Boundary Layer Analysis of Non-Newtonian Nanofluid Flows with Heat and Mass Transfer over Stretching Surfaces

Abstract

The growing energy demand calls for advanced heat and mass transfer technologies in industrial and engineering applications. Conventional fluids with traditional enhancement methods often fall short in meeting these requirements. Nanofluids have shown promise in improving thermal performance. Considering the prevalence of non-Newtonian characteristics in practical systems, this dissertation investigates the heat and mass transfer behavior of non-Newtonian nanofluids flow under a range of physical influences, including MHD, thermal radiation, chemical reactions, Brownian motion, thermophoresis and porous media effects. Special attention is given to the influence of bioconvection, variable thermophysical properties, viscous dissipation, mixed convection, and heat source/sink. The governing PDEs are reduced into ODEs using similarity transformations and solved via spectral methods and MATLAB’s bvp4c solver. Validation against existing benchmarks and residual norm analyses confirm the accuracy of the numerical approaches. The study focuses on Carreau and Williamson nanofluids, as well as binary and ternary hybrid Maxwell nanofluids. Results indicate that shear-thickening Carreau fluids exhibit superior heat and mass transfer performance compared to their shear-thinning counterparts. In Williamson nanofluids, the inclusion of bioconvective microorganisms and Arrhenius activation energy elevate temperature and concentration distributions, respectively. Moreover, thermal Biot numbers and non-Fickian fluxes substantially modulated the heat and mass transfer rates. Hybrid nanofluids flow analysis over rotating disk reveals that ternary hybrid nanofluid exhibits greater resistance to Lorentz and porous medium drag forces compared to binary hybrid nanofluid. Additionally, unsteady flow over a rotating cone reveals that variable thermal conductivity and solutal diffusivity enhance temperature and concentration under specified wall temperature and concentration conditions, but lead to reductions under specified thermosolutal flux conditions. This study advances the understanding of heat and mass transfer behavior in non-Newtonian nanofluids with practical relevance to diverse engineering and biomedical systems. Finally, based on the findings, recommendations for future research are proposed.