Physical, Analytical, and CFD Models of a Long-Throated Flume

U-flumes are a subset of long-throated flumes suitable for use in wastewater metering. Although their mathematical characteristics are well defined so that they can be readily analyzed with existing design tools for long-throated flumes, specific tests of their performance are sparse in the literature. This study compares rating curves developed using a half-scale physical model, a computational fluid dynamics (CFD) model, and an analytical model (WinFlume). The physical model and CFD model were also used to determine the effects of increasing tailwater and to make comparisons to WinFlume's predictions of the limiting tailwater conditions for accurate flow measurement (modular limit). Based on the results obtained from the U-flume physical model, WinFlume estimated the rating curve for the study flume with an accuracy within 3%. The rating curve generated with the CFD model had a similar level of accuracy, corresponding to flow measurement errors of -1.2% to 3.8%. Both WinFlume and the CFD model gave reasonable estimates of the effect of high tailwater on the gauge level reading, but the limited CFD runs used in this study leave room for further work. The results of this portion of the study suggest that both WinFlume and CFD are useful tools for predicting the rating curves of long-throated flumes.