桥墩局部冲刷发展过程的三维动网格模拟

3D numerical investigation of bridge pier-scour development using a dynamic-mesh updating technique

基于FLUENT软件的动网格更新技术和用户自定义函数功能实现了桥墩局部冲刷过程的三维动态模拟。以Melville经典冲刷试验为原型,建立数值模型。将河床面设置为主要的动边界,当床面结点瞬时剪应力大于临界剪应力时,结点位置下移,表现为冲刷,引入Van Rijn提出的沉积输运函数来控制河床面各结点的运动速度。数值模拟结果在流场形态,冲坑发生发展过程及冲坑形态均与试验结果较为吻合,模拟的冲坑深度略小于试验结果,误差约13%。误差产生的主要原因为基于雷诺平均N-S的湍流模型不能有效地反应钝形桥墩前端湍流脉动的影响。

Based on the dynamic-mesh updating technique and user-defined function of FLUENT software,we realized the three-dimensional dynamic simulation of local pier scour.We established the numerical model using the Melville classical scour test as a prototype.The river bed was set as the main moving boundary.When the instantaneous shear stress of the bed surface was larger than the critical shear stress,the position of the node moved down,shown as scour.Van Rijn′s transport function was introduced to control the velocity of each node in the river bed.The numerical results were in good agreement with the experimental results regarding the flow field structure,occurrence and development process of scour holes,and shape of scour holes.The simulated depth of scour holes was slightly smaller than the experimental results,with an error of about 13%.The main reason for the error was the inability of the URANS models to effectively reflect the turbulent fluctuations at the leading edge of blunt piers.