Numerical Investigation of Submerged Vane Effects on Flow Pattern in a 90° Junction of Straight and Bend Open Channels

Open-channel junctions have widespread application in civil and environmental engineering projects. A characteristic feature of flow in a junction is formation of a low-pressure zone with recirculating flow (with high sedimentation potential) accompanied by a high-velocity zone (with high erosion potential). A comprehensive numerical research study was done on submerged vanes to investigate their effect on flow pattern. This research was done in order to reduce sedimentation as well as erosion potential at the junction of bending and straight channels. Firstly, the numerical model was validated by previous studies. Secondly, flow pattern in a junction of bending and straight channels was evaluated numerically. Following that, effects of some geometrical characteristics, number and height of vanes and installation angle, were evaluated in relation to improved flow pattern. Finally, performance of vanes was investigated in terms of reducing maximum velocity after the junction with various discharge ratios. The results showed a comprehensive reduction in sedimentation of the junction as well as partial reduction of erosion potential. Evaluation of the results led to the recommendation of using two submerged vanes of height of 0.2h-0.3h and installation angle of 20 degrees-30 degrees in this type of channel. Results also determined that an installation angle of more than 40 degrees and application of submerged vanes in channels by discharge ratios larger than 0.58 are not suggested.