A numerical study of the turbulent flow driven by rotating and travelling magnetic fields in a cylindrical cavity

Abstract

This paper presents a study of electromagnetic stirring using rotating and travelling magnetic fields, including superpositions with either different or identical frequencies. The resulting turbulent flow was investigated by means of direct numerical simulations based on the low-frequency/low-induction limit of the magnetohydrodynamic equations. The rotating magnetic field drives a vigorous swirling flow with turbulence governed by Taylor–Göortler vortices and, hence, largely confined to the wall region. In contrast, the travelling field yields a meridional circulation, which is accompanied by strong fluctuations that amount to about one half of the total kinetic energy. If the fields are superimposed with comparable forcing parameters but different frequencies, the rotating field prevails although symmetry is broken by the uneven distribution of angular momentum caused by the travelling field. Superposition with identical frequencies leads to a genuinely three-dimensional flow, which holds a promise for high mixing efficiency.

Keywords:

• turbulence
• stirring
• rotating magnetic field
• travelling magnetic field
• direct simulation

Acknowledgments

We thank Prof. H.M. Blackburn for providing the flow solver semtex. Financial support from Deutsche Forschungsgemeinschaft in frame of the Collaborative Research Center SFB 609 is gratefully acknowledged. The computations were performed on an SGI Altix system based on a grant from ZIH at TU Dresden.