水下淹没建筑物局部流场数值模拟及河床冲刷分析

Numerical simulation on local scour at downstream of submerged constructions

采用二维沿水宽平均的水流数学模型对河流中淹没建筑物附近的流场进行了数值模拟。通过将水流在河底的剪应力与相同条件下Shields曲线对应的泥沙临界起动拖曳力做对比,判定河床冲刷与否。文中计算了当淹没建筑物对河道断面压缩比例不同时的流场,给出淹没建筑物下游局部漩涡范围、局部冲刷范围及根据临界剪应力判断的最大冲深部位。结果表明:计算得出的结论合乎规律;当淹没建筑物压缩河道比例小于50%时,在建筑物下游形成一个小范围的漩涡,不是河床冲刷的主因;随着压缩比逐渐增大,建筑物下游漩涡区也增大,由一个涡变化为两个涡,转变为河床冲刷的主要原因。

In this paper,a vertical 2-D k-ε turbulent model is used to simulate the flow field near submerged constructions. Local scour occurs when bed shear stress of flow is higher than or equal to critical bed shear stress for sediment incipient motion according to Shields curve. The model is applied to predict the flow in a channel where submerged constructions constrict water flows in different proportions. The results computed and predicted have been given for local vortex region, the maximum-depth position estimated by critical shear stress and the range of local scours at downstream of submerged constructions, which are reasonable by analysis. A small-size vortex forms downstream of submerged constructions when constriction proportion is less than 50% and the vortex is not the main reason leading to bed local scour. The vortex region extends larger as constriction proportions increase and vortices come to be the main effects on bed local scour.