Numerical investigation of nonlinear heat and mass transfer in Carreau hybrid nanofluid flow over an expanding cylinder with homogeneous–heterogeneous reactions

Recent advancements in nanofluids have significantly enhanced heat and mass transfer performance in complex engineering systems. In particular, hybrid nanofluids combined with non-Newtonian models have emerged as effective solutions for improving thermal efficiency under diverse physical conditions. The current study presents a combined investigation of Carreau hybrid nanofluid flow over an expanding cylinder with viscous dissipation, thermal radiation, and simultaneous homogeneous–heterogeneous reactions, providing a unified framework for analyzing coupled heat and mass transfer characteristics. Olive oil is employed as a biocompatible base fluid due to its high bioavailability and stability, while yttrium oxide (Y2O3) and zirconium oxide (ZrO2) nanoparticles are introduced to enhance thermophysical properties. The Carreau model is used to capture the shear-thinning behavior of the non-Newtonian fluid. The governing partial differential equations are transformed into a system of ordinary differential equations via similarity transformations and solved numerically using MATLAB’s boundary value problem solver (bvp5c). The influence of key parameters, including the Weissenberg number, curvature parameter, Prandtl number, Schmidt number, Brownian motion, and thermophoresis, on the velocity, temperature, and concentration profiles was thoroughly analyzed. Results reveal that hybrid nanofluids significantly outperformed conventional nanofluids in heat and mass transfer efficiency, particularly under high curvature and viscoelastic conditions. The enhanced thermal performance and controllable diffusion characteristics of the hybrid nanofluid make it a promising candidate for applications in biomedical drug delivery systems and advanced thermal management technologies.