Circular & Rectangular
Studio Express uses the standard orifice equation for Circular and Rectangular orifices.
Co = 0.60 (or as set in Settings)
Ag = clear opening area in sqft (sqm)
g = 32.16 (9.8) gravity
d = head as measured from the centroid in ft (m)
This is a special kind of orifice structure as shown below which contains a series of same-sized holes all within a vertical height.
The following formula by McEnroe, 1988 is used to estimate the outflow.
Q = discharge (cfs)
Cp = 0.61
A = cross-sectional area of all the holes (sqft)
Hs = height (ft)
H = distance between water surface and the Invert Elevation (ft)