Modelling of overbank flow structures in meandering channels

Overbank flow in a meandering channel displays a complex coherent flow structure resulting from the interplay between the floodplain and main channel flows. Understanding and modeling such coherent flow structure are of great importance for addressing river engineering and management issues where the design solutions are required to retain natural channel features and to maintain a balance between environmental, ecological and amenity issues. In recent years, numerical models have increasingly been used for river flow modeling in order to understand their flow behavior. The main aim of this paper is to predict and investigate the overbank flow behavior in the physical model of meandering channels using three-dimensional (3D) numerical model. The performance of the model is first assessed by comparing predicted results with the limited experimental data. The experiment data were obtained from a 1:5 scale physical model of the River Blackwater and a flume study in Loughborough University. The predicted distributions of the streamwise velocity, secondary vectors, turbulent parameters and bed shear stress are used to investigate the coherent flow structures along the channel, in both the horizontal and inclined floodplain cases and main channel mobile sand bed case. The results show that the three-dimensional model predicts the coherent flow structures reasonably well.