Numerical analysis of airflow around a passenger train entering the tunnel

In this paper, the characteristics of train-tunnel interaction at a tunnel entrance has been investigated numerically. A three-dimensional numerical model using the remeshing method for the moving boundary of a passenger train in Iran railway was applied. The turbulent flows generated by the moving train in a tunnel were simulated by the RNG κ−ε turbulence model. The simulations have been carried out to understand the effect of the train speed as well as the influences of the hoods and air vents on the pressure waves, drag, and side force coefficients. The results show that the maximum drag coefficient occurs when the train enters the tunnel and is equal to 2.2. The air vents and enlarged hood at the portal are demonstrated to attenuate the pressure gradient and drag coefficient about 28% and 36%, respectively. Furthermore when train is entering the tunnel asymmetrically, a side force is created that pushes the train toward the tunnel wall, which the maximum side force is 900 N.