汽车风洞实际流场对声源识别的干扰与修正

Interference and Correction of Actual Flow Field of Automobile Wind Tunnel on Sound Source Identification

为了提高汽车风洞外场声源识别精度,对因实际流场与空风洞之间区别产生的偏差进行分析.关注汽车绕流场与射流剪切层的速度分布,分别对车辆所在自由空间、空风洞与带实际车辆的风洞3种流场进行数值仿真及试验验证.通过无限薄剪切层及实际流场分层声传播模型,预测有无车辆两种风洞状态下的声漂移量,并与实际整车声学风洞声传播试验结果进行比较.结果表明,放入车辆后,风洞势流核心区因受汽车阻塞而流场速度分布不均匀,进而剪切层区域流场受到汽车绕流场干扰而外扩.进行实际流场分层修正后,车表后方声源漂移结果精度大幅提高,能有效提高实际风洞外场声源识别精度.

In order to improve the accuracy of outfield sound source identification in automobile wind tunnel,the deviation caused by the difference between actual flow field and empty wind tunnel is analyzed.Focusing on the velocity distribution of flow around vehicle and jet shear layer,numerical simulation and experimental verification were carried out on 3 kinds of flow fields,including free space where vehicle is located,empty wind tunnel and wind tunnel with actual vehicle.The amounts of sound drift in wind tunnel with or without vehicles were predicted by using infinite thin shear layer model and layered flow field sound propagation model.The predicted sound drift quantities were compared with actual full-scale acoustic wind tunnel sound propagation test results.The results show that,after vehicle was placed in the wind tunnel,the flow field velocity distribution in core area of potential flow was uneven due to obstruction of the vehicle,and then the flow field in shear layer was disturbed by flow field around vehicle.After stratified correction of the actual flow field,the accuracy of sound drift quantity at rear sound source of vehicle body is greatly improved,which can effectively improve the identification accuracy of the actual wind tunnel.