The Hartmann number (Ha) is the ratio of electromagnetic force to the viscous force, first introduced by Julius Hartmann (1881 – 1951) of Denmark. It is frequently encountered in fluid flows through magnetic fields. It is defined by:
H a = B L σ μ {\displaystyle \mathrm {Ha} =BL{\sqrt {\frac {\sigma }{\mu }}}}
where
B is the magnetic field intensity L is the characteristic length scale σ is the electrical conductivity μ is the dynamic viscosity
See also Magnetohydrodynamics
References
Further reading Jackson, J.D. (1975). "Magnetohydrodynamics and Plasma Physics". Classical Electrodynamics (Second ed.). John Wiley & Sons. ISBN 0-471-43132-X. LCCN 75009962. Retrieved 2020-05-16. Hartmann number is indicated by letter M in analogy with Mach number for aerodynamics.