Transition and Instability Measurements in a Mach 6 Quiet Wind Tunnel

Abstract

This paper details five different projects in the Boeing/AFOSR Mach 6 Quiet Tunnel (BAM6QT) at Purdue University. In the first project, a highly swept fin on a 7 • half-angle cone was examined. Temperature sensitive paint and pressure fluctuation measurements showed the presence of an instability near 200 kHz. In the second, the effect of roughness on the stationary and travelling crossflow instabilities was investigated on a cone at an angle of attack. It was found that when the roughness generated larger stationary waves, the travelling waves were damped. In the third, discrete roughness elements made of epoxy were applied to a flared cone. The roughness elements were sized to interact with the second-mode waves without becoming a trip. Using this technique, the spacing of streaks of increased heating was controlled. The fourth project involves improving the current pulsed jet perturber used to study nozzle-wall boundary-layer perturbations. Two improvements have been designed and have undergone preliminary testing. Finally, a new model was designed to measure what appears to be an entropy-layer instability at Mach 6. Surface pressure measurements and hot-wire data are used to investigate the entropy layer.