Reynolds Number

Quickly classify the flow regime from the inertial-to-viscous ratio.

visual calculatorDimensionless Numbers

Read the flow shape before trusting the number.

This page turns a CFD setup into regime, scale, and dominant-effect cues. Adjust the calculator below and compare the moving graphic with the computed result.

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Reynoldstransitionpipe flow

formula

KaTeX rendered

\begin{aligned}\text{Re = rho U L / mu = U L / nu}\end{aligned}

ASCII source

Re = rho U L / mu = U L / nu

ρ — density (kg/m³)U — velocity (m/s)L — characteristic length (m)μ — dynamic viscosity (Pa·s)

5.00e+4

regime

Turbulent

Pipe flow conventional thresholds: Re < 2300 laminar, 2300–4000 transitional, > 4000 turbulent.

Reynolds transition pipe flow