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 $\begin{array}{l}\rm Re\end{array}$ and roughness $\begin{array}{l}\epsilon\end{array}$ (see Fig. 1).

Moody Diagram Friction Factor

Fig. 1. Schematic chart showing how Darcy friction factor depends on Reynolds number $\begin{array}{l}\rm Re\end{array}$ and roughness $\begin{array}{l}\epsilon\end{array}$

In engineering practice one can use either Moody Chart or Darcy friction factor @model to estimate the actual value of Darcy friction factor .

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See also