Modeling Capabilities of DSMC and Continuum Solvers for Nonequilibrium Hypersonic Flows

The interaction of control jets with hypersonic flow induces complex aerothermodynamic phenomena, characterized by shock-boundary layer interactions, flow separation, and circulation regions. Accurately predicting the surface loads in these regions is critical for vehicle maneuverability. However, such flows are computationally challenging due to strong gradients and localized rarefaction that violate continuum assumptions. This study presents a comparative numerical investigation for interaction of a side jet on an axisymmetric cone under Mach 12 nitrogen flow conditions. The primary objective is to evaluate the validity of a continuum-based Navier-Stokes solver within the slip flow regime against a kinetic-based Direct Simulation Monte Carlo solver. Baseline results demonstrate that while the continuum solver successfully and efficiently captures the overall flow topology. However, it overpredicts the skin friction coefficient due to elevated local Knudsen numbers. To address this discrepancy, modified velocity slip and temperature jump boundary conditions, incorporating near-wall distance coefficients, were implemented to the continuum solver. The implementation successfully aligns the local temperature and velocity profiles with DSMC predictions near the leading edge, although global pressure and skin friction coefficient distributions remain largely unaffected. Furthermore, the investigation is extended to high-enthalpy conditions to characterize the coupling of chemical and thermal non-equilibrium. Results reveal that rather than inducing localized species dissociation, the rise in enthalpy drives the shock wave/boundary-layer interaction system into a highly unsteady nature.