Pipe Reynolds Number

Screen circular pipe flow regime from average velocity, inside diameter, and viscosity.

Concept

Results

Enter inputs and select Calculate to display reviewed results.

Inputs

Viscosity input modeAverage velocity *

Use cross-sectional average velocity.Pipe inside diameter *

Use actual inside diameter, not nominal pipe size.Kinematic viscosity *

Used in kinematic-viscosity mode.Density *

Used with dynamic viscosity mode.Dynamic viscosity *

Used with density in dynamic-viscosity mode.

Formula & Variables

Re =ρVDμ=VDν

Re: Reynolds number; [1]
V: Average velocity; [m/s]
D: Inside diameter; [m]
μ: Dynamic viscosity; [Pa*s]
ν: Kinematic viscosity; [m^2/s]

Assumptions

Internal flow in a circular pipe.
Velocity is the average over the pipe cross section.
Fluid properties are evaluated at the relevant operating conditions.

⚠ Limitations

Noncircular ducts require a reviewed hydraulic-diameter method.
Regime thresholds are screening guidance, not exact physical boundaries.
Compressibility and property variation are not handled.