Study of Compound flow in Compound Sharp Crested Weir and Rectangular Gates

Weir and gates are the structures that used to flow measurement and control water surface. According to the changes discharge in the channels, the weir structure should have a wide range of measurement and control efficiency. This limitation can be addressed by the use of Compound weir. Also in the weirs, sediment accumulation in the upstream on the hydraulic flow and exploitation of irrigation networks is affected. Therefore, simultaneous use of the weir-gate structure can be appropriate. The purpose of this research was to study the hydraulic properties of weirs and weirs-gates with three sections (triangular- trapezoidal -rectangular) in gate openings equal to 1.5, 3 and 4.5 cm and the angle of the vertex 30, 60, 90 and 115 degrees as compared to rectangular weir- gate. Therefore, experiments were performed on a rectangular flume with length of 12 meters and width of 0.5 meter. The results showed that the amount of flow through the models increases with increasing of the vertex angle of the weir. Also the discharge was increased for a known head over the weir with increasing of height of the gate, but the discharge coefficient decreaseds. Based on experimental data the discharge coefficient in compound weir was in the range of 0.48 to 0.95 and in compound weir-gate was in the range of 0.38 to 0.82. The amount of determination coefficient (R2) and the normalized root mean square error (NRMSE) was obtained 0.94 and 0.03, respectively. The results showed that the use of a linear combination of flow equations is able to estimate the discharge coefficient with acceptable accuracy in weir and compound weir-gate.