## 5 Conclusions  
A streamlined flat box girder and a Metro A-type train are taken as the background. The reliability numerical simulation is verified by wind tunnel tests, and the influence of curved wind barriers with four curvatures on crosswind aerodynamic characteristics of a train-bridge system are investigated by commercial CFD software ANSYS FLUENT 19.2. The main conclusions are drawn as follows.  
1. Curved wind barriers can effectively reduce the wind speed in the region below 1.5 times of the height of the wind barrier on the bridge deck. The C4 wind barrier with the largest curvature has the worst deceleration effect on the airflow and may cause strong interference to the flow field around the train. The C1 wind barrier with 0 curvature has the best effect on airflow deceleration, but after the C1 wind barrier is installed, the aerodynamic coefficients of the bridge increase significantly.
2. The smaller the curvature of curved wind barrier, the stronger the protective effect on the train, but the greater the adversely impact on the wind resistance of the bridge. When the wind attack angle of airflow changes from negative to positive, the aerodynamic coefficients of train increase, while the aerodynamic coefficients of bridge decrease. The C3 wind barrier with a curvature of 0.35 can effectively reduce the aerodynamic coefficients and surface wind pressure of the train, and at the same  
Figure 15: Influence of the porosity of curved wind barrier on the pressure coefficients of the train under different arrangements on the bridge: (**a**) \(C_{P}\) of the test train in Case1, (**b**) \(C_{P}\) of the test train in Case2, (**c**) \(C_{P}\) of the test train in Case3, (**d**) \(C_{P}\) of the test train in Case4.  
time, has little impact on the wind resistance of the bridge; thus, it is more suitable for the safety protection of the train-bridge system in this study.
3. The aerodynamic performance of the test train is greatly affected by the combinations of the train and bridge. When only a single test train is arranged on the bridge, whether on the windward side or leeward side of the bridge, the aerodynamic coefficient and surface wind pressure coefficient of the test train increase with the increase of the porosity of the wind barrier. The aerodynamic and wind pressure coefficients of the test train on the windward side of the bridge are larger than those of the test train on the leeward side of the bridge under the same conditions. When there are trains on both sides of the bridge, the aerodynamic performance of the test train on the windward side of the bridge is slightly affected by the train on the leeward side. However, the test train on the leeward side of the bridge is completely in the wake of the bridge, wind barrier, and train on the windward side. The aerodynamic and wind pressure coefficients are small and insensitive to the porosity of the curved wind barrier.  
Conceptualization, P.L.; methodology, W.T., C.C. and Y.A.; software, P.L., X.H. and Y.Z.; validation, W.T. and C.C.; formal analysis, P.L. and X.H.; investigation, Y.Z. and Y.A.; resources, Y.Z. and Y.A.; data curation, P.L., W.T. and C.C.; writing--original draft preparation, P.L., W.T. and C.C.; writing--review and editing, Y.Z. and Y.A.; visualization, X.H.; supervision, P.L. All authors have read and agreed to the published version of the manuscript.  
The work described in this paper was supported by grants from the National Natural Science Foundation of China (Project nos. 52078501 and 51908554).  
Not applicable.  
The authors declare no conflict of interest.