Numerical Simulation of the Effect of Weir Magnification on Hydraulic and Hydrodynamic Characteristics in Diversion Dams

Duck tip weirs have a higher flow rate and fewer upstream changes than conventional weirs. Since the geometry of these types of weirs will bring about the complexity of the problem for theoretical and practical issues, it is important to study the magnification and hydraulic flow changes on these weirs. In this study, the effect of these changes on the hydraulic and hydrodynamic properties of the flow was investigated by numerical simulation using FLOW3D software. Dimensional analysis extracted dimensionless ratios and the relationship between variables in the experiments was determined. The results of comparing the numerical model with the laboratory model showed that the maximum error obtained from numerical simulation for the overflow coefficient of weirs is 12%. The permeability coefficient in the linear overflow with magnification 1 had an increasing trend initially and then a decreasing trend. From a relative head >0.6, the permeability coefficient became constant: 0.7 for experimental data and 0.75 for simulation data. In the weir, with a magnification of 2 to a relative head of 0.4, there was an increasing trend and from a relative head >0.4, there was a decreasing trend. In the weir with magnification 3, the permeability coefficient always decreases with increasing the relative head.