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Mohamed Laradji - One of the best experts on this subject based on the ideXlab platform.
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dissipative particle dynamics simulation of the interplay between spinodal decomposition and wetting in thin film Binary Fluids
Journal of Chemical Physics, 2010Co-Authors: Michael J A Hore, Mohamed LaradjiAbstract:The dynamics of phase separation of thin film Binary Fluids is investigated via dissipative particle dynamics simulation. We consider both cases of symmetric and asymmetric interactions between the walls and the two components. In the case of walls interacting symmetrically with the two fluid components, corresponding to a nonwetting case, relatively fast kinetics is observed when the average domain size is smaller than the slit thickness. A crossover to a slow Lifshitz–Slyozov growth is observed at late times. Faster dynamics is observed when the walls act as a slip boundary condition to the velocity field. In the case of asymmetric interactions, such that the system is in the wetting regime, the interplay between wetting kinetics and spinodal decomposition leads to rich dynamics. The phase separation proceeds through three stages. During the first stage, the dynamics is characterized as surface-directed spinodal decomposition, with growth of both average domain size and thickness of the wetting layers. ...
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prospects of nanorods as an emulsifying agent of immiscible blends
Journal of Chemical Physics, 2008Co-Authors: Michael J A Hore, Mohamed LaradjiAbstract:Immiscible Binary Fluids containing rigid nanorods that are preferentially immersed in one of the two Fluids are systematically investigated via dissipative particle dynamics simulations. For sufficiently high volume fraction and/or aspect ratio, nanorods lead to a pronounced slowing down of the phase separation process, and yield microphase-separated structures with a characteristic length scale that decreases as either the nanorods length or their volume fraction is increased. The slowing down of the dynamics is attributed to a disordered jamming of the nanorods in the preferred component and a dramatic reduction in their diffusion due to kinetic conformational hindrance. The final characteristic length scale of the dispersion, reduced by the nanorods length, is found to depend only on Onsager’s dimensionless parameter ψν, where ψ and ν are the nanorods volume fraction and aspect ratio, respectively. These results indicate that nanorods may be used as an effective emulsifying agent of Binary polymer blends.
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phase separation dynamics in Binary Fluids containing quenched or mobile filler particles
Journal of Chemical Physics, 2003Co-Authors: Mohamed Laradji, Grant MacnevinAbstract:The dynamics of phase separation of Binary Fluids in the presence of quenched or mobile filler particles, with preferential attraction for one of the two fluid components, is investigated by means of extensive molecular dynamics simulations in two dimensions. When the filler particles are quenched, we found that they lead to a slowing-down of the kinetics that is enhanced as the density of the filler particles is increased. The domain growth in this case is found to follow a crossover scaling form which links domain growth in pure Binary mixtures to that in the presence of quenched filler particles. On the other hand, when the filler particles are annealed, systematic simulations for various values of single filler particle mass, μc, and filler particle density, ρc, show that the filler particles only affect the nonuniversal prefactor of the power law. The power law itself remains given by t2/3, characteristic of inertial growth that is typically observed in pure Binary fluid mixtures. The prefactor is fo...
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molecular dynamics simulation of spinodal decomposition in three dimensional Binary Fluids
Physical Review Letters, 1996Co-Authors: Mohamed Laradji, Soren Toxvaerd, Ole G MouritsenAbstract:Using large-scale molecular dynamics simulations of a two-component Lennard-Jones model in three dimensions, we show that the late-time dynamics of spinodal decomposition in concentrated Binary Fluids reaches a viscous scaling regime with a growth exponent $n\phantom{\rule{0ex}{0ex}}=\phantom{\rule{0ex}{0ex}}1$, in agreement with experiments and a theoretical analysis for viscous growth.
Roman O Grigoriev - One of the best experts on this subject based on the ideXlab platform.
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the effect of gas phase transport on marangoni convection in volatile Binary Fluids driven by a horizontal temperature gradient
International Journal of Heat and Mass Transfer, 2020Co-Authors: Tongran Qin, Roman O GrigorievAbstract:Abstract Recent experimental and numerical studies of convection in confined layers of volatile Binary liquids with a free surface subjected to a horizontal temperature gradient have observed a reversal in the direction of interfacial flow as the concentration of air in the vapor space above the liquid is decreased. These observations suggest that transport in the gas phase has a significant effect on the balance between thermocapillary and solutocapillary stresses, the competition between which determines the flow direction. In order to develop a quantitative description of the flow reversal, we use the two-sided (liquid/gas) transport model introduced previously to obtain approximate analytical solutions for the interfacial temperature and composition of the liquid, hence predict thermocapillary and solutocapillary stresses, and the flow direction. Therefore, our solutions provide useful guidelines for choosing the optimal Binary coolants composition and operating conditions for thermal management applications. Despite the complex nature of this problem, we have found that the mass transport in the gas phase is effectively one-dimensional and independent of the flow in moderate to large aspect-ratio cavity for sufficiently low temperature gradients, which allows this problem to be simplified and solved analytically in a sequential manner. Our theoretical predictions agree well with the results of numerical simulations, which indicates that the analytical analysis captures the essential physics of the problem.
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a numerical study of buoyancy marangoni convection of volatile Binary Fluids in confined geometries
International Journal of Heat and Mass Transfer, 2018Co-Authors: Roman O GrigorievAbstract:Abstract A horizontal temperature gradient can cause a flow in a layer of liquid with a free surface via several different mechanisms. The most universal one is due to thermocapillary stresses that arise due to the temperature dependence of surface tension. For Binary liquids, the flow can also be driven by solutocapillary stresses that arise due to the dependence of surface tension on the composition of the liquid. For some Binary liquids, such as water-alcohol mixtures, solutocapillary stresses are primarily due to phase change (e.g., differential evaporation or condensation of the two components), and these two mechanisms can counteract each other. A recent experimental study (Li and Yoda, 2016) has demonstrated that the flow direction can be reversed by changing the amount of air present inside the experimental apparatus. To understand how the presence of air affects the interfacial stresses, we have developed and implemented numerically a comprehensive two-sided transport model, which accounts for transport of heat, mass, and momentum in both phases and phase change across the interface and is able to reproduce the experimental results. The detailed analysis of these results shows that air tends to suppress phase change and hence solutocapillary stresses. Removing the air enhances phase change, instead suppressing the variation in the interfacial temperature and hence thermocapillary stresses.
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convection evaporation and condensation of simple and Binary Fluids in confined geometries
ASME 2012 Third International Conference on Micro Nanoscale Heat and Mass Transfer, 2012Co-Authors: Tongran Qin, Roman O GrigorievAbstract:Rayleigh-Benard and Marangoni convection in a layer of a homogeneous fluid with a free surface in the absence of phase change is a classic (and extensively studied) problem of fluid mechanics. Phase change has a major effect on the convection problem. Most notably, significant latent heat generated at the free surface as a result of phase change can dramatically alter the interfacial temperature, and hence, the thermocapillary stresses. Furthermore, differential evaporation in Binary Fluids can lead to considerable variation in the concentration field, producing solutocapillarity stresses, which can compete with thermocapillarity and buoyancy.This talk describes numerical studies of convection in alcohol and alcohol-water mixtures due to a horizontal temperature gradient in the presence of phase change. We illustrate how the composition of the liquid and the presence of non-condensable gases (e.g., air) can be used to alter the balance of the dominant forces. In particular, by adding or removing air from the test cell, the direction of the flow can be reversed by emphasizing either the thermocapillary or the solutocapillary stresses.© 2012 ASME
Suman Chakraborty - One of the best experts on this subject based on the ideXlab platform.
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interfacial dynamics of immiscible Binary Fluids through ordered porous media the interplay of thermal and electric fields
Physics of Fluids, 2019Co-Authors: Golak Kunti, Anandaroop Bhattacharya, Suman ChakrabortyAbstract:We report the interplay of electrical and thermal fields on the interfacial dynamics of two immiscible Fluids inside a periodic porous domain. The alternating current electrothermal mechanism is employed to generate the two phase flow. The surfaces of the porous blocks are wetted with wettability conditions which are manifested by a predefined static contact angle. Depending on the surface affinity and the electrical parameters, two distinctive spatio-temporal regimes can be identified, namely, trapping of the displaced fluid between the two consecutive porous blocks (formation of liquid bridge) and merging of contact lines after traveling the obstacle (complete interface recovery). Results show that liquid bridge formation and complete interface recovery are strongly influenced by the viscosity and thermal conductivity contrasts, in addition to the relevant electro-thermal parameters.We report the interplay of electrical and thermal fields on the interfacial dynamics of two immiscible Fluids inside a periodic porous domain. The alternating current electrothermal mechanism is employed to generate the two phase flow. The surfaces of the porous blocks are wetted with wettability conditions which are manifested by a predefined static contact angle. Depending on the surface affinity and the electrical parameters, two distinctive spatio-temporal regimes can be identified, namely, trapping of the displaced fluid between the two consecutive porous blocks (formation of liquid bridge) and merging of contact lines after traveling the obstacle (complete interface recovery). Results show that liquid bridge formation and complete interface recovery are strongly influenced by the viscosity and thermal conductivity contrasts, in addition to the relevant electro-thermal parameters.
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alternating current electrothermal modulated moving contact line dynamics of immiscible Binary Fluids over patterned surfaces
Soft Matter, 2017Co-Authors: Golak Kunti, Anandaroop Bhattacharya, Suman ChakrabortyAbstract:In this paper, we report the results of our numerical study on incompressible flow of a Binary system of two immiscible Fluids in a parallel plate capillary using alternating current electrothermal kinetics as the actuation mechanism for flow. The surfaces of the capillary are wetted with two different alternating wettability patches. The dynamic motion of the interface of the two Fluids is tracked using a phase-field order parameter-based approach. The results exhibit a stick-slip behavior involving acceleration and deceleration of the interface due to the interplay of electrothermal (Coulomb and dielectric) and surface tension forces. Controlling the interface motion through effective tuning of the chemical characteristics of the surfaces and forcing parameters was explored in detail. Finally, we were able to find a critical value of the dimensionless strength of the alternating current electrothermal force above which the interface “breaks”, resulting in the formation of isolated droplets. These results have the potential to improve fundamental understanding and design optimization of various biomedical and physiological systems that involve flow of two or more immiscible Fluids over chemically wetted surfaces.
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thermocapillary actuated contact line motion of immiscible Binary Fluids over substrates with patterned wettability in narrow confinement
Physical Review E, 2014Co-Authors: Debabrata Dasgupta, Pranab Kumar Mondal, Suman ChakrabortyAbstract:We investigate thermocapillary-driven contact-line dynamics of two immiscible Fluids in a narrow fluidic confinement comprising substrates with patterned wettability variations. Our study, based on phase field formalism, demonstrates that the velocity of the contact line is a strong function of the combined consequences of the applied thermal gradient and the substrate wetting characteristics. Finally, we evaluate different energy transfer rates and show that the dissipation due to fluid slip over the solid surface plays a dominating role in transferring energy into the contact-line motion. Our analysis, in effect, provides an elegant way of controlling the capillary filling rate in a narrow fluidic confinement by tailoring the applied temperature gradient and the substrate wettability in tandem.
J M Yeomans - One of the best experts on this subject based on the ideXlab platform.
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lattice boltzmann simulations of phase separation in chemically reactive Binary Fluids
Physical Review E, 2006Co-Authors: K Furtado, J M YeomansAbstract:We use a lattice Boltzmann method to study pattern formation in chemically reactive Binary Fluids in the regime where hydrodynamic effects are important. The coupled equations solved by the method are a Cahn-Hilliard equation, modified by the inclusion of a reactive source term, and the Navier-Stokes equations for conservation of mass and momentum. The coupling is twofold, resulting from the advection of the order parameter by the velocity field and the effect of fluid composition on pressure. We study the evolution of the system following a critical quench for a linear and for a quadratic reaction source term. Comparison is made between the high and low viscosity regimes to identify the influence of hydrodynamic flows. In both cases hydrodynamics is found to influence the pathways available for domain growth and the eventual steady states.
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pattern formation in Binary Fluids confined between rough chemically heterogeneous surfaces
Physical Review Letters, 2004Co-Authors: Rolf Verberg, Christopher Pooley, J M Yeomans, Anna C. BalazsAbstract:Using a mesoscale model for hydrodynamics, we simulate driven flow of AB Binary Fluids past surfaces that contain well-defined roughness or asperities. The geometry and wetting properties of the asperities are found to have a dramatic effect on the flow patterns. We isolate conditions where the A fluid forms vertical bands that bridge the asperities and an imposed shear (or pressure gradient) drives the system to form monodisperse droplets of A within the B fluid. The size of the droplets can be tailored by varying the morphology of the asperities. The surfaces needed to create this rich dynamical behavior are used as the stamps in microcontact printing; thus, the parameter space can readily be accessed experimentally, and the predictions suggest an efficient method for forming emulsions with well-controlled morphologies.
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lattice boltzmann simulations of contact line motion ii Binary Fluids
Physical Review E, 2004Co-Authors: A J Briant, J M YeomansAbstract:We investigate the applicability of a mesoscale modeling approach, lattice Boltzmann simulations, to the problem of contact line motion in one- and two-component two phase Fluids. In this, the second of two papers, we consider Binary systems. We show that the contact line singularity is overcome by diffusion which is effective over a length scale L about the contact line and derive a scaling form for the dependence of L on system parameters.
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phase separation under shear in two dimensional Binary Fluids
Physical Review E, 1999Co-Authors: Alexander J. Wagner, J M YeomansAbstract:We use lattice Boltzmann simulations to study the effect of shear on the phase ordering of a two-dimensional Binary fluid. The shear is imposed by generalizing the lattice Boltzmann algorithm to include Lees-Edwards boundary conditions. We show how the interplay between the ordering effects of the spinodal decomposition and the disordering tendencies of the shear, which depends on the shear rate and the fluid viscosity, can lead to a state of dynamic equilibrium where domains are continually broken up and reformed.
Yongping Yang - One of the best experts on this subject based on the ideXlab platform.
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thin film profile and interfacial temperature distribution of Binary fluid sessile droplet evaporating on heated substrate
International Journal of Heat and Mass Transfer, 2019Co-Authors: Leping Zhou, Yongping YangAbstract:Abstract The interfacial profile and temperature distribution in the thin film region near the triple line is important for comprehensive modelling the transport process. For Fluids with multi-components, typically Binary Fluids, the volatilities of the components are different from pure Fluids and hence the interfacial characteristics needs to be properly modeled. In this work, a numerical analysis on the thin film profile, the interfacial temperature and the conjugate heat transfer characteristics in the thin film region of Binary fluid sessile droplets of 5 wt% aqueous methanol and ethanol solutions evaporating on heated glass or copper substrates is given. The concentration of the components of Binary fluid in the thin film region is assumed to be uniform for the low mass fraction of alcohol solution. The results show that the fluid property, substrate wettability and wall superheat have substantial effects on these parameters. The wall superheat has the greatest effect on the thin film heat transfer followed by the substrate wettability and fluid property. It also shows that surface tension gradients play a more important role in the formation of the Marangoni convection in the thin film region than the thermal-induced density differences and inertial motion. The effects of fluid properties and substrate wettability can be efficiently utilized for superior heat removal capacity in phase-change devices involving thin film heat transfer using Binary Fluids.
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Numerical investigation on Marangoni convection of Binary Fluids in a closed microcavity
Applied Thermal Engineering, 2015Co-Authors: Zhenchen Zheng, Leping Zhou, Yongping Yang, Pei-xue Jiang, Bu-xuan WangAbstract:Abstract Phase change can dramatically alter the interfacial temperature, resulting in surface tension gradients and consequently causing Marangoni convection. The numerical investigation on Marangoni convection of Binary Fluids in a closed microcavity is accomplished in this paper by using the volume of fluid (VOF) model with source terms added by user defined functions (UDF) due to mass transfer, with detailed velocity and temperature fields. For simple fluid, surface tension decreases with increasing temperature, resulting in thermal Marangoni convection that can drive the liquid leave from hot regions and leading to film dryout. For Binary Fluids, however, the Marangoni convection could also be caused by concentration gradients, resulting in greatly promoted backflow of the fluid. In particular, for self-rewetting Fluids which have unique surface tension characteristics that increase with increasing temperature above a critical value, the Marangoni flow can drive the liquid flow towards hot regions, avoiding film dryout. The influence of non-condensable gas is also considered by providing detailed velocity fields near the contact region and it proves that non-condensable gas can negatively affect the heat and mass transfer.