## 1 Introduction  
As there has been a rapid development in high-speed railway systems in recent decades, the crosswind stability of trains has become a main concern [1; 2; 3; 4]. In order to ensure a high-speed railway track's smoothness, the bridge mileage accounts for a large proportion. However, the trains run on bridges that are far above the ground, which brings about a more complex wind environment and they are more affected by crosswind. High-speed trains running in a strong crosswind environment are prone to accidents, such as overturning and derailment, which cause heavy economic losses and casualties. The wind barrier can significantly reduce the wind speed in the train running area and ensure the running safety of the train, which is an economical and efficient wind protection measure [5; 6; 7; 8; 9]. Numerical simulation and wind tunnel tests are usually used to study the aerodynamic performance of the wind barrier due to the huge consumption of field measurements and the limitation of test conditions. [PERSON] et al. [10; 11] used particle image velocimetry (PIV) to explore the shielding effect of the wind barrier and its influence on the flow field structure of the bridge, and optimized the height and porosity of the wind barrier. [PERSON] et al. [12] studied the influence of the height and porosity of the wind barrier on the aerodynamic characteristics of the train on the viaduct based on the synchronous pressure measurement technique, and explained the aerodynamic mechanism of the wind barrier from the perspective of fluid mechanics. [PERSON] et al. [13] pointed out that setting up wind barriers can effectively improve the safety index of the train running on a bridge and greatly increase the critical wind speed for the running safety of the train. [PERSON] et al. [14] investigated the influence of the wind barrier on aerodynamic coefficients, flow field structure, and running safety of the high-speed train in the bridge-tunnel section by using numerical simulation. [PERSON] et al. [15] researched the shielding effects of 15 wind barriers with different porosities on the train; their results showed that wind barriers can effectively reduce the aerodynamic coefficients of the train, and wind barriers with 15% porosity had the best wind-proof effect. These studies mainly focused on the influence of the height and porosity of a single wind barrier on its wind protection effects, while there have been relatively few studies on the correlation between the structure type of wind barrier and its aerodynamic characteristics. A wind barrier can significantly improve the running safety of a train, but it will increase the windward area of the bridge, disturb the flow field around the bridge, increase the turbulence effect, and adversely affect the wind resistance of the bridge. [PERSON] et al. [16] analyzed the influence of wind barriers on the aerodynamic and aeroelastic characteristics of three bridges with different cross-sections through wind tunnel tests, and pointed out that wind barriers increase the aerodynamic coefficients of the bridge and reduce the dynamic stability of the bridge deck. [PERSON] et al. [17] discussed the influence of a wind barrier on the aerodynamic effect of the high-speed train-bridge system through experiments; their results revealed that a wind barrier can effectively reduce the drag and moment coefficients of a train, but it will increase the aerodynamic coefficients of the bridge. There are various types of geometrical structures of wind barriers; most of the existing studies focus on the vertical wind barrier, although curved wind barriers are also commonly used in engineering. [PERSON] et al. [18] conducted numerical simulation studies on the decelerate effect on airflow of curved wind barriers with different porosities under various wind attack angles. They found that the wind protection effect of curved wind barrier shows a linear downward trend with the change of wind attack angle from negative to positive, and has an optimal porosity. [PERSON] et al.