NATURAL CONVECTION OF LIQUID METAL IN A CUBE WITH UNIFORM FLUX HEATING FROM A SIDE WALL UNDER HORIZONTAL MAGNETIC FIELDS

摘要

Three-dimensional numerical calculations were carried out for the natural convection of liquid metal in a cube heated from a vertical wall with uniform heat flux and cooled from an opposing vertical wall isothermally under various strengths of horizontal magnetic field. The direction of the magnetic fields are in the X-coordinate (horizontal and perpendicular to the heated wall) or in the Y-coordinate(horizontal and parallel to the heated wall). Computational parameters are Pr (Prandtl number) = 0.025, Ra{sup}* (modified Rayleigh number) = 10{sup}5 - 5×10{sup}6, and Ha (Hartmann number) = 0 - 500. Numerical results are compared with previous experimental results. Under the X-directional magnetic field, the average Nusselt number decreased with the magnetic strength and agreed favorably with the previous experiments for any value of the Hartmann numbers studied. However, under the Y-directional magnetic field, the average Nusselt numbers slightly increased at moderate strength of the magnetic field, then gradually decreased with the magnetic field. This general tendency agrees with previous experiments. Figure A shows perspective views of velocity vectors for various cases. At Ha = 0, the velocity profiles are not uniform along the Y-direction. This non-uniform velocity profile has not been obtained for the Prandtl number greater than 0.7. At Ha = 200Y, the velocity profiles along the Y-direction are almost uniform. The Y-directional magnetic field appears to rectify the flow, while suppressing the convection weakly. The X-directional magnetic fields suppress the convection extensively.