Bottom Currents Flow Structure Characteristics Of Energy Dissipation Down Hom Energy Dissipator

At present, many Hydropower Engineering which are being constructed and plan to be constructed with the characteristics of high water level, large discharge and large power. The dam's energy dissipation becomes especially prominent. Guarantying the flood with huge energy to excrete safely becomes the key technologies in the high dam construction.The step-down bottom energy dissipater is a new kind of energy dissipater which can adapt the high water level and large discharge. It has high energy dissipation efficiency and eliminates the atomization influence, comparing with the traditional bottom energy dissipater; the hydraulics targets are greatly decreased in the baffle basin. Presently, the research on step-down bottom energy dissipater has based on the practical engineering and come into use in the engineering at home, but short of basic research results. The thesis is based on the Yunnan Province Fund (2006A0018M). Through changing the inlet energy, inlet angels and step-down heights, the flow pattern, time-average dynamic pressure and velocity are observed in detail. Basing on the test results and using the theoretical analysis, the following research has done:(1) The law for flow pattern changing and its influencing factors in the baffle basin; (2) Under the bottom flow pattern, the flow's movement structure, the flow's velocity distribution and time-average dynamic pressure in the baffle basin; (3) The law for lateral axis vortex's movement behind the step-down and the hydraulic characteristic in the vortex area are studied. The research results are as following:1. The basic movement phenomena and its mechanism of movement which happen during the energy dissipation are introduced; the basic concept and flow pattern's classification of mixed flow theory are leaded-in. the movement phenomena that happens in the step-down energy dissipater is analyzed through using the mixed flow theory.2. Under the submerged bottom flow pattern, the flow's movement of step-down energy dissipater is studied. According to the flow's movement in the baffle basin, the flow is divided into different regions and studied respectively. The characteristic of irregularity in the flow field is also analyzed under bottom flow pattern.3. Unifying the test, the hydraulic characteristic (including water surface curve, near bottom velocity of flow as well as bottom floor's time-average hydrodynamic pressure) is studied. The governing equation of step-down energy dissipater is deduced under submerged bottom flow pattern.4. The flow's diffusion and the velocity's attenuation in the submerged jet area and the submerged hydraulic jump area are carried on the analysis, through the fitting to the test data, the flow's velocity distribution formula in the submerged jet area and the submerged hydraulic jump area of step-down energy dissipater is deduced; through the research to time-average hydrodynamic pressure, the formula of time-average shock pressure in the baffle basin is got; the law of pressure distribution is also studied by analyzing the test data; the efficiency of energy dissipation to the jet flow along the regulation is also estimated.5. The movement equation of vortex behind the step-down, the movement region as well as the rotating core position's change are preliminary studied, simultaneously the research to the vortex area's hydraulic characteristic combining the hydraulics experiment is done.