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Thermal convection in a duct with a strong axial magnetic field

X. Zhang - O. Zikanov

University of Michigan--Dearborn, Dearborn, MI 48128-1491, USA

Thermal convection caused by non-uniform internal heating in a horizontal duct with an axial magnetic field is studied numerically. The magnetic field is strong enough to make the flow purely or nearly two-dimensional (uniform in the axial direction). The goal is to understand the effect of convection in toroidal ducts of a conceptual liquid metal blanket of a fusion reactor. A model of a separately cooled blanket with walls maintained at constant temperature and with no significant mean flow along the duct is considered. Turbulent convection appears at a high Grashof number when the magnetic field is purely axial. Adding a much weaker (5\% in amplitude) vertical magnetic field suppresses the turbulence, elongates convection structures, and forms strong shear layers in the flow and near-wall jets. Stability analysis reveals that the transformation makes the flow more unstable to three-dimensional perturbations growing in the internal zones of strong shear. The unstable mode takes the form of axially oriented rolls varying slowly along the axis. Figs 6, Refs 10.

Magnetohydrodynamics 53, No. 1, 213-220, 2017 [PDF, 6.93 Mb]

Copyright: Institute of Physics, University of Latvia
ISSN (electronic edition): 1574-0579; ISSN (printed edition): 0024-998X