Bulk motion of granular matter in an agitated cylindrical bed

TL;DR

This study investigates various bulk motion modes in a granular bed within a vibrating cylindrical pan, revealing complex behaviors like heap formation, toroidal circulation, and surface waves as vibration frequency increases.

Contribution

It provides a detailed experimental characterization of the different bulk dynamical modes in a vibrated granular bed and discusses their origins related to pan motion.

Findings

Heap formation and rotation at low frequency

Toroidal mode with circulation patterns at intermediate frequency

Surface modulations such as waves and sectors at high frequency

Abstract

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 centre 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.