Study on Turbulence and Wind Noise Source Characteristics at the Vehicle Front Side Window Area Under Unsteady Airflow

Abstract:

In contrast to steady airflow conditions in wind tunnel tests， vehicles on actual roads experience airflow with varying velocity and direction due to natural wind and wake effects from upstream vehicles. This study employs a simplified vehicle model to investigate turbulence characteristics of unsteady wind and unsteady wind noise sources at the front side window area. The research utilizes DES model， implementing both SEM and preceding vehicle method to generate unsteady wind excitation. Analysis of airflow velocity data collected in front of the model and at the front side window area revealed turbulence intensity ranging from 10% to 25%. The probability density distribution of airflow velocity and yaw angle follows a Gaussian distribution， while the power spectral density of fluctuating wind velocity corresponds to the von Karman spectrum， aligning with real road test conditions. Through integration with APE， distinct convective and acoustic pressure fluctuations at the front side window area were obtained. Results demonstrate that SEM's convective pressure fluctuation energy approximates steady wind excitation across all frequencies， with notably elevated acoustic pressure fluctuation energy between 500-2500 Hz. The preceding vehicle method shows reduced convective and acoustic pressure fluctuation energies compared to steady wind excitation due to upstream vehicle influence. Under unsteady wind excitation， the kurtosis value at the external ear position of the side window increases， contrasting with near-zero values under steady conditions.