Reynolds Number Calculator
Calculate the Reynolds number for pipe or channel flow and determine the flow regime (laminar, transitional, or turbulent).
How to Use the Reynolds Number Calculator
- Enter the fluid density in kg/m³.
- Enter the mean flow velocity in m/s.
- Enter the pipe inner diameter (or hydraulic diameter) in metres and the dynamic viscosity in Pa·s.
クイックリファレンス
| 変換元 | 変換先 |
|---|---|
| Re < 2,300 | Laminar |
| 2,300 < Re < 4,000 | Transitional |
| Re > 4,000 | Turbulent |
| Water in 1 cm pipe at 0.1 m/s | Re ≈ 998 |
| Air over 1 m plate at 10 m/s | Re ≈ 685,000 |
使用例
- •Pipe flow analysis in hydraulic and process engineering.
- •Determining friction factor regime for Darcy-Weisbach calculations.
- •Heat transfer and mass transfer correlations in chemical engineering.
計算式
Re = ρ × v × D / μ, where ρ is density (kg/m³), v is velocity (m/s), D is hydraulic diameter (m), μ is dynamic viscosity (Pa·s). Laminar: Re < 2300; Turbulent: Re > 4000.
よくある質問
What does the Reynolds number tell you?
Re predicts whether flow is laminar (smooth, layered) or turbulent (chaotic). It is the ratio of inertial to viscous forces.
What is dynamic viscosity for common fluids?
Water at 20°C: ~0.001 Pa·s. Air at 20°C: ~1.8×10⁻⁵ Pa·s. Engine oil: ~0.1–0.3 Pa·s.
Is this calculator free?
Yes, all OhMyCalc calculators are completely free to use.