Traveling instability waves in a Mach 8 flow over an elliptic cone

Simultaneous measurements were carried out with three hot-film probes in th e Mach 8 flow over an elliptic cone of 2:1 aspect ratio, and the data obtai ned were compared to the results of computations using the parabolized Navi er-Stokes equations and linear stability theory, The elliptic-cone flow was found to be significantly different from the flows studied in previous hyp ersonic-flow stability experiments, which have focused exclusively on wind- tunnel models with two-dimensional, planar or axial symmetry. At least two instability mechanisms appear to be active in the present flow: one associa ted with the region of maximum crossflow in the vicinity of the shoulder of the cone and the other associated with the inflectional velocity profiles on the top centerline. Between the shoulder and leading edge of the cone, t he dominant flow instability occurred at relatively low frequency, and the direction of the phase velocity was significantly skewed from that of the b oundary-layer-edge streamlines. The results were found to be in rough agree ment with linear stability calculations and are suggestive of a traveling c rossflow instability mode, which apparently has not been observed before in hypersonic flow. The flow in the vicinity of the top centerline of the con e was found to be highly unstable and appeared in the experiments to be tra nsitional, For this region of the flow, both the experiments and the comput ations shelved an unstable frequency band that coincided with the character istic second-mode frequency. The present experimental technique was adequat e to identify the two instabilities present in the flow, but additional wor k will be required to achieve a detailed validation of linear stability com putations for this configuration.