Flow Past: An Artificial Channel Confluence with Mobile Bed

It is important to study the bed evolution in artificial channel confluence as flooding in them causes morphological changes. In this study, a detailed three-dimensional (3D) numerical simulation is conducted in a right-angled channel confluence to investigate the complex fluid-sediment interaction. Important features of the bed like scour hole, bank-attached bar, and flow separation zone in the confluence hydrodynamic zone (CHZ) are investigated for their evolutions by using the CFD software FLOW 3D. Governing equations used are 3D Reynolds-averaged Navier-Stokes (RANS) equations along with the continuity equation for water flow, K-ϵ model for turbulence closure, volume of fluid (VOF) equation for free surface tracking, and Meyer-Peter-Muller (MPM) equation for bed-load transport rate. Simulated results for water surface profiles, velocity profiles, and bed profiles at different time periods are obtained for steady flows at inlets. Effects of bed materials on the scour depth indicate that as the grain size increases, the maximum scour depth downstream of the confluence decreases. However, there is no effect on the location of the maximum scour depth. Similar trends are observed in the simulations for the bank-attached bar. The finding of the present study may be used in the design of artificial channel confluences.