Fluid Flow - Entrance Length and Developed Flow
The entrance length is the length in a tube or duct after an obstruction - until the flow velocity profile is fully developed.
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)
where
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)
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:
Elturbulent = 4.4 Re1/6 (3)
Related Topics
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Fluid Mechanics
The study of fluids - liquids and gases. Involving velocity, pressure, density and temperature as functions of space and time.
Related Documents
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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.
