Inertial Waves Occurring in a Liquid Metal Column due to Pulsed Excitation by a Rotating Magnetic Field

摘要

We present an experimental study concerning the flow inside a liquid metal column exposed to a pulsed rotating magnetic field.This paper is aimed at highly resolved,quantitative velocity measurements in the eutectic GaInSn alloy.A novel ultrasound Doppler system was used two measure two-dimensional velocity fields of the secondary flow in the radial-meridional plane.It employs an array of 25 transducer elements allowing a fast electronic traversing with concurrently high spatial and temporal resolution.The measurements revealed transient flow regimes showing distinct inertial oscillations and coherent vortex structures.The results demonstrate that the arising flow structure depends sensitively on the frequency of the RMF pulses.A maximum intensity of a periodic meridional flow can be observed,if the corresponding pulse frequency fP relates to the eigenperiod of the respective inertial mode in a developed regime.The electromagnetic stirring method that uses a modulated RMF offers considerable potential to enhance the stirring efficiency and to optimize the properties of castings by a well-aimed flow control during solidification.