Orifice equation

The orifice equation describes the rate of flow of liquid through an orifice.

The equation can be represented as:

$Q=CdA{\sqrt {2gh}}$

where Q = flow (cubic metres per second)
Cd = coefficient of discharge
A = area of orifice (square metres)
g = acceleration from gravity (9.81 m/s/s)
h = head acting on the centreline (m)

For a circular orifice, the equation becomes:
$Q=Cd(1/4\pi D^{2}){\sqrt {2gh}}$

Typical values for the coefficient of discharge are:
Sharp orifice: 0.62
Tube: 0.80