Magnetic control of convection in liquid metal heated from above

We investigated experimentally the buoyancy driven convection induced by localized central heating from above in cylindrical tanks filled with liquid metal eutectic alloy (low-Prandtl-number liquid). The experiments were carried out for two aspect ratios A = (radius/height) = 4.125 and 0.333. Time-averaged local temperature distributions and radial and azimuthal velocity components in the liquid at different distances from heater axis were measured. It is shown that maximum temperature gradient is centered in vicinity heater. Temperature difference in radial direction creates pressure gradient between heater and cold wall regions. This gradient leads to upraising of liquid nearly heater and its down in vicinity side cold wall. The Nusselt number tends to a nearly constant value at small aspect ratio and increases considerably at large aspect ratio in the range of heat flux density up to 400 W/cm(2). A static homogeneous magnetic field, in the case of large aspect ratio cell, decreases convective heat transfer intensity by 30% for small enough magnetic field B = 0.1 T because the convective motion in the plane parallel to the field undergoes the most dumping effect.