Detached Eddy Simulation of a Supersonic Cavity Flow With and Without Passive Flow Control

Abstract

Time accurate numerical computations using a detached-eddy simulation approach were conducted to investigate the suppression mechanisms of supersonic cavity flow when controlled with a rod placed near the cavity leading edge and fully immersed inside the boundary layer. The rectangular cavity had a length-to-depth ratio of six and had a turbulent boundary layer at its leading edge. The diameter of the rod was 43% of the approaching boundary layer thickness and was placed with the top of the rod at the top of the boundary layer which was shown to be the most effective configuration in the accompanying wind tunnel experiments. It was observed that the rod leads to an initially thicker shear layer that spreads more rapidly because the turbulent structures in the wake of the rod interact with the cavity shear layer with time periodic excitation which lifts the shear layer near the cavity leading edge. The structures that reside within the shear layer are smaller and less organized. When coupled with the thicker shear layer, it is believed this leads to a lowered receptivity to the disturbances that are known to propagate upstream inside the cavity. The controlled cavity exhibits an altered aft wall impingement point which is due to the combined lifting and altered flapping nature of the shear layer. The upstream propagating disturbance emanating from the aft wall is thus weakened due in part to the lower speed flow impinging on the aft wall. These coupled events lead to drastically reduced tonal components (which are lowered near broadband levels) and notable lowering of the broadband levels of the fluctuating pressure measured on the cavity surfaces.