End Depth as Measuring Device in Inverted Semicircular Channels

摘要

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 horizontal or mildly sloping inverted semicircular channels. 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.