Couple stress is a distinctive fluid property that plays a vital role in predicting flow behavior within microscale channels, where high shear rates are prevalent. Hence, this study presents a numerical investigation of convective heat transfer in a couple stress hybrid nanofluid composed of AA7072-AA7075 nanoparticles dispersed in methanol (CH₃OH). The governing partial differential equations are reduced to ordinary differential equations via similarity transformations and solved using MATLAB’s bvp4c solver. The results reveal significant effects of both couple stress and nanoparticle composition on the fluid’s thermal and flow characteristics. Notably, under conditions of strong opposing flow, the hybrid nanofluid exhibited up to a 5.38% reduction in heat transfer compared to the base fluid. Additionally, increasing the couple stress parameter diminished surface momentum and heat transfer, as evidenced by lower skin friction coefficients and local Nusselt numbers.

couple stress, mixed convection, hybrid nanofluid, bvp4c, methanol