Sharp-crested weir located at the end of a circular channel

Abstract

Sharp-crested weirs are frequently used for discharge measurements in open channels. They offer a simple, reliable and accurate flow measurement approach if they are properly installed and maintained. Suppressed weirs can be installed in channels with different shapes. The standard suppressed rectangular weir is well documented in the literature. The current research is conducted to achieve an accurate and simple formula for flow through the suppressed, sharp-crested weir located at the end of circular, open channels. The discharge equation of a suppressed, circular weir ends up as incomplete elliptic integrals of the first and second kinds, which are not very suitable for practical purposes owing to their complexity. In this study, a simple and accurate theoretical discharge equation has been presented for this weir. A series of laboratory experiments (244 runs) are also performed to investigate the discharge coefficient of sharp-crested weirs located at the end of two horizontal, circular, open channels. Using the data collected from two pipes of diameters 19·1 and 30·1 cm, a suitable discharge coefficient equation with an average relative error of less than 2·3% is presented; thus actual discharge through the channel can be simply estimated using the proposed equations.