Vibrational-excitation effects on a hypersonic turbulent boundary layer over a compression ramp

The effects of vibrational excitation of gas molecules on shock-wave/turbulent-boundary-layer interactions are investigated in this fundamental study via direct numerical simulations (DNS) of a canonical Mach-5 turbulent boundary layer over a cold isothermal compression ramp. The DNSs are performed using an enhanced version of the Hypersonic Task-based Research (HTR) solver (Di Renzo et al., Comp. Phys. Comm. 255, 2020) that is now capable of integrating the conservation equations on curvilinear grids while retaining low numerical-dissipation properties. The numerical results encompass cases obtained using both calorically perfect and imperfect gases, including air, in order to isolate the effects induced by vibrational excitation. The analysis focuses on the peak temperature, skin friction coefficient, wall heat flux, Reynolds analogy factor, and wall pressure spectra that underscore the need for considering high-temperature gasdynamic effects in designing wall models for hypersonic turbulent boundary layers at relevant stagnation enthalpies.