Simulation of Gravity Dynamic Processes of Cohesive Sediment Deposits Near Dam Areas

In this paper a two-layer fluid model is developed to simulate the sedimentation processes of cohesive grain particles near dam areas. The upper layer carrying cohesive sediment is modeled by convection - diffusion equation. And the underlying layer is considered as a Bingham fluid which is modeled by solving the two-dimensional shallow water equations. The model is firstly tested by a ‘V channel’. Then, the model is applied to the upstream of the Three Gorges Dam and consequently reproduces the observation that a nearly flat river bed surface was formed in several cross sections. In contrast, most previous predictions suggested an evenly distribution of deposits over the cross sections. The disagreement of the previous study with observation is resulted in due to neglecting gravity dynamic process of cohesive sediment deposits which has been considered by the present model. Through sensitive analyses, the Bingham yield stress is identified playing an important role in simulating the velocity and distribution of deposits. With the increasing of the yield stress, the velocity becomes slower and the distribution of deposits becomes more evenly over the cross sections.