Stabilization of concentration waves in fluidized beds of magnetic particles

In this work, a linear stability analysis is carried out to evaluate the behavior 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 non-linear model is proposed for the fluid–particle interaction force, so that the inertial effects arising from the wakes behind the particles are incorporated. We see 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 experiments. The interaction of the magnetized particles with an external magnetic field produce a stronger stabilization of linear instabilities in fluidized beds than the one induced by particle pressure, associated with velocity fluctuations and collision of the particles, and by the interaction of the wakes of the particles, associated with the inertia of the flow. All three effects act in the sense of stabilizing fluidized beds against concentration waves.