Experimental Studies of Hypersonic Shock Induced Boundary Layer Separation.

Previous experimental investigations of shock boundary layer interactions on a flat plate at free stream Mach numbers between 6 and 8.7 revealed longitudinal counter-rotating vortices downstream of the interaction region. In subsequent studies the influence of nose radius of blunted plates and of wall curvature on the formation of the vortices was investigated. The experiments were carried out in the hypersonic blow down facility of DLR Cologne. The diagnostics included surface oil flow visualization, infrared thermography, Pitot pressure measurements and Schlieren optics. First numerical results obtained by other authors working in the same research program showed persuasive agreement with the experimentally observed vortex structures, in particular with respect to their diameter and the number of vortex pairs. In the comparison the experimental Schlieren images were also reproduced with good accuracy by the numerically simulated images, obtained from computed density distributions. The numerical flow predictions verified a second flow recirculation inside the separation region, the existence of which had to be postulated by the experimental results