Evaluation of Outflow Relationships from Sluice Gates

One of the structures for controlling and measuring flow in open channels are the sluice gates. In this study, to estimate the outflow from the sluice gates, the existing relationships for orifices evaluated theoretically and experimentally. A new method was established for estimating the contraction coefficient and energy loss coefficient under free-flow condition. Some equations proposed to estimate the outflow from sluice gates under submerged flow conditions using the energy-moment principles and relationships for orifices. In order to evaluate the accuracy of recommended relationships, the outflow from the sluice gates was experimentally tested in a channel of 18 meters long and one meter wide. Comparison of the results showed that all the presented orifice relationships have similarly good capabilities to estimate the outflow from the sluice gates under free-flow conditions. It was concluded that the applying of Henry relationship would be the simplest one in determining the contraction coefficient. Under submerged flow conditions, all the orifice relationships have competent accuracy in estimating the flow rate, with an order of errors less than 10 percent. Under full ranges of free to submerged flow conditions, the discharge coefficient can be determined by the relationship of Rajaratnam and Subramanya as a function of the head loss coefficient, the contraction coefficient and the opening-to-depth ratio.