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Broad Crested Weir Calculator

Broad Crested Weir refers to the flow measurement and regulation of water depth in rivers, canals and other natural open channels. Broad Crested Weirs are a robust structure used to measure the full width of the channel. A broad crested weir is normally a flat topped object which obstructs and extends across the entire channel.

Broad Crested Weir Calculator

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Table of Contents:

    Formula

    q = Cd × b × h2 × (2g (h1 - h2)) 1/2

    Where,
    q = Water Flow Rate
    Cd = Discharge Constant
    b = Width of the Weir
    g = Gravity (9.81 m/s2)
    h1, h2 = Head 1 and Head 2 on the Weir

    An overflow structure on which the nappe is supported for an appreciable length in the direction of flow is called as broad crested weir. It is a flat-crested structure, with a long crest compared to the flow thickness of water in canals and rivers.

    Example:
    Calculate the Broad Crested Weir for the given details.
    Width of the Weir (b) = 5 m
    Head 1 on the Weir (h1) = 3 m
    Head 2 on the Weir (h2) = 1 m
    Discharge Constant (Cd) = 10

    Solution:
    Apply Formula:
    q = Cd × b × h2 × (2g (h1 - h2)) 1/2
    Water Flow Rate (q) = 313.20919526731655 m3/s