## 2 Numerical Model
### Numerical Validation
#### 2.4.2 Moving Model Test Verification  
To verify the accuracy of the numerical simulation results, the pressure-time curves obtained from the numerical simulation measurements were compared with the moving model test results using the conventional tunnel in the programmer table as an example. To ensure consistency between the experimental and computational boundary conditions, slip-ground boundary conditions were used for the numerical simulations. Moving model tests were conducted on the newly built 600-km/h high-speed maglev train moving model test platform at the High-Speed Train Research Center of Central South University. This is the world's largest test platform and the only \"train pneumatic moving model test system\", with CMA and CNAS (certificate number: CNAS L10220) qualifications [22; 23; 24].  
Figure 6: Micro-pressure waves at the tunnel exit for three grid densities with respect to time.  
In the moving model tests, the maglev train and tunnel models were scaled down to 1:20. Therefore, in the numerical simulations, the same scaled-down model was used for the maglev train and tunnel to ensure maximum consistency between the numerical simulation test setup and moving model test setup. Due to the rapid changes in test pressure of a moving model locomotive, it is necessary to ensure that the sensing and measurement channels have sufficient response speed. The sensor signal was amplified in two stages and filtered by second-order low-frequency filtering to eliminate high-frequency spurious interference. The entire range output was fed into a high-speed A/D converter for acquisition as a standard voltage signal of 0-5 V. Each pressure signal channel has an independent circuit structure and A/D converter, and synchronous sampling is controlled by the same time-based signal, thereby ensuring fast data acquisition and consistency in time and space for each channel. Figure 7 shows the scenario of the dynamic model for measuring pressure experimentally.  
The results of this comparison are shown in Figure 8. As the train enters the tunnel, a compression wave forms in front of the train and propagates forward at the speed of sound. As the train reached the measurement point, the pressure-time curve appeared to be extremely high and then rapidly decreased. Subsequently, a micro-pressure wave was detected at the exit of the tunnel. A comparison of the numerical simulation results with the time course curves from the moving model experiments shows that there is a slight difference in either the trend or value. In terms of the pressure values at the tunnel exit, the maximum difference between the dynamic model test data and numerical simulation results is 6.93%, as listed in Table 2, which is in line with the actual engineering requirements. This indicates a high degree of confidence of the numerical simulation results.  
Figure 7: Moving model test site.  
This is because the results of the dynamic model test were derived using a number of sensors which were successively measured and then fitted to the data by the computer. Excessive fluctuations in ambient pressure or long measurement times affect the consistency and accuracy of the computer-generated time curves.