Nonlinear Magnetoconvection of a Power-Law Fluid Saturated Porous Layer

This article examines the thermohaline stability of a power-law fluid saturating a porous layer in the presence of a magnetic field. The system stability is analyzed using both linear and weakly nonlinear instability theories. Within the linear framework, the Galerkin method is employed to derive analytical expressions for the Rayleigh number corresponding to steady and oscillatory modes of instability. Takens–Bogdanov and Hopf bifurcation points are identified, highlighting the transition mechanisms between different instability regimes. An increase in the Hartmann number delays the onset of convection. The critical Rayleigh number is a monotonic increasing function of the solute Rayleigh number, whereas it is a non-monotonic function of the Peclet number. To investigate heat and mass transport characteristics, an amplitude equation is derived in the weakly nonlinear regime. The results reveal that increasing the Hartmann, Lewis, and Peclet numbers enhances both heat and mass transport, whereas an opposite trend is observed with increasing the solute Rayleigh number.