Critical Flow over Circular Crested Weirs

The critical flow principle is a useful approach for the hydraulic analysis of round-crested weirs due to their single head-discharge relationships. The hydraulics of circular-crested weirs is examined using simplified models incorporating streamline curvature effects, comparing their predictions with experimental data. A generalized one-dimensional model based on the critical flow in curvilinear motion has been developed. The discharge coefficient increases with the specific energy normalized with the radius of curvature, E∕R , when streamline curvature effects are included. The relative flow depth at the crest decreases as E∕R increases. The flow at the weir crest is only critical for a normalized specific energy value of E∕R≈0.5–0.6 . For larger heads, the flow at the weir crest has been found to be supercritical.