Numerical Simulation of Bed Evolution in 180 Degree Alluvial Channel Bend

The river bed evolution in 180 degree alluvial channel bend is numerically simulated using FLUENT based on Eulerian two-phase model that implements Euler–Euler coupled governing equations for fluid and solid phases and a modified k–ε turbulence closure for the fluid phase. This two-phase model predicts sediment transport from more fundamental dynamical equations, thereby avoiding the use of purely empirical sediment transport formula. Such formulas have been found to be case-dependent, thus limiting their general use to cover a broad range of flow configurations. Both flow–particle and particle–particle interactions are considered in the model. During the simulations, the interface between sand and water is specified using a threshold volume fraction of sand, and the evolution of the bed form is studied in detail. The predictions of bed form evolution are in good agreement with previous laboratory measurements. In addition, the computational results indicate the presence of a new mechanism in sediment transport that can be called 'Laminated Load' hereafter.