Numerical investigation on distribution characteristics of velocities at equal-width open-channel confluences

The confluence of open channel flows is a common phenomenon in water-related projects. The distribution characteristics of flow velocities at the junction are complex and have a direct impact on the design and maintenance of channels. For the velocity distribution characteristics of combining flows, a three-dimensional numerical model of the equal-width open channel confluence was developed with RSM and the VOF method. Based on the measured results of experiment, the model was verified to study the velocity distribution with different combined scenarios in the junction area. The results reveal that: the flow velocity distribution is zone-featured; at the junction, the streamlines blend and the velocity deflects, and a recirculation structure and secondary flow are located downstream. A greater junction angle leads to larger deflection, stronger recirculation structure and stronger secondary flow, which strengthens the characteristic of velocity distribution and brings a greater impact on the walls of channel. A greater discharge ratio leads to a smaller squeezing effect on the water in the main channel and impacts the zone-featured distribution of velocities, which makes the confluence of water smoother and reduces scour on the walls.