Aerodynamic Characteristics Of Simply Supported Beam-high Speed Train System Under Crosswinds

Simply-supported girder bridges are widely applied in high-speed railway.As a dynamic-static composed system,the train-bridge coupled system shows distinct aerodynamic problems.The air motion around the train-bridge system under lateral winds is extremely complicated,and the structure induced wind load will exert a certain effect on the stability of the bridge and the operation safety of the train.Many achievements have been made by researchers on aerodynamic characteristics of train-bridge system under crosswind.However,further studies need to be conducted on the comparison of the aerodynamic characteristics of dynamic and static systems,the research on the effects of wind speed,vehicle speed and wind angle on the aerodynamic coefficient and pressure coefficient of the system,etc.Combining with computational fluid dynamics(CFD)software,this paper conducted analytical analysis on the aerodynamic characteristics of the train and the bridge in the system.The main contents are as follow:1.The CFD grid model of the vehicle-bridge system was established,and the accuracy of the model was verified by comparing with the train's aerodynamic coefficient and the wind profile's wind speed distribution obtained from wind tunnel test.2.The aerodynamic characteristics of the system under dynamic and static conditions were compared,and the validity of the use of static wind tunnel test for dynamic conditions was evaluated by the differences of the results under the two conditions,it can be obtained that the static wind tunnel test is difficult to simulate the aerodynamic characteristics accurately of trains with high speed,especially for the lift coefficient and in the train's rear-area.3.The flow fields of the system under different yaw angles and wind angles were compared.It is concluded that the change of yaw angle will change the direction of the development of vortices,while the influence of the wind angle on the flow field is relatively small.4.Comparing the aerodynamic parameters of the system under different vehicle speeds,wind speeds and wind angles,the following conclusions were drawn: the increase of the vehicle velocity and decrease of the wind velocity,that is the diminution of the yaw angle,will change the pressure coefficient of the train surface and the bridge deck,which will lead to the increase of the train's aerodynamic coefficient,the reduction of the lateral force coefficient and the lift coefficient of the bridge,and the increase of the moment coefficient of the bridge.When the wind angle changes,the aerodynamic characteristics of the vehicle-bridge system are affected by both the yaw angle and the wind angle.