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

This is an AMP page - Open full page! for all features.

Fluid Flow - Entrance Length and Developed Flow

Sponsored Links

A fluid flow need some length to fully develop the velocity profile after passing through components like bends, valves, pumps, turbines or similar.

Entrance Length

The entrance length can be expressed with the dimensionless Entrance Length Number as

El = le / d                           (1)


El = Entrance Length number

le = length to fully developed velocity profile (m, ft)

d = tube or duct diameter (m, ft)

Entrance Length Number for Laminar Flow

The Entrance length number correlates with the Reynolds Number  and for laminar flow the relation can be expressed as:

Ellaminar = 0.06 Re                       (2)


Re = Reynolds Number

Entrance Length Number for Turbulent Flow

The Entrance length number correlation with the Reynolds Number for turbulent flow can be expressed as:

Elturbulent = 4.4 Re1/6                         (3)

Sponsored Links

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

Darcy-Weisbach Equation - Major Pressure and Head Loss due to Friction

The Darcy-Weisbach equation can be used to calculate the major pressure and head loss due to friction in ducts, pipes or tubes.

Laminar, Transitional and Turbulent Flow

Heat transfer, pressure and head loss in a fluid varies with laminar, transitional or turbulent flow.

Poiseuille's Formula

Calculate the volume flow discharged through a smooth-walled circular pipe.

Reynolds Number

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

Sponsored Links

Search Engineering ToolBox

  • the most efficient way to navigate the Engineering ToolBox!

SketchUp Extension - Online 3D modeling!

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 the amazing, fun and free SketchUp Make and SketchUp Pro . Add the Engineering ToolBox extension to your SketchUp from the Sketchup Extension Warehouse!


We don't collect information from our users. Only emails and answers are saved in our archive. Cookies are only used in the browser to improve user experience.

Some of our calculators and applications let you save application data to your local computer. These applications will - due to browser restrictions - send data between your browser and our server. We don't save this data.

Google use cookies for serving our ads and handling visitor statistics. Please read Google Privacy & Terms for more information about how you can control adserving and the information collected.

AddThis use cookies for handling links to social media. Please read AddThis Privacy for more information.