Evaluation of mixing air with the water flow in different step of skimming flow on stepped spillway by FLUENT model and a physical model

In this paper, physical model of a stepped spillway flow with skimming software,simulated by Fluent and Gambit software.In this simulation, the k- ε model in RNG, Mixture, and Enhanced wall treatment are applied to respectively model the turbulence , the multiphase flow, and the flow near the walls with attention to the specific hydrodynamic of the flow on the stepped spillways.Also , the PRESTO algoritm and the SIMPLE method are respectively used to dissociate pressur equations and to relate pressure-velocity equations.After calibration of the numerical model with experimental model, assuming an experimental model of precision, a margin of error of 6.6% was obtained for the numerical model. Then, by examining the concentration of dissolved air in the water flow, the result was evaluated for geometry and discharge studied,motion in the direction of the flow mixture concentration in the water increases.After concluding the percentage error of the numerical model, the numerical and graphical results analysis of two-phase flow of water - the air is present.