Ternary Amphiphilic Fluids Research Articles

Pore scale study of amphiphilic fluids flow using the Lattice Boltzmann model

We study ternary amphiphilic fluid flow at pore scale using a “bottom-up” Lattice Boltzmann (LB) model. The model introduces a dipole to capture the amphiphilic structure of surfactant molecules, and characterizes microscopic fluid interactions at the kinetic level. We first verify the established model by three examples, i.e., interfacial tension test, phase separation, and droplet dynamics in shear flow. The numerical results show that surfactants reduce the interfacial tension (IFT), and are able to emulsify the amphiphilic fluids, and the contours of the droplets are quantitatively in agreement with the results of level set method. Then we study the droplet dynamics in a confined environment. The surfactants make the droplet easy to deform and break up in shear flow, but inhibit coalescence due to the Marangoni stress. Moreover, there are four typical patterns for droplet collisions, i.e. coalescence, breakup after coalescence, brushing past, and brushing back. Furthermore, we improve the model by considering the wettability reversal effect caused by surfactant adsorption onto walls, and find that surfactants can decrease the critical Bond number for oil detaching from walls by 90%. Finally, we simulate the surfactant-enhanced aquifer remediation (SEAR) or enhanced oil recovery (EOR) process in a 2D porous medium. Surfactants improve the oil recovery in all wetting conditions, but the surfactant loss due to adsorption onto walls diminishes the effect of IFT reduction.

LB3D: A parallel implementation of the Lattice-Boltzmann method for simulation of interacting amphiphilic fluids

We introduce the lattice-Boltzmann code LB3D, version 7.1. Building on a parallel program and supporting tools which have enabled research utilising high performance computing resources for nearly two decades, LB3D version 7 provides a subset of the research code functionality as an open source project. Here, we describe the theoretical basis of the algorithm as well as computational aspects of the implementation. The software package is validated against simulations of meso-phases resulting from self-assembly in ternary fluid mixtures comprising immiscible and amphiphilic components such as water–oil–surfactant systems. The impact of the surfactant species on the dynamics of spinodal decomposition are tested and quantitative measurement of the permeability of a body centred cubic (BCC) model porous medium for a simple binary mixture is described. Single-core performance and scaling behaviour of the code are reported for simulations on current supercomputer architectures. Program summaryProgram Title: LB3DProgram Files doi:http://dx.doi.org/10.17632/9g9x2wr8z8.1Licensing provisions: BSD 3-clauseProgramming language: FORTRAN90, Python, CNature of problem: Solution of the hydrodynamics of single phase, binary immiscible and ternary amphiphilic fluids. Simulation of fluid mixtures comprising miscible and immiscible fluid components as well as amphiphilic species on the mesoscopic scale. Observable phenomena include self-organisation of mesoscopic complex fluid phases and fluid transport in porous media.Solution method: Lattice-Boltzmann (lattice-Bhatnagar–Gross–Krook, LBGK) [1, 2, 3] method describing fluid dynamics in terms of the single particle velocity distribution function in a 3-dimensional discrete phase space (D3Q19) [4, 5, 6]. Multiphase interactions are modelled using a phenomenological pseudo-potential approach [7, 8] with amphiphilic interactions utilising an additional dipole field [9, 10]. Solid boundaries are modelled using simple bounce-back boundary conditions and additional pseudo-potential wetting interactions [11].Additional comments including Restrictions and Unusual features: The purpose of the release is the provision of a refactored minimal version of LB3D suitable as a starting point for the integration of additional features building on the parallel computation and IO functionality. [1]S. Succi, The Lattice Boltzmann Equation: For Fluid Dynamics and Beyond, Oxford University Press, 2001.[2]B. Dünweg, A. Ladd, Lattice Boltzmann simulations of soft matter systems, Adv. Poly. Sci. 221 (2009) 89–166[3]C. K. Aidun, J. R. Clausen, Lattice-Boltzmann Method for Complex Flows, Annual Review of Fluid Mechanics 42 (2010) 439.[4]X. He, L.-S. Luo, A priori derivation of the lattice-Boltzmann equation, Phys. Rev. E 55 (1997) R6333.[5]X. He, L.-S. Luo, Theory of the lattice Boltzmann method: from the Boltzmann equation to the lattice Boltzmann equation, Phys. Rev. E 56.[6]Y. H. Qian, D. D’Humiéres, P. Lallemand, Lattice BGK Models for Navier–Stokes Equation, Europhysics Letters 17 (1992) 479.[7]X. Shan, H. Chen, Lattice-Boltzmann model for simulating flows with multiple phases and components, Physical Review E 47 (1993) 1815.[8]X. Shan, G. Doolen, Multicomponent lattice-Boltzmann model with interparticle interaction, Journal of Statistical Physics 81 (1995) 379.[9]H. Chen, B. Boghosian, P.V. Coveney, M. Nekovee, A ternary lattice-Boltzmann model for amphiphilic fluids, Proceedings of the Royal Society of London A 456 (2000) 2043.[10]M. Nekovee, P. V. Coveney, H. Chen, B. M. Boghosian, Lattice-Boltzmann model for interacting amphiphilic fluids, Phys. Rev. E 62 (2000) 8282.[11]N. S. Martys, H. Chen, Simulation of multicomponent fluids in complex three-dimensional geometries by the lattice-Boltzmann method, Phys. Rev. E 53 (1996) 743.

Structural transitions and arrest of domain growth in sheared binary immiscible fluids and microemulsions

We investigate spinodal decomposition and structuring effects in binary immiscible and ternary amphiphilic fluid mixtures under shear by means of three-dimensional lattice Boltzmann simulations. We show that the growth of individual fluid domains can be arrested by adding surfactant to the system, thus forming a bicontinuous microemulsion. We demonstrate that the maximum domain size and the time of arrest depend linearly on the concentration of amphiphile molecules. In addition, we find that for a well-defined threshold value of amphiphile concentration, the maximum domain size and time of complete arrest do not change. For systems under constant and oscillatory shear we analyze domain growth rates in directions parallel and perpendicular to the applied shear. We find a structural transition from a sponge to a lamellar phase by applying a constant shear and the occurrence of tubular structures under oscillatory shear. The size of the resulting lamellae and tubes depends strongly on the amphiphile concentration, shear rate, and shear frequency.

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 wave numbers show slow decay, and long-term stationarity or growth for the others. We ascribe this behavior to a combination of complex amphiphile dynamics leading to Marangoni flows.

Steering in computational science: Mesoscale modelling and simulation

This paper outlines the benefits of computational steering for high performance computing applications. Lattice-Boltzmann mesoscale fluid simulations of binary and ternary amphiphilic fluids in two and three dimensions are used to illustrate the substantial improvements which computational steering offers in terms of resource efficiency and time to discover new physics. We discuss details of our current steering implementations and describe their future outlook with the advent of computational grids.

Simulations of amphiphilic fluids using mesoscale lattice-Boltzmann and lattice-gas methods

We compare two recently developed mesoscale models of binary immiscible and ternary amphiphilic fluids. We describe and compare the algorithms in detail and discuss their stability properties. The simulation results for the cases of self-assembly of ternary droplet phases and binary water-amphiphile sponge phases are compared and discussed. Both models require parallel implementation and deployment on large scale parallel computing resources in order to achieve reasonable simulation times for three-dimensional models. The parallelization strategies and performance on two distinct parallel architectures are compared and discussed. Large scale three-dimensional simulation of multiphase fluids requires the extensive use of high performance visualization techniques in order to enable the large quantities of complex data to be interpreted. We report on our experiences with two commercial visualization products: AVS and VTK. We also discuss the application and use of novel computational steering techniques for the more efficient utilization of high performance computing resources. We close the paper with some suggestions for the future development of both models.

Three-dimensional hydrodynamic lattice-gas simulations of ternary amphiphilic fluids under shear flow

We describe the implementation of shear flow in a three-dimensional lattice-gas model for amphiphilic fluids. We investigate the effect of shear on the morphology of the bicontinuous ternary microemulsion phase, and in particular its effect on the formation and stability of a lamellar phase. Metastable lamellar phases were observed for both 32(3) and 64(3) systems subjected to shear, and the stability of preformed lamellar phases under shear flow established for both 64(3) and 128(3) systems. The effect of micellization on interfacial behaviour in these phases is discussed in the context of the linear non-equilibrium thermodynamic theory of rate processes and nonlinear Becker-Döring aggregation theory.

Real-coded lattice gas model for ternary amphiphilic fluids.

We have developed an amphiphilic surfactant model in the framework of the real-coded lattice gas (RLG), in order to analyze the dynamics and structure of ternary fluids. Formation of both the oil-in-water and the bicontinuous microemulsion phases, as well as the reduction of surface tension by adsorption of surfactant at interface are successfully reproduced in numerical simulations. Our model is simple in terms of description and implementation, however, complex structures and dynamic behavior of the ternary fluids emerge from the collective dynamics of the RLG and surfactant particles.

Three-dimensional hydrodynamic lattice-gas simulations of domain growth and self-assembly in binary immiscible and ternary amphiphilic fluids.

We simulate the dynamics of phase assembly in binary immiscible fluids and ternary microemulsions using a three-dimensional hydrodynamic lattice-gas approach. For critical spinodal decomposition we perform the scaling analysis in reduced variables introduced by Jury et al. [Phys. Rev. E 59, R2535 (1999)] and by Bladon et al. [Phys. Rev. Lett. 83, 579 (1999)]. We find a late-stage scaling exponent consistent with the R approximately t(2/3) inertial regime. However, as observed with the previous lattice-gas model of Appert et al. [J. Stat. Phys. 81, 181 (1995)] our data do not fall in the same range of reduced length and time as those of Jury et al. and Bladon et al. For off-critical binary spinodal decomposition we observe a reduction of the effective exponent with decreasing volume fraction of the minority phase. However, the n=1 / 3 Lifshitz-Slyzov-Wagner droplet coalescence exponent is not observed. Adding a sufficient number of surfactant particles to a critical quench of binary immiscible fluids produces a ternary bicontinuous microemulsion. We observe a change in scaling behavior from algebraic to logarithmic growth for amphiphilic fluids in which the domain growth is not arrested. For formation of a microemulsion where the domain growth is halted we find that a stretched exponential growth law provides the best fit to the data.

Lattice-boltzmann model for interacting amphiphilic fluids

We develop our recently proposed lattice-Boltzmann method for the nonequilibrium dynamics of amphiphilic fluids [H. Chen, B. M. Boghosian, P. V. Coveney, and M. Nekovee, Proc. R. Soc. London, Ser. A 456, 2043 (2000)]. Our method maintains an orientational degree of freedom for the amphiphilic species and models fluid interactions at a microscopic level by introducing self-consistent mean-field forces between the particles into the lattice-Boltzmann dynamics, in a way that is consistent with kinetic theory. We present the results of extensive simulations in two dimensions which demonstrate the ability of our model to capture the correct phenomenology of binary and ternary amphiphilic fluids.

Two-dimensional hydrodynamic lattice-gas simulations of binary immiscible and ternary amphiphilic fluid flow through porous media

The behavior 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 focused 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 is 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 micellization. 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).

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.

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.

Lattice-gas simulations of minority-phase domain growth in binary immiscible and ternary amphiphilic fluids

We investigate the growth kinetics of binary immiscible fluids and emulsions in two dimensions using a hydrodynamic lattice-gas model. We perform off-critical quenches in the binary fluid case and find that the domain size within the minority phase grows algebraically with time in accordance with theoretical predictions. In the late-time regime we find a growth exponent $n=0.45\ifmmode\pm\else\textpm\fi{}0.02$ over a wide range of concentrations, in good agreement with other simulations. In the early-time regime we find no universal growth exponent but a strong dependence on the concentration of the minority phase. In the ternary amphiphilic fluid case the kinetics of self-assembly of the droplet phase are studied. At low surfactant concentrations, we find that, after an early algebraic growth, a nucleation regime dominates the late-time kinetics, which is enhanced by an increasing concentration of surfactant. With a further increase in the concentration of surfactant, we see a crossover to logarithmically slow growth, and finally saturation of the oil droplets, which we fit phenomenologically by a stretched-exponential function. Finally, the transition between the droplet and the sponge phase is studied.

The shear-induced isotropic-to-lamellar transition in a lattice-gas model of ternary amphiphilic fluids

Although shear-induced isotropic-to-lamellar transitions in ternary systems of oil, water and surfactant have been observed experimentally and predicted theoretically by simple models for some time now, their numerical simulation has not been achieved so far. In this work we demonstrate that a recently introduced hydrodynamic lattice-gas model of amphiphilic fluids is well suited for this purpose: the two-dimensional version of this model does indeed exhibit a shear-induced isotropic-to-lamellar phase transition.