Shear of granular materials composed of ellipses

Granular systems of disks (2D) and spheres (3D) under shear have been studied extensively. However, less attention has been paid to systems of non-spherical particles, i.e., ellipses, polygons, etc. Here we studied a quasi 2D granular system composed of ellipses under homogeneous simple shear. By tracking the positions and orientations of the ellipses, we have observed that they gradually rotate to align along a preferred direction as the shear strain increases. This preferred direction asymptotically approach a density-independent value at large strain. While first reported for disk systems, shear jamming is also observed for our ellipse system, as indicated by the increase of system pressure and coordination number with shear strain.