Terms Of Surface Tension Research Articles

High-order spectral method for the simulation of capillary waves with complete order consistency

We develop the simulation capability for surface capillary waves based on the high-order spectral method, which solves the primitive Euler equations truncated to a prescribed nonlinearity order in wave steepness. The uniqueness in this development is to construct an order-consistent scheme to model the surface tension term, so that the simulation at arbitrary order forms a Hamiltonian system with complete energy conservation. The model equations are integrated in time using an integration factor scheme coupled with a 4th-order Runge-Kutta method (IF-RK4), where the linear terms are solved analytically (i.e., under machine precision in the numerical implementation), and nonlinear terms explicitly. The performance of the model is tested by simulation of a progressive Crapper wave and a broadband capillary wave spectrum. The property of order consistency as well as the enhanced accuracy and stability due to the IF-RK4 (compared to RK4 only) are clearly benchmarked. We finally show the effectiveness of the model to reproduce (for the first time) the thermal equilibrium spectrum of capillary waves when energy is injected at small scales of the wave field.

Aging effect of atmospheric pressure plasma jet treated polycaprolactone polymer solutions on electrospinning properties

ABSTRACTIn previous work, an atmospheric pressure plasma jet was applied to successfully improve the electrospinnability of poly‐ε‐caprolactone (PCL) which enabled the fabrication of beadless nanofibers. In this paper, we report the aging effect of the plasma treatment to evaluate the robustness of the developed process. For this purpose, plasma‐treated PCL polymer solutions with different exposure time were stored for 1 and 8 days and the aged solutions were analyzed in terms of conductivity, viscosity, surface tension, pH, and polymer molecular weight. During storage, the surface tension and acidity of the plasma‐treated solutions were maintained constant. However, the viscosity was found to be significantly lower after 8 days which was attributed to PCL degradation. Electrospinning of all stored PCL solutions resulted in the generation of beadless PCL nanofibers. The plasma treatment effects were thus found to be highly stable over time and capable of producing high‐quality PCL nanofibers up to 8 days. © 2020 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2020, 137, 48914.

Inkjet Printing of Li‐Rich Cathode Material for Thin‐Film Lithium‐Ion Microbatteries

The observed downsizing tendency of microelectronic devices leads to a higher demand in new types of miniaturized energy sources. Thin‐film Li‐ion batteries (LiBs) are promising candidates to fulfil this function. New materials and technologies should be investigated for customized production of miniaturized, high‐efficient solid‐state batteries. Herein, inkjet printing technology is considered as a promising one for the fabrication of LiBs. The modification of crystalline lattice of Li‐rich cathode material by aluminium, sodium, and potassium and their influence on power efficiency are studied in detail. Lithium‐manganese‐rich compounds are chosen as the most suitable composition of an active component for LiBs fabrication. The stable aqueous colloidal ink composition is synthesized and its rheological parameters are optimized for inkjet printing in terms of viscosity, surface tension, and contact angle. Protocols for inkjet printing for the fabrication of thin‐film cathodes with the thickness of less than 10 μm are reported. The good correlation of electrochemical properties such as average voltage, capacity, and energy between inkjet printed and conventionally fabricated electrodes confirms the feasibility of the suggested technological approach and selected cathode material composition.

Numerical analysis of coupled Kelvin–Helmholtz and Rayleigh–Taylor instability on inclined walls

The front tracking method was used to study the 2D Kelvin–Helmholtz (K–H) instability on an inclined wall for three-component immiscible fluids. Coupled effects between K–H instability and Rayleigh–Taylor (R–T) instability were studied by analyzing the effect of inclination angle, Atwood number (At), and Richardson number (Ri) on interface evolution. The results show that the coupling of R–T instability has an important influence on the development of K–H instability. The R–T instability first affects the lower interface and then the upper interface at different inclination angles, and it is also observed that the critical time of the coupled effect is earlier with an inclined wall. The R–T instability promotes the development of upper and lower interfaces at different At numbers. In addition, the billow height increases with the increase in At number and the influence of R–T instability on the upper interface can be neglected when the dimensionless time is less than critical time t = 0.6. The R–T instability has little effect on the different surface tension in terms of Richardson number (Riσ).

Pyrimethanil Ionic Liquids Paired with Various Natural Organic Acid Anions for Reducing Its Adverse Impacts on the Environment.

In this study, nine pyrimethanil ionic liquids (PILs) were synthesized through an acid-base reaction with nine naturally derived organic acid anions to improve the physicochemical properties and reduce the environmental adverse impacts. The PILs presented lower volatilization, higher photostability, better soil adsorption capacity, and improved fungicidal activity relative to pyrimethanil. When the length of the carbon chains in the anions was increased, the PILs showed better properties in terms of melting point, water solubility, volatility, and surface tension. The photostabilities and fungicidal activities of the PILs were significantly improved when cyclic compounds were used as the paired anion ions. With enhanced physicochemical properties and better fungicidal activity, PIL7 was selected as the best alternative to pyrimethanil. The intrinsic disadvantages of pyrimethanil could be surmounted using the system developed in the study; thus, ILs could have immense potential in the development of eco-friendly and efficient fungicides in the future.

Reproducibility of Gaseous Phase Area on Journal Bearing Utilizing Multi-Phase Flow CFD Analysis under Flooded and Starved Lubrication Conditions

It is important to predict the gaseous phase area of journal bearing. However, a detailed calculation method for such gaseous phase areas has not yet been proposed. In this study, the gaseous-phase areas in small bore journal bearings under flooded and starved lubrication conditions are analyzed in terms of the computational fluid dynamics (CFD) of two-phase flow while using a volume of fluid (VOF) method. Furthermore, the influence of surface tension and vapor pressure conditions were investigated, and the analytical and experimental results were compared. The analytical results of VOF for vapor pressure and surface tension were observed to be consistent with the experimental observations under both flooded and starved lubrication conditions. Furthermore, under starved lubrication condition, the analytical results agree well with the observed results for the interface of the oil film and cavitation upon the rupture of the oil film. While using these results, CFD analysis of the two-phase flow of the VOF can be conducted in terms of vapor pressure and surface tension to estimate the gaseous-phase areas of journal bearings under flooded and starved lubrication conditions.

Computer simulations to approach surface tension by means of a simple mesoscopic mechanical model

AbstractA small insect can stand or walk on water surface, drops of mercury do not spread on a solid surface, and a meniscus is formed at the free surface of a liquid contained in a thin vessel. These phenomena can be seen as macroscopic manifestations of molecular interactions and can be explained macroscopically in terms of surface tension. In this study, we deal with an approach to surface tension from a mechanical point of view, presenting a simple mesoscopic mechanical model of surface tension and the results of its implementation in numerical fluid dynamics simulations. Particularly, phenomena like droplet formation without gravity and with gravity when it can drop from a narrow hole like a trickling tap, the formation of a meniscus at the free surface of a liquid contained in a vessel, the behavior of a small piece of solid on a liquid surface, and a sessile droplet are studied. Student and teachers can study the behavior of a liquid due to the surface tension by using the numeric simulations as a “tool” for analyzing several different situations.

A mesoscopic mechanical model of the surface tension and some simulation results

Drops of mercury do not spread on a surface. A metal paper clip can float on water. These phenomena are macroscopic manifestations of molecular interactions and can be explained in terms of surface tension. In this study, we discuss a simple mesoscopic mechanical model of the surface tension and the results of numerical fluid dynamics simulations implemented on the basis of it. We study the droplet formation without and with gravity when it can drop from a narrow hole like a trickling tap and finally the behaviour of free surface liquid in a vessel. Teachers and students can be able to study the surface tension by using the computer simulation as a “tool” for analysing and discussing the droplet and the liquid behaviour in several different conditions.

Fabrication of β-carotene loaded glucuronoxylan-based nanostructures through electrohydrodynamic processing

Various concentrations of β-carotene (2.5–20% w/w dry mucilage weight) were loaded within Cydonia oblonga mucilage (COM) which further processed through electrohydrodynamic processing (EHP) to attain BC-Loaded nanostructures of high thermochemical stability. The BC loaded COM systems were characterized in terms of droplet size, rheological properties, surface tension, and electrical conductivity and their subsequent impacts on the morphology and physicochemical attributes of the produced nanostructures were studied. Increasing the β-carotene content, increased the viscosity and droplet size of colloidal systems but diminished their conductivity and surface tension. A transition from monomodal to bimodal size distribution was also observed at higher levels of β-carotene incorporation. In the case of EHP-produced nanostructures, scanning electron microscopy observations revealed a transition from nanoparticle to nanofiber by increasing the BC content from 2.5 to 20%. At lower concentrations of BC (2.5 and 5%) electrospraying was the dominant phenomenon that resulted in producing homogenous nanoparticles while the beaded fibers and nanofiber structures were obtained at 10 and 20% concentrations of BC, respectively. Attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and encapsulation efficiency of the produced nanostructures revealed successful encapsulation of BC into the COM polymer structure through EHP. The results of these assessments showed that the nano-particles comprising BC had more homogenous structure and higher encapsulated BC compared to the BC-loaded nano-fibers. The results of X-ray diffraction (XRD) and differential scanning calorimetry (DSC) measurements revealed amorphous structure of the produced nanostructures. Thermogravimetric assessments corroborated the higher thermal stability of BC loaded nanostructures compared with the free BC. These results provided novel information on the ability of COM in encapsulating bioactive agents through electrohydrodynamic processing.

A volume of fluid method algorithm for simulation of surface tension dominant two-phase flows

In this article, a two-phase flow algorithm that uses an explicit Adams–Bashforth scheme coupled with volume of fluid (VOF) method in a uniform staggered Cartesian grid for surface tension dominant simulation is presented. The interface reconstruction procedure is implemented using the Weighed Linear Interface Calculation (WLIC) algorithm. The level set (LS) function instead of VOF function is adopted for calculation of not only the interface normal vectors in the WLIC algorithm but also the surface tension terms in the Navier–Stokes equations. This VOF method is compared with LS method and other experiment results in the literature for vortex deforming, milk crown, droplet impacting into deep liquid pool and bubble bursting at a free surface problems to show whether mass can be well conserved and breaking and merging phenomena can be accurately simulated.

Surface properties in surfactant systems containing amino acid-based surfactants

The development of green surfactants produced from renewable raw materials at the expense of petrochemical-based surfactants took into account the increasing requirements for environmental protection and the demand of the society for sustainable development. A variety of renewable raw materials such as triglycerides, carbohydrates or amino acids are used in green surfactant synthesis. The natural structure of green surfactants induces low toxicity and high biodegradability. In this work was investigated the behaviour of surfactant systems containing synthesized amino acid-based surfactants (sodium lauroy lglycinate and sodium lauroyl sarcosinate) and amphoteric or nonionic surfactants, highlighting the differences between surfactant systems containing sodium lauroyl glycinate or sodium lauroyl sarcosinate due to nitrogen methylation of the amide nitrogen in the latter. Synergetic behaviour of aqueous surfactant systems were found, leading to improved properties in terms of surface tension and foaming power.

Radial postbuckling of nanoscaled shells embedded in elastic foundations based on Ru's surface stress elasticity theory

In this article, the nonlinear buckling and postbuckling response of cylindrical nanoshells under radial compressive load is investigated on the basis of a new surface elasticity theory. To this point, in contrast to the previous models based on the Gurtin-Murdoch elasticity theory, a new non-classical shell model based on the Ru's surface elasticity theory is developed in which the non-strain displacement gradient terms are eliminated from the surface stress-strain relations. The non-classical governing equations are derived using the principle of virtual work. Then they are deduced to boundary layer-type equations including simultaneously the nonlinear prebuckling deformations and the large postbuckling deflections. By using a singular perturbation technique, the new size-dependent problem is solved. It is indicated that due to the immovable edge supports and in the absence of the hydrostatic pressure, surface effects lead to an initial shortening caused by the induced residual strains. Additionally, the residual strain and initial surface tension terms vanish in the size-dependent nonlinear governing equations. Moreover, it is observed that this initial shortening diminishes quickly for thicker nanoshells.

Simulation of evolution mechanism of dynamic interface of aqueous foam in narrow space base on level set method

The properties of foam fluid are substantially determined by its interfacial dynamics changes during foam transport. In this research, a foam flow simulation model based on the level set method and the N–S equation with surface tension term is established to simulate the dynamic interface evolution mechanism of group foam and individual foam from various aspects such as drainage process and foam migration in porous media, coalescence and Jamin effect. The results show that the foam life decreases linearly with the logarithm of the surface tension and enhances linearly with the liquid viscosity. For foam transport in porous media, both flowing foam and trapped foam exist, and the pressure fluctuates at a certain pressure value and the best foam structure is achieved at the optimum conditions with the optimum values of gas-liquid ratio, surface tension, and porosity being 1:1˜3:2, 0.1˜0.3, and 44.4%, respectively. Besides, the temporary blocking effect of foam has been verified. During the foam coalescence, foam gradually evolves towards minimum interfacial energy with oscillating and gradually decreasing foam volume. During the process of the foam passing through the throat, the maximum pressure occurs when the front end of the foam reaches the narrowest point, and the minimum pressure occurs when half of the foam passes through the narrowest point. The maximum pressure elevates linearly with the surface tension and the inverse of the throat radius.

Experimental Study of Air Entrainment Rates due to Inclined Liquid Jets

AbstractThe air entrainment rate due to inclined liquid jet plunging into a pool was investigated experimentally. Three types of fluids with varying physical properties in terms of viscosity and surface tension were utilized. For the impinging jet test section, nozzles with different inner diameters were selected. The inclination angles and liquid jet velocities at the nozzle outlet were varied and the entrained air rate was measured by the soap meniscus method. Taking the falling velocity of the liquid jet as a characteristic velocity, it was found that the air entrainment rate under the present experimental condition largely depended on the Weber number. From the obtained database, a new empirical model dependent on the Weber number and Laplace length scale is proposed which is capable of predicting the air entrainment flow rate at a mean absolute relative deviation of 21.7 %.

Investigation on turbulence in the vicinity of liquid-liquid interfaces – Large eddy simulation and PIV experiment

In this work, the turbulence in the vicinity of the liquid-liquid interfaces in an incompressible interfacial flow is investigated numerically and experimentally. A new large eddy simulation formulation is employed where all the subgrid scale (SGS) terms appearing in the filtered governing equations are closed by a volume of fluid-based Approximate Deconvolution Model (ADM-VOF) (Saeedipour et al., 2018). In this structural turbulence modelling approach, the SGS terms of stress tensor and surface tension in the Navier-Stokes equations, as well as the interface dynamics in the VOF transport equation, are mathematically reconstructed from the resolved scales. An oil-water benchmark experiment was designed for validation purposes where an oil layer is poured on the top of the water into which a submerged turbulent jet is injected and interacts with the oil–water interface. The interactions of the turbulence with the liquid-liquid interfaces are then studied by shadowgraphy visualization and time-resolved PIV measurement. Two sets of LES were performed using the ADM-VOF and a conventional LES model based on eddy-viscosity approach. The statistics of interfacial turbulence including velocity fluctuations and interface dynamics are analyzed and compared with the ones obtained from the experiment. The results reveal that in the interface vicinity the ADM-VOF approach, which reconstructs more turbulent scales and includes the SGS terms of turbulence-interface interactions, is of superior performance in predicting the energy spectra and statistics of turbulence. Far from the interface no particular difference between the LES models was observed. In addition, the temporal average of the interface motion as well as the evolution of the interfacial area is studied. While both models predict the averaged temporal evolution of the interface similarly, the ADM-VOF revealed its potentials for high fluctuating regions as it accounts for the effect of SGS term interface dynamics. This study provides a perspective for connecting the interfacial turbulence to metallurgical aspects of the continuous casting process.

Effects of metastable phases on surface tension, nucleation, and the disappearance of polymorphs.

In nature, we often find that multiple solid phases form from the same solution. Zeolites present the best-known example. The preferential formation of one solid form over the other, at specific temperatures, is often explained by invoking a competition between thermodynamic and kinetic control. A quantitative theory, however, could not be developed because of the lack of accurate values of relevant surface tension terms, although some estimates of thermodynamic functions (like enthalpy and entropy) are becoming available. Motivated by the observation that wetting of the interface between two stable phases by multiple metastable phases of intermediate order can reduce the surface tension significantly [T. R. Kirkpatrick, D. Thirumalai, and P. G. Wolynes, Phys. Rev. A 40(2), 1045 (1989)], we develop a statistical mechanical approach based on a Landau-Ginzburg type free energy landscape to calculate the surface tension under various free energy situations. We analyze the trapping of a metastable phase in the presence of a thermodynamically stable phase. The interplay between free energy differences and the surface tension is partly captured in classical nucleation theory. We provide an explanation of the quickly disappearing polymorphs (QDPMs) that often melt back to the liquid (or the sol) phase. To this aim, we have presented the failure of classical nucleation theory and the importance of considering a multidimensional nucleation theory. Simple model calculations are performed to show that the surface tension between two coexisting stable phases (melt and the stable crystalline forms) depends significantly on the number, relative depths, and arrangements of the free energy minima of the metastable phases. Even a change in the curvature of the free energy surfaces induced by the change in temperature (T) can play a role in determining the sequence of the formation of phases. Finally, we show that our model systems could describe some of the real polymorphic systems, like phosphates and zeolites.

Synthesis and properties of dihydroxyoleic acid methyl ester ethoxylates

In this paper, epoxy methyl oleate (EMO) was used as the raw material to obtain the dihydroxyoleic acid methyl ester (DHOME) through ring-opening reaction. Then, the DHOME was reacted with ethylene oxide (EO) under Al-Mg composite oxide catalyst to synthesize a novel nonionic surfactant: dihydroxyoleic acid methyl ester ethoxylate (DHOMEE), which has both alcohol polyether and ester polyether chains. FT-IR was used to characterize the molecular structure of target product. Products with different EO addenda (DHOMEE-10, DHOMEE-15, DHOMEE-20) and conventional nonionic surfactants fatty acid methyl ester ethoxylate (FMEE) and methyl oleate ethoxylate (OMEE) were compared in terms of application performance. The results showed that DHOMEE is superior to conventional surfactants in terms of wetting, emulsification, foam and surface tension. In similar products, the performance of DHOMEE-15 is better than those of DHOMEE-10 and DHOMEE-20.

Numerical analysis on cavitation effects in submerged water jet added with turbulent drag-reducing additives of CTAC

In this paper the cavitation phenomenon and bubble collapse in submerged water jet added with CTAC were studied. The cavitation simulation was based on an improved cavitation model established by introducing coefficients into traditional cavitation model. The coefficients were obtained by fitting the numerical solutions of Rayleigh-Plesset equation in which the viscosity term and surface tension term were not neglected. Cross model was also employed to express the shear-thinning character of the surfactant solution. Simulation results show that the whole cavitation intensity decreased but the scale of cavitation region increased in drag-reducer solution. The submerged water jet added with drag-reducer was less dispersed and the stagnation pressure near the wall was significantly improved. Simulation results of the bubble collapse process show that the bubble collapsed more slowly in drag-reducer solution in comparison with that in pure water. The two pressure peaks near the wall during the collapse process appeared later in drag-reducer solution and the maximum value of the pressure generated in drag-reducer solution was less than that in pure water.

A weakly compressible scheme with a diffuse-interface method for low Mach number two-phase flows

A weakly compressible scheme for gas–liquid two-phase flows with low Mach number is proposed for a fully-explicit time integration. The scheme is based on the fractional-step method with the Euler equation solver and time integration for viscous, surface tension and gravity terms. For the efficient solution of the Euler equation, we introduce the directional-splitting method and the method of characteristics which is applicable to semi-Lagrangian methods. A reduction of the speed of sound is also taken into consideration to enlarge the time step intervals. The primitive flow variables are time-integrated on the node-center configuration. To capture the gas–liquid interface, the conservative phase-field equation is solved by using the multi-moment method. It is computed as a conservative form for the volume-averaged value defined at the cell center, in which the flow velocities are given on the node. We discard the exact momentum conservation, however the total mass of gas and liquid is conserved by introducing a phase-field variable. Several benchmark problems are examined and the results of the explicit scheme are in good agreement with the experimental and computational references.

Interface effects of strange quark matter with density dependent quark masses

We study the interface effects in strangelets adopting mean-field approximation (MFA). Based on an equivparticle model, the linear confinement and leading-order perturbative interactions are included with density-dependent quark masses. By increasing the confinement strength, the surface tension and curvature term of strange quark matter (SQM) become larger, while the perturbative interaction does the opposite. For those parameters constrained according to the 2$M_\odot$ strange star, the surface tension is $\sim$2.4 MeV/fm${}^2$, while unstable SQM indicates a slightly larger surface tension. The obtained results are then compared with those predicted by the multiple reflection expansion (MRE) method. In contrast to the bag model case, it is found that MRE method overestimates the surface tension and underestimates the curvature term. To reproduce our results, the density of states in the MRE approach should be modified by proper damping factors.