Stationary and rotational axisymmetric granular column collapse
The experiments presented investigate the collapse of a granular column on a stationary surface and a rotating table. A cylinder of radius r0 was positioned on the surface and filled with particulate to a height h0, giving an aspect ratio a = h0/r0. The cylinder was quickly removed and the resultant pile investigated. Spatial and geometric data obtained pre and post collapse were used to derive empirical relations. A high speed camera collected temporal data of the collapse in both cases.

In the stationary case a 3D laser scanner quantified measurements of the resultant pile from which scalings involving aspect ratio were derived. The spatial data revealed that the final runout of the pile is not only dependent on the aspect ratio of the initial geometry as previously thought [Lube et al., 2004; Lajeunesse et al., 2004] but also the initial column radius. This was also observed to be true for the angle at the base of the deposit. Theoretical considerations and obtained data allowed the summital angle to be described by material parameters and aspect ratio. X-ray computer tomography allowed observation and quantification of the internal phenomenology to include the granular packing and the failure surface over which the collapse occurs.

Consideration was given to the effect of rotation on previously obtained spatial and temporal scalings. Increasing the rotation rate encourages growth in the final pile radius until a critical frequency is reached where material loss begins to occur. Any further increase for fixed a results in further material loss and a decrease in the final pile radius. Initial results from DEM (discrete element method) simulations of granular collapse on a rotating table are presented for the case of spherical particles. In these simulations a spiral pattern evolves where all particles have left the central pile. Laboratory experiments have yet to demonstrate this exact patterning, but comparison to similar investigations suggests its existence.