Document Type : Research Paper
Authors
Department of Hydraulic Structures, Faculty of Water and Environmental Engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran
Abstract
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Main Subjects
EXTENDED ABSTRACT
This study investigates the discharge coefficient and efficiency of a pivot side weir model with a flow sill, examining various opening angles relative to the main channel. The weir model developed in this study consists of a fixed right-angle sill and an inclined hinge section that allows for angle adjustments.
The models were installed and tested in the hydraulic laboratory at the Faculty of Water and Environmental Sciences, Shahid Chamran University, Ahvaz. A total of 60 experiments were conducted to achieve the objectives of this study. Based on dimensional analysis using the Buckingham method, the key variables identified are: flow Froude number (Fr), opening angle of the pivot weir in relation to the main channel (α), upstream flow depth relative to the height of the weir (yu/P), and the ratio of the length of the overflow crown to the length of the catchment section (Lw/b). Tests were conducted across a total flow range of 25 to 45 L/s (Froude numbers from 0.3 to 0.54) with opening angles of 30, 45, and 60 degrees, while maintaining a constant upstream depth (Yu = 16.5 cm) and a consistent ratio of upstream depth to overflow height (Yu/P) for each model.
Following the tests, we evaluated the applicability of Di Marchi's hypothesis for calculating the overflow flow coefficient. The specific energy difference percentage values obtained indicate that comparisons of discharge coefficients based on Di Marchi's hypothesis are acceptable for deriving study results, albeit with caution. Calculations revealed that the discharge coefficient and efficiency of various models increased by an average of 80% and 70%, respectively, compared to the control model. Additionally, results indicate that within the investigated range of Froude numbers, the flow rate coefficient increased up to Froude numbers of 0.4 to 0.45; beyond this range, as the upstream Froude number increased, the flow coefficient decreased for all models. It was also observed that for all upstream Froude numbers, increasing the opening angle enhanced efficiency compared to the control sample conditions. Notably, under the highest opening angle, model efficiency—particularly in the Froude number range of 0.3 to 0.4—was significantly higher than in other scenarios. Conversely, for Froude numbers of 0.4 and above, efficiency values decreased across all models.
The findings indicate that for all three models across various opening angles (α), increasing the angle of the model facing the main channel—thereby extending the length of the side overflow crown—leads to improvements in both discharge coefficient and efficiency, positively impacting the performance of the pivot side weir. Furthermore, closing off the sides of the pivot side weir model at angle α negatively affects its performance, resulting in decreased efficiency compared to when the sides are open. However, if only the entrance of the model is open while the end is closed, weir efficiency increases and surpasses that of other configurations.
Conceptualization, S.M.S.; methodology, J.A.; software, H.K. and S.M.S; validation, H.K., S.M.S, J.A and M.G.; formal analysis, H.K.; investigation, H.K., S.M.S, J.A and M.G.; resources, S.M.S.; data curation, H.K.; writing—original draft preparation, H.K.; writing—review and editing, H.K., S.M.S, J.A and M.G.; visualization, H.K., S.M.S, J.A and M.G.; supervision, S.M.S.; project administration, S.M.S.; funding acquisition, S.M.S.
All authors have read and agreed to the published version of the manuscript.
Data is available on reasonable request from the authors.
The authors would like to thank Shahid Chamran University of Ahvaz for providing all the needed facilities.
The authors avoided data fabrication, falsification, plagiarism, and misconduct.
The authors declare no conflict of interests.
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