## 4 Results and Discussion
### Effects of the Curved Wind Barrier on the Aerodynamic Characteristics of the Train-Bridge System  
The influence of curved wind barriers with four curvatures on the aerodynamic characteristics of the train-bridge system have been investigated under an incoming flow \(U_{0}\)= 10 m/s. The train is arranged on the windward side of the bridge, and the porosity of the wind barrier is 30%. The pressure distribution, velocity field, and wind pressure coefficients of the train-bridge system with wind barriers of four curvatures are compared, and the variations of aerodynamic coefficients of the train and bridge under different wind attack angle are also concerned. Figure 10 shows the effects of different curved wind barriers on the pressure distribution of the train-bridge system (wind attack angle \(\alpha\) = 0\({}^{\circ}\)). It can be seen from Figure 10a-e that the wind pressure on the windward surface of the train drops significantly for the wind barrier installed on the bridge, and the blocking effect of the curved wind barrier on the airflow weakens as the curvature increases. The maximum wind pressure on the windward surface of the train is 8.86 Pa with the installation of the C1 wind barrier, while when the C4 wind barrier is installed on the bridge, the maximum wind pressure on the windward surface of the train is 24.97 Pa. Similar to when there is no train on the bridge, the high wind pressure area and wind pressure value between the wind fairing and the wind barrier on windward side of the bridge decrease with the increase of curvature, and the negative pressure area under the bridge is less affected by the wind barrier. Figure 11 presents pressure taps on the section of the train, and pressure coefficients of the train's section in respect of different curved wind barriers (wind attack angle \(\alpha\) = 0\({}^{\circ}\)). A total of 34 pressure taps are evenly arranged on the train's section, as shown in Figure 11a. It can be seen from Figure 11b that without the installation of wind barriers on the bridge, the wind pressures at all pressure taps on the windward surface of the train are positive, while wind pressures on the roof, bottom, and leeward surface of the train are all negative. The negative pressure of point 11 is the largest, followed by point 12, which shows that the airflow is separated near these two points. After the curved wind barrier is installed  
Figure 10: Pressure contours of the train-bridge system: (**a**) without a wind barrier, (**b**) with the C1 wind barrier, (**c**) with the C2 wind barrier, (**d**) with the C3 wind barrier, (**e**) with the C4 wind barrier. on the bridge, the positive pressures on the windward surface of the train are significantly decreased due to the suppression effect of the wind barrier on the airflow, and the wind pressures at some points even change from positive to negative. The negative pressure on the roof of train decreases, while the wind pressures on the bottom and leeward surface change slightly. The negative pressure at point 11 is significantly reduced, and the pressure at point 12 becomes the maximum negative pressure. The wind pressures on the windward surface of the train increase with the curvature increases, and hardly fluctuate in the vertical direction. The pressure on the bottom and leeward surface of the train is less affected by the wind barrier, which is consistent with existing results by [PERSON] et al. [9] and [PERSON] et al. [12]. Figure 12 shows the velocity streamline of the train-bridge system without and with wind barriers (wind attack angle \(\alpha=0^{\circ}\)). As shown in Figure 12a, for the bridge without a wind barrier, the wind speeds at the bottom and roof of the train are about 9 m/s and 11 m/s, respectively, which can adversely affect the safety of the train. It can be seen from Figure 12b-e that with the installation of the wind barrier on the bridge, the entire running area of the train is completely immersed in the wake of the wind barrier, and the wind speed decreases significantly.