基于二维RANS模型计算扁平箱梁漩涡脱落的可行性分析

Feasibility Investigation on Prediction of Vortex Shedding of Flat Box Girders Based on 2D RANS Model

为研究二维雷诺时均Navier-Stokes(RANS)模型在获取桥梁扁平箱梁漩涡脱落特性时的可行性,采用基于SSTk-ω湍流模型的二维RANS方程,对大带东桥主桥加劲梁进行了CFD计算(雷诺数Re=1.06×105),获得了加劲梁在不同迭代时间步长、不同网格划分上的气动力系数平均值和脉动值,以及漩涡脱落Strouhal(Sr)数,突出了计算时间步和网格无关检查的重要性。结果表明:相对于漩涡脱落周期T,采用较大的时间步长就能获得气动力系数平均值的近似估计,而要获得漩涡脱落Sr数的收敛估计之计算时间步长应小于T/260;采用二维RANS模型能获得此种箱梁平均气动力系数的近似估计,但得到的漩涡脱落Sr数与风洞试验结果有较大差别。

In order to investigate the feasibility of two-dimensional（2D）RANS model on prediction of vortex shedding characteristics of bridge flat box girders,the CFD simulations were performed to represent the flow field around the stiffening girder of the Great Belt East Bridge main crossing,based on 2DRANS model combined with SSTk-ωturbulent model at Re=1.06×10^5.The flow results,including mean and fluctuating aerodynamic coefficients,as well as vortexshedding Strouhal number were presented under different time step sizes and grid arrangements.The research highlighted the quality insurance on time step size and grid resolution when performing CFD simulation.The results show that referring to the computed vortex-shedding period of T,2D RANS model can present an approximate estimation of mean aerodynamic coefficients on large time step size,but can not estimate a stable vortex-shedding Sr number until the time step size is smaller than T/260.Also 2D RANS model can present a good approximate estimation of mean aerodynamic coefficients,but the predicted vortex shedding Sr number is quite different from the results from wind tunnel tests.