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 numerical simulation is conducted in a right-angled channel confluence using Flow-3D, 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 are investigated for their evolutions. Governing equations used are 3D Reynolds-averaged Navier-Stokes equations along with the continuity equation for the water flow, a k-ε model for turbulence closure, the volume of fluid equation for free surface tracking, and Meyer-Peter-Muller equation for bed-load transport rate. Simulated results for water surface profiles, velocity profiles, and bed profiles at different time instants match satisfactorily with corresponding experimental results. 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 channels.