Study On Flow Structure And Sediment Transport Processes Of The Bend River

The statistical theory of sediment movement proposed by Han Qiwei and modeltest method are adopted to study the structural properties of flow and sedimenttransport processes of bend rivers.Based on the methods of fully considering low transport rate of starting, degreeof exposure, and lateral slope of water surface and the effect of transverse circulatingcurrent which are induced by hydraulic structure of bend flow, a clear physicalgraphics is established. The five kinds of forces and their roles are considered andanalyzed comprehensively. A theoretic formula about the incipient velocity ofsediment particles is derived which is suitable for the most general conditionsincluding coarse and fine sediment at different positions on the river bed. The formulais all-embracing wide. It can be simplified as the formula for calculating the incipientvelocity on the side wall of a straight river and on the bed surface.Based on the statistical theory of sediment movement proposed by Han Qiwei,transition probability, and the impact of sediment arousing period, a theoreticalformula is developed for the equilibrium concentration of non-uniform sediment atnear-bottom reference level.The structural properties of bend flow are studied by the method of physicalmodel test. Including the analysis of time-averaged experimental data of flowhydrodynamic axis, the vertical distributions of longitudinal average velocity, thevertical distributions of transverse average velocity, the vertical distributions ofvertical average velocity, the circulation intensity and circulation structure and theanalysis of fluctuating value of turbulence intensity, Reynolds shear stress, turbulentbursting phenomenon.The physical model test is carried out in the initial straight river channel which ismade before by changing the flow rate, the initial river width and the angle ofincidence to study the formation mechanism of the process of the evolution of a river.During the experiments particle tracking technology (PTV) is used to measure thesurface velocity of the open channel. Qualitative analysis of the evolution of the riveris the major method used in this article to analyze the experimental phenomena, testterrain, the planar shape of the river and other aspects. And also straight river, braided river, meandering river, emerging shallows, point bar, riverbank, straightening andother typical experimental phenomena are successfully created. By analyzing theexperimental results, some basic conclusions are concluded such as the formation ofalluvion, the forming process of meandering river and the effect of flow on the type ofthe river.