Characteristics of liquid metal motion driven by quasi-sinusoidal magnetic fields

The free surface motion of a liquid metal has been investigated by changing the wave patterns of a quasi-sinusoidal magnetic field and a modulated quasi-sinusoidal one. The theoretical expression of Lorentz force induced by the quasi-sinusoidal magnetic field applied on an electrically conductive cylinder has been derived. The Lorentz force consists of a time-averaged part F-ave and oscillating parts F-omega and F-2 omega with angular frequencies omega and 2 omega, respectively. The surface disturbance of a liquid gallium was observed under the imposition of the magnetic fields. it was found that the oscillating part of F-omega dominants the surface wave motion in the low frequency range and the substantial frequency of the surface wave is the same as that of a coil current. This result agrees with the theoretical derivation. While in the high frequency range, the induced recirculating flow causes an irregular fluctuation on a free surface. It is noticed that the disturbance on the free surface is intensified at the resonance frequency and the around of 1 000 Hz.