Volumetric Flow Rate from Velocity
Volumetric Flow Rate from Velocity
The continuity equation links velocity, area and flow rate — the starting point for every pipe-sizing calculation.
The flow rate is Q = A·v with A = πD²/4. where D is the pipe diameter and v the mean velocity.
Inputs
D := 100 mm=100 mm
v := 2.5 m/s=2.5 m/s
The flow area of a round pipe.
A := pi·D^2/4=7.85e-03 m^2
Flow rate is area times velocity.
Q := A·v=0.02 m^3/s
Results
The flow rate sets pump and supply sizing. For a fixed flow, a larger pipe lowers velocity and friction losses but costs more.
Assumptions & limitations
- Pipe running full, steady flow.
- Uniform (mean) velocity over the section.
- Round cross-section.