Thermal convection under spatially varying magnetic fields

We study the properties of turbulent large-scale structures in an extended fluid layer of aspect ratio 16:32:1 under the influence of non-uniform magnetic field. The layer is heated from below and cooled from above (Rayleigh-Bénard configuration). The magnetic field is generated by two semi-infinite planar magnetic poles, with the convection layer located near the edge of the gap between the poles. We employ direct numerical simulations of the above setup for fixed Rayleigh and Prandtl numbers but vary the magnetic field profiles determined by the gap between the convection cell and the magnets. The simulations are conducted using an efficient parallel finite-difference solver. We investigate how the magnetic field profile impacts the evolution of superstructures (coherent large-scale flow patterns that extend over scales in the lateral direction that are significantly larger than the domain height) and their characteristic time and length scales. We also conduct a detailed study on the implications of these structures in turbulent heat transfer. Further, we study the properties of convective movements in the vicinity of sidewalls (wall modes) in the high magnetic flux region, and how their behavior changes with the magnetic field profile.