Hydrodynamtcal and magnetic effects on the stabilization of concentration waves in fluidized beds

Abstract

In this work, a linear stability analysis is carried out to evaluate the behaviour of concentration waves in polarized fluidized beds. The magnetic effects are taken into account by the addition of a magnetic stress tensor on the particulate phase stress tensor. A nonlinear model is proposed for the fluid-particle interaction force, so that the inertial effects arising from the wakes behind the particles are incorporated. It is seen that the alignment of the magnetic particles with the magnetic field stabilizes the fluidized bed flow and the efficiency of this stabilization is maximum when the field lines are parallel to the fluidization direction. The results are in qualitative agreement with recent experiments. In addition, the interactions among the wakes behind the particles and a particle pressure reduce the magnetic field intensity necessary for complete stabilization. This indicates that these three effects act in the sense of stabilizing fluidized beds against concentration waves.