SEGNER

GERMANY (see also List of Individuals)

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9.10.1704 Pressburg/SK - 5.10.1777 Halle/D

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Johann Andreas Segner was born in today's Bratislava, Slovakia. He studied in Jena medi- cine, physics and mathematics from 1725 and obtained the PhD title in medicine in 1730. He there was appointed professor of mathematics in 1733 and in 1735 professor of mathematics and physics at the University of Göttingen. In 1755 he moved to Halle at Saale River as an ennobled Prussian Geheimrat. Segner was a Member of the Royal Society from 1739, and the Academies of Berlin from 1747 and of Saint Petersburg from 1754.

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Segner was a scientist working both in medicine and in the exact sciences. He is known for the Segner water-wheel that added essentially to the development of turbines in hydropower engineering. His 1747 book introduces the principle of hydrodynamic repulsion on which his later works were based. The main work on turbine design appeared in 1750, whereas design specifications for the turbine followed in 1755. The 1750 work contains also a section on the shape of a rain drop by accounting for the effect of surface tension. The Segner water-wheel is essentially a cylindrical water container with radially arranged pipes at its bottom that end with an orifice. The outflowing water generates a rotation of the device that is transmitted to the axis and may be used to drive a mechanical unit. To increase the rotation, more water pressure and thus more discharge is required, or larger orifices must be drilled into the branch pipes. Leonhard Euler was personally acquainted with Segner and published in 1752 a note on the turbine. In contrast to Segner, he proposed curved branch pipes to increase the reaction force and noted that such a turbine is more efficient than the usual water wheel. Euler realized the significance of the Segner turbine for force generation.

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_{Euler, L. (1750). Recherches sur l'effet d'une machine hydraulique proposée par M. Segner à Göttingen. Histoire de l'Académie Royale des Sciences Berlin: 331-354.}

_{Kaiser, W. (1975). Johann Andreas Segner als Arzt und medizinischer Lehrer. NTM-Schriften}

_{Geschichte Naturwissenschaften und Medizin Leipzig 12(1): 88-97. P}

_{Keller, K. (1913). Johann Andreas Segner. Beiträge zur Geschichte der Technik 5: 54-72. P Killy, W., Vierhaus, R., eds. (1998). Segner. Deutsche biographische Enzyklopädie 9: 264. Michel (1985). Johannes Andreas Segner. Hungary stamp 2985. Schwaneberger: Munich. P Segner, J.A. (1747). Exercitatonum hydraulicarum fasciculus. Vandenhoeck: Göttingen. Segner, J.A. (1750). Programma quo theoriam machinae cujusdam hydraulicae praemittit. Göttingen.}

_{Segner, J.A. (1755). Specimen theoriae turbinum. Halle.}