Data de nastere: 
Locul nasterii: 
Data mortii: 
Locul mortii: 
23 Aug 1797 
VilliersenBière, SeineetMarne, France 
6 Jan 1886 
St Ouen, LoiretCher, France 
Jean Claude SaintVenant was a student at the École Polytechnique, entering the school in 1813 when he was sixteen years old. He graduated in 1816 and spent the next 27 years as a civil engineer. For the first seven of these 27 years SaintVenant worked for the Service des Poudres et Salpêtres, then he spent the next twenty years working for the Service des Ponts et Chaussées. SaintVenant attended lectures at the Collège de France and the lecture notes he took in Liouville 's 183940 class still survive. He taught mathematics at the École des Ponts et Chaussées where he succeeded Coriolis . SaintVenant worked mainly on mechanics, elasticity, hydrostatics and hydrodynamics. Perhaps his most remarkable work was that which he published in 1843 in which he gave the correct derivation of the Navier  Stokes equations. Anderson writes in : Seven years after Navier 's death, SaintVenant rederived Navier 's equations for a viscous flow, considering the internal viscous stresses, and eschewing completely Navier 's molecular approach. That 1843 paper was the first to properly identify the coefficient of viscosity and its role as a multiplying factor for the velocity gradients in the flow. He further identified those products as viscous stresses acting within the fluid because of friction. SaintVenant got it right and recorded it. Why his name never became associated with those equations is a mystery. certainly it is a miscarriage of technical attribution.
We should remark that Stokes , like SaintVenant, correctly derived the Navier  Stokes equations but he published the results two years after SaintVenant. SaintVenant developed a vector calculus similar to that of Grassmann which he published in 1845. He then entered into a dispute with Grassmann about which of the two had thought of the ideas first. Grassmann had published his results in 1844, but SaintVenant claimed (and there is little reason to doubt him) that he had first developed these ideas in 1832. Again it would appear that SaintVenant was unlucky. Itard writes in : SaintVenant used this vector calculus in his lectures at the Institut Agronomique, which were published in 1851 as "Principes de mécanique fondés sur la cinématique". In this book SaintVenant, a convinced atomist, presented forces as divorced from the metaphysical concept of cause and from the physiological concept of muscular effort, both of which, in his opinion, obscured force as a kinematic concept accessible to the calculus. Although his atomistic conceptions did not prevail, his use of the vector calculus was adopted in the French school system.
In the 1850s SaintVenant derived solutions for the torsion of noncircular cylinders. He extended Navier 's work on the bending of beams, publishing a full account in 1864. In 1871 he derived the equations for nonsteady flow in open channels. In 1868 SaintVenant was elected to succeed Poncelet in the mechanics section of the Académie des Sciences . By this time he was 71 years old, but he continued his research and lived for a further 18 years after this time. At age 86 he translated (with A Flamant) Clebsch 's work on elasticity into French and published it as Théorie de l'élasticité des corps solides and SaintVenant added notes to the text which he wrote himself. Note that SaintVenant's cotranslator A Flamant was a coauthor of the obituary notice for SaintVenant.
Source:School of Mathematics and Statistics University of St Andrews, Scotland
