Contaminated sediments are common in river networks. The flow convergence and particular flow structures in confluences, such as the flow separation zone, may result in greater accumulation of contaminated sediments than in other river locations, but this issue is rarely studied. In addition, the contaminated sediment transport is driven by the particular morphodynamics occurring at confluences. This article describes a novel confluence flume experiment on both morphodynamics and deposition patterns of contaminated sediments as a function of geometric and flow conditions. The initial equilibrium bed geometry was developed from a mobile bed and then fixed, allowing for subsequent flow velocimetry and sediment feeding. Colored sediments of fine gradation, which mimic contaminated sediments, were then fed to the tributary channel. The results suggest that the junction angle primarily determines the confluence bed morphology and sediment transport pattern while the discharge ratio is a secondary factor. It was also observed that most introduced sediments tended to deposit immediately after the cessation of feeding at the stoss of the bar in the flow separation zone. The time history of the transport of the contaminated sediments was also investigated. Sediment that initially deposited at the stoss of the bar eventually moved to the lee of the bar and deposited around the bar downstream of the confluence, demonstrating that the sedimentation pattern evolved to a state similar to the equilibrium bed morphology.

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明渠汇流的形态动力学实验：对污染沉积物积累的影响

受污染的沉积物在河网中很常见。汇流中的汇流和特定的流结构（例如分流区）可能会导致受污染的沉积物比其他河流位置更多地积聚，但很少对此问题进行研究。此外，受污染的沉积物迁移是由汇合处发生的特定形态动力学驱动的。本文介绍了一种新颖的汇流水槽实验，该实验研究了受污染沉积物的形态动力学和沉积模式，它们是几何条件和流动条件的函数。最初的平衡床几何形状是从移动床中开发出来的，然后进行固定，从而可以进行后续的测速和沉积物进料。然后将模仿污染沉积物的精细渐变的有色沉积物送入支流河道。结果表明，结角主要决定了汇合床的形态和沉积物的输送方式，而出水率是次要因素。还观察到，大多数引入的沉积物趋于在停止进料后立即在流分离区中的棒的底部沉积。还研究了污染沉积物的运输时间历史。最初沉积在杆身底部的沉积物最终移动到杆身的后部，并在汇合处下游沉积在杆身周围，这表明沉积模式演变为类似于平衡床形态的状态。还观察到，大多数引入的沉积物趋于在停止进料后立即在流分离区中的棒的底部沉积。还研究了污染沉积物的运输时间历史。最初沉积在杆身底部的沉积物最终移动到杆身的后部，并在汇合处下游沉积在杆身周围，这表明沉积模式演变为类似于平衡床形态的状态。还观察到，大多数引入的沉积物趋于在停止进料后立即在流分离区中的棒的底部沉积。还研究了污染沉积物的运输时间历史。最初沉积在杆身底部的沉积物最终移至杆身的后部，并在汇合处下游沉积在杆身周围，这表明沉积模式演变为类似于平衡床形态的状态。