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Darcy friction factor

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Darcy friction factor diagram
calc
Serghide's solution to the Colebrook-White equation is used to approximate the Darcy friction factor within full flowing pipes with a Reynolds number (Re) above 4000. It tends to be very accurate to the iteratively determined Colebrook-White equation - within ~30 ppm accuracy.
Pipe diameter:
Roughness height (ε)
Reynolds number:

Darcy friction factor:
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notes
Note that the Darcy friction factor is directly related to the Fanning friction factor (which is 1/4 of the Darcy factor). In pure laminar flow, the Darcy factor can be taken as 64/Re (Reynolds number), but when the Reynolds number is above ~2300, turbulent flow means that an approach such as the Colebrook equation must be used.