Slip effects in near continuum hypersonic flow over canonical geometries

Effects of velocity slip and temperature jump are investigated for near continuum hypersonic flows. Specifically, flow over the hollow cylinder flare (HCF) geometry and expand-ing/compressing flow over the “Tick” geometry is simulated using both direct simulation Monte Carlo (DSMC) and computational fluid dynamics (CFD) methods. The CFD calculations are performed using both slip and no-slip models, while the DSMC method inherently models slip effects since it resolves molecular transport at the mean-free-path scale. Boundary layer profiles for the cylindrical portion of the HCF case, predicted by DSMC and CFD with slip, agree remarkably well, including the velocity slip and temperature jump values near the wall. The heat flux predictions between DSMC and CFD with slip are found to also agree closely, and both predictions remain below the heat flux measured experimentally. This indicates that slip flow may not be the reason for discrepancy between CFD results and the experimental heat flux measurements reported recently in the literature. More significant differences between DSMC and CFD are found near the leading edge of the Tick geometry. However, establishment of steady-state flow and precise grid convergence is not completely demonstrated for the DSMC solutions in this study, which may explain some of the discrepancy.