Robust shape formation of driven granular matter by autotuning friction

Synopsis

A single layer of granular spheres and disks in a cylindrical orbital shaker self organizes to form a distinct asymmetrical shape. The shape formed, has several interesting features. The area of the shape has a power scaling with the number of spheres which is sublinear. It is marked by a sharp edge at the minimum of the confining centrifugal potential and has a curved rear end. Experimental data further indicate that the motion of individual spheres occur by toggling between rolling and sliding and due to the significant difference in rolling and sliding fricition the individual sphere attain a local time average coefficient of friction.