Orifice Outlet allows an Orifice plate control to be modelled.
The Orifice outlet uses an orifice fomula to calculate the flow when the orifice is surcharged. When the orifice is not surcharged, the flow through the orifice is calculated using a circular shaped weir formula.
Diameter - Enter the diameter of the orifice. If you are working to a maximum allowable discharge a Calculator is provided to help size the control. This gives two additional parameters:
Coefficient of Discharge - Enter the discharge coefficient of the orifice.
A coefficient of 0.6 may be used for square edged inlets (see 1). The coefficient may be increased to 0.95 if the inlet is well rounded using a rounding radius 15% of the orifice diameter (see 2). It should be decreased to 0.5 if the orifice is formed by a pipe protruding into the flow.
Invert Level - The invert level of the orifice.
The following formulae are used to calculate the orifice flow:
D = diameter of the Orifice.
h = depth to the centre of the orifice (free discharge is assumed).
C = coefficient of discharge. A default value of 0.6 is suitable for sharp edged orifices but can be changed.
Formula (1) represent the flow through an orifice in charge. The formulae (2) to (12) represent the flow through the orifice when it acts like a weir (i.e. a circular shaped weir).
Workflow - What's next...?