Research On Crosswind Effect And Control Method Of High-speed Train Passing Through Subgrade-tunnel Transition Section

Compared with windless environment,the aerodynamic characteristics of highspeed trains(HSTs)will change significantly when the HSTs encounter strong winds.In recent years,high-speed railway has gradually extended to the midwestern regions of China with complex terrain and harsh wind conditions.In order to better meet the line requirements of high-speed railways,infrastructures such as tunnel and bridge are inevitable,and it will be very common for different types of infrastructure to be connected.At present,many results have been achieved in domestic and foreign studies on the aerodynamic effects of tunnels and the aerodynamic characteristics of HSTs passing bridges and embankments under strong winds.However,the researches on the aerodynamic effects when HSTs pass through the subgrade-tunnel,bridge-tunnel transition section under strong winds are less.Based on HST moving model test,fluid dynamics theory and numerical simulation,the interaction mechanism between crosswind-train-tunnel,aerodynamic effects and train aerodynamic characteristics as a single HST or two HSTs pass through the subgrade-tunnel transient section have been studied.At the same time,the influence of factors such as train speed,train marshalling,crosswind speed,wind angle and tunnel type on the aerodynamic effects and the aerodynamic characteristics of the train is discussed.The main research contents and results are as follows:(1)Combining wind tunnel test and HST moving model test,the aerodynamic effects as the HST enters the tunnel with crosswind are studied.Results show that the variation law of transient pressure in the tunnel is basically not affected by the crosswind,but the magnitude of the transient pressure is affected by the effect of the crosswind.The crosswindwind speed has little effect on the values of the initial compression wave,and the transient pressure near the tunnel entrance is significantly affected by the crosswind wind speed during the passage of the train.The transient pressure peak and peak-peak value in the tunnel increase with the increase of train speed and crosswind wind speed.The higher the train speed and wind speed,the more significant the aerodynamic effect in the tunnel.(2)The aerodynamic effects as a single HST passes through a tunnel under strong winds are studied.Researches show that the aerodynamic effects at the tunnel entrance are most serious impacted when a HST passes through the tunnel under strong crosswind.As the distance from the tunnel entrance increases,the influence of crosswind on the aerodynamic effects decreases.Regardless of whether the HST enters or exits the tunnel,the side force,the lift and the overturning moment of the head vehicle(HV)change the most,and the amplitude of the side force of the HV when entering the tunnel is 9.7% larger than that when exiting the tunnel.The aerodynamic characteristics the train when entering the tunnel are poor.Under the same line conditions,the aerodynamic characteristics of HST are significantly affected by train speed and crosswind speed.The greater the train speed and crosswind speed,the greater the variation amplitude in the side force and the overturning moment of the HV,and the worse the safety of the entire vehicles.Under the same train speed and crosswind speed,the aerodynamic characteristics of trains with different marshalling types are diverse,but the aerodynamic characteristics of the HV are basically the same,and it is hardly affected by the marshalling types of HST.The pressure peak,train wind and the aerodynamic load first increase and then decrease with the increase of wind angle,and the peak values of the aerodynamic pressure,the train wind reach the maximum,and the aerodynamic characteristics of the whole vehicle are the worst when the wind angle is 30°.The influence of tunnel types on the side force and the overturning moment is relatively small,but the influence on the lift is relatively large.The changes of the aerodynamic load in double-track tunnels are generally greater than those in singletrack tunnels,and the aerodynamic characteristics of HSTs in double-track tunnel are relatively poor.(3)The influences of strong crosswind on the aerodynamic effects as HSTs intersect at tunnel entrance are studied.Moreover,the influences of the meeting position,crosswind speed and wind angle on the aerodynamic characteristics of the train are analyzed.Researches show that variation amplitude of the aerodynamic load as the HSTs meet each other with strong crosswinds is much greater than that in noncrosswind environment.The aerodynamic characteristics of the trains change significantly before and after the meeting.The side force change of the HV is most obviously,and that of the tail vehicle is the smallest.In addition,the variation amplitude of the side force of the HV entering the tunnel is 8.3% larger than that of the HV exiting the tunnel,so the safety of the HST entering the tunnel is poor.Under the conditions of the same train speed and crosswind speed,the aerodynamic effect near the tunnel entrance is closely related to the positions of the intersection.The aerodynamic characteristics of HSTs are greatly affected by the location of intersection.When the trains meet outside the tunnel at twice the length of the HV,the side force of the HV entering the tunnel changes the most,and the aerodynamic characteristics are the worst.However,when HSTs meet each other in the tunnel,the side force and the lift of the HV leaving the tunnel change the most,and the operational safety is the worst.The crosswind speed has a prominent influence on the aerodynamic characteristics of the train.The side force of the HSTs increases with the increase of the crosswind speed,and the change of the lift is related to the crosswind speed.The aerodynamic load of the HSTs increases first and then decreases with the increase of the wind angle.When the wind angle is about 60°,the changes of the side force of the HV are the most and the operational safety is the worst.(4)The protective measures for the HSTs passing through the subgrade-tunnel transition section under strong crosswind are studied.Researches show that the windbreaker reduces the positive peak and the change amplitude of the side force of HV by 48.9% and 36%,respectively,which significantly improves the aerodynamic performance and improves the safety of the train.Based on the analysis of optimizing study on the windbreaker height and the horizontal distance to the center of the line,the most economical and reasonable parameters of windbreaker are determined.