Author(s): A. M. Binnie

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Abstract: Published details of the flow over weirs of this type indicate the existence of fixed waves on the free surface in front of the weir. Bonham's extensive results are analyzed, and it appears that measurable waves occurred when the Froude number F of the approaching stream exceeded about 0.4. This is exactly the limit at which waves are seen in an open channel supplied through a contraction, which forms the waves by reducing the momentum of the stream without altering the energy. Thus the waves seen at the weir were caused, not by the weir, but by the arrangements for producing the stream. This conclusion was supported by experiments in a channel so long that the waves formed by the entry contraction died away before the stream reached the weir. It is shown that, as waves unavoidably formed in a short channel do not greatly disturb the pressure near the bottom, the indications of a float in a well used to measure the weir discharge are not much invalidated if F is kept below about 0.6.

DOI: https://doi.org/10.1080/00221687809499609

Year: 1978