# Dynamic Response of Outer Windshield Structure in Different Schemes under Aerodynamic Load
## 4 Results and Discussion
### Pressure Distribution and Flow-Field Structure at the Outer Windshield  
To obtain the initial flow-field characteristics of the external windshield without deformation and vibration response, the surface pressure distribution and flow-field structure around the external windshield between the middle carriage and the tail carriage are shown. Taking the rubber external windshield of Case 1 as an example, three horizontal sections of the external windshield with different spatial heights are selected. The heights of sections 1 to 3 from the ground are 1.5, 2, and 3 m, respectively, as shown in Figure 7. Owing to the good symmetry of the train body and the external windshield structure, the side structure of the external windshield was emphasized in the analysis of the initial flow field. The side part of the rubber outer windshield installed on the middle carriage was defined as W1, and the side part of the rubber external windshield installed on the tail carriage was defined as W2. Figure 8 shows a cloud diagram of the time-average pressure distribution on one side of sections 1 to 3 in the initial flow field. Figure 9 shows the pressure distribution on the outer contour line of the windshield in sections 1 to 3. The inner side of the windshield is defined as the starting point, and the pressure distribution laws on the three sections at different heights are quantitatively displayed along the outer contour line of the windshield. According to the principle of relative wind speed, the W1 capsule dome is on the leeward side and the W2 capsule dome is on the windward side, determined by comparing the cloud diagram of the time-average pressure of the different height horizontal sections shown in Figure 8. Since there is an installation distance of 20 mm between the vehicle body and the outer windshield, when the air flows through the connection between the vehicle body and W1, a negative pressure area is generated, and when the air flows through the connection between W2 and the vehicle body, a positive pressure and negative pressure area are formed. The sidewall of the windward side W2 is affected by positive pressure, while the sidewall of the leeward side W1 is mainly affected by negative pressure. With the change in the section height, the pressure distribution around the outer windshield is quite different. In S2, the positive pressure on the outer wall of W2 and the negative pressure on the outer wall of W1 are greater than S1 and S3, and there is a small negative pressure area at the arc position outside W1 and at the top of the arc of W2. Figure 9 shows the quantitative results of the pressure distribution on the outer surface of the windshield at three different height sections. It can be seen from the comparison that the pressure distribution on the inner wall surface of the outer windshield of sections 1 to 3 is similar \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Type** & **FSI Simulation** & **Full-Scale Test** & **Relative Deviation** \\ \hline AVG of Pressure/Pa & 387.42 & 404.08 & 4.3\% \\ PSD of Pressure/Hz & 16.0 & 16.3 & 1.9\% \\ PSD of Vibration/Hz & 16.0 & 16.8 & 5.0\% \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Comparison of pressure and vibration data for the FSI simulation and the full-scale test. and positive. The change in height mainly affects the top of the capsule arc of the rubber external windshield, and the pressure environment of S2 is worse than that for S1 and S3. Since section S2 is located at the widest position of the vehicle body, the airflow is less affected by the ground and the vehicle roof, and the airflow rate here is fast, resulting in a higher negative pressure distribution on the outer side of W1 and a higher positive pressure distribution on the outer side of W2 than on the other two sections. Figure 8: Average pressure distribution at the cross-section under the initial flow field. Figure 7: The position distribution of the horizontal section. Figure 10 shows the time-averaged flow-field structure of sections 1 to 3 in the initial flow-field state.