Entrance Length and Developed Flow

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A fluid need some length to develop the velocity profile after entering the pipe or after passing through components as bends, valves, pumps, turbines or similar.

Entrance Length

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

El = l_e / d         (1)

where

El = Entrance Length Number

l_e = 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 correlation with the Reynolds Number for laminar flow can be expressed as:

El_laminar = 0.06 Re         (2)

where

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:

El_turbulent = 4.4 Re^1/6         (3)

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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.

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