Interaction Length Analysis of Hypersonic Shock-Boundary-Layer Interaction Including High-Enthalpy Effects

Shock-induced flow separation plays an important role in practical applications of hypersonic flows, like intake unstart and unsteady aeroelastic phenomena. The size of the shock-boundary-layer interaction (SBLI) region determines the extent of choking in engine inlet ducts. Recent scaling studies have shown that interaction length is a function of shock-induced pressure jump, upstream Mach number, Reynolds number, wall heating/cooling, and flow deflection angle at the shock wave. In this work, we analyze the interaction length scaling for different hypersonic SBLI cases at varying flow enthalpies. We perform Reynolds-averaged Navier-Stokes (RANS) simulations, using a shock-strength-dependent turbulence model, of hypersonic SBLI flows over a range of Mach numbers and at flow enthalpies where vibrational nonequilibrium starts to be important. The numerical results closely match the experimental data, validating the RANS predictions. The size of the separation bubble in such high-enthalpy cases is found to not follow the known scaling relations. We propose a modified scaling that collapses a wide range of hypersonic Mach numbers and freestream enthalpy conditions. We also derive the high-Mach-number limit to demonstrate that wall cooling/heating and geometry are the main factors affecting the size of the SBLI region in hypersonic flows.