A study of the effects of the longitudinal arrangement sediment behavior near intake structures

Constructing intake structures to divert some part of the flow from rivers causes some changes in hydraulic conditions of the flow in front of the intake port. These changes, like flows in river bends, induce secondary flows, thereby causing sedimentation in the intake port and erosion in the bank facing the intake. Submerged vanes have been used for different purposes such as reducing erosion in river bends, bank stabilization, increasing flow into the intake and so on. The vanes are typically installed with an angle of 15°–25° to the flow direction and with an initial height of about 20%–50% of the flow depth (Marelius and Sinha, 1998; Nakato et al., 1990). In this study, the possibility of the submerged vanes to control and direct the flow and river thalweg toward the intake port with different longitudinal arrangements has been investigated. Three longitudinal distances 3H, 4H, and 6H (H being the initial height of the vanes) have been considered and the experiments have been done for the regular and zigzag arrangements for different intake discharges. The results showed that using submerged vanes in the longitudinal spacing of 3H to 6H in regular and zigzag arrangements makes it possible to direct the thalweg toward the intake port. In addition, with the use of the vanes, a trench is made toward the intake, which in turn increases the impoundment efficiency by 50%–80% in the regular arrangement and by 25%–50% in the zigzag arrangement. Submerged vanes can also reduce the sedimentation by 40% over that without vanes.