Author(s): Jie Zeng; George Constantinescu; Larry Weber
Keywords: Near-wall RANS models; Movable bed; Sediment transport; Open channel
Abstract: The development and validation of a model to solve for the flow, bed load sediment transport and bed morphology changes in open channel flows is presented. The non- hydrostatic model solves the three-dimensional (3D) incompressible, Reynolds-Averaged Navier-Stokes (RANS) equations in generalized curvilinear coordinates and integrates the equations up to the wall such that the use of wall-functions is avoided. The low-Reynolds- number version of the Spalart-Allmaras (SA) model and the k-ω model are implemented. The k-ω has the capability to account for the small-scale bed roughness distribution via the wall boundary condition for ω. The model uses adaptive grids in the vertical direction needed to account for changes in the free surface elevation and bathymetry. At the free surface the proper kinematic and dynamic conditions are satisfied at convergence. A non-equilibrium bed load sediment transport model similar to the one used in Wu et. al  is used with the additional introduction of down-slope gravitational force effects. The model is used to predict flow through meandering open channels for which detailed validation data are available. One of the experimental cases studied by Yen  is used to validate the deformable free surface module and the experiments by Odgaard and Bergs  are used to validate the bed load transport module by predicting the flow and bed bathymetry at equilibrium.