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Orifice & Venturi Flow

A restriction converts pressure into velocity, so measuring Δp gives you flow: Q = C_d·A₂·√(2Δp / (ρ(1−β⁴))). The discharge coefficient C_d is ~0.6 for a sharp orifice and ~0.98 for a smooth venturi.

Pipe bore D (mm)

Throat/orifice d (mm)

Differential pressure (kPa)

Density ρ (kg/m³)

Discharge coefficient Cd

Flow rate

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Flow

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Throat velocity

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β ratio

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Incompressible, turbulent, fully-developed flow. Venturis recover most of the pressure; a sharp orifice permanently loses much of it.

A helper, not a substitute for engineering judgment. Verify against the governing standard.