title: Spiral trajectory in the horizontal Brazil nut effect.
abstract: An intruder to a group of identical beads contained in a circular plate which is subjected to a circular vibration will trace approximately a cyclic spiral. The trajectory is a result of both migration and rotation. The intruder migrates in the radial direction while rotating with a constant speed with respect to the center of mass of the whole group of beads. The rotation velocity is due to friction between the beads and the container wall and determined by the vibration amplitude and the number of beads. The migration direction is dependent on the size ratio and mass ratio of the intruder to the background beads. The migration speed is constant for the outward migration, but decreases gradually when the intruder migrates toward the center of mass of the whole cluster for the inward case.
authors.affiliation: Department of Physics, National Chung-Hsing University, Taichung, Taiwan.
authors.forename: Fei Fang
authors.initials: FF
authors.lastname: Chung
authors.forename: Chia-Yi
authors.initials: CY
authors.lastname: Ju
authors.forename: Sy-Sang
authors.initials: SS
authors.lastname: Liaw