Study On Aerodynamic Noise Generation Mechanism And Distribution Characteristics For High-Speed Train’s Pantograph

The running noise of high-speed trains mainly includes wheel-rail noise, electrical noise, and aerodynamic noise. The influence of the aerodynamic noise will exceed the traditional track noise and becomes the main noise source when the speed of the trains is over 300km/h. The aerodynamic noise primary results from the interaction between the train and the air, as the train is traveling at a high speed, the flowing air around the rod structure of pantograph formed a significant flow phenomenon, and then induced large aerodynamic noise. However, with the continuous raising of the train speed, the aerodynamic noise pollution will become more and more serious. In this paper, according to the fluid mechanics and the basic theory of acoustics, we study the aerodynamic noise of pantograph by utilizing numerical simulation methods. The main contents and conclusions are summarized as follows:(1) First of all, the generating mechanism of the aerodynamic noise caused by high-speed train’ pantograph is investigated based on fluid mechanics and acoustic theory, and the type of sound source, noise characteristics and evaluation standards of the pantograph aerodynamic noise is analyzed.(2) The model of pantograph, insulator, the base of pantograph and exterior space is established to analysis aerodynamic noise by using three-dimensional modeling software CATIA. Then using ANSYS Fluent software, LES (large eddy simulation) method is selected to study the near-field aerodynamic noise which caused by pantograph. The flow field distribution, static pressure, fluctuating pressure, frequency spectrum and other characteristics of aerodynamic noise under different speed of pantograph surface were searched. It can be concluded that, the flow field near the surface of the pantograph changes very complicated and formed vortex shedding at the leeward of the pantograph, then caused acutely pressure pulsation. In addition, with the train’s speed increasing, the static pressure of pantograph surface and the amplitude of fluctuating pressure of each monitoring are increased obviously. There is no clear main frequency of aerodynamic noise and distribution in wide frequency band, and the energy is mainly concentrated in low frequency range.(3) By using the boundary element method, far-field aerodynamic noise of high-speed train pantograph are analyzed. The results showed that, the spectrum of far-field aerodynamic noise is mainly concentrated in 200Hz～1600Hz, and the noise energy on other band of frequency is smaller. Besides, the sound pressure level of each monitoring point is proportional to the train’s speed, and it is inversely proportional to the distance to the pantograph. The influence of height of sound pressure level can be neglected when the monitoring point is far away from pantograph. The higher the train speed, the stronger the intensity of the sound pressure level in the monitoring points where distance from pantograph center side at 25meters,height from ground at 3.5meters.Furthermore, the sound pressure level in front of 10 meters from pantograph is bigger than the sound pressure level in the rear of pantograph about 1～2dB.