Tony L. Wahl. 2000. "New Developments in Design and Application of Long-Throated Flumes". Bureau of Reclamation, Report Number PAP-842.
Abstract: Long-throated flumes provide economical and flexible water measurement capabilities for a wide variety of open-channel flow situations. Primary advantages of long-throated flumes include minimal headloss, low construction cost, adaptability to a variety of channel types, and ability to measure wide ranges of flows with custom-designed structures. Long-throated flumes can be calibrated using computer programs that apply proven hydraulic theory, thus eliminating the need for laboratory calibration. This paper describes recent advances in the computer software available for design and calibration of long-throated flumes, and highlights two potential flume design issues that have recently come to light. Specifically, there have been field observations of an apparent suction effect below flumes having a vertical drop at the end of the control section; this can lead to significant differences between the actual and theoretical head-discharge rating curve. Second, in flumes that are primarily width-contracted-as opposed to those with a sill that creates a bottom contraction-there is potential for non-modular flow in the throat section when the width to crest length ratio is large, despite the fact that traditional hydraulic theory predicts critical flow. Again, this can cause a significant discrepancy between the actual and theoretical rating curves of a structure.
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