On Influence of Aspect Ratio on Jamming Probability for Flows of Elliptical Disks in a Two-dimensional Rotating Hopper

Jamming arches and jamming probability of flowing elliptical disks at the opening of a two-dimensional rotating hopper is studied experimentally. A two-dimensional rotating hopper of Plexiglas with variable opening width and slope is constructed to conduct quasi two-dimensional flows of elliptical disks with different aspect ratios. Results show that the jamming probability and jamming arch structures are significantly influenced by the aspect ratio. There exist an upper and a lower limit of the hopper opening width, in which the jamming probability decreases monotonically as the opening width increases. When the opening is smaller than the lower limit, completely jamming takes place, while above the upper limit no jamming appears. As the aspect ratio increases, the jamming probability increases correspondingly for fixed hopper slope and opening width. For the jamming arch structures, increasing the aspect ratio tends to induce smaller horizontal average span, with a fluctuating tendency of the vertical average span for fixed values of the average arch number. For a fixed horizontal average span, increasing the aspect ratio gives rise to increase the average arch number. These imply that, for less narrow disks, the induced jamming arches are more semi-circular, while relatively flat jamming arches are triggered when disks are more narrow. The study delivers a physical mechanism of jamming phenomena of elliptical disks in a two-dimensional rotating hopper.