Efficient melt stirring using pulse sequences of a rotating magnetic field: I - Flow field in a liquid metal column

The utilization of a pulsed rotating magnetic field (RMF) is presented as an auspicious method to obtain an intensive stirring and mixing in a pool of liquid metal. The RMF pulses within a sequence have been applied with constant or alternating direction, respectively. The resulting flow structure in a cylindrical liquid metal column has been explored by numerical simulations and by model experiments using the ternary alloy GaInSn. The ultrasonic Doppler velocimetry (UDV) has been used to determine profiles of the vertical velocity. The numerical results as well as the velocity measurements demonstrate the capability of the proposed stirring regimes to overcome the limited mixing character of conventional rotary stirring. The application of a time-modulated RMF offers a considerable potential to provide optimal flow pattern in a solidifying melt for reasons of a well-aimed modification of casting properties.