Numerical investigation of hypersonic turbulent boundary layers with high-temperature effects

Abstract

A hypersonic turbulent boundary layer over a flat plate is numerically investigated. The large Mach number and temperature values in the freestream (M e = 12.48 and T e = 594.3 K, respectively) lead to a high-enthalpy regime and to the occurrence of thermochemical non-equilibrium effects. Vibrational relaxation phenomena are shown to be predominant with respect to chemical activity. In this context, high-fidelity results obtained by means of a Direct Numerical Simulation (DNS) are used as a benchmark to assess the quality of a Large-Eddy Simulation (LES) performed with a coarser wall-resolved grid. The wall-adapting local eddy viscosity approach is selected as sub-grid scale (SGS) model. The LES strategy is shown to capture the mean and fluctuating dynamic fields in the fully turbulent region quite satisfactorily, whereas transition to turbulence is slightly anticipated with respect to DNS. Both the chemical and vibrational source terms are evaluated with the filtered aerothermochemical quantities, resulting in an overestimation of the translational-vibrational energy exchange and an underestimation of dissociation chemical production rates. These results shed light on the necessity of developing more accurate closure models for the source terms, the SGS turbulence-thermochemistry interactions being important for the configuration under investigation.