Instability Measurements on an Axisymmetric Separation Bubble at Mach 6

Abstract

An axisymmetric sharp cone-cylinder-flare model was tested in the Boeing/AFOSR Mach 6 Quiet Tunnel (BAM6QT) at 0.0-degree angle of attack. Heat transfer and surface-pressure-fluctuation measurements were made in both conventional noise and quiet Mach 6 flow. Off-the-surface density fluctuation measurements were made with focused laser differential interferometry (FLDI) in quiet flow. Second mode fluctuations as well as a different type of travelling wave were observed downstream in PCB, Kulite, and FLDI measurements. These travelling waves are not predicted by linear stability computations, and are believed to be generated by the shear layer above the separation bubble.