Experimental Investigation of Discharge Coefficient in Prismatic Weir-Gate

Weir and gate have many applications in irrigation networks because of their simple and accurate equations for flow measurement and their ability in water level controlling. Water flow in river and canal pathes always contains suspended sediment particles and floating materials. In this condition, weir and gate can be combined together and create an integrated system entitled weir-gate that can convey sediment particles under the gate and floating materials over the weir. In this research, discharge coefficient of prismatic weir-gate was studied under free flow condition with different gate openings and flow discharges. Variation of discharge coefficient of prismatic weir-gate was investigated in different angles of prism surfaces including 60˚ vs. 60˚ (symmetrical prismatic), 45˚ vs. 47˚ (upper prismatic) and 75˚ vs. 45˚ (lower prismatic). Results showed that discharge coefficient increased by increasing, and parameters. Comparing the results of different angles of prisms showed that the lower prismatic weir-gate had the highest discharge coefficient among the models in different hydraulic conditions. Discharge coefficient of the symmetrical prismatic weir-gate was higher than the upper prismatic model. This could be resulted from the extreme contraction of flow passing under the gate and increasing the local losses. Linear equations were proposed with acceptable accuracy for the weir-gates. Comparison of the results with the reported results by other researchers showed that the discharge coefficient of prismatic weir-gate was higher than the other kinds of weir-gates within the tested condition.