- Graetz number
In

fluid dynamics , the**Graetz number**(**Gz**) is adimensionless number that characterises laminar flow in a conduit. The number is defined as::$Gz=\{d\_iover\; L\}RePr$

where

:"d

_{i}" is the internal diameter in round tubes or hydraulic diameter in arbitrary cross-section ducts:"L" is the length:"Re" is the

Reynolds number and:"Pr" is thePrandtl number .When used in connection with mass transfer the Prandtl number is replaced by the

Schmidt number which expresses the ratio of the momentum diffusivity to the mass diffusivity.:$Gz=\{d\_iover\; L\}ReSc$

The quantity is named after the physicist

Leo Graetz .

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**Graetz**— or Grätz is a German surname and place name and can refer to:* Heinrich Graetz (1817–1891), the first modern historian to write a comprehensive history of the Jewish people from a Jewish perspective * Leo Graetz (1856–1941), German physicist and… … Wikipedia**GRAETZ**— GERMANY (see also List of Individuals) 26.9.1856 Breslau/PL 12.11.1941 Munich/D Leo Graetz studied mathematics and physics at the Universities of Breslau, today s Wrocław in Poland, Berlin and Strasburg. From 1881 he was an assistant at Strasburg … Hydraulicians in Europe 1800-2000**GRAETZ, HEINRICH**— (Hirsch; 1817–1891), Jewish historian and Bible scholar. Graetz was born in Xions (Ksiaz Wielkopolski), Poznan, the son of a butcher. From 1831 to 1836 he went to the yeshivah in Wolstein (now Wolsztyn) near Poznan. At the same time, Graetz… … Encyclopedia of Judaism**Leo Graetz**— (September 26, 1856 ndash; November 12, 1941) was a German physicist. He was born in Breslau (Wrocław), Poland as the son of the historian Heinrich Graetz.Graetz was one of the first to investigate the propagation of electromagnetic energy. The… … Wikipedia**Heinrich Graetz**— (October 31, 1817 September 7, 1891) was amongst the first historians to write a comprehensive history of the Jewish people from a Jewish perspective.Born Tzvi Hirsh Graetz to a butcher family in Książ Wielkopolski (Poznań) in Germany (now in… … Wikipedia**Nusselt number**— In heat transfer at a boundary (surface) within a fluid, the Nusselt number is the ratio of convective to conductive heat transfer across (normal to) the boundary. Named after Wilhelm Nusselt, it is a dimensionless number. The conductive… … Wikipedia**Rayleigh number**— In fluid mechanics, the Rayleigh number for a fluid is a dimensionless number associated with buoyancy driven flow (also known as free convection or natural convection). When the Rayleigh number is below the critical value for that fluid, heat… … Wikipedia**Magnetic Reynolds number**— The Magnetic Reynolds number is a dimensionless group that occurs in magnetohydrodynamics. It gives an estimate of the effects of magnetic advection to magnetic diffusion, and is typically defined by: where U is a typical velocity scale of the… … Wikipedia**Morton number**— For Morton number in number theory, see Morton number (number theory). In fluid dynamics, the Morton number (Mo) is a dimensionless number used together with the Eötvös number to characterize the shape of bubbles or drops moving in a surrounding… … Wikipedia**Ohnesorge number**— The Ohnesorge number, Oh, is a dimensionless number that relates the viscous forces to inertial and surface tension forces. It is defined as: Where μ is the liquid viscosity ρ is the liquid density σ is the surface tension L is the characteristic … Wikipedia