TABLE OF CONTENTS DSMC (direct simulation Monte Carlo) is a direct particle simulation method based on kinetic theory (Bird 1963; 1965a, b; 1976; 1978; 1994). The fundamental idea is to track thousands or millions of randomly selected, statistically representative particles, and to use their motions and interactions to modify their positions and states appropriately in time. Each simulated particle represents a number of real molecules. The primary approximation of DSMC is the uncoupling of the molecular motions and the intermolecular collisions over small time intervals that are less than the mean collision time. The DSMC computation is started from some initial conditions and followed in small time steps that can be related to physical time. Collision pairs of molecule in a small computational cell in physical space are randomly selected based on a probability distribution after each computation time step. Complex physics such as radiation, chemical reactions, and species concentrations can be included in the simulations without invoking nonequilibrium thermodynamic assumptions that commonly afflict nonequilibrium continuum flow calculations. The DSMC technique is explicit and time marching, and therefore can produce unsteady flow simulations. For steady flows, DSMC simulation proceeds until a stationary flow is established within a desired accuracy. The macroscopic flow quantities can then be obtained by time averaging the cell-based values. For unsteady flows, ensemble averaging of many independent Monte Carlo simulations can be carried out to obtain the final results within a prescribed statistical accuracy.
A significant advantage of DSMC is that the total computation...
