Showing papers on "Surface tension published in 1980"
TL;DR: In this article, the effects of replacing the usual no-slip boundary condition by a slip-coefficient boundary condition on solid walls are determined by means of Galerkin finite element solutions of the Navier-Stokes equation system for steady two-dimensional discharge of liquid from a sharp-edged slot.
216 citations
TL;DR: In this article, the authors measured the growth rate of air bubbles in water by rectified diffusion at 22.1 kHz and determined that although both the threshold and growth rate were in agreement with theory for normal values of the surface tension of water, the addition of a surfactant caused the observed thresholds and growth rates to deviate from the predicted values.
Abstract: Measurements are reported of the growth of air bubbles in water by rectified diffusion at 22.1 kHz. Values of the threshold acoustic pressure amplitude were obtained as a function of bubble radius, liquid surface tension, and gas concentration. Measurements of the rate of growth of bubbles by rectified diffusion were also obtained as a function of acoustic pressure amplitude for a range of different values of the liquid–vapor surface tension. It was determined that although both the threshold and the growth rate were in agreement with theory for normal values of the surface tension of water, the addition of a surfactant caused the observed thresholds and growth rates to deviate from the predicted values. Surface wave activity that could increase the diffusion rate by acoustic streaming was not detected at low radii and is not thought to be the principal mechanism for the increased diffusion. Some possible explanations are given for the effect.
197 citations
TL;DR: In this article, the equilibria of small solid solution crystals with isotropic surfaces in contact with vapor or fluid solutions are considered when the surface stress differs numerically from the surface free energy.
195 citations
TL;DR: In this paper, surface tensions of several binary mixtures are computed using the gradient theory of inhomogeneous fluids and the interfacial influence parameters are determined from mixing rules and pure fluid experimental tensions.
Abstract: Surface tensions of several binary mixtures are computed using the gradient theory of inhomogeneous fluids. The interfacial influence parameters are determined from mixing rules and pure fluid experimental tensions. A comparison of the compositional dependence of the predicted and experimental tensions indicates that the best results for nonpolar hydrocarbons are obtained from a geometric mixing rule for the influence parameter. Predicted tensions vs. composition for nonpolar systems are in excellent agreement with experiment, generally lying within 2% of observed data. Predictions are poor for alcohol solutions.
167 citations
TL;DR: In this paper, surface oxides on various carbon fibres were determined after modified oxidation treatment with nitric acid and improved wetting was investigated by contact angle measurements, by surface tension measurements and by chemical analysis of the chemisorpted diamine hardener.
148 citations
TL;DR: In this article, a variational energy stability theory for two-dimensional buoyancy-thermocapillary convection in a layer with a free surface is presented. But the authors do not consider the case of planar interfaces.
Abstract: Energy stability theory has been formulated for two-dimensional buoyancy–thermocapillary convection in a layer with a free surface. The theory yields a critical Rayleigh number RE for which R < RE is a sufficient condition for stability of the layer. RE emerges from the variational formulation as an eigenvalue of a nonlinear system of Euler–Lagrange equations. For the case of small capillary number (large mean surface tension) explicit values are obtained for RE. The analogous linear-theory results for this case are obtained in terms of a critical Rayleigh number RL. These are compared. It is found that the existence of the deformable interface can lead to a stabilization relative to the case of a planar interface. This result is explained in physical terms. The energy theory is then generalized to include general flow problems having three-dimensional disturbances, non-Newtonian bulk fluids and general interfacial mechanics such as surface viscosity and elasticity.
135 citations
TL;DR: In this article, the spreading on a water-air interface of a thin liquid film is examined for the situation in which surface tension gradients drive the motion, and a similarity solution is obtained numerically for unidirectional spreading when some general restrictions concerning the form of the liquid film constitutive relation is made.
Abstract: The spreading on a water–air interface of a thin liquid film is examined for the situation in which surface tension gradients drive the motion. A similarity solution is obtained numerically for unidirectional spreading when some general restrictions concerning the form of the liquid film constitutive relation is made. This solution gives the size of the film as a function of time and also the velocity and thickness distribution along the spreading film. Experiments are performed which show good agreement with the theory.
127 citations
01 Nov 1980
TL;DR: In this article, the equilibrium spreading pressure of a spreading liquid or vapor on polyethylene polymers was predicted exactly by π e = 2(γ d L γ d S ) 1 2 −2γ L where γLd is the dispersion force contribution to the surface tension of the spreading liquid and γSd is a contribution to surface energy of the substrate.
Abstract: When a spreading liquid or vapor can interact with a substrate only by dispersion forces, as with alkanes on any substrate, or with any spreading liquid on saturated hydrocarbon polymers, the equilibrium spreading pressure is shown to be predicted exactly by: π e =2(γ d L γ d S ) 1 2 −2γ L where γLd is the dispersion force contribution to the surface tension γL of the spreading liquid and γSd is the dispersion force contribution to the surface energy of the substrate. A new laboratory technique is introduced for direct measurement of πe of a spreading vapor on hydrophobic solids, using the difference in contact angles of a test liquid on the solid in air and in the presence of the spreading vapor. For cyclohexane on polyethylene at 20°C πe is found to be 7.19 dyn/cm; the above equation predicts 7.15 dyn/cm. By using this new technique it is proven unequivocably that high-energy liquids such as methylene iodide and water do not adsorb or spread on low-energy surfaces such as polyethylene or polytetrafluoroethylene.
126 citations
TL;DR: In this article, the authors derived the surface tension values of the contact angle of a given contact angle with a given liquid of known surface tension using the Young's equation of state.
Abstract: From the contact angle θ determined with one liquid (of known surface tension) only, it is possible to obtain the values of the surface tensions γSV and γSL, via the equation of state (1): where the subscripts S and L stand for the solid S and the liquid L, whilst the subscript V stands for vapor. In conjunction with Young's equation (2): relation [l] yields: With the help of a computer program values for γsv (1) and for γSl (3) can be derived for different values of the contact angle 8 obtained with a liquid of given γLV
120 citations
TL;DR: In this paper, a unified theory is proposed to explain the ultra-low inter-facial tension minimum observed in dilute petroleum sulfonate solution/oil systems encountered in tertiary oil recovery process.
Abstract: A unified theory is proposed to explain the ultra-low inter-facial tension minimum observed in dilute petroleum sulfonate solution/ oil systems encountered in tertiary oil recovery process. The relative distribution of the surfactant in oil and aqueous phase was determined using UV spectrophotometry as well as the monolayer technique. The critical micelle concentration ( CMC) of the aqueous phase equilibrated with oil was measured using surface tension, osmotic pressure and light scattering measurements. For three major variables namely, the surfactant concentration, the chain length of oil and the salinity of brine, the interfacial tension minimum was found to occur whenever the equilibrated aqueous phase was at CMC. This minimum in interfacial tension also coincided with partition coefficient of unity for surfactant distribution in oil and brine. The increase of the interfacial tension after reaching a minimum was attributed to the decrease in the onomer concentration in the aqueous phase. Thre...
115 citations
TL;DR: In this paper, a series of surface active azo and stilbene compounds are synthesized and their monolayer properties at the air-water interface are studied by surface pressure-surface area measurements and spectroscopic techniques.
Abstract: In order to develop new molecules as function components of monolayer assemblies, a series of 9 surface-active azo and stilbene compounds are synthesized. Their monolayer properties at the air-water interface are studied by surface pressure-surface area measurements and spectroscopic techniques. The results show that small changes in the molecular structure of the surfactants (such as, length of the fatty acid chain and type of the chromphore) have an immense influence on the monolayer properties. For monolayers of compounds I and III-VIII, van der Walls-like isotherms are obtained, which show a liquid expanded state, a phase transition region, and a condensed state. From monolayer absorbance spectra it is found that in the liquid expanded state at 100 to 110 sq angstroms/molecule the chromphores lie flatly on the water surface, forming monomers. The phase transition region of the isotherms can be assigned to a change of orientation of the chromophore axis (horizontal to vertical) and an aggregation process of the chromophores (monomers to H aggregates). 20 references.
TL;DR: In this paper, the adsorption of two ionic surfactants, sodium alkyl sulfate and potassium oleate, was investigated using polystyrene, poly(methyl methacrylate), and their copolymer latices.
TL;DR: In this paper, a physical model is presented to explain the dramatic interfacial tension minima that may sometimes occur during the equilibration of a surface-active solute between two liquid phases.
TL;DR: In this article, the surface tension of mixed fluorocarbon (NF) and hydrocarbon (STS) surfactants was measured in 0.01 and 0.05 M sodium chloride solutions, and 2 kinds of mixed micelles were found to coexist in equilibrium.
Abstract: The surface tension of mixed fluorocarbon (NF) and hydrocarbon (STS) surfactants was measured in 0.01 and 0.05 M sodium chloride solutions, and 2 kinds of mixed micelles were found to coexist in equilibrium. The micellar composition was determined from the surface tension data on NF-STS solutions above the critical micelle concentration (CMC). In the relation between the surface tension at the CMC and micellar composition, a plateau region was observed, and both ends of this region represent the mutual solubility of NF and STS in the mixed micelles. The CMC vs. monomeric composition curve breaks where 2 micellar
TL;DR: In this paper, the effects of surface tension on steep water waves in deep water were investigated and a Stokes-type expansion method was given which can be applied to most wavelengths.
Abstract: This paper continues an investigation of the effects of surface tension on steep water waves in deep water begun in Hogan (1979a). A Stokes-type expansion method is given which can be applied to most wavelengths. For capillary waves (2 cm or less) it is found that the surface of the highest wave encloses a bubble of air, as was found for pure capillary waves by Crapper (1957). For intermediate waves (20 cm) the wave profiles are similar to those of pure gravity waves and the wave properties increase monotonically. For gravity waves (200 cm) the wave properties all exhibit a maximum just short of the maximum wave height obtained by the method. The integral properties for all the waves are drawn and given in numerical form in the appendix.
TL;DR: In this article, a density functional theory for the one particle densities and the thermodynamic properties of multicomponent, classical, inhomogeneous, charged fluids was formulated and applied to the liquid-vapour interface of a molten alkali halide and some formally exact results for ionic density profiles and surface tension were derived.
Abstract: We formulate a density functional theory for the one particle densities and the thermodynamic properties of multicomponent, classical, inhomogeneous, charged fluids. We show that for slowly varying densities, the Helmholtz free energy can be expanded as a series of density gradients plus an explicit electrostatic contribution. The coefficients in this expansion are directly proportional to moments of the non-coulombic part of the Ornstein-Zernike direct correlation functions of a uniform mixture. An explicit formula for the stress tensor is derived. The theory is applied to the liquid-vapour interface of a molten alkali halide and some formally exact results for the ionic density profiles and surface tension are derived. Using the truncated gradient expansion, we develop a tractable approximation scheme for the surface properties. The surface tension is of the van der Waals form plus a contribution which involves the integral of the off-diagonal part of the Maxwell stress tensor through the interface. The...
TL;DR: When the sum of the interactions of two different materials with a liquid medium is larger than the sum between the interactions between the two materials and those between the molecules of the liquid medium themselves, the net van der Waals interaction between two materials immersed in that liquid medium will be repulsive.
TL;DR: In this article, the electrical conductance, density, and surface tension of more than ninety multi-component salt systems have been systematically collected and evaluated and the results were given for mixtures over a range of compositions and temperatures.
Abstract: Data on the electrical conductance, density, and surface tension of more than ninety additional multi‐component salt systems have been systematically collected and evaluated. Results are given for mixtures over a range of compositions and temperatures. Values of the above properties for some sixty single salt systems are also reported.
TL;DR: In this article, a mathematical model consisting of the Navier-Stokes and thermal energy equations, together with the appropriate boundary conditions for both media, is presented to solve this boundary value problem, with the expansion parameter being the Marangoni number.
Abstract: The Marangoni phenomenon is shown to be the primary mechanism for the movement of a gas bubble in a nonisothermal liquid in a low-gravity environment. In such a two-phase system, local variations in surface tension at the bubble surface are caused by a temperature gradient in the liquid. Shearing stresses thus generated at the bubble surface lead to convection in both media, as a result of which the bubble moves. A mathematical model consisting of the Navier-Stokes and thermal energy equations, together with the appropriate boundary conditions for both media, is presented. Parameter perturbation theory is used to solve this boundary value problem, with the expansion parameter being the Marangoni number. The zeroth, first- and second-order approximations for the velocity, temperature and pressure distributions in the liquid and in the bubble, and the deformation and terminal velocity of the bubble are determined. Experimental zero-gravity data for a nitrogen bubble in ethylene glycol, ethanol, and silicone...
TL;DR: An experimental procedure that can be used to measure the interfacial free energy density for the adhesion of membranes of large vesicle to other surfaces is outlined and analyzed and the measurable range of membrane surface affinity is 10(-4)-3 erg/cm2 for large phospholipid bilayer vesicles and 10(-2)-10 erg/ cm2 for red blood cells.
TL;DR: In this paper, a Monte Carlo calculation of the surface tension of water at 25°C is described, where the free energy required to create a surface in a system of 256 water molecules with periodic boundary conditions imposed.
Abstract: In this paper we describe a Monte Carlo calculation of the surface tension of water at 25 °C. The procedure used involves computing the free energy required to create a surface in a system of 256 water molecules with periodic boundary conditions imposed. In order to optimize computing time we have used a modified version of an umbrella sampling algorithm suggested by Torrie and Valleau. The excess surface free energy is computed in a series of steps, the most important of which consist of incremental calculations in which the interface is gradually created. Our final result is γ=97±6 dynes/cm, larger than the experimental value of 72 dyn/cm. Reasons for the rather large difference are discussed. Our result can be used as a basis for comparison of the surface tension of water/air interfaces with the surface tension of other aqueous interfaces calculated using the same technique.
TL;DR: In this article, a review of classical systems to which capillarity is relevant is given, with particular emphasis on pendent and sessile drops, emergent and captive bubbles, holms and fluid bridges.
Abstract: An indication is given of the wide range of classical systems to which capillarity is relevant. The basic laws are outlined with the introduction of the term effective area and Gauss's law. Interface configurations are classified, with particular emphasis on pendent and sessile drops, emergent and captive bubbles, holms and fluid bridges. These types of fluid body in a gravitational field form a major portion of the review, their properties being described from the phenomenological and thermodynamic approaches to criteria for equilibrium and stability. A distinction is made between Laplace or mechanical and Kelvin, physicochemical or diffusional equilibrium and stability. Some applications, including aspects of interfacial tension determination, are given in more detail than those used for illustration.
TL;DR: In this paper, a solution for transient flow in infinite thin layers is presented, where the layer is thin enough so that inertial forces are negligible, and the equations of motion are non-dimensionalized by an explicit scaling procedure.
Abstract: A spatially varying temperature distribution imposed on the free surface of a liquid leads to an effective tractive force on the surface because of the dependence of surface tension on temperture. A solution for transient flow in infinite thin layers is presented. The layer is thin enough so that inertial forces are negligible. The equations of motion are nondimensionalized by an explicit scaling procedure. Small‐time and large‐time solutions are obtained with variation of surface height as part of the solution.
TL;DR: In this article, the authors present results of calculations of the equilibrium surface tension and density profiles for the liquid-vapour interface of a binary mixture of 12-6 fluids, based on a density-functional theory for the Helmholtz free energy of the inhomogeneous mixture.
Abstract: We present results of calculations of the equilibrium surface tension and density profiles for the liquid-vapour interface of a binary mixture of Lennard-Jones 12-6 fluids. The calculations are based on a density-functional theory for the Helmholtz free energy of the inhomogeneous mixture. This is a ‘microscopic’ generalization of the van der Waals-Cahn-Hilliard theory for the interface of a binary mixture. Our calculations cover the full range of liquid-vapour coexistence and the whole range of concentration. We find a correlation between the excess surface tension of the mixture and the surface segregation (adsorption) of the species with the lower surface tension. The ways in which segregation and excess surface tension depend on the Lennard-Jones parameters of the pure components are briefly discussed. Our results for the excess surface tension of mixtures of Ar and N2 and Ar and CH4 are compared with experiment; the agreement is reasonable.
TL;DR: In this paper, the authors present an analysis of ρ(T) curves which allows the signs of dσ SL dT and dσ GB dT to be directly determined.
TL;DR: In this paper, the deformation mode at the end of a water tree channel is described and the strain amplitude of the PE at the water interface can be calculated using a simple model.
Abstract: Water treeing is a well known fracture phenomenon in polyethylene (PE) and crosslinked polyethylene (XLPE) high voltage cable insulation. We studied two phenomena: (1) The insulation material is mechanically fatigued by electrostriction as is shown by measuring the relevant electrostriction constant, which moreover is compared with literature values on other polymers. The observed "electrostriction" is found to originate mainly from the Coulomb force. Using a simple model, the deformation mode at the end of a water tree channel can be described and the strain amplitude of the PE at the water interface can be calculated. (2) Under high voltage, the surface tension at the PE-water interface decreases strongly as we found experimentally. The observation that this decrease is proportional to the square of the applied field strength is explained. The joint effect of the Coulomb force and the reduced surface tension may cause a fracture phenomenon, well known in the field of polymers, called environmental fatigue failure (or thermal softening). The same assumption is made as in "common" environmental stress cracking of PE with aqueous detergents, viz. that the low surface tension plays an essential and not a coincidental role.
TL;DR: Cloud point measurements have been performed on the mixtures isobutyric acid + water and perfluoromethylcyclohexane + methylcyclo hexane in the neighborhood of their critical solution temperatures as mentioned in this paper.
Abstract: Cloud‐point measurements have been performed on the mixtures isobutyric acid + water and perfluoromethylcyclohexane + methylcyclohexane in the neighborhood of their critical solution temperatures. The stability limit is in accord with classical nucleation theory for values of the reduced temperature e = (Tc−T)/Tc greater than about 10−4 but rises sharply as the critical point is approached. Interfacial tension measurements on both mixtures are also reported.
TL;DR: In this article, the critical velocity of engulfing V c of acetal, nylon-6,6, and nylon-12 particles when encountered by the solidification front of salol is reported as a function of particle size.