FLUIDIZATION, CONDENSATION AND CLUSTERIZATION OF A VIBRATING COLUMN OF BEADS

We present numerical and experimental results for the response under e xternal vibration of one-dimensional columns of beads. Such systems ar e toy-models for dissipative granular materials. We show that a simple algorithm is able to reproduce the basic experimental features. Our m ain result is that an increase in acceleration leads to a transition f rom a condensed to a fluidized state of the columns. We discuss this c ross-over acceleration as a function of the number of beads and of the restitution coefficient (dissipation) per collision. Also, we show th at at high dissipation level clustered states (where all the beads are in contact) exist. The algorithm used by us reproduces well this clus ter dynamics.