Estimation Method for Automobile Aerodynamic Noise 920205

Cost and weight reduction considerations make it very important to evaluate and reduce aerodynamic noise in the early stage of vehicle develpment. For these reasons, a method to evaluate aerodynamic noise quantitatively is needed. As an initial step, our first paper investigated airflow around the A-pillar of a full-scale vehicle. As a result, vortical flow structure and the influence of the vortical flow on the pressure fluctuations were clarified. As the second step, this paper presents an estimation method for the aerodynamic noise from a vehicle. Based on Lighthill's equation, we propose an evaluation equation to estimate aerodynamic noise. The aerodynamic noise radiated externally from a vehicle is estimated as ∑(P_fi,f_i,S_fi)² Where P_fi is the fluctuating pressure on the surface of the vehicle, f_i the frequency and S_fi the correlation area. The method is applied to the aerodynamic noise problem associated with the A-pillar of a vehicle. The proposed method clarifies how the aerodynamic noise is increased depending on the vehicle speed at typical frequencies.