Orifice Flow Rate
Orifice Flow Rate
Orifice plates meter flow cheaply and reliably by relating the discharge to the head across the plate.
The discharge is Q = C_d·A·√(2gh). where C_d is the discharge coefficient, A the orifice area, g gravity and h the head.
Inputs
C_d := 0.62=0.62
d := 50 mm=50 mm
g := 9.81 m/s^2=9.81 m/s^2
h := 2 m=2 m
The orifice flow area.
A := pi·d^2/4=1.96e-03 m^2
Discharge is the ideal flow reduced by the discharge coefficient.
Q := C_d·A·sqrt(2·g·h)=7.63e-03 m^3/s
Results
The discharge coefficient (about 0.6 for a sharp orifice) captures contraction and friction losses. The flow varies with the square root of head.
Assumptions & limitations
- Steady incompressible flow.
- Constant head during measurement.
- Discharge coefficient from calibration.