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Magnetohydrodynamics
The interaction of moving conducting
fluids with electric and magnetic fields provides for a rich variety of
phenomena associated with electro-fluid-mechanical energy conversion. Effects
from such an interaction can be observed in liquids, gases, two-phase mixtures,
or plasmas. Numerous scientific and technical applications exist, such as
heating and flow control in metals processing, power generation from seeded
high-temperature gases, magnetic confinement of high-temperature plasmas - even
dynamos that create magnetic fields in planetary bodies. Several terms have
been applied to the broad field of electromagnetic effects in conducting
fluids, such as magneto-fluid-mechanics, magneto-gas-dynamics, and the more
common one used here - magnetohydrodynamics, or "MHD".
Practical MHD devices have been in use since the early part of the 20th
century; for example, electromagnetic pumping of liquid metals was first
described in 1937 by Julian Hartmann [1]. MHD devices also have been used for
stirring, levitating, and otherwise controlling flows of liquid metals for
metallurgical processing and other applications [2]. Gas-phase MHD is best
known in MHD power generation, where, since 1959 [3,4], major efforts have been
carried out around the world to develop this technology in order to improve
electric conversion efficiency, increase reliability by eliminating moving
parts, and reduce emissions from coal and gas plants. Closed-cycle liquid
metal MHD systems using both single-phase and two-phase flows also have been
explored.
Still more novel applications are in development or on the horizon. For
example, recent research has shown the possibility of seawater propulsion using
MHD [5] and control of turbulent boundary layers to reduce drag [6]. Extensive
worldwide research on magnetic confinement of plasmas has led to attainment of
conditions approaching those needed to sustain fusion reactions [7].
MHD studies in the Energy Technology program at UC San Diego are concentrated
on solving energy recovery problems for magnetic fusion reactors and on
advanced energy conversion systems.
Links:
 HYDROMAG
International Association for Hydromagnetic Phenomena and Applications
References:
[1] Julian Hartmann, "Theory of the Laminar Flow of an Electrically
Conductive Liquid in a Homogeneous Magnetic Field," 1937.
[2] A. F. Kolesnichenko, "Electromagnetic Processes in Liquid Material
in the USSR and Eastern European Countries," Iron and Steel Institute
of Japan (ISIJ) 30 (1) pp. 8P26, 1990.
[3] P. Sporn and A. Kantrowitz, "Magnetohydrodynamics: Future Power
Process?," Power 103 (11), November 1959, pp. 62P65.
[4] L. Steg and G. W. Sutton, "Prospects of MHD Power Generation,"
Astronautics 5, August 1960, pp. 22P25.
[5] P. Graneau, "Electrodynamic Seawater Jet: An Alternative to the
Propeller?," IEEE Transactions of Magnetics 25 (5) pp. 3275-3277,
1989.
[6] A. Tsinober, "MHD Flow Drag Reduction," in Viscous Drag Reduction
in Boundary Layers, American Institute of Astronoutics and
Aeronautics, 1990.
[7] C. C. Baker, R. W. Conn, F. Najmabadi, and M. S. Tillack, "Status
and Prospects for Fusion Energy from Magnetically Confined Plasmas,"
Energy 23 (7/8) pp. 649-694, 1998.
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