Spatio-temporal analysis of wall pressure fluctuations on several automotive side-glasses
by Sandrine Vergne, Francois Van Herpe, Jonathan Viot
International Journal of Aerodynamics (IJAD), Vol. 1, No. 3/4, 2011

Abstract: For modern cars, aerodynamic noise is becoming the major source of annoyance during peri-urban trips (above 100 km/h) and for frequencies higher than 400 Hz. The origin of the aerodynamic noise in the cabin is the flow around the vehicle and more particularly in the neighbourhood of the front side glass (side mirror wake, A-pillar vortex etc). A complex and unsteady pressure field excites the glass panels which vibrates and radiates noise inside the cabin. The evaluation of the acoustic radiations induced by the external flow in the car is a challenging issue. In this article, an in-depth experimental and computational study of wall pressure fluctuations (WPF) generated by turbulent flow in the side glass region of different A-pillar architectures of an automobile is presented. The vehicles are placed in an anechoic wind tunnel at a velocity corresponding to highway trips (i.e., 140 km/h) at 0 and 10 yaw angle. The WPF measurements are obtained using flush-mounted microphones located on the side glass. Fifty to 90 microphones are used according to the window shape. The numerical results are obtained with a time-explicit fluid flow solver based on the Lattice Boltzmann method (LBM); the wall pressure power spectral density (PSD) results are analysed and compared to experimental data. The flow topologies induced by the different A-pillar architectures are compared; the effect of the yaw angle is analysed. The spatio-temporal characteristics of the computed WPF are then studied by examining the evolution of two points' coherence and convective velocity when one moves on the side glass.

Online publication date: Sat, 28-Feb-2015

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