Effect Of Interfacial Tension Research Articles

Formation and regulation of bicontinuous structured nanocomposites with interfacially jammed nanoparticles

Bicontinuous structured nanocomposites with nanoparticles (NPs) assembled at the interface between two fluids have a wealth of proposed applications. Here, we used a universal and facile strategy to prepare such various bicontinuous stable nanocomposites filled with homopolymer-brush grafted NPs of various dimensions. We investigated the detailed formation of such nanocomposites online and proposed a model to fit and predict the effect of NPs at the interface on the domain coarsening of blend matrix and further stabilizing their bicontinuous morphology, based on the influence of NPs percolation on the time-dependent effective interfacial tension. The morphology evolution of nanocomposites can be predicted from the volume fraction of NPs, annealing time and temperature, which may provide some guidelines for the design and preparation of bicontinuous structured nanocomposites with the controllable and stable structure.

Effect of interfacial composition on the physical stability and co-oxidation of proteins and lipids in a soy protein isolate-(−)-epigallocatechin gallate conjugate emulsion

In this study, oil-in-water emulsions were co-stabilized by a soy protein isolate-(−)-epigallocatechin gallate (SPI-EGCG) conjugate, tea saponin (TS), and hexadecyltrimethylammonium bromide (CTAB) (0.01–1.00%, w/v), and the influence of the mixed SPI-EGCG-conjugate–surfactant interface on the physical stability and protein–lipid co-oxidation properties of each emulsions was investigated. Our results demonstrated that TS exhibits a better emulsifying ability than CTAB by significantly reducing interfacial tension; this emulsion contained the smallest particles at a TS concentration of 1.0% (w/v). In addition, the interfacial protein content revealed the existence of synergistic (CTAB) and competitive (TS) adsorption between the protein and surfactant. The presence of TS displaced protein molecules at the interface and inhibited protein oxidation, which reveals that proteins adsorbed at the oil–water interface are more sensitive to oxidation than unadsorbed proteins. The degrees of protein and lipid oxidation were enhanced in the presence of CTAB. Furthermore, the addition of TS delayed lipid oxidation; this phenomenon was most pronounced at a TS concentration of 1.0% (w/v). Our results indicate that combining SPI-EGCG conjugates with TS provides an optimal design for the development of nutritionally fortified products with longer shelf lives. • Effects of the surfactant concentration and type on the emulsions were investigated. • TS gave the best emulsification ability and effective interfacial tension reduction. • The co-oxidation of proteins and lipids occurred depending on the protein location.

Kinetics of wettability alteration and droplet detachment from a solid surface by low-salinity: A lattice-Boltzmann method

The dynamics of droplet detachment from a surface is a fundamental topic studied in coating engineering, fluid mechanics, and subsurface engineering applications. This topic has direct relevance to wettability alteration using the modified ionic composition of water in contact with oil droplet, low salinity waterflooding (LSWF). Previous experimental studies of LSWF have shown a very long timescale in wettability alteration which cannot be explained using bulk diffusion coefficient. In the present study, we address both the time scale of detachment, as well as the impact of buoyancy and interfacial forces (referred to as Bond number) on droplet detachment by proposing an advanced GPU-enhanced lattice Boltzmann model. In this model, the immiscible two-phase flow has been coupled with wettability alteration due to the salinity dilution. After full validation of the model against the former experiments, a set of computational setups with distinct Bond numbers were designed to investigate the effect of interfacial tension and droplet size on the dynamics of droplet detachment. Results demonstrate that droplet detachment from a surface is not a unique function of Bond number and diffusion length scale is critical in detachment time. In summary, this study provides a fully validated model of LSWF and delineates the significant difference in impacts of interfacial tension and bubble size on detachment time, which can be used to predict capability for LSWF, to determine favorable conditions, as well as to observe and explain low-salinity-effect.

The Liquid Young's Law on SLIPS: Liquid-Liquid Interfacial Tensions and Zisman Plots.

Slippery liquid-infused porous surfaces (SLIPS) are an innovation that reduces droplet-solid contact line pinning and interfacial friction. Recently, it has been shown that a liquid analogue of Young’s law can be deduced for the apparent contact angle of a sessile droplet on SLIPS despite there never being contact by the droplet with the underlying solid. Since contact angles on solids are used to characterize solid–liquid interfacial interactions and the wetting of a solid by a liquid, it is our hypothesis that liquid–liquid interactions and the wetting of a liquid surface by a liquid can be characterized by apparent contact angles on SLIPS. Here, we first present a theory for deducing liquid–liquid interfacial tensions from apparent contact angles. This theory is valid irrespective of whether or not a film of the infusing liquid cloaks the droplet–vapor interface. We show experimentally that liquid–liquid interfacial tensions deduced from apparent contact angles of droplets on SLIPS are in excellent agreement with values from the traditional pendant drop technique. We then consider whether the Zisman method for characterizing the wettability of a solid surface can be applied to liquid surfaces created using SLIPS. We report apparent contact angles for a homologous series of alkanes on Krytox-infused SLIPS and for water–IPA mixtures on both the Krytox-infused SLIPS and a silicone oil-infused SLIPS. The alkanes on the Krytox-infused SLIPS follow a linear relationship in the liquid form of the Zisman plot provided that the effective droplet–vapor interfacial tension is used. All three systems follow a linear relationship on a modified Zisman plot. We interpret these results using the concept of the critical surface tension (CST) for the wettability of a solid surface introduced by Zisman. In our liquid surface case, the obtained critical surface tensions were found to be lower than the infusing liquid–vapor surface tensions.

Control of purely-elastic instabilities in cross-slot geometries

<h2>Abstract</h2> The cross-slot stagnation point flow is one of the benchmark problems in fluid mechanics as it allows large strains to develop and can therefore be used in extensional rheometry. In such a flow, for purely-elastic cases in creeping flow regimes, elasticity can break symmetry which is perhaps an unwanted phenomenon if used as a rheometer and will limit the maximum deformation rate in which these tests can be performed, or beneficial once used as mixing device. Here, this instability will be investigated in more detail using a combination of numerical, experimental and analytical analysis and a series of methods will be proposed that can potentially be used to delay and control the start point of the instability. The first part of this presentation focuses on the effect of elongational dominated flow on the onset criteria of symmetry-breaking purely-elastic instability in the cross-slot geometry by applying a fundamental change on the kinematics of the flowfield in this region. Here, the standard geometry is modified by adding a cylinder at the geometric centre and replacing the free stagnation point by pinned stagnation points at the cylinder walls. Next, two-phase flows of Newtonian and/or viscoelastic fluids in a "cross-slot" geometry will be investigated in the creeping-flow limit. In this part, the effect of injecting two fluids with different elastic properties from each inlet arm, and effects of interfacial tension and the viscosity ratio of these flow streams will be investigated.

Computing the viscous effect in early-time drop impact dynamics

The impact of a liquid drop on a solid surface involves many intertwined physical effects, and is influenced by drop velocity, surface tension, ambient pressure and liquid viscosity, among others. Experiments by Kolinski et al. (Phys. Rev. Lett., vol. 112, no. 13, 2014b, p. 134501) show that the liquid–air interface begins to deviate away from the solid surface even before contact. They found that the lift-off of the interface starts at a critical time that scales with the square root of the kinematic viscosity of the liquid. To understand this, we study the approach of a liquid drop towards a solid surface in the presence of an intervening gas layer. We take a numerical approach to solve the Navier–Stokes equations for the liquid, coupled to the compressible lubrication equations for the gas, in two dimensions. With this approach, we recover the experimentally captured early time effect of liquid viscosity on the drop impact, but our results show that lift-off time and liquid kinematic viscosity have a more complex dependence than the square-root scaling relationship. We also predict the effect of interfacial tension at the liquid–gas interface on the drop impact, showing that it mediates the lift-off behaviour.

Discrete Boltzmann modeling of Rayleigh-Taylor instability: Effects of interfacial tension, viscosity, and heat conductivity.

The two-dimensional Rayleigh-Taylor instability (RTI) in compressible flow with intermolecular interactions is probed via the discrete Boltzmann method. The effects of interfacial tension, viscosity, and heat conduction are investigated. It is found that the influences of interfacial tension on the perturbation amplitude, bubble velocity, and two kinds of entropy production rates all show differences at different stages of RTI evolution. It inhibits the RTI evolution at the bubble acceleration stage, while at the asymptotic velocity stage, it first promotes and then inhibits the RTI evolution. Viscosity and heat conduction inhibit the RTI evolution. Viscosity shows a suppressive effect on the entropy generation rate related to heat flow at the early stage but a first promotive and then suppressive effect on the entropy generation rate related to heat flow at a later stage. Heat conduction shows a promotive effect on the entropy generation rate related to heat flow at an early stage. Still, it offers a first promotive and then suppressive effect on the entropy generation rate related to heat flow at a later stage. By introducing the morphological boundary length, we find that the stage of exponential growth of the interface length with time corresponds to the bubble acceleration stage. The first maximum point of the interface length change rate and the first maximum point of the change rate of the entropy generation rate related to viscous stress can be used as a criterion for RTI to enter the asymptotic velocity stage.

Open-source finite volume solvers for multiphase (n-phase) flows involving either Newtonian or non-Newtonian complex fluids

Two new control volume solvers multiFluidInterFoam and rheoMultiFluidInterFoam are presented for the simulation of Newtonian and non-Newtonian n-phase flows (n≥2), respectively, fully accounting for interfacial tension and contact-angle effects for each phase. The multiFluidInterFoam solver modifies certain crucial aspects of the regular multiphaseInterFoam solver provided by OpenFOAM for Newtonian flows, improving its efficiency and robustness, but most importantly improving considerably its accuracy for surface tension driven flows. The new solver uses the volume-of-fluid (VOF) method based on the MULES method and artificial interface compression for the interface capturing, in combination with a suitable continuum surface force model; i.e. the interfacial tension coefficient decomposition method is employed to treat pairings of interfacial tension between the phases. VOF smoothing is also implemented by applying a Laplacian filter on the distribution of volume fractions, and the SIMPLEC algorithm is employed for the velocity–pressure coupling. The above algorithm has also been extended with the development of the rheoMultiFluidInterFoam solver which is capable of fully taking into account complex non-Newtonian effects (e.g. yield stress, viscoelasticity, etc.) of the involved liquids. To this end, the developed solver incorporates the RheoTool toolbox (Pimenta and Alves, 2017), utilizing a wealth of constitutive equations suitable for modeling different types of fluids with complex rheology. Our solvers are tested for both the implementation of the surface tension and of the constitutive equations in a wide range of different flow setups, considering typical benchmark two-phase and three-phase flows, such as the cases of dam break with an obstacle, spreading of a floating lens, a levitating drop, and a bubble rising in an ambient fluid; flows involving Newtonian, viscoplastic and viscoelastic liquids have been considered. Comparisons against analytical solutions or previously published numerical data are performed clearly demonstrating the capability of the new solvers to efficiently and accurately simulate interfacial tension dominated three-phase flows (and n-phase flows in general) for both simple and complex liquids.

Numerical Study of Viscous Fingering in Heterogeneous Porous Media

The displacement of a fluid by a second immiscible fluid is a fundamental process which is relevant for many technological applications, particularly in the petroleum industry.&nbsp; Water is the fluid widely used to push oil to production wells. During this immiscible displacement, a viscous fingering instability appears at the water-oil interface. This undesirable phenomenon leads to a low oil sweeping efficiency. To prevent this situation, techniques called EOR (Enhance Oil Recovery) are used. These methods have technical, economic and environmental disadvantages. &nbsp;Therefore, the objective of this work is to seek a rational use of EOR techniques by determining the right place and the appropriate time to operate them. In many previous studies, the effects of viscosity ratio, interfacial tension and flow rate are investigated. In this study, we numerically investigate the effect of the heterogeneity of the medium and the presence of the fracture on this phenomenon. Three different configurations are studied. The obtained results allowed to locate the regions where the behaviour of the instability varies during displacement in the porous medium, regions where instability is increasing and others where it remains constant. a qualitative comparison between the different cases is also made.

Generation of monodisperse micro-droplets within the stable narrowing jetting regime: effects of viscosity and interfacial tension

Generation of monodisperse micro-droplets within the stable narrowing jetting regime: effects of viscosity and interfacial tension

Study of the water displacing oil process in low permeability porous media based on digital rock technology

Unconventional oil has played increasingly important roles for the sustainable development of human society. Understanding the two-phase displacement mechanism in low permeability porous media is therefore essential for the efficient development of unconventional reservoirs. In this study, the water displacing oil process and characteristics in low permeability cores are numerically investigated based on digital rock technology (DRT). The complex internal structure of the low permeability core is directly constructed based on micro-CT images and the pore-scale two-phase displacement behavior is mechanistically studied by solving the Navier-Stokes equations which incorporate the interfacial tension (IFT) and wettability effect. The oil recovery rate obtained from the simulation results agrees well with that obtained from the experimental results under the same pressure drop condition. Parameter studies on the effect of the displacement pressure, IFT, and fluid-rock wettability on the oil recovery ratio are further performed. The numerical results show that the micro-throats in the rock have a significant impact on the recovery ratio. Larger displacement pressures can overcome the capillary force in the micro-throats, thus enhancing the oil recovery due to the expanded sweep region of the displacing fluid in the core spaces. IFT and wettability affect the magnitude and direction of the capillary force in the pore-throats, and a smaller IFT and a higher wetting angle can lead to a higher displacement efficiency. More specifically, it is revealed changing the pore wettability from oil-wet to water-wet could improve the oil recovery ratio significantly. In addition, a numerical simulation of the nanoparticle solution displacement process has been performed to study the synergistic effect of IFT reduction and fluid-rock wettability improvement on oil recovery enhancement. It is demonstrated that DRT can substantially apply in mechanistical studies of the displacement process. in low permeability porous media. The findings of this study can help better understanding of the water displacing oil mechanisms in the complex pore scale geometries and thereby contribute to the low permeable oil recovery practices.

Wellbore drift flow relation suitable for full flow pattern domain and full dip range

Aiming at the simulation of multi-phase flow in the wellbore during the processes of gas kick and well killing of complex-structure wells (e.g., directional wells, extended reach wells, etc.), a database including 3561 groups of experimental data from 32 different data sources is established. Considering the effects of fluid viscosity, pipe size, interfacial tension, fluid density, pipe inclination and other factors on multi-phase flow parameters, a new gas-liquid two-phase drift flow relation suitable for the full flow pattern and full dip range is established. The distribution coefficient and gas drift velocity models with a pipe inclination range of −90°–90° are established by means of theoretical analysis and data-driven. Compared with three existing models, the proposed models have the highest prediction accuracy and most stable performance. Using a well killing case with the backpressure method in the field, the applicability of the proposed model under the flow conditions with a pipe inclination range of −90°–80° is verified. The errors of the calculated shut in casing pressure, initial back casing pressure and casing pressure when adjusting the displacement are 2.58%, 3.43%, 5.35%, respectively. The calculated results of the model are in good agreement with the field backpressure data.

Effect of Interfacial Tension on Relative Permeability Curves Obtained by Considering Surfactant Adsorption and Diffusion

Abstract To consider the effect of adsorption and diffusion of surfactant on relative permeability, a method for estimating the relative permeability was developed by matching production data obtained through an unsteady-state core flooding experiment and numerical simulation. After the robustness of the method was proven, the necessity of considering surfactant adsorption and diffusion in calculating the relative permeability was proven. Compared with relative permeability curves obtained by neglecting surfactant adsorption and diffusion, the average error of the relative permeability curve obtained by considering surfactant adsorption and diffusion decreases from 11.5% to 3.5% for the oil phase and from 13.1% to 4.2% for the aqueous phase. Finally, the effects of interfacial tension (IFT) on relative permeability curves obtained by considering surfactant adsorption and diffusion were studied. The results show that surfactant adsorption and diffusion affect the relative permeability but not the change in the relative permeability curves for varying IFT. The individual relative permeability curve does straighten with decreasing IFT. As the IFT decreases in a semilog plot, the relative permeability values at the equal-permeability point (i.e., the same relative permeability for oil–water) and residual oil endpoint increase following a logistic function and an exponential function, respectively.

Development of a Novel Green Bio-Nanofluid from Sapindus Saponaria for Enhanced Oil Recovery Processes

The main objective of this study is to develop a novel green-nanofluid from Sapindus Saponaria for its application in enhanced oil recovery (EOR) processes. The bio-nanofluid is composed of a green active compound (AGC), bio-ethanol, and commercial surfactant (SB) at a low concentration. The AGC was obtained from soapberry “Sapindus Saponaria” using the alcoholic extraction method and characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and critical micellar concentration (CMC) to verify the content of saponins as active agents with surface-active behavior. Three types of silica-based nanoparticles were used and characterized by FTIR, TGA, and dynamic light scattering (DLS) analysis. Two commercial nanoparticles (SiO2-C1 and SiO2-C2) were evaluated, and a third one (SiO2-RH) was synthesized from rice husks as an ecological nanomaterial alternative. The performance of the adjusted systems was evaluated by capillary number (effective interfacial tension (σe), wettability and viscosity) and finally with coreflooding tests under reservoir conditions. The FTIR results confirm the presence of saponins in the AGC. In addition, according to the TGA, the AGC is stable under the reservoir temperature of interest. Regarding nanoparticles, siloxane and silanol groups were observed in all samples. For SiO2-C1 and SiO2-C2 samples, the weight loss was lower than 5% for temperatures up to 700 °C. Meanwhile, SiO2-RH had a weight loss of 12% at 800 °C, and 8% at reservoir temperature. Results show a decrease in the interfacial tension (IFT) of up to 83% of the tuned system with only 100 mg·L−1 of rice husk nanoparticles compared to the system without nanoparticles, reaching values of 1.60 × 10−1 mN·m−1. In the coreflooding test, increases of up to 13% of additional crude oil were obtained using the best bio-nanofluid. This work presents an excellent opportunity to include green alternatives to improve conventional techniques with added value during the injection of chemicals in chemical-enhanced oil recovery (CEOR) processes.

Effects of high viscosity ratio and interfacial tension on droplet formation

Effects of high viscosity ratio and interfacial tension on droplet formation

The effect of surfactant partition coefficient and interfacial tension on oil displacement in low-tension polymer flooding

This paper presents an experimental study of low-tension polymer (LTP) flooding with a short-hydrophobe surfactant as a sole additive. Such a simple surfactant makes low-tension displacement fronts in polymer flooding (e.g., 10−2 mN/m) without involving micro-emulsions of ultra-low interfacial tension (IFT). The envisioned application of LTP flooding is to enhance the displacement of a continuous oil phase with such a moderate reduction in IFT as an effective improvement of polymer flooding.In our previous research, 2-ethylhexanol-7PO-15EO (2-EH-7PO-15EO) was selected as an optimal short-hydrophobe surfactant that resulted in the lowest IFT between polymer solution and oil, and achieved the greatest final oil recovery. However, this paper presents the effect of surfactant partition coefficients on the LTP flooding as an additional important factor for surfactant optimization.A series of LTP floods showed that the IFT primarily affected the final oil recovery when the sandpack was swept sufficiently by LTP. Comparison of two cases with similar IFT values (2-EH-4PO-15EO and 2-EH-7PO-25EO) showed that the surfactant partition coefficient affected the oil recovery through its impact on the surfactant in-situ propagation. The case with 2-EH-7PO-25EO resulted in a greater oil recovery because the surfactant propagated more efficiently with a smaller partition coefficient than 2-EH-4PO-15EO.Results collectively showed that optimization of 2-EH-xPO-yEO for LTP flooding involves two competing factors. One is to minimize the water/oil IFT for increasing the local oil displacement efficiency, and the other is to minimize the partition coefficient for more efficient in-situ propagation of the surfactant. It is critical to take a balance between these two factors for the surfactant used for LTP flooding. The importance of the surfactant partition coefficient became more obvious when a limited amount of surfactant was injected.

Spontaneous Emulsions: Adjusting Spontaneity and Phase Behavior by Hydrophilic-Lipophilic Difference-Guided Surfactant, Salt, and Oil Selection.

Spontaneous emulsion behavior has been difficult to predict and could be influenced by many variables including salinity, temperature, and chemical composition of the oil and surfactant. In this work, the hydrophilic-lipophilic difference (HLD) framework was used to predict the formation of spontaneous emulsions using a mixture of Span-80 and SLES surfactants. The spontaneity and emulsion behavior of different systems were modeled by estimating the HLDmix. The influence of surfactant ratio, salinity, and oil type was investigated. Spontaneous emulsification could only be observed when the HLDmix was between -0.96 and 1.04. Within this range, a negative HLDmix resulted in a greater spontaneity to form o/w emulsion, and a w/o emulsion was more likely to form when the HLDmix was positive. When the HLDmix was close to 0 (between -0.22 and 0.56 in our systems), emulsions were formed in both the oil and aqueous phases with high spontaneity. A combined effect of ultralow interfacial tension, Span-80 micelle swelling, and interfacial turbulence due to Marangoni effects is likely the main mechanism of the spontaneous emulsification observed in this study. A synergistic reduction in interfacial tension was observed between Span-80 and SLES (<1 mN/m). When the HLD of the system was close to 0, a bicontinuous emulsion phase was formed at the oil-water interface. The bicontinuous emulsion broke-up over time due to the ultralow interfacial tension and interfacial turbulence, forming dispersed oil and water droplets. Results from this work provide a practical method to suggest what surfactant composition, salinity, and oil type could promote (or eliminate) the conditions favorable for spontaneous emulsification.

A NEW APPROACH OF COMPOSITIONAL SIMULATION FOR A VOLATILE OIL RESERVOIR MODELING

This paper proposes a new compositional simulation approach for a volatile oil reservoirmodelling. The proposed formulation has an implicit equation for the oil-phase pressureand water saturation, an explicit equation for the hydrocarbon saturation, and explicitequation for the overall composition of each hydrocarbon component that satisfiesthermodynamic equilibrium. An Equation of State for phase equilibrium and property calculationsis used in this new formulation. Interfacial tension effects are included in thisapproach to characterise the thermodynamically dynamic nature of the relative permeability.A two-dimensional relative permeability algorithm is included which handles lumpedhydrocarbon phase hydrocarbon phase as well as individual phase flows. For each gridblock two equations are required, namely total hydrocarbon and water-phase flow equations.These equations are highly non-linear and they are linearised by using Newton-Raphson method. The resulting equations are solved by an efficient Conjugate Gradientbased iterative technique to obtain pressures and saturations simultaneously, and hydrocarbon-phase saturations are deduced from their respective equations.The new compositional simulation approach is validated through analytical and numericalmethods. It is demonstrated in this present paper that the results are comparedfavourably with analytical techniques and published numerical results. They also confirmthat the proposed codified formulation is unconditionally stable and it is as stable as fullycompositional model yet the computational cost reduction was substantial.

Distribution of a water film confined in inorganic nanopores in real shale gas reservoirs

Distribution of the water film and initial water saturation within inorganic nanopores of shale are key problems for the evaluation and prediction of recoverable gas resources. Numerous research on the distribution and quantitative characterization of water film confined in nanopores have been conducted to the present. However, quantitation of water confined in inorganic nanopores of shale gas reservoir still remains challenging due to the complexity of porous media and reservoir conditions. In the present study, a novel model with disjoining pressure, interfacial tension and real gas effect taken into consideration, was proposed to disclose the distribution of water film confined inside circular or elliptic pores. In addition, the phenomena of capillary condensation and partial condensation have been revealed in elliptic pores. The proposed model was verified by comparing the calculation results with data from previous paper. Results show that the capillary condensation behavior of the water film is remarkably affected by the real gas effect. Water condenses easily into water films under the actual gas reservoir conditions, especially for small pores. However, the interfacial tension and high temperature can inhibit the formation of the water film in the confined space at a nanometer scale. Finally, the partial condensation is more likely to occur at both ends of elliptic pores.

The Effect of Interfacial Tension on Co2 Oil-Based Foam Stability Under Different Temperatures and Pressures

The Effect of Interfacial Tension on Co2 Oil-Based Foam Stability Under Different Temperatures and Pressures