复式断面河槽流速横向分布及其对滩唇形成的影响

Transverse distribution of flow velocity in compound channel and its effects on floodplains levees

通过对水流微小控制体进行受力分析,建立了复式断面流速横向分布模型,该模型考虑了侧向副流惯性力的影响。采用实验资料对该模型进行检验,模型计算值与实测值符合较好。运用该模型计算了不同条件下复式断面流速和挟沙力的横向分布,并定量分析了横向分布特性对滩唇形成的影响。分析表明,水流漫滩时,复式断面的横向挟沙力变幅较大,尤其是在主槽和河漫滩交界处,挟沙力减小迅速,而含沙量减小相对较小,泥沙发生淤积,容易形成滩唇。单从水流挟沙力角度考虑,水流漫滩后水深越小、滩槽的糙率差越大,越容易形成滩唇。

Based on the analysis of forces acting on compound channel flows, a model of transverse flow velocity was established with inertia force of lateral secondary flow taken into account. The transverse distributions of flow velocity calculated by this model well agree with experimental data. It was used to calculate the transverse distribution of flow velocity and sediment carrying capability of a compound channel under different flow conditions, and the formation causes of floodplain were analyzed quantitatively. The result reveals that the transverse suspended sediment transport capacity of compound channel changes significantly when floodplains are drowned, especially at the edges of the floodplains near the main channel where the sediment transport capacity decreases sharply resulting in the formation of sediment deposition and floodplain levees. This tendency is more obvious for the floodplains with small water depths and larger roughness.