OVERFLOW CHARACTERISTICS OF CYLINDRICAL WEIRS

The most common types of weirs are the broad-crested weir, the sharp-crested weir, the circular-crested weir and nowadays the ogee crest weir. Advantages of the cylindrical weir shape include the stable overflow pattern, the ease to pass floating debris, the simplicity of design compared to ogee crest design and the associated lower costs. Related applications include roller gates and inflated rubber dams. In this report, the authors describe new experiments of circular weir overflows, with eight cylinder sizes, for several weir heights and for five types of inflow conditions : partially-developed inflow, fully-developed inflow, upstream ramp, upstream undular hydraulic jump and upstream (breaking) hydraulic jump. Within the range of the experiments, the cylinder size, the weir height D/R and the presence of an upstream ramp had no effect on the discharge coefficient, flow depth at crest and energy dissipation. But the inflow conditions had substantial effects on the discharge characteristics and flow properties at the crest.