807 research outputs found
Lattice-Gas Simulations of Ternary Amphiphilic Fluid Flow in Porous Media
We develop our existing two-dimensional lattice-gas model to simulate the
flow of single-phase, binary-immiscible and ternary-amphiphilic fluids. This
involves the inclusion of fixed obstacles on the lattice, together with the
inclusion of ``no-slip'' boundary conditions. Here we report on preliminary
applications of this model to the flow of such fluids within model porous
media. We also construct fluid invasion boundary conditions, and the effects of
invading aqueous solutions of surfactant on oil-saturated rock during
imbibition and drainage are described.Comment: 9 pages, 6 figures (1 and 6 are in color), RevTeX with epsf and
graphic
Two-dimensional hydrodynamic lattice-gas simulations of binary immiscible and ternary amphiphilic fluid flow through porous media
The behaviour of two dimensional binary and ternary amphiphilic fluids under
flow conditions is investigated using a hydrodynamic lattice gas model. After
the validation of the model in simple cases (Poiseuille flow, Darcy's law for
single component fluids), attention is focussed on the properties of binary
immiscible fluids in porous media. An extension of Darcy's law which explicitly
admits a viscous coupling between the fluids is verified, and evidence of
capillary effects are described. The influence of a third component, namely
surfactant, is studied in the same context. Invasion simulations have also been
performed. The effect of the applied force on the invasion process is reported.
As the forcing level increases, the invasion process becomes faster and the
residual oil saturation decreases. The introduction of surfactant in the
invading phase during imbibition produces new phenomena, including
emulsification and micellisation. At very low fluid forcing levels, this leads
to the production of a low-resistance gel, which then slows down the progress
of the invading fluid. At long times (beyond the water percolation threshold),
the concentration of remaining oil within the porous medium is lowered by the
action of surfactant, thus enhancing oil recovery. On the other hand, the
introduction of surfactant in the invading phase during drainage simulations
slows down the invasion process -- the invading fluid takes a more tortuous
path to invade the porous medium -- and reduces the oil recovery (the residual
oil saturation increases).Comment: 48 pages, 26 figures. Phys. Rev. E (in press
A reduced model for shock and detonation waves. I. The inert case
We present a model of mesoparticles, very much in the Dissipative Particle
Dynamics spirit, in which a molecule is replaced by a particle with an internal
thermodynamic degree of freedom (temperature or energy). The model is shown to
give quantitavely accurate results for the simulation of shock waves in a
crystalline polymer, and opens the way to a reduced model of detonation waves
Resolution of the Nested Hierarchy for Rational sl(n) Models
We construct Drinfel'd twists for the rational sl(n) XXX-model giving rise to
a completely symmetric representation of the monodromy matrix. We obtain a
polarization free representation of the pseudoparticle creation operators
figuring in the construction of the Bethe vectors within the framework of the
quantum inverse scattering method. This representation enables us to resolve
the hierarchy of the nested Bethe ansatz for the sl(n) invariant rational
Heisenberg model. Our results generalize the findings of Maillet and Sanchez de
Santos for sl(2) models.Comment: 25 pages, no figure
On factorizing -matrices in and spin chains
We consider quantum spin chains arising from -fold tensor products of the
fundamental evaluation representations of and .
Using the partial -matrix formalism from the seminal work of Maillet and
Sanchez de Santos, we derive a completely factorized expression for the
-matrix of such models and prove its equivalence to the expression obtained
by Albert, Boos, Flume and Ruhlig. A new relation between the -matrices and
the Bethe eigenvectors of these spin chains is given.Comment: 30 page
A reduced model for shock and detonation waves. II. The reactive case
We present a mesoscopic model for reactive shock waves, which extends a
previous model proposed in [G. Stoltz, Europhys. Lett. 76 (2006), 849]. A
complex molecule (or a group of molecules) is replaced by a single
mesoparticle, evolving according to some Dissipative Particle Dynamics.
Chemical reactions can be handled in a mean way by considering an additional
variable per particle describing a rate of reaction. The evolution of this rate
is governed by the kinetics of a reversible exothermic reaction. Numerical
results give profiles in qualitative agreement with all-atom studies
Permutation-type solutions to the Yang-Baxter and other n-simplex equations
We study permutation type solutions to n-simplex equations, that is,
solutions whose R matrix can be written as a product of delta- functions
depending linearly on the indices. With this ansatz the D^{n(n+1)} equations of
the n-simplex equation reduce to an [n(n+1)/2+1]x[n(n+1)/2+1] matrix equation
over Z_D. We have completely analyzed the 2-, 3- and 4-simplex equations in the
generic D case. The solutions show interesting patterns that seem to continue
to still higher simplex equations.Comment: 20 pages, LaTeX2e. to appear in J. Phys. A: Math. Gen. (1997
Current Algebra of Super WZNW Models
We derive the current algebra of supersymmetric principal chiral models with
a Wess-Zumino term. At the critical point one obtains two commuting super
Kac-Moody algebra as expected, but in general there are intertwining fields
connecting both right and left sectors, analogously to the bosonic case.
Moreover, in the present supersymmetric extension we have a quadratic algebra,
rather than an affine Lie algebra, due to the mixing between bosonic and
fermionic fields since the purely fermionic sector displays a Lie algebra as
well.Comment: 13 page
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.
Drinfeld Twists and Symmetric Bethe Vectors of Supersymmetric Fermion Models
We construct the Drinfeld twists (factorizing -matrices) of the
-invariant fermion model. Completely symmetric representation of the
pseudo-particle creation operators of the model are obtained in the basis
provided by the -matrix (the -basis). We resolve the hierarchy of the
nested Bethe vectors in the -basis for the supersymmetric model.Comment: Latex File, 24 pages, no figure, some misprints are correcte
- …