Robert Manning (engineer)

Robert Manning (* October 1816 in Normandy, † 1897 in Ireland) was an Irish engineer. He has the Gauckler - Manning - Strickler flow formula given its name.

Life

Manning was one year after the Battle of Waterloo, where his father had attended, was born. In 1826 he moved to Waterford in Ireland and worked as an accountant.

1846, during the great famine, Manning in the " arterial drainage department " of the Irish Office of Public Works ( Office of Public Works ) was employed. After working a while as a draftsman, he was still appointed in the same year as assistant engineer of Samuel Roberts. In 1848 he was district engineer, and retained this position until 1855. As district engineer he read " Traité d' Hydraulique " by Jean François d' Aubuisson de Voisins, and then developed a keen interest in hydraulics.

From 1855 to 1869 Manning was employed by Downshire, where he oversaw the construction of the port Dundrum Bay in Ireland and designed a water supply in Belfast at the Marquis. After the death of the Marquis in 1869, Manning returned to the Irish Office of Public Works back as assistant to the chief engineer. He became chief engineer in 1874, and retained this position until his retirement in 1891.

Manning 's formula

Manning had no engineering education, but was self-taught in fluid mechanics. His accountant background and pragmatism influenced his work and led him to reduce problems to their simplest form. He compared and tested seven well- known flow formulas of the time: You Buat (1786 ), Eytelwein (1814 ), Weisbach (1845 ), de St. Venant ( 1851), Neville ( 1860), Darcy and Bazin (1865 ), also Ganguillet and Kutter (1869). He calculated the speed of each formula for a given slope S and for hydraulic radius R varying from 0.25 m to 30 m. Then he took for each case the mean value of the seven speeds and developed a formula that best fit the data.

His first formula was:

Then he simplified the formula to:

1885 Manning gave x the value 2 /3 and wrote his formula as:

In a letter to Alfred Aimé Flamant Manning wrote: " The reciprocal value of C corresponds closely to n, as have already Ganguillet and Kutter found, both, C and n are constant for the same flume. "

On December 4, 1889, at the age of 73, Manning presented for the first time before his formula of the Institution of Civil Engineers of Ireland. This formula saw the light of day in 1891, in his paper "On the flow of water in open channels and pipe" appeared in the Transactions of the Institution of Civil Engineers (Ireland).

Manning did not like his own equation for two reasons: First, it was then difficult to take the square root of a number and to raise a number by 2/3. Second, the equation was not dimensionally genuine, and to obtain accurate physical dimensions, it developed the following equation:

Where m is the " height of a column of mercury in the equilibrium with the atmosphere ", and C was a dimensionless number, " which varies with the nature of the surface. "

However, the Manning formula written in some books of the late 19th century as follows:

The "Handbook of Hydraulics " by Horace Williams King ( 1918) led to the widespread use of Manning 's formula as we know it today, and also to the realization that the Manning coefficient C is the reciprocal of Kutter's n.

In the U.S., n is referred to as Manning's roughness or Manning 's constant. In Europe, Strickler factor K is the same as Manning C, that is, the reciprocal value of n