Boundary-layer transition on an axisymmetric body at incidence at Mach 1.2

Experimental investigation of the boundary-layer transition on an axisymmetric nose model at 1- and 2-deg incidence was conducted at Mach 1.2. The configuration of the model is the forward part of a Sears-Haack body defined to have minimum wave drag caused by volume at 0-deg incidence in supersonic flow. Transition locations were obtained with small surface roughness on the order of 0.1 mu using an infrared camera. An unsteady pressure transducer was applied to investigate instability mechanisms that lead to transition. These results show that the most aft transition occurred on the leeward ray rather than on the windward rays as observed on sharp cones. Tollmien-Schlichting instability dominated the transition process on the windward ray, and crossflow instability was assumed to dominate on the side similar to the transition on the sharp cones. However, transition occurred more aft on the leeward ray than for the case of the sharp cones, and the transition front was determined by turbulent wedges formed as a consequence of the more forward transition on the side. The disturbance believed to be a traveling crossflow wave was observed at 1-deg incidence, and its measured frequency was in good agreement with the maximum amplified frequency, which was calculated using a compressible linear e(N) code.