Acoustic propagation using the direct simulation Monte Carlo method

Abstract

In the simulation of fluid dynamics, one can either treat the fluid as a continuum or as discrete particles. Although popular for acoustics, the continuum model is limited to small Knudsen numbers (the ratio of mean free path to a length scale). Particle methods are necessary for, but not limited to, problems with Knudsen numbers greater than 0.1, which can occur in shockwaves, microdevices, or rarefied gases. Some well known particle methods include Molecular Dynamics, Monte Carlo methods, and the Lattice Boltzmann Method. The Direct Simulation Monte Carlo (DSMC) method describes gas flows through direct physical modeling of particle motions and collisions. DSMC can model linear and nonlinear acoustics, as well as the details of viscous dissipation. DSMC results will be shown and compared with continuum theory. A DSMC method has been implemented for 1-dimensional linear and nonlinear acoustics problems on parallel computers using object-oriented C++ and the message passing interface (MPI). The code has been run on large Beowulf clusters. The results have been compared to solutions to the linear wave equation. The complete paper will include two-dimensional solutions as well as comparisons to nonlinear continuum results. [Work supported by Consortium for Education in Many-Body Applications, Grant No. NSF-DGE-9987589.]