冲刷环境对桥墩冲刷空间形态影响的仿真分析

A simulation analysis on 3D bridge scour developments by various environment parameters

为研究环境对桥墩冲刷的影响,基于K-ε湍流模型建立了桥墩冲刷及冲刷环境数值仿真模型.对其三维仿真建模过程中的4个关键问题分别进行深入研究并提出优选的解决方法,特别关注三维边界条件的动态更新以及计算收敛性的算法改进.进而利用B.W.Melville经典实验对提出的桥墩冲刷精细化仿真方法从空间形态的角度进行多方面准确性验证.最后基于该精细化仿真方法,对CFD计算软件Fluent二次开发,进行精细化参数分析.计算结果表明:桥墩尺寸与最大冲刷深度以及流速与最大冲刷深度均存在近似线性关系,选择合适的桥墩形式、降低桥墩有效宽度、降低墩前水流流速以及选择合适的水流深度均可明显降低桥墩冲刷深度.不同冲刷环境参数取值对桥墩冲刷空间形态所产生的不同影响可以为桥墩主动抗冲刷设计与选型提供合理的理论基础与依据.

To investigate the influence on bridge scour from environments,a K-ε turbulence model was applied in the present study to simulate the complicated flow filed and local scour around bridge pier. Four key problems for a fine 3D scour simulation were discussed in details and the corresponding solutions were also given. More attentions were especially paid to the dynamic updating of boundary condition and the optimized iteration convergence of programing algorithm. The accuracy of the proposed simulation was fully verified by comparing to the classic B. W.Melville experiment from the viewpoint of 3D performance during the scour. By re-developing the CFD Fluent program following the proposed solution,a parametric study was conducted by varying several scour environment parameters. The results show that the maximum scour depth has an approximate linear relationship with the pier measurements and average velocity of flow. A good selection of pier shapes,a narrow effective pier width,a slow average velocity of flow,and a proper water depth would all reduce the scour depth of piers. A conclusion can also be drawn regarding the influences of different environment parameters on the 3D scour development,which should be a rational theoretical basis for the active anti-scour design for piers.