Predictions of turbulent momentumless wakes and flows over a step with inclined wall

Abstract

In order to investigate performance of turbulent model and flow characteristics, the κ-ε-γ model has been applied to predict the two-dimensional momentumless wake where a jet and a wake coexist, and a nonlinear low-Reynolds-number κ-ε model has been modified to predict the flows over a step with inclined wall. The κ-ε-γ model performance is extended to resolve the jet/wake anomaly, which is encountered in calculating free shear flows by the standard κ-ε model. In the κ-ε-γ model, the relation between the rate of dissipation (ε) and the level of intermittency (γ) is well incorporated. The model is run to predict the two-dimensional momentumless wake where a jet and a wake coexist. The predictions of the κ-ε-γ model are compared with those by the κ-ε model as well as the experiment. It is shown that the model performance is generally satisfactory. A nonlinear low-Reynolds-number κ-ε model of Park and Sung is extended to predict the flows over a step with inclined wall, where the boundary layer flow without separation and the separated and reattaching flow coexist. An extensive test of the model of Park and Sung indicates that a slight modification of their model is needed. The main reason, which calls for a modification, is attributable to the fact that the model of Park and Sung has been developed on the basis of two extremities, i.e., the boundary layer flow and the flow over a backward-facing step (α=90℃). The predictions of the modified model are compared with those of the model of Abe, Kondoh and Nagano as well as the experiment. It is shown that the flows over a step with inclined wall are simulated successfully with the present model.