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ANALYSIS OF SHOCK MOTION IN STBLI USING DNS DATA

Minwei Wu
Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA

Pino Martin
Department of Mechanical and Aerospace Engineering, Princeton University, Princeton, NJ 08544, USA

Abstract

Direct numerical simulation data of a 24° compression ramp configuration are used to analyze the shock motion. The motion can be observed from wall-pressure and mass- flux signals measured in the free stream. The characteristic low frequency is in the range of 0.007-0.013 U, as found in Wu & Martin (2007). The shock motion also exhibits high-frequency of O(U/δ), small-amplitude spanwise wrinkling , which is mainly caused by the spanwise nonuniformity of turbulent structures in the incoming boundary layer. In studying the low frequency streamwise oscillation, conditional statistics show that there is no significant difference in the properties of the incoming boundary layer when the shock location is upstream or downstream. The spanwise-mean separation point also undergoes a low frequency motion and is found to highly correlate with the shock motion. A small correlation is found between the low-momentum structures in the incoming boundary layer and the separation point. Correlations among the spanwise-mean separation point, reattachment point and the shock location indicate that the low-frequency shock unsteadiness is influenced by the downstream flow.