Investigation of discharge coefficient and energy dissipation in free-flowing Quarter-Circular Gates

Radial and sluices are among the most common hydraulic structures that are used to regulate the water surface elevation and flow discharge in river engineering, irrigation and drainage networks, sediment discharge conduits, diversion dams, river and canal intakes, and large and small dams. It is very important to develop the application of radial gates as a flow control structure in water engineering projects. Recently, a new type of radial gate known as the quarter-circular gate (QCG) has been introduced. This study focuses on investigating its discharge coefficient (Cd) and flow energy dissipation rate (EDR) under free-flow conditions. For the analytical investigation of Cd and EDR, geometric parameters such as gate radius (R), gate opening (w), and hydraulic parameters such as upstream flow depth (y_1) were considered. Through dimensional analysis, it was found that Cd and EDR depend on the y_1⁄w (relative upstream depth flow), y_1⁄R (curvature of the streamlines), and w⁄R (relative gate opening). It was found that when y_1⁄w ranges from 4 to 20, Cd and EDR increase logarithmically from 0.9 to 1.1 and from 10% to 50%, respectively. Changes in y_1⁄R result in linear variations in Cd and EDR. Reducing the curvature of the streamlines reduces EDR by up to 75%.