Shock Wave/Transitional Boundary-Layer Interactions in Hypersonic Flow

The experimental and numerical transitional interactions in hypersonic flow are studied. The experiments were performed on a hollow cylinder-flare model in the ONERA R2Ch wind tunnel at a Mach number of 5 and for varying stagnation pressure. Wall pressure and heat-flux measurements, laser Doppler velocimetry, pitot boundary-layer surveys, surface flow visualizations, and schlieren photographs provide a precise and complete description of the flowfield. In all of the cases examined here, grid-converged axisymmetric mathematical solutions of the problem were obtained by use of the two-dimensional numerical simulation, but it was found that these solutions do not fit experiments when the Reynolds number is increased. A purely three-dimensional organization of the flow then appears, characterized by the Gortler vortices. Two families of solutions were thus evidenced, and the precise calculation of the physical one remains a numerical challenge. The prediction of transition by use of stability calculations is only partly possible because the waves used do not have a sufficiently general form to model such a complex physical problem. New information on the true nature of what is commonly called a transition mechanism in this kind of flow is deduced from these results.