水库异重流一维水沙耦合模型

建立了基于库区不规则断面的一维非恒定异重流数学模型,并采用明流与异重流水沙输移模型交替运算的两步模式,即用潜入条件动态判别异重流计算的上游边界位置,将潜入点上游的明流浑水段与下游异重流段计算连接起来。水流运动、泥沙输移与河床变形过程完全耦合,采用TVD(Total Variation Diminishing)形式的MUSCL-Hancock格式进行数值求解。将该模型应用于恒定流量与释放定量悬沙两种条件下的异重流水槽实验模拟,比较了有无水面梯度项对模拟精度的影响,计算结果表明该模型能较为准确地预测异重流的厚度、含沙量分布及传播过程。

One-dimensional coupled model for predicting turbidity currents in reservoirs

Among traditional depth-averaged models for predicting turbidity currents, it is difficult to take into account the influence of flow and sediment conditions at the plunge point and the gradient of free water surface. Therefore, a one-dimensional unsteady turbidity current model for reservoirs with irregular cross-sections is proposed, and a two-step calculation mode of alternating the calculations of turbidity current and open channel flow is adopted in this model. The proposed calculation mode can dynamically determine the location of the upstream boundary for the turbidity current simulations using the plunge criterion, and can also connect the reach transported in the pattern of open channel flow and the reach transported in the pattern of turbidity current. Three processes of flow movement, sediment transport and bed evolution in a reservoir are solved by a fully coupled approach, with a TVD (Total Variation Diminishing) version of the MUSCL-Hancock scheme being used in this solution. Turbidity current movements in two laboratory experiments were simulated under different setups, including an instantaneous fixed-volume release and a constant-flux input, with the effect of free surface gradient on the model predictions being investigated. The calculations indicate that the proposed model can satisfactorily predict the thickness and sediment concentration of turbidity currents and their propagation processes, which can be used as a tool for the sediment management in reservoirs.