Adhémar Jean Claude Barré de Saint-Venant
Encyclopedia
Adhémar Jean Claude Barré de Saint-Venant (August 23, 1797, Villiers-en-Bière
Villiers-en-Bière
Villiers-en-Bière is a commune in the Seine-et-Marne department in the Île-de-France region in north-central France.-External links:* * *...

, Seine-et-Marne
Seine-et-Marne
Seine-et-Marne is a French department, named after the Seine and Marne rivers, and located in the Île-de-France region.- History:Seine-et-Marne is one of the original 83 departments, created on March 4, 1790 during the French Revolution in application of the law of December 22, 1789...

 – January 1886, Saint-Ouen, Loir-et-Cher
Saint-Ouen, Loir-et-Cher
Saint-Ouen is a commune in the Loir-et-Cher department of central France.-Geography:Saint-Ouen is situated on the left bank of the Loir. The town of Saint-Ouen is bisected by the RN10, a highway that runs between Paris and Bordeaux.-References:*...

) was a mechanician
Mechanician
A mechanician is an engineer or a scientist working in the field of mechanics, or in a related or sub-field: engineering or computational mechanics, applied mechanics, geomechanics, biomechanics, and mechanics of materials...

 and mathematician
Mathematician
A mathematician is a person whose primary area of study is the field of mathematics. Mathematicians are concerned with quantity, structure, space, and change....

 who contributed to early stress analysis
Stress analysis
Stress analysis is an engineering discipline that determines the stress in materials and structures subjected to static or dynamic forces or loads. A stress analysis is required for the study and design of structures, e.g., tunnels, dams, mechanical parts, and structural frames among others, under...

 and also developed the one-dimensional unsteady open channel flow shallow water equations or Saint-Venant equations
Shallow water equations
The shallow water equations are a set of hyperbolic partial differential equations that describe the flow below a pressure surface in a fluid .The equations are derived from depth-integrating the Navier–Stokes...

 that are a fundamental set of equations used in modern hydraulic engineering
Hydraulic engineering
This article is about civil engineering. For the mechanical engineering discipline see Hydraulic machineryHydraulic engineering as a sub-discipline of civil engineering is concerned with the flow and conveyance of fluids, principally water and sewage. One feature of these systems is the extensive...

. 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
Saint-Venant's principle
Saint-Venant's principle, named after the French elasticity theorist Jean Claude Barré de Saint-Venant can be stated as saying thatThe original statement was published in French by Saint-Venant in 1855...

 of statically equivalent systems of load, Saint-Venant's theorem
Saint-Venant's theorem
In solid mechanics, it is common to analyze the properties of beams with constant cross section. Saint-Venant's theorem states that the simply connected cross section with maximal torsional rigidity is a circle...

 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
Navier-Stokes equations
In physics, the Navier–Stokes equations, named after Claude-Louis Navier and George Gabriel Stokes, describe the motion of fluid substances. These equations arise from applying Newton's second law to fluid motion, together with the assumption that the fluid stress is the sum of a diffusing viscous...

 for a viscous flow 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
Stokes
-Science:* Stokes , a measure of viscosity*Stokes flow*Stokes law*Stokes' law *Stokes parameters*Stokes radius*Stokes relations*Stokes shift*Stokes' theorem*Navier-Stokes equations-Places:* 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 form
Differential form
In the mathematical fields of differential geometry and tensor calculus, differential forms are an approach to multivariable calculus that is independent of coordinates. Differential forms provide a better definition for integrands in calculus...

s) which he published in 1845. A dispute arose between Saint-Venant 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
Villiers-en-Bière
Villiers-en-Bière is a commune in the Seine-et-Marne department in the Île-de-France region in north-central France.-External links:* * *...

, 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
École Polytechnique
The École Polytechnique is a state-run institution of higher education and research in Palaiseau, Essonne, France, near Paris. Polytechnique is renowned for its four year undergraduate/graduate Master's program...

, in 1813 at sixteen years old. 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 Saltpeter Service) and then as a civil engineer at the Corps des Ponts et Chaussées
Corps of Bridges and Roads (France)
The Corps of Bridges is a great technical corps of the French state. It is formed of the State Engineers of the Bridges.People entering the Corps are educated at the École Nationale 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.

He went on to teach mathematics at the École des Ponts et Chaussées (National school of Bridges and Roads) where he succeeded Coriolis
Gaspard-Gustave Coriolis
Gaspard-Gustave de Coriolis or Gustave Coriolis was a French mathematician, mechanical engineer and scientist. He is best known for his work on the supplementary forces that are detected in a rotating frame of reference. See the Coriolis Effect...

.

In 1868, at 71 years old, he was elected to succeed Poncelet
Poncelet
The poncelet is an obsolete unit of power, once used in France and replaced by cheval vapeur . The unit was named after Jean-Victor 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
Saint-Ouen, Loir-et-Cher
Saint-Ouen is a commune in the Loir-et-Cher department of central France.-Geography:Saint-Ouen is situated on the left bank of the Loir. The town of Saint-Ouen is bisected by the RN10, a highway that runs between Paris and Bordeaux.-References:*...

. (sources differ on his date of death gives January 6 whereas January 22). In 1869 he was given the title 'Count' (comte
Comte
Comte is a title of Catalan, Occitan and French nobility. In the English language, the title is equivalent to count, a rank in several European nobilities. The corresponding rank in England is earl...

) by Pope Pius IX
Pope Pius IX
Blessed Pope Pius IX , born Giovanni Maria Mastai-Ferretti, was the longest-reigning elected Pope in the history of the Catholic Church, serving from 16 June 1846 until his death, a period of nearly 32 years. During his pontificate, he convened the First Vatican Council in 1869, which decreed papal...

.
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