A numerical study of the train-induced unsteady airflow in a tunnel and its effects on the performance of jet fans

Analyzing the airflow generated by a moving train in tunnels ventilated by jet fans is of significant importance because of the piston effects and the alternating pressure and velocity fields inside the tunnel. Moreover, high blockage ratio and train velocity in these tunnels have caused serious concerns about the impact of train-induced airflow on the performance of jet fans. This study aims at simulating the train movement in such tunnels and investigating the above-mentioned effects. To this purpose, a finite-volume numerical approach with dynamic mesh technique is used to perform several simulations of a large tunnel with eight rows of jet fans and different train velocities. The results demonstrate that for the case in which the train moves in the opposite direction of the jet fans' flow, their volume flow rates increase and decrease sharply, as the train head and tail reach the jet fans, respectively. However, the trend is opposite when the train travels along the direction of jet fans flow. From an electric perspective, it is shown that the generated flow field does not increase the motor torque and the current of the jet fans to a degree that causes the motors to shut down.