Discharge Coefficient in Oblique Side Weirs

Side weirs are flow diversion devices that are widely used in irrigation,drainage and urban sewage systems. The present study focuses on the investigation of theeffect of oblique side weirs on the discharge coefficient of a side weir under subcritical flowcondition in rectangular channels. In this study 106 laboratory tests were conducted and theresults were analyzed to find out the influence of non-dimensional parameters on the dischargecoefficient of the weirs. The angles of side weirs varied from 0 to 17.5 degrees in six steps,three heights (5, 10 and 15 centimeters) and three lengths (100, 80 and 40 centimeters). Twodescriptions of the discharge coefficient (traditional side weir coefficients, Cd, and De-Marchi,CM), along with different discharges and related parameters were used. According to theresults, Cd is more sensitive to b1/b2 (ratio of channel bottom widths), whereby CM is sensitiveto L/b1 (ratio of side weir length to bottom width). The correction formula for estimating theoblique side weir discharge coefficient with a traditional shape shows that a 17.5 degree anglewith side wall causes 40 percent change in the discharge coefficient.