HYPERSONIC TURBULENT EXPANSION-CORNER FLOW WITH SHOCK IMPINGEMENT

Mean and fluctuating surface pressure data were obtained in a Mach 8, turbulent, cold flow past an expansion corner subjected to shock impin gement. The expansion corner of 2.5 or 4.25 deg was located at 0.77 m (30.25 in.) from the leading edge of a sharp-edged Bat plate, while an external shock, generated by either a 2- or 4-deg sharp wedge, imping ed at the corner, or at one boundary-layer thickness ahead or behind t he corner. The mean pressure distribution was strongly influenced by t he mutual interaction between the shock and the expansion. For example , the upstream influence decreased when the shock impinged downstream of the corner. Also, the unsteadiness of the interactions was characte rized by an intermittent region and a local rms pressure peak near the upstream influence, The peak rms pressure fluctuations increased with a larger overall interaction strength. Shock impingement downstream o f the corner resulted in lower fluctuation peaks and also in a shorter region of reduced fluctuation levels, These features may be exploited in inlet design by impinging the cowl shock downstream of an expansio n corner instead of at the corner. In addition, a limited pitot pressu re survey showed a thinning of the boundary layer downstream of the co rner.