Forced convection magnetohydrodynamic Al2O3-Cu/water hybrid nanofluid flow over a backward-facing step

Forced convection hybrid nanofluid flow over a backward-facing step under a non-uniform magnetic field is numerically studied using a finite volume method. The external magnetic source is placed in the step edge. The study is performed for a range of nanoparticles volume fraction, phi, from 0 to 2%, Hartmann number, Ha, from 0 to 50, and Reynolds number, Re, from 100 to 300. Results show that the reattachment length reduces by increasing volume fraction of nanoparticles and by decreasing Reynolds number. The recirculation bubble weakens and the conductive heat transfer mode growth by increasing Hartmann number at weak magnetic field intensity. It totally disappears at high Hartmann number when the convective mode dominates. The average Nusselt number increases by increasing volume fraction of nanoparticles and varies with the Hartmann number. The effects of Lorentz force and hybrid nanoparticles on the heat transfer enhancement rates are strongly linked with volume fraction of nanoparticles and Hartmann and Reynolds numbers.