双层桁架桥上列车气动特性风洞试验研究

Wind tunnel test study of aerodynamic characteristics of trains on double truss bridges

为研究双层桁架桥上列车位于主梁断面上、下层的气动特性,通过节段模型风洞试验对双层桁架主梁断面上列车进行测力、测压。以某大跨度公铁两用悬索桥和CRH2列车为背景,研究双层桁架主梁断面上列车在迎、背风侧时,列车位于上、下层时的三分力系数、平均风压系数以及脉动风压系数,并且分析风攻角对上、下层列车气动特性的影响。研究结果表明:1)上层列车的阻力系数要显著小于下层列车,当列车位于迎风侧时,下层列车的阻力系数可达到上层列车阻力系数的1.6倍,上、下层列车的力矩系数大小基本相同,但是上层列车的升力系数大于下层列车;上、下层列车的阻力系数随风攻角的增加逐渐减小并且两者的差值也逐渐减小。2)上层列车的迎风面、背风面的压差明显小于下层列车的情况,使得上层列车的总体阻力小于下层列车,并且上层列车的顶面、底面的压差要大于下层列车的情况,使得上层列车的总体升力大于下层列车;上层列车迎风面的平均风压随风攻角的增加而减小,下层列车则无明显变化。3)上层列车圆弧过渡段顶部和底部脉动风压系数小于下层列车,并且随着风攻角的增加,下层列车脉动风压系数减小,而上层列车无明显变化,风攻角对上层列车风压系数的脉动性影响较小。研究结果可为双层桁架桥上列车线路布置提供参考和依据。

In order to study the aerodynamic characteristics of trains on the upper and lower levels of a doublelayer truss bridge,force and pressure measurements of trains on the main girder section of double deck trusses were carried out by segmental model wind tunnel tests.In this paper,a large span public-rail suspension bridge and a CRH2 train were used as the background to study the aerodynamic coefficient,mean pressure coefficient and fluctuating pressure coefficient of trains on the upper and lower levels of the main section of the double-layer truss bridge under headwinds and crosswinds,and the effect of the attack angle on the aerodynamic coefficients of the trains on the upper and lower were analyzed.The research results show that:(1)the drag coefficient of the upper train is significantly smaller than that of the lower train,when the train is located windward side,the drag coefficient of the lower train can reach 1.6 timesthat of the upper-level train.,and the magnitude of their moment coefficients basically the same,but the lift coefficient of the upper train is larger than of the lower train;the drag coefficients of the upper and lower trains decrease gradually with the increase of the attack angle and the difference between them also decreases.(2)The pressure difference between the windward and leeward sides of the upper train id significantly smaller than that of the lower train,making the overall drag of the upper train is smaller than that of the lower train,and the pressure difference between the top and bottom of the upper train is greater than that of the lower train,making the overall lift of the upper train greater than that of the lower train;the mean pressure on the windward side of the upper train decreases with the increase of the attack angle,while there is no significant change in the lower train.(3)The fluctuating pressure coefficient at the top and bottom of the circular transition section of the upper train is smaller than that of the lower train,and with the increase of the wind attack angle,the fluctuating pressure coefficient of the lower train decreases,while there is no significant change in the upper train,the attack angle has less effect on the fluctuating of the pressure coefficient in the upper train.The results of this study can provide reference and guidance for train line arrangement on double deck truss bridge.