title: Gas-driven subharmonic waves in a vibrated two-phase granular material.
abstract: Vibrated powders exhibit striking phenomena: subharmonic waves, oscillons, convection, heaping, and even bubbling. We demonstrate novel rectangular profile subharmonic waves for vibrated granular material, that occur uniquely in the two-phase case of grains, and a fluid, such as air. These waves differ substantially from those for the gas-free case, exhibit different dispersion relations, and occur for specific shaking parameters and air pressure, understandable with gas-particle flow models. These waves occur when the gas diffusively penetrates the granular layer in a time comparable to the shaker period. As the pressure is lowered towards P =0, the granular-gas system exhibits a Knudsen regime. This instability provides an opportunity to quantitatively test models of two-phase flow.
authors.affiliation: Department of Physics & Center for Nonlinear and Complex Systems, Duke University, Durham, NC 27708-0305, USA. matas@hmg.inpg.fr
authors.forename: J-P
authors.initials: JP
authors.lastname: Matas
authors.forename: J
authors.initials: J
authors.lastname: Uehara
authors.forename: R P
authors.initials: RP
authors.lastname: Behringer
mesh_terms: D000388:Air; D004058:Diffusion; D005740:Gases; D008962:Models, Theoretical; D011827:Radiation; D013997:Time Factors; D014732:Vibration
chemical_list: D005740:Gases