Effective parameters for calculating discharge of radial gates

This study presents some theoretical relationships to estimate the discharge exiting from various types of radial gates under free and submerged flow conditions. These equations, which are based on energy and momentum concepts, were calibrated by means of a large number of experimental records retrieved from research conducted on three types of radial gates: hard rubber bar, sharp and music note gates. Results showed that the proposed equations could more accurately estimate the discharge of these radial gates where the mean absolute relative errors were less than 1.5 and 3.5% for free and submerged flow conditions, respectively. It was also observed that under specific circumstances, a hard rubber bar gate permits more discharge than sharp and music note gates. It is recognised that the discharge coefficient decreases with increase of lip angle. The reliability of the proposed equations was tested using 514 field data of multi-radial gates under operation in different irrigation canals. The study showed that calculating the total discharge exiting from individual gates by means of proposed equations was in close agreement with field observations. The predictive errors of the total flow discharge for 78% of the flow data were about +/- 10%.