Flow structure at reservoir-tributary confluence with high sediment load

Fluvial flow with high sediment load may plunge into the reservoir to form turbidity current, which may feature strong interaction with inflow from a tributary. However, to date, the understanding of confluent flow structure with high sediment load has remained poor. Here, a computational fluid dynamic software, Flow-3D, is applied to resolve such flows for a series of cases at laboratory-scale by solving unsteady, 3D Reynolds-averaged Navier-Stokes and sediment transport equations, based on finite difference method with structured meshes. The 3D results are compared with those due to a recently established 2D double layer-averaged shallow water hydro-sediment-morphodynamic model. One distinctive flow structure pattern is generated at the confluence with the intrusion of reservoir turbidity current from the main channel into the tributary. Apparent bed aggradation occurs inside the tributary mouth after a long-term hydro-sediment-morphodynamic process. The present finding has a more profound influence on sediment transport and morphological evolution at a reservoir–tributary confluence with high sediment load.