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.