The Model Test And Three-dimensional Numerrical Simulation Of Pinshan Spillway Tunnels Discharge

With the development of socialist modernization in China,it is utterly important to accelerate the construction of key water conservancy projects and make full use of the economic and ecological environment function given by water conservancy construction.During the construction of hydropower engineering,the optimization of dam body shape,the capacity of overflowing,and aeration and erosion in high-head water release structures are fatal problems that are frequently suffered.In order to ensure the security of the water conservancy project,studying high-head water release structures and the characteristics of internal flow field in water dam is very necessary.The spillway tunnel of Pingshan hydro-power station located in Nayong County was choosen as research object in this research.By establishing the hydraulic model of spillway tunnel,firstly the original scheme was tested to measure water discharge,after improving the shape of the imported side pier,the basic scheme was proposed.Then the scheme was verified by CFD software FLUENT as well as physical hydraulic model,counterpart results of discharge capacity,shape optimization,aeration and erosion condition from hydraulic model research and numerical simulation about the spillway tunnel were carried out respectively.The main research contents and achievements are as follows:(1)The situation about flow regime,longitudinal water line and deflecting flow of the spillway tunnel under different flood frequencies and radial gate opening conditions that appeared in basic scheme were observed.The flow around condition was found obviously at two sides of inlet pier,and the water flow overflow surface was unstable.By advancing and modifying the body shape of the inlet side piers,the flow patterns at inlet and overflow weir were improved,and the discharge capacity can meet the flood discharge requirements.(2)The aerated water depth,flow rate and transverse cavitation number in the chute section of basic scheme was analyzed.The average flow velocity at 0+454m section was about 28m/s,and the number of water cavitation was about 0.30,indicating that the lower part of the chute was required to add aeration facilities to be protected.After comparing various kinds of combinations between different sized aerated groove and aerated ridge,the most suitable location and shape of aeration facility was determined.The flowing state of the discharge flow is confirmed to be smoother after the aeration facility is added.What is more,a stable aerated cavity is formed on the downstream of aeration facility,which means the aeration facility worked well.(3)According to the topography of the energy dissipation area in spillway tunnel and experimental results of basic scheme,the outlet energy dissipator was adjusted from the bottom-curved flip bucket to the narrow-seamed flip bucket.Experiments shown that the recommended single-sided angle-guided narrow-seamed flip bucket can lead the water tongue to a fully opened situation as well as a reasonable placement point longitudinal,thereby the role of modified energy dissipation section can be fully played to discharge flood,and the energy dissipation effect is significant.(4)Three-dimensional numerical simulation of spillway tunnel was conducted.Simulation results of the spillway tunnel discharge capacity,the hydraulic characteristics in various locations along the spillway were compared and analyzed with the measured values of the hydraulic model test,from which the flow and pressure state of spillway overflow weir surface,the distribution of the longitudinal water line,the distribution of longitudinal bottom line pressure,as well as the typical cross-sectional flow velocity are in good agreement,indicated that the numerical simulation method applied in this study is reasonable and feasible.(5)Results of model experiments and numerical simulations were further analyzed to verified that the discharge capacity of the spillway tunnel can satisfy the design requirements.Through the analysis of the flow velocity,water line and bottom pressure,the reasonable shape and size of overflow weir surface and spillway tunnel were carried out,as well as their advanced arrangement.