三岛型群汊河道平面流场与分流特性研究

Study on plane flow field and distributary characteristics of three island group branch channel

对三岛型群汊河道平面流场与分流特性的研究是预测污染物混合、富集和分散等水环境保护工作的基础。选取天然河流中三岛型群汊河段,建立三岛型群汊河道水流运动物理模型试验系统,在各汊道布置20个测量断面。详细测量三岛型群汊河道中水流结构参数,得到了7个不同水深处的平面流速分布。基于各测点三维流速与各汊道的流量计算数据,分析高、中、底三层不同水深的平面流场和各汊道分流比的特点。通过绘制分汊岛几何边界的切线,来确定分汊岛附近主流区范围,分析三岛型群汊河道分汊岛布局对分流效果的影响。结果表明:三岛型群汊河道各支汊流量分配存在明显差异,各汊道的分流比例由分汊点位置、分汊岛几何边界位置和汊道平面流速分布共同决定;当分汊点在主流区以内时,分汊点的位置对各汊道分流比例有明显作用。

The study of the plane flow field and distributary characteristics of three-island group branch river is the basis of predicting the mixing,enrichment and dispersion of pollutants and other water environmental protection work.A physical model test system for flow movement of three-island group backwaters in natural rivers is established.Twenty measuring sections are arranged in each backwaters.The flow structure parameters in the branch of three-island group are measured in detail and the flow velocity distributions in seven different depths are obtained.Based on the calculation data of the three-dimensional velocity of each measuring point and the flow of each branch,the characteristics of the plane flow field and the bifurcation ratio of each branch with different water depths in the three layers of high,middle and bottom are analyzed.By drawing the tangent line of the geometric boundary of the branching island,the scope of the main stream area near the branching island is determined,and the influence of the branching island layout on the branching effect is analyzed.The results show that there are obvious differences in the flow distribution of each branch of the three-island group,and the distributive proportion of each branch is determined by the location of the branch point,the location of the geometric boundary of the branch island and the distribution of the plane velocity of the branch.When the branching point is within the main stream area,the location of the branching point has an obvious effect on the branching ratio of each branching point.