The size segregation of polydispersed particles stored in a container was studied experimentally by tapping varying the number of taps and the falling height of the container. Tested particles ranged from 150-600μm in size.
It was found that the smaller particles were concentrated at the vicinity of the container bottom, while larger particles were concentrated at the upper-side. The mass median diameter (MMD) of the particles concentrated along the container bottom became smaller as the number of tapping increased and converged to a certain value. The deviation of this value from the MMD of the feed-particles was almost proportional to the square root of the falling height. This fact showed that the deviation in MMD was related to the impact force of particles which was induced by the tapping.
Visualization of particle movement was also carried out by the use of colored particles. It was found that the particle recirculation was induced in the container by the tapping; i. e. at the center of the container, particles were rising from the bottom to the surface of the particle-layer, while particles were dropping in the vicinity of the periphery where smaller particles moved down faster than larger particles. On the other hand, larger particles moved faster than smaller particles from the periphery to the center. Thus, it was confirmed that such differences in the movement between larger and smaller particles caused the vertical size segregation of the particles in the container.