What is a Venturi tube calculator?

It is an online tool for sizing a Venturi tube as a multiphase flow meter: given liquid and gas rates, PVT and throat geometry, it shows which rates the meter can measure and whether it covers the specified conditions.

How do I run a Venturi tube calculation?

Enter min/max liquid flow, gas flow (standard or operating conditions, or GOR), pressure, temperature, densities, inner diameter and throat diameter, then click Calculate. The tool returns a range table, a coverage check and a Flow Map.

How is flow calculated on a Venturi tube in multiphase flow?

Venturi flow is related to the pressure drop between inlet and throat, but for an oil–water–gas mixture that is not enough: GVF, phase densities, slip and velocity limits are included. The single-phase relation Q ∝ √(ΔP/ρ) is not used for the mixture.

How is Venturi flow calculation different from sizing a single-phase meter?

A single-phase meter is described by one ΔP–Q curve. Multiphase Venturi sizing checks a two-dimensional range (liquid and gas together), flow regimes and PVT conversion between standard and operating conditions.

GVF Calc — multiphase flow calculations online

Engineering calculator for multiphase oil + water + gas flow.

What makes GVF Calc unique

Focus on multiphase oil & gas flow, not generic engineering converters. Even the GVF section ties to pipe flow regimes — rare for online calculators.
End-to-end physical model from Venturi range sizing to direct and inverse ΔP problems — calculations are consistent, not isolated formulas.
Two-dimensional measurement range (Flow Map) with coverage checks — an engineering sizing tool, not a single-formula calculator.
PDF + QR for reproducible Venturi calculations — share and verify parameters.
API to integrate the flow calculator into external systems (SCADA, reports, partner services).
Well profiles — link calculations to real user assets.

Why single-phase meter approaches fail for multiphase flow?

For a single-phase (liquid) meter, physics is relatively simple: one fluid with known density ρ flows in the pipe; the pressure-drop ↔ flow relation is one equation (often Q ∝ √(ΔP/ρ)), and metrology is a single curve or even one number. For multiphase flow (oil + water + gas) this breaks down for several reasons.

1. Single phase vs phase mixture

A multiphase meter must work where gas and liquid coexist with different densities, viscosities, and velocities. Pressure drop depends on mixture composition — GVF, phase densities, and flow regime. You cannot take a “10–100 m³/day” water range and apply it to a mixture: at the same ΔP, flow differs at GVF = 5% vs 95%.

2. Phase slip and flow heterogeneity

Gas and liquid move at different speeds (slip). The same pressure drop maps to different Q_gas and Q_liq combinations. Classic Venturi with one “mixture” density and no phase distribution model fails — a drift-flux Zuber–Findlay model is used instead.

3. Flow regime changes measurement physics

Flow type (bubbly, slug, annular, dispersed, etc.) depends on GVF, phase velocities, diameter, viscosity, and surface tension. For multiphase meters, regime is part of the metrology model. The GVF section here determines flow structure — meaningless for pure liquid.

4. PVT conversions and multiple data sources

Gas rate may be given at standard, normal, or operating conditions; liquid includes WLR; gas may come via GOR. All quantities are reconciled in one model with P, T, densities, and compressibility Z (Peng–Robinson from gas composition).

5. Direct and inverse problems need iteration

For multiphase Venturi: direct (ΔP → rates) and inverse (rates → ΔP) problems are solved by bisection with convergence checks — not a tabulated K-factor from a meter datasheet.

6. Metrological interpretation of ranges

Multiphase meters must verify that the instrument covers the specified liquid and gas ranges simultaneously. This site implements that as coverage checking in Venturi sizing.

In short: multiphase metering needs mixture models, GVF, flow regime, and iterative solvers.

Site features

Calculators are grouped in the menu: Basic, Venturi, Pro. Access depends on sign-in and access level.

Basic

Gas volume fraction (GVF)

Open section →

Fundamental gas volume fraction in oil + water + gas flow at operating conditions. With pipe diameter — flow regime from phase velocities. For engineers who need quick gas saturation and regime estimates.

H₂S partial pressure (ISO 15156)

Open section →

H₂S partial pressure calculation and ISO 15156 material screening. Two modes: simplified (pH₂S only) and engineering — with pH, temperature, chlorides input and an alloy-group recommendation table (carbon steels, martensitic, duplex, nickel alloys).

Gas flow: standard / normal / operating

Open section →

Convert gas volumetric flow to a unified condition set. Input in std., normal, or operating conditions with P and T; output in all three systems.

Gas density from composition

Open section →

Gas density at standard (20 °C) and specified operating conditions from molar composition. Molar mass from the components; operating density uses Peng–Robinson (compressibility Z).

Liquid volume converter (m³ / bbl)

Open section →

Fast bidirectional conversion between cubic metres and oil barrels. Useful when reports and equipment mix SI and field units.

Temperature converter (°C / °F)

Open section →

Bidirectional Celsius ↔ Fahrenheit conversion in real time. Handy when comparing inputs from international specs and datasheets.

Absolute / gauge pressure

Open section →

Convert between absolute and gauge pressure. Input in Pa, kPa, MPa, bar, atm, kgf/cm², psi, mm Hg, mm H₂O; output in all units both ways.

Pressure unit converter

Open section →

Bidirectional pressure unit conversion: editing any field instantly updates the others.

Venturi

Flow calculation — Venturi tube

Open section →

Venturi tube calculator — flow calculation for a Venturi meter as a multiphase instrument. Liquid and gas rates (range or point), PVT, geometry, ΔP and velocity limits. Results table, coverage check, Flow Map, inverse calc, PDF export with QR code.

Flow from pressure drop

Open section →

Direct MPFM problem: from measured ΔP determine oil, water, and gas rates (drift-flux model, Peng–Robinson gas composition, well profiles, saved calculations in account).

Pressure drop from flow rates

Open section →

Inverse problem: given oil, water, and gas rates, find throat ΔP. Same physics as the flow calculator.

Pro

Flow Map and advanced analysis

Open section →

Simultaneous calculation for seven Venturi sizes (DN48, DN77, DN94), summary table, flow map with all size contours, and range summation mode.

GVF calculation — gas volume fraction | flow regime

GVF (Gas Volume Fraction) is the volumetric gas fraction in oil + water + gas flow at operating (reservoir) conditions.

Enter liquid and gas flow rates — the calculator computes GVF and converts gas flow to standard, normal, and operating conditions.

Liquid flow rate

Liquid flow unit

Gas flow rate, m³/day or std m³/day

Gas flow conditions

Reservoir pressure

Pressure unit

Reservoir temperature

Temperature unit

Pipe inner diameter, mm (optional — for flow regime determination)

ISO 15156 H₂S screening

When a gas phase is present, H₂S partial pressure is calculated as pH₂S = yH₂S × Pabs. The output below is a preliminary material-group recommendation; final selection still requires full ISO 15156 verification for environment, hardness, welding and temperature limits.

Simplified calculation (pH₂S) Engineering calculation (materials)

H₂S content in gas phase, mol %

System pressure (total)

Pressure type

Absolute Gauge / manometric

Gas volumetric flow converter between conditions

Convert gas volumetric flow to standard, normal, or operating conditions.

Gas flow rate (input), m³/day

Source conditions

Operating pressure

Pressure unit

Operating temperature

Temperature unit

Gas density at std. conditions, kg/m³

If gas density at standard conditions is entered, conversion uses that value (ideal gas, Z = 1). If the field is empty, density is calculated from the molar composition (Peng–Robinson).

Gas composition (mole %, %) — density from composition

Molar gas composition (default values shown — edit as needed). Used to calculate density when the “gas density at std. conditions” field is empty. The sum should be ≈ 100% (normalised automatically).

Methane CH₄

Ethane C₂H₆

Propane C₃H₈

n-Butane n-C₄H₁₀

iso-Butane i-C₄H₁₀

n-Pentane n-C₅H₁₂

iso-Pentane i-C₅H₁₂

n-Hexane n-C₆H₁₄

iso-Hexane i-C₆H₁₄

Hydrogen sulfide H₂S

Nitrogen N₂

Carbon dioxide CO₂

Oxygen O₂

Other

Sum: 0 % (should be ≈ 100%)

Gas density from molar composition

Calculate gas density at standard (20 °C, 0.101325 MPa) and specified operating conditions from molar composition. Molar mass is taken from the components; operating density uses the Peng–Robinson equation (compressibility Z).

Operating conditions

Operating pressure

Pressure unit

Operating temperature

Temperature unit

Pressure type

Gas molar composition

Component mole fractions, %. The sum should be ≈ 100% (composition is normalised automatically).

Methane CH₄

Ethane C₂H₆

Propane C₃H₈

n-Butane n-C₄H₁₀

iso-Butane i-C₄H₁₀

n-Pentane n-C₅H₁₂

iso-Pentane i-C₅H₁₂

n-Hexane n-C₆H₁₄

iso-Hexane i-C₆H₁₄

Hydrogen sulfide H₂S

Nitrogen N₂

Carbon dioxide CO₂

Oxygen O₂

Other

Sum: 0 % (should be ≈ 100%)

Liquid volume converter: m³ ↔ barrel

Bidirectional conversion between cubic metres and oil barrels. Standard: 1 bbl = 0.158987294928 m³.

Volume, m³

Volume, bbl

Temperature converter: °C ↔ °F

Instant bidirectional conversion between Celsius and Fahrenheit.

Temperature, °C

Temperature, °F

Pressure converter — absolute and gauge

Converts between absolute and gauge (manometric) pressure.

Pressure value

Unit

Pressure type

Atmospheric pressure, Pa

Pressure unit converter

Instant bidirectional conversion between common pressure units.

Pascal (Pa)

Kilopascal (kPa)

Megapascal (MPa)

Bar

Physical atmosphere (atm)

Technical atmosphere (kgf/cm²)

Pound per square inch (psi)

mm Hg (Torr)

mm H₂O

Flow calculation — Venturi tube

Sizing range for a Venturi tube as a multiphase flow meter (oil + water + gas).

Calculation identifier Optional identifier for PDF export

Calculation mode

Range Point

In Point mode, enter a single flow value used as the operating point.

Flow parameters — input data

Min. liquid flow

Max. liquid flow

Liquid flow unit

Min. gas flow (std.), std m³/day

Max. gas flow (std.), std m³/day

Min. gas flow (oper.), m³/day optional

Max. gas flow (oper.), m³/day optional

Enter gas flow in either standard conditions, or operating conditions, or via gas-oil ratio. Standard and operating rates cannot be filled at the same time.

Gas-oil ratio min, std m³/m³ oil optional

Gas-oil ratio max, std m³/m³ oil optional

Water cut WLR, fraction 0…1

PVT parameters

Pressure

Pressure unit

Temperature

Temperature unit

Oil density at std. (20 °C), kg/m³

Water density at std. conditions, kg/m³

Gas density at std. conditions, kg/m³

Venturi geometry

Pipe inner diameter, mm

Throat diameter (constriction), mm

Operating limits

Min. pressure drop on MPFM, Pa

Max. pressure drop on MPFM, Pa

Max. gas velocity, m/s

Max. liquid velocity, m/s

— Sign in is required to calculate. Sign in / Register

Calculation results

Parameter	Minimum	Maximum	Units

Inverse calculation

Minimum gas flow

Min. liquid flow

Minimum liquid flow

Min. gas flow (std.), std m³/day

Venturi tube calculator — flow calculation for a Venturi meter

The Venturi tube calculator on GVF Calc sizes a multiphase meter (oil + water + gas) from throat geometry, PVT data, and limits on pressure drop and velocities. This is an engineering Venturi calculation, not a single-phase K-factor lookup.

For a Venturi flow calculation, enter liquid rates (min/max or a point), gas rate at standard or operating conditions or via GOR, water cut WLR, pressure, temperature and phase densities. The calculator checks whether the selected Venturi covers liquid and gas ranges together and plots a Flow Map.

In multiphase flow the ΔP–Q relation depends on GVF, phase slip and flow regime. The Venturi calculation here uses a drift-flux model: the direct problem (rates from ΔP) and the inverse problem (ΔP from rates) are consistent with range sizing.

Results can be exported to PDF with a QR code so the Venturi inputs can be reproduced. To compare several sizes, use the Pro section (Flow Map for seven geometries).

Contact

Send a message to the service administrator. Sign in is required.

GVF Calc — multiphase flow calculations online

What makes GVF Calc unique

Why single-phase meter approaches fail for multiphase flow?

1. Single phase vs phase mixture

2. Phase slip and flow heterogeneity

3. Flow regime changes measurement physics

4. PVT conversions and multiple data sources

5. Direct and inverse problems need iteration

6. Metrological interpretation of ranges

Site features

Basic

Gas volume fraction (GVF)

H₂S partial pressure (ISO 15156)

Gas flow: standard / normal / operating

Gas density from composition

Liquid volume converter (m³ / bbl)

Temperature converter (°C / °F)

Absolute / gauge pressure

Pressure unit converter

Venturi

Flow calculation — Venturi tube

Flow from pressure drop

Pressure drop from flow rates

Pro

Flow Map and advanced analysis

GVF calculation — gas volume fraction | flow regime

Result

ISO 15156 H₂S screening

Result

Materials recommendations (alloy groups)

Gas volumetric flow converter between conditions

Conversion result

Gas density from molar composition

Operating conditions

Gas molar composition

Result

Liquid volume converter: m³ ↔ barrel

Temperature converter: °C ↔ °F

Pressure converter — absolute and gauge

Conversion result

Pressure unit converter

Flow calculation — Venturi tube

Flow parameters — input data

PVT parameters

Venturi geometry

Operating limits

Calculation results

Flow map (log scale)

Inverse calculation

Venturi tube calculator — flow calculation for a Venturi meter

Contact