KEVOS® MAKEOS · Hydraulics
Liquid Pipe Velocity and Reynolds Number
What velocity and flow regime follow from diameter, flow and viscosity?
Calculate mean velocity and Reynolds number for a full circular pipe carrying a single-phase Newtonian liquid.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Internal diameter | mm | Actual internal bore, not nominal pipe size. |
| Liquid flow | L/min | Volumetric flow at operating conditions. |
| Kinematic viscosity | mm²/s | Fluid viscosity at the operating temperature. |
Method and formulas
- Velocity = (flow / 60000) ÷ (π × (diameter / 1000)² / 4), in m/s.
- Re = velocity × (diameter / 1000) ÷ (kinematic viscosity × 10⁻⁶).
- The guide bands are Re < 2000, 2000–4000 and Re > 4000; real transition depends on disturbances. Example: 25 mm, 20 L/min and 1 mm²/s gives 0.679061 m/s and Re = 16976.53.
Limitations
- Not for compressed gas, open channels, two-phase flow or non-Newtonian fluids.
- No pressure drop, cavitation, erosion or suitable-velocity approval is inferred.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- pipe velocity
- Reynolds
- liquid flow
Who it is for
- Hydraulic engineers
- Process engineers
What you get
- Mean velocity
- Reynolds number
- Regime indication
Interpreting the result
- Use Reynolds number to select a suitable friction model and include fittings and roughness in pressure-drop work.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 365–366; CD pp. 3022–3024. Topic reference; no source tables or recommended settings are reproduced.
- US Department of Energy, DOE-HDBK-1012/3-92, Fluid Flow, pp. 9–11 and 19–20 — https://www.energy.gov/sites/default/files/2026-04/DOE-HDBK-1012-92_VOL3.pdf
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