Nonlinear acoustic simulations using direct simulation Monte Carlo

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, high frequency sound or rarefied gases. Some well known particle methods include Monte Carlo, cellular automata, discrete velocity, lattice Boltzmann, and molecular dynamics. The direct simulation Monte Carlo (DSMC) method describes gas flows through direct physical modeling of particle motions and collisions. DSMC can model problems for the entire range of Knudsen numbers. In particular, DSMC is capable of simulating nonlinear acoustics, as well as the details of viscous dissipation, dispersion, nonequilibrium effects, and other physical properties. A DSMC method has been implemented for one-dimensional nonlinear acoustics problems on parallel computers using object-oriented C++ and the message passing interface (MPI). DSMC results will be shown and compared with continuum theory and continuum simulations.