Research On Windblown Sand Flow Field Characteristics Of Ballasted Track Based On CFD

Windblown sand is main factor restricting the development of ballasted track in desert area.Windblown sand easily causes a series of problems such as train stopping,derailment,rusting of track components and bed compaction,etc.Aiming at sandstorm disaster of ballasted track in desert area,scholars have done a lot of research and put forward different kinds of sand control measures.However,the study on characteristic of windblown sand flow field of ballasted track is basically blank,understanding influence of geometrical section form of bed on the characteristic of windblown sand flow field and distribution of sand sediment is insufficient,some sand retaining walls still have certain defects.Based on CFD numerical simulation method,three-dimensional Euler two-fluid unsteady model is used to study influence the characteristic of windblown flow field around ballasted track,form of sand sediment,geometrical section of bed on characteristic of windblown flow field and sand control performance of new sand retaining wall.Compared with literature results,the results show that model proposed in this paper is suitable for studying characteristics of wind-blown flow field around ballasted track and sand retaining wall.The main conclusion of this research is as follows:1.Response law of wind-sand two-phase flow to ballasted track(1)When windblown sand passes through ballasted track,flow field is disturbed by ballasted track,and airflow velocity forms an obvious division;Horizontal velocity profile of airflow around ballasted track distributes as the shape of“M”,while the vertical velocity profile distributes as the shape of "W";Profile of airflow velocity on the windward foot and leeward shoulder increases logarithmically,The profile of the airflow velocity on the windward shoulder is similar to "proboscis effect",airflow velocity profile of leeward foot distributes as an inverted "S" shape.(2)When windblown sand passes through ballasted track,the amount of sand sediment in the windward bed is larger than that of leeward bed,and the amount of sand sediment in the top of bed is "normal distribution",so there is more sand in the middle and less on both sides,sand sediment of leeward bed can be divided into three stages,namely leeward bed sand sediment,sliding along bed surface and secondary sediment at the foot of the leeward bed.When the wind direction is orthogonal to ballasted track,the amount of sand sediment on ballasted track surface decreases with the increase of the inlet wind speed;when earth surface changes from Gobi to desert,the amount of sand sediment on ballasted track increases obviously.(3)The height of shoulder and the slope of ballast bed are main factors affecting characteristics of windblown sand flow field and distribution of sand sediment on ballasted track,When the height of shoulder increases from 0 to 150 mm,the amount of sand sediment on top and leeward bed of ballast track increases gradually;with slope of ballast bed increasing from 1:1.5 to 1:2,the amount of sand sediment at the foot of leeward decreases gradually;width of the ballast bed has little effect on characteristic of windblown sand flow field and distribution of sand sediment;When the height of the track-bearing platform is increased,the amount of sand sediment in the top of ballasted track is significantly reduced.2.Performance of sand control and parameter optimization of new sand retaining wallArc retaining wall is superior to vertical retaining wall in sand control performance.As the height of the sand retaining wall increases,length of recirculation zone in leeward side increases significantly,and sand control performance is better,But it cannot be ignored that the absolute value of the airflow velocity on the leeward side increases gradually,which makes the sand deposited on the leeward side possible to start again and form sand hazards.In addition,the area of the sand sediment on the leeward side of sand retaining wall increases gradually and may become a new source of sand in windy areas;Considering engineering cost and sand control performance,the height of arc sand retaining wall should be 1.5m～2.0m;The distance between retaining wall and ballasted track is not less than the length of recirculation zone on the leeward side of the retaining wall.