| The low-head water diversion project usually have common problems of sediment. It is either bed load of large particle size on the mountain river with sleep slope, or fine silt of plain rivers. So in the low-head water diversion projects, its waterer diversion problems and its sediment washing problems are closely related. Depending on different facilities and the arrangements, different types of structure for water diversion and sediment washing are formed. The layered water-taking structure is located in the upstream of the headwork with bend. This layout is a combination of the headwork with bend and the headwork with layered water-taking. And the headwork with layered water-taking is as the prime structure to solve the problem of water diversion and sediment washing.In this paper, based on collecting a vast amount of literature and the previous research results, making a further study on the hydraulic characteristics of the layered water-taking structure. Two study methods were used in this paper. They are the physical model test and the numerical investigation. The main contents of this thesis are listed as follows:(1) Collecting the relevant information about the low-head water diversion project, summarizing its function and classification. And mastering the current construction situation. Focusing on the current situation of the headwork with bend and the headwork with layered water-taking at home and abroad and their running situation in the practical engineering. Most of the previous research was about the flow characteristics on the headwork with bend. But in this paper, paying more attention on the layered water-taking structure. And checking the layered water-taking structure as the prime structure whether can reach the purpose of water diversion and sediment washing.(2)Focusing on introducing the model experiment of layered water-taking structure. Taking a renovation project of headwork with bend as the study project, a layered water-taking structure was designed in the upstream of the floodgates of the project of headwork. The layered water-taking is divided into two parts by a suspension lab. The upper layer is used for water diversion and the lower layer is used for sediment washing. The hydraulic characteristics of the layered water-taking have been analyzed, and an the same time the water diversion problem and sediment problem can also be solved. In this paper,through the overall 1:25 hydraulic model test, doing experiments includes two working conditions. One condition is that all the water is flowing into the headwork with bend. The other condition is that some water is flowing into the headwork with bend and the other is used for sediment washing. We can get the conclusion that the layered water-taking structure can satify the design requirements of the water diversion. And for the second condition, the larger the gate opening, the better its washing sediment efficiency.(3) Introducing the theory knowledge of numerical simulation. Those include basic concepts of numerical simulation, the basic control equations of fluid flow, the method of calculating the numerical simulation, the method of turbulent model. At the same time detailed introducing the VOF method of simulating the free water surface.(4) Introducing the application of numerical simulation in water conservancy projects. Making a list of the softwares used in the whole process of numerical simulation. The whole process includes the preliminary treatment, the process of calculating and the postprocessing. And making a detailed list about the numerical simulation in this paper.(5)The results of numerical simulation is discussed in detail. Listing and analysing the flow pattern,the flow profile and the flow velocity of the three working conditions. Making comparisons about the discharge for water diversion, the discharge for sediment washing and the velocity of sediment washing by the two study methods. Then reaching the conclusion that the results of two study methods are identical.The study on hydraulic characteristic of layered water-taking structure can be used for reference in the comprehensive treatment for similar structures. It is important for dealing with the problems of water diversion and sediment washing in water conservancy projects. |
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