## Colebrook equation solver

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.

Hydraulic diameter - dh - (m, ft)

Roughness of surface - k - (m, ft)

Reynolds Number - Re

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

Hydraulic diameter - dh - (m, ft)

Roughness of surface - k - (m, ft)

Velocity - u - (m/s, ft/s)

Kinematic Viscosity - ν - (m2/s, ft2/s)

The friction coefficients used to calculate pressure loss (or major loss) in ducts, tubes and 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)

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