Engineering ToolBox - Resources, Tools and Basic Information for Engineering and Design of Technical Applications!

Colebrook Equation

Friction loss coefficients in pipes, tubes and ducts.

The friction coefficients used when calculating resistance or pressure loss (or major loss) in ducts, tubes or pipes can be calculated with the Colebrook equation

1 / λ1/2= -2 log [ 2.51 / (Re λ1/2)  +  (k / dh) / 3.72 ]                           (1)

where

λ = Darcy-Weisbach friction coefficient

Re = Reynolds Number

k = roughness of duct, pipe or tube surface (m, ft)

dh= hydraulic diameter (m, ft)

The Colebrook equation is only valid at turbulent flow conditions .

Note! - the friction coefficient is involved on both sides of the equation. The equation must therefore be solved by iteration.

The Colebrook equation is generic and can be used to calculate friction coefficients for different kinds of fluid flows - like air ventilation ducts, pipes and tubes with water or oil, compressed air and much more.

Colebrook Online Calculator

The friction coefficient can be calculated with the online Colebrook calculator below.

The default values used are for turbulent air flow in a 315 mm duct with 6 m/s (0.47 m3/s) . The kinematic viscosity used to calculate the Reynolds Number is 15 10-6 m2/s .

Replace the parameters with the appropriate values for your application.

The calculator below can be used to calculate the friction coefficient if velocity and kinematic viscosity of the fluid are known.

The friction coefficient can also be estimated with the Moody diagram (SI based):

moody diagram SI

Download and print Moody Diagram

Simplified Moody Diagram - SI

Moody diagram SI - simplified

Download and print simplified Moody Diagram

Related Topics

  • Fluid Mechanics

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

  • Ventilation Systems

    Design of systems for ventilation and air handling - air change rates, ducts and pressure drops, charts and diagrams and more.

Related Documents

Search

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 - enabled for use with older versions of the amazing SketchUp Make and the newer "up to date" SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp Make/Pro from the Extension Warehouse !

Translate this Page

Translate this page to Your Own Language .

About the Engineering ToolBox!

Privacy Policy

We don't collect information from our users. More about

We use a third-party to provide monetization technologies for our site. You can review their privacy and cookie policy here.

You can change your privacy settings by clicking the following button: .

Citation

This page can be cited as

  • The Engineering ToolBox (2008). Colebrook Equation. [online] Available at: https://www.engineeringtoolbox.com/colebrook-equation-d_1031.html [Accessed Day Month Year].

Modify the access date according your visit.

3D Engineering ToolBox - draw and model technical applications! 2D Engineering ToolBox - create and share online diagram drawing templates! Engineering ToolBox Apps - mobile online and offline engineering applications!

Unit Converter

















































4.19.9

.