Influence Of Wind Barriers On Aerodynamic Characteristics Of Train-bridge System Under Random Wind Field

Among the high-speed railways currently in operation and planned to be built in China,railway bridges account for a large proportion.Due to the random natural wind acting on the train bridge system,the bridge deck height,the flow around the side flange and the beam rib velocity increase,which seriously affects the aerodynamic characteristics of the train bridge system.After the wind barrier is arranged on the bridge,due to the wind shielding effect of the wind barrier,the wind environment around the vehicle bridge system under random wind can be effectively improved,providing a reasonable reference for the safe operation of trains in random wind environment.Taking the train bridge system composed of a CRH high-speed train and a 32 m simply supported box girder railway bridge as the research object,this paper establishes the aerodynamic model of wind barrier high-speed train bridge system,the aerodynamic characteristics of train bridge system with different wind barrier structural parameters under random wind field are studied,and the optimal combination of wind barrier structural parameters is summarized;by changing the train speed under the optimal structural parameters,the variation law of aerodynamic load with train speed is obtained;at the same time,the comparison between double track train and single track train in the process of constant speed intersection of trains is considered,and the changes of aerodynamic characteristics when the two train meet at constant speed at different speeds are summarized,the running safety of high-speed train is evaluated;finally,the influence of random wind on the hysteresis of high-speed train is analyzed.The results show that:(1)Under the random wind field,after the train completely enters the sheltered area of the wind barrier,the aerodynamic parameters of the head train decrease;The pressure value of the maximum positive pressure area at the nose of the head truck decreases,and the pressure value of the maximum negative pressure area near the top of the head truck increases.(2)When the height is 3.5m and the opening rate is 30%,it is the optimal structural parameter combination of wind barrier under random wind field.When the height is3.5m,the lifting force of the train is the smallest,and the lateral force coefficient and torsion coefficient of the bridge are also the lowest.When the opening ratio is 30%,and the lift coefficient of the bridge is closest to 0.(3)When the running speed increases from 200 km / h to 400 km / h,the lateral force,lift,roll moment and shaking moment of the head train increase by 94.47%,64.47%,86.17% and 76.44% respectively.(4)Compared with the operation of single track trains,the aerodynamic load in the process of double track meeting is significantly increased.In the process of intersection,violent vortices will be generated at the top of the gap between the two trains and on the side of the train on the leeward side,and the vortices will be greater with the increase of intersection speed.(5)The operation safety index increases with the increase of train speed.Among them,the derailment coefficient and wheel load reduction rate are less affected by the train speed,and the axle transverse force and wheel rail vertical force are more affected by the train speed.When the train speed exceeds 350 km /h,both exceed the safety limit.(6)Random wind has a hysteretic effect on high-speed trains,which is mainly affected by the train running speed and the wind speed of the fundamental frequency of random wind.The hysteresis effect decreases with the increase of train speed and fundamental frequency wind speed.