Comparison of Wind Tunnel Transition and Freestream Disturbance Measurements

Boundary-layer transition measurements have been made on two 5° half-angle cones at M^ « 7 in the Ames 3.5-ft Hypersonic Wind Tunnel and the Langley Variable Density Wind Tunnel. Although there were differences between the measured freestream disturbance scales and pressure fluctuation levels, the choice of consistent locations within the transition region, using either thin-film fluctuation or surface heat-transfer data results in excellent agreement between the transition Reynolds number in both facilities. However, there is an apparent connection between changes in freestream pressure fluctuation levels and movement of boundary-laye r transition location in the two facilities. Nomenclature D — wind-tunnel test section diameter / = frequency p = pressure pc — surface pressure on cone p02 — pitot pressure Re — local Reynolds number based on distance from cone apex Rxx, RZZ — spatial correlation coefficients along the wind-tunnel axis and normal to the axis, respectively ST = Stanton number T0 = stagnation temperature Tw — wall temperature u — velocity p — density 6C = cone half-angle x,z — separation distances along the wind-tunnel axis and normal to the axis, respectively