Soret Effects on Triple‐Diffusive Convection With Parabolic and Inverted Parabolic Temperature Gradients

The role of the Soret parameter in the onset of triple‐diffusive convection in a fluid‐porous composite system, with parabolic and inverted parabolic nonuniform temperature gradients, is assessed. The composite structure with the porous layer being modeled using the Darcy–Brinkman framework is assumed to have adiabatic, solute‐impermeable, and rigid–rigid boundary states. The stability of the system, driven by temperature and solute gradients, along with the Soret effect, is effectively characterized through the analytical determination of the critical thermal Rayleigh number using regular perturbation techniques. The effect of different physical attributes on the stability of the system is evaluated through graphical analysis. It is observed that the Soret parameter of fluid and porous structure, solute Rayleigh numbers of the two concentrations considered, and thermal diffusivities in the fluid layer contribute to stabilizing the system; on the other hand, the thermal diffusivity ratios of the porous layer and the Darcy number exhibit a destabilizing effect on the onset of triple‐diffusive convection within the composite structure.