title: Sedimentation instabilities: impact of the fluid compressibility and viscosity.
abstract: The effect of an interstitial fluid on the mixing of sedimenting grains is studied numerically in a closed rectangular Hele-Shaw cell. We investigate the impact of the fluid compressibility and fluid viscosity on the dynamics and structures of the granular Rayleigh-Taylor instability. First we discuss the effect of the fluid compressibility on the initial fluid pressure evolution and on the dynamics of the particles. Here, the emerging patterns do not seem highly affected by the compressibility change studied. To characterize the patterns and motion the combined length of the particle trajectories in relation to the movement of the center of mass is analyzed, and the separation of particle pairs is measured as a function of the fluid viscosity.
authors.affiliation: Department of Physics, University of Oslo, PO Box 1048, 0316 Oslo, Norway.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Niebling
authors.forename: Eirik G
authors.initials: EG
authors.lastname: Flekkøy
authors.forename: Knut Jørgen
authors.initials: KJ
authors.lastname: Måløy
authors.forename: Renaud
authors.initials: R
authors.lastname: Toussaint
mesh_terms: D004058:Diffusion; D057446:Hydrodynamics; D008962:Models, Theoretical; D014783:Viscosity