Effect of train length on fluctuating aerodynamic pressure wave in tunnels and method for determining the amplitude of pressure wave on trains

In this study, the aerodynamic performance of full-scale trains of different lengths going through or crossing each other in a tunnel was investigated using sliding mesh technology and a numerical algorithm developed and verified through a full-scale train test. The waveforms of the fluctuating pressure distribution on the train and in the tunnel were compared and analyzed, and the effect of the train length on the flow field in the tunnel examined. The results show that, because of the significant difference in pressure amplitude, long trains cannot be replaced by short trains when simulating trains going through or crossing each other in tunnels. However, some common regular patterns, such as the distribution of the peak values of the time evolution of pressure on the train and in the tunnel, can still be found in both cases. It was found that, for the evaluation of the fatigue effect induced by pressure on the train body, the equivalent load method based on the Paris formula is more secure and reliable than the root-mean-square equivalent load method. It was also discovered that, while analyzing the effect of the fluctuating aerodynamic pressure, it is better from the viewpoint of safety to consider the maximum pressure on the constant-section part of the train body as the representative parameter.