Analysis on Pressure Excitation on Automotive Front Side Window and Its Source

DOI：

 作者 单位 袁海东1，2，杨志刚1，2，3，李启良1，2 （1. 同济大学 上海地面交通工具风洞中心，上海 201804； 2. 上海市地面交通工具空气动力与热环境模拟重点实验室，上海 201804； 3. 北京民用飞机技术研究中心，北京 102211）

汽车前侧窗表面的压力激励是前侧窗区域非定常流动和气动噪声的重要体现指标. 这一区域复杂的非定常流动产生更大尺度范围的涡结构，从而导致前侧窗表面复杂的非定常压力激励. 本文通过基于声学扰动量方程组（APE）的混合计算气动声学（CAA）方法分别获得汽车前侧窗表面的湍流压力激励和声学压力激励. 引入动力学模态分解（DMD）对前侧窗表面的压力激励进行分析，指出湍流压力激励基于频率的区域分布特征和声学压力激励辐射声场特征.讨论了湍流压力激励、声学压力激励以及不同的激励源对车内噪声的相对贡献量. DMD识别的前侧窗表面主要的湍流压力激励是由后视镜尾迹的脱落涡产生的，其特征频率为59 Hz，与试验测量结果一致，验证了湍流压力激励计算结果的有效性. 通过对比前侧窗区域空间截面上相同频率的湍流压力和声学压力的DMD模态，识别出前侧窗区域主要的声源位置，一个位于后视镜基座处，由这一区域的后视镜基座涡的涡对流产生. 另一个位于后视镜镜体的下缘，由这一区域的分离涡产生. 后者由风洞试验中的传声器阵列识别出来，验证了声学场计算结果的有效性.

The pressure excitation on the front window surface of the vehicle is an important indicator of unsteady flow and aerodynamic noise in the front window area. The complex unsteady flow in this area produces a larger scale vortex structure, which leads to complex unsteady pressure excitation on the front side window surface. In this paper, the turbulent pressure and acoustic pressure excitations on the front window surface of the vehicle are obtained by the hybrid Computational Aeroacoustics（CAA） method based on Acoustic Perturbation Equations（APE）. The Dynamical Mode Decomposition（DMD） is introduced to analyze the pressure excitation on the front side window surface, which demonstrates that the turbulent pressure excitation has the frequency-based regional distribution characteristics and the acoustic pressure excitation acts as radiation sound field characteristics. The turbulent pressure excitation, acoustic pressure excitation and the relative contributions of different excitation sources to the car interior noise are discussed. The main turbulent pressure excitation on the front side window surface identified by the DMD is generated by the wake vortex shedding of the rear view mirror trail. Its characteristic frequency is 59 Hz, which is consistent with the experimental measurement results and it also verifies the validation of the turbulent pressure excitation calculation results. Comparing the DMD modes of the turbulent pressure and acoustic pressure with the same frequency in the space section of the front side window region, the main sound source position in the front side window region is identified. One is located at the pedestal of the rearview mirror, which is generated by the convection of the pedestal vortex in this region. The other is located at the lower edge of the mirror body, resulting from the separation vortex in this area. The latter is identified by the microphone array in the wind tunnel test，which validates of the estimation of the acoustic field.