Magnetic Reynolds number
Physical key figure | |||||||||||
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Surname | Magnetic Reynolds number | ||||||||||
Formula symbol | |||||||||||
dimension | dimensionless | ||||||||||
definition | |||||||||||
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Named after | Osborne Reynolds | ||||||||||
scope of application | magnetic fluids | ||||||||||
See also: Reynolds number |
In magnetohydrodynamics , a magnetic Reynolds number is defined analogous to the Reynolds number in hydrodynamics . It is a dimensionless number and describes the ratio of convection to diffusion in a magnetic fluid .
It is defined as:
- .
Where:
- the magnetic field constant ,
- the electrical conductivity (conductivity) of the fluid,
- the magnetic diffusivity ,
- the characteristic length of the application and
- the amount of the characteristic velocity for the application .
Scale and examples
If a copper loop of the diameter is moved with the speed (conductivity ), this results
- For the magnetic field is diffuse or is hardly influenced by the movement.
The magnetic Reynolds number is of the order of magnitude:
- a liquid metal , e.g. B. Mercury : ,
- in industrial applications: ,
- in the outer core of the earth : and
- in astrophysics : .
Web links
- Magnetic Reynolds number. In: Property Sources Index (EQI). Chemistry Biology Pharmacy Information Center, ETH Zurich, accessed on July 21, 2009 .
- Marcus Gellert: Generation of magnetic fields in helical flows. In: Fluid Dynamics. University of Potsdam, archived from the original on November 1, 2008 ; Retrieved July 21, 2009 .
Individual evidence
- ↑ OV Filipenko, BG Zinchenko, DD Sokoloff: Turbulent Dynamo and the Geomagnetic Secular Variation . In: Solar and Planetary Dynamos . tape 1 . Cambridge University Press, 2008, ISBN 0-521-05415-X , pp. 229 ( limited preview in Google Book search).