2D Simulation of Flow over Stepped Spillways with Turbulent Models and Comparing the Results with Physical Model

Stepped spillways have significant importance for their indisputable effect on energy dissipation and for compatibility with roller compact concrete method in construction. In order to design these spillways, physical models are commonly used in spite of spending great time and cost. Progress of high speed computers, however, permits to utilize computational fluid dynamic (CFD) method and therefore diminishing time and cost. In this research, some physical results are used for simulation of flow on stepped spillways, by applying FLUENT CFD package. Skimming and transitional regimes are investigated for the spillway. The simulated parameters were characteristic depth (y90), characteristic velocity (V90), clear water velocity and mean air concentration. Multiphase models consisting of volume of fluid (VOF), mixture and Eulerian and also turbulence models of k-ε, also coupling pressure-velocity algorithms of PISO and Simple were used both two and three dimensionally. Mixture and RNG k-ε for multiphase and turbulence models totally produced satisfactory results. The results were good for evaluation of the hydraulic parameters considering air bubble entrainment in skimming regime and relatively poor for transitional regime.