Numerical strategy to perform direct numerical simulations of hypersonic shock/boundary-layer interaction in chemical nonequilibrium

Abstract

Literature regarding hypersonic shock/boundary-layer interaction (SBLI) is mostly restricted to calorically perfect gases, even though this condition is far from reality when temperature rises. Hightemperature effects alter physical and transport properties of the fluid, due to vibrational excitation and gas dissociation, and chemical reactions must be considered in order to compute the flow field. In this work, a code for hypersonic aerodynamics with reactions using parallel machines (CHARLIE ) is described and a numerical methodology is developed to perform direct numerical simulations of shock/boundary-layer interaction in chemical nonequilibrium. The numerical scheme and the characterization of non-reflecting boundary conditions are addressed. Results show that the flow properties differ considerably if chemical reactions are taken into account. A direct numerical simulation of a shock interacting with a turbulent boundary-layer in the hypersonic regime with high-temperature effects is also presented for the first time. Keywords numerical methodology • hypersonic flow • shock/boundary-layer interactions • chemical nonequilibrium 1 IntroductionUnderstanding shock/boundary layer interactions (SBLI) is an imperative step to correctly predict the performance of hypersonic vehicles. These complex phenomena can affect considerably the aerodynamic drag and in a more drastic scenario, be responsible for low-frequency unsteadiness, leading to structural failure, loss of the control surfaces or the unstart in an engine intake. SBLI also increases the wall heat flux, a key factor when designing thermal protection systems. To ensure the safety of the space shuttle these systems are most of the time specified with a large safety factor, with the drawback of carrying extra weight. Therefore, the accurate prediction of aerodynamic heating in hypersonic flight is an important step in the design process, which can reduce the weight of the vehicle, increase the payload and enhance fuel efficiency, amongst various advantages.The majority of the work dealing with shock/boundary-layer interaction considers a calorically perfect gas [