风洞射流和汽车绕流对声传播的影响

汽车风洞气动噪声测试中,由于射流和汽车绕流场的存在,流场外测量不能获取汽车声源的准确信息?研究以两种流场对声传播方向(声源漂移量)的影响开展?通过在风洞射流核心区安放特定声源和实车的试验,分别得到了射流和汽车绕流场对声传播的影响?研究表明两种流场对声传播都会产生较大影响,试验分析应加以考虑;研究分别对风洞射流和汽车绕流进行了气动数值仿真,据此拟合出剪切层和汽车绕流场速度分布线性化模型,并结合几何声学方法,建立了连续多层均匀运动介质声传播模型,得到了预测射流和汽车绕流产生声漂移量的方法?研究表明该方法可以有效预测风洞声学实验中介质运动对声传播方向的影响,并可用于风洞声学试验中流动对传播方向影响的修正?

The influences of wind tunnel jet flow and airflow around vehicle on sound propagation

For aero-acoustic measurement in open-jet automotive wind tunnel, the sound source information of the test vehicle cannot be accurately obtained due to the presence of jet shear layer and the airflow around the test vehicle. Through wind tunnel tests for a particular sound source and a test vehicle both positioned in the jet core of test section, the influences of jet flow and flow around the vehicle on sound propagation are studied. Result shows that the two flow fields all lead to significant acoustic drift phenomenon which should be taken into consideration in test data analysis. The linear velocity distribution profiles of jet shear layer and flow around the vehicle are acquired by fitting algorithm, and combined with geometric acoustics, a continuous multi-layer sound propagation model is established to predict the sound source drift quantities of jet flow and flow around vehicle. Comparison with test data indicates that the sound propagation model proposed in this paper can effectively predict the influence of medium motion on sound transmission direction; therefore, it can have widespread application in test data correction for automotive aero-acoustic wind tunnel test.