Double-diffusive stability analysis of micropolar fluid-saturated horizontal porous layers in the presence of a concentration-based internal heat source

Concentration-based internal heat sources significantly influence the stability of micropolar fluid flow, playing a vital role in biomedical engineering by accounting for metabolic heat in drug delivery and tissue engineering and in chemical reactors and polymer processing by preventing thermal instability due to exothermic reactions or ion gradients. This article analyzes the stability of a micropolar fluid-saturated porous layer with a concentration-based internal heat source and vertical throughflow. Linear stability is assessed using the normal mode technique, while nonlinear stability is investigated through an energy method. Numerical solutions are obtained using MATLAB's bvp4c routine. The effects of vertical throughflow direction (Péclet number, Pe) and parameters, such as the Darcy number (Da), Lewis number (Le), micropolar parameter (m2), coupling number (N1), and solutal Rayleigh number (Rs), are examined. A comparison of linear and nonlinear thresholds identifies regions of subcritical instability. The study reveals that the internal heat source enhances stability during upward throughflow but promotes instability during downward throughflow. Additionally, at high Péclet numbers, its effect on downward flow becomes negligible.