The orifice equation describes the rate of flow of liquid through an orifice. The equation can be represented as: where Q = flow (cubic metres per second) C(d) = coefficient of discharge A = area of orifice (square metres) g = acceleration from gravity (9.81 m/s^2) h = head acting on the centreline (m) For a circular orifice, the equation becomes: Typical values for the coefficient of discharge are: Sharp orifice: 0.62 Tube: 0.80