激波湍动边界层相互作用失稳特性的双平面PIV研究
The unsteady organization and temporal dynamics of the interaction between a planarshock wave impinging on a turbulent boundary layer at a free stream Mach number ofM∞ =1.69 is investigated experimentally by means of dual-plane Particle Image Velocimetry(dual-PIV). Two independent PIV systems were combined in two component mode to obtaininstantaneous velocity fields separated by a prescribed small time delay. This enables toobtain, in addition to mean and statistical flow properties, also instantaneously time resolveddata to characterize the temporal dynamics of the flow phenomenon in terms of time scales,temporal correlations and convective velocities. The characteristic time scales for theincoming boundary layer, the separation region and the reflected shock are evaluated bymeans of measuring the temporal auto-correlation coefficient in the complete flow field for arange of time delays from 5 ms to 2000 ms. These auto-correlation fields are used to quantifythe time scales in selected regions of the flow. This permits resolving the dominant timescales within the boundary layer and the interaction region.I. Introduction