Application of the Crosscorrelation Technique to Wall-Pressure Fluctuations below Free Shear Layers and Oscillating Shocks

Abstract

Recent flight and wind-tunnel tests indicate that the skin of large launch vehicles might suffer a high-frequency vibration caused by flow separation and oscillating shocks. It is proposed to classify the noise sources by a crosscorrelation of the wall-pressure fluctuations. For design purposes, the correlation distances of narrow-band pressure components would be mapped. If the transverse flexural wave of a present or future skin panel matches the measured correlation distances, a dangerous skin vibration is probable. A “quick look” is described that will reduce the enormous amount of necessary data to an acceptable minimum. An analysis of systematic and statistical errors is given showing that the power spectrum of the exciting force could be predicted within acceptable confidence by the crosscorrelation technique.