## 4 Results and Discussion
### Effects of the Curved Wind Barrier on the Aerodynamic Characteristics of the Train-Bridge System
The curvature of the curved wind barrier has an important impact on the deceleration effects of the airflow. Compared with the C2 and C4 wind barriers, the wind speed in the train's running area is lower after the C1 and C3 wind barriers are installed on the bridge. Moreover, the airflow accelerates at the top of the curved wind barrier on windward side of the bridge, resulting in increased wind speed near the left roof of the train. The greater the curvature of the curved wind barrier, the stronger the airflow acceleration effects. Consequently, the wind barriers disturb the flow field of the train-bridge system, and the vortices are formed between the train and the curved wind barrier, which will be detrimental to the stability of the train. As the curvature of the wind barrier increases, the vortex near the back of the wind barrier on the windward side of the bridge gradually increases. Figure 13 illustrates the variations of aerodynamic coefficients of the train and bridge with various wind attack angles for the wind barriers with four curvatures. It can be seen from Figure 13a-c that the aerodynamic coefficients of the train decrease with the increase of the wind attack angle from negative to positive. This is because the shielding effect of the bridge is enhanced when the wind attack angle increases, and more incoming flow is blocked by the front edge of the bridge, resulting in the reduction of airflow acting on the train. After the wind attack angle exceeds \(4^{\circ}\), the blocking effect of the bridge  
Figure 11: Schematic diagram of pressure taps on the train and pressure coefficients of the train with different curved wind barriers: (**a**) pressure taps on the train’s section, (**b**) pressure coefficients of the train’s surface. hardly increases and the aerodynamic coefficients of the train tend to be stable. In contrary to the train, as shown in Figure 13d-f, the aerodynamic coefficients of bridge increase approximately linearly with the increases of wind attack angle. In particular, the increase in the aerodynamic coefficients of the bridge is more emphasized in the range of positive wind attack angles. The curvature of the wind barrier has a significant impact on the aerodynamic coefficients of the train-bridge system. As the curvature of the wind barrier increases, the aerodynamic coefficients of the train increase, while the aerodynamic coefficients of the bridge decrease. With the installation of C1 wind barrier, the aerodynamic coefficients of the train can be best reduced, but those of the bridge are greatly increased. After setting the C4 wind barrier on the bridge, the aerodynamic coefficients of the bridge are relatively small; however, the train's drag and moment coefficients cannot be effectively reduced. Compared with the C1 and C4 wind barriers, the C2 and C3 wind barriers effectively reduce the aerodynamic force of the train and have less impact on the wind resistance of the bridge. C2 and C3 wind barriers have similar performance in reducing aerodynamic force of the train, while the wind load that the C2 wind barrier adds to the bridge is significantly higher than that of the C3 wind barrier. Above all, the C3 wind barrier with curvature of 0.35 is more suitable for the safety protection of the train-bridge system in the present study. Influence of Curved Wind Barrier on the Aerodynamic Characteristics of the Train with Different Train-Bridge Combinations  
When the train is on the bridge, the train and the bridge form a train-bridge combination. There are three different train-bridge combinations in this paper: (1) one train on the track of the windward side of the bridge; (2) one train on the track of the leeward side of the bridge; and (3) two trains on both tracks of the bridge.