Surface Tension Of Fluid Research Articles

Boussinesq model for two-fluid system with surface- and interfacial tension

A Boussinesq model associated with surface and internal waves with surface tension and interfacial tension in a two-layer fluid is presented in the application range of weakly dispersive nonlinear. The nonlinear form of model definitions in terms of surface and interfacial tensions along with velocity potentials are provided. Based on the perturbation technique, the Boussinesq equations for both layers are derived. The present Boussinesq result is validated against existing published results and it has a good level of agreement. Further, the present model results of crests of surface and interface displacements are compared with existing published numerical OpenFOAM simulations. The dispersion relations for fast- and slow modes are derived in the quadratic form of wave frequencies in the presence of surface and interfacial tensions. The second-order surface and internal wave displacements along with velocity potentials for upper- and lower-layer fluids are presented. The effects of surface and interfacial tensions on dispersion characteristics, harmonic transfer functions, and shoaling gradients on different physical parameters associated with the present model are studied by analyzing several numerical results. In the end, a real physical problem is demonstrated in the application of surface tension with solvents in the gas-liquid interface.

Surface light scattering: the capability of precisely measuring the interfacial properties of Newtonian fluids within the capillary wave transition region

This work employs a theoretical power spectrum of the dynamics of surface fluctuations in the frequency domain to elucidate the dissipation of capillary waves of fluids in the near-critical oscillation or transition region, seeking to resolve the problem of large discrepancies in viscosity and surface tension measurements in the region. The frequency-domain analysis approach was suggested, involving the discrete Fourier transform to transform the time domain data to the frequency domain and the fitting algorithm for the power spectrum. A total of three refrigerants, four alkanes and six fatty esters were chosen to examine the approach, with a range of the dimensionless number Y between 1.3 and 101.9. The findings demonstrate that frequency-domain approach is an effective way of dealing with dissipation issues for surface light scattering method when approaching the critical oscillation region, and thus could extend the technique for determining the viscosity and surface tension of Newtonian fluids to a sufficient wide viscosity range.

Genetically modified indigenous Pseudomonas aeruginosa drove bacterial community to change positively toward microbial enhanced oil recovery applications.

Microbial enhanced oil recovery (MEOR) is cost-effective and eco-friendly for oil exploitation. Genetically modified biosurfactants-producing high-yield strains are promising for ex-situ MEOR. However, can they survive and produce biosurfactants in petroleum reservoirs for in-situ MEOR? What is their effect on the native bacterial community? A genetically modified indigenous biosurfactants-producing strain Pseudomonas aeruginosa PrhlAB was bioaugmented in simulated reservoir environments. Pseudomonas aeruginosa PrhlAB could stably colonize in simulated reservoirs. Biosurfactants (200mg l-1) were produced in simulated reservoirs after bio-augmenting strain PrhlAB. The surface tension of fluid was reduced to 32.1 mN m-1. Crude oil was emulsified with an emulsification index of 60.1%. Bio-augmenting strain PrhlAB stimulated the MEOR-related microbial activities. Hydrocarbon-degrading bacteria and biosurfactants-producing bacteria were activated, while the hydrogen sulfide-producing bacteria were inhibited. Bio-augmenting P. aeruginosa PrhlAB reduced the diversity of bacterial community, and gradually simplified the species composition. Bacteria with oil displacement potential became dominant genera, such as Shewanella, Pseudomonas, and Arcobacter. Culture-based and sequence-based analyses reveal that genetically modified biosurfactants-producing strain P. aeruginosa PrhlAB are promising for in-situ MEOR as well.

In-situ manipulating nanochannel wettability to evaluate fluid transport under nanoconfinement

Understanding the transport of nanoconfined fluid and its underlying mechanism is essential for manipulating fluid transport in nanochannels and nanoporous media. The wettability of the channel wall is one of the most important factors that determine the property and transport of nanoconfined fluid. However, the experimental studies of wettability adjustment for manipulating nanofluid transport were rarely reported. In this work, the wettability of nanochannels in nanofluidic chips was tuned in situ to investigate the transport of water and alkane. The surface hydrophobicity of the channel wall was adjusted through hydroxylation and silanization. The friction factor of water increased with the hydroxylation time of the channel wall, and decreased after surface hydrophobization with octadecyltrichlorosilane (OTS) and trimethylchlorosilane (TMCS), indicating surface hydrophobization had a significant effect on friction reduction. The linear correlation between the transport distance ΔX2 and time t could be theoretically described based on the Lucas-Washburn equation for fully developed flow. With the same channel depth, the fitted apparent contact angle θapp for nanochannels of different hydrophobicity followed the trend of OTS > TMCS > pristine > hydroxylation. The transport of water in hydrophobized nanochannels was faster than that in pristine and hydroxylated nanochannels, which coincided with the friction factor results. The transport of n-hexane was significantly faster than that of water, which could be explained by the differences in the fluid viscosity, surface tension and wettability. This work provides experimental evidence and useful insights into the understanding of the wettability effect of nanochannel on the transport of different fluids, which has implications for the transportation characteristics of nanoconfined fluids in the applications, such as advanced batteries, separation membranes, unconventional reservoirs, etc.

A hierarchical level-set numerical approach for immiscible incompressible n-phase flows ([formula omitted])

In this article, we propose an approach for interface-resolved simulations of immiscible incompressible n-phase flows (n≥3). The standard level set (LS) method can accurately simulate the motion of two phases. However, when more than two phases are considered, the interfaces cannot intersect and numerical overlaps occur, leading to unphysical spurious velocities and unrealistic distortions of the interfaces. The proposed approach organizes a group of n−1 LS functions into a hierarchy to resolve the issue of numerical overlaps. The n-phase flow field is discretized using the extended finite element method (XFEM), which adequately addresses the discontinuities occurring in the pressure and velocity fields due to distinct fluid properties and surface tension effects at the interface between the fluids. This approach is applied to three-phase and four-phase fluid dynamics, involving gas and liquids under various conditions of surface tension. The 2D numerical tests prove that the proposed numerical methods can effectively model interactions between multi-fluid interfaces, avoiding numerical overlaps.

Anomalous hydraulic fluid absorption by carbon fiber/PEKK composites: Physical and mechanical aspects

AbstractCarbon fiber (CF)/polyetherketoneketone (PEKK) composites are exposed to Skydrol, a hydraulic fluid made of phosphate esters widely used in the aviation field. The present study investigates Skydrol absorption of CF/PEKK composite layups and the associated PEKK matrix. A significant unexpected increase of Skydrol uptake is observed for cross‐ply composites (0.50%) compared to unidirectional ones (0.06%), independently of ply number. The use of ‘model’ fluids like water and ethanol allows to identify the origin of this anomalous Skydrol absorption in the case of cross‐ply layup. We propose that the latter involves an imbibition process governed by the fluid surface tension and the presence of submicronic cavities. SEM imaging of composite cross‐section after ion beam polishing confirms fiber‐matrix submicronic debonding in the interlaminar region in the cross‐ply composite. SEM–EDX confirms the presence of Skydrol into the submicronic cavities. Despite this anomalous absorption, off‐axis tensile testing as well as ILSS testing show no significant impact of Skydrol on CF/PEKK mechanical properties with less than 10% difference compared to the initial values.Highlights Absorption by diffusion of Skydrol in neat PEKK and CF/PEKK composites Link between fluid surface tension and anomalous Skydrol absorption Evidence of submicronic cavities in CF/PEKK composites by means of SEM–EDX Low impact of Skydrol on CF/PEKK mechanical properties

Finite-displacement elastic solution due to a triple contact line

At the line of triple contact of an elastic body with two immiscible fluids, the body is subjected to a force concentrated on this line, the fluid–fluid surface tension. In the simple case of a semi-infinite body, limited by a plane, a straight contact line on this plane, and a fluid–fluid surface tension normal to the plane, the classical elastic solution leads to an infinite displacement at the contact line and an infinite elastic energy. By taking into account the body–fluid surface tension (i.e., isotropic surface stress) and applying Kolosov’s approach of plane strain elasticity, we present a new and simple expression of the solution concerning the semi-infinite body, which gives a finite displacement and a ridge at the contact line, and finite elastic energy. A detailed description of the displacements, strains, and stresses in the neighborhood of the contact line is given. This solution also shows that Green’s formulae, in the volume and on the surfaces, are valid (these formulae play a central role in the theory).

Stagnation point heat transfer under a free-surface jet

Laminar free-surface jet impingement is a crucial configuration for heat transfer processes. Focusing on the link between stagnation-point heat transfer and near-axis radial acceleration, its dependence on jet width and profile is studied. Thus, heat transfer depends on: fluid properties, flow rate, nozzle length, nozzle-to-plate spacing, surface tension and gravity (Pr, Re, L/d, H/d, We & Fr, accordingly). As existing theory is limited to specific cases, a new general description is developed from analogy to submerged jets. Validated by two-phase flow simulations, this description captures key jet dynamics evolution (centerline velocity, profile curvature). It reveals significant property changes during jet flight due to relaxation (L dependence) and contraction (Re/Fr dependence). Unlike submerged jets, contraction raises arrival Reynolds number, leading to additional dependencies Nu ∝ L and Nu ∝ H/Fr, and further deviations at low-We and -Re. The theory successfully predicts heat transfer across diverse conditions and converges to negligible gravity (horizontal jet) as expected.

Finite size effects and optimization of the calculation of the surface tension in surfactant mixtures at liquid/vapour interfaces

The surface tension of monolayers with mixtures of anionic and nonionic surfactant at the liquid/vapour interface is studied. Previous works have observed that calculations of the surface tension of simple fluids show artificial oscillations for small interfacial areas, indicating that the surface tension data fluctuate due to the finite size effects and periodic boundary conditions. In the case of simulations of monolayers composed of surfactant mixtures, the surface tension not only oscillates for small areas but can also give non-physical data, such as negative values. Analysis of the monolayers with different surfactant mixtures, ionic (DTAB, CTAB, SDS) and nonionic (SB3-12), was done for density profiles, parameters of order and pair correlation functions for small and large box areas and all of them present similar behaviour. The fluctuations and the non-physical values of the surface tension are corrected when boxes with large interfacial areas are considered. The results indicate that in order to obtain reliable values of the surface tension, in computer simulations, it is important to choose not only the correct force field but also the appropriate size of the simulation box.

Bioaerosol Emission from Vortex Liquids Contaminated with Escherichia coli Bacteria

Vortex fluids are often present in natural and artificial aquatic environments and are also widely used in industrial water treatment and product manufacturing processes. Vortex processes have been studied quite extensively; however, little attention has been paid to the potential release of biological aerosols to the ambient air in common situations involving microbial-contaminated vortex liquids. The model organism was Escherichia coli, a common Gram-negative coliform bacterium widely present in the aquatic and air environments. This study examines the influence of various parameters, including liquid rotation speed, column height, temperature, surface tension and vessel size, on the rate of bioaerosol formation. A commonly used single-stage bioaerosol impactor was employed to collect microbial aerosols at different process parameters under controlled laboratory conditions. The main results show that bioaerosol production increases markedly with increasing rotation speed, reaching a maximum rate at the highest value used in this project (1300 rpm). The tallness of the liquid column is strongly responsible for the bioaerosol production efficiency reaching a difference of almost one order of magnitude along the range between 45 mm (highest bioaerosol release) and 110 mm used in this research. Fluid temperature and surface tension are also very influential parameters responsible for bioaerosol generation during fluid vortex motion; corresponding results are discussed in this manuscript.

Why Is the Baker Classification Inadequate for Classifying Silicone Implant Fibrous Capsules?

Baker's clinical classification is adopted as the gold standard for grading complications related to silicone implants. Despite being widely used for this purpose, the classification has several limitations, highlighting subjectivity, reproducibility, and interobserver agreement. In this technical report, we aim to present the reasons for the inadequacy of the Baker classification for breast implants and the main factors contributing to false-negative results using recent theories of surface tension of fluids and gel bleeding. We also present an alternative classification proposal using magnetic resonance imaging of the breasts.

On the inhibition of Rayleigh–Taylor instability by surface tension in stratified incompressible viscous fluids under Lagrangian coordinates

On the inhibition of Rayleigh–Taylor instability by surface tension in stratified incompressible viscous fluids under Lagrangian coordinates

Numerical investigation of injection characteristics on normal saline irrigation quality in curved root canals using computational fluid dynamics

ObjectivesThe primary aim of this research was to find the effects of Normal saline injection rate and position on irrigation quality in curved root canals. MethodsComputational Fluid Dynamics (CFD) was used to simulate irrigation in root canals. Root canal geometries were obtained by considering the complete shaping of a rotary file in four root groups with 0, 10, 30, and 60° of curvatures. Fluid surface tension, bouncy, gravity, and air entrance were considered in the numerical simulation using Ansys-CFX software. For each root canal, the flow regime and wall shear stresses were calculated at three different syringe plunger speeds, and three different injection locations of a beveled open-ended needle and their effects on the irrigation quality were investigated in this paper. ResultsWall shear stress is considered the main parameter determining irrigation quality. It was calculated for all 36 test cases. Injection rate and normal saline accumulating near the apex and their effects on washed area ratio were shown for the test cases. Results showed significant effects of injection characteristics, incredibly faster injection, and deeper needle position on the irrigation quality of curved root canals. ConclusionsA higher injection rate and deeper needle position are required to achieve the best irrigation quality and a more washed area ratio in root canals with greater curvature.

Study of melt pool dynamics and porosity forming mechanism of laser beam oscillation welding of titanium and aluminum

In this study, a numerical model of oscillation weld butt joint is developed to investigate the welding of titanium alloy with aluminum alloy. Three oscillation paths, namely, straight, sine, and circular, are used to study the distribution of force in the molten pool, the welding temperature field, and the formation and evolution of porosity within the weld. A 3D Gaussian heat source is used to represent the laser beam. The volume of the fluid method is employed to track the gas-liquid free surface, and the gas-liquid interface force is transformed by using the continuous surface force model. The mechanism of keyhole collapse and pore formation was examined along with the fluid flow, surface tension, and recoil pressure on the molten pool. The results confirmed that the highest welding quality is acquired by using a laser welding circular path. Notably, numerical simulation results are validated through experimental data, and circular oscillating laser welding significantly reduced weld seam porosity in the welding of Ti–Al dissimilar alloys. The circular oscillation path with an offset of 0.6 mm and an oscillation amplitude of 0.6 mm is identified as the optimal approach for suppressing pores in the weld joint. This research provides valuable insights into the fundamental mechanisms of keyhole collapse and pore formation in laser welding, which contributes to the advancement of effective welding strategies for dissimilar alloys.

Visual analysis of interface deformation in multiphase flow

In multiphase flows, the evolution of fluid-fluid interfaces is of interest in many applications. In addition to fluid dynamic forces governing the flow in the entire volume, surface tension determines droplet interfaces. Here, the analysis of interface kinematics can help in the investigation of interface deformation and the identification of potential breakups. To this end, we developed a visualization technique using metric and shape tensors to analyze interface stretching and bending. For interface stretching, we employ the eigenpairs of the metric tensor defined for the deformation rate of the fluid surface. For interface bending, we present a technique that locally captures the interface curvature change in terms of a shape tensor, extracting its principal directions and curvatures. We then visualize interface deformation by combining both representations into a novel glyph design. We apply our method to study multiphase flow simulations with particular emphasis on interface effects. These include the interplay between fluid dynamics and surface tension forces leading to breakup processes following droplet collisions, as well as droplet-droplet interactions of different fluids where Marangoni convection along the surface is explicitly taken into account.Graphical abstract

Study on Slag Splashing Behavior in a 120 t Converter Based on Physical and Mathematical Simulation

The service life of converter linings is crucial for efficiency and emission reduction. Slag splashing performance is essential in steelmaking. This study constructs a physical model based on a specific 120 ton converter using similarity principles. Dimensional analysis is employed to investigate process parameters and fluid properties. The influence of various process parameters on slag splashing performance is analyzed. Mathematical simulations using the volume of fluid method are conducted to quantitatively assess the volume of slag splashing, determine the optimum lance height, and examine the effects of nitrogen flow rate on the impact crater profile, splashing shape, and angle. The results demonstrate that when the fluid viscosity and surface tension meet specific conditions, the lance height in the physical model and the prototype satisfy geometric similarity. However, as no suitable fluid meeting the conditions is found, a corrective relation for the lance height between the physical model and the prototype is established to optimize the process parameters. By adjusting the lance height and bottom gas flow rate, damaged areas can be repaired, while modifying the nitrogen flow rate alters the shape of the slag splashing, resulting in uniform slag splashing.

The influence of surface tension of interstitial fluid on the structural and surface properties of silicon dioxide obtained from nepheline-containing raw materials

The influence of surface tension of interstitial fluid on the structural and surface properties of silicon dioxide obtained from nepheline-containing raw materials

Numerical investigation of the gravity effect on two-phase flow and heat transfer of neon condensation inside horizontal tubes

The condensation flow and heat transfer characteristics of cryogenic neon inside horizontal tubes with diameters of 1 mm and 2 mm were numerically investigated. The mass flux ranged from 20 to 187 kg/(m2·s) for gravity levels includes zero gravity, Lunar gravity, Martian gravity, and Earth gravity. The effects of gravity on the condensation flow pattern, local condensate film distribution, and local and global heat transfer were analyzed in detail. The gravity effect on the condensation heat transfer showed three states, including enhancement, deterioration and gravity-independence, which were mainly determined by the mass flux and vapor quality. Under normal gravity, the condensation heat transfer coefficients increased with increasing mass flux and decreasing tube diameter. Under low mass flux, the cryogenic neon underwent enhanced condensation heat transfer under zero gravity and reduced gravity in the high vapor quality region but deteriorated condensation heat transfer in the low vapor quality region. By increasing the mass flux, the gravity effect was effectively suppressed, which resulted in gravity-independent behavior of condensation heat transfer in the high vapor quality region. The gravity effect significantly affected the liquid film distribution in the condensation process, with a more uniform distribution of the liquid film appearing along the circumferential direction as the gravity level decreased. However, due to the low surface tension of the deep cryogenic fluid, the condensation interface was more prone to flow instability under reduced gravity levels.

Mechanism underlying effect of expansive agent and shrinkage reducing admixture on mechanical properties and fiber-matrix bonding of fiber-reinforced mortar

Expansive agent (EA) and shrinkage reducing admixture (SRA) are utilized to reduce shrinkage and risk of cracking in concrete. EA compensates shrinkage by initial expansion, and SRA reduces surface tension in the pore fluid. Although EA and SRA effectively reduce shrinkage, they can impair micro-structure of concrete at high contents. The shrinkage reduction effect of EA and SRA is well known; however, there is limited knowledge about their negative effect on microstructure and fiber matrix interfacial transition zone (ITZ). The current study explores the effect of using 10 % CaO-based EA, 2 % SRA, and their combination on mechanical, shrinkage, and microstructural properties of fiber-reinforced mortar (FRM) made with 0.5 % steel fiber. The hydration products are characterized by X-ray diffraction and derivative thermogravimetric. Backscatter scanning electron microscopy, energy dispersive spectroscopy (EDS), and micro-hardness experiments are employed to characterize the microstructure of fiber-matrix ITZ at two distances of 50 and 100 μm surrounding the fibers. Experiment results indicate that the quality of ITZ and fiber-matrix bonding is impaired by using either EA or SRA. The highest drop is obtained by the combination of EA and SRA. The element analysis by EDS line and point scanning reveals the presence of longer silicate chain and stronger fiber-matrix ITZ in the reference mixture. Micro-hardness measurements confirm higher mechanical properties at the ITZ between 50 and 100 μm surrounding the fibers. Thermodynamic simulations and phase assemblages interpret the influence of EA and SRA on mechanical properties and shrinkage.

The variations and mechanisms of coal wettability affected by fracturing fluids with different concentrations of Ca2+ during fracturing

In low-porosity, low-permeability, and high-adsorption coalbed methane (CBM) reservoirs, the flow of fracturing fluid and methane gas is strongly affected by the wettability of coal. Ca2+ in mine water can affect the wettability of coal by changing the properties of the fracturing fluid, thus affecting the recovery efficiency of CBM. To investigate the mechanism of the wetting properties of bituminous coal by fracturing fluid with different concentrations of Ca2+, contact angle and T2 distribution curves were tested using an interfacial rheometer and low-field nuclear magnetic resonance (LF-NMR), and changes in water absorption and functional groups of coal soaked by fracturing fluid with different concentrations of Ca2+ were described using a precision electronic balance, X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR) to evaluate the wetting properties of coal. Molecular dynamics simulation was used to characterize the microscopic wetting properties of water molecules on the coal surface. Results show that when the concentration of Ca2+ is lower than 50 mg/L, the surface tension of the fracturing fluid gradually decreases, and the lowest value is 27.66 mN/m at 50 mg/L. The overall change in the contact angle and T2g value was lower than that of the control group (no Ca2+). The content of oxygen-containing functional groups on the surface of coal increased by 22.30%, and the content of C-O functional groups inside coal increased by 3.55%. The relative concentration and density of water molecules on the coal surface increase with increasing molecular diffusion ability. These results indicate that when the Ca2+ concentration is lower than 50 mg/L, the wettability of coal is enhanced, and thus, the fracturing fluid and methane gas flow capacity is improved. However, with increasing Ca2+ concentration, this phenomenon is reversed, and the water absorption of coal decreases, indicating that the wetting ability of coal decreases. The results of this study provide theoretical guidance that can be used to improve the recovery of CBM by fracturing and permeability enhancement measures, and preparing fracturing fluid in mine water to strengthen the protection of freshwater resources.