title: Core precession and global modes in granular bulk flow.
abstract: We report a novel transition to core precession for granular flows in a split-bottomed shear cell. This transition is related to a qualitative change in the 3D flow structure: For shallow layers of granular material, the shear zones emanating from the split reach the free surface, while for deep layers the shear zones meet below the surface, causing precession. The surface velocities reflect this transition by a change of symmetry. As a function of layer depth, we find that three qualitatively different smooth and robust granular flows can be created in this simple shearing geometry.
authors.affiliation: Kamerlingh Onnes Lab, Leiden University, Post Office box 9504, 2300 RA Leiden, Netherlands.
authors.forename: Denis
authors.initials: D
authors.lastname: Fenistein
authors.forename: Jan-Willem
authors.initials: JW
authors.lastname: van de Meent
authors.forename: Martin
authors.initials: M
authors.lastname: van Hecke