Abstract
Circular-crested weirs have gained recognition for their high discharge coefficients in recent times. This study focuses on the experimental investigation of circular-crested weirs, specifically normal (ε = 0°) and oblique (ε = 30°) weirs, in a rectangular flume. The experiments were conducted under nine different flow conditions with progressively increasing discharge. Two distinct approaches were proposed to calculate the discharge coefficients for normal and oblique weirs during the gradual increase of flow discharge. In the flume, a flow with varying discharge rates was generated, and multiple discharge coefficients were considered at regular intervals. The first approach aimed to determine the instantaneous discharge coefficient of circular-crested weirs, while the second approach calculated the calibrated discharge coefficient for each flow condition. A comparative analysis of the findings from both approaches, conducted for each weir and flow condition, revealed that the average discharge coefficients obtained using the instantaneous method closely aligned with those derived from the calibrated method. Importantly, the discharge coefficients were determined without assuming dCd/dt = 0, thereby reducing inaccuracies compared to previous studies. The results indicated that increasing the weir angle in the channel, at a constant upstream flow depth, led to higher flow rates. Furthermore, this experimental study involved the calibration of the discharge coefficient for a 30º oblique crested weir, yielding a range of values between 0.52 and 1.07. Similarly, the discharge coefficient was calibrated for a normal crested weir, resulting in values ranging from 0.57 to 1.09.
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Abbreviations
- b :
-
Weir width (m)
- g :
-
Gravity acceleration (m2/s)
- H :
-
Height over the weir (m)
- h :
-
Upstream water height (m)
- P :
-
Weir height (m)
- R :
-
Weir radius (m)
- L :
-
Weir length (m)
- Q :
-
Flow discharge (m3/s)
- C d :
-
Discharge coefficient of oblique weir
- C D :
-
Discharge coefficient of normal weir
- Ɛ:
-
Weir angle in the channel (o)
- α :
-
The angle of the upstream side of the weir with respect to the vertical direction (o)
- β :
-
The angle of the downstream side of the weir with respect to the vertical direction (o)
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SMM helped in data curation, methodology, writing—original draft preparation. EI was involved in conceptualization, investigation, visualization, writing—review & editing, and supervision. AK helped in investigation, visualization, writing—review & editing.
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Mahdavi, S.M., Izadinia, E. & Khoshfetrat, A. Discharge Coefficient Calibrations of Normal and Oblique Circular-Crested Weirs Under Incremental Flow Conditions. Iran J Sci Technol Trans Civ Eng 48, 2679–2689 (2024). https://doi.org/10.1007/s40996-023-01277-6
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DOI: https://doi.org/10.1007/s40996-023-01277-6