HALL EFFECT ON COUPLE-STRESS FLUID HEATED FROM BELOW IN POROUS MEDIUM IN THE PRESENCE OF A HORIZONTAL MAGNETIC FIELD

摘要

A layer of couple-stress fluid heated from below in porous medium is considered in the presence of a uniform horizontal magnetic field to include the effect of Hall currents. For the stationary convection case, the magnetic field postpones the onset of convection while the Hall current hastens the onset of convection. The medium permeability and couple-stress both postpone and hasten the onset of convection depending on the Hall parameter M. Graphs have been plotted by giving numerical values to the parameters, to depict the stability characteristics. The magnetic field (and corresponding Hall currents) is found to introduce oscillatory modes in the system, which was non-existent in their absence. The sufficient condition for the non-existence of overstability is also obtained.