terms of the detonation velocity (D), the extent of decomposition (λ), the polytropic index (K), and two nonideal parameters ɛ3 and ɛ1, and reduce to the equations for steady-state, one-dimensional detonation as ɛ3 and ɛ1 approach zero. In contrast to the FD approach, the equations for u and c are obtained from first integrals of a tangent vector à on (u,c,λ) space, and the invariant condition, ÃB=aB=0, bypasses the FD eigenvalue problem by defining ɛ3 in terms of the detonation velocity deficit D/D∞ and K. In contrast to the WK approach, the equations for p and ρ are obtained from equations expressing the conservation of axial momentum and energy. Because the equations for these flow variables are derived without using the conservation of mass, the axial radial particle velocity gradient (war) associated with the flow can be obtained from the continuity equation without making approximations. The relationship between ɛ1 and ɛ3 that closes the solution is obtained from equations expressing constraints imposed on the axial flow at the shock front by the axial and radial momentum equations, the curved shock and the decomposition rate law, and a particular solution is constructed from the ɛ1-ɛ3 relationship determined by a prescribed rate law and value of K. Properties of particular solutions are presented to provide a better understanding of two-dimensional detonation
Saffer, D.M.; Bekins, B.A.
1998-01-01
Down-hole geochemical anomalies encountered in active accretionary systems can be used to constrain the timing, rates, and localization of fluid flow. Here we combine a coupled flow and solute transport model with a kinetic model for smectite dehydration to better understand and quantify fluid flow in the Nankai accretionary complex offshore of Japan. Compaction of sediments and clay dehydration provide fluid sources which drive the model flow system. We explicitly include the consolidation rate of underthrust sediments in our calculations to evaluate the impact that variations in this unknown quantity have on pressure and chloride distribution. Sensitivity analysis of steady state pressure solutions constrains bulk and flow conduit permeabilities. Steady state simulations with 30% smectite in the incoming sedimentary sequence result in minimum chloride concentrations at site 808 of 550 mM, but measured chlorinity is as low as 447 mM. We simulate the transient effects of hydrofracture or a strain event by assuming an instantaneous permeability increase of 3-4 orders of magnitude along a flow conduit (in this case the de??collement), using steady state results as initial conditions. Transient results with an increase in de??collement permeability from 10-16 m2 to 10-13 m2 and 20% smectite reproduce the observed chloride profile at site 808 after 80-160 kyr. Modeled chloride concentrations are highly sensitive to the consolidation rate of underthrust sediments, such that rapid compaction of underthrust material leads to increased freshening. Pressures within the de??collement during transient simulations rise rapidly to a significant fraction of lithostatic and remain high for at least 160 kyr, providing a mechanism for maintaining high permeability. Flow rates at the deformation front for transient simulations are in good agreement with direct measurements, but steady state flow rates are 2-3 orders of magnitude smaller than observed. Fluid budget calculations
Meyer, E.; Yamamoto, Y.L.
1984-04-01
This study evaluates the discrepancy between the true CBF value and CBF value calculated according to the C/sup 15/O/sub 2/ steady-state model, for situations where the arterial input function, Ca(t), deviates considerably from its steady-state value, Ca. The fact that arterial input function and tissue O-15 concentration are not independent variables is taken into account. Inconstant or variable arterial input functions are simulated and the corresponding tissue O-15 concentrations calculated. The steady-state CBF values are evaluated for several temporal variations of Ca over the period of imaging, all derived from Ca(t) by simulation of various blood-sampling schemes, and are compared with the true CBF value. The study indicates that reliable CBF values are obtained by the C/sup 15/O/sub 2/ steady-state method even under severely impaired ''unsteady-state'' conditions, provided that either the true average arterial concentration over the entire scan, or the average concentration from multiple arterial samples, is used.
NASA Lewis Steady-State Heat Pipe Code Architecture
NASA Technical Reports Server (NTRS)
Mi, Ye; Tower, Leonard K.
2013-01-01
NASA Glenn Research Center (GRC) has developed the LERCHP code. The PC-based LERCHP code can be used to predict the steady-state performance of heat pipes, including the determination of operating temperature and operating limits which might be encountered under specified conditions. The code contains a vapor flow algorithm which incorporates vapor compressibility and axially varying heat input. For the liquid flow in the wick, Darcy s formula is employed. Thermal boundary conditions and geometric structures can be defined through an interactive input interface. A variety of fluid and material options as well as user defined options can be chosen for the working fluid, wick, and pipe materials. This report documents the current effort at GRC to update the LERCHP code for operating in a Microsoft Windows (Microsoft Corporation) environment. A detailed analysis of the model is presented. The programming architecture for the numerical calculations is explained and flowcharts of the key subroutines are given
On Steady-State Tropical Cyclones
2014-01-01
temperature, Te, in analogy to the model for the Hadley circulation of Schneider (1977) and Held and Hou (1980). The model is nearly inviscid in the flow...tangential wind speed is approximately constant. However, in many of our own calculations the upper and outer circulations are by no means steady at... circulation (Ooyama, 1969; Shapiro and Willoughby, 1982). Above the frictional boundary layer, this steady-state circulation must be along absolute angular
ERIC Educational Resources Information Center
Owens, J. A.
1982-01-01
Options for faculty utilization in a steady state are examined, with consideration for their economy or ability to increase turnover or flexibility: early retirement, part retirement, retraining, exchange with other institutions or industry, and fixed-term appointments or lecturer positions. (MSE)
Liu, Xin; Fan, Zhaoyang; Zhang, Na; Yang, Qi; Feng, Fei; Liu, Pengcheng; Zheng, Hairong; Li, Debiao
2014-09-01
To assess image quality and diagnostic performance of unenhanced magnetic resonance (MR) angiography with use of flow-sensitive dephasing (FSD)-prepared steady-state free precession (SSFP) of the foot arteries in patients with diabetes. This prospective study was approved by institutional review board. Informed consent was obtained from all subjects. Thirty-two healthy volunteers and 38 diabetic patients who had been scheduled for lower-extremity contrast material-enhanced MR angiography were recruited to undergo unenhanced MR angiography with a 1.5-T MR unit. Image quality and diagnostic accuracy of unenhanced MR angiography in the detection of significant arterial stenosis (≥50%) were assessed by two independent reviewers. Contrast-enhanced MR angiography was used as the reference standard. The difference in the percentage of diagnostic arterial segments at unenhanced MR angiography between healthy volunteers and diabetic patients was evaluated with the McNemar test and generalized estimating equation for correlated data. Signal-to-noise ratio (SNR) and artery-to-muscle contrast-to-noise ratio (CNR) of pedal arteries were measured and compared between the two MR angiography techniques by using the paired t test. All subjects successfully underwent unenhanced MR angiography of the foot. Unenhanced MR angiography yielded a high percentage of diagnostic arterial segments in both healthy volunteers (303 of 320 segments, 95%) and patients (341 of 370 segments, 92%), and there was no difference in the percentage between the two populations (P = .195). In patients, the average SNR and CNR at unenhanced MR angiography were higher than those at contrast-enhanced MR angiography (SNR: 90.7 ± 38.1 vs 81.7 ± 34.7, respectively, P = .023; CNR: 85.2 ± 33.2 vs 76.6 ± 33.5, respectively, P = .013). The average sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of unenhanced MR angiography were 88% (35 of 40 segments), 93% (107 of
Liu, Xin; Fan, Zhaoyang; Zhang, Na; Yang, Qi; Feng, Fei; Liu, Pengcheng; Li, Debiao
2014-01-01
Purpose To assess image quality and diagnostic performance of unenhanced magnetic resonance (MR) angiography with use of flow-sensitive dephasing (FSD)–prepared steady-state free precession (SSFP) of the foot arteries in patients with diabetes. Materials and Methods This prospective study was approved by institutional review board. Informed consent was obtained from all subjects. Thirty-two healthy volunteers and 38 diabetic patients who had been scheduled for lower-extremity contrast material–enhanced MR angiography were recruited to undergo unenhanced MR angiography with a 1.5-T MR unit. Image quality and diagnostic accuracy of unenhanced MR angiography in the detection of significant arterial stenosis (≥50%) were assessed by two independent reviewers. Contrast-enhanced MR angiography was used as the reference standard. The difference in the percentage of diagnostic arterial segments at unenhanced MR angiography between healthy volunteers and diabetic patients was evaluated with the McNemar test and generalized estimating equation for correlated data. Signal-to-noise ratio (SNR) and artery-to-muscle contrast-to-noise ratio (CNR) of pedal arteries were measured and compared between the two MR angiography techniques by using the paired t test. Results All subjects successfully underwent unenhanced MR angiography of the foot. Unenhanced MR angiography yielded a high percentage of diagnostic arterial segments in both healthy volunteers (303 of 320 segments, 95%) and patients (341 of 370 segments, 92%), and there was no difference in the percentage between the two populations (P = .195). In patients, the average SNR and CNR at unenhanced MR angiography were higher than those at contrast-enhanced MR angiography (SNR: 90.7 ± 38.1 vs 81.7 ± 34.7, respectively, P = .023; CNR: 85.2 ± 33.2 vs 76.6 ± 33.5, respectively, P = .013). The average sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of unenhanced MR angiography
Mechanisms of steady-state nucleate pool boiling in microgravity.
Lee, Ho Sung
2002-10-01
Research on nucleate pool boiling in microgravity using R-113 as a working fluid was conducted using a five-second drop tower and five space flights at a/g approximately 10(-4). A 19 x 38-mm flat gold film heater was used that allowed cine camera viewing both from the side and the bottom of the heater. It was concluded that for both subcooled and saturated liquids long-term steady-state pool boiling can take place in reduced gravity, but the effectiveness of the boiling heat transfer appears to depend on the heater geometry and on the size and the properties of fluids. Heat transfer is enhanced at lower heat flux levels and the CHF increases as the subcooling increases. It was found that several mechanisms are responsible for the steady-state nucleate pool boiling in the absence of buoyancy. The mechanisms considered here are defined and summarized as bubble removal, bubble coalescence, thermocapillary flow, bubble migration, and latent heat transport.
Billeter, Thomas R.; Philipp, Lee D.; Schemmel, Richard R.
1976-01-01
A microwave fluid flow meter is described utilizing two spaced microwave sensors positioned along a fluid flow path. Each sensor includes a microwave cavity having a frequency of resonance dependent upon the static pressure of the fluid at the sensor locations. The resonant response of each cavity with respect to a variation in pressure of the monitored fluid is represented by a corresponding electrical output which can be calibrated into a direct pressure reading. The pressure drop between sensor locations is then correlated as a measure of fluid velocity. In the preferred embodiment the individual sensor cavities are strategically positioned outside the path of fluid flow and are designed to resonate in two distinct frequency modes yielding a measure of temperature as well as pressure. The temperature response can then be used in correcting for pressure responses of the microwave cavity encountered due to temperature fluctuations.
Hew-Butler, Tamara; Noakes, Timothy D; Soldin, Steven J; Verbalis, Joseph G
2008-12-01
Maintenance of fluid homeostasis during periods of heightened physical stress can be best evaluated in humans using exercise as a model. Although it is well established that arginine vasopressin (AVP), aldosterone and atrial natriuretic peptide (ANP) are the principle hormones regulating fluid balance at rest, the potential contributions of other related endocrine factors, such as oxytocin (OT) and brain natriuretic peptide (BNP), have not been well described during exercise. Seven endurance-trained runners completed three separate running trials: a maximal test to exhaustion (high intensity), a 60-min treadmill run (steady state), and a 56 km ultramarathon (prolonged endurance exercise). Statistically significant pre- to post-run increases were found only following the ultramarathon in [AVP](p) (1.9 vs 6.7 pg/ml; P<0.05), [OT](p) (1.5 vs 3.5 pg/ml; P<0.05), [NT-proBNP](p) (23.6 vs 117.9 pg/ml; P<0.01), [interleukin 6](p) (4.0 vs 59.6 pg/ml; P<0.05), [cortisol](p) (14.6 vs 32.6 microg/ml; P<0.01), [corticosterone](p) (652.8 vs 3491.4 ng/ml; P<0.05) and [11-deoxycortisol](p) (0.1 vs 0.5 microg/ml; P<0.05) while a significant post-run increase in [aldosterone](p) was documented after high-intensity (4.9 vs 12.5 ng/ml; P<0.05), steady-state (6.1 vs 16.9 ng/ml; P<0.05) and prolonged endurance running (2.6 vs 19.7 ng/ml; P<0.05). Similarly, changes in fluid balance parameters were significantly different between the ultramarathon versus high-intensity and steady-state running with regard to plasma volume contraction (less % contraction), body weight loss (increased % weight loss), plasma [Na(+)] Delta (decreased from baseline), and urine osmolality Delta (increase from baseline). Hypothetically driven relationships between [OT](p) and [AVP](p) (r=0.69; P<0.01) and between [NT-proBNP](p) Delta and plasma [Na(+)] Delta (r=-0.79; P<0.001)--combined with the significant and unexpected pre- to post-race increases after prolonged endurance exercise--allows for possible
Geophysical fluid flow experiment
NASA Technical Reports Server (NTRS)
Broome, B. G.; Fichtl, G.; Fowlis, W.
1979-01-01
The essential fluid flow processes associated with the solar and Jovian atmospheres will be examined in a laboratory experiment scheduled for performance on Spacelab Missions One and Three. The experimental instrumentation required to generate and to record convective fluid flow is described. Details of the optical system configuration, the lens design, and the optical coatings are described. Measurement of thermal gradient fields by schlieren techniques and measurement of fluid flow velocity fields by photochromic dye tracers is achieved with a common optical system which utilizes photographic film for data recording. Generation of the photochromic dye tracers is described, and data annotation of experimental parameters on the film record is discussed.
Steady states and stability in metabolic networks without regulation.
Ivanov, Oleksandr; van der Schaft, Arjan; Weissing, Franz J
2016-07-21
Metabolic networks are often extremely complex. Despite intensive efforts many details of these networks, e.g., exact kinetic rates and parameters of metabolic reactions, are not known, making it difficult to derive their properties. Considerable effort has been made to develop theory about properties of steady states in metabolic networks that are valid for any values of parameters. General results on uniqueness of steady states and their stability have been derived with specific assumptions on reaction kinetics, stoichiometry and network topology. For example, deep results have been obtained under the assumptions of mass-action reaction kinetics, continuous flow stirred tank reactors (CFSTR), concordant reaction networks and others. Nevertheless, a general theory about properties of steady states in metabolic networks is still missing. Here we make a step further in the quest for such a theory. Specifically, we study properties of steady states in metabolic networks with monotonic kinetics in relation to their stoichiometry (simple and general) and the number of metabolites participating in every reaction (single or many). Our approach is based on the investigation of properties of the Jacobian matrix. We show that stoichiometry, network topology, and the number of metabolites that participate in every reaction have a large influence on the number of steady states and their stability in metabolic networks. Specifically, metabolic networks with single-substrate-single-product reactions have disconnected steady states, whereas in metabolic networks with multiple-substrates-multiple-product reactions manifolds of steady states arise. Metabolic networks with simple stoichiometry have either a unique globally asymptotically stable steady state or asymptotically stable manifolds of steady states. In metabolic networks with general stoichiometry the steady states are not always stable and we provide conditions for their stability. In order to demonstrate the biological
Fluid Mechanics of Inhalant Siphon Flows
NASA Astrophysics Data System (ADS)
True, A. C.; Crimaldi, J. P.
2016-02-01
Inhalant siphon and suction flows are ubiquitous in marine ecosystems. From biological flows in filter-feeding benthic bivalves and predation by planktivorous fishes, to engineered flows in water samplers and production of hydrodynamic stimuli for laboratory assays, inhalant siphon flows span much of the laminar range (Reynolds number 0.01 - 2,000) and fundamentally influence many transport and exchange processes. Direct numerical simulations (DNS) of inhalant siphon flows with varying Reynolds numbers and geometries have informed design and construction of an index of refraction-matched flow facility (mineral oil, borosilicate glass tubing) in which we are employing particle image velocimetry (PIV) to quantify transient and steady-state flow fields outside and inside the siphon tube. Varying siphon diameter, flow rate, and extraction height allows us to evaluate effects of Reynolds number and siphon geometry on local hydrodynamics. This complementary experimental and numerical modeling investigation of siphon flow hydrodynamics was motivated recently by a colleague whose biologically inspired numerical modeling of inhalant siphons using a boundary condition of constant volumetric outflow (as opposed to the classically assumed uniform inlet velocity profile) revealed nontrivial departures from idealized flows: inviscid potential flows (i.e. point sink) and pipe flows (the classical pipe entry problem), particularly in the low Reynolds number regime. Reduced entrance lengths, larger radial inflows, and modifications to fluid capture zones seen numerically at low Reynolds number are being tested experimentally and may have important implications for both biological and engineered siphons.
Fluid-solid transition in unsteady shearing flows
NASA Astrophysics Data System (ADS)
Vescovi, Dalila; Berzi, Diego; di Prisco, Claudio
2017-06-01
This paper focuses on the mechanical behaviour of granular systems under shearing, unsteady conditions. The results of numerical simulations of time evolving, homogeneous, shear flows of an assembly of frictional spheres, under constant volume conditions are illustrated. Simulations have been performed considering three volume fractions corresponding to fluid, solid and near-to-critical conditions at steady state. The three systems follow very different evolutionary paths, in terms of pressure, coordination number and stress ratio. Fluid-like and solid-like systems exhibit large and small fluctuations, respectively, in those quantities. A critical value of the coordination number seems to govern the transition from fluid to solid.
A locally implicit method for fluid flow problems
NASA Technical Reports Server (NTRS)
Reddy, K. C.
1986-01-01
The fluid flow inside the space shuttle main engine (SSME) traverses through a complex geometrical configuration. The flow is compressible, viscous, and turbulent with pockets of separated regions. Several computer codes are being developed to solve three dimensional Navier-Stokes equations with different turbulence models for analyzing the SSME internal flow. The locally implicit scheme is a computationally efficient scheme which converges rapidly in multi-grid modes for elliptic problems. It has the promise of providing a rapidly converging algorithm for steady-state viscous flow problems.
Enceladus is not in Steady State
NASA Astrophysics Data System (ADS)
Cheunchitra, T.; Stevenson, D. J.
2016-12-01
Libration data tell us there is a global ocean. Topography and gravity tell us that there is substantial compensation at degree 2, meaning that the underside of the ice shell must have topography. This topography will decay, typically on a timescale of order a million years (fortuitously similar to thermal diffusion times through the ice shell), by viscous lateral flow of the ice. This could in principle be compensated in steady state by net melting beneath the poles and a compensating net freezing at the equator. In that model, the ice shell beneath the poles is partially melted with water being continuously produced and percolating to the base (or expelled if there are cracks, as at the South Pole). We have modeled this without an a priori assumption about the strength of tidal heating. We find that even if the tidal heating is zero on average around the equator, then the latent heat release from the required freezing can only be accommodated in steady state if the ice shell is 18km. The ice thickness must be even less at the poles in order to satisfy gravity and topography. Moreover, there must then be substantial tidal heating at the poles and it is physically unreasonable to have the volumetric tidal heating at the equator be enormously less than at the North Pole. For example, if the volumetric tidal heating at the equator is on average one quarter of that at the North Pole then marginal consistency with gravity and topography may be possible for a mean ice thickness at the equator of 12km. The global heat flow may exceed 40GW, much higher than the detectable IR excess (the observed south polar tiger stripe heat flow). Recent work (Fuller et al.) admits orbital evolutions with large heat flow at least for a recent part of the orbital history. However, this thin shell steady state model has difficulty reconciling observed gravity and topography as well as the libration data. We conclude that it is unlikely that Enceladus has no net melting or freezing. The ice
NASA Astrophysics Data System (ADS)
Fix, Brandon R.; Popma, Christopher J.; Bulusu, Kartik V.; Plesniak, Michael W.
2013-11-01
Each year, hundreds of thousands of aortic and mitral heart valves are replaced with prosthetic valves. In efforts to develop a valve that does not require lifelong anticoagulation therapy, previous experimental research has been devoted to analyzing the hemodynamics of various heart valve designs, limited to the flow up to only 2 diameters downstream of the valve. Two-component, two-dimensional (2C-2D) particle image velocimetry (PIV) was used in this study to examine secondary flow velocity fields in a curved tube modeling an aorta at five locations (0-, 45-, 90-, 135-, 180-degrees). A bileaflet valve, opened to 30-, 45-, and 59-degrees, and one (no-valve) baseline condition were examined under three steady flow inflows (Re = 218, 429, 634). In particular, variations in the two-dimensional turbulent shear stresses at each cross sectional plane were analyzed. The results suggest that bileaflet valves in the aortic model produce significant turbulence and vorticity up to 5.5 downstream diameters, i.e. up to the 90-degrees location. Expanding this research towards aortic heart valve hemodynamics highlights a need for additional studies extending beyond the typical few diameters downstream to fully characterize valvular function. Supported by the NSF Grant No. CBET- 0828903 and GW Center for Biomimetics and Bioinspired Engineering.
Inconsistencies in steady state thermodynamics
NASA Astrophysics Data System (ADS)
Dickman, Ronald; Motai, Ricardo
2014-03-01
We address the issue of extending thermodynamics to nonequilibrium steady states. Using driven stochastic lattice gases, we ask whether consistent definitions of an effective chemical potential μ, and an effective temperature Te, are possible. These quantities are determined via zero-flux conditions of particles and energy between the driven system and a reservoir. For the models considered here, the fluxes are given in terms of certain stationary average densities, eliminating the need to perturb the system by actually exchanging particles; μ and Te are thereby obtained via open-circuit measurements, using a virtual reservoir. In the lattice gas with nearest-neighbor exclusion, temperature is not relevant, and we find that the effective chemical potential, a function of density and drive strength, satisfies the zeroth law, and correctly predicts the densities of coexisting systems. In the Katz-Lebowitz-Spohn driven lattice gas, both μ and Te need to be defined. We show analytically that the zeroth law is violated, and determine the size of the violations numerically. Our results highlight a fundamental inconsistency in the extension of thermodynamics to nonequilibrium steady states. Research supported by CNPq, Brazil.
Multimode optical fibers: steady state mode exciter.
Ikeda, M; Sugimura, A; Ikegami, T
1976-09-01
The steady state mode power distribution of the multimode graded index fiber was measured. A simple and effective steady state mode exciter was fabricated by an etching technique. Its insertion loss was 0.5 dB for an injection laser. Deviation in transmission characteristics of multimode graded index fibers can be avoided by using the steady state mode exciter.
Irreversible processes at nonequilibrium steady states
Fox, Ronald Forrest
1979-01-01
It is shown that a Liapunov criterion exists for the stability of nonequilibrium steady states. This criterion is based upon the fluctuation-dissipation relation, as was first pointed out by Keizer. At steady states, the Liapunov function is constructed from the covariance matrix for the thermodynamic variables. Unlike the situation around equilibrium, at steady states the covariance matrix and the “excess entropy” matrix are not equivalent. The excess entropy, which serves as the Liapunov function around equilibrium, does not work in this capacity at steady states. Keizer's Liapunov function must be viewed as the first correct candidate for a proper Liapunov function for steady states. PMID:16592649
Steady state He II heat transfer through random packed spheres
NASA Astrophysics Data System (ADS)
Vanderlaan, M. H.; Van Sciver, S. W.
2013-10-01
Heat flow through superfluid helium (He II) contained in porous media is examined. In particular, heat transfer experiments were performed on He II contained in a bed of polyethylene spheres of uniform size arranged in random packs. Measured results include the steady state temperature drops across the three random packs of spheres (35, 49, and 98 μm diameter) and the associated steady heat inputs. Bath temperatures range from 1.7 to 2.1 K to help grasp the superfluid effects. Two pure flow regimes (laminar and turbulent) are decipherable from the heat flux dependence of the temperature gradient. Turbulent results are fitted to an empirically derived turbulent He II heat equation for large channels with an added tortuosity (extra length traveled) term that accounts for the porous media. An average tortuosity of 1.33 was obtained, which is comparable with values of 1.36-1.41 concluded from published work on classical fluid pressure drop across random packed spheres. Laminar permeability and shape factor results are compared to past studies of He II in porous media and in channel flows. The onset of turbulence is determined through a critical heat flux from which a critical Reynolds number is formulated but, does not describe He II turbulence in the normal fluid component. The addition of the laminar and turbulent heat flow equations into a unifying prediction fits the transition regime data within 25%.
Hutchinson, C.B.
1984-01-01
This report describes a quasi-three-dimensional finite-difference model for simulation of steady-state ground-water flow in the Floridan aquifer over a 932-square-mile area that contains 10 municipal well fields. The over-lying surficial aquifer contains a water table and is coupled to the Floridan aquifer by leakage term that represents flow through a confining layer separating the two aquifers. Under the steady-state condition, all storage terms are set to zero. Use of the head-controlled flux condition allows simulated head and flow changes to occur in the Floridan aquifer at the model boundaries. Procedures used to calibrate the model, test its sensitivity to input-parameter errors, and validate its accuracy for predictive purposes are described. Also included are attachments that describe setting up and running the model. Example model-interrogation runs show anticipated drawdowns under high, average, and low recharge conditions with 10 well fields pumping simultaneously at the maximum annual permitted rates totaling 186.9 million gallons per day. (USGS)
Hutchinson, C.B.; Johnson, Dale M.; Gerhart, James M.
1981-01-01
A two-dimensional finite-difference model was developed for simulation of steady-state ground-water flow in the Floridan aquifer throughout a 932-square-mile area, which contains nine municipal well fields. The overlying surficial aquifer contains a constant-head water table and is coupled to the Floridan aquifer by a leakage term that represents flow through a confining layer separating the two aquifers. Under the steady-state condition, all storage terms are set to zero. Utilization of the head-controlled flux condition allows head and flow to vary at the model-grid boundaries. Procedures are described to calibrate the model, test its sensitivity to input-parameter errors, and verify its accuracy for predictive purposes. Also included are attachments that describe setting up and running the model. An example model-interrogation run shows anticipated drawdowns that should result from pumping at the newly constructed Cross Bar Ranch and Morris Bridge well fields. (USGS)
Hasenkam, J M; Westphal, D; Reul, H; Gormsen, J; Giersiepen, M; Stodkilde-Jorgensen, H; Paulsen, P K
1987-01-01
Hot-film anemometry was used for in vitro steady-state measurements downstream of six mechanical aortic valve prostheses at flow rates 10, 20 and 30 l.min-1. Three-dimensional visualizations of velocity profiles at two downstream levels were made with the valves rotated 0 and 60 degrees in relation to the sinuses of valsalvae. The velocity fields downstream of the disc valves were generally skew with increasing velocity gradients and laminar shear stresses with increasing flow rates. Furthermore, increased skewness of the velocity profiles was noticed when the major orifices of the disc valves were towards the commissure than when approaching a sinus of valsalvae. The velocity profiles downstream of the ball valve were generally flat but with considerably more disturbed flow, consistent with the findings in turbulent flow.
Magnetically stimulated fluid flow patterns
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.
Magnetically stimulated fluid flow patterns
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.
Statistical steady state in turbulent droplet condensation
NASA Astrophysics Data System (ADS)
Siewert, Christoph; Bec, Jérémie; Krstulovic, Giorgio
2017-01-01
Motivated by systems in which droplets grow and shrink in a turbulence-driven supersaturation field, we investigate the problem of turbulent condensation in a general manner. Using direct numerical simulations we show that the turbulent fluctuations of the supersaturation field offer different conditions for the growth of droplets which evolve in time due to turbulent transport and mixing. Based on that, we propose a Lagrangian stochastic model for condensation and evaporation of small droplets in turbulent flows. It consists of a set of stochastic integro-differential equations for the joint evolution of the squared radius and the supersaturation along the droplet trajectories. The model has two parameters fixed by the total amount of water and the thermodynamic properties, as well as the Lagrangian integral timescale of the turbulent supersaturation. The model reproduces very well the droplet size distributions obtained from direct numerical simulations and their time evolution. A noticeable result is that, after a stage where the squared radius simply diffuses, the system converges exponentially fast to a statistical steady state independent of the initial conditions. The main mechanism involved in this convergence is a loss of memory induced by a significant number of droplets undergoing a complete evaporation before growing again. The statistical steady state is characterised by an exponential tail in the droplet mass distribution. These results reconcile those of earlier numerical studies, once these various regimes are considered.
High power steady state MPD thrusters
NASA Astrophysics Data System (ADS)
Auweter-Kurtz, Monika; Habiger, Harald; Kurtz, Helmut; Schrade, Herbert; Sleziona, Cristian
1993-04-01
At the Institut fuer Raumfahrtsysteme (IRS) rotation symmetric magnetoplasmadynamic thrusters with self induced magnetic fields are investigated at high current levels in a steady state operation mode. MPD thrusters with different geometrics were compared, and the influence of mass flow rate and power input on the operating conditions of the thrusters explored. By optical and probe measurements, a systematic investigation of the plasma plume has been started. The investigation of the various instabilities of the arc and the plasma flow appearing at high power levels was continued. The computer code development for the geometry optimization of continuous self-field MPD thrusters, running with argon, was modified by considering higher degrees of ionization, which showed better agreement with the experiment.
Steady state and a general scale law of deformation
NASA Astrophysics Data System (ADS)
Huang, Yan
2017-07-01
Steady state deformation has been characterized based on the experimental results for dilute single-phase aluminium alloys. It was found that although characteristic properties such as flow stress and grain size remained constant with time, a continuous loss of grain boundaries occurred as an essential feature at steady state. A physical model, which takes into account the activity of grain boundary dislocations, was developed to describe the kinetics of steady state deformation. According to this model, the steady state as a function of strain rate and temperature defines the limit of the conventional grain size and strength relationship, i.e., the Hall-Petch relation holds when the grain size is larger than that at the steady state, and an inverse Hall-Petch relation takes over if grain size is smaller than the steady state value. The transition between the two relationships relating grain size and strength is a phenomenon that depends on deformation conditions, rather than an intrinsic property as generally perceived. A general scale law of deformation is established accordingly.
Venusian hydrology: Steady state reconsidered
NASA Technical Reports Server (NTRS)
Grinspoon, David H.
1992-01-01
In 1987, Grinspoon proposed that the data on hydrogen abundance, isotopic composition, and escape rate were consistent with the hypothesis that water on Venus might be in steady state rather than monotonic decline since the dawn of time. This conclusion was partially based on a derived water lifetime against nonthermal escape of approximately 10(exp 8) yr. De Bergh et al., preferring the earlier Pioneer Venus value of 200 ppm water to the significantly lower value detected by Bezard et al., found H2O lifetimes of greater than 10(exp 9) yr. Donahue and Hodges derived H2O lifetimes of 0.4-5 x 10 (exp 9) yr. Both these analyses used estimates of H escape flux between 0.4 x 10(exp 7) and 1 x 10(exp 7) cm(exp -2)s(exp -1) from Rodriguez et al. Yet in more recent Monte Carlo modeling, Hodges and Tinsley found an escape flux due to charge exchange with hot H(+) of 2.8 x 10(exp 7) cm(exp -2)s(exp -1). McElroy et al. estimated an escape flux of 8 x 10(exp 6) cm(exp -2)s(exp -1) from collisions with hot O produced by dissociative recombination of O2(+). Brace et al. estimated an escape flux of 5 x 10(exp 6) cm(exp -2)s(exp -1) from ion escape from the ionotail of Venus. The combined estimated escape flux from all these processes is approximately 4 x 10(exp 7) cm(exp -2)s(exp -1). The most sophisticated analysis to date of near-IR radiation from Venus' nightside reveals a water mixing ratio of approximately 30 ppm, suggesting a lifetime against escape for water of less than 10(exp 8) yr. Large uncertainties remain in these quantities, yet the data point toward a steady state. Further evaluation of these uncertainties, and new evolutionary modeling incorporating estimates of the outgassing rate from post-Magellan estimates of the volcanic resurfacing rate are presented.
Spatial variation of the magnetic field inside laminar flows of a perfect conductive fluid
NASA Astrophysics Data System (ADS)
Duka, Bejo; Boçi, Sonila
2017-01-01
The steady state of a perfect conductive fluid in laminar flow resulting from the ‘Hall effect’ is studied. Using the Maxwell equations, the spatial variation of the magnetic field in the steady state is calculated for three cases of different fluid flow geometries: flow between two infinite parallel planes, flow between two coaxial infinite-long cylinders and flow between two concentric spheres. According to our calculation of the three cases, the spatial variation of the magnetic field depends on the flow velocity. The magnetic field is strengthened in layers where the velocity is greater, but this dependency is negligible for non relativistic flows. Our approach in this study provides an example of how to receive interesting results using only basic knowledge of physics and mathematics.
Belcher, Wayne R.; Faunt, Claudia C.; D'Agnese, Frank A.
2002-01-01
The U.S. Geological Survey, in cooperation with the Department of Energy and other Federal, State, and local agencies, is evaluating the hydrogeologic characteristics of the Death Valley regional ground-water flow system. The ground-water flow system covers an area of about 100,000 square kilometers from latitude 35? to 38?15' North to longitude 115? to 118? West, with the flow system proper comprising about 45,000 square kilometers. The Death Valley regional ground-water flow system is one of the larger flow systems within the Southwestern United States and includes in its boundaries the Nevada Test Site, Yucca Mountain, and much of Death Valley. Part of this study includes the construction of a three-dimensional hydrogeologic framework model to serve as the foundation for the development of a steady-state regional ground-water flow model. The digital framework model provides a computer-based description of the geometry and composition of the hydrogeologic units that control regional flow. The framework model of the region was constructed by merging two previous framework models constructed for the Yucca Mountain Project and the Environmental Restoration Program Underground Test Area studies at the Nevada Test Site. The hydrologic characteristics of the region result from a currently arid climate and complex geology. Interbasinal regional ground-water flow occurs through a thick carbonate-rock sequence of Paleozoic age, a locally thick volcanic-rock sequence of Tertiary age, and basin-fill alluvium of Tertiary and Quaternary age. Throughout the system, deep and shallow ground-water flow may be controlled by extensive and pervasive regional and local faults and fractures. The framework model was constructed using data from several sources to define the geometry of the regional hydrogeologic units. These data sources include (1) a 1:250,000-scale hydrogeologic-map compilation of the region; (2) regional-scale geologic cross sections; (3) borehole information, and (4
Fluid flow in nanopores: Accurate boundary conditions for carbon nanotubes
NASA Astrophysics Data System (ADS)
Sokhan, Vladimir P.; Nicholson, David; Quirke, Nicholas
2002-11-01
Steady-state Poiseuille flow of a simple fluid in carbon nanopores under a gravitylike force is simulated using a realistic empirical many-body potential model for carbon. Building on our previous study of slit carbon nanopores we show that fluid flow in a nanotube is also characterized by a large slip length. By analyzing temporal profiles of the velocity components of particles colliding with the wall we obtain values of the Maxwell coefficient defining the fraction of molecules thermalized by the wall and, for the first time, propose slip boundary conditions for smooth continuum surfaces such that they are equivalent in adsorption, diffusion, and fluid flow properties to fully dynamic atomistic models.
Implicit Total Variation Diminishing (TVD) schemes for steady-state calculations
NASA Technical Reports Server (NTRS)
Yee, H. C.; Warming, R. F.; Harten, A.
1983-01-01
The application of a new implicit unconditionally stable high resolution total variation diminishing (TVD) scheme to steady state calculations. It is a member of a one parameter family of explicit and implicit second order accurate schemes developed by Harten for the computation of weak solutions of hyperbolic conservation laws. This scheme is guaranteed not to generate spurious oscillations for a nonlinear scalar equation and a constant coefficient system. Numerical experiments show that this scheme not only has a rapid convergence rate, but also generates a highly resolved approximation to the steady state solution. A detailed implementation of the implicit scheme for the one and two dimensional compressible inviscid equations of gas dynamics is presented. Some numerical computations of one and two dimensional fluid flows containing shocks demonstrate the efficiency and accuracy of this new scheme.
ERIC Educational Resources Information Center
Blanck, Harvey F.
2012-01-01
Naturally occurring gravity currents include events such as air flowing through an open front door, a volcanic eruption's pyroclastic flow down a mountainside, and the spread of the Bhopal disaster's methyl isocyanate gas. Gravity currents typically have a small height-to-distance ratio. Plastic models were designed and constructed with a…
ERIC Educational Resources Information Center
Blanck, Harvey F.
2012-01-01
Naturally occurring gravity currents include events such as air flowing through an open front door, a volcanic eruption's pyroclastic flow down a mountainside, and the spread of the Bhopal disaster's methyl isocyanate gas. Gravity currents typically have a small height-to-distance ratio. Plastic models were designed and constructed with a…
Steady state thermal radiation analysis between the TOPAZ-II radiator and a heat exchanger
Maveety, J.G.; Wold, S.K.
1995-12-31
In this study the authors investigate the feasibility and efficiency of coupling a single-pass heat exchanger to the TOPAZ-II space power system operating at steady state conditions. A first and second law analysis was performed in order to determine the optimal operating conditions which minimize the pumping power and maximize the flow exergy of the working fluid. The results of this study show that (1) the space power system is basically unaffected by the addition of this heat exchanger and (2) as much as 60% of the availability is destroyed by irreversibilities while operating at optimal flow conditions.
Bobarykina, T A; Malov, A N; Orishich, A M; Chirkashenko, V F; Yakovlev, V I
2014-09-30
We report a study of the wave structure formed by an optical discharge plasma upon the absorption of repetitively pulsed CO{sub 2} laser radiation in a supersonic (M = 1.36) air flow. Experimental data are presented on the configuration of the head shock wave and the geometry and characteristic dimensions of breakdown regions behind a laser plasma pulsating in the flow at a frequency of up to 150 kHz. The data are compared to calculation in a point explosion model with allowance for counterpressure, which makes it possible to identify the relationship between laser radiation and supersonic flow parameters that ensures quasisteady- state energy delivery and is necessary for extending the possibilities of controlling the structure of supersonic flows. (interaction of laser radiation with matter)
Conjugate Compressible Fluid Flow and Heat Transfer in Ducts
NASA Technical Reports Server (NTRS)
Cross, M. F.
2011-01-01
A computational approach to modeling transient, compressible fluid flow with heat transfer in long, narrow ducts is presented. The primary application of the model is for analyzing fluid flow and heat transfer in solid propellant rocket motor nozzle joints during motor start-up, but the approach is relevant to a wide range of analyses involving rapid pressurization and filling of ducts. Fluid flow is modeled through solution of the spatially one-dimensional, transient Euler equations. Source terms are included in the governing equations to account for the effects of wall friction and heat transfer. The equation solver is fully-implicit, thus providing greater flexibility than an explicit solver. This approach allows for resolution of pressure wave effects on the flow as well as for fast calculation of the steady-state solution when a quasi-steady approach is sufficient. Solution of the one-dimensional Euler equations with source terms significantly reduces computational run times compared to general purpose computational fluid dynamics packages solving the Navier-Stokes equations with resolved boundary layers. In addition, conjugate heat transfer is more readily implemented using the approach described in this paper than with most general purpose computational fluid dynamics packages. The compressible flow code has been integrated with a transient heat transfer solver to analyze heat transfer between the fluid and surrounding structure. Conjugate fluid flow and heat transfer solutions are presented. The author is unaware of any previous work available in the open literature which uses the same approach described in this paper.
A Generalized Fluid System Simulation Program to Model Flow Distribution in Fluid Networks
NASA Technical Reports Server (NTRS)
Majumdar, Alok; Bailey, John W.; Schallhorn, Paul; Steadman, Todd
1998-01-01
This paper describes a general purpose computer program for analyzing steady state and transient flow in a complex network. The program is capable of modeling phase changes, compressibility, mixture thermodynamics and external body forces such as gravity and centrifugal. The program's preprocessor allows the user to interactively develop a fluid network simulation consisting of nodes and branches. Mass, energy and specie conservation equations are solved at the nodes; the momentum conservation equations are solved in the branches. The program contains subroutines for computing "real fluid" thermodynamic and thermophysical properties for 33 fluids. The fluids are: helium, methane, neon, nitrogen, carbon monoxide, oxygen, argon, carbon dioxide, fluorine, hydrogen, parahydrogen, water, kerosene (RP-1), isobutane, butane, deuterium, ethane, ethylene, hydrogen sulfide, krypton, propane, xenon, R-11, R-12, R-22, R-32, R-123, R-124, R-125, R-134A, R-152A, nitrogen trifluoride and ammonia. The program also provides the options of using any incompressible fluid with constant density and viscosity or ideal gas. Seventeen different resistance/source options are provided for modeling momentum sources or sinks in the branches. These options include: pipe flow, flow through a restriction, non-circular duct, pipe flow with entrance and/or exit losses, thin sharp orifice, thick orifice, square edge reduction, square edge expansion, rotating annular duct, rotating radial duct, labyrinth seal, parallel plates, common fittings and valves, pump characteristics, pump power, valve with a given loss coefficient, and a Joule-Thompson device. The system of equations describing the fluid network is solved by a hybrid numerical method that is a combination of the Newton-Raphson and successive substitution methods. This paper also illustrates the application and verification of the code by comparison with Hardy Cross method for steady state flow and analytical solution for unsteady flow.
Dionne, B.; Tzanos, C. P.
2011-05-23
To support the safety analyses required for the conversion of the Belgian Reactor 2 (BR2) from highly-enriched uranium (HEU) to low-enriched uranium (LEU) fuel, the simulation of a number of loss-of-flow tests, with or without loss of pressure, has been undertaken. These tests were performed at BR2 in 1963 and used instrumented fuel assemblies (FAs) with thermocouples (TC) imbedded in the cladding as well as probes to measure the FAs power on the basis of their coolant temperature rise. The availability of experimental data for these tests offers an opportunity to better establish the credibility of the RELAP5-3D model and methodology used in the conversion analysis. In order to support the HEU to LEU conversion safety analyses of the BR2 reactor, RELAP simulations of a number of loss-of-flow/loss-of-pressure tests have been undertaken. Preliminary analyses showed that the conservative power distributions used historically in the BR2 RELAP model resulted in a significant overestimation of the peak cladding temperature during the transient. Therefore, it was concluded that better estimates of the steady-state and decay power distributions were needed to accurately predict the cladding temperatures measured during the tests and establish the credibility of the RELAP model and methodology. The new approach ('best estimate' methodology) uses the MCNP5, ORIGEN-2 and BERYL codes to obtain steady-state and decay power distributions for the BR2 core during the tests A/400/1, C/600/3 and F/400/1. This methodology can be easily extended to simulate any BR2 core configuration. Comparisons with measured peak cladding temperatures showed a much better agreement when power distributions obtained with the new methodology are used.
Quantum quasi-steady states in current transport
NASA Astrophysics Data System (ADS)
D'Agosta, Roberto; Zwolak, Michael; di Ventra, Massimiliano
2007-03-01
We investigate quasi-steady state solutions to transport in quantum systems by finding states which at some time minimize the change in density throughout all space and have a given current density flowing from one part of the system to another [1]. Contrary to classical dynamics, in a quantum mechanical system there are many states with a given energy and particle number which satisfy this minimization criterion. Taking as an example spinless fermions on a one-dimensional lattice, we explicitly show the phase space of a class of quasi-steady states. We also discuss the possibility of coherent and incoherent mixing of these steady state solutions leading to a new type of noise in quantum transport. [1] M. Di Ventra and T.N. Todorov J. Phys. Cond. Matt. 16, 8025 (2004).
CONTROL OF CRYPTOSPORIDIUM OOCYSTS BY STEADY-STATE CONVENTIONAL TREATMENT
Pilot-scale experiments have been performed to assess the ability of conventional treatment to control Cryptosporidium oocysts under steady-state conditions. The work was performed with a pilot plant that was designed to minimize flow rates and, as a result, the number of oocyst...
Acceleration to a steady state for the Euler equations
NASA Technical Reports Server (NTRS)
Turkel, E.
1984-01-01
A multi-stage Runge-Kutta method is analyzed for solving the Euler equations exterior to an airfoil. Highly subsonic, transonic and supersonic flows are evaluated. Various techniques for accelerating the convergence to a steady state are introduced and analyzed.
CONTROL OF CRYPTOSPORIDIUM OOCYSTS BY STEADY-STATE CONVENTIONAL TREATMENT
Pilot-scale experiments have been performed to assess the ability of conventional treatment to control Cryptosporidium oocysts under steady-state conditions. The work was performed with a pilot plant that was designed to minimize flow rates and, as a result, the number of oocyst...
Hydromechanical Modeling of Fluid Flow in the Lower Crust
NASA Astrophysics Data System (ADS)
Connolly, J.
2011-12-01
The lower crust lies within an ambiguous rheological regime between the brittle upper crust and ductile sub-lithospheric mantle. This ambiguity has allowed two schools of thought to develop concerning the nature of fluid flow in the lower crust. The classical school holds that lower crustal rocks are inviscid and that any fluid generated by metamorphic devolatilization is squeezed out of rocks as rapidly as it is produced. According to this school, permeability is a dynamic property and fluid flow is upward. In contrast, the modern school uses concepts from upper crustal hydrology that presume implicitly, if not explicitly, that rocks are rigid or, at most, brittle. For the modern school, the details of crustal permeability determine fluid flow and as these details are poorly known almost anything is possible. Reality, to the extent that it is reflected by inference from field studies, offers some support to both schools. In particular, evidence of significant lateral and channelized fluid flow are consistent with flow in rigid media, while evidence for short (104 - 105 y) grain-scale fluid-rock interaction during much longer metamorphic events, suggests that reaction-generated grain-scale permeability is sealed rapidly by compaction; a phenomenon that is also essential to prevent extensive retrograde metamorphism. These observations provide a compelling argument for recognizing in conceptual models of lower crustal fluid flow that rocks are neither inviscid nor rigid, but compact by viscous mechanisms on a finite time-scale. This presentation will review the principle consequences of, and obstacles to, incorporating compaction in such models. The role of viscous compaction in the lower crust is extraordinarily uncertain, but ignoring this uncertainty in models of lower crustal fluid flow does not make the models any more certain. Models inevitably invoke an initial steady state hydraulic regime. This initial steady state is critical to model outcomes because it
NASA Astrophysics Data System (ADS)
Sharif-Kashani, Pooria; Juan, Tingting; Hubschman, Jean-Pierre; Eldredge, Jeff D.; Pirouz Kavehpour, H.
2011-11-01
Vitrectomy is a microsurgical technique to remove the vitreous gel from the vitreous cavity. Due to the viscoelastic nature of the vitreous gel, its complex fluidic behavior during vitrectomy affects the outcome of the procedure. Therefore, the knowledge of such behavior is essential for better designing the vitrectomy devices, such as vitreous cutters, and tuning the system settings such as port and shaft diameters, infusion, vacuum, and cutting rate. We studied the viscoelastic properties of porcine vitreous humor using a stressed-control shear rheometer and obtained its relaxation time, retardation time, and shear-zero viscosity. We performed a computational study of the flow in a vitreous cutter using the viscoelastic parameters obtained from the rheology experiments. We found significant differences between the modeled vitreous gel and a Newtonian surrogate fluid in the flow behavior and performance of the vitreous cutter. Our results will help in understanding of the vitreous behavior during vitrectomy and providing guidelines for new vitreous cutter design.
NASA Astrophysics Data System (ADS)
Yousfi, Ammar; Mechergui, Mohammed
2016-04-01
The seepage face is an important feature of the drainage process when recharge occurs to a permeable region with lateral outlets. Examples of the formation of a seepage face above the downstream water level include agricultural land drained by ditches. Flow problem to these drains has been investigated extensively by many researchers (e.g. Rubin, 1968; Hornberger et al. 1969; Verma and Brutsaert, 1970; Gureghian and Youngs, 1975; Vauclin et al., 1975; Skaggs and Tang, 1976; Youngs, 1990; Gureghian, 1981; Dere, 2000; Rushton and Youngs, 2010; Youngs, 2012; Castro-Orgaz et al., 2012) and may be tackled either using variably saturated flow models, or the complete 2-D solution of Laplace equation, or using the Dupuit-Forchheimer approximation; the most widely accepted methods to obtain analytical solutions for unconfined drainage problems. However, the investigation reported by Clement et al. (1996) suggest that accounting for the seepage face alone, as in the fully saturated flow model, does not improve the discharge estimate because of disregarding flow the unsaturated zone flow contribution. This assumption can induce errors in the location of the water table surface and results in an underestimation of the seepage face and the net discharge (e.g. Skaggs and Tang, 1976; Vauclin et al., 1979; Clement et al., 1996). The importance of the flow in the unsaturated zone has been highlighted by many authors on the basis of laboratory experiments and/or numerical experimentations (e.g. Rubin, 1968; Verma and Brutsaert, 1970; Todsen, 1973; Vauclin et al., 1979; Ahmad et al., 1993; Anguela, 2004; Luthin and Day, 1955; Shamsai and Narasimhan, 1991; Wise et al., 1994; Clement et al., 1996; Boufadel et al., 1999; Romano et al., 1999; Kao et al., 2001; Kao, 2002). These studies demonstrate the failure of fully saturated flow models and suggested that the error made when using these models not only depends on soil properties but also on the infiltration rate as reported by Kao et
Near critical swirling flow of a viscoelastic fluid
NASA Astrophysics Data System (ADS)
Ly, Nguyen; Rusak, Zvi; Tichy, John; Wang, Shixiao
2016-11-01
The interaction between flow inertia and elasticity in high Re, axisymmetric, and near-critical swirling flows of a viscoelastic fluid in a finite-length straight circular pipe is studied. The viscous stresses are described by the Giesekus constitutive model. The application of this model to columnar streamwise vortices is first investigated. Then, a nonlinear small-disturbance analysis is developed from the governing equations of motion. It explores the complicated interactions between flow inertia, swirl, and fluid viscosity and elasticity. An effective Re that links between steady states of swirling flows of a viscoelastic fluid and those of a Newtonian fluid is revealed. The effects of the fluid viscosity, relaxation time, retardation time and mobility parameter on the flow development and on the critical swirl for the appearance of vortex breakdown are explored. Decreasing the ratio of the viscoelastic characteristic times from one increases the critical swirl for breakdown. Increasing the Weissenberg number from zero or increasing the fluid mobility parameter from zero cause a similar effect. Results may explain changes in the appearance of breakdown zones as a function of swirl level that were observed in Stokes et al. (2001) experiments, where Boger fluids were used.
Belcher, W.R.; Faunt, C.C.; D'Agnese, F.A.
2002-04-26
The U.S. Geological Survey, in cooperation with the Department of Energy and other Federal, State, and local agencies, is evaluating the hydrogeologic characteristics of the Death Valley regional ground-water flow system. The ground-water flow system covers and area of about 100,000 square kilometers from latitude 35 degrees to 38 degrees 15 minutes North to longitude 115 degrees to 118 degrees West, with the flow system proper comprising about 45,000 square kilometers. The Death Valley regional ground-water flow system is one of the larger flow systems within the Southwestern United States and includes in its boundaries the Nevada Test Site, Yucca Mountain, and much of Death Valley. Part of this study includes the construction of a three-dimensional hydrogeologic framework model to serve as the foundation for the development of a steady-state regional ground-water flow model. The digital framework model provides a computer-based description of the geometry and composition of the hydro geologic units that control regional flow. The framework model of the region was constructed by merging two previous framework models constructed for the Yucca Mountain Project and the Environmental Restoration Program Underground Test Area studies at the Nevada Test Site. The hydrologic characteristics of the region result from a currently arid climate and complex geology. Interbasinal regional ground-water flow occurs through a thick carbonate-rock sequence of Paleozoic age, a locally thick volcanic-rock sequence of Tertiary age, and basin-fill alluvium of Tertiary and Quaternary age. Throughout the system, deep and shallow ground-water flow may be controlled by extensive and pervasive regional and local faults and fractures. The framework model was constructed using data from several sources to define the geometry of the regional hydrogeologic units. These data sources include (1) a 1:250,000-scale hydrogeologic-map compilation of the region; (2) regional-scale geologic cross
Non-Markovianity-assisted steady state entanglement.
Huelga, Susana F; Rivas, Ángel; Plenio, Martin B
2012-04-20
We analyze the steady state entanglement generated in a coherently coupled dimer system subject to dephasing noise as a function of the degree of Markovianity of the evolution. By keeping fixed the effective noise strength while varying the memory time of the environment, we demonstrate that non-Markovianity is an essential, quantifiable resource that may support the formation of steady state entanglement whereas purely Markovian dynamics governed by Lindblad master equations lead to separable steady states. This result illustrates possible mechanisms leading to long-lived entanglement in purely decohering, possibly local, environments. We present a feasible experimental demonstration of this noise assisted phenomenon using a system of trapped ions.
Waddell, R.K.
1986-10-01
A two-dimensional, steady-state, finite-element model of the ground-water flow system of the Nevada Test Site and vicinity in Nye and Clark Counties, Nevada, and Inyo County, California, was developed using parameter-estimation techniques. The model simulates flow in an area underlain by clastic and carbonate rocks of Precambrian and Paleozoic age, and volcanic rocks and alluvial deposits of Tertiary and Quaternary age. Normal Basin-and-Range faulting and both right- and left-lateral strike-slip faults have caused the juxtaposition of rocks of differing hydraulic conductivities. Characteristics of the flow system are principally determined by locations of low-hydraulic-conductivity rocks (barriers); by amounts of recharge originating in the Spring Mountains, Pahranaget, Timpahute, and Sheep Ranges, and in Pahute Mesa; and by amount in flow into the study area from Gold Flat and Kawich Valley. Discharge areas (Ash Meadows, Oasis Valley, Alkali Flat, and Furnace Creek Ranch) are upgradient from barriers. Analyses of sensitivity of hydraulic head with respect to model-parameter variations indicate that the flux terms having the greatest impact on model output are recharge on Pahute Mesa, underflow from Cold Flat and Kawich Valley, and discharge at Ash Meadows. The most important transmissivity terms are those for rocks underlying the Amargosa Desert (exclusive of Amargosa Flat area), the Eleana Formation along the west side of Yucca Flat, and the Precambrian and Cambrian clastic rocks underlying the Groom Range.
NASA Astrophysics Data System (ADS)
Singh, S.; Lowell, R. P.; Lewis, K. C.
2012-12-01
The Main Endeavour Field (MEF) on the Juan de Fuca Ridge consists of a large number of chimney structures occupying an area approximately 400 m x 150 m along the ridge axis. For nearly a decade, the MEF exhibited quasi-steady north-south trending spatial gradients of both temperature and salinity. We have constructed 2-D across-axis numerical models of two-phase flow using the code FISHES to investigate possible causes for this variation. We considered the effect of bottom boundary temperature and both a homogeneous permeability structure and a geometry incorporating a more-permeable layer 2A. From these model results we argue that such a trend is more likely to be the result of heterogeneous permeability structure of the shallow oceanic crust than a result of bottom boundary temperature variations. After a magmatic event in 1999, this trend was disrupted; and thermal data using the Autonomous Benthic Explorer (ABE) indicates that there has been a significant decline in the heat output from a value of approximately 450 MW in 2000 to approximately 300 MW in 2004. In the southern part of the vent field, vent salinities have also increased from values well below those of seawater to values close to seawater. We therefore extend our investigation to include the effect of a temporally-decaying basal heat flow, which may result from cooling, crystallizing magma chamber, on the system. Our aim is to determine whether such a phenomenon could cause the observed rapid decline of heat flow and changes in vent salinity at the MEF. We find that the thermal inertia in the system is such that changes in basal heat flow would be difficult to detect in the given time frame, if magma replenishment ceased following the 1999 magmatic event. The time delay between changes in bottom conditions and the observed decay in observed heat output suggests that the 1999 event represented a small replenishment event and that the AMC may have begun cooling some time before that. Moreover, because
Stochastic effects on single phase fluid flow in porous media.
Mansfield, P; Bencsik, M
2001-01-01
The flow encoded PEPI technique has been used to measure the fluid velocity distribution and fluid flow of water passing through a phantom comprising randomly distributed 10 mm glass beads. The object of these experiments is to determine the degree of causality between one steady-state flow condition and another. That is to say, knowing the mean fluid velocity and velocity distribution, can one predict what happens at a higher mean fluid velocity? In a second related experiment flow is established at a given mean fluid velocity. The velocity distribution is measured. The flow is then turned off and later re-established. In both kinds of experiment we conclude that the errors in predicting the flow velocity distribution and the errors in re-establishing a given velocity distribution lie well outside the intrinsic thermal noise associated with velocity measurement. It follows, therefore, that the causal approach to prediction of flow velocity distributions in porous media using the Navier-Stokes approach is invalid.
Morphodynamics: Rivers beyond steady state
NASA Astrophysics Data System (ADS)
Church, M.; Ferguson, R. I.
2015-04-01
The morphology of an alluvial river channel affects the movement of water and sediment along it, but in the longer run is shaped by those processes. This interplay has mostly been investigated empirically within the paradigm of Newtonian mechanics. In rivers, this has created an emphasis on equilibrium configurations with simple morphology and uniform steady flow. But transient adjustment, whether between equilibrium states or indefinitely, is to be expected in a world in which hydrology, sediment supply, and base level are not fixed. More fundamentally, water flows and all the phenomena that accompany them are inherently unsteady, and flows in natural channels are characteristically nonuniform. The morphodynamics of alluvial river channels is the striking consequence. In this paper, we develop the essential connection between the episodic nature of bed material transport and the production of river morphology, emphasizing the fundamental problems of sediment transport, the role of bar evolution in determining channel form, the role of riparian vegetation, and the wide range of time scales for change. As the key integrative exercise, we emphasize the importance of physics-based modeling of morphodynamics. We note consequences that can be of benefit to society if properly understood. These include the possibility to better be able to model how varying flows drive morphodynamic change, to understand the influence of the sediments themselves on morphodynamics, and to recognize the inherent necessity for rivers that transport bed material to deform laterally. We acknowledge pioneering contributions in WRR and elsewhere that have introduced some of these themes.
Flexibility in a Steady State University
ERIC Educational Resources Information Center
Campbell, Richard
1977-01-01
Problems posed by abrupt transition to a steady state following rapid expansion in Australian universities are reviewed. Focus is on demography of departments, new developments in academic disciplines, tenure, and early retirement. (LBH)
Steady-state permanent magnet MPD thruster
Arakawa, Y.; Sasoh, A.
1987-01-01
A steady-state MPD arc thruster with permanent magnets has been made. The effect of the permanent magnets on thruster performance and the plasma acceleration mechanism was examined through measurements of thrust, chamber pressure, current densities, and plasma properties in the exhaust plume. Experimental results show that the use of the permanent magnets is desirable in steady-state MPD thrusters of the greater than 10 kW power range. 7 references.
Kuznetsov, Nikita A.; Vorobjev, Yuri N.; Krasnoperov, Lev N.; Fedorova, Olga S.
2012-01-01
Formamidopyrimidine-DNA glycosylase, Fpg protein from Escherichia coli, initiates base excision repair in DNA by removing a wide variety of oxidized lesions. In this study, we perform thermodynamic analysis of the multi-stage interaction of Fpg with specific DNA-substrates containing 7,8-dihydro-8-oxoguanosine (oxoG), or tetrahydrofuran (THF, an uncleavable abasic site analog) and non-specific (G) DNA-ligand based on stopped-flow kinetic data. Pyrrolocytosine, highly fluorescent analog of the natural nucleobase cytosine, is used to record multi-stage DNA lesion recognition and repair kinetics over a temperature range (10–30°C). The kinetic data were used to obtain the standard Gibbs energy, enthalpy and entropy of the specific stages using van’t Hoff approach. The data suggest that not only enthalpy-driven exothermic oxoG recognition, but also the desolvation-accompanied entropy-driven enzyme-substrate complex adjustment into the catalytically active state play equally important roles in the overall process. PMID:22584623
Thews, O; Hummel, M; Kelleher, D K; Lecher, B; Vaupel, P
2002-12-02
Isolated limb perfusion allows the direct application of therapeutic agents to a tumour-bearing extremity. The present study investigated whether the dihydropyridine-type Ca(2+)-channel blocker nifedipine could improve blood flow and oxygenation status of experimental tumours during isolated limb perfusion. Perfusion was performed by cannulation of the femoral artery and vein in rats bearing DS-sarcoma on the hind foot dorsum. Perfusion rate was adjusted to maintain a perfusion pressure of 100-140 mmHg throughout the experiment. Following equilibration, nifedipine was continuously infused for 30 min (8.3 microg min(-1) kg(-1) BW). During constant-pressure isolated limb perfusion, nifedipine can significantly increase perfusion rate (+100%) and RBC flux (+60%) through experimental leg tumours. "Steal phenomena" in favour of the surrounding normal tissue and oedema formation were not observed. Despite the increased oxygen availability (+63%) seen upon application of this calcium channel blocker, nifedipine does not result in a substantial reduction of tumour hypoxia, most probably due to an increase in O(2) uptake with rising O(2) supply to the tumour-bearing hind limb. Nifedipine application during isolated limb perfusion can enhance tumour microcirculation and may therefore promote the delivery (pharmacokinetics) of anti-cancer drugs to the tumour and by this improve the efficacy of pressure-controlled isolated limb perfusion.
McKay, Mark D.; Sweeney, Chad E.; Spangler, Jr., B. Samuel
1993-01-01
A flow meter and temperature measuring device comprising a tube with a body centered therein for restricting flow and a sleeve at the upper end of the tube to carry several channels formed longitudinally in the sleeve to the appropriate axial location where they penetrate the tube to allow pressure measurements and temperature measurements with thermocouples. The high pressure measurement is made using a channel penetrating the tube away from the body and the low pressure measurement is made at a location at the widest part of the body. An end plug seals the end of the device and holes at its upper end allow fluid to pass from the interior of the tube into a plenum. The channels are made by cutting grooves in the sleeve, the grooves widened at the surface of the sleeve and then a strip of sleeve material is welded to the grooves closing the channels. Preferably the sleeve is packed with powdered graphite before cutting the grooves and welding the strips.
Steady-State Solution of a Flexible Wing
NASA Technical Reports Server (NTRS)
Karkehabadi, Reza; Chandra, Suresh; Krishnamurthy, Ramesh
1997-01-01
A fluid-structure interaction code, ENSAERO, has been used to compute the aerodynamic loads on a swept-tapered wing. The code has the capability of using Euler or Navier-Stokes equations. Both options have been used and compared in the present paper. In the calculation of the steady-state solution, we are interested in knowing how the flexibility of the wing influences the lift coefficients. If the results of a flexible wing are not affected by the flexibility of the wing significantly, one could consider the wing to be rigid and reduce the problem from fluid-structure interaction to a fluid problem.
NASA Lewis steady-state heat pipe code users manual
Tower, L.K.; Baker, K.W.; Marks, T.S.
1992-06-01
The NASA Lewis heat pipe code has been developed to predict the performance of heat pipes in the steady state. The code can be used as a design tool on a personal computer or, with a suitable calling routine, as a subroutine for a mainframe radiator code. A variety of wick structures, including a user input option, can be used. Heat pipes with multiple evaporators, condensers, and adiabatic sections in series and with wick structures that differ among sections can be modeled. Several working fluids can be chosen, including potassium, sodium, and lithium, for which the monomer-dimer equilibrium is considered. The code incorporates a vapor flow algorithm that treats compressibility and axially varying heat input. This code facilitates the determination of heat pipe operating temperatures and heat pipe limits that may be encountered at the specified heat input and environment temperature. Data are input to the computer through a user-interactive input subroutine. Output, such as liquid and vapor pressures and temperatures, is printed at equally spaced axial positions along the pipe as determined by the user.
NASA Lewis steady-state heat pipe code users manual
NASA Technical Reports Server (NTRS)
Tower, Leonard K.; Baker, Karl W.; Marks, Timothy S.
1992-01-01
The NASA Lewis heat pipe code was developed to predict the performance of heat pipes in the steady state. The code can be used as a design tool on a personal computer or with a suitable calling routine, as a subroutine for a mainframe radiator code. A variety of wick structures, including a user input option, can be used. Heat pipes with multiple evaporators, condensers, and adiabatic sections in series and with wick structures that differ among sections can be modeled. Several working fluids can be chosen, including potassium, sodium, and lithium, for which monomer-dimer equilibrium is considered. The code incorporates a vapor flow algorithm that treats compressibility and axially varying heat input. This code facilitates the determination of heat pipe operating temperatures and heat pipe limits that may be encountered at the specified heat input and environment temperature. Data are input to the computer through a user-interactive input subroutine. Output, such as liquid and vapor pressures and temperatures, is printed at equally spaced axial positions along the pipe as determined by the user.
Modeling on the Steady State of Thwaites Glacier
NASA Astrophysics Data System (ADS)
Yu, H.; Rignot, E. J.; Morlighem, M.; Seroussi, H.
2013-12-01
Thwaites Glacier (TWG) is the second largest ice stream in West Antarctica in terms of ice discharge, and the broadest ice stream in Antarctica (120 km wide). Observations and theory suggest that its configuration is inherently unstable in a warming climate. Satellite observations have revealed grounding line retreat, ice thinning, ice stream broadening and in more recent years ice flow acceleration. The most important part of the glacier evolution involves its grounding line dynamics and the impact of ice-ocean interactions. In a region between the grounding line and the limit of the flexure zone, some 10 km downstream, however, the glacier is not in hydrostatic equilibrium. Proper treatment of the grounding line dynamics requires full Stokes solution. Here, we model the grounding line of TWG in 2D, full Stokes, with the goal to examine whether the glacier is in a steady state configuration or not. The model treats ice sheet and ice shelf as two fluids coupled through the ice mass flux (Nowicki, 2008). Water stress is used as a constraint on the ice shelf instead of hydrostatic equilibrium. We use radar interferometry (InSAR) measurements of ice velocity and grounding line position through time, Bedmap2 and IceBridge thickness, and surface mass balance from RACMO to constrain the model. The results are used to conclude on the state of dynamic balance of the glacier. This work is funded by NASA Cryospheric Science Program.
Acoustic concentration of particles in fluid flow
Ward, Michael D.; Kaduchak, Gregory
2010-11-23
An apparatus for acoustic concentration of particles in a fluid flow includes a substantially acoustically transparent membrane and a vibration generator that define a fluid flow path therebetween. The fluid flow path is in fluid communication with a fluid source and a fluid outlet and the vibration generator is disposed adjacent the fluid flow path and is capable of producing an acoustic field in the fluid flow path. The acoustic field produces at least one pressure minima in the fluid flow path at a predetermined location within the fluid flow path and forces predetermined particles in the fluid flow path to the at least one pressure minima.
Acoustic concentration of particles in fluid flow
Ward, Michael W.; Kaduchak, Gregory
2017-08-15
Disclosed herein is a acoustic concentration of particles in a fluid flow that includes a substantially acoustically transparent membrane and a vibration generator that define a fluid flow path therebetween. The fluid flow path is in fluid communication with a fluid source and a fluid outlet and the vibration generator is disposed adjacent the fluid flow path and is capable of producing an acoustic field in the fluid flow path. The acoustic field produces at least one pressure minima in the fluid flow path at a predetermined location within the fluid flow path and forces predetermined particles in the fluid flow path to the at least one pressure minima.
Kodaira, Hiroshi; Kusuhara, Hiroyuki; Fuse, Eiichi; Ushiki, Junko; Sugiyama, Yuichi
2014-06-01
A pharmacokinetic model was constructed to explain the difference in brain- and cerebrospinal fluid (CSF)-to-plasma and brain-to-CSF unbound drug concentration ratios (Kp,uu,brain, Kp,uu,CSF, and Kp,uu,CSF/brain, respectively) of drugs under steady-state conditions in rats. The passive permeability across the blood-brain barrier (BBB), PS1, was predicted by two methods using log(D/molecular weight(0.5)) for PS1(1) or the partition coefficient in octanol/water at pH 7.4 (LogD), topologic van der Waals polar surface area, and van der Waals surface area of the basic atoms for PS1(2). The coefficients of each parameter were determined using previously reported in situ rat BBB permeability. Active transport of drugs by P-glycoprotein (P-gp) and breast cancer resistance protein (Bcrp) measured in P-gp- and Bcrp-overexpressing cells was extrapolated to in vivo by introducing scaling factors. Brain- and CSF-to-plasma unbound concentration ratios (Kp,uu,brain and Kp,uu,CSF, respectively) of 19 compounds, including P-gp and Bcrp substrates (daidzein, dantrolene, flavopiridol, genistein, loperamide, quinidine, and verapamil), were simultaneously fitted to the equations in a three-compartment model comprising blood, brain, and CSF compartments. The calculated Kp,uu,brain and Kp,uu,CSF of 17 compounds were within a factor of three of experimental values. Kp,uu,CSF values of genistein and loperamide were outliers of the prediction, and Kp,uu,brain of dantrolene also became an outlier when PS1(2) was used. Kp,uu,CSF/brain of the 19 compounds was within a factor of three of experimental values. In conclusion, the Kp,uu,CSF/brain of drugs, including P-gp and Bcrp substrates, could be successfully explained by a kinetic model using scaling factors combined with in vitro evaluation of P-gp and Bcrp activities.
CA_OPPUSST - Cantera OPUS Steady State
Moffat, Harry K.
2005-03-01
The Cantera Opus Steady State (ca-opusst) applications solves steady reacting flow problems in opposed-flow geometries. It is a 1-0 application that represents axisymmetnc 3-0 physical systems that can be reduced via a similarity transformation to a 1-0 mathematical representation. The code contain solutions of the general dynamic equations for the particle distribution functions using a sectional model to describe the particle distribution function. Operators for particle nucleation, coagulation, condensation (i.e., growth/etching via reactions with the gas ambient), internal particle reactions. particle transport due to convection and due to molecular transport, are included in the particle general dynamics equation. Heat transport due to radiation exchange of the environment with particles in local thermal equilibrium to the surrounding gas will be included in the enthalpy conservation equation that is solved for the coupled gas! particle system in an upcoming version of the code due in June 2005. The codes use Cantera , a C++ Cal Tech code, for determination of gas phase species transport, reaction, and thermodynamics physical properties and source terms. The Codes use the Cantera Aerosol Dynamics Simulator (CADS) package, a general library for aerosol modeling, to calculate properties and source terms for the aerosol general dynamics equation, including particle formation from gas phase reactions, particle surface chemistry (growth and oxidation), bulk particle chemistry, particle transport by Brownian diffusion, thermophoresis, and diffusiophoresis, and thermal radiative transport involving particles. Also included are post-processing programs, cajost and cajrof, to extract ascii data from binary output files to produce plots.
Geophysical Fluid Flow Cell Simulation
NASA Technical Reports Server (NTRS)
1998-01-01
Computer simulation of atmospheric flow corresponds well to imges taken during the second Geophysical Fluid Flow Cell (BFFC) mission. The top shows a view from the pole, while the bottom shows a view from the equator. Red corresponds to hot fluid rising while blue shows cold fluid falling. This simulation was developed by Anil Deane of the University of Maryland, College Park and Paul Fischer of Argorne National Laboratory. Credit: NASA/Goddard Space Flight Center
Network inference in the nonequilibrium steady state
NASA Astrophysics Data System (ADS)
Dettmer, Simon L.; Nguyen, H. Chau; Berg, Johannes
2016-11-01
Nonequilibrium systems lack an explicit characterization of their steady state like the Boltzmann distribution for equilibrium systems. This has drastic consequences for the inference of the parameters of a model when its dynamics lacks detailed balance. Such nonequilibrium systems occur naturally in applications like neural networks and gene regulatory networks. Here, we focus on the paradigmatic asymmetric Ising model and show that we can learn its parameters from independent samples of the nonequilibrium steady state. We present both an exact inference algorithm and a computationally more efficient, approximate algorithm for weak interactions based on a systematic expansion around mean-field theory. Obtaining expressions for magnetizations and two- and three-point spin correlations, we establish that these observables are sufficient to infer the model parameters. Further, we discuss the symmetries characterizing the different orders of the expansion around the mean field and show how different types of dynamics can be distinguished on the basis of samples from the nonequilibrium steady state.
Practical steady-state enzyme kinetics.
Lorsch, Jon R
2014-01-01
Enzymes are key components of most biological processes. Characterization of enzymes is therefore frequently required during the study of biological systems. Steady-state kinetics provides a simple and rapid means of assessing the substrate specificity of an enzyme. When combined with site-directed mutagenesis (see Site-Directed Mutagenesis), it can be used to probe the roles of particular amino acids in the enzyme in substrate recognition and catalysis. Effects of interaction partners and posttranslational modifications can also be assessed using steady-state kinetics. This overview explains the general principles of steady-state enzyme kinetics experiments in a practical, rather than theoretical, way. Any biochemistry textbook will have a section on the theory of Michaelis-Menten kinetics, including derivations of the relevant equations. No specific enzymatic assay is described here, although a method for monitoring product formation or substrate consumption over time (an assay) is required to perform the experiments described. © 2014 Elsevier Inc. All rights reserved.
Depth resolved granular transport driven by shearing fluid flow
NASA Astrophysics Data System (ADS)
Allen, Benjamin; Kudrolli, Arshad
2017-02-01
We investigate granular transport by a fluid flow under steady-state driving conditions, from the bed-load regime to the suspension regime, with an experimental system based on a conical rheometer. The mean granular volume fraction ϕg, the mean granular velocity ug, and the fluid velocity uf are obtained as a function of depth inside the bed using refractive index matching and particle-tracking techniques. A torque sensor is utilized to measure the applied shear stress to complement estimates obtained from measured strain rates high above the bed where ϕg≈0 . The flow is found to be transitional at the onset of transport and the shear stress required to transport grains rises sharply as grains are increasingly entrained by the fluid flow. A significant slip velocity between the fluid and the granular phases is observed at the bed surface before the onset of transport as well as in the bed-load transport regime. We show that ug decays exponentially deep into the bed for ϕg>0.45 with a decay constant which is described by a nonlocal rheology model of granular flow that neglects fluid stress. Further, we show that uf and ug can be described using the applied shear stress and the Krieger-Dougherty model for the effective viscosity in the suspension regime, where 0 <ϕg<0.45 and where ug≈uf .
Steady state response of unsymmetrically laminated plates
Hosokawa, Kenji; Kawashima, Katsuya; Sakata, Toshiyuki
1995-11-01
A numerical approach for analyzing the forced vibration problem of a symmetrically laminated FRP (fiber reinforced plastic) composite plate was proposed by the authors. In the present paper, this approach is modified for application to an unsymmetrically laminated FRP composite plate. Numerical calculations are carried out for the clamped antisymmetrically laminated rectangular and elliptical plates which are a kind of unsymmetrically laminated plate. Then,, the effects of the lamina material and the fiber orientation angle on the steady state response are discussed. Furthermore, it is investigated that what structural damping factor is most influenced on the steady state response of an antisymmetrically laminated plate.
Relaminarization of fluid flows
NASA Technical Reports Server (NTRS)
Narasimha, R.; Sreenivasan, K. R.
1979-01-01
The mechanisms of the relaminarization of turbulent flows are investigated with a view to establishing any general principles that might govern them. Three basic archetypes of reverting flows are considered: the dissipative type, the absorptive type, and the Richardson type exemplified by a turbulent boundary layer subjected to severe acceleration. A number of other different reverting flows are then considered in the light of the analysis of these archetypes, including radial Poiseuille flow, convex boundary layers, flows reverting by rotation, injection, and suction, as well as heated horizontal and vertical gas flows. Magnetohydrodynamic duct flows are also examined. Applications of flow reversion for turbulence control are discussed.
NASA Technical Reports Server (NTRS)
Yee, H. C.; Sweby, P. K.; Griffiths, D. F.
1991-01-01
Spurious stable as well as unstable steady state numerical solutions, spurious asymptotic numerical solutions of higher period, and even stable chaotic behavior can occur when finite difference methods are used to solve nonlinear differential equations (DE) numerically. The occurrence of spurious asymptotes is independent of whether the DE possesses a unique steady state or has additional periodic solutions and/or exhibits chaotic phenomena. The form of the nonlinear DEs and the type of numerical schemes are the determining factor. In addition, the occurrence of spurious steady states is not restricted to the time steps that are beyond the linearized stability limit of the scheme. In many instances, it can occur below the linearized stability limit. Therefore, it is essential for practitioners in computational sciences to be knowledgeable about the dynamical behavior of finite difference methods for nonlinear scalar DEs before the actual application of these methods to practical computations. It is also important to change the traditional way of thinking and practices when dealing with genuinely nonlinear problems. In the past, spurious asymptotes were observed in numerical computations but tended to be ignored because they all were assumed to lie beyond the linearized stability limits of the time step parameter delta t. As can be seen from the study, bifurcations to and from spurious asymptotic solutions and transitions to computational instability not only are highly scheme dependent and problem dependent, but also initial data and boundary condition dependent, and not limited to time steps that are beyond the linearized stability limit.
NASA Technical Reports Server (NTRS)
Yee, H. C.; Sweby, P. K.; Griffiths, D. F.
1991-01-01
Spurious stable as well as unstable steady state numerical solutions, spurious asymptotic numerical solutions of higher period, and even stable chaotic behavior can occur when finite difference methods are used to solve nonlinear differential equations (DE) numerically. The occurrence of spurious asymptotes is independent of whether the DE possesses a unique steady state or has additional periodic solutions and/or exhibits chaotic phenomena. The form of the nonlinear DEs and the type of numerical schemes are the determining factor. In addition, the occurrence of spurious steady states is not restricted to the time steps that are beyond the linearized stability limit of the scheme. In many instances, it can occur below the linearized stability limit. Therefore, it is essential for practitioners in computational sciences to be knowledgeable about the dynamical behavior of finite difference methods for nonlinear scalar DEs before the actual application of these methods to practical computations. It is also important to change the traditional way of thinking and practices when dealing with genuinely nonlinear problems. In the past, spurious asymptotes were observed in numerical computations but tended to be ignored because they all were assumed to lie beyond the linearized stability limits of the time step parameter delta t. As can be seen from the study, bifurcations to and from spurious asymptotic solutions and transitions to computational instability not only are highly scheme dependent and problem dependent, but also initial data and boundary condition dependent, and not limited to time steps that are beyond the linearized stability limit.
NASA Technical Reports Server (NTRS)
Yee, H. C.; Sweby, P. K.; Griffiths, D. F.
1990-01-01
Spurious stable as well as unstable steady state numerical solutions, spurious asymptotic numerical solutions of higher period, and even stable chaotic behavior can occur when finite difference methods are used to solve nonlinear differential equations (DE) numerically. The occurrence of spurious asymptotes is independent of whether the DE possesses a unique steady state or has additional periodic solutions and/or exhibits chaotic phenomena. The form of the nonlinear DEs and the type of numerical schemes are the determining factor. In addition, the occurrence of spurious steady states is not restricted to the time steps that are beyond the linearized stability limit of the scheme. In many instances, it can occur below the linearized stability limit. Therefore, it is essential for practitioners in computational sciences to be knowledgeable about the dynamical behavior of finite difference methods for nonlinear scalar DEs before the actual application of these methods to practical computations. It is also important to change the traditional way of thinking and practices when dealing with genuinely nonlinear problems. In the past, spurious asymptotes were observed in numerical computations but tended to be ignored because they all were assumed to lie beyond the linearized stability limits of the time step parameter delta t. As can be seen from the study, bifurcations to and from spurious asymptotic solutions and transitions to computational instability not only are highly scheme dependent and problem dependent, but also initial data and boundary condition dependent, and not limited to time steps that are beyond the linearized stability limit.
Fluid Flow Phenomena during Welding
Zhang, Wei
2011-01-01
MOLTEN WELD POOLS are dynamic. Liquid in the weld pool in acted on by several strong forces, which can result in high-velocity fluid motion. Fluid flow velocities exceeding 1 m/s (3.3 ft/s) have been observed in gas tungsten arc (GTA) welds under ordinary welding conditions, and higher velocities have been measured in submerged arc welds. Fluid flow is important because it affects weld shape and is related to the formation of a variety of weld defects. Moving liquid transports heat and often dominates heat transport in the weld pool. Because heat transport by mass flow depends on the direction and speed of fluid motion, weld pool shape can differ dramatically from that predicted by conductive heat flow. Temperature gradients are also altered by fluid flow, which can affect weld microstructure. A number of defects in GTA welds have been attributed to fluid flow or changes in fluid flow, including lack of penetration, top bead roughness, humped beads, finger penetration, and undercutting. Instabilities in the liquid film around the keyhole in electron beam and laser welds are responsible for the uneven penetration (spiking) characteristic of these types of welds.
A p-version finite element method for steady incompressible fluid flow and convective heat transfer
NASA Technical Reports Server (NTRS)
Winterscheidt, Daniel L.
1993-01-01
A new p-version finite element formulation for steady, incompressible fluid flow and convective heat transfer problems is presented. The steady-state residual equations are obtained by considering a limiting case of the least-squares formulation for the transient problem. The method circumvents the Babuska-Brezzi condition, permitting the use of equal-order interpolation for velocity and pressure, without requiring the use of arbitrary parameters. Numerical results are presented to demonstrate the accuracy and generality of the method.
Flow in left atrium using MR fluid motion estimation
NASA Astrophysics Data System (ADS)
Wong, Kelvin K. L.; Kelso, Richard M.; Worthley, Steve M.; Sanders, Prash; Mazumdar, Jagannath; Abbott, Derek
2007-12-01
A recent development based on optical flow applied onto Fast Imaging in Steady State Free Precession (TrueFISP) magnetic resonance imaging is able to deliver good estimation of the flow profile in the human heart chamber. The examination of cardiac flow based on tracking of MR signals emitted by moving blood is able to give medical doctors insight into the flow patterns within the human heart using standard MRI procedure without specifically subjecting the patient to longer scan times using more dedicated scan protocols such as phase contrast MRI. Although MR fluid motion estimation has its limitations in terms of accurate flow mapping, the use of a comparatively quick scan procedure and computational post-processing gives satisfactory flow quantification and can assist in management of cardiac patients. In this study, we present flow in the left atria of five human subjects using MR fluid motion tracking. The measured flow shows that vortices exist within the atrium of heart. Although the scan is two-dimensional, we have produced multiple slices of flow maps in a spatial direction to show that the vortex exist in a three-dimensional space.
Investigation of the steady state measurement process
Nagy, J. L.; Leisztner, L.; Hangos, K. M.
1988-01-01
Based on the role of steady state concept in the model of analytical chemical measurement and deduction, the definition of ‘practically sleady slate’ (PSS) has been inlroduced. The defnition does not require the process to be in steady state in a strictly mathematical sense. In order to fulfil the requiremenls of ‘practically steady state’ the random error and the syslematic error must vary within a suitable limit, and the expected fgure for the measured value must be within a specified range. The goal of the present investigation was to detect the steady state of the measurement process with respect to the analytical information (peak area ratio) based on the measured values. The method proposed proved to be useful for the determination of the simultaneously present systematic error and random error. Control based on the measured values of the internal standard is useful, but additional information is necessary. There are several advantages to the method described: the results for the internal standard indicate possible sources of disturbances and allow the end of the steady state measurement process to be predicted. PMID:18925195
Steady-state inductive spheromak operation
Janos, Alan C.; Jardin, Stephen C.; Yamada, Masaaki
1987-01-01
The inductively formed spheromak plasma can be maintained in a highly stable and controlled fashion. Steady-state operation is obtained by forming the plasma in the linked mode, then oscillating the poloidal and toroidal fields such that they have different phases. Preferably, the poloidal and magnetic fields are 90.degree. out of phase.
Thermodynamics of Stability of Nonequilibrium Steady States.
ERIC Educational Resources Information Center
Rastogi, R. P.; Shabd, Ram
1983-01-01
Presented is a concise and critical account of developments in nonequilibrium thermodynamics. The criterion for stability of nonequilibrium steady states is critically examined for consecutive and monomolecular triangular reactions, autocatalytic reactions, auto-inhibited reactions, and the Lotka-Volterra model. (JN)
Steady-state inductive spheromak operation
Janos, A.C.; Jardin, S.C.; Yamada, M.
1985-02-20
The inductively formed spheromak configuration (S-1) can be maintained in a highly stable and controlled fashion. The method described eliminates the restriction to pulsed spheromak plasmas or the use of electrodes for steady-state operation, and, therefore, is a reactor-relevant formation and sustainment method.
Steady-State Staffing: A Second Report.
ERIC Educational Resources Information Center
Furniss, W. Todd
This is a folow-up report on developments in long-range faculty personnel planning since the publication of "Steady-State Staffing in Tenure-Granting Institutions and Related Papers," covering the period from March through December 1973. Following references to newly available data, the paper deals first with work done at SUNY-Buffalo, Stanford,…
The Politics of the Steady State
ERIC Educational Resources Information Center
Taylor, Charles
1978-01-01
A steady state society has limits pertaining to population size, non-renewable resources, and production which emits heat or substances into soil, water, or the atmosphere. Respecting these limits means renouncing exponential quantitative growth and accepting a universally available consumption standard. (SW)
Steady-state spheromak reactor studies. Revision
Krakowski, R.A.; Hagenson, R.L.
1985-01-01
After summarizing the essential elements of a gun-sustained spheromak, the potential for a steady-state is explored by means of a comprehensive physics/engineering/costing model. A range of cost-optimized reactor design point is presented, and the sensitivity of cost to key physics, engineering, and operational variables is reported.
Experimental observation of fluid flow channels in a single fracture
NASA Astrophysics Data System (ADS)
Brown, Stephen; Caprihan, Arvind; Hardy, Robert
1998-03-01
A method for obtaining precise replicas of real fracture surfaces using transparent epoxy resins was developed, allowing detailed study of fluid flow paths within a fracture plane. A natural rock fracture was collected from the field and prepared for study. Silicon rubber molds of the fracture surfaces were used to make a transparent epoxy replica of the original fracture. Clear and dyed water were injected into the fracture pore space allowing examination of the flow field. Digitized optical images were used to observe wetting, saturated flow, and drying of the specimen. Nuclear magnetic resonance imaging was used for quantitative measurements of flow velocity. Both video imaging and nuclear magnetic resonance imaging techniques show distinct and strong channeling of the flow at the submillimeter to several-centimeter scale. Each phenomenon, including wetting, drying, dye transport, and velocity channeling, has its own distinct geometric structure and scale. We find that fluid velocities measured simultaneously at various locations in the fracture plane during steady state flow range over several orders of magnitude, with the maximum velocity a factor of 5 higher than the mean velocity. This suggests that flow channeling in fractured rock can cause the breakthrough velocity of contaminants to far exceed the mean flow.
Nunz, G.J.
1993-10-01
A dimensionless group, called a Pressure Loss Modulus (N{sub PL}), is introduced which, in conjunction with an appropriately defined Reynolds number, is of considerable engineering utility in correlating steady-state {Delta}P vs. flow calibration data and subsequently as a predictor, using the same or a different fluid, in uniformly distributed pressure loss devices. It is particularly useful under operation in the transition regime. Applications of this simple bivariate correlation to three diverse devices of particular interest for small liquid rocket engine fluid systems are discussed: large L/D capillary tube restrictors; packed granular catalyst beds; and stacked vortex-loss disc restrictors.
Hydrodynamics of stratified epithelium: Steady state and linearized dynamics
NASA Astrophysics Data System (ADS)
Yeh, Wei-Ting; Chen, Hsuan-Yi
2016-05-01
A theoretical model for stratified epithelium is presented. The viscoelastic properties of the tissue are assumed to be dependent on the spatial distribution of proliferative and differentiated cells. Based on this assumption, a hydrodynamic description of tissue dynamics at the long-wavelength, long-time limit is developed, and the analysis reveals important insights into the dynamics of an epithelium close to its steady state. When the proliferative cells occupy a thin region close to the basal membrane, the relaxation rate towards the steady state is enhanced by cell division and cell apoptosis. On the other hand, when the region where proliferative cells reside becomes sufficiently thick, a flow induced by cell apoptosis close to the apical surface enhances small perturbations. This destabilizing mechanism is general for continuous self-renewal multilayered tissues; it could be related to the origin of certain tissue morphology, tumor growth, and the development pattern.
Insertable fluid flow passage bridgepiece and method
Jones, Daniel O.
2000-01-01
A fluid flow passage bridgepiece for insertion into an open-face fluid flow channel of a fluid flow plate is provided. The bridgepiece provides a sealed passage from a columnar fluid flow manifold to the flow channel, thereby preventing undesirable leakage into and out of the columnar fluid flow manifold. When deployed in the various fluid flow plates that are used in a Proton Exchange Membrane (PEM) fuel cell, bridgepieces of this invention prevent mixing of reactant gases, leakage of coolant or humidification water, and occlusion of the fluid flow channel by gasket material. The invention also provides a fluid flow plate assembly including an insertable bridgepiece, a fluid flow plate adapted for use with an insertable bridgepiece, and a method of manufacturing a fluid flow plate with an insertable fluid flow passage bridgepiece.
Zhang, Nan; Fan, Zhaoyang; Luo, Nan; Bi, Xiaoming; Zhao, Yike; An, Jing; Liu, Jiayi; Chen, Zhong; Fan, Zhanming; Li, Debiao
2015-01-01
Purpose To evaluate the feasibility and diagnostic performance of flow-sensitive dephasing (FSD)-prepared steady-state free precession (SSFP) MR angiography (MRA) for imaging infragenual arteries at 3.0T, with contrast enhanced MR angiography (CE MRA) as reference. Materials And Methods Twenty consecutive patients with suspicion of lower extremity arterial disease undergoing routine CE MRA were recruited. FSD MRA was performed at calf before CE MRA. Image quality and stenosis degree of infragenual arteries from both techniques were independently evaluated and compared. Six patients in this study underwent DSA examination. Results Three undiagnostic segments were excluded with severe venous contamination in CE MRA. A total of 197 calf arterial segments images were analyzed. No significant difference existed in the relative signal intensity (rSI) of arterial segments between FSD MRA and CE MRA techniques (0.92±0.09 vs. 0.93±0.05; P=0.207). However, the subjective image quality score was slightly higher in FSD MRA (3.66±0.81 vs. 3.49±0.87; P=0.050). With CE MRA images as reference standard, slight overestimation existed in FSD MRA (2.19±1.24 vs. 2.09±1.18; P=0.019), with total agreement of 84.3% on the basis of all arterial segments. The sensitivity, specificity, NPV, and PPV of FSD MRA was 96.4%, 93.0%, 98.5%, and 84.1%. No significant difference in the stenosis degree score was detected between MRA (FSD MRA and CE MRA) and DSA (P > 0.05). Conclusion FSD MRA performed on at 3.0Twithout the use of contrast medium provides diagnostic images allowing for arterial stenosis assessment of calf arteries that was highly comparable with CE MRA. Moreover, venous contamination was less problematic with FSD MRA. PMID:26185106
Bubble Formation in Yield Stress Fluids Using Flow-Focusing and T -Junction Devices
NASA Astrophysics Data System (ADS)
Laborie, Benoit; Rouyer, Florence; Angelescu, Dan E.; Lorenceau, Elise
2015-05-01
We study the production of bubbles inside yield stress fluids (YSFs) in axisymmetric T -junction and flow-focusing devices. Taking advantage of yield stress over capillary stress, we exhibit a robust break-up mechanism reminiscent of the geometrical operating regime in 2D flow-focusing devices for Newtonian fluids. We report that when the gas is pressure driven, the dynamics is unsteady due to hydrodynamic feedback and YSF deposition on the walls of the channels. However, the present study also identifies pathways for potential steady-state production of bubbly YSFs at large scale.
Transient fluid flow and heat transfer in petroleum production systems
NASA Astrophysics Data System (ADS)
Lin, Dongqing
Heat transfer is an important phenomenon in both wellbore and reservoir. The pertinent temperature distribution can provide a valuable perspective in analyzing and optimizing the oil production. In this work, two kinds of co-production, production fluid through the annulus and tubing, and through two independent tubings, have been modeled using steady state analysis. The fluid temperatures in the production string and annulus have been solved analytically in both cases. Furthermore, we extended the theory of steady state energy transport to remedy asphaltene deposition problem by circulating the cooling fluid in the annulus. Due to the complex nature of two-phase flow in the oil/gas production, more reliable mechanistic modeling approaches have been developed since early 1980's. Rooted in Hasan-Kabir model, we have developed a wellbore/reservoir coupling simulator for the transient non-Darcy two-phase flow in the flow-after-flow well test. The entire historical flow behavior has been modeled using superposition method and validated with field data. Our second simulation is for the investigation of a blowout well, which is a great concern in the oil field. When the pressure in the wellbore is sufficiently high, the fluids will attain sonic velocity at the wellhead. We presented a computational algorithm to estimate the blowout rate in a given wellbore/reservoir system and examined four major parameters, such as formation permeability, Gas-Oil-Ratio (GOR), reservoir pressure and tubing diameter. The transient nature of this approach also illustrates the evolution process of a blowout. We have also developed a transient simulator to determine the location and severity of a blockage in a gas pipeline based on the theory of two-phase flow and pressure transient analysis. The presence of a sizeable blockage will affect the outlet gas pressure response by decreasing the available pipe volume and increasing the friction loss of the fluid flow. The simulator solves for the
Steady state compact toroidal plasma production
Turner, William C.
1986-01-01
Apparatus and method for maintaining steady state compact toroidal plasmas. A compact toroidal plasma is formed by a magnetized coaxial plasma gun and held in close proximity to the gun electrodes by applied magnetic fields or magnetic fields produced by image currents in conducting walls. Voltage supply means maintains a constant potential across the electrodes producing an increasing magnetic helicity which drives the plasma away from a minimum energy state. The plasma globally relaxes to a new minimum energy state, conserving helicity according to Taylor's relaxation hypothesis, and injecting net helicity into the core of the compact toroidal plasma. Controlling the voltage so as to inject net helicity at a predetermined rate based on dissipative processes maintains or increases the compact toroidal plasma in a time averaged steady state mode.
Cavitation modeling for steady-state CFD simulations
NASA Astrophysics Data System (ADS)
Hanimann, L.; Mangani, L.; Casartelli, E.; Widmer, M.
2016-11-01
Cavitation in hydraulic turbomachines is an important phenomenon to be considered for performance predictions. Correct analysis of the cavitation onset and its effect on the flow field while diminishing the pressure level need therefore to be investigated. Even if cavitation often appears as an unsteady phenomenon, the capability to compute it in a steady state formulation for the design and assessment phase in the product development process is very useful for the engineer. In the present paper the development and corresponding application of a steady state CFD solver is presented, based on the open source toolbox OpenFOAM®. In the first part a review of different cavitation models is presented. Adopting the mixture-type cavitation approach, various models are investigated and developed in a steady state CFD RANS solver. Particular attention is given to the coupling between cavitation and turbulence models as well as on the underlying numerical procedure, especially the integration in the pressure- correction step of pressure-based solvers, which plays an important role in the stability of the procedure. The performance of the proposed model is initially assessed on simple cases available in the open literature. In a second step results for different applications are presented, ranging from airfoils to pumps.
Steady state statistical correlations predict bistability in reaction motifs.
Chakravarty, Suchana; Barik, Debashis
2017-03-01
Various cellular decision making processes are regulated by bistable switches that take graded input signals and convert them to binary all-or-none responses. Traditionally, a bistable switch generated by a positive feedback loop is characterized either by a hysteretic signal response curve with two distinct signaling thresholds or by characterizing the bimodality of the response distribution in the bistable region. To identify the intrinsic bistability of a feedback regulated network, here we propose that bistability can be determined by correlating higher order moments and cumulants (≥2) of the joint steady state distributions of two components connected in a positive feedback loop. We performed stochastic simulations of four feedback regulated models with intrinsic bistability and we show that for a bistable switch with variation of the signal dose, the steady state variance vs. covariance adopts a signatory cusp-shaped curve. Further, we find that the (n + 1)th order cross-cumulant vs. nth order cross-cumulant adopts a closed loop structure for at least n = 3. We also propose that our method is capable of identifying systems without intrinsic bistability even though the system may show bimodality in the marginal response distribution. The proposed method can be used to analyze single cell protein data measured at steady state from experiments such as flow cytometry.
Variational methods in steady state diffusion problems
Lee, C.E.; Fan, W.C.P.; Bratton, R.L.
1983-01-01
Classical variational techniques are used to obtain accurate solutions to the multigroup multiregion one dimensional steady state neutron diffusion equation. Analytic solutions are constructed for benchmark verification. Functionals with cubic trial functions and conservational lagrangian constraints are exhibited and compared with nonconservational functionals with respect to neutron balance and to relative flux and current at interfaces. Excellent agreement of the conservational functionals using cubic trial functions is obtained in comparison with analytic solutions.
Theory of Steady-State Superradiance
NASA Astrophysics Data System (ADS)
Xu, Minghui
In this thesis, I describe the theoretical development of the superradiant laser, or laser in the extreme bad-cavity regime. In this regime, the cavity decay rate is much greater than the atomic dynamics. The atoms emit photons into the cavity mode superradiantly in steady state. We develop group-theoretic methods that enable us to exactly solve mesoscopic systems with hundreds of atoms. We demonstrate the synchronization of atomic dipoles in steady-state superradiance. With this synchronized system, we propose conditional Ramsey spectroscopy which allows us to observe Ramsey fringes indefinitely, even in the presence of atomic decoherence. Furthermore, we explore manifestations of synchronization in the quantum realm with two superradiant atomic ensembles. We show that two such ensembles exhibit a dynamical phase transition from two disparate oscillators to quantum phase-locked dynamics. Finally, we study the mechanical eect of the light-atom interaction in the steady-state superradiance. We find efficient many-body cooling of atoms. The work described in this thesis lays the theoretical foundation for the superradiant laser and for a potential future of active optical frequency standards.
On Typicality in Nonequilibrium Steady States
NASA Astrophysics Data System (ADS)
Evans, Denis J.; Williams, Stephen R.; Searles, Debra J.; Rondoni, Lamberto
2016-08-01
From the statistical mechanical viewpoint, relaxation of macroscopic systems and response theory rest on a notion of typicality, according to which the behavior of single macroscopic objects is given by appropriate ensembles: ensemble averages of observable quantities represent the measurements performed on single objects, because " almost all" objects share the same fate. In the case of non-dissipative dynamics and relaxation toward equilibrium states, " almost all" is referred to invariant probability distributions that are absolutely continuous with respect to the Lebesgue measure. In other words, the collection of initial micro-states (single systems) that do not follow the ensemble is supposed to constitute a set of vanishing, phase space volume. This approach is problematic in the case of dissipative dynamics and relaxation to nonequilibrium steady states, because the relevant invariant distributions attribute probability 1 to sets of zero volume, while evolution commonly begins in equilibrium states, i.e., in sets of full phase space volume. We consider the relaxation of classical, thermostatted particle systems to nonequilibrium steady states. We show that the dynamical condition known as Ω T-mixing is necessary and sufficient for relaxation of ensemble averages to steady state values. Moreover, we find that the condition known as weak T-mixing applied to smooth observables is sufficient for ensemble relaxation to be independent of the initial ensemble. Lastly, we show that weak T-mixing provides a notion of typicality for dissipative dynamics that is based on the (non-invariant) Lebesgue measure, and that we call physical ergodicity.
Geophysical fluid flow cell experiment
NASA Technical Reports Server (NTRS)
Hart, J. E.
1982-01-01
The primary purpose of the geophysical flow experiments is to simulate large-scale baroclinic (density-stratified) flows which occur naturally in the atmospheres of rotating planets and stars and to gain insights and obtain answers to crucial questions concerning the large-scale nonlinear mechanics of the global geophysical flows. Those external conditions related to fluid viscosity, rotation, gravity are identified, which allow qualitatively different modes of instability or waves in the model.
Shear-thinning of molecular fluids in Couette flow
NASA Astrophysics Data System (ADS)
Raghavan, Bharath V.; Ostoja-Starzewski, Martin
2017-02-01
We use non-equilibrium molecular dynamics simulations, the Boltzmann equation, and continuum thermomechanics to investigate and characterize the shear-thinning behavior of molecular fluids undergoing Couette flow, interacting via a Lennard-Jones (LJ) potential. In particular, we study the shear-stress under steady-state conditions and its dependency on fluid density and applied shear-strain rate. Motivated by kinetic theory, we propose a rheological equation of state that fits observed system responses exceptionally well and captures the extreme shear-thinning effect. We notice that beyond a particular strain-rate threshold, the fluid exhibits shear-thinning, the degree of which is dependent on the density and temperature of the system. In addition, we obtain a shear-rate dependent model for the viscosity which matches the well established Cross viscosity model. We demonstrate how this model arises naturally from the Boltzmann equation and possesses an inherent scaling parameter that unifies the rheological properties of the LJ fluid. We compare our model with those in the literature. Finally, we formulate a dissipation function modeling the LJ fluid as a quasilinear fluid.
The Stability and Dynamics of Elastic Structures and Fluid Flows
1990-09-01
stable) for R > RH (< RH). We find that, depending on the length of the observation time and on the initial conditions, the system may appear to be...either in a single steady state, or jumping between multiple steady states, or in a periodic state, or in a transient state. If the observation time is... disturbance to the flow that results from experimental imperfections, or as an externally imposed motion. The -4- frequency of this disturbance depends
Rotational fluid flow experiment
NASA Technical Reports Server (NTRS)
1991-01-01
This project which began in 1986 as part of the Worcester Polytechnic Institute (WPI) Advanced Space Design Program focuses on the design and implementation of an electromechanical system for studying vortex behavior in a microgravity environment. Most of the existing equipment was revised and redesigned by this project team, as necessary. Emphasis was placed on documentation and integration of the electrical and mechanical subsystems. Project results include reconfiguration and thorough testing of all hardware subsystems, implementation of an infrared gas entrainment detector, new signal processing circuitry for the ultrasonic fluid circulation device, improved prototype interface circuits, and software for overall control of experiment operation.
Fluid flow effects in evaporation from liquid-vapor meniscus
Khrustalev, D.; Faghri, A.
1996-12-31
A mathematical model of the evaporating liquid-vapor meniscus in a capillary slot has been developed. The model includes two-dimensional steady-state momentum conservation and energy equations for both the vapor and liquid phases, and incorporates the existing simplified one-dimensional model of the evaporating microfilm. The numerical results, obtained for water, demonstrate the importance of accounting for the fluid flow in calculating the effective evaporative heat transfer coefficient and the superheat of the vapor over the liquid-vapor meniscus due to the heat transfer from the heated wall. With higher heat fluxes, a recirculation zone appears in the vapor near the heated wall due to the extensive evaporation in the thin-film region of the liquid-vapor meniscus.
Zhang, Na; Zou, Liqiu; Huang, Yi; Liu, Dexiang; Tang, Yukuan; Fan, Zhaoyang; Chen, Hanwei; Liu, Xin
2015-01-01
To compare the image quality and diagnostic performance of two non-contrast enhanced MR angiography (NCE-MRA) techniques using flow-sensitive dephasing (FSD) prepared steady-state free precession (SSFP) and quiescent-interval single-shot (QISS) for the calf arteries in patients with diabetes. Twenty six patients underwent the two NCE-MRA techniques followed by contrast-enhanced MRA (CE-MRA) of lower extremity on a 1.5T MR system. Image quality scores, arterial stenosis scores, signal-to-noise ratio (SNR), contrast-to-noise ratio (CNR), vessel sharpness, and diagnostic accuracy for detecting more than 50% arterial stenosis were evaluated and statistically compared using CE-MRA as the reference standard. All examinations were performed successfully. Of the total 153 calf arterial segments obtained in the 26 patients, FSD and QISS showed no significant difference in the number of diagnostic arterial segments (151 [98%] vs. 147 [96%], respectively, P>0.05). The image quality of FSD was higher than that of QISS in the peroneal artery and posterior tibial artery (P<0.05), but no significant difference in the anterior tibial artery (P>0.05). SNR and CNR of FSD were higher than those of QISS (P<0.01), while FSD showed comparable vessel sharpness compared with QISS (P>0.05). The time efficiency of SNR and CNR between FSD and QISS showed no significant difference when taking into account the times for FSD-related scout scans. There was no difference in sensitivity (95% vs. 93%, P>0.05) and negative predictive value (98% vs. 97%, P>0.05) between FSD and QISS for detecting stenosis greater than 50%. However, FSD showed higher specificities (99% vs. 92%, P<0.05) and diagnostic accuracy (98% vs. 92%, P<0.05) compared to QISS. Both FSD and QISS had similar high sensitivity and negative predictive value for detecting calf arteries with over 50% stenosis, but FSD showed slightly higher diagnostic specificity and better depiction of arterial lesions due to its isotropic
Zhang, Nan; Fan, Zhaoyang; Luo, Nan; Bi, Xiaoming; Zhao, Yike; An, Jing; Liu, Jiayi; Chen, Zhong; Fan, Zhanming; Li, Debiao
2016-02-01
To evaluate the feasibility and diagnostic performance of flow-sensitive dephasing (FSD)-prepared steady-state free precession (SSFP) MR angiography (MRA) for imaging infragenual arteries at 3.0T, with contrast enhanced MR angiography (CE MRA) as reference. Twenty consecutive patients with suspicion of lower extremity arterial disease undergoing routine CE MRA were recruited. FSD MRA was performed at calf before CE MRA. Image quality and stenosis degree of infragenual arteries from both techniques were independently evaluated and compared. Six patients in this study underwent DSA examination. Three undiagnostic segments were excluded with severe venous contamination in CE MRA. A total of 197 calf arterial segments images were analyzed. No significant difference existed in the relative signal intensity (rSI) of arterial segments between FSD MRA and CE MRA techniques (0.92 ± 0.09 versus 0.93 ± 0.05; P = 0.207). However, the subjective image quality score was slightly higher in FSD MRA (3.66 ± 0.81 versus 3.49 ± 0.87; P = 0.050). With CE MRA images as reference standard, slight overestimation existed in FSD MRA (2.19 ± 1.24 versus 2.09 ± 1.18; P = 0.019), with total agreement of 84.3% on the basis of all arterial segments. The sensitivity, specificity, negative predictive value, and positive predictive value of FSD MRA was 96.4%, 93.0%, 98.5%, and 84.1%. No significant difference in the stenosis degree score was detected between MRA (FSD MRA and CE MRA) and DSA (P > 0.05). FSD MRA performed on at 3.0T without the use of contrast medium provides diagnostic images allowing for arterial stenosis assessment of calf arteries that was highly comparable with CE MRA. Moreover, venous contamination was less problematic with FSD MRA. © 2015 Wiley Periodicals, Inc.
Rod Bundle Heat Transfer: Steady-State Steam Cooling Experiments
Spring, J.P.; McLaughlin, D.M.
2006-07-01
Through the joint efforts of the Pennsylvania State University and the United States Nuclear Regulatory Commission, an experimental rod bundle heat transfer (RBHT) facility was designed and built. The rod bundle consists of a 7 x 7 square pitch array with spacer grids and geometry similar to that found in a modern pressurized water reactor. From this facility, a series of steady-state steam cooling experiments were performed. The bundle inlet Reynolds number was varied from 1 400 to 30 000 over a pressure range from 1.36 to 4 bars (20 to 60 psia). The bundle inlet steam temperature was controlled to be at saturation for the specified pressure and the fluid exit temperature exceeded 550 deg. C in the highest power tests. One important quantity of interest is the local convective heat transfer coefficient defined in terms of the local bulk mean temperature of the flow, local wall temperature, and heat flux. Steam temperatures were measured at the center of selected subchannels along the length of the bundle by traversing miniaturized thermocouples. Using an analogy between momentum and energy transport, a method was developed for relating the local subchannel centerline temperature measurement to the local bulk mean temperature. Wall temperatures were measured using internal thermocouples strategically placed along the length of each rod and the local wall heat flux was obtained from an inverse conduction program. The local heat transfer coefficient was calculated from the data at each rod thermocouple location. The local heat transfer coefficients calculated for locations where the flow was fully developed were compared against several published correlations. The Weisman and El-Genk correlations were found to agree best with the RBHT steam cooling data, especially over the range of turbulent Reynolds numbers. The effect of spacer grids on the heat transfer enhancement was also determined from instrumentation placed downstream of the spacer grid locations. The local
Energy repartition in the nonequilibrium steady state
NASA Astrophysics Data System (ADS)
Yan, Peng; Bauer, Gerrit E. W.; Zhang, Huaiwu
2017-01-01
The concept of temperature in nonequilibrium thermodynamics is an outstanding theoretical issue. We propose an energy repartition principle that leads to a spectral (mode-dependent) temperature in steady-state nonequilibrium systems. The general concepts are illustrated by analytic solutions of the classical Heisenberg spin chain connected to Langevin heat reservoirs with arbitrary temperature profiles. Gradients of external magnetic fields are shown to localize spin waves in a Wannier-Zeemann fashion, while magnon interactions renormalize the spectral temperature. Our generic results are applicable to other thermodynamic systems such as Newtonian liquids, elastic solids, and Josephson junctions.
Steady state stresses in ribbon parachute canopies
NASA Technical Reports Server (NTRS)
Garrard, W. L.; Wu, K. Y.; Muramoto, K. K.
1984-01-01
An experimental study of the steady state stresses in model ribbon parachute canopies is presented. The distribution of circumferential stress was measured in the horizontal ribbons of two parachutes using Omega sensors. Canopy pressure distributions and overall drag were also measured. Testing was conducted in the University of Minnesota Low-Speed Wind Tunnel at dynamic pressures ranging from 1.0 to 1.5 inches of water. The stresses in the parachute canopies were calculated using the parachute structural analysis code, CANO. It was found that the general shape of the measured and calculated stress distributions was fairly similar; however, the measured stresses were somewhat less than the calculated stresses.
Gravitational steady states of solar coronal loops
NASA Astrophysics Data System (ADS)
Sugiyama, Linda E.; Asgari-Targhi, M.
2017-02-01
Coronal loops on the surface of the sun appear to consist of curved, plasma-confining magnetic flux tubes or "ropes," anchored at both ends in the photosphere. Toroidal loops carrying current are inherently unstable to expansion in the major radius due to toroidal-curvature-induced imbalances in the magnetic and plasma pressures. An ideal MHD analysis of a simple isolated loop with density and pressure higher than the surrounding corona, based on the theory of magnetically confined toroidal plasmas, shows that the radial force balance depends on the loop internal structure and varies over parameter space. It provides a unified picture of simple loop steady states in terms of the plasma beta βo, the inverse aspect ratio ɛ =a /Ro , and the MHD gravitational parameter G ̂≡g a /vA2 , all at the top of the loop, where g is the acceleration due to gravity, a the average minor radius, and vA the shear Alfvén velocity. In the high and low beta tokamak orderings, βo=2 noT /(Bo2/2 μo)˜ɛ1 and ɛ2 , that fit many loops, the solar gravity can sustain nonaxisymmetric steady states at G ̂˜ɛ βo that represent the maximum stable height. At smaller G ̂≤ɛ2βo , the loop is axisymmetric to leading order and stabilized primarily by the two fixed loop ends. Very low beta, nearly force-free, steady states with βo˜ɛ3 may also exist, with or without gravity, depending on higher order effects. The thin coronal loops commonly observed in solar active regions have ɛ ≃0.02 and fit the high beta steady states. G ̂ increases with loop height. Fatter loops in active regions that form along magnetic neutral lines and may lead to solar flares and Coronal Mass Ejections have ɛ ≃0.1 -0.2 and may fit the low beta ordering. Larger loops tend to have G ̂>ɛ βo and be unstable to radial expansion because the exponential hydrostatic reduction in the density at the loop-top reduces the gravitational force -ρG ̂ R ̂ below the level that balances expansion, in agreement with
Intense steady state electron beam generator
Hershcovitch, Ady; Kovarik, Vincent J.; Prelec, Krsto
1990-01-01
An intense, steady state, low emittance electron beam generator is formed by operating a hollow cathode discharge plasma source at critical levels in combination with an extraction electrode and a target electrode that are operable to extract a beam of fast primary electrons from the plasma source through a negatively biased grid that is critically operated to repel bulk electrons toward the plasma source while allowing the fast primary electrons to move toward the target in the desired beam that can be successfully transported for relatively large distances, such as one or more meters away from the plasma source.
Intensity fluctuations in steady-state superradiance
Meiser, D.; Holland, M. J.
2010-06-15
Alkaline-earth-metal-like atoms with ultranarrow optical transitions enable superradiance in steady state. The emitted light promises to have an unprecedented stability with a linewidth as narrow as a few millihertz. In order to evaluate the potential usefulness of this light source as an ultrastable oscillator in clock and precision metrology applications, it is crucial to understand the noise properties of this device. In this paper, we present a detailed analysis of the intensity fluctuations by means of Monte Carlo simulations and semiclassical approximations. We find that the light exhibits bunching below threshold, is to a good approximation coherent in the superradiant regime, and is chaotic above the second threshold.
Non-steady-state aerosol filtration in nanostructured fibrous media.
Przekop, Rafal; Gradoń, Leon
2011-06-28
The filtration of aerosol particles using composites of nano- and microsized fibrous structures is a promising method for the effective separation of nanoparticles from gases. A multi-scale physical system describing the flow pattern and particle deposition at a non-steady-state condition requires an advanced method of modelling. The combination of lattice Boltzmann and Brownian dynamics was used for analysis of the particle deposition pattern in a fibrous system. The dendritic structures of deposits for neutral and charged fibres and particles are present. The efficiency of deposition, deposit morphology, porosity and fractal dimension were calculated for a selected operational condition of the process.
NASA Astrophysics Data System (ADS)
Fraggedakis, D.; Kouris, Ch.; Dimakopoulos, Y.; Tsamopoulos, J.
2015-08-01
We study the flow of two immiscible, Newtonian fluids in a periodically constricted tube driven by a constant pressure gradient. Our volume-of-fluid algorithm is used to solve the governing equations. First, the code is validated by comparing its predictions to previously reported results for stratified and pulsing flow. Then, it is used to capture accurately all the significant topological changes that take place. Initially, the fluids have a core-annular arrangement, which is found to either remain the same or change to a different arrangement depending on the fluid properties, the pressure driving the flow, or the flow geometry. The flow-patterns that appear are the core-annular, segmented, churn, spray, and segregated flow. The predicted scalings near pinching of the core fluid concur with similarity predictions and earlier numerical results [I. Cohen et al., "Two fluid drop snap-off problem: Experiments and theory," Phys. Rev. Lett. 83, 1147-1150 (1999)]. Flow-pattern maps are constructed in terms of the Reynolds and Weber numbers. Our result provides deeper insights into the mechanism of the pattern transitions and is in agreement with previous studies on core-annular flow [Ch. Kouris and J. Tsamopoulos, "Core-annular flow in a periodically constricted circular tube, I. Steady state, linear stability and energy analysis," J. Fluid Mech. 432, 31-68 (2001) and Ch. Kouris et al., "Comparison of spectral and finite element methods applied to the study of interfacial instabilities of the core-annular flow in an undulating tube," Int. J. Numer. Methods Fluids 39(1), 41-73 (2002)], segmented flow [E. Lac and J. D. Sherwood, "Motion of a drop along the centreline of a capillary in a pressure-driven flow," J. Fluid Mech. 640, 27-54 (2009)], and churn flow [R. Y. Bai et al., "Lubricated pipelining—Stability of core annular-flow. 5. Experiments and comparison with theory," J. Fluid Mech. 240, 97-132 (1992)].
Absolute Steady-State Thermal Conductivity Measurements by Use of a Transient Hot-Wire System.
Roder, H M; Perkins, R A; Laesecke, A; Nieto de Castro, C A
2000-01-01
A transient hot-wire apparatus was used to measure the thermal conductivity of argon with both steady-state and transient methods. The effects of wire diameter, eccentricity of the wire in the cavity, axial conduction, and natural convection were accounted for in the analysis of the steady-state measurements. Based on measurements on argon, the relative uncertainty at the 95 % level of confidence of the new steady-state measurements is 2 % at low densities. Using the same hot wires, the relative uncertainty of the transient measurements is 1 % at the 95 % level of confidence. This is the first report of thermal conductivity measurements made by two different methods in the same apparatus. The steady-state method is shown to complement normal transient measurements at low densities, particularly for fluids where the thermophysical properties at low densities are not known with high accuracy.
Steady flow of a non-Newtonian fluid through a contraction
NASA Technical Reports Server (NTRS)
Gatski, T. B.; Lumley, J. L.
1978-01-01
A steady-state analysis is conducted to examine the basic flow structure of a non-Newtonian fluid in a domain including an inflow region, a contraction region, and an outflow region. A Cartesian grid system is used throughout the entire flow domain, including the contraction region, thus creating an irregular grid cell structure adjacent to the curved boundary. At node points adjacent to the curved boundary symmetry conditions are derived for the different flow variables in order to solve the governing difference equations. Attention is given to the motion and non-Newtonian constitutive equations, the boundary conditions, the numerical modeling of the non-Newtonian equations, the stream function contour lines for the non-Newtonian fluid, the vorticity contour lines for the non-Newtonian fluid, the velocity profile across the contraction, and the shear stress contour lines for the non-Newtonian fluid.
Steady flow of a non-Newtonian fluid through a contraction
NASA Technical Reports Server (NTRS)
Gatski, T. B.; Lumley, J. L.
1978-01-01
A steady-state analysis is conducted to examine the basic flow structure of a non-Newtonian fluid in a domain including an inflow region, a contraction region, and an outflow region. A Cartesian grid system is used throughout the entire flow domain, including the contraction region, thus creating an irregular grid cell structure adjacent to the curved boundary. At node points adjacent to the curved boundary symmetry conditions are derived for the different flow variables in order to solve the governing difference equations. Attention is given to the motion and non-Newtonian constitutive equations, the boundary conditions, the numerical modeling of the non-Newtonian equations, the stream function contour lines for the non-Newtonian fluid, the vorticity contour lines for the non-Newtonian fluid, the velocity profile across the contraction, and the shear stress contour lines for the non-Newtonian fluid.
Flow sensor for biomedical fluids
NASA Technical Reports Server (NTRS)
Winkler, H. E.
1981-01-01
Electronic sensor accurately measures and controls flow of plasma, whole blood, or drugs in solution. Since sensor does not directly contact fluid, it does not have to be sterilized. It is compatible with disposable bottles, tubes, and hypodermic needles widely used in hospitals. Only modification necessary is in tube, which must contain two small metal inserts, spaced to fit in curved thermistor plates.
An Intuitive Approach to Steady-State Kinetics.
ERIC Educational Resources Information Center
Raines, Ronald T.; Hansen, David E.
1988-01-01
Attempts to provide an intuitive understanding of steady state kinetics. Discusses the meaning of steady state and uses free energy profiles to illustrate and follow complex kinetic and thermodynamic relationships. Provides examples with explanations. (MVL)
An Intuitive Approach to Steady-State Kinetics.
ERIC Educational Resources Information Center
Raines, Ronald T.; Hansen, David E.
1988-01-01
Attempts to provide an intuitive understanding of steady state kinetics. Discusses the meaning of steady state and uses free energy profiles to illustrate and follow complex kinetic and thermodynamic relationships. Provides examples with explanations. (MVL)
Interfacing a General Purpose Fluid Network Flow Program with the SINDA/G Thermal Analysis Program
NASA Technical Reports Server (NTRS)
Schallhorn, Paul; Popok, Daniel
1999-01-01
A general purpose, one dimensional fluid flow code is currently being interfaced with the thermal analysis program Systems Improved Numerical Differencing Analyzer/Gaski (SINDA/G). The flow code, Generalized Fluid System Simulation Program (GFSSP), is capable of analyzing steady state and transient flow in a complex network. The flow code is capable of modeling several physical phenomena including compressibility effects, phase changes, body forces (such as gravity and centrifugal) and mixture thermodynamics for multiple species. The addition of GFSSP to SINDA/G provides a significant improvement in convective heat transfer modeling for SINDA/G. The interface development is conducted in multiple phases. This paper describes the first phase of the interface which allows for steady and quasi-steady (unsteady solid, steady fluid) conjugate heat transfer modeling.
Fluid flow in nanopores: An examination of hydrodynamic boundary conditions
NASA Astrophysics Data System (ADS)
Sokhan, V. P.; Nicholson, D.; Quirke, N.
2001-08-01
Steady-state Poiseuille flow of a simple fluid in carbon slit pores under a gravity-like force is simulated using a realistic empirical many-body potential model for carbon. In this work we focus on the small Knudsen number regime, where the macroscopic equations are applicable, and simulate different wetting conditions by varying the strength of fluid-wall interactions. We show that fluid flow in a carbon pore is characterized by a large slip length even in the strongly wetting case, contrary to the predictions of Tolstoi's theory. When the surface density of wall atoms is reduced to values typical of a van der Waals solid, the streaming velocity profile vanishes at the wall, in accordance with earlier findings. From the velocity profiles we have calculated the slip length and by analyzing temporal profiles of the velocity components of particles colliding with the wall we obtained values of the Maxwell coefficient defining the fraction of molecules thermalized by the wall.
Steady state rheology from homogeneous and locally averaged simple shear simulations
NASA Astrophysics Data System (ADS)
Shi, Hao; Luding, Stefan; Magnanimo, Vanessa
2017-06-01
Granular materials and particulate matter are ubiquitous in our daily life and they display interesting bulk behaviors from static to dynamic, solid to fluid or gas like states, or even all these states together. To understand how the micro structure and inter-particle forces influence the macroscopic bulk behavior is still a great challenge today. This short paper presents stress controlled homogeneous simple shear results in a 3D cuboidal box using MercuryDPM software. An improved rheological model is proposed for macroscopic friction, volume fraction and coordination number as a function of inertial number and pressure. In addition, the results are compared with the locally averaged data from steady state shear bands in a split bottom ring shear cell and very good agreement is observed in low to intermediate inertia regime at various confining pressure but not for high inertia collisional granular flow.
Do seismic waves and fluid flow sense the same permeability in fluid-saturated porous rocks?
NASA Astrophysics Data System (ADS)
Rubino, J. G.; Monachesi, L. B.; Guarracino, L.; Müller, T. M.; Holliger, K.
2012-04-01
Wave-induced flow due to the the presence of mesoscopic heterogeneities, that is, heterogeneities that are larger than the pore size but smaller than the prevailing seismic wavelengths, represents an important seismic attenuation mechanism in fluid-saturated porous rocks. In this context, it is known that in the presence of strong permeability fluctuations, there is a discrepancy between the effective flow permeability and the effective seismic permeability, that is, the effective permeability controlling seismic attenuation due to wave-induced fluid flow. While this subject has been analyzed for the case of random 1D media, the corresponding 2D and 3D cases remain unexplored, mainly due to the fact that, as opposed to the 1D case, there is no simple expression for the effective flow permeability. In this work we seek to address this problem through the numerical analysis of 2D rock samples having strong permeability fluctuations. In order to do so, we employ a numerical oscillatory compressibility test to determine attenuation and velocity dispersion due to wave-induced fluid flow in these kinds of media and compare the responses with those obtained by replacing the heterogeneous permeability field by homogeneous fields, with permeability values given by the average permeability as well as the effective flow permeability of the sample. The latter is estimated in a separate upscaling procedure by solving the steady-state flow equation in the rock sample under study. Numerical experiments let us verify that the attenuation levels are less significant and the attenuation peak gets broader in the presence of such strong permeability fluctuations. Moreover, we observe that for very low frequencies the effective seismic permeability is similar to the effective flow permeability, while for very high frequencies it approaches the arithmetic average of the permeability field.
Minimal gain marching schemes: searching for unstable steady-states with unsteady solvers
NASA Astrophysics Data System (ADS)
de S. Teixeira, Renan; S. de B. Alves, Leonardo
2017-03-01
Reference solutions are important in several applications. They are used as base states in linear stability analyses as well as initial conditions and reference states for sponge zones in numerical simulations, just to name a few examples. Their accuracy is also paramount in both fields, leading to more reliable analyses and efficient simulations, respectively. Hence, steady-states usually make the best reference solutions. Unfortunately, standard marching schemes utilized for accurate unsteady simulations almost never reach steady-states of unstable flows. Steady governing equations could be solved instead, by employing Newton-type methods often coupled with continuation techniques. However, such iterative approaches do require large computational resources and very good initial guesses to converge. These difficulties motivated the development of a technique known as selective frequency damping (SFD) (Åkervik et al. in Phys Fluids 18(6):068102, 2006). It adds a source term to the unsteady governing equations that filters out the unstable frequencies, allowing a steady-state to be reached. This approach does not require a good initial condition and works well for self-excited flows, where a single nonzero excitation frequency is selected by either absolute or global instability mechanisms. On the other hand, it seems unable to damp stationary disturbances. Furthermore, flows with a broad unstable frequency spectrum might require the use of multiple filters, which delays convergence significantly. Both scenarios appear in convectively, absolutely or globally unstable flows. An alternative approach is proposed in the present paper. It modifies the coefficients of a marching scheme in such a way that makes the absolute value of its linear gain smaller than one within the required unstable frequency spectra, allowing the respective disturbance amplitudes to decay given enough time. These ideas are applied here to implicit multi-step schemes. A few chosen test cases
NASA Astrophysics Data System (ADS)
Huang, Yadong
The study of two-fluid pipe flow was largely inspired by the potential application of using less viscous fluid to lubricate very viscous fluids such as heavy crude oil in oil transporting system. In this thesis, starting from the basic assumptions and mathematical formations of the governing equations for general two-phase flows, we first discuss the simple steady solutions of two immiscible fluids flowing coaxially in a pipe. There are basically two types of solutions, one is the stratified solution, and the other is the core-annular solution, in which the viscous phase stays in the center while the less viscous phase forms an annular around it. This solution is favored from the perspective of lubricated pipelining. The numerical results of the linear stability analysis of these solutions are then obtained using a finite element approximation with an iterative eigenvalue solver for the large matrices generated by the approximation. The core-annular flow configuration is, in general unstable due to capillarity, interfacial friction force and Reynolds stress or the combination of the three. In most of the industrial practices, the Reynolds number is so high that the flow of the less viscous phase is turbulent. For these cases we apply a k - epsilon turbulence model to the less viscous phase while assume the viscous core is still laminar and solve for the steady solution. The friction factor, which measures the drag in a pipe system, and the holdup ratio are computed for typical cases. The results are compared with available experimental data and the agreement is rather good.
Steady-state mushy layers: Experiments and theory
NASA Astrophysics Data System (ADS)
Peppin, S.; Aussillous, P.; Huppert, Herbert E.; Grae Worster, M.
2006-11-01
A new facility has been developed to investigate mushy layers formed during the steady directional solidification of transparent aqueous solutions in a quasi-two-dimensional system. Experiments have been conducted on NaCl--H20 solutions by translating a Hele-Shaw cell at prescribed rates between fixed heat exchangers providing a temperature gradient of approximately 1,^0C/mm. Ice formed the primary solid phase and the dense residual fluid ponded within the mushy layer at the base of the system. Mathematical predictions of the steady-state temperature profile and mushy layer thickness as functions of freezing rate are in excellent agreement with experimental results. Experiments have also been performed on aqueous NH4Cl solutions, with the salt forming the primary solid phase, yielding buoyancy-driven convection in the mushy layer and the development of chimneys. The lifetime of the chimneys increased with decreasing freezing rate; however, no steady-state chimneys have been observed. Rather, a convecting chimney appears to deplete the surrounding solution and is eventually extinguished. At freezing rates larger than about 5.5,μm/s a uniform mushy layer develops with no chimneys. However, at rates larger than about 5,μm/s a second mode of behaviour is observed in which the mushy layer is thin and there is significant supercooling and nucleation above it. There is hysteresis between the two modes.
Steady-state wear and friction in boundary lubrication studies
NASA Technical Reports Server (NTRS)
Loomis, W. R.; Jones, W. R., Jr.
1980-01-01
A friction and wear study was made at 20 C to obtain improved reproducibility and reliability in boundary lubrication testing. Ester-base and C-ether-base fluids were used to lubricate a pure iron rider in sliding contact with a rotating M-50 steel disk in a friction and wear apparatus. Conditions included loads of 1/2 and 1 kg and sliding velocities of 3.6 to 18.2 m/min in a dry air atmosphere and stepwise time intervals from 1 to 250 min for wear measurements. The wear rate results were compared with those from previous studies where a single 25 min test period was used. Satisfactory test conditions for studying friction and wear in boundary lubrication for this apparatus were found to be 1 kg load; sliding velocities of 7.1 to 9.1 m/min (50 rpm disk speed); and use of a time stepwise test procedure. Highly reproducible steady-state wear rates and steady-state friction coefficients were determined under boundary conditions. Wear rates and coefficients of friction were constant following initially high values during run-in periods.
Steady-state models of photosynthesis.
von Caemmerer, Susanne
2013-09-01
In the challenge to increase photosynthetic rate per leaf area mathematical models of photosynthesis can be used to help interpret gas exchange measurements made under different environmental conditions and predict underlying photosynthetic biochemistry. To do this successfully it is important to improve the modelling of temperature dependencies of CO₂ assimilation and gain better understanding of internal CO₂ diffusion limitations. Despite these shortcomings steady-state models of photosynthesis provide simple easy to use tools for thought experiments to explore photosynthetic pathway changes such as redirecting photorespiratory CO₂, inserting bicarbonate pumps into C₃ chloroplasts or inserting C₄ photosynthesis into rice. Here a number of models derived from the C₃ model by Farquhar, von Caemmerer and Berry are discussed and compared.
Steady-State Chemotaxis in Escherichia coli
NASA Astrophysics Data System (ADS)
Kafri, Yariv; da Silveira, Rava Azeredo
2008-06-01
The bacterium E. coli maneuvers itself to regions with high chemoattractant concentrations by performing two stereotypical moves: “runs,” in which it moves in near-straight lines, and “tumbles,” in which it does not advance but changes direction randomly. The duration of each move is stochastic and depends upon the chemoattractant concentration experienced in the recent past. We relate this stochastic behavior to the steady-state density of a bacterium population, and we derive the latter as a function of chemoattractant concentration. In contrast to earlier treatments, here we account for the effects of temporal correlations and variable tumbling durations. A range of behaviors is obtained that depends subtly upon several aspects of the system—memory, correlation, and tumbling stochasticity, in particular.
NASA Technical Reports Server (NTRS)
Ostrach, S.
1982-01-01
The behavior of fluids in micro-gravity conditions is examined, with particular regard to applications in the growth of single crystals. The effects of gravity on fluid behavior are reviewed, and the advent of Shuttle flights are noted to offer extended time for experimentation and processing in a null-gravity environment, with accelerations resulting solely from maneuvering rockets. Buoyancy driven flows are considered for the cases stable-, unstable-, and mixed-mode convection. Further discussion is presented on g-jitter, surface-tension gradient, thermoacoustic, and phase-change convection. All the flows are present in both gravity and null gravity conditions, although the effects of buoyancy and g-jitter convection usually overshadow the other effects while in a gravity field. Further work is recommended on critical-state and sedimentation processes in microgravity conditions.
Fluid flow electrophoresis in space
NASA Technical Reports Server (NTRS)
Griffin, R. N.
1975-01-01
Four areas relating to free-flow electrophoresis in space were investigated. The first was the degree of improvement over earthbound operations that might be expected. The second area of investigation covered the problems in developing a flowing buffer electrophoresis apparatus. The third area of investigation was the problem of testing on the ground equipment designed for use in space. The fourth area of investigation was the improvement to be expected in space for purification of biologicals. The results of some ground-based experiments are described. Other studies included cooling requirements in space, fluid sealing techniques, and measurement of voltage drop across membranes.
Ferroelectric Fluid Flow Control Valve
NASA Technical Reports Server (NTRS)
Jalink, Antony, Jr. (Inventor); Hellbaum, Richard F. (Inventor); Rohrbach, Wayne W. (Inventor)
1999-01-01
An active valve is controlled and driven by external electrical actuation of a ferroelectric actuator to provide for improved passage of the fluid during certain time periods and to provide positive closure of the valve during other time periods. The valve provides improved passage in the direction of flow and positive closure in the direction against the flow. The actuator is a dome shaped internally prestressed ferroelectric actuator having a curvature, said dome shaped actuator having a rim and an apex. and a dome height measured from a plane through said rim said apex that varies with an electric voltage applied between an inside and an outside surface of said dome shaped actuator.
General Transient Fluid Flow Algorithm
Amsden, A. A.; Ruppel, H. M.; Hirt, C. W.
1992-03-12
SALE2D calculates two-dimensional fluid flows at all speeds, from the incompressible limit to highly supersonic. An implicit treatment of the pressure calculation similar to that in the Implicit Continuous-fluid Eulerian (ICE) technique provides this flow speed flexibility. In addition, the computing mesh may move with the fluid in a typical Lagrangian fashion, be held fixed in an Eulerian manner, or move in some arbitrarily specified way to provide a continuous rezoning capability. This latitude results from use of an Arbitrary Lagrangian-Eulerian (ALE) treatment of the mesh. The partial differential equations solved are the Navier-Stokes equations and the mass and internal energy equations. The fluid pressure is determined from an equation of state and supplemented with an artificial viscous pressure for the computation of shock waves. The computing mesh consists of a two-dimensional network of quadrilateral cells for either cylindrical or Cartesian coordinates, and a variety of user-selectable boundary conditions are provided in the program.
Quasi-steady state conditions in heterogeneous aquifers during pumping tests
NASA Astrophysics Data System (ADS)
Zha, Yuanyuan; Yeh, Tian-Chyi J.; Shi, Liangsheng; Huang, Shao-Yang; Wang, Wenke; Wen, Jet-Chau
2017-08-01
Classical Thiem's well hydraulic theory, other aquifer test analyses, and flow modeling efforts often assume the existence of ;quasi-steady; state conditions. That is, while drawdowns due to pumping continue to grow, the hydraulic gradient in the vicinity of the pumping well does not change significantly. These conditions have built upon two-dimensional and equivalent homogeneous conceptual models, but few field data have been available to affirm the existence of these conditions. Moreover, effects of heterogeneity and three-dimensional flow on this quasi-steady state concept have not been thoroughly investigated and discussed before. In this study, we first present a quantitative definition of quasi-steady state (or steady-shape conditions) and steady state conditions based on the analytical solution of two- or three-dimensional flow induced by pumping in unbounded, homogeneous aquifers. Afterward, we use a stochastic analysis to investigate the influence of heterogeneity on the quasi-steady state concept in heterogeneous aquifers. The results of the analysis indicate that the time to reach an approximate quasi-steady state in a heterogeneous aquifer could be quite different from that estimated based on a homogeneous model. We find that heterogeneity of aquifer properties, especially hydraulic conductivity, impedes the development of the quasi-steady state condition before the flow reaching steady state. Finally, 280 drawdown-time data from the hydraulic tomographic survey conducted at a field site corroborate our finding that the quasi-steady state condition likely would not take place in heterogeneous aquifers unless pumping tests last a long period. Research significance (1) Approximate quasi-steady and steady state conditions are defined for two- or three-dimensional flow induced by pumping in unbounded, equivalent homogeneous aquifers. (2) Analysis demonstrates effects of boundary condition, well screen interval, and heterogeneity of parameters on the
Cerebrospinal fluid flow in adults.
Bradley, William G; Haughton, Victor; Mardal, Kent-Andre
2016-01-01
This chapter uses magnetic resonance imaging phase-contrast cerebrospinal fluid (CSF) flow measurements to predict which clinical normal-pressure hydrocephalus (NPH) patients will respond to shunting as well as which patients with Chiari I are likely to develop symptoms of syringomyelia. Symptomatic NPH patients with CSF flow (measured as the aqueductal CSF stroke volume) which is shown to be hyperdynamic (defined as twice normal) are quite likely to respond to ventriculoperitoneal shunting. The hyperdynamic CSF flow results from normal systolic brain expansion compressing the enlarged ventricles. When atrophy occurs, there is less brain expansion, decreased aqueductal CSF flow, and less likelihood of responding to shunting. It appears that NPH is a "two-hit" disease, starting as benign external hydrocephalus in infancy, followed by deep white-matter ischemia in late adulthood, which causes increased resistance to CSF outflow through the extracellular space of the brain. Using computational flow dynamics (CFD), CSF flow can be modeled at the foramen magnum and in the upper cervical spine. As in the case of NPH, hyperdynamic CSF flow appears to cause the signs and symptoms in Chiari I and can provide an additional indication for surgical decompression. CFD can also predict CSF pressures over the cardiac cycle. It has been hypothesized that elevated pressure pulses may be a significant etiologic factor in some cases of syringomyelia.
Steady-state operation of spheromaks by inductive techniques
Janos, A.
1984-04-01
A method to maintain a steady-state spheromak configuration inductively using the S-1 Spheromak device is described. The S-1 Spheromak formation apparatus can be utilized to inject magnetic helicity continuously (C.W., not pulsed or D.C.) into the spheromak configuration after equilibrium is achieved in the linked mode of operation. Oscillation of both poloidal- and toroidal-field currents in the flux core (psi-phi Pumping), with proper phasing, injects a net time-averaged helicity into the plasma. Steady-state maintenance relies on flux conversion, which has been earlier identified. Relevant experimental data from the operation of S-1 are described. Helicity flow has been measured and the proposed injection scheme simulated. In a reasonable time practical voltages and frequencies can inject an amount of helicity comparable to that in the initial plasma. Plasma currents can be maintained or increased. This pumping technique is similar to F-THETA Pumping of a Reversed-Field-Pinch but is applied to this inverse-pinch formation.
Relativistic hydrodynamics and non-equilibrium steady states
NASA Astrophysics Data System (ADS)
Spillane, Michael; Herzog, Christopher P.
2016-10-01
We review recent interest in the relativistic Riemann problem as a method for generating a non-equilibrium steady state. In the version of the problem under consideration, the initial conditions consist of a planar interface between two halves of a system held at different temperatures in a hydrodynamic regime. The new double shock solutions are in contrast with older solutions that involve one shock and one rarefaction wave. We use numerical simulations to show that the older solutions are preferred. Briefly we discuss the effects of a conserved charge. Finally, we discuss deforming the relativistic equations with a nonlinear term and how that deformation affects the temperature and velocity in the region connecting the asymptotic fluids.
2008-03-01
function, its value at zero time is indeterminate; however, by using techniques of calculus , it is found to be zero. The third is the 3 parameter Hill...cavitation and collapse of the fluid. Based on these results, it makes sense that the application of CFD modeling for an incompressible Newtonian fluid...regard to execution time. In addition the trend is non -linear in that the time increases by a factor of 70 from the smallest to the largest ratio and
Steady-state and non-steady state operation of counter-current chromatography devices.
Kostanyan, Artak E; Ignatova, Svetlana N; Sutherland, Ian A; Hewitson, Peter; Zakhodjaeva, Yulya A; Erastov, Andrey A
2013-11-01
Different variants of separation processes based on steady-state (continuous sample loading) and non-steady state (batch) operating modes of CCC columns have been analyzed and compared. The analysis is carried out on the basis of the modified equilibrium cell model, which takes into account both mechanisms of band broadening - interphase mass transfer and axial mixing. A full theoretical treatment of the intermittent counter-current chromatography with short sample loading time is performed. Analytical expressions are presented allowing the simulation of the intermittent counter-current chromatography separations for various experimental conditions. Chromatographic and extraction separations have been compared and advantages and disadvantages of the two methods have been evaluated. Further technical development of the CCC machines to implement counter-current extraction separations is considered.
Maximal lactate steady state in Judo
de Azevedo, Paulo Henrique Silva Marques; Pithon-Curi, Tania; Zagatto, Alessandro Moura; Oliveira, João; Perez, Sérgio
2014-01-01
Summary Background: the purpose of this study was to verify the validity of respiratory compensation threshold (RCT) measured during a new single judo specific incremental test (JSIT) for aerobic demand evaluation. Methods: to test the validity of the new test, the JSIT was compared with Maximal Lactate Steady State (MLSS), which is the gold standard procedure for aerobic demand measuring. Eight well-trained male competitive judo players (24.3 ± 7.9 years; height of 169.3 ± 6.7cm; fat mass of 12.7 ± 3.9%) performed a maximal incremental specific test for judo to assess the RCT and performed on 30-minute MLSS test, where both tests were performed mimicking the UchiKomi drills. Results: the intensity at RCT measured on JSIT was not significantly different compared to MLSS (p=0.40). In addition, it was observed high and significant correlation between MLSS and RCT (r=0.90, p=0.002), as well as a high agreement. Conclusions: RCT measured during JSIT is a valid procedure to measure the aerobic demand, respecting the ecological validity of Judo. PMID:25332923
Inconsistencies in steady-state thermodynamics
NASA Astrophysics Data System (ADS)
Dickman, Ronald; Motai, Ricardo
2014-03-01
We address the issue of extending thermodynamics to nonequilibrium steady states. Using driven stochastic lattice gases, we ask whether consistent definitions of an effective chemical potential μ, and an effective temperature Te, are possible. μ and Te are determined via coexistence, i.e., zero flux of particles and energy between the driven system and a reservoir. In the lattice gas with nearest-neighbor exclusion, temperature is not relevant, and we find that the effective chemical potential, a function of density and drive strength, satisfies the zeroth law, and correctly predicts the densities of coexisting systems. In the Katz-Lebowitz-Spohn driven lattice gas both μ and Te need to be defined. We show analytically that in this case the zeroth law is violated for Metropolis exchange rates, and determine the size of the violations numerically. The zeroth law appears to be violated for generic exchange rates. Remarkably, the system-reservoir coupling proposed by Sasa and Tasaki [J. Stat. Phys. 125, 125 (2006), 10.1007/s10955-005-9021-7] is free of inconsistencies, and the zeroth law holds. This is because the rate depends only on the state of the donor system, and is independent of that of the acceptor.
Fluctuations When Driving Between Nonequilibrium Steady States
NASA Astrophysics Data System (ADS)
Riechers, Paul M.; Crutchfield, James P.
2017-06-01
Maintained by environmental fluxes, biological systems are thermodynamic processes that operate far from equilibrium without detailed-balanced dynamics. Yet, they often exhibit well defined nonequilibrium steady states (NESSs). More importantly, critical thermodynamic functionality arises directly from transitions among their NESSs, driven by environmental switching. Here, we identify the constraints on excess heat and dissipated work necessary to control a system that is kept far from equilibrium by background, uncontrolled "housekeeping" forces. We do this by extending the Crooks fluctuation theorem to transitions among NESSs, without invoking an unphysical dual dynamics. This and corresponding integral fluctuation theorems determine how much work must be expended when controlling systems maintained far from equilibrium. This generalizes thermodynamic feedback control theory, showing that Maxwellian Demons can leverage mesoscopic-state information to take advantage of the excess energetics in NESS transitions. We also generalize an approach recently used to determine the work dissipated when driving between functionally relevant configurations of an active energy-consuming complex system. Altogether, these results highlight universal thermodynamic laws that apply to the accessible degrees of freedom within the effective dynamic at any emergent level of hierarchical organization. By way of illustration, we analyze a voltage-gated sodium ion channel whose molecular conformational dynamics play a critical functional role in propagating action potentials in mammalian neuronal membranes.
Steady State Vapor Bubble in Pool Boiling
Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C.; Maroo, Shalabh C.
2016-01-01
Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics. PMID:26837464
Fluctuations When Driving Between Nonequilibrium Steady States
NASA Astrophysics Data System (ADS)
Riechers, Paul M.; Crutchfield, James P.
2017-08-01
Maintained by environmental fluxes, biological systems are thermodynamic processes that operate far from equilibrium without detailed-balanced dynamics. Yet, they often exhibit well defined nonequilibrium steady states (NESSs). More importantly, critical thermodynamic functionality arises directly from transitions among their NESSs, driven by environmental switching. Here, we identify the constraints on excess heat and dissipated work necessary to control a system that is kept far from equilibrium by background, uncontrolled "housekeeping" forces. We do this by extending the Crooks fluctuation theorem to transitions among NESSs, without invoking an unphysical dual dynamics. This and corresponding integral fluctuation theorems determine how much work must be expended when controlling systems maintained far from equilibrium. This generalizes thermodynamic feedback control theory, showing that Maxwellian Demons can leverage mesoscopic-state information to take advantage of the excess energetics in NESS transitions. We also generalize an approach recently used to determine the work dissipated when driving between functionally relevant configurations of an active energy-consuming complex system. Altogether, these results highlight universal thermodynamic laws that apply to the accessible degrees of freedom within the effective dynamic at any emergent level of hierarchical organization. By way of illustration, we analyze a voltage-gated sodium ion channel whose molecular conformational dynamics play a critical functional role in propagating action potentials in mammalian neuronal membranes.
Steady State Vapor Bubble in Pool Boiling.
Zou, An; Chanana, Ashish; Agrawal, Amit; Wayner, Peter C; Maroo, Shalabh C
2016-02-03
Boiling, a dynamic and multiscale process, has been studied for several decades; however, a comprehensive understanding of the process is still lacking. The bubble ebullition cycle, which occurs over millisecond time-span, makes it extremely challenging to study near-surface interfacial characteristics of a single bubble. Here, we create a steady-state vapor bubble that can remain stable for hours in a pool of sub-cooled water using a femtosecond laser source. The stability of the bubble allows us to measure the contact-angle and perform in-situ imaging of the contact-line region and the microlayer, on hydrophilic and hydrophobic surfaces and in both degassed and regular (with dissolved air) water. The early growth stage of vapor bubble in degassed water shows a completely wetted bubble base with the microlayer, and the bubble does not depart from the surface due to reduced liquid pressure in the microlayer. Using experimental data and numerical simulations, we obtain permissible range of maximum heat transfer coefficient possible in nucleate boiling and the width of the evaporating layer in the contact-line region. This technique of creating and measuring fundamental characteristics of a stable vapor bubble will facilitate rational design of nanostructures for boiling enhancement and advance thermal management in electronics.
Conveyor belt effect in the flow through a tube of a viscous fluid with spinning particles.
Felderhof, B U
2012-04-28
The extended Navier-Stokes equations describing the steady-state hydrodynamics of a viscous fluid with spinning particles are solved for flow through a circular cylindrical tube. The flow caused by an applied torque density in the azimuthal direction and linear in the radial distance from the axis is compared with the flow caused by a uniform applied force density directed along the axis of the tube. In both cases the flow velocity is of Poiseuille type plus a correction. In the first case the flow velocity is caused by the conveyor belt effect of spinning particles. The corrections to the Poiseuille flow pattern in the two cases differ only by a proportionality factor. The spin velocity profiles in the two cases are also proportional.
Steady state volcanism - Evidence from eruption histories of polygenetic volcanoes
NASA Technical Reports Server (NTRS)
Wadge, G.
1982-01-01
Cumulative volcano volume curves are presented as evidence for steady-state behavior at certain volcanoes and to develop a model of steady-state volcanism. A minimum criteria of five eruptions over a year was chosen to characterize a steady-state volcano. The subsequent model features a constant head of magmatic pressure from a reservoir supplied from depth, a sawtooth curve produced by the magma arrivals or discharge from the subvolcanic reservoir, large volume eruptions with long repose periods, and conditions of nonsupply of magma. The behavior of Mts. Etna, Nyamuragira, and Kilauea are described and show continuous levels of plasma output resulting in cumulative volume increases. Further discussion is made of steady-state andesitic and dacitic volcanism, long term patterns of the steady state, and magma storage, and the lack of a sufficient number of steady-state volcanoes in the world is taken as evidence that further data is required for a comprehensive model.
Method and Apparatus for Predicting Unsteady Pressure and Flow Rate Distribution in a Fluid Network
NASA Technical Reports Server (NTRS)
Majumdar, Alok K. (Inventor)
2009-01-01
A method and apparatus for analyzing steady state and transient flow in a complex fluid network, modeling phase changes, compressibility, mixture thermodynamics, external body forces such as gravity and centrifugal force and conjugate heat transfer. In some embodiments, a graphical user interface provides for the interactive development of a fluid network simulation having nodes and branches. In some embodiments, mass, energy, and specific conservation equations are solved at the nodes, and momentum conservation equations are solved in the branches. In some embodiments, contained herein are data objects for computing thermodynamic and thermophysical properties for fluids. In some embodiments, the systems of equations describing the fluid network are solved by a hybrid numerical method that is a combination of the Newton-Raphson and successive substitution methods.
Two-fluid model for two-phase flow
Ishii, M.
1987-01-01
The two-fluid model formulation is discussed in detail. The emphasis of the paper is on the three-dimensional formulation and the closure issues. The origin of the interfacial and turbulent transfer terms in the averaged formulation is explained and their original mathematical forms are examined. The interfacial transfer of mass, momentum, and energy is proportional to the interfacial area and driving force. This is not a postulate but a result of the careful examination of the mathematical form of the exact interfacial terms. These two effects are considered separately. Since all the interfacial transfer terms involve the interfacial area concentration, the accurate modeling of the local interfacial area concentration is the first step to be taken for a development of a reliable two-fluid model closure relations. The interfacial momentum interaction has been studied in terms of the standard-drag, lift, virtual mass, and Basset forces. Available analytical and semi-empirical correlations and closure relations are reviewed and existing shortcomings are pointed out. The other major area of importance is the modeling of turbulent transfer in two-phase flow. The two-phase flow turbulence problem is coupled with the phase separation problem even in a steady-state fully developed flow. Thus the two-phase turbulence cannot be understood without understanding the interfacial drag and lift forces accurately. There are some indications that the mixing length type model may not be sufficient to describe the three-dimensional turbulent and flow structures. Although it is a very difficult challenge, the two-phase flow turbulence should be investigated both experimentally and analytically with long time-scale research. 87 refs.
Steady laminar flow of fractal fluids
NASA Astrophysics Data System (ADS)
Balankin, Alexander S.; Mena, Baltasar; Susarrey, Orlando; Samayoa, Didier
2017-02-01
We study laminar flow of a fractal fluid in a cylindrical tube. A flow of the fractal fluid is mapped into a homogeneous flow in a fractional dimensional space with metric induced by the fractal topology. The equations of motion for an incompressible Stokes flow of the Newtonian fractal fluid are derived. It is found that the radial distribution for the velocity in a steady Poiseuille flow of a fractal fluid is governed by the fractal metric of the flow, whereas the pressure distribution along the flow direction depends on the fractal topology of flow, as well as on the fractal metric. The radial distribution of the fractal fluid velocity in a steady Couette flow between two concentric cylinders is also derived.
D0 Silicon Upgrade: Control Dewar Steady State Thermodynamic Operating Goals
Rucincki, Russ; /Fermilab
1995-10-20
This engineering note documents the thermodynamic operating parameter goals for the steady state operation of the control dewar/solenoid system. Specifically, how the control dewar pressure control valve, PV-3062-H and the magnet flow control valve EVMF are operated to give the lowest possible temperature fluid at the solenoid magnet. The goals are: (1) For PV-3062-H - The process variable is the helium reservoir pressure, minimize the reservoir pressure, provide only enough pressure plus a little margin to ensure leads flow; and (2) For EVMF - The process variable is firstly a manual setpoint of flowrate as read by the flow venturi, FE3253-H, and secondly the reservoir liquid level, minimize the pressure drop thru the solenoid cooling tubes, provide at least enough flow to maintain reservoir level and stable operation of the magnet. The thermodynamic states for the fluid thru the system are shown on the Pressure versus Temperature graph. Lines of constant enthalpy are also shown. State A is shown as two phase liquid entering the inlet of the subcooler. The subcooler subcools the fluid to State B. State B to State C is caused by the pressure drop across EVMF. State C to D is the estimated pressure drop from the outlet of EVMF thru the solenoid cooling tubes and back up to the helium reservoir inlet. To give the coolest fluid in the cooling tubes, the two phase fluid in the reservoir should be at the lowest pressure (and thus temperature). This lowest pressure is limited by the required pressure for leads flow and if this does not dominate, the low pressure side pressure drop thru the refrigerator and suction pressure set point. My guess is the lead flow requirement will dominate. I suggest putting the PV-3062-H set point such that the lead flow control valves operate at about 80% open. The second parameter that will give the coolest fluid in the cooling tubes is a minimized pressure drop thru the cooling tubes. This can be accomplished by providing a minimized
Finite Element Analysis of Magnetic Damping Effects on G-Jitter Induced Fluid Flow
NASA Technical Reports Server (NTRS)
Pan, Bo; Li, Ben Q.; deGroh, Henry C., III
1997-01-01
This paper reports some interim results on numerical modeling and analyses of magnetic damping of g-jitter driven fluid flow in microgravity. A finite element model is developed to represent the fluid flow, thermal and solute transport phenomena in a 2-D cavity under g-jitter conditions with and without an applied magnetic field. The numerical model is checked by comparing with analytical solutions obtained for a simple parallel plate channel flow driven by g-jitter in a transverse magnetic field. The model is then applied to study the effect of steady state g-jitter induced oscillation and on the solute redistribution in the liquid that bears direct relevance to the Bridgman-Stockbarger single crystal growth processes. A selection of computed results is presented and the results indicate that an applied magnetic field can effectively damp the velocity caused by g-jitter and help to reduce the time variation of solute redistribution.
Olson, A. P.; Kalimullah; Feldman, E. E.; Nuclear Engineering Division
2006-01-01
Recent reactor conversion studies in the RERTR Program have required expansion or revision of modeling capabilities for steady state thermalhydraulic analysis. For example, some reactors operate in laminar flow, necessitating new correlations for Nusselt number and for friction loss. Others have single-sided heating of edge channels. And some have geometrical details that require new modeling approaches to either simulate or validate. Computational fluid dynamics was compared with the 2-dimensional approximation to heat flow used by the PLTEMP/ANL V3.0 code. A very systematic approach to hot channel factors is implemented. A closed-form solution is now used in flat-plate geometry to improve both speed and accuracy of the solution. Direct heating to clad and coolant is now included. The Groenveld table lookup method is now available for determination of CHF. Flow excursion prediction is updated. All of these improvements have been incorporated in the PLTEMP/ANL V3.0 code.
NASA Astrophysics Data System (ADS)
Rahmatipour, Hamed; Azimian, Ahmad-Reza; Atlaschian, Omid
2017-01-01
The method of molecular dynamics simulation is applied in order to study the behavior of liquid Argon flow within oscillatory Couette flows, in both smooth and rough nanochannels. To accomplish this study, the fluid velocity and the fluid slip in oscillatory Couette flows were used to assess the effects of: oscillatory velocity amplitude, speed frequency rate, channel height, wall density, and the amount of interaction between fluid and wall particles. Both smooth and rough walls were modelled in order to investigate the effect on the fluid patterns as well. Rectangular and triangular wall roughnesses in different dimensions were used to study this effect. The results indicate that an increase in the velocity amplitude increases the fluid slip, and decreases the fluid velocity fluctuations near the walls. Similar to the steady-state Couette flow, in oscillatory flow we observe a decrease in fluid slip by reducing the wall density. Moreover, by reducing the energy parameter between the fluid and wall, the fluid slip increases, and by reducing the length parameter the fluid slip decreases. Implementing the rectangular and triangular roughness to the bottom wall in the oscillatory flow results in a decrease in fluid slip, which is also similar to the usual non-oscillating flows.
Constitutive laws for steady state deformation of metals, a microstructural model
Nes, E.
1995-07-15
Based on extensive investigations of the steady state conditions for creep and hot working, Sellars and McG. Tegart demonstrated that the flow stress was well represented by the following relation: {sigma}{sub s} = 1/{alpha}{prime} Arc sinh (Z/A{prime}){sup 1/n} where {alpha}{prime}, A{prime}, n are temperature independent constants and Z is the Zener-Hollomon parameter, Z = {dot {var_epsilon}} exp U/kT, where {dot {var_epsilon}} is the applied strain rate and U is an activation energy. This relationship is widely used in the modelling of metal forming processes such as hot rolling, forging and extrusion. The objective this work is to explore the possibilities for deriving an alternative, physically based, relationship which is capable of correlating the steady state flow stress both to the alloy condition and the microstructural characteristics of steady state deformation.
Diehl, S; Zambrano, J; Carlsson, B
2016-01-01
A reduced model of a completely stirred-tank bioreactor coupled to a settling tank with recycle is analyzed in its steady states. In the reactor, the concentrations of one dominant particulate biomass and one soluble substrate component are modelled. While the biomass decay rate is assumed to be constant, growth kinetics can depend on both substrate and biomass concentrations, and optionally model substrate inhibition. Compressive and hindered settling phenomena are included using the Bürger-Diehl settler model, which consists of a partial differential equation. Steady-state solutions of this partial differential equation are obtained from an ordinary differential equation, making steady-state analysis of the entire plant difficult. A key result showing that the ordinary differential equation can be replaced with an approximate algebraic equation simplifies model analysis. This algebraic equation takes the location of the sludge-blanket during normal operation into account, allowing for the limiting flux capacity caused by compressive settling to easily be included in the steady-state mass balance equations for the entire plant system. This novel approach grants the possibility of more realistic solutions than other previously published reduced models, comprised of yet simpler settler assumptions. The steady-state concentrations, solids residence time, and the wastage flow ratio are functions of the recycle ratio. Solutions are shown for various growth kinetics; with different values of biomass decay rate, influent volumetric flow, and substrate concentration.
NASA Technical Reports Server (NTRS)
Schweikhard, W. G.; Dennon, S. R.
1986-01-01
A review of the Melick method of inlet flow dynamic distortion prediction by statistical means is provided. These developments include the general Melick approach with full dynamic measurements, a limited dynamic measurement approach, and a turbulence modelling approach which requires no dynamic rms pressure fluctuation measurements. These modifications are evaluated by comparing predicted and measured peak instantaneous distortion levels from provisional inlet data sets. A nonlinear mean-line following vortex model is proposed and evaluated as a potential criterion for improving the peak instantaneous distortion map generated from the conventional linear vortex of the Melick method. The model is simplified to a series of linear vortex segments which lay along the mean line. Maps generated with this new approach are compared with conventionally generated maps, as well as measured peak instantaneous maps. Inlet data sets include subsonic, transonic, and supersonic inlets under various flight conditions.
Fluid Flow Experiment for Undergraduate Laboratory.
ERIC Educational Resources Information Center
Vilimpochapornkul, Viroj; Obot, Nsima T.
1986-01-01
The undergraduate fluid mechanics laboratory at Clarkson University consists of three experiments: mixing; drag measurements; and fluid flow and pressure drop measurements. The latter experiment is described, considering equipment needed, procedures used, and typical results obtained. (JN)
Fluid Flow Experiment for Undergraduate Laboratory.
ERIC Educational Resources Information Center
Vilimpochapornkul, Viroj; Obot, Nsima T.
1986-01-01
The undergraduate fluid mechanics laboratory at Clarkson University consists of three experiments: mixing; drag measurements; and fluid flow and pressure drop measurements. The latter experiment is described, considering equipment needed, procedures used, and typical results obtained. (JN)
Fluid flow, mineral reactions, and metasomatism
Ferry, J.M.; Dipple, G.M. )
1991-03-01
A general model that relates fluid flow along a temnperature gradient to chemical reaction in rocks can be used to quantitatively interpret petrologic and geochemical data on metasomatism from ancient flow systems in terms of flow direction and time-integrated fluid flux. The model is applied to regional metamorphism, quartz veins, and a metasomatized ductile fault zone.
Defining Features of Steady-State Timbres
NASA Astrophysics Data System (ADS)
Hall, Michael D.
1995-01-01
Three experiments were conducted to define steady -state features of timbre for a group of well-trained musicians. Experiment 1 evaluated whether or not pairs of three critical dimensions of timbre--spectral slope (6 or 12 dB/octave), formant structure (/a/ or /i/ vowel), and inharmonicity of partials (harmonic or inharmonic)--were processed in a separable or integral fashion. Accuracy and speed for classification of values along one dimension were examined under different conditions of variability along a second dimension (fixed, correlated, or orthogonal). Spectral slope and formant structure were integral, with classification speed for the target dimension depending upon variability along the orthogonal dimension. In contrast, evidence of asymmetric separability was obtained for inharmonicity. Classification speed for slope and formant structure did not depend on inharmonicity, whereas RT for the target dimension of inharmonicity was strongly influenced by variability along either slope or formant structure. Since the results of Experiment 1 provided a basis for manipulating spectral slope and formant structure as a single feature, these dimensions were correlated in Experiment 2. Subjects searched for targets containing potential features of timbre within arrays of 1-4 inharmonic distractor pitches. Distractors were homogeneous with respect to the dimensions of timbre. When targets had /a/ formants with shallow spectral slopes, search time increased nonlinearly with array size in a manner consistent with the parallel processing of items, and thus feature search. Feature search was not obtained for targets with /i/ formants and steep slopes. Thus, the feature was coded as the presence or absence of /a/ formants with shallow spectral slopes. A search task using heterogeneous distractor values along slope/formant structure was used in Experiment 3 to evaluate whether or not the feature of timbre and pitch were automatically conjoined (integral). Search times for
Steady-state boundary lubrication with formulated C-ethers to 260 C
NASA Technical Reports Server (NTRS)
Loomis, W. R.
1981-01-01
Steady state wear and friction studies were made at boundary lubrication conditions in a pin on disk (pure iron on rotating CVM M 50 steel) sliding friction apparatus with five C ether formulated fluids (modified polyphenyl ether containing phosphrous ester, organic acid, and other additives). Conditions included 20, 150, and 260 C disk temperatures, dry air test atmosphere, 1 kilogram load, 50 rpm disk speed, and test times to 130 minutes. Results were compared with those obtained with a formulated MIL L 27502 candidate ester and the C ether base fluid. Three of the C ether formulations gave better lubrication than both reference fluids under most conditions. The other two C ether formulations yielded higher wear rates and friction coefficients than the C ether base fluid for most of the temperature range. Only one C ether formulation showed consistently higher steady state wear rates than the ester.
The steady-state assumption in oscillating and growing systems.
Reimers, Alexandra-M; Reimers, Arne C
2016-10-07
The steady-state assumption, which states that the production and consumption of metabolites inside the cell are balanced, is one of the key aspects that makes an efficient analysis of genome-scale metabolic networks possible. It can be motivated from two different perspectives. In the time-scales perspective, we use the fact that metabolism is much faster than other cellular processes such as gene expression. Hence, the steady-state assumption is derived as a quasi-steady-state approximation of the metabolism that adapts to the changing cellular conditions. In this article we focus on the second perspective, stating that on the long run no metabolite can accumulate or deplete. In contrast to the first perspective it is not immediately clear how this perspective can be captured mathematically and what assumptions are required to obtain the steady-state condition. By presenting a mathematical framework based on the second perspective we demonstrate that the assumption of steady-state also applies to oscillating and growing systems without requiring quasi-steady-state at any time point. However, we also show that the average concentrations may not be compatible with the average fluxes. In summary, we establish a mathematical foundation for the steady-state assumption for long time periods that justifies its successful use in many applications. Furthermore, this mathematical foundation also pinpoints unintuitive effects in the integration of metabolite concentrations using nonlinear constraints into steady-state models for long time periods.
Steady State Analysis of Small Molten Salt Reactor
NASA Astrophysics Data System (ADS)
Yamamoto, Takahisa; Mitachi, Koshi; Suzuki, Takashi
The Molten Salt Reactor (MSR) is a thermal neutron reactor with graphite moderation and operates on the thorium-uranium fuel cycle. The feature of the MSR is that fuel salt flows inside the reactor during the nuclear fission reaction. In the previous study, the authors developed numerical model with which to simulate the effects of fuel salt flow on the reactor characteristics. In this study, we apply the model to the steady-state analysis of a small MSR system and estimate the effects of fuel flow. The model consists of two-group neutron diffusion equations for fast and thermal neutron fluxes, transport equations for six-group delayed neutron precursors and energy conservation equations for fuel salt and the graphite moderator. The following results are obtained: (1) in the rated operation condition, the peaks of the neutron fluxes slightly move toward the bottom from the center of the reactor and the delayed neutron precursors are significantly carried by the fuel salt flow, and (2) the extension of residence time in the external-loop system and the rise of the fuel inflow temperature show weak negative reactivity effects, which decrease the neutron multiplication factor of the small MSR system.
Grand canonical steady-state simulation of nucleation
NASA Astrophysics Data System (ADS)
Horsch, Martin; Vrabec, Jadran
2009-11-01
Grand canonical molecular dynamics (GCMD) is applied to the nucleation process in a metastable phase near the spinodal, where nucleation occurs almost instantaneously and is limited to a very short time interval. With a variant of Maxwell's demon, proposed by McDonald [Am. J. Phys. 31, 31 (1963)], all nuclei exceeding a specified size are removed. In such a steady-state simulation, the nucleation process is sampled over an arbitrary time span and all properties of the metastable state, including the nucleation rate, can be obtained with an increased precision. As an example, a series of GCMD simulations with McDonald's demon is carried out for homogeneous vapor to liquid nucleation of the truncated-shifted Lennard-Jones (tsLJ) fluid, covering the entire relevant temperature range. The results are in agreement with direct nonequilibrium MD simulation in the canonical ensemble. It is confirmed for supersaturated vapors of the tsLJ fluid that the classical nucleation theory underpredicts the nucleation rate by two orders of magnitude.
Vortex generator installation studies on steady state and dynamic inlet distortion
NASA Technical Reports Server (NTRS)
Anderson, Bernhard H.; Gibb, James
1996-01-01
The theoretical and experimental work carried out under the NASA/MOD Joint Aeronautical Program has shown that CFD vortex generator installations designs successfully managed inlet duct flow distortion and that significant benefits in flow unsteadiness at the engine face were also present. The main conclusions to date from the collaborative effort between NASA/Lewis and DRA/Bedford are as follows: (1) vortex generator installations can be designed to be effective over a wide range of inlet operating conditions using Computational Fluid Dynamics and formal optimization procedures, (2) reductions in steady state engine face distortion of up to 80% have been measured in the M2129 inlet S-duct using CFD designed vortex generator installations, (3) reductions in flow unsteadiness of up to 80% have been measured in the W129 inlet S-duct using CFD designed vortex generator installations, and (4) the Reduced Navier-Stokes code RNS3D is a useful tool to design vortex generator installations to manage engine face distortions over a wide range of inlet operating conditions.
A two-step iterative method for evolving nonlinear acoustic systems to a steady-state
NASA Technical Reports Server (NTRS)
Watson, Willie R.; Myers, Michael K.
1990-01-01
A new approach for evolving two-dimensional nonlinear acoustic systems with flow to a steady state is presented. The approach is a two-step iterative method which is tested on a benchmark acoustic problem for which an exact analytical solution is available. Results are also calculated for a nonlinear acoustic problem for which an exact analytical solution is not known. Results indicate that the two-step method represents a powerful, efficient, and stable method for evolving two-dimensional acoustic systems to a steady state, and that the method is applicable to any number of spatial dimensions and to other hyperbolic systems. It is noted that for the benchmark problem only a single iteration on the method is required when the transient and steady-state field are of the same order of magnitude; however, four iterations are required when the steady-state field is several orders of magnitude smaller than the transient field. This method requires six iterations before achieving a steady state for the nonlinear test problem.
Steady State Growth of Continental Crust?
NASA Astrophysics Data System (ADS)
Bowring, S. A.; Bauer, A.; Dudas, F. O.; Schoene, B.; McLean, N. M.
2012-12-01
any age. If one accepts that the probability of preserving old crust decreases with increasing age, the few exposures of rocks older than 3.5 Ga should not be surprising. The thickness and compositional differences between Archean and younger lithospheric mantle are not fully understood nor is the role of thicker buoyant mantle in preserving continental crust; these lead to the question of whether the preserved rock record is representative of what formed. It is notable that the oldest known rocks, the ca. 4.0 Ga Acasta Gneisses, are tonalities-granodiorites-granites with evidence for the involvement of even older crust and that the oldest detrital zircons from Australia (ca. 4.0-4.4 Ga) are thought to have been derived from granitoid sources. The global Hf and Nd isotope databases are compatible with both depleted and enriched sources being present from at least 4.0 Ga to the present and that the lack of evolution of the MORB source or depleted mantle is due to recycling of continental crust throughout earth history. Using examples from the Slave Province and southern Africa, we argue that Armstrong's concept of steady state crustal growth and recycling via plate tectonics still best explains the modern geological and geochemical data.
SUPERENERGY-2: a multiassembly, steady-state computer code for LMFBR core thermal-hydraulic analysis
Basehore, K.L.; Todreas, N.E.
1980-08-01
Core thermal-hydraulic design and performance analyses for Liquid Metal Fast Breeder Reactors (LMFBRs) require repeated detailed multiassembly calculations to determine radial temperature profiles and subchannel outlet temperatures for various core configurations and subassembly structural analyses. At steady-state, detailed core-wide temperature profiles are required for core restraint calculations and subassembly structural analysis. In addition, sodium outlet temperatures are routinely needed for each reactor operating cycle. The SUPERENERGY-2 thermal-hydraulic code was designed specifically to meet these designer needs. It is applicable only to steady-state, forced-convection flow in LMFBR core geometries.
Characterization of polyester films used in capacitors. 1: Transient and steady-state conductivity
NASA Astrophysics Data System (ADS)
Thielen, A.; Niezette, J.; Feyder, G.; Vanderschueren, J.
1994-10-01
Charging and discharging currents flowing through polyethylene terephthalate (PET) ultrathin films (1.5 - 12 micrometers) were measured by the use of a two-electrode configuration involving opposite lateral contacts. A study of the influence of electrification time, applied electric field, film thickness, nature of electrodes, and water content was carried out on both transient and steady-state conduction. The transient behavior can be interpreted in terms of dipolar orientation and relaxation processes while steady-state conductivity can be mainly accounted for in terms of Schottky emission. A comparison between PET and polyethylene naphthalate films is also reported.
Fully-coupled solution of pressure-linked fluid flow equations
Vanka, S.P.; Leaf, G.K.
1983-08-01
A robust and efficient numerical scheme has been developed for the solution of the finite-differenced pressure linked fluid flow equations. The algorithm solves the set of nonlinear simultaneous equations by a combination of Newton's method and efficient sparse matrix techniques. In tests on typical recirculating flows the method is rapidly convergent. The method does not require any under-relaxation or other convergence-enhancing techniques employed in iterative schemes. It is currently described for two-dimensional steady state flows but is extendible to three dimensions and mildly time-varying flows. The method is robust to changes in Reynolds number, grid aspect ratio, and mesh size. This paper reports the algorithm and the results of calculations performed.
Vectorization on the star computer of several numerical methods for a fluid flow problem
NASA Technical Reports Server (NTRS)
Lambiotte, J. J., Jr.; Howser, L. M.
1974-01-01
A reexamination of some numerical methods is considered in light of the new class of computers which use vector streaming to achieve high computation rates. A study has been made of the effect on the relative efficiency of several numerical methods applied to a particular fluid flow problem when they are implemented on a vector computer. The method of Brailovskaya, the alternating direction implicit method, a fully implicit method, and a new method called partial implicitization have been applied to the problem of determining the steady state solution of the two-dimensional flow of a viscous imcompressible fluid in a square cavity driven by a sliding wall. Results are obtained for three mesh sizes and a comparison is made of the methods for serial computation.
NASA Astrophysics Data System (ADS)
Rigola, J.; Aljure, D.; Lehmkuhl, O.; Pérez-Segarra, C. D.; Oliva, A.
2015-08-01
The aim of this paper is to carry out a group of numerical experiments over the fluid flow through a valve reed, using the CFD&HT code TermoFluids, an unstructured and parallel object-oriented CFD code for accurate and reliable solving of industrial flows. Turbulent flow and its solution is a very complex problem due to there is a non-lineal interaction between viscous and inertial effects further complicated by their rotational nature, together with the three-dimensionality inherent in these types of flow and the non-steady state solutions. In this work, different meshes, geometrical conditions and LES turbulence models (WALE, VMS, QR and SIGMA) are tested and results compared. On the other hand, the fluid flow boundary conditions are obtained by means of the numerical simulation model of hermetic reciprocating compressors tool, NEST-compressor code. The numerical results presented are based on a specific geometry, where the valve gap opening percentage is 11% of hole diameter and Reynolds numbers given by the one-dimensional model is 4.22 × 105, with density meshes of approximately 8 million CVs. Geometrical aspects related with the orifice's shape and its influence on fluid flow behaviour and pressure drop are analysed in detail, furthermore, flow results for different valve openings are also studied.
Kameo, Yoshitaka; Ootao, Yoshihiro; Ishihara, Masayuki
2016-04-01
Trabecula, an anatomical unit of the cancellous bone, is a porous material that consists of a lamellar bone matrix and interstitial fluid in a lacuno-canalicular porosity. The flow of interstitial fluid caused by deformation of the bone matrix is believed to initiate a mechanical response in osteocytes for bone remodeling. In order to clarify the effect of the lamellar structure of the bone matrix--i.e., variations in material properties--on the fluid flow stimuli to osteocytes embedded in trabeculae, we investigated the mechanical behavior of an individual trabecula subjected to cyclic loading based on poroelasticity. We focused on variations in the trabecular permeability and developed an analytical solution containing both transient and steady-state responses for interstitial fluid pressure in a single trabecular model represented by a multilayered two-dimensional poroelastic slab. Based on the obtained solution, we calculated the pressure and seepage velocity of the interstitial fluid in lacuno-canalicular porosity, within the single trabecula, under various permeability distributions. Poroelastic analysis showed that a heterogeneous distribution of permeability produces remarkable variations in the fluid pressure and seepage velocity in the cross section of the individual trabecula, and suggests that fluid flow stimuli to osteocytes are mostly governed by the value of permeability in the neighborhood of the trabecular surfaces if there is no difference in the average permeability in a single trabecula.
Armoring, stability, and transport driven by fluid flow over a granular bed
NASA Astrophysics Data System (ADS)
Allen, Benjamin; Kudrolli, Arshad
2015-03-01
We discuss experiments investigating the evolution of a granular bed by a fluid flow as a function of shear rate at the fluid-bed interface. This is a model system to investigate a variety of physical examples including wind blowing over sand, sediment transport in rivers, tidal flows interacting with beaches, flows in slurry pipelines, and sand proppants in hydraulic fracturing. In order to examine the onset and entrainment of the granular bed under steady state conditions, we have constructed a novel conical rheometer system which allows a variable amount of shear to be applied to the granular bed. The grain-fluid system is index matched so that we can visualize the grains away from the sides as well as visualize the fluid flow above and below the interface by using fluorescent tracer particles. We demonstrate that the onset of erosion arises as particles rotate out of their stable position highlighting the importance of torque balance to onset. We find significant armoring of the bed, as the bed is sheared by the fluid flow. Above onset, at least three distinct regions of bed mobility can be found. We will discuss the measured integrated granular flux as a function of shear rate and compare them with empirical laws found in the geophysical literature. Supported by NSF Grant Number CBET 1335928.
Network-Theoretic Modeling of Fluid Flow
2015-07-29
Final Report STIR: Network-Theoretic Modeling of Fluid Flow ARO Grant W911NF-14-1-0386 Program manager: Dr. Samuel Stanton ( August 1, 2014–April 30...Morzyński, M., and Comte , P., “A finite-time thermodynamics of unsteady fluid flows,” Journal of Non-Equilibrium Thermody- namics, Vol. 33, No. 2
Value for controlling flow of cryogenic fluid
Knapp, Philip A.
1996-01-01
A valve is provided for accurately controlling the flow of cryogenic fluids such as liquid nitrogen. The valve comprises a combination of disc and needle valves affixed to a valve stem in such a manner that the disc and needle are free to rotate about the stem, but are constrained in lateral and vertical movements. This arrangement provides accurate and precise fluid flow control and positive fluid isolation.
Intracellular fluid flow in rapidly moving cells.
Keren, Kinneret; Yam, Patricia T; Kinkhabwala, Anika; Mogilner, Alex; Theriot, Julie A
2009-10-01
Cytosolic fluid dynamics have been implicated in cell motility because of the hydrodynamic forces they induce and because of their influence on transport of components of the actin machinery to the leading edge. To investigate the existence and the direction of fluid flow in rapidly moving cells, we introduced inert quantum dots into the lamellipodia of fish epithelial keratocytes and analysed their distribution and motion. Our results indicate that fluid flow is directed from the cell body towards the leading edge in the cell frame of reference, at about 40% of cell speed. We propose that this forward-directed flow is driven by increased hydrostatic pressure generated at the rear of the cell by myosin contraction, and show that inhibition of myosin II activity by blebbistatin reverses the direction of fluid flow and leads to a decrease in keratocyte speed. We present a physical model for fluid pressure and flow in moving cells that quantitatively accounts for our experimental data.
Development of steady-state model for MSPT and detailed analyses of receiver
NASA Astrophysics Data System (ADS)
Yuasa, Minoru; Sonoda, Masanori; Hino, Koichi
2016-05-01
Molten salt parabolic trough system (MSPT) uses molten salt as heat transfer fluid (HTF) instead of synthetic oil. The demonstration plant of MSPT was constructed by Chiyoda Corporation and Archimede Solar Energy in Italy in 2013. Chiyoda Corporation developed a steady-state model for predicting the theoretical behavior of the demonstration plant. The model was designed to calculate the concentrated solar power and heat loss using ray tracing of incident solar light and finite element modeling of thermal energy transferred into the medium. This report describes the verification of the model using test data on the demonstration plant, detailed analyses on the relation between flow rate and temperature difference on the metal tube of receiver and the effect of defocus angle on concentrated power rate, for solar collector assembly (SCA) development. The model is accurate to an extent of 2.0% as systematic error and 4.2% as random error. The relationships between flow rate and temperature difference on metal tube and the effect of defocus angle on concentrated power rate are shown.
Steady-state decoupling and design of linear multivariable systems
NASA Technical Reports Server (NTRS)
Thaler, G. J.
1974-01-01
A constructive criterion for decoupling the steady states of a linear time-invariant multivariable system is presented. This criterion consists of a set of inequalities which, when satisfied, will cause the steady states of a system to be decoupled. Stability analysis and a new design technique for such systems are given. A new and simple connection between single-loop and multivariable cases is found. These results are then applied to the compensation design for NASA STOL C-8A aircraft. Both steady-state decoupling and stability are justified through computer simulations.
A Note on Equations for Steady-State Optimal Landscapes
Liu, H.H.
2010-06-15
Based on the optimality principle (that the global energy expenditure rate is at its minimum for a given landscape under steady state conditions) and calculus of variations, we have derived a group of partial differential equations for describing steady-state optimal landscapes without explicitly distinguishing between hillslopes and channel networks. Other than building on the well-established Mining's equation, this work does not rely on any empirical relationships (such as those relating hydraulic parameters to local slopes). Using additional constraints, we also theoretically demonstrate that steady-state water depth is a power function of local slope, which is consistent with field data.
Mahomed, F. M.
2014-01-01
In this communication, we utilize some basic symmetry reductions to transform the governing nonlinear partial differential equations arising in the study of third-grade fluid flows into ordinary differential equations. We obtain some simple closed-form steady-state solutions of these reduced equations. Our solutions are valid for the whole domain [0,∞) and also satisfy the physical boundary conditions. We also present the numerical solutions for some of the underlying equations. The graphs corresponding to the essential physical parameters of the flow are presented and discussed. PMID:25143962
Aziz, Taha; Mahomed, F M
2014-01-01
In this communication, we utilize some basic symmetry reductions to transform the governing nonlinear partial differential equations arising in the study of third-grade fluid flows into ordinary differential equations. We obtain some simple closed-form steady-state solutions of these reduced equations. Our solutions are valid for the whole domain [0,∞) and also satisfy the physical boundary conditions. We also present the numerical solutions for some of the underlying equations. The graphs corresponding to the essential physical parameters of the flow are presented and discussed.
Steady-state compartmentalization of lipid membranes by active proteins.
Sabra, M C; Mouritsen, O G
1998-01-01
Using a simple microscopic model of lipid-protein interactions, based on the hydrophobic matching principle, we study some generic aspects of lipid-membrane compartmentalization controlled by a dispersion of active integral membrane proteins. The activity of the proteins is simulated by conformational excitations governed by an external drive, and the deexcitation is controlled by interaction of the protein with its lipid surroundings. In response to the flux of energy into the proteins from the environment and the subsequent dissipation of energy into the lipid bilayer, the lipid-protein assembly reorganizes into a steady-state structure with a typical length scale determined by the strength of the external drive. In the specific case of a mixed dimyristoylphosphatidylcholine-distearoylphosphatidylcholine bilayer in the gel-fluid coexistence region, it is shown explicitly by computer simulation that the activity of an integral membrane protein can lead to a compartmentalization of the lipid-bilayer membrane. The compartmentalization is related to the dynamical process of phase separation and lipid domain formation. PMID:9533687
VISCOPLASTIC FLUID MODEL FOR DEBRIS FLOW ROUTING.
Chen, Cheng-lung
1986-01-01
This paper describes how a generalized viscoplastic fluid model, which was developed based on non-Newtonian fluid mechanics, can be successfully applied to routing a debris flow down a channel. The one-dimensional dynamic equations developed for unsteady clear-water flow can be used for debris flow routing if the flow parameters, such as the momentum (or energy) correction factor and the resistance coefficient, can be accurately evaluated. The writer's generalized viscoplastic fluid model can be used to express such flow parameters in terms of the rheological parameters for debris flow in wide channels. A preliminary analysis of the theoretical solutions reveals the importance of the flow behavior index and the so-called modified Froude number for uniformly progressive flow in snout profile modeling.
Reactive Fluid Flow and Applications to Diagenesis, Mineral Deposits, and Crustal Rocks
Rye, Danny M.; Bolton, Edward W.
2002-11-04
The objective is to initiate new: modeling of coupled fluid flow and chemical reactions of geologic environments; experimental and theoretical studies of water-rock reactions; collection and interpretation of stable isotopic and geochemical field data at many spatial scales of systems involving fluid flow and reaction in environments ranging from soils to metamorphic rocks. Theoretical modeling of coupled fluid flow and chemical reactions, involving kinetics, has been employed to understand the differences between equilibrium, steady-state, and non-steady-state behavior of the chemical evolution of open fluid-rock systems. The numerical codes developed in this project treat multi-component, finite-rate reactions combined with advective and dispersive transport in multi-dimensions. The codes incorporate heat, mass, and isotopic transfer in both porous and fractured media. Experimental work has obtained the kinetic rate laws of pertinent silicate-water reactions and the rates of Sr release during chemical weathering. Ab-initio quantum mechanical techniques have been applied to obtain the kinetics and mechanisms of silicate surface reactions and isotopic exchange between water and dissolved species. Geochemical field-based studies were carried out on the Wepawaug metamorphic schist, on the Irish base-metal sediment-hosted ore system, in the Dalradian metamorphic complex in Scotland, and on weathering in the Columbia River flood basalts. The geochemical and isotopic field data, and the experimental and theoretical rate data, were used as constraints on the numerical models and to determine the length and time scales relevant to each of the field areas.
Analysis of Fluid Flow and Heat Transfer in a Liquid Hydrogen Storage Vessel for Space Applications
NASA Astrophysics Data System (ADS)
Mukka, Santosh K.; Rahman, Muhammad M.
2004-02-01
This paper presents a systematic analysis of fluid flow and heat transfer in a liquid hydrogen storage vessel for both earth and space applications. The study considered a cylindrical tank with elliptical top and bottom. The tank wall is made of aluminum and a multi-layered blanket of cryogenic insulation (MLI) has been attached on the top of the aluminum. The tank is connected to a cryocooler to dissipate the heat leak through the insulation and tank wall into the fluid within the tank. The cryocooler has not been modeled; only the flow in and out of the tank to the cryocooler system has been included. The primary emphasis of this research has been the fluid circulation within the tank for different fluid distribution scenario and for different level of gravity to simulate potential earth and space based applications. The equations solved in the liquid region included the conservation of mass, conservation of energy, and conservation of momentum. For the solid region only the heat conduction equation was solved. The steady-state velocity, temperature, and pressure distributions were calculated for different inlet positions, inlet velocities, and for different gravity values. The above simulations were carried out for constant heat flux and constant wall temperature cases. It was observed that a good flow circulation could be obtained when the cold entering fluid was made to flow in radial direction and the inlet opening was placed close to the tank wall.
Hamel, William R.
1984-01-01
This invention relates to a new method and new apparatus for determining fluid mass flowrate and density. In one aspect of the invention, the fluid is passed through a straight cantilevered tube in which transient oscillation has been induced, thus generating Coriolis damping forces on the tube. The decay rate and frequency of the resulting damped oscillation are measured, and the fluid mass flowrate and density are determined therefrom. In another aspect of the invention, the fluid is passed through the cantilevered tube while an electrically powered device imparts steady-state harmonic excitation to the tube. This generates Coriolis tube-damping forces which are dependent on the mass flowrate of the fluid. Means are provided to respond to incipient flow-induced changes in the amplitude of vibration by changing the power input to the excitation device as required to sustain the original amplitude of vibration. The fluid mass flowrate and density are determined from the required change in power input. The invention provides stable, rapid, and accurate measurements. It does not require bending of the fluid flow.
An Operational Definition of the Steady State in Enzyme Kinetics.
ERIC Educational Resources Information Center
Barnsley, E. A.
1990-01-01
The Briggs-Haldane assumption is used as the basis for the development of a kinetic model for enzyme catalysis. An alternative definition of the steady state and examples of realistic mechanisms are provided. (KR)
An Operational Definition of the Steady State in Enzyme Kinetics.
ERIC Educational Resources Information Center
Barnsley, E. A.
1990-01-01
The Briggs-Haldane assumption is used as the basis for the development of a kinetic model for enzyme catalysis. An alternative definition of the steady state and examples of realistic mechanisms are provided. (KR)
Preconditioning and the limit to the incompressible flow equations
NASA Technical Reports Server (NTRS)
Turkel, E.; Fiterman, A.; Vanleer, B.
1993-01-01
The use of preconditioning methods to accelerate the convergence to a steady state for both the incompressible and compressible fluid dynamic equations are considered. The relation between them for both the continuous problem and the finite difference approximation is also considered. The analysis relies on the inviscid equations. The preconditioning consists of a matrix multiplying the time derivatives. Hence, the steady state of the preconditioned system is the same as the steady state of the original system. For finite difference methods the preconditioning can change and improve the steady state solutions. An application to flow around an airfoil is presented.
Pseudo-compressibility methods for the incompressible flow equations
NASA Technical Reports Server (NTRS)
Turkel, Eli; Arnone, A.
1993-01-01
Preconditioning methods to accelerate convergence to a steady state for the incompressible fluid dynamics equations are considered. The analysis relies on the inviscid equations. The preconditioning consists of a matrix multiplying the time derivatives. Thus the steady state of the preconditioned system is the same as the steady state of the original system. The method is compared to other types of pseudo-compressibility. For finite difference methods preconditioning can change and improve the steady state solutions. An application to viscous flow around a cascade with a non-periodic mesh is presented.
The Enlisted Steady State-Simulation (ESS-SIM) Tool
2014-07-01
The Enlisted Steady State-Simulation ( ESS -SIM) Tool David M. Rodney • Peggy A. Golfin • Molly F. McIntosh DIM-2014-U-007587-Final July 2014 This...situation. We built and made use of a simulation model, ESS -Sim (Enlisted Steady- State Simulation), to obtain insights into attainable levels of...fleet manning and estimate the impact of policy changes on fleet man- ning. This information memorandum describes this model. Model overview We built ESS
Mechanism of Non-Steady State Dissolution of Goethite in the Presence of Siderophores
NASA Astrophysics Data System (ADS)
Reichard, P. U.; Kretzschmar, R.; Kraemer, S. M.
2003-12-01
Iron is an essential micronutrient for almost all known organisms. Bacteria, fungi, and graminaceous plants are capable of exuding siderophores as part of an iron acquisition strategy. The production of these strong iron chelating ligands is induced by iron limited conditions. Grasses under iron stress, for example, exude phytosiderophores into the rhizosphere in a special diurnal rhythm (Roemheld and Marschner 1986). A few hours after sunrise the exudation starts, culminates around noon and is shut down again until about 4 hours after noon. The phytosiderophores diffuse into the rhizosphere (Marschner et al. 1986) and are passively back transported to the plants by advective flow induced by high transpiration around noon. Despite a fairly short residence time of the phytosiderophores in the rhizosphere, it is a very effective strategy for iron acquisition. To investigate the effect of such pulse inputs of siderophores on iron acquisition, we studied the dissolution mechanism of goethite (alpha-FeOOH), a mineral phase common in soils, under non-steady state conditions. In consideration of the chemical complexity of the rhizosphere, we also investigated the effect of other organic ligands commonly found in the rhizosphere (e. g. oxalate) on the dissolution kinetics. The dissolution experiments were conducted in batch reactors with a constant goethite solids concentration of 2.5 g/l, an ionic strength of 0.01 M, a pH of 6 and 100 microM oxalate. To induce non-steady state conditions, 3 mM phytosiderophores were added to a batch after the goethite-oxalate suspension reacted for a certain time period. Before the siderophore was added to the goethite-oxalate suspension, no dissolution of iron was observed. But, with the addition of the siderophore, a high rate was observed for the iron mobilization under these non-steady state conditions that subsequently was followed by a slow steady state dissolution rate. The results of these non-steady state experiments are very
Chevalier, Thibaud; Salin, Dominique; Talon, Laurent; Yiotis, Andreas G
2015-04-01
We investigate experimentally the sweeping of a nonwetting fluid by a wetting one in a quasi-two-dimensional porous medium consisting of random obstacles. We focus primarily on the resulting phase distributions and the residual nonwetting phase saturation as a function of the normalized wetting fluid flow rate-the capillary number Ca-at steady state. The wetting liquid is then flowing in the medium partially saturated by immobile nonwetting liquid blobs. The decrease of the nonwetting saturation is an irreversible process that depends strongly on flow history and more specifically on the highest value of Ca reached in the past. At lower Ca values, when capillary forces are dominant, the residual steady state saturation depends significantly on the initial phase configuration. However, at higher Ca, the saturation becomes independent of the history and thus follows a master curve that converges to an asymptotic residual value. Blob sizes range over four orders of magnitude in our experimental domain, following a probability distribution function P that scales with the blob size s as P(s)∝s(-2) for blob sizes larger than the typical pore size. It also exhibits a maximum size cutoff s(max), that decreases as s(max)∝Ca(-1). To determine the flow properties, we have measured the pressure drop (B) versus the flow rate (Ca). In the ranges of low and high Ca values, the relationship between Ca and B is found to be linear, following Darcy's law (B∝Ca). In the intermediate regime, the progressive mobilization of blobs leads to a nonlinear dependence B∝Ca(0.65), due to an increase of the available flow paths.
Impact of aquifer desaturation on steady-state river seepage
NASA Astrophysics Data System (ADS)
Morel-Seytoux, Hubert J.; Miracapillo, Cinzia; Mehl, Steffen
2016-02-01
Flow exchange between surface and ground water is of great importance be it for beneficial allocation and use of the water resources or for the proper exercise of water rights. That exchange can take place under a saturated or unsaturated flow regime. Which regimes occur depend on conditions in the vicinity of the interactive area. Withdrawals partially sustained by seepage may not bring about desaturation but greater amounts eventually will. The problem considered in this paper deals only with the steady-state case. It is meant as a first step toward a simple, yet accurate and physically based treatment of the transient situation. The primary purpose of the article is to provide simple criteria for determination of the initiation of desaturation in an aquifer originally in saturated hydraulic connection with a river or a recharge area. The extent of the unsaturated zone in the aquifer will increase with increasing withdrawals while at the same time the seepage rate from the river increases. However the seepage increase will stop once infiltration takes place strictly by gravity in the aquifer and is no longer opposed by the capillary rise from the water table below the riverbed. Following desaturation simple criteria are derived and simple analytical formulae provided to estimate the river seepage based on the position of the water table mound below the clogging layer and at some distance away from the river bank. They fully account for the unsaturated flow phenomena, including the existence of a drainage entry pressure. Two secondary objectives were to verify that (1) the assumption of uniform vertical flow through a clogging layer and that (2) the approximation of the water table mound below the seepage area as a flat surface were both reasonably legitimate. This approach will be especially advantageous for the implementation of the methodology in large-scale applications of integrated hydrologic models used for management.
An implicit steady-state initialization package for the RELAP5 computer code
Paulsen, M.P.; Peterson, C.E.; Odar, F.
1995-08-01
A direct steady-state initialization (DSSI) method has been developed and implemented in the RELAP5 hydrodynamic analysis program. It provides a means for users to specify a small set of initial conditions which are then propagated through the remainder of the system. The DSSI scheme utilizes the steady-state form of the RELAP5 balance equations for nonequilibrium two-phase flow. It also employs the RELAP5 component models and constitutive model packages for wall-to-phase and interphase momentum and heat exchange. A fully implicit solution of the linearized hydrodynamic equations is implemented. An implicit coupling scheme is used to augment the standard steady-state heat conduction solution for steam generator use. It solves the primary-side tube region energy equations, heat conduction equations, wall heat flux boundary conditions, and overall energy balance equation as a coupled system of equations and improves convergence. The DSSI method for initializing RELAP5 problems to steady-state conditions has been compared with the transient solution scheme using a suite of test problems including; adiabatic single-phase liquid and vapor flow through channels with and without healing and area changes; a heated two-phase test bundle representative of BWR core conditions; and a single-loop PWR model.
Flow visualization in fluid mechanics
NASA Astrophysics Data System (ADS)
Freymuth, Peter
1993-01-01
The history of flow visualization is reviewed and basic methods are examined. A classification of the field of physical flow visualization is presented. The introduction of major methods is discussed and discoveries made using flow visualization are reviewed. Attention is given to limitations and problem areas in the visual evaluation of velocity and vorticity fields and future applications for flow visualization are suggested.
Steady State Pyrolysis and Ablation Investigation
2008-03-31
since the probe wall is kept at a low surface temperature. This effect was measured using a Gardon gage for air and CO2 plasma at various static...p , ■ - ■ 2v_ : f. * . «] »~\\. »o » - IMK ■ r \\ r ^ " / ■ 1 . 1 1 A... -o -•-130kWAir -o...0.30 0.35 0.40 0.45 Mass flow [fl/s] Figure 1.2: Heat flux vs. transpirational rha liOO 550 m 250 200 150 ; f ■. R
Visualizing vector field topology in fluid flows
NASA Technical Reports Server (NTRS)
Helman, James L.; Hesselink, Lambertus
1991-01-01
Methods of automating the analysis and display of vector field topology in general and flow topology in particular are discussed. Two-dimensional vector field topology is reviewed as the basis for the examination of topology in three-dimensional separated flows. The use of tangent surfaces and clipping in visualizing vector field topology in fluid flows is addressed.
Steady State Turbulent Transport in Magnetic Fusion Plasmas
Lee, W. W.; Ethier, S.; Kolesnikov, R.; Wang, W. X.; Tang, W. M.
2007-12-20
For more than a decade, the study of microturbulence, driven by ion temperature gradient (ITG) drift instabilities in tokamak devices, has been an active area of research in magnetic fusion science for both experimentalists and theorists alike. One of the important impetus for this avenue of research was the discovery of the radial streamers associated the ITG modes in the early nineties using a Particle-In-Cell (PIC) code. Since then, ITG simulations based on the codes with increasing realism have become possible with the dramatic increase in computing power. The notable examples were the demonstration of the importance of nonlinearly generated zonal flows in regulating ion thermal transport and the transition from Bohm to GyroBoham scaling with increased device size. In this paper, we will describe another interesting nonlinear physical process associated with the parallel acceleration of the ions, that is found to play an important role for the steady state turbulent transport. Its discovery is again through the use of the modern massively parallel supercomputers.
Fluid flow and dissipation in intersecting counter-flow pipes
NASA Astrophysics Data System (ADS)
Pekkan, Kerem
2005-11-01
Intersecting pipe junctions are common in industrial and biomedical flows. For the later application, standard surgical connections of vessel lumens results a ``+'' shaped topology through a side-to-side or end-to-side anastomosis. Our earlier experimental/computational studies have compared different geometries quantifying the hydrodynamic power loss through the junction where dominant coherent structures are identified. In this study we have calculated the contribution of these structures to the total energy dissipation and its spatial distribution in the connection. A large set of idealized models are studied in which the basic geometric configuration is parametrically varied (from side-to-side to end-to-side anastomosis) which quantified the strength of the secondary flows and coherent structures as a function of the geometric configuration. Steady-state, 3D, incompressible computations are performed using the commercial CFD code FIDAP with unstructured tetrahedral grids. Selected cases are compared with the in-house code results (in Cartesian and structured grids). Grid verification and experimental validation with flow-vis and PIV are presented. Identifying the dissipation hot-spots will enable a targeted inverse design of the junction by reducing the degree of optimization with a focused parameter space.
Method and Apparatus for Measuring Fluid Flow
NASA Technical Reports Server (NTRS)
Arndt, G. Dickey (Inventor); Nguyen, Thanh X. (Inventor); Carl, James R. (Inventor)
1997-01-01
Method and apparatus for making measurements on fluids related to their complex permeability are disclosed. A microwave probe is provided for exposure to the fluids. The probe can be non-intrusive or can also be positioned at the location where measurements are to be made. The impedance of the probe is determined. in part. by the complex dielectric constant of the fluids at the probe. A radio frequency signal is transmitted to the probe and the reflected signal is phase and amplitude detected at a rapid rate for the purpose of identifying the fluids. Multiple probes may be selectively positioned to monitor the behavior of the fluids including their flow rate. Fluids may be identified as between two or more different fluids as well as multiple phases of the same fluid based on differences between their complex permittivities.
Comparing Steady State to Time Interval and Non-Steady State Measurements of Resting Metabolic Rate.
Irving, Chelsea Jayne; Eggett, Dennis L; Fullmer, Susan
2017-02-01
The 2 most common methods to determine resting metabolic rate (RMR) with indirect calorimetry are steady state (SS) and time intervals. Studies have suggested SS more accurately reflects RMR, but further research is needed. Our objective was to compare the bias, precision, and accuracy of SS to time intervals and non-SS measurements in a healthy adult population. Seventy-seven participants were measured for 45 minutes using a Quark RMR. Inclusion criteria included healthy participants aged 18-65 years. Pregnant and lactating women were excluded. Paired t tests compared differences between measures. Bland-Altman plots were used to determine precision. Bias occurred if there was a significant difference between the means. Accuracy was determined by counting the number of absolute differences between SS compared with non-SS and time intervals that were <75 calories. Of 77 participants, 84% achieved SS, and 95% achieved SS by minute 30. Most differences between SS and time intervals were statistically but not practically significant. Bland-Altman plots showed SS measurements were generally lower than any time interval, suggesting SS is more indicative of RMR. Non-SS was significantly more biased ( P = .0005), less precise (spread of limits of agreement was 269 calories), and less accurate (65%) than SS. We conclude that non-SS is not equivalent to SS. We also conclude that using 5-minute SS is more indicative of RMR than any time interval that was tested in healthy populations. If SS cannot be achieved, we recommend repeating the measurement.
Computation of two-fluid, flowing equilibria
NASA Astrophysics Data System (ADS)
Steinhauer, Loren; Kanki, Takashi; Ishida, Akio
2006-10-01
Equilibria of flowing two-fluid plasmas are computed for realistic compact-toroid and spherical-tokamak parameters. In these examples the two-fluid parameter ɛ (ratio of ion inertial length to overall plasma size) is small, ɛ ˜ 0.03 -- 0.2, but hardly negligible. The algorithm is based on the nearby-fluids model [1] which avoids a singularity that otherwise occurs for small ɛ. These representative equilibria exhibit significant flows, both toroidal and poloidal. Further, the flow patterns display notable flow shear. The importance of two-fluid effects is demonstrated by comparing with analogous equilibria (e.g. fixed toroidal and poloidal current) for a static plasma (Grad-Shafranov solution) and a flowing single-fluid plasma. Differences between the two-fluid, single-fluid, and static equilibria are highlighted: in particular with respect to safety factor profile, flow patterns, and electrical potential. These equilibria are computed using an iterative algorithm: it employs a successive-over-relaxation procedure for updating the magnetic flux function and a Newton-Raphson procedure for updating the density. The algorithm is coded in Visual Basic in an Excel platform on a personal computer. The computational time is essentially instantaneous (seconds). [1] L.C. Steinhauer and A. Ishida, Phys. Plasmas 13, 052513 (2006).
Thermo-miscible fluid displacement in a porous media flow
NASA Astrophysics Data System (ADS)
Ward, Thomas; Soori, Tejaswi
2016-11-01
The an-isoviscous displacement of a generalized Newtonian liquid in an impulsively heated axisymmetric pipe geometry is studied at low to moderate Reynolds numbers using computational analysis. The temperature dependent viscosity is modeled using an empirical correlation that has been shown to fit experimental data for a range of temperature values. The governing Cauchy momentum equations for the generalized Newtonian fluid are solved in primitive variables using a 4th order Runge-Kutta method. For viscous liquids with a high Prandtl number radial and axial variations in temperature are significant leading to modification of the steady state pressure loss when compared to isoviscous displacements. We characterize the steady state pressure loss and average Nusselt number using the Reynolds 0 . 1 < Re < 10 , viscous Atwood 0 < At < 0 . 8 , and Peclet 100 < Pe < 10 , 000 numbers.
Ding, Weiping; Zhou, Xiaoming; Heimfeld, Shelly; Reems, Jo-Anna; Gao, Dayong
2010-01-01
Hollow fiber modules are commonly used to conveniently and efficiently remove cryoprotective agents (CPAs) from cryopreserved cell suspensions. In this paper, a steady-state model coupling mass transfers across cell and hollow fiber membranes is theoretically developed to evaluate the removal of CPAs from cryopreserved blood using hollow fiber modules. This steady-state model complements the unsteady-state model which was presented in our previous study. As the steady-state model, unlike the unsteady-state model, can be used to evaluate the effect of ultrafiltration flow rates on the clearance of CPAs. The steady-state model is validated by experimental results and then is compared with the unsteady-state model. Using the steady-state model, the effects of ultrafiltration flow rates, NaCl concentrations in dialysate, blood flow rates and dialysate flow rates on CPA concentration variation and cell volume response are investigated in detail. According to the simulative results, the osmotic damage of red blood cells (RBCs) can easily be reduced by increasing ultrafiltration flow rates, increasing NaCl concentrations in dialysate, increasing blood flow rates or decreasing dialysate flow rates. PMID:20524740
On the time to steady state: insights from numerical modeling
NASA Astrophysics Data System (ADS)
Goren, L.; Willett, S.; McCoy, S. W.; Perron, J.
2013-12-01
How fast do fluvial landscapes approach steady state after an application of tectonic or climatic perturbation? While theory and some numerical models predict that the celerity of the advective wave (knickpoint) controls the response time for perturbations, experiments and other landscape evolution models demonstrate that the time to steady state is much longer than the theoretically predicted response time. We posit that the longevity of transient features and the time to steady state are controlled by the stability of the topology and geometry of channel networks. Evolution of a channel network occurs by a combination of discrete capture events and continuous migration of water divides, processes, which are difficult to represent accurately in landscape evolution models. We therefore address the question of the time to steady state using the DAC landscape evolution model that solves accurately for the location of water divides, using a combination of analytical solution for hillslopes and low-order channels together with a numerical solution for higher order channels. DAC also includes an explicit capture criterion. We have tested fundamental predictions from DAC and show that modeled networks reproduce natural network characteristics such as the Hack's exponent and coefficient and the fractal dimension. We define two steady-state criteria: a topographic steady state, defined by global, pointwise steady elevation, and a topological steady state defined as the state in which no further reorganization of the drainage network takes place. Analyzing block uplift simulations, we find that the time to achieve either topographic or topological steady state exceeds by an order of magnitude the theoretical response time of the fluvial network. The longevity of the transient state is the result of the area feedback, by which, migration of a divide changes the local contributing area. This change propagates downstream as a slope adjustment, forcing further divide migrations
Mühler, R
2012-05-01
Recording human auditory steady-state responses (ASSR) at different frequencies allows objective assessment of auditory thresholds. Common practice has been to record ASSR to pure tones that are sinusoidally modulated in amplitude and frequency. Recently, optimized chirp stimuli have been proposed to evoke transient as well as steady-state responses. Because of the resulting uncertainty about the different methods, this paper aims to reconsider the terminology of transient and steady-state responses. Two experiments demonstrate the smooth transition between transient and steady-state responses. In experiment 1, click-evoked auditory brainstem responses (ABR) were recorded over a wide range of stimulus repetition rates (24/s to 72/s). In experiment 2, auditory steady-state responses were recorded for the same stimulus repetition rates, using three different stimulus types: an amplitude modulated 1-kHz tone (AM), a 1-kHz tone-burst (TB) and a flat-spectrum chirp. Experiment 1 demonstrates the merging of the typical ABR wave complexes at higher repetition rates, forming a steady-state response. This effect can only be observed if the time window is extended far beyond the window traditionally used for clinical ABR recordings. Experiment 2 reveals similar ASSR amplitude spectra regardless of the stimulus type and repetition rate used. Steady-state responses can be evoked for a large variety of stimulus types and repetition rates. Thus, from a clinician's point of view, steady-state responses cannot be considered a new type of evoked responses. They differ from transient responses primarily in the frequency response method and the longer timeframe required.
Focused fluid flow in passive continental margins.
Berndt, Christian
2005-12-15
Passive continental margins such as the Atlantic seaboard of Europe are important for society as they contain large energy resources, and they sustain ecosystems that are the basis for the commercial fish stock. The margin sediments are very dynamic environments. Fluids are expelled from compacting sediments, bottom water temperature changes cause gas hydrate systems to change their locations and occasionally large magmatic intrusions boil the pore water within the sedimentary basins, which is then expelled to the surface. The fluids that seep through the seabed at the tops of focused fluid flow systems have a crucial role for seabed ecology, and study of such fluid flow systems can also help in predicting the distribution of hydrocarbons in the subsurface and deciphering the climate record. Therefore, the study of focused fluid flow will become one of the most important fields in marine geology in the future.
Geomorphic and Thermal Steady State Regimes: Reality or Wishful Thinking?
NASA Astrophysics Data System (ADS)
Lock, J.; Furlong, K.
2003-04-01
In many tectonic geomorphic studies, it is assumed that rates of uplift within an orogen are matched by rates of exhumation producing a steady-state orogen. However, the tools used to determine exhumation are thermally driven (e.g. Fission Track, U-Th/He) and exhumation can substantially perturb the crustal thermal regime. Since knowing the thermal regime is key to determining exhumation from thermochronology, problems arise. In order to interpret a rate of exhumation we make the assumption that an area is in thermal 'steady state', which in young active orogens unlikely exists. Taiwan, the Southern Alps, Fiordland, and Nanga Parbat are relatively young mountain belts that have begun to uplift or have experienced increased rates of uplift during the past 5-10 Ma. As there is a time lag between the onset of uplift and achieving geomorphic steady state and again between reaching geomorphic steady state and thermal steady state, these orogens may be too young to have achieved this final stage. Additionally, young orogens may not have experienced a constant rate of uplift and denudation in the time over which the thermochronometers average. Certainly, in the case of the Southern Alps, present uplift rates can not have existed since uplift begun. Therefore, an apparent age is recording a transient thermal state. Even in a case where geomorphic steady state exists i.e. exhumation balances uplift, it is unlikely that a thermal steady state has been reached. This precludes the simple interpretation of exhumation rates often made. When multiple thermochronometers are used, inconsistencies can arise. For example, an increase in the rate of uplift is often observed when comparing the rates of exhumation using different thermochronometers. Our modeling shows that in some cases this phenomena is actually eliminated by considering the transient nature of the thermal regime following the onset of uplift and exhumation of an active orogen. To accurately determine exhumation rate
Method and device for measuring fluid flow
Atherton, Richard; Marinkovich, Phillip S.; Spadaro, Peter R.; Stout, J. Wilson
1976-11-23
This invention is a fluid flow measuring device for determining the coolant flow at the entrance to a specific nuclear reactor fuel region. The device comprises a plurality of venturis having the upstream inlet and throat pressure of each respectively manifolded together to provide one static pressure signal for each region monitored. The device provides accurate flow measurement with low pressure losses and uniform entrance and discharge flow distribution.
There are no steady state processes in compaction
NASA Astrophysics Data System (ADS)
Dysthe, D. K.
2003-04-01
Compaction of sediments is normally thought to start with grain sliding and cataclastic grain crushing. Then the ductile dissolution-precipitation creep processes take over. Modeling of this process normally neglects all collective rearrangement processes and regard simple packings of grains that slowly deform by steady state pressure solution creep. From simple geometrical reasoning we know, however that imperfect packings of plastic grains must undergo rearrangement during compaction. Such rearrangement will drastically alter the microscopic, or "primitive processes" of compaction. Recent research has questioned the fundamental mechanisms ("primitive processes") of dissolution-precipitation creep. Do grain contacts heal or dissolve? Why is there asymmetric dissolution? Does pressure solution creep in single contacts ever reach steady state? Can transient free face dissolution feed back on pressure solution creep in the contacts? The emerging radical change in our understanding of dissolution-precipitation creep as a dynamic, transient process is driven by new experiments and reevaluation of the fundamental theory. The same change in viewpoint is necessary on all time and length scales. I will present experiments [1-8] and simulations [9-11] of complex compaction behaviour [1], transient primitive processes of pressure solution creep in the contacts [2-4], free face dissolution [5] and crack healing [6]. I will also show that macroscopic observation of compaction shows smooth, universal behaviour [7]. Microscopic observation of compaction shows transient collective behaviour at all scales. Evidence points in the direction that compaction is dominated by transient processes with interacting instabilities. The interaction causes intermittency or switching between processes. A new, more complex theory of compaction is necessary to explain how the cooperative microscopic phenomena contribute to the simple, universal, macroscopic behaviour. 1. Uri, L., et. al., in
Shear augmented dispersion of a solute in a casson fluid flowing in a conduit.
Dash, R K; Jayaraman, G; Mehta, K N
2000-04-01
The unsteady dispersion of a solute in a Casson fluid flowing in a conduit (pipe/channel) is studied using the generalized dispersion model of Gill and Sankarasubramanian. With this approach, the entire dispersion process is described appropriately in terms of a simple diffusion process with the effective diffusion coefficient as a function of time, in addition to its dependence on the yield stress of the fluid. The results are accurate up to a first approximation for small times, but verified with Sharp to be exact for large times. The model brings out mainly the effect of yield stress, or equivalently, the plug flow region on the overall dispersion process. It is found that the rate of dispersion is reduced (i.e., the effective diffusivity decreases) due to the yield stress of the fluid, or equivalently, the plug flow region in the conduit. Also, the effective diffusivity increases with time, but eventually attains its steady state value below a critical time [0.48(a2/Dm) for dispersion in a pipe and 0.55(a2/Dm) for dispersion in a channel-the critical transient time for a Newtonian fluid-where "a" is the radius of the pipe and Dm is the molecular diffusivity]. At steady state, for dispersion in a pipe with the plug flow radius one tenth of the radius of the pipe, the effective diffusivity is reduced to about 0.78 times of the corresponding value for a Newtonian fluid at equivalent flow rates; for dispersion in a channel, the reduction factor is about 0.73 confirming the earlier result of Sharp. Further, the location of the center of mass of a passive species over a cross section is found to remain unperturbed during the course of dispersion and for different values of the plug flow parameter (i.e., the yield stress of the fluid). The study can be used as a starting first approximate solution for studying the dispersion in the cardiovascular system or blood oxygenators.
Hayashi, Ryosuke; Shimakawa, Ginga; Shaku, Keiichiro; Shimizu, Satoko; Akimoto, Seiji; Yamamoto, Hiroshi; Amako, Katsumi; Sugimoto, Toshio; Tamoi, Masahiro; Makino, Amane; Miyake, Chikahiro
2014-01-01
To determine whether alternative electron flow (AEF) can replace the photosynthetic electron flow in cyanobacteria, we used an open O2-electrode system to monitor O2-exchange over a long period. In air-grown Synechocystis sp. PCC 6803 (S. 6803(WT)), the quantum yield of PSII, Y(II), held even after photosynthesis was suppressed by CO2 shortage. The S. 6803 mutant, deficient in flavodiiron (FLV) proteins 1 and 3, showed the same phenotype as S. 6803(WT). In contrast, Y(II) decreased in Synechococcus sp. PCC 7942 (S. 7942). These results suggest that AEF functioned as the Y(II) in S. 6803 and replaced the photosynthetic electron flux. In contrast, the activity of AEF in S. 7942 was lower. The affinity of AEF for O2 in S. 6803 did not correspond to those of FLVs in bacteria or terminal oxidases in respiration. AEF might be driven by photorespiration.
Engineering fluid flow using sequenced microstructures
NASA Astrophysics Data System (ADS)
Amini, Hamed; Sollier, Elodie; Masaeli, Mahdokht; Xie, Yu; Ganapathysubramanian, Baskar; Stone, Howard A.; di Carlo, Dino
2013-05-01
Controlling the shape of fluid streams is important across scales: from industrial processing to control of biomolecular interactions. Previous approaches to control fluid streams have focused mainly on creating chaotic flows to enhance mixing. Here we develop an approach to apply order using sequences of fluid transformations rather than enhancing chaos. We investigate the inertial flow deformations around a library of single cylindrical pillars within a microfluidic channel and assemble these net fluid transformations to engineer fluid streams. As these transformations provide a deterministic mapping of fluid elements from upstream to downstream of a pillar, we can sequentially arrange pillars to apply the associated nested maps and, therefore, create complex fluid structures without additional numerical simulation. To show the range of capabilities, we present sequences that sculpt the cross-sectional shape of a stream into complex geometries, move and split a fluid stream, perform solution exchange and achieve particle separation. A general strategy to engineer fluid streams into a broad class of defined configurations in which the complexity of the nonlinear equations of fluid motion are abstracted from the user is a first step to programming streams of any desired shape, which would be useful for biological, chemical and materials automation.
Light-controlled flows in active fluids
NASA Astrophysics Data System (ADS)
Dervaux, Julien; Capellazzi Resta, Marina; Brunet, Philippe
2017-03-01
Many photosynthetic microorganisms are able to detect light and move towards optimal intensities. This ability, known as phototaxis, plays a major role in ecology by affecting natural phytoplankton mass transfers, and has important applications in bioreactor and artificial micro-swimmers technologies. Here we show that this property can be exploited to generate macroscopic fluid flows using a localized light source directed towards shallow suspensions of phototactic microorganisms. Within the intensity range of positive phototaxis, algae accumulate beneath the excitation light, where collective effects lead to the emergence of radially symmetric convective flows. These flows can thus be used as hydrodynamic tweezers to manipulate small floating objects. At high cell density and layer depth, we uncover a new kind of instability, wherein the viscous torque exerted by self-generated fluid flows on the swimmers induces the formation of travelling waves. A model coupling fluid flow, cell concentration and orientation finely reproduces the experimental data.
Mechanics of coupled granular/fluid flows
NASA Astrophysics Data System (ADS)
Vinningland, J.; Toussaint, R.; Johnsen, O.; Flekkoy, E. G.; Maloy, K. J.
2006-12-01
We introduce a hybrid numerical model for coupled flow of solid grains and intersticial fluid, which renders for complex hydrodynamic interactions between mobile grains. This model treats the solid phase as discrete particles, interacting mechanically with the other particles and with the intersticial flowing fluid. The fluid is described by continuum equations rendering for its advection by the local grains, superposed to a pressure diffusion ruled by a Darcy flow with a permeability depending on the local solid fraction. This model is aimed at describing accurately such coupled flow. This model is tested for two model situations, where it is compared to experimental results: 1/ Injection of a localized overpressure in a grain/fluid filled cell lying horizontally, where gravity is unimportant. 2/ Sedimentation of heavy grains falling into an initially grain-free fluid region. The development of pattern-forming instabilities is obtained in these two situations, corresponding to granular/fluid equivalents of the two-fluids Saffman-Taylor and Rayleigh-Taylor instabilities. Numerical and experimental results are shown to be consistent with each other.
Apparatus for measuring fluid flow
Smith, Jack E.; Thomas, David G.
1984-01-01
Flow measuring apparatus includes a support loop having strain gages mounted thereon and a drag means which is attached to one end of the support loop and which bends the sides of the support loop and induces strains in the strain gages when a flow stream impacts thereon.
Apparatus for measuring fluid flow
Smith, J.E.; Thomas, D.G.
Flow measuring apparatus includes a support loop having strain gages mounted thereon and a drag means which is attached to one end of the support loop and which bends the sides of the support loop and induces strains in the strain gages when a flow stream impacts thereon.
Weatherill, D.; Simmons, C.T.; Voss, C.I.; Robinson, N.I.
2004-01-01
This study proposes the use of several problems of unstable steady state convection with variable fluid density in a porous layer of infinite horizontal extent as two-dimensional (2-D) test cases for density-dependent groundwater flow and solute transport simulators. Unlike existing density-dependent model benchmarks, these problems have well-defined stability criteria that are determined analytically. These analytical stability indicators can be compared with numerical model results to test the ability of a code to accurately simulate buoyancy driven flow and diffusion. The basic analytical solution is for a horizontally infinite fluid-filled porous layer in which fluid density decreases with depth. The proposed test problems include unstable convection in an infinite horizontal box, in a finite horizontal box, and in an infinite inclined box. A dimensionless Rayleigh number incorporating properties of the fluid and the porous media determines the stability of the layer in each case. Testing the ability of numerical codes to match both the critical Rayleigh number at which convection occurs and the wavelength of convection cells is an addition to the benchmark problems currently in use. The proposed test problems are modelled in 2-D using the SUTRA [SUTRA-A model for saturated-unsaturated variable-density ground-water flow with solute or energy transport. US Geological Survey Water-Resources Investigations Report, 02-4231, 2002. 250 p] density-dependent groundwater flow and solute transport code. For the case of an infinite horizontal box, SUTRA results show a distinct change from stable to unstable behaviour around the theoretical critical Rayleigh number of 4??2 and the simulated wavelength of unstable convection agrees with that predicted by the analytical solution. The effects of finite layer aspect ratio and inclination on stability indicators are also tested and numerical results are in excellent agreement with theoretical stability criteria and with
Directed flow fluid rinse trough
Kempka, Steven N.; Walters, Robert N.
1996-01-01
Novel rinse troughs accomplish thorough uniform rinsing. The tanks are suitable for one or more essentially planar items having substantially the same shape. The troughs ensure that each surface is rinsed uniformly. The new troughs also require less rinse fluid to accomplish a thorough rinse than prior art troughs.
Directed flow fluid rinse trough
Kempka, S.N.; Walters, R.N.
1996-07-02
Novel rinse troughs accomplish thorough uniform rinsing. The tanks are suitable for one or more essentially planar items having substantially the same shape. The troughs ensure that each surface is rinsed uniformly. The new troughs also require less rinse fluid to accomplish a thorough rinse than prior art troughs. 9 figs.
Evaluation of a steady state MPD thruster test facility
Reed, C.B.; Carlson, L.W.; Herman, H.; Doss, E.D.; Kilgore, O.
1985-01-01
The successful development of multimegawatt MPD thrusters depends, to a great extent, on testing them under steady state high altitude space conditions. Steady state testing is required to provide thermal characteristics, life cycle, erosion, and other essential data. the major technical obstacle for ground testing of MPD thrusters in a space simulation facility is the inability of state-of-the-art vacuum systems to handle the tremendous pumping speeds required for multimegawatt MPD thrusters. This is true for other types of electric propulsion devices as well. This paper discusses the results of the first phase of an evaluation of steady state MPD thruster test facilities. The first phase addresses the conceptual design of vacuum systems required to support multimegawatt MPD thruster testing. Three advanced pumping system concepts were evaluated and are presented here.
Poissonian steady states: from stationary densities to stationary intensities.
Eliazar, Iddo
2012-10-01
Markov dynamics are the most elemental and omnipresent form of stochastic dynamics in the sciences, with applications ranging from physics to chemistry, from biology to evolution, and from economics to finance. Markov dynamics can be either stationary or nonstationary. Stationary Markov dynamics represent statistical steady states and are quantified by stationary densities. In this paper, we generalize the notion of steady state to the case of general Markov dynamics. Considering an ensemble of independent motions governed by common Markov dynamics, we establish that the entire ensemble attains Poissonian steady states which are quantified by stationary Poissonian intensities and which hold valid also in the case of nonstationary Markov dynamics. The methodology is applied to a host of Markov dynamics, including Brownian motion, birth-death processes, random walks, geometric random walks, renewal processes, growth-collapse dynamics, decay-surge dynamics, Ito diffusions, and Langevin dynamics.
Efficient steady-state solver for hierarchical quantum master equations
NASA Astrophysics Data System (ADS)
Zhang, Hou-Dao; Qiao, Qin; Xu, Rui-Xue; Zheng, Xiao; Yan, YiJing
2017-07-01
Steady states play pivotal roles in many equilibrium and non-equilibrium open system studies. Their accurate evaluations call for exact theories with rigorous treatment of system-bath interactions. Therein, the hierarchical equations-of-motion (HEOM) formalism is a nonperturbative and non-Markovian quantum dissipation theory, which can faithfully describe the dissipative dynamics and nonlinear response of open systems. Nevertheless, solving the steady states of open quantum systems via HEOM is often a challenging task, due to the vast number of dynamical quantities involved. In this work, we propose a self-consistent iteration approach that quickly solves the HEOM steady states. We demonstrate its high efficiency with accurate and fast evaluations of low-temperature thermal equilibrium of a model Fenna-Matthews-Olson pigment-protein complex. Numerically exact evaluation of thermal equilibrium Rényi entropies and stationary emission line shapes is presented with detailed discussion.
Fractality in nonequilibrium steady states of quasiperiodic systems
NASA Astrophysics Data System (ADS)
Varma, Vipin Kerala; de Mulatier, Clélia; Žnidarič, Marko
2017-09-01
We investigate the nonequilibrium response of quasiperiodic systems to boundary driving. In particular, we focus on the Aubry-André-Harper model at its metal-insulator transition and the diagonal Fibonacci model. We find that opening the system at the boundaries provides a viable experimental technique to probe its underlying fractality, which is reflected in the fractal spatial dependence of simple observables (such as magnetization) in the nonequilibrium steady state. We also find that the dynamics in the nonequilibrium steady state depends on the length of the chain chosen: generic length chains harbour qualitatively slower transport (different scaling exponent) than Fibonacci length chains, which is in turn slower than in the closed system. We conjecture that such fractal nonequilibrium steady states should arise in generic driven critical systems that have fractal properties.
Structural simplification of chemical reaction networks in partial steady states.
Madelaine, Guillaume; Lhoussaine, Cédric; Niehren, Joachim; Tonello, Elisa
2016-11-01
We study the structural simplification of chemical reaction networks with partial steady state semantics assuming that the concentrations of some but not all species are constant. We present a simplification rule that can eliminate intermediate species that are in partial steady state, while preserving the dynamics of all other species. Our simplification rule can be applied to general reaction networks with some but few restrictions on the possible kinetic laws. We can also simplify reaction networks subject to conservation laws. We prove that our simplification rule is correct when applied to a module of a reaction network, as long as the partial steady state is assumed with respect to the complete network. Michaelis-Menten's simplification rule for enzymatic reactions falls out as a special case. We have implemented an algorithm that applies our simplification rules repeatedly and applied it to reaction networks from systems biology. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.
Instrument continuously measures density of flowing fluids
NASA Technical Reports Server (NTRS)
Jacobs, R. B.; Macinko, J.; Miller, C. E.
1967-01-01
Electromechanical densitometer continuously measures the densities of either single-phase or two-phase flowing cryogenic fluids. Measurement is made on actual flow. The instrument operates on the principle that the mass of any vibrating system is a primary factor in determining the dynamic characteristics of the system.
Uncertainties from the determination of the steady state in borehole climatology
NASA Astrophysics Data System (ADS)
Matharoo, G. S.; Beltrami, H.; Smerdon, J. E.
2010-12-01
Temperature changes at the Earth's surface propagate and are recorded underground as perturbations to the equilibrium thermal regime associated with the heat flow from the Earth's interior. Borehole climatology is concerned with the analysis and interpretation of these downward propagating subsurface temperature anomalies in terms of surface climate; as such proper determination of the steady-state geothermal regime is crucial because it is the reference that determines the size and shape of the climate induced subsurface temperature anomalies. Here we examine the effects of data noise, of lithological or instrumental origin, on the determination of the steady-state geothermal regime of the subsurface and provide error bounds for a particular choice of ground surface temperature (GST) history. From a series of 1000 Montecarlo experiments using Gaussian noise (mean = 0; standard devation = ±0.02 K), a 100 m steady-state fitting interval, and a data sampling rate of 0.02 m, our results indicate that typical uncertainties for 50-year averages are on the order of ± 0.02 K for the most recent 100 year period. These uncertainties grow with decreasing sampling rate reaching about ± 0.1 K for a 10-m sampling rate under identical conditions and target period. Uncertainties increase for progressively older periods, reaching ±0.2K at 500 year before present for a 10-m sampling rate. The uncertainties in reconstructed GST histories are also inversely proportional to the length of the fitting range used to estimate the reference steady-state thermal regime. We suggest that continuous logging should be the preferred approach when measuring geothermal data for climate reconstructions and that the steady-state geothermal gradient be estimated from a large depth range(>100 m).
A simplified approach to estimating the maximal lactate steady state.
Snyder, A C; Woulfe, T; Welsh, R; Foster, C
1994-01-01
The exercise intensity associated with an elevated but stable blood lactate (HLa) concentration during constant load work (the maximal steady state, MSS) has received attention as a candidate for the "optimal" exercise intensity for endurance training. Identification of MSS ordinarily demands direct measurement of HLa or respiratory metabolism. The purpose of this study was to test the ability of heart rate (HR) to identify MSS during steady state exercise, similar to that used in conventional exercise prescription. Trained runners (n = 9) and cyclists (n = 12) performed incremental and steady state exercise. MSS was defined as the highest intensity in which blood lactate concentration increased < 1.0 mM from minutes 10 to 30. The next higher intensity workbout completed was defined as > MSS. HR models related to the presence or absence of steady state conditions were developed from the upper 95% confidence interval of MSS and the lower 95% confidence interval of > MSS. Cross validation of the model to predict MSS was performed using 21 running and 45 cycling exercise bouts in a separate group. Using the MSS upper 95% confidence interval model 84% and 76% of workbouts were correctly predicted in cyclists and runners, respectively. Using the > MSS lower 95% confidence interval model, 76% and 81% of workbouts were correctly predicted in cyclists and runners, respectively. Prediction errors tended to incorrectly predict non-steady state conditions when steady state had occurred (16/26) (62%). We conclude that use of these simple HR models may predict MSS with sufficient accuracy to be useful when direct HLa measurement is not available.
Electromagnetic probe technique for fluid flow measurements
NASA Technical Reports Server (NTRS)
Arndt, G. D.; Carl, J. R.
1994-01-01
The probes described herein, in various configurations, permit the measurement of the volume fraction of two or more fluids flowing through a pipe. Each probe measures the instantaneous relative dielectric constant of the fluid in immediate proximity. As long as separation of the relative dielectric constant of the fluid is possible, several or even many fluids can be measured in the same flow stream. By using multiple probes, the velocity of each fluid can generally be determined as well as the distribution of each constituent in the pipe. The values are determined by statistical computation. There are many potential applications for probes of this type in industry and government. Possible NASA applications include measurements of helium/hydrazine flow during rocket tests at White Sands, liquid/gas flow in hydrogen or oxygen lines in Orbiter engines, and liquid/gaseous Freon flow in zero gravity tests with the KS135 aircraft at JSC. Much interest has been shown recently by the oil industry. In this a good method is needed to measure the fractions of oil, water, and natural gas flowing in a pipeline and the velocity of each. This particular problem involves an extension of what has been developed to date and our plans to solve this problem will be discussed herein.
Electromagnetic probe technique for fluid flow measurements
NASA Astrophysics Data System (ADS)
Arndt, G. D.; Carl, J. R.
1994-02-01
The probes described herein, in various configurations, permit the measurement of the volume fraction of two or more fluids flowing through a pipe. Each probe measures the instantaneous relative dielectric constant of the fluid in immediate proximity. As long as separation of the relative dielectric constant of the fluid is possible, several or even many fluids can be measured in the same flow stream. By using multiple probes, the velocity of each fluid can generally be determined as well as the distribution of each constituent in the pipe. The values are determined by statistical computation. There are many potential applications for probes of this type in industry and government. Possible NASA applications include measurements of helium/hydrazine flow during rocket tests at White Sands, liquid/gas flow in hydrogen or oxygen lines in Orbiter engines, and liquid/gaseous Freon flow in zero gravity tests with the KS135 aircraft at JSC. Much interest has been shown recently by the oil industry. In this a good method is needed to measure the fractions of oil, water, and natural gas flowing in a pipeline and the velocity of each. This particular problem involves an extension of what has been developed to date and our plans to solve this problem will be discussed herein.
Beckermann, C.; Ramadhyani, S.; Viskanta, R. )
1987-05-01
A numerical and experimental study is performed to analyze the steady-state natural convection fluid flow and heat transfer in a vertical rectangular enclosure that is partially filled with a vertical layer of a fluid-saturated porous medium. The flow in the porous layer is modeled utilizing the Brinkman-Forchheimer-extended Darcy equations. The numerical model is verified by conducting a number of experiments, with spherical glass beads as the porous medium and water and glycerin as the fluids, in rectangular test cells. The agreement between the flow visualization results and temperature measurements and the numerical model is, in general, good. It is found that the amount of fluid penetrating from the fluid region into the porous layer depends strongly on the Darcy (Da) and Rayleigh (Ra) numbers. For a relatively low product of Ra {times} Da, the flow takes place primarily in the fluid layers, and heat transfer in the porous layer is by conduction only. On other hand, fluid penetrating into a relatively highly permeable porous layer has a significant impact on the natural convection flow patterns in the entire enclosure.
Fluid flow in carbon nanotubes and nanopipes
NASA Astrophysics Data System (ADS)
Whitby, M.; Quirke, N.
2007-02-01
Nanoscale carbon tubes and pipes can be readily fabricated using self-assembly techniques and they have useful electrical, optical and mechanical properties. The transport of liquids along their central pores is now of considerable interest both for testing classical theories of fluid flow at the nanoscale and for potential nanofluidic device applications. In this review we consider evidence for novel fluid flow in carbon nanotubes and pipes that approaches frictionless transport. Methods for controlling such flow and for creating functional device architectures are described and possible applications are discussed.
PEBBLE: a two-dimensional steady-state pebble bed reactor thermal hydraulics code
Vondy, D.R.
1981-09-01
This report documents the local implementation of the PEBBLE code to treat the two-dimensional steady-state pebble bed reactor thermal hydraulics problem. This code is implemented as a module of a computation system used for reactor core history calculations. Given power density data, the geometric description in (RZ), and basic heat removal conditions and thermal properties, the coolant properties, flow conditions, and temperature distributions in the pebble fuel elements are predicted. The calculation is oriented to the continuous fueling, steady state condition with consideration of the effect of the high energy neutron flux exposure and temperature history on the thermal conductivity. The coolant flow conditions are calculated for the same geometry as used in the neutronics calculation, power density and fluence data being used directly, and temperature results are made available for subsequent use.
Steady-state error of a system with fuzzy controller.
Butkiewicz, B S
1998-01-01
We consider the problem of control error of a fuzzy system with feedback. The system consists of a plant, linear or nonlinear, fuzzy controller, and feedback loop. As controller we use both PD and PI fuzzy type controllers. We apply different t-norm and co-norm: logic, algebraic, Yager, Hamacher, bounded, drastic, etc. in the process of fuzzy reasoning. Triangular shape of membership functions is supposed, but we generalize the results obtained. Steady-state error of a system is calculated. We have obtained very interesting results. The steady-state error is identical for pairs of triangular t- and co-norms.
Steady-state coherent transfer by adiabatic passage.
Huneke, Jan; Platero, Gloria; Kohler, Sigmund
2013-01-18
We propose steady-state electron transport based on coherent transfer by adiabatic passage (CTAP) in a linearly arranged triple quantum dot with leads attached to the outer dots. Its main feature is repeated steering of single electrons from the first dot to the last dot without relevant occupation of the middle dot. The coupling to leads enables a steady-state current, whose shot noise is significantly suppressed provided that the CTAP protocol performs properly. This represents an indication for the direct transfer between spatially separated dots and, thus, may resolve the problem of finding experimental evidence for the nonoccupation of the middle dot.
Steady state decoupling and design of linear multivariable systems
NASA Technical Reports Server (NTRS)
Huang, J. Y.; Thaler, G. J.
1974-01-01
A constructive criterion for decoupling the steady states of linear multivariable systems is developed. The criterion consists of n(n-1) inequalities with the type numbers of the compensator transfer functions as the unknowns. These unknowns can be chosen to satisfy the inequalities and hence achieve a steady state decoupling scheme. It turns out that pure integrators in the loops play an important role. An extended root locus design method is then developed to take care of the stability and transient response. The overall procedure is applied to the compensation design for STOL C-8A aircraft in the approach mode.
Descriptive Linear modeling of steady-state visual evoked response
NASA Technical Reports Server (NTRS)
Levison, W. H.; Junker, A. M.; Kenner, K.
1986-01-01
A study is being conducted to explore use of the steady state visual-evoke electrocortical response as an indicator of cognitive task loading. Application of linear descriptive modeling to steady state Visual Evoked Response (VER) data is summarized. Two aspects of linear modeling are reviewed: (1) unwrapping the phase-shift portion of the frequency response, and (2) parsimonious characterization of task-loading effects in terms of changes in model parameters. Model-based phase unwrapping appears to be most reliable in applications, such as manual control, where theoretical models are available. Linear descriptive modeling of the VER has not yet been shown to provide consistent and readily interpretable results.
Adaptive steady-state stabilization for nonlinear dynamical systems
NASA Astrophysics Data System (ADS)
Braun, David J.
2008-07-01
By means of LaSalle’s invariance principle, we propose an adaptive controller with the aim of stabilizing an unstable steady state for a wide class of nonlinear dynamical systems. The control technique does not require analytical knowledge of the system dynamics and operates without any explicit knowledge of the desired steady-state position. The control input is achieved using only system states with no computer analysis of the dynamics. The proposed strategy is tested on Lorentz, van der Pol, and pendulum equations.
Mapping current fluctuations of stochastic pumps to nonequilibrium steady states
NASA Astrophysics Data System (ADS)
Rotskoff, Grant M.
2017-03-01
We show that current fluctuations in a stochastic pump can be robustly mapped to fluctuations in a corresponding time-independent nonequilibrium steady state. We thus refine a recently proposed mapping so that it ensures equivalence of not only the averages, but also optimal representation of fluctuations in currents and density. Our mapping leads to a natural decomposition of the entropy production in stochastic pumps similar to the "housekeeping" heat. As a consequence of the decomposition of entropy production, the current fluctuations in weakly perturbed stochastic pumps are shown to satisfy a universal bound determined by the steady state entropy production.
Mean field treatment of heterogeneous steady state kinetics
NASA Astrophysics Data System (ADS)
Geva, Nadav; Vaissier, Valerie; Shepherd, James; Van Voorhis, Troy
2017-10-01
We propose a method to quickly compute steady state populations of species undergoing a set of chemical reactions whose rate constants are heterogeneous. Using an average environment in place of an explicit nearest neighbor configuration, we obtain a set of equations describing a single fluctuating active site in the presence of an averaged bath. We apply this Mean Field Steady State (MFSS) method to a model of H2 production on a disordered surface for which the activation energy for the reaction varies from site to site. The MFSS populations quantitatively reproduce the KMC results across the range of rate parameters considered.
Steady state growth of E. Coli in low ammonium environment
NASA Astrophysics Data System (ADS)
Kim, Minsu; Deris, Barret; Zhang, Zhongge; Hwa, Terry
2011-03-01
Ammonium is the preferred nitrogen source for many microorganisms. In medium with low ammonium concentrations, enteric bacteria turn on the nitrogen responsive (ntr) genes to assimilate ammonium. Two proteins in E. coli, Glutamine synthetase (GS) and the Ammonium/methylammonium transporter AmtB play crucial roles in this regard. GS is the major ammonium assimilation enzyme below 1mM of NH4 + . AmtB is an inner membrane protein that transports NH4 + across the cell membrane against a concentration gradient. In order to study ammonium uptake at low NH4 + concentration at neutral pH, we developed a microfluidic flow chamber that maintains a homogenous nutrient environment during the course of exponential cell growth, even at very low concentration of nutrients. Cell growth can be accurately monitored using time-lapse microscopy. We followed steady state growth down to micro-molar range of NH4 + for the wild type and Δ amtB strains. The wild type strain is able to maintain the growth rate from 10mM down to a few uM of NH4 + , while the mutant exhibited reduced growth below ~ 20 ~uM of NH4 + . Simultaneous characterization of the expression levels of GS and AmtB using fluorescence reporters reveals that AmtB is turned on already at 1mM, but contributes to function only below ~ 30 ~uM in the wild-type. Down to ~ 20 ~uM of NH4 + , E.~coli can compensate the loss of AmtB by GS alone.
Transient and steady state expansions for water infiltration into dual permeability soils
NASA Astrophysics Data System (ADS)
Lassabatere, Laurent; Di Prima, Simone; Angulo-Jaramillo, Rafael; Iovino, Massimo; Bagarello, Vincenzo
2017-04-01
In the vadose zone, preferential flow in strongly heterogeneous soils is more the rule than homogeneous flow in uniform soils. Consequently, research activity has recently focused on the investigation and the modeling of preferential flow in heterogeneous soils and the characterization of hydraulic properties of heterogeneous soils including dual permeability soils. Within this framework, some studies have investigated the quantification of water infiltration at the surface of dual-permeability soils (Lassabatere et al., 2014). These authors developed a new analytical model for water infiltration into dual-permeability soils. However, the proposed model is based on an implicit formulation quite tricky to compute. In this study, we proposed new explicit approximate expansions for transient and steady states for the model of Lassabatere et al. (2014). The proposed methodology to compute these approximations is based on the methodology proposed by Haverkamp et al. (1994) for modeling water infiltration at the surface of single permeability soils. The main point to overcome is related the fact, in dual-permeability soils, the two subdomains, namely the fracture and the matrix domains, may have contrasting time intervals for transient and steady states. More explicitly, quasi-steady state flow may be reached in advance in the fracture domain. Consequently, at a given time, there may be the concomitancy of steady state in the fracture domain and transient state in the matrix. This point is developed further with mathematical and practical consideration. Approximate expansions and related validity time intervals are clearly identified and discussed with regards to both numerically generated and experimental data. Haverkamp R, Ross PJ, Smettem KRJ, Parlange JY (1994) 3-Dimensional analysis of infiltration from the disc Infiltrometer .2. Physically-based infiltration equation. Water Resour Res 30:2931-2935. Lassabatere L, Yilmaz D, Peyrard X, et al (2014) New analytical
Fundamental Processes of Atomization in Fluid-Fluid Flows
NASA Technical Reports Server (NTRS)
McCready, M. J.; Chang, H.-C.; Leighton, D. T.
2001-01-01
This report outlines the major results of the grant "Fundamental Processes of Atomization in Fluid-Fluid Flows." These include: 1) the demonstration that atomization in liquid/liquid shear flow is driven by a viscous shear instability that triggers the formation of a long thin sheet; 2) discovery of a new mode of interfacial instability for oscillatory two-layer systems whereby a mode that originates within the less viscous liquid phase causes interfacial deformation as the oscillation proceeds; 3) the demonstration that rivulet formation from gravity front occurs because the local front shape specified by gravity and surface tension changes from a nose to a wedge geometry, thus triggering a large increase in viscous resistance; and 4) extension of the studies on nonlinear wave evolution on falling films and in stratified flow, particularly the evolution towards large-amplitude solitary waves that tend to generate drops.
Salt loaded heat pipes: steady-state operation and related heat and mass transport
NASA Astrophysics Data System (ADS)
Simakin, A.; Ghassemi, A.
2003-10-01
Fluids in the deep-seated zones (3.5-4.5 km) of active geothermal zones are known to have increased salinity and acidity that can enhance interaction with surrounding porous rocks. A possible mechanism for brine generation is the separation of the rising magmatic fluid into a gas-like and a liquid-like component. This work illustrates the main features of this mechanism by investigating the conditions for heat pipe convection of natural brines in hydrothermal systems. The well-established heat pipe regime for convection of two-phase pure water (vapor-liquid) in a porous column is extended to the case of boiling brines. In particular, the NaCl-H 2O system is used to model the 1-D reactive flow with dissolution-precipitation in geothermal reservoirs. The quasi steady-state equations of the conservation of matter, Darcy's law for the gas and liquid phases, and the heat balance equation have been examined while neglecting the temporal variation of porosity. A semi-analytical procedure is used to solve these equations for a two-phase fluid in equilibrium with a solid salt. The solution is in the form of the dependence of liquid volume fraction as a function of temperature for different heat fluxes. The solution is separated into two isolated regions by the temperature T=596°C, at the maximum fluid pressure for three-phase (H-L-V) equilibrium. In the case of unsaturated two-phase flow at the reference permeability of porous rocks (3·10 -16 m 2), the maximum heat flux that can be transferred through the porous column via convection is analytically estimated to be 4.3 W/m 2. This is close to the corresponding value for the three-phase case that is numerically calculated to be 6 W/m 2. Due to dissolution (partial leaching of oxide components by acid condensates) and precipitation of salt at the boiling front, heat transfer in a heat pipe in soluble media occurs in a direction opposite to the associated mass transfer. This can cause deep hydrothermal karsting that is
Global chaotization of fluid particle trajectories in a sheared two-layer two-vortex flow.
Ryzhov, Evgeny A; Koshel, Konstantin V
2015-10-01
In a two-layer quasi-geostrophic approximation, we study the irregular dynamics of fluid particles arising due to two interacting point vortices embedded in a deformation flow consisting of shear and rotational components. The two vortices are arranged within the bottom layer, but an emphasis is on the upper-layer fluid particle motion. Vortices moving in one layer induce stirring of passive scalars in the other layer. This is of interest since point vortices induce singular velocity fields in the layer they belong to; however, in the other layer, they induce regular velocity fields that generally result in a change in passive particle stirring. If the vortices are located at stagnation points, there are three different types of the fluid flow. We examine how properties of each flow configuration are modified if the vortices are displaced from the stagnation points and thus circulate in the immediate vicinity of these points. To that end, an analysis of the steady-state configurations is presented with an emphasis on the frequencies of fluid particle oscillations about the elliptic stagnation points. Asymptotic relations for the vortex and fluid particle zero-oscillation frequencies are derived in the vicinity of the corresponding elliptic points. By comparing the frequencies of fluid particles with the ones of the vortices, relations between the parameters that lead to enhanced stirring of fluid particles are established. It is also demonstrated that, if the central critical point is elliptic, then the fluid particle trajectories in its immediate vicinity are mostly stable making it harder for the vortex perturbation to induce stirring. Change in the type of the central point to a hyperbolic one enhances drastically the size of the chaotic dynamics region. Conditions on the type of the central critical point also ensue from the derived asymptotic relations.
Global chaotization of fluid particle trajectories in a sheared two-layer two-vortex flow
Ryzhov, Evgeny A.; Koshel, Konstantin V.
2015-10-15
In a two-layer quasi-geostrophic approximation, we study the irregular dynamics of fluid particles arising due to two interacting point vortices embedded in a deformation flow consisting of shear and rotational components. The two vortices are arranged within the bottom layer, but an emphasis is on the upper-layer fluid particle motion. Vortices moving in one layer induce stirring of passive scalars in the other layer. This is of interest since point vortices induce singular velocity fields in the layer they belong to; however, in the other layer, they induce regular velocity fields that generally result in a change in passive particle stirring. If the vortices are located at stagnation points, there are three different types of the fluid flow. We examine how properties of each flow configuration are modified if the vortices are displaced from the stagnation points and thus circulate in the immediate vicinity of these points. To that end, an analysis of the steady-state configurations is presented with an emphasis on the frequencies of fluid particle oscillations about the elliptic stagnation points. Asymptotic relations for the vortex and fluid particle zero–oscillation frequencies are derived in the vicinity of the corresponding elliptic points. By comparing the frequencies of fluid particles with the ones of the vortices, relations between the parameters that lead to enhanced stirring of fluid particles are established. It is also demonstrated that, if the central critical point is elliptic, then the fluid particle trajectories in its immediate vicinity are mostly stable making it harder for the vortex perturbation to induce stirring. Change in the type of the central point to a hyperbolic one enhances drastically the size of the chaotic dynamics region. Conditions on the type of the central critical point also ensue from the derived asymptotic relations.
NASA Astrophysics Data System (ADS)
Naaim, Mohamed; Faug, Thierry
2017-04-01
The discontinuities in height and velocity, namely jumps, formed in free-surface flows are important processes in geophysics, for instance when they are formed during the interaction of avalanche-flows with protection structures. The present study investigates steady state jumps formed in free-surface flows with the help of numerical simulations based on depth-averaged equations. A control constant mass discharge is supplied to an incline. By imposing a difference in basal friction between a upper part of the chute bottom and a lower part of the chute bottom, a supercritical flow is produced upstream while a subcritical flow appears downstream. The transition between both gives birth to a jump located at the transition between the two portions of the chute with different basal friction. Different constitutive equations are tested (laminar, turbulent, local granular rheology, Voellmy, Herschel Bulkley), thus allowing us to quantify the influence of the fluid rheology on the jump properties : position, geometry and size.
Fluid flow nozzle energy harvesters
NASA Astrophysics Data System (ADS)
Sherrit, Stewart; Lee, Hyeong Jae; Walkemeyer, Phillip; Winn, Tyler; Tosi, Luis Phillipe; Colonius, Tim
2015-04-01
Power generation schemes that could be used downhole in an oil well to produce about 1 Watt average power with long-life (decades) are actively being developed. A variety of proposed energy harvesting schemes could be used to extract energy from this environment but each of these has their own limitations that limit their practical use. Since vibrating piezoelectric structures are solid state and can be driven below their fatigue limit, harvesters based on these structures are capable of operating for very long lifetimes (decades); thereby, possibly overcoming a principle limitation of existing technology based on rotating turbo-machinery. An initial survey [1] identified that spline nozzle configurations can be used to excite a vibrating piezoelectric structure in such a way as to convert the abundant flow energy into useful amounts of electrical power. This paper presents current flow energy harvesting designs and experimental results of specific spline nozzle/ bimorph design configurations which have generated suitable power per nozzle at or above well production analogous flow rates. Theoretical models for non-dimensional analysis and constitutive electromechanical model are also presented in this paper to optimize the flow harvesting system.
Fluid Flow Nozzle Energy Harvesters
NASA Technical Reports Server (NTRS)
Sherrit, Stewart; Lee, Hyeong Jae; Walkenmeyer, Phillip; Winn, Tyler; Tosi, Luis Phillipe; Colonius, Tim
2015-01-01
Power generation schemes that could be used downhole in an oil well to produce about 1 Watt average power with long-life (decades) are actively being developed. A variety of proposed energy harvesting schemes could be used to extract energy from this environment but each of these has their own limitations that limit their practical use. Since vibrating piezoelectric structures are solid state and can be driven below their fatigue limit, harvesters based on these structures are capable of operating for very long lifetimes (decades); thereby, possibly overcoming a principle limitation of existing technology based on rotating turbo-machinery. An initial survey identified that spline nozzle configurations can be used to excite a vibrating piezoelectric structure in such a way as to convert the abundant flow energy into useful amounts of electrical power. This paper presents current flow energy harvesting designs and experimental results of specific spline nozzle/ bimorph design configurations which have generated suitable power per nozzle at or above well production analogous flow rates. Theoretical models for non-dimensional analysis and constitutive electromechanical model are also presented in this paper to optimize the flow harvesting system.
Unsteady fluid flow in smart material actuated fluid pumps
NASA Astrophysics Data System (ADS)
John, Shaju; Cadou, Christopher
2005-05-01
Smart materials' ability to deliver large block forces in a small package while operating at high frequencies makes them extremely attractive for converting electrical to mechanical power. This has led to the development of hybrid actuators consisting of co-located smart material actuated pumps and hydraulic cylinders that are connected by a set of fast-acting valves. The overall success of the hybrid concept hinges on the effectiveness of the coupling between the smart material and the fluid. This, in turn, is strongly dependent on the resistance to fluid flow in the device. This paper presents results from three-dimensional unsteady simulations of fluid flow in the pumping chamber of a prototype hybrid actuator powered by a piezo-electric stack. The results show that the forces associated with moving the fluid into and out of the pumping chamber already exceed 10% of the piezo stack blocked force at relatively low frequencies ~120 Hz and approach 40% of the blocked force at 800 Hz. This reduces the amplitude of the piston motion in such a way that the volume flow rate remains approximately constant above operating frequencies of 500 Hz while the efficiency of the pump decreases rapidly.
Patterns and flow in frictional fluid dynamics
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
Stojanovic, B.; Hallberg, D.; Akander, J.
2010-10-15
This paper presents the thermal modelling of an unglazed solar collector (USC) flat panel, with the aim of producing a detailed yet swift thermal steady-state model. The model is analytical, one-dimensional (1D) and derived by a fin-theory approach. It represents the thermal performance of an arbitrary duct with applied boundary conditions equal to those of a flat panel collector. The derived model is meant to be used for efficient optimisation and design of USC flat panels (or similar applications), as well as detailed thermal analysis of temperature fields and heat transfer distributions/variations at steady-state conditions; without requiring a large amount of computational power and time. Detailed surface temperatures are necessary features for durability studies of the surface coating, hence the effect of coating degradation on USC and system performance. The model accuracy and proficiency has been benchmarked against a detailed three-dimensional Finite Difference Model (3D FDM) and two simpler 1D analytical models. Results from the benchmarking test show that the fin-theory model has excellent capabilities of calculating energy performances and fluid temperature profiles, as well as detailed material temperature fields and heat transfer distributions/variations (at steady-state conditions), while still being suitable for component analysis in junction to system simulations as the model is analytical. The accuracy of the model is high in comparison to the 3D FDM (the prime benchmark), as long as the fin-theory assumption prevails (no 'or negligible' temperature gradient in the fin perpendicularly to the fin length). Comparison with the other models also shows that when the USC duct material has a high thermal conductivity, the cross-sectional material temperature adopts an isothermal state (for the assessed USC duct geometry), which makes the 1D isothermal model valid. When the USC duct material has a low thermal conductivity, the heat transfer course of
Two-fluid equilibrium with flow: FLOW2
Guazzotto, L.; Betti, R.
2015-09-15
The effects of finite macroscopic velocities on axisymmetric ideal equilibria are examined using the two-fluid (ions and electrons) model. A new equilibrium solver, the code FLOW2, is introduced for the two-fluid model and used to investigate the importance of various flow patterns on the equilibrium of tight aspect ratio (NSTX) and regular tokamak (DIII-D) configurations. Several improvements to the understanding and calculation of two-fluid equilibria are presented, including an analytical and numerical proof of the single-fluid and static limits of the two-fluid model, a discussion of boundary conditions, a user-friendly free-function formulation, and the explicit evaluation of velocity components normal to magnetic surfaces.
Steady State Load Characterization Fact Sheet: 2012 Chevy Volt
Scoffield, Don
2015-03-01
This fact sheet characterizes the steady state charging behavior of a 2012 Chevy Volt. Both level 1 charging (120 volt) and level 2 charging (208 volts) is investigated. This fact sheet contains plots of efficiency, power factor, and current harmonics as vehicle charging is curtailed. Prominent current harmonics are also displayed in a histogram for various charge rates.
Steady States of the Parametric Rotator and Pendulum
ERIC Educational Resources Information Center
Bouzas, Antonio O.
2010-01-01
We discuss several steady-state rotation and oscillation modes of the planar parametric rotator and pendulum with damping. We consider a general elliptic trajectory of the suspension point for both rotator and pendulum, for the latter at an arbitrary angle with gravity, with linear and circular trajectories as particular cases. We treat the…
Density Functional Theory for Steady-State Nonequilibrium Molecular Junctions
Liu, Shuanglong; Nurbawono, Argo; Zhang, Chun
2015-01-01
We present a density functional theory (DFT) for steady-state nonequilibrium quantum systems such as molecular junctions under a finite bias. Based on the steady-state nonequilibrium statistics that maps nonequilibrium to an effective equilibrium, we show that ground-state DFT (GS-DFT) is not applicable in this case and two densities, the total electron density and the density of current-carrying electrons, are needed to uniquely determine the properties of the corresponding nonequilibrium system. A self-consistent mean-field approach based on two densities is then derived. The theory is implemented into SIESTA computational package and applied to study nonequilibrium electronic/transport properties of a realistic carbon-nanotube (CNT)/Benzene junction. Results obtained from our steady-state DFT (SS-DFT) are compared with those of conventional GS-DFT based transport calculations. We show that SS-DFT yields energetically more stable nonequilibrium steady state, predicts significantly lower electric current, and is able to produce correct electronic structures in local equilibrium under a limiting case. PMID:26472080
Equilibrium Binding and Steady-State Enzyme Kinetics.
ERIC Educational Resources Information Center
Dunford, H. Brian
1984-01-01
Points out that equilibrium binding and steady-state enzyme kinetics have a great deal in common and that related equations and error analysis can be cast in identical forms. Emphasizes that if one type of problem solution is taught, the other is also taught. Various methods of data analysis are evaluated. (JM)
Comment on ``Dynamically maintained steady-state pressure gradients''
NASA Astrophysics Data System (ADS)
Duncan, Todd L.
2000-04-01
Sheehan [Phys. Rev. E 57, 6660 (1998)] recently discussed the possibility of establishing a dynamically maintained, steady-state pressure gradient in a gas filling a cavity. In this Comment it is pointed out that the pressure gradients in such a system, if attainable in the laboratory, could be used to violate the second law of thermodynamics.
Aperiodically Driven Integrable Systems and Their Emergent Steady States
NASA Astrophysics Data System (ADS)
Nandy, Sourav; Sen, Arnab; Sen, Diptiman
2017-07-01
Does a closed quantum many-body system that is continually driven with a time-dependent Hamiltonian finally reach a steady state? This question has only recently been answered for driving protocols that are periodic in time, where the long-time behavior of the local properties synchronizes with the drive and can be described by an appropriate periodic ensemble. Here, we explore the consequences of breaking the time-periodic structure of the drive with additional aperiodic noise in a class of integrable systems. We show that the resulting unitary dynamics leads to new emergent steady states in at least two cases. While any typical realization of random noise causes eventual heating to an infinite-temperature ensemble for all local properties in spite of the system being integrable, noise that is self-similar in time leads to an entirely different steady state (which we dub the "geometric generalized Gibbs ensemble") that emerges only after an astronomically large time scale. To understand the approach to the steady state, we study the temporal behavior of certain coarse-grained quantities in momentum space that fully determine the reduced density matrix for a subsystem with size much smaller than the total system. Such quantities provide a concise description for any drive protocol in integrable systems that are reducible to a free-fermion representation.
Steady-State Squeezing in the Micromaser Cavity Field
NASA Technical Reports Server (NTRS)
Nayak, N.
1996-01-01
It is shown that the radiation field in the presently operated micromaser cavity may be squeezed when pumped with polarized atoms. The squeezing is in the steady state field corresponding to the action similar to that of the conventional micromaser, with the effect of cavity dissipation during entire t(sub c) = tau + t(sub cav).
Effects of curvature on asymmetric steady states in catalyst particles
Lucier, B J
1981-02-01
The effects of curvature on steady states of chemical catalytic reactions are investigated by studying the cases of the catalytic particle being a spherical or cylindrical shell. Existence and stability of solutions are studied. It is shown that the solutions converge to the solutions for the catalytic slab when the curvature goes to 0 in each case.
Equilibrium Binding and Steady-State Enzyme Kinetics.
ERIC Educational Resources Information Center
Dunford, H. Brian
1984-01-01
Points out that equilibrium binding and steady-state enzyme kinetics have a great deal in common and that related equations and error analysis can be cast in identical forms. Emphasizes that if one type of problem solution is taught, the other is also taught. Various methods of data analysis are evaluated. (JM)
Identification of enzyme inhibitory mechanisms from steady-state kinetics.
Fange, David; Lovmar, Martin; Pavlov, Michael Y; Ehrenberg, Måns
2011-09-01
Enzyme inhibitors are used in many areas of the life sciences, ranging from basic research to the combat of disease in the clinic. Inhibitors are traditionally characterized by how they affect the steady-state kinetics of enzymes, commonly analyzed on the assumption that enzyme-bound and free substrate molecules are in equilibrium. This assumption, implying that an enzyme-bound substrate molecule has near zero probability to form a product rather than dissociate, is valid only for very inefficient enzymes. When it is relaxed, more complex but also more information-rich steady-state kinetics emerges. Although solutions to the general steady-state kinetics problem exist, they are opaque and have been of limited help to experimentalists. Here we reformulate the steady-state kinetics of enzyme inhibition in terms of new parameters. These allow for assessment of ambiguities of interpretation due to kinetic scheme degeneracy and provide an intuitively simple way to analyze experimental data. We illustrate the method by concrete examples of how to assess scheme degeneracy and obtain experimental estimates of all available rate and equilibrium constants. We suggest simple, complementary experiments that can remove ambiguities and greatly enhance the accuracy of parameter estimation.
Identifiability of steady-state chemical kinetic models
Shvetsova-Shilovskaya, T.N.; Gorskii, V.G.
1995-01-01
The methodology for the local and global identifiability analysis of steady-state kinetic models of catalytic reactions is discussed. This methodology is based on the prior transformation of the model into the linear form so that the coefficients of the linear form are uniquely identifiable combinations of constants (observed parameters). Identifiability analysis is applied to several particular models.
Steady-State Pharmacokinetics of Bupropion SR in Juvenile Patients
ERIC Educational Resources Information Center
Daviss, W. Burleson; Perel, James M.; Rudolph, George R.; Axelson, David A.; Gilchrist, Richard; Nuss, Sharon; Birmaher, Boris; Brent, David A.
2005-01-01
Objective: To examine the steady-state pharmacokinetic properties of bupropion sustained release (SR) and their potential developmental differences in youths. Method: Eleven boys and eight girls aged 11 to 17 years old were prescribed bupropion SR monotherapy for attention-deficit/hyperactivity disorder (n = 16) and/or depressive disorders (n =…
Pre-Steady-State Decoding of the Bicoid Morphogen Gradient
Bergmann, Sven; Sandler, Oded; Sberro, Hila; Shnider, Sara; Schejter, Eyal; Shilo, Ben-Zion; Barkai, Naama
2007-01-01
Morphogen gradients are established by the localized production and subsequent diffusion of signaling molecules. It is generally assumed that cell fates are induced only after morphogen profiles have reached their steady state. Yet, patterning processes during early development occur rapidly, and tissue patterning may precede the convergence of the gradient to its steady state. Here we consider the implications of pre-steady-state decoding of the Bicoid morphogen gradient for patterning of the anterior–posterior axis of the Drosophila embryo. Quantitative analysis of the shift in the expression domains of several Bicoid targets (gap genes) upon alteration of bcd dosage, as well as a temporal analysis of a reporter for Bicoid activity, suggest that a transient decoding mechanism is employed in this setting. We show that decoding the pre-steady-state morphogen profile can reduce patterning errors caused by fluctuations in the rate of morphogen production. This can explain the surprisingly small shifts in gap and pair-rule gene expression domains observed in response to alterations in bcd dosage. PMID:17298180
Steady-State Pharmacokinetics of Bupropion SR in Juvenile Patients
ERIC Educational Resources Information Center
Daviss, W. Burleson; Perel, James M.; Rudolph, George R.; Axelson, David A.; Gilchrist, Richard; Nuss, Sharon; Birmaher, Boris; Brent, David A.
2005-01-01
Objective: To examine the steady-state pharmacokinetic properties of bupropion sustained release (SR) and their potential developmental differences in youths. Method: Eleven boys and eight girls aged 11 to 17 years old were prescribed bupropion SR monotherapy for attention-deficit/hyperactivity disorder (n = 16) and/or depressive disorders (n =…
Steady-State Multiplicity Features of Chemically Reacting Systems.
ERIC Educational Resources Information Center
Luss, Dan
1986-01-01
Analyzes steady-state multiplicity in chemical reactors, focusing on the use of two mathematical tools, namely, the catastrophe theory and the singularity theory with a distinguished parameter. These tools can be used to determine the maximum number of possible solutions and the different types of bifurcation diagrams. (JN)
Combined Steady-State and Dynamic Heat Exchanger Experiment
ERIC Educational Resources Information Center
Luyben, William L.; Tuzla, Kemal; Bader, Paul N.
2009-01-01
This paper describes a heat-transfer experiment that combines steady-state analysis and dynamic control. A process-water stream is circulated through two tube-in-shell heat exchangers in series. In the first, the process water is heated by steam. In the second, it is cooled by cooling water. The equipment is pilot-plant size: heat-transfer areas…
Steady-State Multiplicity Features of Chemically Reacting Systems.
ERIC Educational Resources Information Center
Luss, Dan
1986-01-01
Analyzes steady-state multiplicity in chemical reactors, focusing on the use of two mathematical tools, namely, the catastrophe theory and the singularity theory with a distinguished parameter. These tools can be used to determine the maximum number of possible solutions and the different types of bifurcation diagrams. (JN)
The concave river long profile: a morphodynamic steady state?
NASA Astrophysics Data System (ADS)
Blom, A.
2011-12-01
By definition, a morphodynamic steady state is governed by a spatially constant sediment transport rate. As the sediment transport rate is a function of shear stress associated with skin friction, the morphodynamic steady state has been considered to be governed by a spatially constant bed slope. For this reason, the typical concave river long profile has been considered to be a quasi-steady state. The river's steady state has been considered to be one with a spatially constant bed slope, with tributaries inducing a stepwise decrease in bed slope in streamwise direction. Yet, for the sediment transport rate to be spatially constant, it rather is the product of water surface slope and water depth associated with skin friction that needs to be constant. This implies that physical mechanisms that induce streamwise variation in the sediment transport rate can be compensated by a streamwise variation in bed slope so as to guarantee a spatially constant sediment transport rate. Following the river course, such physical mechanisms can be bedrock exposure, partial transport, and a spatially lagging bedform growth. At locations where tributaries increase the water discharge, the above mechanisms cause the river bed profile to be upward concave over a significant reach. At bifucations or at locations where river widening prevails, the river bed profile is upward convex.
Steady States of the Parametric Rotator and Pendulum
ERIC Educational Resources Information Center
Bouzas, Antonio O.
2010-01-01
We discuss several steady-state rotation and oscillation modes of the planar parametric rotator and pendulum with damping. We consider a general elliptic trajectory of the suspension point for both rotator and pendulum, for the latter at an arbitrary angle with gravity, with linear and circular trajectories as particular cases. We treat the…
Nonlinear elements in the EMTP: Steady-state initialization
Perkins, B.K.; Marti, J.R.; Dommel, H.W.
1995-05-01
A methodology is presented for the formulation and solution of networks containing a class of nonlinear elements within the framework of electromagnetic transient programs. The method facilitates steady-state initialization formulated in the time-domain as a two-point boundary value problem. The techniques developed are applied to a simple network exhibiting harmonics due to transformer saturation.
Kinematic Cosmology & a new ``Steady State'' Model of Continued Creation
NASA Astrophysics Data System (ADS)
Wegener, Mogens
2006-03-01
Only a new "steady state" model justifies the observations of fully mature galaxies at ever increasing distances. The basic idea behind the world model presented here, which is a synthesis of the cosmologies of Parmenides and Herakleitos, is that the invariant structure of the infinite contents of a universe in flux may be depicted as a finite hyperbolic pseudo-sphere.
Combined Steady-State and Dynamic Heat Exchanger Experiment
ERIC Educational Resources Information Center
Luyben, William L.; Tuzla, Kemal; Bader, Paul N.
2009-01-01
This paper describes a heat-transfer experiment that combines steady-state analysis and dynamic control. A process-water stream is circulated through two tube-in-shell heat exchangers in series. In the first, the process water is heated by steam. In the second, it is cooled by cooling water. The equipment is pilot-plant size: heat-transfer areas…
MEANS FOR VISUALIZING FLUID FLOW PATTERNS
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.
Electro-osmotic flow in bicomponent fluids
NASA Astrophysics Data System (ADS)
Bazarenko, Andrei; Sega, Marcello
The electroosmotic flow (EOF) is a widely used technique that uses the action of external electric fields on solvated ions to move fluids around in microfluidics devices. For homogeneous fluids, the characteristics of the flow can be well approximated by simple analytical models, but in multicomponent systems such as oil-in-water droplets one has to rely to numerical simulations. The purpose of this study is to investigate physical properties of the EOF in a bicomponent fluid by solving the coupled equations of motions of explicit ions in interaction with a continuous model of the flow. To do so we couple the hydrodynamics equations as solved by a Shan-Chen Lattice-Boltzmann method to the molecular dynamics of the ions. The presence of explicit ions allows us to go beyond the simple Poisson-Boltzmann approximations, and investigate a variety of EOF regimes. ETN-COLLDENSE (H2020-MCSA-ITN-2014, Grant No. 642774).
MINET: transient analysis of fluid-flow and heat-transfer networks
Van Tuyle, G.J.; Guppy, J.G.; Nepsee, T.C.
1983-01-01
MINET, a computer code developed for the steady-state and transient analysis of fluid-flow and heat-transfer networks, is described. The code is based on a momentum integral network method, which offers significant computational advantages in the analysis of large systems, such as the balance of plant in a power-generating facility. An application is discussed in which MINET is coupled to the Super System Code (SSC), an advanced generic code for the transient analysis of loop- or pool-type LMFBR systems. In this application, the ability of the Clinch River Breeder Reactor Plant to operate in a natural circulation mode following an assumed loss of all electric power, was assessed. Results from the MINET portion of the calculations are compared against those generated independently by the Clinch River Project, using the DEMO code.
The importance of flow pulsatility for the rate of transvascular fluid filtration in lungs.
Hauge, A; Nicolaysen, G
1979-05-01
1. The rate of transvascular fluid filtration has been studied with a gravimetric technique in isolated perfused rabbit lungs during periods of elevated left atrial pressure (PLA). 2. Fluid filtration was expressed as the filtration coefficient, Kf (g/min x 100 g bloodless lung x mmHg PLA) and determined during alternately pulsatile and non-pulsatile perfusion in six zone III and three zone II/I lung preparations. Perfusion pattern was changed without interruption of flow. Mean in- and outflow pressures were kept constant. 3. In all the lungs it was found that Kf was higher during pulsatile than during non-pulsatile flow (P less than 0.01). Mean Kf (+/- S.E. of mean) for the zone III preparations was 0.42 (+/- 0.089) and 0.27 (+/- 0.057) for pulsatile and non-pulsatile perfusion, respectively. The corresponding figures for the zone II/I preparations were 0.11 (+/- 0.035) and 0.04 (+/- 0.030). 4. We suggest that the difference is due to a larger filtration area and/or a higher mean microvascular hydrostatic pressure during pulsatile than during non-pulsatile flow and not to a rise in hydraulic conductivity due to pressure pulsations ('stretched pores'). 5. When the water-exchange function of the lung is considered, flow pattern should be taken into account as an entity in its own right in addition to the steady state or the mean component of blood flow.
Dynamics of fluid mixing in separated flows
NASA Astrophysics Data System (ADS)
Leder, A.
1991-05-01
Separated flows at high Re (>103) are highly turbulent. In some situations the turbulence generation and mixing processes associated with flow separation are desirable, e.g., in heat exchangers or in many chemical engineering applications. In others, e.g., stalled airfoils, separation must be avoided as it causes loss in pressure and kinetic energy. To control the phenomenon effectively, physical mechanisms of flow separation and related aspects, such as the growth of flow instabilities in shear layers, the process of vortex formation, and the dynamics of fluid mixing in recirculating flow regions, must be understood. In many cases numerical procedures, e.g., Navier-Stokes calculations including k-ɛ turbulence modeling, fail to predict real physical mechanisms in separated flows.1,2 Separated flows in the lee of bluff bodies have been studied for many years.3,4 However, accurate measurements of the magnitude and direction of velocities and the magnitude of the terms of the Reynolds stress tensor have been restricted by the unsuitability of the hot-wire anemometer in recirculating flows. The development of the pulsed-wire anemometer, flying hot-wire anemometer, and laser-Doppler anemometry (LDA) allows more reliable measurements also in turbulent separated flows.5-8 The aim of this paper is to investigate the dynamics of undisturbed fluid mixing in separated regions of 2-D, incompressible flows with visualization techniques and LDA. Measurements were performed with a vertical flat plate model, mounted in a closed-circuit wind tunnel at low blockage ratio. Because of the noninvasive character, optical techniques like LDA are more suitable to analyze complex fluid motions than pulsed-wire and flying-wire anemometry. The LDA system used to investigate turbulent flow structures consists of a two-channel version operating in backscatter mode and a specifically developed phase detector to extract phase-averaged information from recorded measurement ensembles.9 Endplates
Method and Apparatus for Measuring Fluid Flow
NASA Technical Reports Server (NTRS)
Arndt, G. Dickey (Inventor); Nguyen, Than X. (Inventor); Carl, James R. (Inventor)
1995-01-01
The invention is a method and apparatus for monitoring the presence, concentration, and the movement of fluids. It is based on utilizing electromagnetic measurements of the complex permittivity of the fluids for detecting and monitoring the fluid. More particularly the apparatus uses one or more microwave probes which are placed at the locations where the measurements are to be made. A radio frequency signal is transmitted to the probe and the reflected signal is phase and amplitude detected at a rapid rate for the purpose of identifying the fluids, based on their dielectric constant at the probe. The apparatus can be used for multiple purposes including measures of flow rates, turbulence, dispersion, fluid identification, and changes in flow conditions of multiple fluids or multiple states of a single fluid in a flowline or a holding container. The apparatus includes a probe consisting of two electrical conductors separated by an insulator. A radio frequency signal is communicated to the probe and is reflected back from the portion of the probe exposed to the fluid. The radio frequency signal also provides a reference signal. An oscillator generates a second signal which combined with each of the reference signal and the reflected signal to produce signals of lower frequencies to facilitate filtering and amplifying those signals. The two signals are then mixed in a detector to produce an output signal that is representative of the phase and amplitude change caused by the reflection of the signal at the probe exposed to the fluid. The detector may be a dual phase detector that provides two such output signals that are in phase quadrature. A phase shifter may be provided for selectively changing the phase of the reference signal to improve the sensitivity of at least one of the output signals for more accurate readings and/or for calibration purposes. The two outputs that are in quadrature with respect to each other may be simultaneously monitored to account for
Levin, A.E.; Carbajo, J.J.; Lloyd, D.B.; Montgomery, B.H.; Rose, S.D.; Wantland, J.L.
1985-01-01
Temperature data from steady state tests in two parallel, simulated liquid metal reactor fuel assemblies with identical design specifications have been compared to determine the extent to which they agree. In general, good agreement was found in data at low flows and in bundle-center data at higher flows. Discrepancies in the data wre noted near the bundle edges at higher flows. An analysis of bundle thermal boundary conditions showed that the possible eccentric placement of one bundle within the housing could account for these discrepancies.
Fluid Flow in An Evaporating Droplet
NASA Technical Reports Server (NTRS)
Hu, H.; Larson, R.
1999-01-01
Droplet evaporation is a common phenomenon in everyday life. For example, when a droplet of coffee or salt solution is dropped onto a surface and the droplet dries out, a ring of coffee or salt particles is left on the surface. This phenomenon exists not only in everyday life, but also in many practical industrial processes and scientific research and could also be used to assist in DNA sequence analysis, if the flow field in the droplet produced by the evaporation could be understood and predicted in detail. In order to measure the fluid flow in a droplet, small particles can be suspended into the fluid as tracers. From the ratio of gravitational force to Brownian force a(exp 4)(delta rho)(g)/k(sub B)T, we find that particle's tendency to settle is proportional to a(exp 4) (a is particle radius). So, to keep the particles from settling, the droplet size should be chosen to be in a range 0.1 -1.0 microns in experiments. For such small particles, the Brownian force will affect the motion of the particle preventing accurate measurement of the flow field. This problem could be overcome by using larger particles as tracers to measure fluid flow under microgravity since the gravitational acceleration g is then very small. For larger particles, Brownian force would hardly affect the motion of the particles. Therefore, accurate flow field could be determined from experiments in microgravity. In this paper, we will investigate the fluid flow in an evaporating droplet under normal gravity, and compare experiments to theories. Then, we will present our ideas about the experimental measurement of fluid flow in an evaporating droplet under microgravity.
Thermal-Conductivity Apparatus for Steady-State, Comparative Measurement of Ceramic Coatings
Slifka, A. J.
2000-01-01
An apparatus has been developed to measure the thermal conductivity of ceramic coatings. Since the method uses an infrared microscope for temperature measurement, coatings as thin as 20 μm can, in principle, be measured using this technique. This steady-state, comparative measurement method uses the known thermal conductivity of the substrate material as the reference material for heat-flow measurement. The experimental method is validated by measuring a plasma-sprayed coating that has been previously measured using an absolute, steady-state measurement method. The new measurement method has a relative standard uncertainty of about 10 %. The measurement of the plasma-sprayed coating gives 0.58 W·m−1·K−l which compares well with the 0.62 W·m−1·K−l measured using the absolute method. PMID:27551628
Quantum transport in networks and photosynthetic complexes at the steady state.
Manzano, Daniel
2013-01-01
Recently, several works have analysed the efficiency of photosynthetic complexes in a transient scenario and how that efficiency is affected by environmental noise. Here, following a quantum master equation approach, we study the energy and excitation transport in fully connected networks both in general and in the particular case of the Fenna-Matthew-Olson complex. The analysis is carried out for the steady state of the system where the excitation energy is constantly "flowing" through the system. Steady state transport scenarios are particularly relevant if the evolution of the quantum system is not conditioned on the arrival of individual excitations. By adding dephasing to the system, we analyse the possibility of noise-enhancement of the quantum transport.
Thermal-Conductivity Apparatus for Steady-State, Comparative Measurement of Ceramic Coatings.
Slifka, A J
2000-01-01
An apparatus has been developed to measure the thermal conductivity of ceramic coatings. Since the method uses an infrared microscope for temperature measurement, coatings as thin as 20 μm can, in principle, be measured using this technique. This steady-state, comparative measurement method uses the known thermal conductivity of the substrate material as the reference material for heat-flow measurement. The experimental method is validated by measuring a plasma-sprayed coating that has been previously measured using an absolute, steady-state measurement method. The new measurement method has a relative standard uncertainty of about 10 %. The measurement of the plasma-sprayed coating gives 0.58 W·m(-1)·K(-l) which compares well with the 0.62 W·m(-1)·K(-l) measured using the absolute method.
Computation of steady-state probability distributions in stochastic models of cellular networks.
Hallen, Mark; Li, Bochong; Tanouchi, Yu; Tan, Cheemeng; West, Mike; You, Lingchong
2011-10-01
Cellular processes are "noisy". In each cell, concentrations of molecules are subject to random fluctuations due to the small numbers of these molecules and to environmental perturbations. While noise varies with time, it is often measured at steady state, for example by flow cytometry. When interrogating aspects of a cellular network by such steady-state measurements of network components, a key need is to develop efficient methods to simulate and compute these distributions. We describe innovations in stochastic modeling coupled with approaches to this computational challenge: first, an approach to modeling intrinsic noise via solution of the chemical master equation, and second, a convolution technique to account for contributions of extrinsic noise. We show how these techniques can be combined in a streamlined procedure for evaluation of different sources of variability in a biochemical network. Evaluation and illustrations are given in analysis of two well-characterized synthetic gene circuits, as well as a signaling network underlying the mammalian cell cycle entry.
Yuen, Po Ki
2013-05-07
This article presents a simple method for controlling fluid in microfluidic devices without the need for valves or pumps. A fluid conveyance extension is fluidly coupled to the enclosed outlet chamber of a microfluidic device. After a fluid is introduced into the microfluidic device and saturates the fluid conveyance extension, a fluid flow in the microfluidic device is generated by contacting an absorbent microfluidic flow modulator with the fluid conveyance extension to absorb the fluid from the fluid conveyance extension through capillary action. Since the fluid in the microfluidic device is fluidly coupled with the fluid conveyance extension and the fluid conveyance extension is fluidly coupled with the absorbent microfluidic flow modulator, the absorption rate of the absorbent microfluidic flow modulator, which is the rate at which the absorbent microfluidic flow modulator absorbs fluid, matches the fluid flow rate in the microfluidic device. Thus, the fluid flow rate in the microfluidic device is set by the absorption rate of the absorbent microfluidic flow modulator. Sheath flow and fluid switching applications are demonstrated using this simple fluid control method without the need for valves or pumps. Also, the ability to control the fluid flow rate in the microfluidic device is demonstrated using absorbent microfluidic flow modulators with various absorbent characteristics and dimensions.
Messinian Salinity Crisis and basin fluid flow
NASA Astrophysics Data System (ADS)
Bertoni, Claudia; Cartwight, Joe
2014-05-01
Syn- and post-depositional movement of fluids through sediments is one of the least understood aspects in the evolution of a basin. The conventional hydrostratigraphic view on marine sedimentary basins assumes that compactional and meteoric groundwater fluid circulation drives fluid movement and defines its timing. However, in the past few years, several examples of instantaneous and catastrophic release of fluids have been observed even through low-permeability sediments. A particularly complex case-study involves the presence of giant salt bodies in the depocentres of marine basins. Evaporites dramatically change the hydrostratigraphy and fluid-dynamics of the basin, and influence the P/T regimes, e.g. through changes in the geothermal gradient and in the compaction of underlying sediments. Our paper reviews the impact of the Messinian Salinity Crisis (MSC) and evaporites on fluid flow in the Mediterranean sub-basins. The analysis of geological and geophysical sub-surface data provides examples from this basin, and the comparison with analogues in other well-known evaporitic provinces. During the MSC, massive sea-level changes occurred in a relatively limited time interval, and affected the balance of fluid dynamics, e.g. with sudden release or unusual trapping of fluids. Fluid expulsion events are here analysed and classified in relation to the long and short-term effects of the MSC. Our main aim is to build a framework for the correct identification of the fluid flow-related events, and their genetic mechanisms. On basin margins, where evaporites are thin or absent, the sea-level changes associated with the MSC force a rapid basinward shift of the mixing zone of meteoric/gravity flow and saline/compactional flow, 100s-km away from its pre-MSC position. This phenomenon changes the geometry of converging flows, creates hydraulic traps for fluids, and triggers specific diagenetic reactions in pre-MSC deep marine sediments. In basin-centre settings, unloading and
A waved journal bearing concept with improved steady-state and dynamic performance
NASA Technical Reports Server (NTRS)
Dimofte, Florin
1994-01-01
Analysis of the waved journal bearing concept featuring a waved inner bearing diameter for use with a compressible lubricant (gas) is presented. A three wave, waved journal bearing geometry is used to show the geometry of this concept. The performance of generic waved bearings having either three, four, six, or eight waves is predicted for air lubricated bearings. Steady-state performance is discussed in terms of bearing load capacity, while the dynamic performance is discussed in terms of dynamic coefficients and fluid film stability. It was found that the bearing wave amplitude has an important influence on both steady-state and dynamic performance of the waved journal bearing. For a fixed eccentricity ratio, the bearing steady-state load capacity and direct dynamic stiffness coefficient increase as the wave amplitude increases. Also, the waved bearing becomes more stable as the wave amplitude increases. In addition, increasing the number of waves reduces the waved bearing's sensitivity to the direction of the applied load relative to the wave. However, the range in which the bearing performance can be varied decreases as the number of waves increases. Therefore, both the number and the amplitude of the waves must be properly selected to optimize the waved bearing design for a specific application. It is concluded that the stiffness of an air bearing, due to the hydrodynamic effect, could be doubled and made to run stably by using a six or eight wave geometry with a wave amplitude approximately half of the bearing radial clearance.
Steady-State and Transient Boundary Element Methods for Coupled Heat Conduction
NASA Technical Reports Server (NTRS)
Kontinos, Dean A.
1997-01-01
Boundary element algorithms for the solution of steady-state and transient heat conduction are presented. The algorithms are designed for efficient coupling with computational fluid dynamic discretizations and feature piecewise linear elements with offset nodal points. The steady-state algorithm employs the fundamental solution approach; the integration kernels are computed analytically based on linear shape functions, linear elements, and variably offset nodal points. The analytic expressions for both singular and nonsingular integrands are presented. The transient algorithm employs the transient fundamental solution; the temporal integration is performed analytically and the nonsingular spatial integration is performed numerically using Gaussian quadrature. A series solution to the integration is derived for the instance of a singular integrand. The boundary-only character of the algorithm is maintained by integrating the influence coefficients from initial time. Numerical results are compared to analytical solutions to verify the current boundary element algorithms. The steady-state and transient algorithms are numerically shown to be second-order accurate in space and time, respectively.
Method and apparatus for controlling fluid flow
Miller, J.R.
1980-06-27
A method and apparatus for precisely controlling the rate (and hence amount) of fluid flow are given. The controlled flow rate is finely adjustable, can be extremely small (on the order of microliter-atmospheres per second), can be adjusted to zero (flow stopped), and is stable to better than 1% with time. The dead volume of the valve can be made arbitrarily small, in fact essentially zero. The valve employs no wearing mechanical parts (including springs, stems, or seals). The valve is finely adjustable, has a flow rate dynamic range of many decades, can be made compatible with any fluid, and is suitable for incorporation into an open or closed loop servo-control system.
Hsieh, Paul A.
2001-01-01
This report serves as a user?s guide for two computer models: TopoDrive and ParticleFlow. These two-dimensional models are designed to simulate two ground-water processes: topography-driven flow and advective transport of fluid particles. To simulate topography-driven flow, the user may specify the shape of the water table, which bounds the top of the vertical flow section. To simulate transport of fluid particles, the model domain is a rectangle with overall flow from left to right. In both cases, the flow is under steady state, and the distribution of hydraulic conductivity may be specified by the user. The models compute hydraulic head, ground-water flow paths, and the movement of fluid particles. An interactive visual interface enables the user to easily and quickly explore model behavior, and thereby better understand ground-water flow processes. In this regard, TopoDrive and ParticleFlow are not intended to be comprehensive modeling tools, but are designed for modeling at the exploratory or conceptual level, for visual demonstration, and for educational purposes.
Modeling Steady-State Groundwater Flow Using Microcomputer Spreadsheets.
ERIC Educational Resources Information Center
Ousey, John Russell, Jr.
1986-01-01
Describes how microcomputer spreadsheets are easily adapted for use in groundwater modeling. Presents spreadsheet set-ups and the results of five groundwater models. Suggests that this approach can provide a basis for demonstrations, laboratory exercises, and student projects. (ML)
Steady-state flow of solid CO2: preliminary results
Durham, William B.; Kirby, Stephen H.; Stern, Laura A.
1999-01-01
To help answer the question of how much solid CO2 exists in the Martian south polar cap, we performed a series of laboratory triaxial deformation experiments at constant displacement rate in compression on jacketed cylinders of pure, polycrystalline CO2. Test conditions were temperatures 150 −8 ≤ ε ≤4.3×10−4 s−1. Most of the measurements follow a constitutive law of the form ε = Aσnexp(−Q/RT), where σ is the applied differential stress, R is the gas constant, and the other constants have values as follows: A = 103 86 MPa−ns−1, n = 5.6, and Q = 33 kJ/mol. Solid CO2 is markedly weaker than water ice. Our results suggest that the south polar cap on Mars is unlikely to be predominately solid CO2, because the elevation and estimated age of the cap is difficult to reconcile with the very weak rheology of the material.
Modeling Steady-State Groundwater Flow Using Microcomputer Spreadsheets.
ERIC Educational Resources Information Center
Ousey, John Russell, Jr.
1986-01-01
Describes how microcomputer spreadsheets are easily adapted for use in groundwater modeling. Presents spreadsheet set-ups and the results of five groundwater models. Suggests that this approach can provide a basis for demonstrations, laboratory exercises, and student projects. (ML)
Fluid flow along faults in carbonate rocks
NASA Astrophysics Data System (ADS)
Romano, Valentina; Battaglia, Maurizio; Bigi, Sabina
2015-04-01
The study of fluid flow in fractured rocks plays a key role in reservoir management, including CO2 sequestration and waste isolation. We present a mathematical model of fluid flow in a fault zone, based on field data acquired in Majella Mountain, in the Central Apennines (Italy). The Majella is a thrust related, asymmetric, box shaped anticline. The mountain carbonate outcrops are part of a lower Cretaceous-Miocene succession, covered by a siliciclastic sequence of lower Pliocene age. We study a fault zone located in the Bolognano Formation (Oligo-Miocene age) and exposed in the Roman Valley Quarry near the town of Lettomanoppello, in the northern sector of the Majella Mountain. This is one of the best places in the Apennines to investigate a fault zone and has been the subject of numerous field studies. Faults are mechanical and permeability heterogeneities in the upper crust, so they strongly influence fluid flow. The distribution of the main components (core, damage zone) can lead a fault zone to act as a conduit, a barrier or a combined conduit-barrier system. We integrated existing and our own structural surveys of the area to better identify the major fault features (e.g., kind of fractures, statistical properties, geometry and pertrophysical characteristics). Our analytical model describe the Bolognano Formation using a dual porosity/dual permeability model: global flow occurs through the fracture network only, while rock matrix contain the majority of fluid storage and provide fluid drainage to the fractures. Pressure behavior is analyzed by examining the pressure drawdown curves, the derivative plots and the effects of the characteristic parameters. The analytical model has been calibrated against published data on fluid flow and pressure distribution in the Bolognano Formation.
Ascon-Cabrera, M A; Thomas, D; Lebeault, J M
1995-01-01
The maintenance of a steady-state biofilm in a continuous-flow fixed-bed reactor, as a consequence of the reproduction-detachment of cells (an interfacial cell physiology phenomenon of steady-state biofilm) during the biodegradation of 2,4,6-trichlorophenol by Pseudomonas cells, was determined. After cell adhesion on an open-pore glass support, the biofilm was formed in a packed-bed recirculated reactor. After the steady-state biofilm was reached, the mechanisms of the interfacial cell detachment (at the biofilm-liquid interface) were determined. It was established that (i) the hydrophobicity of immobilized sessile cells (parent cells) increased (from 50 to 80%) as the dilution rate increased, while the hydrophobicity of detached suspended cells (daughter cells) remained constant (about 45%); and (ii) the immediately detached suspended cells showed a synchronized growth in about three generations. These results indicate that (i) the immobilized sessile and suspended detached cells grew synchronically at the end and at the beginning of the cell cycle, respectively; and (ii) the hydrophobicity difference of immobilized sessile and suspended detached cells permitted the cells detachment. Therefore, it is probable that independent of shear stress (due to recirculated flow), the synchronized growth and hydrophobicity of cells (which vary during the cell cycle) are the main factors permitting the maintenance of a steady-state xenobiotic-degrading biofilm reactor (in which the overall accumulation of biofilm is determined by the average growth rate of the biofilm cells minus the rate of detachment of cells from the biofilm). PMID:7793923
COMPRESSIBLE FLOW, ENTRAINMENT, AND MEGAPLUME
It is generally believed that low Mach number, i.e., low-velocity, flow may be assumed to be incompressible flow. Under steady-state conditions, an exact equation of continuity may then be used to show that such flow is non-divergent. However, a rigorous, compressible fluid-dynam...
COMPRESSIBLE FLOW, ENTRAINMENT, AND MEGAPLUME
It is generally believed that low Mach number, i.e., low-velocity, flow may be assumed to be incompressible flow. Under steady-state conditions, an exact equation of continuity may then be used to show that such flow is non-divergent. However, a rigorous, compressible fluid-dynam...
Advanced designs for fluid flow visualization
NASA Technical Reports Server (NTRS)
1978-01-01
Research was carried out on existing and new designs for minimally intrusive measurement of flow fields in the Geophysical Fluid Flow Cell and the proposed Atmospheric General Circulation Experiment. The following topics are discussed: (1) identification and removal of foreign particles, (2) search for higher dielectric photochromic solutions, (3) selection of uv light source, (4) analysis of refractive techniques and (5) examination of fresnel lens applicability.
NASA Technical Reports Server (NTRS)
Dimofte, Florin
1993-01-01
Analysis of the waved journal bearing concept featuring a waved inner bearing diameter for use with a compressible lubricant (gas) is presented. The performance of generic waved bearings having either three or four waves is predicted for air lubricated bearings. Steady-state performance is discussed in terms of bearing load capacity, while the dynamic performance is discussed in terms of fluid film stability and dynamic coefficients. It was found that the bearing wave amplitude has an important influence on both the steady-state and the dynamic performance of the waved journal bearing. For a fixed eccentricity ratio, the bearing steady-state load capacity and direct dynamic stiffness coefficient increase as the wave amplitude increases.
NASA Technical Reports Server (NTRS)
Dimofte, Florin
1993-01-01
Analysis of the waved journal bearing concept featuring a waved inner bearing diameter for use with a compressible lubricant (gas) is presented. The performance of generic waved bearings having either three or four waves is predicted for air lubricated bearings. Steady-state performance is discussed in terms of bearing load capacity, while the dynamic performance is discussed in terms of fluid film stability and dynamic coefficients. It was found that the bearing wave amplitude has an important influence on both the steady-state and the dynamic performance of the waved journal bearing. For a fixed eccentricity ratio, the bearing steady-state load capacity and direct dynamic stiffness coefficient increase as the wave amplitude increases.
Heidt, Timo; Courties, Gabriel; Dutta, Partha; Sager, Hendrik B; Sebas, Matt; Iwamoto, Yoshiko; Sun, Yuan; Da Silva, Nicolas; Panizzi, Peter; van der Laan, Anja M; van der Lahn, Anja M; Swirski, Filip K; Weissleder, Ralph; Nahrendorf, Matthias
2014-07-07
Macrophages populate the steady-state myocardium. Previously, all macrophages were thought to arise from monocytes; however, it emerged that, in several organs, tissue-resident macrophages may self-maintain through local proliferation. Our aim was to study the contribution of monocytes to cardiac-resident macrophages in steady state, after macrophage depletion in CD11b(DTR/+) mice and in myocardial infarction. Using in vivo fate mapping and flow cytometry, we estimated that during steady state the heart macrophage population turns over in ≈1 month. To explore the source of cardiac-resident macrophages, we joined the circulation of mice using parabiosis. After 6 weeks, we observed blood monocyte chimerism of 35.3±3.4%, whereas heart macrophages showed a much lower chimerism of 2.7±0.5% (P<0.01). Macrophages self-renewed locally through proliferation: 2.1±0.3% incorporated bromodeoxyuridine 2 hours after a single injection, and 13.7±1.4% heart macrophages stained positive for the cell cycle marker Ki-67. The cells likely participate in defense against infection, because we found them to ingest fluorescently labeled bacteria. In ischemic myocardium, we observed that tissue-resident macrophages died locally, whereas some also migrated to hematopoietic organs. If the steady state was perturbed by coronary ligation or diphtheria toxin-induced macrophage depletion in CD11b(DTR/+) mice, blood monocytes replenished heart macrophages. However, in the chronic phase after myocardial infarction, macrophages residing in the infarct were again independent from the blood monocyte pool, returning to the steady-state situation. In this study, we show differential contribution of monocytes to heart macrophages during steady state, after macrophage depletion or in the acute and chronic phase after myocardial infarction. We found that macrophages participate in the immunosurveillance of myocardial tissue. These data correspond with previous studies on tissue-resident macrophages
NASA Astrophysics Data System (ADS)
Boulin, P. F.; Bretonnier, P.; Gland, N.
2010-12-01
Very low permeability geomaterials (order of nanoDarcy (10-21 m2)), such as clays rocks, are studied for many industrial applications such as production from unconventional reserves of oil and gas, CO2 geological storage and deep geological disposal of high-level long-lived nuclear wastes. For these last two applications, clay efficiency as barrier relies mainly on their very low permeability. Laboratory measurement of low permeability to water (below 10-19 m2) remains a technical challenge. Some authors argue that steady state methods are irrelevant due to the time required to stabilize water fluxes in such low permeability media. Most of the authors measuring low permeabilities use a transient technique called pulse decay. This study aims to compare objectively these different types of permeability tests performed on a single clay sample. For the steady state method, a high precision pump was used to impose a pressure gradient and to measure the small resulting water flow rate at steady state. We show that with a suitable set-up, the steady state method enables to measure a very low permeability of 8 10-22 m2 in a period of three days. For a comparable duration, the pulse decay test, most commonly used for such low permeability measurements, provides only an average estimate of the permeability. Permeability measurements by pulse decay require to perform simulations to interpret the pressure relaxation signals. Many uncertainties remain such as the determination of the reservoirs storage factor, micro leakage effect, or the determination of the initial pulse pressure. All these uncertainties have a very significant impact on the determination of sample permeability and specific storage. Opposite to the wide-spread idea that transient techniques are required to measure very low permeability, we show that direct steady state measurement of water permeability with suitable equipments can be much faster and more accurate than measurement by pulse decay, especially in
NASA Astrophysics Data System (ADS)
Niu, Y.; Yang, J.
2009-05-01
A finite element computer modeling approach, integrated with existing geological, geochemical and geophysical data, was used to address the diagenetic process of dolomitization in Western Canada Sedimentary Basin (WCSB). A 2-D conceptualized model was developed to simulate hydrothermal flow in particular for the packland play type dolomitization in Peace River Arch of WCSB. Our numerical results indicate that faults serve as important pathways for the ascending hydrothermal fluids driven by buoyancy force due to temporal and spatial changes in temperature. Both steady state and transient computations were conducted to reveal suitable hydraulic conditions under which the modeled temperature within the aquifer system is consistent with observed values in the targeted study area. A series of numerical case studies were carried out to investigate key factors controlling hydrothermal fluid flow, including fault penetration depth, width and permeability, and its connectivity with the host rock units.
Steady state volcanism: Evidence from eruption histories of polygenetic volcanoes
Wadge, G.
1982-05-10
Some volcanoes erupt magma at average rates which are constant over periods of many years, even through this magma may appear in a complex series of eruptions. This constancy of output is tested by construction of a curve of cumulative volume of erupted magma, which is linear for steady state volcanism, and whose gradient defines the steady state rate Q/sub s/s. The assumption is made that Q/sub s/s is the rate at which magma is supplied to these polygenetic volcanoes. Five general types of eruptive behavior can be distinguished from the cumulative volume studied. These types are interpreted in terms of a simple model of batches of magma rising buoyantly through the crust and interacting with a small-capacity subvolcanic magma reservoir. Recognition of previous steady state behavior at a volcano may enable the cumulative volume curve to be used empirically as a constraint on the timing and volume of the next eruption. The steady state model thus has a limited predictive capability. With the exception of Kilauea (O/sub s/s = 4m/sup 3/ s/sup -1/) all the identified steady state volcanoes have values of Q/sub s/s of a few tenths of one cubic meter per second. These rates are consistent with the minimum flux rates required by theoretical cooling models of batches of magma traversing the crust. The similarity of these Q/sub s/s values of volcanoes (producing basalt, andesite, and dacite magmas) in very different tectonic settings suggests that the common factors of crustal buoyancy forces and the geotherm-controlled cooling rates control the dynamics of magma supply through the crust. Long-term dormancy at active volcanoes may be a manifestation of the steady accumulation of magma in large crustal reservoirs, a process that complements the intermittent periods of steady state output at the surface. This possibility has several implications, the most important of which is that it provides a constraint on the supply rate of new magma to the bases of plutons.
Simulations of KSTAR high performance steady state operation scenarios
NASA Astrophysics Data System (ADS)
Na, Yong-Su; Kessel, C. E.; Park, J. M.; Yi, Sumin; Becoulet, A.; Sips, A. C. C.; Kim, J. Y.
2009-11-01
We report the results of predictive modelling of high performance steady state operation scenarios in KSTAR. Firstly, the capabilities of steady state operation are investigated with time-dependent simulations using a free-boundary plasma equilibrium evolution code coupled with transport calculations. Secondly, the reproducibility of high performance steady state operation scenarios developed in the DIII-D tokamak, of similar size to that of KSTAR, is investigated using the experimental data taken from DIII-D. Finally, the capability of ITER-relevant steady state operation is investigated in KSTAR. It is found that KSTAR is able to establish high performance steady state operation scenarios; βN above 3, H98(y, 2) up to 2.0, fBS up to 0.76 and fNI equals 1.0. In this work, a realistic density profile is newly introduced for predictive simulations by employing the scaling law of a density peaking factor. The influence of the current ramp-up scenario and the transport model is discussed with respect to the fusion performance and non-inductive current drive fraction in the transport simulations. As observed in the experiments, both the heating and the plasma current waveforms in the current ramp-up phase produce a strong effect on the q-profile, the fusion performance and also on the non-inductive current drive fraction in the current flattop phase. A criterion in terms of qmin is found to establish ITER-relevant steady state operation scenarios. This will provide a guideline for designing the current ramp-up phase in KSTAR. It is observed that the transport model also affects the predictive values of fusion performance as well as the non-inductive current drive fraction. The Weiland transport model predicts the highest fusion performance as well as non-inductive current drive fraction in KSTAR. In contrast, the GLF23 model exhibits the lowest ones. ITER-relevant advanced scenarios cannot be obtained with the GLF23 model in the conditions given in this work. Finally
Simulations of KSTAR high performance steady state operation scenarios
Na, Y S; Kessel, C. E.; Park, Jin Myung; Yi, Sumin; Becoulet, A.; Sips, A C C; Kim, J Y
2009-01-01
We report the results of predictive modelling of high performance steady state operation scenarios in KSTAR. Firstly, the capabilities of steady state operation are investigated with time-dependent simulations using a free-boundary plasma equilibrium evolution code coupled with transport calculations. Secondly, the reproducibility of high performance steady state operation scenarios developed in the DIII-D tokamak, of similar size to that of KSTAR, is investigated using the experimental data taken from DIII-D. Finally, the capability of ITER-relevant steady state operation is investigated in KSTAR. It is found that KSTAR is able to establish high performance steady state operation scenarios; beta(N) above 3, H-98(y, 2) up to 2.0, f(BS) up to 0.76 and f(NI) equals 1.0. In this work, a realistic density profile is newly introduced for predictive simulations by employing the scaling law of a density peaking factor. The influence of the current ramp-up scenario and the transport model is discussed with respect to the fusion performance and non-inductive current drive fraction in the transport simulations. As observed in the experiments, both the heating and the plasma current waveforms in the current ramp-up phase produce a strong effect on the q-profile, the fusion performance and also on the non-inductive current drive fraction in the current flattop phase. A criterion in terms of q(min) is found to establish ITER-relevant steady state operation scenarios. This will provide a guideline for designing the current ramp-up phase in KSTAR. It is observed that the transport model also affects the predictive values of fusion performance as well as the non-inductive current drive fraction. The Weiland transport model predicts the highest fusion performance as well as non-inductive current drive fraction in KSTAR. In contrast, the GLF23 model exhibits the lowest ones. ITER-relevant advanced scenarios cannot be obtained with the GLF23 model in the conditions given in this work
The Geophysical Fluid Flow Cell Experiment
NASA Technical Reports Server (NTRS)
Hart, J. E.; Ohlsen, D.; Kittleman, S.; Borhani, N.; Leslie, F.; Miller, T.
1999-01-01
The Geophysical Fluid Flow Cell (GFFC) experiment performed visualizations of thermal convection in a rotating differentially heated spherical shell of fluid. In these experiments dielectric polarization forces are used to generate a radially directed buoyancy force. This enables the laboratory simulation of a number of geophysically and astrophysically important situations in which sphericity and rotation both impose strong constraints on global scale fluid motions. During USML-2 a large set of experiments with spherically symmetric heating were carried out. These enabled the determination of critical points for the transition to various forms of nonaxisymmetric convection and, for highly turbulent flows, the transition latitudes separating the different modes of motion. This paper presents a first analysis of these experiments as well as data on the general performance of the instrument during the USML-2 flight.
Resistance to fluid flow in veins.
Scott, D A; Fox, J A; Cnaan, A; Philip, B K; Lind, L J; Palleiko, M A; Stelling, J M; Philip, J H
1996-07-01
We evaluated the resistance to fluid infusion in the veins of 118 adult patients after intravenous catheter insertion prior to elective surgery. Hydraulic resistance in veins was defined as the slope of the pressure-flow relationship obtained by measuring venous pressure at several fluid flow rates. A resistance unit (RU) was defined as 1 mmHg/L/hr. Resistance in veins ranged from -12.1 to 732 RU, with 50th and 95th percentiles being 22 and 198 RU, respectively. Venous resistance was not significantly affected by site of catheter insertion, tissue characteristics at the insertion site, age, sex, patient anxiety, American Society of Anesthesiologists physical status, or catheter size. This report provides a distribution of resistance to fluid infusion in arm veins of adult patients.
Finite scale equations for compressible fluid flow
Margolin, Len G
2008-01-01
Finite-scale equations (FSE) describe the evolution of finite volumes of fluid over time. We discuss the FSE for a one-dimensional compressible fluid, whose every point is governed by the Navier-Stokes equations. The FSE contain new momentum and internal energy transport terms. These are similar to terms added in numerical simulation for high-speed flows (e.g. artificial viscosity) and for turbulent flows (e.g. subgrid scale models). These similarities suggest that the FSE may provide new insight as a basis for computational fluid dynamics. Our analysis of the FS continuity equation leads to a physical interpretation of the new transport terms, and indicates the need to carefully distinguish between volume-averaged and mass-averaged velocities in numerical simulation. We make preliminary connections to the other recent work reformulating Navier-Stokes equations.
NASA Astrophysics Data System (ADS)
Gao, Xin; Narteau, Clément; Rozier, Olivier
2015-10-01
We investigate the development and steady states of transverse dunes for ranges of flow depths and velocities using a cellular automaton dune model. Subsequent to the initial bed instability, dune pattern coarsening is driven by bed form interactions. Collisions lead to two types of coalescence associated with upstream or downstream dominant dunes. In addition, a single collision-ejection mechanism enhances the exchange of mass between two adjacent bed forms (throughpassing dunes). The power law increases in wavelength and amplitude exhibit the same exponents, which are independent of flow properties. Contrary to the wavelength, dune height is limited not only by flow depth but also by the strength of the flow. Superimposed bed forms may propagate and continuously destabilize the largest dunes. We identify three classes of steady state transverse dune fields according to the periodicity in crest-to-crest spacing and the mechanism of size limitation. In all cases, the steady state is reached and maintained through the dynamic equilibrium between flow strength and dune aspect ratio. In the limit of low flow strength, where it becomes the primary factor of size limitation, the bed shear stress in the dune trough regions is close to its critical value for motion inception. Comparisons with natural dune fields suggest that many of them may have reached a steady state. Finally, we infer that the sedimentary patterns in the model may be used to bring new constraints on the development of modern and ancient dune fields.
Kudo, Kohsuke; Harada, Taisuke; Kameda, Hiroyuki; Uwano, Ikuko; Yamashita, Fumio; Higuchi, Satomi; Yoshioka, Kunihiro; Sasaki, Makoto
2017-08-31
Few studies have been reported for T2 -weighted indirect (17) O imaging. To evaluate the feasibility of steady-state sequences for indirect (17) O brain imaging. Signal simulation, phantom measurements, and prospective animal experiments were performed in accordance with the institutional guidelines for animal experiments. Signal simulations of balanced steady-state free precession (bSSFP) were performed for concentrations of (17) O ranging from 0.037-1.600%. Phantom measurements with concentrations of (17) O water ranging from 0.037-1.566% were also conducted. Six healthy beagle dogs were scanned with intravenous administration of 20% (17) O-labeled water (1 mL/kg). Dynamic 3D-bSSFP scans were performed at 3T MRI. (17) O-labeled water was injected 60 seconds after the scan start, and the total scan duration was 5 minutes. Based on the result of signal simulation and phantom measurement, signal changes in the beagle dogs were measured and converted into (17) O concentrations. The (17) O concentrations were averaged for every 15 seconds, and compared to the baseline (30-45 sec) with Dunnett's multiple comparison tests. Signal simulation revealed that the relationships between (17) O concentration and the natural logarithm of relative signals were linear. The intraclass correlation coefficient between relative signals in phantom measurement and signal simulations was 0.974. In the animal experiments, significant increases in (17) O concentration (P < 0.05) were observed 60 seconds after the injection of (17) O. At the end of scanning, mean respective (17) O concentrations of 0.084 ± 0.026%, 0.117 ± 0.038, 0.082 ± 0.037%, and 0.049 ± 0.004% were noted for the cerebral cortex, cerebellar cortex, cerebral white matter, and ventricle. Dynamic steady-state sequences were feasible for indirect (17) O imaging, and absolute quantification was possible. This method can be applied for the measurement of permeability and blood flow in the brain, and for
14 CFR 23.1095 - Carburetor deicing fluid flow rate.
Code of Federal Regulations, 2010 CFR
2010-01-01
... 14 Aeronautics and Space 1 2010-01-01 2010-01-01 false Carburetor deicing fluid flow rate. 23.1095... Induction System § 23.1095 Carburetor deicing fluid flow rate. (a) If a carburetor deicing fluid system is used, it must be able to simultaneously supply each engine with a rate of fluid flow, expressed...
14 CFR 23.1095 - Carburetor deicing fluid flow rate.
Code of Federal Regulations, 2013 CFR
2013-01-01
... 14 Aeronautics and Space 1 2013-01-01 2013-01-01 false Carburetor deicing fluid flow rate. 23.1095... Induction System § 23.1095 Carburetor deicing fluid flow rate. (a) If a carburetor deicing fluid system is used, it must be able to simultaneously supply each engine with a rate of fluid flow, expressed in...
14 CFR 23.1095 - Carburetor deicing fluid flow rate.
Code of Federal Regulations, 2012 CFR
2012-01-01
... 14 Aeronautics and Space 1 2012-01-01 2012-01-01 false Carburetor deicing fluid flow rate. 23.1095... Induction System § 23.1095 Carburetor deicing fluid flow rate. (a) If a carburetor deicing fluid system is used, it must be able to simultaneously supply each engine with a rate of fluid flow, expressed in...
14 CFR 23.1095 - Carburetor deicing fluid flow rate.
Code of Federal Regulations, 2011 CFR
2011-01-01
... 14 Aeronautics and Space 1 2011-01-01 2011-01-01 false Carburetor deicing fluid flow rate. 23.1095... Induction System § 23.1095 Carburetor deicing fluid flow rate. (a) If a carburetor deicing fluid system is used, it must be able to simultaneously supply each engine with a rate of fluid flow, expressed in...
Enhanced fluid flow through nanoscale carbon pipes.
Whitby, Max; Cagnon, Laurent; Thanou, Maya; Quirke, Nick
2008-09-01
Recent experimental and theoretical studies demonstrate that pressure driven flow of fluids through nanoscale ( d < 10 nm) carbon pores occurs 4 to 5 orders of magnitude faster than predicted by extrapolation from conventional theory. Here, we report experimental results for flow of water, ethanol, and decane through carbon nanopipes with larger inner diameters (43 +/- 3 nm) than previously investigated. We find enhanced transport up to 45 times theoretical predictions. In contrast to previous work, in our systems, decane flows faster than water. These nanopipes were composed of amorphous carbon deposited from ethylene vapor in alumina templates using a single step fabrication process.
Viscoelastic shear wave at thermal steady state in gelatin
NASA Astrophysics Data System (ADS)
Chang, Sheng-Yi; Ho, Chien-Wa; Hsieh, Tong-Sheng; Yu, Li-Ping; Chou, Chien
2013-02-01
Viscoelastic shear waves (VESW) propagation in soft matters such as gelatin under thermal steady state was studied. VESW in a slab of gelatin causes the transverse displacement of the surface in a harmonic wave. The harmonic oscillation frequency of the transverse displacement of gelatin surface was then measured in real time in order to measure the modulus of rigidity of gelatin in terms of the measured oscillation frequency. A polarized heterodyne interferometer (PHI) was setup in this experiment which enables to precisely measure the transverse displacement of surface in real time at 0.3 nm resolution. This results in the proposed VESW method able to characterize gelatin soft material in real time. From the experimental demonstration, the properties of VESW propagation in soft material at thermal steady state potentially can become a novel nano-scale non-intrusion strain-stress sensor able to characterize the modulus rigidity of soft material.
Non-equilibrium steady states in supramolecular polymerization
NASA Astrophysics Data System (ADS)
Sorrenti, Alessandro; Leira-Iglesias, Jorge; Sato, Akihiro; Hermans, Thomas M.
2017-06-01
Living systems use fuel-driven supramolecular polymers such as actin to control important cell functions. Fuel molecules like ATP are used to control when and where such polymers should assemble and disassemble. The cell supplies fresh ATP to the cytosol and removes waste products to sustain steady states. Artificial fuel-driven polymers have been developed recently, but keeping them in sustained non-equilibrium steady states (NESS) has proven challenging. Here we show a supramolecular polymer that can be kept in NESS, inside a membrane reactor where ATP is added and waste removed continuously. Assembly and disassembly of our polymer is regulated by phosphorylation and dephosphorylation, respectively. Waste products lead to inhibition, causing the reaction cycle to stop. Inside the membrane reactor, however, waste can be removed leading to long-lived NESS conditions. We anticipate that our approach to obtain NESS can be applied to other stimuli-responsive materials to achieve more life-like behaviour.
Task-specific stability of multifinger steady-state action.
Reschechtko, Sasha; Zatsiorsky, Vladimir M; Latash, Mark L
2015-01-01
The authors explored task-specific stability during accurate multifinger force production tasks with different numbers of instructed fingers. Subjects performed steady-state isometric force production tasks and were instructed not to interfere voluntarily with transient lifting-and-lowering perturbations applied to the index finger. The main results were (a) intertrial variance in the space of finger modes at steady states was larger within the subspace that had no effect on the total force (the uncontrolled manifold [UCM]); (b) perturbations caused large deviations of finger modes within the UCM (motor equivalence); and (c) deviations caused by the perturbation showed larger variance within the UCM. No significant effects of the number of task fingers were noted in any of the 3 indicators. The results are discussed within the frameworks of the UCM and referent configuration hypotheses. The authors conclude, in particular, that all the tasks were effectively 4-finger tasks with different involvement of task and nontask fingers.
Multiplying steady-state culture in multi-reactor system.
Erm, Sten; Adamberg, Kaarel; Vilu, Raivo
2014-11-01
Cultivation of microorganisms in batch experiments is fast and economical but the conditions therein change constantly, rendering quantitative data interpretation difficult. By using chemostat with controlled environmental conditions the physiological state of microorganisms is fixed; however, the unavoidable stabilization phase makes continuous methods resource consuming. Material can be spared by using micro scale devices, which however have limited analysis and process control capabilities. Described herein are a method and a system combining the high throughput of batch with the controlled environment of continuous cultivations. Microorganisms were prepared in one bioreactor followed by culture distribution into a network of bioreactors and continuation of independent steady state experiments therein. Accelerostat cultivation with statistical analysis of growth parameters demonstrated non-compromised physiological state following distribution, thus the method effectively multiplied steady state culture of microorganisms. The theoretical efficiency of the system was evaluated in inhibitory compound analysis using repeated chemostat to chemostat transfers.
Extending Molecular Theory to Steady-State Diffusing Systems
FRINK,LAURA J. D.; SALINGER,ANDREW G.; THOMPSON,AIDAN P.
1999-10-22
Predicting the properties of nonequilibrium systems from molecular simulations is a growing area of interest. One important class of problems involves steady state diffusion. To study these cases, a grand canonical molecular dynamics approach has been developed by Heffelfinger and van Swol [J. Chem. Phys., 101, 5274 (1994)]. With this method, the flux of particles, the chemical potential gradients, and density gradients can all be measured in the simulation. In this paper, we present a complementary approach that couples a nonlocal density functional theory (DFT) with a transport equation describing steady-state flux of the particles. We compare transport-DFT predictions to GCMD results for a variety of ideal (color diffusion), and nonideal (uphill diffusion and convective transport) systems. In all cases excellent agreement between transport-DFT and GCMD calculations is obtained with diffusion coefficients that are invariant with respect to density and external fields.
A non-inductively driven steady state tokamak reactor
Fenstermacher, M.E.; Devoto, R.S.; Bulmer, R.H.; Lee, J.D.; Miller, J.R.; Schultz, J.
1988-09-20
The physics and engineering guidelines for the ITER device are shown to lead to viable and attractive operating points for a steady state tokamak power reactor. Non-inductive current drive is provided in steady state by high energy neutral beam injection in the plasma core, lower hybrid slow waves in the outer regions of the plasma and bootstrap current. Plasma gain Q (/equivalent to/fusion power/input power) in excess of 20 and average neutron wall loading,
Optimal Control of Transitions between Nonequilibrium Steady States
Zulkowski, Patrick R.; Sivak, David A.; DeWeese, Michael R.
2013-01-01
Biological systems fundamentally exist out of equilibrium in order to preserve organized structures and processes. Many changing cellular conditions can be represented as transitions between nonequilibrium steady states, and organisms have an interest in optimizing such transitions. Using the Hatano-Sasa Y-value, we extend a recently developed geometrical framework for determining optimal protocols so that it can be applied to systems driven from nonequilibrium steady states. We calculate and numerically verify optimal protocols for a colloidal particle dragged through solution by a translating optical trap with two controllable parameters. We offer experimental predictions, specifically that optimal protocols are significantly less costly than naive ones. Optimal protocols similar to these may ultimately point to design principles for biological energy transduction systems and guide the design of artificial molecular machines. PMID:24386112
Turnover of messenger RNA: Polysome statistics beyond the steady state
NASA Astrophysics Data System (ADS)
Valleriani, A.; Ignatova, Z.; Nagar, A.; Lipowsky, R.
2010-03-01
The interplay between turnover or degradation and ribosome loading of messenger RNA (mRNA) is studied theoretically using a stochastic model that is motivated by recent experimental results. Random mRNA degradation affects the statistics of polysomes, i.e., the statistics of the number of ribosomes per mRNA as extracted from cells. Since ribosome loading of newly created mRNA chains requires some time to reach steady state, a fraction of the extracted mRNA/ribosome complexes does not represent steady state conditions. As a consequence, the mean ribosome density obtained from the extracted complexes is found to be inversely proportional to the mRNA length. On the other hand, the ribosome density profile shows an exponential decrease along the mRNA for prokaryotes and becomes uniform in eukaryotic cells.
Granular Material Flows with Interstitial Fluid Effects
NASA Technical Reports Server (NTRS)
Hunt, Melany L.; Brennen, Christopher E.
2004-01-01
The research focused on experimental measurements of the rheological properties of liquid-solid and granular flows. In these flows, the viscous effects of the interstitial fluid, the inertia of the fluid and particles, and the collisional interactions of the particles may all contribute to the flow mechanics. These multiphase flows include industrial problems such as coal slurry pipelines, hydraulic fracturing processes, fluidized beds, mining and milling operation, abrasive water jet machining, and polishing and surface erosion technologies. In addition, there are a wide range of geophysical flows such as debris flows, landslides and sediment transport. In extraterrestrial applications, the study of transport of particulate materials is fundamental to the mining and processing of lunar and Martian soils and the transport of atmospheric dust (National Research Council 2000). The recent images from Mars Global Surveyor spacecraft dramatically depict the complex sand and dust flows on Mars, including dune formation and dust avalanches on the slip-face of dune surfaces. These Aeolian features involve a complex interaction of the prevailing winds and deposition or erosion of the sediment layer; these features make a good test bed for the verification of global circulation models of the Martian atmosphere.
A Series RCL Circuit Theory for Analyzing Non-Steady-State Water Uptake of Maize Plants
NASA Astrophysics Data System (ADS)
Zhuang, Jie; Yu, Gui-Rui; Nakayama, Keiichi
2014-10-01
Understanding water uptake and transport through the soil-plant continuum is vital for ecosystem management and agricultural water use. Plant water uptake under natural conditions is a non-steady transient flow controlled by root distribution, plant configuration, soil hydraulics, and climatic conditions. Despite significant progress in model development, a mechanistic description of transient water uptake has not been developed or remains incomplete. Here, based on advanced electrical network theory (RLC circuit theory), we developed a non-steady state biophysical model to mechanistically analyze the fluctuations of uptake rates in response to water stress. We found that the non-steady-state model captures the nature of instantaneity and hysteresis of plant water uptake due to the considerations of water storage in plant xylem and coarse roots (capacitance effect), hydraulic architecture of leaf system (inductance effect), and soil-root contact (fuse effect). The model provides insights into the important role of plant configuration and hydraulic heterogeneity in helping plants survive an adverse environment. Our tests against field data suggest that the non-steady-state model has great potential for being used to interpret the smart water strategy of plants, which is intrinsically determined by stem size, leaf size/thickness and distribution, root system architecture, and the ratio of fine-to-coarse root lengths.
A Series RCL Circuit Theory for Analyzing Non-Steady-State Water Uptake of Maize Plants
Zhuang, Jie; Yu, Gui-Rui; Nakayama, Keiichi
2014-01-01
Understanding water uptake and transport through the soil-plant continuum is vital for ecosystem management and agricultural water use. Plant water uptake under natural conditions is a non-steady transient flow controlled by root distribution, plant configuration, soil hydraulics, and climatic conditions. Despite significant progress in model development, a mechanistic description of transient water uptake has not been developed or remains incomplete. Here, based on advanced electrical network theory (RLC circuit theory), we developed a non-steady state biophysical model to mechanistically analyze the fluctuations of uptake rates in response to water stress. We found that the non-steady-state model captures the nature of instantaneity and hysteresis of plant water uptake due to the considerations of water storage in plant xylem and coarse roots (capacitance effect), hydraulic architecture of leaf system (inductance effect), and soil-root contact (fuse effect). The model provides insights into the important role of plant configuration and hydraulic heterogeneity in helping plants survive an adverse environment. Our tests against field data suggest that the non-steady-state model has great potential for being used to interpret the smart water strategy of plants, which is intrinsically determined by stem size, leaf size/thickness and distribution, root system architecture, and the ratio of fine-to-coarse root lengths. PMID:25335512
A series RCL circuit theory for analyzing non-steady-state water uptake of maize plants.
Zhuang, Jie; Yu, Gui-Rui; Nakayama, Keiichi
2014-10-22
Understanding water uptake and transport through the soil-plant continuum is vital for ecosystem management and agricultural water use. Plant water uptake under natural conditions is a non-steady transient flow controlled by root distribution, plant configuration, soil hydraulics, and climatic conditions. Despite significant progress in model development, a mechanistic description of transient water uptake has not been developed or remains incomplete. Here, based on advanced electrical network theory (RLC circuit theory), we developed a non-steady state biophysical model to mechanistically analyze the fluctuations of uptake rates in response to water stress. We found that the non-steady-state model captures the nature of instantaneity and hysteresis of plant water uptake due to the considerations of water storage in plant xylem and coarse roots (capacitance effect), hydraulic architecture of leaf system (inductance effect), and soil-root contact (fuse effect). The model provides insights into the important role of plant configuration and hydraulic heterogeneity in helping plants survive an adverse environment. Our tests against field data suggest that the non-steady-state model has great potential for being used to interpret the smart water strategy of plants, which is intrinsically determined by stem size, leaf size/thickness and distribution, root system architecture, and the ratio of fine-to-coarse root lengths.