扁平箱梁气动特性CFD模拟的维数对比研究
Comparative investigation on prediction of aerodynamic characteristics of steel flat box girders by CFD with different simulation dimension

基于三维非定常雷诺时均Navier-Stokes (RANS)方程和SST k-ω湍流模型,数值模拟雷诺数为1.06×105时扁平箱梁气动特性在不同主梁展向长度、不同展向网格分辨率下的气动特性,确定三维CFD模拟合理的主梁展向参数,获得主梁气动力系数和漩涡脱落St数随来流攻角的变化。对相同箱梁开展了不同攻角下二维RANS计算,并将二维和三维主梁的整体气动特性、表面压力分布进行对比。研究结果表明:三维RANS获得的主梁气动特性结果与计算域展向网格分辨率和主梁长度均无关;二维和三维模拟结果非常一致,均能获得箱梁气动力系数平均值的合理估计,因而工程计算可采用二维模拟。开展的节段模型风洞试验表明二维和三维模拟得到的漩涡脱落St数是合理的,典型攻角下扁平箱梁裸梁具有单一St数,且均明显大于成桥状态。
Based on three-dimensional unsteady Reynolds averaged Navier-Stokes (RANS) equations and the SST k-ω turbulent model, the aerodynamic characteristics of a flat box girders under various spanwise length and grid resolution were numerically computed at the Reynolds number of 1.06×105. According to the determined optimal spanwise parameters in CFD, the aerodynamic force coefficients and vortex-shedding Strouhal number were obtained under different wind angles of attack. Flow results of the girder under the same condition were also simulated on the basis of the two-dimensional RANS equations, its aerodynamic forces and pressure on girder surface were compared to the three-dimensional modeling. It is found that the results obtained from three-dimensional simulations is independent on grid resolution and girder length in spanwise direction, and agree well with the results from two-dimensional simulations. Both the two- and three-dimensional RANS modeling can present reasonable estimation on mean aerodynamic coefficients of the girder. Therefore, the two-dimensional modeling is feasible for bridge engineering application. The wind tunnel tests provided confirmed that the estimated vortex-shedding Strouhal number from two- and three-dimensional RANS modeling, and under typical wind angle of attack(-3°~+3°), the bare deck presents only one St number, which is significantly larger than that of girder in service