شبیه‌سازی جریان آب با انتقال رسوب در آبگیرهای سد انحرافی در پیچ یک آبراهه.

Introduction: 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. Methodology: In this study, FLOW-3D numerical model was used to simulate sediment transport flow into bilateral intakes on both sides of a diversion dam in a channel bend. The geometric conditions of modeling are considered based on the laboratory study (FarhadiBansuleh and Yasi, 2019). The laboratory channel is a rectangular channel with a 90o bend. Numerical model based on physical model information (Farhadi-Bansuleh and Yasi, 2019) for clear water flow conditions, calibration and validation; and validated and adjusted for sediment transport flow. In reality, dewatering from diversion dams takes place at different angles, therefore, in this research, an attempt has been made to investigate the effect of different intake angles on the uniformity of water distribution and the entry of sediments into intakes, so there are seven scenarios to test the effects of intake angles, intake sill, and sluice way, in checking the flow pattern and deposition of sediments in the area of intakes, and the distribution of flow and sediment load to outer and inner intakes. Results and Discussion: In the modeling of sediment transport flow, the results show that the uniformity of water distribution is better in intakes with a zero degree angle. So that the rate of sediment into the outer and inner intakes is 9 and 14 times higher than the 90o intakes, respectively. The rate of sediment into 90o intakes is 6, 4.4 and 3 times lower for the outer intake, and 18, 17 and 15 times lower for the inner intake than at 30, 50 and 60 degrees. Inclusion of sill and sluice way in the intake system results, the uniformity of water distribution in intakes with zero and 90 degrees angle is improved by 47 and 45 percent, respectively. In the zero-degree intakes, the sediment load into the outer intake does not change significantly compared to the condition without a intake sill and sluice way; But this amount decreases by about 65 percent in the inner intake. These results are also true for the 90 degree intakes, so that the sediments load into the outer intake does not change, but in the inner intake it decreases by about 71 percent compared to the condition without intake sill and sluice way. Conclusion: The results showed that the most of the sediment deposition is towards the innerbend 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. [ABSTRACT FROM AUTHOR]