风洞模型棱角制作误差对扁平箱梁气动力和涡脱特性的影响

桥梁节段模型试验研究的顾虑之一,是制作扁平箱梁节段模型时各个棱角制作误差,比如棱角圆化对其气动力和涡脱特性的影响,但至今未见相关报道。该研究采用雷诺时均Navier-Stokes(RANS)方程和SST k-ω湍流模型对大带东桥主跨扁平钢箱梁开展了计算流体动力学模拟(CFD)。在节段模型制作误差可能导致的棱角圆化半径范围内,对比了加劲梁绕流形态、平均气动力系数和漩涡脱落S t数。研究表明:扁平箱梁棱角小半径圆化时半径的增大使得局部流动的分离强度减小,但分离点位置不再固定;模型棱角圆化对扁平箱梁平均气动力和漩涡脱落S t数的影响可忽略不计;前缘棱角圆化后加劲梁气动特性的Re效应不明显。研究认为,可不考虑加劲梁风洞试验模型棱角小半径圆化对主梁气动特性的影响,因而CFD模拟时加劲梁风嘴前缘棱角可作小半径圆化处理,以降低网格数量、提高网格质量和减小CFD的计算量。

Effects of model corner fabrication errors on the aerodynamic forces and vortex shedding characteristics of a shallow box girder

One of major concerns, when carrying out bridge sectional model tests, is the effect of model corner fabrication errors on the aerodynamic forces and vortex shedding property of a shallow box girder, which has not been addressed at current time.The Reynolds-averaged Navier-Stokes equations and SST  k-ω turbulent model were used to do the simulation of the flow field around the rigid box girder section of the main span of the Great Belt East Bridge.For different kinds of corner rounding radius, the flow pattern around the girder section, the mean aerodynamic coefficients and vortex-shedding frequency were obtained.The results show that the increase of corner rounding radius can decreas the flow separation intensity, while the flow separation point will no longer keep fixed.The simulated mean aerodynamic coefficients and Strouhal (St) number indicate the minor influence of different corner rounding configuration.The further study shows that the leading edge rounding presents small and negligible Reynolds number effect on the mean aerodynamic coefficients and St number.It is suggested that the effects of corner rounding with small radius can be neglected in bridge wind resistant design.It is also suggested that corner rounding with small radius at the leading edge can be adopted in CFD simulation, which will help decrease grid number, improve mesh quality and reduce CFD computational cost.