Comprehensive analysis of bioconvective MHD boundary layer flow in a non-Darcian porous medium with variable properties

This study investigates magnetohydrodynamics (MHD) boundary-layer flow through a Darcy–Forchheimer porous medium over a moving horizontal surface containing gyrotactic microorganisms. The combined effects of variable viscosity, variable thermal conductivity, Joule heating, Brownian motion, thermophoresis and chemical reaction are incorporated into the analysis. Suitable similarity transformations are employed to reduce the governing partial differential equations to a system of nonlinear ordinary differential equations, which are solved numerically using the MATLAB bvp5c solver. Following validation of the numerical methodology, simulations are conducted to examine the influence of the governing parameters on the velocity, temperature, concentration and motile microorganism density distributions. The results reveal that increasing the magnetic parameter suppresses the velocity field owing to enhanced Lorentz-force-induced drag, while stronger chemical reactions significantly reduce the concentration distribution. Furthermore, increasing the thermophoresis parameter from ( N t = 0.1 ) to ( N t = 1.0 ) enhances the mass transfer rate by approximately (8.7%), whereas increasing the Brownian motion parameter from ( N b = 0.2 ) to ( N b = 0.8 ) increases the mass transfer rate by about (1.16%). The findings also demonstrate that thermophoretic transport intensifies thermal energy diffusion, leading to a thicker thermal boundary layer. The present study provides a comprehensive understanding of the coupled effects of magnetic field, non-Darcian porous resistance, variable fluid properties, nanoparticle transport and gyrotactic microorganisms on momentum, heat, mass and microorganism transport. In particular, it elucidates how the simultaneous interaction of these mechanisms modifies the flow and transport characteristics, providing a unified framework for analyzing MHD bioconvective transport in porous media with potential relevance to engineering and bio-transport systems.