View source for Hurwitz's theorem (composition algebras)

'''Hartmann number''' ('''Ha''') is the ratio of electromagnetic force to the viscous force first introduced by Hartmann.<ref>{{cite book|author=Kenneth R.Cramer, Shih-l Pai| title=Magnetofluid Dynamics for Engineers and Applied Physicists| publisher=Scripta Publishing Company| year=1973 |isbn=0-07-013425-1}}</ref> It is defined by:

: <math>\mathrm{Ha} = B L\sqrt{\frac{\sigma} {\mu}}</math>
where
* ''B'' is the [[magnetic field]]
* ''L'' is the characteristic length scale
* ''&sigma;'' is the [[electrical conductivity]]
* ''&mu;'' is the [[dynamic viscosity]]

==See also==

* [[Magnetohydrodynamics]]

==References==
{{reflist}}

[[Category:Dimensionless numbers of fluid mechanics]]
[[Category:Fluid dynamics]]
[[Category:Magnetohydrodynamics]]