## 4 Results and Discussion  
The Influence of the Wind Barrier with Different Curvatures on the Aerodynamic Characteristics of the Bridge  
The effects of curved wind barriers with four curvatures on the aerodynamic performance of the bridge have been investigated in this section. The porosity of the curved wind barrier is 30%, and the velocity of the horizontal airflow \(U_{0}=10\) m/s (wind attack angle \(\alpha=0^{\circ}\)). The flow field, wind profile, wind pressure distribution, and aerodynamic coefficients of the bridge are given. Figure 6 shows the mean velocity streamline diagram of the bridge deck without and with wind barriers. It can be seen from Figure 6a that the airflow separates at the wind fairing and accelerates at the leading point of the bridge without a wind barrier. The wind speed around the leading point can reach up to 13 m/s. The wind speed of the entire area above the bridge deck exceeds 10 m/s, which is a threat to the running safety of the train. After the curved wind barrier is set on the bridge, the acceleration area of the airflow moves to the top of the wind barrier. The greater the curvature, the better the diversion effect, and the higher the wind speed near the top of the wind barrier. Due to the shielding effect of the wind barrier, the wind speed around the bridge is significantly reduced. The wind barrier C1 has the best deceleration effect on the airflow, followed by the wind barrier C3, while the wind barriers C2 and C4 are worse. As the curvature increases, the wake height of the wind barrier decreases, indicating that the protection range becomes smaller. \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Aerodynamic Coefficients**} & \multicolumn{2}{c}{\(\mathbf{C_{D}}\)} & \multicolumn{3}{c}{\(\mathbf{C_{L}}\)} & \multicolumn{3}{c}{\(\mathbf{C_{M}}\)} \\ \hline \multirow{3}{*}{Train} & **Porosity** & **0\%** & **20\%** & **40\%** & **0\%** & **20\%** & **40\%** & **0\%** & **20\%** & **40\%** \\ \cline{2-10}  & Test & \(-0.098\) & 0.252 & 0.629 & 0.126 & 0.186 & 0.249  
The wind barrier changes the flow field of the bridge, and the airflow near the bridge deck becomes disordered. Two obvious vortices are generated at the bridge deck and the top of the wind barrier on the windward side of the bridge. The larger the vortex, the stronger the interference of the wind barrier to the flow field of the bridge. The vortex near the top of the wind barrier on the windward side of the bridge expands with the increase in curvature. The vortex close to the bridge deck is less affected by the curvature of the wind barrier, covering almost half of the bridge deck. Figure 7 illustrates the wind profile at different positions behind the wind barrier on the windward side of the bridge, where the horizontal and vertical axes of the coordinate axis are normalized to the inflow wind speed and the vertical height of the wind barrier, respectively. \(y\) is the vertical distance from the bridge deck, \(H_{b}\) is the vertical height of the wind barrier, and \(X\) represents the horizontal distance between a certain place on the bridge deck and the wind barrier of the bridge's windward side. As can be seen from Figure 7, the curved wind barrier can significantly reduce the average wind speed in the area below a certain height of the bridge deck. Due to the interaction between the high-speed airflow accelerated at the top of the wind barrier and the low-speed airflow blocked through the wind barrier, there is an obvious velocity gradient in the vertical direction of the whole bridge deck. In the area below the height of the wind barrier on the bridge deck (\(y/H_{b}<1\)), the deceleration effect of the curved wind barrier on the airflow is obvious, and the average wind speed at different positions behind the wind barrier does not exceed 3 m/s. After the height exceed the height wind barrier on the bridge deck (\(1<y/H_{b}<1.5\)), the average wind speed increases rapidly with the increase of height.