Effect of discharge ratio on flow and passive scalar transport in a T-shaped confluence with a wider downstream channel

Open-channel confluences are important junctions in fluvial and artificial networks, which regulate the mixing phenomena of substances transported by the merging flows. This paper aims at contributing to the study of how the discharge ratio of the incoming flows influences the flow patterns and mixing phenomena at a T-shaped open-channel confluence with a wider downstream channel. In this study, Large Eddy Simulations (LES) are applied to compare the flow and passive scalar transport processes at two discharge ratios. The results clearly show that in the tributary-dominant case, the shear layer and the mixing interface move to the outer bank, due to the larger lateral velocities in the Confluence Hydrodynamics Zone (CHZ). Moreover, the turbulence and the secondary flow are enhanced, leading to a higher degree of mixing, as compared to the case with a dominance of the incoming flow from the main channel.