Experimental and Numerical Investigations of the Effect of Main Channel Side Slope on Flow Pattern in Right Angle Confluence of Channels

Existence of scour holes and depositional bar is directly related to flow pattern in river confluence zone. In channel junction zone، the flow pattern is very complex as a function of different parameters. In the current research، the effects of a 45- degree side slope in main channel on velocity distribution، water surface profile and dimension of separation zone at a 90- degree junction were investigated and compared with those at a 90- degree side slope. For this purpose، the experimental components of 3 dimensional (D) flows were measured and on the basis of them numerical Fluent model was calibrated. The Turbulence model including RNG was applied for numerical simulation. The results indicated that for a 45-degree side slope the length and width of the separation zone in comparison with a 90- degree side slope were smaller in bed and larger in water surface. For a 45- degree side slope، due to very small width of the separation zone near the bed، a region with high acceleration in downstream of junction was not formed and the rate of shear stress was reduced in this region. Also، the results showed that the water depth variations at the beginning and end of main channel for 45 and 90- degree side slopes were 2. 1 and 3. 3 percent، respectively.