Pierre Louis George, count of Buat (born the April 23rd 1734 with Tortisambert - died the October 17th 1809 with Old man-Cop), Engineer and hydraulician French, assisted the abbot Bossut in his searchs for hydrodynamic.

The engineer of the fortifications

Promoted engineer at his exit of the royal school of the genius of Wall in 1750, of Buat exerted the first part of its career on the borders of North. Initially affected with the realization of the junction canal of the Lily in Aa, he worked with the modernization of the fortifications of the citadels of Valencian Condé-sur-Escaut (of 1775 to 1780) and (boring of the arm of Jard, as from 1773).

After having taken share in the Netherlands in the first campaigns of the Convention under the direction of Dumouriez, it passes to the enemy at the same time as his general (1793). The law of amnesty voted by the Consulat enables him to take again service after 1802, this time as director of the Compagnie of the mines of Anzin.

Until work of Bélanger, the Principes of hydraulics of of Buat remained the bible of the engineers hydraulicians: they were translated into German by Woltman and Eytelwein in 1791.

Since 1768, it had introduced into the drawing géométral fortifications an important convention to solve the problem of the run : the representation of the line of greater slope of a slope, via a “scale of conventional slope”. This innovation had been immediately adopted at the school of the genius of Wall, and it was preserved in geometry with dimensions.

The hydraulician

In parallel, it takes part in the research launched by of Alembert and Bossut on the resistance of the Fluide S to the advance of the Navire S (trailed); its research is consigned in a treaty entitled Principes of hydraulics (1779) and which still knew several editions under the Empire. The success of this book is explained by the many experimental data and the explanations on operation of the hydraulic machines, which distinguish it from the speculations too much theoretical of Alembert. Thus, of Buat estimated that the resistance of water was due to the friction of the fluid against the solid walls. Applying this design to the flow in the discovered channels, he proposed a formula similar to that of Chézy for the flow of the rivers:

$U\; =\; 2g\; \backslash \; cdot\; m\; \backslash \; cdot\; I\; \backslash \; cdot\; \backslash \; left\; (\backslash \; frac\; \{lh\}\; \{l+2h\}\; \backslash \; right)$ where U is the mean velocity of water,

• G is the acceleration of gravity,
• m is a coefficient depend on the roughness of the banks,
• I is the slope of the river bed,
• L is the width of the bed,
• H the depth of the river.

He studied the dependence of the Viscosité liquids with the Température.

Works

• Principles of hydraulics and pyrodynamic checked by a great number of experiments made by order of the government (ED. princeps in 1 vol. 1779, 2nd ED. in 2 vol. 1786, last ED. revised in 3 vol. 1816), ED. Firmin Didot, Paris
• Memory on some applications within the competence of the compressed atmospheric air, considered as driving force (1837), ED. B. Henry, Valencians, 32 p.

References

• Andre Guillerme To build the city (1995) ED. Field-small valley, Seyssel ISBN 2-87673-203-3
• Antoine Picon the invention of the modern engineer (1992), Presses of the Bridges & Roadways, Champs-sur-Marne ISBN 2-85978-178-1
• Pierre Dugas History of mechanics (1956), ED. of Griffon, Neufchâtel, Suisse
• G.A. Tokaty have history and philosophy off fluid mechanics (1971), ED. Foulis, rééd. by Dover ISBN 0-486-68103-3

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