title: Frictional Fluid Dynamics and Plug Formation in Multiphase Millifluidic Flow.
abstract: We study experimentally the flow and patterning of a granular suspension displaced by air inside a narrow tube. The invading air-liquid interface accumulates a plug of granular material that clogs the tube due to friction with the confining walls. The gas percolates through the static plug once the gas pressure exceeds the pore capillary entry pressure of the packed grains, and a moving accumulation front is reestablished at the far side of the plug. The process repeats, such that the advancing interface leaves a trail of plugs in its wake. Further, we show that the system undergoes a fluidization transition-and complete evacuation of the granular suspension-when the liquid withdrawal rate increases beyond a critical value. An analytical model of the stability condition for the granular accumulation predicts the flow regime.
authors.affiliation: Department of Physics, University of Oslo, P.O. Box 1048 Blindern Oslo, Norway.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Dumazer
authors.affiliation: College of Engineering, Swansea University, Bay Campus, Swansea SA1 8EN, United Kingdom.
authors.forename: Bjørnar
authors.initials: B
authors.lastname: Sandnes
authors.affiliation: Department of Physics, University of Oslo, P.O. Box 1048 Blindern Oslo, Norway.
authors.forename: Monem
authors.initials: M
authors.lastname: Ayaz
authors.affiliation: Department of Physics, University of Oslo, P.O. Box 1048 Blindern Oslo, Norway.
authors.forename: Knut Jørgen
authors.initials: KJ
authors.lastname: Måløy
authors.affiliation: Department of Physics, University of Oslo, P.O. Box 1048 Blindern Oslo, Norway.
authors.forename: Eirik Grude
authors.initials: EG
authors.lastname: Flekkøy