Experimental Study of Discharge Coefficient of Parabolic Sharp-Crested Weirs

Weirs provide a simple method for measuring the volumetric flow rate in small to mediumsized streams or in industrial discharge locations. Sharp crest weirs can be built in different shapes, such as rectangular, triangular, trapezoidal, circular and parabolic. In general, the discharge of these weirs is expressed byQ = Khn , where the value of n varies with structure shape (e.g. / for rectangular weir and 5/2 for triangular weir) and isn’t usually an integer number, then manual calculation of the discharge is facing a problem. In this study to facilitate the discharge calculations, the governing equations of parabolic crest weirs were reviewed and a simple equation was developed for computing the flow rate. Also, by using a physical model with different angles and heights, hydraulic characteristics of these weirs were investigated. The experimental results showed that with increasing the angle and height of parabolic weirs, the discharge coefficient was increased. The average discharge coefficient of experiments was calculated as 0.605. Furthermore, a proper regression-based equation to determine the discharge coefficient, with coefficient of determination R2=0.922, was obtained.