Numerical study of turbulent flow in pipe with sudden expansion

The turbulent fluid flow through sudden expansion duct studies raise the knowledge of scientific and contribute many practical applications. The sudden change in the surface geometry of the duct cause the severe pressure gradient, the boundary layer separates at the step edge and forms a recirculation zone. The knowledge about the recirculation zone is useful in study turbulent flow properties. This paper presents a numerical study of 2D turbulence flow was modeled by the standard k-?, realizable k-?, and shear stress transport (SST) k-? models. The stimulation was conducted by a sudden expansion duct with Reynolds number of 20000 at the inlet of the solution and expansion ratio of 1:2. In this research, flow characteristics at the recirculation zone in the sudden expansion pipe are analyzed. The recirculation size, velocity profile and turbulent intensity are compared between three models of turbulence flow. The results show that SST k-? model has the best prediction of separation flow compared to two others models. Furthermore, the trends of mean velocity of these three models are same as the experimental results