Example 25 mm drawn tubing

Roughness is the listed value 0.0015 mm.

Worked example

Reynolds number 5000

Regime Turbulent: Re > 4000.

Head loss 0.0309 m

Laminar is below 2300, transition is 2300 to 4000, and turbulent is above 4000. Swamee-Jain is evaluated when its log argument is positive, including laminar flow. That is this page's formula scope.

Friction and ratio

Re = (rho × v × D) / mu = (v × D) / nu

epsilon / D 6.0000e-5

Darcy friction factor 0.037923

f = 0.25 / (log10(epsilon/(3.7×D) + 5.74/Re^0.9))^2

h_f = f × (L / D) × (v^2 / (2 × g))

Diameter is millimeters in the roughness ratio and meters in Re and head loss. g is an input. 9.80665 in an example is entered there, not stored as a place.