| When the train is running at high speed,the aerodynamic performance changes significantly if it is subjected to strong cross wind,the side force and rollover moment will increase significantly,and the possibility of train derailment and overturning will increase greatly,which will seriously affect the safety of train operation.At the same time,in the crosswind environment,the resistance of the train is very different from that when there is no crosswind,and the change of the train resistance will become more complicated.Therefore,the crosswind effect aerodynamic characteristics of high-speed trains should be highly valued,crosswind effect aerodynamic characteristics include lateral stability and aerodynamic resistance characteristics under crosswind environment.The high-speed trains at home and abroad have different shape characteristics,for example,the variable section length of CRH380 A type head train is 12 m,about 9.6m of CRH2,about 6.5m of CRH3,about 4.7m of ICE,and the increase of variable section length makes the transition from nose tip to shoulder section of head train more smoothly.In order to investigate the impact of high-speed trains' head shape on crosswind aerodynamic effect,based on the Navier-Stokes equation and k-? turbulence model,numerical calculation method is applied to figure out the side force,rollover moment and resistance of CRH2,CRH3,CRH380 A and ICE high-speed trains,This measure is under 25 kinds of working conditions,different running and crosswind speed.Different crosswind speeds include 20m/s,25m/s,30m/s,35m/s,40m/s.Different train speeds include 200 km/h,250 km/h,300 km/h,350 km/h,and 400 km/h.By comparing the crosswind effect aerodynamic characteristics between the CRH2,CRH3,CRH380 A and the German ICE highspeed train to determine which type of the train has the best aerodynamic characteristics under crosswind.The calculation results show that:1.When a high-speed train is running under crosswind,the head train receives the maximum side force and rollover moment,followed by the middle train,and the tail train receives the minimal side force and rollover moment.The head train is the most severe carriage with side force and rollover moment.Analyze the lateral stability of the train only need to consider the head train.2.The changing law of the side force and rollover moment of the head train of different models is same when the train running speed and crosswind speed change.When the train is running under crosswind,the side force and rollover moment of the head train increase with the increase of the crosswind speed and the train running speed.When the high speed train encounters crosswind,the train running speed reduction can reduce the risk of rollover of the head train.In general,when the crosswind speed is constant,the side force of the head train has a linear relationship with the train running speed;when the train running speed is constant,the side force of the head train has a quadratic square relationship with the crosswind speed.The influence of crosswind speed on side force and rollover moment is greater than the influence of train running speed on side force and rollover moment.3.In the crosswind environment,there will be a large area of negative pressure at the leeward side of the head train.Under the condition of small train running speed and large crosswind speed,the absolute value of the maximum negative pressure on the leeward side of the head train is greater than the maximum positive pressure value,and the area of the maximum negative pressure zone also increases with the increase of the crosswind speed.Therefore,the pressure differential resistance of the head train will have a negative value,and the head train's resistance direction may be the same as the train running direction.4.The changing law of the resistance of different models is same when the train running speed and crosswind speed change.The resistance of the whole train is mainly affected by the resistance of the middle train and the tail train,and the crosswind speed has little effect on the train resistance,which is mainly affected by the train running speed.As the train running speed increases,the train resistance increases rapidly with the quadratic square of the train running speed.5.The side baffles on pantograph equipment can lead to a substantial increase in side force and rollover moment of the related carriage.It can also cause adverse effect on lateral stability of the following carriages.At the same time,the resistance changes of the following carriages will be more complicated.6.Under the crosswind environment,the absolute values of the positive pressure and negative pressure appearing in the nose-to-shoulder transition section of the CRH3 head train are generally smaller than that of the CRH2,CRH380 A and ICE train heads.Therefore,CRH3 high-speed trains has the best lateral stability,which is better than CRH2,CRH380 A and ICE train models.The rollover moment is an important index to measure the overturning of trains.The CRH3 and CRH380 A trains have little difference in the rollover moment coefficient,indicating that the lateral stability of the CRH380 A train is near from the CRH3 train.7.Under crosswind environment,the absolute values of positive pressure and negative pressure on CRH380 A train body surface are smaller than that of CRH2,CRH3 and ICE trains.Therefore,CRH380 A type train has better aerodynamic resistance characteristics than CRH2 CRH3 and ICE trains.The relationship between the variable section length of each car and the resistance coefficient under the crosswind environment is opposite,indicating that the smooth transition of the variable section will reduce the resistance of the whole train under the crosswind environment.8.The crosswind effect aerodynamic characteristics of CRH380 A and CRH3 high-speed trains are better than that of CRH2 and ICE high-speed trains.The work of this paper has a certain reference value on the lateral stability and resistance characteristics studying of high-speed trains under crosswind environment,and has a certain reference value for the comparison and optimization of high-speed train models. |
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