Experimental Study of Discharge Coefficient and Flow Streamlines in a Trapezoidal Piano Key Side Weir

The main application of spillway in rivers and dams reservoirs is control and diversion of flood and protection of their related structures. In this research, a laboratory study was performed to test 16 trapezoid piano key A type weir models with different pillars 10, 15 and 20 cm in a canal with 10 meters length, 0.6 m width and 0.6 m height. The proposed weirs were placed on the main canal wall with two arrangements. The results showed that the maximum overflow rate coefficient was corresponded to weirs with p=15cm in both arranments (1 and 2) and the dimentionless ratio of 0.4 <H/P> 0.2 0.4 and also to weir with dimentionless ratio of 0.5 <H/P and p=20cm. Finally, the trapezoid piano key weir with a p=15cm and a B=50cm identified to pass the most appropriate flow regime.