The Numerical Study of Open Channel Junctions with Extreme Confluence Angles for Surface Flow Without Wall Roughness

Confluences exist not only in nature, like in streams or rivers but also constructed environment like the structures for sewage and urban rainfall drainage canals. In the natural environment, two tributaries join at an angle from 30° to 135°. Existing related research focuses on tributary angels within this mentioned range. However, in the constructed environment, channel junctions with its angle beyond this range may occur. Hydrodynamic data from a 90-degree flume confluence is taken from experiments, available in the literature. The information is used to build a numerical model on Delft 3D. The similar flow parameters are used, with the comparable cross-sectional dimensions, with three confluence geometries. Firstly, two confluences with a junction-angle of 0°, and then with an angle of 180° are studied, each with three flow cases. Free slip condition is supplied to elude the effect of wall roughness on flow behavior. Interesting results have been found and presented. It is noticed that geometries affect the location of vertical velocity and velocity distribution in the confluence area. The 180° confluence shows a big stagnation zone in the angled tributary. This study improves the understanding of the interaction between flow dynamics and confluence angles better.