Quantitative dimensionless measure of the friction forces between fluid pipe flow and inner pipe walls based on the Darcy–Weisbach equation.
It depends on Reynolds number \rm Re and roughness \epsilon.
In engineering practice one can use either Moody Chart or Darcy friction factor @model to estimate the actual value of Darcy friction factor .
See also
Physics / Fluid Dynamics / Pipe Flow Dynamics / Darcy–Weisbach equation
[ Darcy friction factor @model ] [ Moody Chart ]