Nested dipolar vortices driven by electromagnetic forces in a thin liquid metal layer

C. G. Lara¹ - A. Figueroa² - S. Cuevas¹

¹ Instituto de Energ\'ias Renovables, Universidad Nacional Autónoma de México, Temixco, Morelos, 62580, MEXICO
² CONACYT-Centro de Investigación en Ciencias, Universidad Autónoma del Estado de Morelos, Cuernavaca, Morelos, 62209, MEXICO

Abstract
We present an experimental and numerical study of the vortex pattern in a thin liquid metal layer that results from the interaction of a uniform applied electric current with a localized dipolar magnetic field. While a similar configuration originates a classical vortex dipole when the working fluid is a low conductivity electrolyte, experiments show that in a liquid metal layer a different pattern is observed, namely, a vortex dipole nested inside two external recirculation regions. In the zone of strongest magnetic field, the inner vortex dipole shows a reduced velocity. The vortex pattern results from the superposition of several forces produced by the interaction of the applied and induced currents with the non-uniform magnetic field that presents a north (positive) orientation in the central magnet region and a south (negative) orientation near the edges. Experimental measurements were made using Ultrasonic Doppler Velocimetry as well as Particle Image Velocimetry, using as tracers the bubbles generated in the acid layer on top of the liquid metal. Numerical simulations based on a finite volume quasi-two-dimensional model capture the main features of the experimental flow. Figs 5, Refs 22.