Sinking and recirculation of large intruders in vertically vibrated granular beds

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.