Application of numerical model in determining the discharge coefficient containing suspended sediments passing through side weirs

Side weirs are one of the most common water structures that are used to transfer or pass flood and excess water from headwater to downstream in channels and dams. One of the factors, which is often less considered in the design of such weirs, is the amount of suspended load along with the flow. Basically, suspended sediments along with flow, in addition to changes in the density of the passing water, can change most of the assumptions in the design of weirs. Due to the high cost and time-consuming nature of physical modeling, the powerful Flow-3D numerical model was used to simulate the flow of suspended sediments in this study. A channel with side weir was modeled according to laboratory conditions and the discharge coefficient passing through the side weir at different concentrations of suspended load was calculated. The results, while confirming the ability of the Flow-3D numerical model to simulate the flow containing sediment passing through the side weirs, showed that with increasing the concentration of suspended flow load, the discharge coefficient passing through the side weir increases. Also, using linear regression, experimental relationships were proposed to calculate the discharge coefficient through the side weir, taking into account the suspended load concentration.