Instability and Transition Experiments in the Boeing/AFOSR Mach 6 Quiet Tunnel

Abstract

This paper presents results for three projects in the Boeing/AFOSR Mach 6 Quiet Tunnel (BAM6QT) at Purdue University. The second-mode instability was measured on a straight 3 half-angle cone under quiet conditions using pressure sensors and temperature sensitive paint. Natural transition was observed near the aft end of the model at a unit Reynolds of 12.1×10/m. Maximum pressure fluctuation magnitudes prior to the onset of transition were measured to be 27% of the mean surface pressure. Secondly, experiments on a 7 half-angle cone at 6 angle of attack were performed to verify the presence of a secondary instability of a stationary crossflow wave. Using TSP imaging techniques and PCB pressure transducers, a possible secondary instability with a peak frequency near 300 kHz was measured at azimuthal angles between 125 and 140 at Reynolds numbers near 10.7×10/m. Lastly, Roughness elements and an air jet were tested as boundary layer trips on a generic hypersonic forebody.