Effect of the crest height on the stage-discharge formula of rectangular and triangular sharp-crested weirs under free-flow conditions

Abstract

Weirs are simple devices widely applied for flow measurements in open channels. These hydraulic structures are characterized by a stage-discharge relationship which mainly depends on their shape and dimensions. In this paper, the outflow process of sharp-crested rectangular and triangular weirs is investigated for the free-flow condition, using dimensional analysis and the incomplete self-similarity theory, in order to test the effect of the crest height. Using a wide database available in the literature for rectangular and triangular weirs, the applicability of a theoretical stage-discharge relationship is tested and then modified to introduce the effect of the crest height. The results showed that the proposed relationships assure good accuracy in the discharge estimate and highlighted the usefulness of considering the effect of the weir height in the relationship.