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Sample records for effective surface tension

  1. Surface Tension

    NASA Technical Reports Server (NTRS)

    Theissen, David B.; Man, Kin F.

    1996-01-01

    The effect of surface tension is observed inmany everyday situations. For example, a slowly leaking faucet drips because the force surface tension allows the water to cling to it until a sufficient mass of water is accumulated to break free.

  2. Effect of Gravity on Surface Tension

    NASA Technical Reports Server (NTRS)

    Weislogel, M. M.; Azzam, M. O. J.; Mann, J. A.

    1998-01-01

    Spectroscopic measurements of liquid-vapor interfaces are made in +/- 1-g environments to note the effect of gravity on surface tension. A slight increase is detected at -1-g0, but is arguably within the uncertainty of the measurement technique. An increased dependence of surface tension on the orientation and magnitude of the gravitational vector is anticipated as the critical point is approached.

  3. Effect of capillary waves on surface tension

    NASA Technical Reports Server (NTRS)

    Kayser, R. F.

    1986-01-01

    The present study is concerned with the effect which a cutting off of the capillary waves has on surface tension, taking into account a calculation based on capillary-wave theory. For simplicity, three-dimensional systems are considered, and capillary-wave theory is used to calculate sigma-k, the surface tension of an interface where only those modes with at least one wave-vector component greater than k are allowed. Attention is given to a review of capillary-wave theory, the calculation of surface tensions, a determination of the range of validity of capillary-wave theory, and some numerical examples. The quantitative behavior of sigma-k and its relation to the surface tension of a finite-size system are considered. The most surprising result is that sigma-k can be significantly larger than the unconstrained surface tension.

  4. Surface tension effects on submerged electrosprays

    PubMed Central

    Marín, Álvaro G.; Loscertales, Ignacio G.; Barrero, Antonio

    2012-01-01

    Electrosprays are a powerful technique to generate charged micro/nanodroplets. In the last century, the technique has been extensively studied, developed, and recognized with a shared Nobel price in Chemistry in 2002 for its wide spread application in mass spectrometry. However, nowadays techniques based on microfluidic devices are competing to be the next generation in atomization techniques. Therefore, an interesting development would be to integrate the electrospray technique into a microfluidic liquid-liquid device. Several works in the literature have attempted to build a microfluidic electrospray with disputable results. The main problem for its integration is the lack of knowledge of the working parameters of the liquid-liquid electrospray. The “submerged electrosprays” share similar properties as their counterparts in air. However, in the microfluidic generation of micro/nanodroplets, the liquid-liquid interfaces are normally stabilized with surface active agents, which might have critical effects on the electrospray behavior. In this work, we review the main properties of the submerged electrosprays in liquid baths with no surfactant, and we methodically study the behavior of the system for increasing surfactant concentrations. The different regimes found are then analyzed and compared with both classical and more recent experimental, theoretical and numerical studies. A very rich phenomenology is found when the surface tension is allowed to vary in the system. More concretely, the lower states of electrification achieved with the reduced surface tension regimes might be of interest in biological or biomedical applications in which excessive electrification can be hazardous for the encapsulated entities. PMID:24155865

  5. Surface tension effects in levitated helium drops

    NASA Astrophysics Data System (ADS)

    Vicente, Carlos Luis

    We report our investigations of surface tension driven flows in magnetically levitated 4He drops. By levitating helium drops in a magnetic trap we are able to observe the free surface of drops as they undergo shape oscillations. We also study the dynamics of the free surface during the process of coalescence. Our experimental method allows us to excite shape oscillations in the levitated helium drops and measure their normal mode frequencies. By measuring the frequency of the fundamental (l = 2) mode, we obtain new measurements of the surface tension of helium for temperatures between 1.5 and 0.5 K. Our measurements extrapolate to a value of 0.375 erg cm -2 at T = 0 K. Our results agree with the capillary wave measurements of Roche et al., and Atkins and Narahra. We study how the shape of the trap used to levitate the drops influences the resonant frequency of the l = 2 mode. Measurements of the frequency spectrum were performed using different trap potentials. We have calculated the resonant frequencies for the trap shapes produced by different magnet coil currents. We compare our measurements of the resonant frequencies at various magnet currents with these theoretical predictions and find good agreement. We describe experiments to study the coalescence of He II drops levitated in a magnetic trap. Using a high speed CCD camera, we have produced movies of drops coalescing at temperatures as low as 0.7 K. We examine some interesting features of the motion during and following coalescence.

  6. Surface Tension

    SciTech Connect

    2011-01-01

    Surface tension in the kitchen sink. At Berkeley Lab's Molecular Foundry, scientists study surface tension to understand how molecules "self-assemble." The coin trick in the video uses the re-arrangement of water molecules to seemingly create order out of disorder. The same principle can be used to create order in otherwise hard-to-handle nano materials. Scientists can then transfer these ordered materials onto surfaces by dipping them through the air-water interface, or (as we've recently shown) squeeze them so that they collapse into the water as two-molecule-thick nano sheets. http://newscenter.lbl.gov/feature-stories/2011/10/17/shaken-not-stirred/

  7. Nanopore wall effect on surface tension of methane

    NASA Astrophysics Data System (ADS)

    Bui, Khoa; Yucel Akkutlu, I.

    2015-11-01

    Local pressure is known to be anisotropic across the interfaces separating fluids in equilibrium. Tangential pressure profiles show characteristic negative peaks as a result of surface tension forces parallel to the interface. Nearby attractive forces parallel to the interface are larger than the repulsive forces and, hence, constitute the surface tension. In this work, using molecular dynamics simulations of methane inside nano-scale pores, we show this surface tension behaviour could be significantly influenced by confinement effects. The layering structure, characterised by damped oscillations in local liquid density and tangential pressures, extends deep into the pore and can be a few nanometers thick. The surface tension is measured numerically using local pressures across the interface. Results show that the tension is smaller under confinement and becomes a variable in small pores, mainly controlled by the thickness of the liquid density layering (or liquid saturation) and the pore width. If the liquid saturation inside the pore is high enough, the vapour-liquid interface is not interfered by the pore wall and the surface tension remains the same as the bulk values. The results are important for understanding phase change and multi-phase transport phenomena in nanoporous materials.

  8. Surface tension effects on instability in viscoelastic respiratory fluids.

    PubMed

    Vasudevan, Muraari; Lange, Carlos F

    2007-02-01

    This paper establishes the mathematical formalism for the modeling of the mucus layer in the human trachea as a viscoelastic multiphase fluid system with surface tension with a view toward study of instability properties of the air-mucus system aimed at improving the design of new bioaerosol suppressing medication. The effects of surface tension, previously only conjectured and very poorly understood, are clearly established with quantitative relationships. Several very important physiological conclusions are obtained supporting one method of potential treatment and prevention of disease transmission by alteration of the mucus layer properties over other potential methods.

  9. The Cartesian Diver, Surface Tension and the Cheerios Effect

    ERIC Educational Resources Information Center

    Chen, Chi-Tung; Lee, Wen-Tang; Kao, Sung-Kai

    2014-01-01

    A Cartesian diver can be used to measure the surface tension of a liquid to a certain extent. The surface tension measurement is related to the two critical pressures at which the diver is about to sink and about to emerge. After sinking because of increasing pressure, the diver is repulsed to the centre of the vessel. After the pressure is…

  10. The Cartesian Diver, Surface Tension and the Cheerios Effect

    ERIC Educational Resources Information Center

    Chen, Chi-Tung; Lee, Wen-Tang; Kao, Sung-Kai

    2014-01-01

    A Cartesian diver can be used to measure the surface tension of a liquid to a certain extent. The surface tension measurement is related to the two critical pressures at which the diver is about to sink and about to emerge. After sinking because of increasing pressure, the diver is repulsed to the centre of the vessel. After the pressure is…

  11. Effects of varying interfacial surface tension on macroscopic polymer lenses

    NASA Astrophysics Data System (ADS)

    Zimmerman, Charlotte; White, Mason; Baylor, Martha-Elizabeth

    2015-09-01

    We investigate macroscopic polymer lenses (0.5- to 2.5-cm diameter) fabricated by dropping hydrophobic photocurable resin onto the surface of various hydrophilic liquid surfaces. Due to the intermolecular forces along the interface between the two liquids, a lens shape is formed. We find that we can vary the lens geometry by changing the region over which the resin is allowed to spread and the surface tension of the substrate to produce lenses with theoretically determined focal lengths ranging from 5 to 25 mm. These effects are varied by changing the container width, substrate composition, and substrate temperature. We present data for five different variants, demonstrating that we can control the lens dimensions for polymer lens applications that require high surface quality.

  12. Effect of organic matter on bubble surface tension

    NASA Astrophysics Data System (ADS)

    Slauenwhite, David E.; Johnson, Bruce D.

    1996-02-01

    Bubble surface tension (BST) is measured by spinning single bubbles in a rotating cell and relating the resulting bubble deformation to the Centrifugal number Ce. Using this method, bubbles in "clean" fresh water (distilled, deionized, passed through activated charcoal and filtered at 0.2 μm) are found to have a BST similar to that reported for the "clean" air-water interface (72.4 mN/m), whereas adsorption of organic films are observed to decrease the BST, with the effect increasing as the bubbles are aged. In natural coastal sea water (North West Arm, Halifax Harbour (10 m)) the BST decreases to 70.5 mN/m, and in phytoplankton culture (Nitzschia pungens) decreases to 67 mN/m. Saturated stearic acid solution shows a BST of 57 mN/m. Coalescence of two bubbles with equilibrium surface film is accompanied by a rapid decrease in the surface tension, a decrease that we attribute to compression of the merging surface films at the newly created smaller interface. The decrease is most pronounced in water rich in organic surfactants.

  13. Surface Tension Gradients Induced by Temperature: The Thermal Marangoni Effect

    ERIC Educational Resources Information Center

    Gugliotti, Marcos; Baptisto, Mauricio S.; Politi, Mario J.

    2004-01-01

    Surface tensions gradients were generated in a thin liquid film because of the local increase in temperature, for demonstration purposes. This is performed using a simple experiment and allows different alternatives for heat generation to be used.

  14. Surface Tension Gradients Induced by Temperature: The Thermal Marangoni Effect

    ERIC Educational Resources Information Center

    Gugliotti, Marcos; Baptisto, Mauricio S.; Politi, Mario J.

    2004-01-01

    Surface tensions gradients were generated in a thin liquid film because of the local increase in temperature, for demonstration purposes. This is performed using a simple experiment and allows different alternatives for heat generation to be used.

  15. Demonstration of Surface Tension.

    ERIC Educational Resources Information Center

    Rosenthal, Andrew J.

    2001-01-01

    Surface tension is a fundamental obstacle in the spontaneous formation of bubbles, droplets, and crystal nuclei in liquids. Describes a simple overhead projector demonstration that illustrates the power of surface tension that can prevent so many industrial processes. (ASK)

  16. Demonstration of Surface Tension.

    ERIC Educational Resources Information Center

    Rosenthal, Andrew J.

    2001-01-01

    Surface tension is a fundamental obstacle in the spontaneous formation of bubbles, droplets, and crystal nuclei in liquids. Describes a simple overhead projector demonstration that illustrates the power of surface tension that can prevent so many industrial processes. (ASK)

  17. Effects of Induced Surface Tension in Nuclear and Hadron Matter

    NASA Astrophysics Data System (ADS)

    Sagun, V. V.; Bugaev, K. A.; Ivanytskyi, A. I.; Oliinychenko, D. R.; Mishustin, I. N.

    2017-03-01

    Short range particle repulsion is rather important property of the hadronic and nuclear matter equations of state. We present a novel equation of state which is based on the virial expansion for the multicomponent mixtures with hard-core repulsion. In addition to the hard-core repulsion taken into account by the proper volumes of particles, this equation of state explicitly contains the surface tension which is induced by another part of the hard-core repulsion between particles. At high densities the induced surface tension vanishes and the excluded volume treatment of hard-core repulsion is switched to its proper volume treatment. Possible applications of this equation of state to a description of hadronic multiplicities measured in A+A collisions, to an investigation of the nuclear matter phase diagram properties and to the neutron star interior modeling are discussed.

  18. Effects of surface tension and axis stress on piezoelectric behaviors of ferroelectric nanowires

    NASA Astrophysics Data System (ADS)

    Chen, Y. Q.; En, Y. F.; Huang, Y.; Kong, X. D.; Zheng, X. J.; Lu, Y. D.

    2011-11-01

    The effects of surface tension and axis stress on piezoelectric behaviors of ferroelectric nanowires with radius polarization were investigated by the time-dependent Ginzburg-Landau theory. When surface tension increases, both of coercive field and remnant strain decrease. The larger the surface tension is, the more they decrease. The axis compressive stress enhances the coercive field and remnant strain, while the axis tensile stress has contrary effect. The reason for the stress-modulated piezoelectricity is that radius polarization is forced by axis compressive stress but restrained by surface tension and axis tensile stress. The research is useful for ferroelectric nanostructures in strain engineering.

  19. Surface tension and microgravity

    NASA Astrophysics Data System (ADS)

    Meseguer, J.; Sanz-Andrés, A.; Pérez-Grande, I.; Pindado, S.; Franchini, S.; Alonso, G.

    2014-09-01

    The behaviour of confined liquids on board an orbiting spacecraft is mainly driven by surface tension phenomena, which cause an apparently anomalous response of the liquid when compared with the behaviour that can be observed on an Earth laboratory provided that the amount of liquid is high enough. The reason is that in an orbiting spacecraft the different inertial forces acting on the bulk of the liquid are almost zero, causing thus capillary forces to be the dominant ones. Of course, since gravity forces are proportional to the liquid volume, whereas surface tension forces are proportional to the liquid surface, there are situations on Earth where capillarity can be the dominant effect, as it happens when very small volume liquid samples are considered. However, work with small size samples may require the use of sophisticated optical devices. Leaving aside the neutral buoyancy technique, a way of handling large liquid interfaces is by using drop towers, where the sample falls subjected to the action of Earth’s gravity. This approach is suitable when the characteristic time of the problem under consideration is much smaller than the drop time. In this work the transformation of an out-of-use chimney into a drop tower is presented. Because of the miniaturization, hardiness and low cost of current electronic devices, a drop tower can be used as an inexpensive tool for undergraduate students to experimentally analyse a large variety of surface tension driven phenomena.

  20. Effect of surface tension on electrocaloric effects in the ferroelectric nanomaterial with vortex domain structures

    NASA Astrophysics Data System (ADS)

    Li, B.; Wang, J. B.; Zhong, X. L.; Wang, F.; Wang, L. J.; Zhou, Y. C.

    2013-07-01

    The influence of intrinsic surface tension on the electrocaloric effect (ECE) in the ferroelectric nanomaterial with vortex domain structures is studied by using the phase field method. The calculation results show that a giant adiabatic temperature change (ΔT = 5.8 K) related to the toroidal moment change appears in the PbTiO3 (PTO) ferroelectric nanoparticle with the surface tension coefficient μ = 5 N/m under the vorticity vector of curled electric field (Q1 = 0 mV/Å2, ΔQ1 = 0.9 mV/Å2) at room temperature. The magnitude of the adiabatic temperature change decreases with the increase in surface tension. The decrease in size is found to enhance the ECE of PTO nanoparticle with vortex domain structures when the surface tension is not considered.

  1. Effect of gravity and electric field on shape and surface tension of drops

    NASA Astrophysics Data System (ADS)

    Bateni, A.; Ababneh, A.; Elliott, J. A. W.; Neumann, A. W.; Amirfazli, A.

    Experimental work was performed in reduced gravity conditions using a novel methodology to investigate the effect of external forces, i.e., gravity and electric field, on shape and surface tension of drops. The new methodology, called axisymmetric drop-shape analysis - electric fields (ADSA-EF), can generate numerical drop profiles as a function of surface tension, at any given gravity and/or electric field. When an image of an experimental drop is available, ADSA-EF can calculate the true value of the surface tension by matching the numerical profiles with the shape of the experimental drop, taking the surface tension as an adjustable parameter. ADSA-EF is a novel technique, which can be employed to predict and simulate drop shapes in the electric field, determine the effect of external fields on surface tensions, or measure surface tensions in reduced gravity conditions, where other drop-shape techniques are not applicable. The results of the reduced gravity experiment suggested that the electric field significantly increases the surface tension of water. No significant effect of gravity on surface tension was detected.

  2. Surface Tension Microscopy

    NASA Astrophysics Data System (ADS)

    Neumann, Burkhard; Engel, Horst; Schleifenbaum, Bernd

    1989-12-01

    A new microscopic technique will be presented for imaging surface topography and the locally varying surface tension of the object. With this technique it is possible to image the locally varying chemical composition of the specimen surface on a microscopic scale because the surface tension depends on the chemical composition. The imaging technique can be described as follows: By a simple preparation technique a thin (thickness several microns) liquid layer (e.g. immersion oil), is placed on the surface of the specimen. The resulting surface tension forces the boundary of the liquid layer to move. As the surface tension is a function of the location the boundary is modulated according to the magnitude of the surface tension at each place. Thus registering the shape of the moving boundary of the liquid layer at equidistant time intervals yields information on the specimen surface. The shape of the moving boundary is detected by a light microscope with differential interference contrast in combination with an image analysis system suited for real-time processing of image sequences in a threshold detection mode.

  3. The Effect of Surface Tension on the Shape of the Kirchhoff Jet.

    DTIC Science & Technology

    1983-05-01

    S. TYPE Of REPORT & PERIOD COVERED Summary Report - no specific THE EFFECT OF SURFACE TENSION ON THE SHAPE OF reporting period THE KIRCHOPF JET s...2524 THE EFFECT OF SURFACE TENSION ON THE SHAPE OF THE KIRCHHOFF JET a Jean-Marc Vanden-Broeck Mathematics Research Center University of Wisconsin...OF WISCONSZN-4ADISON ’-,MA TH1HTC8 RN. ACH CXNTZR FI. lTU EFFECT Or SURfACE TENSION ON TU SHKAP OF T=E KIRCEHOFF JET Jean-Marc Vanden-Broeck* 6

  4. Surface Tension of Spacetime

    NASA Astrophysics Data System (ADS)

    Perko, Howard

    2017-01-01

    Concepts from physical chemistry and more specifically surface tension are introduced to spacetime. Lagrangian equations of motion for membranes of curved spacetime manifold are derived. The equations of motion in spatial directions are dispersion equations and can be rearranged to Schrodinger's equation where Plank's constant is related to membrane elastic modulus. The equation of motion in the time-direction has two immediately recognizable solutions: electromagnetic waves and corpuscles. The corpuscular membrane solution can assume different genus depending on quantized amounts of surface energy. A metric tensor that relates empty flat spacetime to energetic curved spacetime is found that satisfies general relativity. Application of the surface tension to quantum electrodynamics and implications for quantum chromodynamics are discussed. Although much work remains, it is suggested that spacetime surface tension may provide a classical explanation that combines general relativity with field theories in quantum mechanics and atomic particle physics.

  5. Finite-Size Effects of Surface Tension in Two Segregated BECs Confined by Two Hard Walls

    NASA Astrophysics Data System (ADS)

    Van Thu, Nguyen; Phat, Tran Huu; Song, Pham The

    2017-01-01

    The finite-size effects of the surface tension in two segregated Bose-Einstein condensates limited by two hard walls are studied respectively in canonical ensemble and grand canonical ensemble by means of the Gross-Pitaevskii theory in the modified double-parabola approximation. The analytical formulae of surface tensions and their finite-size effects are found together with a new type of long-range forces acting on two walls.

  6. Effects of internal pressure and surface tension on the growth-induced wrinkling of mucosae.

    PubMed

    Xie, Wei-Hua; Li, Bo; Cao, Yan-Ping; Feng, Xi-Qiao

    2014-01-01

    Surface wrinkling of mucosae is crucial for the biological functions of many living tissues. In this paper, we investigate the instability of a cylindrical tube consisting of a mucosal layer and a submucosal layer. Our attention is focused on the effects of internal pressure and surface tension on the critical condition and mode number of surface wrinkling induced by tissue growth. It is found that the internal pressure plays a stabilizing role but basically has no effect on the critical mode number. Surface tension also stabilizes the system and reduces the critical mode number of surface patterns. Besides, the thinner the mucosal layer, the more significant the effect of surface tension. This work may help gain insights into the surface wrinkling and morphological evolution of such tubular organs as airways and esophagi. Copyright © 2013 Elsevier Ltd. All rights reserved.

  7. Surface tension of spherical drops from surface of tension

    SciTech Connect

    Homman, A.-A.; Bourasseau, E.; Malfreyt, P.; Strafella, L.; Ghoufi, A.

    2014-01-21

    The determination of surface tension of curved interfaces is a topic that raised many controversies during the last century. Explicit liquid-vapor interface modelling (ELVI) was unable up to now to reproduce interfacial behaviors in drops due to ambiguities in the mechanical definition of the surface tension. In this work, we propose a thermodynamic approach based on the location of surface of tension and its use in the Laplace equation to extract the surface tension of spherical interfaces from ELVI modelling.

  8. COMPUTER SIMULATIONS OF SPRAY RETENTION BY A 3D BARLEY PLANT: EFFECT OF FORMULATION SURFACE TENSION.

    PubMed

    Massinon, M; De Cock, N; Salah, S Ouled Taleb; Lebeau, F

    2015-01-01

    A spray retention model was used in this study to explore theoretically the effect of a range of mixture surface tension on the spray retention and the variability of deposits. The spray retention model was based on an algorithm that tested whether droplets from a virtual nozzle intercepted a 3D plant model. If so, the algorithm determined the contribution of the droplet to the overall retention depending on the droplet impact behaviour on the leaf; adhesion, rebound or splashing. The impact outcome probabilities, function of droplet impact energy, were measured using high-speed imaging on an excised indoor grown barley leaf (BBCH12) both for pure water (surface tension of 0.072 N/m) and a non-ionic super spreader (static surface tension of 0.021 N/m) depending on the surface orientation. The modification of spray mixture properties in the simulations was performed by gradually changing the spray the droplet impact probabilities between pure water and a solution with non-ionic surfactant exhibiting super spreading properties. The plant architecture was measured using a structured light scanner. The final retention was expressed as the volume of liquid retained by the whole plant relative to the projected leaf surface area in the main spray direction. One hundred simulations were performed at different volumes per hectare and flat-fan nozzles for each formulation surface tension. The coefficient of variation was used as indicator of variability of deposits. The model was able to discriminate between mixture surface tension. The spray retention increased as the mixture surface tension decreased. The variability of deposits also decreased as the surface tension decreased. The proposed modelling approach provides a suited tool for sensitivity analysis: nozzle kind, pressure, volume per hectare applied, spray mixture physicochemical properties, plant species, growth stage could be screened to determine the best spraying characteristics maximizing the retention. The

  9. Effect of surface tension on the onset of convection in a double-diffusive layer

    NASA Technical Reports Server (NTRS)

    Chen, C. F.; Su, T. F.

    1992-01-01

    The effect of surface tension on the stability of a double-diffusive layer is considered using linear stability analysis. The surface tension is assumed to vary linearly with temperature and solute concentration. The eigenvalue problem is solved by the Galerkin method. Results show that the predicted stability boundary based on Marangoni effects alone is completely altered in the presence of buoyancy effects induced by low gravity levels (about 10 exp -5 g). At reduced gravity levels, salt-finger instability may onset in the overstable mode due to the stabilizing effect of surface tension. Fluid properties in terms of the Prandtl and the Lewis numbers have a profound effect on the stability conditions; opposite stability characteristics are found in salt solutions and in molten metals.

  10. The surface tension effect on viscous liquid spreading along a superhydrophobic surface

    NASA Astrophysics Data System (ADS)

    Aksenov, A. V.; Sudarikova, A. D.; Chicherin, I. S.

    2017-01-01

    Within the Stokes film approximation, unsteady plane-parallel spreading of a thin layer of a heavy viscous fluid along a horizontal superhydrophobic surface is studied. The forced spreading regimes induced by the mass supply are considered. Plane-parallel flow along the principal direction of the slip tensor of the superhydrophobic surface is studied in case that the corresponding slip tensor component is a power function of the spatial coordinate. An evolution equation for the film thickness is derived taking into account surface tension that is dependent on the spatial coordinate. The group classification problem is solved. Self-similar and invariant solutions are constructed for power and exponent time dependences on mass supply respectively at a special form of the surface tension coefficient. Surface tension is shown to have a significant influence on the character of the liquid spreading.

  11. Effect of concentration and temperature on surface tension of sodium hyaluronate saline solutions.

    PubMed

    Ribeiro, Walkiria; Mata, José Luis; Saramago, Benilde

    2007-06-19

    The effect of concentration and temperature on the surface tension of sodium hyaluronate (NaHA) saline solutions was investigated using the technique of the shape of pendant drops. The decay rate of the surface tension with the increase of NaHA concentration was well-described by the empirical Hua-Rosen equation. Adsorption at the air-liquid interface was estimated using the Gibbs equation. The temperature dependence of a dilute solution and a semidilute entangled solution was numerically fitted with a second-order polynomial equation. The surface behavior of the NaHA saline solutions was interpreted in terms of their known viscoelastic properties.

  12. Effects of additives on volume change on melting, surface tension, and viscosity of liquid aluminum oxide

    NASA Technical Reports Server (NTRS)

    Bates, J. L.; Rasmussen, J. J.

    1972-01-01

    The effects of various oxide additives on the volume change on melting, the surface tension, and the viscosity of liquid Al2O3 were studied. Additives of Sm2O3, MgO, and Y2O3 which form solid solutions, compounds, and multiphase solids with Al2O3 were studied. A review of the property data for Al2O3 and Al2O3 containing oxide additives is presented. Oxide additives to Al2O3 reduce the volume change on melting and with the exception of SiO2 lower the viscosity; surface tensions change with oxide additives, but changes vary with different container material. Viscosity and volume change on melting appeared to be significantly more important for studying the properties of liquid oxides than surface tension. Supercooling of 270 K of yttrium aluminum garnet was observed.

  13. Surface Tension and Capillary Rise

    ERIC Educational Resources Information Center

    Walton, Alan J.

    1972-01-01

    Discussion of the shortcomings of textbook explanations of surface tension, distinguishing between concepts of tension and capillary rise. The arguments require only a clear understanding of Newtonian mechanics, notably potential energy. (DF)

  14. Effects of Oxygen Partial Pressure on the Surface Tension of Liquid Nickel

    NASA Technical Reports Server (NTRS)

    SanSoucie, Michael P.; Rogers, Jan R.; Gowda, Vijaya Kumar Malahalli Shankare; Rodriguez, Justin; Matson, Douglas M.

    2015-01-01

    The NASA Marshall Space Flight Center's electrostatic levitation (ESL) laboratory has been recently upgraded with an oxygen partial pressure controller. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled, theoretically in the range from 10-36 to 100 bar. The oxygen control system installed in the ESL laboratory's main chamber consists of an oxygen sensor, oxygen pump, and a control unit. The sensor is a potentiometric device that determines the difference in oxygen activity in two gas compartments (inside the chamber and the air outside of the chamber) separated by an electrolyte, which is yttria-stabilized zirconia. The pump utilizes coulometric titration to either add or remove oxygen. The system is controlled by a desktop control unit, which can also be accessed via a computer. The controller performs temperature control for the sensor and pump, PID-based current loop, and a control algorithm. Oxygen partial pressure has been shown to play a significant role in the surface tension of liquid metals. Oxide films or dissolved oxygen may lead to significant changes in surface tension. The effects of oxygen partial pressure on the surface tension of undercooled liquid nickel will be analyzed, and the results will be presented. The surface tension will be measured at several different oxygen partial pressures while the sample is undercooled. Surface tension will be measured using the oscillating drop method. While undercooled, each sample will be oscillated several times consecutively to investigate how the surface tension behaves with time while at a particular oxygen partial pressure.

  15. Effect of temperature and concentration on the surface tension of chia seed mucilage

    NASA Astrophysics Data System (ADS)

    Fu, Yuting; Arye, Gilboa

    2017-04-01

    The production of mucilage by the seed coat during hydration is a common adaptation of many different plant species. The mucilage may play many ecological roles in adaptation and seed germination in diverse environments, especially in extreme desert conditions. The major compound of the seed mucilage is polysaccharides (e.g. pectins and hemicelluloses), which makes it highly hydrophilic. Consequently, it can hydrate quickly in the presence of water; forming a gel like coating surrounding the seed. However, the seed mucilage also reported to contain small amounts of protein and lipid which may exhibit surface activity at the water-air interface. As a result, decay in the surface tension of water can be occur and consequently a reduction in soil capillary pressure. This in turn may affect the water retention and transport during seed germination. The physical properties of the seeds mucilage have been studied mainly in conjunction with its rheological properties. To the best of our knowledge, its surface activity at the water-air interface has been reported mainly in the realms of food engineering, using a robust method of extraction. The main objective of this study was to quantify the effect of temperature and concentration on the surface tension of seed mucilage. The mucilage in this study was extracted from chia (Salvia hispanica L.) seeds, using distilled water (1:20 w/w) by shaking for 12 h at 4°C. The extracts were freeze dried after centrifuge (5000rpm for 20min). Fresh samples of different concentrations, ranging from 0.5 to 6 mg/ml, were prepared before each surface tension measurements. The equilibrium surface tension was measured by the Wilhelmy plate method using a tensiometer (DCAT 11, Data Physics) with temperature control unit. For a given mucilage concentration, surface tension measurements carried out at 5, 15, 25, 35, 45 °C. The quantitative and thermodynamic analysis of the results will be presented and discussed.

  16. The effect of surface tension reduction on the clinical performance of sodium hypochlorite in endodontics.

    PubMed

    Rossi-Fedele, G; Prichard, J W; Steier, L; de Figueiredo, J A P

    2013-06-01

    Sodium hypochlorite (NaOCl) is recommended as an endodontic irrigant in view of its broad antimicrobial and tissue dissolution capacities. To enhance its penetration into inaccessible areas of root canals and to improve its overall effect, the addition of surface-active agents has been suggested. The aim of this investigation was to review the effect of the reduction of the surface tension on the performance of NaOCl in endodontics. A search was performed in the Medline electronic database (articles published up to 28 July 2012, in English) with the search terms and combinations as follows: 'sodium hypochlorite AND surface tension or interfacial force or interfacial tension or surface-active agent or amphiphilic agent or surface active agent or surfactant or tenside or detergent'. The purpose of this search was to identify publications that compared NaOCl alone and NaOCl modified with the addition of a surface-active agent in endodontics. A hand search of articles published online ('in-press' and 'early view'), and appearing in the reference list of the articles included, was further performed, using the same search criteria as the electronic search. The search identified 302 publications, of which 11 fulfilled the inclusion/exclusion criteria of the review. The evidence available suggests that surface-active agents improve the penetration of NaOCl in the main canal and have no effect on its pulp tissue dissolution ability. There are, however, insufficient data to enable a sound conclusion to be drawn regarding the effect of modifying NaOCl's surface tension on lubrication, antimicrobial and smear layer or debris removal abilities. © 2012 International Endodontic Journal.

  17. Surface tension prevails over solute effect in organic-influenced cloud droplet activation

    NASA Astrophysics Data System (ADS)

    Ovadnevaite, Jurgita; Zuend, Andreas; Laaksonen, Ari; Sanchez, Kevin J.; Roberts, Greg; Ceburnis, Darius; Decesari, Stefano; Rinaldi, Matteo; Hodas, Natasha; Facchini, Maria Cristina; Seinfeld, John H.; O' Dowd, Colin

    2017-06-01

    The spontaneous growth of cloud condensation nuclei (CCN) into cloud droplets under supersaturated water vapour conditions is described by classic Köhler theory. This spontaneous activation of CCN depends on the interplay between the Raoult effect, whereby activation potential increases with decreasing water activity or increasing solute concentration, and the Kelvin effect, whereby activation potential decreases with decreasing droplet size or increases with decreasing surface tension, which is sensitive to surfactants. Surface tension lowering caused by organic surfactants, which diminishes the Kelvin effect, is expected to be negated by a concomitant reduction in the Raoult effect, driven by the displacement of surfactant molecules from the droplet bulk to the droplet-vapour interface. Here we present observational and theoretical evidence illustrating that, in ambient air, surface tension lowering can prevail over the reduction in the Raoult effect, leading to substantial increases in cloud droplet concentrations. We suggest that consideration of liquid-liquid phase separation, leading to complete or partial engulfing of a hygroscopic particle core by a hydrophobic organic-rich phase, can explain the lack of concomitant reduction of the Raoult effect, while maintaining substantial lowering of surface tension, even for partial surface coverage. Apart from the importance of particle size and composition in droplet activation, we show by observation and modelling that incorporation of phase-separation effects into activation thermodynamics can lead to a CCN number concentration that is up to ten times what is predicted by climate models, changing the properties of clouds. An adequate representation of the CCN activation process is essential to the prediction of clouds in climate models, and given the effect of clouds on the Earth’s energy balance, improved prediction of aerosol-cloud-climate interactions is likely to result in improved assessments of future

  18. SURFACE TENSION OF SERUM

    PubMed Central

    du Noüy, P. Lecomte

    1925-01-01

    1. The injection of antigen into an animal determines a gradual change in the blood fluid which finds expression in two physicochemical manifestations that can readily be followed, namely a decrease in the static value of the surface tension of serum solutions, and a special form of crystallization when serum diluted with isotonic sodium chloride solution is allowed to evaporate under certain conditions. 2. The change in the blood is at a maximum around the 13th day after the first antigen injection, and decreases progressively thereafter until it can no longer be observed, which is usually around the 30th day. 3. The change follows the same course, whether a single large injection of antigen is made, or many smaller ones. It begins at the same time in either case, it comes to a maximum after the same period, and in its subsequent course it is not affected by the reinjection of antigen. The manifestations of the change would appear to be independent of the presence of antigen in the circulation. 4. The mean length of the protein molecules of the immune serum obtained after the injection of the antigen dealt with is little if at all different from that of the protein molecules of normal serum. 5. It is possible that this reaction is independent of the antibody formation. PMID:19869026

  19. Surface Tension Measurements of Chemically Modified Oleochemical

    USDA-ARS?s Scientific Manuscript database

    Surface tension is an important physical property of a substance, which plays a part in a variety of physical phenomenon relevant to many industrial processes. For example, the efficiency of the atomization of a fuel has been shown to be effected dramatically by surface tension and viscosity. Beca...

  20. Finite-size effects in surface tension: Thermodynamics and the Gaussian interface model

    NASA Astrophysics Data System (ADS)

    Gelfand, Martin P.; Fisher, Michael E.

    1988-09-01

    It has been suggested by Kayser that finite-size effects associated with capillary waves might play a significant role in some surface tension measurements; for capillary rise between plates a distance D apart, an effect varying as 1/ D and apparently observable in measurements, was proposed. In reconsidering this problem, one must analyze the thermodynamics of finite-size corrections to surface tension. In particular, one sees that capillary rise between plates does not measure the interfacial free energy density but, rather, a derivative of the interfacial free energy with respect to a system dimension. The quantity needed to draw definite conclusions, the “finite-size residual” free energy, can be calculated within the harmonic or Gaussian capillary wave model in d spatial dimensions with the aid of Poisson summation techniques and should yield the correct leading asymptotic behavior. For d=3 and experimentally relevant parameter values, the results are independent of the short-wavelength cutoff needed in the model and can be checked against the theory of conformai covariance at two-dimensional critical points. It is found that the finite-size effects in capillary-rise measurements of surface tension vary as 1/ D 2 (with a universal coefficient) but are too small to be seen in current experiments.

  1. Effective Darcy-Scale Contact Angles in Porous Media Imbibing Solutions of Various Surface Tensions

    SciTech Connect

    Weisbrod, Noam; McGinnis, Thomas; Rockhold, Mark L.; Niemet, Mike; Selker, John S.

    2009-10-17

    Surface tensions of high-salinity solutions are significantly different from those of pure water. Our objective was to develop and test a methodology to determine whether these surface-tension effects predictably alter imbibition into dry and moist porous media. Static and dynamic experiments were performed using four grades of quartz sand to determine the effects of solution salinity on imbibition. Results were quantified as apparent contact angles between the sand and three solutions (pure water, 5 molal NaNO3, n-hexane). Contact angles determined using a static method in initially air-dried sand ranged from 23° to 31°, with the same values found for both water and the NaNO3 solution. Effective contact angles determined for the air-dried sand using a dynamic method based on a modified version of the Green and Ampt model were about twice those found using the static method, averaging 45° and 62° for water and the NaNO3 solution, respectively. In pre-wetted sands, the dynamic imbibition data yielded apparent contact angles of 2° and 21° for water and the NaNO3 solution, respectively, with the latter value comparing well to a predicted value of 25° for the NaNO3 solution based solely on surface-tension contrast. The results of this study indicate that on the Darcy-scale, saline solutions appear to follow the relationship of non-zero contact angles with other miscible fluids of different surface tensions used to pre-wet the sand grains, in agreement with the macro-scale infiltration results of Weisbrod et al. [2004].

  2. Effect of capillary pressure and surface tension on the deformation of elastic surfaces by sessile liquid microdrops: an experimental investigation.

    PubMed

    Pericet-Cámara, Ramón; Best, Andreas; Butt, Hans-Jürgen; Bonaccurso, Elmar

    2008-10-07

    Sessile liquid drops are predicted to deform an elastic surface onto which they are placed because of the combined action of the liquid surface tension at the periphery of the drop and the capillary pressure inside the drop. Here, we show for the first time the in situ experimental confirmation of the effect of capillary pressure on this deformation. We demonstrate micrometer-scale deformations made possible by using a low Young's modulus material as an elastic surface. The experimental profiles of the deformed surfaces fit well the theoretical predictions for surfaces with a Young's modulus between 25 and 340 kPa.

  3. The energy release rate of a pressurized crack in soft elastic materials: effects of surface tension and large deformation.

    PubMed

    Liu, Tianshu; Long, Rong; Hui, Chung-Yuen

    2014-10-21

    In this paper we present a theoretical study on how surface tension affects fracture of soft solids. In classical fracture theory, the resistance to fracture is partly attributed to the energy required to create new surfaces. Thus, the energy released to the crack tip must overcome the surface energy in order to propagate a crack. In soft materials, however, surface tension can cause significant deformation and can reduce the energy release rate for crack propagation by resisting the stretch of crack surfaces. We quantify this effect by studying the inflation of a penny-shaped crack in an infinite elastic body with applied pressure. To avoid numerical difficulty caused by singular fields near the crack tip, we derived an expression for the energy release rate which depends on the applied pressure, the surface tension, the inflated crack volume and the deformed crack area. This expression is evaluated using a newly developed finite element method with surface tension elements. Our calculation shows that, when the elasto-capillary number ω ≡ σ/Ea is sufficiently large, where σ is the isotropic surface tension, E is the small strain Young's modulus and a is the initial crack radius, both the energy release rate and the crack opening displacement of an incompressible neo-Hookean solid are significantly reduced by surface tension. For a sufficiently high elasto-capillary number, the energy release rate can be negative for applied pressure less than a critical amount, suggesting that surface tension can cause crack healing in soft elastic materials.

  4. The effect of temperature induced surface tension gradients on bubble mechanics

    NASA Technical Reports Server (NTRS)

    Mcgrew, J. L.; Rehm, T. L.; Griskey, R. G.

    1974-01-01

    Experiments were conducted to examine in detail the influence of surface tension gradient induced flow, the Marangoni effect. One set of studies provided visual results that demonstrated the occurrence and magnitude of the Marangoni effect. Another portion of the work was directed to bubble force measurements. These studies used in deflection of a very fine cantilevered wire with an attached bubble as a means of measuring force with and without temperature gradients. The experimental force data were found to check existing theoretical predictions reasonably well except for the case where the test fluid had a sizeable vapor pressure. In this situation the thermophoretic force on the bubble was much higher than predicted.

  5. Simple theoretical model for ion cooperativity in aqueous solutions of simple inorganic salts and its effect on water surface tension.

    PubMed

    Gao, Yi Qin

    2011-11-03

    Careful analysis of experimental data showed that the salt aqueous solution/air surface tension depends on a rather complicated manner of salt composition and points to the importance of ion cooperativity. In this short article, we include the selective binding of anions over cations at interfaces (as revealed from molecular dynamics simulations, spectroscopic measurements, and Record's analysis of the surface tension data) and the anion-cation association (based on the observation of matching water affinity) in a simple theoretical model to understand salt effects on surface tension. The introduction of the surface effect and ion association provides a qualitative explanation of the experimental data, in particular, the strong anion dependence of the cations' rank according to their ability of increasing water surface tension. We hope that the physical insight provided by this study can be used to point to new directions for more detailed studies.

  6. The Dynamic Surface Tension of Water

    PubMed Central

    2017-01-01

    The surface tension of water is an important parameter for many biological or industrial processes, and roughly a factor of 3 higher than that of nonpolar liquids such as oils, which is usually attributed to hydrogen bonding and dipolar interactions. Here we show by studying the formation of water drops that the surface tension of a freshly created water surface is even higher (∼90 mN m–1) than under equilibrium conditions (∼72 mN m–1) with a relaxation process occurring on a long time scale (∼1 ms). Dynamic adsorption effects of protons or hydroxides may be at the origin of this dynamic surface tension. However, changing the pH does not significantly change the dynamic surface tension. It also seems unlikely that hydrogen bonding or dipole orientation effects play any role at the relatively long time scale probed in the experiments. PMID:28301160

  7. The Dynamic Surface Tension of Water.

    PubMed

    Hauner, Ines M; Deblais, Antoine; Beattie, James K; Kellay, Hamid; Bonn, Daniel

    2017-03-23

    The surface tension of water is an important parameter for many biological or industrial processes, and roughly a factor of 3 higher than that of nonpolar liquids such as oils, which is usually attributed to hydrogen bonding and dipolar interactions. Here we show by studying the formation of water drops that the surface tension of a freshly created water surface is even higher (∼90 mN m(-1)) than under equilibrium conditions (∼72 mN m(-1)) with a relaxation process occurring on a long time scale (∼1 ms). Dynamic adsorption effects of protons or hydroxides may be at the origin of this dynamic surface tension. However, changing the pH does not significantly change the dynamic surface tension. It also seems unlikely that hydrogen bonding or dipole orientation effects play any role at the relatively long time scale probed in the experiments.

  8. Investigations of surface-tension effects due to small-scale complex boundaries

    NASA Astrophysics Data System (ADS)

    Feng, Jiansheng

    In this Ph.D. dissertation, we have investigated some important surface-tension phenomena including capillarity, wetting, and wicking. We mainly focus on the geometric aspects of these problems, and to learn about how structures affect properties. . In the first project (Chapter 2), we used numerical simulations and experiments to study the meniscus of a fluid confined in capillaries with complicated cross-sectional geometries. In the simulations, we computed the three-dimensional shapes of the menisci formed in polygonal and star-shaped capillaries with sharp or rounded corners. Height variations across the menisci were used to quantify the effect of surface tension. Analytical solutions were derived for all the cases where the cross-sectional geometry was a regular polygon or a regular star-shape. Power indices that characterize the effects of corner rounding were extracted from simulation results. These findings can serve as guide for fabrications of unconventional three-dimensional structures in Capillary Force Lithography experiments. Experimental demonstrations of the working principle was also performed. Although quantitative matching between simulation and experimental results was not achieved due to the limitation of material properties, clear qualitative trends were observed and interesting three-dimensional nano-structures were produced. A second project (Chapter 3) focused on developing techniques to produce three-dimensional hierarchically structured superhydrophobic surfaces with high aspect ratios. We experimented with two different high-throughput electron-beam-lithography processes featuring single and dual electron-beam exposures. After a surface modification procedure with a hydrophobic silane, the structured surfaces exhibited two distinct superhydrophobic behaviors---high and low adhesion. While both types of superhydrophobic surfaces exhibited very high (approximately 160° water advancing contact angles, the water receding contact angles on

  9. Surface tension effects on the onset of double-diffusive convection

    NASA Astrophysics Data System (ADS)

    Chen, C. F.

    Experiments have been carried out to determine the critical thermal Rayleigh number for onset of convection in a horizontal layer of density-stratified fluid with a free surface when heated from below. Three different aqueous solutions were used: salt, glycerol, and acetic acid. The rates of change in surface tension with concentration for these three solutions are positive, nearly zero, and negative, respectively. Compared to the rigid-rigid boundaries, the critical thermal Rayleigh number was found to be larger by 11.2 percent for the salt solution and smaller by 10.0 percent for the glycerol solution. With the acetic acid solution, however, the effect of the free surface was found to be negligible.

  10. Surface tension effects on the onset of double-diffusive convection

    NASA Technical Reports Server (NTRS)

    Chen, C. F.

    1992-01-01

    Experiments have been carried out to determine the critical thermal Rayleigh number for onset of convection in a horizontal layer of density-stratified fluid with a free surface when heated from below. Three different aqueous solutions were used: salt, glycerol, and acetic acid. The rates of change in surface tension with concentration for these three solutions are positive, nearly zero, and negative, respectively. Compared to the rigid-rigid boundaries, the critical thermal Rayleigh number was found to be larger by 11.2 percent for the salt solution and smaller by 10.0 percent for the glycerol solution. With the acetic acid solution, however, the effect of the free surface was found to be negligible.

  11. Effects of surface tension and electrochemical reactions in Li-ion battery electrode nanoparticles

    NASA Astrophysics Data System (ADS)

    Stein, Peter; Zhao, Ying; Xu, Bai-Xiang

    2016-11-01

    The size- and shape-dependency of the chemo-mechanical behavior of spherical and ellipsoidal nanoparticles in Li-ion battery electrodes are investigated by a stress-assisted diffusion model and 3D finite element simulations. The model features surface tension, a direct coupling between diffusion and elasticity, concentration-dependent diffusivity, and a Butler-Volmer relation for the description of electrochemical reactions that is modified to account for mechanical effects. Simulation results on spherical particles reveal that surface tension causes additional pressure fields in the particles, shifting the stress state towards the compressive regime. This provides mechanical stabilization, allowing, in principle, for higher charge/discharge rates. However, due to this pressure the attainable lithiation for a given potential difference is reduced during insertion, whereas a higher amount of ions is given off during extraction. Ellipsoidal particles with an aspect ratio deviating from that of a sphere with the same volume expose a larger surface area to the intercalation reactions. Consequently, they exhibit accelerated (dis)charge rates. However, due to the enhanced pressure in regions with high curvature, the accessible capacity of ellipsoidal particles is less than that of spherical particles.

  12. Evaluation of surface tension and ion occupancy effects on gramicidin A channel lifetime.

    PubMed Central

    Ring, A.; Sandblom, J.

    1988-01-01

    The surface tension of glycerylmonooleate-hexadecane lipid bilayer membranes and the lifetime of gramicidin A channels were measured at various concentrations of the surrounding solutions. For HCl the surface tension is essentially constant at approximately 5 mN/m up to approximately 1 M, whereas the average lifetime increases approximately 40-fold. At higher concentrations the surface tension decreases markedly. For CsCl the surface tension is constant up to about 1 M then increases with salt level. The average lifetime in this case increases about sixfold. In both cases the lifetime levels off and even decreases at higher salt levels. The increase in lifetime observed with ion activity is therefore qualitatively different from, and not explained by, the established dependence of lifetime on membrane properties (Elliot, J.R., D. Needham, J.P. Dilger, and D.A. Haydon. 1983. Biochim. Biophys. Acta. 735:95-103). We have previously proposed that ion occupancy is a determinant of channel stability, and to test this hypothesis the voltage dependence of channel lifetime was measured in asymmetrical solutions. For the case of a potassium chloride solution on one side of the membrane and a hydrogen chloride solution, on the other, the voltage dependence of the lifetime is asymmetrical. The asymmetry is such that when the electrical field is applied in the direction of the chemical gradient for each of the ions, the channel lifetime approaches, at increasing field strengths, that of a symmetrical solution of the respective ion. The voltage dependence of the surface tension, on the other hand, is negligible for the range of voltages used. These results, and the earlier findings that the order of the lifetimes for the alkali cations generally agree with the order of the permeability selectivity of the gramicidin A channel, support the hypothesis that ion occupancy is a major factor determining the lifetime of gramicidin A channels. The effects of multivalent blockers and

  13. Effects of surface tension and viscosity on the forming and transferring process of microscale droplets

    NASA Astrophysics Data System (ADS)

    Chen, Shulei; Liu, Kun; Liu, Cunbin; Wang, Dongyang; Ba, Dechun; Xie, Yuanhua; Du, Guangyu; Ba, Yaoshuai; Lin, Qiao

    2016-12-01

    Surface tension and viscosity act as important roles on the fluid flow in microchannel channels. In order to understand the influencing mechanism, three dimensional numerical simulations as well as experimental investigations were carried out on the slug formation and transfer in a rectangle T-junction microchannel. The simulation showed that the increasing Capillary number (Ca) resulted in the decreasing slug volume. Due to the existence of film thickness and corner flow, the characteristic length of slug was not the same trend completely. The results also showed that the pressure of junction point fluctuated periodically in the process of slug formation, which can reflect the slug formation period and the effect of the various conditions on pressure change. Two other pressure monitoring points were located in vertical channel and main channel and they monitored the pressure of two phase flow respectively. The increasing surface tension resulted in an increasing of total pressure, the interface pressure drop of two phases and the period of slug formation. The frequency of slug formation and two phases total pressure increased with the viscosity of continuous phase.

  14. Unusual shapes for a catenary under the effects of surface tension and gravity: A variational treatment

    SciTech Connect

    Behroozi, F. ); Mohazzabi, P.; McCrickard, J. )

    1995-02-01

    The familiar catenary is the shape assumed by a chain or string as it hangs from two points. The mathematical equation of the catenary was first published more than three hundred years ago by Leibnitz and Huygen, among others. Here we consider the shapes assumed by a hanging string in the presence of gravity and surface tension. The surface tension is introduced by suspending the string from a thin horizontal rod while the area bounded by the string and the rod is covered with a soap film. The string then assumes new and wonderful shapes depending on the relative strength of the surface tension and the weight per unit length of the string. When surface tension dominates, the string is pulled inward, assuming a convex shape similar to the Greek letter [gamma]. On the other hand, when gravity is dominant the string is pulled outward and assumes a concave shape best described as a distorted catenary. However, when the gravitational force normal to the string matches the surface tension, the string takes a linear configuration similar to the letter [ital V]. Under suitable conditions, the string can be made to assume any of the three configurations by adjusting the separation of its end points. The equations that describe the shape of the string are derived by minimizing the total energy of the system and are presented for the three principal configurations.

  15. The effect of surface tension on steadily translating bubbles in an unbounded Hele-Shaw cell

    NASA Astrophysics Data System (ADS)

    Green, Christopher C.; Lustri, Christopher J.; McCue, Scott W.

    2017-05-01

    New numerical solutions to the so-called selection problem for one and two steadily translating bubbles in an unbounded Hele-Shaw cell are presented. Our approach relies on conformal mapping which, for the two-bubble problem, involves the Schottky-Klein prime function associated with an annulus. We show that a countably infinite number of solutions exist for each fixed value of dimensionless surface tension, with the bubble shapes becoming more exotic as the solution branch number increases. Our numerical results suggest that a single solution is selected in the limit that surface tension vanishes, with the scaling between the bubble velocity and surface tension being different to the well-studied problems for a bubble or a finger propagating in a channel geometry.

  16. Computational modeling of GTA (gas tungsten arc) welding with emphasis on surface tension effects

    SciTech Connect

    Zacharia, T.; David, S.A.

    1990-01-01

    A computational study of the convective heat transfer in the weld pool during gas tungsten arch (GTA) welding of Type 304 stainless steel is presented. The solution of the transport equations is based on a control volume approach which utilized directly, the integral form of the governing equations. The computational model considers buoyancy and electromagnetic and surface tension forces in the solution of convective heat transfer in the weld pool. In addition, the model treats the weld pool surface as a deformable free surface. The computational model includes weld metal vaporization and temperature dependent thermophysical properties. The results indicate that consideration of weld pool vaporization effects and temperature dependent thermophysical properties significantly influence the weld model predictions. Theoretical predictions of the weld pool surface temperature distributions and the cross-sectional weld pool size and shape wee compared with corresponding experimental measurements. Comparison of the theoretically predicted and the experimentally obtained surface temperature profiles indicated agreement with {plus minus} 8%. The predicted weld cross-section profiles were found to agree very well with actual weld cross-sections for the best theoretical models. 26 refs., 8 figs.

  17. Effect of polymer-polymer interactions on the surface tension of colloid-polymer mixtures

    NASA Astrophysics Data System (ADS)

    Moncho-Jordá, A.; Rotenberg, B.; Louis, A. A.

    2003-12-01

    The density profile and surface tension for the interface of phase-separated colloid-polymer mixtures have been studied in the framework of the square gradient approximation for both ideal and interacting polymers in good solvent. The calculations show that in the presence of polymer-polymer excluded volume interactions the interfaces have lower widths and surface tensions compared to the case of ideal polymers. These results are a direct consequence of the shorter range and smaller depth of the depletion potential between colloidal particles induced by interacting polymers.

  18. Surface tension of polyelectrolyte coacervates

    NASA Astrophysics Data System (ADS)

    Qin, Jian; Priftis, Dimitrios; Farina, Robert; Perry, Sarah; Leon, Lorraine; Whitmer, Jonathan; Hoffman, Kyle; Tirrell, Matthew; de Pablo, Juan J.

    2014-03-01

    Stoichiometric solutions of polycations and polyanions can phase separate, resulting in the coexistence of a supernatant phase and a polymer-rich complex phase. The complex phase may be liquid-like or solid-like, depending on the ionic strength and the temperature. Liquid-like complexes, known as ``coacervates'', retain a large amount of water, up to 70-80% by weight, and exhibit an ultra-low interfacial tension with the coexisting supernatant phase (smaller than the water surface tension by three orders of magnitude). Previous experiments have observed that this interfacial tension decreases with the amount of salt, and vanishes near a critical salt concentration according to a 3 / 2 power of the salt undersaturation. In this work we derive analytical expressions for the interfacial tension in both the low and high charge density limits. For solutions with added salts, we provide explicit expressions for the interfacial tension near the critical salt concentration and explain the 3 / 2 power dependence. Our results are shown to be in good agreement with experiment.

  19. Effects of polymer stiffness on surface tension and pressure in confinement

    NASA Astrophysics Data System (ADS)

    Milchev, Andrey

    2015-08-01

    We study the effect of chain rigidity on the behavior of semiflexible polymers in the vicinity of flat walls in a slit, and of surfactants at the liquid-liquid interface between immiscible liquids. Using molecular dynamics simulations, it is demonstrated that the impact of bending angle forces is particularly strong within the depletion layer at the phase boundary whereas at distance Re away from the interface, where Re is the mean distance between the ends of a semiflexible chain, the contribution of these non-local triplet interactions to pressure tensor virtually disappears. The present study also demonstrates that growing stiffness of the macromolecules leads to an increase in surface tension and total pressure.

  20. The Effect of Surface Tension on the Gravity-driven Thin Film Flow of Newtonian and Power-law Fluids

    PubMed Central

    Hu, Bin; Kieweg, Sarah L.

    2012-01-01

    Gravity-driven thin film flow is of importance in many fields, as well as for the design of polymeric drug delivery vehicles, such as anti-HIV topical microbicides. There have been many prior works on gravity-driven thin films. However, the incorporation of surface tension effect has not been well studied for non-Newtonian fluids. After surface tension effect was incorporated into our 2D (i.e. 1D spreading) power-law model, we found that surface tension effect not only impacted the spreading speed of the microbicide gel, but also had an influence on the shape of the 2D spreading profile. We observed a capillary ridge at the front of the fluid bolus. Previous literature shows that the emergence of a capillary ridge is strongly related to the contact line fingering instability. Fingering instabilities during epithelial coating may change the microbicide gel distribution and therefore impact how well it can protect the epithelium. In this study, we focused on the capillary ridge in 2D flow and performed a series of simulations and showed how the capillary ridge height varies with other parameters, such as surface tension coefficient, inclination angle, initial thickness, and power-law parameters. As shown in our results, we found that capillary ridge height increased with higher surface tension, steeper inclination angle, bigger initial thickness, and more Newtonian fluids. This study provides the initial insights of how to optimize the flow and prevent the appearance of a capillary ridge and fingering instability. PMID:23687391

  1. The Effect of Surface Tension on the Gravity-driven Thin Film Flow of Newtonian and Power-law Fluids.

    PubMed

    Hu, Bin; Kieweg, Sarah L

    2012-07-15

    Gravity-driven thin film flow is of importance in many fields, as well as for the design of polymeric drug delivery vehicles, such as anti-HIV topical microbicides. There have been many prior works on gravity-driven thin films. However, the incorporation of surface tension effect has not been well studied for non-Newtonian fluids. After surface tension effect was incorporated into our 2D (i.e. 1D spreading) power-law model, we found that surface tension effect not only impacted the spreading speed of the microbicide gel, but also had an influence on the shape of the 2D spreading profile. We observed a capillary ridge at the front of the fluid bolus. Previous literature shows that the emergence of a capillary ridge is strongly related to the contact line fingering instability. Fingering instabilities during epithelial coating may change the microbicide gel distribution and therefore impact how well it can protect the epithelium. In this study, we focused on the capillary ridge in 2D flow and performed a series of simulations and showed how the capillary ridge height varies with other parameters, such as surface tension coefficient, inclination angle, initial thickness, and power-law parameters. As shown in our results, we found that capillary ridge height increased with higher surface tension, steeper inclination angle, bigger initial thickness, and more Newtonian fluids. This study provides the initial insights of how to optimize the flow and prevent the appearance of a capillary ridge and fingering instability.

  2. Computational Study of Surface Tension and Wall Adhesion Effects on an Oil Film Flow Underneath an Air Boundary Layer

    NASA Technical Reports Server (NTRS)

    Celic, Alan; Zilliac, Gregory G.

    1998-01-01

    The fringe-imaging skin friction (FISF) technique, which was originally developed by D. J. Monson and G. G. Mateer at Ames Research Center and recently extended to 3-D flows, is the most accurate skin friction measurement technique currently available. The principle of this technique is that the skin friction at a point on an aerodynamic surface can be determined by measuring the time-rate-of-change of the thickness of an oil drop placed on the surface under the influence of the external air boundary layer. Lubrication theory is used to relate the oil-patch thickness variation to shear stress. The uncertainty of FISF measurements is estimated to be as low as 4 percent, yet little is known about the effects of surface tension and wall adhesion forces on the measured results. A modified version of the free-surface Navier-Stokes solver RIPPLE, developed at Los Alamos National Laboratories, was used to compute the time development of an oil drop on a surface under a simulated air boundary layer. RIPPLE uses the volume of fluid method to track the surface and the continuum surface force approach to model surface tension and wall adhesion effects. The development of an oil drop, over a time period of approximately 4 seconds, was studied. Under the influence of shear imposed by an air boundary layer, the computed profile of the drop rapidly changes from its initial circular-arc shape to a wedge-like shape. Comparison of the time-varying oil-thickness distributions computed using RIPPLE and also computed using a greatly simplified numerical model of an oil drop equation which does not include surface tension and wall adhesion effects) was used to evaluate the effects of surface tension on FISF measurement results. The effects of surface tension were found to be small but not necessarily negligible in some cases.

  3. Fluoride glass: Crystallization, surface tension

    NASA Technical Reports Server (NTRS)

    Doremus, R. H.

    1988-01-01

    Fluoride glass was levitated acoustically in the ACES apparatus on STS-11, and the recovered sample had a different microstructure from samples cooled in a container. Further experiments on levitated samples of fluoride glass are proposed. These include nucleation, crystallization, melting observations, measurement of surface tension of molten glass, and observation of bubbles in the glass. Ground experiments are required on sample preparation, outgassing, and surface reactions. The results should help in the development and evaluation of containerless processing, especially of glass, in the development of a contaminent-free method of measuring surface tensions of melts, in extending knowledge of gas and bubble behavior in fluoride glasses, and in increasing insight into the processing and properties of fluoride glasses.

  4. Introducing surface tension to spacetime

    NASA Astrophysics Data System (ADS)

    Perko, H. A.

    2017-05-01

    Concepts from physical chemistry of surfaces and surface tension are applied to spacetime. More specifically, spacetime is modeled as a spatial fluid continuum bound together by a multi-dimensional membrane of time. A metric tensor that relates empty flat spacetime to energetic curved spacetime is found. Equations of motion for an infinitesimal unit of spacetime are derived. The equation of motion in a time-like direction is a Klein-Gordon type equation. The equations of motion in space-like directions take the form of Schrodinger’s equation where Plank’s constant is related to membrane elastic modulus. Although much work remains, it is suggested that the spacetime surface tension may serve as a mechanical model for many phenomena in quantum mechanics and atomic particle physics.

  5. The effect of the partial pressure of water vapor on the surface tension of the liquid water-air interface.

    PubMed

    Pérez-Díaz, José L; Álvarez-Valenzuela, Marco A; García-Prada, Juan C

    2012-09-01

    Precise measurements of the surface tension of water in air vs. humidity at 5, 10, 15, and 20 °C are shown. For constant temperature, surface tension decreases linearly for increasing humidity in air. These experimental data are in good agreement with a simple model based on Newton's laws here proposed. It is assumed that evaporating molecules of water are ejected from liquid to gas with a mean normal component of the speed of "ejection" greater than zero. A high humidity in the air reduces the net flow of evaporating water molecules lowering the effective surface tension on the drop. Therefore, just steam in air acts as an effective surfactant for the water-air interface. It can partially substitute chemical surfactants helping to reduce their environmental impact.

  6. Effects of Environmental Oxygen Content and Dissolved Oxygen on the Surface Tension and Viscosity of Liquid Nickel

    NASA Astrophysics Data System (ADS)

    SanSoucie, M. P.; Rogers, J. R.; Kumar, V.; Rodriguez, J.; Xiao, X.; Matson, D. M.

    2016-07-01

    The NASA Marshall Space Flight Center's electrostatic levitation (ESL) laboratory has recently added an oxygen partial pressure controller. This system allows the oxygen partial pressure within the vacuum chamber to be measured and controlled in the range from approximately 10^{-28} {to} 10^{-9} bar, while in a vacuum atmosphere. The oxygen control system installed in the ESL laboratory's main chamber consists of an oxygen sensor, oxygen pump, and a control unit. The sensor is a potentiometric device that determines the difference in oxygen activity in two gas compartments (inside the chamber and the air outside of the chamber) separated by an electrolyte. The pump utilizes coulometric titration to either add or remove oxygen. The system is controlled by a desktop control unit, which can also be accessed via a computer. The controller performs temperature control for the sensor and pump, has a PID-based current loop and a control algorithm. Oxygen partial pressure has been shown to play a significant role in the surface tension of liquid metals. Oxide films or dissolved oxygen may lead to significant changes in surface tension. The effects on surface tension and viscosity by oxygen partial pressure in the surrounding environment and the melt dissolved oxygen content will be evaluated, and the results will be presented. The surface tension and viscosity will be measured at several different oxygen partial pressures while the sample is undercooled. Surface tension and viscosity will be measured using the oscillating droplet method.

  7. Surface Tension Confines Cryogenic Liquid

    NASA Technical Reports Server (NTRS)

    Castles, Stephen H.; Schein, Michael E.

    1989-01-01

    New type of Dewar provides passive, constant-temperature cryogenic cooling for scientific instruments under normal-to low-gravity conditions. Known as Surface-Tension-Contained Liquid Cryogen Cooler (STCLCC), keeps liquid cryogen in known location inside the Dewar by trapping liquid inside spongelike material. Unique sponge material fills most of volume of inner tank. Sponge is all-silica, open-cell material similar to that used for Space Shuttle thermal-protection tiles.

  8. Surface Tension Confines Cryogenic Liquid

    NASA Technical Reports Server (NTRS)

    Castles, Stephen H.; Schein, Michael E.

    1989-01-01

    New type of Dewar provides passive, constant-temperature cryogenic cooling for scientific instruments under normal-to low-gravity conditions. Known as Surface-Tension-Contained Liquid Cryogen Cooler (STCLCC), keeps liquid cryogen in known location inside the Dewar by trapping liquid inside spongelike material. Unique sponge material fills most of volume of inner tank. Sponge is all-silica, open-cell material similar to that used for Space Shuttle thermal-protection tiles.

  9. Light Scattering by Surface Tension Waves.

    ERIC Educational Resources Information Center

    Weisbuch, G.; Garbay, F.

    1979-01-01

    This simple and inexpensive experiment is an illustration of the physical concepts of interaction between light and surface tension waves, and provides a new method of measuring surface tension. (Author/GA)

  10. Surface-tension properties of hyaluronic Acid.

    PubMed

    Knepper, P A; Covici, S; Fadel, J R; Mayanil, C S; Ritch, R

    1995-06-01

    The maintenance of flow channels in the trabecular meshwork is dependent, in part, on the patency of the trabecular spaces. Because the amount of hyaluronic acid decreases in the trabecular meshwork of patients with primary open-angle glaucoma, a change in surface tension may be one of the effects of hyaluronic acid on aqueous outflow. The surface-active properties of hyaluronic acid (concentration of 0.156-2.5 mg/ml; molecular weights of 100,000, 500,000, and 4,000,000) in deionized water, Ringer's lactate, Ringer's lactate plus 0.06 mg/ml bovine serum albumin, and mock aqueous solution were tested using the drop volume method. At a hyaluronic acid concentration of 0.312 mg/ml, surface tension decreased; at higher concentrations, a further decrease in surface tension was observed. In the presence of Ringer's lactate, the 100,000-MW hyaluronic acid was more active than the 4,000,000-MW hyaluronic acid. In the presence of Ringer's lactate plus bovine serum albumin or mock aqueous solution, the influence of surface tension of the 100,000-MW hyaluronic acid was moderated: with lower hyaluronic acid concentrations, the decline in surface tension was more than with Ringer's lactate, but with higher hyaluronic acid concentrations, the decline in surface tension was less than with Ringer's lactate. At high concentration, hyaluronic acid behaves like a non-Newtonian fluid, becomes more viscous, and may act to "seal" the trabecular space. The results of this study indicate that hyaluronic acid possesses surface-active properties, which is just one of several properties of hyaluronic acid that may influence aqueous outflow resistance.

  11. Effect of surface tension and surfactant administration on Eustachian tube mechanics.

    PubMed

    Ghadiali, Samir N; Banks, Julie; Swarts, J Douglas

    2002-09-01

    Development of otitis media has been related to abnormal Eustachian tube (ET) mechanics. ET is a collapsible tube that is periodically opened to regulate middle ear pressure and to clear middle ear fluid into the nasopharynx. The ability to perform these physiological functions depends on several mechanical properties, including the ET's opening pressure (P(open)), compliance (ETC), and hysteresis (eta). In this study, a previously developed modified force-response protocol was used to determine ET mechanical properties after experimental manipulation of the mucosal surface condition. Specifically, these properties were measured in the right ear of six cynomologous monkeys under baseline conditions after "washing out" the normal ET mucous layer and after instillation of a pulmonary surfactant, Infasurf. Removal of the normal mucosa did not significantly alter P(open) but did result in a decrease in ETC and eta (P < 0.05). Treatment of the mucosa with Infasurf was effective in reducing P(open) and increasing both ETC and eta to baseline values (P < 0.05). These results indicate that the mucosa-air surface tension can affect the overall ETC and eta properties of the ET. In addition, this study indicates that surfactant therapy may only be beneficial in patients with rigid or inelastic ETs (large P(open) and low ETC and eta).

  12. Surface tension driven convection experiment

    NASA Technical Reports Server (NTRS)

    Ostrach, Simon; Kamotani, Yasuhiro

    1988-01-01

    Thermocapillary flow is driven by a thermally induced surface tension variation along a liquid free surface. In the Earth-gravity environment such flows are usually overshadowed by buoyancy driven flows, but at reduced gravity conditions their influence could be significant. A comprehensive theoretical and experimental research program was stated 12 years ago and is still being continued. Past work done at Case Western Reserve University as well as work done by others is reviewed. The justification for low-gravity experiments is presented.

  13. Superficial composition in binary solid solutions A(B): Drastic effect of pure element surface tensions

    NASA Astrophysics Data System (ADS)

    Rolland, A.; Aufray, B.

    1985-10-01

    This paper deals with a comparative study of surface segragation of Pb and Ni respectively from Ag(Pb)(111) and Ag(Ni)(111) solid solutions. A high level of segregation of the solute is observed for both systems characterized by very low solute solubility. However, the superficial composition strongly depends on the relative surface tensions of the pure elements: the solute atoms are strictly on superficial sites when γ solute is smaller than γ solvent; in contrast uppermost layer consists purely of solvent when γ solute is greater than γ solvent. Two schematic distributions in close proximity to the surface are proposed in the last case.

  14. The effects of surface tension on the initial development of a free surface adjacent to an accelerated plate

    NASA Astrophysics Data System (ADS)

    Uddin, Jamal; Needham, David

    2014-11-01

    When a vertical rigid plate is uniformly accelerated from rest into an initially stationary layer of inviscid incompressible fluid, the free surface will undergo a deformation in the locality of the intersection point between the free surface and the plate. This deformation of the free surface will, in the early stages, cause a jet to rise up the plate. An understanding of the local structure of the free surface in the early stages of motion is vital in many situations and has been developed in detail by King & Needham (1994). In this work we consider the effects of introducing weak surface tension, characterized by the inverse Weber number, W, into the problem considered by King & Needham (1994). Our approach is based upon matched asymptotic expansions as W to 0. It is found that four asymptotic regions are needed to describe the problem. The three largest regions have analytical solutions whilst a numerical method based on finite differences is used to solve the time dependent harmonic boundary value problem in the last region. We also present some preliminary comparisons between experiments and theory.

  15. The in vitro Effect of Irrigants with Low Surface Tension on Enterococcus faecalis

    PubMed Central

    Giardino, Luciano; Estrela, Carlos; Generali, Luigi; Mohammadi, Zahed; Asgary, Saeed

    2015-01-01

    Introduction: Due to the complex anatomy of the root canal system and high surface tension of common root canal irrigants (RCI), conducting an investigation on RCIs containing surfactants is a priority. The aim of this in vitro study was to verify the antibacterial potential of RCI with low surface tension in root canals infected with Enterococcus faecalis (E. faecalis). Methods and Materials: Thirty-five extracted human maxillary anterior teeth were prepared and inoculated with E. faecalis for 60 days. After root canal preparation, the teeth were randomly divided to one positive and one negative control groups and 5 experimental groups: Hypoclean/Tetraclean NA, Hypoclean, Tetraclean, NaOCl/Tetraclean and NaOCl. Bacterial growth was observed by turbidity of culture medium and then measured using a UV spectrophotometer. Data were analyzed in three time intervals (pre-instrumentation and, 20 min and 72 h after canal preparation) using the ANOVA and post hoc Tukey’s tests. The level of significance was set at 0.05. Results: The results indicated the presence of E. faecalis in all post-irrigation samples irrespective of the RCI. However, the optical densities in both post-irrigation periods showed bacterial reduction and significant differences between groups. Conclusion: RCI with low surface tension showed antibacterial potential in E. faecalis infected roots. PMID:26229541

  16. Effect of pH on dynamic and equilibrium surface tension of dissolve organic matter

    NASA Astrophysics Data System (ADS)

    Arye, Gilboa; Trifonov, Pavel; Ilani, Talli

    2014-05-01

    Dissolved organic matter (DOM) in the terrestrial environment may originate from the decomposition of soil organic matter accumulated from the degradation of vegetative residues, the release of root exudates, the lysis of microorganisms and addition of organic wastes, such as livestock manure, biosolids, and different composted organic residues, or from irrigation with wastewater. The structure of DOM macromolecules is known to vary with the following aqueous solution properties: ionic strength, the nature of the inorganic ions, pH and dissolved organic carbon (DOC) concentration. In aqueous solution, the DOM molecules are amphiphilic, that is, it possesses both hydrophilic and hydrophobic functional groups in the same molecule. This simultaneous presence, gave rise to the conceptual surfactant like model for DOM which has been studies in conjunction with the equilibrium surface tension at the liquid-air interface (STeq, mN/m). Measurements of STeq of DOM solution were reported in a relatively small number of studies for the conditions of the aqueous solution (e.g., temperature, pH, ionic strength, the valence of the metal ions, and DOC concentration). All studies demonstrate the decrease in STeq with increase aqueous concentration of the DOC. The effect of pH, however, exhibit contradictory results. Specifically, for a given DOC concentration, the patterns reported for STeq versus pH were different. With increasing pH values, STeq has been reported to decrease, increase or exhibit a minimum. These contradictory results have been attributed to the different DOC concentration examined in each of the studies. In current study we hypothesized that the inconsistent results of STeq vs. pH may also stem from the adsorption kinetics of the DOM amphiphilic molecules at the liquid air interface, which can be evaluated form dynamic surface tension measurements (STt). The STt is approaching STeq values and commonly exhibiting an exponential decay pattern. If for different p

  17. A novel methodology to study effects of the electric field on shape and surface tension of drops in microgravity

    NASA Astrophysics Data System (ADS)

    Bateni, A.; Susnar, S. S.; Amirfazli, A.; Neumann, A. W.

    The behavior of liquid drops and bubbles in an electric field is of importance both for improving existing and developing new technologies on the ground and in space. Examples are electrostatic spraying, ink jet printing, electro wetting, physical and chemical separations and alloy research in space. Of particular interest is the effect of electric fields on shape and surface tension of drops and bubbles. Because of mathematical limitations as well as for practical reasons we have been developing a tool for studying these two quantities under microgravity conditions. The new methodology, called Axisymmetric Drop Shape Analysis - Electric Field (ADSA- EF), generates numerical drop profiles in the electric field, for a given surface tension. Then, it calculates the surface tension by matching the theoretical profiles with the shape of the experimental drops. The new methodology predicts the shape of conducting drops in the electric field with high accuracy. Preliminary ground-based experiments suggest that the surface tension of liquids is changed by one or two percent in the electric field. The magnitude of this change depends on the polarity of the liquid. More definitive results for drops as well as the effect of the polarity of the electric field will be presented at the conference. However, ultimate validation requires experimental work under reduced and/or microgravity conditions. Finally, under such conditions, because of the absence of convection, the developed methodology can be a valuable tool to study electric field driven adsorption and diffusion in two component liquids.

  18. Axelrod's model with surface tension

    NASA Astrophysics Data System (ADS)

    Pace, Bruno; Prado, Carmen P. C.

    2014-06-01

    In this work we propose a subtle change in Axelrod's model for the dissemination of culture. The mechanism consists of excluding from the set of potentially interacting neighbors those that would never possibly exchange. Although the alteration proposed does not alter the state space topologically, it yields significant qualitative changes, specifically the emergence of surface tension, driving the system in some cases to metastable states. The transient behavior is considerably richer, and cultural regions become stable leading to the formation of different spatiotemporal patterns. A metastable "glassy" phase emerges between the globalized phase and the disordered, multicultural phase.

  19. Effect of electric fields on contact angle and surface tension of drops.

    PubMed

    Bateni, A; Laughton, S; Tavana, H; Susnar, S S; Amirfazli, A; Neumann, A W

    2005-03-01

    Contact angles of sessile drops were experimentally investigated in the electric field. The experimental setup was designed such that the electric field was applied to all three interfaces. The advanced Automated Polynomial Fitting (APF) methodology was employed to measure contact angles with high accuracy. The significance of the observations and trends was examined by conducting statistical tests of hypothesis. It was found that contact angles of polar liquids such as alcohols increase in the electric field. However, no significant trend was observed for nonpolar liquids such as alkanes. The change in the contact angle was found to be stronger for liquids with longer molecules. It was shown that the polarity of the electric field is not an underlying factor in the observed trends. Using the equation of state for interfacial tensions, the observed shift in contact angles was translated into a corresponding change in surface tension of the liquids. The results suggest that the surface tension of alcohols increases by one to two percent (depending on the size of molecules) when an electric field of the order of magnitude of 10(6) V/m is applied.

  20. Method for Measuring Changes in Surface Tension on Agar

    PubMed Central

    Weisberg, David S.; Dworkin, Martin

    1983-01-01

    The surface tension of agar surfaces was determined by measuring the contact angles formed by drops of various hydrophobic liquids on the surface and then calculating the composite surface free energy function by solving a series of simultaneous equations derived from these data. This method was used to measure the change in the surface tension of agar produced by the addition of various concentrations of albumin. The resulting curve was typical of the effect of increasing concentrations of surfactants on surface tension. The method was compared with other methods of determining surface tension of solids, and it was concluded that the technique used here provided the most reliable results. PMID:16346273

  1. Surface tension of evaporating nanofluid droplets

    SciTech Connect

    Chen, Ruey-Hung; Phuoc, Tran X.; Martello, Donald

    2011-05-01

    Measurements of nanofluid surface tension were made using the pendant droplet method. Three different types of nanoparticles were used - laponite, silver and Fe2O3 - with de-ionized water (DW) as the base fluid. The reported results focus on the following categories; (1) because some nanoparticles require surfactants to form stable colloids, the individual effects of the surfactant and the particles were investigated; (2) due to evaporation of the pendant droplet, the particle concentration increases, affecting the apparent surface tension; (3) because of the evaporation process, a hysteresis was found where the evaporating droplet can only achieve lower values of surface tension than that of nanofluids at the same prepared concentrations: and (4) the Stefan equation relating the apparent surface tension and heat of evaporation was found to be inapplicable for nanofluids investigated. Comparisons with findings for sessile droplets are also discussed, pointing to additional effects of nanoparticles other than the non-equilibrium evaporation process.

  2. Surface Tension of Nano-Confined Lattice Polymers

    NASA Astrophysics Data System (ADS)

    Zhang, Pengfei; Wang, Qiang

    2015-03-01

    Surface tension at solid/liquid interface is a key concept in understanding many important surface and interfacial phenomena such as wetting and capillarity. It is, however, not trivial to accurately calculate surface tension in lattice Monte Carlo (LMC) simulations, which are much faster than simulations in continuum. Here we propose a novel, efficient, and accurate method for calculating the surface tension of polymers confined between two parallel and impenetrable surfaces in LMC simulations, and examine how surface tension varies with the degree of confinement (i.e., separation distance between the two surfaces). Direct comparisons between our LMC results and the corresponding lattice self-consistent field (LSCF) calculations also unambiguously and quantitatively reveal the fluctuation/correlation effects on surface tension neglected in LSCF theory. Keywords: Surface tension, lattice polymers, Monte Carlo simulations

  3. Effect of surface modification on interfacial nanobubble morphology and contact line tension.

    PubMed

    Rangharajan, Kaushik K; Kwak, Kwang J; Conlisk, A T; Wu, Yan; Prakash, Shaurya

    2015-07-14

    Past research has confirmed the existence of surface nanobubbles on various hydrophobic substrates (static contact angle >90°) when imaged in air-equilibrated water. Additionally, the use of solvent exchange techniques (based on the difference in saturation levels of air in various solvents) also introduced surface nanobubbles on hydrophilic substrates (static contact angle <90°). In this work, tapping mode atomic force microscopy was used to image interfacial nanobubbles formed on bulk polycarbonate (static contact angle of 81.1°), bromo-terminated silica (BTS; static contact angle of 85.5°), and fluoro-terminated silica (FTS; static contact angle of 105.3°) surfaces when immersed in air-equilibrated water without solvent exchange. Nanobubbles formed on the above three substrates were characterized on the basis of Laplace pressure, bubble density, and contact line tension. Results reported here show that (1) the Laplace pressures of all nanobubbles formed on both BTS and polycarbonate were an order of magnitude higher than those of FTS, (2) the nanobubble number density per unit area decreased with an increase in substrate contact angle, and (3) the contact line tension of the nanobubbles was calculated to be positive for both BTS and polycarbonate (lateral radius, Rs < 50 nm for all nanobubbles), and negative for FTS (Rs > 50 nm for all nanobubbles). The nanobubble morphology and distribution before and after using the solvent exchange method (ethanol-water), on the bulk polycarbonate substrate was also characterized. Analysis for these polycarbonate surface nanobubbles showed that both the Laplace pressure and nanobubble density reduced by ≈98% after ethanol-water exchange, accompanied by a flip in the magnitude of contact line tension from positive (0.19 nN) to negative (-0.11 nN).

  4. Natural convection with evaporation in a vertical cylindrical cavity under the effect of temperature-dependent surface tension

    NASA Astrophysics Data System (ADS)

    Kozhevnikov, Danil A.; Sheremet, Mikhail A.

    2017-07-01

    The effect of surface tension on laminar natural convection in a vertical cylindrical cavity filled with a weak evaporating liquid has been analyzed numerically. The cylindrical enclosure is insulated at the bottom, heated by a constant heat flux from the side, and cooled by a non-uniform evaporative heat flux from the top free surface having temperature-dependent surface tension. Governing equations with corresponding boundary conditions formulated in dimensionless stream function, vorticity, and temperature have been solved by finite difference method of the second-order accuracy. The influence of Rayleigh number, Marangoni number, and aspect ratio on the liquid flow and heat transfer has been studied. Obtained results have revealed that the heat transfer rate at free surface decreases with Marangoni number and increases with Rayleigh number, while the average temperature inside the cavity has an opposite behavior; namely, it growths with Marangoni number and reduces with Rayleigh number.

  5. Surface tension profiles of nanofluid containing surfactant during microwave irradiation

    NASA Astrophysics Data System (ADS)

    Tanaka, K.; Asakuma, Y.; Saptoro, A.; Phan, C.

    2017-06-01

    Manipulation of the surface tension is useful in improving heat and mass transfer performances of nanofluids in thermal systems. In our previous study, the effect of microwave irradiation on the reduction of surface tension of nanofluids (Fe2O3) was found even after it was turned off. In this study, a synergistic effect of microwave irradiation and surfactant addition (SDS) was investigated to obtain further surface tension reduction of nanofluid. Experimental results indicate that surfactant addition is effective for wider particle number density in reducing surface tension, and the reduction level strongly depends on the surfactant concentration. On the other hand, effect of the number density on the surface tension reduction is less significant for the same concentration of surfactant. From the obtained data, a combination of microwave irradiation and surfactant addition shows potential to be used as a promising method to manipulate surface tension of nanofluids.

  6. Dynamical Modeling of Surface Tension

    NASA Technical Reports Server (NTRS)

    Brackbill, Jeremiah U.; Kothe, Douglas B.

    1996-01-01

    In a recent review it is said that free-surface flows 'represent some of the difficult remaining challenges in computational fluid dynamics'. There has been progress with the development of new approaches to treating interfaces, such as the level-set method and the improvement of older methods such as the VOF method. A common theme of many of the new developments has been the regularization of discontinuities at the interface. One example of this approach is the continuum surface force (CSF) formulation for surface tension, which replaces the surface stress given by Laplace's equation by an equivalent volume force. Here, we describe how CSF formulation might be made more useful. Specifically, we consider a derivation of the CSF equations from a minimization of surface energy as outlined by Jacqmin (1996). This reformulation suggests that if one eliminates the computation of curvature in terms of a unit normal vector, parasitic currents may be eliminated. For this reformulation to work, it is necessary that transition region thickness be controlled. Various means for this, in addition to the one discussed by Jacqmin (1996), are discussed.

  7. Effects of tension-compression asymmetry on the surface wrinkling of film-substrate systems

    NASA Astrophysics Data System (ADS)

    Huang, Xiao; Li, Bo; Hong, Wei; Cao, Yan-Ping; Feng, Xi-Qiao

    2016-09-01

    Many soft materials and biological tissues are featured with the tension-compression asymmetry of constitutive relations. The surface wrinkling of a stiff thin film lying on a compliant substrate is investigated through theoretical analysis and numerical simulations. It is found that the tension-compression asymmetry of the soft substrate not only affects the critical strain of buckling but, more importantly, may also influence the wrinkling pattern that occurs in the film-substrate system under specified loading conditions. Due to this mechanism, the thin film subjected to equi-biaxial compression may first buckle into a hexagonal array of dimples or bulges, instead of the checkerboard pattern, and consequently evolve into labyrinths with further loading. Under non-equi-biaxial compression, the system may buckle either into a parallel bead-chain pattern or a stripe pattern, depending on the substrate nonlinearity and the loading biaxiality. Phase diagrams are established for the wrinkling patterns in a wide range of geometric and mechanical parameters, which facilitate the design of surface patterns with desired properties and functions.

  8. Surface tension of low-temperature aqueous solutions

    SciTech Connect

    Horibe, A.; Fukusako, S.; Yamada, M.

    1996-03-01

    Measurements of the surface tension have been carried out to determine the effects of both temperature and concentration on the surface tension of aqueous solutions of sodium chloride, propylene glycol, and ethylene glycol. A differential capillary-rise method was employed for the measurements. The results show that the surface tension of the ethylene glycol solution and the propylene glycol solution increases as the concentration of the solution decreases, while for the sodium chloride solution the surface tension increases monotonically as the concentration increases. The surface tension of the liquids was found to be an almost-linear function of temperature from 20{degrees}C to just above the freezing temperature. Equations for the surface tension of the three binary aqueous solutions as a function of temperature and concentration are presented.

  9. Actin cortex architecture regulates cell surface tension.

    PubMed

    Chugh, Priyamvada; Clark, Andrew G; Smith, Matthew B; Cassani, Davide A D; Dierkes, Kai; Ragab, Anan; Roux, Philippe P; Charras, Guillaume; Salbreux, Guillaume; Paluch, Ewa K

    2017-06-01

    Animal cell shape is largely determined by the cortex, a thin actin network underlying the plasma membrane in which myosin-driven stresses generate contractile tension. Tension gradients result in local contractions and drive cell deformations. Previous cortical tension regulation studies have focused on myosin motors. Here, we show that cortical actin network architecture is equally important. First, we observe that actin cortex thickness and tension are inversely correlated during cell-cycle progression. We then show that the actin filament length regulators CFL1, CAPZB and DIAPH1 regulate mitotic cortex thickness and find that both increasing and decreasing thickness decreases tension in mitosis. This suggests that the mitotic cortex is poised close to a tension maximum. Finally, using a computational model, we identify a physical mechanism by which maximum tension is achieved at intermediate actin filament lengths. Our results indicate that actin network architecture, alongside myosin activity, is key to cell surface tension regulation.

  10. Growth of a Gas Bubble in a Supersaturated Liquid Under the Effect of Variant Cases of Surface Tension

    NASA Astrophysics Data System (ADS)

    Mohammadein, S. A.; Mohamed, K. G.

    In this paper, the growth of a gas bubble in a supersaturated liquid is discussed for a constant and variable cases of surface tension effect. The mathematical model is solved analytically by using the method of Plesset and Zwick18 after modified it. The growth process is affected by: diffusion coefficient D, Jacob number Ja, surface tension σ, adjustment factor b and void fraction ϕ0. The famous formula of Plesset and Zwick is produced as a special case of the results at some values of the adjustment factors. Moreover, for some values of the adjustment factors, good approximation is obtained when a comparison between our results and the result that produced by Hashemi et al., 9 who solved the problem with the method of combining variables.

  11. Effect of surface tension on a liquid-jet produced by the collapse of a laser-induced bubble against a rigid boundary

    NASA Astrophysics Data System (ADS)

    Liu, Xiu Mei; He, Jie; Lu, Jian; Ni, Xiao Wu

    2009-02-01

    The effect of surface tension on the behavior of a liquid-jet is investigated experimentally by means of a fiber-coupled optical beam deflection (OBD) technique. It is found that a target under water is impacted in turn by a laser-plasma ablation force and by a high-speed liquid-jet impulse induced by bubble collapse in the vicinity of a rigid boundary. The liquid-jet impact is found to be the main damage mechanism in cavitation erosion. Furthermore, the liquid-jet increases monotonously with surface tension, so cavitation erosion rises sharply with increasing surface tension. Surface tension also reduces bubble collapse duration. From the experimental results and the modified Rayleigh theory, the maximum bubble radius is obtained and it is found to reduce with increasing surface tension.

  12. Multiphase Allen-Cahn and Cahn-Hilliard models and their discretizations with the effect of pairwise surface tensions

    NASA Astrophysics Data System (ADS)

    Wu, Shuonan; Xu, Jinchao

    2017-08-01

    In this paper, the mathematical properties and numerical discretizations of multiphase models that simulate the phase separation of an N-component mixture are studied. For the general choice of phase variables, the unisolvent property of the coefficient matrix involved in the N-phase models based on the pairwise surface tensions is established. Moreover, the symmetric positive-definite property of the coefficient matrix on an (N - 1)-dimensional hyperplane - which is of fundamental importance to the well-posedness of the models - can be proved equivalent to some physical condition for pairwise surface tensions. The N-phase Allen-Cahn and N-phase Cahn-Hilliard equations can then be derived from the free-energy functional. A natural property is that the resulting dynamics of concentrations are independent of phase variables chosen. Finite element discretizations for N-phase models can be obtained as a natural extension of the existing discretizations for the two-phase model. The discrete energy law of the numerical schemes can be proved and numerically observed under some restrictions pertaining to time step size. Numerical experiments including the spinodal decomposition and the evolution of triple junctions are described in order to investigate the effect of pairwise surface tensions.

  13. Effect of surface tension on self-termination in Au tip fabrication for tip-enhanced Raman spectroscopy

    NASA Astrophysics Data System (ADS)

    Chaunchaiyakul, Songpol; Yano, Takeshi; Krukowski, Pawel; Kuwahara, Yuji

    2016-09-01

    The effect of surface tension on the fabrication of Au tips was investigated. When using a 12 M HCl aqueous solution, the etching process did not consistently self-terminate after the lower part of the wire dropped, resulting in the poor reproducibility of the tip sharpness. However, using an ethanolic solution of 12 mol/l HCl, a self-terminating etching process was always observed, resulting in the improved reproducibility of sharp tips. We attribute this to the reduced surface compared to that of aqueous HCl. The obtained tips were used in tip-enhanced Raman spectroscopy experiments, in which significant signal enhancement was observed.

  14. Small membranes under negative surface tension

    NASA Astrophysics Data System (ADS)

    Avital, Yotam Y.; Farago, Oded

    2015-03-01

    We use computer simulations and a simple free energy model to study the response of a bilayer membrane to the application of a negative (compressive) mechanical tension. Such a tension destabilizes the long wavelength undulation modes of giant vesicles, but it can be sustained when small membranes and vesicles are considered. Our negative tension simulation results reveal two regimes—(i) a weak negative tension regime characterized by stretching-dominated elasticity and (ii) a strong negative tension regime featuring bending-dominated elastic behavior. This resembles the findings of the classic Evans and Rawicz micropipette aspiration experiment in giant unilamellar vesicles (GUVs) [E. Evans and W. Rawicz, Phys, Rev. Lett. 64, 2094 (1990)]. However, in GUVs the crossover between the two elasticity regimes occurs at a small positive surface tension, while in smaller membranes it takes place at a moderate negative tension. Another interesting observation concerning the response of a small membrane to negative surface tension is related to the relationship between the mechanical and fluctuation tensions, which are equal to each other for non-negative values. When the tension decreases to negative values, the fluctuation tension γ drops somewhat faster than the mechanical tension τ in the small negative tension regime, before it saturates (and becomes larger than τ) for large negative tensions. The bending modulus exhibits an "opposite" trend. It remains almost unchanged in the stretching-dominated elastic regime, and decreases in the bending-dominated regime. Both the amplitudes of the thermal height undulations and the projected area variations diverge at the onset of mechanical instability.

  15. Surface Tension in Unitary Fermi Gases with Population Imbalance

    SciTech Connect

    De Silva, Theja N.; Mueller, Erich J.

    2006-08-18

    We study the effects of surface tension between normal and superfluid regions of a trapped Fermi gas at unitarity. We find that surface tension causes notable distortions in the shape of large aspect ratio clouds. Including these distortions in our theories resolves many of the apparent discrepancies among different experiments and between theory and experiments.

  16. Pendant-Drop Surface-Tension Measurement On Molten Metal

    NASA Technical Reports Server (NTRS)

    Man, Kin Fung; Thiessen, David

    1996-01-01

    Method of measuring surface tension of molten metal based on pendant-drop method implemented in quasi-containerless manner and augmented with digital processing of image data. Electrons bombard lower end of sample rod in vacuum, generating hanging drop of molten metal. Surface tension of drop computed from its shape. Technique minimizes effects of contamination.

  17. Effects of surface tension and viscosity on the growth rates of Rayleigh-Taylor and Richtmyer-Meshkov instabilities.

    PubMed

    Sohn, Sung-Ik

    2009-11-01

    We present an analytical model for unstable interfaces with surface tension in fluids of arbitrary viscosity. Linear and nonlinear asymptotic solutions are obtained for growth rates of Rayleigh-Taylor and Richtmyer-Meshkov instabilities. In Rayleigh-Taylor instability, both surface tension and viscosity decrease the asymptotic bubble velocity. For Richtmyer-Meshkov instability, the analysis of the model suggests a dependence of the decaying rate of the bubble velocity on the relative importance of viscosity and surface tension. Results of numerical simulations are also given, and comparisons of the solutions of the model with numerical results are in good agreement.

  18. The surface tension of liquid gallium

    NASA Technical Reports Server (NTRS)

    Hardy, S. C.

    1985-01-01

    The surface tension of liquid gallium has been measured using the sessile drop technique in an Auger spectrometer. The experimental method is described. The surface tension in mJ/sq m is found to decrease linearly with increasing temperature and may be represented as 708-0.66(T-29.8), where T is the temperature in centigrade. This result is of interest because gallium has been suggested as a model fluid for Marangoni flow experiments. In addition, the surface tension is of technological significance in the processing of compound semiconductors involving gallium.

  19. Measuring Surface Tension of a Flowing Soap Film

    NASA Astrophysics Data System (ADS)

    Sane, Aakash; Kim, Ildoo; Mandre, Shreyas

    2016-11-01

    It is well known that surface tension is sensitive to the presence of surfactants and many conventional methods exist to measure it. These techniques measure surface tension either by intruding into the system or by changing its geometry. Use of conventional methods in the case of a flowing soap film is not feasible because intruding the soap film changes surface tension due to Marangoni effect. We present a technique in which we measure the surface tension in situ of a flowing soap film without intruding into the film. A flowing soap film is created by letting soap solution drip between two wires. The interaction of the soap film with the wires causes the wires to deflect which can be measured. Surface tension is calculated using a relation between curvature of the wires and the surface tension. Our measurements indicate that the surface tension of the flowing soap film for our setup is around 0.05 N/m. The nature of this technique makes it favorable for measuring surface tension of flowing soap films whose properties change on intrusion.

  20. Surface tension and the dodecahedron model for lung elasticity.

    PubMed

    Kimmel, E; Budiansky, B

    1990-05-01

    Macroscopic elastic moduli governing the incremental deformations of lung parenchyma are calculated on the basis of a model for an individual lung element in the shape of a regular dodecahedron. Elastic stiffness within the element is provided by pin-jointed tension members along the edges of the dodecahedron, surface tension is incorporated into its pentagonal faces, and the influence of transpulmonary pressure is simulated by an externally applied hydrostatic tension. The analysis is based on a variational statement of nonlinear structural mechanics, and the results show how the moduli depend on the effective inflation pressure, the constitutive behavior of the idealized truss members, and the surface-area dependent surface tension. The theory is discussed in the light of available experimental information. A more general analysis is needed to account for the effects of structural as well as surface-tension hysteresis.

  1. CROSS-DISCIPLINARY PHYSICS AND RELATED AREAS OF SCIENCE AND TECHNOLOGY: The effect of anisotropic surface tension on the morphological stability of planar interface during directional solidification

    NASA Astrophysics Data System (ADS)

    Chen, Ming-Wen; Lan, Man; Yuan, Lin; Wang, Yu-Yan; Wang, Zi-Dong; Xu, Jian-Jun

    2009-04-01

    This paper considers the effect of the anisotropic surface tension on the morphological stability of the planar interface during directional solidification. When the expression exhibiting the four-fold symmetry is included, the modified absolute stability criterion is obtained by employing the multi-variable expansion method. The linear stability analysis reveals that for the given temperature gradient, as the anisotropic surface tension parameter increases, the stability zone tends to decrease.

  2. Analysis of effect of temperature gradients on surface-tension phenomena in gas-tungsten-arc welds

    SciTech Connect

    Lee, H.A.; Chien, P.S.J.

    1982-10-01

    Fluid motion directed by surface tension is considered as a contributor to heat penetration in a weld pool. The potential phenomena at the gas-liquid interface were analyzed, and the dependence of surface motion on temperature in the gas-tungsten-arc (GTA) welding process was examined. An existing heat-transfer model was used and was able to predict weld size to +- 50% of the actual value. A momentum-transfer equation was derived by considering the contribution of Lorentz force. The momentum boundary condition was developed and was able to predict the Marangoni effect. The magnitude of surface-tension-driven force is comparable to the gravitational force on one gram. An empirical approach was proposed to couple heat-transfer and momentum-transfer phenomena. A dimensional analysis identified the pertinent dimensionless groups as Reynolds, Weber, Froude, Peclet, and Power numbers and a dimensionless velocity. A simplified form of the correction was developed by combining dimensionless groups to yield a correlation with the Bond, Prandtl, and modified power numbers. Future experimental work was proposed to test the functionality of the dimensionless groups.

  3. Effect of substance properties on the appearance and characteristics of repeated surface tension auto-oscillation driven by Marangoni force.

    PubMed

    Kovalchuk, N M; Vollhardt, D

    2004-01-01

    The effect of substance properties (solution viscosity and density, surfactant bulk and surface diffusion coefficient, activity, and solubility) on the appearance and characteristics of surface tension auto-oscillation that occurs by dissolution of a surfactant drop under the water-air interface is considered in the framework of a simple mathematical model, taking into account the convection driven by the Marangoni effect and convective diffusion together with adsorption/desorption processes at the air-water interface. Numerical simulations show that apart from the Marangoni and Schmidt number, the system behavior is governed also by the exchange number, which determines the surfactant exchange with the interface. The criterion for the instability onset in a system with both normal and tangential (with respect to the interface) concentration gradient, the correlation between the global and local Marangoni numbers, as well as a comparison with experiment are discussed.

  4. Surface tension of Nanofluid-type fuels containing suspended nanomaterials

    NASA Astrophysics Data System (ADS)

    Tanvir, Saad; Qiao, Li

    2012-04-01

    The surface tension of ethanol and n-decane based nanofluid fuels containing suspended aluminum (Al), aluminum oxide (Al2O3), and boron (B) nanoparticles as well as dispersible multi-wall carbon nanotubes (MWCNTs) were measured using the pendant drop method by solving the Young-Laplace equation. The effects of nanoparticle concentration, size and the presence of a dispersing agent (surfactant) on surface tension were determined. The results show that surface tension increases both with particle concentration (above a critical concentration) and particle size for all cases. This is because the Van der Waals force between particles at the liquid/gas interface increases surface free energy and thus increases surface tension. At low particle concentrations, however, addition of particles has little influence on surface tension because of the large distance between particles. An exception is when a surfactant was used or when (MWCNTs) was involved. For such cases, the surface tension decreases compared to the pure base fluid. The hypothesis is the polymer groups attached to (MWCNTs) and the surfactant layer between a particle and the surround fluid increases the electrostatic force between particles and thus reduce surface energy and surface tension.

  5. Butler-Sugimoto monomolecular bilayer interface model: the effect of oxygen on the surface tension of a liquid metal and its wetting of a ceramic.

    PubMed

    Yen, Pei-Shan; Datta, Ravindra

    2014-07-15

    The influence of oxygen on liquid-gas surface tension of molten metals has been well-investigated experimentally and modeled theoretically via the Szyszkowski equation, derivable from the Butler molecular monolayer interface model. However, there is no corresponding model describing the experimentally observed profound effect of oxygen partial pressure on solid-liquid surface tension as well as on contact angle of molten metals on ceramic substrates. Here, we utilize the Butler-Sugimoto thermodynamic approach based on a monomolecular bilayer interface model to investigate the effect of oxygen partial pressure on liquid-gas as well as solid-liquid surface tension of molten Cu/Al2O3 and molten Ag/Al2O3 systems. It is shown that both liquid-gas and solid-liquid surface tension are a strong function of oxygen activity in the melt, which, in turn, depends on gas-phase oxygen partial pressure, in conformity with experiments. The change in solid-liquid surface tension and wetting is also greatly affected by the change in liquid-gas surface tension. This improved understanding is of practical significance in many applications.

  6. Front-surface fluorometry with fura-2 and effects of nitroglycerin on cytosolic calcium concentrations and on tension in the coronary artery of the pig.

    PubMed Central

    Abe, S.; Kanaide, H.; Nakamura, M.

    1990-01-01

    1. By use of front-surface fluorometry and fura-2-loaded strips of the coronary artery of the pig, the effects of nitroglycerin (NG) on cytosolic Ca2+ concentrations ([Ca2+]i) and on tension development were measured simultaneously. 2. Both high K+ depolarization and histamine increased [Ca2+]i and tension in a concentration-dependent manner. However, the tension development in relation to the [Ca2+]i increase ([Ca2+]i-tension relation) observed with histamine was much greater than that observed with K+ depolarization. 3. NG reduced in a concentration-dependent manner both [Ca2+]i and tension, irrespective of whether the vascular strips were in a resting state or during exposure to high K+ or to histamine stimulation. However, the extent of reduction in tension (relaxation) was greater than that expected from the reduction in [Ca2+]i based on the [Ca2+]i-tension relationship observed with K(+)-depolarization. 4. In the absence of extracellular Ca2+, NG depleted stored Ca2+ and also inhibited Ca2+ release from histamine-sensitive stores, but had no effect on the caffeine-sensitive stores. NG inhibited the caffeine-induced tension development with no change in [Ca2+]i. 5. We suggest that NG relaxes the coronary artery of the pig by reducing [Ca2+]i and also by directly controlling contractile elements through second messengers not related to changes in [Ca2+]i. PMID:2127551

  7. Thermostatics and thermodynamics of surface tension in weld pools

    SciTech Connect

    Papazian, H.A.

    1986-02-01

    Thermostatics (classical or ''global'' thermodynamics) in the form of the Gibbs' adsorption isotherm is used to demonstrate the relationship of surface-active solutes to the temperature coefficient of surface tension. The structure of the surface layer may also be deduced. Thermodynamics (irreversible or ''local'') has been applied to the surface. The analysis provides a thermodynamic basis for the Marangoni effect.

  8. Effect of amino acids on aggregation behaviors of sodium deoxycholate at air/water surface: surface tension and oscillating bubble studies.

    PubMed

    He, Fang; Xu, Guiying; Pang, Jinyu; Ao, Mingqi; Han, Tingting; Gong, Houjian

    2011-01-18

    The aggregation behaviors of sodium deoxycholate (NaDC) at the air/water surface were investigated via surface tension and oscillating bubble measurements in the absence and presence of three alkaline amino acids, namely, L-Lysine (L-Lys), L-Arginine (L-Arg), and L-Histidine (L-His). The results of surface tension measurements show that NaDC has a lower ability to reduce the surface tension of water, because NaDC molecules orient at the surface in an oblique direction and tend to aggregate together, which is approved by molecular dynamics (MD) simulation. L-Lys is the most efficient of the three amino acids in reducing the critical aggregation concentration (cac) of NaDC in aqueous solution. The influence of amino acids on the dilational rheological properties of NaDC was studied using the drop shape analysis method in the frequency range from 0.02 to 0.5 Hz. The results reveal that the absolute modulus passes through a maximum value with increasing NaDC concentration. The addition of amino acids increases the absolute modulus of NaDC, and the maximum value is observed at much lower concentration. From the perspective of structures of amino acids, the performance of L-Arg is similar to that of L-His, and both of them bring out a smaller effect on the absolute modulus than that of L-Lys. From the above results, it may be presumed that electrostatic and hydrophobic effects are important impetus during the interaction between amino acids and NaDC at the air/water surface. Hydrogen bonding is so ubiquitous in the system that the difference of hydrogen bonding between NaDC and amino acid is ignored.

  9. Laplacian drop shapes and effect of random perturbations on accuracy of surface tension measurement for different drop constellations.

    PubMed

    Saad, Sameh M I; Neumann, A Wilhelm

    2015-08-01

    Theoretical drop shapes are calculated for three drop constellations: pendant drops, constrained sessile drops, and unconstrained sessile drops. Based on total Gaussian curvature, shape parameter and critical shape parameter are discussed as a function of different drop sizes and surface tensions. The shape parameter is linked to physical parameters for every drop constellation. The as yet unavailable detailed dimensional analysis for the unconstrained sessile drop is presented. Results show that the unconstrained sessile drop shape depends on a dimensionless volume term and the contact angle. Random perturbations are introduced and the accuracy of surface tension measurement is assessed for precise and perturbed profiles of the three drop constellations. It is concluded that pendant drops are the best method for accurate surface tension measurement, followed by constrained sessile drops. The unconstrained sessile drops come last because they tend to be more spherical at low and moderate contact angles. Of course, unconstrained sessile drops are the only option if contact angles are to be measured.

  10. Non-Newtonian Fluids Spreading with Surface Tension Effect: 3D Numerical Analysis Using FEM and Experimental Study

    NASA Astrophysics Data System (ADS)

    Hu, Bin; Kieweg, Sarah

    2010-11-01

    Gravity-driven thin film flow down an incline is studied for optimal design of polymeric drug delivery vehicles, such as anti-HIV topical microbicides. We develop a 3D FEM model using non-Newtonian mechanics to model the flow of gels in response to gravity, surface tension and shear-thinning. Constant volume setup is applied within the lubrication approximation scope. The lengthwise profiles of the 3D model agree with our previous 2D finite difference model, while the transverse contact line patterns of the 3D model are compared to the experiments. With incorporation of surface tension, capillary ridges are observed at the leading front in both 2D and 3D models. Previously published studies show that capillary ridge can amplify the fingering instabilities in transverse direction. Sensitivity studies (2D & 3D) and experiments are carried out to describe the influence of surface tension and shear-thinning on capillary ridge and fingering instabilities.

  11. Softening of edges of solids by surface tension

    NASA Astrophysics Data System (ADS)

    Mora, Serge; Pomeau, Yves

    2015-05-01

    Surface tension tends to minimize the area of interfaces between pieces of matter in different thermodynamic phases, be they in the solid or the liquid state. This can be relevant for the macroscopic shape of very soft solids and lead to a roughening of initially sharp edges. We calculate this effect for a Neo-Hookean elastic solid, with assumptions corresponding to actual experiments, namely the case where an initially sharp edge is rounded by the effect of surface tension felt when the fluid surrounding the soft solid (and so surface tension) is changed at the solid/liquid boundary. We consider two opposite limits where the analysis can be carried to the end, the one of a shallow angle and the one of a very sharp angle. Both cases yield a discontinuity of curvature in the state with surface tension although the initial state had a discontinuous slope.

  12. Softening of edges of solids by surface tension.

    PubMed

    Mora, Serge; Pomeau, Yves

    2015-05-20

    Surface tension tends to minimize the area of interfaces between pieces of matter in different thermodynamic phases, be they in the solid or the liquid state. This can be relevant for the macroscopic shape of very soft solids and lead to a roughening of initially sharp edges. We calculate this effect for a Neo-Hookean elastic solid, with assumptions corresponding to actual experiments, namely the case where an initially sharp edge is rounded by the effect of surface tension felt when the fluid surrounding the soft solid (and so surface tension) is changed at the solid/liquid boundary. We consider two opposite limits where the analysis can be carried to the end, the one of a shallow angle and the one of a very sharp angle. Both cases yield a discontinuity of curvature in the state with surface tension although the initial state had a discontinuous slope.

  13. The inviscid and viscous instability of an unbounded shear layer: Effect of surface tension, density, viscosity and velocity profile

    NASA Astrophysics Data System (ADS)

    Alabduljalil, Saad Abdulateef

    Parallel flows constitute prototypical configurations in many important applications in industry such as atomization and spraying of liquid fuels. A full description and understanding of the inviscid and viscous instability of realistic velocity profiles in unbounded two-phase shear layers without restriction on the range of the physical parameters of the flow are yet to be accomplished. The inviscid and viscous instability characteristics of unbounded parallel flows of two fluids with different viscosities and densities are extensively investigated by performing a full linear stability analysis. The effects of density and viscosity stratifications, surface tension, Reynolds number and velocity profile are determined. The neutral stability and the maximal growth rate for the instability modes are calculated for a wide range of flow parameters. The inviscid instability is first studied for the piecewise-linear profile and the error-function profile. Apart from the stabilizing effect observed in most of the cases, surface tension is found to destabilize the neutrally-stable waves that exist when surface tension is absent. A mathematical explanation and a physical explanation are given. The piecewise-linear profile does not match the more realistic results obtained with the error-function profile in the short-wavelength range, especially in nonhomogeneous shear layers. The viscous instability is then studied for the error-function profile. A numerical scheme which is efficiently capable of handling a broad range of flow configurations and parameters is developed. The inclusion of viscosity alters the inviscid perturbations and produces additional modes, most remarkably, the interfacial mode that arises at large wavenumbers. The coexistence of three distinct modes in gas-liquid systems is observed. The parameters that control the mode crossing between these modes are determined. Energy considerations and parametric properties are found to be efficient tools to identify

  14. Effect of two hydrocarbon and one fluorocarbon surfactant mixtures on the surface tension and wettability of polymers.

    PubMed

    Szymczyk, Katarzyna; González-Martín, Maria Luisa; Bruque, Jose Morales; Jańczuk, Bronisław

    2014-03-01

    The advancing contact angle of water, formamide and diiodomethane on polytetrafluoroethylene (PTFE) and polymethyl methacrylate (PMMA) surfaces covered with the film of ternary mixtures of surfactants including p-(1,1,3,3-tetramethylbutyl) phenoxypoly(ethyleneglycols), Triton X-100 (TX100) and Triton X-165 (TX165) and the fluorocarbon surfactants, Zonyl FSN-100 (FSN100) or Zonyl FSO-100 (FSO100) was measured. The obtained results were used for the surface tension of PTFE and PMMA covered with this film determination from the Young equation on the basis of van Oss et al. and Neumann et al. approaches to the interfacial tension. The surface tension of PTFE and PMMA was also determined using the Neumann et al. equation and the contact angle values for the aqueous solutions of the above mentioned ternary surfactants mixtures which were taken from the literature. As follows from our calculations mainly the presence of the fluorocarbon surfactant in the mixture considerably changes the surface properties of PTFE and PMMA causing that in contrast to hydrocarbon surfactants and their mixtures there is no linear dependence between adhesion and surface tension in the whole range of concentration of the ternary mixtures of surfactants including the fluorocarbon one. The behavior of fluorocarbon surfactants at the polymer-air and polymer-water interfaces is quite different from those of hydrocarbons. In the case of fluorocarbon surfactants not only adsorption but also sorption can occur on the polymer surface.

  15. Travelling-wave similarity solution for gravity-driven rivulet of a Newtonian fluid with strong surface-tension effect

    NASA Astrophysics Data System (ADS)

    Abas, Siti Sabariah; Yatim, Yazariah Mohd

    2017-08-01

    Rivulet flows occur in a wide range of practical situations ranging from industrial situation such as coating processes to geophysical situation such as lava flow, and extensive efforts have been made to investigate it. In this study, a lubrication approximation is used to investigate the gravity-driven draining of unsteady, slender, symmetric rivulet of Newtonian fluid down an inclined plane, with strong surface-tension effect. A travelling-wave similarity solution is obtained representing a quartic transverse profile rivulet and that it has a uniform thickness at any position x and time t which widen or narrow according to (x - ct)1/4, where c is a velocity of a rivulet and thicken or thin according to a free parameter F0.

  16. Carbon speciation and surface tension of fog

    USGS Publications Warehouse

    Capel, P.D.; Gunde, R.; Zurcher, F.; Giger, W.

    1990-01-01

    The speciation of carbon (dissolved/particulate, organic/inorganic) and surface tension of a number of radiation fogs from the urban area of Zurich, Switzerland, were measured. The carbon species were dominated by "dissolved" organic carbon (DOC; i.e., the fraction that passes through a filter), which was typically present at levels of 40-200 mg/L. Less than 10% of the DOC was identified as specific individual organic compounds. Particulate organic carbon (POC) accounted for 26-41% of the mass of the particles, but usually less than 10% of the total organic carbon mass. Inorganic carbon species were relatively minor. The surface tensions of all the measured samples were less than pure water and were correlated with their DOC concentrations. The combination of high DOC and POC and low surface tension suggests a mechanism for the concentration of hydrophobic organic contaminants in the fog droplet, which have been observed by numerous investigators. ?? 1990 American Chemical Society.

  17. Effects of the kinematic viscosity and surface tension on the bubble take-off period in a catalase-hydrogen peroxide system.

    PubMed

    Sasaki, Satoshi; Iida, Yoshinori

    2009-06-01

    The effect of kinematic viscosity and surface tension of the solution was investigated by adding catalase, glucose oxidase, or glucose on the bubble movement in a catalase-hydrogen peroxide system. The kinematic viscosity was measured using a Cannon-Fenske kinematic viscometer. The surface tension of the solution was measured by the Wilhelmy method using a self-made apparatus. The effects of the hole diameter/cell wall thickness, catalase concentration, glucose concentration, and glucose oxidase concentration on the kinematic viscosity, surface tension, and bubble take-off period were investigated. With our system, the effects of the changes in the solution materiality on the bubble take-off period were proven to be very small in comparison to the change in the oxygen-producing rate.

  18. Organic cloud condensation nuclei: the effect of phase, surface tension, trace soluble species, and oxidative processing on particle activation.

    NASA Astrophysics Data System (ADS)

    Broekhuizen, K. E.; Thornberry, T.; Abbatt, J. P.

    2003-12-01

    The ability of organic aerosols to act as cloud condensation nuclei (CCN) will be discussed. A variety of laboratory experiments will be presented which address several key questions concerning organic particle activation. Does the particle phase impact activation? How does surface tension play a role and can a trace amount of a surface active species impact activation? Does a trace amount of a highly soluble species impact the activation of organic particles of moderate to low solubility? Can the activation properties of organic aerosols be enhanced through oxidative processing? To systematically address these issues, the CCN activity of various diacids such as oxalic, malonic, succinic, adipic and azelaic acid have been studied, as well as the addition of trace amounts of nonanoic acid and ammonium sulfate to examine the roles of surface active and soluble species, respectively. The first examination of the role of oxidative processing on CCN activity has involved investigating the effect of ozone oxidation on the activity of oleic acid particles.

  19. Surface Tensions and Their Variations with Temperature and Impurities

    NASA Technical Reports Server (NTRS)

    Hardy, S. C.; Fine, J.

    1985-01-01

    The surface tensions in this work were determined using the sessile drop technique. This method is based on a comparison of the profile of a liquid drop with the profile calculated by solving the Young-Laplace equation. The comparison can be made in several ways; the traditional Bashforth-Adams procedure was used in conjunction with recently calculated drop shape tables which virtually eliminate interpolation errors. Although previous study has found little difference in measurements with pure and oxygen doped silicon, there is other evidence suggesting that oxygen in dilute concentrations severely depresses the surface tension of silicon. The surface tension of liquid silicon in purified argon atmospheres was measured. A temperature coefficient near -0.28 mJ/square meters K was found. The experiments show a high sensitivity of the surface tension to what is believed are low concentrations of oxygen. Thus one cannot rule out some effect of low levels of oxygen in the results. However, the highest surface tension values obtained in conditions which minimized the residual oxygen pressure are in good agreement with a previous measurement in pure hydrogen. Therefore, depression of the surface tension by oxygen is insignificant in these measurements.

  20. Measuring the surface tension of soap bubbles

    NASA Technical Reports Server (NTRS)

    Sorensen, Carl D.

    1992-01-01

    The objectives are for students to gain an understanding of surface tension, to see that pressure inside a small bubble is larger than that inside a large bubble. These concepts can be used to explain the behavior of liquid foams as well as precipitate coarsening and grain growth. Equipment, supplies, and procedures are explained.

  1. Viscosity and surface tension effects during multiphase flow in propped fractures

    NASA Astrophysics Data System (ADS)

    Dzikowski, Michał; Dąbrowski, Marcin

    2017-04-01

    Geological sequestration of CO2 was proposed as an important mechanism to reduce its emission into atmosphere. CO2 exhibits a higher affinity to organic matter than methane molecules and, potentially, it could be pumped and stored in shale reservoirs while enhancing late stage shale gas production. A successful analysis of CO2 sequestration in low matrix permeability rocks such as shales requires a thorough understanding of multiphase flow in stimulated rock fractures, which provide most significant pathways for fluids in such systems. Multiphase fracture flows are also of great relevance to brine, oil and gas migration in petroleum systems, water and stream circulation in geothermal reservoirs, and chemical transport of non-aqueous phase liquids in shallow hydrogeological systems, particularly in partially saturated zones. There are various physical models that describe phenomena taking place during multiphase flow through porous media. One of key aspects that need to be considered are pore-scale effects related to capillarity. Unfortunately, detailed models that describe motion and evolution of phase or component boundary require direct numerical simulations and spatial resolutions that are hard to reach when considering industrial relevant systems. Main aim of the presented work was the development of reduced 2.5D models based on Brinkman approximation of thin domain flow that would be able to capture local scale phenomena without expensive 3D simulations. Presented approach was designed specifically to tackle incompressible and immiscible systems and is based on Continuous Surface Force approach presented by Brackbill et al., implemented using Lattice Boltzmann Method. Presented approach where firstly validated against standard test cases with known classical solution and known experimental data. In the second part, we present and discuss two component, immiscible permeability data for rough and propped fracture obtained with our code for a rage of proppants

  2. Strong evidence of surface tension reduction in microscopic aqueous droplets

    NASA Astrophysics Data System (ADS)

    Ruehl, C. R.; Chuang, P. Y.; Nenes, A.; Cappa, C. D.; Kolesar, K. R.; Goldstein, A. H.

    2012-12-01

    The ability of airborne particles to take up water may be enhanced by surface-active components, but the importance of this effect is controversial because direct measurement of the surface tension of microscopic droplets has not been possible. Here we infer droplet surface tension from water uptake measurements of mixed organic-inorganic particles at relative humidities just below saturation (99.3-99.9%). The surface tension of droplets formed on particles composed of NaCl and α-pinene ozonolysis products was reduced by 50-75%, but only when enough organic material was present to form a film on the droplet surface at least 0.8 nm thick. This study suggests that if atmospheric particles are predominantly (≳80%) composed of surface-active material, their influence on cloud properties and thus climate could be enhanced, and their atmospheric lifetimes could be reduced.

  3. The Jones-Ray effect reinterpreted: Surface tension minima of low ionic strength electrolyte solutions are caused by electric field induced water-water correlations

    NASA Astrophysics Data System (ADS)

    Okur, H. I.; Chen, Y.; Wilkins, D. M.; Roke, S.

    2017-09-01

    The surface tension of electrolyte solutions exhibits a minimum at millimolar electrolyte concentrations and then rises with increasing concentration. This minimum, known as the Jones-Ray effect, has been hotly debated over the past ∼80 years. If not considered as an artifact, it is typically ascribed to a phenomenological rare binding site for ions or ion pairs. Here, we propose an alternative underlying mechanism, namely that the hydrogen bond network of water responds to the collective electrostatic field of ions by increasing its orientational order, supported by recent surface tension measurements of NaCl solutions in H2O and D2O, and second harmonic scattering experiments in combination with ion resonant second harmonic reflection experiments. Recent thermodynamic and purely electrostatic treatments of the surface tension provide support for this interpretation. In addition, concerns related to possible artifacts influencing the measurements are quantified experimentally.

  4. Type the title of your paper here Effect of the focused light from the xenon arc lamp on the surface tension of the molten enamel

    NASA Astrophysics Data System (ADS)

    Aleutdinov, A. D.; Ghyngazov, S. A.; Mylnikova, T. S.; Aleutdinov, K. A.

    2016-02-01

    The effect of exposure to the focused light from the xenon arc lamp on the surface tension of molten enamels was studied with a designed light beam setup as compared to that observed in conventional heating in a resistance furnace. The objects under investigation were enamels No. 261, UES-200 and UES-300. The power density of the light beam was varied in the range of (30-80) W/cm2. When exposed to light, the surface tension is shown to be an order of magnitude lower than that obtained in conventional furnace heating.

  5. Curvature effects on the surface thickness and tension at the free interface of 4He systems

    NASA Astrophysics Data System (ADS)

    Szybisz, Leszek; Urrutia, Ignacio

    2003-08-01

    The thickness W and the surface energy σA at the free interface of superfluid 4He are studied. Results of calculations carried out using density functionals for cylindrical and spherical systems are presented in a unified way, including a comparison with the behavior of planar slabs. It is found that for large species W is independent of the geometry. The obtained values of W are compared with prior theoretical results and experimental data. Experimental data favor results evaluated by adopting finite range approaches. The behavior of σA and WσA exhibits overshoots similar to that found previously for the central density, and the trend of these observables towards their asymptotic values is examined.

  6. Thermocapillary-driven motion of a sessile drop: effect of non-monotonic dependence of surface tension on temperature.

    PubMed

    Karapetsas, George; Sahu, Kirti Chandra; Sefiane, Khellil; Matar, Omar K

    2014-04-22

    We study the thermocapillary-driven spreading of a droplet on a nonuniformly heated substrate for fluids associated with a non-monotonic dependence of the surface tension on temperature. We use lubrication theory to derive an evolution equation for the interface that accounts for capillarity and thermocapillarity. The contact line singularity is relieved by using a slip model and a Cox-Voinov relation; the latter features equilibrium contact angles that vary depending on the substrate wettability, which, in turn, is linked to the local temperature. We simulate the spreading of droplets of fluids whose surface tension-temperature curves exhibit a turning point. For cases wherein these turning points correspond to minima, and when these minima are located within the droplet, then thermocapillary stresses drive rapid spreading away from the minima. This gives rise to a significant acceleration of the spreading whose characteristics resemble those associated with the "superspreading" of droplets on hydrophobic substrates. No such behavior is observed for cases in which the turning point corresponds to a surface tension maximum.

  7. Surface tension propellant control for Viking 75 Orbiter

    NASA Technical Reports Server (NTRS)

    Dowdy, M. W.; Hise, R. E.; Peterson, R. G.; Debrock, S. C.

    1976-01-01

    The paper describes the selection, development and qualification of the surface tension system and includes results of low-g drop tower tests of scale models, 1-g simulation tests of low-g large ullage settling and liquid withdrawal, structural qualification tests, and propellant surface tension/contact angle studies. Subscale testing and analyses were used to evaluate the ability of the system to maintain or recover the desired propellant orientation following possible disturbances during the Viking mission. This effort included drop tower tests to demonstrate that valid wick paths exist for moving any displaced propellant back over the tank outlet. Variations in surface tension resulting from aging, temperature, and lubricant contamination were studied and the effects of surface finish, referee fluid exposure, aging, and lubricant contamination on contact angle were assessed. Results of movies of typical subscale drop tower tests and full scale slosh tests are discussed.

  8. Surface tension propellant control for Viking 75 Orbiter

    NASA Technical Reports Server (NTRS)

    Dowdy, M. W.; Hise, R. E.; Peterson, R. G.; Debrock, S. C.

    1976-01-01

    The paper describes the selection, development and qualification of the surface tension system and includes results of low-g drop tower tests of scale models, 1-g simulation tests of low-g large ullage settling and liquid withdrawal, structural qualification tests, and propellant surface tension/contact angle studies. Subscale testing and analyses were used to evaluate the ability of the system to maintain or recover the desired propellant orientation following possible disturbances during the Viking mission. This effort included drop tower tests to demonstrate that valid wick paths exist for moving any displaced propellant back over the tank outlet. Variations in surface tension resulting from aging, temperature, and lubricant contamination were studied and the effects of surface finish, referee fluid exposure, aging, and lubricant contamination on contact angle were assessed. Results of movies of typical subscale drop tower tests and full scale slosh tests are discussed.

  9. Lennard-Jones Lattice Summation in Bilayer Simulations Has Critical Effects on Surface Tension and Lipid Properties.

    PubMed

    Wennberg, Christian L; Murtola, Teemu; Hess, Berk; Lindahl, Erik

    2013-08-13

    The accuracy of electrostatic interactions in molecular dynamics advanced tremendously with the introduction of particle-mesh Ewald (PME) summation almost 20 years ago. Lattice summation electrostatics is now the de facto standard for most types of biomolecular simulations, and in particular, for lipid bilayers, it has been a critical improvement due to the large charges typically present in zwitterionic lipid headgroups. In contrast, Lennard-Jones interactions have continued to be handled with increasingly longer cutoffs, partly because few alternatives have been available despite significant difficulties in tuning cutoffs and parameters to reproduce lipid properties. Here, we present a new Lennard-Jones PME implementation applied to lipid bilayers. We confirm that long-range contributions are well approximated by dispersion corrections in simple systems such as pentadecane (which makes parameters transferable), but for inhomogeneous and anisotropic systems such as lipid bilayers there are large effects on surface tension, resulting in up to 5.5% deviations in area per lipid and order parameters-far larger than many differences for which reparameterization has been attempted. We further propose an approximation for combination rules in reciprocal space that significantly reduces the computational cost of Lennard-Jones PME and makes accurate treatment of all nonbonded interactions competitive with simulations employing long cutoffs. These results could potentially have broad impact on important applications such as membrane proteins and free energy calculations.

  10. Effects of elasticity and surface tension on the spreading dynamics of a thin film under the influence of intermolecular forces

    NASA Astrophysics Data System (ADS)

    Young, Yuan-Nan; Stone, Howard

    2016-11-01

    The spreading dynamics of a thin layer of viscous Newtonian fluid between an elastic sheet and a wetting solid substrate is examined using the lubrication theory. On the wetting substrate an ultra thin film (precursor film) develops as a result of the intermolecular force between the fluid and the wetting solid substrate. Such a precursor film prevents the stress singularity associated with a moving contact line. Following the methodology by, the effects of elasticity on the macroscopic contact line structure in the quasistatic limit are elucidated by an ordinary differential equation derived from an analysis of the energy and its dissipation. Similar to the case of a regular fluid interface with surface tension (capillary spreading), the elasto-capillary thin film profile also consists of a core at the center, an ultra thin film in the far field, and a contact line region where the core film profile connects smoothly to the precursor film. For capillary spreading, the precursor film transitions monotonically to the core film. Due to the interfacial elasticity, a spatial oscillation of film height in the contact line region is found. In addition, it is found that elasticity causes the sliding motion of the thin film: the contact angle close to zero as

  11. Ice Accretion with Varying Surface Tension

    NASA Technical Reports Server (NTRS)

    Bilanin, Alan J.; Anderson, David N.

    1995-01-01

    During an icing encounter of an aircraft in flight, super-cooled water droplets impinging on an airfoil may splash before freezing. This paper reports tests performed to determine if this effect is significant and uses the results to develop an improved scaling method for use in icing test facilities. Simple laboratory tests showed that drops splash on impact at the Reynolds and Weber numbers typical of icing encounters. Further confirmation of droplet splash came from icing tests performed in the NaSA Lewis Icing Research Tunnel (IRT) with a surfactant added to the spray water to reduce the surface tension. The resulting ice shapes were significantly different from those formed when no surfactant was added to the water. These results suggested that the droplet Weber number must be kept constant to properly scale icing test conditions. Finally, the paper presents a Weber-number-based scaling method and reports results from scaling tests in the IRT in which model size was reduced up to a factor of 3. Scale and reference ice shapes are shown which confirm the effectiveness of this new scaling method.

  12. Numerical studies of the surface tension effect of cryogenic liquid helium

    NASA Technical Reports Server (NTRS)

    Hung, R. J.

    1994-01-01

    The generalized mathematical formulation of sloshing dynamics for partially filled liquid of cryogenic superfluid helium II in dewar containers driven by both the gravity gradient and jitter accelerations applicable to scientific spacecraft which is eligible to carry out spinning motion and/or slew motion for the purpose of performing scientific observation during the normal spacecraft operation is investigated. An example is given with Gravity Probe-B (GP-B) spacecraft which is responsible for the sloshing dynamics. The jitter accelerations include slew motion, spinning motion, atmospheric drag on the spacecraft, spacecraft attitude motions arising from machinery vibrations, thruster firing, pointing control of spacecraft, crew motion, etc. Explicit mathematical expressions to cover these forces acting on the spacecraft fluid systems are derived. The numerical computation of sloshing dynamics has been based on the non-inertia frame spacecraft bound coordinate, and solve time-dependent, three-dimensional formulations of partial differential equations subject to initial and boundary conditions. The explicit mathematical expressions of boundary conditions to cover capillary force effect on the liquid vapor interface in microgravity environments are also derived. The formulations of fluid moment and angular moment fluctuations in fluid profiles induced by the sloshing dynamics, together with fluid stress and moment fluctuations exerted on the spacecraft dewar containers, have been derived.

  13. Pumpless Transport of Low Surface Tension Liquids in Surface Tension Confined (STC) Tracks

    NASA Astrophysics Data System (ADS)

    Megaridis, Constantine; Schutzius, Thomas; Elsharkawy, Mohamed; Tiwari, Manish

    2012-11-01

    Surfaces with patterned wettability have potential applications in microfluidics, fog capture, pool boiling, etc. With recent fabrication advancements, surfaces with adjacent superhydrophobic and superhydrophilic regions are feasible at a reasonable cost; with properly designed patterns, one can produce microfluidic paths (a.k.a. surface tension confined or STC tracks) where a liquid is confined and transported by surface tension alone. The surface tension of water is relatively high (72 mN/m), as compared with oils (~25 mN/m) and organic solvents (~20 mN/m). This makes the design of STC channels for oils and organic solvents far more difficult. In this study, open STC tracks for pumpless transport of low-surface tension liquids (acetone, ethanol, and hexadecane) on microfluidic chips are fabricated using a large-area, wet-processing technique. Wettable, wax-based, submillimeter-wide tracks are applied by a fountain-pen procedure on superoleophobic, fluoroacrylic carbon nanofiber (CNF) composite coatings. The fabricated anisotropic wetting patterns confine the low-surface tension liquids onto the flow tracks, driving them with meniscus velocities exceeding 3 cm/s. Scaling arguments and Washburn's equation provide estimates of the liquid velocities measured in these tracks, which also act as rails for directional sliding control of mm-sized water droplets. The present facile patterned wettability approach can be extended to deposit micrometer-wide tracks.

  14. Effects of a semi-infinite stratification on the Rayleigh-Taylor instability in an interface with surface tension

    NASA Astrophysics Data System (ADS)

    de Andrea González, Ángel; González-Gutiérrez, Leo M.

    2017-09-01

    The Rayleigh-Taylor instability (RTI) in an infinite slab where a constant density lower fluid is initially separated from an upper stratified fluid is discussed in linear regime. The upper fluid is of increasing exponential density and surface tension is considered between both of them. It was found useful to study stability by using the initial value problem approach (IVP), so that we ensure the inclusion of certain continuum modes, otherwise neglected. This methodology includes the branch cut in the complex plane, consequently, in addition to discrete modes (surface RTI modes), a set of continuum modes (internal RTI modes) also appears. As a result, the usual information given by the normal mode method is now complete. Furthermore, a new role is found for surface tension: to transform surface RTI modes (discrete spectrum) into internal RTI modes belonging to a continuous spectrum at a critical wavenumber. As a consequence, the cut-off wavenumber disappears: i.e. the growth rate of the RTI surface mode does not decay to zero at the cut-off wavenumber, as previous researchers used to believe. Finally, we found that, due to the continuum, the asymptotic behavior of the perturbation with respect to time is slower than the exponential when only the continuous spectrum exists.

  15. Variational Methods For Sloshing Problems With Surface Tension

    NASA Astrophysics Data System (ADS)

    Tan, Chee Han; Carlson, Max; Hohenegger, Christel; Osting, Braxton

    2016-11-01

    We consider the sloshing problem for an incompressible, inviscid, irrotational fluid in a container, including effects due to surface tension on the free surface. We restrict ourselves to a constant contact angle and we seek time-harmonic solutions of the linearized problem, which describes the time-evolution of the fluid due to a small initial disturbance of the surface at rest. As opposed to the zero surface tension case, where the problem reduces to a partial differential equation for the velocity potential, we obtain a coupled system for the velocity potential and the free surface displacement. We derive a new variational formulation of the coupled problem and establish the existence of solutions using the direct method from the Calculus of Variations. In the limit of zero surface tension, we recover the variational formulation of the classical Steklov eigenvalue problem, as derived by B. A. Troesch. For the particular case of an axially symmetric container, we propose a finite element numerical method for computing the sloshing modes of the coupled system. The scheme is implemented in FEniCS and we obtain a qualitative description of the effect of surface tension on the sloshing modes.

  16. Effect of surface tension, viscosity, and process conditions on polymer morphology deposited at the liquid-vapor interface.

    PubMed

    Haller, Patrick D; Bradley, Laura C; Gupta, Malancha

    2013-09-17

    We have observed that the vapor-phase deposition of polymers onto liquid substrates can result in the formation of polymer films or particles at the liquid-vapor interface. In this study, we demonstrate the relationship between the polymer morphology at the liquid-vapor interface and the surface tension interaction between the liquid and polymer, the liquid viscosity, the deposition rate, and the deposition time. We show that the thermodynamically stable morphology is determined by the surface tension interaction between the liquid and the polymer. Stable polymer films form when it is energetically favorable for the polymer to spread over the surface of the liquid, whereas polymer particles form when it is energetically favorable for the polymer to aggregate. For systems that do not strongly favor spreading or aggregation, we observe that the initial morphology depends on the deposition rate. Particles form at low deposition rates, whereas unstable films form at high deposition rates. We also observe a transition from particle formation to unstable film formation when we increase the viscosity of the liquid or increase the deposition time. Our results provide a fundamental understanding about polymer growth at the liquid-vapor interface and can offer insight into the growth of other materials on liquid surfaces. The ability to systematically tune morphology can enable the production of particles for applications in photonics, electronics, and drug delivery and films for applications in sensing and separations.

  17. Surface Tension and Fingering of Miscible Interfaces

    NASA Technical Reports Server (NTRS)

    Abib, Mohammed; Liu, Jian-Bang; Ronney, Paul D.

    1999-01-01

    Experiments on miscible, buoyantly unstable reaction-diffusion fronts and non-reacting displacement fronts in Hele-Shaw cells show a fingering-type instability whose wavelengths (lambda*) are consistent with an interfacial tension (sigma) at the front caused by the change in chemical composition, even though the solutions are miscible in all proportions. In conjunction with the Saffman-Taylor model, the relation sigma = K/tau, where tau is the interface thickness and K approximately equal 4 +/- 2 x 10(exp -6) dyne, enables prediction of our measured values of lambda* as well as results from prior experiments on miscible interfaces. These results indicate that even for miscible fluids, surface tension is generally a more significant factor than diffusion in interfacial stability and flow characteristics.

  18. Dropwise Condensation of Low Surface Tension Fluids on Omniphobic Surfaces

    PubMed Central

    Rykaczewski, Konrad; Paxson, Adam T.; Staymates, Matthew; Walker, Marlon L.; Sun, Xiaoda; Anand, Sushant; Srinivasan, Siddarth; McKinley, Gareth H.; Chinn, Jeff; Scott, John Henry J.; Varanasi, Kripa K.

    2014-01-01

    Compared to the significant body of work devoted to surface engineering for promoting dropwise condensation heat transfer of steam, much less attention has been dedicated to fluids with lower interfacial tension. A vast array of low-surface tension fluids such as hydrocarbons, cryogens, and fluorinated refrigerants are used in a number of industrial applications, and the development of passive means for increasing their condensation heat transfer coefficients has potential for significant efficiency enhancements. Here we investigate condensation behavior of a variety of liquids with surface tensions in the range of 12 to 28 mN/m on three types of omniphobic surfaces: smooth oleophobic, re-entrant superomniphobic, and lubricant-impregnated surfaces. We demonstrate that although smooth oleophobic and lubricant-impregnated surfaces can promote dropwise condensation of the majority of these fluids, re-entrant omniphobic surfaces became flooded and reverted to filmwise condensation. We also demonstrate that on the lubricant-impregnated surfaces, the choice of lubricant and underlying surface texture play a crucial role in stabilizing the lubricant and reducing pinning of the condensate. With properly engineered surfaces to promote dropwise condensation of low-surface tension fluids, we demonstrate a four to eight-fold improvement in the heat transfer coefficient. PMID:24595171

  19. Dropwise Condensation of Low Surface Tension Fluids on Omniphobic Surfaces

    NASA Astrophysics Data System (ADS)

    Rykaczewski, Konrad; Paxson, Adam T.; Staymates, Matthew; Walker, Marlon L.; Sun, Xiaoda; Anand, Sushant; Srinivasan, Siddarth; McKinley, Gareth H.; Chinn, Jeff; Scott, John Henry J.; Varanasi, Kripa K.

    2014-03-01

    Compared to the significant body of work devoted to surface engineering for promoting dropwise condensation heat transfer of steam, much less attention has been dedicated to fluids with lower interfacial tension. A vast array of low-surface tension fluids such as hydrocarbons, cryogens, and fluorinated refrigerants are used in a number of industrial applications, and the development of passive means for increasing their condensation heat transfer coefficients has potential for significant efficiency enhancements. Here we investigate condensation behavior of a variety of liquids with surface tensions in the range of 12 to 28 mN/m on three types of omniphobic surfaces: smooth oleophobic, re-entrant superomniphobic, and lubricant-impregnated surfaces. We demonstrate that although smooth oleophobic and lubricant-impregnated surfaces can promote dropwise condensation of the majority of these fluids, re-entrant omniphobic surfaces became flooded and reverted to filmwise condensation. We also demonstrate that on the lubricant-impregnated surfaces, the choice of lubricant and underlying surface texture play a crucial role in stabilizing the lubricant and reducing pinning of the condensate. With properly engineered surfaces to promote dropwise condensation of low-surface tension fluids, we demonstrate a four to eight-fold improvement in the heat transfer coefficient.

  20. Dropwise condensation of low surface tension fluids on omniphobic surfaces.

    PubMed

    Rykaczewski, Konrad; Paxson, Adam T; Staymates, Matthew; Walker, Marlon L; Sun, Xiaoda; Anand, Sushant; Srinivasan, Siddarth; McKinley, Gareth H; Chinn, Jeff; Scott, John Henry J; Varanasi, Kripa K

    2014-03-05

    Compared to the significant body of work devoted to surface engineering for promoting dropwise condensation heat transfer of steam, much less attention has been dedicated to fluids with lower interfacial tension. A vast array of low-surface tension fluids such as hydrocarbons, cryogens, and fluorinated refrigerants are used in a number of industrial applications, and the development of passive means for increasing their condensation heat transfer coefficients has potential for significant efficiency enhancements. Here we investigate condensation behavior of a variety of liquids with surface tensions in the range of 12 to 28 mN/m on three types of omniphobic surfaces: smooth oleophobic, re-entrant superomniphobic, and lubricant-impregnated surfaces. We demonstrate that although smooth oleophobic and lubricant-impregnated surfaces can promote dropwise condensation of the majority of these fluids, re-entrant omniphobic surfaces became flooded and reverted to filmwise condensation. We also demonstrate that on the lubricant-impregnated surfaces, the choice of lubricant and underlying surface texture play a crucial role in stabilizing the lubricant and reducing pinning of the condensate. With properly engineered surfaces to promote dropwise condensation of low-surface tension fluids, we demonstrate a four to eight-fold improvement in the heat transfer coefficient.

  1. Instantons and surface tension at a first-order transition

    NASA Astrophysics Data System (ADS)

    Gupta, Sourendu

    1994-04-01

    We study the dynamics of the first-order phase transition in the two-dimensional 15-state Potts model, both at and off equilibrium. We find that phase changes take place through nucleation in both cases, and finite volume effects are described well through an instanton computation. Thus a dynamical measurement of the surface tension is possible. We find that the order-disorder surface tension is compatible with perfect wetting. An accurate treatment of fluctuations about the instanton solution is seen to be of great importance. Current Address: Theory Group, TIFR, Homi Bhabha Road, Bombay 400005, India.

  2. Contact Angles and Surface Tension of Germanium-Silicon Melts

    NASA Technical Reports Server (NTRS)

    Croell, A.; Kaiser, N.; Cobb, S.; Szofran, F. R.; Volz, M.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Precise knowledge of material parameters is more and more important for improving crystal growth processes. Two important parameters are the contact (wetting) angle and the surface tension, determining meniscus shapes and surface-tension driven flows in a variety of methods (Czochralski, EFG, floating-zone, detached Bridgman growth). The sessile drop technique allows the measurement of both parameters simultaneously and has been used to measure the contact angles and the surface tension of Ge(1-x)Si(x) (0 less than or equal to x less than or equal to 1.3) alloys on various substrate materials. Fused quartz, Sapphire, glassy carbon, graphite, SiC, carbon-based aerogel, pyrolytic boron nitride (pBN), AIN, Si3N4, and polycrystalline CVD diamond were used as substrate materials. In addition, the effect of different cleaning procedures and surface treatments on the wetting behavior were investigated. Measurements were performed both under dynamic vacuum and gas atmospheres (argon or forming gas), with temperatures up to 1100 C. In some experiments, the sample was processed for longer times, up to a week, to investigate any changes of the contact angle and/or surface tension due to slow reactions with the substrate. For pure Ge, stable contact angles were found for carbon-based substrates and for pBN, for Ge(1-x)Si(x) only for pBN. The highest wetting angles were found for pBN substrates with angles around 170deg. For the surface tension of Ge, the most reliable values resulted in gamma(T) = (591- 0.077 (T-T(sub m)) 10(exp -3)N/m. The temperature dependence of the surface tension showed similar values for Ge(1-x)Si(x), around -0.08 x 10(exp -3)N/m K, and a compositional dependence of 2.2 x 10(exp -3)N/m at%Si.

  3. Contact Angles and Surface Tension of Germanium-Silicon Melts

    NASA Technical Reports Server (NTRS)

    Croell, A.; Kaiser, N.; Cobb, S.; Szofran, F. R.; Volz, M.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    Precise knowledge of material parameters is more and more important for improving crystal growth processes. Two important parameters are the contact (wetting) angle and the surface tension, determining meniscus shapes and surface-tension driven flows in a variety of methods (Czochralski, EFG, floating-zone, detached Bridgman growth). The sessile drop technique allows the measurement of both parameters simultaneously and has been used to measure the contact angles and the surface tension of Ge(1-x)Si(x) (0 less than or equal to x less than or equal to 1.3) alloys on various substrate materials. Fused quartz, Sapphire, glassy carbon, graphite, SiC, carbon-based aerogel, pyrolytic boron nitride (pBN), AIN, Si3N4, and polycrystalline CVD diamond were used as substrate materials. In addition, the effect of different cleaning procedures and surface treatments on the wetting behavior were investigated. Measurements were performed both under dynamic vacuum and gas atmospheres (argon or forming gas), with temperatures up to 1100 C. In some experiments, the sample was processed for longer times, up to a week, to investigate any changes of the contact angle and/or surface tension due to slow reactions with the substrate. For pure Ge, stable contact angles were found for carbon-based substrates and for pBN, for Ge(1-x)Si(x) only for pBN. The highest wetting angles were found for pBN substrates with angles around 170deg. For the surface tension of Ge, the most reliable values resulted in gamma(T) = (591- 0.077 (T-T(sub m)) 10(exp -3)N/m. The temperature dependence of the surface tension showed similar values for Ge(1-x)Si(x), around -0.08 x 10(exp -3)N/m K, and a compositional dependence of 2.2 x 10(exp -3)N/m at%Si.

  4. Basic surface properties of Aedes albopictus cells: effect of Mayaro virus infection on electrostatic charge and surface tension.

    PubMed

    Mezêncio, J M; Costa e Silva Filho, F; Rebello, M A

    1997-01-01

    Aedes albopictus cells possess a negative cell surface charge of -12.7 mV with an isoelectrophoretic point (IEP) located between pH 3.0 and 4.0. Infection with Mayaro virus rendered the surface of A. albopictus cells less negative reaching a zeta-potential value of -9.7 mV after 100 h of infection. Concomitantly, the IEP of the infected cells were also altered from 3.0-4.0 to 4.0-5.0. Furthermore, the contact angle measurements clearly showed qualitative alterations in the cell surface of infected cells.

  5. Effect of the removal of the surface layer of a TRIP steel sheet on its phase composition after static tension at various strain rates

    NASA Astrophysics Data System (ADS)

    Terent'ev, V. F.; Slizov, A. K.; Sirotinkin, V. P.; Prosvirnin, D. V.; Kobeleva, L. I.; Eliseev, E. A.; Rybal'chenko, O. V.; Ashmarin, A. A.

    2016-01-01

    The effect of the removal of the surface layer of a thin strip made of austenitic-martensitic VNS9-Sh (23Kh15N5AM3-Sh) TRIP steel on the phase composition of the strip surface is studied after static tension at various strain rates. An increase in the strain rate is shown to increase the austenite content in the surface layer of the metal. The removal of a 10-μm-thick surface layer by electropolishing results in an increase in the austenite content due to the initial nonuniform phase composition of the thin TRIP steel strip across its thickness after cold rolling.

  6. STAND: Surface Tension for Aggregation Number Determination.

    PubMed

    Garrido, Pablo F; Brocos, Pilar; Amigo, Alfredo; García-Río, Luis; Gracia-Fadrique, Jesús; Piñeiro, Ángel

    2016-04-26

    Taking advantage of the extremely high dependence of surface tension on the concentration of amphiphilic molecules in aqueous solution, a new model based on the double equilibrium between free and aggregated molecules in the liquid phase and between free molecules in the liquid phase and those adsorbed at the air/liquid interface is presented and validated using literature data and fluorescence measurements. A key point of the model is the use of both the Langmuir isotherm and the Gibbs adsorption equation in terms of free molecules instead of the nominal concentration of the solute. The application of the model should be limited to non ionic compounds since it does not consider the presence of counterions. It requires several coupled nonlinear fittings for which we developed a software that is publicly available in our server as a web application. Using this tool, it is straightforward to get the average aggregation number of an amphiphile, the micellization free energy, the adsorption constant, the maximum surface excess (and so the minimum area per molecule), the distribution of solute in the liquid phase between free and aggregate species, and the surface coverage in only a couple of seconds, just by uploading a text file with surface tension vs concentration data and the corresponding uncertainties.

  7. Surface energy and surface tension at holes and cracks

    NASA Technical Reports Server (NTRS)

    Rajapakse, Y. D. S.

    1975-01-01

    The concept of surface tension and surface energy of solids was used by Griffith to obtain a criterion for the extension of cracks in brittle materials. Griffith, however, neglected the stresses due to the normal traction at the crack implied by the surface tension. A complete solution to the problem of an elliptic hole in an infinite plate with surface tension loading at the hole is given. Complex potentials are given in closed form in terms of elliptic integrals of the first, second, and third kinds. Stress distributions are studied. For a flat crack, the nature of the singularity at the tip is shown to be radically different from that usually encountered in fracture mechanics. The implications of our analysis for theories of fracture in brittle materials are discussed.

  8. Surface tensions of inorganic multicomponent aqueous electrolyte solutions and melts.

    PubMed

    Dutcher, Cari S; Wexler, Anthony S; Clegg, Simon L

    2010-11-25

    A semiempirical model is presented that predicts surface tensions (σ) of aqueous electrolyte solutions and their mixtures, for concentrations ranging from infinitely dilute solution to molten salt. The model requires, at most, only two temperature-dependent terms to represent surface tensions of either pure aqueous solutions, or aqueous or molten mixtures, over the entire composition range. A relationship was found for the coefficients of the equation σ = c(1) + c(2)T (where T (K) is temperature) for molten salts in terms of ion valency and radius, melting temperature, and salt molar volume. Hypothetical liquid surface tensions can thus be estimated for electrolytes for which there are no data, or which do not exist in molten form. Surface tensions of molten (single) salts, when extrapolated to normal temperatures, were found to be consistent with data for aqueous solutions. This allowed surface tensions of very concentrated, supersaturated, aqueous solutions to be estimated. The model has been applied to the following single electrolytes over the entire concentration range, using data for aqueous solutions over the temperature range 233-523 K, and extrapolated surface tensions of molten salts and pure liquid electrolytes: HCl, HNO(3), H(2)SO(4), NaCl, NaNO(3), Na(2)SO(4), NaHSO(4), Na(2)CO(3), NaHCO(3), NaOH, NH(4)Cl, NH(4)NO(3), (NH(4))(2)SO(4), NH(4)HCO(3), NH(4)OH, KCl, KNO(3), K(2)SO(4), K(2)CO(3), KHCO(3), KOH, CaCl(2), Ca(NO(3))(2), MgCl(2), Mg(NO(3))(2), and MgSO(4). The average absolute percentage error between calculated and experimental surface tensions is 0.80% (for 2389 data points). The model extrapolates smoothly to temperatures as low as 150 K. Also, the model successfully predicts surface tensions of ternary aqueous mixtures; the effect of salt-salt interactions in these calculations was explored.

  9. Review of literature surface tension data for molten silicon

    NASA Technical Reports Server (NTRS)

    Hardy, S.

    1981-01-01

    Measurements of the surface tension of molten silicon are reported. For marangoni flow, the important parameter is the variation of surface tension with temperature, not the absolute value of the surface tension. It is not possible to calculate temperature coefficients using surface tension measurements from different experiments because the systematic errors are usually larger than the changes in surface tension because of temperature variations. The lack of good surface tension data for liquid silicon is probably due to its extreme chemical reactivity. A material which resists attack by molten silicon is not found. It is suggested that all of the sessile drip surface tension measurements are probably for silicon which is contaminated by the substrate materials.

  10. Molecular basis for calculating the surface tension of binary droplets

    NASA Astrophysics Data System (ADS)

    Tovbin, Yu. K.; Zaitseva, E. S.; Rabinovich, A. B.

    2017-01-01

    A procedure for calculating the surface tension of droplets consisting of two components in the vapor phase is considered. The calculations are performed using the lattice gas model in the quasi-chemical approximation with allowance for the correlation effects of the nearest interacting molecules. A layered model of the structure of a vapor-liquid interface is used. Ways of calculating the surface tension of droplets with different radii are considered. They are based on different thermodynamic definitions of reference surfaces. Typical dependences of the surface tension of metastable and equilibrium droplets on the droplets' radii are analyzed for four types of phase diagram. It is found that if the energy of interaction between the components of one type exceeds by 150% the energies of interaction between components of another type and between particles of different types, and if the component with the highest energy of interaction predominates in a droplet, this results in a nonmonotonic profile of the component with the lowest energy of interaction in the region of transition. Mixture components are distributed in the region of transition such that the component with the highest energy of interaction is concentrated on the liquid side and the other component is concentrated on the vapor side. The surface tension of equilibrium droplets is less than that of metastable droplets.

  11. Surface tension confined (STC) tracks for capillary-driven transport of low surface tension liquids.

    PubMed

    Schutzius, Thomas M; Elsharkawy, Mohamed; Tiwari, Manish K; Megaridis, Constantine M

    2012-12-21

    Surface tension confined (STC) open tracks for pumpless transport of low-surface tension liquids (e.g., acetone, ethanol, hexadecane) on microfluidic chips are fabricated using a large-area, wet-processing technique. Wettable, paraffin-wax, submillimeter-wide tracks are applied by a fountain-pen procedure on superoleophobic, fluoroacrylic-carbon nanofiber (CNF) composite coatings. The fabricated anisotropic wetting patterns confine the low-surface-tension liquids onto the flow tracks, driving them with meniscus velocities up to 3.1 cm s(-1). Scaling arguments and Washburn's equation provide estimates of the liquid velocities measured in the STC tracks. These tracks are also shown to act as rails for directional sliding control of mm-sized water droplets. The present facile top-down patterned wettability approach can be extended to deposit micrometer-wide tracks, which bear promise for pumpless handling of low-surface tension liquids (e.g., aqueous solutions containing alcohols or surfactants) in lab-on-a-chip type applications or in low power, high-throughput bio-microfluidics for health care applications.

  12. Marangoni Flow and Surface Tension of High Temperature Melts

    NASA Astrophysics Data System (ADS)

    Hibiya, Taketoshi; Ozawa, Shumpei

    Marangoni flow plays an important role in the heat and mass transport for highly value-added high-temperature processes, such as crystal growth, welding, casting, and electron beam melting. For silicon single crystal growth, the effect of the oscillatory Marangoni flow on the introduction of growth striation was discussed by Chen and Wilcox for the first time in 1972 [1]. The existence of the Marangoni flow within molten silicon was proved through microgravity experiments in space on board a sounding rocket in 1983 by Eyer et al. [2], who found formation of growth striation in single crystals even under microgravity, where buoyancy-driven flow was suppressed. To explain the Marangoni effect at the melt surface, surface tension is essential. Keene [3] discussed the oxygen contamination in the surface tension measurement and recommended the use of a levitation technique, which is a containerless process and assures the contamination-free condition from measurement devices. It is well known that flow direction in the weld pool is dependent on surface contamination and that this is related to weldability [4, 5]. Flow direction is controlled by the temperature coefficient of surface tension for molten steels; contaminants are oxygen and sulfur. In the electron beam button melting system, the Marangoni flow is dominant because of intense heating at the melt surface [5]. In this chapter, surface tension of high temperature metallic melts is discussed from the viewpoint of the Marangoni effect in the value-added high temperature processes, particularly from the viewpoint of the effect of oxygen and sulfur. Theoretical treatment for oxygen adsorption is also discussed.

  13. Surface tension of ionic liquids and ionic liquid solutions.

    PubMed

    Tariq, Mohammad; Freire, Mara G; Saramago, Benilde; Coutinho, João A P; Lopes, José N Canongia; Rebelo, Luís Paulo N

    2012-01-21

    Some of the most active scientific research fronts of the past decade are centered on ionic liquids. These fluids present characteristic surface behavior and distinctive trends of their surface tension versus temperature. One way to explore and understand their unique nature is to study their surface properties. This critical review analyses most of the surface tension data reported between 2001 and 2010 (187 references).

  14. A novel methodology to study shape and surface tension of drops in Electric Fields

    NASA Astrophysics Data System (ADS)

    Bateni, A.; Susnar, S. S.; Amirfazli, A.; Neumann, A. W.

    2005-03-01

    A novel methodology is introduced that can be used to study the behavior of conducting drops in electrostatic fields, when gravity effects are negligible. This methodology, called Axisymmetric Drop Shape Analysis — Electric Field (ADSA-EF), generates numerical drop profiles in the electrostatic field, for a given surface tension. Then, it calculates the true value of the surface tension by matching the theoretical profiles with the shape of the experimental drops, with the surface tension as an adjustable parameter. ADSA-EF can be employed for simulating drop shapes in the electric field, detecting the effect of an electric field on liquid surface tensions, and measuring surface tensions in microgravity, where current drop-shape techniques are not applicable. The predicted drop shapes in the electric field were compared with experimental images, indicating good agreement. Preliminary experiments according to ADSA-EF methodology suggested that the surface tension of water increases by about one percent in the electric field.

  15. Surface Tension Driven Convection Experiment (STDCE)

    NASA Technical Reports Server (NTRS)

    Ostrach, S.; Kamotani, Y.

    1996-01-01

    This document reports the results obtained from the Surface Tension Driven Convection Experiment (STDCE) conducted aboard the USML-1 Spacelab in 1992. The experiments used 10 cSt silicone oil placed in an open circular container that was 10 cm wide and 5 cm deep. Thermocapillary flow was induced by using either a cylindrical heater placed along the container centerline or by a CO2 laser. The tests were conducted under various power settings, laser beam diameters, and free surface shapes. Thermistors located at various positions in the test section recorded the temperature of the fluid, heater, walls, and air. An infrared imager was used to measure the free surface temperature. The flow field was studied by flow visualization and the data was analyzed by a PTV technique. The results from the flow visualization and the temperature measurements are compared with the numerical analysis that was conducted in conjunction with the experiment. The compared results include the experimental and numerical velocity vector plots, the streamline plots, the fluid temperature, and the surface temperature distribution.

  16. Direct determination of surface tension in the lung.

    PubMed

    Schürch, S; Goerke, J; Clements, J A

    1976-12-01

    We have used the spreading behavior of small drops of several fluorocarbon fluids and silicone oil on air-liquid interfaces to measure the surface tension of lungs in situ. The test fluids were calibrated in a surface balance at 37 degrees on monolayers of dipalmitoylphosphatidylcholine. At particular surface tensions characteristic of each fluid used, an increase in the tension of 1 mN/m or less caused the droplets to spread reversibly from a sphere to a lens shape. Using micropipettes we placed such droplets on the alveolar surfaces of excised rat lungs held at functional residual capacity and 37 degrees and found that the surface tension remained below 9 mN/m for at least 30 min. The surface tension-volume relationship was linear for tensions ranging from 9 to 20 mN/m.

  17. Free Energies of Solvation with Surface, Volume, and Local Electrostatic Effects and Atomic Surface Tensions to Represent the First Solvation Shell.

    PubMed

    Liu, Junjun; Kelly, Casey P; Goren, Alan C; Marenich, Aleksandr V; Cramer, Christopher J; Truhlar, Donald G; Zhan, Chang-Guo

    2010-03-04

    Building on the SVPE (surface and volume polarization for electrostatics) model for electrostatic contributions to the free energy of solvation with explicit consideration of both surface and volume polarization effects, on the SMx approach to including first-solvation-shell contributions, and on the linear relationship between the electric field and short-range electrostatic contributions found by Chipman, we have developed a new method for computing absolute aqueous solvation free energies by combining the SVPE method with semiempirical terms that account for effects beyond bulk electrostatics. The new method is called SMVLE, and the elements it contains are denoted by SVPE-CDSL where SVPE denotes accounting for bulk electrostatic interactions between solute and solvent with both surface and volume contributions, CDS denotes the inclusion of solvent cavitation, changes in dispersion energy, and possible changes in local solvent structure by a semiempirical term utilizing geometry-dependent atomic surface tensions as implemented in SMx models, and L represents the local electrostatic effect derived from the outward-directed normal electric field on the cavity surface. The semiempirical CDS and L terms together represent the deviation of short-range contributions to the free energy of solvation from those accounted for by the SVPE term based on the bulk solvent dielectric constant. A solute training set containing a broad range of molecules used previously in the development of SM6 is used here for SMVLE model calibration. The aqueous solvation free energies predicted by the parameterized SMVLE model correlate exceedingly well with experimental values. The square of the correlation coefficient is 0.9949 and the slope is 1.0079. Comparison of the final SMVLE model against the earlier SMx solvation model shows that the parameterized SMVLE model not only yields good accuracy for neutrals but also significantly increases the accuracy for ions, making it the best

  18. CRITICAL SURFACE TENSION FOR SPREADING ON A LIQUID SUBSTRATE

    DTIC Science & Technology

    A plot of the initial spreading pressures (F sub ba) or initial spreading coefficients (S sub ba) against the surface tensions of a homologous series...of organic liquids b can be used to determine the critical surface tension for spreading on a second substrate liquid phase a. Straight-line...floating on liquid a, it can be applied to any liquid substrate, and it is applicable even when spreading does not lie within the range of surface tensions

  19. Surface tension propulsion of fungal spores by use of microdroplets

    NASA Astrophysics Data System (ADS)

    Noblin, Xavier; Yang, Sylvia; Dumais, Jacques

    2010-11-01

    Most basidiomycete fungi (such as edible mushrooms) actively eject their spores. The process begins with the condensation of a water droplet at the base of the spore. The fusion of the droplet onto the spore creates a momentum that propels the spore forward. The use of surface tension for spore ejection offers a new paradigm to perform work at small length scales. However, this mechanism of force generation remains poorly understood. To elucidate how fungal spores make effective use of surface tension, we performed high-speed video imaging of spore ejection in Auricularia auricula and Sporobolomyces yeast, along with a detailed mechanical analysis of the spore ejection. We developed an explicit relation for the conversion of surface energy into kinetic energy during the coalescence process. The relation was validated with a simple artificial system.

  20. Tunable Superomniphobic Surfaces for Sorting Droplets by Surface Tension

    NASA Astrophysics Data System (ADS)

    Movafaghi, Sanli; Wang, Wei; Metzger, Ari; Williams, Desiree; Williams, John; Kota, Arun

    2016-11-01

    Manipulation of liquid droplets on super-repellent surfaces (i.e., surfaces that are extremely repellent to liquids) has been widely studied because droplets exhibit high mobility on these surfaces due to the ultra-low adhesion, which leads to minimal sample loss and contamination. Although droplet manipulation has been demonstrated using electric fields, magnetic fields, guiding tracks and wettability gradients, to the best of our knowledge, there are no reports of droplet manipulation methods that can sort droplets by surface tension on super-repellent surfaces. In this work, we utilized tunable superomniphobic surfaces (i.e., surfaces that are extremely repellent to virtually all liquids) to develop a simple device with precisely tailored solid surface energy domains that, for the first time, can sort droplets by surface tension. Droplet sorting occurs on our device entirely due to a balance between the work done by gravity and the work expended due to adhesion, without the need for any external energy input. Our device can be fabricated easily in a short time and is particularly useful for in-the-field and on-the-go operations, where complex analysis equipment is unavailable. We envision that our methodology for droplet sorting will enable inexpensive and energy-efficient analytical devices for personalized point-of-care diagnostic platforms and lab-on-a-chip systems.

  1. Surface tension and long range corrections of cylindrical interfaces.

    PubMed

    Bourasseau, E; Malfreyt, P; Ghoufi, A

    2015-12-21

    The calculation of the surface tension of curved interfaces has been deeply investigated from molecular simulation during this last past decade. Recently, the thermodynamic Test-Area (TA) approach has been extended to the calculation of surface tension of curved interfaces. In the case of the cylindrical vapour-liquid interfaces of water and Lennard-Jones fluids, it was shown that the surface tension was independent of the curvature of the interface. In addition, the surface tension of the cylindrical interface is higher than that of the planar interface. Molecular simulations of cylindrical interfaces have been so far performed (i) by using a shifted potential, (ii) by means of large cutoff without periodic boundary conditions, or (iii) by ignoring the long range corrections to the surface tension due to the difficulty to estimate them. Indeed, unlike the planar interfaces there are no available operational expressions to consider the tail corrections to the surface tension of cylindrical interfaces. We propose here to develop the long range corrections of the surface tension for cylindrical interfaces by using the non-exponential TA (TA2) method. We also extend the formulation of the Mecke-Winkelmann corrections initially developed for planar surfaces to cylindrical interfaces. We complete this study by the calculation of the surface tension of cylindrical surfaces of liquid tin and copper using the embedded atom model potentials.

  2. Surface tension and long range corrections of cylindrical interfaces

    SciTech Connect

    Bourasseau, E.; Ghoufi, A.

    2015-12-21

    The calculation of the surface tension of curved interfaces has been deeply investigated from molecular simulation during this last past decade. Recently, the thermodynamic Test-Area (TA) approach has been extended to the calculation of surface tension of curved interfaces. In the case of the cylindrical vapour-liquid interfaces of water and Lennard-Jones fluids, it was shown that the surface tension was independent of the curvature of the interface. In addition, the surface tension of the cylindrical interface is higher than that of the planar interface. Molecular simulations of cylindrical interfaces have been so far performed (i) by using a shifted potential, (ii) by means of large cutoff without periodic boundary conditions, or (iii) by ignoring the long range corrections to the surface tension due to the difficulty to estimate them. Indeed, unlike the planar interfaces there are no available operational expressions to consider the tail corrections to the surface tension of cylindrical interfaces. We propose here to develop the long range corrections of the surface tension for cylindrical interfaces by using the non-exponential TA (TA2) method. We also extend the formulation of the Mecke-Winkelmann corrections initially developed for planar surfaces to cylindrical interfaces. We complete this study by the calculation of the surface tension of cylindrical surfaces of liquid tin and copper using the embedded atom model potentials.

  3. Density profiles and surface tension of polymers near colloidal surfaces

    NASA Astrophysics Data System (ADS)

    Louis, A. A.; Bolhuis, P. G.; Meijer, E. J.; Hansen, J. P.

    2002-06-01

    The surface tension of interacting polymers in a good solvent is calculated theoretically and by computer simulations for a planar wall geometry and for the insertion of a single colloidal hard sphere. This is achieved for the planar wall and for the larger spheres by an adsorption method, and for smaller spheres by a direct insertion technique. Results for the dilute and semidilute regimes are compared to results for ideal polymers, the Asakura-Oosawa penetrable-sphere model, and to integral equations, scaling and renormalization group theories. The largest relative changes with density are found in the dilute regime, so that theories based on noninteracting polymers rapidly break down. A recently developed "soft colloid" approach to polymer-colloid mixtures is shown to correctly describe the one-body insertion free-energy and the related surface tension.

  4. Acoustic measurement of the surface tension of levitated drops

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Marston, P. L.; Robey, J. L.

    1988-01-01

    The measurement of the frequency of the fundamental mode of shape oscillation of acoustically levitated drops has been carried out to determine the surface tension of the drop material. Sound fields of about 20 kHz in frequency allow the suspension of drops a few millimeters in size, as well as the necessary drive for oscillations. The surface tension of water, hexadecane, silicone oil, and aqueous solutions of glycerin levitated in air has been measured, and the results have been compared with those obtained with standard ring tensiometry. The two sets of data are in good agreement, the largest discrepancy being about 10 percent. Uncertainties in the effects of the nonspherical static shape of drops levitated in the earth's gravitational field and the rotation state of the sample are the major contributors to the experimental error. A decrease of the resonance frequency of the fundamental mode indicates a soft nonlinearity as the oscillation amplitude increases.

  5. Acoustic measurement of the surface tension of levitated drops

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Marston, P. L.; Robey, J. L.

    1988-01-01

    The measurement of the frequency of the fundamental mode of shape oscillation of acoustically levitated drops has been carried out to determine the surface tension of the drop material. Sound fields of about 20 kHz in frequency allow the suspension of drops a few millimeters in size, as well as the necessary drive for oscillations. The surface tension of water, hexadecane, silicone oil, and aqueous solutions of glycerin levitated in air has been measured, and the results have been compared with those obtained with standard ring tensiometry. The two sets of data are in good agreement, the largest discrepancy being about 10 percent. Uncertainties in the effects of the nonspherical static shape of drops levitated in the earth's gravitational field and the rotation state of the sample are the major contributors to the experimental error. A decrease of the resonance frequency of the fundamental mode indicates a soft nonlinearity as the oscillation amplitude increases.

  6. Surface tension driven flow on a thin reaction front

    NASA Astrophysics Data System (ADS)

    Guzman, Roberto; Vasquez, Desiderio A.

    2016-11-01

    Surface tension driven convection affects the propagation of chemical reaction fronts in liquids. The changes in surface tension across the front generate this type of convection. The resulting fluid motion increases the speed and changes the shape of fronts as observed in the iodate-arsenous acid reaction. We calculate these effects using a thin front approximation, where the reaction front is modeled by an abrupt discontinuity between reacted and unreacted substances. We analyze the propagation of reaction fronts of small curvature. In this case the front propagation equation becomes the deterministic Kardar-Parisi-Zhang (KPZ) equation with the addition of fluid flow. These results are compared to calculations based on a set of reaction-diffusion-convection equations.

  7. Investigation of surface tension phenomena using the KC-135 aircraft

    NASA Technical Reports Server (NTRS)

    Alter, W. S.

    1982-01-01

    The microgravity environment of the KC-135 aircraft was utilized in three experiments designed to determine the following: (1) the feasibility of measuring critical wetting temperatures; (2) the effectiveness of surface tension as a means of keeping the cushioning heat transfer liquid in the furnace during ampoule translation; and (3) whether a non-wetting fluid would separate from the ampoule wall under low gravity conditions. This trio of investigations concerning surface phenomena demonstrates the effectiveness of the KC-135 as a microgravity research environment for small-scale, hand-held experiments.

  8. Surface tension in human pathophysiology and its application as a medical diagnostic tool

    PubMed Central

    Fathi-Azarbayjani, Anahita; Jouyban, Abolghasem

    2015-01-01

    Introduction: Pathological features of disease appear to be quite different. Despite this diversity, the common feature of various disorders underlies physicochemical and biochemical factors such as surface tension. Human biological fluids comprise various proteins and phospholipids which are capable of adsorption at fluid interfaces and play a vital role in the physiological function of human organs. Surface tension of body fluids correlates directly to the development of pathological states. Methods: In this review, the variety of human diseases mediated by the surface tension changes of biological phenomena and the failure of biological fluids to remain in their native state are discussed. Results: Dynamic surface tension measurements of human biological fluids depend on various parameters such as sex, age and changes during pregnancy or certain disease. It is expected that studies of surface tension behavior of human biological fluids will provide additional information and might become useful in medical practice. Theoretical background on surface tension measurement and surface tension values of reference fluids obtained from healthy and sick patients are depicted. Conclusion: It is well accepted that no single biomarker will be effective in clinical diagnosis. The surface tension measurement combined with routine lab tests may be a novel non-invasive method which can not only facilitate the discovery of diagnostic models for various diseases and its severity, but also be a useful tool for monitoring treatment efficacy. We therefore expect that studies of surface tension behavior of human biological fluids will provide additional useful information in medical practice. PMID:25901295

  9. SURFACE TENSION OF SERUM OF THE SENSITIZED GUINEA PIG

    PubMed Central

    Ramsdell, Susan Griffith

    1928-01-01

    The primary change in surface tension of serum incident to anaphylactic shock is probably due to a lowering of the surface tension of the serum by the addition of the antigen serum. But this may be followed by further decrease or by an increase depending on the intensity and duration of certain secondary tissue changes. PMID:19869462

  10. Sintering of viscous droplets under surface tension

    PubMed Central

    Vasseur, Jérémie; Llewellin, Edward W.; Schauroth, Jenny; Dobson, Katherine J.; Scheu, Bettina; Dingwell, Donald B.

    2016-01-01

    We conduct experiments to investigate the sintering of high-viscosity liquid droplets. Free-standing cylinders of spherical glass beads are heated above their glass transition temperature, causing them to densify under surface tension. We determine the evolving volume of the bead pack at high spatial and temporal resolution. We use these data to test a range of existing models. We extend the models to account for the time-dependent droplet viscosity that results from non-isothermal conditions, and to account for non-zero final porosity. We also present a method to account for the initial distribution of radii of the pores interstitial to the liquid spheres, which allows the models to be used with no fitting parameters. We find a good agreement between the models and the data for times less than the capillary relaxation timescale. For longer times, we find an increasing discrepancy between the data and the model as the Darcy outgassing time-scale approaches the sintering timescale. We conclude that the decreasing permeability of the sintering system inhibits late-stage densification. Finally, we determine the residual, trapped gas volume fraction at equilibrium using X-ray computed tomography and compare this with theoretical values for the critical gas volume fraction in systems of overlapping spheres. PMID:27274687

  11. Sintering of viscous droplets under surface tension

    NASA Astrophysics Data System (ADS)

    Wadsworth, Fabian B.; Vasseur, Jérémie; Llewellin, Edward W.; Schauroth, Jenny; Dobson, Katherine J.; Scheu, Bettina; Dingwell, Donald B.

    2016-04-01

    We conduct experiments to investigate the sintering of high-viscosity liquid droplets. Free-standing cylinders of spherical glass beads are heated above their glass transition temperature, causing them to densify under surface tension. We determine the evolving volume of the bead pack at high spatial and temporal resolution. We use these data to test a range of existing models. We extend the models to account for the time-dependent droplet viscosity that results from non-isothermal conditions, and to account for non-zero final porosity. We also present a method to account for the initial distribution of radii of the pores interstitial to the liquid spheres, which allows the models to be used with no fitting parameters. We find a good agreement between the models and the data for times less than the capillary relaxation timescale. For longer times, we find an increasing discrepancy between the data and the model as the Darcy outgassing time-scale approaches the sintering timescale. We conclude that the decreasing permeability of the sintering system inhibits late-stage densification. Finally, we determine the residual, trapped gas volume fraction at equilibrium using X-ray computed tomography and compare this with theoretical values for the critical gas volume fraction in systems of overlapping spheres.

  12. Experimental Values of the Surface Tension of Supercooled Water

    NASA Technical Reports Server (NTRS)

    Hacker, P. T.

    1951-01-01

    The results of surface-tension measurements for supercooled water are presented. A total of 702 individual measurements of surface tension of triple-distilled water were made in the temperature range, 27 to -22.2 C, with 404 of these measurements at temperatures below 0 C. The increase in magnitude of surface tension with decreasing temperature, as indicated by measurements above 0 C, continues to -22.2 C. The inflection point in the surface-tension - temperature relation in the vicinity of 0 C, as indicated by the International Critical Table values for temperatures down to -8 C, is substantiated by the measurements in the temperature range, 0 to -22.2 C. The surface tension increases at approximately a linear rate from a value of 76.96+/-0.06 dynes per centimeter at -8 C to 79.67+/-0.06 dynes per centimeter at -22.2 C.

  13. Effect of surface tension and coefficient of thermal expansion in 30 nm scale nanoimprinting with two flexible polymer molds.

    PubMed

    Kim, Jae Kwan; Cho, Hye Sung; Jung, Ho-Sup; Lim, Kipil; Kim, Ki-Bum; Choi, Dae-Geun; Jeong, Jun-Ho; Suh, Kahp-Yang

    2012-06-15

    We report on nanoimprinting of polymer thin films at 30 nm scale resolution using two types of ultraviolet (UV)-curable, flexible polymer molds: perfluoropolyether (PFPE) and polyurethane acrylate (PUA). It was found that the quality of nanopatterning at the 30 nm scale is largely determined by the combined effects of surface tension and the coefficient of thermal expansion of the polymer mold. In particular, the polar component of surface tension may play a critical role in clean release of the mold, as evidenced by much reduced delamination or broken structures for the less polarized PFPE mold when patterning a relatively hydrophilic PMMA film. In contrast, such problems were not notably observed with a relatively hydrophobic PS film for both polymer molds. In addition, the demolding characteristic was also influenced by the coefficient of thermal expansion so that no delamination or uniformity problems were observed when patterning a UV-curable polymer film at room temperature. These results suggest that a proper polymeric mold material needs to be chosen for patterning polymer films under different surface properties and processing conditions, providing insights into how a clean demolding characteristic can be obtained at 30 nm scale nanopatterning.

  14. Influence of hyperbranched polyesters on the surface tension of polyols.

    PubMed

    Ziemer, Antje; Azizi, Mazen; Pleul, Dieter; Simon, Frank; Michel, Stefan; Kreitschmann, Mirko; Kierkus, Paul; Voit, Brigitte; Grundke, Karina

    2004-09-14

    The influence of hyperbranched polyesters with different functional end groups on the surface tension of mixtures with an oligo(ester diol) was investigated. The temperature dependence of the surface tension of the pure components and of the mixtures was measured by a modified Wilhelmy balance technique. The results indicate that the surface tension of the pure hyperbranched polyesters strongly depends on the functionality of the end groups. The functionalization of the hydroxyl end groups by short alkyl chains (methyl, tert-butyl) reduced the surface tension depending on the degree of substitution. The surface tension of the mixtures with the hydroxyl-terminated hyperbranched polyester was slightly increased at higher concentrations of the hyperbranched polymer compared to the surface tension of the pure ester diol. On the other hand, the surface tension of mixtures could be considerably decreased using 1% of hyperbranched polyester polyols partially substituted with short alkyl chains. In that case, the modified hyperbranched polyesters act as surface active agents. On the molecular level, the enrichment of the modified hyperbranched polyester in the surface region was proven by X-ray photoelectron spectroscopy measurements.

  15. A new method for measuring the dynamic surface tension of complex-mixture liquid drops

    SciTech Connect

    Zhang, X.; Harris, M.T.; Basaran, O.A.

    1994-06-29

    A simple and accurate technique has been developed for measuring dynamic surface tension. The new technique is based on growing a drop at the end of a fine capillary into another immiscible fluid and can follow the changes in tension at a freshly formed interface during its entire period of evolution. When the relative importance of the surface tension force is large compared to gravitational and viscous forces, shapes of growing drops are sections of spheres and the difference in pressure between the interior and the exterior of the drop {triangle}p is related to the surface tension {sigma} and the radius of curvature R by the static Young-Laplace formula {triangle}p = 2{sigma}/R. In contrast to related work, the new technique can determine the surface tension of an interface with a surface age of a few to tens of milliseconds by measuring transient drop shapes and pressures in 1/6 to 1 millisecond. The capabilities of the new method are demonstrated by performing tension measurements on liquid systems that do not exhibit dynamic surface tension as well as ones that exhibit significant dynamic tension effects. Tension measurements made with surfactant-laden solutions show that variation of surface tension is nonmonotonic in time. In such systems, the dynamic behavior of surface tension is shown to depend upon both the rate of interfacial dilatation and that of surfactant transport. A maximum in the surface tension is attained when the lowering of the surfactant concentration on the drop interface due to its dilatation is balanced by the addition of fresh surfactant to the interface by convection and diffusion.

  16. Liquids: Surface tension, compressibility, and invariants

    NASA Astrophysics Data System (ADS)

    Sanchez, Isaac C.

    1983-07-01

    A new equation has been dervied which relates the surface tension (σ) to a liquid's isothermal compressibility (κ) and mass density (ρ). The derivation is based on a generalized square-gradient approximation for the free energy density of a nonuniform fluid. The equation is σ(κ/ρ)1/2=A1/20=constant in the normal liquid range. Except for water, A0 is temperature independent for a variety of inorganic, organic, and polymer liquids. Among 50 nonpolar and polar organic liquids, including hydrogen bonding liquids, A1/20 appears to be an invariant with a value of 2.78±0.13×10-4 (erg cm2/g)1/2. Among the diatomic elements (except hydrogen), A1/20 is an invariant with a value of 1.8×10-4. Among the heavy noble elements, A1/20 is an invariant with a value of 1.36×10-4. For the quantum noble elements helium and neon, A1/20=1.0×10-4. The constant A0 is shown to be proportional to a second moment of a direct correlation function. A semiempirical formula has been derived for A0 relating it to the parameters ɛ0 and σ0 that characterize the pair interaction potential. For a Lennard-Jones 6-12 potential, it is shown that A1/20=0.26(ɛ0σ20/M)1/2, where M is molecular weight. This result combined with the experimental evaluations of A0 implies that the parameter combination (ɛ0σ20/M) is an invariant for certain classes of molecules. It appears that this surprising observation has never been made before; its physical implications remain unclear.

  17. Nonzero Ideal Gas Contribution to the Surface Tension of Water.

    PubMed

    Sega, Marcello; Fábián, Balázs; Jedlovszky, Pál

    2017-06-15

    Surface tension, the tendency of fluid interfaces to behave elastically and minimize their surface, is routinely calculated as the difference between the lateral and normal components of the pressure or, invoking isotropy in momentum space, of the virial tensor. Here we show that the anisotropy of the kinetic energy tensor close to a liquid-vapor interface can be responsible for a large part of its surface tension (about 15% for water, independent from temperature).

  18. Fingers in a Hele-Shaw Cell with Surface Tension.

    DTIC Science & Technology

    1983-05-01

    A138 548 FINGERS IN A HELE-SHAid CELL WITH SURFACE TENSION (U) i/i WISCONSIN UN! V-*MADISON MATHEMATICS RESEARCH CENTER J YANDEN-BROECI( MAY 83 MRC...NATIONAL BUREAU OF STANDARDS-1963-A A-4" MRC Technical Simimary Report #2518 i. FINGERS IN A HELE-SHAW CELLQ WITH SURFACE TENSION V=4 Jean-Marc...H CENTER "’ FINGERS IN A HXLZ-SHAW CELL WITH SURFACE TENSION Jean-Marc Vanden-Broeck Technical Summary Report #2518 May 1983 ABSTRACT McLean and

  19. A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction.

    PubMed

    Eaker, Collin B; Khan, M Rashed; Dickey, Michael D

    2016-01-26

    Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where interfacial tension is a dominant force. A variety of methods exist for controlling the interfacial tension of aqueous and organic liquids on this scale; however, these techniques have limited utility for liquid metals due to their large interfacial tension. Liquid metals can form soft, stretchable, and shape-reconfigurable components in electronic and electromagnetic devices. Although it is possible to manipulate these fluids via mechanical methods (e.g., pumping), electrical methods are easier to miniaturize, control, and implement. However, most electrical techniques have their own constraints: electrowetting-on-dielectric requires large (kV) potentials for modest actuation, electrocapillarity can affect relatively small changes in the interfacial tension, and continuous electrowetting is limited to plugs of the liquid metal in capillaries. Here, we present a method for actuating gallium and gallium-based liquid metal alloys via an electrochemical surface reaction. Controlling the electrochemical potential on the surface of the liquid metal in electrolyte rapidly and reversibly changes the interfacial tension by over two orders of magnitude ( ̴500 mN/m to near zero). Furthermore, this method requires only a very modest potential (< 1 V) applied relative to a counter electrode. The resulting change in tension is due primarily to the electrochemical deposition of a surface oxide layer, which acts as a surfactant; removal of the oxide increases the interfacial tension, and vice versa. This technique can be applied in a wide variety of electrolytes and is independent of the substrate on which it rests.

  20. Experiments on buoyancy and surface tension following Galileo Galilei

    NASA Astrophysics Data System (ADS)

    Straulino, S.; Gambi, C. M. C.; Righini, A.

    2011-01-01

    We analyze passages of Galileo's writings on aspects of floating. Galileo encountered peculiar effects such as the "floating" of light objects made of dense material and the creation of large drops of water that were difficult to explain because they are related to our current understanding of surface tension. Even though Galileo could not understand the phenomenon, his proposed explanations and experiments are interesting from an educational point of view. We replicate the experiment on water and wine that was described by Galileo in his Two New Sciences.

  1. NEW APPROACHES: Surface tension from deflating a soap bubble

    NASA Astrophysics Data System (ADS)

    Rämme, Göran

    1997-05-01

    The surface tension of soap bubbles can be measured using simple apparatus. Results found using the method described here can be compared with a modified standard method also described, to allow students to evaluate the different approaches.

  2. Molecular Dynamic Simulations on Surface Tension of Methanol

    NASA Astrophysics Data System (ADS)

    Obeidat, Abdalla

    2015-04-01

    Molecular dynamic simulations have been performed to study the surface tension of methanol at low temperatures. Six different models of methanol have been studied to compute the surface tension of different models. The models have been used to predict the surface tensions are: OPLS, Gromos 96, H1, J1, J2, and van Leeuwen model. Our results show that the most accurate model compared to true methanol was van Leeuwen model. The results were fitted to a straight line to predict other data of surface tension at specific temperature. The simulation were performed using the Gromacs package at temperatures: 200, 210, 220, 230, 240, 250, 260, 270, 280, 290, and 300 K. This work is supported by JUST.

  3. Correlation between surface tension and critical temperatures of liquid metals.

    PubMed

    Blairs, Sidney; Abbasi, Mohammad Hassan

    2006-12-15

    The inter-relationship of surface tension sigma, molar volume V, and critical temperature Tc has been examined using experimental values for eighteen liquid metals. Hard-sphere diameters a correlate with the equation a(5/2) = 8.9733 x 10(-19) V (sigma/Tc)(1/4) - 1.0459 x 10(-25). Unknown Tc may be estimated using surface tension and liquid density values.

  4. Surface tension of highly magnetized degenerate quark matter

    NASA Astrophysics Data System (ADS)

    Lugones, G.; Grunfeld, A. G.

    2017-01-01

    We study the surface tension of highly magnetized three-flavor quark matter within the formalism of multiple reflection expansion. Quark matter is described as a mixture of free Fermi gases composed of quarks u , d , s and electrons in chemical equilibrium under weak interactions. Due to the presence of strong magnetic fields the particles' transverse motion is quantized into Landau levels, and the surface tension has a different value in the parallel and transverse directions with respect to the magnetic field. We calculate the transverse and longitudinal surface tension for different values of the magnetic field and for quark-matter drops with different sizes, from a few fm to the bulk limit. For baryon number densities between 2 to 10 times the nuclear saturation density, the surface tension falls in the range of 2 to 20 MeV /fm2 . The largest contribution comes from strange quarks which have a surface tension an order of magnitude larger than the one for u or d quarks and more than two orders of magnitude larger than for electrons. Our results show that the total surface tension is quite insensitive to the size of the drop. We also find that the surface tensions in the transverse and parallel directions are almost unaffected by the magnetic field if e B is below ˜5 ×10-3GeV2 . Nevertheless, for higher values of e B , there is a significant increase in the parallel surface tension and a significant decrease in the transverse one with respect to the unmagnetized case.

  5. Hard Surface Detergency. Part I. Interfacial Tensions of Candidate Surface Decontaminating Agents in Contact with Model Fluids.

    DTIC Science & Technology

    1982-04-23

    malathion . The effect of surfactant structure and model fluid on the adsorption process were catalogued with the aid of the Szyszkowski equation and the...the interfacial tension to low values by the surfactant when combined with the kinetic energy of the flow process assists in significant erosion of...methyl salicylate, malathion and ortho- dichlorobenzene. The interfacial tension properties of the fluids used are shown in Table 3. The surface tension

  6. The ripplon and surface tension of a ? liquid

    NASA Astrophysics Data System (ADS)

    Tamura, Akira

    1998-11-01

    For a 0953-8984/10/45/003/img2 liquid surface, we derive an analytical form of the ripplon dispersion relation considering surface diffusiveness. The diffusiveness reduces the ripplon frequency for a 0953-8984/10/45/003/img2 liquid with an abrupt surface. Comparison of our dispersion curve with the recently measured spectrum gives the width of the diffusiveness and surface tension. Using the dispersion relation and applying the Atkins theory, we can explain well the measured surface tension in the temperature range from 0 K to 0953-8984/10/45/003/img4 K.

  7. Surface tension of liquid metals and alloys--recent developments.

    PubMed

    Egry, I; Ricci, E; Novakovic, R; Ozawa, S

    2010-09-15

    Surface tension measurements are a central task in the study of surfaces and interfaces. For liquid metals, they are complicated by the high temperatures and the consequently high reactivity characterising these melts. In particular, oxidation of the liquid surface in combination with evaporation phenomena requires a stringent control of the experimental conditions, and an appropriate theoretical treatment. Recently, much progress has been made on both sides. In addition to improving the conventional sessile drop technique, new containerless methods have been developed for surface tension measurements. This paper reviews the experimental progress made in the last few years, and the theoretical framework required for modelling and understanding the relevant physico-chemical surface phenomena.

  8. Measurement of dynamic surface tension by mechanically vibrated sessile droplets.

    PubMed

    Iwata, Shuichi; Yamauchi, Satoko; Yoshitake, Yumiko; Nagumo, Ryo; Mori, Hideki; Kajiya, Tadashi

    2016-04-01

    We developed a novel method for measuring the dynamic surface tension of liquids using mechanically vibrated sessile droplets. Under continuous mechanical vibration, the shape of the deformed droplet was fitted by numerical analysis, taking into account the force balance at the drop surface and the momentum equation. The surface tension was determined by optimizing four parameters: the surface tension, the droplet's height, the radius of the droplet-substrate contact area, and the horizontal symmetrical position of the droplet. The accuracy and repeatability of the proposed method were confirmed using drops of distilled water as well as viscous aqueous glycerol solutions. The vibration frequency had no influence on surface tension in the case of pure liquids. However, for water-soluble surfactant solutions, the dynamic surface tension gradually increased with vibration frequency, which was particularly notable for low surfactant concentrations slightly below the critical micelle concentration. This frequency dependence resulted from the competition of two mechanisms at the drop surface: local surface deformation and surfactant transport towards the newly generated surface.

  9. Measurement of dynamic surface tension by mechanically vibrated sessile droplets

    NASA Astrophysics Data System (ADS)

    Iwata, Shuichi; Yamauchi, Satoko; Yoshitake, Yumiko; Nagumo, Ryo; Mori, Hideki; Kajiya, Tadashi

    2016-04-01

    We developed a novel method for measuring the dynamic surface tension of liquids using mechanically vibrated sessile droplets. Under continuous mechanical vibration, the shape of the deformed droplet was fitted by numerical analysis, taking into account the force balance at the drop surface and the momentum equation. The surface tension was determined by optimizing four parameters: the surface tension, the droplet's height, the radius of the droplet-substrate contact area, and the horizontal symmetrical position of the droplet. The accuracy and repeatability of the proposed method were confirmed using drops of distilled water as well as viscous aqueous glycerol solutions. The vibration frequency had no influence on surface tension in the case of pure liquids. However, for water-soluble surfactant solutions, the dynamic surface tension gradually increased with vibration frequency, which was particularly notable for low surfactant concentrations slightly below the critical micelle concentration. This frequency dependence resulted from the competition of two mechanisms at the drop surface: local surface deformation and surfactant transport towards the newly generated surface.

  10. Multiscale surface roughening of commercial purity titanium during uniaxial tension

    SciTech Connect

    Panin, Alexey; Kazachenok, Marina Kozelskaya, Anna Sinyakova, Elena; Lider, Andrey Sklyarova, Elena

    2015-10-27

    The mechanisms of the surface roughening of the titanium specimens during uniaxial tension were demonstrated. By means of optical profilometry and electron backscattered diffraction it was shown that the formation of surface roughening is a multilevel process. The correlation between the density of slip in some grains, and grain rotation, and their displacement towards the free surface was investigated.

  11. Surface-tension-driven flow in a glass melt

    NASA Technical Reports Server (NTRS)

    Mcneil, Thomas J.; Cole, Robert; Shankar Subramanian, R.

    1985-01-01

    Motion driven by surface tension gradients was observed in a vertical capillary liquid bridge geometry in a sodium borate melt. The surface tension gradients were introduced by maintaining a temperature gradient on the free melt surface. The flow velocities at the free surface of the melt, which were measured using a tracer technique, were found to be proportional to the applied temperature difference and inversely proportional to the melt viscosity. The experimentally observed velocities were in reasonable accord with predictions from a theoretical model of the system.

  12. Development of a new methodology to study drop shape and surface tension in electric fields.

    PubMed

    Bateni, A; Susnar, S S; Amirfazli, A; Neumann, A W

    2004-08-31

    Development of a new methodology for the study of both shape and surface tension of conducting drops in an electric field is presented. This methodology, called axisymmetric drop shape analysis-electric fields (ADSA-EF), generates numerical drop profiles in an electrostatic field, for a given surface tension. Then, it calculates the true value of the surface tension by matching theoretical profiles to the shape of experimental drops, using the surface tension as an adjustable parameter. ADSA-EF can be employed to simulate and study drop shapes in the electric field and to determine its effect on liquid surface tension. The method can also be used to measure surface tension in microgravity, where current drop-shape techniques are not applicable. The axisymmetric shape of the drop is the only assumption made in the development of ADSA-EF. The new scheme is applicable when both gravity and electrostatic forces are present. Preliminary measurements using ADSA-EF suggest that the surface tension of water increases by about 2% when an electric field with the magnitude of 10(6) V/m is applied.

  13. The interconnection between the surface tension and fluctuations within fine drops, bubbles, and their nuclei.

    PubMed

    Veitsman, E V

    2007-04-01

    We consider the effect of surface tension upon fluctuations within the core of drops and bubbles. We also investigate the fluctuations of the substance density rho, volume V, and particle number N within the objects under study. It is demonstrated that cores of drops and bubbles are homogeneous when they contain several thousand nanoparticles (molecules, atoms). Fluctuations of particle number are very large within the nucleus core containing only a few nanoparticles. Therefore, the surface tension has a probabilistic character since there is no surface separating the nucleus substance from the surrounding medium, only a transitional zone whose radius fluctuates considerably in time. In this case, it is more correct to consider not the surface tension but a certain quantity that we named the quasi surface tension.

  14. Surface tension regularizes the crack singularity of adhesion.

    PubMed

    Karpitschka, Stefan; van Wijngaarden, Leen; Snoeijer, Jacco H

    2016-05-11

    The elastic and adhesive properties of a solid surface can be quantified by indenting it with a rigid sphere. Indentation tests are classically described by the JKR-law when the solid is very stiff, while recent work highlights the importance of surface tension for exceedingly soft materials. Here we show that surface tension plays a crucial role even in stiff solids: Young's wetting angle emerges as a boundary condition and this regularizes the crack-like singularity at the edge of adhesive contacts. We find that the edge region exhibits a universal, self-similar structure that emerges from the balance of surface tension and elasticity. The similarity theory is solved analytically and provides a complete description of adhesive contacts, by which we reconcile global adhesion laws and local contact mechanics.

  15. The role of dynamic surface tension in cloud droplet activation

    NASA Astrophysics Data System (ADS)

    Petters, Markus D.; Suda, Sarah R.; Christensen, Sara I.

    2013-05-01

    We present new data on the cloud droplet forming abilities of two-component particles that contain the surfactant sodium dodecyl sulfate and sodium chloride or ammonium sulfate. The experiments were designed to test specific predictions made by Kohler theory that accounts for the reduction of surface tension and the partitioning of the surfactant between the interior and the surface of the droplet. We also introduced a pre-humidification step followed by a six minute time delay to test whether dynamic surface tension may lead to kinetic limitations on the partitioning process. Our results confirm previous studies that show that surfactants do not enhance cloud droplet activation relative to what would be predicted from water activity alone. The data obtained with and without time delay were indistinguishable within measurement uncertainty, suggesting that dynamic surface tension does not need to be considered in Kohler theory.

  16. Spontaneous Pattern Formation Induced by Bénard-Marangoni Convection for Sol-Gel-Derived Titania Dip-Coating Films: Effect of Co-solvents with a High Surface Tension and Low Volatility.

    PubMed

    Uchiyama, Hiroaki; Matsui, Tadayuki; Kozuka, Hiromitsu

    2015-11-17

    Evaporation-driven surface tension gradient in the liquid layer often causes the convective flow, i.e., Bénard-Marangoni convection, resulting in the formation of cell-like patterns on the surface. Here, we prepared sol-gel-derived titania films from Ti(OC3H7(i))4 solutions by dip coating and discussed the effect of the addition of co-solvents with a high surface tension and low volatility on the spontaneous pattern formation induced by Bénard-Marangoni convection. Propylene glycol (PG, with a surface tension of 38.6 mN m(-1)) and dipropylene glycol (DPG, with a surface tension of 33.9 mN m(-1)) were added to the coating solutions containing 2-propanol (2-Pr, with a surface tension of 22.9 mN m(-1)) for controlling the evaporation-driven surface tension gradient in the coating layer on a substrate. During dip coating at a substrate withdrawal speed of 50 cm min(-1) in a thermostatic oven at 60 °C, linearly arranged cell-like patterns on a micrometer scale were spontaneously formed on the titania gel films, irrespective of the composition of coating solutions. Such surface patterns remained even after the heat treatment at 200 and 600 °C, where the densification and crystallization of the titania films progressed. The width and height of the cell-like patterns increased with increasing PG and DPG contents in the coating solutions, where the addition of PG resulted in the formation of cells with a larger height than DPG.

  17. Surface tension driven flow in glass melts and model fluids

    NASA Technical Reports Server (NTRS)

    Mcneil, T. J.; Cole, R.; Subramanian, R. S.

    1982-01-01

    Surface tension driven flow has been investigated analytically and experimentally using an apparatus where a free column of molten glass or model fluids was supported at its top and bottom faces by solid surfaces. The glass used in the experiments was sodium diborate, and the model fluids were silicone oils. In both the model fluid and glass melt experiments, conclusive evidence was obtained to prove that the observed flow was driven primarily by surface tension forces. The experimental observations are in qualitative agreement with predictions from the theoretical model.

  18. Surface tension driven flow in glass melts and model fluids

    NASA Technical Reports Server (NTRS)

    Mcneil, T. J.; Cole, R.; Subramanian, R. S.

    1982-01-01

    Surface tension driven flow has been investigated analytically and experimentally using an apparatus where a free column of molten glass or model fluids was supported at its top and bottom faces by solid surfaces. The glass used in the experiments was sodium diborate, and the model fluids were silicone oils. In both the model fluid and glass melt experiments, conclusive evidence was obtained to prove that the observed flow was driven primarily by surface tension forces. The experimental observations are in qualitative agreement with predictions from the theoretical model.

  19. A new drop-shape methodology for surface tension measurement

    NASA Astrophysics Data System (ADS)

    Cabezas, M. G.; Bateni, A.; Montanero, J. M.; Neumann, A. W.

    2004-11-01

    Drop-shape techniques, such as axisymmetric drop-shape analysis (ADSA), have been widely used to measure surface tension. In the current schemes, theoretical curves are fitted to the experimental profiles by adjusting the value of surface tension. The best match between theoretical and experimental profiles identifies the surface tension of the drop. Extracting the experimental drop profile using edge detection, is an important part of the current drop-shape techniques. However, edge detections fail when acquisition of sharp images is not possible due to experimental or optical limitations. A new drop-shape approach is presented, which eliminates the need for the edge detection and provides a wider range of applicability. The new methodology, called theoretical image fitting analysis (TIFA), generates theoretical images of the drop and forms an error function that describes the pixel-by-pixel deviation of the theoretical image from the experimental one. Taking surface tension as an adjustable parameter, TIFA minimizes the error function, i.e. fits the theoretical image to the experimental one. The validity of the new methodology is examined by comparing the results with those of ADSA. Using the new methodology it is finally possible to enhance the study of the surface tension of lung surfactants at higher concentrations. Due to the opaqueness of the solution, such studies were limited to the low concentrations of surfactants heretofore.

  20. On the existence of small amplitude solitary waves with strong surface tension

    NASA Astrophysics Data System (ADS)

    Sachs, Robert L.

    An existence theory for small amplitude solitary waves with surface tension effects included is developed for large values of the surface tension parameter ( β > {1}/{3}). Using ideas of Beale, the Nash-Moser implicit function theorem is applied to justify the well-known approximation of Korteweg and deVries. Some of the recent results of Amick and Kirchgässner are thereby achieved more directly and additional insight obtained for the open case β < {1}/{3}.

  1. Surface tension of the Widom-Rowlinson model.

    PubMed

    de Miguel, E; Almarza, N G; Jackson, G

    2007-07-21

    We consider the computation of the surface tension of the fluid-fluid interface for the Widom-Rowlinson [J. Chem. Phys. 52, 1670 (1970)] binary mixture from direct simulation of the inhomogeneous system. We make use of the standard mechanical route, in which the surface tension follows from the computation of the normal and tangential components of the pressure tensor of the system. In addition to the usual approach, which involves simulations of the inhomogeneous system in the canonical ensemble, we also consider the computation of the surface tension in an ensemble where the pressure perpendicular (normal) to the planar interface is kept fixed. Both approaches are seen to provide consistent values of the interfacial tension. The issue of the system-size dependence of the surface tension is addressed. In addition, simulations of the fluid-fluid coexistence properties of the mixture are performed in the semigrand canonical ensemble. Our results are compared with existing data of the Widom-Rowlinson mixture and are also examined in the light of the vapor-liquid equilibrium of the thermodynamically equivalent one-component penetrable sphere model.

  2. Measuring and Modeling the Surface Tensions of Organic Aqueous Solutions With Atmospheric Significance

    NASA Astrophysics Data System (ADS)

    Aumann, E.; Tabazadeh, A.

    2008-12-01

    Organic compounds account for a substantial fraction of dry submicron atmospheric aerosol mass. Additionally, single particle composition data suggest that individual aerosols are often mixtures of organic and inorganic components. This study measured the surface tensions of atmospherically relevant pure and mixed organic / inorganic aqueous solutions. Measurements were performed using the Wilhelmy plate method at 25°C and 5°C. Small water-soluble organic compounds previously identified in aerosols (i.e. sugars, dicarboxylic acids) were found to alter the surface tension of water to a limited extent. Humic and fulvic acids were used as analog species for the unidentifiable humic-like substances (HULIS) found in atmospheric particles. Natural humic substances were considerably more effective at reducing the surface tension of water than small water-soluble species. However, humic matter reduced the surface tension of water to a lesser degree than measurements reported for atmospheric HULIS. The addition of inorganic species was found to significantly affect the surface activity of natural humic materials. Surface tension data were fit to the Szyszkowski equation to extract Langmuir adsorption parameters (maximum surface excess, Γmax, and the adsorption constant, β) for the aqueous systems. Adsorption parameters were used to model the surface tensions of multi-component solutions.

  3. Theoretical Studies of the Surface Tension of Liquid Metal System

    NASA Technical Reports Server (NTRS)

    Stroud, D. G.; Shih, W. H.

    1985-01-01

    A major goal of this project is to understand the surface tension and other thermophysical properties of liquid metals and alloys from a fundamental viewpoint. The approach is to calculate these quantities by a first principles technique which combines the statistical-mechanical theory of the liquid state with an electronic pseudopotential theory of electrons in metals. The inhomogeneity of the surface is treated using an ionic-density-functional formalism developed with the support of NASA. Of particular interest are the variation of surface tension with temperature and impurity concentration: such variations strongly influence the types of convection which make take place in a low-gravity environment. Some progress has already been achieved in computing the reduction of surface tension due to the presence of low-surface-tension impurities, and the corresponding surface segregation of such impurities. In the coming year, it is planned to concentrate on the surface properties of materials of particular interest to the MSA program: Si, Ga and GaSn alloys. An additional goal is to gain some theoretical understanding of the high temperature thermophysical properties of liquid metals, particularly high melting point materials which have not been studied extensively from a theoretical viewpoint.

  4. Theoretical Studies of the Surface Tension of Liquid Metal System

    NASA Technical Reports Server (NTRS)

    Stroud, D. G.; Shih, W. H.

    1985-01-01

    A major goal of this project is to understand the surface tension and other thermophysical properties of liquid metals and alloys from a fundamental viewpoint. The approach is to calculate these quantities by a first principles technique which combines the statistical-mechanical theory of the liquid state with an electronic pseudopotential theory of electrons in metals. The inhomogeneity of the surface is treated using an ionic-density-functional formalism developed with the support of NASA. Of particular interest are the variation of surface tension with temperature and impurity concentration: such variations strongly influence the types of convection which make take place in a low-gravity environment. Some progress has already been achieved in computing the reduction of surface tension due to the presence of low-surface-tension impurities, and the corresponding surface segregation of such impurities. In the coming year, it is planned to concentrate on the surface properties of materials of particular interest to the MSA program: Si, Ga and GaSn alloys. An additional goal is to gain some theoretical understanding of the high temperature thermophysical properties of liquid metals, particularly high melting point materials which have not been studied extensively from a theoretical viewpoint.

  5. Measurement of Surface Tension of Solid Cu by Improved Multiphase Equilibrium

    NASA Astrophysics Data System (ADS)

    Nakamoto, Masashi; Liukkonen, Matti; Friman, Michael; Heikinheimo, Erkki; Hämäläinen, Marko; Holappa, Lauri

    2008-08-01

    The surface tension of solid Cu was measured with the multiphase equilibrium (MPE) method in a Pb-Cu system at 700 °C, 800 °C, and 900 °C. A special focus was on the measurement of angles involved in MPE. First, the effect of reading error in each angle measurement on the final result of surface tension of solid was simulated. It was found that the two groove measurements under atmosphere conditions are the primary sources of error in the surface tension of solid in the present system. Atomic force microscopy (AFM) was applied to these angle measurements as a new method with high accuracy. The obtained surface-tension values of solid Cu in the present work were 1587, 1610, and 1521 mN/m at 700 °C, 800 °C, and 900 °C, respectively, representing reasonable temperature dependence.

  6. Hygroscopic properties of Amazonian biomass burning and European background HULIS and investigation of their effects on surface tension with two models linking H-TDMA to CCNC data

    NASA Astrophysics Data System (ADS)

    Fors, E. O.; Rissler, J.; Massling, A.; Svenningsson, B.; Andreae, M. O.; Dusek, U.; Frank, G. P.; Hoffer, A.; Bilde, M.; Kiss, G.; Janitsek, S.; Henning, S.; Facchini, M. C.; Decesari, S.; Swietlicki, E.

    2010-06-01

    HUmic-LIke Substances (HULIS) have been identified as major contributors to the organic carbon in atmospheric aerosol. The term "HULIS" is used to describe the organic material found in aerosol particles that resembles the humic organic material in rivers and sea water and in soils. In this study, two sets of filter samples from atmospheric aerosols were collected at different sites. One set of samples was collected at the K-puszta rural site in Hungary, about 80 km SE of Budapest, and a second was collected at a site in Rondônia, Amazonia, Brazil, during the Large-Scale Biosphere-Atmosphere Experiment in Amazonia - Smoke Aerosols, Clouds, Rainfall and Climate (LBA-SMOCC) biomass burning season experiment. HULIS were extracted from the samples and their hygroscopic properties were studied using a Hygroscopicity Tandem Differential Mobility Analyzer (H-TDMA) at relative humidity (RH) <100%, and a cloud condensation nucleus counter (CCNC) at RH >100%. The H-TDMA measurements were carried out at a dry diameter of 100 nm and for RH ranging from 30 to 98%. At 90% RH the HULIS samples showed diameter growth factors between 1.04 and 1.07, reaching values of 1.4 at 98% RH. The cloud nucleating properties of the two sets of aerosol samples were analysed using two types of thermal static cloud condensation nucleus counters. Two different parameterization models were applied to investigate the potential effect of HULIS surface activity, both yielding similar results. For the K-puszta winter HULIS sample, the surface tension at the point of activation was estimated to be lowered by between 34% (47.7 mN/m) and 31% (50.3 mN/m) for dry sizes between 50 and 120 nm in comparison to pure water. A moderate lowering was also observed for the entire water soluble aerosol sample, including both organic and inorganic compounds, where the surface tension was decreased by between 2% (71.2 mN/m) and 13% (63.3 mN/m).

  7. Surface tension mediated conversion of light to work

    DOEpatents

    Okawa, David; Pastine, Stefan J; Zettl, Alexander K; Frechet, Jean M. J

    2014-12-02

    Disclosed are a method and apparatus for converting light energy to mechanical energy by modification of surface tension on a supporting fluid. The apparatus comprises an object which may be formed as a composite object comprising a support matrix and a highly light absorptive material. The support matrix may comprise a silicon polymer. The highly light absorptive material may comprise vertically aligned carbon nanotubes (VANTs) embedded in the support matrix. The composite object is supported on a fluid. By exposing the highly light absorptive material to light, heat is generated, which changes the surface tension of the composite object, causing it to move physically within the fluid.

  8. Surface-tension-induced convection experiment MA-041

    NASA Technical Reports Server (NTRS)

    Reed, R. E.

    1976-01-01

    In the absence of gravity, stirring in a liquid is suppressed because of density differences caused by thermal or compositional gradients. However, other mechanisms resulting in natural convection in a microgravity environment exist. One of the most important mechanisms for liquid metals is surface tension driven convection, which becomes predominant in the low gravity environment. In this case, surface tension differences caused by compositional or temperature gradients have been demonstrated to cause stirring in liquids during experiments performed onboard Skylab. Compositional gradients were created by adding a soap solution to a large water globule, which caused vigorous fluid motion for some moments after the addition.

  9. From viscosity and surface tension to marangoni flow in melts

    NASA Astrophysics Data System (ADS)

    Sun, Shouyi; Zhang, Ling; Jahanshahi, Sharif

    2003-10-01

    This article covers some of our recent work on slag viscosity, the surface tension of liquid Cu-O alloys, and the relative role of Marangoni and bulk flow on refractory wear in iron-silicate slags. A viscosity model developed for slags containing SiO2, Al2O3, Fe2O3, CaO, MgO, MnO, FeO, PbO, NiO, Cu2O, ZnO, CoO, and TiO2 is capable of representing the effects of temperature, silica, and network-modifier cations within a wide range of temperatures and compositions. It forms a useful part of a computational package for multiphase-equilibrium (MPE) calculations and for predicting slag viscosities. The models are well applicable to a range of industrial slags (blast furnace, new iron making, base-metal and Platinum Group Metals (PGM) smelting, and coal-ash slags). The package has also some capability of predicting the viscosity of slags containing suspended solids. The surface tension of liquid copper-oxygen alloys has also been analyzed. The adsorption behavior of oxygen in liquid copper is well represented by the combined Langmuir-Gibbs isotherm. According to the rate data for silica-rod dissolution in liquid iron-silicate slags at 1573 K, the preferential attack at the slag line diminishes as the linear velocity of flow at the surface of the rotating silica rod reaches 9 to 16 cm/s. A tentative analysis gives the critical condition, that relates the critical Reynolds (Re) and Marangoni (Ma) number by the equation Re*2=0.13 Ma*.

  10. The interactive effects of pH, surface tension, and solution density for flotation systems for separation of equivalent-density materials: separation of ABS from HIPS

    SciTech Connect

    Karvelas, D.E.; Jody, B.J.; Pomykala, J.A.; Daniels, E.J.

    1996-07-01

    This paper presents the results of research being conducted at Argonne National Laboratory, to develop a cost-effective and environmentally acceptable process for the separation of high-value plastics from discarded household appliances. The process under development has separated high-purity (greater than 99.5%) acrylonitrile-butadiene-styrene (ABS) and high-impact polystyrene (HIPS) from commingled plastics generated by appliance-shredding and metal recovery operations. Plastics of similar densities, such as ABS and HIPS are further separated by using a chemical solution. By controlling the surface tension, the density and the temperature of the chemical solution, we are able to selectively float/separate plastics that have equivalent densities. In laboratory-scale tests, this technique has proven highly effective in recovering high-purity plastics materials from discarded household appliances and other obsolete durable goods. A pilot plant is under construction to demonstrate and assess the technical and economic performance of this process. In this paper, we examine the technical and economic issues that affect the recovery and separation of plastics and provide an update on Argonne`s plastics separation research and development activities.

  11. A comprehensive study on the effects of temperature, surface age, added surfactant, salinity, and bulk viscosity on coalescence time, film rigidity, and interfacial tension: Topical report

    SciTech Connect

    Peru, D.A.; Lorenz, P.B.

    1988-01-01

    The interfacial behavior of a Wilmington crude oil was studied as part of our investigations of enhanced oil recovery by weakly alkaline solutions. For some systems, the spinning drop appratus can be used to measure transient interfacial tension (IFT) effects, coalescence times of oil drops, and film rigidity simultaneously, for rapid screening of chemical slug composition for the potential of improving oil recovery by the mechanisms of oil mobilization and oil bank formation. The experimental results presented include the effects of temperature, surface age, salinity, added surfactant, and polymer on coalescence time, film rigidity, and IFT behavior. Oil displacement tests were performed using surfactant-enhanced bicarbonte solutions formulated for improved mobility control and for improved oil mobilization and oil drop coalescence. The most significant result of this work was that we were able to measure the dynamics in IFT between 2 coalescing oil drops as perturbations in the equilibrium concentration of surfactant at the interface occurred during film drainage. The accuracy of the technique for measuring IFT and film rigidity improved as the contact radii between the oil drops increased. 17 refs., 13 figs., 11 tabs.

  12. Effect of surface tension on the dynamical behavior of bubble in rotating fluids under low gravity environment

    NASA Technical Reports Server (NTRS)

    Hung, R. J.; Tsao, Y. D.; Leslie, Fred W.; Hong, B. B.

    1988-01-01

    Time dependent evolutions of the profile of free surface (bubble shapes) for a cylindrical container partially filled with a Newtonian fluid of constant density, rotating about its axis of symmetry, have been studied. Numerical computations of the dynamics of bubble shapes have been carried out with the following situations: (1) linear functions of spin-up and spin-down in low and microgravity environments, (2) linear functions of increasing and decreasing gravity enviroment in high and low rotating cylidner speeds, (3) step functions of spin-up and spin-down in a low gravity environment, and (4) sinusoidal function oscillation of gravity environment in high and low rotating cylinder speeds. The initial condition of bubble profiles was adopted from the steady-state formulations in which the computer algorithms have been developed by Hung and Leslie (1988), and Hung et al. (1988).

  13. Dynamic surface tension analysis of dodecyl sulfate association complexes.

    PubMed

    Quigley, W W; Nabi, A; Prazen, B J; Lenghor, N; Grudpan, K; Synovec, R E

    2001-09-13

    First, a novel calibration method is used to expand the current understanding of spherical drop growth and elongation that occurs during on-line measurements of surface pressure using the dynamic surface tension detector (DSTD). Using a novel surface tension calibration method, the drop radius is calculated as a function of time from experimental drop pressure data and compared to the theoretical drop radius calculated from volumetric flow rate. From this comparison, the drop volume at which the drop shape starts to deviate ( approximately 4 mul) from a spherical shape is readily observed and deviates more significantly by approximately 6 mul drop volume (5% deviation in the ideal spherical drop radius) for the capillary sensing tip employed in the DSTD. From this assessment of drop shape, an experimental method for precise drop detachment referred to as pneumatic drop detachment is employed at a drop volume of 2 mul (two second drops at 60 mul/min) in order to provide rapid dynamic surface tension measurements via the novel on-line calibration methodology. Second, the DSTD is used to observe and study kinetic information for surface-active molecules and association complexes adsorbing to an air-liquid drop interface. Dynamic surface tension measurements are made for sodium dodecyl sulfate (SDS) in the absence and presence of either tetra butyl ammonium (TBA) or chromium (III). Sensitive, indirect detection of chromium and other multiply charged metals at low concentrations is also investigated. The DSTD is utilized in examining the dynamic nature of SDS: cation association at the air-liquid interface of a growing drop. Either TBA or Cr(III) were found to substantially enhance the surface tension lowering of dodecyl sulfate (DS), but the surface tension lowering is accompanied by a considerable kinetic dependence. Essentially, the surface tension lowering of these DS: cation complexes is found to be a fairly slow process in the context of the two second DSTD

  14. Surface Tension Characteristics of Aqueous Lithium Bromide Solution with Alcoholic Surfactant

    NASA Astrophysics Data System (ADS)

    Sasaki, Naoe; Ogawa, Kiyoshi

    At present, the combination of aqueous lithium bromide (LiBr) solution as an absorbent and water as a refrigerant have widely been used as the working fluid for absorption refrigerating machines. In order to obtain absorption enhancement of water vapor into the LiBr solution by Marangoni convection, an alcoholic surfactant is being added in the LiBr solution. In that case, the surface tension of the LiBr solution with the surfactant plays an important role for the vapor absorption. In this study, the surface tensions of the LiBr solution with several alcoholic surfactants such as 1-butanol, 1-hexanol, 2-ethyl-1-butanol, 2-methyl-1-pentanol, 1-heptanol, 1-octanol and 2-ethyl-1-hexanol were measured by Wilhelmy plate method. As a result, the surface tensions of 50 wt% LiBr solution with several surfactants were obtained over the LiBr solution temperature range from 298 K to 318 K and the surfactant concentration range from 0 to 104 ppm by mass. The measured surface tension has decreased with the increasing number of carbons included in the surfactant at constant concentration, and the surface tension has increased with the increasing temperature of 50 wt% LiBr solution. The surface tension increase of 1-octanol became greater than any other surfactant used in this work. The effective carbon number of the surfactant for the absorption enhancement was in the range from 7 to 8.

  15. Computer modelling of the surface tension of the gas-liquid and liquid-liquid interface.

    PubMed

    Ghoufi, Aziz; Malfreyt, Patrice; Tildesley, Dominic J

    2016-03-07

    This review presents the state of the art in molecular simulations of interfacial systems and of the calculation of the surface tension from the underlying intermolecular potential. We provide a short account of different methodological factors (size-effects, truncation procedures, long-range corrections and potential models) that can affect the results of the simulations. Accurate calculations are presented for the calculation of the surface tension as a function of the temperature, pressure and composition by considering the planar gas-liquid interface of a range of molecular fluids. In particular, we consider the challenging problems of reproducing the interfacial tension of salt solutions as a function of the salt molality; the simulations of spherical interfaces including the calculation of the sign and size of the Tolman length for a spherical droplet; the use of coarse-grained models in the calculation of the interfacial tension of liquid-liquid surfaces and the mesoscopic simulations of oil-water-surfactant interfacial systems.

  16. Drops, Sieves, and Paintbrushes: Teaching About Surface Tension

    ERIC Educational Resources Information Center

    Barnes, George B.

    1978-01-01

    Surface tension, a characteristic of liquids, is discussed in this article. Several activities appropriate to the elementary grades are described and explained. Each activity uses common materials to explore this tendancy of water to act as if it were surrounded by a membrane. (MA)

  17. A Modified Jaeger's Method for Measuring Surface Tension.

    ERIC Educational Resources Information Center

    Ntibi, J. Effiom-Edem

    1991-01-01

    A static method of measuring the surface tension of a liquid is presented. Jaeger's method is modified by replacing the pressure source with a variable pressure head. By using this method, stationary air bubbles are obtained thus resulting in controllable external parameters. (Author/KR)

  18. Competing effects of viscosity and surface-tension depression on the hygroscopicity and CCN activity of laboratory surrogates for oligomers in atmospheric aerosol

    NASA Astrophysics Data System (ADS)

    Hodas, N.; Zuend, A.; Shiraiwa, M.; Flagan, R. C.; Seinfeld, J.; Schilling, K.; Berkemeier, T.

    2015-12-01

    The presence of oligomers in biomass burning aerosol, as well as secondary organic aerosol derived from other sources, influences particle viscosity and can introduce kinetic limitations to water uptake. This, in turn, impacts aerosol optical properties and the efficiency with which these particles serve as cloud condensation nuclei (CCN). To explore the influence of organic-component viscosity on aerosol hygroscopicity, the water-uptake behavior of aerosol systems comprised of polyethylene glycol (PEG) and mixtures of PEG and ammonium sulfate (AS) was measured under sub- and supersaturated relative humidity (RH) conditions. Experiments were conducted with systems containing PEG with average molecular weights ranging from 200 to 10,000 g/mol, corresponding to a range in viscosity of 0.004 - 4.5 Pa s under dry conditions. While evidence suggests that viscous aerosol components can suppress water uptake at RH < 90%, under supersaturated conditions (with respect to RH), an increase in CCN activity with increasing PEG molecular weight was observed. We attribute this to an increase in the efficiency with which PEG serves as a surfactant with increasing molecular weight. This effect is most pronounced for PEG-AS mixtures and, in fact, a modest increase in CCN activity is observed for the PEG 10,000-AS mixture as compared to pure AS, as evidenced by a 4% reduction in critical activation diameter. Experimental results are compared with calculations of hygroscopic growth at thermodynamic equilibrium using the Aerosol Inorganic-Organic Mixtures Functional groups Activity Coefficients model and the potential influence of kinetic limitations to observed water uptake is further explored with the Kinetic Multi-Layer Model of Gas-Particle Interactions. Results suggest the competing effects of organic-component viscosity and surface-tension depression may lead to RH-dependent differences in hygroscopicity for oligomers and other surface-active compounds present in atmospheric

  19. Surface Tension Driven Convection Experiment-2 (STDCE-2)

    NASA Technical Reports Server (NTRS)

    Masud, J.; Kamotani, Y.; Ostrach, S.

    1999-01-01

    Thermocapillary flows are known to become oscillatory (time-periodic), but how and when they become oscillatory in containers of unit-order aspect ratio are not yet fully understood. The present work is a part of our continuous effort to obtain a better understanding of the phenomenon. Thermocapillary flow experiments in normal gravity are limited to a narrow parametric range in order to minimize gravity and buoyancy effects, which is an important reason for our lack of full understanding of the oscillation phenomenon. One important unanswered question is what role, if any, free surface deformation plays in the oscillation mechanism. For that reason we performed thermocapillary flow experiments, called the Surface Tension Driven Convection Experiment-2 (STDCE-2), aboard the USML-2 Spacelab in 1995. The main objectives of the experiments were to investigate oscillatory thermocapillary flows in microgravity and to clarify the importance of free surface deformation in such flows. Steady and oscillatory thermocapillary flows were generated in cylindrical containers by employing two heating modes. A CO2 laser with adjustable power and beam diameter was used in the Constant Flux (CF) configuration to heat the free surface. The other configuration investigated in STDCE-2 was the Constant Temperature (CT) configuration in which a submerged cylindrical cartridge heater placed at the symmetry (axial) axis of the test container heated the fluid. Both heating modes cause non-uniform temperature distributions on the free surface, which generates thermocapillary flow. The flow field was investigated by flow visualization, and the temperature field was measured by thermistors and an infrared imager. The free surface shape and motion were measured by a Ronchi system. The hardware performed well and we were able to conduct more tests than originally planned. From the successful experiments a large amount of data was acquired. The analysis of the data is now nearly complete. Some

  20. Almost Exponential Decay of Periodic Viscous Surface Waves without Surface Tension

    NASA Astrophysics Data System (ADS)

    Guo, Yan; Tice, Ian

    2013-02-01

    We consider a viscous fluid of finite depth below the air, occupying a three-dimensional domain bounded below by a fixed solid boundary and above by a free moving boundary. The fluid dynamics are governed by the gravity-driven incompressible Navier-Stokes equations, and the effect of surface tension is neglected on the free surface. The long time behavior of solutions near equilibrium has been an intriguing question since the work of Beale (Commun Pure Appl Math 34(3):359-392, 1981). This paper is the third in a series of three (Guo in Local well-posedness of the viscous surface wave problem without surface tension, Anal PDE 2012, to appear; in Decay of viscous surface waves without surface tension in horizontally infinite domains, Preprint, 2011) that answers this question. Here we consider the case in which the free interface is horizontally periodic; we prove that the problem is globally well-posed and that solutions decay to equilibrium at an almost exponential rate. In particular, the free interface decays to a flat surface. Our framework contains several novel techniques, which include: (1) a priori estimates that utilize a "geometric" reformulation of the equations; (2) a two-tier energy method that couples the boundedness of high-order energy to the decay of low-order energy, the latter of which is necessary to balance out the growth of the highest derivatives of the free interface; (3) a localization procedure that is compatible with the energy method and allows for curved lower surface geometry. Our decay estimates lead to the construction of global-in-time solutions to the surface wave problem.

  1. Surface tension, surface energy, and chemical potential due to their difference.

    PubMed

    Hui, C-Y; Jagota, A

    2013-09-10

    It is well-known that surface tension and surface energy are distinct quantities for solids. Each can be regarded as a thermodynamic property related first by Shuttleworth. Mullins and others have suggested that the difference between surface tension and surface energy cannot be sustained and that the two will approach each other over time. In this work we show that in a single-component system where changes in elastic energy can be neglected, the chemical potential difference between the surface and bulk is proportional to the difference between surface tension and surface energy. By further assuming that mass transfer is driven by this chemical potential difference, we establish a model for the kinetics by which mass transfer removes the difference between surface tension and surface energy.

  2. Surface folding-induced attraction and motion of particles in a soft elastic gel: cooperative effects of surface tension, elasticity, and gravity.

    PubMed

    Chakrabarti, Aditi; Chaudhury, Manoj K

    2013-12-17

    We report some experimental observations regarding a new type of long-range interaction between rigid particles that prevails when they are suspended in an ultrasoft elastic gel. A denser particle submerges itself to a considerable depth inside the gel and becomes elasto-buoyant by balancing its weight against the elastic force exerted by the surrounding medium. By virtue of a large elasto-capillary length, the surface of the gel wraps around the particle and closes to create a line singularity connecting the particle to the free surface of the gel. A substantial amount of tensile strain is thus developed in the gel network parallel to the free surface that penetrates to a significant depth inside the gel. The field of this tensile strain is rather long-range because of a large gravito-elastic correlation length and sufficiently strong to pull two submerged particles into contact. The particles move toward each other with an effective force following an inverse linear distance law. When more monomers or dimers of the particles are released inside the gel, they orient rather freely inside the capsules where they are located and attract each other to form closely packed clusters. Eventually, these clusters themselves interact and coalesce. This is an emergent phenomenon in which gravity, capillarity, and elasticity work in tandem to create a long-range interaction. We also present the results of a related experiment, in which a particle suspended inside a thickness-graded gel moves accompanied by the continuous folding and the relaxation of the gel's surface.

  3. Elastocapillarity: Surface Tension and the Mechanics of Soft Solids

    NASA Astrophysics Data System (ADS)

    Style, Robert W.; Jagota, Anand; Hui, Chung-Yuen; Dufresne, Eric R.

    2017-03-01

    It is widely appreciated that surface tension can dominate the behavior of liquids at small scales. Solids also have surface stresses of a similar magnitude, but they are usually overlooked. However, recent work has shown that these can play a central role in the mechanics of soft solids such as gels. Here, we review this emerging field. We outline the theory of surface stresses, from both mechanical and thermodynamic perspectives, emphasizing the relationship between surface stress and surface energy. We describe a wide range of phenomena at interfaces and contact lines where surface stresses play an important role. We highlight how surface stresses cause dramatic departures from classic theories for wetting (Young-Dupré), adhesion (Johnson-Kendall-Roberts), and composites (Eshelby). A common thread is the importance of the ratio of surface stress to an elastic modulus, which defines a length scale below which surface stresses can dominate.

  4. Surface Tension of Acid Solutions: Fluctuations beyond the Nonlinear Poisson-Boltzmann Theory.

    PubMed

    Markovich, Tomer; Andelman, David; Podgornik, Rudi

    2017-01-10

    We extend our previous study of surface tension of ionic solutions and apply it to acids (and salts) with strong ion-surface interactions, as described by a single adhesivity parameter for the ionic species interacting with the interface. We derive the appropriate nonlinear boundary condition with an effective surface charge due to the adsorption of ions from the bulk onto the interface. The calculation is done using the loop-expansion technique, where the zero loop (mean field) corresponds of the full nonlinear Poisson-Boltzmann equation. The surface tension is obtained analytically to one-loop order, where the mean-field contribution is a modification of the Poisson-Boltzmann surface tension and the one-loop contribution gives a generalization of the Onsager-Samaras result. Adhesivity significantly affects both contributions to the surface tension, as can be seen from the dependence of surface tension on salt concentration for strongly absorbing ions. Comparison with available experimental data on a wide range of different acids and salts allows the fitting of the adhesivity parameter. In addition, it identifies the regime(s) where the hypotheses on which the theory is based are outside their range of validity.

  5. Effect of wire tension on stiffness of tensioned fine wires in external fixation: a mechanical study.

    PubMed

    Antoci, Valentin; Voor, Michael J; Antoci, Valentin; Roberts, Craig S

    2007-09-01

    To determine the effect of changes in magnitude of transfixion wire tension on stiffness of fine-wire external-fixation load deformation, we compared results obtained with different wire tensions (50-140 kg) under identical conditions of central axial compression, medial compression-bending, posterior compression-bending, posteromedial compression-bending, and torsion. Stiffness values were calculated from the load-deformation and torque-angle curves. Tension of 140 kg provided the most stiffness, and there was a trend toward increasing overall stiffness with increasing wire tension. The 1.8-mm wires should be tensioned to at least 110 kg in most cases of fine-wire external fixation; compared with all tensions less than 110 kg, this tension provides significantly more mechanical stability in all loading modes.

  6. Temperature Dependence of Surface Tension of Sn-Ag Alloys

    NASA Astrophysics Data System (ADS)

    Ohira, Chika; Fujii, Hidetoshi; Morisada, Yoshiaki

    2014-05-01

    The surface tension of molten Sn-Ag alloys was measured using a specially developed high-accuracy sessile drop apparatus. In this apparatus, a molten sample is dropped onto a R-Al2O3 substrate in order to prevent any reaction between the sample and substrate during the heating process. The droplet shape was recorded from two perpendicular directions to confirm its symmetry. The oxygen partial pressure () was controlled by a Mg furnace to a value of about 10-16 to 10-15 Pa. The sample compositions used were Sn-20Ag, Sn-50Ag, and Sn-80Ag (at.%) and were alloyed from pure Sn (99.999%) and Ag (99.99%) in the dropping tube. The accuracy of the experimental results was confirmed by an extremely small scatter. The measured temperature dependence of the surface tension of the molten Sn-50Ag (at.%) alloy indicated a characteristic curve that changed from positive to negative with increasing temperature. Furthermore, the surface tension of the molten Sn-20Ag (at.%) alloy has a temperature dependence that changes from flat to negative, while the Sn-80Ag (at.%) alloy has a negative temperature dependence across the whole temperature range. Based on a theoretical discussion using Butler's equation, these temperature dependencies can be determined by negative straight lines when assuming the surface composition.

  7. Surface tension dominates insect flight on fluid interfaces

    PubMed Central

    Mukundarajan, Haripriya; Bardon, Thibaut C.; Kim, Dong Hyun; Prakash, Manu

    2016-01-01

    ABSTRACT Flight on the 2D air–water interface, with body weight supported by surface tension, is a unique locomotion strategy well adapted for the environmental niche on the surface of water. Although previously described in aquatic insects like stoneflies, the biomechanics of interfacial flight has never been analysed. Here, we report interfacial flight as an adapted behaviour in waterlily beetles (Galerucella nymphaeae) which are also dexterous airborne fliers. We present the first quantitative biomechanical model of interfacial flight in insects, uncovering an intricate interplay of capillary, aerodynamic and neuromuscular forces. We show that waterlily beetles use their tarsal claws to attach themselves to the interface, via a fluid contact line pinned at the claw. We investigate the kinematics of interfacial flight trajectories using high-speed imaging and construct a mathematical model describing the flight dynamics. Our results show that non-linear surface tension forces make interfacial flight energetically expensive compared with airborne flight at the relatively high speeds characteristic of waterlily beetles, and cause chaotic dynamics to arise naturally in these regimes. We identify the crucial roles of capillary–gravity wave drag and oscillatory surface tension forces which dominate interfacial flight, showing that the air–water interface presents a radically modified force landscape for flapping wing flight compared with air. PMID:26936640

  8. Surface tension dominates insect flight on fluid interfaces.

    PubMed

    Mukundarajan, Haripriya; Bardon, Thibaut C; Kim, Dong Hyun; Prakash, Manu

    2016-03-01

    Flight on the 2D air-water interface, with body weight supported by surface tension, is a unique locomotion strategy well adapted for the environmental niche on the surface of water. Although previously described in aquatic insects like stoneflies, the biomechanics of interfacial flight has never been analysed. Here, we report interfacial flight as an adapted behaviour in waterlily beetles (Galerucella nymphaeae) which are also dexterous airborne fliers. We present the first quantitative biomechanical model of interfacial flight in insects, uncovering an intricate interplay of capillary, aerodynamic and neuromuscular forces. We show that waterlily beetles use their tarsal claws to attach themselves to the interface, via a fluid contact line pinned at the claw. We investigate the kinematics of interfacial flight trajectories using high-speed imaging and construct a mathematical model describing the flight dynamics. Our results show that non-linear surface tension forces make interfacial flight energetically expensive compared with airborne flight at the relatively high speeds characteristic of waterlily beetles, and cause chaotic dynamics to arise naturally in these regimes. We identify the crucial roles of capillary-gravity wave drag and oscillatory surface tension forces which dominate interfacial flight, showing that the air-water interface presents a radically modified force landscape for flapping wing flight compared with air. © 2016. Published by The Company of Biologists Ltd.

  9. Dynamic surface tension of surfactant TA: experiments and theory.

    PubMed

    Otis, D R; Ingenito, E P; Kamm, R D; Johnson, M

    1994-12-01

    A bubble surfactometer was used to measure the surface tension of an aqueous suspension of surfactant TA as a function of bubble area over a range of cycling rates and surfactant bulk concentrations. Results of the surface tension-interfacial area loops exhibited a rich variety of phenomena, the character of which varied systematically with frequency and bulk concentration. A model was developed to interpret and explain these data and for use in describing the dynamics of surface layers under more general circumstances. Surfactant was modeled as a single component with surface tension taken to depend on only the interfacial surfactant concentration. Two distinct mechanisms were considered for the exchange of surfactant between the bulk phase and interface. The first is described by a simple kinetic relationship for adsorption and desorption that pertains only when the interfacial concentration is below its maximum equilibrium value. The second mechanism is "squeeze-out" by which surfactant molecules are expelled from an interface compressed past a maximum packing state. The model provided good agreement with experimental measurements for cycling rates from 1 to 100 cycles/min and for bulk concentrations between 0.0073 and 7.3 mg/ml.

  10. Modeling the surface tension of complex, reactive organic-inorganic mixtures

    NASA Astrophysics Data System (ADS)

    Schwier, A. N.; Viglione, G. A.; Li, Z.; McNeill, V. F.

    2013-01-01

    Atmospheric aerosols can contain thousands of organic compounds which impact aerosol surface tension, affecting aerosol properties such as cloud condensation nuclei (CCN) ability. We present new experimental data for the surface tension of complex, reactive organic-inorganic aqueous mixtures mimicking tropospheric aerosols. Each solution contained 2-6 organic compounds, including methylglyoxal, glyoxal, formaldehyde, acetaldehyde, oxalic acid, succinic acid, leucine, alanine, glycine, and serine, with and without ammonium sulfate. We test two surface tension models and find that most reactive, complex, aqueous organic mixtures which do not contain salt are well-described by a weighted Szyszkowski-Langmuir (S-L) model which was first presented by Henning et al. (2005). Two approaches for modeling the effects of salt were tested: (1) the Tuckermann approach (an extension of the Henning model with an additional explicit salt term), and (2) a new implicit method proposed here which employs experimental surface tension data obtained for each organic species in the presence of salt used with the Henning model. We recommend the use of method (2) for surface tension modeling because the Henning model (using data obtained from organic-inorganic systems) and Tuckermann approach provide similar modeling fits and goodness of fit (χ2) values, yet the Henning model is a simpler and more physical approach to modeling the effects of salt, requiring less empirically determined parameters.

  11. Modeling the surface tension of complex, reactive organic-inorganic mixtures

    NASA Astrophysics Data System (ADS)

    Schwier, A. N.; Viglione, G. A.; Li, Z.; McNeill, V. Faye

    2013-11-01

    Atmospheric aerosols can contain thousands of organic compounds which impact aerosol surface tension, affecting aerosol properties such as heterogeneous reactivity, ice nucleation, and cloud droplet formation. We present new experimental data for the surface tension of complex, reactive organic-inorganic aqueous mixtures mimicking tropospheric aerosols. Each solution contained 2-6 organic compounds, including methylglyoxal, glyoxal, formaldehyde, acetaldehyde, oxalic acid, succinic acid, leucine, alanine, glycine, and serine, with and without ammonium sulfate. We test two semi-empirical surface tension models and find that most reactive, complex, aqueous organic mixtures which do not contain salt are well described by a weighted Szyszkowski-Langmuir (S-L) model which was first presented by Henning et al. (2005). Two approaches for modeling the effects of salt were tested: (1) the Tuckermann approach (an extension of the Henning model with an additional explicit salt term), and (2) a new implicit method proposed here which employs experimental surface tension data obtained for each organic species in the presence of salt used with the Henning model. We recommend the use of method (2) for surface tension modeling of aerosol systems because the Henning model (using data obtained from organic-inorganic systems) and Tuckermann approach provide similar modeling results and goodness-of-fit (χ2) values, yet the Henning model is a simpler and more physical approach to modeling the effects of salt, requiring less empirically determined parameters.

  12. Tissue surface tension measurement by rigorous axisymmetric drop shape analysis.

    PubMed

    David, Robert; Ninomiya, Hiromasa; Winklbauer, Rudolf; Neumann, A Wilhelm

    2009-09-01

    Certain behaviours of embryonic cell aggregates can be modelled by ascribing to them a tissue surface tension, with each cell analogous to a liquid molecule. Under normal gravity, aggregates are nearly spherical, but they can be partially flattened in a centrifuge. This allows measurement of their tissue surface tensions by a drop shape method such as axisymmetric drop shape analysis (ADSA). We study ectodermal embryonic cells from the frog Xenopus laevis subjected to centrifugation at 100 x g and 200 x g. We show that ADSA can be applied to irregular aggregate profiles and compare results with those from a previous, simpler version called ADSA-IP. With a modification in the experimental method, the two algorithms give similar results and the aggregate profiles more closely follow Laplacian curves. The ADSA fitting error allows an estimate of the relative uncertainty in the results.

  13. Measurement of surface and interfacial tension using pendant drop tensiometry.

    PubMed

    Berry, Joseph D; Neeson, Michael J; Dagastine, Raymond R; Chan, Derek Y C; Tabor, Rico F

    2015-09-15

    Pendant drop tensiometry offers a simple and elegant solution to determining surface and interfacial tension - a central parameter in many colloidal systems including emulsions, foams and wetting phenomena. The technique involves the acquisition of a silhouette of an axisymmetric fluid droplet, and iterative fitting of the Young-Laplace equation that balances gravitational deformation of the drop with the restorative interfacial tension. Since the advent of high-quality digital cameras and desktop computers, this process has been automated with high speed and precision. However, despite its beguiling simplicity, there are complications and limitations that accompany pendant drop tensiometry connected with both Bond number (the balance between interfacial tension and gravitational forces) and drop volume. Here, we discuss the process involved with going from a captured experimental image to a fitted interfacial tension value, highlighting pertinent features and limitations along the way. We introduce a new parameter, the Worthington number, Wo, to characterise the measurement precision. A fully functional, open-source acquisition and fitting software is provided to enable the reader to test and develop the technique further.

  14. A micro surface tension pump (MISPU) in a glass microchip.

    PubMed

    Peng, Xing Yue Larry

    2011-01-07

    A non-membrane micro surface tension pump (MISPU) was fabricated on a glass microchip by one-step glass etching. It needs no material other than glass and is driven by digital gas pressure. The MISPU can be seen working like a piston pump inside the glass microchip under a microscope. The design of the valves (MISVA) and pistons (MISTON) was based on the surface tension theory of the micro surface tension alveolus (MISTA). The digital gas pressure controls the moving gas-liquid interface to open or close the input and output MISVAs to refill or drive the MISTON for pumping a liquid. Without any moving parts, a MISPU is a kind of long-lasting micro pump for micro chips that does not lose its water pumping efficiency over a 20-day period. The volumetric pump output varied from 0 to 10 nl s(-1) when the pump cycle time decreased from 5 min to 15 s. The pump head pressure was 1 kPa.

  15. Features of the concentration dependences of the surface tension of water suspensions of bentonites

    NASA Astrophysics Data System (ADS)

    Dadashev, R. Kh.; Dzhambulatov, R. S.; Elimkhanov, D. Z.

    2015-08-01

    The concentration dependence of the surface tension of water suspensions of bentonites is studied experimentally. Possible reasons for the emergence of the minima on isotherms of the surface tensions of dispersed systems are analyzed.

  16. Binding of globular proteins to DNA from surface tension measurement.

    PubMed

    Mitra, A; Chattoraj, D K; Chakraborty, P

    2001-10-01

    Extent of binding (gammap) of globular proteins to calf-thymus DNA have been measured in mole per mole of nucleotide as function of equilibrium protein concentration. We have exploited measurement of the surface tension of the protein solution in the presence and absence of DNA to calculate the binding ration (gammap). Interaction of bovine serum albumin with DNA has been studied at different pH. Interaction of bovine serum albumin with DNA has been studied at different pH, ionic strength and in presence of Ca2+. Interaction of BSA with denatured DNA has also been investigated. Binding isotherms for other globular proteins like beta-lactoglobulin, alpha-lactalbumin and lysozyme have been compared under identical physicochemical condition. It has been noted with considerable interest that globular form of protein is important to some extent in protein-DNA interaction. An attempt has been made to explain the significance of difference in binding ratios of these two biopolymers in aqueous medium for different systems in the light of electrostatic and hydrophobic effects. Values of maximum binding ration (gammap(m)) at saturated level for different systems have been also presented. The Gibb's free energy decrease (-deltaG0) of the binding of proteins to DNA has been compared more precisely for the saturation of binding sites in the DNA with the change of activity of protein in solution from zero to unity in the rational mole fraction scale.

  17. Comparing contact angle measurements and surface tension assessments of solid surfaces.

    PubMed

    Cwikel, Dory; Zhao, Qi; Liu, Chen; Su, Xueju; Marmur, Abraham

    2010-10-05

    Four types of contact angles (receding, most stable, advancing, and "static") were measured by two independent laboratories for a large number of solid surfaces, spanning a large range of surface tensions. It is shown that the most stable contact angle, which is theoretically required for calculating the Young contact angle, is a practical, useful tool for wettability characterization of solid surfaces. In addition, it is shown that the experimentally measured most stable contact angle may not always be approximated by an average angle calculated from the advancing and receding contact angles. The "static" CA is shown in many cases to be very different from the most stable one. The measured contact angles were used for calculating the surface tensions of the solid samples by five methods. Meaningful differences exist among the surface tensions calculated using four previously known methods (Owens-Wendt, Wu, acid-base, and equation of state). A recently developed, Gibbsian-based correlation between interfacial tensions and individual surface tensions was used to calculate the surface tensions of the solid surfaces from the most stable contact angle of water. This calculation yielded in most cases higher values than calculated with the other four methods. On the basis of some low surface energy samples, the higher values appear to be justified.

  18. Measurement of surface tension and viscosity by open capillary techniques

    DOEpatents

    Rye,Robert R. , Yost,Frederick G.

    1998-01-01

    An open-channel capillary is provided, having preferably a v-shaped groove in a flat wettable surface. The groove has timing marks and a source marker in which the specimen to be tested is deposited. The time of passage between the timing marks is recorded, and the ratio of surface tension .gamma. to viscosity .mu. is determined from the equation given below: ##EQU1## where h.sub.0 is the groove depth, .alpha. is the groove angle, .theta. is the liquid/solid contact angle, and t is the flow time. It has been shown by the

  19. The gas-liquid surface tension of argon: A reconciliation between experiment and simulation

    NASA Astrophysics Data System (ADS)

    Goujon, Florent; Malfreyt, Patrice; Tildesley, Dominic J.

    2014-06-01

    We present a simulation of the liquid-vapor interface of argon with explicit inclusion of the three-body interactions. The three-body contributions to the surface tension are calculated using the Kirkwood-Buff approach. Monte Carlo calculations of the long-range corrections to the three-body contribution are calculated from the radial distribution function g(2)(z1, cos θ12, r12). Whereas the effective two-body potentials overestimate the surface tension by more than 15%, the inclusion of the three-body potential provides an excellent agreement with the experimental results for temperatures up to 15 K below the critical temperature. We conclude that the three-body interactions must be explicitly included in accurately modelling the surface tension of argon.

  20. Drops settling in a fluid with surface tension increasing with depth

    NASA Astrophysics Data System (ADS)

    Shapiro, Avi; Blanchette, Francois

    2011-11-01

    We investigated numerically drops settling across layers of miscible fluids, representing oil droplets settling in a fluid stratified by temperature or salinity variations. The top layer is lighter than the lower one, while the drop itself is heavier than both layers. As the drop settles into the lower, its surface tension with the ambient fluid increases, which generates significant Marangoni effects. If the surface tension difference is small, the drop is delayed as it settles into the lower layer. Above a critical surface tension difference, the drop may be altogether prevented from crossing into the lower layer. We determine the conditions under which a drop may remain suspended at the transition region, and study the mixing generated by suspended drops. We acknowledge support from NSF grant DMS 0808129.

  1. A study on air bubble wetting: Role of surface wettability, surface tension, and ionic surfactants

    NASA Astrophysics Data System (ADS)

    George, Jijo Easo; Chidangil, Santhosh; George, Sajan D.

    2017-07-01

    Fabrication of hydrophobic/hydrophilic surfaces by biomimicking nature has attracted significant attention recently due to their potential usage in technologies, ranging from self-cleaning to DNA condensation. Despite the potential applications, compared to surfaces of tailored wettability, less attention has been paid towards development and understanding of air bubble adhesion and its dynamics on surfaces with varying wettability. In this manuscript, following the commonly used approach of oxygen plasma treatment, polydimethylsiloxane surfaces with tunable wettability are prepared. The role of plasma treatment conditions on the surface hydrophilicity and the consequent effect on adhesion dynamics of an underwater air bubble is explored for the first time. The ATR-FTIR spectroscopic analysis reveals that the change in hydrophilicity arises from the chemical modification of the surface, manifested as Si-OH vibrations in the spectra. The thickness of the formed thin liquid film at the surface responsible for the experimentally observed air bubble repellency is estimated from the augmented Young-Laplace equation. The concentration dependent studies using cationic as well as anionic surfactant elucidate that the reduced surface tension of the aqueous solution results in a stable thicker film and causes non-adherence of air bubble to the aerophilic surface. Furthermore, the study carried out to understand the combined effect of plasma treatment and surfactants reveals that even below critical micelle concentration, a negatively charged surface results in air bubble repellency for the anionic surfactant, whereas only enhanced air bubble contact angle is observed for the cationic surfactant.

  2. Estimation of solid–liquid interfacial tension using curved surface of a soft solid

    PubMed Central

    Mondal, Subrata; Phukan, Monmee; Ghatak, Animangsu

    2015-01-01

    Unlike liquids, for crystalline solids the surface tension is known to be different from the surface energy. However, the same cannot be said conclusively for amorphous materials like soft cross-linked elastomers. To resolve this issue we have introduced here a direct method for measuring solid–liquid interfacial tension by using the curved surface of a solid. In essence, we have used the inner surface of tiny cylindrical channels embedded inside a soft elastomeric film for sensing the effect of the interfacial tension. When a liquid is inserted into the channel, because of wetting-induced alteration in interfacial tension, its thin wall deflects considerably; the deflection is measured with an optical profilometer and analyzed using the Föppl–von Kármán equation. We have used several liquids and cross-linked poly(dimethylsiloxane) as the solid to show that the estimated values of the solid–liquid interfacial tension matches with the corresponding solid–liquid interfacial energy reasonably well. PMID:26420871

  3. Accuracy of surface tension measurement from drop shapes: the role of image analysis.

    PubMed

    Kalantarian, Ali; Saad, Sameh M I; Neumann, A Wilhelm

    2013-11-01

    Axisymmetric Drop Shape Analysis (ADSA) has been extensively used for surface tension measurement. In essence, ADSA works by matching a theoretical profile of the drop to the extracted experimental profile, taking surface tension as an adjustable parameter. Of the three main building blocks of ADSA, i.e. edge detection, the numerical integration of the Laplace equation for generating theoretical curves and the optimization procedure, only edge detection (that extracts the drop profile line from the drop image) needs extensive study. For the purpose of this article, the numerical integration of the Laplace equation for generating theoretical curves and the optimization procedure will only require a minor effort. It is the aim of this paper to investigate how far the surface tension accuracy of drop shape techniques can be pushed by fine tuning and optimizing edge detection strategies for a given drop image. Two different aspects of edge detection are pursued here: sub-pixel resolution and pixel resolution. The effect of two sub-pixel resolution strategies, i.e. spline and sigmoid, on the accuracy of surface tension measurement is investigated. It is found that the number of pixel points in the fitting procedure of the sub-pixel resolution techniques is crucial, and its value should be determined based on the contrast of the image, i.e. the gray level difference between the drop and the background. On the pixel resolution side, two suitable and reliable edge detectors, i.e. Canny and SUSAN, are explored, and the effect of user-specified parameters of the edge detector on the accuracy of surface tension measurement is scrutinized. Based on the contrast of the image, an optimum value of the user-specified parameter of the edge detector, SUSAN, is suggested. Overall, an accuracy of 0.01mJ/m(2) is achievable for the surface tension determination by careful fine tuning of edge detection algorithms.

  4. Controlling the Motion of Ferrofluid Droplets Using Surface Tension Gradients and Magnetoviscous Pinning.

    PubMed

    Ody, T; Panth, M; Sommers, A D; Eid, K F

    2016-07-12

    This work demonstrates the controlled motion and stopping of individual ferrofluid droplets due to a surface tension gradient and a uniform magnetic field. The surface tension gradients are created by patterning hydrophilic aluminum regions, shaped as wedges, on a hydrophobic copper surface. This pattern facilitates the spontaneous motion of water-based ferrofluid droplets down the length of the wedge toward the more hydrophilic aluminum end due to a net capillarity force created by the underlying surface wettability gradient. We observed that applying a magnetic field parallel to the surface tension gradient direction has little or no effect on the droplet's motion, while a moderate perpendicular magnetic field can stop the motion altogether effectively "pinning" the droplet. In the absence of the surface tension gradient, droplets elongate in the presence of a parallel field but do not travel. This control of the motion of individual droplets might lend itself to some biomedical and lab-on-a-chip applications. The directional dependence of the magnetoviscosity observed in this work is believed to be the consequence of the formation of nanoparticle chains in the fluid due to the existence of a minority of relatively larger magnetic particles.

  5. Surface Tension Driven Convection Experiment-2 (STDCE-2. )

    NASA Technical Reports Server (NTRS)

    Ostrach, Simon; Kamotani, Yasuhiro

    1996-01-01

    The surface tension driven convection experiment-2 (STDCE-2) was conducted onboard the U.S. Microgravity Laboratory (USML)-2 Spacelab which was launched on October 20, 1995. The main objectives of the experiment was to study oscillatory thermocapillary flows in microgravity. Thermocapillary flows were generated in cylindrical test chambers filled with 2 centistokes silicone oil. Six modules were used to study three different chamber diameters and two different heating modes. Tests with both flat and curved free surfaces were conducted. The flow field was studied by flow visualization and an infrared imaging system recorded the oil free-surface temperature. An optical (Ronchi) system was used to measure the oil free-surface deformation and motions. A total of 55 tests were conducted and oscillations were found in most of them. The data are being analyzed.

  6. Surface tension and quasi-emulsion of cavitation bubble cloud.

    PubMed

    Bai, Lixin; Chen, Xiaoguang; Zhu, Gang; Xu, Weilin; Lin, Weijun; Wu, Pengfei; Li, Chao; Xu, Delong; Yan, Jiuchun

    2017-03-01

    A quasi-emulsion phenomenon of cavitation structure in a thin liquid layer (the thin liquid layer is trapped between a radiating surface and a hard reflector) is investigated experimentally with high-speed photography. The transformation from cloud-in-water (c/w) emulsion to water-in-cloud (w/c) emulsion is related to the increase of cavitation bubble cloud. The acoustic field in the thin liquid layer is analyzed. It is found that the liquid region has higher acoustic pressure than the cloud region. The bubbles are pushed from liquid region to cloud region by the primary Bjerknes forces. The rate of change of CSF increased with the increase of CSF. The cavitation bubbles on the surface of cavitation cloud are attracted by the cavitation bubbles inside the cloud due to secondary Bjerknes forces. The existence of surface tension on the interface of liquid region and cloud region is proved. The formation mechanism of disc-shaped liquid region and cloud region are analysed by surface tension and incompressibility of cavitation bubble cloud.

  7. Casimir force and its relation to surface tension

    NASA Astrophysics Data System (ADS)

    Høye, J. S.; Brevik, I.

    2017-05-01

    From energy considerations there is reason to expect that the work done by Casimir forces during a slow displacement of the parallel plates reflects the free energy of the surface tension of the adjacent surfaces. We show this explicitly, for a one-component ionic fluid or plasma with qc as ionic charge, where the particles are neutralized by a uniform continuous oppositely charged background. For two equal half-planes, the surface-associated free energy for one half-plane turns out to be just one half of the total Casimir energy for the conventional Casimir setup. We also comment, from a wider perspective, on the intriguing possibility that knowledge about the magnitude of the surface tension coefficient obtained from statistical mechanics or experiments may give insight into the value of the conventional cutoff time-splitting parameter τ =t -t' occurring in quantum field theory. A simple analysis suggests that the minimal distance τ c is of the order of atomic dimensions, which is a physically natural result.

  8. Synthetic Tracheal Mucus with Native Rheological and Surface Tension Properties

    PubMed Central

    Hamed, R.; Fiegel, J.

    2016-01-01

    In this study the development of a model tracheal mucus with chemical composition and physical properties (bulk viscoelasticity and surface tension) matched to that of native tracheal mucus is described. The mucus mimetics were formulated using components that are abundant in tracheal mucus (glycoproteins, proteins, lipids, ions and water) at concentrations similar to those found natively. Pure solutions were unable to achieve the gel behavior observed with native mucus. The addition of a bi-functional crosslinking agent enabled control over the viscoelastic properties of the mucus mimetics by tailoring the concentration of the crosslinking agent and the duration of crosslinking. Three mucus mimetic formulations with different bulk viscoelastic properties, all within the normal range for non-diseased tracheal mucus, were chosen for investigation of surfactant spreading at the air-mimetic interface. Surfactant spread quickly and completely on the least viscoelastic mimetic surface, enabling the surface tension of the mimetic to be lowered to match native tracheal mucus. However, surfactant spreading on the more viscoelastic mimetics was hindered, suggesting that the bulk properties of the mimetics dictate the range of surface properties that can be achieved. PMID:23813841

  9. On simulating lipid bilayers with an applied surface tension: periodic boundary conditions and undulations.

    PubMed Central

    Feller, S E; Pastor, R W

    1996-01-01

    As sketched in Fig. 1, a current molecular dynamics computer simulation of a lipid bilayer fails to capture significant features of the macroscopic system, including long wavelength undulations. Such fluctuations are intrinsically connected to the value of the macroscopic (or thermodynamic) surface tension (cf. Eqs. 1 and 9; for a related treatment, see Brochard et al., 1975, 1976). Consequently, the surface tension that might be evaluated in an MD simulation should not be expected to equal the surface tension obtained from macroscopic measurements. Put another way, the largest of the three simulations presented here contained over 16,000 atoms and required substantial computer time to complete, but modeled a system of only 36 lipids per side. From this perspective it is not surprising that the system is not at the thermodynamic limit. An important practical consequence of this effect is that simulations with fluctuating area should be carried out with a nonzero applied surface tension (gamma 0 of Fig. 2) even when the macroscopic tension is zero, or close to zero. Computer simulations at fixed surface area, which can explicitly determine pressure anisotropy at the molecular level, should ultimately lend insight into the value of gamma 0, including its dependence on lipid composition and other membrane components. As we have noted and will describe further in separate publications (Feller et al., 1996; Feller et al., manuscript in preparation), surface tensions obtained from simulations can be distorted by inadequate initial conditions and convergence, and are sensitive to potential energy functions, force truncation methods, and system size; it is not difficult, in fact, to tune terms in the potential energy function so as to yield surface tensions close to zero. This is why parameters should be tested extensively on simpler systems, for example, monolayers. The estimates of gamma 0 that we have presented here should be regarded as qualitative, and primarily

  10. Surface tension and the mechanics of liquid inclusions in compliant solids

    NASA Astrophysics Data System (ADS)

    Style, Robert W.; Wettlaufer, John S.; Dufresne, Eric R.

    Eshelby's theory of inclusions has wide-reaching implications across the mechanics of materials and structures including the theories of composites, fracture, and plasticity. However, it does not include the effects of surface stress, which has recently been shown to control many processes in soft materials such as gels, elastomers and biological tissue. To extend Eshelby's theory of inclusions to soft materials, we consider liquid inclusions within an isotropic, compressible, linear-elastic solid. We solve for the displacement and stress fields around individual stretched inclusions, accounting for the bulk elasticity of the solid and the surface tension (\\textit{i.e.} isotropic strain-independent surface stress) of the solid-liquid interface. Surface tension significantly alters the inclusion's shape and stiffness as well as its near- and far-field stress fields. These phenomenon depend strongly on the ratio of inclusion radius, $R$, to an elastocapillary length, $L$. Surface tension is significant whenever inclusions are smaller than $100L$. While Eshelby theory predicts that liquid inclusions generically reduce the stiffness of an elastic solid, our results show that liquid inclusions can actually stiffen a solid when $R<3L/2$. Intriguingly, surface tension cloaks the far-field signature of liquid inclusions when $R=3L/2$. These results are have far-reaching applications from measuring local stresses in biological tissue, to determining the failure strength of soft composites.

  11. Surface tension and the mechanics of liquid inclusions in compliant solids.

    PubMed

    Style, Robert W; Wettlaufer, John S; Dufresne, Eric R

    2015-01-28

    Eshelby's theory of inclusions has wide-reaching implications across the mechanics of materials and structures including the theories of composites, fracture, and plasticity. However, it does not include the effects of surface stress, which has recently been shown to control many processes in soft materials such as gels, elastomers and biological tissue. To extend Eshelby's theory of inclusions to soft materials, we consider liquid inclusions within an isotropic, compressible, linear-elastic solid. We solve for the displacement and stress fields around individual stretched inclusions, accounting for the bulk elasticity of the solid and the surface tension (i.e. isotropic strain-independent surface stress) of the solid-liquid interface. Surface tension significantly alters the inclusion's shape and stiffness as well as its near- and far-field stress fields. These phenomena depend strongly on the ratio of the inclusion radius, R, to an elastocapillary length, L. Surface tension is significant whenever inclusions are smaller than 100L. While Eshelby theory predicts that liquid inclusions generically reduce the stiffness of an elastic solid, our results show that liquid inclusions can actually stiffen a solid when R<3L/2. Intriguingly, surface tension cloaks the far-field signature of liquid inclusions when R=3L/2. These results are have far-reaching applications from measuring local stresses in biological tissue, to determining the failure strength of soft composites.

  12. Communication: Slab thickness dependence of the surface tension: toward a criterion of liquid sheets stability.

    PubMed

    Filippini, G; Bourasseau, E; Ghoufi, A; Goujon, F; Malfreyt, P

    2014-08-28

    Microscopic Monte Carlo simulations of liquid sheets of copper and tin have been performed in order to study the dependence of the surface tension on the thickness of the sheet. It results that the surface tension is constant with the thickness as long as the sheet remains in one piece. When the sheet is getting thinner, holes start to appear, and the calculated surface tension rapidly decreases with thickness until the sheet becomes totally unstable and forms a cylinder. We assume here that this decrease is not due to a confinement effect as proposed by Werth et al. [Physica A 392, 2359 (2013)] on Lennard-Jones systems, but to the appearance of holes that reduces the energy cost of the surface modification. We also show in this work that a link can be established between the stability of the sheet and the local fluctuations of the surface position, which directly depends on the value of the surface tension. Finally, we complete this study by investigating systems interacting through different forms of Lennard-Jones potentials to check if similar conclusions can be drawn.

  13. Test-area surface tension calculation of the graphene-methane interface: Fluctuations and commensurability

    NASA Astrophysics Data System (ADS)

    d'Oliveira, H. D.; Davoy, X.; Arche, E.; Malfreyt, P.; Ghoufi, A.

    2017-06-01

    The surface tension (γ) of methane on a graphene monolayer is calculated by using the test-area approach. By using a united atom model to describe methane molecules, strong fluctuations of surface tension as a function of the surface area of the graphene are evidenced. In contrast with the liquid-vapor interfaces, the use of a larger cutoff does not fully erase the fluctuations in the surface tension. Counterintuitively, the description of methane and graphene from the Optimized Potentials for Liquid Simulations all-atom model and a flexible model, respectively, led to a lessening in the surface tension fluctuations. This result suggests that the origin of fluctuations in γ is due to a model-effect rather than size-effects. We show that the molecular origin of these fluctuations is the result of a commensurable organization between both graphene and methane. This commensurable structure can be avoided by describing methane and graphene from a flexible force field. Although differences in γ with respect to the model have been often reported, it is the first time that the model drastically affects the physics of a system.

  14. Surface tension mediated conversion of light to work.

    PubMed

    Okawa, David; Pastine, Stefan J; Zettl, Alex; Fréchet, Jean M J

    2009-04-22

    As energy demands increase, new, more direct, energy collection and utilization processes must be explored. We present a system that intrinsically combines the absorption of sunlight with the production of useful work in the form of locomotion of objects on liquids. Focused sunlight is locally absorbed by a nanostructured composite, creating a thermal surface tension gradient and, subsequently, motion. Controlled linear motion and rotational motion are demonstrated. The system is scale independent, with remotely powered and controlled motion shown for objects in the milligram to tens of grams range.

  15. Surface tension of phenol-formaldehyde wood adhesives

    Treesearch

    C. -Y. Hse

    1972-01-01

    Thirty-six phenol (P) fermaldehyde (F) resins were formulated to complete a factorial arrangement: three NAOH/P molar ratios (0.4, 0.7, and 1.0), three solid contents (37, 40, and 43 percent), and four F/P molar rations (1.6, 1.9, 2.2, and 2.5). Surface tension ranged from 68.4 to 79.9 dynes/cm. and was affected most by NAOH/P ratio, next by F/P ratio, and least by...

  16. Flow rate analysis of a surface tension driven passive micropump.

    PubMed

    Berthier, Erwin; Beebe, David J

    2007-11-01

    A microfluidic passive pumping method relying on surface tension properties is investigated and a physical model is developed. When a small inlet drop is placed on the entrance of a microfluidic channel it creates more pressure than a large output drop at the channel exit, causing fluid flow. The behavior of the input drop occurs in two characteristic phases. An analytical solution is proposed and verified by experimental results. We find that during the first phase the flow rate is stable and that this phase can be prolonged by refilling the inlet drop to produce continuous flow in the microchannel.

  17. Drop formation by thermal fluctuations at an ultralow surface tension.

    PubMed

    Hennequin, Y; Aarts, D G A L; van der Wiel, J H; Wegdam, G; Eggers, J; Lekkerkerker, H N W; Bonn, Daniel

    2006-12-15

    We present experimental evidence that drop breakup is caused by thermal noise in a system with a surface tension that is more than 10(6) times smaller than that of water. We observe that at very small scales classical hydrodynamics breaks down and the characteristic signatures of pinch-off due to thermal noise are observed. Surprisingly, the noise makes the drop size distribution more uniform, by suppressing the formation of satellite droplets of the smallest sizes. The crossover between deterministic hydrodynamic motion and stochastic thermally driven motion has repercussions for our understanding of small-scale hydrodynamics, important in many problems such as micro- or nanofluidics and interfacial singularities.

  18. Restraint of Liquid Jets by Surface Tension in Microgravity Modeled

    NASA Technical Reports Server (NTRS)

    Chato, David J.

    2001-01-01

    Tension in Microgravity Modeled Microgravity poses many challenges to the designer of spacecraft tanks. Chief among these are the lack of phase separation and the need to supply vapor-free liquid or liquidfree vapor to the spacecraft processes that require fluid. One of the principal problems of phase separation is the creation of liquid jets. A jet can be created by liquid filling, settling of the fluid to one end of the tank, or even closing a valve to stop the liquid flow. Anyone who has seen a fountain knows that jets occur in normal gravity also. However, in normal gravity, the gravity controls and restricts the jet flow. In microgravity, with gravity largely absent, jets must be contained by surface tension forces. Recent NASA experiments in microgravity (Tank Pressure Control Experiment, TPCE, and Vented Tank Pressure Experiment, VTRE) resulted in a wealth of data about jet behavior in microgravity. VTRE was surprising in that, although it contained a complex geometry of baffles and vanes, the limit on liquid inflow was the emergence of a liquid jet from the top of the vane structure. Clearly understanding the restraint of liquid jets by surface tension is key to managing fluids in low gravity. To model this phenomenon, we need a numerical method that can track the fluid motion and the surface tension forces. The fluid motion is modeled with the Navier-Stokes equation formulated for low-speed incompressible flows. The quantities of velocity and pressure are placed on a staggered grid, with velocity being tracked at cell faces and pressure at cell centers. The free surface is tracked via the introduction of a color function that tracks liquid as 1/2 and gas as -1/2. A phase model developed by Jacqmin is used. This model converts the discrete surface tension force into a barrier function that peaks at the free surface and decays rapidly. Previous attempts at this formulation have been criticized for smearing the interface. However, by sharpening the phase

  19. The effect of vesicle shape, line tension, and lateral tension on membrane-binding proteins

    NASA Astrophysics Data System (ADS)

    Hutchison, Jaime B.

    Model membranes allow for the exploration of complex biological phenomena with simple, controllable components. In this thesis we employ model membranes to determine the effect of vesicle properties such as line tension, lateral tension, and shape on membrane-binding proteins. We find that line tension at the boundary between domains in a phase separated vesicle can accumulate model membrane-binding proteins (green fluorescent protein with a histidine tag), and that those proteins can, in turn, alter vesicle shape. These results suggest that domains in biological membranes may enhance the local concentration of membrane-bound proteins and thus alter protein function. We also explore how membrane mechanical and chemical properties alter the function of the N-BAR domain of amphiphysin, a membrane-binding protein implicated in endocytosis. We find that negatively charged lipids are necessary for N-BAR binding to membranes at detectable levels, and that, at least for some lipid species, binding may be cooperative. Measurements of N-BAR binding as a function of vesicle tension reveal that modest membrane tension of around 2 mN/m, corresponding to a strain of around 1%, strongly increases N-BAR binding. We attribute this increase in binding with tension to the insertion of N-BAR's N-terminal amphipathic helix into the membrane which increases the membrane area. We propose that N-BAR, which was previously described as being able to sense membrane curvature, may be sensing strain instead. Measurements of membrane deformation by N-BAR as a function of membrane tension reveal that tension can hinder membrane deformation. Thus, tension may favor N-BAR binding yet suppress membrane deformation/tubulation, which requires work against tension. These results suggest that membrane tension, a parameter that is often not controlled in model membranes but is tightly controlled in biological cells, may be important in regulating protein binding and assembly and, hence, protein

  20. Surface tension and orthobaric densities for vibrating square well dumbbells. I.

    PubMed

    Chapela, Gustavo A; Alejandre, José

    2010-03-14

    Surface tensions and liquid-vapor orthobaric densities are calculated for a wide variety of vibrating square well dumbbells using discontinuous molecular dynamics simulations. The size of the vibration well, the elongation or bond distance of the two particles of the dumbbell, the asymmetry in size (and interaction range) of the two particles, and the depth of the interaction well are the variables whose effects are systematically evaluated in this work. Extensive molecular dynamics simulations were carried out and the orthobaric liquid-vapor densities are compared with those obtained previously by other authors using different methods of simulation for rigid and vibrating square well dumbbells. Surface tension values are reported for the first time for homonuclear and heteronuclear vibrating square well dumbbells as well as for all the simulated series. The molecular dynamics results of tangent homonuclear dumbbells are compared with those from Monte Carlo simulations also obtained in this work, as a way of checking the order of magnitude of the molecular dynamics results. The size of the vibration well is shown to have a small influence on the resulting properties. Decreasing elongation and the size of the second particle increase critical temperatures, liquid densities, and surface tensions. Moderate increases in the depth of the interaction well have the same effect. For larger asymmetries of the depth of the interaction well on the dumbbell particles, a strong association phenomenon is observed and the main effects are a maximum on the critical temperature for increasing well depth and a decrease in the surface tension.

  1. A thermodynamical model for the surface tension of silicate melts in contact with H2O gas

    USGS Publications Warehouse

    Colucci, Simone; Battaglia, Maurizio; Trigila, Raffaello

    2016-01-01

    Surface tension plays an important role in the nucleation of H2O gas bubbles in magmatic melts and in the time-dependent rheology of bubble-bearing magmas. Despite several experimental studies, a physics based model of the surface tension of magmatic melts in contact with H2O is lacking. This paper employs gradient theory to develop a thermodynamical model of equilibrium surface tension of silicate melts in contact with H2O gas at low to moderate pressures. In the last decades, this approach has been successfully applied in studies of industrial mixtures but never to magmatic systems. We calibrate and verify the model against literature experimental data, obtained by the pendant drop method, and by inverting bubble nucleation experiments using the Classical Nucleation Theory (CNT). Our model reproduces the systematic decrease in surface tension with increased H2O pressure observed in the experiments. On the other hand, the effect of temperature is confirmed by the experiments only at high pressure. At atmospheric pressure, the model shows a decrease of surface tension with temperature. This is in contrast with a number of experimental observations and could be related to microstructural effects that cannot be reproduced by our model. Finally, our analysis indicates that the surface tension measured inverting the CNT may be lower than the value measured by the pendant drop method, most likely because of changes in surface tension controlled by the supersaturation.

  2. A thermodynamical model for the surface tension of silicate melts in contact with H2O gas

    NASA Astrophysics Data System (ADS)

    Colucci, Simone; Battaglia, Maurizio; Trigila, Raffaello

    2016-02-01

    Surface tension plays an important role in the nucleation of H2O gas bubbles in magmatic melts and in the time-dependent rheology of bubble-bearing magmas. Despite several experimental studies, a physics based model of the surface tension of magmatic melts in contact with H2O is lacking. This paper employs gradient theory to develop a thermodynamical model of equilibrium surface tension of silicate melts in contact with H2O gas at low to moderate pressures. In the last decades, this approach has been successfully applied in studies of industrial mixtures but never to magmatic systems. We calibrate and verify the model against literature experimental data, obtained by the pendant drop method, and by inverting bubble nucleation experiments using the Classical Nucleation Theory (CNT). Our model reproduces the systematic decrease in surface tension with increased H2O pressure observed in the experiments. On the other hand, the effect of temperature is confirmed by the experiments only at high pressure. At atmospheric pressure, the model shows a decrease of surface tension with temperature. This is in contrast with a number of experimental observations and could be related to microstructural effects that cannot be reproduced by our model. Finally, our analysis indicates that the surface tension measured inverting the CNT may be lower than the value measured by the pendant drop method, most likely because of changes in surface tension controlled by the supersaturation.

  3. New thermodynamics for evaluating the surface-phase enrichment in the lower surface tension component.

    PubMed

    Santos, M Soledade C S; Reis, João Carlos R

    2014-09-15

    Regarding the surface phase of liquid mixtures as a thermodynamic phase, ideal surface phases are designed so that at fixed bulk-phase composition, real and ideal surface phases have the same chemical composition and identical limiting slopes for the dependence of surface tension on mole fraction. Standard chemical potentials are introduced for surface phase components, and quasi-exact expressions are worked out to compute ideal surface tensions and surface-phase compositions of real liquid mixtures. Guidelines for choosing molecular models to estimate the molar surface area of pure constituents are given. Ideal and excess surface tensions are calculated by using literature data for aqueous ethanol solutions at 298 K. These results show treatment based on Butler's equations grossly overestimate predicted surface tensions, thus leading to lower ethanol content in the surface phase. These inaccuracies are ascribed to the use of molar surface areas in model equations that are too small. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  4. Crack-mouth displacements for semielliptical surface cracks subjected to remote tension and bending loads

    NASA Technical Reports Server (NTRS)

    Raju, Ivatury S.; Newman, James C., Jr.; Atluri, Satya N.

    1992-01-01

    The exact analytical solution for an embedded elliptical crack in an infinite body subjected to arbitrary loading was used in conjunction with the finite element alternating method to obtain crack-mouth-opening displacements (CMOD) for surface cracks in finite plates subjected to remote tension. Identical surface-crack configurations were also analyzed with the finite element method using 20-noded element for plates subjected to both remote tension and bending. The CMODs from these two methods generally agreed within a few percent of each other. Comparisons made with experimental results obtained from surface cracks in welded aluminum alloy specimens subjected to tension also showed good agreement. Empirical equations were developed for CMOD for a wide range of surface-crack shapes and sizes subjected to tension and bending loads. These equations were obtained by modifying the Green-Sneddon exact solution for an elliptical crack in an infinite body to account for finite boundary effects. These equations should be useful in monitoring surface-crack growth in tests and in developing complete crack-face-displacement equations for use in three-dimensional weight-function methods.

  5. Crack-mouth displacements for semielliptical surface cracks subjected to remote tension and bending loads

    NASA Technical Reports Server (NTRS)

    Raju, Ivatury S.; Newman, James C., Jr.; Atluri, Satya N.

    1992-01-01

    The exact analytical solution for an embedded elliptical crack in an infinite body subjected to arbitrary loading was used in conjunction with the finite element alternating method to obtain crack-mouth-opening displacements (CMOD) for surface cracks in finite plates subjected to remote tension. Identical surface-crack configurations were also analyzed with the finite element method using 20-noded element for plates subjected to both remote tension and bending. The CMODs from these two methods generally agreed within a few percent of each other. Comparisons made with experimental results obtained from surface cracks in welded aluminum alloy specimens subjected to tension also showed good agreement. Empirical equations were developed for CMOD for a wide range of surface-crack shapes and sizes subjected to tension and bending loads. These equations were obtained by modifying the Green-Sneddon exact solution for an elliptical crack in an infinite body to account for finite boundary effects. These equations should be useful in monitoring surface-crack growth in tests and in developing complete crack-face-displacement equations for use in three-dimensional weight-function methods.

  6. Liquid drops and surface tension with smoothed particle applied mechanics

    NASA Astrophysics Data System (ADS)

    Nugent, S.; Posch, H. A.

    2000-10-01

    Smoothed particle applied mechanics (SPAM), also referred to as smoothed particle hydrodynamics, is a Lagrangian particle method for the simulation of continuous flows. Here we apply it to the formation of a liquid drop, surrounded by its vapor, for a van der Waals (vdW) fluid in two dimensions. The cohesive pressure of the vdW equation of state gives rise to an attractive, central force between the particles with an interaction range which is assumed to exceed the interaction range of all the other smoothed forces in the SPAM equations of motion. With this assumption, stable drops are formed, and the vdW phase diagram is well reproduced by the simulations. Below the critical temperature, the surface tension for equilibrated drops may be computed from the pressure excess in their centers. It agrees very well with the surface tension independently determined from the vibrational frequency of weakly excited drops. We also study strongly deformed drops performing large-amplitude oscillations, which are reminiscent of the oscillations of a large ball of water under microgravity conditions. In an appendix we comment on the limitations of SPAM by studying the violation of angular momentum conservation, which is a consequence of noncentral forces contributed by the full Newtonian viscous stress tensor.

  7. Effects of neutral posture on muscle tension during computer use.

    PubMed

    Dowler, E; Kappes, B; Fenaughty, A; Pemberton, G

    2001-01-01

    This study focused on developing a new approach to seated work positions was conducted on 67 office workers who use a Visual Display Terminal (VDT) as a major function of their working day. Muscle tension was measured by surface electromyography (sEMG) while participants were asked to adopt 4 selected working postures. Pain was measured before and after ergonomic intervention on the Nordic scale, which was modified for this study. Adjustable workstations were used to place participants in desired positions during the clinical testing sessions and the extended intervention period. Results indicate the effects of this ergonomic intervention may have positive effects on muscle tension and pain, significant enough to encourage employers to implement training and workstation modifications following these guidelines.

  8. Surface tension and contact with soft elastic solids

    NASA Astrophysics Data System (ADS)

    Style, Robert W.; Hyland, Callen; Boltyanskiy, Rostislav; Wettlaufer, John S.; Dufresne, Eric R.

    2013-11-01

    The Johnson-Kendall-Roberts theory is the basis of modern contact mechanics. It describes how two deformable objects adhere together, driven by adhesion energy and opposed by elasticity. Here we characterize the indentation of glass particles into soft, silicone substrates using confocal microscopy. We show that, whereas the Johnson-Kendall-Roberts theory holds for particles larger than a critical, elastocapillary lengthscale, it fails for smaller particles. Instead, adhesion of small particles mimics the adsorption of particles at a fluid interface, with a size-independent contact angle between the undeformed surface and the particle given by a generalized version of the Young's law. A simple theory quantitatively captures this behaviour and explains how solid surface tension dominates elasticity for small-scale indentation of soft materials.

  9. Interfacial tension and surface elasticity of carbon black (CB) covered oil-water interface.

    PubMed

    Powell, Kristin Conrad; Chauhan, Anuj

    2014-10-21

    Carboxyl-terminated carbon black (CB) particles have been proposed as readily available, biocompatible dispersants to stabilize oil-in-water emulsions after an oil spill. Since the reduction in interfacial tension and the increase in interfacial elasticity are the key parameters which relate interfacial mechanics to emulsion stability, this investigation explores the effect of CB adsorption and surface coverage on oil-water interfacial tension and elasticity. Flocculation of CB was explored as ionic strength was increased from 0 to 0.6 M, approximately the salinity of seawater. As salinity increases, CB aggregates into larger particles from 100 nm to 6 μm. The interfacial tension and dilational viscoelasticity were measured for two systems: a drop of a CB suspension in oil and an inverted oil drop in a CB suspension. For the arrangement of a CB suspension drop in oil, most of the CB settles and accumulates toward the bottom of the drop with only small surface adsorption and no appreciable effect is observed on the dynamic interfacial tension or the dilational viscoelasticity. On reversing the arrangement to an inverted oil drop in CB suspension and increasing the convection of the outer phase, the surface coverage increases considerably. The CB coverage becomes more uniform with higher convection with an average value of approximately 2.6 g/m(2), which is representative of the coverage in Pickering emulsions stabilized by CB particles. The CB coverage decreases the surface tension from about 30 to 8.5 mN/m accompanied by an increase in the surface elasticity to 20.7 mN/m. The sharp contrast between the results from the CB suspension drop and the oil drop could be partially due to the effect of the wetting characteristics of the particles or due to the significant differences between the convection in the two cases.

  10. Exploration of turbulence/surface tension interaction through direct numerical simulation

    NASA Astrophysics Data System (ADS)

    McCaslin, Jeremy; Desjardins, Olivier

    2014-11-01

    Two canonical multiphase flows are constructed that provide a platform for a statistical description of surface tension effects on a surrounding turbulent flow field. In the first flow, short-time behavior is studied by inserting an initially flat interface into a triply periodic box of decaying homogeneous isotropic turbulence (HIT). Long-time behavior is studied in the second flow by inserting a randomly distributed interface into forced HIT. Simulations are performed for a variety of turbulent Reynolds and Weber numbers, including an infinite Weber number (no surface tension), on mesh sizes ranging from 2563 to 10243. The interaction between fluid inertia and the surface tension force is isolated by utilizing unity density and viscosity ratios. The probability density function of principal curvature and global interface statistics are presented and discussed, highlighting the importance of the Kolmogorov critical radius on the spatial scales of interfacial corrugations that form. A spectral analysis of energy transfer is conducted, shedding light on the role played by surface tension in this process.

  11. Surface tension and a self-consistent theory of soft composite solids with elastic inclusions.

    PubMed

    Mancarella, Francesco; Wettlaufer, John S

    2017-02-07

    The importance of surface tension effects is being recognized in the context of soft composite solids, where they are found to significantly affect the mechanical properties, such as the elastic response to an external stress. It has recently been discovered that Eshelby's inclusion theory breaks down when the inclusion size approaches the elastocapillary length L≡γ/E, where γ is the inclusion/host surface tension and E is the host Young's modulus. Extending our recent results for liquid inclusions, here we model the elastic behavior of a non-dilute distribution of isotropic elastic spherical inclusions in a soft isotropic elastic matrix, subject to a prescribed infinitesimal far-field loading. Within our framework, the composite stiffness is uniquely determined by the elastocapillary length L, the spherical inclusion radius R, and the stiffness contrast parameter C, which is the ratio of the inclusion to the matrix stiffness. We compare the results with those from the case of liquid inclusions, and we derive an analytical expression for elastic cloaking of the composite by the inclusions. Remarkably, we find that the composite stiffness is influenced significantly by surface tension even for inclusions two orders of magnitude more stiff than the host matrix. Finally, we show how to simultaneously determine the surface tension and the inclusion stiffness using two independent constraints provided by global and local measurements.

  12. Size dependence of the surface tension of a free surface of an isotropic fluid

    NASA Astrophysics Data System (ADS)

    Burian, Sergii; Isaiev, Mykola; Termentzidis, Konstantinos; Sysoev, Vladimir; Bulavin, Leonid

    2017-06-01

    We report on the size dependence of the surface tension of a free surface of an isotropic fluid. The size dependence of the surface tension is evaluated based on the Gibbs-Tolman-Koenig-Buff equation for positive and negative values of curvatures and the Tolman lengths. For all combinations of positive and negative signs of curvature and the Tolman length, we succeed to have a continuous function, avoiding the existing discontinuity at zero curvature (flat interfaces). As an example, a water droplet in the thermodynamical equilibrium with the vapor is analyzed in detail. The size dependence of the surface tension and the Tolman length are evaluated with the use of experimental data of the International Association for the Properties of Water and Steam. The evaluated Tolman length of our approach is in good agreement with molecular dynamics and experimental data.

  13. Analysis of surface tension driven flow in floating zone melting

    NASA Technical Reports Server (NTRS)

    Chang, C. E.; Wilcox, W. R.

    1976-01-01

    Surface tension driven flow in a cylindrical melt suspended between two rods was investigated by numerical solution of the steady state differential equations for heat and momentum transfer. Radiation heating and electron beam heating were considered approximately. For small values of the driving force, one rotating ring was formed in the top half of the zone, and its mirror image in the bottom half. At larger driving forces, secondary cells form which probably would undergo oscillatory motion. The influence of Prandtl number, zone movement, and buoyancy on the convection was also studied. The primary resistance to mass transfer in the laminar regime was in the center of the zone rather than at the solid-liquid interfaces.

  14. The wave numbers of supercritical surface tension driven Benard convection

    NASA Technical Reports Server (NTRS)

    Koschmieder, E. L.; Switzer, D. W.

    1991-01-01

    The cell size or the wave numbers of supercritical hexagonal convection cells in primarily surface tension driven convection on a uniformly heated plate was studied experimentally in thermal equilibrium in thin layers of silicone oil of large aspect ratio. It was found that the cell size decreases with increased temperature difference in the slightly supercritical range, and that the cell size is unique within the experimental error. It was also observed that the cell size reaches a minimum and begins to increase at larger temperature differences. This reversal of the rate of change of the wave number with temperature difference is attributed to influences of buoyancy on the fluid motion. The consequences of buoyancy were tested with three fluid layers of different depth.

  15. Surface tension drawing of liquid from microplate capillary wells.

    PubMed

    Schwalb, Willem; Ng, Tuck Wah; Lye, Jonathan Kok Keung; Liew, Oi Wah; Cheong, Brandon Huey-Ping

    2012-01-01

    Pressure differentials are routinely used to actuate flow in capillaries. We advance here an alternative means of flow generation that capitalizes on the extension of a liquid bridge achieved by the drawing of a rod through the action of surface tension. This meets the exigencies of creating controllable flow using simpler and more compact means. We found the ability to generate controllable flow to be strongly affected by the liquid bridge sustaining features, and that the use of rod diameters larger than the capillary was more conducive. The extensional flow resulting from the rupture of the liquid bridge was also found to have a strong circulation component which facilitated mixing. The approach here is highly amenable for use in capillary well microplates which have significant advantages over standard microplates. The features of this approach offer usage possibilities in biochemical applications in the field, such as in the leukocyte cell adhesion and hemagglutination tests of blood samples.

  16. Experiment 6: Surface Tension Driven Convection Experiment-2 (STDCE-2)

    NASA Technical Reports Server (NTRS)

    Ostrach, Simon; Kamotani, Yasuhiro; Pline, Alexander D.

    1998-01-01

    Results are reported from the Second Surface Tension Driven Convection Experiment (STDCE-2) performed aboard the Second United States Microgravity Laboratory (USML-2), which flew as Space Shuttle mission STS-73 and launched on October 20, 1995. Oscillatory thermocapillary flows were investigated in open cylindrical containers filled with 2 centistokes kinematic viscosity (Pr=27 at 25 C) silicone oil. Two different heating modes were investigated in detail. The main objectives of the experiments were to determine the onset of oscillatory thermocapillary flow under highly reduced buoyancy and gravity conditions and to study the important features of the oscillatory flow. The onset conditions were determined in three different size containers (1.2-, 2-, and 3-cm diameter) and for various free surface shapes (flat and curved). Numerical and scaling analyses were also performed to understand the basic steady flows. The analysis shows that the main flow is viscous-dominated near the onset of oscillations. The onset conditions determined in the present experiments together with our earlier ground-based data show that one could not describe the oscillation phenomenon if the fluid free surface is assumed to be rigid. Therefore, a parameter representing free surface deformation was derived, and the data are shown to be correlated well by that parameter. The oscillation patterns and frequencies are also presented.

  17. Structural changes on the surface of tungsten foils under uniaxial tension

    NASA Astrophysics Data System (ADS)

    Korsukov, V. E.; Knyazev, S. A.; Butenko, P. N.; Gilyarov, V. L.; Korsukova, M. M.; Nyapshaev, I. A.; Obidov, B. A.

    2017-02-01

    A change in the surface morphology of recrystallized tungsten foil under the effect of uniaxial tension in ultrahigh vacuum is studied by low-energy electron diffraction and atomic force microscopy. It is found by using low-energy electron diffraction that on the foil surface consisting of separate blocks with dominant face (112), there is a turn in orientation of the structural blocks. The analysis of the topograms of different areas of the side surface of a broken sample, obtained by atomic force microscopy, enabled the association of changes in the atomic structure of the surface layers of foil with a change in its relief by mechanical action.

  18. Lubricant-Infused Surfaces for Low-Surface-Tension Fluids: Promise versus Reality.

    PubMed

    Sett, Soumyadip; Yan, Xiao; Barac, George; Bolton, Leslie W; Miljkovic, Nenad

    2017-10-06

    The past few decades have seen substantial effort for the design and manufacturing of hydrophobic structured surfaces for enhanced steam condensation in water-based applications. Such surfaces promote dropwise condensation and easy droplet removal. However, less priority has been given to applications utilizing low-surface-tension fluids as the condensate. Lubricant-infused surfaces (LISs) or slippery liquid-infused porous surfaces (SLIPSs) have recently been developed, where the atomically smooth, defect-free slippery surface leads to reduced pinning of water droplets and omniphobic characteristics. The remarkable results of LISs and SLIPSs with a range of working fluid droplets give hope of their viability with low-surface-tension condensates. However, the presence of the additional liquid in the form of lubricant brings other issues to consider. Here, in an effort to study the dropwise condensation potential of LISs and SLIPSs, we investigate the miscibility of a range of low-surface-tension fluids with widely used lubricants in LIS and SLIPS design. We consider a wide range of condensate surface tensions (12-73 mN/m) and different categories of lubricants with varied viscosities (5-2700 cSt), namely, fluorinated Krytox oils, hydrocarbon silicone oils, mineral oil, and ionic liquids. In addition, we use both theory and pendant drop experiments to predict the cloaking behavior of the lubricants and immiscible condensate working fluid pairs. Our work not only shows that careful attention must be paid to lubricant-condensate selection to create long-lasting LISs or SLIPSs but also develops lubricant selection design guidelines for stable LISs and SLIPSs for enhanced condensation in applications utilizing low-surface-tension working fluids.

  19. Dynamics of surface tension driven mixing of an alcohol droplet with water

    NASA Astrophysics Data System (ADS)

    Dandekar, Raj; Pant, Anurag; Puthenveettil, Baburaj

    2016-11-01

    We study the flow induced by the surface tension driven spreading of an ethanol droplet of radius rd on the surface of a 5mm water layer, visualizing the flow using aluminium flakes on the surface of the water layer with backlighting and high speed imaging. The concentration of tracer aluminium particles was found to have no effect on the scaling law for spreading.The drop,when brought in contact with the water surface causes a local depression in surface tension ,resulting in a thin circular region to expand radially outwards.We observe that the dimensionless radius of the expanding front (r* =r/rd) scales with the dimensionless time (t* = μ rd/ Δγ) , as r* t*1/4,where μ is the viscosity of water and Δγ is the surface tension difference between water and the ethanol droplet.A scaling analysis taking the viscous and the marangoni forces into account explains the observed scaling law.Our observations differ from that in the case of continuous alcohol supply where the observed scaling law is r* t*1/2. The expanding front radius reaches a maximum value and then decreases with time.

  20. The Behavior of Large Low Surface Tension Water Drops Falling at Terminal Velocity in Air.

    DTIC Science & Technology

    To study the behavior of large low surface tension drops in free fall a vertical wind tunnel was constructed. The tunnel is simple, but provides a...low turbulence (0.7%) flow which stably supports large water drops falling at terminal velocity. The influence of reduced surface tension on maximum...drop size, drop terminal velocity and drop shape was investigated. It was found that drops of low surface tension break up at a smaller size than

  1. Surface tension isotherms of the dioxane-acetone-water and glycerol-ethanol-water ternary systems

    NASA Astrophysics Data System (ADS)

    Dzhambulatov, R. S.; Dadashev, R. Kh.; Elimkhanov, D. Z.; Dadashev, I. N.

    2016-10-01

    The results of the experimental and theoretical studies of the concentration dependence of surface tension of aqueous solutions of the 1,4-dioxane-acetone-water and glycerol-ethanol-water ternary systems were given. The studies were performed by the hanging-drop method on a DSA100 tensiometer. The maximum error of surface tension was 1%. The theoretical models for calculating the surface tension of the ternary systems of organic solutions were analyzed.

  2. Design of a surface deformation measuring instrument for the Surface Tension Driven Convection Experiment (STDCE-2)

    NASA Technical Reports Server (NTRS)

    Stahl, H. Philip

    1993-01-01

    This final technical report covers the work accomplished (under NAG3-1300) from 1 October 1991 to 1 October 1993. The grant is a direct result of Dr. H. Philip Stahl's (of Rose-Hulman Institute of Technology) participation in the NASA/ASEE Summer Faculty Fellowship Program at NASA Lewis Research Center sponsored by Case Western Reserve University and the Ohio Aerospace Institute. The Surface Tension Driven Convection Experiment (STDCE) is a fundamental fluid physics experiment designed to provide quantitative data on the thermocapillary flow of fluid under the influence of an increased localized surface temperature. STDCE flew on the Space Shuttle Columbia in the First United States Microgravity Laboratory (USML-1) in June 1992. The second flight of this experiment (STDCE-2) is scheduled for 1995. The specific science objectives of STDCE-2 are to determine the extent and nature of thermocapillary flows, the effect of heating mode and level, the effect of the liquid free-surface shape, and the onset conditions for and nature of oscillatory flows. In order to satisfy one of these objectives, an instrument for measuring the shape of an air/oil free surface must be developed.

  3. Design of a surface deformation measuring instrument for the Surface Tension Driven Convection Experiment (STDCE-2)

    NASA Astrophysics Data System (ADS)

    Stahl, H. Philip

    1993-12-01

    This final technical report covers the work accomplished (under NAG3-1300) from 1 October 1991 to 1 October 1993. The grant is a direct result of Dr. H. Philip Stahl's (of Rose-Hulman Institute of Technology) participation in the NASA/ASEE Summer Faculty Fellowship Program at NASA Lewis Research Center sponsored by Case Western Reserve University and the Ohio Aerospace Institute. The Surface Tension Driven Convection Experiment (STDCE) is a fundamental fluid physics experiment designed to provide quantitative data on the thermocapillary flow of fluid under the influence of an increased localized surface temperature. STDCE flew on the Space Shuttle Columbia in the First United States Microgravity Laboratory (USML-1) in June 1992. The second flight of this experiment (STDCE-2) is scheduled for 1995. The specific science objectives of STDCE-2 are to determine the extent and nature of thermocapillary flows, the effect of heating mode and level, the effect of the liquid free-surface shape, and the onset conditions for and nature of oscillatory flows. In order to satisfy one of these objectives, an instrument for measuring the shape of an air/oil free surface must be developed.

  4. Wetting Angle and Surface Tension of Germanium Melts on Different Substrate Materials

    NASA Technical Reports Server (NTRS)

    Kaiser, N.; Croell, A.; Szofran, F. R.; Benz, K. W.; Rose, M. Franklin (Technical Monitor)

    2001-01-01

    The sessile drop technique has been used to measure the wetting angle and the surface tension of molten germanium (Ge) on various substrate materials. Sapphire, fused silica, glassy carbon, graphite, SiC, carbon-based aerogel, pyrolytic boron nitride (pBN), AlN, Si3N4, and CVD diamond were used as substrate materials. In addition, the effects of different cleaning procedures and surface treatments on the wetting behavior were investigated. The highest wetting angles with values around 170 deg. were found for pBN substrates under active vacuum or with a slight overpressure of 5N Argon or forming gas (2% Hydrogen in 5N Argon). The measurement of the surface tension and its temperature dependence for Ge under a forming gas atmosphere resulted in gamma(T) = 591 - 0.077 (T-T(sub m).

  5. Reduction of water surface tension significantly impacts gecko adhesion underwater.

    PubMed

    Stark, Alyssa Y; McClung, Brandon; Niewiarowski, Peter H; Dhinojwala, Ali

    2014-12-01

    The gecko adhesive system is dependent on weak van der Waals interactions that are multiplied across thousands of fine hair-like structures (setae) on geckos' toe pads. Due to the requirements of van der Waals forces, we expect that any interruption between the setae and substrate, such as a water layer, will compromise adhesion. Our recent results suggest, however, that the air layer (plastron) surrounding the superhydrophobic toe pads aid in expelling water at the contact interface and create strong shear adhesion in water when in contact with hydrophobic surfaces. To test the function of the air plastron, we reduced the surface tension of water using two surfactants, a charged anionic surfactant and a neutral nonionic surfactant. We tested geckos on three substrates: hydrophilic glass and two hydrophobic surfaces, glass with a octadecyl trichlorosilane self-assembled monolayer (OTS-SAM) and polytetrafluoroethylene (PTFE). We found that the anionic surfactant inhibited the formation of the air plastron layer and significantly reduced shear adhesion to all three substrates. Interestingly, the air plastron was more stable in the nonionic surfactant treatments than the anionic surfactant treatments and we found that geckos adhered better in the nonionic surfactant than in the anionic surfactant on OTS-SAM and PTFE but not on glass. Our results have implications for the evolution of a superhydrophobic toe pad and highlight some of the challenges faced in designing synthetic adhesives that mimic geckos' toes.

  6. Surface tension of water-alcohol mixtures from Monte Carlo simulations.

    PubMed

    Biscay, F; Ghoufi, A; Malfreyt, P

    2011-01-28

    Monte Carlo simulations are reported to predict the dependence of the surface tension of water-alcohol mixtures on the alcohol concentration. Alcohols are modeled using the anisotropic united atom model recently extended to alcohol molecules. The molecular simulations show a good agreement between the experimental and calculated surface tensions for the water-methanol and water-propanol mixtures. This good agreement with experiments is also established through the comparison of the excess surface tensions. A molecular description of the mixture in terms of density profiles and hydrogen bond profiles is used to interpret the decrease of the surface tension with the alcohol concentration and alcohol chain length.

  7. A Study of the Measurement of Surface and Interfacial Tension by the Maximum Liquid Drop Volume Method.

    PubMed

    Pu, Bingyin; Chen, Donghao

    2001-03-15

    The maximum liquid drop volume (v(max)) is measured by using a back-suction micrometer syringe piston technique. Different very viscous liquids are measured by (v(max)) and (v(f)) methods to observe the effect of viscosity on tension measurement. No apparent viscosity effect was observed in surface tension data obtained by using Harkins-Brown factors and the theoretical correction factors in the viscosity range 5.9-100,900 mP. Copyright 2001 Academic Press.

  8. Neutron-skin thickness determines the surface tension of a compressible nuclear droplet

    NASA Astrophysics Data System (ADS)

    Horiuchi, W.; Ebata, S.; Iida, K.

    2017-09-01

    We systematically investigate the neutron-skin thickness of neutron-rich nuclei within a compressible droplet model, which includes several parameters characterizing the surface tension and the equation of state (EOS) of asymmetric nuclear matter as well as corrections due to the surface diffuseness. Such a systematic analysis helps towards constraining the EOS parameters of asymmetric nuclear matter and the poorly known density dependence of the surface tension; the latter is estimated with help of available experimental data for the neutron and proton density distributions and the nuclear masses. Validity of the present approach is confirmed by calculating realistic density distributions of Ca, Ni, Zr, Sn, Yb, and Pb isotopes within a microscopic Skyrme-Hartree-Fock+BCS method for various sets of the effective nuclear force. Our macroscopic model accompanied by the diffuseness corrections works well in the sense that it well reproduces the evolution of the microscopically deduced neutron-skin thickness with respect to the neutron number for selected sets of the effective nuclear force. We find that the surface tension of the compressible nuclear droplet is a key to bridging a gap between microscopic and macroscopic approaches.

  9. Surface Tension Driven Instability in the Regime of Stokes Flow

    NASA Astrophysics Data System (ADS)

    Yao, Zhenwei; Bowick, Mark; Xing, Xiangjun

    2010-03-01

    A cylinder of liquid inside another liquid is unstable towards droplet formation. This instability is driven by minimization of surface tension energy and was analyzed first by [1,2] and then by [3]. We revisit this problem in the limit of small Laplace number, where the inertial of liquids can be completely ignored. The stream function is found to obey biharmonic equation, and its analytic solutions are found. We rederive Tomotika's main results, and also obtain many new analytic results about the velocity fields. We also apply our formalism to study the recent experiment on toroidal liquid droplet[4]. Our framework shall have many applications in micro-fluidics. [1] L.Rayleigh, On The Instability of A Cylinder of Viscous Liquid Under Capillary Force, Scientific Papers, Cambridge, Vol.III, 1902. [2] L.Rayleigh, On The Instability of Cylindrical Fluid Surfaces, Scientific Papers, Cambridge, Vol.III, 1902. [3] S.Tomotika, On the Instability of a Cylindrical Thread of a Viscous Liquid surround by Another Viscous Fluid, Proceedings of the Royal Society of London. Series A, Mathematical and Physical Sciences, Volume 150, Issue 870, pp. 322-337. [4] E.Pairam and A.Fern'andez-Nieves, Generation and Stability of Toroidal Droplets in a Viscous Liquid, Physical Review Letters 102, 234501 (2009).

  10. Precise, contactless measurements of the surface tension of picolitre aerosol droplets.

    PubMed

    Bzdek, Bryan R; Power, Rory M; Simpson, Stephen H; Reid, Jonathan P; Royall, C Patrick

    2016-01-01

    The surface composition and surface tension of aqueous droplets can influence key aerosol characteristics and processes including the critical supersaturation required for activation to form cloud droplets in the atmosphere. Despite its fundamental importance, surface tension measurements on droplets represent a considerable challenge owing to their small volumes. In this work, we utilize holographic optical tweezers to study the damped surface oscillations of a suspended droplet (<10 μm radius) following the controlled coalescence of a pair of droplets and report the first contactless measurements of the surface tension and viscosity of droplets containing only 1-4 pL of material. An advantage of performing the measurement in aerosol is that supersaturated solute states (common in atmospheric aerosol) may be accessed. For pairs of droplets starting at their equilibrium surface composition, surface tensions and viscosities are consistent with bulk equilibrium values, indicating that droplet surfaces respond to changes in surface area on microsecond timescales and suggesting that equilibrium values can be assumed for growing atmospheric droplets. Furthermore, droplet surfaces are shown to be rapidly modified by trace species thereby altering their surface tension. This equilibration of droplet surface tension to the local environmental conditions is illustrated for unknown contaminants in laboratory air and also for droplets exposed to gas passing through a water-ethanol solution. This approach enables precise measurements of surface tension and viscosity over long time periods, properties that currently are poorly constrained.

  11. Pressure, Surface Tension, and Dripping of Self-Trapped Laser Beams

    SciTech Connect

    Novoa, David; Michinel, Humberto; Tommasini, Daniele

    2009-07-10

    We show that a laser beam which propagates through an optical medium with Kerr (focusing) and higher order (defocusing) nonlinearities displays pressure and surface-tension properties yielding capillarity and dripping effects totally analogous to usual liquid droplets. The system is reinterpreted in terms of a thermodynamic grand potential, allowing for the computation of the pressure and surface tension beyond the usual hydrodynamical approach based on Madelung transformation and the analogy with the Euler equation. We then show both analytically and numerically that the stationary soliton states of such a light system satisfy the Young-Laplace equation and that the dynamical evolution through a capillary is described by the same law that governs the growth of droplets in an ordinary liquid system.

  12. Surface Tension Mediated Under-Water Adhesion of Rigid Spheres on Soft, Charged Surfaces

    NASA Astrophysics Data System (ADS)

    Sinha, Shayandev; Das, Siddhartha

    2015-11-01

    Understanding the phenomenon of surface-tension-mediated under-water adhesion is necessary for studying a plethora of physiological and technical phenomena, such as the uptake of bacteria or nanoparticle by cells, attachment of virus on bacterial surfaces, biofouling on large ocean vessels and marine devices, etc. This adhesion phenomenon becomes highly non-trivial in case the soft surface where the adhesion occurs is also charged. Here we propose a theory for analyzing such an under-water adhesion of a rigid sphere on a soft, charged surface, represented by a grafted polyelectrolyte layer (PEL). We develop a model based on the minimization of free energy that, in addition to considering the elastic and the surface-tension-mediated adhesion energies, also accounts for the PEL electric double layer (EDL) induced electrostatic energies. We show that in the presence of surface charges, adhesion gets enhanced. This can be explained by the fact that the increase in the elastic energy is better balanced by the lowering of the EDL energy associated with the adhesion process. The entire behaviour is further dictated by the surface tension components that govern the adhesion energy.

  13. A finite-volume HLLC-based scheme for compressible interfacial flows with surface tension

    NASA Astrophysics Data System (ADS)

    Garrick, Daniel P.; Owkes, Mark; Regele, Jonathan D.

    2017-06-01

    Shock waves are often used in experiments to create a shear flow across liquid droplets to study secondary atomization. Similar behavior occurs inside of supersonic combustors (scramjets) under startup conditions, but it is challenging to study these conditions experimentally. In order to investigate this phenomenon further, a numerical approach is developed to simulate compressible multiphase flows under the effects of surface tension forces. The flow field is solved via the compressible multicomponent Euler equations (i.e., the five equation model) discretized with the finite volume method on a uniform Cartesian grid. The solver utilizes a total variation diminishing (TVD) third-order Runge-Kutta method for time-marching and second order TVD spatial reconstruction. Surface tension is incorporated using the Continuum Surface Force (CSF) model. Fluxes are upwinded with a modified Harten-Lax-van Leer Contact (HLLC) approximate Riemann solver. An interface compression scheme is employed to counter numerical diffusion of the interface. The present work includes modifications to both the HLLC solver and the interface compression scheme to account for capillary force terms and the associated pressure jump across the gas-liquid interface. A simple method for numerically computing the interface curvature is developed and an acoustic scaling of the surface tension coefficient is proposed for the non-dimensionalization of the model. The model captures the surface tension induced pressure jump exactly if the exact curvature is known and is further verified with an oscillating elliptical droplet and Mach 1.47 and 3 shock-droplet interaction problems. The general characteristics of secondary atomization at a range of Weber numbers are also captured in a series of simulations.

  14. Surface tension, viscosity, and rheology of water-based nanofluids: a microscopic interpretation on the molecular level

    NASA Astrophysics Data System (ADS)

    Lu, Gui; Duan, Yuan-Yuan; Wang, Xiao-Dong

    2014-09-01

    Nanofluids are suspensions of nanometer-sized particles which significantly modify the properties of the base fluids. Nanofluids exhibit attractive properties, such as high thermal conductivity, tunable surface tension, viscosity, and rheology. Various attempts have been made to understand the mechanisms for these property modifications caused by adding nanoparticles; however, due to the lack of direct nanoscale evidence, these explanations are still controversial. This work calculated the surface tension, viscosity, and rheology of gold-water nanofluids using molecular dynamics simulations which provide a microscopic interpretation for the modified properties on the molecular level. The gold-water interaction potential parameters were changed to mimic various nanoparticle types. The results show that the nanoparticle wettability is responsible for the modified surface tension. Hydrophobic nanoparticles always tend to stay on the free surface so they behave like a surfactant to reduce the surface tension. Hydrophilic nanoparticles immersed into the bulk fluid impose strong attractive forces on the water molecules at the free surface which reduces the free surface thickness and increases the surface tension of the nanofluid. Solid-like absorbed water layers were observed around the nanoparticles which increase the equivalent nanoparticle radius and reduce the mobility of the nanoparticles within the base fluid which increases the nanofluid viscosity. The results show the water molecule solidification between two or many nanoparticles at high nanoparticle loadings, but the solidification effect is suppressed for shear rates greater than a critical shear rate; thus Newtonian nanofluids can present shear-thinning non-Newtonian behavior.

  15. Achieving tunable surface tension in the pseudopotential lattice Boltzmann modeling of multiphase flows

    NASA Astrophysics Data System (ADS)

    Li, Qing; Luo, K. H.

    2013-11-01

    In this paper, we aim to address an important issue about the pseudopotential lattice Boltzmann (LB) model, which has attracted much attention as a mesoscopic model for simulating interfacial dynamics of complex fluids, but suffers from the problem that the surface tension cannot be tuned independently of the density ratio. In the literature, a multirange potential was devised to adjust the surface tension [Sbragaglia , Phys. Rev. EPLEEE81063-651X10.1103/PhysRevE.75.026702 75, 026702 (2007)]. However, it was recently found that the density ratio of the system will be changed when the multirange potential is employed to adjust the surface tension. An alternative approach is therefore proposed in the present work. The basic strategy is to add a source term to the LB equation so as to tune the surface tension of the pseudopotential LB model. The proposed approach can guarantee that the adjustment of the surface tension does not affect the mechanical stability condition of the pseudopotential LB model, and thus provides a separate control of the surface tension and the density ratio. Meanwhile, it still retains the mesoscopic feature and the computational simplicity of the pseudopotential LB model. Numerical simulations are carried out for stationary droplets, capillary waves, and droplet splashing on a thin liquid film. The numerical results demonstrate that the proposed approach is capable of achieving a tunable surface tension over a very wide range and can keep the density ratio unchanged when adjusting the surface tension.

  16. Correlation between surface tension, density, and sound velocity of liquid metals.

    PubMed

    Blairs, Sidney

    2006-10-01

    The inter-relationship of surface tension sigma, density rho, and sound velocity c has been examined for forty-one liquid metals. Sound velocities correlate with the equation, log c=0.5526log(sigma/rho)+5.4364. Unknown sound velocities may be estimated using surface tension and liquid density values.

  17. Mapping surface tension induced menisci with application to tensiometry and refractometry.

    PubMed

    Mishra, Avanish; Kulkarni, Varun; Khor, Jian-Wei; Wereley, Steve

    2015-07-28

    In this work, we discuss an optical method for measuring surface tension induced menisci. The principle of measurement is based upon the change in the background pattern produced by the curvature of the meniscus acting as a lens. We measure the meniscus profile over an inclined glass plate and utilize the measured meniscus for estimation of surface tension and refractive index.

  18. Criticality and surface tension in rotating horizon thermodynamics

    NASA Astrophysics Data System (ADS)

    Hansen, Devin; Kubizňák, David; Mann, Robert B.

    2016-08-01

    We study a modified horizon thermodynamics and the associated criticality for rotating black hole spacetimes. Namely, we show that under a virtual displacement of the black hole horizon accompanied by an independent variation of the rotation parameter, the radial Einstein equation takes a form of a ‘cohomogeneity two’ horizon first law, δ E=Tδ S+{{Ω }}δ J-σ δ A, where E and J are the horizon energy (an analogue of the Misner-Sharp mass) and the horizon angular momentum, Ω is the horizon angular velocity, A is the horizon area, and σ is the surface tension induced by the matter fields. For fixed angular momentum, the above equation simplifies and the more familiar (cohomogeneity one) horizon first law δ E=Tδ S-Pδ V is obtained, where P is the pressure of matter fields and V is the horizon volume. A universal equation of state is obtained in each case and the corresponding critical behavior is studied.

  19. Thomas Young's Surface Tension Diagram: Its History, Legacy, and Irreconcilabilities

    NASA Astrophysics Data System (ADS)

    Finn, Robert; McCuan, John; Wente, Henry C.

    2012-09-01

    The Young diagram for determining the contact angle at a triple interface formed by two fluids with a solid, although based on speculative reasoning, found on its publication in 1805 a universal acceptance, without reservation. Later expository articles pointed out consequences that had initially been overlooked, but which were consistent in the specific configurations considered. More recently, reasoning disputing the construction has appeared, and examples—the most recent of them by the present initial author—were introduced, putting the underlying concept into serious doubt. Nevertheless, the construction remains firmly embedded in the curricula of major universities and institutes throughout the world; it continues to be used in engineering design, and two articles emphatically defending it have appeared recently in major journals. In the present note we outline past literature and provide a more precise statement of the Young criterion than is customary. We present explicit examples displaying contradictions arising from it, and corresponding erroneous reasoning in one of the articles defending the criterion (the other having already been refuted in an earlier publication). Finally, we call attention to a direct conflict between the Young construction as interpreted in that article and the classical Wilhelmy method for measuring surface tension at fluid/fluid interfaces.

  20. Surface Tension of Alcohols. Data Selection and Recommended Correlations

    NASA Astrophysics Data System (ADS)

    Mulero, A.; Cachadiña, I.; Sanjuán, E. L.

    2015-09-01

    In previous papers, we have proposed specific correlations to reproduce the surface tension values for several sets of fluids and for wide ranges of temperatures. In this paper, we focus our attention on alcohols and consider the available data for 152 fluids grouped into five families. We use the most recent versions of the DIPPR and DETHERM databases and also Wohlfarth and Wohlfarth's (1997) book as our main sources of data. In some cases we have also considered new data. All the data have been carefully filtered in order to discard those that are in clear disagreement with most of the available data for the same fluid. In some cases, two or more different data sets versus temperature trends were observed, and where possible we considered only one of these trends. To fit the finally selected data, we used the model currently implemented in National Institute of Standards and Technology's refprop program, calculating two, four, or six adjustable coefficients for each fluid. As a result, we proposed recommended correlations for 147 alcohols, providing mean average percentage deviations below 1.7% for each fluid, with only two exceptions: 1,2-butanediol (2.77%) and benzyl alcohol (3.20%).

  1. Surface tension in situ in flooded alveolus unaltered by albumin.

    PubMed

    Kharge, Angana Banerjee; Wu, You; Perlman, Carrie E

    2014-09-01

    In the acute respiratory distress syndrome, plasma proteins in alveolar edema liquid are thought to inactivate lung surfactant and raise surface tension, T. However, plasma protein-surfactant interaction has been assessed only in vitro, during unphysiologically large surface area compression (%ΔA). Here, we investigate whether plasma proteins raise T in situ in the isolated rat lung under physiologic conditions. We flood alveoli with liquid that omits/includes plasma proteins. We ventilate the lung between transpulmonary pressures of 5 and 15 cmH2O to apply a near-maximal physiologic %ΔA, comparable to that of severe mechanical ventilation, or between 1 and 30 cmH2O, to apply a supraphysiologic %ΔA. We pause ventilation for 20 min and determine T at the meniscus that is present at the flooded alveolar mouth. We determine alveolar air pressure at the trachea, alveolar liquid phase pressure by servo-nulling pressure measurement, and meniscus radius by confocal microscopy, and we calculate T according to the Laplace relation. Over 60 ventilation cycles, application of maximal physiologic %ΔA to alveoli flooded with 4.6% albumin solution does not alter T; supraphysiologic %ΔA raise T, transiently, by 51 ± 4%. In separate experiments, we find that addition of exogenous surfactant to the alveolar liquid can, with two cycles of maximal physiologic %ΔA, reduce T by 29 ± 11% despite the presence of albumin. We interpret that supraphysiologic %ΔA likely collapses the interfacial surfactant monolayer, allowing albumin to raise T. With maximal physiologic %ΔA, the monolayer likely remains intact such that albumin, blocked from the interface, cannot interfere with native or exogenous surfactant activity. Copyright © 2014 the American Physiological Society.

  2. Transparent, Superhydrophobic Surface with Varied Surface Tension Responsiveness in Wettability Based on Tunable Porous Silica Structure for Gauging Liquid Surface Tension.

    PubMed

    Wang, Yan; Zhu, Yingjie; Zhang, Chunyang; Li, Jun; Guan, Zisheng

    2017-02-01

    Any solid surface can spontaneously exhibit variational wettability toward liquids with varied surface tension (γ). However, this correspondence has seldom been proposed or used on an artificial superhydrophobic surface, which should be more remarkable and peculiar. Herein, we fabricated robust, transparent superhydrophobic surfaces utilizing acid- and base-catalyzed silica (AC- and BC-silica) particles combined with candle soot template for structural construction and the CVD process for chemical modification. Three types of porous silica structures were devised, which presented distinctive surface tension responsiveness in wettability. Interestingly, all types of surfaces (i.e., AC-, AC/BC-, and BC-silica) show high repellence to high surface tension liquid (γ > 35 mN/m), and small differences are observed. With decreasing γ of the ethanol-water mixtures (γ < 35 mN/m), the static contact angles (SCAs) on all surfaces have an evident decline, but the features of the decreases are fairly different. As γ decreases, the SCA on the AC-silica surface decreases gradually, but the extent of decline becomes larger when γ < 27.42 mN/m. However, the SCA on the BC-silica surface decreases gradually except for γ ≈ 30.81 mN/m, and the SCA undergoes a sharp decline at γ ≈ 30.81 mN/m. The SCA on the AC/BC-silica surface has a similar variation as that of the SCA on the BC-silica surface, but a lower rate of BC-silica particles, e.g., 1/16, 1/8, 1/1 (AC/BC), further diminishes the critical γ values (where a sharp SCA drop occurs) to 30.16, 29.56, and 28.04 mN/m, respectively. The diversity is believed to be ascribed to the structure-induced selectivity of pore infiltration for the liquid. The tunable responsiveness can be generalized to various classes of organic aqueous solutions including methanol, acetic acid, acetone, and N,N-dimethylformamide. Benefiting from this, we can estimate organics concentration of an organic aqueous solution as well as its liquid

  3. Thin Film Morphology of Block Copolymers Containing Polydimethylsiloxane as a Function of the Surface Tension of the Opposing Block

    NASA Astrophysics Data System (ADS)

    Wadley, Maurice; Cavicchi, Kevin

    2008-03-01

    The self-assembly of block copolymers into ordered nanostructures such as spheres, cylinders, and lamellae in the range of 10-100 nm makes them interesting materials for patterning surfaces. Thin films of block copolymers containing poly(dimethylsiloxane) (PDMS) are attractive for patterning due to their high oxygen etch resistance compared to other polymers. The main disadvantage of these polymers for patterning is the low surface tension of PDMS. This causes the preferential migration of PDMS to the air/film interface driving the formation of domains parallel to the interface and surface wetting layers. In this work a series of AB block copolymers containing PDMS have been prepared where the surface tension of the opposing block was varied. The effect of changing the surface tension mismatch between the blocks on the thin film morphology will be discussed.

  4. Analysis of surface cracks in finite plates under tension or bending loads

    NASA Technical Reports Server (NTRS)

    Newman, J. C., Jr.; Raju, I. S.

    1979-01-01

    Stress-intensity factors calculated with a three-dimensional, finite-element analysis for shallow and deep semielliptical surface cracks in finite elastic isotropic plates subjected to tension or bending loads are presented. A wide range of configuration parameters was investigated. The ratio of crack depth to plate thickness ranged from 0.2 to 0.8 and the ratio of crack depth to crack length ranged from 0.2 to 2.0. The effects of plate width on stress-intensity variations along the crack front was also investigated. A wide-range equation for stress-intensity factors along the crack front as a function of crack depth, crack length, plate thickness, and plate width was developed for tension and bending loads. The equation was used to predict patterns of surface-crack growth under tension or bending fatigue loads. A modified form of the equation was also used to correlate surface-crack fracture data for a brittle epoxy material within + or - 10 percent for a wide range of crack shapes and crack sizes.

  5. SS/RCS surface tension propellant acquisition/expulsion tankage technology program

    NASA Technical Reports Server (NTRS)

    1974-01-01

    An evaluation of published propellant physical property data together with bubble point tests of fine-mesh screen in propellants, was conducted. The effort consisted of: (1) the collection and evaluation of pertinent physical property data for hydrazine (N2H4), monomethylhydrazine (MMH), and nitrogen tetroxide (N2O4); (2) testing to determine the effect of dissolved pressurant gas, temperature, purity, and system cleanliness or contamination on system bubble point, and (3) the compilation and publishing of both the literature and test results. The space shuttle reaction control system (SS/RCS) is a bipropellant system using N2O4 and MMH, while the auxiliary power system (SS/APU) employs monopropellant N2H4. Since both the RCS and the APU use a surface tension device for propellant acquisition, the propellant properties of interest are those which impact the design and operation of surface tension systems. Information on propellant density, viscosity, surface tension, and contact angle was collected, compiled, and evaluated.

  6. Correlation between Surface Tension and Water Activity in New Particle Formation

    NASA Astrophysics Data System (ADS)

    Daskalakis, E.; Salameh, A.

    2016-12-01

    The impact of aerosol properties on cloud dynamics and the radiative balance of the atmosphere relies on the parametrizations of cloud droplet formation. Such parametrization is based on equilibrium thermodynamics proposed by Köhler in 1936. There is considerable debate in the literature on the importance of factors like the surface tension depression or the water activity decrease for the correct parametrization. To gain fundamental insight into New Particle Formation (NPF), or Cloud Condensation Nuclei (CCN) activation one has to study microscopic properties of aqueous droplets, involving surface and bulk dynamics. The surface tension of droplets can be associated with the effects from Organic Matter (OM), whereas the static dielectric constant of water reflects the structure and dynamics of ions within solutions and can present a measure of water activity. In this study we employ Molecular Dynamics Simulations on aquatic droplets that contain surface active OM (acetaldehyde, methylglyoxal) and salts. We give insight into the dynamics of aquatic droplets with radials of 3.6nm at a level of detail that is not accessible experimentally (J. Phys. Chem. C 2016, 120:11508). We propose that as the surface tension of an aquatic droplet is decreased in the presence of surface-active OM, the water activity is affected as well. This is due to the fact that the water dipoles are oriented based on the salt morphology within the droplet. We suggest that the surface tension depression can be accompanied by the water activity change. This can be associated with the possible effects of surface-active species in terms of salt morphology transitions within an aerosol at the NPF and early particle growth time scales. Based on this study, surface-active OM seems important in controlling (a) the salt morphology transitions within a nucleus during NPF and particle growth and (b) a correlation between surface activity and water activity of ionic aquatic droplets. The latter

  7. Rotating Molten Metallic Drops and Their Applications for Surface Tension Measurements

    NASA Technical Reports Server (NTRS)

    Rhim, W. K.; Ishikawa, T.

    1998-01-01

    Shapes and stability of rotating molten metal drops carrying net surface electric charges are experimentally investigated, and the feasibility of measureing surface tension based on drop rotation is examined.

  8. Surface tension of aqueous lithium bromide solutions containing 1-octanol as a heat-transfer additive

    SciTech Connect

    Ishida, Kenji; Mori, Y.H.

    1996-11-01

    The surface tension of simulated heat-pump working fluids, aqueous solutions of lithium bromide containing 1-octanol, has been measured, for the first time using a recently developed technique (Ishida et al., Rev. Sci. Instrum. 64, 1,324 (1993)) which is inherently suitable for characterizing the surfactant solution surfaces from the aspects of thermodynamic adsorption equilibrium and adsorption kinetics. The measurement has revealed that even the highest-grade reagents of lithium bromide commercially available are not necessarily free from surfactant impurities. Obtained data on the surface tension vs 1-octanol concentration have been examined on the basis of an equilibrium adsorption model. Through the optimal fitting of the Langmuir-type surface equation of state to the data, they have calculated the surface tension vs surface excess relation and also the variation in surface tension vs 1-octanol concentration relation with the surface area per unit volume of a given solution.

  9. Critical Surface Tension, Critical Surface Energy and Parachor of MnSO3 Thin Film

    NASA Astrophysics Data System (ADS)

    Kariper, I. A.

    2016-02-01

    This study examines the critical surface energy of manganese sulfite (MnSO3) crystalline thin film, produced via chemical bath deposition (CBD) on substrates. In addition, parachor, which is an important parameter of chemical physics, and its relationship with grain size, film thickness, etc., has been investigated for thin films. For this purpose, MnSO3 thin films were deposited at room temperature using different deposition times. Structural properties of the films, such as film thickness and average grain size, were examined using X-ray diffraction; film thickness and surface properties were measured by and atomic force microscope; and critical surface tension of MnSO3 thin films was measured with Optical Tensiometer and calculated using Zisman method. The results showed that critical surface tension and parachor of the films have varied with average grain size and film thickness. Critical surface tension was calculated as 32.97, 24.55, 21.03 and 12.76mN/m for 14.66, 30.84, 37.07 and 44.56nm grain sizes, respectively. Film thickness and average grain size have been increased with the deposition time and they were found to be negatively correlated with surface tension and parachor. The relationship between film thickness and parachor was found as P=-0.1856t+183.45; whereas the relationship between average grain size and parachor was found as P=-0.8911D+150.52. We also showed the relationships between parachor and some thin films parameters.

  10. Surface tension depression by low-solubility organic material in aqueous aerosol mimics

    NASA Astrophysics Data System (ADS)

    Schwier, Allison; Mitroo, Dhruv; McNeill, V. Faye

    2012-07-01

    Surface-active material, including long-chain fatty acids (LCFAs), comprises a significant fraction of organic aerosol mass. Surface-active species are thought to form a film at the gas-aerosol interface, with implications for aerosol heterogeneous chemistry and cloud formation. However, LCFA phase behavior and surface-bulk partitioning has not been characterized under most conditions typical of tropospheric aerosol water (i.e. acidic, high ionic content), making it challenging to predict surface film formation in aerosols. In this study, we present measurements of the surface tension of aqueous solutions containing the slightly soluble LCFAs oleic and stearic acid. The effect of varying pH, organic concentration, and inorganic salt content was tested for each system. We observe surface tension depression compared to water of up to ˜30 and 45% for aqueous solutions containing stearic or oleic acid at pH 0-8 and high inorganic salt concentrations (NaCl and (NH4)2SO4). This suggests that surface film formation is favorable for these species in atmospheric aerosols.

  11. Tension-compression asymmetry and twin boundaries spacings effects in polycrystalline Ni nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, Feng; Zhou, Jianqiu

    2016-07-01

    Tension-compression asymmetry could be a notable feature in many nanocrystalline (NC) materials. The scientific and practical research on the tension-compression asymmetry may play an important role of improving the mechanical behavior of NC materials. Using large-scale molecular dynamics (MD) simulations at the strain rate of 109 s-1, both tension and compression tests are complemented in twin-structural polycrystalline Ni nanowires (NWs). The MD simulation suggests that twin boundaries spacing (TBS) has an interesting effect on the tension-compression asymmetry. For NW (radius = 9 nm) with different TBSs, the flow stresses are totally higher under compression than under tension. The asymmetry gets a minimum value at a particular TBS. Such results can be explained by the interplay of the work of dislocations mechanism under various TBSs and the free surface in NWs.

  12. The dynamics of nucleation and growth of a particle in the ternary alloy melt with anisotropic surface tension

    NASA Astrophysics Data System (ADS)

    Chen, Ming-Wen; Li, Lin-Yan; Guo, Hui-Min

    2017-08-01

    The dynamics of nucleation and growth of a particle affected by anisotropic surface tension in the ternary alloy melt is studied. The uniformly valid asymptotic solution for temperature field, concentration field, and interface evolution of nucleation and particle growth is obtained by means of the multiple variable expansion method. The asymptotic solution reveals the critical radius of nucleation in the ternary alloy melt and an inward melting mechanism of the particle induced by the anisotropic effect of surface tension. The critical radius of nucleation is dependent on isotropic surface tension, temperature undercooling, and constitutional undercooling in the ternary alloy melt, and the solute diffusion melt decreases the critical radius of nucleation. Immediately after a nucleus forms in the initial stage of solidification, the anisotropic effect of surface tension makes some parts of its interface grow inward while some parts grow outward. Until the inward melting attains a certain distance (which is defined as "the melting depth"), these parts of interface start to grow outward with other parts. The interface of the particle evolves into an ear-like deformation, whose inner diameter may be less than two times the critical radius of nucleation within a short time in the initial stage of solidification. The solute diffusion in the ternary alloy melt decreases the effect of anisotropic surface tension on the interface deformation.

  13. Surface tension and related thermodynamic parameters of alcohols using the Traube stalagmometer

    NASA Astrophysics Data System (ADS)

    Dilmohamud, B. A.; Seeneevassen, J.; Rughooputh, S. D. D. V.; Ramasami, P.

    2005-11-01

    An apparatus was devised using the Traube Stalagmometer for the determination of the surface tension of the alcohols methanol, ethanol, propan-1-ol and butan-1-ol. Measurements were made under atmospheric pressure at temperatures between 288.15 K and 313.15 K. The surface tension values were correlated with temperature and surface thermodynamic parameters, namely surface entropy and surface enthalpy, were also calculated. The results obtained are in agreement with the literature and they are promising for the use of this low cost arrangement for accurate measurement of surface tension. Surface tension values were obtained with a maximum error of 0.5 mN m-1 and a maximum standard deviation of 0.8 mN m-1. We recommend this arrangement for students in advanced university courses and it can also be used for research work.

  14. The surface tension of aqueous solutions of some atmospheric water-soluble organic compounds

    NASA Astrophysics Data System (ADS)

    Tuckermann, Rudolf; Cammenga, Heiko K.

    The surface tensions of aqueous solutions of levoglucosan, 3-hydroxybutanoic acid, 3-hydroxybenzoic acid, azelaic acid, pinonic acid, and humic acid have been measured. These compounds are suggested as model substances for the water-soluble organic compounds (WSOC) in atmospheric aerosols and droplets which may play an important role in the aerosol cycle because of their surface-active potentials. The reductions in surface tension induced by single and mixed WSOC in aqueous solution of pure water is remarkable. However, the results of this investigation cannot explain the strong reduction in surface tension in real cloud and fog water samples at concentrations of WSOC below 1 mg/mL.

  15. A free energy-based surface tension force model for simulation of multiphase flows by level-set method

    NASA Astrophysics Data System (ADS)

    Yuan, H. Z.; Chen, Z.; Shu, C.; Wang, Y.; Niu, X. D.; Shu, S.

    2017-09-01

    In this paper, a free energy-based surface tension force (FESF) model is presented for accurately resolving the surface tension force in numerical simulation of multiphase flows by the level set method. By using the analytical form of order parameter along the normal direction to the interface in the phase-field method and the free energy principle, FESF model offers an explicit and analytical formulation for the surface tension force. The only variable in this formulation is the normal distance to the interface, which can be substituted by the distance function solved by the level set method. On one hand, as compared to conventional continuum surface force (CSF) model in the level set method, FESF model introduces no regularized delta function, due to which it suffers less from numerical diffusions and performs better in mass conservation. On the other hand, as compared to the phase field surface tension force (PFSF) model, the evaluation of surface tension force in FESF model is based on an analytical approach rather than numerical approximations of spatial derivatives. Therefore, better numerical stability and higher accuracy can be expected. Various numerical examples are tested to validate the robustness of the proposed FESF model. It turns out that FESF model performs better than CSF model and PFSF model in terms of accuracy, stability, convergence speed and mass conservation. It is also shown in numerical tests that FESF model can effectively simulate problems with high density/viscosity ratio, high Reynolds number and severe topological interfacial changes.

  16. Semi-implicit surface tension formulation with a Lagrangian surface mesh on an Eulerian simulation grid

    NASA Astrophysics Data System (ADS)

    Schroeder, Craig; Zheng, Wen; Fedkiw, Ronald

    2012-02-01

    We present a method for applying semi-implicit forces on a Lagrangian mesh to an Eulerian discretization of the Navier Stokes equations in a way that produces a sparse symmetric positive definite system. The resulting method has semi-implicit and fully-coupled viscosity, pressure, and Lagrangian forces. We apply our new framework for forces on a Lagrangian mesh to the case of a surface tension force, which when treated explicitly leads to a tight time step restriction. By applying surface tension as a semi-implicit Lagrangian force, the resulting method benefits from improved stability and the ability to take larger time steps. The resulting discretization is also able to maintain parasitic currents at low levels.

  17. Density-functional calculations of the surface tension of liquid Al and Na

    NASA Technical Reports Server (NTRS)

    Stroud, D.; Grimson, M. J.

    1984-01-01

    Calculations of the surface tensions of liquid Al and Na are described using the full ionic density functional formalism of Wood and Stroud (1983). Surface tensions are in good agreement with experiment in both cases, with results substantially better for Al than those found previously in the gradient approximation. Preliminary minimization with respect to surface profile leads to an oscillatory profile superimposed on a nearly steplike ionic density disribution; the oscillations have a wavellength of about a hardsphere diameter.

  18. Density-functional calculations of the surface tension of liquid Al and Na

    NASA Technical Reports Server (NTRS)

    Stroud, D.; Grimson, M. J.

    1984-01-01

    Calculations of the surface tensions of liquid Al and Na are described using the full ionic density functional formalism of Wood and Stroud (1983). Surface tensions are in good agreement with experiment in both cases, with results substantially better for Al than those found previously in the gradient approximation. Preliminary minimization with respect to surface profile leads to an oscillatory profile superimposed on a nearly steplike ionic density disribution; the oscillations have a wavellength of about a hardsphere diameter.

  19. Measurement of surface tension of liquid microdroplets through observation of droplet collision

    NASA Astrophysics Data System (ADS)

    Hayakawa, Daichi; Hirano, Taichi; Mitani, Shujiro; Sakai, Keiji

    2017-07-01

    We investigate the applicability of measuring surface tension of liquid microdroplets by analyzing their oscillatory behavior induced by droplet collision. The eigenfrequency of droplet oscillation reflects surface tension for small-amplitude oscillation. In this study, the oscillation frequencies of ethanol-ethanol and water-water droplet collisions are measured by direct observation. We experimentally verify that surface tension can be measured for deformation smaller than 10% of the droplet radius. The collision between ethanol-water droplets is also analyzed. The eigenfrequency induced by unlike-droplet collision exhibits a peculiar behavior, which may be attributed to the temporal hybrid structure of a combined droplet.

  20. Hydrophobicity, surface tension, and zeta potential measurements of glass-reinforced hydroxyapatite composites.

    PubMed

    Lopes, M A; Monteiro, F J; Santos, J D; Serro, A P; Saramago, B

    1999-06-15

    Wettability and zeta potential studies were performed to characterize the hydrophobicity, surface tension, and surface charge of P2O5-glass-reinforced hydroxyapatite composites. Quantitative phase analysis was performed by the Rietveld method using GSAS software applied to X-ray diffractograms. Surface charge was assessed by zeta potential measurements. Protein adsorption studies were performed using vitronectin. Contact angles and surface tensions variation with time were determined by the sessile and pendent drop techniques, respectively, using ADSA-P software. The highest (-18.1 mV) and lowest (-28.7 mV) values of zeta potential were found for hydroxyapatite (HA) and beta-tricalcium phosphate (beta-TCP), respectively, with composite materials presenting values in between. All studied bioceramic materials showed similar solid surface tension. For HA and beta-TCP, solid surface tensions of 46.7 and 45.3 mJ/m2, respectively, were obtained, while composites presented intermediate surface tension values. The dispersive component of surface tension was the predominant one for all materials studied. Adhesion work values between the vitronectin solution and HA and beta-TCP were found to be 79.8 and 88.0 mJ/m2, respectively, while the 4.0 wt % glass composites showed slightly lower values than the 2.5 wt % ones. The presence of beta-TCP influenced surface charge, hydrophobicity, and protein adsorption of the glass-reinforced HA composites, and therefore indirectly affected cell-biomaterial interactions.

  1. Dynamic surface tension of complex fluid-fluid interfaces: A useful concept, or not?

    NASA Astrophysics Data System (ADS)

    Sagis, L. M. C.

    2013-05-01

    Dilatational moduli are typically determined by subjecting interfaces to oscillatory area deformations, and are often defined in terms of the difference between the dynamic or transient surface tension of the interface (the surface tension in its deformed state), and the surface tension of the interface in its non-deformed state. Here we will discuss the usefulness of the dynamic surface tension concept in the characterization of dilatational properties of complex fluid-fluid interfaces. Complex fluid-fluid interfaces are interfaces stabilized by components which form mesophases (two-dimensionional gels, glasses, or (liquid) crystalline phases), as a result of in-plane interactions between the components. We will show that for such interfaces dilatational properties are not exclusively determined by the exchange of surface active components between interface and adjoining bulk phases, but also by in-plane viscoelastic stresses. The separation of these contributions remains a challenging problem which remains to be solved.

  2. The effects of massage in patients with chronic tension headache.

    PubMed

    Puustjärvi, K; Airaksinen, O; Pöntinen, P J

    1990-01-01

    21 female patients suffering from chronic tension headache received 10 sessions of upper body massage consisting of deep tissue techniques in addition to softer techniques in the beginning. When found, trigger points were carefully and forcefully massaged. The range of cervical movements, surface ENMG on mm. frontalis and trapezius, visual analogue scale (VAS) and Finnish Pain Questionnaire (FPQ), and the incidence of neck pain during a two week period before and after the treatment, and at 3 and 6 months during the follow-up period together with Beck depression inventory were taken for evaluation and follow-up. The range of movement in all directions increased, and FPQ, VAS and the number of days with neck pain decreased significantly. There was a significant change in ENMG on the frontalis muscle whereas changes in trapezius remained insignificant. Beck inventory showed an improvement after the treatment. This study confirmed clinical and physiological effects of massage.

  3. Surface tension of liquid mercury: a comparison of density-dependent and density-independent force fields

    NASA Astrophysics Data System (ADS)

    Iakovlev, Anton; Bedrov, Dmitry; Müller, Marcus

    2015-12-01

    Motivated by growing interest in interfacial properties of liquid mercury we investigate by atomistic Molecular Dynamics simulation the ability of density-independent, empiric density-dependent, and recently proposed embedded-atom force fields to predict the surface tension and coexistence density of liquid mercury at room temperature, 293 K. The effect of the density dependence of the studied models on the liquid-vapor coexistence and surface tension is discussed in detail and our results are corroborated by Monte Carlo simulations and semi-analytic liquid-state theory. The latter approach is particularly useful to identify and rationalize artifacts that arise from an ad-hoc generalization of density-independent potentials by introducing density-dependent coefficients. In view of computational efficiency and thermodynamic robustness of density-independent model we optimize its functional form to obtain higher surface tension values in order to improve agreement with experiment.

  4. A new experimental method for determining liquid density and surface tension

    NASA Astrophysics Data System (ADS)

    Chou, Kjo-Chih; Hu, Jian-Hong

    1991-02-01

    A summary concerning the measurement of liquid density relying on the Archimedes principle has been presented, based on which a new effective method with a specially designed bob for determining liquid density has been suggested. The application of this method to ethyl alcohol solution and liquid glycerol, as well as a theoretical error analysis, shows that this new method is significant, because not only can it simplify the procedure of measurement but it can also offer more precise results. Besides, this method can further provide surface tension or contact angle simultaneously. It is expected that this new method will find its application in hightemperature melts.

  5. Evaluation of the Effect of the Volume Throughput and Maximum Flux of Low-Surface-Tension Fluids on Bacterial Penetration of 0.2 Micron-Rated Filters during Process-Specific Filter Validation Testing.

    PubMed

    Folmsbee, Martha

    2015-01-01

    Approximately 97% of filter validation tests result in the demonstration of absolute retention of the test bacteria, and thus sterile filter validation failure is rare. However, while Brevundimonas diminuta (B. diminuta) penetration of sterilizing-grade filters is rarely detected, the observation that some fluids (such as vaccines and liposomal fluids) may lead to an increased incidence of bacterial penetration of sterilizing-grade filters by B. diminuta has been reported. The goal of the following analysis was to identify important drivers of filter validation failure in these rare cases. The identification of these drivers will hopefully serve the purpose of assisting in the design of commercial sterile filtration processes with a low risk of filter validation failure for vaccine, liposomal, and related fluids. Filter validation data for low-surface-tension fluids was collected and evaluated with regard to the effect of bacterial load (CFU/cm(2)), bacterial load rate (CFU/min/cm(2)), volume throughput (mL/cm(2)), and maximum filter flux (mL/min/cm(2)) on bacterial penetration. The data set (∼1162 individual filtrations) included all instances of process-specific filter validation failures performed at Pall Corporation, including those using other filter media, but did not include all successful retentive filter validation bacterial challenges. It was neither practical nor necessary to include all filter validation successes worldwide (Pall Corporation) to achieve the goals of this analysis. The percentage of failed filtration events for the selected total master data set was 27% (310/1162). Because it is heavily weighted with penetration events, this percentage is considerably higher than the actual rate of failed filter validations, but, as such, facilitated a close examination of the conditions that lead to filter validation failure. In agreement with our previous reports, two of the significant drivers of bacterial penetration identified were the total

  6. Effects of a surfactant monolayer on the measurement of equilibrium interfacial tension of a drop in extensional flow.

    PubMed

    González-Mancera, Andrés; Gupta, Vijay Kumar; Jamal, Mustapha; Eggleton, Charles D

    2009-05-15

    The effect of surfactant monolayer concentration on the measurement of interfacial surface tension using transient drop deformation methods is studied using the Boundary Integral Method. Emulsion droplets with a surfactant monolayer modeled with the Langmuir equation of state initially in equilibrium are suddenly subjected to axisymmetric extensional flows until a steady state deformation is reached. The external flow is then removed and the retraction of the drops to a spherical equilibrium shape in a quiescent state is simulated. The transient response of the drop to the imposed flow is analyzed to obtain a characteristic response time, tau(s)( *). Neglecting the initial and final stages, the retraction process can be closely approximated by an exponential decay with a characteristic time, tau(r)( *). The strength of the external flow on each model drop is increased in order to investigate the coupled effect of deformation and surfactant distribution on the characteristic relaxation time. Different model drops are considered by varying the internal viscosity and the equilibrium surfactant concentrations from a surfactant free state (clean) to high concentrations approaching the maximum packing limit. The characteristic times obtained from the simulated drop dynamics both in extension and retraction are used to determine an apparent surface tension employing linear theory. In extension the apparent surface tension under predicts the prescribed equilibrium surface tension. The error increases monotonically with the equilibrium surfactant concentration and diverges as the maximum packing limit is approached. In retraction the apparent surface tension under predicts the prescribed equilibrium surface tension depends non-monotonically on the equilibrium surfactant concentration. The error is highest for moderate surfactant concentrations and decreases as the maximum packing limit is approached. It was found that the difference between the prescribed surface tension

  7. Accurate surface tension measurement of glass melts by the pendant drop method.

    PubMed

    Chang, Yao-Yuan; Wu, Ming-Ya; Hung, Yi-Lin; Lin, Shi-Yow

    2011-05-01

    A pendant drop tensiometer, coupled with image digitization technology and a best-fitting algorithm, was built to accurately measure the surface tension of glass melts at high temperatures. More than one thousand edge-coordinate points were obtained for a pendant glass drop. These edge points were fitted with the theoretical drop profiles derived from the Young-Laplace equation to determine the surface tension of glass melt. The uncertainty of the surface tension measurements was investigated. The measurement uncertainty (σ) could be related to a newly defined factor of drop profile completeness (Fc): the larger the Fc is, the smaller σ is. Experimental data showed that the uncertainty of the surface tension measurement when using this pendant drop tensiometer could be ±3 mN∕m for glass melts.

  8. [Determination of critical surface tension--a comparison of 2 methods].

    PubMed

    Lippold, B C; Ohm, A

    1988-03-01

    Two methods for the determination of the critical surface tension (gamma c) of pharmaceutical powders are compared: the so called "sinking-technique", which works by measuring the complete sinking of powders in liquids of varying surface tension and the determination of the critical surface tension by measuring the contact angle in dependence on the surface tension of wetting solvent/water-mixtures by means of the sessile drop-technique. The simple sinking-technique gives gamma c-values which only show a moderate degree of agreement with those determined by the sessile drop-technique. Thus the values determined by the sinking-technique are usually 1-3 mN/m higher than those determined by the sessile drop-technique.

  9. Surface Tension of Organic Liquids Using the OPLS/AA Force Field.

    PubMed

    Zubillaga, Rafael A; Labastida, Ariana; Cruz, Bibiana; Martínez, Juan Carlos; Sánchez, Enrique; Alejandre, José

    2013-03-12

    Molecular dynamics simulations are performed to obtain the surface tension of 61 organic liquids using the OPLS/AA (all-atom optimized potential for liquid simulations). The force field parameters are the same as those recently used (Caleman et al. J. Chem. Theory Comput.2012, 8, 61) to determine several thermodynamic properties of 146 organic liquids. The correct evaluation of surface tension using slab simulations of liquids requires one to properly take into account the long-range interactions (Trukhymchuk and Alejandre J. Chem. Phys.1999, 111, 8510). In addition, the liquid density from slab simulations has to be the same as that obtained in liquid simulations at constant temperature and pressure. The new results of surface tensions from this work improve those reported by Caleman et al. The OPLS/AA force field gives good surface tensions compared with experimental data for most of the systems studied in this work, although it was developed to simulate liquids.

  10. Prediction of surface tension of binary mixtures with the parachor method

    NASA Astrophysics Data System (ADS)

    Němec, Tomáš

    2015-05-01

    The parachor method for the estimation of the surface tension of binary mixtures is modified by considering temperature-dependent values of the parachor parameters. The temperature dependence is calculated by a least-squares fit of pure-solvent surface tension data to the binary parachor equation utilizing the Peng-Robinson equation of state for the calculation of equilibrium densities. A very good agreement between experimental binary surface tension data and the predictions of the modified parachor method are found for the case of the mixtures of carbon dioxide and butane, benzene, and cyclohexane, respectively. The surface tension is also predicted for three refrigerant mixtures, i.e. propane, isobutane, and chlorodifluoromethane, with carbon dioxide.

  11. Surface Tension and Critical Supersaturations for Mixed Aerosol Particles Composed of Inorganic and Organic Compounds of Atmospheric Relevance

    NASA Astrophysics Data System (ADS)

    Zamora, I. R.; Jacobson, M. Z.

    2012-12-01

    The interaction between water vapor and aerosol particles in the atmosphere has implications on important processes. Among these are cloud droplet formation and growth, which impact cloud properties and therefore have an indirect effect on climate. A significant fraction of the dry submicron mass of atmospheric aerosols is composed of water-soluble organic carbon (WSOC). Although the WSOC fraction contains a large amount of compounds, most yet unidentified, it can be partitioned into three main categories in order to use a set of model substances to reproduce its behavior. In this study, we chose levoglucosan, succinic acid and Nordic Reference fulvic acid (NRFA) to represent the WSOC categories of neutral compounds, mono-/di-carboxylic acids, and polycarboxylic acids, respectively. We measured the surface tension of aqueous pure NRFA and of five of its mixtures at 298 K using the Wilhemy plate method. Langmuir adsorption parameters for the organic mixtures were extracted by fitting the surface tension measurements and corresponding solute concentrations to the Szyszkowski-Langmuir equation. The measured surface tension as a function of aqueous NRFA concentration was identical to that of Suwannee River (SR) and Waskish Peat fulvic acids below 0.02 g/L but up to 12% and 15% higher, respectively, at higher concentrations. Similar to previous findings by Aumann et al. (2010) with SRFA, the surface tension of a NRFA/inorganic salt solution was mainly controlled by the organic compound even when the salt comprised 75% of the added solute mass. This effect was observed for mixtures of NRFA with both sodium chloride and ammonium sulfate salts up to 5 g/L of NRFA. From 5 g/L to about 50 g/L of NRFA, the surface tension for both NRFA/salt mixtures stopped decreasing, remained constant at 52-53 mN/m and then started slowly increasing indicating that the salt component might start dominating at higher concentrations. For a solution of 25% NRFA / 75% levoglucosan, the surface

  12. Practical significance and calculation of surface tension of glass, enamels and glazes

    NASA Technical Reports Server (NTRS)

    Dietzel, A.

    1987-01-01

    Surface tension is important in the formation of streaks in the whole procedure of enameling and glazing., in the action of TiO2 as opacifier, in the addition of borax to enamels, or metals to glasses, and in the corrosion of refractories by molten charges. By the use of known methods for measuring surface tension additive constants are found which give correct results within 1% with no discrepancy due to B2O3.

  13. The Role of Surface Tension in Colloid Retention and Remobilization during Two-phase Flow

    NASA Astrophysics Data System (ADS)

    Zhang, Q.

    2015-12-01

    During unsaturated flow, the accumulation of colloids at fluid-fluid interfaces (AWIs) and fluid-fluid-solid contact lines (AWSs) depend on those areas and surface tension. The area and capillary forces exerting on colloids can be different by adjusting the liquid-liquid surface tension. In the present work, we adjust only surface tension to change the configuration of AWI and AWSs. Experiments were performed in a Polydimethylsiloxane (PDMS) micro-model. Fluorescent carboxylate-modified polystyrene microspheres, with diameter of 300nm were used as model colloids. Water and fluorinert-FC43 were used as the two immiscible liquids. Given the fact that PDMS is a hydrophobic material, fluorinert was the wetting phase and water was the non-wetting phase in this micro-model. Surface tension was changed by adding fluorinert soluble surfactant into fluorinert-FC43. We visualized colloids interacting with the moving fluid-fluid interfaces by confocal microscopy. We also obtained colloid concentration breakthrough curves by measuring the fluorescent intensities in the outlet of the micro-model. The breakthrough curves showed that under steady-state unsaturated flow, less colloid were retained in the system under low surface tension. The visualization results showed that, under low surface tension, the fluid-fluid interfaces are almost flat, thus less area and short contact line available for colloids to attach to. During transient flow, more colloids were remobilized by the moving fluorinert-water interfaces (FWIs) and fluorinert-water-solid contact lines (FWSCs) under high surface tension. Confocal results and measured breakthrough curves confirmed that lowing surface tension decreased capillary force and liquid-liquid area, resulting less retention and remobilization of colloids.

  14. Critical-point analysis of the liquid-vapor interfacial surface tension

    NASA Technical Reports Server (NTRS)

    Salvino, R. E.

    1990-01-01

    The interfacial surface tension of the liquid-vapor system is analyzed near the critical point in a manner similar to bulk thermodynamic critical-point analyses. This is accomplished by a critical-point analysis of the single-phase hard-wall surface tension. Both a Landau expansion and a scaling theory equation of state are investigated. Some general exponent relations are derived and, in addition, some thermodynamically defined correlation lengths are discussed.

  15. General purpose in-situ surface tension measurement

    NASA Astrophysics Data System (ADS)

    Lapham, Gary S.; Dowling, David R.; Schultz, William W.

    1996-11-01

    While the Wilhelmy method is over a century old, there is a need for clear hydrodynamic explanations for corrections to the basic weight-divided-by-slide-perimeter measurement. A technique tailored for a free surface with surfactants has been developed including the effects of hydrostatic pressure and for the angle that the free surface meets with the Wilhelmy plate. A two-dimensional hydrostatic analysis has captured much of the discrepency between the typically-applied simple model and experiments. However, three-dimensional end effects play an important role and add experimental uncertainty. To avoid these end effects, a circular geometry was used and compared to axisymmetric analysis. Unlike, the du Noüy ring, this apparatus has sharp corners and well-defined corrections. The technique can be used in any basin, with any liquid, and with any surface contamination condition provided the plate can be wetted. Experiments with standard Wilhelmy plates that prompted technique development and results from the new technique are discussed. This research is supported by the Office of Naval Research.

  16. Role of surface tension and roughness on the wettability of Er:YAG laser irradiated dentin: In vitro study

    PubMed Central

    Brulat, Nathalie; Rocca, Jean-Paul; Darque-Ceretti, Evelyne

    2013-01-01

    Introduction: The aim of this “in vitro” study was to evaluate the role of surface tension and surface roughness in the wettability, considered essential for a good adhesion, comparing Er:YAG laser - to bur-prepared dentin. Materials and Methods: Dentin surfaces of third human molars were Er:YAG laser- and bur-prepared to evaluate the effects of surface tension and roughness on wettability and interferometric analysis was used to compare the roughness of the two groups surfaces, after gold-coating them. Results: In bur-prepared samples the time taken for the water drop to spread out was approximately the same with or without metallization while, in the Er:YAG laser-prepared surfaces the spreading-out time was less than 10 seconds but longer after metallization i.e. nearly two minutes. Large differences in wettability measurements were observed because the water drop was almost immediately absorbed on the Er:YAG laser-prepared surface. The wettability test demonstrated that the porous and hydrophilic properties of Er:YAG laser-prepared surfaces are higher than bur-prepared surfaces. Conclusion: Surface tension, surface morphology and porosity had different effects on the spreading time of a water drop on both Er:YAG laser- and bur-prepared surfaces. And, while surface tension does not seem to influence the results, roughness appears to be the main parameter involved in water drop spreading, this being an indication, by the clinical point of view, to the choice of Er:YAG laser parameters in conservative dentistry. PMID:24204092

  17. Surface tension phenomena in the xylem sap of three diffuse porous temperate tree species.

    PubMed

    Christensen-Dalsgaard, Karen K; Tyree, Melvin T; Mussone, Paolo G

    2011-04-01

    In plant physiology models involving bubble nucleation, expansion or elimination, it is typically assumed that the surface tension of xylem sap is equal to that of pure water, though this has never been tested. In this study we collected xylem sap from branches of the tree species Populus tremuloides, Betula papyrifera and Sorbus aucuparia over 3 months. We measured the instantaneous surface tension and followed changes over a period of 0.5-5 h using the pendant drop technique. In all three species the instantaneous surface tension was equal to or within a few percent of that of pure water. Further, in B. papyrifera and S. aucuparia the change over time following drop establishment, although significant, was very small. In P. tremuloides, however, there was a steep decline in surface tension over time that leveled off towards values 21-27% lower than that of pure water. This indicated the presence of surfactants. The values were lower for thinner distal branch segments than for proximal ones closer to the trunk. In some species it appears valid to assume that the surface tension of xylem sap is equal to that of water. However, in branch segments of P. tremuloides close to the terminal bud and hence potentially in other species as well, it may be necessary to take into account the presence of surfactants that reduce the surface tension over time.

  18. Changes in droplet surface tension affect the observed hygroscopicity of photochemically aged biomass burning aerosol.

    PubMed

    Giordano, Michael R; Short, Daniel Z; Hosseini, Seyedehsan; Lichtenberg, William; Asa-Awuku, Akua A

    2013-10-01

    This study examines the hygroscopic and surface tension properties as a function of photochemical aging of the aerosol emissions from biomass burning. Experiments were conducted in a chamber setting at the UC-Riverside Center for Environmental Research and Technology (CE-CERT) Atmospheric Processes Lab using two biomass fuel sources, manzanita and chamise. Cloud condensation nuclei (CCN) measurements and off-line filter sample analysis were conducted. The water-soluble organic carbon content and surface tension of the extracted filter samples were measured. Surface tension information was then examined with Köhler theory analysis to calculate the hygroscopicity parameter, κ. Laboratory measurement of biomass burning smoke from two chaparral fuels is shown to depress the surface tension of water by 30% or more at organic matter concentrations relevant at droplet activation. Accounting for surface tension depression can lower the calculated κ by a factor of 2. This work provides evidence for surface tension depression in an important aerosol system and may provide closure for differing sub- and supersaturated κ measurements.

  19. Surface tension of short flexible Lennard-Jones chains: Corresponding states behavior.

    PubMed

    Galliero, Guillaume

    2010-08-21

    Molecular dynamics simulations of surface tensions of short flexible Lennard-Jones chains, composed of 2, 3, 4, and 5 segments, have been performed in this work. Using the simulation results, it is shown that the reduced surface tension depends only on the chain length and the reduced temperature. As a consequence, simple three parameters corresponding states using the acentric factor is shown to yield an excellent estimation of the reduced surface tension of the flexible Lennard-Jones chain fluid model. In addition, it has been noticed that the reduced surface tension of this fluid model is a unique function of the coexisting liquid and vapor reduced densities (i.e., there exist a universal Parachor behavior) for all chain lengths tested. When applied to real fluids, this universal behavior holds rather well for a large class of real species which can be nonspherical, nonlinear, and even polar. Only the surface tension of hydrogen-bonding compounds seems to largely deviate from this universal Parachor behavior. These interesting features of the surface tension, written in appropriate scaled forms, can probably be used to improve molecular models, in particular, those on which modern molecular based equations of state rely on.

  20. Surface tension of the two center Lennard-Jones plus point dipole fluid.

    PubMed

    Werth, Stephan; Horsch, Martin; Hasse, Hans

    2016-02-07

    Molecular dynamics simulations are used for systematically studying the surface tension of the two center Lennard-Jones plus point dipole (2CLJD) model fluid. In a dimensionless representation, this model fluid has two parameters describing the elongation and the dipole moment. These parameters were varied in the entire range relevant for describing real fluids resulting in a grid of 38 individual models. For each model, the surface tension was determined at temperatures between 60% and 90% of the critical temperature. For completeness, the vapor pressure and the saturated densities were also determined. The latter results agree well with the literature data, whereas for the surface tension, only few data were previously available. From the present results, an empirical correlation for the surface tension of the 2CLJD model as a function of the model parameters is developed. The correlation is used to predict the surface tension of 46 2CLJD molecular models from the literature, which were adjusted to bulk properties, but not to interfacial properties. The results are compared to the experimental data. The molecular models overestimate the surface tension, and deviations between the predictions and experimental data are below 12% on average.

  1. Surface tension of nitric oxide and its binary mixtures with krypton, methane, and ethene

    SciTech Connect

    Calado, J.C.G.; Santos Mendonca, A.F.S. dos; Saramago, B.J.V.; Soares, V.A.M.

    1997-05-15

    The surface tension of three binary liquid mixtures of NO with Kr, CH{sub 4}, and C{sub 2}H{sub 4} has been determined as a function of composition in the temperature range 102.0 to 119.0 K. These measurements are a contribution to the study of binary liquid mixtures in which one component is unassociated while the molecules of the other can associate between themselves. Nitric oxide is the simplest molecule capable of forming dimers, but not larger aggregates. This results in the surface tension of liquid nitric oxide having a strong temperature dependence: when the temperature increases the degree of dimerization decreases, contributing to a larger decrease of the surface tension. The surface tension of NO mixtures shows strong deviations from ideality. The mixtures containing Kr and CH{sub 4} exhibit negative deviations, while for the NO + C{sub 2}H{sub 4} system the surface tension shows a complex dependence on the composition. This strong departure from ideality had already been found for the bulk properties of these three systems. The surface tension of the CH{sub 4} + Kr system, already well characterized in the literature, was also measured to test the equipment.

  2. Quantitative analysis of surface tension of liquid nano-film with thickness: Two stage stability mechanism, molecular dynamics and thermodynamics approach

    NASA Astrophysics Data System (ADS)

    Peng, Tiefeng; Li, Qibin; Chen, Jie; Gao, Xuechao

    2016-11-01

    The effects of thickness on surface tension of aqueous nano-films under the same lateral size were studied by molecular dynamics (MD) simulations. The surface tension was found to decrease with decreasing thickness when film thickness is below 1.5 nm. Between 4 and 1.5 nm, the trend is for the surface tension to decrease but this is not as significant as between 1.5 and 1.2 nm. For the surface tension of salt nano-films, with low temperatures resulting in monotonous decreasing with thickness, while high temperature (e.g. 479 K) exhibited a first increase then decrease for surface tension with thickness. Filippini et al. (2014) suggested that surface tension is constant with the thickness as long as the sheet remains in one piece, also the decrease observed and as proposed by Werth et al. (2013) is not due to a confinement effect on Lennard-Jones systems. However, in this study for aqueous nano-films, a two stage mechanism was proposed to interpret this effect, for which the stability was classified according to thickness range and validated by disjoining pressure. The results are important in describing the role of surface tension in determining the behaviour of disjoining pressure.

  3. The surface tension of TIP4P/2005 water model using the Ewald sums for the dispersion interactions.

    PubMed

    Alejandre, José; Chapela, Gustavo A

    2010-01-07

    The liquid-vapor phase equilibria and surface tension of the TIP4P/2005 water model is obtained by using the Ewald summation method to determine the long range Lennard-Jones and electrostatic interactions. The method is implemented in a straightforward manner into standard simulation programs. The computational cost of using Ewald sums in dispersion interactions of water is estimated in direct simulation of interfaces. The results of this work at 300 K show a dramatic change in surface tension with an oscillatory behavior for surface areas smaller than 5x5sigma(2), where sigma is the Lennard-Jones oxygen diameter. The amplitude of such oscillations substantially decreases with temperature. Finite size effects are less important on coexisting densities. Phase equilibria and interfacial properties can be determined using a small number of water molecules; their fluctuations are around the same size of simulation error at all temperatures, even in systems where the interfaces are separated a few molecular diameters only. The difference in surface tension of this work compared to the results of other authors is not significant (on the contrary, there is a good agreement). What should be stressed is the different and more consistent approach to obtain the surface tension using the Ewald sums for dispersion interactions. There are two relevant aspects at the interface: An adsorption of water molecules is observed at small surface areas and its thickness systematically increases with system size.

  4. The surface tension of TIP4P/2005 water model using the Ewald sums for the dispersion interactions

    NASA Astrophysics Data System (ADS)

    Alejandre, José; Chapela, Gustavo A.

    2010-01-01

    The liquid-vapor phase equilibria and surface tension of the TIP4P/2005 water model is obtained by using the Ewald summation method to determine the long range Lennard-Jones and electrostatic interactions. The method is implemented in a straightforward manner into standard simulation programs. The computational cost of using Ewald sums in dispersion interactions of water is estimated in direct simulation of interfaces. The results of this work at 300 K show a dramatic change in surface tension with an oscillatory behavior for surface areas smaller than 5×5σ2, where σ is the Lennard-Jones oxygen diameter. The amplitude of such oscillations substantially decreases with temperature. Finite size effects are less important on coexisting densities. Phase equilibria and interfacial properties can be determined using a small number of water molecules; their fluctuations are around the same size of simulation error at all temperatures, even in systems where the interfaces are separated a few molecular diameters only. The difference in surface tension of this work compared to the results of other authors is not significant (on the contrary, there is a good agreement). What should be stressed is the different and more consistent approach to obtain the surface tension using the Ewald sums for dispersion interactions. There are two relevant aspects at the interface: An adsorption of water molecules is observed at small surface areas and its thickness systematically increases with system size.

  5. Surface Tension, Adsorption, and Molecular Orientations at the Liquid-Vapor Interface of Molecular Mixtures.

    NASA Astrophysics Data System (ADS)

    Thurtell, John Harland

    A generalized van der Waal's Mean Field Theory and Molecular Dynamics computer simulations have been used to study the liquid-vapor interface of simple liquid crystals, atomic mixtures, polar mixtures, and polar solvent-surfactant mixtures. Surface tensions, density profiles, and orientational order parameters have been calculated at the planar liquid -vapor interfaces of liquid crystals, argon-krypton mixtures, and polar mixtures using a mean field theory of molecular liquids. The effect of size, shape and dipole strength on the thickness, concentration and orientational ordering of adsorbed layers have been studied in detail. These parameters yield widely varying interfacial structures and can lead to interfacial and bulk phase transitions. Molecular dynamics simulations of simple surfactant models in a polar solvent have been carried out for varying intermolecular potentials. In particular the effect of the surfactant dipole strength, orientation and position were examined. The dipole has a large influence on the surface tension, molecular orientations and thickness of the interfacial region of these systems. We find a number of competing effects which result in unpredictable behavior in some situations.

  6. Membrane tension homeostasis of epithelial cells through surface area regulation in response to osmotic stress.

    PubMed

    Pietuch, Anna; Brückner, Bastian R; Janshoff, Andreas

    2013-03-01

    Osmotic stress poses one of the most fundamental challenges to living cells. Particularly, the largely inextensible plasma membrane of eukaryotic cells easily ruptures under in-plane tension calling for sophisticated strategies to readily respond to osmotic stress. We describe how epithelial cells react and adapt mechanically to the exposure to hypotonic and hypertonic solutions in the context of a confluent monolayer. Site-specific indentation experiments in conjunction with tether pulling on individual cells have been carried out with an atomic force microscope to reveal spatio-temporal changes in membrane tension and surface area. We found that cells compensate for an increase in lateral tension due to hypoosmotic stress by sacrificing excess of membrane area stored in protrusions and invaginations such as microvilli and caveolae. At mild hypotonic conditions lateral tension increases partly compensated by surface are regulation, i.e. the cell sacrifices some of its membrane reservoirs. A loss of membrane-actin contacts occurs upon exposure to stronger hypotonic solutions giving rise to a drop in lateral tension. Tension release recovers on longer time scales by an increasing endocytosis, which efficiently removes excess membrane from the apical side to restore the initial pre-stress. Hypertonic solutions lead to shrinkage of cells and collapse of the apical membrane onto the cortex. Exposure to distilled water leads to stiffening of cells due to removal of excess surface area and tension increase due to elevated osmotic pressure across the plasma membrane. Copyright © 2012 Elsevier B.V. All rights reserved.

  7. Non-equilibrium surface tension of the vapour-liquid interface of active Lennard-Jones particles.

    PubMed

    Paliwal, Siddharth; Prymidis, Vasileios; Filion, Laura; Dijkstra, Marjolein

    2017-08-28

    We study a three-dimensional system of self-propelled Brownian particles interacting via the Lennard-Jones potential. Using Brownian dynamics simulations in an elongated simulation box, we investigate the steady states of vapour-liquid phase coexistence of active Lennard-Jones particles with planar interfaces. We measure the normal and tangential components of the pressure tensor along the direction perpendicular to the interface and verify mechanical equilibrium of the two coexisting phases. In addition, we determine the non-equilibrium interfacial tension by integrating the difference of the normal and tangential components of the pressure tensor and show that the surface tension as a function of strength of particle attractions is well fitted by simple power laws. Finally, we measure the interfacial stiffness using capillary wave theory and the equipartition theorem and find a simple linear relation between surface tension and interfacial stiffness with a proportionality constant characterized by an effective temperature.

  8. Non-equilibrium surface tension of the vapour-liquid interface of active Lennard-Jones particles

    NASA Astrophysics Data System (ADS)

    Paliwal, Siddharth; Prymidis, Vasileios; Filion, Laura; Dijkstra, Marjolein

    2017-08-01

    We study a three-dimensional system of self-propelled Brownian particles interacting via the Lennard-Jones potential. Using Brownian dynamics simulations in an elongated simulation box, we investigate the steady states of vapour-liquid phase coexistence of active Lennard-Jones particles with planar interfaces. We measure the normal and tangential components of the pressure tensor along the direction perpendicular to the interface and verify mechanical equilibrium of the two coexisting phases. In addition, we determine the non-equilibrium interfacial tension by integrating the difference of the normal and tangential components of the pressure tensor and show that the surface tension as a function of strength of particle attractions is well fitted by simple power laws. Finally, we measure the interfacial stiffness using capillary wave theory and the equipartition theorem and find a simple linear relation between surface tension and interfacial stiffness with a proportionality constant characterized by an effective temperature.

  9. Quantification of surface tension and internal pressure generated by single mitotic cells

    NASA Astrophysics Data System (ADS)

    Fischer-Friedrich, Elisabeth; Hyman, Anthony A.; Jülicher, Frank; Müller, Daniel J.; Helenius, Jonne

    2014-08-01

    During mitosis, adherent cells round up, by increasing the tension of the contractile actomyosin cortex while increasing the internal hydrostatic pressure. In the simple scenario of a liquid cell interior, the surface tension is related to the local curvature and the hydrostatic pressure difference by Laplace's law. However, verification of this scenario for cells requires accurate measurements of cell shape. Here, we use wedged micro-cantilevers to uniaxially confine single cells and determine confinement forces while concurrently determining cell shape using confocal microscopy. We fit experimentally measured confined cell shapes to shapes obeying Laplace's law with uniform surface tension and find quantitative agreement. Geometrical parameters derived from fitting the cell shape, and the measured force were used to calculate hydrostatic pressure excess and surface tension of cells. We find that HeLa cells increase their internal hydrostatic pressure excess and surface tension from ~ 40 Pa and 0.2 mNm-1 during interphase to ~ 400 Pa and 1.6 mNm-1 during metaphase. The method introduced provides a means to determine internal pressure excess and surface tension of rounded cells accurately and with minimal cellular perturbation, and should be applicable to characterize the mechanical properties of various cellular systems.

  10. Quantification of surface tension and internal pressure generated by single mitotic cells.

    PubMed

    Fischer-Friedrich, Elisabeth; Hyman, Anthony A; Jülicher, Frank; Müller, Daniel J; Helenius, Jonne

    2014-08-29

    During mitosis, adherent cells round up, by increasing the tension of the contractile actomyosin cortex while increasing the internal hydrostatic pressure. In the simple scenario of a liquid cell interior, the surface tension is related to the local curvature and the hydrostatic pressure difference by Laplace's law. However, verification of this scenario for cells requires accurate measurements of cell shape. Here, we use wedged micro-cantilevers to uniaxially confine single cells and determine confinement forces while concurrently determining cell shape using confocal microscopy. We fit experimentally measured confined cell shapes to shapes obeying Laplace's law with uniform surface tension and find quantitative agreement. Geometrical parameters derived from fitting the cell shape, and the measured force were used to calculate hydrostatic pressure excess and surface tension of cells. We find that HeLa cells increase their internal hydrostatic pressure excess and surface tension from ≈ 40 Pa and 0.2 mNm(-1) during interphase to ≈ 400 Pa and 1.6 mNm(-1) during metaphase. The method introduced provides a means to determine internal pressure excess and surface tension of rounded cells accurately and with minimal cellular perturbation, and should be applicable to characterize the mechanical properties of various cellular systems.

  11. Multidimensional analysis of poly(ethylene glycols) by size exclusion chromatography and dynamic surface tension detection

    PubMed

    Miller; Bramanti; Prazen; Prezhdo; Skogerboe; Synovec

    2000-09-15

    Substantial improvements in a multidimensional dynamic surface tension detector (DSTD) are presented. Rapid, online calibration and measurement of the dynamic surface tension for high-performance liquid chromatography separations is achieved. Dynamic surface tension is determined by measuring the differential pressure across the liquid-air interface of repeatedly growing and detaching drops. Continuous surface tension measurement throughout the entire drop growth (50 ms to 2 s) is achieved, for each eluting drop, providing insight into the kinetic behavior of molecular orientation processes at the liquid-air interface. Three-dimensional data are obtained, with surface tension first converted to surface pressure, which is plotted as a function of elution time axis versus drop time axis. Two key innovations will be reported. First, a novel calibration procedure is described and implemented. Differential pressure signals from three drops (mobile phase, standard in mobile phase, and analyte in mobile phase) are utilized to make the dynamic surface tension measurement, thereby eliminating the need for optical imaging, and viscosity and hydrostatic pressure corrections, as required by other methods. Only pressure signals from one mobile-phase drop and one standard drop pressure signal are required, while the analyte drop pressure signal is measured along the chromatographic time axis. Second, corrections for drop elongation are not required, because the drops are precisely detached by an air burst actuation method in a regime were the surface tension forces significantly dominate gravitational forces. Drops that would fall with a volume of approximately 10 microL due to gravity are precisely and repeatedly detached earlier at a volume of 2 microL. The sensitivity and unique selectivity of the DSTD opens up new possibilities in the analysis of small molecular weight polymers of varying degrees of surface activity, as illustrated for the size-exclusion chromatography

  12. Molecular Dynamics Simulation of Surface Tension of NaCl Aqueous Solution at 298.15K: from Diluted to Highly Supersaturated Concentrations

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoxiang; Chen, Chuchu; Poeschl, Ulirch; Su, Hang; Cheng, Yafang

    2017-04-01

    Sodium chloride (NaCl) is one of the key components of atmospheric aerosol particles. Concentration-depend surface tension of aqueous NaCl solution is essential to determine the equilibrium between droplet NaCl solution and water vapor, which is important in regards to aerosol-cloud interaction and aerosol climate effects. Although supersaturated NaCl droplets can be widely found under atmospheric conditions, the experimental determined concentration dependency of surface tension is limited up to the saturated concentration range due to technical difficulties, i.e., heterogeneous nucleation since nearly all surface tension measurement techniques requires contact of the sensor and solution surface. In this study, the surface tension of NaCl aqueous solution with solute mass fraction from 0 to 1 was calculated using molecular dynamics (MD) simulation. The surface tension increases monotonically and near linearly when mass fraction of NaCl (xNaCl) is lower than 0.265 (saturation point), which follows theoretical predictions (e.g., E-AIM, SP parameterization, and PK parameterization). Once entering into the supersaturated concentration range, the calculated surface tension starts to deviate from the near-linear extrapolation and adopts a slightly higher increasing rate until xNaCl of 0.35. We found that these two increasing phases (xNaCl 0.35) is mainly driven by the increase of excessive surface enthalpy when the solution becomes concentrated. After that, the surface tension remains almost unchanged until xNaCl of 0.52. This phenomenon is supported by the results from experiment based Differential Koehler Analyses. The stable surface tension in this concentration range is attributed to a simultaneous change of surface excess enthalpy and entropy at similar degree. When the NaCl solution is getting more concentrated than xNaCl of 0.52, the simulated surface tension regains an even faster growing momentum and shows the tendency of ultimately approaching the surface

  13. Magma differentiation in shallow sills controlled by compaction and surface tension: San Rafael desert, Utah

    NASA Astrophysics Data System (ADS)

    Diez, M.; Savov, I. P.; Connor, C.

    2010-12-01

    Veinlets, veins, sheet or layers of syenite are common structures found in alkaline basalt sills. The mechanism usually invoked to explain their formation are liquid immiscibility, multiple intrusion or crystal fractionation from primitive mafic melt. Syenite veins of few centimeters to sheets of up to 1-2 m thick are ubiquitous in remarkably well-exposed sills of the San Rafael subvolcanic field in the Colorado Plateau, Utah. In some of these exposures we have found an intriguing configuration in which the main body of the alkaline sill is underlain by a lower density sheet of syenite of ~ 1 m thick. The contact is flat and is not a chilled margin, therefore a multiple intrusion scenario with long intervals between injections can be disregarded. This implies that both layers were fluid at the time of magma emplacement. As the more felsic less dense syenite is at the bottom of the sill any mechanism governed exclusively by bouyancy would be problematic. In an attempt to shed light on this apparent riddle we propose the following geological scenario: The sill is built by continuous injections. Magma starts to cool and fractional crystallization operates at this stage to differentiate the alkaline magma into syenite. By the time ~60% of crystallization is attained the system can be described as two-phase flow consisting of pore-syenite melt in hot-creeping matrix. The forces acting to segregate melt into veins or sheets are the gravitational force and surface tension. When surface tension is stronger than the gravitational force, differences in average curvature or surface tension translates into pressure differences that drive melt flow from low to high porosity regions. If the last injections occur at the bottom of the sill a syenite layer may be formed. With the aid of dimensional analysis and two-phase numerical models that account for gravitational compaction and surface tension effects, we explore the conditions that allow for centimeter-scale veins to meter

  14. Sodium hypochlorite with reduced surface tension does not improve in situ pulp tissue dissolution.

    PubMed

    De-Deus, Gustavo; de Berredo Pinho, Marco André; Reis, Claudia; Fidel, Sandra; Souza, Erick; Zehnder, Matthias

    2013-08-01

    Sodium hypochlorite (NaOCl) solutions with added wetting agents are advertised to dissolve necrotic tissue in root canals faster than their counterparts without a lowered surface tension. This was tested in the current study, and the null hypothesis formulated was that there was no difference between a commercially available NaOCl solution with a lowered surface tension (Chlor-XTRA; Vista Dental Products, Racine, WI) and a counterpart containing the same amount of available chlorine without added wetting agents regarding the soft tissue that remains in oval-shaped canals after mechanical preparation and irrigation. Formerly vital extracted teeth (N = 44, 22 pairs) with similar anatomy were radiographically paired and chemomechanically prepared. In 1 tooth from each pair, a 5.25% NaOCl solution with reduced surface tension was used; in the other, a pure, technical-grade NaOCl solution of 5.25% was used. The percentage of remaining pulp tissue (PRPT) was histologically assessed in root cross-sections. The non-Gaussian raw data were subjected to Kruskal-Wallis and Mann-Whitney U tests to verify the respective effect of the cross-section level and solution on the PRPT. The relationship between the cross-section level and the PRPT was estimated by the Spearman correlation test. The alpha-type error was set at 5%. The cross-section level significantly influenced the PRPT (P < .05), whereas the PRPT was not influenced by the solution used (P > .05). A significant inverse correlation was found between the cross-section level and the PRPT (P < .05, r = -0.330). The lower the distance to the apex, the higher the PRPT regardless of the solution used. Contrary to the advertised statement, the dental solution with a reduced surface tension did not dissolve vital pulp tissue in oval root canals any better than a conventional NaOCl solution of similar strength. Closer to the apex, pulp tissue dissolution is less efficient irrespective of the solution. Copyright © 2013 American

  15. A sharp interface method for compressible liquid-vapor flow with phase transition and surface tension

    NASA Astrophysics Data System (ADS)

    Fechter, Stefan; Munz, Claus-Dieter; Rohde, Christian; Zeiler, Christoph

    2017-05-01

    The numerical approximation of non-isothermal liquid-vapor flow within the compressible regime is a difficult task because complex physical effects at the phase interfaces can govern the global flow behavior. We present a sharp interface approach which treats the interface as a shock-wave like discontinuity. Any mixing of fluid phases is avoided by using the flow solver in the bulk regions only, and a ghost-fluid approach close to the interface. The coupling states for the numerical solution in the bulk regions are determined by the solution of local two-phase Riemann problems across the interface. The Riemann solution accounts for the relevant physics by enforcing appropriate jump conditions at the phase boundary. A wide variety of interface effects can be handled in a thermodynamically consistent way. This includes surface tension or mass/energy transfer by phase transition. Moreover, the local normal speed of the interface, which is needed to calculate the time evolution of the interface, is given by the Riemann solution. The interface tracking itself is based on a level-set method. The focus in this paper is the description of the two-phase Riemann solver and its usage within the sharp interface approach. One-dimensional problems are selected to validate the approach. Finally, the three-dimensional simulation of a wobbling droplet and a shock droplet interaction in two dimensions are shown. In both problems phase transition and surface tension determine the global bulk behavior.

  16. Effects of tension on vortex-induced vibration (VIV) responses of a long tensioned cylinder in uniform flows

    NASA Astrophysics Data System (ADS)

    Kang, Ling; Ge, Fei; Wu, Xiaodong; Hong, Youshi

    2017-02-01

    The effects of tension on vortex-induced vibration (VIV) responses for a tension-dominated long cylinder with an aspect ratio of 550 in uniform flows are experimentally investigated in this paper. The results show that elevated tension suppresses fluctuations of maximum displacement with respect to flow velocity and makes chaotic VIV more likely to appear. With respect to periodic VIV, if elevated tension is applied, the dominant vibration frequency in the in-line (IL) direction will switch from a fundamental vibration frequency to twice the value of the fundamental vibration frequency, which results in a ratio of the dominant vibration frequency in the IL direction to that in the cross-flow direction of 2.0. The suppression of the elevated tension in the fluctuation of the maximum displacement causes the axial tension to become an active control parameter for the VIV maximum displacement of a tension-dominated long riser or tether of an engineering structure in deep oceans. However, the axial tension must be optimized before being used since the high dominant vibration frequency due to the elevated tension may unfavorably affect the fatigue life of the riser or tether.

  17. Surface tension of the core-crust interface of neutron stars with global charge neutrality

    NASA Astrophysics Data System (ADS)

    Rueda, Jorge A.; Ruffini, Remo; Wu, Yuan-Bin; Xue, She-Sheng

    2014-03-01

    It has been shown recently that taking into account strong, weak, electromagnetic, and gravitational interactions, and fulfilling the global charge neutrality of the system, a transition layer will happen between the core and crust of neutron stars, at the nuclear saturation density. We use relativistic mean field theory together with the Thomas-Fermi approximation to study the detailed structure of this transition layer and calculate its surface and Coulomb energy. We find that the surface tension is proportional to a power-law function of the baryon number density in the core bulk region. We also analyze the influence of the electron component and the gravitational field on the structure of the transition layer and the value of the surface tension, to compare and contrast with known phenomenological results in nuclear physics. Based on the above results we study the instability against Bohr-Wheeler surface deformations in the case of neutron stars obeying global charge neutrality. Assuming the core-crust transition at nuclear density ρcore≈2.7×1014 g cm-3, we find that the instability sets the upper limit to the crust density, ρcrustcrit≈1.2×1014 g cm-3. This result implies a nonzero lower limit to the maximum electric field of the core-crust transition surface and makes inaccessible a limit of quasilocal charge neutrality in the limit ρcrust=ρcore. The general framework presented here can be also applied to study the stability of sharp phase transitions in hybrid stars as well as in strange stars, both bare and with outer crust. The results of this work open the way to a more general analysis of the stability of these transition surfaces, accounting for other effects such as gravitational binding, centrifugal repulsion, magnetic field induced by rotating electric field, and therefore magnetic dipole-dipole interactions.

  18. Adhesion of bubbles and drops to solid surfaces, and anisotropic surface tensions studied by capillary meniscus dynamometry.

    PubMed

    Danov, Krassimir D; Stanimirova, Rumyana D; Kralchevsky, Peter A; Marinova, Krastanka G; Stoyanov, Simeon D; Blijdenstein, Theodorus B J; Cox, Andrew R; Pelan, Eddie G

    2016-07-01

    Here, we review the principle and applications of two recently developed methods: the capillary meniscus dynamometry (CMD) for measuring the surface tension of bubbles/drops, and the capillary bridge dynamometry (CBD) for quantifying the bubble/drop adhesion to solid surfaces. Both methods are based on a new data analysis protocol, which allows one to decouple the two components of non-isotropic surface tension. For an axisymmetric non-fluid interface (e.g. bubble or drop covered by a protein adsorption layer with shear elasticity), the CMD determines the two different components of the anisotropic surface tension, σs and σφ, which are acting along the "meridians" and "parallels", and vary throughout the interface. The method uses data for the instantaneous bubble (drop) profile and capillary pressure, but the procedure for data processing is essentially different from that of the conventional drop shape analysis (DSA) method. In the case of bubble or drop pressed against a substrate, which forms a capillary bridge, the CBD method allows one to determine also the capillary-bridge force for both isotropic (fluid) and anisotropic (solidified) adsorption layers. The experiments on bubble (drop) detachment from the substrate show the existence of a maximal pulling force, Fmax, that can be resisted by an adherent fluid particle. Fmax can be used to quantify the strength of adhesion of bubbles and drops to solid surfaces. Its value is determined by a competition of attractive transversal tension and repulsive disjoining pressure forces. The greatest Fmax values have been measured for bubbles adherent to glass substrates in pea-protein solutions. The bubble/wall adhesion is lower in solutions containing the protein HFBII hydrophobin, which could be explained with the effect of sandwiched protein aggregates. The applicability of the CBD method to emulsion systems is illustrated by experiments with soybean-oil drops adherent to hydrophilic and hydrophobic substrates in

  19. Effects of eugenol on resting tension of rat atria.

    PubMed

    Olivoto, R R; Damiani, C E N; Kassouf Silva, I; Lofrano-Alves, M S; Oliveira, M A; Fogaça, R T H

    2014-04-01

    In cardiac and skeletal muscle, eugenol (μM range) blocks excitation-contraction coupling. In skeletal muscle, however, larger doses of eugenol (mM range) induce calcium release from the sarcoplasmic reticulum. The effects of eugenol are therefore dependent on its concentration. In this study, we evaluated the effects of eugenol on the contractility of isolated, quiescent atrial trabeculae from male Wistar rats (250-300 g; n=131) and measured atrial ATP content. Eugenol (1, 3, 5, 7, and 10 mM) increased resting tension in a dose-dependent manner. Ryanodine [100 µM; a specific ryanodine receptor (RyR) blocker] and procaine (30 mM; a nonspecific RyR blocker) did not block the increased resting tension induced by eugenol regardless of whether extracellular calcium was present. The myosin-specific inhibitor 2,3-butanedione monoxime (BDM), however, reversed the increase in resting tension induced by eugenol. In Triton-skinned atrial trabeculae, in which all membranes were solubilized, eugenol did not change resting tension, maximum force produced, or the force vs pCa relationship (pCa=-log [Ca2+]). Given that eugenol reduced ATP concentration, the increase in resting tension observed in this study may have resulted from cooperative activation of cardiac thin filaments by strongly attached cross-bridges (rigor state).

  20. Second-order wave effects on TLP tendon tension responses

    SciTech Connect

    Xue, H.; Mercier, R.S.

    1996-12-31

    This paper presents a general procedure for analyzing the second-order wave effects on the tendon tension responses of a TLP. The approach solves both first- and second-order equation of motions for a TLP system in frequency domain. Viscous effects are included in the form of statistically linearized damping coefficients. An efficient algorithm has been devised for reducing the burden of second-order wave diffraction analysis, which selects the interacting frequency pairs according to springing frequency of interest to minimize the cost of computing quadratic transfer functions (QTFs) and allow accurate interpolation of QTFs. Moment statistics of the tension process are computed through an eigenvalue analysis. The developed method is applied to analyze the tendon tension responses of a TLP design in water depth of 3,000 ft.

  1. The Stabilizing Effect of Bending-Under-Tension

    SciTech Connect

    Emmens, W. C.; Boogaard, A. H. van den

    2011-05-04

    A well know effect is that work hardening can stabilize tension processes, as can be shown by the so-called maximum force condition. It is not well known that bending-under-tension can have a similar effect, namely that it can create a situation where the tension force increases with elongation therefore stabilizing the process. This happens in situations where the bending is so severe that the fibers at the inner side are in compression. This mechanism is explained. In cases where the bending radius is constant, for example determined by a tool, the created stable elongation is proportional to the thickness of the material. In cases where the radius is not constant but results from an equilibrium between pulling force and bending moment the situation is more complex. The situations are analyzed by a simple model and successfully verified with experimental results.

  2. Surface tension and contact angles: Molecular origins and associated microstructure

    NASA Technical Reports Server (NTRS)

    Davis, H. T.

    1982-01-01

    Gradient theory converts the molecular theory of inhomogeneous fluid into nonlinear boundary value problems for density and stress distributions in fluid interfaces, contact line regions, nuclei and microdroplets, and other fluid microstructures. The relationship between the basic patterns of fluid phase behavior and the occurrence and stability of fluid microstructures was clearly established by the theory. All the inputs of the theory have molecular expressions which are computable from simple models. On another level, the theory becomes a phenomenological framework in which the equation of state of homogeneous fluid and sets of influence parameters of inhomogeneous fluids are the inputs and the structures, stress tensions and contact angles of menisci are the outputs. These outputs, which find applications in the science and technology of drops and bubbles, are discussed.

  3. Elastic modulus and surface tension of a polyurethane rubber in nanometer thick films

    NASA Astrophysics Data System (ADS)

    Zhai, Meiyu; McKenna, Gregory

    2014-03-01

    Estane is a kind of polyurethane with thermodynamically incompatible hard and soft segments. In this study the macro and micro properties of Estane have been characterized and compared. The viscoelastic properties of this material in bulk scale have been determined using dynamic rheometry. Time-temperature superposition was found to be applicable for this material, and a master curve was successfully constructed from the dynamic shear responses of G'(ω) and G''(ω) . Also a novel nano bubble inflation method was used to obtain the creep compliance of the Estane ultrathin films and the results show stiffening in the rubbery region for the Estane over thicknesses ranging from 110nm to 22nm. The dependence of the rubbery stiffening on film thickness is studied and the relative influences of nano confinement and surface tension effect are analyzed using both a direct stress strain analysis and an energy balance method for the membrane. The contributions of surface tension and nano confinement are considered separately. Office of Naval Research under project No.N00014-11-1-0424.

  4. Surface Tension Components Based Selection of Cosolvents for Efficient Liquid Phase Exfoliation of 2D Materials.

    PubMed

    Shen, Jianfeng; Wu, Jingjie; Wang, Man; Dong, Pei; Xu, Jingxuan; Li, Xiaoguang; Zhang, Xiang; Yuan, Junhua; Wang, Xifan; Ye, Mingxin; Vajtai, Robert; Lou, Jun; Ajayan, Pulickel M

    2016-05-01

    A proper design of direct liquid phase exfoliation (LPE) for 2D materials as graphene, MoS2 , WS2 , h-BN, Bi2 Se3 , MoSe2 , SnS2 , and TaS2 with common cosolvents is carried out based on considering the polar and dispersive components of surface tensions of various cosolvents and 2D materials. It has been found that the exfoliation efficiency is enhanced by matching the ratio of surface tension components of cosolvents to that of the targeted 2D materials, based on which common cosolvents composed of IPA/water, THF/water, and acetone/water can be designed for sufficient LPE process. In this context, the library of low-toxic and low-cost solvents with low boiling points for LPE is infinitely enlarged when extending to common cosolvents. Polymer-based composites reinforced with a series of different 2D materials are compared with each other. It is demonstrated that the incorporation of cosolvents-exfoliated 2D materials can substantially improve the mechanical and thermal properties of polymer matrices. Typically, with the addition of 0.5 wt% of such 2D material as MoS2 nanosheets, the tensile strength and Young's modulus increased up to 74.85% and 136.97%, respectively. The different enhancement effect of 2D materials is corresponded to the intrinsic properties and LPE capacity of 2D materials.

  5. Reduction of the surface-tension-lowering ability of surfactant after exposure to hypochlorous acid.

    PubMed Central

    Merritt, T A; Amirkhanian, J D; Helbock, H; Halliwell, B; Cross, C E

    1993-01-01

    The reactive species hypochlorous acid (HOCl/OCl-) is a major product of the respiratory burst in activated neutrophils. We studied the effects of HOCl/OCl- on human surfactant and upon surfactants Survanta, KL4 and Exosurf, utilizing a pulsating surfactometer for measuring surface tension. HOCl/OCl- induced a marked dose-dependent decrease in the surface-tension-lowering activity of human surfactant. The surfactant containing surfactant proteins B and C (Survanta) was less sensitive; however, synthetic surfactants with or without peptides were not affected by HOCl/OCl- (KL4, Exosurf). Ascorbic acid and GSH protected human surfactant against inactivation by HOCl/OC1-. We suggest that HOCl/OCl- produced by activated phagocytes in the alveolar compartment of the lung could damage endogenous surfactant and affect the function of exogenously administered natural or other surfactants, especially if ascorbic acid and GSH levels in the lung lining fluids are subnormal, as is known to be the case in some inflammatory lung diseases. PMID:8216215

  6. Modeling of surface-tension-driven flow of blood in capillary tubes.

    PubMed

    Wang, Jun; Huang, Wei; Bhullar, Raghbir S; Tong, Pin

    2004-06-01

    Surface-tension-driven blood flow into a capillary tube, as in some medical devices, is studied. In a previous article, we considered the early stages of the entry flow from a drop of blood into a capillary, and solved the problem analytically under the assumption that the resistance of the air is negligible. In the present note we consider a capillary tube of finite length, with the far end containing a small window which opens to the atmosphere. The dynamic reverberation of the air in the capillary tube is analyzed in conjunction with the dynamics of the blood. Existing computing programs are used to solve the Navier-Stokes equations. The interface is characterized by the surface tension between the blood and the air, and the contact angle at the triple point where the air-blood interface meets the capillary tube wall. The results tell us how good our earlier simplified analysis is. The new numerical results show that the smaller the window, the larger is the effect of aerodynamic reverberation. However, even for a window as small as 4% of the capillary cross section, and located at the end of the capillary, the difference of the time of arrival of the interface at the window is less than 5%.

  7. Reduction of Water/Oil Interfacial Tension by Model Asphaltenes: The Governing Role of Surface Concentration.

    PubMed

    Jian, Cuiying; Poopari, Mohammad Reza; Liu, Qingxia; Zerpa, Nestor; Zeng, Hongbo; Tang, Tian

    2016-06-30

    In this work, pendant drop techniques and molecular dynamics (MD) simulations were employed to investigate the effect of asphaltene concentrations on the interfacial tension (IFT) of the oil/water interface. Here, oil and asphaltene were represented by, respectively, common organic solvents and Violanthrone-79, and two types of concentration, i.e., bulk concentration and surface concentration, were examined. Correlations between the IFTs from experiments and MD simulations revealed that surface concentration, rather than the commonly used bulk concentration, determines the reduction of oil/water IFTs. Through analyzing the hydrogen bonding, the underlying mechanism for the IFT reduction was proposed. Our discussions here not only enable the direct comparison between experiments and MD simulations on the IFTs but also help with future interfacial studies using combined experimental and simulation approaches. The methodologies used in this work can be extended to many other oil/water interfaces in the presence of interfacially active compounds.

  8. Surface Tensions of Ionic Liquids: Non-Regular Trend Along the Number of Cyano Groups.

    PubMed

    Almeida, Hugo F D; Carvalho, Pedro J; Kurnia, Kiki A; Lopes-da-Silva, José A; Coutinho, João A P; Freire, Mara G

    2016-02-15

    Ionic liquids (ILs) with cyano-functionalized anions are a set of fluids that are still poorly characterized despite their remarkably low viscosities and potential applications. Aiming at providing a comprehensive study on the influence of the number of -CN groups through the surface tension and surface organization of ILs, the surface tensions of imidazolium-based ILs with cyano-functionalized anions were determined at atmospheric pressure and in the (298.15 to 343.15) K temperature range. The ILs investigated are based on 1-alkyl-3-methylimidazolium cations (alkyl = ethyl, butyl and hexyl) combined with the [SCN](-), [N(CN)2](-), [C(CN)3](-) and [B(CN)4](-)anions. Although the well-known trend regarding the surface tension decrease with the increase of the size of the aliphatic moiety at the cation was observed, the order obtained for the anions is more intricate. For a common cation and at a given temperature, the surface tension decreases according to: [N(CN)2](-) > [SCN](-) > [C(CN)3](-) > [B(CN)4](-). Therefore, the surface tension of this homologous series does not decrease with the increase of the number of -CN groups at the anion as has been previously shown by studies performed with a more limited matrix of ILs. A maximum in the surface tension and critical temperature was observed for [N(CN)2]-based ILs. Furthermore, a minimum in the surface entropy, indicative of a highly structured surface, was found for the same class of ILs. All these evidences seem to be a result of stronger hydrogen-bonding interactions occurring in [N(CN)2]-based ILs, when compared with the remaining CN-based counterparts, and as sustained by cation-anion interaction energies derived from the Conductor Like Screening Model for Real Solvents (COSMO-RS).

  9. Surface Tensions of Ionic Liquids: Non-Regular Trend Along the Number of Cyano Groups

    PubMed Central

    Almeida, Hugo F. D.; Carvalho, Pedro J.; Kurnia, Kiki A.; Lopes-da-Silva, José A.; Coutinho, João A. P.; Freire, Mara G.

    2016-01-01

    Ionic liquids (ILs) with cyano-functionalized anions are a set of fluids that are still poorly characterized despite their remarkably low viscosities and potential applications. Aiming at providing a comprehensive study on the influence of the number of –CN groups through the surface tension and surface organization of ILs, the surface tensions of imidazolium-based ILs with cyano-functionalized anions were determined at atmospheric pressure and in the (298.15 to 343.15) K temperature range. The ILs investigated are based on 1-alkyl-3-methylimidazolium cations (alkyl = ethyl, butyl and hexyl) combined with the [SCN]-, [N(CN)2]−, [C(CN)3]− and [B(CN)4]-anions. Although the well-known trend regarding the surface tension decrease with the increase of the size of the aliphatic moiety at the cation was observed, the order obtained for the anions is more intricate. For a common cation and at a given temperature, the surface tension decreases according to: [N(CN)2]- > [SCN]- > [C(CN)3]- > [B(CN)4]-. Therefore, the surface tension of this homologous series does not decrease with the increase of the number of –CN groups at the anion as has been previously shown by studies performed with a more limited matrix of ILs. A maximum in the surface tension and critical temperature was observed for [N(CN)2]-based ILs. Furthermore, a minimum in the surface entropy, indicative of a highly structured surface, was found for the same class of ILs. All these evidences seem to be a result of stronger hydrogen-bonding interactions occurring in [N(CN)2]-based ILs, when compared with the remaining CN-based counterparts, and as sustained by cation-anion interaction energies derived from the Conductor Like Screening Model for Real Solvents (COSMO-RS). PMID:27642224

  10. Effects of rotation and magnetic field on the onset of convective instability in a liquid layer due to buoyancy and surface tension

    NASA Technical Reports Server (NTRS)

    Sarma, G. S. R.

    1982-01-01

    Thermocapillary stability characteristics of a horizontal liquid layer heated from below rotating about a vertical axis and subjected to a uniform vertical magnetic field are analyzed under a variety of thermal and electromagnetic boundary conditions. Results based on analytical solutions to the pertinent eigenvalue problems are discussed in the light of earlier work on special cases of the more general problem considered here to show in particular the effects of the heat transfer, nonzero curvature and gravity waves at the two-fluid interface. Although the expected stabilizing action of the Coriolis and Lorentz force fields in this configuration are in evidence the optimal choice of an appropriate range for the relevant parameters is shown to be critically dependent on the interfacial effects mentioned above.

  11. Dropwise Condensation of Low Surface Tension Fluids on iCVD Grafted Polymer Films

    NASA Astrophysics Data System (ADS)

    Khalil, Karim; Gleason, Karen; Varanasi, Kripa

    2016-11-01

    A large majority of the work devoted to surface engineering for promoting dropwise condensation heat transfer has focused on steam. Much less attention has been dedicated to the condensation of low surface tension fluids such as hydrocarbons, cryogens, and fluorinated refrigerants, which are used in several industrial applications, including LNG storage and organic Rankine cycles used for heat recovery from low temperature sources such as biomass combustion, industrial waste, or geothermal heat sources. Most hydrophobic modifiers used previously to promote dropwise condensation are silane-based monolayers that have been shown to rapidly degrade under industrial conditions. Here we investigate condensation behavior of a variety of low surface tension liquids on durable covalently-grafted polymer films deposited using initiated chemical vapor deposition (iCVD) on metals such as titanium. We observe a four to seven-fold improvement in the vapor-side heat transfer coefficient by promoting dropwise condensation of low surface tension fluids on these stable films.

  12. Design of an experimental apparatus for measurement of the surface tension of metastable fluids

    NASA Astrophysics Data System (ADS)

    Vinš, V.; Hrubý, J.; Hykl, J.; Blaha, J.; Šmíd, B.

    2013-04-01

    A unique experimental apparatus for measurement of the surface tension of aqueous mixtures has been designed, manufactured, and tested in our laboratory. The novelty of the setup is that it allows measurement of surface tension by two different methods: a modified capillary elevation method in a long vertical capillary tube and a method inspired by the approach of Hacker (National Advisory Committee for Aeronautics, Technical Note 2510, 1-20, 1951), i.e. in a short horizontal capillary tube. Functionality of all main components of the apparatus, e.g., glass chamber with the capillary tube, temperature control unit consisting of two thermostatic baths with special valves for rapid temperature jumps, helium distribution setup allowing pressure variation above the liquid meniscus inside the capillary tube, has been successfully tested. Preliminary results for the surface tension of the stable and metastable supercooled water measured by the capillary elevation method at atmospheric pressure are provided. The surface tension of water measured at temperatures between +26 °C and -11 °C is in good agreement with the extrapolated IAPWS correlation (IAPWS Release on Surface Tension of Ordinary Water Substance, September 1994); however it disagrees with data by Hacker.

  13. A dynamic technique for measuring surface tension at high temperatures in microgravity environment

    NASA Technical Reports Server (NTRS)

    Miiller, A. P.; Cezairliyan, A.

    1990-01-01

    The feasibility of a dynamic technique for measuring surface tension of liquid metals at high temperatures in a microgravity environment was demonstrated. The basic method involves heating a tubular specimen resistively from ambient temperature through its melting point in about 1 sec by passing an electrical current pulse through it, while simultaneously recording the pertinent experimental quantities. Static equilibrium for the molten specimen is achieved in a microgravity environment by splitting the current after it passes through the specimen tube and returning a fraction along the tube axis, and the remaining fraction outside the specimen. Adjustments to the current split enable a balance between the magnetic and surface tension forces acting on the specimen. Values for surface tension are determined from measurements of the equilibrium dimensions of the molten specimen tube, and the magnitudes of the currents. Rapid melting experiments, performed during microgravity simulations with the NASA KC-135 aircraft, yield a value for the surface tension of copper at its melting point which is in agreement with literature data. Measurements of surface tension of a refractory metal (tantalum) are underway.

  14. Line tension and its influence on droplets and particles at surfaces

    NASA Astrophysics Data System (ADS)

    Law, Bruce M.; McBride, Sean P.; Wang, Jiang Yong; Wi, Haeng Sub; Paneru, Govind; Betelu, Santigo; Ushijima, Baku; Takata, Youichi; Flanders, Bret; Bresme, Fernando; Matsubara, Hiroki; Takiue, Takanori; Aratono, Makoto

    2017-02-01

    In this review we examine the influence of the line tension τ on droplets and particles at surfaces. The line tension influences the nucleation behavior and contact angle of liquid droplets at both liquid and solid surfaces and alters the attachment energetics of solid particles to liquid surfaces. Many factors, occurring over a wide range of length scales, contribute to the line tension. On atomic scales, atomic rearrangements and reorientations of submolecular components give rise to an atomic line tension contribution τatom (∼1 nN), which depends on the similarity/dissimilarity of the droplet/particle surface composition compared with the surface upon which it resides. At nanometer length scales, an integration over the van der Waals interfacial potential gives rise to a mesoscale contribution |τvdW| ∼ 1-100 pN while, at millimeter length scales, the gravitational potential provides a gravitational contribution τgrav ∼ +1-10 μN. τgrav is always positive, whereas, τvdW can have either sign. Near wetting, for very small contact angle droplets, a negative line tension may give rise to a contact line instability. We examine these and other issues in this review.

  15. Surface-tension phenomena in organismal biology: an introduction to the symposium.

    PubMed

    Bourouiba, Lydia; Hu, David L; Levy, Rachel

    2014-12-01

    Flows driven by surface tension are both ubiquitous and diverse, involving the drinking of birds and bees, the flow of xylem in plants, the impact of raindrops on animals, respiration in humans, and the transmission of diseases in plants and animals, including humans. The fundamental physical principles underlying such flows provide a unifying framework to interpret the adaptations of the microorganisms, animals, and plants that rely upon them. The symposium on "Surface-Tension Phenomena in Organismal Biology" assembled an interdisciplinary group of researchers to address a large spectrum of topics, all articulated around the role of surface tension in shaping biology, health, and ecology. The contributions to the symposium and the papers in this issue are meant to be a starting point for novices to familiarize themselves with the fundamentals of flows driven by surface tension; to understand how they can play a governing role in many settings in organismal biology; and how such understanding of nature's use of surface tension can, in turn, inspire humans to innovate.

  16. Effect of Neck Formation on the Measurement of Dynamic Interfacial Tension in a Drop Volume Tensiometer

    PubMed

    Campanelli; Wang

    1997-06-15

    Dynamic interfacial tension values obtained by drop volume tensiometry will be affected under certain experimental conditions by the formation of a neck between the drop and the capillary tip. This phenomenon must be accounted for to obtain accurate values of interfacial tension. In this work, neck formation for a water-mineral oil system is studied under conditions where hydrodynamic effects can be neglected. A model originally developed for the determination of the surface tension of a suspended drop is modified for application to dynamic interfacial tensions of surfactant-containing liquids. The model relates apparent values of interfacial tension calculated from drops possessing necks to actual values. Experiments with Span 80 (sorbitan monooleate) and sodium dodecyl sulfate (SDS) surfactants in a mineral oil-water system are used to test the validity of the developed model. For the small tip diameter used, good agreement is obtained for Span 80 up to the critical micelle concentration, and for low concentrations of SDS, when the surfactant adsorption is diffusion-limited. In both cases, the neck diameter of the growing drop can be considered constant over the range of dynamic interfacial tensions tested.

  17. A Quasi-Containerless Pendant Drop Method for Surface Tension Measurements of Molten Metals and Alloys

    NASA Technical Reports Server (NTRS)

    Thiessen, David B.; Man, Kin F.

    1994-01-01

    A quasi-containerless pendant drop method for measuring the surface tension of molten metals and alloys is being developed. The technique involves melting the end of a high-purity metal rod by bombardment with an electron beam to form a pendant drop under ultra-high vacuum conditions to minimize surface contamination.

  18. A Method to Calculate the Surface Tension of a Cylindrical Droplet

    ERIC Educational Resources Information Center

    Wang, Xiaosong; Zhu, Ruzeng

    2010-01-01

    The history of Laplace's equations for spherical and cylindrical droplets and the concept of dividing surface in Gibbs' thermodynamic theory of capillary phenomena are briefly reviewed. The existing theories of surface tensions of cylindrical droplets are briefly reviewed too. For cylindrical droplets, a new method to calculate the radius and the…

  19. A Method to Calculate the Surface Tension of a Cylindrical Droplet

    ERIC Educational Resources Information Center

    Wang, Xiaosong; Zhu, Ruzeng

    2010-01-01

    The history of Laplace's equations for spherical and cylindrical droplets and the concept of dividing surface in Gibbs' thermodynamic theory of capillary phenomena are briefly reviewed. The existing theories of surface tensions of cylindrical droplets are briefly reviewed too. For cylindrical droplets, a new method to calculate the radius and the…

  20. Modeling phase distribution of water-soluble organics in aqueous solutions using surface tension data

    NASA Astrophysics Data System (ADS)

    Cline, B.; Hiatt, J.; Aumann, E.; Cabrera, J.; Tabazadeh, A.

    2006-12-01

    A good fraction (greater than 30 percent) of submicron particle mass in the atmosphere is often composed of water-soluble organic carbon. Identifiable, water-miscible organics, such as, known sugars, small alcohols, small diacids, etc. comprise only a small fraction of the water-soluble mass (about 1-2 percent). Most of the water-soluble mass is often composed of unidentifiable, humic-like materials, which are commonly refereed to as HULIS. Humic substances are known to form colloids in aqueous solutions at very low aqueous concentrations. Thus, it is likely for HULIS to also be colloid-forming in aqueous solutions. Here, we present surface tension measurements of water-miscible and colloid-forming organics, using methanol and sodium laurate as analogs, respectively. By relating the change in surface tension to chemical potential of the solution, we determine a relationship between surface tension and the surface excess of solute; that is, the number of molecules of solute adsorbed at the surface. Assuming surface acts as a monolayer, we model the adsorption with a Langmuir isotherm to extract the surface excess as a function of solute mole fraction. This relationship allows us to calculate the solute's distribution between bulk and surface phases for methanol, and in bulk, surface and colloid phases for sodium laurate. A colloid of sodium laurate contains approximately 100 laurate anions in a spherical cluster. We present adsorption constants for methanol and sodium laurate (derived from our surface tension data), critical micelle concentration for sodium laurate (derived from our surface tension data), and all the other thermocehmical constants (obtained from the literature) required to constrain a model for determining phase partitioning of organics in aqueous solutions.

  1. Convergence and accuracy of kernel-based continuum surface tension models

    SciTech Connect

    Williams, M.W.; Kothe, D.B.; Puckett, E.G.

    1998-12-01

    Numerical models for flows of immiscible fluids bounded by topologically complex interfaces possessing surface tension inevitably start with an Eulerian formulation. Here the interface is represented as a color function that abruptly varies from one constant value to another through the interface. This transition region, where the color function varies, is a thin O(h) band along the interface where surface tension forces are applied in continuum surface tension models. Although these models have been widely used since the introduction of the popular CSF method [BKZ92], properties such as absolute accuracy and uniform convergence are often not exhibited in interfacial flow simulations. These properties are necessary if surface tension-driven flows are to be reliably modeled, especially in three dimensions. Accuracy and convergence remain elusive because of difficulties in estimating first and second order spatial derivatives of color functions with abrupt transition regions. These derivatives are needed to approximate interface topology such as the unit normal and mean curvature. Modeling challenges are also presented when formulating the actual surface tension force and its local variation using numerical delta functions. In the following they introduce and incorporate kernels and convolution theory into continuum surface tension models. Here they convolve the discontinuous color function into a mollified function that can support accurate first and second order spatial derivatives. Design requirements for the convolution kernel and a new hybrid mix of convolution and discretization are discussed. The resulting improved estimates for interface topology, numerical delta functions, and surface force distribution are evidenced in an equilibrium static drop simulation where numerically-induced artificial parasitic currents are greatly mitigated.

  2. The surface crack problem in an orthotropic plate under bending and tension

    NASA Technical Reports Server (NTRS)

    Wu, Bing-Hua; Erdogan, F.

    1987-01-01

    The elasticity problem for an infinite orthotropic flat plate containing a series of through and part through cracks and subjected to bending and tension loads is considered. The problem is formulated by using Reissner's plate bending theory and considering three-dimensional material orthotropy. The Line-spring model developed by Rice and Levy is used to formulate the surface crack problem in which a total of nine material constants were used. The effects of material orthotropy on the stress intensity factors was determined, the interaction between two asymmetrically arranged collinear cracks was investigated, and extensive numerical results regarding the stress intensity factors are provided. The problem is reduced to a system of singular integral equations which is solved by using the Gauss-Chebyshev quadrature formulas. The calculated results show that the material orthotropy does have a significant effect on the stress intensity factor.

  3. The surface crack problem in an orthotropic plate under bending and tension

    NASA Technical Reports Server (NTRS)

    Wu, B. H.; Erdogan, F.

    1986-01-01

    The elasticity problem for an infinite orthotropic flat plate containing a series of through and part-through cracks and subjected to bending and tension loads is considered. The problem is formulated by using Reissner's plate bending theory and considering three dimensional materials orthotropy. The Line-spring model developed by Rice and Levy is used to formulate the surface crack problem in which a total of nine material constants has been used. The main purpose of this study is to determine the effect of material orthotropy on the stress intensity factors, to investigate the interaction between two asymmetrically arranged collinear cracks, and to provide extensive numerical results regarding the stress intensity factors. The problem is reduced to a system of singular integral equations which is solved by using the Gauss-Chebyshev quadrature formulas. The calculated results show that the material orthotropy does have a significant effect on the stress intensity factor.

  4. Statistical analysis of multimode weakly nonlinear Rayleigh-Taylor instability in the presence of surface tension.

    PubMed

    Garnier, J; Cherfils-Clérouin, C; Holstein, P-A

    2003-09-01

    A weakly nonlinear model is proposed for the Rayleigh-Taylor instability in the presence of surface tension. The dynamics of a multimode perturbation of the interface between two incompressible, inviscid, irrotational, and immiscible fluids is analyzed. The quadratic and cubic nonlinear effects are taken into account. They include the nonlinear corrections to the exponential growths of the fundamental modulations. The role of the initial modulation spectrum is discussed. A saturation criterion in terms of the product of a local rms and a particular wave number is exhibited. It gives theoretical foundations for numerical conjectures and allows one to analyze the effects of fundamental parameters of the problem such as the dimension or the Atwood number.

  5. Influence of the size dependence of surface tension on the dynamics of a bubble in a liquid

    NASA Astrophysics Data System (ADS)

    Rekhviashvili, S. Sh.; Kishtikova, E. V.

    2014-06-01

    The Gibbs dividing surface method is used to derive the differential equation defining the dependence of the surface tension of a bubble in a nonpolar single-component liquid on its radius. Exact and asymptotic solutions of this equation have been obtained. It follows from the calculations that the bubble surface tension increases with decreasing radius. The Rayleigh-Plesset equation describing the bubble collapse dynamics is solved numerically by taking into account the size dependence of surface tension. The size dependence of surface tension is shown to affect significantly the final bubble collapse stage and, on the whole, accelerates this process.

  6. Ultrafast imaging method to measure surface tension and viscosity of inkjet-printed droplets in flight

    NASA Astrophysics Data System (ADS)

    Staat, Hendrik J. J.; van der Bos, Arjan; van den Berg, Marc; Reinten, Hans; Wijshoff, Herman; Versluis, Michel; Lohse, Detlef

    2017-01-01

    In modern drop-on-demand inkjet printing, the jetted droplets contain a mixture of solvents, pigments and surfactants. In order to accurately control the droplet formation process, its in-flight dynamics, and deposition characteristics upon impact at the underlying substrate, it is key to quantify the instantaneous liquid properties of the droplets during the entire inkjet-printing process. An analysis of shape oscillation dynamics is known to give direct information of the local liquid properties of millimeter-sized droplets and bubbles. Here, we apply this technique to measure the surface tension and viscosity of micrometer-sized inkjet droplets in flight by recording the droplet shape oscillations microseconds after pinch-off from the nozzle. From the damped oscillation amplitude and frequency we deduce the viscosity and surface tension, respectively. With this ultrafast imaging method, we study the role of surfactants in freshly made inkjet droplets in flight and compare to complementary techniques for dynamic surface tension measurements.

  7. Density, Molar Volume, and Surface Tension of Liquid Al-Ti

    NASA Astrophysics Data System (ADS)

    Wessing, Johanna Jeanette; Brillo, Jürgen

    2017-02-01

    Al-Ti-based alloys are of enormous technical relevance due to their specific properties. For studies in atomic dynamics, surface physics and industrial processing the precise knowledge of the thermophysical properties of the liquid phase is crucial. In the present work, we systematically measure mass density, ρ (g cm-3), and the surface tension, γ (N m-1), as functions of temperature, T, and compositions of binary Al-Ti melts. Electromagnetic levitation in combination with the optical dilatometry method is used for density measurements and the oscillating drop method for surface tension measurements. It is found that, for all compositions, density and surface tension increase linearly upon decreasing temperature in the liquid phase. Within the Al-Ti system, we find the largest values for pure titanium and the smallest for pure aluminum, which amount to ρ(L,Ti) = 4.12 ± 0.04 g cm-3 and γ(L,Ti) = 1.56 ± 0.02 N m-1; and ρ(L,Al) = 2.09 ± 0.01 g cm-3 and γ(L,Al) = 0.87 ± 0.06 N m-1, respectively. The data are analyzed concerning the temperature coefficients, ρ T and γ T, excess molar volume, V E, excess surface tension, γ E, and surface segregation of the surface active component, Al. The results are compared with thermodynamic models. Generally, it is found that Al-Ti is a highly nonideal system.

  8. A new curvature technique calculation for surface tension contribution in PLIC-VOF method

    NASA Astrophysics Data System (ADS)

    Martinez, J.-M.; Chesneau, X.; Zeghmati, B.

    2006-01-01

    The volume of fluid (VOF) methods have been used for numerous numerical simulations. Among these techniques used to define the moving interface, the piecewise linear interface reconstruction (PLIC-VOF) is one of the most accurate. A study of the superficial tension impact on two-phase flow with free surface is presented. A new method based on direct staggered grid is developped to include surface tension in PLIC-VOF. The new numerical curvature calculation method doesn't need smoothed colour function and leads to less “spurious current”. This technique is applied to the calculus of surface tension force in the case of the rise of air bubble in viscous liquid and the fall of liquid drop in the same liquid on free surface. Droplets, thin layer and capillarity waves are observed after the free surface rupture for different Bond number. The influence of surface tension calculus is then obvioused and when the drop hit the free surface, wavelets propagate toward the virtual boundaries imposed.

  9. Surface tensions, viscosities, and diffusion constants in mixed component single aerosol particles

    NASA Astrophysics Data System (ADS)

    Bzdek, Bryan; Marshall, Frances; Song, Young-Chul; Haddrell, Allen; Reid, Jonathan

    2016-04-01

    Surface tension and viscosity are important aerosol properties but are challenging to measure on individual particles owing to their small size and mass. Aerosol viscosity impacts semivolatile partitioning from the aerosol phase, molecular diffusion in the bulk of the particle, and reaction kinetics. Aerosol surface tension impacts how particles activate to serve as cloud condensation nuclei. Knowledge of these properties and how they change under different conditions hinders accurate modelling of aerosol physical state and atmospheric impacts. We present measurements made using holographic optical tweezers to directly determine the viscosity and surface tension of optically trapped droplets containing ~1-4 picolitres of material (corresponding to radii of ~5-10 micrometres). Two droplets are captured in the experimental setup, equilibrated to a relative humidity, and coalesced through manipulation of the relative trap positions. The moment of coalescence is captured using camera imaging as well as from elastically backscattered light connected to an oscilloscope. For lower viscosity droplets, the relaxation in droplet shape to a sphere follows the form of a damped oscillator and gives the surface tension and viscosity. For high viscosity droplets, the relaxation results in a slow merging of the two droplets to form a sphere and the timescale of that process permits determination of viscosity. We show that droplet viscosity and surface tension can be quantitatively determined to within <10% of the expected value for low viscosity droplets and to better than 1 order of magnitude for high viscosity droplets. Examples illustrating how properties such as surface tension can change in response to environmental conditions will be discussed. Finally, a study of the relationship between viscosity, diffusion constants, vapour pressures, and reactive uptake coefficients for a mixed component aerosol undergoing oxidation and volatilisation will be discussed.

  10. Interrelation of surface tension, optical turbidity, and color of operational transformer oils

    SciTech Connect

    L'vov, S. Yu.; Lyut'ko, E. O.; Lankau, Ya. V.; Komarov, V. B.; Seliverstov, A. F.; Bondareva, V. N.; L'vov, Yu. N.; L'vov, M. Yu.; Ershov, B. G.

    2011-09-15

    Measurements of the acidity, optical turbidity, surface tension, and color of transformer oil from 54 power transformers, autotransformers, and shunt reactors are reported. Changes in surface tension, optical turbidity, and color are found to obey adequate linear correlations, while the acidity has no correlation with any of these properties. Numerical criteria for the maximum permissible state (quality) of the oil with respect to optical turbidity and color are obtained. Recommendations to operating staff are provided for cases in which the criteria for optical turbidity and color are exceeded.

  11. Vapor-liquid surface tension of strong short-range Yukawa fluid.

    PubMed

    Odriozola, G; Bárcenas, M; Orea, P

    2011-04-21

    The thermodynamic properties of strong short-range attractive Yukawa fluids, κ = 10, 9, 8, and 7, are determined by combining the slab technique with the standard and the replica exchange Monte Carlo (REMC) methods. A good agreement was found among the coexistence curves of these systems calculated by REMC and those previously reported in the literature. However, REMC allows exploring the coexistence at lower temperatures, where dynamics turns glassy. To obtain the surface tension we employed, for both methods, a procedure that yields the pressure tensor components for discontinuous potentials. The surface tension results obtained by the standard MC and REMC techniques are in good agreement.

  12. Surface tension measurements of aqueous ammonium chloride (NH4Cl) in air

    NASA Technical Reports Server (NTRS)

    Lowry, S. A.; Mccay, M. H.; Mccay, T. D.; Gray, P. A.

    1989-01-01

    Aqueous NH4Cl's solidification is often used to model metal alloy solidification processes. The present determinations of the magnitude of the variation of aqueous NH4Cl's surface tension as a function of both temperature and solutal concentration were conducted at 3, 24, and 40 C over the 72-100 wt pct water solutal range. In general, the surface tension increases 0.31 dyn/cm per percent decrease in wt pct of water, and decreases 0.13 dyn/cm for each increase in deg C. Attention is given to the experimental apparatus employed.

  13. A simple laboratory experiment to measure the surface tension of a liquid in contact with air

    NASA Astrophysics Data System (ADS)

    Riba, Jordi-Roger; Esteban, Bernat

    2014-09-01

    A simple and accurate laboratory experiment to measure the surface tension of liquids has been developed, which is well suited to teach the behaviour of liquids to first- or second-year students of physics, engineering or chemistry. The experimental setup requires relatively inexpensive equipment usually found in physics and chemistry laboratories, since it consists of a used or recycled burette, an analytical balance and a stereoscopic microscope or a micrometer. Experimental data and error analysis show that the surface tension of distilled water, 1-butanol and glycerol can be determined with accuracy better than 1.4%.

  14. Increased phosphatidylcholine concentration in saliva reduces surface tension and improves airway patency in obstructive sleep apnoea.

    PubMed

    Kawai, M; Kirkness, J P; Yamamura, S; Imaizumi, K; Yoshimine, H; Oi, K; Ayuse, T

    2013-10-01

    Surface tension may have important role for maintaining upper airway patency in patients with obstructive sleep apnoea. It has been demonstrated that elevated surface tension increases the pharyngeal pressures required to reopen the upper airway following collapse. The aim of the study was to evaluate the associations between the concentrations of endogenous surfactants in saliva with indices of upper airway patency in obstructive sleep apnoea. We studied 20 male patients with obstructive sleep apnoea (age: 60·3 ± 10·3 years; BMI: 25·9 ± 4·6 kg m(-2); AHI: 41·5 ± 18·6 events h(-1)). We obtained 100-μL samples of saliva prior to overnight polysomnographic sleep study. The surface tension was determined using the pull-off force technique. The concentration of phosphatidylcholine (PC) was evaluated by liquid chromatography-mass spectrometry (LC-MS/MS). Regression analysis between apnoea, hypopnoea and apnoea/hypopnoea indices and the ratio of hypopnoea time/total disordered breathing time (HT/DBT) with surface tension and PC were performed. P < 0·05 was considered significant. The mean saliva surface tension was 48·8 ± 8·0 mN m(-1) and PC concentration was 15·7 ± 11·1 nM. The surface tension was negatively correlated with the PC concentration (r = -0·48, P = 0·03). There was a significant positive correlation between surface tension with hypopnoea index (r = 0·50, P = 0·03) and HT/DBT (r = 0·6, P = 0·006), but not apnoea or apnoea/hypopnoea index (P > 0·11). Similarly, PC concentration negatively correlated with hypopnoea index (r = -0·45, P = 0·04) and HT/DBT (r = -0·6, P = 0·004), but not with apnoea index or AHI (P > 0·08). An increase in salivary PC concentration may increase upper airway patency in obstructive sleep apnoea through a reduction in surface tension.

  15. Surface Tension and Viscosity of Quasicrystal-Forming Ti-Zr-Ni Alloys

    NASA Technical Reports Server (NTRS)

    Hyers, R. W.; Bradshaw, R. C.; Rogers, J. R.; Rathz, T. J.; Lee, G. W.; Kelton, K. F.; Gangopadhyay, A. K.

    2003-01-01

    The surface tension and viscosity of quasicrystal-forming Ti-Zr-Ni alloys were measured over a range of temperature, including both stable and undercooled liquids by an Electrostatic Levitation (ESL) technique. ESL is a containerless technique which allows processing of samples without contact, greatly reducing contamination and increasing access to the metastable undercooled liquid. The measured viscosity is typical of glass-forming alloys of similar composition to the quasicrystal-forming alloys studied here, while the surface tension shows an anomaly at deep undercoolings.

  16. A discontinuous Galerkin front tracking method for two-phase flows with surface tension

    SciTech Connect

    Nguyen, V.-T.; Peraire, J.; Cheong, K.B.; Persson, P.-O.

    2008-12-28

    A Discontinuous Galerkin method for solving hyperbolic systems of conservation laws involving interfaces is presented. The interfaces are represented by a collection of element boundaries and their position is updated using an arbitrary Lagrangian-Eulerian method. The motion of the interfaces and the numerical fluxes are obtained by solving a Riemann problem. As the interface is propagated, a simple and effective remeshing technique based on distance functions regenerates the grid to preserve its quality. Compared to other interface capturing techniques, the proposed approach avoids smearing of the jumps across the interface which leads to an improvement in accuracy. Numerical results are presented for several typical two-dimensional interface problems, including flows with surface tension.

  17. Restudy of surface tension of QGP with one-loop correction in the mean-field potential

    NASA Astrophysics Data System (ADS)

    Singh, S. Somorendro; Gupta, K. K.; Jha, A. K.

    2014-07-01

    Surface tension of quark-gluon plasma (QGP) evolution with one-loop correction in the mean-field potential is studied. First, with the correction, the stable QGP droplet size decreases. Then, the value of surface tension is found to be improved and it approaches to the lattice value of surface tension 0.24Tc3. Moreover, the ratio of the surface tension to the cube of the critical temperature is found to increase the value in comparison to earlier studies without correction factor [R. Ramanathan, K. K. Gupta, A. K. Jha and S. S. Singh, Pram. J. Phys. 68, 757 (2007)].

  18. The design and fabrication of autonomous polymer-based surface tension-confined microfluidic platforms

    NASA Astrophysics Data System (ADS)

    Swickrath, Michael J.

    The field of microfluidics, lab-on-a-chip technologies in particular, promises the capacity to automate sophisticated laboratory analyses into a platform that can be implemented by a user with minimal analytical experience. However, the fabrication methods traditionally employed to manufacture microfluidic devices are cost ineffective and time intensive. Consequently, current production techniques render exploiting this technology for clinical application problematic. This work describes an alternative fabrication technique to mitigate the aforementioned problems through surface tension-driven flow. Hydrophilic conduits are patterned on a variety of commodity polymeric substrates. The opposing two-dimensionally patterned devices are brought within close proximity for the fabrication of a parallel plate configured microfluidic device. The microfluidic platforms demonstrate the ability to facilitate spontaneous capillary pumping with a high degree of precision and minimal expenditure of fluid reagent. In particular, several cost-effective fabrication procedures are illustrated as well as the capacity to manipulate fluids within the platforms utilizing volumes less than 20 total microliters. Furthermore, applications are demonstrated within the devices such as enzymatic-catalysis, on-chip urinalysis (i.e. glucose and protein detection), and micromixing; demonstrating the efficacy of the platform to automate fluid transport concomitantly with reaction processes. In addition, preliminary designs and protocols are suggested in the last chapter of this work for surface tension-confined devices capable of performing enzyme-linked immunosorbent assay (ELISA) and fluorescence resonance energy transfer (FRET). Moreover, theoretical aspects of microfluidic flow are explored within this document including the physics of wetting and wetting energetics, factors influencing surface tension (and thereby the system driving force), the conservative level set method coupling two

  19. Fabrication of heterogeneous microlenses using self-surface tension

    NASA Astrophysics Data System (ADS)

    Chiang, Cheng-Han; Su, Guo-Dung J.

    2014-09-01

    Solar optical modeling tools are valuable for modeling and predicting the performance of solar technology systems. Four optical modeling tools were evaluated using the National Solar Thermal Test Facility heliostat field combined with flat plate receiver geometry as a benchmark. The four optical modeling tools evaluated were DELSOL, HELIOS, SolTrace, and Tonatiuh. All are available for free from their respective developers. DELSOL and HELIOS both use a convolution of the sunshape and optical errors for rapid calculation of the incident irradiance profiles on the receiver surfaces. SolTrace and Tonatiuh use ray-tracing methods to intersect the reflected solar rays with the receiver surfaces and construct irradiance profiles. We found the ray-tracing tools, although slower in computation speed, to be more flexible for modeling complex receiver geometries, whereas DELSOL and HELIOS were limited to standard receiver geometries such as flat plate, cylinder, and cavity receivers. We also list the strengths and deficiencies of the tools to show tool preference depending on the modeling and design needs. We provide an example of using SolTrace for modeling nonconventional receiver geometries. The goal is to transfer the irradiance profiles on the receiver surfaces calculated in an optical code to a computational fluid dynamics code such as ANSYS Fluent. This approach eliminates the need for using discrete ordinance or discrete radiation transfer models, which are computationally intensive, within the CFD code. The irradiance profiles on the receiver surfaces then allows for thermal and fluid analysis on the receiver.

  20. Motion driven by the interface. [pendant drop surface tension in microgravity

    NASA Technical Reports Server (NTRS)

    Jayaraj, K.; Cole, R.; Subramanian, R. S.

    1983-01-01

    Due to the reduction in buoyant forces aboard orbiting spacecraft such as the Space Shuttle, fluid motion driven by gradients in interfacial tension will be important in the processing of materials in space. In this paper, preliminary results from a study of surface tension driven flow in a pendant drop are reported. The drop is heated from above, and the resulting temperature gradients on the drop surface give rise to interfacial tension gradients. These, in turn, drive a circulation in the drop which is made visible by suitable tracers. The velocities are measured using a video technique, and the data on core velocities are found to agree well with results from a predictive theoretical model.

  1. Increased surface tension of the lung and surfactant in bleomycin-induced pulmonary fibrosis in rats.

    PubMed

    Horiuchi, T; Ikegami, M; Cherniack, R M; Mason, R J

    1996-10-01

    The increased elastic recoil of the lung in bleomycin-induced pulmonary fibrosis in the rat is due in part to increased surface forces. This study was designed to determine the role of surface tension in situ and in vitro 21 d after instillation of bleomycin. Using sequentially measured pressure-volume curves generated with air, saline, air after lavage with Tween 20, and saline, surface tension was significantly higher in bleomycin-treated lungs than in untreated lungs (4.7 +/- 1.1 versus 1.8 +/- 0.2 dyne/cm, p < 0.01). Surface tension was determined in vitro with a Wilhelmy balance using bronchoalveolar lavage fluid, surfactant, and organic solvent lipid extracts of surfactant. Bleomycin treatment resulted in elevated minimal surface tensions: BALF (20.7 +/- 0.6 versus 13.6 +/- 3.8 dyne/cm, p < 0.02), isolated surfactant (12.0 +/- 1.3 versus 3.0 +/- 0.5 dyne/cm, p < 0.02), and the organic solvent lipid extracted surfactant (11.0 versus 3.2 dyne/cm). These results indicate that the physical properties of surfactant in lungs of rats treated with bleomycin are abnormal and contribute to the increased elastic recoil in this model of pulmonary fibrosis.

  2. Capillary waves at the liquid-vapor interface and the surface tension of water.

    PubMed

    Ismail, Ahmed E; Grest, Gary S; Stevens, Mark J

    2006-07-07

    Capillary waves occurring at the liquid-vapor interface of water are studied using molecular dynamics simulations. In addition, the surface tension, determined thermodynamically from the difference in the normal and tangential pressure at the liquid-vapor interface, is compared for a number of standard three- and four-point water models. We study four three-point models (SPC/E, TIP3P, TIP3P-CHARMM, and TIP3P-Ew) and two four-point models (TIP4P and TIP4P-Ew). All of the models examined underestimate the surface tension; the TIP4P-Ew model comes closest to reproducing the experimental data. The surface tension can also be determined from the amplitude of capillary waves at the liquid-vapor interface by varying the surface area of the interface. The surface tensions determined from the amplitude of the logarithmic divergence of the capillary interfacial width and from the traditional thermodynamic method agree only if the density profile is fitted to an error function instead of a hyperbolic tangent function.

  3. Combined Molecular Dynamics Simulation-Molecular-Thermodynamic Theory Framework for Predicting Surface Tensions.

    PubMed

    Sresht, Vishnu; Lewandowski, Eric P; Blankschtein, Daniel; Jusufi, Arben

    2017-08-22

    A molecular modeling approach is presented with a focus on quantitative predictions of the surface tension of aqueous surfactant solutions. The approach combines classical Molecular Dynamics (MD) simulations with a molecular-thermodynamic theory (MTT) [ Y. J. Nikas, S. Puvvada, D. Blankschtein, Langmuir 1992 , 8 , 2680 ]. The MD component is used to calculate thermodynamic and molecular parameters that are needed in the MTT model to determine the surface tension isotherm. The MD/MTT approach provides the important link between the surfactant bulk concentration, the experimental control parameter, and the surfactant surface concentration, the MD control parameter. We demonstrate the capability of the MD/MTT modeling approach on nonionic alkyl polyethylene glycol surfactants at the air-water interface and observe reasonable agreement of the predicted surface tensions and the experimental surface tension data over a wide range of surfactant concentrations below the critical micelle concentration. Our modeling approach can be extended to ionic surfactants and their mixtures with both ionic and nonionic surfactants at liquid-liquid interfaces.

  4. Microscopic surface tension down to molecular dimensions and microthermodynamic surface areas of molecules or clusters

    NASA Astrophysics Data System (ADS)

    Sinanoǧlu, Oktay

    1981-07-01

    Surface tension, surface energy, and entropy of small droplets, n clusters, and of cavities in liquids for sizes down to a single molecule are obtained. Rigourous relations are derived that relate microsurface properties to the usual handbook properties of bulk liquids. The microvalues and their dependence on the ratio of the cluster, droplet, or cavity size to the average liquid molecular size are given for common solvents, polar and nonpolar, including alcohols, water, hydrocarbons, rare gas liquids, and liquid (or solid) metals. Microscopic values are less than bulk-planar values by around 40% for nonpolar liquids, and greater for polar liquids by around 60%. The n-cluster (or cavity) sizes ? at which the microsurface properties approach the bulk values within a desired percentage, e.g., 5%, are given. The ordinary, bulk thermodynamic properties of liquids are also related to new useful quantities: ''microthermodynamic surface areas'' of molecules from which, using the equations given, ''experimental'' geometric (van der Waals) surface areas of molecules are calculated. The molecular surface properties introduced in the theory of ''solvophobic forces'' by this author earlier are finding applications presently in areas like HPLC (''high pressure liquid chromatogrphy''), multicomponent adsorption from solution phase (e.g., purification of waters from trace carcinogens), large ion association, protein structure, and drug-biopolymer binding, as well as the earlier ones for the prediction of rates and equilibria in diverse solvents in physical organic chemistry. The microsurface properties given now apply also to the convex case, e.g., the n clusters in nucleation and in metal cluster phenomena.

  5. Particle-induced indentation of the alveolar epithelium caused by surface tension forces

    PubMed Central

    Kojic, M.; Tsuda, A.

    2010-01-01

    Physical contact between an inhaled particle and alveolar epithelium at the moment of particle deposition must have substantial effects on subsequent cellular functions of neighboring cells, such as alveolar type-I, type-II pneumocytes, alveolar macrophage, as well as afferent sensory nerve cells, extending their dendrites toward the alveolar septal surface. The forces driving this physical insult are born at the surface of the alveolar air-liquid layer. The role of alveolar surfactant submerging a hydrophilic particle has been suggested by Gehr and Schürch's group (e.g., Respir Physiol 80: 17–32, 1990). In this paper, we extended their studies by developing a further comprehensive and mechanistic analysis. The analysis reveals that the mechanics operating in the particle-tissue interaction phenomena can be explained on the basis of a balance between surface tension force and tissue resistance force; the former tend to move a particle toward alveolar epithelial cell surface, the latter to resist the cell deformation. As a result, the submerged particle deforms the tissue and makes a noticeable indentation, which creates unphysiological stress and strain fields in tissue around the particle. This particle-induced microdeformation could likely trigger adverse mechanotransduction and mechanosensing pathways, as well as potentially enhancing particle uptake by the cells. PMID:20634359

  6. Constrained sessile drop as a new configuration to measure low surface tension in lung surfactant systems.

    PubMed

    Yu, Laura M Y; Lu, James J; Chan, Yawen W; Ng, Amy; Zhang, Ling; Hoorfar, Mina; Policova, Zdenka; Grundke, Karina; Neumann, A Wilhelm

    2004-08-01

    Existing methodology for surface tension measurements based on drop shapes suffers from the shortcoming that it is not capable to function at very low surface tension if the liquid dispersion is opaque, such as therapeutic lung surfactants at clinically relevant concentrations. The novel configuration proposed here removes the two big restrictions, i.e., the film leakage problem that is encountered with such methods as the pulsating bubble surfactometer as well as the pendant drop arrangement, and the problem of the opaqueness of the liquid, as in the original captive bubble arrangement. A sharp knife edge is the key design feature in the constrained sessile drop that avoids film leakage at low surface tension. The use of the constrained sessile drop configuration in conjunction with axisymmetric drop shape analysis to measure surface tension allows complete automation of the setup. Dynamic studies with lung surfactant can be performed readily by changing the volume of a sessile drop, and thus the surface area, by means of a motor-driven syringe. To illustrate the validity of using this configuration, experiments were performed using an exogenous lung surfactant preparation, bovine lipid extract surfactant (BLES) at 5.0 mg/ml. A comparison of results obtained for BLES at low concentration between the constrained sessile drop and captive bubble arrangement shows excellent agreement between the two approaches. When the surface area of the BLES film (0.5 mg/ml) was compressed by about the same amount in both systems, the minimum surface tensions attained were identical within the 95% confidence limits.

  7. Oxygen tension modulates the effects of TNFα in compressed chondrocytes.

    PubMed

    Tilwani, R K; Vessillier, S; Pingguan-Murphy, B; Lee, D A; Bader, D L; Chowdhury, T T

    2017-01-01

    Oxygen tension and biomechanical signals are factors that regulate inflammatory mechanisms in chondrocytes. We examined whether low oxygen tension influenced the cells response to TNFα and dynamic compression. Chondrocyte/agarose constructs were treated with varying concentrations of TNFα (0.1-100 ng/ml) and cultured at 5 and 21 % oxygen tension for 48 h. In separate experiments, constructs were subjected to dynamic compression (15 %) and treated with TNFα (10 ng/ml) and/or L-NIO (1 mM) at 5 and 21 % oxygen tension using an ex vivo bioreactor for 48 h. Markers for catabolic activity (NO, PGE2) and tissue remodelling (GAG, MMPs) were quantified by biochemical assay. ADAMTS-5 and MMP-13 expression were examined by real-time qPCR. 2-way ANOVA and a post hoc Bonferroni-corrected t test were used to analyse data. TNFα dose-dependently increased NO, PGE2 and MMP activity (all p < 0.001) and induced MMP-13 (p < 0.05) and ADAMTS-5 gene expression (pp < 0.01) with values greater at 5 % oxygen tension than 21 %. The induction of catabolic mediators by TNFα was reduced by dynamic compression and/or L-NIO (all p < 0.001), with a greater inhibition observed at 5% than 21 %. The stimulation of GAG synthesis by dynamic compression was greater at 21 % than 5 % oxygen tension and this response was reduced with TNFα or reversed with L-NIO. The present findings revealed that TNFα increased production of NO, PGE2 and MMP activity at 5 % oxygen tension. The effects induced by TNFα were reduced by dynamic compression and/or the NOS inhibitor, linking both types of stimuli to reparative activities. Future therapeutics should develop oxygen-sensitive antagonists which are directed to interfering with the TNFα-induced pathways.

  8. Line tension effects on the wetting of nanostructures: an energy method

    NASA Astrophysics Data System (ADS)

    Guo, Hao-Yuan; Li, Bo; Feng, Xi-Qiao

    2017-09-01

    The superhydrophobicity and self-cleaning property of micro/nano-structured solid surfaces require a stable Cassie–Baxter (CB) wetting state at the liquid–solid interface. We present an energy method to investigate how the three-phase line tension affects the CB wetting state on nanostructured materials. For some nanostructures, the line tension may engender a distinct energy barrier, which restricts the position of the three-phase contact line and affects the stability of the CB wetting state. We ascertain the upper and lower limits of the critical pressure at the CB–Wenzel transition. Our results suggest that superhydrophobicity on nanostructures can be modulated by tailoring the line tension and harnessing the curvature effect. This study also provides new insights into the sinking phenomena observed in the nanoparticle-floating experiment.

  9. Line tension effects on the wetting of nanostructures: an energy method.

    PubMed

    Guo, Hao-Yuan; Li, Bo; Feng, Xi-Qiao

    2017-09-20

    The superhydrophobicity and self-cleaning property of micro/nano-structured solid surfaces require a stable Cassie-Baxter (CB) wetting state at the liquid-solid interface. We present an energy method to investigate how the three-phase line tension affects the CB wetting state on nanostructured materials. For some nanostructures, the line tension may engender a distinct energy barrier, which restricts the position of the three-phase contact line and affects the stability of the CB wetting state. We ascertain the upper and lower limits of the critical pressure at the CB-Wenzel transition. Our results suggest that superhydrophobicity on nanostructures can be modulated by tailoring the line tension and harnessing the curvature effect. This study also provides new insights into the sinking phenomena observed in the nanoparticle-floating experiment.

  10. Line Tension of Twist-Free Carbon Nanotube Lyotropic Liquid Crystal Microdroplets on Solid Surfaces.

    PubMed

    Jamali, Vida; Biggers, Evan G; van der Schoot, Paul; Pasquali, Matteo

    2017-09-12

    Line tension, i.e., the force on a three-phase contact line, has been a subject of extensive research due to its impact on technological applications including nanolithography and nanofluidics. However, there is no consensus on the sign and magnitude of the line tension, mainly because it only affects the shape of small droplets, below the length scale dictated by the ratio of line tension to surface tension σ/τ. This ratio is related to the size of constitutive molecules in the system, which translates to a nanometer for conventional fluids. Here, we show that this ratio is orders of magnitude larger in lyotropic liquid crystal systems comprising micrometer-long colloidal particles. Such systems are known to form spindle-shaped elongated liquid crystal droplets in coexistence with the isotropic phase, with the droplets flattening when in contact with flat solid surfaces. We propose a method to characterize the line tension by fitting measured droplet shape to a macroscopic theoretical model that incorporates interfacial forces and elastic deformation of the nematic phase. By applying this method to hundreds of droplets of carbon nanotubes dissolved in chlorosulfonic acid, we find that σ/τ ∼ -0.84 ± 0.06 μm. This ratio is 2 orders of magnitude larger than what has been reported for conventional fluids, in agreement with theoretical scaling arguments.

  11. Bifurcation for a free boundary problem with surface tension modeling the growth of multi-layer tumors

    NASA Astrophysics Data System (ADS)

    Zhou, Fujun; Escher, Joachim; Cui, Shangbin

    2008-01-01

    This paper is devoted to the study of the bifurcation of a free boundary problem modeling the growth of tumors with the effect of surface tension being considered. The existence of infinitely many branches of bifurcation solutions is proved. The method of analysis is based on reducing the problem to an operator equation in certain Hölder space with a nonlinear Fredholm operator of index 0. The desired result then follows from the Crandall-Rabinowitz bifurcation theorem.

  12. The Hydrophobic Effect in Solute Partitioning and Interfacial Tension

    NASA Astrophysics Data System (ADS)

    Jackson, Meyer B.

    2016-01-01

    Studies of the partitioning of hydrophobic solutes between water and nonpolar solvents provide estimates for the energy cost of creating hydrophobic-water contacts. This energy is a factor of three lower than the work of adhesion derived from interfacial tension measurements. This discrepancy noted by Tanford in 1979 is widely viewed as a serious challenge to our understanding of hydrophobic interactions. However, the interfacial energy of a water-alkane interface depends on chain length. A simple analysis of published data shows that the loss of rotational freedom of an alkane chain at an interface accounts quantitatively for the length-dependent contribution to interfacial tension, leaving a length-independent contribution very close to the free energy of transfer per unit of solvent accessible surface area. This analysis thus clarifies the discrepancy between the thermodynamic and interfacial tension measurements of hydrophobic interaction energy. Alkanes do not loose rotational freedom when transferred between two different liquid phases but they do at an interface. This reconciles the difference between microscopic and macroscopic measurements. Like the partitioning free energy, the work of adhesion also has a large entropy and small enthalpy at 20 oC.

  13. Development of a low resource RNA extraction cassette based on surface tension valves

    PubMed Central

    Bordelon, Hali; Adams, Nicholas M.; Klemm, Amy S.; Russ, Patricia K.; Williams, John V.; Talbot, H. Keipp; Wright, David W.; Haselton, Frederick R.

    2011-01-01

    Nucleic acid-based diagnostics are highly sensitive and specific, but are easily disrupted by the presence of interferents in biological samples. In a laboratory or hospital setting, the influence of these interferents can be minimized using an RNA or DNA extraction procedure prior to analysis. However, in low resource settings, limited access to specialized instrumentation and trained personnel presents challenges that impede sample preparation. We have developed a self-contained nucleic acid extraction cassette suitable for operation in a low resource setting. This simple design contains processing solutions preloaded within a continuous length of 1.6 mm inner diameter Tygon tubing. Processing solutions are separated by air gaps and held in place during processing by the surface tension forces at the liquid-air interface, viz. surface tension valves. Nucleic acids preferentially adsorbed to silica-coated magnetic particles are separated from sample interferents by using an external magnet to transfer the nucleic acid biomarker through successive solutions to precipitate, wash and elute in the final cassette solution. The efficiency of the extraction cassette was evaluated using quantitative reverse transcriptase PCR (qRT-PCR) following extraction of respiratory syncytial virus (RSV) RNA. RNA was recovered from TE buffer or from lysates of RSV infected HEp-2 cells with 55 and 33% efficiency, respectively, of the Qiagen RNeasy kit. Recovery of RSV RNA from RSV infected HEp-2 cells was similar at 30% of the RNeasy kit. An overall limit of detection after extraction was determined to be nearly identical (97.5%) to a laboratory-based commercially available kit. These results indicate that this extraction cassette design has the potential to be an effective sample preparation device suitable for use in a low resource setting. PMID:21604768

  14. Development and applications of the interfacial tension between water and organic or biological surfaces.

    PubMed

    van Oss, Carel Jan

    2007-01-15

    The interfacial tension (gamma(SW)) between a condensed-phase material (S) and water (W) is one of the most important terms occurring (directly or indirectly) in the major surface thermodynamic combining rules, such as the different variants of the Dupré equation, as well as the Young and the Young-Dupré equations. Since the late 1950s, gamma(SL) (where L stands for liquid in general) could be correctly expressed, as long as one only took van der Waals attractions and electrical double layer repulsions into account, i.e., as long as both S and L were apolar. However for interfacial interactions taking place in water among apolar as well as polar solutes, particles or surfaces, gamma(SW) was not properly worked out until the late 1980s, due in particular to uncertainties about the treatment of the polar properties of liquid water and other condensed-phase materials. In this review the historical development of the understanding of these polar properties is outlined and the polar equation for gamma(SW), as well as the equations derived there from for the free energies of interaction between apolar or polar entities, immersed in water (deltaG(SWS)) are discussed. Also discussed is the role of the various terms of deltaG(SWS), in hydrophobic attraction (the "hydrophobic effect"), hydrophilic repulsion ("hydration forces") and in the quantitative expression of hydrophobicity and hydrophilicity. The DLVO theory of attractive and repulsive free energies between particles immersed in liquids, as a function of distance between suspended particles, was extended to allow its use in the expression of the polar interactions occurring in water. Finally, the free energy term, deltaG(SWS) and the related gamma(SW), have been directly linked to the aqueous solubility of organic and biological solutes, which allows the determination of interfacial tensions between such solutes and water from their solubilities.

  15. Surface tension and energy in multivariant martensitic transformations: phase-field theory, simulations, and model of coherent interface.

    PubMed

    Levitas, Valery I; Javanbakht, Mahdi

    2010-10-15

    The Ginzburg-Landau theory for multivariant martensitic phase transformations is advanced in three directions: the potential is developed that introduces the surface tension at interfaces; a mixed term in gradient energy is introduced to control the martensite-martensite interface energy independent of that for austenite-martensite; and a noncontradictory expression for variable surface energy is suggested. The problems of surface-induced pretransformation, barrierless multivariant nucleation, and the growth of an embryo in a nanosize sample are solved to elucidate the effect of the above contributions. The obtained results represent an advanced model for coherent interface.

  16. Critical Steady Surface Waves of Idea Fluid over a Bump with Surface Tension

    NASA Astrophysics Data System (ADS)

    Choi, Jeongwhan; Lee, Sangwon; Kim, Joonkyoung; Whang, Sungim

    2016-11-01

    The paper deals with steady forced surface waves propagating on a two-dimensional incompressible and inviscid fluid with a small bump placed on a rigid flat bottom. If the surface tension coefficient T on the free surface is not zero and the wave is moving with a constant speed C, the wave motion is determined by two non-dimensional constants, F = √ gh and I = T / (ρgh 2) , where g is the gravity constant and h is the height of the fluid at infinity. It has been known that F = 1 and t = 1/3 are the critical values of F and t, respectively. In the critical case F = 1 + λ 1 ɛ 2 and t = 1/3 + t1 ɛ with ɛ > 0 a small parameter, a time-dependent forced Kawahara (F-Kawahara)equation is derived to model the wave propagation on the free surface and the steady F-Kawahara equation is studied both theoretically and merically. It is shown that the steady F-Kawahara equation has many different kinds of one and multi-hump solutions when t1 and λ 1 vary. In particular, for a fixed t 1, there is a λ 0 < 0 such that if λ 1 < λ 0 , two one-hump steady solutions can be obtained, one with small amplitude and the other with large amplitude. By using the unsteady F-Kawahara equation, it appears that the small one-hump solution is stable while the large one is nstable. In addition, two-hump solutions are unstable.

  17. Evolution of melt-vapor surface tension in silicic volcanic systems: Experiments with hydrous melts

    USGS Publications Warehouse

    Mangan, M.; Sisson, T.

    2005-01-01

    We evaluate the melt-vapor surface tension (??) of natural, water-saturated dacite melt at 200 MPa, 950-1055??C, and 4.8-5.7 wt % H2O. We experimentally determine the critical supersaturation pressure for bubble nucleation as a function of dissolved water and then solve for ?? at those conditions using classical nucleation theory. The solutions obtained give dacite melt-vapor surface tensions that vary inversely with dissolved water from 0.042 (??0.003) J m-2 at 5.7 wt% H2O to 0.060 (??0.007) J m-2 at 5.2 wt% H2O to 0.073 (??0.003) J m-2 at 4.8 wt% H2O. Combining our dacite results with data from published hydrous haplogranite and high-silica rhyolite experiments reveals that melt-vapor surface tension also varies inversely with the concentration of mafic melt components (e.g., CaO, FeOtotal, MgO). We develop a thermodynamic context for these observations in which melt-vapor surface tension is represented by a balance of work terms controlled by melt structure. Overall, our results suggest that cooling, crystallization, and vapor exsolution cause systematic changes in ?? that should be considered in dynamic modeling of magmatic processes.

  18. Surface tension phenomena in the xylem sap of three diffuse porous temperate tree species

    Treesearch

    K. K. Christensen-Dalsgaard; M. T. Tyree; P. G. Mussone

    2011-01-01

    In plant physiology models involving bubble nucleation, expansion or elimination, it is typically assumed that the surface tension of xylem sap is equal to that of pure water, though this has never been tested. In this study we collected xylem sap from branches of the tree species Populus tremuloides, Betula papyrifera and Sorbus...

  19. Indentation of a rigid sphere into an elastic substrate with surface tension and adhesion

    PubMed Central

    Hui, Chung-Yuen; Liu, Tianshu; Salez, Thomas; Raphael, Elie; Jagota, Anand

    2015-01-01

    The surface tension of compliant materials such as gels provides resistance to deformation in addition to and sometimes surpassing that owing to elasticity. This paper studies how surface tension changes the contact mechanics of a small hard sphere indenting a soft elastic substrate. Previous studies have examined the special case where the external load is zero, so contact is driven by adhesion alone. Here, we tackle the much more complicated problem where, in addition to adhesion, deformation is driven by an indentation force. We present an exact solution based on small strain theory. The relation between indentation force (displacement) and contact radius is found to depend on a single dimensionless parameter: ω=σ(μR)−2/3((9π/4)Wad)−1/3, where σ and μ are the surface tension and shear modulus of the substrate, R is the sphere radius and Wad is the interfacial work of adhesion. Our theory reduces to the Johnson–Kendall–Roberts (JKR) theory and Young–Dupre equation in the limits of small and large ω, respectively, and compares well with existing experimental data. Our results show that, although surface tension can significantly affect the indentation force, the magnitude of the pull-off load in the partial wetting liquid-like limit is reduced only by one-third compared with the JKR limit and the pull-off behaviour is completely determined by ω. PMID:25792953

  20. On the interfacial behavior of ionic liquids: surface tensions and contact angles.

    PubMed

    Restolho, José; Mata, José L; Saramago, Benilde

    2009-12-01

    In this work the liquid/vapour and the solid/liquid interfaces of a series of ionic liquids: 1-ethyl-3-methylpyridinium ethyl sulfate, [EMPy][EtSO4], 1-ethyl-3-methylimidazolium ethyl sulfate, [EMIM][EtSO4], 1-ethanol-3-methylimidazolium tetrafluoroborate, [C2OHMIM][BF4], 1-butyl-3-methylimidazolium tetrafluoroborate, [BMIM][BF4], and 1-octyl-3-methylimidazolium tetrafluoroborate, [OMIM][BF4], were investigated. The surface tension was measured in a wide temperature range, (298-453) K. The contact angles were determined on substrates of different polarities. Both on the polar (glass) and the non-polar substrates ((poly-(tetrafluoroethylene) and poly-(ethylene)), the liquids with maximum and minimum surface tensions lead, respectively, to the highest and the lowest contact angles. The dispersive, gamma(L)(d), and non-dispersive, gamma(L)(nd), components of the liquid surface tension, gamma(L), were calculated from the contact angles on the non-polar substrates using the Fowkes approach. The polarity fraction, gamma(L)(nd)/gamma(L), was compared with the polarity parameter, k, obtained from the fitting of the surface tension vs. temperature data to the Eötvös equation. Good agreement was found for the extreme cases: [OMIM][BF4] exhibits the lowest polarity and [BMIM][BF4], the highest. When compared with the polarity fractions of standard liquids considered as "polar" liquids, the ionic liquids studied may be considered as moderately polar.

  1. Modeling the Mechanics of Cell Division: Influence of Spontaneous Membrane Curvature, Surface Tension, and Osmotic Pressure

    PubMed Central

    Beltrán-Heredia, Elena; Almendro-Vedia, Víctor G.; Monroy, Francisco; Cao, Francisco J.

    2017-01-01

    Many cell division processes have been conserved throughout evolution and are being revealed by studies on model organisms such as bacteria, yeasts, and protozoa. Cellular membrane constriction is one of these processes, observed almost universally during cell division. It happens similarly in all organisms through a mechanical pathway synchronized with the sequence of cytokinetic events in the cell interior. Arguably, such a mechanical process is mastered by the coordinated action of a constriction machinery fueled by biochemical energy in conjunction with the passive mechanics of the cellular membrane. Independently of the details of the constriction engine, the membrane component responds against deformation by minimizing the elastic energy at every constriction state following a pathway still unknown. In this paper, we address a theoretical study of the mechanics of membrane constriction in a simplified model that describes a homogeneous membrane vesicle in the regime where mechanical work due to osmotic pressure, surface tension, and bending energy are comparable. We develop a general method to find approximate analytical expressions for the main descriptors of a symmetrically constricted vesicle. Analytical solutions are obtained by combining a perturbative expansion for small deformations with a variational approach that was previously demonstrated valid at the reference state of an initially spherical vesicle at isotonic conditions. The analytic approximate results are compared with the exact solution obtained from numerical computations, getting a good agreement for all the computed quantities (energy, area, volume, constriction force). We analyze the effects of the spontaneous curvature, the surface tension and the osmotic pressure in these quantities, focusing especially on the constriction force. The more favorable conditions for vesicle constriction are determined, obtaining that smaller constriction forces are required for positive spontaneous

  2. Modeling the Mechanics of Cell Division: Influence of Spontaneous Membrane Curvature, Surface Tension, and Osmotic Pressure.

    PubMed

    Beltrán-Heredia, Elena; Almendro-Vedia, Víctor G; Monroy, Francisco; Cao, Francisco J

    2017-01-01

    Many cell division processes have been conserved throughout evolution and are being revealed by studies on model organisms such as bacteria, yeasts, and protozoa. Cellular membrane constriction is one of these processes, observed almost universally during cell division. It happens similarly in all organisms through a mechanical pathway synchronized with the sequence of cytokinetic events in the cell interior. Arguably, such a mechanical process is mastered by the coordinated action of a constriction machinery fueled by biochemical energy in conjunction with the passive mechanics of the cellular membrane. Independently of the details of the constriction engine, the membrane component responds against deformation by minimizing the elastic energy at every constriction state following a pathway still unknown. In this paper, we address a theoretical study of the mechanics of membrane constriction in a simplified model that describes a homogeneous membrane vesicle in the regime where mechanical work due to osmotic pressure, surface tension, and bending energy are comparable. We develop a general method to find approximate analytical expressions for the main descriptors of a symmetrically constricted vesicle. Analytical solutions are obtained by combining a perturbative expansion for small deformations with a variational approach that was previously demonstrated valid at the reference state of an initially spherical vesicle at isotonic conditions. The analytic approximate results are compared with the exact solution obtained from numerical computations, getting a good agreement for all the computed quantities (energy, area, volume, constriction force). We analyze the effects of the spontaneous curvature, the surface tension and the osmotic pressure in these quantities, focusing especially on the constriction force. The more favorable conditions for vesicle constriction are determined, obtaining that smaller constriction forces are required for positive spontaneous

  3. Dynamic Nucleation of Supercooled Melts and Measurement of the Surface Tension and Viscosity

    NASA Technical Reports Server (NTRS)

    Trinh, E. H.; Ohsaka, K.

    1999-01-01

    We investigate the phenomenon of acoustic pressure-induced nucleation by using a novel approach involving the large amplitude resonant radial oscillations and collapse of a single bubble intentionally injected into a supercooled liquid. Using a combination of previously developed and proven techniques, the bubble is suspended in a fluid host by an ultrasonic field which supplies both the levitation capability as well as the forcing of the radial oscillations. We observe the effects of an increase in pressure (due to bubble collapse) in a region no larger than 100 microns within the supercooled melt to rigorously probe the hypothesis of pressure-induced nucleation of the solid phase. The use of single bubbles operating in narrow temporal and spatial scales will allow the direct and unambiguous correlation between the origin and location of the generation of the disturbance and the location and timing of the nucleation event. In a companion research effort, we are developing novel techniques for the non-contact measurements of the surface tension and viscosity of highly viscous supercooled liquids. Currently used non-invasive methods of surface tension measurement for the case of undercooled liquids generally rely of the quantitative determination of the resonance frequencies of drop shape oscillations, of the dynamics of surface capillary waves, or of the velocity of streaming flows. These methods become quickly ineffective when the liquid viscosity rises to a significant value. An alternate and accurate method which would be applicable to liquids of significant viscosity is therefore needed. We plan to develop such a capability by measuring the equilibrium shape of levitated undercooled melt droplets as they undergo solid-body rotation. The experimental measurement of the characteristic point of transition (bifurcation point) between axisymmetric and two-lobed shapes will be used to calculate the surface tension of the liquid. Such an approach has already been

  4. [The tension band effect of the iliotibial tract].

    PubMed

    Tichy, P; Tillmann, B

    1989-05-01

    There is an unreconciled discrepancy between the course of the iliotibial tract described in most anatomical textbooks and the results of photoelastic experiments performed by Pauwels (1948), in which he demonstrated the principle of the tension band effect that decreases the bending stress of the femur. If the photoelastic experiments are performed according to the anatomical description of the attachments of the iliotibial tract between iliac bone and tibial condyle not only is the tension band effect lacking; the stress is even increased. Our reinvestigation of the course of the iliotibial tract shows that the iliotibial tract is not fixed at the greater trochanter, as Pauwels assumed in his photoelastic experiments. Rather, the tendon of the gluteus maximus and a major portion of the iliotibial tract intermingle near the gluteal tuberosity. As a result, the iliotibial tract is also attached to the proximal end of the femur. If a model is constructed on the basis of this finding, the simulation of traction between gluteal tuberosity and the tibial condyle results in a decrease in the bending stress on the femoral shaft. Thus, the results of the present morphological and functional investigations confirm the biomechanical tension band effect of the iliotibial tract on the femur via the attachment to the femur mediated by the tendon of the gluteus maximus.

  5. Reactive processing of formaldehyde and acetaldehyde in aqueous aerosol mimics: surface tension depression and secondary organic products

    NASA Astrophysics Data System (ADS)

    Li, Z.; Schwier, A. N.; Sareen, N.; McNeill, V. F.

    2011-11-01

    The reactive uptake of carbonyl-containing volatile organic compounds (cVOCs) by aqueous atmospheric aerosols is a likely source of particulate organic material. The aqueous-phase secondary organic products of some cVOCs are surface-active. Therefore, cVOC uptake can lead to organic film formation at the gas-aerosol interface and changes in aerosol surface tension. We examined the chemical reactions of two abundant cVOCs, formaldehyde and acetaldehyde, in water and aqueous ammonium sulfate (AS) solutions mimicking tropospheric aerosols. Secondary organic products were identified using Aerosol Chemical Ionization Mass Spectrometry (Aerosol-CIMS), and changes in surface tension were monitored using pendant drop tensiometry. Hemiacetal oligomers and aldol condensation products were identified using Aerosol-CIMS. Acetaldehyde depresses surface tension to 65(±2) dyn cm-1 in pure water (a 10% surface tension reduction from that of pure water) and 62(±1) dyn cm-1 in AS solutions (a 20.6% reduction from that of a 3.1 M AS solution). Surface tension depression by formaldehyde in pure water is negligible; in AS solutions, a 9% reduction in surface tension is observed. Mixtures of these species were also studied in combination with methylglyoxal in order to evaluate the influence of cross-reactions on surface tension depression and product formation in these systems. We find that surface tension depression in the solutions containing mixed cVOCs exceeds that predicted by an additive model based on the single-species isotherms.

  6. Development of Maximum Bubble Pressure Method for Surface Tension Measurement of High Viscosity Molten Silicate

    NASA Astrophysics Data System (ADS)

    Takeda, Osamu; Iwamoto, Hirone; Sakashita, Ryota; Iseki, Chiaki; Zhu, Hongmin

    2017-07-01

    A surface tension measurement method based on the maximum bubble pressure (MBP) method was developed in order to precisely determine the surface tension of molten silicates in this study. Specifically, the influence of viscosity on surface tension measurements was quantified, and the criteria for accurate measurement were investigated. It was found that the MBP apparently increased with an increase in viscosity. This was because extra pressure was required for the flowing liquid inside the capillary due to viscous resistance. It was also expected that the extra pressure would decrease by decreasing the fluid velocity. For silicone oil with a viscosity of 1000 \\hbox {mPa}{\\cdot }\\hbox {s}, the error on the MBP could be decreased to +1.7 % by increasing the bubble detachment time to 300 \\hbox {s}. However, the error was still over 1 % even when the bubble detachment time was increased to 600 \\hbox {s}. Therefore, a true value of the MBP was determined by using a curve-fitting technique with a simple relaxation function, and that was succeeded for silicone oil at 1000 \\hbox {mPa}{\\cdot } \\hbox {s} of viscosity. Furthermore, for silicone oil with a viscosity as high as 10 000 \\hbox {mPa}{\\cdot }\\hbox {s}, the apparent MBP approached a true value by interrupting the gas introduction during the pressure rising period and by re-introducing the gas at a slow flow rate. Based on the fundamental investigation at room temperature, the surface tension of the \\hbox {SiO}2-40 \\hbox {mol}%\\hbox {Na}2\\hbox {O} and \\hbox {SiO}2-50 \\hbox {mol}%\\hbox {Na}2\\hbox {O} melts was determined at a high temperature. The obtained value was slightly lower than the literature values, which might be due to the influence of viscosity on surface tension measurements being removed in this study.

  7. Design of a vapor-liquid-equilibrium, surface tension, and density apparatus

    SciTech Connect

    Holcomb, C.D.; Outcalt, S.L.

    1997-12-31

    The design and performance of a unique vapor-liquid equilibrium (VLE) apparatus with density and surface tension capabilities is presented. The apparatus operates at temperatures ranging from 218 to 423 K, at pressures to 17 MPa, at densities to 1100 kg/m{sup 3}, and at surface tensions ranging from 0.1 to 75 mN/m. Temperatures are measured with a precision of {+-}0.02 K, pressures with a precision of {+-}0.1% of full scale, densities with a precision of {+-}0.5 kg/m{sup 3}, surface tensions with a precision of {+-}0.2 mN/m, and compositions with a precision of {+-}0.005 mole fraction. The apparatus is designed to be both accurate and versatile. Capabilities include: (1) the ability to operate the apparatus as a bubble point pressure or an isothermal pressure-volume-temperature (PVT) apparatus, (2) the ability to measure densities and surface tensions of the coexisting phases, and (3) the ability for either trapped or capillary sampling. We can validate our VLE and density data by measuring PVT or bubble point pressures in the apparatus. The use of the apparatus for measurements of VLE, densities, and surface tensions over wide ranges of temperature and pressure is important in equation of state and transport property model development. The use of different sampling procedures allows measurement of a wider variety of fluid mixtures. VLE measurements on the alternative refrigerant system R32/134a are presented and compared to literature results to verify the performance of the apparatus.

  8. Correlation of Dynamic Surface Tension with Sedimentation of PTFE Particles and Water Penetration in Powders.

    PubMed

    Shah, Vidhi; Bharatiya, Bhavesh; Shah, Dinesh O; Mukherjee, Tulsi

    2015-12-29

    The dynamic surface tension of aqueous poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) [(PEO-PPO-PEO)]-type polymeric surfactant (P103, P105, F108, P123, and F127) solutions were correlated with water penetration in packed Teflon powders, the sedimentation of Teflon suspensions in these solutions, foamability, and contact angle measurements on a Teflon surface. The DST trend with bubble lifetime indicated that the overall slowdown in the diffusion process in aqueous solutions is a function of a higher poly(ethylene oxide) (PEO) molecular weight for a given series of block copolymers containing equal PPO molecular weights, favoring slower diffusion kinetics to the air-water interface caused by preferential partitioning in bulk water. The wettability of poly(tetrafluoroethylene) (PTFE) powder illustrates better water penetration for polymers with low molecular weight and lower HLB values. The wettability of F127 solutions decreases with corresponding increases in concentration resulting from higher viscosity, which restrains the diffusion kinetics at the PTFE-water interface. The foamability decreases drastically with higher PEO molecular weight as attributed by slower diffusion kinetics, leading to a decrease in the effective concentration of molecules at the foam interface. The contact angle on glass and the PTFE surface are in good agreement with assumptions made by other analytical techniques showing a lower value of the contact angle with a lower HLB of the Pluronic, which relates to the higher adsorption of molecules at the interface. It is concluded that the adsorption of molecules at the PTFE-water interface decreases in aqueous Pluronic solutions with corresponding increases in the hydrophilic lipophilic balance (HLB), which is consistent with foaming, water penetration in a packed powder of PTFE, the rate of sedimentation, and DST data. A PTFE dispersion containing P123 showed the maximum wettability and lowest sedimentation among the series

  9. Tension induced surface plasmon-polaritons at graphene-based structure

    NASA Astrophysics Data System (ADS)

    Khalandi, G.; Namdar, A.; Entezar, S. Roshan

    2017-02-01

    Dispersion properties and field distributions of TM (or p-polarized) surface plasmon-polaritons have been investigated in the system that a strained graphene sheet cladded by two dielectrics. The outcomes show that graphene TM surface plasmon-polaritons are bound confined modes, and the field components penetrate into the dielectric layers in the rang that is very smaller than the wavelength in the free space. At low photon energies, when the tension is along the zigzag (armchair) direction and parallel (perpendicular) to the tangential electric field, the wavelength, propagation length and penetration depth of TM surface plasmon-polaritons increase (decrease) with increasing the strain. Changing the angle between the tension direction and tangential electric field at cases with the constant strain, cause to existence of TM surface plasmon-polaritons in the wider range of frequency.

  10. Perceiving the affordance of string tension for power strokes in badminton: expertise allows effective use of all string tensions.

    PubMed

    Zhu, Qin

    2013-01-01

    Affordances mean opportunities for action. These affordances are important for sports performance and relevant to the abilities developed by skilled athletes. In racquet sports such as badminton, different players prefer widely different string tension because it is believed to provide opportunities for effective strokes. The current study examined whether badminton players can perceive the affordance of string tension for power strokes and whether the perception of affordance itself changed as a function of skill level. The results showed that string tension constrained the striking performance of both novice and recreational players, but not of expert players. When perceptual capability was assessed, perceptual mode did not affect perception of the optimal string tension. Skilled players successfully perceived the affordance of string tension, but only experts were concerned about saving energy. Our findings demonstrated that perception of the affordance of string tension in badminton was determined by action abilities. Furthermore, experts could adjust the action to maintain a superior level of performance based on the perception of affordance.

  11. Surface properties of aqueous amino acid solutions. I. Surface tension of hydrochloric acid-glycine and glycine-sodium hydroxide systems.

    PubMed

    Matubayasi, Norihiro; Namihira, Junji; Yoshida, Masao

    2003-11-01

    The surface tensions of aqueous solutions of four mixtures (hydrochloric acid-glycine hydrochloride, glycine hydrochloride-glycine, glycine-sodium glycinate, and sodium glycinate-sodium hydroxide) were measured as a function of total molality and mole fraction. The measurements correspond to the change in surface tension with variation of pH. The contribution of glycine hydrochloride to the increments in surface tension is equivalent to that observed for the aqueous solution of glycine, while the contribution of sodium glycinate is much larger than that of glycine. The variations in surface tension on mixing in the surface region are discussed using comparisons with mixtures of simple salts.

  12. Quantitative estimation of the parameters for self-motion driven by difference in surface tension.

    PubMed

    Suematsu, Nobuhiko J; Sasaki, Tomohiro; Nakata, Satoshi; Kitahata, Hiroyuki

    2014-07-15

    Quantitative information on the parameters associated with self-propelled objects would enhance the potential of this research field; for example, finding a realistic way to develop a functional self-propelled object and quantitative understanding of the mechanism of self-motion. We therefore estimated five main parameters, including the driving force, of a camphor boat as a simple self-propelled object that spontaneously moves on water due to difference in surface tension. The experimental results and mathematical model indicated that the camphor boat generated a driving force of 4.2 μN, which corresponds to a difference in surface tension of 1.1 mN m(-1). The methods used in this study are not restricted to evaluate the parameters of self-motion of a camphor boat, but can be applied to other self-propelled objects driven by difference in surface tension. Thus, our investigation provides a novel method to quantitatively estimate the parameters for self-propelled objects driven by the interfacial tension difference.

  13. Surface tension of polytetrafluoroethylene and its wetting by aqueous solution of some surfactants and their mixtures

    NASA Astrophysics Data System (ADS)

    Mańko, Diana; Zdziennicka, Anna; Jańczuk, Bronisław

    2017-01-01

    Measurements of the contact angle of aqueous solution of rhamnolipid (RL) mixture with n-octyl-β-D-glucopyranoside (OGP), Triton X-100 (TX-100) or/and sodium dodecylsulfate (SDDS) on polytetrafluoroethylene (PTFE) were made. To this aim there was used a plate whose surface topography was analyzed by means of optical profilometry method. Additionally, plate surface chemistry was studied employing the Fourier transform infrared spectroscopy. The obtained values of contact angle were discussed based on the PTFE surface tension (γSV) as well as the Lifshitz-van der Waals component of the water surface tension (γWLW). The contact angle of aqueous solution of several surfactants and their mixtures on PTFE was also considered on the basis of γSV and γWLW . It occured that by using the values of γSV , γWLW and surface tension of the aqueous solution of surfactants and their mixtures, the contact angle on PTFE can be predicted. It also occured that changes of adhesion tension of aqueous solutions of surfactants as a function of their concentration can be determined by the exponential function of the first or second order. Using such functions Gibbs surface excess concentration of surfactants at the PTFE-water interface, mole fraction of surfactant in the mixed monolayer and fraction of the area occupied by given surfactants in the monolayer were determined. Gibbs surface free energy of adsorption of a given surfactant in the presence of another one and adhesion work of the aqueous solution of surfactants to the PTFE surface were also evaluated.

  14. On self-diffusion and surface energy upon compression or tension of an iron crystal

    NASA Astrophysics Data System (ADS)

    Magomedov, M. N.

    2013-03-01

    The dependences of the activation parameters (formation of vacancies and self-diffusion) and specific surface energy on the volume fraction ( V/ V 0) are calculated in terms of the Mie-Lenard-Jones pair potential of interatomic interaction for bcc-Fe along the 300-K and 3000-K isotherms. It is shown that under strong compressions ( V/ V 0 < 1) or tensions ( V/ V 0 > 1), the surface energy has a negative value, which must lead to the crystal structure fragmentation.

  15. Inclusion of line tension effect in classical nucleation theory for heterogeneous nucleation: A rigorous thermodynamic formulation and some unique conclusions

    SciTech Connect

    Singha, Sanat K.; Das, Prasanta K. Maiti, Biswajit

    2015-03-14

    A rigorous thermodynamic formulation of the geometric model for heterogeneous nucleation including line tension effect is missing till date due to the associated mathematical hurdles. In this work, we develop a novel thermodynamic formulation based on Classical Nucleation Theory (CNT), which is supposed to illustrate a systematic and a more plausible analysis for the heterogeneous nucleation on a planar surface including the line tension effect. The appreciable range of the critical microscopic contact angle (θ{sub c}), obtained from the generalized Young’s equation and the stability analysis, is θ{sub ∞} < θ{sub c} < θ′ for positive line tension and is θ{sub M} < θ{sub c} < θ{sub ∞} for negative line tension. θ{sub ∞} is the macroscopic contact angle, θ′ is the contact angle for which the Helmholtz free energy has the minimum value for the positive line tension, and θ{sub M} is the local minima of the nondimensional line tension effect for the negative line tension. The shape factor f, which is basically the dimensionless critical free energy barrier, becomes higher for lower values of θ{sub ∞} and higher values of θ{sub c} for positive line tension. The combined effect due to the presence of the triple line and the interfacial areas (f{sup L} + f{sup S}) in shape factor is always within (0, 3.2), resulting f in the range of (0, 1.7) for positive line tension. A formerly presumed appreciable range for θ{sub c}(0 < θ{sub c} < θ{sub ∞}) is found not to be true when the effect of negative line tension is considered for CNT. Estimation based on the property values of some real fluids confirms the relevance of the present analysis.

  16. Surface Tension Estimates for Droplet Formation in Slurries with Low Concentrations of Hydrophobic Particles, Polymer Flocculants or Surface-Active Contaminants

    SciTech Connect

    Gauglitz, Phillip A.; Mahoney, Lenna A.; Blanchard, Jeremy; Bamberger, Judith A.

    2011-06-10

    In support of the K-Basin project, Pacific Northwest National Laboratory (PNNL) was requested to evaluate the appropriate surface tension value to use in models predicting the formation of droplets from spray leaks of K-Basin slurries. The specific issue was whether it was more appropriate to use the surface tension of pure water in model predictions for all plausible spray leaks or to use a lower value. The surface tension of K-Basin slurries is potentially affected not only by particles but by low concentrations of nonionic polyacrylamide flocculant and perhaps by contaminants with surfactant properties, which could decrease the surface tension below that of water. A lower surface tension value typically results in smaller droplets being formed with a larger fraction of droplets in the respirable size range, so using the higher surface tension value of pure water is not conservative and thus needs a strong technical basis.

  17. Convective Instability of a Gravity Modulated Fluid Layer with Surface Tension Variation

    NASA Technical Reports Server (NTRS)

    Skarda, J. Raymond Lee

    1998-01-01

    Gravity modulation of an unbounded fluid layer with surface tension variations along its free surface is investigated. In parameter space of (wavenumber, Marangoni number) modulation has a destabilizing effect on the unmodulated neutral stability curve for large Prandtl number, Pr, and small modulation frequency, Omega, while a stabilizing effect is observed for small Pr and large Omega. As Omega yields infinity, the modulated neutral stability curves approach the unmodulated neutral stability curve. At certain values of Pr and L2 multiple minima are observed and the neutral stability curves become highly distorted. Closed regions of subharmonic instability are also observed. Alternating regions of synchronous and subharmonic instability separated by very thin stable regions are observed in (1/Omega,g(sub 1)) space for the singly diffusive cases. Quasiperiodic behavior in addition to the synchronous and subharmonic responses, are observed for the case of a double diffusive fluid layer. Minimum acceleration amplitudes were observed to closely correspond with a subharmonic response, Lambda(sub im) = Omega/2 .

  18. Surface tension driven processes densify and retain permeability in magma and lava

    NASA Astrophysics Data System (ADS)

    Kennedy, Ben M.; Wadsworth, Fabian B.; Vasseur, Jérémie; Ian Schipper, C.; Mark Jellinek, A.; von Aulock, Felix W.; Hess, Kai-Uwe; Kelly Russell, J.; Lavallée, Yan; Nichols, Alexander R. L.; Dingwell, Donald B.

    2016-01-01

    We offer new insights into how an explosive eruption can transition into an effusive eruption. Magma containing >0.2 wt% dissolved water has the potential to vesiculate to a porosity in excess of 80 vol.% at atmospheric pressure. Thus all magmas contain volatiles at depth sufficient to form foams and explosively fragment. Yet gas is often lost passively and effusive eruptions ensue. Magmatic foams are permeable and understanding permeability in magma is crucial for models that predict eruptive style. Permeability also governs magma compaction models. Those models generally imply that a reduction in magma porosity and permeability generates an increased propensity for explosivity. Here, our experimental results show that surface tension stresses drive densification without creating an impermeable 'plug', offering an additional explanation of why dense magmas can avoid explosive eruption. In both an open furnace and a closed autoclave, we subject pumice samples with initial porosity of ∼70 vol.% to a range of isostatic pressures (0.1-11 MPa) and temperatures (350-950 °C) relevant to shallow volcanic environments. Our experimental data and models constrain the viscosity, permeability, timescales, and length scales over which densification by pore-scale surface tension stresses competes with density-driven compaction. Where surface tension dominates the dynamics, densification halts at a plateau connected porosity of ∼25 vol.% for our samples. SEM, pycnometry and micro-tomography show that in this process (1) microporous networks are destroyed, (2) the relative pore network surface area decreases, and (3) a remaining crystal framework enhances the longevity of macro-pore connectivity and permeability critical for sustained outgassing. We propose that these observations are a consequence of a surface tension-driven retraction of viscous pore walls at areas of high bubble curvature (micro-vesicular network terminations), and that this process drives bulk

  19. Contact angle and surface tension measurements of a five-ring polyphenyl ether

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.

    1985-01-01

    Contact angle measurements were performed for a five-ring polyphenyl ether isomeric mixture on M-50 steel in a dry nitrogen atmosphere. Two different techniques were used: (1) a tilting plate apparatus, and (2) a sessile drop apparatus. Measurements were made for the temperature range 25 to 190 C. Surface tension was measured by a differential maximum bubble pressure technique over the range 23 to 220C in room air. The critical surface energy of spreading (gamma (sub c)) was determined for the polyphenyl ether by plotting the cosine of the contact angle (theta) versus the surface tension (gamma (sub LV)). The straight line intercept at cosine theta = 1 is defined as gamma (sub c). Gamma (sub c) was found to be 30.1 dyn/cm for the tilting plate technique and 31.3 dyn/cm for the sessile drop technique. These results indicate that the polyphenyl ether is inherently autophobic (i.e., it will not spread on its own surface film until its surface tension is less than gamma (sub c). This phenomenon is discussed in light of the wettability and wear problems encountered with this fluid.

  20. Spreading and mixing of drops on a miscible liquid of different surface tension

    NASA Astrophysics Data System (ADS)

    Afkhami, S.; Seric, I.; Kondic, L.; Kim, H.; Shardt, O.; Stone, H. A.

    2016-11-01

    We carry out Volume-of-Fluid based numerical simulations of a Marangoni-driven spreading of isopropyl alcohol (IPA) drops placed on water-air interface. The two fully miscible liquids create a spatially varying surface tension, leading to the spreading of the IPA drop on the water surface. We study the spreading of drops as IPA concentration is varied. In particular, we compute the spreading velocity and show that the scaling of the front position, L, with time, t, is given by L t 0 . 7 . We observe that while the surface tension difference between the two liquids controls the spreading velocity, it only slightly alters the power-law behavior for the range of considered IPA concentrations. We also provide detailed insight of the mixing of the IPA and water, and show the time evolution of liquid-air surface tension distribution. We show that the mixing results in a volume flux in a thin region on the surface, generating a vortical flow underneath the spreading front; we investigate the details of these flow patterns and show the time evolution of the circulation within the water. The numerical results are supported by new experimental observations reported separately.

  1. Influence of Nanosegregation on the Surface Tension of Fluorinated Ionic Liquids

    PubMed Central

    Luís, Andreia; Shimizu, Karina; Araújo, João M. M.; Carvalho, Pedro J.; Lopes-da-Silva, José A.; Canongia Lopes, José N.; Rebelo, Luís Paulo N.; Coutinho, João A. P.; Freire, Mara G.; Pereiro, Ana B.

    2017-01-01

    We have investigated, both theoretically and experimentally, the balance between the presence of alkyl and perfluoroalkyl side chains on the surface organization and surface tension of fluorinated ionic liquids (FILs). A series of ILs composed of 1-alkyl-3-methylimidazolium cations ([CnC1im] with n = 2, 4, 6, 8, 10 or 12) combined with the perfluorobutanesulfonate anion was used. The surface tensions of the investigated liquid salts are considerably lower than those reported for non-fluorinated ionic liquids. The most surprising and striking feature was the identification, for the first time, of a minimum at n = 8 in the surface tension versus the length of the IL cation alkyl side chain. Supported by molecular dynamic simulations it was found that this trend is a result of the competition between the two nonpolar domains (perfluorinated and aliphatic) on pointing towards the gas-liquid interface, a phenomenon which occurs in ionic liquids with perfluorinated anions. Furthermore, these ionic liquids present the lowest surface entropy reported to date. PMID:27218210

  2. Contact angle and surface tension measurements of a five-ring polyphenyl ether

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.

    1986-01-01

    Contact angle measurements were performed for a five-ring polyphenyl ether isomeric mixture on M-50 steel in a dry nitrogen atmosphere. Two different techniques were used: (1) a tilting plate apparatus, and (2) a sessile drop apparatus. Measurements were made for the temperature range 25 to 190 C. Surface tension was measured by a differential maximum bubble pressure technique over the range 23 to 220 C in room air. The critical surface energy of spreading (gamma /sub c/) was determined for the polyphenyl ether by plotting the cosine of the contact angle (theta) versus the surface tension (gamma /sub LV/). The straight line intercept at cosine theta = 1 is defined as gamma (sub c). Gamma (sub c) was found to be 30.1 dyn/cm for the tilting plate technique and 31.3 dyn/cm for the sessile drop technique. These results indicate that the polyphenyl ether is inherently autophobic (i.e., it will not spread on its own surface film until its surface tension is less than gamma /sub c/). This phenomenon is discussed in light of the wettability and wear problems encountered with this fluid.

  3. Surface tension of dilute alcohol-aqueous binary fluids: n-Butanol/water, n-Pentanol/water, and n-Hexanol/water solutions

    NASA Astrophysics Data System (ADS)

    Cheng, Kuok Kong; Park, Chanwoo

    2017-07-01

    Surface tension of pure fluids, inherently decreasing with regard to temperature, creates a thermo-capillary-driven (Marangoni) flow moving away from a hot surface. It has been known that few high-carbon alcohol-aqueous solutions exhibit an opposite behavior of the surface tension increasing with regard to temperature, such that the Marangoni flow moves towards the hot surface (self-rewetting effect). We report the surface tensions of three dilute aqueous solutions of n-Butanol, n-Pentanol and n-Hexanol as self-rewetting fluids measured for ranges of alcohol concentration (within solubility limits) and fluid temperatures (25-85 °C). A maximum bubble pressure method using a leak-tight setup was used to measure the surface tension without evaporation losses of volatile components. It was found from this study that the aqueous solutions with higher-carbon alcohols exhibit a weak self-rewetting behavior, such that the surface tensions remain constant or slightly increases above about 60 °C. These results greatly differ from the previously reported results showing a strong self-rewetting behavior, which is attributed to the measurement errors associated with the evaporation losses of test fluids during open-system experiments.

  4. Surface tension of dilute alcohol-aqueous binary fluids: n-Butanol/water, n-Pentanol/water, and n-Hexanol/water solutions

    NASA Astrophysics Data System (ADS)

    Cheng, Kuok Kong; Park, Chanwoo

    2017-01-01

    Surface tension of pure fluids, inherently decreasing with regard to temperature, creates a thermo-capillary-driven (Marangoni) flow moving away from a hot surface. It has been known that few high-carbon alcohol-aqueous solutions exhibit an opposite behavior of the surface tension increasing with regard to temperature, such that the Marangoni flow moves towards the hot surface (self-rewetting effect). We report the surface tensions of three dilute aqueous solutions of n-Butanol, n-Pentanol and n-Hexanol as self-rewetting fluids measured for ranges of alcohol concentration (within solubility limits) and fluid temperatures (25-85 °C). A maximum bubble pressure method using a leak-tight setup was used to measure the surface tension without evaporation losses of volatile components. It was found from this study that the aqueous solutions with higher-carbon alcohols exhibit a weak self-rewetting behavior, such that the surface tensions remain constant or slightly increases above about 60 °C. These results greatly differ from the previously reported results showing a strong self-rewetting behavior, which is attributed to the measurement errors associated with the evaporation losses of test fluids during open-system experiments.

  5. Surface Tension Prediction Using Characteristics of the Density Profile Through the Interfacial Region

    NASA Astrophysics Data System (ADS)

    Wemhoff, A. P.; Carey, V. P.

    2006-03-01

    A simple surface tension estimation technique is described that is based solely upon the characteristics of the density profile in the interfacial region and the physical properties of the molecules in the fluid. This method, denoted free energy integration (FEI), links interfacial tension to known interfacial region density profile characteristics obtained via experiment or simulation. The general FEI methodology is provided here, and specific relations are derived for a methodology that incorporates the Redlich-Kwong fluid model. The Redlich-Kwong based FEI method was used to predict interfacial tension using the density profile characteristics of molecular dynamics (MD) simulations of argon using the Lennard-Jones potential, diatomic nitrogen using the two-center Lennard-Jones potential, and water using the extended simple point-charge (SPC/E) model. These results for argon compare favorably to values calculated by the traditional virial approach, known values from the literature using the finite-size scaling technique, and ASHRAE recommended values. In addition, the FEI predictions agree well with ASHRAE values and predictions using the virial method for nitrogen for the simulated range of temperatures in this study, and for water for reduced temperatures above 0.7. In addition, the FEI method results agree well with other established theoretical techniques for predictions of the surface tension of sulfur hexafluoride close to the critical point.

  6. The effects of temperature and light elements on the interfacial tension of liquid iron under high pressure

    NASA Astrophysics Data System (ADS)

    Terasaki, H.; Urakawa, S.; Funakoshi, K.; Ohtani, E.; Suzuki, A.; Nishida, K.; Sakamaki, T.; Nishiyama, N.; Wang, Y.

    2007-12-01

    Interfacial tension is one of the most important properties of liquid iron-alloy to control the core formation process in the Earth and planets. The aim of this study is to clarify the effects of temperature and light elements (S and P) on the interfation tension of liquid iron under high pressure. In this study, high pressure in-situ measurement of interfacial tension was carried out for the liquid Fe-S and Fe-P alloys using sessile drop method combined with X-ray radiography technique up to 2 GPa and 1923 K. The sessile drop method has been widely used for measurement of surface and interfacial tensions at ambient pressure. The effect of temperature on the interfacial tension for both Fe-S and Fe-P liquids is quite small in the range of measurement (1623 - 1923 K). The interfacial tension of liquid Fe-S decreases linearly from 802 to 112 mN/m with increasing sulphur content of 0 - 40 at%. Thus, sulphur reduces significantly the interfacial tension of liquid iron. On the other hand, phosphorus does not affect to the interfacial tension of liquid iron. These tendencies are in good agreement with the data measured at ambient pressure. Therefore, the behaviour of light elements on the interface at ambient pressure is maintained at least up to 2 GPa and the effect of light elements on the interfacial tension of liquid iron depends on the element species. The shape change of the liquid Fe-S was observed before and after quenching. This suggests that the in-situ measurement at high pressure and temperature is essential in order to obtain the true interfacial tension, i.e. interconnectivity of liquid iron-alloy.

  7. Stabilization of lysozyme by benzyl alcohol: surface tension and thermodynamic parameters.

    PubMed

    Goyal, Monu Kumari; Roy, Ipsita; Amin, Aeshna; Banerjee, Uttam Chand; Bansal, Arvind Kumar

    2010-10-01

    The aim of the study was to understand the effect of benzyl alcohol on biological activity, aggregation behavior, denaturant and heat-induced unfolding of lysozyme. Compatibility studies of lysozyme carried out with a number of anti-microbial preservatives, indicated benzyl alcohol to be the best suppressor of protein aggregation against heat stress. The effect of this preservative was checked at various pH values ranging from 4.0 to 9.0. In spite of reducing the thermal denaturation temperature (T(m)) at all pH values, benzyl alcohol had a stabilizing effect on lysozyme in terms of retaining the biological activity when the enzyme was incubated at 75 degrees C. The reduction in T(m) with increasing benzyl alcohol concentration was correlated with decreasing surface tension of surrounding medium. A detailed thermodynamic study of lysozyme in the presence of benzyl alcohol was carried out at pH 6.2. Change in Gibb's free energy of thermal unfolding at 25 degrees C was found to remain constant in the presence of benzyl alcohol, indicating no interaction of benzyl alcohol with the native protein at room temperature. Both the enthalpy and entropy change at mid point of thermal unfolding were found to increase in the presence of benzyl alcohol indicating the stabilization of partially unfolded state.

  8. Non-invasive high throughput approach for protein hydrophobicity determination based on surface tension.

    PubMed

    Amrhein, Sven; Bauer, Katharina Christin; Galm, Lara; Hubbuch, Jürgen

    2015-12-01

    The surface hydrophobicity of a protein is an important factor for its interactions in solution and thus the outcome of its production process. Yet most of the methods are not able to evaluate the influence of these hydrophobic interactions under natural conditions. In the present work we have established a high resolution stalagmometric method for surface tension determination on a liquid handling station, which can cope with accuracy as well as high throughput requirements. Surface tensions could be derived with a low sample consumption (800 μL) and a high reproducibility (<0.1‰ for water) within a reasonable time (3.5 min per sample). This method was used as a non-invasive HTP compatible approach to determine surface tensions of protein solutions dependent on protein content. The protein influence on the solutions' surface tension was correlated to the hydrophobicity of lysozyme, human lysozyme, BSA, and α-lactalbumin. Differences in proteins' hydrophobic character depending on pH and species could be resolved. Within this work we have developed a pH dependent hydrophobicity ranking, which was found to be in good agreement with literature. For the studied pH range of 3-9 lysozyme from chicken egg white was identified to be the most hydrophilic. α-lactalbumin at pH 3 exhibited the most pronounced hydrophobic character. The stalagmometric method occurred to outclass the widely used spectrophotometric method with bromophenol blue sodium salt as it gave reasonable results without restrictions on pH and protein species.

  9. Surface Tension and Viscosity Measurements in Microgravity: Some Results and Fluid Flow Observations during MSL-1

    NASA Technical Reports Server (NTRS)

    Hyer, Robert W.; Trapaga, G.; Flemings, M. C.

    1999-01-01

    The viscosity of a liquid metal was successfully measured for the first time by a containerless method, the oscillating drop technique. This method also provides a means to obtain a precise, non-contact measurement of the surface tension of the droplet. This technique involves exciting the surface of the molten sample and then measuring the resulting oscillations; the natural frequency of the oscillating sample is determined by its surface tension, and the damping of the oscillations by the viscosity. These measurements were performed in TEMPUS, a microgravity electromagnetic levitator (EML), on the Space Shuttle as a part of the First Microgravity Science Laboratory (MSL-1), which flew in April and July 1997 (STS-83 and STS-94). Some results of the surface tension and viscosity measurements are presented for Pd82Si18. Some observations of the fluid dynamic characteristics (dominant flow patterns, turbulent transition, cavitation, etc.) of levitated droplets are presented and discussed together with magnetohydrodynamic calculations, which were performed to justify these findings.

  10. Analytical description of concentration dependence of surface tension in multicomponent systems

    NASA Astrophysics Data System (ADS)

    R, Dadashev; R, Kutuev; D, Elimkhanov

    2008-02-01

    From the basic fundamental thermodynamic expressions the equation of isotherms of the surface tension of a ternary system is received. Various assumptions concerning the concentration dependence of molar areas are usually made when the equation is derived. The dependence of the molar areas is calculated as an additive function of the structure of a volumetric phase or the structure of a surface layer. To define the concentration dependence of the molar areas we used a stricter thermodynamic expression offered by Butler. In the received equation the dependence of molar areas on the structure of the solution is taken into account. Therefore, the equation can be applied for the calculation of surface tension over a wide concentration range of the components. Unlike the known expressions, the equation includes the surface tension properties of lateral binary systems, which makes the accuracy of the calculated values considerably higher. Thus, among the advantages of the offered equation we can point out the mathematical simplicity of the received equation and the fact that the equation includes physical parameters the experimental definition of which does not present any special difficulties.

  11. Slow viscous gravity-driven interaction between a bubble and a free surface with unequal surface tensions

    NASA Astrophysics Data System (ADS)

    Guémas, Marine; Sellier, Antoine; Pigeonneau, Franck

    2015-04-01

    The axisymmetric gravity-driven dynamics of a bubble rising toward a free surface is addressed for gas-liquid interfaces having unequal surface tensions. The liquid flow is governed by the Stokes equations which are here solved using a boundary element method in axisymmetric configuration. Within this framework, two dimensionless numbers arise: the Bond number Bo1 based on the surface tension of the bubble interface and the surface tension ratio γ ˆ comparing the free surface and bubble surface tensions. Under a careful and discussed selection of the code key settings (number of boundary elements, initial bubble location, and distance beyond which the free surface is truncated), it has been possible to numerically and accurately track in time the bubble and free surface shapes for several values of ( Bo 1 , γ ˆ ) . The long-time shapes are found to deeply depend upon both Bo1 and γ ˆ and also to compare well with the shapes predicted in Princen and Mason ["Shape of a fluid drop at a fluid-liquid interface. II. Theory for three-phase systems," J. Colloid. Sci. 20, 246-266 (1965)] using a hydrostatic model in which both surfaces are touching. Similarly, the drainage dynamics of the liquid film thickness between the bubble and the free surface depends on ( Bo 1 , γ ˆ ) . The long-time film thickness exponentially decays in time and a so-called thinning rate α for which the numerical behaviors and a simple model reveal two basic behaviors: (i) at small Bond number, α behaves as 1/Bo1 and (ii) at large Bond number, α is nearly constant. In addition, it is found that in the entire range of the quantity χ = ( 1 + γ ˆ ) Bo 1 / ( 2 γ ˆ ) , the thinning rate α is well approximated by the function 1/(18χ) + α∞ with α∞ ≈ 0.158. Such a result also permits one to estimate the typical drainage time versus the initial bubble radius a, the liquid density ρ and viscosity μ, the gravity and the free surface, and bubble surface tensions.

  12. Dynamic surface tension of polyelectrolyte/surfactant systems with opposite charges: two states for the surfactant at the interface.

    PubMed

    Ritacco, Hernán A; Busch, Jorge

    2004-04-27

    The molecular reorientation model of Fainerman et al. is conceptually adapted to explain the dynamic surface tension behavior in polyelectrolyte/surfactant systems with opposite charges. The equilibrium surface tension curves and the adsorption dynamics may be explained by assuming that there are two different states for surfactant molecules at the interface. One of these states corresponds to the adsorption of the surfactant as monomers, and the other to the formation of a mixed complex at the surface. The model also explains the plateaus that appear in the dynamic surface tension curves and gives a picture of the adsorption process.

  13. Reactive processing of formaldehyde and acetaldehyde in aqueous aerosol mimics: surface tension depression and secondary organic products

    NASA Astrophysics Data System (ADS)

    Li, Z.; Schwier, A. N.; Sareen, N.; McNeill, V. F.

    2011-07-01

    The reactive uptake of carbonyl-containing volatile organic compounds (cVOCs) by aqueous atmospheric aerosols is a likely source of particulate organic material. The aqueous-phase secondary organic products of some cVOCs are surface-active. Therefore, cVOC uptake can lead to organic film formation at the gas-aerosol interface and changes in aerosol surface tension. We examined the chemical reactions of two abundant cVOCs, formaldehyde and acetaldehyde, in water and aqueous ammonium sulfate (AS) solutions mimicking tropospheric aerosols. Secondary organic products were identified using Aerosol Chemical Ionization Mass Spectrometry (Aerosol-CIMS), and changes in surface tension were monitored using pendant drop tensiometry. Hemiacetal oligomers and aldol condensation products were identified using Aerosol-CIMS. A hemiacetal sulfate ester was tentatively identified in the formaldehyde-AS system. Acetaldehyde depresses surface tension to 65(±2) dyn cm-1 in pure water and 62(±1) dyn cm-1 in AS solutions. Surface tension depression by formaldehyde in pure water is negligible; in AS solutions, a 9 % reduction in surface tension is observed. Mixtures of these species were also studied in combination with methylglyoxal in order to evaluate the influence of cross-reactions on surface tension depression and product formation in these systems. We find that surface tension depression in the solutions containing mixed cVOCs exceeds that predicted by an additive model based on the single-species isotherms.

  14. Development of a space qualified Surface Tension Confined Liquid Cryogen Cooler (STCLCC)

    NASA Technical Reports Server (NTRS)

    Castles, Stephen H.; Schein, Michael E.

    1988-01-01

    The Surface Tension Confined Liquid Cryogen Cooler (STCLCC), a new type of cryogenic cooler which is being developed by the NASA-GSFC for spaceflight payloads, is described. The STCLCC will be capable of maintaining instrumentation within the temperature range of 10-120 K and will allow liquid cryogens to be flown in space without the risk of liquid being entrained in the vent gas. A low-density open-cell material in the STCLCC acts as a 'sponge', with the surface tension trapping the liquid cryogen within its pores and keeping the liquid away from the cooler's vent during launch, zero-g operations, and landing. It is emphasized that the STCLCC concept is amenable to a wide variety of applications, whenever a passive low-cost cooler is required or when the on-orbit service of a cooler would increase a mission's lifetime.

  15. Possible Evidence for a New Form of Liquid Buried in the Surface Tension of Supercooled Water

    PubMed Central

    Rogers, T. Ryan; Leong, Kai-Yang; Wang, Feng

    2016-01-01

    Contrary to the historical data, several recent experiments indicate that the surface tension of supercooled water follows a smooth extrapolation of the IAPWS equation in the supercooled regime. It can be seen, however, that a small deviation from the IAPWS equation is present in the recent experimental measurements. It is shown with simulations using the WAIL water potential that the small deviation in the experimental data is consistent with the tail of an exponential growth in surface tension as temperature decreases. The emergence temperature, Te, of a substantial deviation from the IAPWS equation is shown to be 227 K for the WAIL water and 235 K for real water. Since the 227 K Te is close to the Widom line in WAIL water, we argue that real water at 235 K approaches a similar crossover line at one atmospheric pressure. PMID:27615518

  16. Light Meets Water in Nonlocal Media: Surface Tension Analogue in Optics.

    PubMed

    Horikis, Theodoros P; Frantzeskakis, Dimitrios J

    2017-06-16

    Shallow water wave phenomena find their analogue in optics through a nonlocal nonlinear Schrödinger (NLS) model in 2+1 dimensions. We identify an analogue of surface tension in optics, namely, a single parameter depending on the degree of nonlocality, which changes the sign of dispersion, much like surface tension does in the shallow water wave problem. Using multiscale expansions, we reduce the NLS model to a Kadomtsev-Petviashvili (KP) equation, which is of the KPII (KPI) type, for strong (weak) nonlocality. We demonstrate the emergence of robust optical antidark solitons forming Y-, X-, and H-shaped wave patterns, which are approximated by colliding KPII line solitons, similar to those observed in shallow waters.

  17. Surface Tension of Methanol as a Function of cut-off Radius and Temperature Controllers

    NASA Astrophysics Data System (ADS)

    Obeidat, Abdalla; Jaradat, Adnan; Hamdan, Bushra

    Molecular dynamics is used to calculate the surface tension of van Leeuwen methanol. The van Leeuwen model of methanol is chosen over other models of methanol, since this model is widely used to study nucleation at low temperature. Usually, scientists use the cut-off radius to be three order of magnitude of segment diameter. In this study, we varied the cut-off radius to estimate the best cut-off at which the surface tension reaches its plateau. After deciding the best cut-off radius for van der Waals and Coulomb interactions (CUT-OFF and PME were used for Coulomb interaction), we varied the temperature controller (van-Housen, Berendsen, and v-rescale) to decide the best temperature controller to be used to study methanol. In all simulations, Gromacs is used at T =200-300K with periodic boundary conditions in all dimensions. JUST.

  18. Development of a space qualified Surface Tension Confined Liquid Cryogen Cooler (STCLCC)

    NASA Technical Reports Server (NTRS)

    Castles, Stephen H.; Schein, Michael E.

    1988-01-01

    The Surface Tension Confined Liquid Cryogen Cooler (STCLCC), a new type of cryogenic cooler which is being developed by the NASA-GSFC for spaceflight payloads, is described. The STCLCC will be capable of maintaining instrumentation within the temperature range of 10-120 K and will allow liquid cryogens to be flown in space without the risk of liquid being entrained in the vent gas. A low-density open-cell material in the STCLCC acts as a 'sponge', with the surface tension trapping the liquid cryogen within its pores and keeping the liquid away from the cooler's vent during launch, zero-g operations, and landing. It is emphasized that the STCLCC concept is amenable to a wide variety of applications, whenever a passive low-cost cooler is required or when the on-orbit service of a cooler would increase a mission's lifetime.

  19. Modeling surface tension using a ghost fluid technique within a volume of fluid formulation

    SciTech Connect

    Francois, M. M.; Kothe, D. B.; Cummins, S. J.

    2004-01-01

    Ghost fluid methods (GFM) are a viable approach for imposing sharp boundary conditions on interfaces that are arbitrarily embedded within the computational mesh. All GFM to date are formulated with an interface distance function that resides within a level-set (LS) framework. Recently we proposed a technique for reconstructing distance functions from volume fractions. This technique enables the exploitation of GFM within a volume of fluid formulation for modeling an interfacial phenomenon like surface tension. Combining GFM with a volume of fluid (VOF) formulation is attractive because of the VOF method's superior mass conservation and because of the ability of GFM to maintain sharp jump conditions. The continuum surface tension force (CSF) method, however, has the propensity to produce smooth jump. In the following, the combined VOF-GFM and more classical VOF-CSF formulations are compared and contrasted. Static and dynamic numerical results are used to illustrate our findings and support our claims.

  20. Calculation of the surface tension of liquid metals using a one-component-plasma reference system

    NASA Technical Reports Server (NTRS)

    Zeng, X. C.; Stroud, D.

    1987-01-01

    The one-component-plasma (OCP) model is used as a reference system instead of the traditional hard-sphere fluid to calculate the liquid-vapor interfacial surface tension of liquid metals within the density functional formalism. The calculated surface tensions of the alkali metals are in excellent agreement with experiment. For the polyvalent metal Al, the result obtained is larger than experimental measurements. It is concluded that the OCP system is not suitable to describe the liquid-vapor phase transition in simple metals which have a nominal plasma parameter larger than the usual freezing value of about 178. The calculated interfacial widths in all cases are narrower than the expected experimental values.

  1. Surface tension and adhesion of photo- and electron-beam resists

    NASA Astrophysics Data System (ADS)

    Bauer, Joachim J.; Drescher, G.; Silz, H.; Frankenfeld, H.; Illig, M.

    1997-07-01

    In order to reduce the defect density of resist structures, a general optimization of surface tension was developed and successfully applied, using Si, SiO2, Si3N4, AlCu, WTi and Cr as substrates, modified by priming. We demonstrate that the contact angle water (Theta) w can be used to reach the optimal conditions for adhesion of resists. We use models based on the Young and Dupre equations and the model of interaction of molecules by Wu to determine the surface tension and work of adhesion. Good resist adhesion results if the work of adhesion is greater than 5 dyn/cm. We outline preferred process windows for the contact angle for certain combinations of different types of resist and developer.

  2. Experimental study of surface tension, specific heat and thermal diffusivity of liquid and solid titanium

    NASA Astrophysics Data System (ADS)

    Zhou, K.; Wang, H. P.; Chang, J.; Wei, B.

    2015-10-01

    The thermophysical properties of liquid and solid titanium such as the surface tension, specific heat and thermal diffusivity have been investigated over a wide temperature range. By using electromagnetic levitation and oscillating drop method, the surface tension of liquid titanium was measured in the temperature range of 1802-2188 K. The viscosity and density of undercooled liquid titanium were calculated by some well-known models using the measured data as input. In addition, the specific heat of liquid titanium was determined over the experimental range using electromagnetic levitation and drop calorimetry obtaining the value of 33.64 J mol-1 K-1. In addition, the thermal diffusivity of solid titanium was measured by laser flash method in the temperature range of 171-1080 K.

  3. Possible Evidence for a New Form of Liquid Buried in the Surface Tension of Supercooled Water

    NASA Astrophysics Data System (ADS)

    Rogers, T. Ryan; Leong, Kai-Yang; Wang, Feng

    2016-09-01

    Contrary to the historical data, several recent experiments indicate that the surface tension of supercooled water follows a smooth extrapolation of the IAPWS equation in the supercooled regime. It can be seen, however, that a small deviation from the IAPWS equation is present in the recent experimental measurements. It is shown with simulations using the WAIL water potential that the small deviation in the experimental data is consistent with the tail of an exponential growth in surface tension as temperature decreases. The emergence temperature, Te, of a substantial deviation from the IAPWS equation is shown to be 227 K for the WAIL water and 235 K for real water. Since the 227 K Te is close to the Widom line in WAIL water, we argue that real water at 235 K approaches a similar crossover line at one atmospheric pressure.

  4. Theoretical study of phase transition, surface tension, and nucleation rate predictions for argon.

    PubMed

    Zhou, Di; Zeng, Ming; Mi, Jianguo; Zhong, Chongli

    2011-01-13

    In this work, a weighted density functional theory has been used to study the equilibrium and metastable processes for argon. In the theoretical approach, the two- and three-body interactions of the fluid molecules are considered simultaneously, and the renormalization group transformation is applied to address the long-range fluctuations inside the critical region. The global phase equilibria, planar and curvature-dependent surface tensions, critical radius, and nucleation rates of argon are investigated systematically. The results are in good agreement with the experimental data. Meanwhile, this work applies a methodology for calculating the curved surface tension in local supersaturated environments, showing that the Tolman length is negligible far from the critical region. Near the critical point, however, the Tolman length becomes positive and appears to diverge.

  5. Densities, surface tensions, and refractive indices of the water + 1,3-propanediol system

    SciTech Connect

    Lee, J.W.; Park, S.B.; Lee, H.

    2000-04-01

    Various working fluids have been proposed to satisfy specific conditions required for such systems as air-cooled absorption chillers, low-temperature heat-driven heat pumps, and solar-powered absorption chillers. Densities, surface tensions, and refractive indices of the binary water + 1,3-propanediol system were measured at temperatures of 298.15, 303.15, 308.15, 313.15, 318.15, and 323.15 K and at 1,3-propanediol mass fractions of 0.00, 0.10, 0.20, 0.40, 0.60, 0.80, and 1.00, respectively. The measured data were well correlated with the simple polynomial equations. The average absolute deviations were found to be 0.123% for density, 0.77% for surface tension, and 0.045% for refractive index.

  6. A Synthetic Phased Array Surface Acoustic Wave Sensor for Quantifying Bolt Tension

    PubMed Central

    Martinez, Jairo; Sisman, Alper; Onen, Onursal; Velasquez, Dean; Guldiken, Rasim

    2012-01-01

    In this paper, we report our findings on implementing a synthetic phased array surface acoustic wave sensor to quantify bolt tension. Maintaining proper bolt tension is important in many fields such as for ensuring safe operation of civil infrastructures. Significant advantages of this relatively simple methodology is its capability to assess bolt tension without any contact with the bolt, thus enabling measurement at inaccessible locations, multiple bolt measurement capability at a time, not requiring data collection during the installation and no calibration requirements. We performed detailed experiments on a custom-built flexible bench-top experimental setup consisting of 1018 steel plate of 12.7 mm (½ in) thickness, a 6.4 mm (¼ in) grade 8 bolt and a stainless steel washer with 19 mm (¾ in) of external diameter. Our results indicate that this method is not only capable of clearly distinguishing properly bolted joints from loosened joints but also capable of quantifying how loose the bolt actually is. We also conducted detailed signal-to-noise (SNR) analysis and showed that the SNR value for the entire bolt tension range was sufficient for image reconstruction.

  7. Surface Tension Demonstration using Water and Food Coloring in the U.S. Laboratory

    NASA Image and Video Library

    2003-01-19

    ISS006-E-18446 (19 January 2003) --- View of surface tension demonstration using water that is being held in place by a metal loop. Food coloring has been added to the water for demonstration purposes only. Astronaut Donald R. Pettit, Expedition Six NASA ISS science officer, photographed these demonstrations for educational purposes. The experiment took place in the Destiny laboratory on the International Space Station (ISS).

  8. Surface Tension Demonstration using Water and Food Coloring in the U.S. Laboratory

    NASA Image and Video Library

    2003-01-19

    ISS006-E-18432 (19 January 2003) --- View of surface tension demonstration using water that is being held in place by a metal loop. Food coloring has been added to the water for demonstration purposes only. Astronaut Donald R. Pettit, Expedition Six NASA ISS science officer, photographed these demonstrations for educational purposes. The experiment took place in the Destiny laboratory on the International Space Station (ISS).

  9. Surface Tension Demonstration using Water and Food Coloring in the U.S. Laboratory

    NASA Image and Video Library

    2003-01-19

    ISS006-E-18405 (19 January 2003) --- View of surface tension demonstration using water that is being held in place by a metal loop. Food coloring has been added to the water for demonstration purposes only. Astronaut Donald R. Pettit, Expedition Six NASA ISS science officer, photographed these demonstrations for educational purposes. The experiment took place in the Destiny laboratory on the International Space Station (ISS).

  10. Surface Tension Demonstration using Water and Food Coloring in the U.S. Laboratory

    NASA Image and Video Library

    2003-01-19

    ISS006-E-18431 (19 January 2003) --- View of surface tension demonstration using water that is being held in place by a metal loop. Food coloring has been added to the water for demonstration purposes only. Astronaut Donald R. Pettit, Expedition Six NASA ISS science officer, photographed these demonstrations for educational purposes. The experiment took place in the Destiny laboratory on the International Space Station (ISS).

  11. Let’s not forget the critical role of surface tension in xylem water relations

    Treesearch

    Jean-Christophe Domec

    2011-01-01

    The widely supported cohesion–tension theory of water transport explains the importance of a continuous water column and the mechanism of long-distance ascent of sap in plants (Dixon 1914, Tyree 2003, Angeles et al. 2004). The evaporation of water from the surfaces of mesophyll cells causes the air–water interface to retreat into the cellulose matrix of the plant cell...

  12. Global Solvability of a Free Boundary Three-Dimensional Incompressible Viscoelastic Fluid System with Surface Tension

    NASA Astrophysics Data System (ADS)

    Xu, Li; Zhang, Ping; Zhang, Zhifei

    2013-06-01

    Motivated by Beale (Commun Pure Appl Math 34:359-392, 1981; Arch Ration Mech Anal 84:307-352, 1983/1984), we investigate the global well-posedness of a free boundary problem of a three-dimensional incompressible viscoelastic fluid system in an infinite strip and with surface tension on the upper free boundary, provided that the initial data is sufficiently close to the equilibrium state.

  13. The Life and Work of Joseph Plateau: Father of Film and Discoverer of Surface Tension

    NASA Astrophysics Data System (ADS)

    Wautier, Kristel; Jonckheere, Alexander; Segers, Danny

    2012-09-01

    In 1835 Joseph Plateau (1801-1883) was appointed Professor of Physics and Applied Physics at Ghent University, Belgium. By then he was well known for his groundbreaking work on the aftereffect of light on the human retina, and he would go on to become the first person to produce moving images, for which he is considered to be the Father of Film. His greatest scientific achievement, however, was his discovery of surface tension.

  14. The influence of electric fields and surface tension on Kelvin-Helmholtz instability in two-dimensional jets

    NASA Astrophysics Data System (ADS)

    Grandison, Scott; Papageorgiou, Demetrios T.; vanden-Broeck, Jean-Marc

    2012-02-01

    We consider nonlinear aspects of the flow of an inviscid two-dimensional jet into a second immiscible fluid of different density and unbounded extent. Velocity jumps are supported at the interface, and the flow is susceptible to the Kelvin-Helmholtz instability. We investigate theoretically the effects of horizontal electric fields and surface tension on the nonlinear evolution of the jet. This is accomplished by developing a long-wave matched asymptotic analysis that incorporates the influence of the outer regions on the dynamics of the jet. The result is a coupled system of long-wave nonlinear, nonlocal evolution equations governing the interfacial amplitude and corresponding horizontal velocity, for symmetric interfacial deformations. The theory allows for amplitudes that scale with the undisturbed jet thickness and is therefore capable of predicting singular events such as jet pinching. In the absence of surface tension, a sufficiently strong electric field completely stabilizes (linearly) the Kelvin-Helmholtz instability at all wavelengths by the introduction of a dispersive regularization of a nonlocal origin. The dispersion relation has the same functional form as the destabilizing Kelvin-Helmholtz terms, but is of a different sign. If the electric field is weak or absent, then surface tension is included to regularize Kelvin-Helmholtz instability and to provide a well-posed nonlinear problem. We address the nonlinear problems numerically using spectral methods and establish two distinct dynamical behaviors. In cases where the linear theory predicts dispersive regularization (whether surface tension is present or not), then relatively large initial conditions induce a nonlinear flow that is oscillatory in time (in fact quasi-periodic) with a basic oscillation predicted well by linear theory and a second nonlinearly induced lower frequency that is responsible for quasi-periodic modulations of the spatio-temporal dynamics. If the parameters are chosen so that

  15. A method for the direct measurement of surface tension of collected atmospherically relevant aerosol particles using atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Hritz, Andrew D.; Raymond, Timothy M.; Dutcher, Dabrina D.

    2016-08-01

    Accurate estimates of particle surface tension are required for models concerning atmospheric aerosol nucleation and activation. However, it is difficult to collect the volumes of atmospheric aerosol required by typical instruments that measure surface tension, such as goniometers or Wilhelmy plates. In this work, a method that measures, ex situ, the surface tension of collected liquid nanoparticles using atomic force microscopy is presented. A film of particles is collected via impaction and is probed using nanoneedle tips with the atomic force microscope. This micro-Wilhelmy method allows for direct measurements of the surface tension of small amounts of sample. This method was verified using liquids, whose surface tensions were known. Particles of ozone oxidized α-pinene, a well-characterized system, were then produced, collected, and analyzed using this method to demonstrate its applicability for liquid aerosol samples. It was determined that oxidized α-pinene particles formed in dry conditions have a surface tension similar to that of pure α-pinene, and oxidized α-pinene particles formed in more humid conditions have a surface tension that is significantly higher.

  16. The roles of wettability and surface tension in droplet formation during inkjet printing.

    PubMed

    He, Bing; Yang, Sucui; Qin, Zhangrong; Wen, Binghai; Zhang, Chaoying

    2017-09-19

    This paper describes a lattice Boltzmann-based binary fluid model for inkjet printing. In this model, a time-dependent driving force is applied to actuate the droplet ejection. As a result, the actuation can be accurately controlled by adjusting the intensity and duration of the positive and negative forces, as well as the idle time. The present model was verified by reproducing the actual single droplet ejection process captured by fast imaging. This model was subsequently used to investigate droplet formation in piezoelectric inkjet printing. It was determined that the wettability of the nozzle inner wall and the surface tension of the ink are vital factors controlling the print quality and speed. Increasing the contact angle of the nozzle inner delays the droplet breakup time and reduces the droplet velocity. In contrast, higher surface tension values promote earlier droplet breakup and faster drop velocity. These results indicate that the hydrophilic modification of the nozzle inner wall and the choice of inks with high surface tensions will improve printing quality.

  17. Computational analysis of microbubble flows in bifurcating airways: role of gravity, inertia, and surface tension.

    PubMed

    Chen, Xiaodong; Zielinski, Rachel; Ghadiali, Samir N

    2014-10-01

    Although mechanical ventilation is a life-saving therapy for patients with severe lung disorders, the microbubble flows generated during ventilation generate hydrodynamic stresses, including pressure and shear stress gradients, which damage the pulmonary epithelium. In this study, we used computational fluid dynamics to investigate how gravity, inertia, and surface tension influence both microbubble flow patterns in bifurcating airways and the magnitude/distribution of hydrodynamic stresses on the airway wall. Direct interface tracking and finite element techniques were used to simulate bubble propagation in a two-dimensional (2D) liquid-filled bifurcating airway. Computational solutions of the full incompressible Navier-Stokes equation were used to investigate how inertia, gravity, and surface tension forces as characterized by the Reynolds (Re), Bond (Bo), and Capillary (Ca) numbers influence pressure and shear stress gradients at the airway wall. Gravity had a significant impact on flow patterns and hydrodynamic stress magnitudes where Bo > 1 led to dramatic changes in bubble shape and increased pressure and shear stress gradients in the upper daughter airway. Interestingly, increased pressure gradients near the bifurcation point (i.e., carina) were only elevated during asymmetric bubble splitting. Although changes in pressure gradient magnitudes were generally more sensitive to Ca, under large Re conditions, both Re and Ca significantly altered the pressure gradient magnitude. We conclude that inertia, gravity, and surface tension can all have a significant impact on microbubble flow patterns and hydrodynamic stresses in bifurcating airways.

  18. Well-posedness for the Classical Stefan Problem and the Zero Surface Tension Limit

    NASA Astrophysics Data System (ADS)

    Hadžić, Mahir; Shkoller, Steve

    2017-01-01

    We develop a framework for a unified treatment of well-posedness for the Stefan problem with or without surface tension. In the absence of surface tension, we establish well-posedness in Sobolev spaces for the classical Stefan problem. We introduce a new velocity variable which extends the velocity of the moving free-boundary into the interior domain. The equation satisfied by this velocity is used for the analysis in place of the heat equation satisfied by the temperature. Solutions to the classical Stefan problem are then constructed as the limit of solutions to a carefully chosen sequence of approximations to the velocity equation, in which the moving free-boundary is regularized and the boundary condition is modified in a such a way as to preserve the basic nonlinear structure of the original problem. With our methodology, we simultaneously find the required stability condition for well-posedness and obtain new estimates for the regularity of the moving free-boundary. Finally, we prove that solutions of the Stefan problem with positive surface tension {σ} converge to solutions of the classical Stefan problem as {σ to 0}.

  19. Surface Tension and Lamellar Spacing in Polyelectrolyte Blends and Block Copolymers

    NASA Astrophysics Data System (ADS)

    Sing, Charles; Olvera de La Cruz, Monica

    2015-03-01

    Heterogeneous polymer systems such as block copolymers (BCPs) are governed primarily by a competition between the surface tension between different chemical species and the entropic stretching of the polymer chains. Charged BCPs represent a class of materials that is currently of great interest to the polymer community due to the promise of charged BCPs as nanostructured membranes for batteries and fuel cells. The inclusion of charge presents a powerful way to tune the structure of BCPs, and we develop our understanding of how to do so by investigating the interfacial properties (surface tension and microstructure size) of polyelectrolyte blends and block copolymers. We use a new method that combines the features of liquid state (LS) theory and self consistent field theory (SCFT) into a multiscale LS-SCFT theory that provides beyond-mean-field predictions of polyelectrolyte systems. We find that charge size, charge correlations, and the fraction of charged monomers plays a crucial role in determining surface tension, and we therefore demonstrate how BCP structure changes upon inclusion of charges. Finally, we will show that these predictions provide the ideal basis for comparison to experiment and subsequent refinement of LS-SCFT theory.

  20. Surface tensions of linear and branched alkanes from Monte Carlo simulations using the anisotropic united atom model.

    PubMed

    Biscay, F; Ghoufi, A; Goujon, F; Lachet, V; Malfreyt, P

    2008-11-06

    The anisotropic united atoms (AUA4) model has been used for linear and branched alkanes to predict the surface tension as a function of temperature by Monte Carlo simulations. Simulations are carried out for n-alkanes ( n-C5, n-C6, n-C7, and n-C10) and for two branched C7 isomers (2,3-dimethylpentane and 2,4-dimethylpentane). Different operational expressions of the surface tension using both the thermodynamic and the mechanical definitions have been applied. The simulated surface tensions with the AUA4 model are found to be consistent within both definitions and in good agreement with experiments.

  1. Experimental study of surface tension of ethane-methane solution in temperature range 213-283 K

    NASA Astrophysics Data System (ADS)

    Andbaeva, V. N.; Khotienkova, M. N.

    2013-09-01

    The differential variation of the method of capillary rise was used to measure the capillary constant and to determine the surface tension of ethane-methane solution at "high" temperatures. Measurements were performed on the isotherms in the range of temperatures 213.15 ÷ 283.15 K at pressures up to 4 MPa. Decrease of ethane surface tension with the increase of pressure and concentration of methane in the solution is shown. The experimental data are compared with the results of surface tension calculation according to Rowlinson theory. Methane adsorption in the interface layer of solution is calculated.

  2. Electrostatic interaction effects on tension-induced pore formation in lipid membranes

    NASA Astrophysics Data System (ADS)

    Karal, Mohammad Abu Sayem; Levadnyy, Victor; Tsuboi, Taka-aki; Belaya, Marina; Yamazaki, Masahito

    2015-07-01

    We investigated the effects of electrostatic interactions on the rate constant (kp) for tension-induced pore formation in lipid membranes of giant unilamellar vesicles under constant applied tension. A decrease in salt concentration in solution as well as an increase in surface charge density of the membranes increased kp. These data indicate that kp increases as the extent of electrostatic interaction increases. We developed a theory on the effect of the electrostatic interactions on the free energy profile of the membrane containing a prepore and also on the values of kp; this theory explains the experimental results and fits the experimental data reasonably well in the presence of weak electrostatic interactions. Based on these results, we conclude that a decrease in the free energy barrier of the prepore state due to electrostatic interactions is the main factor causing an increase in kp.

  3. Influence of the local morphology on the surface tension of injection molded polypropylene

    NASA Astrophysics Data System (ADS)

    Gomes, M.; Pontes, A. J.; Viana, J. C.

    2014-05-01

    In this work, we investigate the development of the morphology of an injection molding polypropylene under the local thermomechanical environment imposed during processing, and its effect on the contact angle and, hence, on the surface tension of the moldings. Melt and mold temperatures were varied in two levels. The local thermomechanical environment was characterized by mold filling computational simulations that allow the calculation of thermomechanical variables (e.g., local temperatures, shear stresses) and indices (related to the local morphology development). In order to investigate the structural hierarchy variations of the moldings in the thickness direction, samples from skin to core were used. The molecular orientation and degree of crystallinity were determined as function of the thickness, as well as the contact angle. The variations of the degree of crystallinity were assessed by differential scanning calorimetry. The level of molecular orientation was evaluated by birefringence measurements. The contact angles were measured in deionized water by sessile drop (needle in) method at room temperature, to determine the wettability of the samples. The contact angles were found to vary along the molding thickness in the skin, transition and core layers. These variations are related to the local morphologies developed. Results suggest that water contact angle increases with the level of molecular orientation and for finer microstructures.

  4. A study of surface tension driven segregation in monotectic alloy systems

    NASA Technical Reports Server (NTRS)

    Andrews, J. Barry; Andrews, Rosalia N.; Gowens, Terrell F.

    1988-01-01

    The compatibilities of various monotectic alloy systems with several different crucible materials were evaluated. The study was carried out using small candidate alloy samples of compositions that produced fifty volume percent of each liquid phase at the monotectic temperature. Compatibility was based on the evaluation of the wetting tendency of the two immiscible phases with the crucible material in a one-g solidified sample. Three types of wetting phenomena were observed during the evaluation. Type 1 indicates an alloy-crucible combination where the L2 phase preferentially wets the crucible material. Since L2 is usually the minority phase in desirable alloys, this material combination would be difficult to process and is therefore considered incompatible. Type 2 behavior indicates an alloy-crucible combination where the L1 phase preferentially wets the crucible material. This type of combination is considered compatible since surface tension effects should aid in processing the alloy to a useful form. Type 3 indicates any combination that leads to major reactions between the alloy and crucible material, gas entrapment, or separation of the metal from the crucible wall. Additional compatibility evaluations would have to be carried out on combinations of this category. The five alloy systems studied included aluminum-bismuth, copper-lead, aluminum-indium, aluminum-lead and cadmium-gallium. The systems were combined with crucibles of alumina, boron nitride, mullite, quartz, silicon carbide and zirconia.

  5. The self-interaction of a fluid interface, the wavevector dependent surface tension and wedge filling.

    PubMed

    Parry, Andrew O; Rascón, Carlos

    2011-01-12

    We argue that whenever an interface, separating bulk fluid phases, adopts a non-planar configuration (induced by a confining geometry or thermal fluctuations, say), the energy cost of it will contain a non-local self-interaction term. For systems with short-ranged forces and Ising symmetry, we determine the self-interaction by integrating out bulk-like degrees of freedom from a more microscopic Landau-Ginzburg-Wilson model. The self-interaction can be written in a simple diagrammatic form involving integrals over effective two-body forces acting at the interface and consistently accounts for a number of known features of the microscopic model, including the wavevector dependence of the surface tension describing the fluctuations of a near planar interface. When applied to wedge filling transitions, the self-interaction describes the attraction between the wetting films on either side of the wedge. We show that, for sufficiently acute wedges, this can alter the order of the filling phase transition.

  6. The self-interaction of a fluid interface, the wavevector dependent surface tension and wedge filling

    NASA Astrophysics Data System (ADS)

    Parry, Andrew O.; Rascón, Carlos

    2011-01-01

    We argue that whenever an interface, separating bulk fluid phases, adopts a non-planar configuration (induced by a confining geometry or thermal fluctuations, say), the energy cost of it will contain a non-local self-interaction term. For systems with short-ranged forces and Ising symmetry, we determine the self-interaction by integrating out bulk-like degrees of freedom from a more microscopic Landau-Ginzburg-Wilson model. The self-interaction can be written in a simple diagrammatic form involving integrals over effective two-body forces acting at the interface and consistently accounts for a number of known features of the microscopic model, including the wavevector dependence of the surface tension describing the fluctuations of a near planar interface. When applied to wedge filling transitions, the self-interaction describes the attraction between the wetting films on either side of the wedge. We show that, for sufficiently acute wedges, this can alter the order of the filling phase transition.

  7. Surface tension transport of prey by feeding shorebirds: the capillary ratchet.

    PubMed

    Prakash, Manu; Quéré, David; Bush, John W M

    2008-05-16

    The variability of bird beak morphology reflects diverse foraging strategies. One such feeding mechanism in shorebirds involves surface tension-induced transport of prey in millimetric droplets: By repeatedly opening and closing its beak in a tweezering motion, the bird moves the drop from the tip of its beak to its mouth in a stepwise ratcheting fashion. We have analyzed the subtle physical mechanism responsible for drop transport and demonstrated experimentally that the beak geometry and the dynamics of tweezering may be tuned to optimize transport efficiency. We also highlight the critical dependence of the capillary ratchet on the beak's wetting properties, thus making clear the vulnerability of capillary feeders to surface pollutants.

  8. Influence of Surface Tension Inhomogeneity on the Wave Flow of a Liquid Film

    NASA Astrophysics Data System (ADS)

    Prokudina, L. A.

    2014-01-01

    This paper presents a mathematical model of the three-dimensional liquid film flow taking into account the inhomogeneity of its surface tension in the condensation and evaporation processes. The wave characteristics of this flow have been calculated and the instability regions of such films have been determined. The analytical dependence for the wave flow of the liquid film in the condensation and evaporation processes taking into account the influence of the thermocapillary forces and the surface viscosity on the wave form of the liquid has been obtained.

  9. Interfacial layers from the protein HFBII hydrophobin: dynamic surface tension, dilatational elasticity and relaxation times.

    PubMed

    Alexandrov, Nikola A; Marinova, Krastanka G; Gurkov, Theodor D; Danov, Krassimir D; Kralchevsky, Peter A; Stoyanov, Simeon D; Blijdenstein, Theodorus B J; Arnaudov, Luben N; Pelan, Eddie G; Lips, Alex

    2012-06-15

    The pendant-drop method (with drop-shape analysis) and Langmuir trough are applied to investigate the characteristic relaxation times and elasticity of interfacial layers from the protein HFBII hydrophobin. Such layers undergo a transition from fluid to elastic solid films. The transition is detected as an increase in the error of the fit of the pendant-drop profile by means of the Laplace equation of capillarity. The relaxation of surface tension after interfacial expansion follows an exponential-decay law, which indicates adsorption kinetics under barrier control. The experimental data for the relaxation time suggest that the adsorption rate is determined by the balance of two opposing factors: (i) the barrier to detachment of protein molecules from bulk aggregates and (ii) the attraction of the detached molecules by the adsorption layer due to the hydrophobic surface force. The hydrophobic attraction can explain why a greater surface coverage leads to a faster adsorption. The relaxation of surface tension after interfacial compression follows a different, square-root law. Such behavior can be attributed to surface diffusion of adsorbed protein molecules that are condensing at the periphery of interfacial protein aggregates. The surface dilatational elasticity, E, is determined in experiments on quick expansion or compression of the interfacial protein layers. At lower surface pressures (<11 mN/m) the experiments on expansion, compression and oscillations give close values of E that are increasing with the rise of surface pressure. At higher surface pressures, E exhibits the opposite tendency and the data are scattered. The latter behavior can be explained with a two-dimensional condensation of adsorbed protein molecules at the higher surface pressures. The results could be important for the understanding and control of dynamic processes in foams and emulsions stabilized by hydrophobins, as well as for the modification of solid surfaces by adsorption of such

  10. Impact tension of sheet metals - Effect of initial specimen length

    NASA Astrophysics Data System (ADS)

    Rusinek, A.; Klepaczko, J. R.

    2003-09-01

    It is well known that a specimen for impact testing of materials must be optimized concerning its dimensions. The main reason is to reduce strain gradients due to the effects of elastic-plastic wave propagation. On the other hand, when Split Hopkinson Bar (SHB) is applied for tension test, the net displacement of the specimen ends is very limited, usually from 2.0 to 3.0mm. Thus, to reach maximum strain 0.5 the specimen length must be reduced to dimensions from 4.0mm to 6.0mm. Consequently small diameter, or lateral dimensions in case of flat specimen, must be applied to assure one-dimensional deformation. Such small lengths substantially perturb the real material behavior to be determined. So the main motivation of this study was to perform a systematic analysis, numerical and analytical, to find differences in behavior of short and long specimens loaded in impact tension. The FE code Abaqus/Explicit has been used to simulate several specimen lengths from 10mm to 40mm, and several velocities from 10m/s to 100m/s.

  11. Macroscopic surface tension in a lattice Bhatnagar-Gross-Krook model of two immiscible fluids

    NASA Astrophysics Data System (ADS)

    Halliday, I.; Thompson, S. P.; Care, C. M.

    1998-01-01

    We present a method by which an interface generating algorithm, similar to that of earlier lattice Boltzmann models of immiscible fluids, may be extended to a two component, two-speed two-dimensional (D2), nine-link (Q9) lattice Bhatnagar-Gross-Krook fluid. For two-dimensional, microcurrent-free planar interfaces between the two immiscible fluids we derive expressions for static interfacial tensions and interfacial distributions of the two fluids. Extending our analysis to curved interfaces, we propose a scheme for incorporating the influence of interfacial microcurrents that is based upon general symmetry arguments and is correct to second order in lattice velocity. The analysis demonstrates that the interfacial microcurrents have only second-order influence upon the macroscopic behavior of the model. We find good agreement between our calculations and simulation results based on the microcurrent stream function and surface tension results from the pressure tensor or Laplace law.

  12. Macroscopic Surface Tension in a Lattice Boltzmann BGK Model of Two Immiscible Fluids.

    NASA Astrophysics Data System (ADS)

    Thompson, S. P.; Halliday, I.; Care, C. M.

    1997-08-01

    We present a method by which an interface generating algorithm, similar to that of earlier lattice Boltzmann models of immisible fluids, may be extended to a two component, two-speed D2Q9 lattice Bhatnagar Gross Krook fluid. For two-dimensional, microcurrent-free planar interfaces between the two immiscible fluids we derive expressions for static interfacial tensions and interfacial distributions of the two fluids. Extending our analysis to curved interfaces we propose a scheme for incorporating the influence of interfacial microcurrents which is based upon general symmetry arguments and is correct to second order in lattice velocity. The analysis demonstrates that the interfacial microcurrents have only second order influence upon the macroscopic behaviour of the model. We find good agreement between our calculations and simulation results based on the microcurrent stream function and surface tension results from the pressure tensor or Laplace law.

  13. Investigating the effects of strap tension during non-invasive ventilation mask application: a combined biomechanical and biomarker approach

    PubMed Central

    Worsley, Peter R; Prudden, George; Gower, George; Bader, Dan L

    2016-01-01

    Non-invasive ventilation is commonly used for respiratory support. However, in some cases, mask application can cause pressure ulcers to specific features of the face, resulting in pain and reduced quality of life for the individual. This study investigated the effects of mask strap tension on the biomechanical and biomarker responses at the skin interface. Healthy participants (n = 13) were recruited and assigned two different masks in a random order, which were fitted with three strap conditions representing increments of 5 mm to increase tension. Masks were worn for 10 minutes at each tension followed by a 10-minute refractory period. Assessment at the device–skin interface included measurements of pressures at the nose and cheeks, temperature and humidity, a selection of inflammatory cytokine concentrations collected from sebum and scores of comfort. The results indicated significantly higher interface pressures at the bridge of the nose compared to the cheeks for both masks (p < 0.05), with nasal interface pressures significantly increasing with elevated strap tension (p < 0.05). One inflammatory cytokine, IL-1α, increased following mask application at the highest tension, with median increases from baselines ranging from 21 to 33%. The other cytokines revealed a less consistent trend with strap tension. The participants reported statistically greater discomfort during elevated strap tension. Temperature and humidity values under the mask were elevated from ambient conditions, although no differences were observed between mask type or strap tension. The bony prominence on the bridge of the nose represented a vulnerable area of skin during respiratory mask application. This study has shown that mask strap tension has a significant effect on the pressure exerted on the nose. This can result in discomfort and an inflammatory response at the skin surface. Further studies are required to investigate respiratory mask application for appropriate individuals with

  14. Influence of Turbulence on the Restraint of Liquid Jets by Surface Tension in Microgravity Investigated

    NASA Technical Reports Server (NTRS)

    Chato, David J.

    2002-01-01

    Microgravity poses many challenges to the designer of spacecraft tanks. Chief among these are the lack of phase separation and the need to supply vapor-free liquid or liquidfree vapor to the spacecraft processes that require fluid. One of the principal problems of phase separation is the creation of liquid jets. A jet can be created by liquid filling, settling of the fluid to one end of the tank, or even closing a valve to stop the liquid flow. Anyone who has seen a fountain knows that jets occur in normal gravity also. However, in normal gravity, the gravity controls and restricts the jet flow. In microgravity, with gravity largely absent, surface tension forces must contain jets. To model this phenomenon, a numerical method that tracks the fluid motion and the surface tension forces is required. Jacqmin has developed a phase model that converts the discrete surface tension force into a barrier function that peaks at the free surface and decays rapidly away. Previous attempts at this formulation were criticized for smearing the interface. This can be overcome by sharpening the phase function, double gridding the fluid function, and using a higher order solution for the fluid function. The solution of this equation can be rewritten as two coupled Poisson equations that also include the velocity. After the code was implemented in axisymmetric form and verified by several test cases at the NASA Glenn Research Center, the drop tower runs of Aydelott were modeled. Work last year with a laminar model was found to overpredict Aydelott's results, except at the lowest Reynolds number conditions of 400. This year, a simple turbulence model was implemented by adding a turbulent viscosity based on the mixing-length hypothesis and empirical measurements of previous works. Predictions made after this change was implemented have been much closer to experimentally observed flow patterns and geyser heights. Two model runs is shown. The first, without any turbulence correction

  15. Determination of the Surface Tension of Microporous Membranes Using Contact Angle Measurements

    PubMed

    Tröger; Lunkwitz; Bürger

    1997-10-15

    In this paper, a new method of determining the surface tension of the solid material that a microporous membrane is made from is introduced. The method is based on the well known determination of the so-called contact angle that is formed on the solid/liquid/gaseous three phase line. A nonideal state of the solid phase leads to a deviation of the contact angle that can be observed experimentally from the equilibrium angle that arises from the thermodynamically state of lowest energy, as it must be used to calculate the solid surface tension via the Young equation. The deviation caused from the porous structure of the solid material will be taken into account in this work. Doing so, we derived an equation that connects the surface porosity, the measured contact angle, and the equilibrium contact angle. Using this equation, the measured and therefore deviated contact angles can be corrected for the porosity of the solid material, yielding the contact angle observable on a surface made from the same but nonporous material. The equation derived was tested on different microporous membranes made from expanded poly(tetrafluoroethylene). The surface porosity needed was determined using scanning electron microscopy followed by computerized image analysis. Copyright 1997 Academic Press. Copyright 1997Academic Press

  16. Corneal Equilibrium Flux as a Function of Corneal Surface Oxygen Tension.

    PubMed

    Compañ, Vicente; Aguilella-Arzo, Marcel; Weissman, Barry A

    2017-06-01

    Oxygen is essential for aerobic mammalian cell physiology. Oxygen tension (PO2) should reach a minimum at some position within the corneal stroma, and oxygen flux should be zero, by definition, at this point as well. We found the locations and magnitudes of this "corneal equilibrium flux" (xmin) and explored its physiological implications. We used an application of the Monod kinetic model to calculate xmin for normal human cornea as anterior surface PO2 changes from 155 to 20 mmHg. We find that xmin deepens, broadens, and advances from 1.25 μm above the endothelial-aqueous humor surface toward the epithelium (reaching a position 320 μm above the endothelial-aqueous humor surface) as anterior corneal surface PO2 decreases from 155 to 20 mmHg. Our model supports an anterior corneal oxygen flux of 9 μL O2 · cm · h and an epithelial oxygen consumption of approximately 4 μL O2 · cm · h. Only at the highest anterior corneal PO2 does our model predict that oxygen diffuses all the way through the cornea to perhaps reach the anterior chamber. Of most interest, corneal oxygen consumption should be supported down to a corneal surface PO2 of 60 to 80 mmHg but declines below this range. We conclude that the critical oxygen tension for hypoxia induced corneal swelling is more likely this range rather than a fixed value.

  17. Effects of Thermal Tension Transients on the Muscle Crossbridge

    NASA Astrophysics Data System (ADS)

    Greene, Peter R.

    2016-09-01

    The transverse thermal fluctuations of the myosin molecule are significant. This paper explores the contribution of lateral myosin bending to the developed crossbridge force and power stroke. The equipartition theorem is used to calculate the mode amplitudes for myosin bending. Crossbridge axial force Fx and power stroke Δx are developed by transverse in-plane fluctuations along the y- and z-axes. Practical applications include the effects of temperature on the flexibility of the myosin molecule stiffness and tension, relevant to man-made fabrication of synthetic muscle using micromachines and nanowires. Scaling laws for the S2 bending amplitude depend on filament length, mode number, and stiffness, as n-2,L2, and (EI)-1. This paper quantifies the effects of thermal motion on the mechanics of miniature molecular motors, including the muscle crossbridge.

  18. Secondary organic material formed by methylglyoxal in aqueous aerosol mimics - Part 1: Surface tension depression and light-absorbing products

    NASA Astrophysics Data System (ADS)

    Schwier, A. N.; Shapiro, E. L.; Sareen, N.; McNeill, V. F.

    2009-07-01

    We show that methylglyoxal forms light-absorbing secondary organic material in aqueous ammonium sulfate and ammonium nitrate solutions mimicking tropospheric aerosol particles. The light-absorbing products form on the order of minutes, and solution composition continues to change over several days. The results suggest an aldol condensation pathway involving the participation of the ammonium ion. Aqueous solutions of methylglyoxal, with and without inorganic salts, exhibit surface tension depression. Methylglyoxal uptake could potentially change the optical properties, climate effects, and heterogeneous chemistry of the seed aerosol over its lifetime.

  19. Online measurements of surface tensions and viscosities based on the hydrodynamics of Taylor flow in a microchannel.

    PubMed

    Sun, Yanhong; Guo, Chaohong; Jiang, Yuyan; Wang, Tao; Zhang, Lei

    2016-11-01

    This paper demonstrates an online measurement technique which can measure both surface tension and viscosity for confined fluids in microflui