242 research outputs found
Nonequilibrium identities of granular vibrating beds
We derive the integral fluctuation theorem around a nonequilibrium stationary
state for frictionless and soft core granular particles under an external
vibration achieved by a balance between an external vibration and inelastic
collisions. We also discuss the connection between the integral fluctuation
theorem and the generalized Green-Kubo formula.Comment: 15 pages, no figures to be published in Comptes rendus - M\'ecanique
as Proceedings of EuroMech2012 at Graz, Austri
Generalized Green-Kubo formula for a dissipative quantum system
A generalized Green-Kubo formula is derived for a quantum dissipative system
of driven Brownian particle, in which the coupling between the system and the
environment is linear. The structure is essentially the same as that for the
generalized Green-Kubo formula for driven granular particles. It is
demonstrated that the correction to the conventional Green-Kubo formula is zero
for a free Brownian particle.Comment: 12 pages, no figures. Prog. Theor. Phys. Suppl. (to be published
Impact-Induced Hardening in Dense Frictional Suspensions
By employing the lattice Boltzmann method, we perform simulations of dense
suspensions under impacts, which incorporate the contact between suspended
particles as well as the free surface of the suspension. Our simulation for a
free falling impactor on a dense suspension semi-quantitatively reproduces
experimental results, where we observe rebounds of the impactor by the
suspension containing frictional particles for high speed impact and high
volume fraction shortly after the impact before subsequently sinking. We
observe that the response depends on the radius of the impactor, which leads to
fitting our simulation data to a phenomenological model based on the Hertzian
contact theory. When the rebound takes place, percolated force chains are
formed by the frictional contacts between suspended particles. Furthermore,
persistent homology analysis is used to elucidate the significance of the
topological structure of the force chains, where the total persistence of
connected components correlates with the force supporting the impactor
Kinetic theory of discontinuous shear thickening
A simple kinetic theory to exhibit a discontinuous shear thickening (DST) is
proposed. The model includes the collision integral and the friction from
environment as well as a thermostat term characterized by . The
viscosity of this model is proportional to for large shear rate
, while it is Newtonian for low . The emergence of the
DST is enhanced for lower density and lower nonzero .Comment: 4 pages, 2 figures, Powders and Grains 2017 (in press
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