Energy accommodation modeling of rarefied flow over re-entry vehicle geometries using DSMC (Direct Simulation Monte Carlo)

The influence of energy accommodation in the modeling of the gas/wall interaction is examined for rarefied flow over re-entry vehicle geometries using the Direct Simulation Monte Carlo (DSMC) algorithm. The reflected molecule's energy accommodation was varied while a uniform angular distribution was assumed. DSMC results are compared for the first time with flight data obtained from four tests using two different re-entry vehicle geometries. The altitude conditions vary from 58 to 113 km. The Knudsen number varied from less than 0.005 to greater than 10, indicating fluid conditions from the continuum to the free molecular regime. The ratio of the freestream stagnation temperature to the wall temperature was approximately 60. Surface heat fluxes and vehicle drag are compared between the flight data and the DSMC code predictions. The results indicate that a thermal accommodation coefficient less than 1.0 is appropriate for the transitional flow regime. Trends in the surface energy accommodation coefficient variation with altitude are discussed. 15 refs., 4 figs.