Transient loads and their influence on the dynamic responses of trains in a tunnel

Using compressible, unsteady and sliding meshing technologies, the aerodynamic loads including transient pressure, lateral force, and overturning moment that are caused by a single train moving through a double-track tunnel or two trains passing each other in a tunnel were calculated. The dynamic response generated by applying these loads to a train body was also analysed. The results show a large difference in the pressure on both sides of the vehicle nose when a single train moves through a double-track tunnel and when two trains pass each other in a tunnel. The pressures at the symmetric measuring points on both sides of the middle of the train body are approximately the same except at the moment of passing. When the train passes the measuring points, the pressure change at the symmetric measuring points on the tunnel wall closer to the train is obviously larger than that farther from the train; the pressure changes are approximately the same at all other times. Therefore, the propagation of the pressure wave in the tunnel has good one-dimensional characteristics. Under dynamic loads in the tunnel, especially those generated by two trains passing each other in the tunnel, the lateral and vertical displacements of the underframe and side walls all increase significantly. The lateral acceleration on the roof is significantly greater than that of the underframe, which has a rolling movement below the centre of gravity. For the measuring points on both the side wall and underframe, the vertical accelerations at both ends are larger than that in the middle of the body because of a pitching motion. The horizontal and vertical vibration acceleration for a train passing another train in a tunnel are 33.8% and 47.2% larger than those for a train operating in open air, respectively.