Subsonic Flow Over Open Cavities: Part 2 — Passive Control Methods

A global description of the intrinsic instabilities of shear layer for further understanding of the aeroacoustical oscillation of subsonic flow over open cavities has been given in the companion paper. The needs to suppress dynamic pressure loads in open cavities play an important role in many aeronautical applications. Large eddy simulation (LES) of passive control methods including recessed leading edge step and sloping trailing edge wall arrangements is performed. The unsteady flow characteristics and aeroacoustical oscillation mechanism of baseline cavity are given in advance. Effects of both passive control methods on resonant frequency and sound pressure levels are demonstrated and analyzed. Recessed leading edge step tends to decrease the resonant Strouhal numbers and the maximal reduction of overall sound pressure levels (OASPL) reaches 8.5dB. Sloping trailing edge wall reduces OASPL by shifting down the impinging location on cavity back wall. The optimal reduction of OASPL arrives at 11dB when the angle of inclination is maximal. The drag induced by cavity flows is found to be highly correlated with dynamic loads on cavity walls.