35,044 research outputs found
A three-dimensional lattice gas model for amphiphilic fluid dynamics
We describe a three-dimensional hydrodynamic lattice-gas model of amphiphilic
fluids. This model of the non-equilibrium properties of oil-water-surfactant
systems, which is a non-trivial extension of an earlier two-dimensional
realisation due to Boghosian, Coveney and Emerton [Boghosian, Coveney, and
Emerton 1996, Proc. Roy. Soc. A 452, 1221-1250], can be studied effectively
only when it is implemented using high-performance computing and visualisation
techniques. We describe essential aspects of the model's theoretical basis and
computer implementation, and report on the phenomenological properties of the
model which confirm that it correctly captures binary oil-water and
surfactant-water behaviour, as well as the complex phase behaviour of ternary
amphiphilic fluids.Comment: 34 pages, 13 figures, high resolution figures available on reques
Three dimensional hysdrodynamic lattice-gas simulations of binary immiscible and ternary amphiphilic flow through porous media
We report the results of a study of multiphase flow in porous media. A
Darcy's law for steady multiphase flow was investigated for both binary and
ternary amphiphilic flow. Linear flux-forcing relationships satisfying Onsager
reciprocity were shown to be a good approximation of the simulation data. The
dependence of the relative permeability coefficients on water saturation was
investigated and showed good qualitative agreement with experimental data.
Non-steady state invasion flows were investigated, with particular interest in
the asymptotic residual oil saturation. The addition of surfactant to the
invasive fluid was shown to significantly reduce the residual oil saturation.Comment: To appear in Phys. Rev.
Design of Gas - Surfactant Injection for Carbon Dioxide Storage in a North Sea Aquifer using Streamline-Based Simulation
Imperial Users onl
Kinetics of Phase ordering in Microemulsions and Micellar Solutions
We review the models developed and techniques used in recent years to study
the kinetics of phase ordering in a class of complex fluids, namely, ternary
microemulsions and micellar solutions.Comment: 10 pages in REVTEX, 4 Postscript figures. To appear in "Phase
Transitions in Complex Fluids", Eds. P. Toledano and A. M. Figueiredo Neto
(World Scientific, 1997
Experimental and computational studies of water drops falling through model oil with surfactant and subjected to an electric field
The behaviour of a single sub-millimetre-size water drop falling through a
viscous oil while subjected to an electric field is of fundamental importance
to industrial applications such as crude oil electrocoalescers. Detailed
studies, both experimental and computational, have been performed previously,
but an often challenging issue has been the characterization of the fluids. As
numerous authors have noted, it is very difficult to have a perfectly clean
water-oil system even for very pure model oils, and the presence of trace
chemicals may significantly alter the interface behaviour. In this work, we
consider a well- characterized water-oil system where controlled amounts of a
surface active agent (Span 80) have been added to the oil. This addition
dominates any trace contaminants in the oil, such that the interface behaviour
can also be well-characterized. We present the results of experiments and
corresponding two-phase- flow simulations of a falling water drop covered in
surfactant and subjected to a monopolar square voltage pulse. The results are
compared and good agreement is found for surfactant concentrations below the
critical micelle concentration.Comment: 7 pages, 9 figures, to be presented at the ICDL 2014 conferenc
Lattice-gas simulations of Domain Growth, Saturation and Self-Assembly in Immiscible Fluids and Microemulsions
We investigate the dynamical behavior of both binary fluid and ternary
microemulsion systems in two dimensions using a recently introduced
hydrodynamic lattice-gas model of microemulsions. We find that the presence of
amphiphile in our simulations reduces the usual oil-water interfacial tension
in accord with experiment and consequently affects the non-equilibrium growth
of oil and water domains. As the density of surfactant is increased we observe
a crossover from the usual two-dimensional binary fluid scaling laws to a
growth that is {\it slow}, and we find that this slow growth can be
characterized by a logarithmic time scale. With sufficient surfactant in the
system we observe that the domains cease to grow beyond a certain point and we
find that this final characteristic domain size is inversely proportional to
the interfacial surfactant concentration in the system.Comment: 28 pages, latex, embedded .eps figures, one figure is in colour, all
in one uuencoded gzip compressed tar file, submitted to Physical Review
Charge frustration in complex fluids and in electronic systems
The idea of charge frustration is applied to describe the properties of such
diverse physical systems as oil-water-surfactant mixtures and metal-ammonia
solutions. The minimalist charge-frustrated model possesses one energy scale
and two length scales. For oil-water-surfactant mixtures, these parameters have
been determined starting from the microscopic properties of the physical
systems under study. Thus microscopic properties are successfully related to
the observed mesoscopic structure.Comment: latex type, 13 page
Coarsening dynamics of ternary amphiphilic fluids and the self-assembly of the gyroid and sponge mesophases: lattice-Boltzmann simulations
By means of a three-dimensional amphiphilic lattice-Boltzmann model with
short-range interactions for the description of ternary amphiphilic fluids, we
study how the phase separation kinetics of a symmetric binary immiscible fluid
is altered by the presence of the amphiphilic species. We find that a gradual
increase in amphiphile concentration slows down domain growth, initially from
algebraic, to logarithmic temporal dependence, and, at higher concentrations,
from logarithmic to stretched-exponential form. In growth-arrested
stretched-exponential regimes, at late times we observe the self-assembly of
sponge mesophases and gyroid liquid crystalline cubic mesophases, hence
confirming that (a) amphiphile-amphiphile interactions need not be long-ranged
in order for periodically modulated structures to arise in a dynamics of
competing interactions, and (b) a chemically-specific model of the amphiphile
is not required for the self-assembly of cubic mesophases, contradicting claims
in the literature. We also observe a structural order-disorder transition
between sponge and gyroid phases driven by amphiphile concentration alone or,
independently, by the amphiphile-amphiphile and the amphiphile-binary fluid
coupling parameters. For the growth-arrested mesophases, we also observe
temporal oscillations in the structure function at all length scales; most of
the wavenumbers show slow decay, and long-term stationarity or growth for the
others. We ascribe this behaviour to a combination of complex amphiphile
dynamics leading to Marangoni flows.Comment: 16 pages, 13 figures. Accepted for publication in Phys. Rev. E.
(Replaced for the latest version, in press.) Higher-quality figures can be
sent upon reques
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