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Abstract
In the present numerical study the effect of a vertically applied magnetic field on convection of low Prandtl number liquid metal, rotating in a cubical cavity of aspect-ratio 8:8:1 has been investigated. The bottom wall is heated while the top wall is cooled and all the other walls are kept thermally insulated. The simulations have been carried out for liquid metal flows having a fixed Prandtl number Pr = 0.01, Rayleigh number Ra = 107 and magnetic Prandtl number Pm = 4.0 × 10−4, while the Chandrasekhar number Q varies from 5.0625 × 104 to 4.9 × 105 and the Taylor number Ta is varied from 0 to 1010.
It is found that the magnetic field generates a strong damping effect on flow velocities and heat transfer at low rotation rates corresponding to Ta = 106 and Ta = 2.5 × 107, though at higher rotation rates Ta = 1010 the Coriolis forces become comparable to the Lorentz forces thus generating conditions conducive for incipience of dynamo. At the same Ta, with an increase in magnetic fields corresponding to Qh = 4.9 × 105 there is a sharp fall in rms velocities near the top and bottom walls due to the formation of thin Hartmann layers. At low rotation rates, vertically stretched multi-cellular rolls perpendicular to the gravity axis are found. As the rotation increases, the rolls change their spatial orientation and align themselves parallel to the rotation axis. At the highest rotation rate Ta = 1010, a cylindrical vortical column forms at the centre of the cavity.