Aerodynamic behaviors on a streamlined-passenger train and an expressfreight train meeting in a same tunnel

Mixed passenger and freight railway is a common form in rail transportation, while the intersection of a streamlined electric-multiple-unit (EMU) train and a blunt freight train in a same tunnel may lead to unforeseen adverse effects due to differences in shape configurations. This paper examines the aerodynamic interactions that occur when these two types of trains pass each other in a tunnel. A three-dimensional, compressible, and unsteady Reynolds-Averaged Navier-Stokes (URANS) equations along with the RNG k-ε turbulence model is employed for numerical solution, which was validated by experiments. The results indicate that the freight train experienced 45% higher initial compressive pressure rise and a 75% greater initial pressure gradient compared to the EMU upon tunnel entry. However, the peak-to-peak pressure for leading car of the EMU is 39% greater than that of the freight train, with an average increase of 18% per vehicle. Slipstream analysis shows the EMU has uniform rearward flow at both sides, while the freight train exhibits asymmetric slipstream directions. During the intersection of EMU and freight trains, the average drag on the freight train's leading car is 65% higher than that on the EMU. However, the maximum peak-to-peak lateral force occurs when the noses of the freight train and EMU meet, with the EMU exhibiting a 23% higher risk of overturning compared to the freight train. The findings could inform the practical engineering operations related to mixed passenger and freight railway.