Quadratic thermal radiation effects on hybrid nanoliquid flow near saddle and nodal stagnation points over a Howarth wavy cylinder using mass‑based thermophysical relations

Flows near saddle and nodal stagnation points possess applications in solar collectors, high-performance systems, drag reduction systems, and catalytic reactors. Motivated by these applications, the primary objective of the present study is to investigate three-dimensional stagnation-point flow of a hybrid nanoliquid over a sinusoidal wavy cylinder, with potential relevance to thermal management and heat-transfer systems involving boundary-layer transport phenomena. The fluid consists of a water-based mixture of copper oxide ( CuO ) and zinc oxide ( ZnO ) nanoparticles and flows through a porous medium with spatially varying porosity. The novelty of the anticipated model is enhanced by considering the thermophysical properties using mass-based relations instead of conventional thermophysical relations involving volume fraction directly. Heat transfer is analyzed using a quadratic thermal radiation approximation, and the governing equations are solved numerically via the bvp4c approach. The results indicate that increasing the CuO nanoparticle mass parameter enhances both axial and transverse velocity profiles, while slightly reducing fluid temperature at both stagnation points. Axial velocity is higher at the saddle point, whereas transverse velocity is higher at the nodal point. The thermal radiation sensitivity is highly topology-dependent. The Nusselt number is almost independent of Rd at the nodal stagnation point, while it becomes significantly larger as Rd increases at the saddle stagnation point. The inclusion of 30 g CuO in 100 g of base fluid leads to a substantial increase in surface drag, whereas within the investigated range (Da = 1.0 − 1.2), the Darcy parameter produces only a marginal variation (below 0.2%) in the reported engineering quantity. Model validation is also provided.