title: Spiral patterns in oscillated granular layers.
abstract: Cell-filling spiral patterns are observed in a vertically oscillated layer of granular material when the oscillation amplitude is suddenly increased from below the onset of pattern formation into the region where stripe patterns appear for quasistatic increases in amplitude. These spirals are transients and decay to stripe patterns with defects. A transient spiral defect chaos state is also observed. We describe the behavior of the spirals, and the way in which they form and decay. Our results are compared with those for similar spiral patterns in Rayleigh-Bénard convection in fluids.
authors: Department of Physics and Physical Oceanography, Memorial University of Newfoundland, St. John's, Newfoundland, Canada A1B 3X7. jdebruyn@physics.mun.ca
authors: J R
authors: JR
authors: de Bruyn
authors: B C
authors: BC
authors: Lewis
authors: M D
authors: MD
authors: Shattuck
authors: H L
authors: HL
authors: Swinney