Bulletin of the American Physical Society
APS March Meeting 2010
Volume 55, Number 2
Monday–Friday, March 15–19, 2010; Portland, Oregon
Session P5: Lattice Boltzmann Method and Its Applications |
Hide Abstracts |
Sponsoring Units: DFD Chair: Li-Shi Luo, Old Dominion University Room: Portland Ballroom 256 |
Wednesday, March 17, 2010 8:00AM - 8:36AM |
P5.00001: Lattice Boltzmann modeling of microchannel flow in slip flow regime Invited Speaker: We present the lattice Boltzmann equation (LBE) with multiple relaxation times (MRT) to simulate pressure-driven gaseous flow in a long microchannel. We obtain analytic solutions of the MRT-LBE with various boundary conditions for the incompressible Poiseuille flow with its walls aligned with a lattice axis. The analytical solutions are used to realize the Dirichlet boundary conditions in the LBE. We use the first-order slip boundary conditions at the walls and consistent pressure boundary conditions at both ends of the long microchannel. We validate the LBE results using the compressible Navier-Stokes (NS) equations with a first-order slip velocity, the information-preservation direct simulation Monte Carlo (IP-DSMC) and DSMC methods. As expected, the LBE results agree very well with IP-DSMC and DSMC results in the slip velocity regime, but deviate significantly from IP-DSMC and DSMC results in the transition-flow regime in part due to the inadequacy of the slip velocity model, while still agreeing very well with the slip NS results. Possible extensions of the LBE for transition flows are discussed. This work has been published in Journal of Computational Physics. [Preview Abstract] |
Wednesday, March 17, 2010 8:36AM - 9:12AM |
P5.00002: Particle-Resolved Numerical Simulation of Turbulent Suspension Flow Using the Lattice Boltzmann Equation Invited Speaker: Particle-laden turbulent flow is of importance to many engineering applications and natural phenomena, such as aerosol and pollutant transport, interaction of cloud droplets, spay combustion, and chemical processes. In general, the dynamics of dispersed phase and that of the carrier fluid phase are closely coupled. Most previous studies utilize the point particle approach to study the effects of particles on the carrier turbulence, under the assumptions that the particle size is significantly smaller than the smallest turbulence length scale and the particle volume fraction is low. The present study focuses on the motion and hydrodynamic interactions of finite-size freely moving particles in a turbulent background flow. To simulate carrier fluid turbulence, a mesoscopic lattice Boltzmann approach is applied with the multiple relaxation-time collision model, which yields a more robust viscous flow simulation method than the single-relaxation collision model. The no-slip boundary condition on the moving surface of each particle is implemented using an interpolated bounce-back scheme. The refill problem resulting from the moving boundary is handled by a non-equilibrium correction method to reduce the unphysical force fluctuations acting on the particles. The short-range lubrication force not resolved by the simulation is represented by a physical model involving particle relative location and velocity. For the carrier fluid phase, computational results are discussed in terms of the change of energy spectrum compared with the particle-free turbulence, the time evolution of the turbulent kinetic energy and the dissipation rate. For the dispersed phase, the focus will be on the particle-pair statistics such as the relative velocity and radial distribution function as well as particle-particle collision rate. The effects of varying particle size, volume fraction, and particle-to-fluid density ratio will be examined. The results will be compared to those from the previous point-particle approach and related particle-resolved approach. [Preview Abstract] |
Wednesday, March 17, 2010 9:12AM - 9:48AM |
P5.00003: Lattice Boltzmann approaches to magnetohydrodynamics and electromagnetism Invited Speaker: \newcommand{\Jv}{\mathbf{J}} \newcommand{\uv}{\mathbf{u}} \newcommand{\Bv}{\mathbf{B}} \newcommand{\Ev}{\mathbf{E}} \newcommand{\gv}{\mathbf{g}} We present a lattice Boltzmann approach for magnetohydrodynamics and electromagnetism that expresses the magnetic field using a discrete set of vector distribution functions $\gv_i$. The $\gv_i$ were first postulated to evolve according to a vector Boltzmann equation of the form $$ \partial_t \gv_i + \xi_i \cdot \nabla \gv_i = - \frac{1}{\tau} \left( \gv_i - \gv_i^{(0)} \right), $$ where the $\xi_i$ are a discrete set of velocities. The right hand side relaxes the $\gv_i$ towards some specified functions $\gv_i^{(0)}$ of the fluid velocity $\uv$, and of the macroscopic magnetic field given by $\Bv = \sum_i \gv_i$. Slowly varying solutions obey the equations of resistive magnetohydrodynamics. This lattice Boltzmann formulation has been used in large-scale (up to $1800^3$ resolution) simulations of magnetohydrodynamic turbulence. However, this is only the simplest form of Ohm's law. We may simulate more realistic extended forms of Ohm's law using more complex collision operators. A current-dependent relaxation time yields a current-dependent resistivity $\eta(|\nabla\times\Bv|)$, as used to model ``anomalous'' resistivity created by small-scale plasma processes. Using a \textit{hydrodynamic} matrix collision operator that depends upon the magnetic field $\Bv$, we may simulate Braginskii's magnetohydrodynamics, in which the viscosity for strains parallel to the magnetic field lines is much larger than the viscosity for strains in perpendicular directions. Changing the collision operator again, from the above vector Boltzmann equation we may derive the full set of Maxwell's equations, including the displacement current, and Ohm's law, $$ - \frac{1}{c^2} \partial_t \mathbf{E}+ \nabla \times \Bv = \mu_o \Jv, \quad \Jv = \sigma ( \mathbf{E} + \uv \times \Bv). $$ The original lattice Boltzmann scheme was designed to reproduce resistive magnetohydrodynamics in the non-relativistic limit. However, the kinetic formulation requires a system of first order partial differential equations with collision terms. This system coincides with the full set of Maxwell's equations and Ohm's law, so we capture a much wider range of electromagnetic phenomena, including electromagnetic waves. [Preview Abstract] |
Wednesday, March 17, 2010 9:48AM - 10:24AM |
P5.00004: Massively parallel simulations of multiphase flows using Lattice Boltzmann methods Invited Speaker: In the last two decades the lattice Boltzmann method (LBM) has matured as an alternative and efficient numerical scheme for the simulation of fluid flows and transport problems. Unlike conventional numerical schemes based on discretizations of macroscopic continuum equations, the LBM is based on microscopic models and mesoscopic kinetic equations. The fundamental idea of the LBM is to construct simplified kinetic models that incorporate the essential physics of microscopic or mesoscopic processes so that the macroscopic averaged properties obey the desired macroscopic equations. Especially applications involving interfacial dynamics, complex and/or changing boundaries and complicated constitutive relationships which can be derived from a microscopic picture are suitable for the LBM. In this talk a modified and optimized version of a Gunstensen color model is presented to describe the dynamics of the fluid/fluid interface where the flow field is based on a multi-relaxation-time model. Based on that modeling approach validation studies of contact line motion are shown. Due to the fact that the LB method generally needs only nearest neighbor information, the algorithm is an ideal candidate for parallelization. Hence, it is possible to perform efficient simulations in complex geometries at a large scale by massively parallel computations. Here, the results of drainage and imbibition (Degree of Freedom $>$ 2E11) in natural porous media gained from microtomography methods are presented. Those fully resolved pore scale simulations are essential for a better understanding of the physical processes in porous media and therefore important for the determination of constitutive relationships. [Preview Abstract] |
Wednesday, March 17, 2010 10:24AM - 11:00AM |
P5.00005: Lattice Boltzmann Modeling of Multi-phase Interfacial Flows Invited Speaker: A free-energy based lattice Boltzmann method (LBM) for liquid-vapor and binary two-phase flows will be presented. Although very efficient and simple to implement, two-phase LBMs have been known to be unstable when the difference in material properties of two phases or the Reynolds number is large. Two major issues associated with the numerical stability of the free-energy based two-phase LBM under these conditions will be discussed. The intermolecular force needs to be in the potential form and its discretization needs to be compact and isotropic in order to eliminate parasitic currents, whose magnitude and extent usually increase as surface tension. High-order polynomial boundary conditions for free-energy are employed to correctly predict the equilibrium contact angle and the density profile at solid surfaces for large density contrast. Test cases include bubble generation in microfluidic devices, and droplet spreading and impact on flat and structured surfaces with different wetting characteristics. [Preview Abstract] |
Follow Us |
Engage
Become an APS Member |
My APS
Renew Membership |
Information for |
About APSThe American Physical Society (APS) is a non-profit membership organization working to advance the knowledge of physics. |
© 2024 American Physical Society
| All rights reserved | Terms of Use
| Contact Us
Headquarters
1 Physics Ellipse, College Park, MD 20740-3844
(301) 209-3200
Editorial Office
100 Motor Pkwy, Suite 110, Hauppauge, NY 11788
(631) 591-4000
Office of Public Affairs
529 14th St NW, Suite 1050, Washington, D.C. 20045-2001
(202) 662-8700