This study investigates experimentally and numerically the effects of sills with different geometric specifications at various positions on the hydraulic characteristics of flow through sluice gates. The simulation results showed that the RNG turbulence model’s statistical indicators yield high accuracy compared to the k-ε, k-ω, and LES turbulence models. The discharge coefficient (Cd) has an inverse relationship with gate opening. Regarding sill state, the discharge coefficient is higher than no-sill state. In the case of non-suppressed sills, the Cd decreases compared to the smaller openings as the opening of the gate changes. The results showed that the Cd with a sill in the tangent position upstream of the gate is higher than the downstream tangent and below situations. Increasing the sill length leads to an increase in flow shear stress and consequently a decrease in Cd. The Cd of gates with different sill thicknesses is always higher than the no-sill state, but due to the constant ratio of the fluid depth above the sill to the gate opening, the Cd increases to a certain extent and then decreases with increasing sill thickness.
