The influence of the configuration of travelling magnetic fields on the efficiency of liquid metal stirring in a rectangular cell

Abstract

This paper aims to investigate numerically a vortex flow of liquid metal in a rectangular mould excited by two linear inductors  of magnetic fields located at different distances and at different magnetic couplings . The occurrence of magnetic coupling between the inductors is due to  their connection via passive ferromagnetic elements, which intensify the electromagnetic interaction between the coils of adjacent inductors leading to  significant non-uniformity of electromagnetic field. The stirring efficiency of the flow driven by electromagnetic forces  is estimated in terms of the integral parameter of homogeneity of passive impurity, whose concentration directly depends on the evolution of vortex structures of different size. It has been shown that the most effective stirring of liquid metal in the mould is achieved at relatively close distance between the inductors but in the absence of direct magnetic coupling. This ensures consistency between the mould geometry and the topology of electromagnetic field, and, as a result, generates along the mould length  a large-scale elongated vortex, facilitating thereby the transport of impurity throughout the bulk of the liquid metal. The vortex itself loses stability and breaks  down with a certain periodicity into many small vortex structures. The flow  becomes chaotic  and stirring is intensified. In the case of strong magnetic coupling between the inductors the resulting flows exhibit pronounced instability and asymmetry responsible for the generation of several vortices along the principal mould direction. One of the vortices can trap the impurity producing a blocking effect, which impedes the transport of impurity across the mould . The study was conducted using numerical modeling. The model was verified using data from  the laboratory experiment.