Study On The Water Diversion And Sand Control Measures Of Jinping-Ⅱ Hydropower Station

Sediment deposition in water diversion projects directly affects the quality and quantity of water diversion,and even threatens the normal operation of water diversion projects.At present,a large number of scholars at home and abroad have studied the water and sediment movement characteristics of the diversion outlet by means of theoretical analysis,numerical simulation and physical model test,However,most of the research focuses on the transport law of suspended load,and less on bed load.In particular,the particle size in a few centimeters to dozens of centimeters of bed load research is very few.This kind of large particle size of sediment is more harmful to the water diversion power generation system,so it is necessary to study its transport law.In this paper,based on the diversion project of Jinping II hydropower station,numerical simulation is used to study the flow field characteristics,sand distribution characteristics and the effectiveness of sand control measures in the water near the intake area of the hydropower station when different operating conditions are adopted.The main research contents and results of this paper are as follows:(1)The three-dimensional hydraulic characteristic calculation model of the inlet area of Jinping II Hydropower Station is established by using Flow-3D software.The accuracy of the model is verified by comparing the numerical simulation results with the measured data.The model is used to calculate the flow field in the water intake area of the power station.The results show that: The water flow in the inlet area of the power station has obvious three-dimensional movement characteristics.In the area before the sand barrier,the transverse velocity of the water flow gradually increases in the direction of the hole,and the peak velocity reaches its peak near the sand barrier,and the peak velocity tends to increase first and then decrease in the direction of the flow,and gradually increases in the direction of the water depth,and the peak velocity gradually pushes upstream as the incoming flow decreases;the longitudinal velocity exists in the upstream side of the inlet,and the velocity gradually decreases in the direction of the flow,and the peak velocity and the range of the acceleration zone gradually decrease as the incoming flow decreases,and the stagnation zone exists near the lower lip of the inlet;the vertical velocity value is small and the distribution is relatively uniform.In the area behind the sand barrier,the water turbulence is more intense,and there is longitudinal reflux.At the location of the right bank of the inlet,there is vertical reflux,and the range of the reflux area decreases with the increase of water depth,and there is transverse reflux at the left bank of the inlet,which is the main inlet area of the inlet,and the range of the vertical reflux area gradually decreases and the range of the inlet area gradually increases with the decrease of the upstream incoming flow.The flow field at the inlet section also has obvious three-dimensional characteristics,and the flow velocity distribution is different from that of the conventional open channel.(2)Using the particle model in Flow-3D software,the proposed sediment particles are randomly generated by Monte Carlo method to simulate the sediment movement in the inlet area of the hydropower station.The results show that when the flow velocity can make the sediment particles turn over the barrage,the curvature of the trajectory of the sediment particles gradually increases as the upstream incoming flow decreases,and the position of turning over the barrage gradually pushes upstream,the number of large-size sediment particles turning over the barrage decreases and the number of small-size sediment particles increases.(3)Through numerical simulation to study the hydraulic characteristics and sediment particle transport law of the power station inlet after adding four kinds of sand control measures,and combined with the economy and construction difficulties,the comparative analysis concluded that: from a long-term perspective,the single sand guide can be the preferred solution.