桁架对列车气动特性的影响及其内部风场分析

Influence of Truss on Aerodynamic Characteristics of Train and Analysis of Internal Wind Field

为研究桁架结构对车桥系统气动特性的影响及其内部风场的分布特征,对某大跨度公铁两用斜拉桥的桁架主桥和箱梁引桥进行节段模型风洞试验,对比不同梁型的车桥系统三分力系数。基于试验结果建立CFD模型,推导适合桁架结构的等效风速计算公式,研究桁架横断面、纵断面及各车道位置处的等效风速分布及侧风折算系数。结果表明,桁架对列车的遮风效应较为显著,零攻角时,列车在桁梁上的阻力、升力及力矩系数约为其在箱梁上的66%、17%、50%;横风流经桁架结构出现了风速三维分布,迎风侧外侧车道上的风速高于其他车道;在各车道上方0.15~0.45倍梁高处的风速较大,最大风速出现的位置与车体形心高度较为吻合;桁架内部的平均风速显著低于来流风速,但在节间两个直角三角形形心附近出现了高风区域,最大侧风折算系数达到了0.92。

In order to investigate the influence of a truss structure on the aerodynamic characteristics of the vehicle-bridge system and the spatial distribution characteristics of the wind field inside the truss,a section-model wind tunnel test was performed on the main bridge with truss girder and approach bridge with box girder of a long-span rail-cum-road cable-stayed bridge.The tri-component force coefficients of the vehicle-bridge system with different girder types were compared.Based on the wind tunnel test results,a CFD model was established to derive the calculation formula of equivalent wind speed suitable for the truss structure,and to study the equivalent wind speed and the crosswind reduction coefficients of the truss cross section,vertical section and the position of each track.The results show significant shielding effect of the truss structure on the train.At zero angle of attack,the drag,lift and moment coefficients of the train on the truss girder are about 66%,17%,and 50%of those on the box girder.The cross wind is distributed in three dimensions when it passes through the truss structure,with the wind speed above the outer track on the windward side higher than other tracks.The wind speed at 0.15~0.45 times of the girder height above each track is higher.The height where the maximum wind speed appears coincides with the centroid height of the vehicle.The average wind speed inside the truss is significantly lower than the incoming wind speed,but high winds appear near the centroids of the two right-angled triangles in each truss panel,with the maximum crosswind reduction coefficient of 0.92.