Control of the shear layer above a supersonic cavity using energy deposition

An experimental study was conducted to investigate the effectiveness of pulsed energy deposition as a means of active flow control for the shear layer over a supersonic cavity in the open configuration. The excitation was generated with a Q-switched Nd:YAG pulsed laser and was applied as a spanwise oriented "line" along the leading edge of a cavity. The study was conducted at a freestream Mach number of 1.4 and for a cavity length-to-depth ratio of 5.29. The flow field was analyzed over a range of delay times from the excitation laser pulse using schlieren photography and particle image velocimetry measurements. Analysis of phase averaged schlieren images indicated considerable alterations to the cavity flow field in the wake of the generated disturbance. Specifically, the formation and growth of a coherent large-scale structure (consisting of two adjoining vortices) was identified. This result was confirmed through two-component velocity field data obtained from particle image velocimetry measurements. The velocity information was also used to determine the instantaneous convective velocity of a large-scale structure that developed in the shear layer. The large-scale structure generated by the laser induced excitation also appeared to have similar characteristics and a theoretical convective velocity as that proposed by past researchers for compressible shear layers.