Calculation of flow rate through weirs is particularly interesting in water systems engineering, for the calculation of flow of rivers, dams, sewage system...etc... that have an overflow system that takes the form of a weir.
Different weir designs are available :
The equations below [Perry] are valid for water flow. With a different fluid, a correction due to the viscosity is required.
The flow capacity through a rectangular weir is given by the following formula, which applies to sharp edged rectangular weirs :
Q = volume flow rate (m3/s)
L = crest length (m)
h0 = weir head (m)
g = gravity acceleration = 9.81 m.s-2
In case h0 > L, a modification of the calculation formula must be considered :
The flowrate that can be achieved through a triangular notch weir (also called V notch weir), sharp edged, is calculated with the following equation :