Moody Diagram

Moody Diagram to estimate friction coefficients

There are two definitions of the friction factor

  • SI based
  • Imperial based

The SI based friction factor is four times larger than the Imperial based friction factor.

SI based Moody Diagram

The Moody friction factor - λ (or f) - is used in the Darcy-Weisbach major loss equation. The coefficient can be estimated with the diagram below:

moody diagram

If the flow is transient - 2300 < Re < 4000 - the flow varies between laminar and turbulent flow and the friction coefiicient is not possible to determine. The friction factor can usually be interpolated between the laminar value at Re = 2300 and the turbulent value at Re = 4000.

Example - SI based Friction Factor

For a PVC pipe with absolute roughness  k = 0.0015 10-3 (m), hydraulic diameter Dh = 0.1 (m) and Reynolds number Re = 107 - the relative rougness can be calculated as 

k/Rh = (0.0015 10-3 m) / (0.02 m) 

       = 0.000075

From the diagram above, with the relative rougness and the Reynolds number - the friction factor can be estimated to aprox. 0.011

Alternative Moody Diagram

A very nice Moody diagram in pdf-format from Glasgow College of Nautical Studies can be found here:

moody diagram

Related Topics

  • Fluid Mechanics - The study of fluids - liquids and gases. Involves various properties of the fluid, such as velocity, pressure, density and temperature, as functions of space and time.

Related Documents

Tag Search

  • en: moody diagram major friction

Search the Engineering ToolBox

- "Search is the most efficient way to navigate the Engineering ToolBox!"

Engineering ToolBox - SketchUp Extension - Online 3D modeling!

3D Engineering ToolBox Extension to SketchUp - add parametric components to your SketchUp model

Add standard and customized parametric components - like flange beams, lumbers, piping, stairs and more - to your SketchUp model with the Engineering ToolBox - SketchUp Extension/Plugin - enabled for use with the amazing, fun and free SketchUp Make and SketchUp Pro. Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!

Translate the Engineering ToolBox!
About the Engineering ToolBox!

close