Numerical study of flows driven by screw magnetic field in cylindrical container

In order to enhance the stirring efficiency in the molten metal, a new electromagnetic stirrer by tilting the yokes to a certain angle was proposed. The main merit of this stirrer is that it can generate simultaneously both rotating and travelling electromagnetic forces. In the current work, a numerical model was established to calculate the electromagnetic and induced flow fields. The effect of the tilt angle of the yokes on the stirring efficiency was studied. It is found that when the tilt angle is increased from 15 to 30u, the maximum absolute value of the electromagnetic force in the vertical direction is double. The average absolute value of the electromagnetic force in the vertical direction reaches 1?26610 22 N, which is more than half of the electromagnetic force in the x or y direction. The electromagnetic force in the vertical direction is strong enough to induce a meridional flow in the vertical section. The flow patterns driven by the traditional rotating magnetic stirrer and the new stirrer were compared. The results show that with the traditional one, the flow pattern is mainly annular. With the new one, however, both annular and meridional flows are achieved. Finally, effects of the various electromagnetic force on the microstructure of Sn–20 wt%Pb were analysed.