Motivation

As initially proposed by Koura (Physics of Fluids 9 (11), 1997, pp. 3543-3549), it is possible to imbed trajectory calculations within the DSMC method, thereby effectively replacing stochastic DSMC collision models. Similar to Molecular Dynamics (MD), the only simulation input is a potential energy surface (PES) that dictates the interaction forces between atoms. With modern computer power, such simulations are becoming feasible for flow fields of interest. Since pure Molecular Dynamics simulations are also possible, we are in a position to directly compare trajectory-based DSMC solutions to pure MD solutions where the same PES is the only model input to both techniques. If implemented correctly, trajectory-based DSMC solutions should agree precisely with pure MD solutions (for dilute gases) down to the level of the velocity and internal energy distribution functions. Alternatively, trajectory calculations may be performed individually and integrated to obtain state-to-state cross-sections. If full state-to-state cross-section databases can be converged, then state-to-state DSMC calculations would be as accurate as trajectory-based DSMC calculations but much more computationally efficient.

Results and Publications