Influence of initial density of granular stack on transient regime of homogeneous fluidization

Abstract

This study complements a series of preliminary experimental studies of the destabilization of a granular stack immersed by fluidization, the particular case being the transient regime of homogeneous fluidization. The significant influence of the initial density (initial volume fraction) of the granular stack on the transient homogeneous fluidization regime is highlighted. An initially loose stack fluidizes turbulently and chaotically in a few seconds, from the injection zone to the top of the granular layer. Conversely, for the same material in an initially dense state, there is a mass takeoff of the stack, which is added to the propagation of porosity wave instability from the bottom to the top of the stack with fast kinetics that decompacts the medium. The results also showed that the velocity of this porosity wave seems almost constant regardless of the fluidization velocity.