Method for determining wall boundary contitions for DSMC calculations at high speed ratios

摘要

A procedure for determining the velocity distribution function for the molecules that are reflected from an element of surface of a body that is moving in the transition or free-molecule flow regimes at high speed ratios is described. This distribution function could be used as the boundary condition for DSMC calculations. The method uses measurements of the momentum accommodation coefficients to determine the parameters for the Nocilla model of the reflected velocity distribution function. Use of this boundary condition with the DSMC method would yield more accurate predictions of flow fields than are presently obtained using the assumption of diffuse scattering from the body surface. Several examples of the application of the procedure are given.