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Effects of Sweep on the Physics of Unsteady Shock-Induced Turbulent Separated Flows
Final rept. 1 Mar 1989-30 Jun 1991
TEXAS UNIV AT AUSTIN DEPT OF AEROSPACE ENGINEERING AND ENGINEERING MECHANICS
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To examine the effects of sweepback on the unsteady separation in Mach 5 compression ramp interactions, fluctuating wall pressure measurements have been made upstream of the corner line in interactions generated by unswept, and 10, 20, 25, 30, 40, and 50 deg. swept models. The streamwise ramp angle was 28 deg. in all cases. The data were analyzed Lising standard time series analysis techniques and condition all sampling algorithms. The results show that 1 In highly swept interactions i.e., corner line sweeps greater than 25 deg., the rms distributions of pressure fluctuations as well as the mean distributions ire quasi-conically symmetric. Rms levels decrease globally with increasing sweep as does the maximum rms generated by the translating separation shock. 2 The length of the intermittent region, over which the separation shock foot translates, decreases with increasing sweep. In a given interaction, the length of the intermittent region grows spanwise. 3 Dominant separation shock frequencies, observed in both surface pressure fluctuations and separation shock foot histories, increase from about 0.3-0.5 kHz for unswept flow to about 2-7 kHz in highly swept flows. In a given interaction, shock frequencies decrease spanwise. 4 Separation shock dynamics defined in terms of the shock foot history and its statistics are essentially the same in all interactions. The separation shock foot position is normally distributed, and the mean shock velocities are essentially equal. Tile only difference is in the length of the region in which the separation shock moves. Higher frequencies are a direct result of the decrease in the length scale of the separation shock motion. Shock Wave Boundary Layer Interaction, Unsteady Flow, Separated Turbulent Boundary Layers.
APPROVED FOR PUBLIC RELEASE