Study On Overall Layout And Navigation Problem Of Qianwei Navigation And Hydropower Project

The overall layout of a large-scale water control project is a complex systematic project, for which scientific evidence and determine are needed. Layout must make various structures of different functions be located in proper places, and be in coordination with each other during the using period,so that the undertaken tasks can be fully and effectively completed. The plane layout of the hub,that is the relative position of the lock,the sluice and the power station, is related to the exertion of their respective function and the success or failure of the hub construction. In order to search for the best engineering program, the comparative tests of multiple options of the general layout are needed to be performed to demonstrate the rationality of the arrangement of the lock, the sluice, and the power station. Physical model test of hydraulic project can predict the motion law of flow and sediment, the sediment characteristics, the scour and erosion pattern, the river regime change and so on of the reservoir and river channel after the construction of hydraulic structures in natural conditions, which is an important means for studying issues of complicated boundary conditions and strong three-dimensional feature, such as the fluvial processes, the river regulation and the reservoir operation mode. This paper refers to the physical model of Qianwei Navigation and Hydropower Hub to research the layout of large-scale hydraulic hub. The main contents of this study are as follows:(1) The effects of different flow conditions on the length, width, bend radius and the relative location to the station of the straight line of the approach channel are analyzed. In addition, the impact of the flow conditions on the design of the approach channel and the optimization measures of the navigation structures are illustrated.(2) The design ideas of the hydraulic model are described. Hydraulic model must ensure the similarities of the flow pattern, the geometry and the roughness of each part near the model upstream and downstream the hub. The actinomyces accuracy and the fabrication and installation precision of the physical model of Qianwei Navigation and Hydropower Hub both must meet the requirements of "The Procedures of Hydraulic (Conventional) model test (SL155-95)" of the Ministry of Water Resources. Thus, the flow and sediment transport conditions can be better simulated to the prototype.(3)The discharge capacity of Qianwei Navigation and Hydropower Hub is demonstratd. Through experimental analysis, the weir flow coefficient was determined and studied. The calculation formula of the flow coefficient was determined based on the project situation and test results.(4) The energy dissipation effects downstream the dam under different conditions were simulated by the use of hydraulic model, and the most adverse condition of energy dissipation was put forward. Through calculations and repeated model tests, the energy dissipation measures of the hub were reasonably optimized. Aiming at the improved measures of energy dissipation, and combining with the navigation conditions controliing, the open way of the gate was studied.(5)The flow conditions of the station forebay and inlet in the original design scheme of Qianwei Hub were studied.Through the analysis of flow conditions of the power plant intake under different discharge, it is found that there are several issues in the original design scheme, such as the appearance of bending shape concaving toward the shore on the plane form, too long for the watershed partition; the large-range water exchange of free water with the moving water in the right in the low-lying areas around the cutting-edge of the deputy power plant; the existence of the water-falling phenomenon downstream the pool inlet. The specific modification programs were proposed according to the analysis results and were demonstrated through experiments.(6) Through the test, the navigation flow at the approach entrance area and the connecting section of the lock in the original design were analyzed. Aiming at the issues that the horizontal velocity is too large at the approach entrance area under large flow rate and the angle between the mainstream and the navigation route is too big, a variety of amendments to the program were proposed. In addition, the best optimization scheme was selected through the comparison of different optimization programs, and has been demonstrated by experiment.(7) Through the test, the issues of the flow pattern emerging in the lower approach channel in the original design scheme were researched and demonstrated. Similarly, improvement measures were proposed and also has been demonstrated through experiments.The test makes amendments and improvements to the shortcomings existing in the layout design of Qianwei Navigation and Hydropower Project,which not only makes the layout and operation of Qianwei Hub more reasonable, but also provide a method and idea for the layout optimization of large-scale hydro project.