MHD hybrid nanofluid flow and entropy analysis in smooth and wavy channels under non-uniform magnetic field

This study presents a comprehensive numerical investigation of magneto hydrodynamic (MHD) hybrid nanofluid flow in a two-dimensional channel featuring a localized wavy section under the influence of a non-uniform magnetic field. The hybrid nanofluid, composed of Fe₃O₄–Al₂O₃ nanoparticles dispersed in water, is modeled as a single-phase fluid under laminar, steady, and incompressible conditions. The applied transverse magnetic field follows an exponential decay along the channel height, inducing a spatially varying Lorentz force and Joule heating effect. The governing equations are solved using the finite volume method implemented in ANSYS Fluent, with the SIMPLE algorithm employed for pressure–velocity coupling. A comparative analysis between smooth (SC) and wavy (WC) channel configurations is conducted to evaluate the impact of Reynolds number (200 ≤ Re ≤ 800) and magnetic field intensity (1 T ≤ B₀ ≤ 8 T) on flow structure, heat transfer, and thermodynamic irreversibility. The results reveal that the magnetic field significantly suppresses fluid velocity within the magnetized region due to Lorentz force damping, while simultaneously enhancing fluid temperature through Joule heating. Overall, the results demonstrate that the combination of localized wall waviness and a non-uniform magnetic field provides an effective strategy for enhancing heat transfer while minimizing thermodynamic irreversibility. This study offers valuable insights for the design of advanced MHD-based cooling systems and energy applications involving hybrid nanofluids.