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Robert Manning (a historical perspective)

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Fischenich, J. Craig, 1962-

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Engineer Research and Development Center (U.S.)


Robert Manning (1816-1897) wrote his first paper on hydraulics in 1851 and his last in 1895. During this period, Manning devoted considerable effort to the development of a simple, dimensionally homogeneous formula for open-channel flow. In the end, his paper "On the Flow of Water in Open Channels and Pipes," published in Transactions of the Institution of Civil Engineers of Ireland (Manning 1891), became the primary reference for his work and the source of Manning's monomial equation: V = n k n R 3 2 S 2 1 (1) where V is the cross-sectional average velocity, R is the hydraulic radius, S is the energy slope, kn=1.486 for English units and kn=1 for SI units, and n is the Manning resistance coefficient. (The original equation was presented with kn/n represented as C, rather than the current convention presented here). Understanding the applicability and limitations of any analytical tool requires an understanding of the context in which it was developed and the use for which it was intended. This is the story of the Manning equation.


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Hydraulics, History--Mathematical models, Ecosystem Management and Restoration Research Program (U.S.)



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