Aerodynamic Noise Source Identification for a Coupe Passenger Car by Numerical Method Focusing on the Effect of the Rear Spoiler 2013-01-1013

Nowadays, outer surface design of passenger cars is not just a matter of styling and safety but air flow around car body and exterior accessories has significant effect on fuel consumption, performance and dominantly on the wind noise. In recent years, passenger comfort is one of the most challenging and important automotive attributes for car makers. Controlling the turbulence eddies that causes aerodynamic noise can remarkably affect passenger's comfort quality. Identification of aerodynamic sources is considered as the first step in order to control the wind noise.

In this research, computational fluid dynamics method is applied to simulate the wind flow around the car and the investigation of aerodynamic noise pattern is performed by numerical method which is the most prevalent way that is used by auto industries. By the advent of virtual simulations and by implementing these methods for the purpose of predicting and modifying in the whole car design phase, a considerable reduction in the automotive design process time and cost has been achieved. This study includes two main sections: Firstly, identification of aerodynamic noise source around a coupe passenger car is investigated. For this purpose after CAD modeling, preparing model for simulation is performed in preprocessing CAE software and numerical calculations are done by using finite volume method. In fact, fluctuations of pressure on external surfaces of body are considered as the main cause for aerodynamic noise and in practice this phenomena is detected for the identification purpose. Hence, acoustic power level is the reference parameter for studying the wind acoustic quality. In order to investigate acoustic power, broad band noise model is applied for acoustics and realizable k-ε model is used for solving turbulence fluid. In the second section, rear spoiler is added to the vehicle and acoustic effects are studied. Results are compared with each other and the acoustic effects of the rear spoiler on the rear section of the car surface including the windshield, trunk lid and rear end parts are summarized using CAE tools.