Optimal Sunroof Buffeting Predictions with Compressibility and Surface Impedance Effects

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Computational Fluid Dynamic (CFD) studies of sunroof buffeting on production vehicles demonstrate accurate prediction of the main buffeting frequency and its harmonics. For production vehicles, none to date has illustrated the phenomenon of buffeting intensity maximization over a vehicle speed range, at a frequency related to the volume of the passenger compartment. All assume that the interior surfaces of the vehicle are rigid, potentially overestimating in-cabin noise intensities by failing to account for surface impedance from non-acoustically rigid trims and linings. In this paper, a modelling study of both effects is presented. Advanced LES-type turbulence modelling, in the form of Detached Eddy Simulation (DES), is used. The hybrid approach, linking acoustic source generation in CFD to acoustic pressure wave propagation with Boundary Element Methods (BEM), is adopted. The former is used to predict the surface pressure excitations induced by the flow, the latter to interpret these as equivalent dipoles to be propagated. The results confirm both the necessity of accounting for compressibility effects in the CFD solver when predicting the buffeting intensity maximization, and surface impedance affects on noise levels perceived by the driver and passengers at higher frequencies closer to the peak audibility range.

Author Name: 
Alex Read
Fred Mendonca
Christophe Schram
Michel Tournour
Kenneth Karbon
Conference Location: 
Monterey, California,USA
Copyright © 2005 by the authors
Conference Date: 
Monday, May 23, 2005
Paper Reference: 
AIAA 2005- 2859
American Institute of Aeronautics and Astronautics
Conference Name: 
1th AIAA/CEAS Aeroacoustics Conference