The discharge coefficient of sharp triangular weir pierced by orifices

Abstract

Although triangular sharp-crested weirs have less discharge-passing ability compared to rectangular weirs, they have greater accuracy and sensitivity for measuring discharge. In order to enhance the passing-discharge and the discharge coefficient from a sharp-crested-triangular weir, an orifice was created in the weir. In this research, for the first time, several square orifices were created in the weir of the sharp crested triangular weir with different numbers and dimensions. The results of the discharge-passage investigation revealed that by creating one orifice, the discharge passage rose by 41.3%; with the increase of each orifice, the discharge passage increases by 37.2 % on average. It was also observed that upon increasing the relative dimensions (the ratio of the side-square-orifice length to the flume width) by 0.033, the discharge passage grew by 36% in average. Also, the results of discharge-coefficient investigations-showed that with creation of one orifice, it increased by 5.1% in average. But based on the novelty of this research, by increasing one orifice from 2 to 4, the discharge coefficient increases by 1.92 percentage. By upstream velocity measurement in control weir (weir without orifice) and combined weirs (weirs with orifices), a noticeable change in the lateral and depth velocity-profiles was observed, and these changes led to increase in the passing-discharge and also an increase in the discharge coefficient. Finally, an equation was presented to determine the discharge coefficient with high accuracy.