小浪底水库淤积形态数值模拟

水库淤积形态是影响库容分布、水库排沙的一项重要因素。小浪底水库近坝段淤积泥沙粒径极细,具有流动性,针对其细颗粒泥沙淤积特点,揭示了水库细颗粒淤积物的流变特性与流型特征;通过引入水、淤积物、床面之间的界面受力分析,构建了细颗粒淤积物失稳流动描述模式,并与水沙输移模型相耦合,建立了考虑细颗粒淤积物流动特性的水库淤积形态模拟方法,在此基础上对小浪底水库淤积形态进行了验证分析。研究结果表明:低密度细颗粒淤积物为宾汉型流体,淤积平衡坡降较小,当其密度大于1.25 g/cm³后,流动性快速减弱;考虑细颗粒淤积物流动特征的水库淤积形态模拟结果与实测结果吻合较好。研究成果可为水库淤积形态形成机理及其对水沙调控的响应研究提供技术支撑。

Numerical study on the sedimentation pattern of Xiaolangdi Reservoir on the Yellow River

Sedimentation pattern is one of the important factors affecting reservoir capacity and reservoir sediment flushing. In the near-dam area of Xiaolangdi Reservoir on the Yellow River,fine-grained muddy deposits are easy to flow like fluid. In this paper,the rheological property and flow pattern of muddy deposits were investigated. It was found out that the flow pattern of low density muddy deposits is that of Bingham flow,and its fluidity will decrease quickly when its density exceeds 1.25 g/ cm³. Base on analysis of shear stresses at interfaces between water and muddy deposits and between muddy deposits and channel bed,governing equations for the movement of muddy deposits were established. A simulation method for fine-grained sedimentation processes was developed by coupling the model for water flow and sediment transport with the model for muddy deposits movement. Calculation results indicate that sedimentation pattern of fine-grained particles in the Xiaolangdi Reservoir can be simulated accurately by considering the effect of muddy deposits movement. This investigation could improve our understanding of sediment deposition mechanisms in reservoirs,especially for fine-grained sediment.