Collapse of a granular column under rotation

• A granular column is aligned centrally on table which is then set into rotation.
• The column is released and the flow dynamics of the pile is analysed.
• Scalings for the final height and final pile radius are derived.
• The time evolution of the deposit is considered.
• The duration of collapse was investigated where there was no volume loss.

Experimental results for the collapse of granular columns on a rotating table are presented. In the non-rotating case two flow regimes are exhibited dependent on the aspect ratio a = h0/r0, where h0 is the initial height and r0 is the initial column radius. Scaling relations for the characteristic geometrical properties of the collapsed column under varying rotation rates are obtained. As the rotation rate increases, material is lost from the main pile and travels to the edge of the rotating table. This results in a decrease in the final radius of the main collapsed pile, as material is lost during this secondary, rotation-induced spreading phase. The degree of mass ejection in the secondary spread increases with rotation frequency for a given initial aspect ratio. Analysis of the flow characteristics including time evolution and final pile height are also described.

Normalised final pile radius, r⁎, versus rotation frequency for various initial granular column aspect ratios. As frequency increases, final pile radius increases up to a critical value. Beyond this value, increasing frequency leads to a reduction in final pile radius following the envelope of critical radii for various aspect ratios.Figure optionsDownload as PowerPoint slide