Running Safety Analysis Of The Train Running On The Bridge In The Downwind Wind Field

In recent years,downbursts have occurred more frequently.As a natural disaster,downbursts have a huge threat to the safety of infrastructure within the scope of their impact.As the main artery of the national economy,important infrastructure and popular transportation,high-speed trains are directly related to the safety of people’s lives and property.This article focuses on the study of the running safety of high-speed trains in the downwind wind field.First,based on the impact jet theory,this paper uses CFD software to simulate the downwind wind field,and verifies the accuracy of the simulation.The influence of grid size,jet height,inlet wind speed and other parameters on the wind speed distribution in the wind field is calculated and analyzed.The analysis results show that the grid size affects the accuracy of the calculation results;the jet height determines the wall blocking effect of the jet entrance;the entrance wind speed only determines the size of the wind speed at various locations in the wind field,and does not affect the distribution of wind speed.The analysis of the wind speed profile shows that the distance between the location of the maximum wind speed and the center of the wind field is equal to 1.0 times the jet diameter;from the vertical wind profile,the height of the location of the maximum wind speed to the ground is 0.02 times the jet diameter.Then,using the overset grid technology,the time course of the wind on the surface of the train when the train is moving in the downburst wind field is calculated.According to the calculation results,the train mainly receives the lateral force(U_y)and lift(U_z),Rx direction torque,Rz direction torque.With the increase of the moving distance,the wind force acting on the surface of the train shows a change rule that increases first and then decreases.When the train axis is perpendicular to the diameter of the wind field,the wind force on the train surface reaches the maximum value.Due to the local disturbance of the wind field caused by the movement of the train,there are differences in the laws of the wind load change of the first car,the middle car and the tail car with time.Finally,the wind time history is brought into the vehicle-bridge dynamic interaction program,and the values of the derailment coefficient of the wheel set,the wheel load reduction rate,and the lateral force of the wheel set are calculated at every moment during the train operation.Compare the calculated value with the specification limit to judge the safety of the train.The analysis shows that In the downburst storm wind field,when the wind speed at the bridge position is 20m/s,the downburst has little effect on the driving safety of the train on the bridge.There is no risk of derailment when the train runs at three design speeds.When the wind speed at the bridge position is 30m/s,and the train on the bridge is running at a speed of 350km/h,the train will derail due to the impact of the downburst.When the wind speed at the bridge position is 35m/s,and the train on the bridge is running at a speed of 300km/h,the train will derail due to the impact of the downburst.When the wind speed at the bridge is 40m/s,the running safety of the train on the bridge is greatly affected.When the train on the bridge runs at a speed of 250km/h,the train will derail due to the impact of the downburst.