Active flow control of a transitional-open, three-dimensional cavity with lateral apertures in a channel flow configuration: Mitigation of the pressure footprint and fluctuations.

Flows over transitional-open cavities, with a shear-layer that partly enters the cavity are relevant to many branches of engineering. These flows are known to be a source of instabilities, high pressure disturbances and large recirculation regions, leading to excessive wall pressure footprint. The subject of this study is a 6.44 length-to-depth ratio and 3.29 width-to-depth ratio cavity, considering wall proximity effects. The objective is to investigate the mitigation of the wall pressure footprint and fluctuations through steady blowing upstream of the cavity leading edge.

Unsteady numerical CFD simulations and experiments have been conducted to identify the mechanisms underlying the flow dynamics of both baseline and controlled cases. Concomitant pressure, and Particle Image Velocimetry (PIV) measurements have been performed at a Reynolds number of 2.8*10⁵. Centerline wall pressure coefficient distribution Cp and cavity inner flow fields are compared between experimental and numerical data. They show good agreement.

The control strategy changes the flow drastically upstream of the cavity. The boundary layer is thickened, and the ground clearance flow rate is reduced. It transforms the dynamics of the shear layer impinging onto the cavity and impacts the inner recirculation bubble. The steady blowing is successful to reduce the pressure gradient between upstream and downstream cavity walls, with almost 20%. It has also reduced the fluctuations all along the cavity walls with an amount of 20%.