Circular Kinks on the Surface of Granular Material Rotated in a Tilted Spinning Bucket

摘要

We find that circular kinks form on the surface of granular material when theaxis of rotation is tilted more than the angle of internal friction of thematerial. Radius of the kinks is measured as a function of the spinning speedand the tilting angle. Stability consideration of the surface results in anexplanation that the kink is a boundary between the inner unstable and outerstable regions. A simple cellular automata model also displays kinks at thestability boundary.