Simulation of Sediment Transporting Flow at River Intakes of a Diversion Dam in a Channel Bend

There is a number of evidence for the construction of weirs and diversion dams in river bends, and sometimes building water intakes on both sides of the river bend are needed. However, this encounters problems in terms of asymmetry of flow distribution into the intake structures. Most recent studies have been conducted for clear water flow conditions. The main purpose of this study was to investigate the uniformity of sediment transporting flows into bilateral intakes on both sides of a spillway in a channel bend. FLOW-3D numerical model was used to test the effects of intake angle, intake sill and sluice way on the uniformity of flow and sediment load entering the intakes and the distribution of sediment deposits in the intake area. The numerical model was calibrated and confirmed based on the information of the physical model for clear water flow conditions. Then, the numerical model for sediment transport flow was validated and adjusted, and it was implemented for seven scenarios of the arrangement of the weir and its related structures in the channel bend. The results showed that the most of the sediment deposition is towards the inner-bend intake. Without the intake sill and sluiceway, the ratio of outer to inner intake for five intake angles of zero, 30, 50, 60 and 90 degrees is about 2.1, 3.8, 5.0, 4.17 and 2.4, respectively. Using a 90-degree intake is more efficient due to less sediment entry and uniform inflow distribution to both bilateral intakes. Inclusion of sill and sluiceway in the intake system results in the reduction of the ratio of outer to inner intake to be reduced to 1.1 and 1.3 for the two intake angles of zero and 90 degrees, respectively. The results show that it is necessary to use the intake sill and the sluice way to control the sediments entering to the intakes, especially in inner intake.