Experimental Study of the Structure of Shock-Induced Turbulent Separated Flow and its Role in Flowfield Unsteadiness.

摘要

This project was aimed at understanding the fundamental cause of the low frequency unsteadiness present in shock-induced turbulent separated flows. A particular emphasis was placed on investigating the role that the upstream boundary layer plays in driving the motion of the separated flow. Three different interactive flows were studied, which included interactions generated by Mach 2 and 5 unswept compression ramps a Mach 5 blunt fin. This study emphasized the use of imaging techniques - such as planar laser scattering and particle image velocimetry (PIV) -- to monitor the conditions in the upstream turbulent boundary layer. For the first time in a shock-induced separated flow, a new multi-camera, multi-laser PIV system was used that enabled both wide-field PIV and time sequenced PIV measurements to be made. Velocity fluctuations in the lower part of the upstream boundary layer were found to be strongly correlated with shock foot motion. This same correlation was demonstrated in both compression ramp and blunt fin interactions. In corroboration of this mechanism, pulsed jet injection was used in the upstream boundary layer to show that the shock can be made to respond to changes in the velocity field induced by the pulsed jets.