激波中湍动边界层相互作用失稳特性的双平面PIV研究检测方案(粒子图像测速)

The unsteady organization and temporal dynamics of the interaction between a planar shock wave impinging on a turbulent boundary layer at a free stream Mach number of M∞=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 obtain instantaneous velocity fields separated by a prescribed small time delay. This enables to obtain, in addition to mean and statistical flow properties, also instantaneously time resolved data to characterize the temporal dynamics of the flow phenomenon in terms of time scales, temporal correlations and convective velocities. The characteristic time scales for the incoming boundary layer, the separation region and the reflected shock are evaluated by means of measuring the temporal auto-correlation coefficient in the complete flow field for a range of time delays from 5 ms to 2000 ms. These auto-correlation fields are used to quantify the time scales in selected regions of the flow. This permits resolving the dominant time scales within the boundary layer and the interaction region. I. Introduction