title: Stochastic transitions and jamming in granular pipe flow.
abstract: We study a model granular suspension driven down a channel by an embedding fluid via computer simulations. We characterize the different system flow regimes and the stochastic nature of the transitions between them. For packing fractions below a threshold ϕ{m}, granular flow is disordered and exhibits an Ostwald-de Waele-type power-law shear-stress constitutive relation. Above ϕ{m}, two asymptotic states exist; disordered flow can persist indefinitely, yet, in a fraction of samples, the system self-organizes in an ordered form of flow where grains move in parallel ordered layers. In the latter regime, the Ostwald-de Waele relationship breaks down and a nearly solid plug appears in the center, with linear shear regions at the boundaries. Above a higher threshold ϕ{g}, an abrupt jamming transition is observed if ordering is avoided.
authors.affiliation: Department of Physics and Complexity Science Centre, University of Warwick, United Kingdom.
authors.forename: Samuel
authors.initials: S
authors.lastname: Brand
authors.forename: Robin C
authors.initials: RC
authors.lastname: Ball
authors.forename: Mario
authors.initials: M
authors.lastname: Nicodemi