The Study On Hydraulic Characteristics Of Qiaotian Reservoir Spillway

The spillway is an important part of water control project,whether its layout is reasonable and discharge meets the requirements,they are crucial to the safety of the whole hydraulic complex project.Therefore,studying the hydraulic characteristics of the spillway and optimizing the shape of the spillway,it is important application value to ensure the safe operation of the water conservancy project and guide the engineering practice.Taking qiaotian reservoir as the engineering background,this paper combines model test and numerical simulation.The overall physical model test of the side channel spillway is carried out under the design scheme.Through the study of the design scheme hydraulic characteristics,the spillway rationality of the shape layout is verified,the optimal modification scheme is selected and the optimization test is supplemented.The flow field under the design flood flow is calculated by three-dimensional numerical simulation,the hydraulic parameters such as flow pattern,velocity and pressure are compared and analyzed,the engineering suggestions to improve the scouring of the downstream river channel and the opposite mountain are put forward.The main research results are as follows:(1)Physical model test review of spillway designscheme hydraulic characteristics.According to relevant data,the physical model established with a geometric scale of 1:30 is used to review the design scheme.The design scheme has problems such as excessive discharge capacity of side weir,poor flow pattern in spillway,large fluctuation range of water surface,overflow of side wall of stilling basin and serious scouring of downstream riverbed.(2)Formulation the optimization scheme for improvement of spillway hydraulic characteristics.Considering the discharge capacity of side weir,cavitation damage,flow pattern,energy dissipation effect and engineering practice,the optimization scheme is studied and determined:the width of overflow weir is narrowed from 25m to 22m,the diffusion section is increased by 6.056m,the floor elevation of stilling basin is reduced by 1.5m,the side wall of stilling basin is increased to 16m,and the bottom width of outlet channel is changed to 10m..(3)Multi condition test is physical model of spillway optimization scheme hydraulic characteristics.According to the physical model research results of the comprehensive optimization scheme,the comprehensive discharge coefficient of the overflow weir is between 0.4340 and 0.4838,and the discharge capacity of the side weir meets the discharge requirements;The height of spillway side wall shall meet the water depth requirements;The flow velocity reaches the maximum at the diffusion section and does not exceed 30m/s,and the minimum flow cavitation number also appears at the diffusion section and is greater than 0.3,so it is not cavitation damage in the spillway and it is not necessary to set corrosion reduction facilities;In view of the fact that the outflow from the pond is greater than the allowable non scouring velocity of the downstream riverbed,the engineering measures to expand the apron range and strengthen the protection of the scouring range of the opposite mountain are put forward.(4)Numerical simulation evaluation of spillway optimization scheme hydraulic characteristics.Using three-dimensional K-S turbulence model,combined with VOF method,fluent is used to simulate flow under the design flood level discharge,and the hydraulic parameters such as flow pattern,velocity and pressure are compared.The numerical simulation results are generally consistent with the physical model test results.