ORIFICE CALCULATOR

The orifice equation is used to analyse the flow through a hole through the side of a vessel.

- Q = Discharge (flow rate).
- Cd = Co-efficient of discharge (difference between theoretical and real discharge).
- A = Cross sectional area
- h = Depth from center of orifice to upstream water level (free discharge orifice) or difference between upstream and downstream water level (drowned orifice).

However for large orifices (Height greater than depth/5) **under free discharge ** the equation above is no longer considered valid due to the variation in flow velocity across the orifice. For rectangular orifices the following equation can be used as it integrates over the orifice's height. No easy integration is available for large circular orifice's and as such they are not included in the calculator.

- b = Rectangular orifice width.
- H2 = Depth from bottom of orifice to upstream water level
- H1 = Depth from top of orifice to upstream water level