Effects of transient actuation on shear-layer oscillation dynamics in open-cavity flow

Active control of the shear-layer oscillation in a compressible open-cavity flow through an energy-based actuator remains an attractive technique. However, an efficient design of an unsteady actuation strategy is a great challenge due to our limited understanding of the transient dynamics of the interaction between the shear-layer oscillation and the actuation. In this work, we examine the response of cavity flow oscillations modified by various transient actuation introduced upstream of the cavity leading edge. The free stream Mach number is 0.5. Single- and multiple-cycle actuation with different duty cycles and wall-normal velocity amplitude are studied. The response captured from the probes in the shear layer and aftwall of the cavity exhibit significant transient dynamics, which amplifies or suppresses flow oscillation. The phase and the frequency of the oscillation change due to the actuation. Moreover, we perform modal analysis of the flow fields to gain insights into the dynamics of the dominant modes over a range of time periods during this transient process. The findings highlight the role of different actuation strategies on the dynamics of the shear-layer oscillation, which can serve as a foundation to develop more efficient unsteady active flow control strategies.