Showing papers on "Velocity gradient published in 2014"
TL;DR: The Global Strain Rate Model (GSRM v.2.1) as mentioned in this paper is a new global model of plate motions and strain rates in plate boundary zones constrained by horizontal geodetic velocities.
Abstract: We present a new global model of plate motions and strain rates in plate boundary zones constrained by horizontal geodetic velocities. This Global Strain Rate Model (GSRM v.2.1) is a vast improvement over its predecessor both in terms of amount of data input as in an increase in spatial model resolution by factor of ∼2.5 in areas with dense data coverage. We determined 6739 velocities from time series of (mostly) continuous GPS measurements; i.e., by far the largest global velocity solution to date. We transformed 15,772 velocities from 233 (mostly) published studies onto our core solution to obtain 22,511 velocities in the same reference frame. Care is taken to not use velocities from stations (or time periods) that are affected by transient phenomena; i.e., this data set consists of velocities best representing the interseismic plate velocity. About 14% of the Earth is allowed to deform in 145,086 deforming grid cells (0.25° longitude by 0.2° latitude in dimension). The remainder of the Earth's surface is modeled as rigid spherical caps representing 50 tectonic plates. For 36 plates we present new GPS-derived angular velocities. For all the plates that can be compared with the most recent geologic plate motion model, we find that the difference in angular velocity is significant. The rigid-body rotations are used as boundary conditions in the strain rate calculations. The strain rate field is modeled using the Haines and Holt method, which uses splines to obtain an self-consistent interpolated velocity gradient tensor field, from which strain rates, vorticity rates, and expected velocities are derived. We also present expected faulting orientations in areas with significant vorticity, and update the no-net rotation reference frame associated with our global velocity gradient field. Finally, we present a global map of recurrence times for Mw=7.5 characteristic earthquakes.
608 citations
TL;DR: In this paper, the effects of power-law viscosity on temperature field are taken into account by assuming that the temperature field is similar to the velocity field and that the thermal conductivity of the non-Newtonian fluids is powerlaw-dependent on the velocity gradient.
169 citations
TL;DR: In this paper, the authors compared single-phase and two-phase models to predict convective heat transfer coefficient and friction factor at the entry region of uniformly heated pipe, and found that the simulation results showed that the Eulerian-Eulerian model can reduce the computational cost by up to 50% in terms of accuracy and computational cost.
147 citations
TL;DR: In this article, an analytical model for predicting the vertical distribution of mean streamwise velocity in an open channel with double-layered rigid vegetation is proposed, and good agreement between the analytical predictions and experimental data demonstrated the validity of the model.
78 citations
TL;DR: It is discovered that the directed large-scale cell flow altered fluctuations in cellular motion at short length scales: vorticity maps showed a reduced frequency of swirl formation in channel flow compared with resting sheets of equal cell density.
67 citations
TL;DR: In this paper, the impact of the pressure Hessian as well as viscous diffusion on the statistics of the velocity gradient tensor in the framework of an exact statistical evolution equation is studied.
Abstract: Understanding the non-local pressure contributions and viscous effects on the small-scale statistics remains one of the central challenges in the study of homogeneous isotropic turbulence. Here we address this issue by studying the impact of the pressure Hessian as well as viscous diffusion on the statistics of the velocity gradient tensor in the framework of an exact statistical evolution equation. This evolution equation shares similarities with earlier phenomenological models for the Lagrangian velocity gradient tensor evolution, yet constitutes the starting point for a systematic study of the unclosed pressure Hessian and viscous diffusion terms. Based on the assumption of incompressible Gaussian velocity fields, closed expressions are obtained as the results of an evaluation of the characteristic functionals. The benefits and shortcomings of this Gaussian closure are discussed, and a generalization is proposed based on results from direct numerical simulations. This enhanced Gaussian closure yields, for example, insights on how the pressure Hessian prevents the finite-time singularity induced by the local self-amplification and how its interaction with viscous effects leads to the characteristic strain skewness phenomenon.
66 citations
TL;DR: In this paper, the first and second-order spatial derivatives of velocity and pressure for turbulent channel flow at Re τ = 590 were extracted from a high-resolution direct numerical simulation and compared with the theoretical values for isotropic turbulence.
Abstract: Statistical profiles of the first- and second-order spatial derivatives of velocity and pressure are reported for turbulent channel flow at Re τ = 590. The statistics were extracted from a high-resolution direct numerical simulation. To quantify the anisotropic behavior of fine-scale structures, the variances of the derivatives are compared with the theoretical values for isotropic turbulence. It is shown that appropriate combinations of first- and second-order velocity derivatives lead to (directional) viscous length scales without explicit occurrence of the viscosity in the definitions. To quantify the non-Gaussian and intermittent behavior of fine-scale structures, higher-order moments and probability density functions of spatial derivatives are reported. Absolute skewnesses and flatnesses of several spatial derivatives display high peaks in the near wall region. In the logarithmic and central regions of the channel flow, all first-order derivatives appear to be significantly more intermittent than in isotropic turbulence at the same Taylor Reynolds number. Since the nine variances of first-order velocity derivatives are the distinct elements of the turbulence dissipation, the budgets of these nine variances are shown, together with the budget of the turbulence dissipation. The comparison of the budgets in the near-wall region indicates that the normal derivative of the fluctuating streamwise velocity (∂u ′/∂y) plays a more important role than other components of the fluctuating velocity gradient. The small-scale generation term formed by triple correlations of fluctuations of first-order velocity derivatives is analyzed. A typical mechanism of small-scale generation near the wall (around y + = 1), the intensification of positive ∂u ′/∂y by local strain fluctuation (compression in normal and stretching in spanwise direction), is illustrated and discussed.
65 citations
TL;DR: In this paper, the bottom of the cathode channel was fabricated in a wave shape to increase the velocity gradient of the flow from the gas diffusion layers to the catalyst layers, and the fuel cell's performance was improved by 5.76% in the experiment using a 25 cm 2 unit-cell and by approximately 5.17% in numerical analysis using a 84cm 2 unitcell.
63 citations
TL;DR: In this article, an extensive set of nonlinear gyrokinetic simulations are performed based on the experimental discharges, investigating the physical mechanism behind the observations, and the impact on the ion heat flux of various parameters that differ within the data-set are explored.
Abstract: Recent experimental observations at JET show evidence of reduced ion temperature profile stiffness. An extensive set of nonlinear gyrokinetic simulations are performed based on the experimental discharges, investigating the physical mechanism behind the observations. The impact on the ion heat flux of various parameters that differ within the data-set are explored. These parameters include the safety factor, magnetic shear, toroidal flow shear, effect of rotation on the magnetohydrodynamic equilibrium, R/L-n, beta(e), Z(eff), T-e/T-i, and the fast-particle content. While previously hypothesized to be an important factor in the stiffness reduction, the combined effect of toroidal flow shear and low magnetic shear is not predicted by the simulations to lead to a significant reduction in ion heat flux, due both to an insufficient magnitude of flow shear and significant parallel velocity gradient destabilization. It is however found that nonlinear electromagnetic effects due to both thermal and fast-particle pressure gradients, even at low beta(e), can significantly reduce the ion heat flux, and is a key factor in explaining the experimental observations. A total of four discharges are examined, at both inner and outer radii. For all cases studied, the simulated and experimental ion heat flux values agree within reasonable variations of input parameters around the experimental uncertainties.
52 citations
TL;DR: In this paper, the impact of the pressure Hessian as well as viscous diffusion on the statistics of the velocity gradient tensor in the framework of an exact statistical evolution equation is studied.
Abstract: Understanding the non-local pressure contributions and viscous effects on the small-scale statistics remains one of the central challenges in the study of homogeneous isotropic turbulence. Here we address this issue by studying the impact of the pressure Hessian as well as viscous diffusion on the statistics of the velocity gradient tensor in the framework of an exact statistical evolution equation. This evolution equation shares similarities with earlier phenomenological models for the Lagrangian velocity gradient tensor evolution, yet constitutes the starting point for a systematic study of the unclosed pressure Hessian and viscous diffusion terms. Based on the assumption of incompressible Gaussian velocity fields, closed expressions are obtained as the results of an evaluation of the characteristic functionals. The benefits and shortcomings of this Gaussian closure are discussed, and a generalization is proposed based on results from direct numerical simulations. This enhanced Gaussian closure yields, for example, insights on how the pressure Hessian prevents the finite-time singularity induced by the local self-amplification and how its interaction with viscous effects leads to the characteristic strain skewness phenomenon.
51 citations
TL;DR: The importance of a fully tensorial description of the stress and of the inclusion of (coarse-grained) convection in the model is investigated; scalar and tensorial models yield similar results, while convection enhances fluctuations and breaks the spurious symmetry between the flow and velocity gradient directions.
Abstract: We study the two-dimensional (2D) shear flow of amorphous solids within variants of an elastoplastic model, paying particular attention to spatial correlations and time fluctuations of, e.g., local stresses. The model is based on the local alternation between an elastic regime and plastic events during which the local stress is redistributed. The importance of a fully tensorial description of the stress and of the inclusion of (coarse-grained) convection in the model is investigated; scalar and tensorial models yield similar results, while convection enhances fluctuations and breaks the spurious symmetry between the flow and velocity gradient directions, for instance when shear localisation is observed. Besides, correlation lengths measured with diverse protocols are discussed. One class of such correlation lengths simply scale with the spacing between homogeneously distributed, simultaneous plastic events. This leads to a scaling of the correlation length with the shear rate as −1/2 in 2D in the athermal regime, regardless of the details of the model. The radius of the cooperative disk, defined as the near-field region in which plastic events induce a stress redistribution that is not amenable to a mean-field treatment, notably follows this scaling. On the other hand, the cooperative volume measured from the four-point stress susceptibility and its dependence on the system size and the shear rate are model-dependent.
TL;DR: In this paper, a computational fluid dynamics (CFD) model that characterizes gas mixing in anaerobic digesters was developed, where four gas mixing designs were studied: (1) unconfined mixing by two bottom diffusers, (2) confined mixing by one draft tube, (3) un confining mixing with two cover mounted lances, and (4) confining with two bubble guns.
TL;DR: The TRT is as effective in removing the boundary slip as the MRT and the drag coefficient, the wake length, and the separation points calculated by the present IB-LBM agree well with previous studies at Re = 10, 20, and 40.
Abstract: In the present paper, we verify the effectiveness of the two-relaxation-time (TRT) collision operator in reducing boundary slip computed by the immersed boundary--lattice Boltzmann method (IB-LBM). In the linear collision operator of the TRT, we decompose the distribution function into symmetric and antisymmetric components and define the relaxation parameters for each part. The Chapman-Enskog expansion indicates that one relaxation time for the symmetric component is related to the kinematic viscosity. Rigorous analysis of the symmetric shear flows reveals that the relaxation time for the antisymmetric part controls the velocity gradient, the boundary velocity, and the boundary slip velocity computed by the IB-LBM. Simulation of the symmetric shear flows, the symmetric Poiseuille flows, and the cylindrical Couette flows indicates that the profiles of the numerical velocity calculated by the TRT collision operator under the IB-LBM framework exactly agree with those of the multirelaxation time (MRT). The TRT is as effective in removing the boundary slip as the MRT. We demonstrate analytically and numerically that the error of the boundary velocity is caused by the smoothing technique using the $\ensuremath{\delta}$ function used in the interpolation method. In the simulation of the flow past a circular cylinder, the IB-LBM based on the implicit correction method with the TRT succeeds in preventing the flow penetration through the solid surface as well as unphysical velocity distortion. The drag coefficient, the wake length, and the separation points calculated by the present IB-LBM agree well with previous studies at Re = 10, 20, and 40.
TL;DR: In this article, the spectral and polarization properties of photospheric emissions from stratified jets were explored. And the authors found that the presence of the lateral structure within the jet leads to the nonthermal feature of the spectra and significant polarization signal in the resulting emission, and that deviation from thermal spectra, as well as the polarization degree, tends to be enhanced as the velocity gradient in the shear region increases.
Abstract: We explore the spectral and polarization properties of photospheric emissions from stratified jets in which multiple components, separated by sharp velocity shear regions, are distributed in lateral directions. Propagation of thermal photons injected at a high optical depth region are calculated until they escape from the photosphere. It is found that the presence of the lateral structure within the jet leads to the nonthermal feature of the spectra and significant polarization signal in the resulting emission. The deviation from thermal spectra, as well as the polarization degree, tends to be enhanced as the velocity gradient in the shear region increases. In particular, we show that emissions from multicomponent jet can reproduce the typical observed spectra of gamma-ray bursts irrespective of the position of the observer when a velocity shear region is closely spaced in various lateral (θ) positions. The degree of polarization associated with the emission is significant (>few percent) at a wide range of observer angles and can be higher than 30%.
TL;DR: In this paper, the authors investigated the degree-one velocity structure in the inner core of the central Pacific and found that the velocity gradient and attenuation in the lowermost 200 km of the outer core (F region) are correlated with the average mantle attenuation.
TL;DR: In this paper, the authors proposed the use of the gradient of the velocity profile from 0 to 30 m depth, denoted by B30, to improve the site effect assessment.
Abstract: Site effects may be assessed using a standard soil classification parameter, VS30 (the harmonic average shear-wave velocity in the first 30 m); however, this index does not account for the complexity of the velocity profile, especially its variability at depth. In the present study, in addition to VS30, we propose consideration of the gradient of the VS profile from 0 to 30 m depth, denoted B30. A lower gradient value means low velocity increases with depth; a higher gradient indicates a rapid velocity increase with depth in the shallow layers. In addition, we consider the fundamental resonance frequency of the soil (f0), which has been shown to be a relevant parameter for site-effect assessment and which is obtained from the empirical site response. Using the Japanese KiK-net database, we analyze the variability of the VS profiles and the empirical borehole site responses of selected sites through the VS30, the velocity gradient B30, and f0. We select 289 sites for which the 1D linear numerical modeling is close to the empirical site response and a VS at the downhole station is greater than 1000 m=s. For a given VS30 class, B30, and f0 can be used to distinguish between two types of sites: deep sedimentary sites and sites with high velocity contrast at shallow depths. We find that, even if the gradient is calculated using shallow information, its use improves the site amplification characterization, compared to using only VS30, by reducing the intersite site-response variability. As expected, however, this improvement is limited for deep sedimentary sites. On the other hand, f0 is able to reduce the intersite response variability for deep sedimentary sites even though it is limited to specific VS30 classes. Thus, the combined use of VS30, B30, and f0 improves the assessment of linear site amplification.
TL;DR: A phase Doppler particle analyzer (PDPA) system was developed to measure the axial velocity field in axial cross sections in ∅ 35mm hydrocyclones with various vortex finders lengths, overflow orifice diameters, cone angles, inlet flow rates, and split ratios.
TL;DR: In this paper, the effect of copper nanoparticles on the solid contact between friction surfaces was investigated by applying a molecular dynamics method to reveal the mechanisms responsible for the favorable friction properties of nanoparticles.
TL;DR: In this article, the shape of the mixing layer appears to be strongly affected by the streamwise acceleration and complex lateral confinement due to the side walls and the corners of the junction, leading to a streamwise increase of the mean velocity along the centerline and a decrease of the velocity difference.
Abstract: When two open-channel flows merge in a three-branch subcritical junction, a mixing layer appears at the interface between the two inflows. If the width of the downstream channel is equal to the width of each inlet channel, this mixing layer is accelerated and is curved due to the junction geometry. The present work is dedicated to simplified geometries, considering a flat bed and a $$90^{\circ }$$
angle where two configurations with different momentum ratios are tested. Due to the complex flow pattern in the junction, the so-called Serret–Frenet frame-axis based on the local direction of the velocity must be employed to characterize the flow pattern and the mixing layer as Cartesian and cylindrical frame-axes are not adapted. The analysis reveals that the centerline of the mixing layer, defined as the location of maximum Reynolds stress and velocity gradient, fairly fits the streamline separating at the upstream corner, even though a slight shift of the mixing layer towards the center of curvature is observed. The shape of the mixing layer appears to be strongly affected by the streamwise acceleration and the complex lateral confinement due to the side walls and the corners of the junction, leading to a streamwise increase of the mean velocity along the centerline and a decrease of the velocity difference. This results in a specific streamwise evolution of the mixing layer width, which reaches a plateau in the downstream region of the junction. Finally, the evaluation of the terms in the Reynolds-Averaged-Navier–Stokes equations reveals that the streamwise and normal acceleration and the pressure gradient remain dominant, which is typical of accelerated and rotational flows.
TL;DR: In this article, the side-ratio-dependent aerodynamic force of shear flow over rectangular cylinders with different side ratios of B / D ǫ = 1, 5 and 8 (B : breadth of cylinder, D : depth of the cylinder).
TL;DR: Representative results using the methods outlined here demonstrate the useful nature of spatial resolution for measuring the microstructure of a wormlike micelle solution that exhibits shear banding, a phenomenon that can only be investigated by resolving the structure along the velocity gradient direction.
Abstract: A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is presented. The SANS shear cell consists of a concentric cylinder Couette geometry that is sealed and rotating about a horizontal axis so that the vorticity direction of the flow field is aligned with the neutron beam enabling scattering from the 1-2 plane of shear (velocity-velocity gradient, respectively). This approach is an advance over previous shear cell sample environments as there is a strong coupling between the bulk rheology and microstructural features in the 1-2 plane of shear. Flow-instabilities, such as shear banding, can also be studied by spatially resolved measurements. This is accomplished in this sample environment by using a narrow aperture for the neutron beam and scanning along the velocity gradient direction. Time resolved experiments, such as flow start-ups and large amplitude oscillatory shear flow are also possible by synchronization of the shear motion and time-resolved detection of scattered neutrons. Representative results using the methods outlined here demonstrate the useful nature of spatial resolution for measuring the microstructure of a wormlike micelle solution that exhibits shear banding, a phenomenon that can only be investigated by resolving the structure along the velocity gradient direction. Finally, potential improvements to the current design are discussed along with suggestions for supplementary experiments as motivation for future experiments on a broad range of complex fluids in a variety of shear motions.
TL;DR: In this article, a numerical model for flow separation from a spherical particle in supercritical water fluidized bed (SCWFB) was developed in the pseudo-critical zone, and flow separation parameters for forced convection, assisting convection and opposing convection were obtained at intermediate Reynolds numbers.
Abstract: Flow separation from a spherical particle in supercritical water (SCW) is the basic flow structure in supercritical water fluidized bed (SCWFB). In order to study flow separation from a spherical particle in SCW in detail, a numerical model fully accounting for variations in thermo-physical properties has been developed in the pseudo-critical zone. Flow separation parameters (separation angle, length of wake vortex, width of wake vortex, and drag coefficient) for forced convection, assisting convection, and opposing convection have been obtained at intermediate Reynolds numbers. Results show that variable viscosity has a remarkable effect on flow separation, and the decreasing viscosity results in higher velocity gradient around the sphere particle surface and a larger wake vortex on the rear particle surface. A simple expression of Cd / Cd c = ( μ w / μ f ) 0.15 is achieved to predicate the drag coefficient of the SCW flow with μ w / μ f between 0.7 and 1.0. Free convection inhibits the flow separation of the assisting convection, but enhances the flow separation of the opposing convection. Three flow separation zones (the rear-end separation zone, the transition zone, and the reversed flow zone) are observed for the opposing convection.
TL;DR: In this article, a hybrid lattice Boltzmann and finite-volume model is proposed to solve the natural-convection-controlled melting problem, and the results from the present hybrid method are validated with experimental results, and good agreement is obtained.
Abstract: A hybrid lattice Boltzmann and finite-volume model is proposed to solve the natural-convection-controlled melting problem. The lattice Boltzmann method (LBM) is applied to solve the velocity field, while the temperature field is obtained by the finite-volume method (FVM). The D2Q9 model and finite-difference velocity gradient boundary condition are used in the LBM and the SIMPLE algorithm with QUICK scheme is employed in the FVM. An interfacial tracking model based on energy balance at the interface is applied to obtain the location of the solid–liquid interface. The results from the present hybrid method are validated with experimental results, and good agreement is obtained.
TL;DR: In this paper, a mesh cylinder was suspended in a tube, dividing the tube cross section into an annular region and a core region, and a set of short mesh cylinders were suspended in the tube.
TL;DR: In this article, the optical polarization properties, the visual extinction, and the 13CO velocities and linewidths of the entire pipe nebula were compared to identify trends among the observables.
Abstract: Context. The Pipe nebula is a molecular cloud that lacks star formation feedback and has a relatively simple morphology and velocity structure. This makes it an ideal target to test cloud evolution through collisions. Aims. We aim at drawing a comprehensive picture of this relatively simple cloud to better understand the formation and evolution of molecular clouds on large scales. Methods. We use archival data to compare the optical polarization properties, the visual extinction, and the 13CO velocities and linewidths of the entire cloud in order to identify trends among the observables. Results. The Pipe nebula can be roughly divided in two filaments with different orientations and gas velocity ranges: E-W at 2-4 km s-1 and N-S at 6-7 km s-1. The two filaments overlap at the bowl, where the gas shows a velocity gradient spanning from 2 to 7 km s-1. Compared to the rest of the Pipe nebula, the bowl gas appears to be denser and exhibits larger linewidths. In addition, the polarization data at the bowl shows lower angular dispersion and higher polarization degree. Cores in the bowl tend to cluster in space and tend to follow the 13CO velocity gradient. In the stem, cores tend to cluster in regions with properties similar to those of the bowl. Conclusions. The velocity pattern points to a collision between the filaments in the bowl region. The magnetic field seems to be compressed and strengthened in the shocked region. The proportional increase of density and magnetic field strength by a factor similar to the Alfvenic Mach number suggests a continuous shock at low Alfvenic Mach number under flux-freezing. Shocked regions seem to enhance the formation and clustering of dense cores.
TL;DR: In this paper, the authors present analytic solutions for 3D swirling strength in both compressible and incompressible flows, exposing functional dependencies that cannot be seen in numerical solutions, and study the difference between using fluctuating and total velocity gradient tensors for vortex identification.
Abstract: Eigenvalues of the 3D critical point equation (∇u)ν = λν are normally computed numerically In the letter, we present analytic solutions for 3D swirling strength in both compressible and incompressible flows The solutions expose functional dependencies that cannot be seen in numerical solutions To illustrate, we study the difference between using fluctuating and total velocity gradient tensors for vortex identification Results show that mean shear influences vortex detection and that distortion can occur, depending on the strength of mean shear relative to the vorticity at the vortex center
TL;DR: In this paper, the hairpin vortices induced by single circular synthetic jets (SJ) in a laminar boundary layer (LBL) and a turbulent boundary layer over a flat plate were investigated.
TL;DR: In this article, a multi-layered and size-resolved second-order closure model is developed using the mean particle turbulent flux budget as a primary closure for the particle turbulent fluid instead of K-theory.
TL;DR: In this paper, a new method for estimating the H2 cooling rate in the optically thick regime in simulations of primordial star formation is presented, which projects matter distributions onto a spherical grid to create maps of column densities for each fluid element in the computational domain.
Abstract: We present a new method for estimating the H2 cooling rate in the optically thick regime in simulations of primordial star formation. Our new approach is based on the TreeCol algorithm, which projects matter distributions onto a spherical grid to create maps of column densities for each fluid element in the computational domain. We have improved this algorithm by using the relative gas velocities, to weight the individual matter contributions with the relative spectral line overlaps, in order to properly account for the Doppler effect. We compare our new method to the widely used Sobolev approximation, which yields an estimate for the column density based on the local velocity gradient and the thermal velocity. This approach generally underestimates the photon escape probability, because it neglects the density gradient and the actual shape of the cloud. We present a correction factor for the true line overlap in the Sobolev approximation and a new method based on local quantities, which fits the exact results reasonably well during the collapse of the cloud, with the error in the cooling rates always being less than 10%. Analytical fitting formulae fail at determining the photon escape probability after formation of the first protostar (error of 40%) because they are based on the assumption of spherical symmetry and therefore break down once a protostellar accretion disc has formed. Our method yields lower temperatures and hence promotes fragmentation for densities above 10^{10}/ccm at a distance of 200AU from the first protostar. Since the overall accretion rates are hardly affected by the cooling implementation, we expect Pop III stars to have lower masses in our simulations, compared to the results of previous simulations that used the Sobolev approximation.
TL;DR: In this article, a low-order continuum-based liquid sloshing model that can be successfully integrated with multibody system (MBS) algorithms is proposed. But the model is based on the Navier-Stokes equations and does not capture the effect of the distributed inertia and viscosity of the fluid.
Abstract: The objective of this investigation is to develop a low order continuum-based liquid sloshing model that can be successfully integrated with multibody system (MBS) algorithms. The liquid sloshing model proposed in this investigation allows for capturing the effect of the distributed inertia and viscosity of the fluid. The fluid viscous forces are defined using the Navier-Stokes equations. In order to demonstrate the use of the approach presented in this study, the assumption of an incompressible Newtonian fluid is considered with a total Lagrangian approach. Fluid properties such as the incompressibility condition are formulated using a penalty method. The low order model that captures the effect of the distributed fluid inertia on the vehicle dynamics is developed in this investigation using the floating frame reference (FFR) formulation. The use of this approach allows for developing an inertia-variant fluid model that accounts for the dynamic coupling between different modes of the fluid displacements. The matrix of position vector gradients and its derivative are formulated using the FFR kinematic description. The position and velocity gradient tensors are used to define the Navier-Stokes stress forces. The proposed liquid sloshing model is integrated with a MBS railroad vehicle model in which the rail/wheel interaction is formulated using a three-dimensional elastic contact formulation that allows for the wheel/rail separation. Several simulation scenarios are used to examine the effect of the distributed liquid inertia on the motion of the railroad vehicle. The results, obtained using the sloshing model, are compared with the results obtained using a rigid body vehicle model. The comparative numerical study presented in this investigation shows that the effect of the sloshing tends to increase the possibility of wheel/rail separation as the forward velocity increases, thereby increasing the possibility of derailments at these relatively high speeds.Copyright © 2014 by ASME