Temporally Heterogeneous Dynamics in Granular Flows

Abstract

Granular simulations are used to probe the particle scale dynamics at short, intermediate, and long time scales for gravity driven, dense granular flows down an inclined plane. On approach to the angle of repose, where motion ceases, the dynamics become intermittent over intermediate times, with strong temporal correlations between particle motionstemporally heterogeneous dynamics. This intermittency is characterised through large scale structural events whereby the contact network periodically spans the system. A characteristic time scale associated with these processes increases as the stopped state is approached. These features are discussed in the context of the dynamics of supercooled liquids near the glass transition.

Avalanche dynamics on a rough inclined plane

“…(3-4) rather than by Eq. (11). We can directly test the conditions for which a < c + is valid in terms of avalanche height.…”

“…The transition between continuous and avalanching flow as a function of input mass flux is hysteretic [3,10]. Studies using diffusing-wave spectroscopy [7] and molecular dynamics simulations [11] provided detailed properties of this intermittency. The experimental results show that the microscopic grain dynamics are similar in the continuous and intermittent flow regimes [8].…”

Dynamic compressibility of dense granular shear flows

“…It has been revealed indirectly by instabilities, in situations where acoustic waves are spontaneously emitted during a dense granular flow (see [2] for a review): when sufficiently dry, avalanches flowing at the surface of a dune produce a loud sound known as the 'song of dunes ' [15-18]; vibrations are also produced during the discharge of a granular flow from a silo or any elongated tube [19]; soft mono-disperse particles flowing on an inclined plane near the angle of repose exhibit spontaneous oscillations at the resonant frequency of elastic waves [20,21]. These phenomena have mostly been associated to the elastic deformations of the grains.…”

Effect of vibration on solid-to-liquid transition in small granular systems under shear

“…[18][19][20], all variables and parameters are scaled by the acceleration due to gravity g, mean particle size d p , and mean particle mass m p (note while we scale for convenience the acceleration by g, there is no force of gravity in our simulations). We model the interaction between individual grains using the "soft contact" approach described in [18][19][20][21][22][23]; the grains are treated as non-cohesive inelastic disk like particles, interacting by normal and shear forces wherever they overlap. Normal interactions are modeled by the spring-dashpot model [31], and shear interactions are modeled by the technique developed by Cundall and Strack [32].…”