Noise Reduction of Open Cavities by Passive Flow Control Methods at Transonic Speeds using OpenFOAM

Abstract

Flow over a cavity is one of the most intriguing problems in aeronautics. Although geometry is simple, the physics of cavity requires uttermost attention. In this study, various novel passive flow control techniques such as reshaping the aft wall as stair-stepped configuration or combinations of spoilers with reshaped aft wall are applied to cavity and effects of these techniques are investigated numerically. Combined configurations that are proposed in the present study are considered as a novelty to the literature. Analyses are performed with Detached Eddy Simulation method three-dimensionally in transonic regime (0.85 Mach) for a Reynolds number of ~107 based on the cavity length, 0.508 m, using open-source software OpenFOAM. Results are compared with both experimental data and each other, fundamentally in terms of Overall Average Sound Pressure Level. Further examinations are also performed for features such as Mach number, turbulent intensity and turbulent coherent structures. It is seen that combined passive flow control methods have reduced Overall Average Sound Pressure Level by ~10 dB. Newly proposed passive flow control methods have also reduced Overall Average Sound Pressure Level by ~6 dB. A high correlation between coherent turbulent structures and generated noise is observed.