A general particle stress equation for fixed and fluidised beds

A general constitutive equation is proposed for the solid particle stress in a fluidised bed. This equation reduces in a straightforward manner to describe the particle stress in a fixed bed, and it implies a Mohr-Coulomb yield criterion for the transition from the fixed-bed to the fluidised-bed state. Experimental evidence is given to show that at incipient fluidisation, the particle stress assumes a form agreeing with that predicted by theory.