Research On Aerodynamic Performance And Safety Of Accelerating Operation Of High-speed Trains Under Strong Wind Conditions

When the train accelerates under strong wind conditions,the aerodynamic load on the train and its surrounding flow field structure change dramatically in a short period of time,which may lead to the deterioration of the dynamic performance of the train and adversely affect the safety of the train operation.In this thesis,based on the improved delayed detached eddy simulation(IDDES)turbulence model of SST K-Omega,the aerodynamic performance change rule was studied during the process of train acceleration from rest to 55.56m/s,and the influence mechanism of train acceleration and cross-wind speed was analyzed.The effects of train acceleration and cross-wind speed on train safety were studied by dynamics simulation.The main results are as follows:(1)During the acceleration of the train,the change rule of aerodynamic performance with train speed under strong wind conditions is revealed.With the increase of train speed,the main vortex structure which has great influence on the surface pressure of the train will be generated at the nose of the head car,streamline shoulder of the leeward side of the head car,windscreen,bogie and streamline area of the tail car.The angle between the main vortex structure and the train gradually decreases.The development distance of the main vortex structure increases gradually.The lift of the head car increases with the increase of train speed,while the lift of the middle car increases first and then decreases,and the lift of the tail car shows a trend of fluctuating rise.With the increase of train speed,the lateral force of the head car increases,while the lateral force of middle car the shows a trend of fluctuating rise,and the lateral force of the tail car shows a trend of decreasing fluctuation.The overturning moment and lateral force have similar variation rules.(2)The effects of cross-wind speed and train acceleration on the flow field structure around the train and aerodynamic load are analyzed.When the train acceleration is the same,the greater the cross-wind speed is,the greater the disturbance to the longitudinal flow along the roof of the train.And there are more vortex structures on the leeward side of the train,which has a greater influence on the surface pressure of the leeward side of the train.The maximum lateral force coefficient of the head car increases with the increase of the cross-wind speed.When the cross-wind speed is the same,the smaller the running acceleration of the train,the greater the absolute value of the negative pressure on the surface pressure of the leeward side of the train.The maximum value of the lateral force coefficient of the head car increases with the decrease of the running acceleration.(3)The influence of cross-wind speed and train acceleration on the safety of accelerating train operation is studied by analyzing the head car with high safety risk under strong wind conditions.When the train speed is 55.56m/s,the overturning coefficient and derailment coefficient of the head car reach the maximum value.When the train runs at a uniform acceleration of 1m/s~2,the cross-wind speed increases from 15m/s to25m/s,and the maximum values of the overturning coefficient and derailment coefficient of the head car increase gradually.When the cross-wind speed is 20m/s,the maximum overturning coefficient and derailment coefficient of the head car have little difference under different acceleration.When the train acceleration increases from 0.7m/s~2to1.3m/s~2,the maximum gradient of the overturning coefficient and derailment coefficient decrease.