Numerical Analisis On Aerodynamic Noise Of The High-Speed Train Bogie And Pantograph

High-speed train has been developed very fast these years. With the speed growing, noise has been becoming a more significant problem. Aerodynamic noise levels increase at a rate of V6(with V the speed), while the rolling noise levels increase in sound power according to V3. Finally aerodynamic noise becomes the dominant instead of rolling noise. And study has shown that bogie and pantograph are the main sections where the aerodynamic noises are generated, so it’s necessary to make aerodynamic noise analysis for these sections. In this paper, a hybrid CFD/AA numerical simulation method based on Lighthil’s acoustic analogy theory is used to capture the unsteady airflow around the bogie and pantograph, then the noise source distribution on the surface and the distribution of the far-field external aerodynamic noise is simulated. The main works are listed as follows:1. Theory study of aerodynamic noise. Based on the aerodynamic noise theories, combined with features of the high-speed train, an appropriate plan for the analysis has been established.2. Numerical simulation of the external air flow field of the high-speed train bogie and pantograph. Firstly the numerical simulation models of the bogie and pantograph are established, then the Large Eddy Simulation is executed to simulate the external flow field at 350km/h. The results show that, complex airflow turbulence has been produced around the external surfaces of the bogie and pantograph, especially near the very unsmooth surfaces or the corners, the turbulent flow result in severe pressure fluctuations on the surface. For pantograph which is consisted of rods, many eddies are generating and then disappear behind the rod, which also gives rise to pressure fluctuations.3. Numerical analysis of the aerodynamic noise sources distribution on the surface. The previously calculated fluctuating pressures at the surface are transformed into the acoustic sources of the bogie and the pantograph. It is shown that the turbulent flow makes great contributions to the surface sound power level of the acoustic sources.4. Calculation and analysis of the external far-field aerodynamic noise of the bogie and pantograph. Taking the acoustic sources at the surface as Boundary conditions, the direct Boundary Element Method is used to evaluate the acoustic radiation on the external region of the bogie and pantograph. Then the characteristics of the far-field aerodynamic noise is discussed by studying the frequency spectrum of measuring points. The results illustrate that noise of the bogie is mainly abroad band noise, while for the pantograph, sound pressure levels at some frequencies(261HZ and 322HZ) are much higher than the others. The spectrum characteristics of sound pressure are the same for all the measuring points, but sound pressure level reduces as the point located far more from the bogie or pantograph.