Study On Hydraulic Characteristics Of Diversion Open Channel Inlet Layout In Xunyang Hydropower Station

Xunyang Hydropower Station is an important water conservancy hub on the Han River.The peak height of the reservoir area during the flood period is large,The open diversion channel bears great discharge pressure during construction.Model test research found that under the condition of large single-width flow,the hydraulic conditions of the diversion are more complicated.The head,bottom slope,and width of the diversion open channel have different degrees of overflow capacity,overflow pattern,and scouring in the channel.In order to solve the related problems,the method of combining model test and numerical simulation is used to optimize the inlet type of diversion open channel and obtain the recommended type of inlet section.The main research results are as follows:(1)Original design body found that the top elevation of the cofferdam basically meeted the requirements of overflow,and the downstream cofferdam shape was relatively reasonable.However,it was a very serious problem on scouring and silting in the open channel formed by the flow pattern around the upstream cofferdam and the right guide wall pier head.Given the problems of the original design body,after conducting analysis and comparison of several different inlet schemes through the diversion model test,the recommended body of the diversion open channel inlet type was finally selected,that is,the extension of the guide wall was shortened by 10 m.The original broken-line axis of the cofferdam was modified to be a straight line.The test results of the recommended body model showed that shortening the length of the guide wall and straightening the upstream cofferdam could reduce the area of the return area,increased the flow capacity of the diversion open channel,and significantly improved the flow pattern in the open channel.(2)Based on the FLOW-3D software,the RNG k-? double equation turbulence model was used,combined with the VOF free liquid surface tracking method for three-dimensional numerical simulation.The comparison between the value and the test value showed that the change trend of the two was consistent and the error was small.The model and method selected for this time value simulation calculation were reasonable.The numerical simulation could be better simulated the flow pattern of the diversion open channel.(3)Using the same method and numerical simulation of the recommended body,an in-depth analysis of the characteristics such as flow pattern,velocity distribution,flow rate and erosion according to the calculation results found that there was no bypass flow at thehead of the recommended body,the return area near the guide wall was small,and the center of the channel The flow velocity distribution law was that in the depth direction,the surface and the middle flow velocity were large,and the bottom flow velocity was small.On the plane,the flow velocity in the center of the channel was large,and the sides were slightly smaller.This flow velocity distribution law can improve the flow capacity of the open channel.According to the velocity distribution,the recommended body flow capacity meets the requirements.No serious erosion occurs at the pier head.The erosion mainly occurs in the central area of the diversion open channel,and siltation may occur on both sides,which is conducive to the stability of the structure of the guide wall.