Fluid to solid transition in magnetofluidized beds of fine powders

Abstract

Experimental observations on the fluid to solid transition in beds of magnetized fine particles fluidized by gas are reported for different particle sizes (dp). Contrarily to stability analysis prediction, the fluidized bed is stabilized by a sufficiently strong magnetic field in the cross-flow configuration. As the strength H of the horizontally applied magnetic field is increased, particle chaining in the bubbling bed becomes apparent due to the induced attractive magnetostatic forces between the particles. In close analogy with magnetorheological fluids chain stability is determined by the balance between gas flow shear and the interparticle magnetostatic force. The jamming transition occurs at a gas velocity scaling proportionally to dp2H2 when the length of the stable chains reaches a critical size which is independent of particle size.