Supersonic Cavity Flow Subjected to Continuous and Transient Leading-Edge Blowing

A rectangular cavity (L/D=5.67) with Mach 1.5 freestream was subjected to a large temporal variation in leading-edge blowing in order to experimentally investigate the effect on aerodynamic and aeroacoustic oscillation. Unsteady pressure data were obtained via pressure-sensitive paint and discrete pressure transducers. Comparison of baseline (without blowing) and continuous blowing conditions affirmed that leading-edge blowing greatly mitigates surface pressure fluctuations. Transient shutoff experiments showed that sharp increases in surface pressure fluctuations were well-related to the pressure response of the wake region downstream of the leading-edge slots. Moreover, a delay in the amplitude rise of mode 1 compared with mode 2 was found to be statistically significant. The reverse operation of transient blowing turn-on produced a nearly instantaneous decrease in pressure fluctuations, with modal amplitudes damping out over a short period of time. For both cases, variabilities from run to run existed and are likely linked to the condition of the cavity flow at the instance of impulsive flow control operation.