Thermosolutal convection of a Casson ternary hybrid nanofluid in a plus-shaped cavity with a Central cold fin

Purpose Despite extensive studies on thermosolutal convection in conventional square and rectangular enclosures, the coupled behavior of Casson non-Newtonian ternary hybrid nanofluids in complex plus-shaped cavities with internal cold obstructions remains unexplored in the literature. The purpose of this study is to investigate steady thermosolutal convection of a Casson ternary hybrid nanofluid confined within a plus-shaped cavity with a central cold fin. The work aims to quantify the combined effects of non-Newtonian fluid behavior, complex enclosure geometry and coupled temperature–concentration gradients on thermosolutal transfer enhancement in confined domains relevant to advanced thermal management systems. Design/methodology/approach The dimensionless governing equations describing momentum, energy and species transport are formulated for a Casson ternary hybrid nanofluid and solved numerically using the finite difference method. A detailed parametric analysis is conducted to examine the influence of key controlling parameters on flow structure, thermal fields and solutal transport characteristics. Findings The results indicate that the centrally located cold plus-shaped obstruction significantly reorganizes the flow patterns and thermal fields, leading to notable enhancement in transport performance. Increasing Da from 10–4 to 10–2 results in improvements of approximately 13.56% in the energy transport and 119.40% in the solutal transfer for γ=10. Originality/value This work fills the identified research gap by providing the first integrated analysis that simultaneously considers Casson rheology, ternary hybrid nanoparticle effects, double-diffusive transport and obstruction-induced flow modification within a plus-shaped enclosure. The findings could be useful in compact heat exchangers, electronic cooling systems, battery thermal management units and other space-constrained thermal applications.