Study On Hydraulic Characteristics Of Stilling Basin With Drop Sill By Numerical Simulation

Stilling basin with drop sill is a new type of bottom-flow energy dissipater. It notonly weakens the atomization compared to the energy dissipation type of ski jump,but also has the smaller underflow speed and fluctuating pressure than conventionalenergy dissipation by hydraulic jump. With the drop sill, it increases the quantity ofwater in stilling basin, so full of shear, turbulent vortex roll and severe blendinghappens between the existence of mainstream and the water in stilling basin todissipate most of the energy. With large number of high head, large vent flowhydropower project construction, it will be more widely applied.However, because of the complexity of flow of stilling basin with drop sill andthe impact to flow by the stream and downstream boundary conditions, there is nomore mature formula to be applied in the design of its body, which is still mainlydependent on the hydraulic model test research. In recent years, with the elevation ofcomputing capabilities, using numerical simulation method to simulate the stillingbasin with drop sill has become a new trend. On the basis of the physical model tests,using numerical simulation method to study the hydraulic characteristics of thestilling basin with drop sill has important practical significance.On the basic of collecting research status quo at home and abroad of hydrauliccharacteristics, shape optimization, engineering applications and research meansrelated to stilling basin with drop sill, this article studied its hydraulic characteristicswith a hydropower station of Yijiang upstream hydropower project as the researchobject, focusing on the three-dimensional numerical simulation and analysis ofhydraulic characteristics about stilling basin with drop sill under the differentcontraction ratio of top hole exports.RNG turbulence model was selected to founding the mathematical model, andVOF method was utilized to tracking the free surface, then a method combining withthe structured grid and unstructured grid for different computational domains wasused to dividing the mesh. Commercial software Fluent was utilized to go tothree-dimensional simulation for stilling basin with drop sill, and the water line, thedistribution of flow speed and time-average pressure, and other hydraulic parameterswere gotten to be compared with the hydraulic model test results of the sameconditions for a comparative analysis. The results are basically the same, indicatingthat the numerical simulation study of stilling basin drop sill is feasible.The numerical results of three programs also show that with the contraction ratiodecreases, the first position of the hydraulic jump move down, the location of themainstream of the top hole flowing to the bottom move down, the upper vortex rollbecomes more focused, intense; the largest underflow speed decreases; pressuredistribution are more gentle. The programs can meet the requirements of the lengthand depth of the stilling basin. However, with the contraction ratio decreases, thelongitudinal diffusion position of the mainstream of surface hole move down, thebottom velocity after the jump and of the tail lip trend to increase. Therefore the right contraction ratio and layout type should be chosen to the top hole exports of stillingbasin with drop sill, which is conductive to the force and stability of the stilling basinboard, and do not affect the protection requirements of the stilling basin downstream.