分体式三箱主梁气动特性数值模拟

Numerical Simulation on Aerodynamic Characteristics of Split Three-box Girder

为研究分体式三箱主梁气动特性,基于某公铁两用斜拉悬索协作体系桥梁分体式三箱主梁,采用FLUENT软件开展了不同槽高比(G/D)、不同风攻角下分体式三箱主梁气动特性二维数值模拟。所述主梁气动特性主要包括气动力系数、涡量场、平均压力系数以及压力系数标准差分布。数值模拟结果表明:在研究参数范围内,不同风攻角下,阻力系数总体随槽高比增大而增大,升力系数和力矩系数未随槽高比单调变化,且力矩系数对槽高比变化更敏感。各槽高比下升力系数随风攻角变化斜率均为正值,这表明该分体式三箱主梁颤振性能良好;0°风攻角下,G/D=0时,仅在箱梁尾流区存在周期性漩涡脱落。G/D=1.61时,0°风攻角下箱梁开槽处及中间箱体和下游箱体表面漩涡脱落显著,相较于0°风攻角,±10°风攻角下中间箱体与下游箱体开槽处及下游箱体表面漩涡脱落减弱;主梁开槽使得中间箱体上表面负的平均压力系数幅值增大,并导致箱梁表面压力系数标准差增大。G/D=1.61时,相较于0°风攻角,±10°风攻角下箱梁表面压力脉动减弱,尤其下游箱体表面压力系数标准差显著减小;该分体式三箱主梁临界槽高比为G/D=2.08。

To investigate the aerodynamic characteristics of split three-box girder,based on the split three-box girder of a highway-railway cable-stayed suspension cooperative system bridge,the 2D numerical simulation on aerodynamic characteristics of split three-box girder with different gap to height ratios(G/D)and different wind attack angles is carried out by using FLUENT software.The described aerodynamic characteristics of main girder mainly include the aerodynamic force coefficients,vorticity magnitude field,mean pressure coefficient distributions,and distributions of standard deviation of pressure coefficient.The numerical simulation result indicates that within the studied parameters and with different wind attack angles,the drag force coefficients increase with the increment of G/D.The lift force coefficients and moment coefficients do not change monotonously with G/D.The moment coefficients are more sensitive to the change of G/D.With different G/Ds,the slopes of lift force coefficients with wind attack angle are all positive,indicating that the flutter performance of split three-box girder is good.At 0°wind attack angle,there is only periodic vortex shedding in the wake of deck when G/D=0.When G/D=1.61,the vortex shedding at gap regions of deck and at the surfaces of middle box,and the downstream box is significant at 0°wind attack angle.Compared with 0°wind attack angle,the vortex shedding at gap region of middle box and downstream box and at the surface of downstream box is weakened at±10°wind attack angles.The existence of deck gaps increases the magnitude of negative mean pressure coefficient on the top surface of middle box,leading to the increment of standard deviation of pressure coefficient of deck.When G/D=1.61,compared with 0°wind attack angle,the pressure fluctuation on deck surface at±10°wind attack angles is weakened,especially the standard deviation of pressure coefficient of downstream box is significantly reduced.The critical G/D of split three-box deck is 2.08.