Sinking and recirculation of large intruders in vertically vibrated granular beds

• Experiments are described in which air-immersed grains within different containers are exposed to vertical vibrations.
• A novel adapted framework for visualization and evaluation of molecular dynamic type simulation results is introduced.
• The vigorous granular convection was observed to drag a large, low-density object into the bed at Γ = 6.
• The importance of air grain interactions in the sinking process is highlighted.
• This work may pave the way for further understanding of dense granular flows.

A series of experiments are described in which air-immersed grains within different containers are exposed to vertical vibrations. When the peak acceleration relative to gravity exceeded Γ = 6 at 49 Hz), tilted cavitating beds were formed. Then, when a large, low-density object was put onto the free surface, the vigorous granular convection dragged it into the bed. The large object was not being dragged into the bed at Γ > 6 when the air pressure inside the container fell well below1 Torr. These findings, as well as those from computer simulations, confirm the key role played by large air cavities such as swallow holes in submerging large, low-density objects into a granular bed.

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