65 research outputs found
Colloidal Jamming at Interfaces: a Route to Fluid-bicontinuous Gels
Colloidal particles or nanoparticles, with equal affinity for two fluids, are
known to adsorb irreversibly to the fluid-fluid interface. We present
large-scale computer simulations of the demixing of a binary solvent containing
such particles. The newly formed interface sequesters the colloidal particles;
as the interface coarsens, the particles are forced into close contact by
interfacial tension. Coarsening is dramatically curtailed, and the jammed
colloidal layer seemingly enters a glassy state, creating a multiply connected,
solid-like film in three dimensions. The resulting gel contains percolating
domains of both fluids, with possible uses as, for example, a microreaction
medium
Path sampling for lifetimes of metastable magnetic skyrmions and direct comparison with Kramers' method
We perform a direct comparison between Kramers' method in many dimensions --
i.e., Langer's theory -- adapted to magnetic spin systems, and a path sampling
method in the form of forward flux sampling, as a means to compute collapse
rates of metastable magnetic skyrmions. We show that a good agreement is
obtained between the two methods. We report variations of the attempt frequency
associated with skyrmion collapse by three to four orders of magnitude when
varying the applied magnetic field by 5 of the exchange strength, which
confirms the existence of a strong entropic contribution to the lifetime of
skyrmions. This demonstrates that in complex systems, the knowledge of the rate
prefactor, in addition to the internal energy barrier, is essential in order to
properly estimate a lifetime.Comment: 5 pages, 5 figures (main text), 8 pages including supplemental
materia
Inertial effects in three dimensional spinodal decomposition of a symmetric binary fluid mixture: A lattice Boltzmann study
The late-stage demixing following spinodal decomposition of a
three-dimensional symmetric binary fluid mixture is studied numerically, using
a thermodynamicaly consistent lattice Boltzmann method. We combine results from
simulations with different numerical parameters to obtain an unprecendented
range of length and time scales when expressed in reduced physical units. Using
eight large (256^3) runs, the resulting composite graph of reduced domain size
l against reduced time t covers 1 < l < 10^5, 10 < t < 10^8. Our data is
consistent with the dynamical scaling hypothesis, that l(t) is a universal
scaling curve. We give the first detailed statistical analysis of fluid motion,
rather than just domain evolution, in simulations of this kind, and introduce
scaling plots for several quantities derived from the fluid velocity and
velocity gradient fields.Comment: 49 pages, latex, J. Fluid Mech. style, 48 embedded eps figs plus 6
colour jpegs for Fig 10 on p.2
Nonequilibrium steady states in sheared binary fluids
We simulate by lattice Boltzmann the steady shearing of a binary fluid
mixture undergoing phase separation with full hydrodynamics in two dimensions.
Contrary to some theoretical scenarios, a dynamical steady state is attained
with finite domain lengths in the directions ( of velocity and
velocity gradient. Apparent scaling exponents are estimated as
and . We discuss
the relative roles of diffusivity and hydrodynamics in attaining steady state.Comment: 4 pages, 3 figure
Binary fluids under steady shear in three dimensions
We simulate by lattice Boltzmann the steady shearing of a binary fluid
mixture with full hydrodynamics in three dimensions. Contrary to some
theoretical scenarios, a dynamical steady state is attained with finite
correlation lengths in all three spatial directions. Using large simulations we
obtain at moderately high Reynolds numbers apparent scaling expon ents
comparable to those found by us previously in 2D. However, in 3D there may be a
crossover to different behavior at low Reynolds number: accessing this regime
requires even larger computational resource than used here.Comment: 4 pages, 3 figure
Lattice Boltzmann for Binary Fluids with Suspended Colloids
A new description of the binary fluid problem via the lattice Boltzmann
method is presented which highlights the use of the moments in constructing two
equilibrium distribution functions. This offers a number of benefits, including
better isotropy, and a more natural route to the inclusion of multiple
relaxation times for the binary fluid problem. In addition, the implementation
of solid colloidal particles suspended in the binary mixture is addressed,
which extends the solid-fluid boundary conditions for mass and momentum to
include a single conserved compositional order parameter. A number of simple
benchmark problems involving a single particle at or near a fluid-fluid
interface are undertaken and show good agreement with available theoretical or
numerical results.Comment: 10 pages, 4 figures, ICMMES 200
3D Spinodal Decomposition in the Inertial Regime
We simulate late-stage coarsening of a 3D symmetric binary fluid using a
lattice Boltzmann method. With reduced lengths and times l and t respectively
(scales set by viscosity, density and surface tension) our data sets cover 1 <
l
100 we find clear evidence of Furukawa's inertial scaling (l ~ t^{2/3}),
although the crossover from the viscous regime (l ~ t) is very broad. Though it
cannot be ruled out, we find no indication that Re is self-limiting (l ~
t^{1/2}) as proposed by M. Grant and K. R. Elder [Phys. Rev. Lett. 82, 14
(1999)].Comment: 4 pages, 3 eps figures, RevTex, minor changes to bring in line with
published version. Mobility values added to Table
- …