Numerical studies on a new strategy to mitigate pressure waves by accelerating trains through a long tunnel

The present work focused on exploring a strategy for mitigating the aerodynamic effects by accelerating through the tunnel. A three-dimensional, unsteady, compressible, and RNG k-& epsilon; turbulence model is adopted to simulate the pressure waves generated by high-speed trains passing through the tunnel at different speed modes. The findings demonstrated that trains cruising inside tunnels in an acceleration mode could effectively reduce the transient pressure on trains and tunnels while maintaining the efficiency of the passage. The acceleration method could alter the time at which the pressure maximum appeared at the head train surface, resulting in hysteresis that could effectively reduce the unexpected increase in the transient pressure due to the high-speed approach of the train into the tunnel. Throughout the pressure variation process, the acceleration mode could effectively improve the pressure variation at the train nose-point region compared to the uniform-speed mode. The accel-eration modes with a lower acceleration (V325-375) and a higher acceleration (V300-400) reduced the pressure peaks by 15.37% and 5.63%, respectively. In addition, for most of the tunnel, the two acceleration modes could reduce various key pressure indicators on the tunnel walls as well. These results indicate that an accelerating train could be an alternative for higher-speed passing through tunnels to balance the passage efficiency and passenger safety and comfort.