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Sunroof buffeting of a simplified car model was investigated experimentally and numerically in order to assess the potential of numerical methods to design sunroofs that are quiet and functional. The numerical results have been obtained using the commercially available software PowerFLOW. The simulation kernel of this software is based on the numerical scheme known as the Lattice Boltzmann Method (LBM), combined with an RNG turbulence model. This scheme accurately captures time-dependent aerodynamic behavior of high Reynolds number flows over complex geometries, together with the acoustic response of resonant systems. In this work, a simplified car model with a sunroof was used for validation. A simulation methodology to determine the acoustic response of the passenger cabin was investigated and verified experimentally. The sunroof buffeting phenomenon was simulated over a range of flow conditions, and the results were found to be in good agreement with experimental data.

Notched spoilers may be used to suppress flow-induced cavity resonance in vehicles with open sunroofs or side windows. The notches are believed to generate streamwise vortices that break down the structure of the leading edge cross-stream vortices predominantly responsible for the cavity excitation. The objectives of the present study were to gain a better understanding of the buffeting suppression mechanisms associated with notched spoilers, and to gather data for computational model verification. To this end, experiments were performed to characterize the surface pressure field downstream of straight and notched spoilers mounted on a rigid wall to observe the effects of the notches on the static and dynamic wall pressure. Detailed flow velocity measurements were made using hot-wire anemometry. The results indicated that the presence of notches on the spoiler reduces drag, and thus tends to move the flow reattachment location closer to the spoiler.