Relating the Hazen-Williams and Darcy-Weisbach friction loss equations for pressurized irrigation
1996
Allen, R.G.
The Hazen-Williams C factors change with Reynolds number and mean flow velocity. Figures are presented for determining pipe roughness heights or relative roughness ratios that are equivalent to values of the Hazen-Williams C factor. The results facilitate the ability to utilize friction data derived with the Hazen-Williams equation with the Darcy-Weisbach equation. C factors were also determined that are equivalent to known or measured pipe roughnesses. The Churchill equation for directly calculating the Darcy-Weisbach friction factor is compared with other established friction factor equations. The Churchill equation accurately predicts friction factors over all ranges in Reynolds number, pipe roughness, and temperature encountered in irrigation systems, including the laminar and transition flow regimes.
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