Excel Spreadsheet Formulas for a V Notch Weir with a Notch Angle other than 90 Degrees
For a V notch weir with a notch angle other than 90 degrees, the equation for calculation of the flow rate over the weir is given by the equation: Q = 4.28 Ce Tan(θ/2)(H + k)5/2, where the effective discharge coefficient, Ce, and the head correction factor, k, are both functions of the notch angle, θ. The equations for Ce and k in terms of θ are:
Ce = 0.607165052 - (0.000874466963)θ + (6.10393334 x 10-6)θ2 and
k = 0.0144902648 - (0.00033955535)θ + (3.29819003 x 10-6)θ2 - (1.06215442 x 10-8)θ3
NOTE: The angle, θ, in the above two equations must be in degrees, not radians.
The Excel spreadsheet formulas in the spreadsheet template at the left will calculate Ce, k, and Q for a given head over a V notch weir with a notch angle other than 90o. Values for P, S, and Hmax are needed, because the same conditions given in the previous section must also be met in order to reliably use these equations. This spreadsheet template is similar to the one in the previous section, except it also provides for input of the notch angle, θ, and calculation of Ce and k.
Click here to download this Excel spreadsheet template.