Brink Depth for Trapezoidal Broad-Crested Weir

Abstract

Brink depth characteristics include the relationship between brink depth (y\do) and critical depth for parallel flow (y\dc); variation of Froude number at the brink with the ratio y\do/y\dc, and variation of pressure coefficient (k\d1). More than 400 tests performed on lucite models of broad-crested weir of trapezoidal cross section with, 1:1 side slope, width varying from 8.5625 ft to 20.1333 ft, slope of crest varying from level to steep, and entrances both square cornered and rounded, reveal the value of y\do/y\dc ranged from 0.700 to 0.757. The value of y\do/y\dc is constant for a particular weir model irrespective of discharge, but is generally different for different weir models, varying with the slope and breadth of the weir crest, and the entrance condition; the Froude nubmer at the brink is a function of only (y\do/y\c); K\d1 and thus the total residual pressure at the brink section depends on the Froude nubmer and is, generally, not zero.