Synthesis, characterization and numerical simulations of hybrid nanofluid flow under electromagnetic fields with Arrhenius activation energy

Abstract

This study presents the synthesis, experimental characterization and numerical investigation of hybrid nanofluid (HNF) flow under the influence of electromagnetic fields and activation energy. HNFs containing carbon nano-onions and titanium dioxide nanoparticles in a base fluid were synthesized, and their structural, morphological, and thermal properties were examined using FESEM, FTIR, and UV–Vis spectroscopy. The enhanced thermophysical properties of the synthesized HNFs were then incorporated into a mathematical model describing stagnation-point flow over a porous stretching surface. The model accounts for the effects of electromagnetic fields, Joule heating, activation energy, and variable viscosity. A similarity transformation was applied to reduce the governing partial differential equations to a system of nonlinear ordinary differential equations, which were solved numerically using the BVP4C method. The influence of key parameters on engineering quantities and flow profiles was thoroughly analysed. The findings from the FESEM assessment affirm that the nanoparticles have a consistent size distribution from around 10 to 50 nm, revealing excellent dispersion in water. The FTIR analysis verifies the presence of TiO₂ within the composite material, indicated by characteristic peaks linked to OH, CO, C–N stretching, and Ti–O modes. The absorbance peak for each sample is noted around 330–350 nm, implying broader bandgap values. Moreover, the study reveals that an increase in radiation results in a 7.3 % decline in the heat transfer rate, whereas the mass transfer rate improves by 3.57 % in HNF due to a higher reaction rate. The skin friction in HNF diminishes by 3.12 % because of an enhanced electric field, whereas it escalates by 5.95 % with an increase in the variable viscosity factor.