EXPERIMENTAL AND COMPUTATIONAL INVESTIGATIONS OF HYPERSONIC FLOW ABOUT COMPRESSION RAMPS

Comprehensive results of a joint experimental and computational study of the two-dimensional flow field over flat plate/compression ramp con figurations at Mach 14 are presented. These geometries are aimed to si mulate, in a simplified manner, the region around deflected control su rfaces of hypersonic re-entry vehicles. The test cases considered cove r a range of realistic flow conditions with Reynolds numbers to the hi nge line varying between 4.5 x 10(5) and 2.6 x 10(6) (with a reference length taken as the distance between the leading edge and the hinge l ine) and a wall-to-total-temperature ratio of 0.12. The combination of flow and geometric parameters gives rise to fully laminar strong shoc k wave/boundary layer interactions with extensive separation, and tran sitional interactions with transition occurring near the reattachment point. A fully turbulent interaction is also considered which, however , was only approximately achieved in the experiments by means of exces sive tripping of the oncoming hypersonic laminar boundary layer. Empha sis has been placed upon the quality and level of confidence of both e xperiments and computations, including a discussion on the laminar-tur bulent transition process and the associated striation phenomenon. The favourable comparison between the experimental and computational resu lts has provided the grounds for an enhanced understanding of the rele vant flow processes and their modelling. Particularly in relation to t ransitional shock wave/boundary layer interactions, where laminar-turb ulent transition is promoted by the adverse pressure gradient and flow concavity in the reattachment region, a method is proposed to compute extreme adverse effects in the interaction region avoiding such inhib iting requirements as transition modelling or turbulence modelling ove r separated regions.