The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
J. C. Desplat - One of the best experts on this subject based on the ideXlab platform.
-
binary Fluids under steady shear in three dimensions
Physical Review E, 2007Co-Authors: J. C. Desplat, P Stansell, Michael E. CatesAbstract:We simulate by the lattice Boltzmann method the steady shearing of a binary Fluid Mixture with full hydrodynamics in three dimensions. Contrary to some theoretical scenarios, a dynamical steady state is attained with finite correlation lengths in all three spatial directions. Using large simulations, we obtain at moderately high Reynolds numbers apparent scaling exponents comparable to those found by us previously in two dimensions (2D). However, in 3D there may be a crossover to different behavior at low Reynolds number: accessing this regime requires even larger computational resources than used here.
-
inertial effects in three dimensional spinodal decomposition of a symmetric binary Fluid Mixture a lattice boltzmann study
Journal of Fluid Mechanics, 2001Co-Authors: Viv Kendon, J. C. Desplat, M E Cates, Ignacio Pagonabarraga, P BladonAbstract:The late-stage demixing following spinodal decomposition of a three-dimensional symmetric binary Fluid Mixture is studied numerically, using a thermodynamically consistent lattice Boltzmann method. We combine results from simulations with different numerical parameters to obtain an unprecedented range of length and time scales when expressed in reduced physical units. (These are the length and time units derived from Fluid density, viscosity, and interfacial tension.) Using eight large (2563) runs, the resulting composite graph of reduced domain size l against reduced time t covers 1 [less, similar] l [less, similar] 105, 10 [less, similar] t [less, similar] 108. Our data are consistent with the dynamical scaling hypothesis that l(t) is a universal scaling curve. We give the first detailed statistical analysis of Fluid motion, rather than just domain evolution, in simulations of this kind, and introduce scaling plots for several quantities derived from the Fluid velocity and velocity gradient fields. Using the conventional definition of Reynolds number for this problem, Reφ = ldl/dt, we attain values approaching 350. At Reφ [greater, similar] 100 (which requires t [greater, similar] 106) we find clear evidence of Furukawa's inertial scaling (l [similar] t2/3), although the crossover from the viscous regime (l [similar] t) is both broad and late (102 [less, similar] t [less, similar] 106). Though it cannot be ruled out, we find no indication that Reφ is self-limiting (l [similar] t1/2) at late times, as recently proposed by Grant & Elder. Detailed study of the velocity fields confirms that, for our most inertial runs, the RMS ratio of nonlinear to viscous terms in the Navier-Stokes equation, R2, is of order 10, with the Fluid Mixture showing incipient turbulent characteristics. However, we cannot go far enough into the inertial regime to obtain a clear length separation of domain size, Taylor microscale, and Kolmogorov scale, as would be needed to test a recent 'extended' scaling theory of Kendon (in which R2 is self-limiting but Reφ not). Obtaining our results has required careful steering of several numerical control parameters so as to maintain adequate algorithmic stability, efficiency and isotropy, while eliminating unwanted residual diffusion. (We argue that the latter affects some studies in the literature which report l [similar] t2/3 for t [less, similar] 104.) We analyse the various sources of error and find them just within acceptable levels (a few percent each) in most of our datasets. To bring these under significantly better control, or to go much further into the inertial regime, would require much larger computational resources and/or a breakthrough in algorithm design.
-
inertial effects in three dimensional spinodal decomposition of a symmetric binary Fluid Mixture a lattice boltzmann study
arXiv: Condensed Matter, 2000Co-Authors: Viv Kendon, J. C. Desplat, M E Cates, Ignacio Pagonabarraga, P BladonAbstract:The late-stage demixing following spinodal decomposition of a three-dimensional symmetric binary Fluid Mixture is studied numerically, using a thermodynamicaly consistent lattice Boltzmann method. We combine results from simulations with different numerical parameters to obtain an unprecendented range of length and time scales when expressed in reduced physical units. Using eight large (256^3) runs, the resulting composite graph of reduced domain size l against reduced time t covers 1 < l < 10^5, 10 < t < 10^8. Our data is consistent with the dynamical scaling hypothesis, that l(t) is a universal scaling curve. We give the first detailed statistical analysis of Fluid motion, rather than just domain evolution, in simulations of this kind, and introduce scaling plots for several quantities derived from the Fluid velocity and velocity gradient fields.
P Bladon - One of the best experts on this subject based on the ideXlab platform.
-
inertial effects in three dimensional spinodal decomposition of a symmetric binary Fluid Mixture a lattice boltzmann study
Journal of Fluid Mechanics, 2001Co-Authors: Viv Kendon, J. C. Desplat, M E Cates, Ignacio Pagonabarraga, P BladonAbstract:The late-stage demixing following spinodal decomposition of a three-dimensional symmetric binary Fluid Mixture is studied numerically, using a thermodynamically consistent lattice Boltzmann method. We combine results from simulations with different numerical parameters to obtain an unprecedented range of length and time scales when expressed in reduced physical units. (These are the length and time units derived from Fluid density, viscosity, and interfacial tension.) Using eight large (2563) runs, the resulting composite graph of reduced domain size l against reduced time t covers 1 [less, similar] l [less, similar] 105, 10 [less, similar] t [less, similar] 108. Our data are consistent with the dynamical scaling hypothesis that l(t) is a universal scaling curve. We give the first detailed statistical analysis of Fluid motion, rather than just domain evolution, in simulations of this kind, and introduce scaling plots for several quantities derived from the Fluid velocity and velocity gradient fields. Using the conventional definition of Reynolds number for this problem, Reφ = ldl/dt, we attain values approaching 350. At Reφ [greater, similar] 100 (which requires t [greater, similar] 106) we find clear evidence of Furukawa's inertial scaling (l [similar] t2/3), although the crossover from the viscous regime (l [similar] t) is both broad and late (102 [less, similar] t [less, similar] 106). Though it cannot be ruled out, we find no indication that Reφ is self-limiting (l [similar] t1/2) at late times, as recently proposed by Grant & Elder. Detailed study of the velocity fields confirms that, for our most inertial runs, the RMS ratio of nonlinear to viscous terms in the Navier-Stokes equation, R2, is of order 10, with the Fluid Mixture showing incipient turbulent characteristics. However, we cannot go far enough into the inertial regime to obtain a clear length separation of domain size, Taylor microscale, and Kolmogorov scale, as would be needed to test a recent 'extended' scaling theory of Kendon (in which R2 is self-limiting but Reφ not). Obtaining our results has required careful steering of several numerical control parameters so as to maintain adequate algorithmic stability, efficiency and isotropy, while eliminating unwanted residual diffusion. (We argue that the latter affects some studies in the literature which report l [similar] t2/3 for t [less, similar] 104.) We analyse the various sources of error and find them just within acceptable levels (a few percent each) in most of our datasets. To bring these under significantly better control, or to go much further into the inertial regime, would require much larger computational resources and/or a breakthrough in algorithm design.
-
inertial effects in three dimensional spinodal decomposition of a symmetric binary Fluid Mixture a lattice boltzmann study
arXiv: Condensed Matter, 2000Co-Authors: Viv Kendon, J. C. Desplat, M E Cates, Ignacio Pagonabarraga, P BladonAbstract:The late-stage demixing following spinodal decomposition of a three-dimensional symmetric binary Fluid Mixture is studied numerically, using a thermodynamicaly consistent lattice Boltzmann method. We combine results from simulations with different numerical parameters to obtain an unprecendented range of length and time scales when expressed in reduced physical units. Using eight large (256^3) runs, the resulting composite graph of reduced domain size l against reduced time t covers 1 < l < 10^5, 10 < t < 10^8. Our data is consistent with the dynamical scaling hypothesis, that l(t) is a universal scaling curve. We give the first detailed statistical analysis of Fluid motion, rather than just domain evolution, in simulations of this kind, and introduce scaling plots for several quantities derived from the Fluid velocity and velocity gradient fields.
Subir K Das - One of the best experts on this subject based on the ideXlab platform.
-
finite size scaling study of shear viscosity anomaly at liquid liquid criticality
arXiv: Statistical Mechanics, 2014Co-Authors: Sutapa Roy, Subir K DasAbstract:We study equilibrium dynamics of a symmetrical binary Lennard-Jones Fluid Mixture near its consolute criticality. Molecular dynamics simulation results for shear viscosity, $\eta$, from microcanonical ensemble are compared with those from canonical ensemble with various thermostats. It is observed that Nos\'{e}-Hoover thermostat is a good candidate for this purpose and so, is adopted for the quantification of critical singularity of $\eta$, to avoid temperature fluctuation (or even drift) that is often encountered in microcanonical simulations. Via finite-size scaling analysis of our simulation data, thus obtained, we have been able to quantify even the weakest anomaly, of all transport properties, that shear viscosity exhibits and confirm the corresponding theoretical prediction.
-
finite size scaling study of shear viscosity anomaly at liquid liquid criticality
Journal of Chemical Physics, 2014Co-Authors: Sutapa Roy, Subir K DasAbstract:We study the equilibrium dynamics of a symmetrical binary Lennard-Jones Fluid Mixture near its consolute criticality. Molecular dynamics simulation results for the shear viscosity, η, from a microcanonical ensemble are compared with those from a canonical ensemble with various thermostats. It is observed that the Nose-Hoover thermostat is a good candidate for this purpose, and is therefore adopted for the quantification of the critical singularity of η, to avoid the temperature fluctuations (or even drifts) that are often encountered in microcanonical simulations. Via a finite-size scaling analysis of our simulation data we have been able to confirm that the shear viscosity exhibits a weak critical singularity in agreement with the theoretical predictions.
-
spinodal decomposition in thin films molecular dynamics simulations of a binary lennard jones Fluid Mixture
Physical Review E, 2006Co-Authors: Subir K Das, Sanjay Puri, Jurgen Horbach, K BinderAbstract:We use molecular dynamics (MD) to simulate an unstable homogeneous Mixture of binary Fluids (AB), confined in a slit pore of width D. The pore walls are assumed to be flat and structureless and attract one component of the Mixture (A) with the same strength. The pairwise interactions between the particles are modeled by the Lennard-Jones potential, with symmetric parameters that lead to a miscibility gap in the bulk. In the thin-film geometry, an interesting interplay occurs between surface enrichment and phase separation. We study the evolution of a Mixture with equal amounts of A and B, which is rendered unstable by a temperature quench. We find that A-rich surface enrichment layers form quickly during the early stages of the evolution, causing a depletion of A in the inner regions of the film. These surface-directed concentration profiles propagate from the walls towards the center of the film, resulting in a transient layered structure. This layered state breaks up into a columnar state, which is characterized by the lateral coarsening of cylindrical domains. The qualitative features of this process resemble results from previous studies of diffusive Ginzburg-Landau-type models [S. K. Das, S. Puri, J. Horbach, and K. Binder, Phys. Rev. E 72, 061603 (2005)], but quantitative aspects differ markedly. The relation to spinodal decomposition in a strictly two-dimensional geometry is also discussed.
Kehming Shyue - One of the best experts on this subject based on the ideXlab platform.
-
a Fluid Mixture type algorithm for compressible multicomponent flow with mie gruneisen equation of state
Journal of Computational Physics, 2001Co-Authors: Kehming ShyueAbstract:Abstract A simple interface-capturing approach proposed previously by the author for efficient numerical resolution of multicomponent problems with a van der Waals Fluid [ J. Comput. Phys. , 156 (1999), pp. 43–88] is extended to a more general case with real materials characterized by a Mie–Gruneisen equation of state. As before, the flow regime of interests is assumed to be homogeneous with no jumps in the pressure and velocity (the normal component of it) across the interfaces that separate two regions of different Fluid components. The algorithm uses a Mixture type of the model system that is formed by combining the Euler equations of gas dynamics for the basic conserved variables and an additional set of effective equations for the problem-dependent material quantities. In this approach, the latter equations are introduced in the algorithm primarily for an easy computation of the pressure from the equation of state, and are derived so as to ensure a consistent modeling of the energy equation near the interfaces where two or more Fluid components are present in a grid cell, and also the fulfillment of the mass equation in the other single component regions. A standard high-resolution wave propagation method designed originally for single component flows is generalized to solve the proposed system for multicomponent flows, giving an efficient implementation of the algorithm. Several numerical results are presented in both one and two space dimensions that show the feasibility of the method with the Roe Riemann solver as applied to a reasonable class of practical problems without introducing any spurious oscillations in the pressure near the interfaces. This includes results obtained using a multicomponent version of the AMRCLAW software package of Berger and LeVeque for the simulation of the impact of an underwater aluminum plate to a copper plate in two space dimensions.
-
regular article a Fluid Mixture type algorithm for compressible multicomponent flow with van der waals equation of state
Journal of Computational Physics, 1999Co-Authors: Kehming ShyueAbstract:In previous work by the author, a simple interface-capturing approach has been developed and validated for compressible multicomponent flows with a stiffened gas equation of state in multiple space dimensions. The algorithm uses a Mixture type of the model equations written in a quasi-conservative form to ensure a consistent approximation of the energy equation near the interfaces where two or more Fluid components are present in a grid cell. A standard high-resolution wave propagation method is employed to solve the proposed system, giving an efficient implementation of the algorithm. In this paper, the method is extended to a more general two-phase (liquid-gas) flow where the Fluid of interests is characterized by a van der Waals-type equation of state. Several numerical results are presented in both one and two space dimensions that show the feasibility of the method with the Roe solver as applied to practical problems without introducing any spurious oscillations in the pressure near the interfaces. This includes a convergence study of a shock wave in liquid over a gas bubble. To deal with a difficult slip line problem where there is a strong shear flow moving along the interface, we implement the method based on the shock-only Riemann solver with an additional update by the scheme to the total kinetic energy. Rather than using solutions from the basic conservation laws for the density and momenta which incurs large errors, the resulting total kinetic energy is used to the computation of the pressure from the equation of state, yielding typically more accurate results than the unmodified method near the slip lines. This is demonstrated by numerical results of some sample two-dimensional Riemann problems.
Swapan K Ghosh - One of the best experts on this subject based on the ideXlab platform.
-
new universal scaling laws of diffusion and kolmogorov sinai entropy in simple liquids
Physical Review Letters, 2004Co-Authors: Alok Samanta, Sk Musharaf Ali, Swapan K GhoshAbstract:A new universal scaling law relating the self-diffusivities of the components of a binary Fluid Mixture to their excess entropies is derived using mode coupling theory. These scaling laws yield numerical results, for a hard sphere as well as Lennard-Jones Fluid Mixtures, in excellent agreement with simulation results even at a low density region, where the empirical scaling laws of Dzugutov [Nature (London) 381, 137 (1996)]] and Hoyt, Asta, and Sadigh [Phys. Rev. Lett. 85, 594 (2001)]] fail completely. A new scaling law relating the Kolmogorov-Sinai entropy to the excess entropy is also obtained.
-
a continued fraction approach to cross diffusivity in a binary Fluid Mixture
Journal of Chemical Physics, 2002Co-Authors: Kajal Dhole, Alok Samanta, Swapan K GhoshAbstract:A microscopic approach to the cross diffusivity in a binary Fluid Mixture has been developed using the theoretical framework of continued fraction method. A suitable transformation of the velocities of distinct particles is used to formulate a continued fraction approach for the cross velocity correlation function. The self diffusivities needed for this calculation are obtained through mode coupling theory. The proposed theory is applied to a Lennard-Jones Fluid Mixture and the calculated cross diffusivities are found to be in good agreement with the available computer simulation results. The theory predicts the correct trend for the variation of cross diffusivity with mass and composition and also explains qualitatively the nature of the time dependence of the cross velocity correlation.
-
theory of cross diffusivity in a binary Fluid Mixture
Principles and Practice of Constraint Programming, 2002Co-Authors: Sk Musharaf Ali, Alok Samanta, Swapan K GhoshAbstract:A microscopic approach for the cross-diffusivity in a binary Fluid Mixture has been developed using the theoretical frameworks of density functional theory (DFT) as well as mode coupling theory (MCT). In MCT, we have identified a particular mode selection which leads to an expression for the cross-diffusivity identical to that obtained from the DFT. An alternative choice based on analogous physical considerations though leads to a different expression, on numerical evaluation shows that the calculated results are close to the predictions from DFT. Both the theories are applied to a Lennard-Jones Fluid Mixture and the calculated cross-diffusivities are found to be in good agreement with the available computer simulation results.
-
mode coupling theory of self and cross diffusivity in a binary Fluid Mixture application to lennard jones systems
Journal of Chemical Physics, 2001Co-Authors: Sk Musharaf Ali, Alok Samanta, Swapan K GhoshAbstract:A microscopic approach has been developed for the self as well as cross diffusivity of a binary Fluid Mixture based on the concepts of mode coupling theory. Illustrative numerical results calculated for a Lennard-Jones Fluid Mixture are presented and are shown to be in good agreement with the available computer simulation results. The effects of mass, composition, interaction strength, and sizes of the components on the diffusivities are studied in order to obtain insight into the role of different modes in the diffusion process. The mass dependence of diffusivity is found to be weak with a power law behavior in contrast to the Enskog theory prediction of strong mass dependence. Also the mass and concentration of one component are found to have significant and interesting effects on the diffusivity of the other component. The new expressions derived here are shown to predict positive values for the cross diffusion constant over the various parameter ranges considered, which is consistent with the simulation results but unpredicted by other commonly used models. It is also found that the cross diffusion is significant in liquid Lorentz–Berthelot Mixture for size ratio unity, strong interaction potential, and intermediate composition range.