Effect of non-equilibrium parameters on the numerical modeling of settling basins

Settling basins are one of the structures required for removing excess sediment entering irrigation or power canals diverting water from a river. A numerical model is needed to simulate the flow and sedimentation pattern in settling basins. In the current research, a depth-averaged two-dimensional numerical model of flow and sediment is developed using the finite volume method and based on the time-splitting scheme, which also allows for simulating sediment in a non-equilibrium state. The simulation of flow and sedimentation is done by the numerical model in a decoupled method. Sensitivity analysis was applied to estimate the effects of non-equilibrium parameters and the settling velocity on the numerical results. The results revealed that Maleki and Khan's formula and Zhang and Xie's formula are suitable for estimating the suspended load adaptation coefficient and the sediment settling velocity in the numerical simulations. Investigation of the formulas for the bed adaptation length indicated that all three methods considered in the current research had almost equal accuracy in predicting the sediment concentration distribution in the settling basin. The developed model has been verified against two experimental tests, showing a good fit between observed data and the simulated results.