Experimental and numerical study of Rayleigh-Bénard convection affected by a rotating magnetic field

In the present paper we experimentally study the effects of a rotating magnetic field (RMF) on the fluid flow in an electrically conducting melt (Gallium), kept in a cylindrical container heated from below (Rayleigh-Bénard configuration). The experimental data are compared to results obtained from three-dimensional, time-dependent numerical calculations. The paper presents the influence of the magnetic induction B, the frequency of the RMF Ω, and the temperature difference ΔT between the hot bottom and cold top of the melt on heat transport and fluid flow, respectively. The results can be summarized in terms of the parameter Nrot, which is defined as the ratio of magnetic Taylor number (∝B2⋅Ω) to Grashof number (∝ΔT). It is shown that for 0.003 0.1 temperature fluctuations with amplitudes smaller than 1%–2% of ΔT and frequencies greater than 0.1 Hz are observed. These oscillations can be attributed to Taylor vortices generated at the vertical cylinder walls. The regions of the different oscillation modes within the parameter space are shown in a stability diagram.