The V-Shaped Broad-Crested Weir

Abstract

A discharge measurement structure with a triangular control section and a broad crest provides a rather wide measuring range while the head-discharge relation remains unaffected by tailwater up to a high submergence ratio. Experiments with the V-shaped broad-crested weirs have been carried out in order to investigate the influence of a boundary layer above the crest. The boundary displacement thickness is replaced by a correction height which includes the effects of a non-uniform velocity distribution, non-parallel streamlines and lateral pressure gradients. The experiments have results in a large collection of laboratory data with the aim to derive the head-discharge relations for different shapes under free flow as well as submerged flow conditions. The weir can be constructed with a fixed crest or a movable crest in vertical runways. The maximum discharge depends on the chosen dimensions. The structure is a suitable device for small and moderate discharges. Results of investigation, design rules and limits of application are given.