A three-dimensional CFD model was built to simulate the pressure fluctuation due to the passage of two Electric Motorized Unit (EMU) trains in a tunnel and to study their effects on passengers aural comfort, tunnel structures and ventilation systems and the stability of the train. The CFD model employed the techniques of moving mesh and arbitrary connectivity to simulate the relative motion of two mesh blocks that define flow domains of the individual train. Wall boundary and turbulent effect were also included in the model. The results were then compared with the one-dimensional Subway Environment Simulation (SES) analysis. The pressure fluctuation of the entire process of train passage were simulated. History of the near-field pressures at the train nose and tail were recorded. The three-dimensional model indicated a continuous and steep change in nose pressure as the two train noses meet and a moderate change in tail pressure as the train nose meet the tail of the other train, instead of discontinuous changes predicted by SES model. This may attribute to the three dimensionality of the air flow around the train noses and the tails. The magnitudes of the simulated pressure changes given by the two models match with each other. These pressure changes and the rate of the change of pressure were within the design criteria. The flow interaction also creates a pressure difference between the inner and outer sides of the trains. Higher pressure was found at the outer side, which would create an over-turning moment that resulting in the potential instability problem of the running trains. Such information cannot be provided by one-dimensional SES model.
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