About Reynolds Number & Flow Regime Calculator
Determine fluid boundary layer flow regimes in internal pipes and channels. Computes the dimensionless Reynolds number (Re = v · D / ν) to classify flow as Laminar (Re < 2,300), Critical Transitional (2,300 ≤ Re ≤ 4,000), or Fully Turbulent (Re > 4,000).
Key Capabilities & Features
- Calculates dimensionless Reynolds number: Re = v · D / ν
- Automatic regime classification: Laminar (<2,300), Transitional (2,300-4,000), or Turbulent (>4,000)
- Built-in kinematic viscosity presets for Water (20°C), Air (20°C), and Lubricating Oil
- Detailed physical behavior descriptions for each hydraulic regime
- Interactive sliders for fluid velocity and pipe internal hydraulic diameter
How to Use Reynolds Number & Flow Regime Calculator
Select Fluid Preset
Choose Water, Air, or Engine Oil to populate kinematic viscosity.
Set Velocity & Diameter
Adjust fluid flow velocity (m/s) and pipe hydraulic diameter (m).
Inspect Flow Regime
View the calculated Reynolds number and whether the fluid flow is laminar or turbulent.
Privacy & In-Browser Execution Guarantee
Client-side fluid dynamics engine runs entirely on your device.
Frequently Asked Questions
What does the Reynolds number represent physically?
The Reynolds number is the ratio of inertial forces to viscous forces within a moving fluid: Re = (ρ · v · D) / μ. At high Re, turbulent eddies form; at low Re, viscous damping keeps streamlines smooth.
What is the critical Reynolds number for internal pipe flow?
For circular pipe flow, the critical Reynolds number is approximately 2,300. Below 2,300, flow is strictly laminar; between 2,300 and 4,000, flow is transitional; above 4,000, flow is fully turbulent.