Prediction and CFD Simulation of the Flow over a Curved Crump Weir Under Different Longitudinal Slopes

The benefit of using a weir is that it allows flowrates to be measured and controlled in open channels and streams. The objectives of this research are: (1) to specify a suitable crest depth position as a control section for estimating the flowrate above a curved crump weir at ten different longitudinal slopes and (2) to compare the proposed flowrate versus measured and computational fluid dynamics (CFD)-simulated flowrates. In this research, the crest point of the curved crump weir was considered to be a control section, relating to the critical depth as a function of the crest depth. Experiments with eight different laboratory flowrates of flume were proposed at ten different channel slopes ranging from 0.0 to 2.5%. Statistical analysis of linear regression indicated that the relationship between critical depth and crest depth is 0.913 on average. Based on this finding, a new equation was derived to predict the discharge over the crump weir, which indicated an excellent match compared to the practical and CFD-simulated results (a maximum differences of 4% based on several standard error indexes and a one-way ANOVA). The CFD technique was performed to simulate the velocity and flow pattern of the curve crump weir based on the volume of fraction method. Six selective sections were tested along the flume with a total length of 1.36 m for a case study of 0.912 m.sup.3/h flowrate and zero bed slope to investigate and describe the water surface profile. The statistical analysis indicated insignificant differences between the measured and simulated water surface profiles, with a maximum difference of less than 15% observed at the section located at 0.69 m, while the average difference was 4.86% for all sections.