大跨度斜拉桥主梁气动力特性的大涡模拟

为验证大涡模拟方法在获得桥梁主梁气动力特性上的可行性,开展了均匀流中大跨度斜拉桥扁平钢箱梁在Re=1.27×105下的绕流场三维计算流体动力学分析.大涡模拟方法采用Smagorinsky压格子湍流封闭模型,基于网格和时间步长无关检查确定的计算参数,获得了主梁气动系数统计平均值、脉动值和漩涡脱落St数随来流攻角的变化,表明三维主梁绕流漩涡脱落的频率带宽分布和展向不同步特征.基于主梁表面非定常压力时程的统计平均值和RMS值分布,分析了主梁表面的流动分离和再附特征,并建议了风洞试验测压孔的合理布置形式.与风洞实验相关结果的对比表明,大涡模拟方法是获得桥梁主梁气动力特性和绕流机理的有效方法.

Large Eddy Simulation of Aerodynamics on Main Girder of Long Span Cable-stayed Bridges

In order to confirm that the Large Eddy Simulation(LES) is applicable to the study of aerodynamics of bridge girder, the wind field around a box girder of a large span cable-stayed bridge, under Reynolds number of Re=1.27×105 in uniform flow, was accomplished by using three-dimensional Computational Fluid Dynamics(CFD) analysis. The LES employes the Smagorinsky subgrid turbulent model. Based on the grid and time step size independent check, the averaged drag, lift and moment coefficients, as well as the Strouhal number at various angles of attack, were obtained. The research shows that the vortex shedding is not synchronous in span-wise direction, and its energy is concentrated to a band including several peaks. Based on the distribution of mean and root-mean-square value of pressure around the girder surface, the flow separation and reattachment pattern on the girder surface were presented, and the reasonable arrangement of pressure taps on wind tunnel models was suggested. The results were compared with the results from wind tunnel tests. It is confirmed that the LES is capable of investigating the aerodynamics of bridge girders and flow mechanism.