Effective parameters for calculating discharge coefficient of sluice gates

• It has derived an equation for gate's discharge coefficient in submerged condition.
• Estimating the energy loss factor in free and submerged flow conditions.
• Distinguishing between the submergence limits of sluice gates and hydraulic jump.
• Investigation on variation of contraction coefficient in free and submerged conditions.
• Estimating the flow through sluice gate using stage-discharge relationship.

The present work demonstrates the characteristics of flow from sluice gates under free and submerged flow conditions using Energy and Momentum Equations (EMEs). The experimental data was used from the research works reported by different investigators to calibrate the proposed equations. An equation for estimation energy loss factor of sluice gate at free flow was presented and effect of this parameter on increasing discharge coefficient's accuracy was demonstrated. It was derived a theoretical equation for variations of sluice gate's discharge coefficient with relative opening and relative tailwater depth. Effects of energy loss factor on discharge coefficient and distinguishing limit were investigated. In this research the concepts of submergence limit of the gate and the submergence limit of hydraulic jump will be distinguished. By determining effective pressure on the gate and using EMEs, equations for variations of sluice gate's contraction coefficient with relative opening and relative submergence were presented. The result shows that at free flow condition, a minimum contraction coefficient obtained under a certain value of relative gate opening. At submerged flow condition, contraction coefficient would be either increased or decreased depending on the level of flow submergence. This paper carefully considered stage-discharge relationships for estimation gate discharge under free and submerged flow conditions.