Fluid Flow - Entrance Length and Developed Flow

Calculate the entrance length and entrance length number for laminar and turbulent flow in tubes and ducts. The entrance length is the distance required for a fluid flow velocity profile to become fully developed after passing through components like bends, valves, or pumps.

Entrance Length Calculator

The entrance length is the length in a tube or duct after an obstruction until the flow velocity profile is fully developed. Use this calculator to determine the entrance length number for laminar and turbulent flow conditions.

Calculator

Inputs

Results

Entrance Length Number - Laminar Flow (El_laminar)-- -
Developed Flow Length - Laminar (le)-- m
Entrance Length Number - Turbulent Flow (El_turbulent)-- -
Developed Flow Length - Turbulent (le)-- m

Formulas

Entrance Length Number (Dimensionless):

  • El = le / d

Laminar Flow:

  • El_laminar = 0.06 × Re

Turbulent Flow:

  • El_turbulent = 4.4 × Re^(1/6)

Developed Flow Length:

  • le = El × d

Where:

  • El = Entrance Length number
  • le = Length to fully developed velocity profile (m, ft)
  • d = Tube or duct diameter (m, ft)
  • Re = Reynolds Number
Fluid Flow - Entrance Length and Developed Flow | MEPKit Engineering Tools | MEPKit