Study On The Response Of Section Fractal Dimension And Navigable Hydraulic Parameters In The Lower Section Of Dam

When water conservancy project was built in rivers upstream, obtaining the benefit of power generation at the same time, unsteady flow the hub drainage not only produce a great impact on the flood control of the downstream city and river bed evolution, but also affects the navigable waterways. Research on the spread regularity and movement characteristics of unsteady flow has a important practical significance on the solution of the engineering problem like shipping and urban flood control. Because there are many factors affecting the unsteady flow, therefore, the fractal dimension is used to replace many factors, from the fractal dimension to study the characteristics of unsteady flow in river channel.But the morphology and fractal characteristics of the river channel are influenced by the research scale, and different research scales have different descriptions for the morphology and fractal features of the river channel. So from the angle of the theory of the relationship between the river and the fractal model, the fractal mechanism of the longitudinal profile of the channel is constructed. It is commonly considered that fractal dimension is a quantitative parameter for the self similarity of fractal structure.In this paper, theoretical analysis and numerical simulation method are used to study the unsteady flow of the regulated discharge hub, and obtains the following results:(1) A one-dimensional unsteady flow-fractal mathematical model is constructed for Shuifu ~ Zhutuo segments of the Yangtze River. The study section is divided into three sections based on the confluence of the Minjiang River and Tuojiang River. Calculate the fractal dimension of the longitudinal section of the river course. Through the calculation and analysis, the fractal dimension of longitudinal section has two order fractal characteristic, general fractal dimensions is smaller than that of the piecewise, the fractal dimension of the left bank is larger than the right bank, longitudinal section fractal dimension decreases as the flow rate increase, longitudinal gradient of each section of the river changing along with the longitudinal section fractal dimension is similar to harmonic wave shape.(2) Two-dimensional unsteady flow-fractal mathematical statistical model is established on taking the rapids section of research section as the research object. The channel width which satisfied the lowest maintenance depth is counted, the fractal dimension of the river width of the river cross section is calculated, and the fractal dimension has one order fractal characteristic. The relationship between the fractal dimension of river width and water depth has a great relationship with the topography of the river and its section, and in the ordinary the fractal dimension of shoal increases with the increasing water depth. The fractal dimension of the cross section is gradually decreasing, that is, the fractal dimension of the cross section increases gradually with the increase of the flow velocity. In addition to the Guobingtan, the cross section fractal dimension of the rest of the beach is gradually decreasing with the longitudinal section fractal dimension decrease.Compared the cross section fractal dimension of the beach in the same channel, the simpler of the cross section landform is.and the fractal dimension of the cross section is smaller, while the upstream flow is the same(3) According to the navigable hydraulic parameters Xuyu section of Yangtze River which is determined by previous research, the relationship between the fractal dimension which is described about longitudinal section and cross section and the navigable hydraulic parameters is worked out roughly on Shuifu~Zhutuo, combined the fractal dimension described about longitudinal section and cross section with hydraulic elements. Then the response of section fractal dimension and navigable hydraulic parameters about Zhanqiao beach and Yangliuqi beach is discussed.