Research And Optimization Of Breakwind Wall Transition Section Flow Characters On Lan-Xin Railway

The natural environment of Lan-Xin railway is bad, influence caused by strong wind on train running safty is extreme serious. Recent years, safety engineering studies against wind has been conducted, breakwind wall construction, cutting application plays a substantial role. The latest full-scale train experiments show that the maximum points of train aerodynamic forces concentrate on the conditions of cutting combined with breakwind wall, transitions between different breakwind walls and particular slope sections. Thus, researching on optimization of transition sections is important for train running safety.In this paper, real vehicle test and field results are both considered. Based on three-dimentional, constant, incompressible, Reynolds average N-S equation and k-epsilon double equations, fluent software was adopted to simulate the aerodynamic forces of train on the wind back side of breakwind walls, high cuttings and transitions between breakwind walls and high cuttings numerically under typical wind condition which cross-wind velocity is 35m/s, and optimized programms of transiton modes and sections which are more danger were proposed. Through calculational analyze, key conclusions are obtained as follows:(1) On the condition of strong wind, the lateral force and overturning moment of train on openning transitions between breakwind walls and cuttings are much more biger than on wind back side of high cuttings, the danger of overturning is possible; Best optimization of transition sections is to make the connection angle of transion gap between cuttings and breakwind walls 30°. (2) For some break walls, the small gap may be beneficial for traffic safety by Increasing the efficiency of ventilation; For the pull, concrete break wall plate, as long as the opening width is not more than lm, it can be ignored; (3) In regard to embankment type breakwind wall with less effect, adding plate type breakwind wall which width is the same as embankment's is extreme beneficial, the most appropriate height is 0.3m. (4) When on the cutting with 20°slop and 3m depth, the lateral force and overturning moment decreases increasingly as the height of breakwind wall increases, when the height of breakwind wall comes to 2m or so, the effect is equal to high embankment type breakwind wall with 2.4m height on ground. As far as special rerrain is concerned, 3-3.5m high sheet type breakwind wall is the best choice.In this paper, optimization of weak links such ascutting combined with breakwind wall, transitions between different breakwind walls and particular slope sections, which have an important guiding significance to protect the safety of train operation and improve the ability of the safe passage of trains.