Document Type : Research Article
A two-dimensional numerical model, based on solution of the Reynolds-averaged navier-stokes equations with k-eand EASM (explicit algebraic stress) turbulence models, is presented to describe' the free surface water flow over bed topography (dune) in open channels.
The model application indicates insufficiency of k-e turbulence model for simulation of flow over dunes (because of separation and streamline curvature). In this case, algebraic stress model that is economic method for calculating stresses can do better. Therefore, an explicit version of it (Wallin and Johanson 2000) is used All of the differential equations are solved with a finite volume method in a nonstaggered grid. The geometric shape of sand dune is simulated by introducing a general non-orthogonal curvilinear coordinate system.
The numerical results were compared with the available experimental data reported by Mierlo and Ruiter (1988) and general agreement was observed. Detailed calculations indicate improving prediction of turbulence characteristics and length of separation zone by EASM model.