Application of Numerical and Experimental Techniques for the Aero-Acoustic Characterisation of a Car Rear-View Mirror

Abstract

Numerical as well as experimental approaches are used to capture aero-acoustic characteristics of a car rear-view mirror. The numerical study splits up into several parts. Using an actual production mirror, particular emphasis must be put on the geometry preparation and mesh generation. Initially, a CFD simulation of the entire car aerodynamics is performed to extract the proper flow boundary conditions for the aero-acoustic simulation of a smaller section surrounding the mirror. Pressure fluctuations on the surfaces extracted during an LES generate the data base required for the aeroacoustic post-processing. The acoustic pressure at several monitoring points is then calculated using Lighthill's Acoustic Analogy. To include refraction effects of the nearby surfaces a direct BEM approach is also employed. Utilizing the PIV method, local areas of increased turbulence are identified experimentally. Microphone measurements with and without the exterior mirror are performed.