# Moody Diagram

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:

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 d

*and Reynolds number*

_{ h }= 0.01 (m)*Re = 10*- the relative rougness can be calculated as

^{ 7 }* r = k / d _{ h } *

* = (0.0015 10 ^{ -3 } m) / (0.01 m) *

* = 0.00015 *

From the diagram above, with the relative rougness and the Reynolds number - the friction factor can be estimated to aprox. * 0.013 * .

### Alternative Moody Diagram

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

## Related Topics

### • Fluid Mechanics

The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.

## Related Documents

### Colebrook Equation

Friction loss coefficients in pipes, tubes and ducts.

### Energy Equation - Pressure Loss vs. Head Loss

Calculate pressure loss - or head loss - in ducts, pipes or tubes.

### Reynolds Number

Introduction and definition of the dimensionless Reynolds Number - online calculators.

### Surface Roughness vs. Mechanical Processing

Mechanical production methods and their surface roughness.