Particle‐level dynamics of clusters: Experiments in a gas‐fluidized bed

Abstract

AbstractClustering is critical to understanding the multiscale behavior of fluidization. However, its time‐resolved evolution at the particle level is seldom touched. Here, we explore both the time‐averaged and time‐resolved dynamics of clusters in a quasi‐2D fluidized bed. Particle tracking velocimetry is adopted, and then clusters are identified by using Voronoi analysis. The time‐averaged results show that the number distribution of the cluster size follows a power law () except for large clusters (nc > 100). Time‐resolved analysis demonstrates that the cluster coalescence can be simplified as a collision between two inelastic clusters, during which the mean speed, kinetic energy, and total Voronoi cell area of particles decrease until the formation of the big cluster. Then, a model is proposed to predict its energy loss, which gives ΔE ~ t3/2. Moreover, the breakup of the cluster is linked to increasing dimensionless torque on the particles.