MHD EFFECTS IN TURBULENT DUCT FLOWS UNDER THE INFLUENCE OF TRANSVERSE UNIFORM AND NONUNIFORM MAGNETIC FIELDS

摘要

Analysis of magnetohydrodynamic (MHD) effects in turbulent duct flows under transverse magnetic fields is of great interest at developing the liquid metal fusion reactor blankets. In this paper, MHD numerical analyses are conducted to study liquid metal flows in rectangular ducts under high uniform and nonuniform magnetic fields. The flow distribution in nonuniform magnetic fields produced by two permanent magnets is characterized by M-shaped velocity profiles in the upstream region and, respectively, by wall jets in the downstream region with decaying magnetic field. The formation of the M-shaped velocity profiles is explained as a result of the Lorentz forces acting parallel to the flow direction, while the velocity wall jets are explained by considering also the electromagnetic forces acting perpendicular to the flow direction. Extending this analysis for the case of high uniform magnetic fields, no wall jets have been found even in the case of electrically conducting walls. This is explained by the induced electric currents which are closed only in the transversal cross-section of the channel, giving rise to electromagnetic forces which are acting parallel to the flow direction.