Study On The Energy Dissipation Mechanism Of Multi-Horizontal Submerged Jets

Because of the construction of high head, large discharge hydraulic projects, a new problem has arised: how to solve the energy dissipation problem of the hydraulic engineering whose unit discharge is large and the total width of the spillway is limited. On the base of the existing research study, Multi-Horizontal Submerged Jets for energy dissipation are proposed. It is a new form of energy dissipation which is based on the theory and method of the multi-submerged jets in hydromechanics and it is the development of the hydraulic jump dissipation . In this paper, the author employed a combination method of theoretical analysis, numerical simulation and model test to analyze and study the energy dissipated mechanism of the Multi-Horizontal Submerged Jets and the stability of flow pattern. The main contents and conclusions are as follows:1. The existing research results show that 3D spatial jump can be used to different downstream water lever, it's stability of the flow pattern and the ratio of the energy dissipation is higher than 2D jump and some problems, such as the velocity of the bottom is large, the scouring to the plunge pool is serious, can be solved. But, now there are no systematic studies on the stability of the flow pattern and the energy dissipated mechanism of the Horizontal Submerged Jets.2. Connecting to the need of certain engineering, a new form of energy dissipation, named Multi-Horizontal Submerged Jets, which based on the energy dissipation mechanism of spatial 3D hydraulic jump and multi-jets trajectory flowbucket, are put forward. Multi-Horizontal Submerged Jets is a new form of energy dissipation which uses strong shear, different shape eddy and strong mixing to dissipate the energy. The jets of it are separated into many strands in different elevation and the main flow is lied in the middle of the plunge pool. The zone of high velocity has certain distance from the floor slab and water surface.3. The Horizontal Submerged jets has three types: single lever and single strand, single lever and multi- strand, multi- lever and multi- strand. From the view of classical hydraulics, the formulas to compute the energy dissipation ratio of the three types are deduced. The energy dissipation ratio and the factor which affect it are analysis qualitatively. It is found that the energy dissipater ratio of Multi-Horizontal Submerged Jets is the highest and the stability of the flow pattern is the best.4. Numerical simulation can make up the shortage of the model test. From it, hydraulic characteristics of flow field, such as the velocities, distributions of pressure and turbulence energy, are gotten. The results of model test and numerical simulation inosculate preferably, which prove that numerical simulation is effective.5. From the numerical simulation of the Multi-Horizontal Submerged Jets and single lever Multi-Horizontal Submerged Jets under three conditions, it is found that the former's energy dissipater ratio is higher than the laster's because of the bump and the strong shear between the jets. The main jet of the former is lied at the middle of the plunge pool, the other is lied at the bottom. The former's stability of the flow pattern is better than the laster's.6. Based on the energy dissipation of Xiangjiaba power station, the hydraulic model of Multi-Horizontal Submerged Jets was made. The results of model test show that Multi-Horizontal Submerged Jets, with the interval layout of surface outlet and intermediate outlet in different elevation, has technical feasibility and has the characteristics of high energy dissipater ratio, stable flow pattern and low bottom velocity. From the model test, the effect of many factors, such as the type of theintermediate outlet, the elevation of the surface outlet and intermediate outlet, the type of drop, on the hydraulic characteristics of Multi-Horizontal Submerged Jets are studied.7. The experimental results show that the height of the drop of the intermediate outlet and surface outlet should high enough to lower the bottom velocity of the plunge pool...