Numerical Study of the Flow-Induced Sunroof Buffeting Noise of a Simplified Cavity Model Based on the Slightly Compressible Model

Numerical computation was conducted to investigate the flow-induced sunroof buffeting noise at low Mach numbers. In order to avoid the stiffness problem which occurs in solving the compressible fluid equations at low Mach numbers, new governing equations were derived with the assumption that there is a slight compressibility effect. The mechanisms of the flow-induced sunroof buffeting noise were investigated by considering a three-dimensional model cavity. Extensive wind tunnel tests were conducted to verify the computational scheme developed in the present study. The results demonstrated that strong pressure fluctuations will be generated inside the cavity and that the modal resonant frequencies are in good agreement with the Rossiter formula and experimental data. Moreover, the results reveal that the sunroof buffeting noise is attributed to the periodicity of flow separation, vortex shedding, vortex impingement and pressure wave feedback, with the addition of the Helmholtz resonance locked effect. Therefore, the current computational approach was validated to have the capability to predict the flow-induced buffeting noise in low-Mach-number flows.