A direct simulation Monte Carlo analysis of a nonequilibrium hypersonic Prandtl–Meyer flow

In this study, a nonequilibrium hypersonic Prandtl–Meyer expansion using a wedge-flat plate afterbody configuration is presented. The freestream conditions and geometry are based on the experimental study of R. J. Vidal and F. Stoddard [“Measurements of nonequilibrium effects in air on wedge-flat-plate afterbody pressures,” Technical Report No. NASA-CR-328 (Cornell Aeronautical Laboratory, Inc., 1965).] The study investigates the numerical capability of direct simulation Monte Carlo (DSMC) in predicting the flow and compares the results with experimental measurements of the surface pressures and heat flux at low (4.1 MJ/kg) and high (10.3 MJ/kg) enthalpy conditions. Investigation of the velocity, temperatures (translational, rotational, and vibrational), and mass fractions were also performed. It was found that viscous and nonequilibrium effects are dominant in high-temperature hypersonic wedge-afterbody combination. In the context of previous analytical studies of the flow, it is concluded that the so-called de-excitation shock wave is more difficult to detect and likely to be subsumed by viscous effects.