ABSTRACT
Mass and momentum exchange between lateral cavities and the main channel in river flow is of special relevance due to their impact in relevant hydrodynamic processes such as sediment deposition or transport of nutrients. Large-eddy simulations are performed to analyse the flow developed within three lateral bank cavity configurations. The hydrodynamics developed inside and nearby cavities depends on their geometric characteristics, being of special importance their longitudinal extension over which the mixing between them and main channel takes place. The modification of the cavity shape directly impacts the shear layer formed between the high-momentum channel flow and recirculating flow within the cavities, which is key in the exchange of mass and momentum. In square-shape cavities the flow is characterised by a single large recirculating eddy, while those featuring a more elongated shape increases the outer flow entrainment enhancing turbulent momentum exchange and promoting mass exchange. These results are linked with the sediment trapping efficiency of the different geometries in order to assess the design of the geometry of lateral bank cavities.
