Effect of Cavity Flow on High Speed Train Pantograph Aerodynamic Noise

摘要

For high-speed trains the aerodynamic noise becomes important for speeds over about 300 km/h. The pantograph is mounted on the train roof, often in a shallow cavity. It is an important source of high-speed train noise because of its elevated position, especially in the presence of noise barriers which shield sources that are lower on the train. In this paper, the flow features and noise sources of a high-speed train pantograph and its recess are numerically investigated for a speed of 300 km/h. The geometry of the pantograph recess is simplified as a 'closed' rectangular cavity and two pantographs (the lower part of a raised one and a full retracted one) are included that are based on a DSA 350 pantograph. To resolve the details of the turbulent flow structures and hence enable accurate noise predictions, the Improved Delayed Detached-Eddy Simulation (IDDES) approach is used to model the flow field. The Ffowcs Williams & Hawkings aeroacoustics model is employed for far-field acoustic calculations based on noise sources on the solid surfaces only, due to low Mach number of the flow. In comparison with the same cavity without pantographs, the flow around the cavity shows slightly different characteristics when the pantographs are placed in the cavity. Strengths of vortices on downstream of the cavity is reduced slightly due to interaction between cavity flow and pantographs. This study indicates that the main noise sources are from the raised pantograph, and the panhead of the retracted pantograph as shear layers impinge on them. The cavity trailing edge also generates significant noise. The far-field noise is found to be broadband. The directivity of the noise radiated from pantographs and cavity is also obtained.