Key words: Rayleigh-Bénard; Magnetoconvection; Entropy; Hartmann number.

Abstract: The present paper focuses, in particular, on aspect ratio (AR) effects on Rayleigh-Bénard convection within enclosure under a uniform magnetic field. Results are presented and analyzed for different values of Hartmann number (60≤ Ha ≤ 80) and for a range of aspect ratios (0.75≤AR≤1) at various Rayleigh numbers (Ra). It is found that both enclosure aspect ratio and magnetic field intensity play a significant role in controlling the onset of the Rayleigh-Bénard convection flow. The entropy generation analysis demonstrates that irreversibility phenomena increase for lower aspect ratio values and moderate Hartmann numbers.