Broad‐crested weir overflow

Описание: A broad-crested weir is a hydraulic structure with a flat crest that is significantly longer than the specific energy, in such a way that the streamlines above the crest are parallel to the crest. In turn, the pressure distribution above the weir crest is basically hydrostatic.
In most prototype situations, the upstream flow conditions are subcritical. Critical flow conditions occur at the weir crest, and the pressure distribution above the crest is hydrostatic, when the crest is "broad" enough for the streamlines to be parallel to the crest. Downstream of the weir, the flow is supercritical in absence of downstream control.
The flow over a broad-crested weir may be treated as a smooth and short transition along which the continuity [C] and Bernoulli [B] principles apply.
The broad-crested weir is a seminal application of the concepts of sub‐ and super‐critical flows, and critical flow conditions in open channels, which are essential to the understanding of open channel hydraulics. These are discussed in the relevant Youtube video movies in the same Playlist at:
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Fluid mechanics and hydraulics in Hubert Chanson Youtube channel {   / @hubert_chanson  }
Fundamentals of open channel hydraulics [Playlist]
Advanced hydraulics of open channel flows [Playlist]
Environmental hydraulics of open channel flows [Playlist]

The broad-crested weir {   • The broad-crested weir  }
Critical flow conditions in open channels {   • Critical flow conditions in open channels  }
Fluvial vs Torrential flows in open channel and free-surface flow {   • Fluvial vs Torrential flows in open channe...  }
The “weir equation” (1) Calculating dam and weir discharge capacity {   • The “weir equation” (1) Calculating dam an...  }
The “weir equation” (2) Its derivation for rectangular dam & weir crest {   • The “weir equation” (2) Its derivation for...  }

Acknowledgements
Reg STONARD
Jason Van DER GEVEL
Stewart MATTHEWS

References
HENDERSON, F.M. (1966). "Open Channel Flow." MacMillan Company, New York, USA.
CHANSON, H. (2004). "The Hydraulics of Open Channel Flow: An Introduction." Butterworth‐Heinemann, 2nd edition, Oxford, UK, 630 pages (ISBN 978 0 7506 5978 9).
GONZALEZ, C.A., and CHANSON, H. (2007). "Experimental Measurements of Velocity and Pressure Distribution on a Large Broad-Crested Weir." Flow Measurement and Instrumentation, Vol. 18, No. 3-4, pp. 107-113 (DOI 10.1016/j.flowmeasinst.2007.05.005).
FELDER, S, and CHANSON, H. (2012). "Free‐surface Profiles, Velocity and Pressure Distributions on a Broad‐Crested Weir: a Physical study." Journal of Irrigation and Drainage Engineering, ASCE, Vol. 138, No. 12, pp. 1068–1074 (DOI:10.1061/(ASCE)IR.1943‐4774.0000515).
ZHANG, G., and CHANSON, H. (2016). "Hydraulics of the Developing Flow Region of Stepped Spillways. I: Physical Modeling and Boundary Layer Development." Journal of Hydraulic Engineering, ASCE, Vol. 142, No. 7, 8 pages (DOI: 10.1061/(ASCE)HY.1943-7900.0001138).
CHAOKITKA, N., and CHANSON, H. (2022). "Hydraulics of a broad-crested weir with rounded edges: physical modelling." Proceedings of 30th Hydrology and Water Resources Symposium HWRS2022, Brisbane, Australia, 30 November-2 December, Published by Engineers Australia, Brisbane, Australia, Paper 07, pp. 43-52 (ISBN 9781925627640).