Abstract: We consider the combined effect of the magnetic field and heat transfer inside a square cavity containing a hybrid nanofluid (Cu-Al₂O₃-water). The upper and bottom walls of the cavity have a wavy shape. The temperature of the vertical walls is lower, the third part in the middle of the bottom wall is kept at a constant higher temperature, and the remaining parts of the bottom wall and the upper wall are thermally insulated. The magnetic field is applied under the angle γ, an opposite clockwise direction. For the numerical simulation, the finite element technique is employed. The ranges of the characteristics are as follows: the Rayleigh number (10³ ≤ Ra ≤ 10⁵), the Hartmann number (0 ≤ Ha ≤ 100), the nanoparticle hybrid concentration (φ_Al2O3, φ_Cu = 0, 0.025, 0.05), the magnetic field orientation (0 ≤ γ ≤ 2π), and the Prandtl number Pr, the amplitude of wavy cavity A, and the number of waviness n are fixed at Pr = 7, A = 0.1, and n = 3, respectively. The comparison with a reported finding in the open literature is done, and the data are observed to be in very good agreement. The effects of the governing parameters on the energy transport and fluid flow parameters are studied. The results prove that the increment of the magnetic influence determines the decrease of the energy transference because the conduction motion dominates the fluid movement. When the Rayleigh number is raised, the Nusselt number is increased, too. For moderate Rayleigh numbers, the maximum ratio of the heat transfer takes place for the hybrid nanofluid and then the Cu-nanofluid, followed by the Al₂O₃-nanofluid. The nature of motion and energy transport parameters has been scrutinized.

Key words: magnetohydrodynamics, natural convection, hybrid nanofluid, heat transfer, bottom heater, wavy top and bottom enclosure