Numerical Simulation Of Hydraulic Scouring Of Silt In Front Of Qingtongxia Reservoir Dam

Reservoir sediment accumulation reduces water regulating capability of reservoir until totally losing. Sediment accumulation damages the benefit of flood protection, irrigation, electric power generation, water feeding, navigation and aquatic product. Furthermore, it blocks the development of industry and agriculture and threatens the lives and possessions of residents. In the Yellow River, because of the rapid expansion of silting, damage problems become more serious. Qingtongxia reservoir has been utilized for more than 40 years, and its effective storage decreases to 0.3918 hundred million cubic meters from the original 6.06 hundred million cubic meters. At present, it becomes the hydroelectric station without storage.In the face of the serious silting, since 1991 Qingtongxia station not only lowers water level to scour in the flood period, but also empties reservoir to scour at the end of flood period. Through the operation for these years, the way is proved to be effective and ensures electric power generation, flood protection and irrigation. In the paper, the method of numerical simulation is used to calculate flow field, scouring zone and topographic profile of scour funnel in the hydraulic scouring period of Qingtongxia reservoir. The principal contents and achievements of the paper are summarized as follows:(1)Three-dimensional numerical model of run-off pipe is established to compute flow capacity with different silting extent in front of dam. The relations between discharge, coefficient of discharge and silting slope are obtained and the influence of silting on flow capacity of run-off pipe is analyzed.(2)Plane two-dimensional mathematic model is set up and the flow field in front of dam is simulated while release structures are scouring. Scouring zone is gained based on computational flow field. Flow characteristics and scouring regularity are analyzed and more appropriate operation schemes at the idle time are yielded.(3)Two-dimensional numerical model of scour funnel is advanced. After the model is verified, the average longitudinal degree of slope and length of scour funnel are calculated. The longitudinal characteristics of topographic profile of scour funnel are analyzed through numerical simulation results. The relation between longitudinal degree of slope and water depth in front of run-off pipe is obtained.(4)Three-dimensional model of scour funnel is put forward and the transverse and longitudinal slope of scour funnel are calculated. The subaqueous land configuration in front of dam and characteristics of transverse and longitudinal profile are studied. The simulation results are in good agreement with the measured findings.