Optimization of entropy generation for hydromagnetic radiative-dissipative Darcy-Forchheimer bioconvective flow of Casson hybrid nanofluid in a porous medium using SQLM

The present work investigates convective transport in a hybrid Casson nanofluid containing gyrotactic microorganisms, with a particular focus on entropy generation and thermodynamic irreversibility. The mathematical model incorporates the effects of an induced magnetic field, nonlinear thermal radiation, internal heat generation, homogeneous chemical reaction, and bioconvection in the presence of a Darcy-Forchheimer porous medium. The inclusion of the Darcy-Forchheimer model accounts for both viscous and inertial resistance within porous structures. Nanoparticle transport is described using the Buongiorno model. The influences of the governing physical parameters on the velocity, temperature, nanoparticle concentration, motile microorganism distribution, entropy generation, and Bejan number are examined in detail. The numerical results demonstrate that entropy generation increases with the Brinkman number, Darcy parameter, Forchheimer parameter, radiation parameter, and Reynolds number, whereas increasing the Casson parameter suppresses entropy production by reducing fluid-friction irreversibility. Furthermore, the magnetic field enhances entropy generation through Joule dissipation while reducing the Bejan number due to the increased contribution of magnetic and frictional irreversibilities. The effects of governing parameters on the local skin-friction coefficient, Nusselt number, Sherwood number, and motile microorganism density number are also systematically evaluated. The findings provide useful insights into heat and mass transfer, thermodynamic irreversibility, and bioconvective transport.