三峡水库库区上段水流特性分析

三峡水库的蓄水运用,使其河道型库区内水流有了明显的壅水型非均匀流特征,其流态的改变显著影响着泥沙输移和洪水传播特性。采取专门实测资料,分析库区上段的三维流速及紊动强度沿垂线的分布特征。结果表明:三峡水库上段纵向流速沿垂线分布基本符合对数流速分布公式,横向流速分布受地形影响较大,垂向流速明显,且方向一般向下;沿程各断面纵向、横向及垂向水流相对紊动强度分布比较均匀,尤其是垂向水流紊动强度沿程随着壅水程度的增大有增大的趋势。壅水型非均匀流在垂向流速及垂向紊动强度的分布特点,将给库区泥沙运动、尤其是悬移质含沙量沿垂线分布带来明显影响。

Flow structure in upper part of Three Gorges reservoir

Since the Three Gorges reservoir (TGR) started to run, the non-uniform flow with backwater characteristics in its upper part has remarkably affected sediment transport and flood travelling. Specific observed data were analyzed to reveal the behaviors of three-dimensional velocity and turbulence intensity in this reservoir region, particularly the characteristics of vertical distribution. Results show that in the region, vertical profiles of longitudinal velocities generally follow the log-law, the distribution of transverse flows is controlled by riverbed forms, and vertical components are considerable and largely in downward direction. Turbulence intensities of all the three components are distributed uniformly on all the cross sections along the flow, but vertical turbulences tend to increase gradually along the flow. Such features of vertical flows and turbulences in the backwater region of non-uniform flow are remarkably different from those in uniform flow, and hence it has brought about significant changes in sediment motions, especially the vertical profiles of suspended sediment concentration in the reservoir area.