Bistability of surface levels in two dimensional vibrating particle beds with two partitions

This paper describes the bistability of surface levels in vibrating particl e beds. When a tube is vertically immersed in a particle bed, and the vesse l containing the particles is subjected to vertical vibrations, the surface of the particle bed in the tube stabilizes at a level different from that outside the tube. The present study uses a two dimensional vessel. The vess el is partitioned into three sections, a central and two side sections, by the use of two vertical plates whose lower ends are set at 25 mm from the v essel base. Five sizes of glass beads (mean diameters in the range 116-1090 mu m) were used. It is found that the bed surface sometimes stabilizes at two different levels when a series of experiments is conducted by changing the initial two surface levels, with other experimental conditions fixed. T he causes of this bistability are discussed.