Numerical prediction of the slipstream caused by the trains with different marshalling forms entering a tunnel

Unsteady Reynolds-averaged Navier-Stokes (URANS) simulations were performed to simulate the flows around three different train types as they enter a tunnel. The three models-a short train, a double train, and a long train-were used to analyze the influence of the train configuration on the surrounding airflows and aerodynamic performance. The numerical predictions showed good agreement with existing experimental data. The maximum positive velocity peak induced by a short train passing through a tunnel was 140% larger than that produced in open air. The amplitudes of the slipstream velocity components decreased as the height from the ground increased. Large differences were found between the velocity fields produced by long and double trains. The velocity field had a large negative peak when a long train traversed the tunnel. This peak grew along the tunnel towards the exit. When a train is running in a double-track tunnel, the airflow above the two tracks moves in opposite directions. The double train induced a 53% higher velocity than the single train, but only a 6% higher velocity than the long train.