Rarefaction Effect on Hypersonic Laminar Compression Corner Flow in Near-Continuum Regime

This study investigates the influence of rarefaction on hypersonic flow over compression corners in the near-continuum regime and evaluates the validity of improved Navier–Stokes models for such flows. Numerical simulations are performed using the direct simulation Monte Carlo (DSMC) method, Navier–Stokes (NS) equations, and a data-improved NS (DiNS) model with constitutive corrections. The rarefaction effects are systematically examined over a range of Knudsen and Mach numbers, with particular emphasis on flow structure, surface aerothermodynamic quantities, and separation behavior. The results show that rarefaction induces coupled modification of interaction region, which is characterized by an upstream shift and augmentation on interaction-induced peaks in coefficients of skin friction and heat flux. Increasing the Knudsen number weakens shock-wave/boundary-layer interaction and suppresses flow separation. A separation criterion map in [Formula: see text] space is constructed, which identifies a regime where rarefaction significantly impacts the prediction of separation. Model comparisons demonstrate that improved NS models provide significant improvement over the NS method. Although the velocity slip enhances prediction accuracy, constitutive corrections in the DiNS model further improve agreement with DSMC results. These findings highlight the critical role of rarefaction in hypersonic compression corner flows and demonstrate that both slip boundary conditions and nonequilibrium transport effects are essential for accurate predictions in the near-continuum regime.