Author(s): Seyed Vahid Nabavi; Alireza Hejazi
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Keywords: Brink depth; Free overfall; Open channel flow; Steady flow; Sub-critical; Semicircular channels
Abstract: A free overfall at the end of an open channel provides a simple means for measuring flow discharge. This paper presents a theoretical model to predict the pressure head distribution at the brink of free overfalls, in a smooth inverted semicircular channel. Based on the momentum equation, the flow upstream of a free overfall is theoretically analyzed to calculate the end-depth-ratio (EDR). The EDR, related to the critical depth, is around 0.7 for a critical depth-diameter ratio up to 0.4. Methods to estimate discharge from the end-depth in sub-critical approaching flows are presented. The computed results agree satisfactorily with the computed and experimental results of Dey.
Year: 2009