Effect of surface waviness on MHD thermo-gravitational convection of Cu−Al₂O₃−water hybrid nanofluid in a porous oblique enclosure

This study investigates thermo-fluid phenomena of magnetohydrodynamic (MHD) free convection utilizing Cu-Al₂O₃/water hybrid nanofluid in a porous oblique enclosure consisting of a heated wavy vertical wall. The coupled transport equations are solved numerically by implementing the dimensionless governing equations and using an indigenous FORTRAN-based CFD code and the finite volume approach (FVM). The flow physics along with heat transfer characteristics are explored thoroughly by varying the number of peaks (n) of the wavy wall at different Darcy-Rayleigh numbers (Ra_m), Darcy numbers (Da), Hartmann numbers (Ha), and nanoparticle volumetric fractions (ϕ) for different inclinations (γ) of the enclosure. The study findings indicate that the wavy curved wall does not always guarantee heat transfer boosting even with the increase in the effective heating surface area. An increase in active length of the wavy heated wall by the undulations (which is ∼320% with 8 undulations) leads to the heat transfer enhancement of ∼20% compared to a no-undulated cavity. The average heat transfer rate is maximum when n = 4, beyond which heat transfer decreases. Depending upon the setting of the value of Ra_m, Da, Ha, ϕ and γ, the flow-structure and associated heat transfer characteristics are severely altered. Cavity inclination angle has a significant role in controlling the overall thermal performance. (paper)