The purpose of this test case to to improve the knowledge of physics appearing in transitional shock-wave / boundary layer interactions. An experiment has been performed in the ONERA S8Ch research wind tunnel at Mach 1.6 to quantify the effect of the shock-wave intensity on the boundary layer transition. The detection of the transition region was obtained by means of Schlieren visualizations, IR (Infra-red) thermography and TSP (Temperature Sensitive Paint) measurements. LES computation with the ONERA elsA solver was carried out on this experiment for two configurations, one at a moderate oblique shock intensity and the other for a strong shock intensity leading to a massive boundary layer separation.
Experimental and numerical Schlieren views and wall temperature distributions along the flat plate were compared for both configurations. Moreover, computations allowed to provide in-depth results of the main and fluctuating flowfields and to detect unsteadiness into the viscous interaction and in the separated region. A low frequency content of the fluctuations was observed in transitional interactions in the same way as in turbulent interactions as soon as the flow deflection is strong enough, for which upstream propagation of the perturbation in the separated region has been evidenced.
As far as the level of perturbation does not play a crucial role since computation is deprived from inflow fluctuations, the knowledge of every type of perturbations is a critical issue for proper comparison between experiments and computations in transitional flows.