Model Test And Numerical Simulation Study On The Hydraulic Characteristics Of The Spillway Of Zhuoyu Reservoir

The spillway is one of the important water discharge structures,it is used in the water conservancy project to release excess flood water beyond the planned storage capacity,which plays a vital role in the safe discharge of water conservancy projects.Therefore,it is very important to study the hydraulic characteristics and shape optimization of the spillway.The research in this paper is based on the hydraulic design of the spillway of Zhuoyu Reservoir in Zhanang County,Shannan City,Tibet Autonomous Region,and combines with two methods including model test and numerical simulation.Carring out model test for the spillway under the original design scheme.Through the study of the hydraulic characteristics to verify the rationality of the shape and layout of the spillway and make suggestions for revision.And then,verifing revision suggestions by the model test.At the same time,the three-dimensional numerical simulation is used to calculate the detailed flow field of the stepped draining groove,which further verifis the rationality of its shape and layout.The main research results and conclusions are as follows:(1)The model test results of the original scheme show that the spillway layout is reasonable and the discharge capacity meets the requirements.The water tongue of the drop sill fell directly into the bottom plate of the side groove.The velocity of the bottom of the side groove is relatively large.If the bottom of the side trough is washed for a long time,a large scour hole may be formed.It is necessary to dissipate energy for the side groove with drop sill.There is a large energy dissipation sump at the end of the stepped draining groove,which leads to large fluctuations in the water flow in the stilling basin and serious scouring of the side wall.It is necessary to optimize the connection between the stepped draining groove and the stilling basin.(2)Digging a 2.5m deep water cushion pond under the water tongue drop to carry out an optimization test on the side groove with drop sill,The comparison and analysis of the hydraulic characteristics of the side groove with drop sill trough before and after optimization have verified the superiority of the optimization scheme.Digging the water cushion pond improves the hydraulic phenomenon of the water tongue directly impacting the bottom plate of the side groove,forming a buffer and energy dissipation of the water cushion pond.In the adjustment section downstream of the water cushion pond,the flow rate is reduced compared with the original scheme,and the water surface line on the cross section of the water is relatively uniform.The flow pattern of the water entering the front of the stepped draining groove is greatly improved,and there is no obvious impact pressure on the bottom of the water cushion pond.(3)The connection between the stepped draining groove and the stilling basin is replaced by the slope connection instead of the dissipation sill connection,making full use of the function of the existing stilling basin,improving the original flow pattern structure in the stilling basin,and forming an underflow energy dissipation form in the stilling basin.When connected by the slop,the fluctuation intensity of the water surface in the stilling basin is lower than that of the dissipation sill connection,and the height of the side wall of the stilling basin basically meets the requirements.There is a surplus in the length of the stilling basin of the slope connection method.It is recommended to shorten the certain length of the stilling basin to reduce the engineering volume.The velocity distribution and pressure distribution in the stilling basin also follow the general law of the underflow energy dissipation(4)Through the numerical simulation,the detailed flow field inside the stepped draining groove under the recommended scheme is studied and analyzed,mainly including the flow state of the gutter,the water surface line,the velocity field distribution,and the pressure field distribution.It is found that the internal vortex of the 2～3 steps before the stepped draining groove is unstable,and the water flow phenomenon similar to the cavity appears,resulting in a large area of negative pressure on the horizontal and vertical steps.In view of the fact that the velocity of the front part of the step drain is less than 10m/s and the negative pressure value is not large,cavitation erosion and cavitation are not considered.