Active supersonic cavity flow control with a pulsed-arc plasma actuator matrix under different phase modulation strategies

A four-column five-row pulsed arc plasma actuator (PAPA) matrix is devised for adaptive supersonic cavity flow control, which is of significance to a wide range of engineering applications such as aircraft weapon bays and scramjet flame holders. By modulating the activation phase of different columns in the matrix, synchronous and traveling wave actuation modes can be achieved. Hotwire measurements demonstrate that in the synchronous mode, the optimal control efficacy with maximum shear layer velocity fluctuation is attained at a discharge frequency of 3 kHz, close to 1/3 of the cavity resonance frequency. With increasing number of actuator columns, the shear layer velocity fluctuations go up monotonically. Cavities with lower back-wall inclination angles tend to have less flow fluctuations in baseline but more improvement under plasma flow control. Compared with the synchronous mode, asynchronous actuation modes demonstrate superior control efficiency. Particularly in the upstream-traveling wave mode, the velocity spectral peak in the shear layer is elevated by 13.7 times, accompanied by an overall improvement in the velocity fluctuation amplitude by 54.7 %, nearly four times that of in the synchronous actuation mode. Physically, the shock waves and thermal bulbs induced by plasma actuation thicken the boundary layer and excite shear layer instabilities, resulting in the observed fluctuation enhancement.