3-D Numerical Simulation Of Scouring Process In Sluice Downstream Of Dangka Hydroelectric Power Station

With the hydropower station discharge,large amounts of water steam drained,and the scouring problems of the downstream of those Hydropower station Construction are become very common.However,most low-head hydropower stations have features such as a low head,big flow,small Froude number and insufficient energy dissipation,were built in thick layer with gravel covered.So that the scouring erosion problems of downstream aprons caused by the discharge of these power stations are very common.In particular,the erosion problems of downstream riverbeds and the riverbank were more serious.While severe development may even result in the destruction of buildings and direct threats,directly affect the safe operation of the hydropower stations.Therefore,accurately predicting the flow field information,maximum scouring depth of the scour pits and scouring range of the downstream of the hydropower stations is of great significance for guaranteeing the safe and stable operation of the hydropower stations.With Dangka Hydropower Station of Yushu Qinghai for the study,based on Dynamic Grid Technology of ANSYS FLUENT software,the three dimensional numerical simulation of flow field and the discharge process water erosion process were simulated.The main conclusions can be summarized as follows:(1)A three-dimensional model of Dangka Hydropower Station were established.Based on ANSYS FLUENT software,by using RNG k-? turbulence model,and combined with SIMPLEC algorithm,a three-dimensional numerical simulation about the sluice,stilling basin and downstream of Dangka Hydropower Station has been performed.Comparing and analyzing the data of discharge flow,water surface profile and velocity distribution on the vertical line,the numerical simulation results agree well with the hydraulic model test results,which verifies the correctness of the mathematic model for water flow simulation in this paper.(2)Based on the movement characteristics of sediment in riverbed,a bedload transfer rate formula which based on randomness of flow velocity and bedload distribution were proposed.According to the principle of erosion and deposition,the critical shear stress of incohesive sediment as the critical condition for deposition,a User Define Function(UDF)about riverbed deformation were used to control moving boundary mesh node movement.(3)The three-dimensional numerical simulation of the local scour pit scouring process downstream of the discharge sluice of the Dangka hydropower station was realized dynamically.The shape and the maximum depth of the scour pit obtained were basically consistent with the measured results of the physical model.(4)During the scour process of the scour hole,the wall shear stress distribution of the movebed changes with the movebed deformation,that is,the scour area gradually develops toward the downstream and continues to decrease.The variation charcateristics of the turbulent kinetic energy and turbulent energy dissipation rate were basically the same.In the initial stages of scouring,the turbulent kinetic energy and the turbulent energy dissipation rate at the end of the apron are large.With the scouring,both the turbulent kinetic energy and turbulent energy dissipation rate were gradually decreasing.Finally,when scouring pit reached the equilibrium stage,the turbulent kinetic energy and turbulent energy dissipation rate in the scouring area no longer reduced.