Study On Hydraulic Characteristics Of Stepped Spillways With Different Sizes

Release structure has an very important position in hydraulic engineering,it can drain water of the reservoir and ensure the safety of hydraulic engineering.As a new type of energy dissipator in release structure,Stepped spillway can shorten the construction period with high energy dissipation.But the flow pattern is relatively complex and touches the atmosphere on dam surface.The flow mixed with a lot of gas and produced air-water two-phase flow.The flow aeration,cavitation erosion and pulsation phenomenon will have significant impact on spillway,and even endanger the safety of release structure.In this paper,the hydraulic problems of a reservoir in the Qinghai-Tibet Plateau are studied by means of hydraulic physical model and numerical simulation.The physical model tests were designed to study the flow pattern,pressure characteristics and energy dissipation characteristics of the flow at four steps of spillway.Numerical simulations were performed using the FLUENT software to calculate the hydraulic characteristics of step spillway.The main research results are as follows: the flow pattern is roughly divided into skimming flow,transition flow and nappe flow on the step overflow dam surface.The distribution law of water surface profile and velocity on the different stepped spillway is studied and analyzed.By analyzing the time-average pressure and the fluctuating pressure data of the steps,we can see that the time-average pressure on the horizontal plane decreases first along the concave angle of the step,and then increases gradually.The negative pressure is formed on the vertical plane of the steps.The fluctuating pressure reaches maximum value on the horizontal plane convex of steps.The time-average pressure and the fluctuating pressure intensity were wave development along the way on the stepped spillway.The distribution of along the energy dissipation and the influence factors of the energy dissipation under different steps are studied,and the energy dissipation mechanism is analyzed.The simulation method is safe and reliable in the calculation of stepped spillway,and can obtain its hydraulicparameters quickly and in detail.