Numerical Simulation Of Pressure Distribution On The Stilling Basins Of Stepped Spillways

The conventional stepped spillway has exchanges arc section at the toe to connect with stilling basin, this style has been widely used in many practical hydraulic engineering since produced, it has displayed good energy dissipation result.At present, most research is in this type of structure, but there is little research about hydraulic characteristics of the step dam and stilling basin when no transition section connect with the downstream step,especially the numerical simulation studies have not yet seen. In this paper, with the the foundation of physical model test. The method of numerical simulation is used to study the hydraulic characteristics of stilling basins of this new style stepped spillways. The fractional volume of fluid(VOF) model of the air-water two phase flow is introduced to theκ-sturbulence model and combined with the geometry reconstruction scheme to solve the free water surface. The unstructured grid is used to treat the irregular boundary,and set three different dam slope,three kinds of step height and three different kinds of discharge. By these methods/the turbulence flow field of stepped spillway is simulated successfully.Pressure and turbulence are analyzed at the first time. The numerical simulation results are analyzed and compared with the test results, and they are agreed well with each other.The pressure of the stilling basin has following characteristics:Time average pressure:In the critical hydraulic jump and submerged hydraulic jump,there is quite similar pressure distribution on the stilling basin, they both have a maximum pressure in the impact of the stilling basin, at the hydraulic jump zone, it showed a larger pressure oscillations, and then a gradual increase in water level after the jump, and the pressure changes gradually steady;When drive hydraulic jump,a maximum pressure still appear in the impact area, but because of lower water leves downstream.the pressure obviously less than the other two kinds of hydraulic jump:discharge, dam slope, step height are important influencing factors in pressure.Under the same conditions, the peak pressure in the impact area increases along with the flow, slope steep increased;While the peak pressure decreases along with the step height increased.Pulsation intensity of pressure:The whole distribution size of the pulsation intensity of pressure are smaller than time average pressure, its distribution rule is similar with the time average pressure, also has the peak value in the fluent impact area.After impact area, pressure became smaller, through jump area and to the end of the stilling basin, pulse pressure is stable;At the hydraulic jump zone of the stilling basin, the pressure is bigger difference when different jump happen, the intensity of pressure is maximum when critical hydraulic jump, and smaller pressure appeared in submerged hydraulic jump, but when drive hydraulic jump, the intensity of pressure is smallest.Discharge, slope,and the step height are still the main factors affect pulse pressure. Different flow conditions greatly impact on the pressure at the jump zone,it is that big pressure value corresponding to big discharge;While slope factor mainly has great effect on pressure in the impact area,in this section pressure increases along with the slope increased;But step height has less effect on on pressure of the stilling basin.