Flow-induced noise around the a-pillar of an idealized car greenhouse

Due to the successes in reducing motor and tire noise as perceived inside cars and trucks, aerodynamically generated noise becomes more and more important. Some time ago the study of aero-acoustics in and around these vehicles was mainly done by wind tunnel test. Nowadays, computational methods become available that allow for numerical simulations of the aerodynamically generated noise. At TNO, a new computational aero-acoustics approach has been developed. This method provides a relatively fast assessment of the aerodynamically generated broadband noise and wall pressure fluctuations. At the same time it is capable of handling complex geometries. The method consists of three steps: 1) time-averaged RANS calculations, 2) unsteady acoustic source generation based on the RANS data, and 3) calculation of the propagation of the pressure fluctuations using the linearized Euler equations on an unstructured mesh. This paper gives an application example of the method and a comparison with results obtained from wind tunnel tests. The case at hand is an idealized shape of a car greenhouse; a rectangular block with a wedged front, representing the windscreen. Simulations have been carried out for two wind speeds: 55 and 70 mph. The calculation results are presented and discussed. Also a comparison with measurements is presented: good agreement between measurement and calculations is found. © 2002 by the author(s). Published by the American Institute of Aeronautics and Astronautics, Inc.