learn.howToCalculate

learn.whatIsHeading

The Reynolds number (Re) predicts whether fluid flow is laminar (smooth, Re < 2,300) or turbulent (chaotic, Re > 4,000). It is dimensionless and fundamental to fluid dynamics.

Formel

Re = ρvL/μ = vL/ν | where ρ = density, v = velocity, L = characteristic length, μ = dynamic viscosity, ν = kinematic viscosity

Re: Reynolds number (dimensionless)
ρ: Fluid density (kg/m³)
v: Flow velocity (m/s)
L: Characteristic length (m)
μ: Dynamic viscosity (Pa·s)
ν: Kinematic viscosity (m²/s)

Trin-for-trin guide

1Re = ρ × v × d / μ
2ρ = density (kg/m³); v = velocity (m/s); d = diameter (m); μ = dynamic viscosity (Pa·s)
3Water at 20°C: μ ≈ 0.001 Pa·s
4Air at 20°C: μ ≈ 1.81×10⁻⁵ Pa·s

Løste eksempler

Input

Water at 0.5m/s in 5cm pipe

Resultat

Re = 998 × 0.5 × 0.05 / 0.001 = 24,950 — Turbulent

Ofte stillede spørgsmål

What is Reynolds Number?

The Reynolds number (Re) predicts whether fluid flow is laminar (smooth, Re < 2,300) or turbulent (chaotic, Re > 4,000). It is dimensionless and fundamental to fluid dynamics

How accurate is the Reynolds Number calculator?

The calculator uses the standard published formula for reynolds number. Results are accurate to the precision of the inputs you provide. For financial, medical, or legal decisions, always verify with a qualified professional.

What units does the Reynolds Number calculator use?

This calculator works with kilograms, inches, Celsius, watts. You can enter values in the units shown — the calculator handles all conversions internally.

What formula does the Reynolds Number calculator use?

The core formula is: Re = ρ × v × d / μ. Each step in the calculation is shown so you can verify the result manually.

Klar til at beregne? Prøv den gratis Reynolds Number-beregner

Prøv det selv →