Hydrodynamics of a Broad-Crested Weir with Rounded Edges

A broad-crested weir is a flat-crested structure, acting as a hydraulic control, which may be used to measure the discharge. Detailed observations of free-surface profiles, pressure, velocity, and boundary shear stress distributions were performed in a large-sizes weir with rounded corners. The data highlighted a rapid redistribution of pressure and velocity profiles. The dimensionless discharge coefficients ranged from 0.92 to 1.04. The velocity data implied a developing boundary layer along the broad crest. The boundary shear stress increased as the flow accelerated toward the downstream end of the crest, where a local peak of shear stress was observed. The shear stress was relatively uniform across the weir, except next to the sidewalls. Based upon the nonhydrostatic pressure and nonuniform velocity distributions, the detailed hydrodynamic characterization demonstrated that the flow was critical along the entire broad crest length.