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Based on the test data of FBI and scientific experiments, and acorrding to the law of pressure wave propagation and superposition in the tunnel, issues of where the maximum negative pressure occurs and the critical length of the tunnel, were investigated theoretically and experimentaly in this paper, then, theoretical calculation method were proposed, which have been verified by full scale experiments.Large-scale commercial flow software Star-ccm +, were used to simulate the train of type 3 running in the open air, during which the characteristic of the external flow field, aerodynamic drag et al were completed. In addition, using the ICEM meshing tools and the dynamic mesh technolodge of general fluid software FLUENT , computation models of train passing each other in the open air and in tunnels were established, whose pressure waves were simulated in three-dimension.The distribution of resistance and flow field outside the train were obtained by the simulation of train running in the open air, which was consisted by three cars, in decreasing order of: trucks, cars and the car end, Simulation results of train passing each other in the open air show that passing each other side is much more affected than the other side, the maximum, minimum, and variations amplitude of pressure wave were almost equal along the train, and increased with running speed, while decreased with the line spacing. For the simulation of EMU passing through the tunnel, behavior of the distribution on aplitude of pressure variation on EMU surface is obtained, also is the flow field around EMU.The caculation method proposed in this thesis of where the largest negative pressure occurs and which is the critical length of the tunnel, can be used to determine the parameters for the tunnel design and to provide the basis for the selection of the tunnel in testing. the preliminary work in simulation provides another means for the research of the high-speed train aerodynamics.
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