Toward turbulent inflow conditions for high-enthalpy hypersonic boundary layers

It is well known that the internal energy of the gas within boundary layers developing on objects moving at hypersonic speed in air is sufficient to trigger chemical dissociation of gas molecules and excite their internal degrees of freedom. These finite-rate processes might happen at time scales comparable to those of the flow. For this reason, the theory for flat-plate laminar hypersonic boundary layers predicts only local similarity of the boundary layer profiles, which inevitably depend on the Damköhler number defined in terms of the gas residence time on the plate. Recently, it has been demonstrated that this concept is altered by the presence of turbulence, which localizes the similarity of the boundary layer by strongly enhancing wall-normal mixing.

Given these results, this work will present the advancements made in developing a turbulent inflow boundary condition, based on Recycle-Rescaling, which can be utilized for fully turbulent hypersonic boundary layer calculations. The performance of this boundary condition will be assessed in the context of direct numerical simulations using the comparison with datasets of Mach-10 boundary layers that undergo a transition to turbulence within the computational domain. A quantitative analysis of the boundary-condition-induced errors and their corresponding relaxation lengths will be discussed.