## 3 Results and Discussion  
### Experimental Validation and Transient Pressure  
A moving model test was used to obtain the experimental data. The real moving model test scene and the comparison between the test results and numerical simulation results are presented in Figure 10. This test was performed at the Central South University in China. [PERSON] et al. [41] had provided detailed information about the experiment. Two 1/16 th-scale MTs with two-car marshalling for each train were adopted, and the trains met at an equal speed of 200 km/h for each train. The transient pressure on the train surface was measured using pressure sensors with a sampling frequency of 10\({}^{4}\) Hz.  
The pressure in the monitoring points on the train surface was computed using different turbulence models (SST, SA\(-\)IDDES, and SST\(-\)IDDES), and the results were compared to the moving model test results for validating the numerical simulations. Figure 10c, d show the time-history curves of pressure at monitoring point No. 5 on the head car surface and monitoring point No. 17 on the tail car surface. As shown, the change trend of the time-history pressure curves obtained by the three models is consistent with the test results, and only the local region of the curves exhibits a small error due to the wake flow passing through it. The values of the negative peak pressure coefficient \(\Delta C_{P\text{min}}\), the positive peak pressure coefficient \(\Delta C_{P\text{max}}\), and peak-to-peak pressure coefficient \(\Delta C_{P}\) simulated by the three turbulence models are slightly different from the experimental results. Among them, the differences in \(\Delta C_{P}\) at monitoring point No. 5 between SST, SA\(-\)IDDES, and SST\(-\)IDDES and the experimental data were 1.2%, 1.7%, and 0.7%, respectively, and the differences in \(\Delta C_{P}\) at monitoring point No. 17 between SST, SA\(-\)IDDES, and SST\(-\)IDDES and the experimental data were 2.9%, 3.2%, and 3.6%, respectively. Thus, the simulated results are in good agreement with the experimental data, and the numerical simulation can be considered sufficiently reliable.  
The results of the simulation suggest that the turbulence model had minimal effect on the transient pressure. Therefore, the pressure change amplitude on the intersection side of the train surface was obtained only with the SST\(-\)IDDES model; the results are shown in Figure 11. For monitoring points along the longitudinal direction of the train surface, the absolute values of \(\Delta C_{P\text{min}}\), \(\Delta C_{P\text{max}}\), and \(\Delta C_{P}\) were higher in the streamlined head and tail nose regions than in other regions of the train surface, and the difference in the pressure variation amplitude in the middle region of the train surface was found to be  
Figure 10: Results of numerical simulation and moving model test: (**a**) photograph of physical test model; (**b**) schematic of numerical model. Time-history curve of pressure coefficient for monitoring points (**c**) No. 5 and (**d**) No. 17.  
small. The maximum value of \(\Delta C_{P}\) for these monitoring points was measured at point No. 1. For monitoring points along the vertical distribution in the middle of the train surface, the absolute values of \(\Delta C_{P\mathrm{min}}\) and \(\Delta C_{P}\) first increased and then decreased, and \(\Delta C_{P\mathrm{max}}\) increased with increasing height of the monitoring points. At these four measurement points, the maximum value of \(\Delta C_{P}\) was measured at point No. 10.