CalcTool: Darcy friction factor calculator

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Darcy friction factor

From Reynolds number and roughness.

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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.

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.