Experimental Research Of Movement Characteristics Of Water And Sediment And Channel Evolution In The Multi-branch Reach

There are a large number of branching river sections in the middle and lower reaches of the Yangtze River.The shape of these rivers is complex and the water flow conditions are complex.The complex evolution of the beach troughs makes some river sections seriously affect the navigation and flood control of the channel.The Dongliu waterway is a multi-divided river section.Compared with the general single-tiller section,there are multiple heart-sands in the river section.The Tiger Beach is near the right bank and the Yudaizhou is located in the river center.The upstream and downstream beaches are intertwined and affect each other.The structure of the water flow and the evolution characteristics of the river are complex.Therefore,studying the characteristics of the water flow structure of the multi-tiller channel represented by the Dongliu waterway and mastering its evolution characteristics have important reference significance for the development and treatment of other related river channels.This paper introduces the general situation of the Dongliu waterway in the first place,then builds the model based on the actual river topography of the current stage of the Dongliu waterway,and then the water flow structure and water and sediment transport characteristics are studied afterwards.Finally,the mechanism of the erosion and deposition of the river section is discussed.The main conclusions can be summarized as follows:(1)The Dongliu waterway is a multi-tiller river,and its complex riverbed boundary conditions have a strong constraint and influence on the water flow.The water flow structure is closely related to the river boundary in the case of small water.The increase of the inflow will weaken the riverbed boundary to the water flow.Even in the case of floods,The Dongliu waterway is consistent with the characteristics of a single straight micro-curved river.(2)The intersection and mutual influence of the heart-sinks in the river channel is the most significant difference between the multi-divided river type and the singledivided river type.The e Dongliu waterway model is gradually widened at the intersection of the Tiger Beach and the Yudaizhou,and the sand carrying capacity of the section is weakened.The effect also affects the outflow of the right bank of the Tiger Beach and adjusts the inflow of the downstream branching section,so that the results of the evolution of the upstream and downstream of the channel are opposite,and the turbulent distribution of the water flow is complex here,so the scouring and silting of the local section is complex.(3)Both the inlet inflow conditions and the adjustment of the local riverbed boundary conditions can affect the water flow structure and the river channel erosion and siltation results.The influence of the inlet inflow change on the Tiger Beach segment is higher than that in the Yudaizhou section,and the local riverbed boundary's influence on the velocity distribution and the split ratio is more limited.(4)The middle and lower reaches of the Yangtze River are clear at this stage,and the river section has a small amount of sediment deposition in the dry year.In the case of other water flows,the river course is flushed.The results of the scouring and silting of the moving bed model test are coupling well with the flow velocity distribution during the fixed bed stage?the wave of the mainstream and the analysis of cross-section sediment.