Research On Water-sediment Two Phase Flow Theory And Sediment Transportation Problems In Pipes Of Diversion Project

Sediment problem is one of the major problems in hydraulics and river dynamics.It's important subject to inquire into movement theory and characteristics of water and sediment in engineering practice.This paper summarizes the results of basic research on sediment movement mechanics,including sediment incipience,transport means of suspended load and bed load,and sediment-carrying capacity,such as some of the classically empirical formula of the vertical distribution of suspended sediment concentration,the transportation modes of the two-phase flow of pipes and the flow stage of water and sediment in the pipes changes according to different intensity of flow are discussed.It summarizes the research status of two-phase flow of water and sediment,on the basis of the characteristics of the two approaches of the particle continuum model and dynamic model,starting from the element analysis,it sets up the basic equations of two-phase flow of solid and liquild under the average sense,providing the uniform interpretation to N S equations of fluid mechanics,B.B.O.equation describing the movement of particles,Brinkman equations of porous media fluid motion and penetration Darcy equation.It gets general form of continuous equation and motion equation of water and sediment two phase flow,the bottom sediment motion equations are derivedSediment characteristics are important factors to hydraulic transport,through the sediment characteristics analysis of the diversion project in central Shanxi,measurement methods are summarized on sediment concentration,grain size analysis,mineral composition and geometry of the particles,on the basis of present shape analysis,it puts forward a new method of plane roundness factor of sediment particles,that is,using the Fourier series to fit the shape of the particles,simulating the edge contour changes.It gets conclusions that the rounded shaped particles account for the major components of the sediment particles.It analyzes the effect on resistance coefficient of spherical coefficient and the shape coefficient according to the resistance coefficient of sediment deposition based on mathematical deduce result on flow past a sphere.Considering the Yellow River is a river of high sediment concentration,therefore,will be essential to the diversion process to contain a certain amount of sediment.the paper firstly proposes the concept of sediment carrying capacity of pipes,uses the classical theory of Einstein sediment theory,transport rate of bed load of pipes instead of the traditional transport rate of bed load,to determine the relationship between flow intensity and transport rate of bed load of pipes,at the same time gets the reference concentration of suspended sediment.Through the revision on diffusion theory of suspended sediment vertical concentration distribution,it gets different concentration distribution corresponding to different reference concentration and applies to vertical distribution validation by collected information.Using the concept of sediment carrying capacity of the pipes,it gets the sediment-carrying capacity according to different particle size and flow intensity,the pipe flow state combined with the empirical formula of slurry transportation,which provides theoretical basis to the operation of diversion projects.Finally on the basis of the bed surface deformation equation of open channel,considering all wearing factors of pipes and pumps,by dimensional analysis,wear equation is established,and relative wear rates of pipes and pump are estimated.