A Predictive Model for the Interior Pressure Oscillations from Flow Over Vehicle Openings 971906
An analytical model based on “vortex sound” theory was investigated for predicting the frequency, the relative magnitude, the onset, and the offset of self-sustained interior pressure fluctuations inside a vehicle with an open sunroof. The “buffeting” phenomenon was found to be caused by the flow-excited resonance of the cavity. The model was applied to investigate the optimal sunroof length and width for a mid-size sedan. The input parameters are the cavity volume, the orifice dimensions, the flow velocity, and one coefficient characterizing vortex diffusion. The analytical predictions were compared with experimental results obtained for a system which geometry approximated the one-fifth scale model of a typical vehicle passenger compartment with a rectangular, open sunroof. Predicted and observed frequencies and relative interior pressure levels were in good agreement around the “critical” velocity, at which the cavity response is near resonance. The tradeoffs between the orifice dimensions and the critical velocity indicated that it may be difficult to avoid self-sustained oscillations from geometrical optimization alone, without the use of suppression devices such as leading edge spoilers.
Citation: Mongeau, L., Brown, D., Kook, H., and Zorea, S., "A Predictive Model for the Interior Pressure Oscillations from Flow Over Vehicle Openings," SAE Technical Paper 971906, 1997, https://doi.org/10.4271/971906. Download Citation
L. Mongeau, D. Brown, H. Kook, S. Zorea
Purdue Univ., Ford Motor Co.
SAE Noise and Vibration Conference and Exposition
Proceedings of the 1997 Noise and Vibration Conference-P-309, SAE 1997 Transactions - Journal of Passenger Cars-V106-6