Mixed convection flow and heat transfer of a Williamson tetra-hybrid (SWCNT–MWCNT–SiO2–TiO2) nanofluid across a rough wedge

Purpose The purpose of this study is to investigate the flow and heat transfer enhancement of a Williamson tetra-hybrid nanofluid over a rough wedge in the presence of mixed convection and a periodic magnetic field. Special attention is given to the combined effects of surface roughness, non-Newtonian fluid behaviour and magnetic modulation on momentum and thermal transport. The study aims to evaluate how tetra-hybrid nanoparticles improve thermal efficiency compared to conventional fluids. Design/methodology/approach The governing nonlinear partial differential equations for Williamson tetra-hybrid nanofluid flow over a rough wedge are transformed into a nondimensional nonsimilar system using appropriate transformations. The resulting equations are solved numerically using an implicit finite-difference scheme coupled with the quasilinearisation technique. Surface roughness and magnetic field effects are incorporated through sinusoidal wall-velocity oscillations and applied magnetic forces. Findings The results demonstrate that surface roughness induces pronounced sinusoidal variations in the skin friction coefficient and heat transfer rate along the wedge. An increase in the roughness-frequency parameter insignificantly amplifies the amplitude of these oscillations, indicating stronger fluctuations in both momentum and thermal transport. Further, the application of a periodic magnetic field markedly intensifies these sinusoidal responses, leading to enhanced overall heat transfer performance. Originality/value This study presents a novel analysis of mixed convection Williamson tetra-hybrid nanofluid flow over a rough wedge under the influence of a periodic magnetic field, a combination that remains largely unexplored in existing literature. The originality lies in the integration of non-Newtonian rheology, tetra-hybrid nanoparticle formulation and sinusoidal surface roughness within a unified numerical framework. The findings provide new insights into the enhancement of heat transfer and momentum transport, offering practical relevance for advanced thermal management and engineering applications.