Numerical Modelling of Bedform Development; Bed-form Initiation in Hydrodynamically Smooth Flows over an Erodible Bed

摘要

Initiation of bed-form from a flat erodible bed in hydrodynamically smooth flow has been studied numerically. The computational model consists of hydrodynamic and sediment transport equations. The unsteady hydrodynamic equations are solved by Large-Eddy-Simulation (LES) and Immersed-Boundary-Method (IBM) on a non-bodyfitted grid. Dynamics of individual grains are neglected and only bedload is considered, as calculated from Van Rijn's equation (1984, Journal of Hydraulic Engineering, Vol. 110). Two-dimensional (2D) bed evolution is coupled with the above 3-dimensional (3D) hydrodynamic equations. Initiation and migration of bed feature results from a sequence of erosion and deposition upstream and downstream of the feature, respectively. Some similar characteristics of the simulated bedforms to the experimental ones have been observed. Quantitative comparison will be conducted in future work.