لیدا اسمعیل پور

Side weir is a hydraulic control structure that is widely used in irrigation, drainage and urban sewage purification. In this research, 220 tests were carried out to study discharge coefficient and water surface profile of one-side semi-circular labyrinth side weir under subcritical flow condition. The effects of upstream Froude number, the ratio of length to width of the channel, weir height to upstream water depth, number of cycles and the radius of the Labyrinth on the discharge coefficient of the weir were investigated. The results showed that discharge coefficient of the semi-circular labyrinth side weir was 21 percent higher than rectangular side weir. Using SPSS software, a general equation based on the dimensionless parameters was presented for calculating the discharge coefficient of the semi-circular labyrinth side weir. The determination coefficient and NRMSE of this equation were obtained, 0.93 and 0.28 respectively. The water surface profile along the central axis of the main channel was almost horizontal.