Inputs
Results
Darcy friction factor
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Fanning friction factor
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Flow regime
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Method
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Relative roughness
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Method
Laminar: f = 64/Re
Transition: Churchill correlation
Turbulent: 1/√f = −2 log₁₀(ε/(3.7D) + 2.51/(Re√f))
Transition: Churchill correlation
Turbulent: 1/√f = −2 log₁₀(ε/(3.7D) + 2.51/(Re√f))
The reported Darcy factor is used in the standard straight-pipe pressure-loss form. The Fanning factor is one quarter of the Darcy factor. Roughness affects turbulent flow but not the laminar relation.