Numerical Simulation Of Flow Field And Local Scour Pit Downstream Of Suoertou Hydropower Station

There has a big velocity and a severe turbulence for the flow downstream of hydraulicstructures, so it often results in the serious erosion of the riverbed and causes the part of orthe whole project seriously damaged, therefore it has a great theoretical and practicalsignificance to study and predict the scour pit downstream of hydraulic structures. Theresearch on the local scour pit of covering layer downstream of gate and dam projects nowis mainly based on the physical model test. In view of the long test cycle of the physicalmodel, high cost and some shortages which cannot analyses the effects of flow condition onscour pit etc., the numerical simulation method has been being a new way to study the localscour pit.This paper aims to develop a mathematical model and calculation method focusing onthe problem of the covering layer scouring downstream of discharge structures based on thereliable measured data. The major works of this paper are as follows:(1) With FLUENT software, a calculation region is established, and the flow field ofSuoertou hydropower station is simulated by a3D turbulent model, in which the standardk-ε two-equation model is adopted, governing equation is discretized by the finitevolume method and VOF method is used to deal with free water surface.(2) Based on FLUENT, by means of c programming, a numerical model oftwo-dimensional erosion was established, and the scour depth and shape is simulated.The major conclusions are as follows：(1) The water surface profile, pressure and velocity get simulated accurately Usingk-ε two-equation model and volume of fluid (VOF) method.(2) Taking the bed surface shear stress as bed load starting criterion and using cprogram, by comparing the flow shear stress on the bed surface with bed load criticalstarting shear stress at every time step to control the movement of the boundary of the grid in the bottom of the riverbed, and the deformation process of the riverbed is obtainedfinally.(3) By spring-base smoothing model and local remeshing model, the local mesh closeto the boundary is automatic adjusted to ensure the quality of the moving boundary grid,and the scour shape is simulated accurately. The numerical scour shape is similar toexperimental results, and the scour depth differences are within the allowable range.