Electromagnetic levitation of liquid metal droplets under a horizontal DC magnetic field

Abstract Electromagnetic levitation of the droplets of Cu and Ni under the superposed horizontal DC magnetic field up to 4.5 T is studied experimentally. The levitation coil alimented with a 140 kHz AC electric current was placed inside a DC magnetic field generated with a Helmholtz coil. It was found that the droplet deformation enhanced at a DC magnetic field of low intensity, <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>B</mml:mi> <mml:mrow> <mml:mrow> <mml:mi>DC</mml:mi> </mml:mrow> </mml:mrow> </mml:msub> <mml:mo>&lt;</mml:mo> <mml:mn>3</mml:mn> </mml:mrow> </mml:math> T, however, with a further increase in the intensity of DC magnetic field, the droplets were almost immobilized. The motion of oxide particles over the droplets’ surface indicated that a residual velocity may still exists in the droplet subjected to the DC magnetic field <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>B</mml:mi> <mml:mrow> <mml:mrow> <mml:mi>DC</mml:mi> </mml:mrow> </mml:mrow> </mml:msub> <mml:mo>=</mml:mo> <mml:mn>4.5</mml:mn> </mml:mrow> </mml:math> T. The amplitude of a triggered oscillatory motion of the droplets under <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msub> <mml:mi>B</mml:mi> <mml:mrow> <mml:mrow> <mml:mi>DC</mml:mi> </mml:mrow> </mml:mrow> </mml:msub> <mml:mtext>⩾</mml:mtext> <mml:mn>3.5</mml:mn> </mml:mrow> </mml:math> T was attenuated exponentially, the amplitude decay rate found to be proportional to the electrical conductivity of the liquid, but not to <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mrow> <mml:msubsup> <mml:mi>B</mml:mi> <mml:mrow> <mml:mrow> <mml:mi>DC</mml:mi> </mml:mrow> </mml:mrow> <mml:mn>2</mml:mn> </mml:msubsup> </mml:mrow> </mml:math> . Finally, the origin of the destabilizing effect of the DC magnetic field on droplet deformation, and its stabilizing effect on droplet displacement, is discussed and is attributed to the spatial variation of the DC magnetic field.