圆柱形桥墩周围局部冲刷的三维数值模拟

Three-dimensional Numerical Simulation for Local Scour Around Cylindric Bridge Pier

为预测圆柱形桥墩周围的局部冲刷坑形态和发展,基于计算流体动力学和泥沙运动理论开展了桥墩周围局部冲刷的三维数值模拟。首先使用雷诺时均Navier-Stokes方程和标准K-ε湍流模型对圆柱形桥墩周围三维复杂流场进行数值模拟,将床面瞬时切应力作为泥沙起动及运输的水动力学条件,计算出床底泥沙的单宽体积输沙率,以此为基础得到河床高程坐标的瞬时变化;再采用边界自适应网格技术修改动边界计算域网格,计算得到圆柱形桥墩周围局部冲刷坑的演化过程。结果表明:桥墩周围局部冲刷三维数值模拟结果与试验结果基本一致,数值模拟方法能用来预测圆柱形桥墩周围的局部冲刷情况。

In order to predict dimensions of local scour hole around the cylindric bridge pier,based on the computational fluid dynamics and theories of sediment movement,three-dimensional numerical simulation on local scour of bridge pier was carried out.Firstly,Navier-Stokes equation and the standard K-ε model were employed to simulate the three-dimensional flow fields around a cylindric bridge pier.The transient shear-stress on river bed was regarded as a crucial hydrodynamic condition of handling sediment incipience and transportation.Then,river bed volumetric sediment transportation rate could be calculated,based on it,the transient change of the vertical coordinate of river bed was got.Boundary self-adaptive mesh technique was employed to modify the grid system with changed river bed boundary.The evolution process of local scour hole around a cylindric bridge pier was obtained.Results show that results of three-dimensional numerical simulation on local scour of bridge pier are in good agreement with the experimental results which demonstrate the applicability of numerical methods to prediction for local scour around bridge pier.