摘要：

A study of stability and transition at Mach 3 has been undertaken. A supersonic wind tunnel of the blowdown type has been developed and thoroughly calibrated to operate at very low stagnation pressure (3.5 psia) with a corresponding range of Reynolds number from Re/m = 2×10^6 to Re/m = 5.5×10^7. At the lowest stagnation pressure with laminar boundary layers on the tunnel walls, the free-stream turbulence level was found to be less than .15%. The mean flow over a flat plate has been mapped in detail and accurate comparisons to numerical simulations made. These comparisons are very accurate; they are then used to calibrate the hot-wire and obtain more accurate measurements of the amplitude distribution across the boundary layer for the narrow band of frequencies of the most unstable, naturally occurring, as well as forced, disturbances. Spectra, growth rates, wave angles, wave speeds and amplitude distributions of naturally occurring instability waves and the background free-stream forcing have been measured using multiple hot wire configurations. The results have been compared with the numerical calculations from stability theory that have been provided both by Mack and Balakumar (private communications). Discrepancies between predicted and measured growth rates are discussed. Measurements of forced instability disturbances using a point source on the surface are also described and further detailed comparisons with predictions are presented.

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