Active Control for Pressure Fluctuation Reductions in an Incompressible Turbulent Cavity Flow

Abstract

Large-eddy simulations of incompressible turbulent boundary layer flows over an open cavity are conducted to investigate the effects of wall-normal steady blowing on the suppression of pressure fluctuations on the cavity walls. The length (L) to depth (D) ratio (L/D) of the cavity is 2 and the Reynolds number based on the depth of the cavity (ReD) is 12,000. Wall-normal steady blowing is imposed through a limited transverse slot in an upstream region of the cavity leading edge with varying the momentum coefficient (Cμ). As the value of Cμ increases, the pressure fluctuations on the cavity walls decrease mostly owing to weakened impingement of turbulent structures residing along the shear layer on the aft wall by lifting effects, reaching a maximum reduction of -7.61% compared to an uncontrolled case when Cμ = 0.015. However, as the value of Cμ increases further, the pressure fluctuations increase continuously, exceeding that of an uncontrolled case when Cμ > 0.05. Because intensified turbulent vortical structures as the value of Cμ increases lead to strong interactions of small-scale vortices with the front and bottom walls with an accompanying large motion for the primary recirculation zone within the cavity, additional pressure fluctuations generated on the cavity walls deteriorate the control performance due to the blowing.