Boundary-Layer Transition on Supersonic Cones in an Aeroballistic Range

Abstract

Research was undertaken with the purpose of determining the effect of the unit Reynolds number on boundary-layer transition under conditions where disturbances associated with wind tunnel flows would not be present. The location of boundary-layer transition was determined from shadowgrams of nominally sharp, 4° and 10° semi-angle cones in an aeroballistic range at freestream Mach numbers of 23 and 5.0 and unit Reynolds numbers of 0.3 x 10 to 8 x 10 per in. Owing to constant and equal freestream and cone skirt temperatures, the average ratio of cone wall-to-adiabatic recovery temperature was 0.52 at Mach 2.3 and 0.19 at Mach 5.0. Features of free-flight experimentation that may be suspected of influencing boundary-layer transition were investigated. These included 1) oscillatory motion and finite angles of attack, 2) surface roughness, 3) vibration of the model, and 4) non-uniform (hot-tip) surface temperature. There was no evidence that any of these conditions influenced the major results. The data show local Reynolds number of transition increasing with unit Reynolds number for both Mach numbers. A siren was used to elevate the fluctuating sound pressure ratio by a factor of 200, but that produced no measurable effect on transition locations.