Magnetothermal convection on the thermally stratified fluid layer by permanent magnets

The Magnetothermal convection can be induced for paramagnetic fluid in the presence of the temperature difference and the magnetic field. In this study, the convection is studied both experimentally and numerically for the thermally stratified fluid layer attained by heating the top wall and cooling the bottom wall. When a single block magnet is placed above the top hot wall, the convection is confirmed near the magnet edges. In the case of multiple magnets, the convection is observed near the magnet junction(s) since the local magnetic force becomes stronger than that at magnet edges. This effect depends on the number of magnets. A pair block magnet that has one junction enhances the convection the most and pair vortex flow is induced. In the case of three magnets, the maxima of the local Nusselt number near the magnet junctions are suppressed. This is because that the magnetothermal force becomes weak due to the low-temperature difference formed by the conflicting convection cells.