Bulk motion of granular matter in an agitated cylindrical bed.

Experimental results are reported for the bulk motion induced in a bed of granular matter contained in a cylindrical pan with a flat bottom subjected to simultaneous vertical and horizontal vibrations. The motion in space of the moving pan is quantified. A number of distinct bulk dynamical modes are observed in which the particle bed adopts different shapes and motions. At the lowest pan excitation frequency omega , the bed forms a "heap," and rotates about the cylinder axis. As omega is increased, a more complex "toroidal" mode appears in which the bed takes the shape of a torus; in this mode, circulation occurs both about the cylinder axis, and also radially, with particles moving from the outer edge of the pan to the center on the top surface of the bed, and back to the outer edge along the pan bottom. At the highest omega , surface modulations ("surface waves" and "sectors") of the toroidal mode occur. The origin of this family of behavior in terms of the pan motion is discussed.