Generic Unified Rating for Cutthroat Flumes

Computational fluid dynamics (CFD) software was used to generate water depth and discharge data for the 24 standard-size Cutthroat flumes (CTF), as well as an additional 27 intermediate sizes. The hydraulic model was validated using information from several sources, including physical model test data for 16 standard sizes and 3 intermediate sizes. Grid-size independence was also confirmed for a range of computational cell sizes, and the calibration results for 16 of the standard-size flumes were compared with previously published calibration parameters. Through the CFD simulations, a full set of calibration and validation data was generated for each of the 51 tested flume sizes, filling the gaps in the experimental data from physical models and permitting a full analysis of flume hydraulic performance. The study resulted in a “generic” (any CTF in the dimensional range of the 24 standard sizes and specified dimensional ratios according to the original design criteria) and “unified” (for both free- and submerged-flow conditions) calibrations. From these results, a single algebraic equation was developed for free and submerged flow, relating upstream water depth and submergence to discharge. The error in the CFD-predicted discharge for all flume sizes is less than 3 % of the full-scale discharge, and the equation is applicable to both standard and nonstandard sizes