A numerical study of heat and mass transport by double-diffusive magnetoconvection in an electrically conducting fluid under sinusoidal/non-sinusoidal rotational modulation

In this paper, we study the effects of rotational modulation on heat and mass transport due to double-diffusive magnetoconvection in an electrically conducting fluid. In the study, different modes of rotational modulation are considered. Using a perturbation method, a Ginzburg-Landau equation which is nonautonomous is obtained for the modulation amplitude. The effect of rotational modulation on the heat and mass transfer is studied. For the investigation of the effect of buoyancy ratio on the onset of convection, the system of Lorenz type equations is solved using the recent multistage spectral relaxation method. Furthermore, the influence of other fluid parameters on thermal convection and heat and mass transport is analyzed and presented graphically. We find among other results that the effect of increasing the Taylor number is to reduce the Nusselt and Sherwood numbers. A comparison between the sinusoidal and non-sinusoidal modes of rotational modulation on their influence on heat and mass transport in a magneto-diffusive fluid layer is made. We show that the square wave rotational modulation is the most destabilizing type of modulation in the sense that it leads to the early onset of thermal instabilities while the triangular modulation is the most stabilizing type of modulation. The effect of the buoyancy ratio on the nature of the flow pattern has been determined using streamlines, isotherms, and isoconcentrations.