ABSTRACT
The hydraulic behavior of spillway overflow structures is such that the discharge increases significantly with the head on the overflow crest. The longitudinal (streamwise) section of the overflow is typically broad-crested, circular-crested, or of standard crest shape. For heads larger than 3 meters, the standard overflow crest shape is recommended. Gated overflows are regulated to a desired or prescribed reservoir level. Circular-crested weirs are used for discharge measurement and serve as an overflow structure in hydraulic applications. Their advantages include stable hydraulic overflow condition, simplicity in design, and associated low cost. The flow over a round-crested weir model is treated by using Prandtl’s boundary layer approximation. The viscous flow features within the boundary layer are modeled using the system of continuity and momentum equations. Weir flow close to the upstream corner of a broad-crested weir is related to the free streamline separation from the crest, provoking a recirculating flow zone.
