Transition Reynolds number comparisons in several major transonic tunnels

Boundary-layer transition and test section environmental noise data were acquired in six major transonic wind tunnels as a part of a broader correlation of the effect of free-stream disturbances on transition Reynolds number. The data were taken at comparative test conditions on a sharp, smooth 10-deg included-angle cone. It was found that aerodynamic noise sources within the test section were the dominant sources of unsteadiness and that transition Reynolds number provided a good indicator for the resulting degradation in flow quality. Amplitudes, frequency composition, directivity, and origin of these disturbances are described.