Research On The Action Mechanism Of Wind-blown Sand On Aerodynamic Performance Of High-speed Train

The safety of high-speed trains operating in complex environments such as the Gobi and desert is one of the most difficult problems in implementing the national Belt and Road Initiative.The structure of the flow field around the train and the aerodynamic load of the train will be changed due to the action of the wind and sand flow when a train runs at high speed under the environment of wind-blown sand.Aerodynamic load of the train and the impact force between the sand particles and the train body in the wind-blown sand will aggravate the risk of overturning and affect the driving efficiency.The mechanism of windblown sand on the flow field and aerodynamic performance around the train is studied by combining wind-sand wind tunnel PIV experiment and numerical simulation.Starting with the influence of wind-blown sand on the aerodynamic performance of the train,this paper analyzes the variation characteristics of the flow field around the body of high-speed trains under the turbulent incoming flow and wind-blown sand flow.The main work is as follows:A research method of measuring the flow field around the high-speed train model in wind tunnel testbed of wind-blown sand flow is proposed after constructing a wind tunnel test platform for pure wind and wind-sand flow.The boundary setting of wind-blown sand flow environment simulation is defined.The gray threshold differentiation method is used to separate the two-phase flow and display the flow field around the train.The function fitting curve w=-18.94lnh-5.7628 of measured sand transport flux and height in the wind-sand wind tunnel is used as the rated sand transport flux to explore the influence of different windward angles on the leeward flow field of transverse dune,which verified the accuracy of the turbulent wind-sand flow field research method.A turbulent model for numerical simulation of wind-sand two-phase flow is established based on the results of wind-sand tunnel experiments.The coherent effects of incoming flow conditions on the near wall flow field,leeward side flow field,wake flow field,body surface pressure and aerodynamic load were studied.The influence law of wind-blown sand on aerodynamic coefficient of high-speed train with different nose length was investigated.The spectral proper orthogonal decomposition method is used to reveal the effect law of the influence of wind-blown sand on the gas phase flow field on the lee side and wake flow field.The influence law of different parameters wind-blown sand on aerodynamic load of highspeed train was investigated.The coefficient of variation method is used to analyze the influence weight of each factor on the aerodynamic coefficient.The influence law of different parameters of wind-sand flow on aerodynamic coefficient of train was investigated.The results show that the influence weights of each factor on the lateral force of the head of the train are 0.503,0.404,and 0.092.The collection method of impact force is used to predict the effect law of sand particles on the impact force of head car in wind-blown sand.When the yaw angle is 0°≤α≤20°,the lifting component of the contact force coefficient between the sand and the train body reaches the maximum value of 6.65% in the lift coefficient when the yaw angle is 10°.Both the drag component and the lateral component of the contact force coefficient increase exponentially.Compared with pure wind,the comprehensive drag force coefficient of the 7.5m nose length train at 15° and 20° yaw angle under the wind-blown sand increases by 12.01% and 25.94%,respectively.This study has important theoretical significance and engineering value for improving the running quality of high-speed trains in the windblown sand.