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How It Works
A Venturi meter measures flow by creating a pressure drop through a pipe constriction. As fluid speeds up through the narrow throat (continuity equation), its pressure drops (Bernoulli's principle). Measuring the pressure difference between the wide section and throat gives the flow rate. This calculator uses the ideal equation (Cd = 1); multiply by 0.95–0.99 for real-world accuracy.
Example Problem
Water (ρ = 1,000 kg/m³) flows through a Venturi meter with pipe area A₁ = 0.01 m² and throat area A₂ = 0.004 m². The pressure difference is 20,000 Pa. What is the flow rate?
- Area ratio: (A₂/A₁)² = (0.004/0.01)² = 0.16
- Q = 0.004 × √(2 × 20,000 / (1,000 × 0.84))
- Q = 0.004 × 6.9 = 0.0276 m³/s
Frequently Asked Questions
How does a Venturi meter work?
Fluid accelerates through a constriction, causing pressure to drop. The pressure difference between the wide section and throat is measured with a differential pressure gauge and converted to flow rate using the Venturi equation.
Venturi meter vs. orifice plate: what is the difference?
Venturi meters have a gradual converging-diverging shape, resulting in lower permanent pressure loss (10–15% of the differential) and higher Cd (0.95–0.99). Orifice plates are cheaper but waste more energy (40–60% permanent loss).
What is the discharge coefficient for a Venturi meter?
Typically 0.95–0.99 depending on manufacturing quality and Reynolds number. This calculator uses the ideal value of 1.0. Multiply the result by your meter's Cdfor real-world accuracy.
Related Calculators
- Bernoulli Theorem Calculator — the energy principle behind the Venturi effect.
- Orifice Flow Calculator — an alternative flow measurement method with higher pressure loss.
- Continuity Equation Calculator — the mass conservation principle used in Venturi analysis.
- Pipe Flow Calculator — compute Reynolds number and flow velocity in the pipe system.
- Pressure Unit Converter — convert differential pressure readings between Pa, psi, and mmHg.