Identify Research Sill Bottom - Flow Dissipation Engineering Design Parameters Fall

In recent years, the development and construction of hydropower in our country has been in the peak period,a large number of practical requirements, promote the development of high dam flood discharge and energy dissipation technology and progress,flood discharge and energy dissipation design tasks become heavier.Because of the high-speed flow and high water head, large discharge spillway discharge to produce vast amounts of energy, on the downstream river bed scour seriously, even cause slope collapse and failure of a dam. The reasonable selection of the energy dissipation measures and design, has the important meaning to the project layout, dam safety and engineering quantity.At the time of design of hydraulic structures, to choose the form of reasonable flow convergence, to take the necessary measures, will be part of the kinetic energy of discharged flow discharge structures be eliminated and transformed into potential energy, the so-called energy dissipation issues, to improve the flow state, ensure the safety of the building. Dam flood discharge and energy dissipation are frequently used in the ski-jump energy dissipation,but the energy dissipation caused by the downstream scour atomizing deposition and strong,but deflecting flow energy dissipation caused by the downstream scour and strong fog, significant damage of soil and water conservation and ecological environment in the downstream.Therefore, many reconstruction and construction of the high dam has abandoned the ski-jump energy dissipation scheme and chose to underflow energy dissipation scheme. Adopt the conventional underflow stilling pool plan,because of high speed flow conditions brings fluctuating pressure, easily cause rise to instability and failure of plunge pool floor.Therefore needed a safe operation under high head、large discharge and reduce the atomizing effect of new type of dissipater spillway.The step-down bottom energy dissipater is a new type energy dissipator which is to reduce the floor height of Stilling basin on the basis of the traditional energy dissipator. And compared to the traditional underflow energy dissipater, can greatly reduce the velocity of the bottom, reducing the energy dissipation pond soleplate of the pressure fluctuation, increase the submerged jets for energy dissipation and reduce the impact of spray water on the surrounding environment, is an effective way to solve the problem of high head, unit discharge of bottom flow energy dissipation technology difficult problem.This paper uses the method of hydraulic model test, the hydraulic index that the flow state of the stilling basin、dynamic water pressure、velocity、depth、inflow velocity、into the pool water depth、the flow velocity、the out pool depth of the step-down bottom energy dissipater were observed.Combining the experimental results and theoretical analysis,the step-down bottom energy dissipater engineering design parameters are determined,scilicet the calculation formula that the still depth of the stilling pool,the flow tanking angle and the stilling basin length were deduced.Based on determining the design parameters of the stilling basin:the stilling pool depth, length of the pool, pool width, bottom elevation and the thickness of the base plate is designed.