Three-dimensional features in non-equal and opposing flow junctions

The main aim of the present study is to simulate three-dimensional features in equal and non-equal opposing flow junctions. In order to achieve this, the three-dimensional unsteady Reynolds-averaged Navier–Stokes equations are solved with the $k-\epsilon$ turbulence model on a non-staggered grid using the indirect addressing treatment. The overall agreement is good between the predictions and the measurement data. Three-dimensional streamlines capture the helical trajectory of particles inside two separation and two stagnation zones. The complex interaction is observed between two stagnation zones so that some particles travel from one stagnation zone to the other. Counter-clockwise and clockwise secondary circulations exist at the branch channel of the opposing flow junctions. The ratio of two upstream main channels discharge affects the size of separation and stagnation zones and shear layers in the opposing flow junctions. One of the secondary circulations located at the branch channel decays due to the discharge ratio variation. The contraction coefficient slightly increases with decreasing discharge ratio in non-equal and opposing flow junctions.