Period doubling motion in vertically vibrated granular beds

Experiments are performed to investigate the impact interaction between granular bed and container bottom, where the container is vertically vibrated. It is observed that the impact strength, controlled by the normalized vibration acceleration, undergoes a series of period doubling bifurcations, typically in the sequence of period-doubling, period-quadrupling, chaos, period-tripling, period-sextupling, chaos, period-quadrupling, period-octupling, and chaos. A condensed state of particles at the bottom of the container is observed, in which the particles are densely compacted and move as a bulk block in the vertical direction. Based on a completely inelastic bouncing ball model, a possible explanation for the bifurcation phenomena is presented.