Computational Process for Wind Noise Evaluation of Rear-View Mirror Design in Cars

A computational approach to evaluate rear-view mirror performance on wind noise in cars is presented in this paper. As a comfort metric at high speeds, wind noise needs to be addressed, for it dominates interior noise at mid-high frequencies. The impetus on rear-view mirror design arises from its crucial role in the flow field and the resulting pressure fluctuations on the greenhouse panels. The motivation to adopt a computational approach arises from the need to evaluate mirror designs early in vehicle design process and thus in conjunction with different vehicle shapes. The current study uses a Lattice Boltzmann method (LBM) based computational fluid dynamics(CFD) solver to predict the transient flow field and a statistical energy analysis(SEA) solver to predict interior noise contribution from the greenhouse panels. The accuracy of this computational procedure has been validated and published in the past. Realistic car geometry is chosen and the transient flow field around the vehicle resulting from mounting two different rear-view mirror designs is analyzed. The mirrors are ranked based on the interior noise contribution from the greenhouse panels. In each case, pressure fluctuations on the panels are decomposed using a wavenumber filter to visualize the turbulent and acoustic fields. Analysis leading to flow features and geometry responsible for the contributing noisy regions is performed.