5 research outputs found
Cooling and aggregation in wet granulates
Wet granular materials are characterized by a defined bond energy in their
particle interaction such that breaking a bond implies an irreversible loss of
a fixed amount of energy. Associated with the bond energy is a nonequilibrium
transition, setting in as the granular temperature falls below the bond energy.
The subsequent aggregation of particles into clusters is shown to be a
self-similar growth process with a cluster size distribution that obeys
scaling. In the early phase of aggregation the clusters are fractals with
D_f=2, for later times we observe gelation. We use simple scaling arguments to
derive the temperature decay in the early and late stages of cooling and verify
our results with event-driven simulations.Comment: 4 pages, 6 figures, suggestions of the referees implemented, EPAPS
supplementary material added:
http://netserver.aip.org/cgi-bin/epaps?ID=E-PRLTAO-102-00391
Dilute Wet Granulates: Nonequilibrium Dynamics and Structure Formation
We investigate a gas of wet granular particles, covered by a thin liquid
film. The dynamic evolution is governed by two-particle interactions, which are
mainly due to interfacial forces in contrast to dry granular gases. When two
wet grains collide, a capillary bridge is formed and stays intact up to a
certain distance of withdrawal when the bridge ruptures, dissipating a fixed
amount of energy. A freely cooling system is shown to undergo a nonequillibrium
dynamic phase transition from a state with mainly single particles and fast
cooling to a state with growing aggregates, such that bridge rupture becomes a
rare event and cooling is slow. In the early stage of cluster growth,
aggregation is a self-similar process with a fractal dimension of the
aggregates approximately equal to D_f ~ 2. At later times, a percolating
cluster is observed which ultimately absorbs all the particles. The final
cluster is compact on large length scales, but fractal with D_f ~ 2 on small
length scales.Comment: 14 pages, 20 figure