Flow characteristics in continuous bends with pool–point bar topography

Abstract

The bar–pool morphology is a typical feature of meandering channels that strongly affects flow and transport patterns. In this study, the three-dimensional flow velocity was measured in detail at six cross-sections in two continuous reverse bends with pool–point bar topography. The streamwise velocity, cross-sectional distributions of circulation, net transversal flow, turbulent kinetic energy (TKE) and turbulent shear stress (TSS) were analysed. High values of the streamwise velocity, TKE and TSS were located in the point bar region (PBR), which were closer to the bed surface in the downstream bend. The circulations, including the main circulation (MC), upper remaining circulation (URC) and outer-bank circulation (OBC), were observed to interact with each other and affect the net transversal flow. The URC was found to exist in the PBR of the downstream bend, which restrained the tendency of the MC to move towards the inner bank. The OBC decreased the net transversal flux of fluid mass towards the inner bank or increased the flux towards the outer bank. The variations in the flow characteristics for different water depths were also analysed. The experimental data can help to validate numerical simulations and predict the evolution of meandering channels, which will provide a technical basis for river regulation.