Influence of ground effect on flow field structure and aerodynamic noise of high-speed trains

The simulation of the ground effect has always been a technical difficulty in wind tunnel tests of high-speed trains. In this paper, large eddy simulation and the curl acoustic integral equation were used to simulate the flow-acoustic field results of high-speed trains under four ground simulation systems (GSSs): “moving ground+rotating wheel”, “stationary ground+rotating wheel”, “moving ground+stationary wheel”, and “stationary ground+stationary wheel”. By comparing the fluid-acoustic field results of the four GSSs, the influence laws of different GSSs on the flow field structure, aero-acoustic source, and far-field radiation noise characteristics were investigated, providing guidance for the acoustic wind tunnel testing of high-speed trains. The calculation results of the aerodynamic noise of a 350 km/h high-speed train show that the moving ground and rotating wheel affect mainly the aero-acoustic performance under the train bottom. The influence of the rotating wheel on the equivalent sound source power of the whole vehicle was not more than 5%, but that of the moving ground slip was more than 15%. The average influence of the rotating wheel on the sound pressure level radiated by the whole vehicle was 0.3 dBA, while that of the moving ground was 1.8 dBA. 目 的 高速列车作为高速地面交通工具, 不可避免地会遇到地面效应问题. 地面效应模拟一直是高速列车风洞试验的技术难点. 地面效应现象的准确模拟对高速列车空气动力学和气动噪声的预测精度有很大的影响. 通过对比4种地面模拟系统(GSS)的流声场结果, 研究不同GSS对流场结构、 气动声源和远场辐射噪声特性的影响规律, 为高速列车声学风洞试验提供指导. 创新点 1. 搭建高速列车地面模拟系统, 模拟不同边界条件; 2. 明确轮对旋转与地面滑移对高速列车气动噪声幅值的相对增量及影响频率范围. 方 法 1. 在仿真系统中建立“移动地面+旋转轮对”、 “静止地面+旋转轮对”、 “移动地面+静止轮对”和“静止地面+静止轮对”四种地面模拟系统; 2. 采用大涡模拟和旋度声学积分方程, 对高速列车的流声场结果进行模拟; 3. 通过对比4种GSS的流声场结果, 研究不同GSS对流场结构、 气动声源和远场辐射噪声特性的影响规律. 结 论 1. 移动地面和旋转轮对是影响列车底部气动声学性能的主要因素; 2. 旋转轮对对整车等效声源功率的影响不大于5%, 且移动地面对整车等效声源功率的影响大于15%; 3. 旋转轮对对整车辐射声压级的平均影响为0.3 dBA, 且运动地面对整车辐射声压级的平均影响为1.8 dBA; 它们主要影响100 Hz以下的气动声学性能.