### From Wikipedia, the free encyclopedia

**Adhémar Jean Claude Barré de Saint-Venant**
(August 23, 1797 – January 1886)^{[1]} was a
mechanician and
mathematician who contributed to early stress analysis and also developed the
one-dimensional unsteady open channel flow shallow water equations
or Saint-Venant equations that are
a fundamental set of equations used in modern hydraulic engineering. Although
his surname was Barré de Saint-Venant in non-French mathematical
literature he is known simply as Saint-Venant. His name is also
associated with Saint-Venant's principle of
statically equivalent systems of load, Saint-Venant's theorem and for Saint-Venant's
compatibility condition, the integrability conditions for a
symmetric tensor field to be a strain.

In 1843 he published the correct derivation of the Navier-Stokes equations for a viscous
flow^{[2]} and was
the first to "properly identify the coefficient of viscosity and its role as a
multiplying factor for the velocity gradients in the flow".
Although he published before Stokes the equations do not bear his name.

Barré de Saint-Venant developed a version of vector calculus
similar to that of Grassmann (now understood as exterior differential
forms) which he published in 1845^{[3]}. A
dispute arose between Saint-Vanant and Grassmann over priority for
this invention. Grassmann had published his results in 1844, but
Barré de Saint-Venant claimed he had developed the method in
1832.

Barré de Saint-Venant was born at the château de Fortoiseau, Villiers-en-Bière, Seine-et-Marne,
France. His father was Jean Barré de Saint-Venant, (1737-1810), a
colonial officer of the Isle of Saint-Domingue. His mother was
Marie-Thérèse Josèphe Laborie (born Haïti, 1769). He entered the École
Polytechnique, in 1813 at sixteen years old.^{[4]}
where he studied under Gay-Lussac. Graduating in 1816 he worked
for the next 27 years as an engineer, initially his passion for
chemistry led him a post as a *élève-commissaire* (student
commissione) for the Service des Poudres et Salpêtres (Powders and
Salt Peter Service) and then as a civil engineer at the Corps des Ponts et
Chaussées. He married in 1837, Rohaut Fleury from Paris.
Following a disagreement on an issue of road with the Municipal
Administration of Paris, he was suddenly retired as "Chief
Engineer, second class", on 1 April 1848. In 1850 Saint-Venant won
a contest to be appointed the chair of Agricultural Engineering at
the Agronomic Institute of Versailles, a post he occupied two
years.^{[5]}

He went on to teach mathematics at the École des
Ponts et Chaussées (National school of Bridges and Roads) where
he succeeded Coriolis.

In 1868, at 71 years old, he was elected to succeed Poncelet in the mechanics
section of the Académie des
Sciences, and continued research work for a further 18 years.
He died in January in 1886 at Saint-Ouen, Loir-et-Cher.
(sources differ on his date of death ^{[4]}
gives January 6 whereas ^{[5]}
January 22). In 1869 he was given the title 'Count' (comte) by Pope Pius IX.

## References

**^** J
Boussinesq and A Flamant, Notice sur la vie et les travaux de M de
Saint-Venant, Annales des ponts et chaussées 12 (1886),
557-595.
**^** J
D Anderson, A History of Aerodynamics (Cambridge, 1997)
**^** J
Itard, Biography in Dictionary of Scientific Biography (New York
1970-1990)
- ^
^{a}
^{b}
O'Connor, John J.; Robertson,
Edmund F., "Adhémar Jean Claude Barré de
Saint-Venant", *MacTutor History of
Mathematics archive*, University of St Andrews, http://www-history.mcs.st-andrews.ac.uk/Biographies/Saint-Venant.html
.
- ^
^{a}
^{b}
E. Sarrau, Adhémar-Jean-Claude BARRÉ de SAINT-VENANT (1797-1886),
le Livre du Centenaire de l'Ecole polytechnique, 1897. [1]