Reynolds Number Calculator
Calculate Reynolds number and determine flow regime. Supports direct velocity input or flow rate with pipe ID. Fluid presets for common oilfield fluids.
Input Parameters
Commercial steel: 0.0018 in | PVC: 0.00006 in | Cast iron: 0.01 in
Re = ρVD / μ
Reynolds Number
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Flow Regime
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Friction Factor (Moody)
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Relative Roughness
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Pressure Drop (psi/ft)
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Velocity (ft/s)
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Velocity (m/s)
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Moody Diagram Position
Laminar
<2,100
Transition
2,100-4,000
Turbulent
>4,000
How this was calculated
Reynolds Number: Re = ρVD/μ where ρ = density, V = velocity, D = diameter, μ = dynamic viscosity (all in consistent units).
Flow regime: Laminar: Re < 2,100. Transition: 2,100 ≤ Re ≤ 4,000. Turbulent: Re > 4,000.
Friction factor: Laminar: f = 64/Re. Turbulent: Colebrook-White equation (solved iteratively). 1/sqrt(f) = -2×log10(ε/D/3.7 + 2.51/(Re×sqrt(f))).
Flow rate conversion: V (ft/s) = Q (bbl/day) × 5.615 / (86400 × π/4 × D²) where D in ft.
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Book a free strategy call →Reynolds Number in Oil and Gas Engineering
The Reynolds number (Re) is a dimensionless quantity that predicts flow patterns in pipes and around objects. It represents the ratio of inertial forces to viscous forces. In petroleum engineering, Re determines whether flow is laminar (smooth, orderly) or turbulent (chaotic, mixing), which directly impacts pressure drop calculations, erosion rates, heat transfer, and equipment sizing.
For pipe flow, Re below 2,100 indicates laminar flow where the Hagen-Poiseuille equation applies. Above 4,000, flow is fully turbulent and the Colebrook-White or Moody friction factor equations are used. The transition zone (2,100-4,000) is unpredictable and should generally be avoided in design.
In oilfield applications, most production tubing flow is turbulent (high velocities, large diameters), while flow through porous media (reservoir) is almost always laminar (very low velocities, tiny pore throats). This distinction is fundamental to both surface facility design and reservoir engineering.
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