Advances in bioconvection of Casson nanofluids over a stretching sheet: Influence of thermal radiation and activation energy

Background Nanofluids possess enhanced thermal properties, making them highly effective in improving heat transfer performance within thermal systems. Owing to their distinctive thermophysical characteristics, nanofluids have attracted considerable interest across various engineering applications. Purpose This study investigates the magnetohydrodynamic (MHD) flow of Casson nanofluids over a stretching sheet, accounting for the effects of thermal radiation, activation energy, bioconvection, and motile microorganisms. The roles of Brownian motion and thermophoresis in heat and mass transfer are also analyzed. Method ology : The governing nonlinear partial differential equations (PDEs) are reduced to a system of nonlinear ordinary differential equations (ODEs) through similarity transformations. These equations, along with the corresponding boundary conditions, are numerically solved using the bvp4c solver in MATLAB. Results The analysis demonstrates that an increase in the Brownian motion parameter promotes thermal energy diffusion, whereas a higher Lewis number inhibits mass transfer. The Casson fluid parameter reduces the velocity boundary layer thickness, resulting in a 12.4 % rise in shear stress. Additionally, a higher Prandtl number leads to a 21.7 % decrease in thermal boundary layer thickness, thereby enhancing heat dissipation. The thermophoretic parameter exerts a pronounced effect on nanoparticle concentration, yielding a 15.3 % increase in concentration gradients. These results offer valuable insights into optimizing heat and mass transfer in nanofluid-based thermal systems.