Stage-Discharge Relationship for Sharp-Crested Rectangular Slit Weirs

Abstract

Sharp-crested slit weirs are used for measuring small flow discharges. Different stage-discharge relationships can be found in the literature for computing the flow discharge of sharp-crested slit weirs. In this study, the performances of different available stage-discharge relationships are discussed using experimental data available in the literature. The flow process of a sharp-crested slit weir was analyzed based on the dimensional analysis theorem. The deduced stage-discharge equation was calibrated using the available experimental data for slit weirs with contraction ratios ranging from 0.017 to 0.25. The deduced stage-discharge relationship allowed measuring discharge values with an average error of 1.02% and a maximum error of 4.6%. The results of this study indicate that while weir Reynolds number is a predominant quantity affecting the flow discharge of rectangular slit weirs, the contraction ratio is a predominant quantity for contracted weirs. At the cost of less accuracy, an overall solution is presented in terms of the contraction ratio, which is applicable for slit, contracted, and suppressed weirs.