Computations of bed deformation and sediment sorting in meander channel using depth-averaged morphodyamic model

Abstract

This paper discusses the bed evolution and the grain sorting process in meandering channel by using a two-dimensional (2D) based morphodyamic model. In river bends, secondary currents, which are three-dimensional (3D) flow structures caused by a balance between centrifugal force and pressure gradient, has important roles for flow structure and the sediment transport. Therefore, a numerical model, which can reproduce this 3D flow structure, is required to describe the morphodynamic phenomena in meandering rivers. This study employed the depth-averaged 2D shallow water equations' integrated effect of secondary currents of the first kind for flow calculations. This flow model can consider the effect of lag between the developments of secondary current and streamline curvatures. In addition, we employed the equilibrium sediment transport model and a multiple layer model for simulating the sediment transport and sorting phenomena due to non-uniform sediments. This study applied the different kind of model for evaluating the secondary current and sediment transport to a meandering channel with simple-rectangular sine-generated curve. We examined the applicability of models and morphodynamic process in a meandering channel through the comparison between the experimental and numerical results. The result shows that the correlation for secondary currents for flow structures and sediment transport is important to reproduce the bed evolution and sorting phenomena in river bends.

Keywords:

• Secondary current
• sorting
• meandering channel
• plane 2D morphodynamic model