Numerical iInvestigation of the Effect of Junction Angle on Flow Dynamic at the Canal Junction of Concordance and Discordance Bed Level

Flow dynamics at river confluences can be characterized by six major regions of flow stagnation, flow deflection, flow separation, maximum velocity, flow recovery and distinct shear layers. The junction angle, discharge ratio channels and bed elevation differences are the parameters that affect the magnitude of these regions. Most of previous studies have paid attention to the concordance canal confluences, but few studies have been conducted on the bed discordance confluences. This study investigates the effect of junction angles on flow dynamics (separation zone, flow patternsand water level) in concordance and discordance bed levels of confluences by using a 3-D numerical model (Flow-3D). Important factors that are considered in this study are the four discharge ratios (ratio of tributary channel discharge to total discharge equal to 0.2, 0.33, 0.5 and 0.67), three angles (45, 60 and 90 degree) and variable river bed levels. The numerical simulation results showed good agreement with the experimental results. The results indicated that there are a lot of differences between dynamic of confluences with concordance and discordance bed levels and the junction angle plays an important role at the river confluences, especially in bed concordance junctions. Also as the angle increases, the flow separation zone dimensions increases; in such a way the separation zone length at 90 degree angle was 2.3 times of 45 degree in concordance bed level. Finally the value in case of relative bed discordance levels of 0.1, 0.2 and 0.33 were found to be 4.5, 3 and 2.1, respectively.