Investigation of the effect of sudden transition on the elliptical-lopac gate discharge coefficient under submerged flow conditions

One of the new structures of water level regulation in irrigation canals is the Lopac gate which has several advantages such as overflow and non-accumulation of sediments. The elliptical-lopac gate (ELG) is a new type of lopac gate that introduces a higher discharge coefficient than the rectangular lopac gate (RLG) as well as the easier passage of floating objects in the flow. In the present study, the effect of sudden transition on the discharge coefficient value of ELG in submerged flow conditions has been evaluated in the laboratory. The results showed that the sudden transition in the ELG reduces the discharge coefficient 14 to 73% compared to the channel width conditions. Also, the discharge coefficient has a direct relationship with the Froude number and opening angle of the ELG and the inverse relationship with the rate of channel narrowing due to the transition and submergence of the ELG. Finally, the empirical equations were presented to estimate the discharge coefficient of ELG with sudden transition under submerged flow conditions with a maximum error of 5% and 15%.