椭圆形障条风障对桥面行车风环境影响的CFD研究

CFD Study of Effect of Elliptical Baffle Wind Barrier on Traffic Wind Environment of a Bridge

以某双边箱组合梁为研究对象,开展详细的椭圆形障条风障(EBWB)对桥面行车风环境影响的CFD数值模拟研究。首先检验湍流模型以及时间步长和网格密度无关性,然后比较在1.71 m防撞栏杆上设置EBWB或常规矩形障条风障(RBWB)的侧风折减系数的差异,进一步分析有无EBWB时的桥面行车风环境。通过研究侧风折减系数、风剖面曲线以及流场结构,分析了风障透风率和风障高度对桥面行车风环境的影响,同时在考虑桥梁阻力系数的基础上引入一个综合指标以比选最优风屏障形式。研究结果表明:SST k-ω、RNG k-ε两种湍流模型的计算三分力系数相差较小,0°风攻角下2种阻力系数相差仅为4.02%,说明当前模拟方法可靠;EBWB与RBWB均具有良好的减风效果,EBWB的侧风折减系数更小,阻力系数也更大;减小风障透风率或增大风障高度可以改善桥面行车风环境,但桥梁风荷载随之增大。对于所提的双边箱组合梁断面,综合考虑桥面行车风环境和桥梁风荷载后,透风率为52%且风障高度为1.486 m的椭圆形障条风障(总屏障高度为3.196 m)最优。

A detailed computational fluid dynamics(CFD)study was conducted to investigate the influence of an elliptical baffle wind barrier(EBWB)on the traffic wind environment of a bridge with a composite double-sided box section.The independence of the turbulence model,time step,and grid density was first analyzed.The crosswind reduction factors of the bridge with EBWB and a conventional rectangular baffle wind barrier(RBWB)on a 1.71 m high crash barrier were compared,and the traffic wind environments with and without RBWB were also obtained.The effects of the porosity and height of the EBWB on the traffic wind environment of the bridge were analyzed using the crosswind reduction factor,wind profile curve,and flow field structure.A comprehensive index that takes into account the static drag coefficient was introduced to determine the optimal wind barrier design.The results show that the difference between the calculated static aerodynamic coefficients of two turbulence models,SST k-w and RNG k-e,is small,with only a 4.02%difference for drag coefficient at zero wind attack angle,indicating that the current numerical simulation method is reliable.The EBWB has a satisfactory wind reduction effect,similar to that of the RBWB,and the bridge with the EBWB has a smaller crosswind reduction factor and a larger drag coefficient.The traffic wind environment of a bridge can be improved by reducing the EBWB porosity or increasing the EBWB height;however,wind loading increases proportionately.For the bridge with a composite double-sided box section in this study,an optimal EBWB design is considered to be one with 52%porosity and a 1.486 m high wind barrier(3.196 m high total barrier),taking into account the traffic wind environment and wind loading.