Research On The Influence Of Wire Surface Roughness On Galloping Response Of Catenary Positive Feeder Under Wind And Sand Environment

The Lanzhou–Urumqi high-speed railway passes through the Gobi gale areas in Xinjiang,and the geological environment along the line is complex.In order to prevent the severe wind and harsh environment from harming the train operation,wind-proof wall was built along the line.However,the structure of the wind-proof wall built with ‘guards against train without guards against nets’ can easily cause violent galloping of the catenary positive feeder,leading to wire trips,clue wear,etc.The occurrence of failures brings safety hazards to the safe operation of electrified railways.In order to ensure the safe operation of the train,it is necessary to study the galloping characteristics of the positive feeder.The change of airflow around the wire is the main reason for the galloping of the positive feeder.Therefore,this thesis analyzes the galloping characteristics of the catenary positive feeder by studying the aerodynamic characteristics and flow field changes of the wire.Firstly,according to the beam bending theory in structural dynamics,the positive feeder is treated as the beam bending problem.The galloping differential equation of the positive feeder is derived by establishing the force model of the micro-element section of the positive feeder.The wind tunnel test device built by the research group is used to verify the correctness of the numerical simulation calculation method used in this thesis.The mesh of the overall calculation domain is divided into blocks,and the smooth and true strand cross-section models are numerically simulated for different wind speeds using fluid simulation software.The results show that with the increase of inlet wind speed,the lift and drag coefficient of the smooth surface model are larger than those of the rough surface model.Combining the differential equation of the positive feeder galloping and analyzing the force analysis of the positive feeder under wind load environment,the galloping response of the positive feeder under different wind speeds is finally calculated.The results show that the galloping amplitude of positive feeder will decrease when considering the wire surface roughness under wind environment.Secondly,on the basis of the previous research conclusions,five kinds of positive feeder models with different surface roughness are established.To ensure that the peripheral mesh of the five wire models remain unchanged,perform numerical simulation calculations in a simulation environment with the same inlet boundary conditions,and analyze the numerical simulation results of positive feeders with different stranded wire surface roughness.The results show that the lower the surface roughness of the positive feeder,the more obvious the aerodynamic lift and drag increase of the wire.When the inlet wind speed is 1m/s,the basic values of the lift and drag coefficient of the positive feeders with different surface roughness remain stable.When the inlet wind speed is greater than 5m/s,the lift and drag coefficient of the positive feeder increases with the surface roughness decreases.Different surface roughness of the wire tail produces different vortices,and different small vortices are produced on the concavities and convexities of the wire.Finally,considering the wind and sand environment,the influence of different sand volume fractions on the aerodynamic characteristics of the positive feeder is studied.The discrete phase model(DPM)in the Eulerian model is used to simulate the wind-sand two-phase flow.The other numerical calculation methods are the same as that of single-phase wind,and the numerical calculation results under different wind-sand environments are analyzed.The results show that: compared with the single-phase wind at the inlet,the aerodynamic lift and drag of the wire are significantly increased after considering the wind and sand environment.When the inlet wind speed is 20m/s,the aerodynamic coefficient of the positive feeder is the largest.With the increase of inlet sand volume fraction,the aerodynamic coefficient of the positive feeder increases gradually.The galloping amplitude of the positive feeder changes due to the difference in the inlet sand phase volume fraction,and the vertical amplitude is approximately twice the horizontal amplitude.