Reynolds Number & Flow Regime Calculator
Computes Reynolds number Re = (ρ·v·D) / μ, classifying fluid regimes for pipes and aerofoils.
Reynolds Number & Regimes
Computes dimensionless inertial-to-viscous force ratio Re = ρ·v·D / μ and classifies laminar, transitional, or turbulent flows.
Inertial forces overwhelm viscous forces. Flow is characterized by chaotic 3D vortices, high fluid mixing, and elevated wall friction.
Reynolds Re = (ρ · v · D) / μ = (998.2 kg/m³ × 1.5 m/s × 0.05 m) / 0.001002 Pa·s = 74,716
Kinematic Viscosity ν = μ / ρ = 0.001002 / 998.2 = 1.0038e-6 m²/s (1.004 cSt)
What is the Reynolds Number?
The Reynolds number is a dimensionless quantity in fluid mechanics used to predict flow patterns in different fluid flow situations, measuring the ratio of inertial forces to viscous forces.
Formula & Step-by-Step Calculation
Ratio of inertial forces to viscous viscous forces.
Worked Step-by-Step Examples
Water (ρ=1000 kg/m³, μ=0.001 Pa·s) flows at 1.5 m/s in a 50mm pipe
Common Real-World & Academic Use Cases
- ✓ Pipeline friction factor Moody chart lookup
- ✓ Aerodynamic wing boundary layer transition modeling
- ✓ Chemical reactor mixing and impeller turbulence
How to Use the Reynolds Number & Flow Regime Calculator
Enter Fluid Parameters
Input fluid density (kg/m³) and dynamic viscosity (Pa·s).
Enter Velocity & Diameter
Input fluid speed (m/s) and pipe diameter (m).
View Flow Regime
Check whether flow is Laminar (<2300), Transitional, or Turbulent (>4000).
Frequently Asked Questions
Q: What happens when flow transitions from laminar to turbulent?
Fluid mixing increases dramatically, momentum transfer rises, and friction head loss across the pipe wall increases significantly.