The Three-dimensional Numerical Simulation Of Aerated Flow For Spillway

With the development of hydropower engineering industry, the discharge of outlet structure is getting greater and greater,unit discharge is further increasing and problems brought by high velocity flow such as pulsating movement,cavitation and erosion become more prominent day by day. The main engineering measure to prevent cavitation damage of the stucture is to add gas into high velocity flow.Therefore,study on the hydraulic characteristics of spillway,especially on aerated flow,becomes more and more important for safe operation of outlet structure.As numerical simulation has the advantages of handleability, low cost and short cycle and so on,it can play a larger role and even replace apart of test in the construction selection and optimization,the period can be shorted.Because the theory of aerification is not very mature,there is mass of numerical simulation research ahout it to be done.In order to understand the hydraulic characteristics of spillway and provide basis for rational design,the numerical simulation of flow field of spillway in BaGong Project is done in this paper. The simulation of aerated flow at aerator is done with multiphase model, A new avenues to better improve the forecast level of aerated flow will be explored by comparisons of the caculation results in the case of characteristic diameter of different bubbles and different forces between phases.Standardκ-εmodel combining with finite volume method are applied to this paper,free surface was trated with VOF method and irregular boundaries were dealed with unstructured grid.Compared with the data of model test of engineering project, a three-dimensional numerical simulation of turbulence of the spillway in this project was done,the discharge, velocity field, pressure field and water surface profile were all obtained. The comparison analysis shows that numerical simulation was in good accordance with experimental results,which satisfied the engineering requirements.In order to exactly study the flow near the aerator, the two-fluid of Eulerian Model is used in this paper.Considering the interaction between gas and liquid.the simulaiton is done with a acharacteristic diameter bubble instead of gas.The results show that the ventilation volume and wind speed by the vent are obtained with Euler model, the different characteristics diameter of bubble has a notable impact on ventilation volume,yet on the whole,the values of simulation are a little greater than the experimental ones. The experimental datas and simulation results show that,air concentration of simulation results is smaller than experiment and negative pressure and cavity is greater than it which lead to the cavity is incomplete.In view of the condiotn of sufficient aeration,the impacts of two different interphase forces model on air concentration of downstream are compared,the diameter of characteristic bubble has a great effect on bubble floating on the water surface with symmetric model in compution,but the phenomenon that on-way attenuation of aerification is inapparent has not been improved better.Because of the complexity of turbulent flow, water-air two-phase flow and free surface, two-phase flow mechanism is still in development stage, because the bubble size and the variation is not clear, the numerical simulation of aerated flow still has many questions to be further explore...