Heat transfer enhancement in Casson ternary hybrid nanofluid flow under quadratic thermal radiation via fuzzy TOPSIS optimization

The present study investigates the unsteady hydromagnetic flow and heat transfer behavior of a Casson ternary hybrid nanofluid (THNF), with water as the base fluid and Ti6Al4V (an alloy of titanium consisting of 90% titanium, 6% aluminum, and 4% vanadium), NiCr (nickel-chromium), and Nimonic80A (a nickel chromium iron alloy) as nanoparticles, over a stretching sheet. Effects of thermophoresis, Brownian motion, activation energy, nanoparticle shapes, and linear, nonlinear, and quadratic thermal radiation (QTR) are analyzed. The governing partial differential equations are converted into ordinary differential equations via similarity transformations and solved using the homotopy perturbation method in MAPLE. The key findings reveal that an increase in the Casson parameter reduces velocity, while Brownian motion and thermophoresis enhance temperature, highlighting its role in nanoparticle dynamics and thermal effects. Nonlinear thermal radiation NLTR gives the highest temperature rise, followed by QTR and LTR. For the LTR case, the heat transfer rate increases by 8.31% for HNF and 13.41% for THNF compared to NF. In the NLTR case, the corresponding enhancements are 5.50% and 9.15%, while for the QTR case, they are 5.74% and 9.52%, respectively. The fuzzy technique for order of preference by similarity to ideal solution identifies the most affecting dimensionless parameters. The outcomes of the study are useful in improving the thermal performance in heat exchangers, drug discovery, solar collectors, and other microfluidic applications.