Calculator · Fluid Mechanics
Venturi Meter Calculator
A Venturi infers a discharge from the pressure it takes to accelerate the flow into a throat. Continuity and the energy equation between the two sections give one relation, read forwards to get the flow from the differential and backwards to get the differential a flow produces.
Inputs
An inclined meter is a normal case; the elevations enter the relation directly.
Prescribed from calibration. It must be positive; no universal upper bound is imposed.
Results
Discharge Q = Cd A2 V2,ideal
The measured differential, read through this meter's own geometry.
| Upstream area A1 | 0.007854 m² |
|---|---|
| Throat area A2 | 0.0019635 m² |
| Area ratio A2/A1 | 0.25 |
| Differential p1 − p2 | 20 kPa |
| Ideal discharge (before Cd) | 0.012825 m³/s |
| Discharge coefficient Cd | 0.98 |
| Throat velocity V2 | 6.532 m/s |
| Upstream velocity V1 | 1.633 m/s |
| Elevation difference z1 − z2 | 0 m |
| Fluid density ρ | 1000 kg/m³ |
Assumptions
- · Steady, incompressible flow between two sections of one stream tube.
- · Losses between the sections are represented solely by the discharge coefficient.
Explore in the Lab
The Lab keeps each principle's own assumptions visible.
Technical reference
A1 V1 = A2 V2
V2 = sqrt( 2[(p1−p2)/ρ + g(z1−z2)] / (1 − (A2/A1)²) )
Q = Cd A2 V2,ideal
- A1, A2
- upstream and throat areas[m²]
- p1 − p2
- measured differential pressure[Pa]
- Cd
- prescribed discharge coefficient, Cd > 0[-]
- z1 − z2
- elevation difference between the sections[m]
A differential that would make the bracket negative is not a small number: it is a state this meter cannot produce, and no flow is reported for it.
Equal upstream and throat areas give no usable differential, and the calculator says so rather than dividing by zero.
The discharge coefficient is a calibration input. This calculator never predicts one.