Quantitative dimensionless measure
f of the friction forces between fluid pipe flow and inner pipe walls based on Darcy–Weisbach equation.
It depends on Reynolds number \rm Re and roughness \epsilon (see Fig. 1): f =f({\rm Re}, \, \epsilon).
Fig. 1. Schematic chart showing how Darcy friction factor depends on Reynolds number \rm Re and roughness \epsilon (following [1]) |
In engineering practice one can use either Moody Chart or Darcy friction factor @model to estimate the actual value of Darcy friction factor.
Darcy friction factor
f takes only positive values
f > 0 but has singularity at zero flow velocity:
{\rm Re} \rightarrow 0 \Rightarrow f \rightarrow \infty which may cause computational challenges.
Using Reduced Friction Factor \Phi = f \cdot {\rm Re} / 64 instead can help in computations as it stays finite for all finite values of Reynolds number \rm Re.
See also
Physics / Fluid Dynamics / Pipe Flow Dynamics / Darcy–Weisbach equation
[ Darcy friction factor Single-phase @model ] [ Darcy friction factor Multiphase @model ]
[ Moody Chart ] [ Reduced Friction Factor (Φ) ]
Reference
[1] https://gmallya.com/moodys-friction-factor-calculator/