Manning's Coefficient for Smooth Pipes

by Henry Liu, Assoc. Prof. of Civ. Engrg.; Univ. of Missouri, Columbia, MO,

Serial Information: Journal of the Sanitary Engineering Division, 1972, Vol. 98, Issue 2, Pg. 353-360

Document Type: Journal Paper


The Manning's n for flow in a smooth pipe depends not only on the size of the pipe but also on flow conditions. It is difficult to estimate n without lengthy computations. Based on a computer calculation, two charts are constructed from which n can be determined either from V (mean velocity), D (diameter), and ν (kinematic viscosity), or from S (slope), D and ν. The charts can be used in a simple manner to determine the magnitude of n for smooth pipes under various conditions. Errors in using these charts are within 5%.

Subject Headings: Pipelines | Pipes | Pipe flow | Computing in civil engineering | Kinematics | Viscosity | Slopes

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