Numerical Simulation On Characteristics Of Unsteady Flow In High-speed Railway Tunnel

Because of the compressibility of air and the limited flowing space, airflow in the tunnelhas a unique rules and characteristics when the high-speed train entering it. During thehigh-speed train entering a tunnel, aerodynamic phenomena such as initial compression wave,pressure waves which can cause damage to the components and train body will be generatedinside tunnel. Pressure waves inside tunnel also can make passenger’ears discomfort. With theincreasing of the train speed, the related aerodynamic problems become increasinglyprominent. Therefore, it is extremely necessary to research on its mechanism andcharacteristics for the next step of mitigation measures.The paper introduced a reasonable method of division of computational domain aboutthe high-speed train entering tunnel based on a aerodynamic train model of Revolution Body.The paper adopted different grid partitioning strategy in order to be suitable for two differentnumerical simulation method: large eddy simulation (LES) and Reynolds Average N-SEquation (RANS). The STAR-CD software based on the finite volume method and itsarbitrary sliding mesh technology was used to simulate the unsteady flow inside tunnel duringthe train entering it. The typical tunnel aerodynamic problems such as initial compressionwave, pressure waves, force and moment on the train body had been studied by LES. Thepaper showed the difference of results of the three different turbulence model includingLES/Smagorinsky, k ωSSThigh Reynolds turbulent model and k ωSSTlow Reynoldsturbulent model.Research shows that all the model in the paper can well reveal the characteristics of theunsteady flow around train. It had been found that the air drag of the high-speed train insidetunnel is greater than the train running on open section by analyzing the results ofLES/Smagorinsky. The propagation of expansion wave and compression wave has a strongimpact on pressure fluctuations of train body, force and moment on train. The large eddysimulation turbulence model has more advantages than RANS turbulence model in simulationof pressure waves, force and moment on train. Besides, The large eddy simulation turbulencemodel can capture coherent structures around train body and tail.The process of the train entering into tunnel was studied by two different numericalsimulation method in this paper. The research method and conclusion of this paper canprovide a beneficial reference for the further study of application of LES to more real trainmodel entering into tunnel.