On the cavity-actuated supersonic mixing layer downstream a thick splitter plate

Abstract

We propose a cavity as an actuator to actuate the supersonic mixing layer downstream a thick splitter plate. The cavity-actuated case at Re = 1.73 × 105 is simulated using large eddy simulation. The forced dynamics is resolved by the cluster-based network model (CNM) from a probabilistic point of view. Introducing a cavity obtains a 50% increase in the growth rate of vorticity thickness. The recirculation region immediately downstream the trailing edge of the splitter plate is largely reduced, which contributes to the advanced and fast growth of the redeveloping mixing layer. The cavity oscillation induces three-dimensional features that are beneficial to the small-scale mixing. Spectral analysis reveals that the cavity-actuated flow field exhibits the phenomena of the strict frequency-lock and temporal mode-switching. The CNM successfully resolves the intermittent dynamics of the supersonic mixing layer using only ten centroids. The CNM’s outcomes reveal two flow regimes of the unforced case: the Kelvin–Helmholtz vortex and vortex pairing. The cavity oscillation significantly affects the flow patterns of the centroids, which exhibit flow structures closely associated with the wake mode and shear-layer mode of the cavity oscillations. The dynamics of the cavity-actuated case is tamed into a strictly periodic transition loop among ten clusters undergoing the cyclic motion of the cluster energy fluctuation from the maximum to the minimum. Each centroid of the cavity-actuated case transports much more turbulent kinetic energy than that of the unforced case. Overall, the cavity-actuated attractor gets a 3.27 times increase in the energy fluctuation.