Theoretical and Numerical Investigation of the Sluice and Radial Gates Discharge Coefficient in the Conditions of Sill Application

Underpass gates are structures in which water moves through the gate. The purpose of this research is to investigate the effect of the sill on the hydraulic characteristics of flow in sluice and radial gates numerically using FLOW-3D software. For this aim, sills with different geometric characteristics in width, thickness, and height were investigated. The results showed that the statistical indicators in the RNG turbulence model have high accuracy compared to the k-ε, k-ω, and LES models in comparison with the experimental results. The RMSE in the RNG turbulence model for the upstream water depth and the discharge coefficient are 0.0079 m and 0.0117 m, respectively, and the average percentage relative error for these parameters is 2.94% and 1.60%, respectively. The Kling Gupta Efficiency (KGE) for the optimal mesh and mentioned turbulence model is in the very good range. In the same opening in the case without and with a suppressed, the discharge coefficient with the sill is higher than without the sill. Among the investigated sills, the discharge coefficient in the semi-circular sill is higher than in the rectangular sill. Also, the discharge coefficient of the radial gate in the without and with a sill is higher than the sluice gate in the corresponding state. The results showed that the increase in the thickness of the sill leads to an increase in the shear stress of the flow and consequently the discharge coefficient decreases. The discharge coefficient of the gate with different heights of the sill is always higher than the one without the sill, but due to the constant ratio of the depth parameter above the sill to the opening, the discharge coefficient increases with the increase of the height of the sill up to a certain level and then decreases.