The Flow Rate for a Broad-crested Weir calculator computes the flow rate of water (or similar liquids) over a weir that is characterized as broad (flat and wider than deep).
Instructions: Choose units and enter the following:
Flow Rate (q): The calculator returns the flow rate in cubic meters per second. However, this can be automatically converted into other volumetric units (e.g. gallons per minute) via the pull-down menu.
A broad-crested weir is a flat-crested structure, with a long crest compared to the flow thickness. When the crest is "broad", the streamlines become parallel to the crest invert and the pressure distribution above the crest is hydrostatic. The net effect is a double drop resulting in two head measurements (h1 and h2).
The hydraulic characteristics of broad-crested weirs were studied during the 19th and 20th centuries. Practical experience showed that the weir overflow is affected by the upstream flow conditions and the weir.
`q = Cd⋅h2⋅b⋅sqrt(2g⋅(h1−h2))`