Surface tension and equilibrium shape of crystals in a wide range of angles

1990 ◽  
Vol 78 (2) ◽  
pp. 289-293 ◽  
Author(s):  
A. Kashuba ◽  
V. Pokrovsky
Keyword(s):  
Surface Tension ◽  
Equilibrium Shape ◽  
Wide Range

Surface Tension and Equilibrium Shape of Crystals in a Wide Range of Angles

1989 ◽  
Vol 10 (6) ◽  
pp. 581-585 ◽  
Author(s):  
A Kashuba ◽  
V Pokrovsky
Keyword(s):  
Surface Tension ◽  
Equilibrium Shape ◽  
Wide Range

scholarly journals Cavity Detachment from a Wedge with Rounded Edges and the Surface Tension Effect

2021 ◽  
Vol 9 (11) ◽  
pp. 1253
Author(s):  
Yuriy N. Savchenko ◽  
Georgiy Y. Savchenko ◽  
Yuriy A. Semenov
Keyword(s):  
Surface Tension ◽  
Weber Number ◽  
Solution Process ◽  
Cavity Flow ◽  
Surface Tension Effect ◽  
Force Coefficient ◽  
Hodograph Method ◽  
Wide Range ◽  
Critical Weber Number ◽  
Cavity Boundary

Cavity flow around a wedge with rounded edges was studied, taking into account the surface tension effect and the Brillouin–Villat criterion of cavity detachment. The liquid compressibility and viscosity were ignored. An analytical solution was obtained in parametric form by applying the integral hodograph method. This method gives the possibility of deriving analytical expressions for complex velocity and for potential, both defined in a parameter plane. An expression for the curvature of the cavity boundary was obtained analytically. By using the dynamic boundary condition on the cavity boundary, an integral equation in the velocity modulus was derived. The particular case of zero surface tension is a special case of the solution. The surface tension effect was computed over a wide range of the Weber number for various degrees of cavitation development. Numerical results are presented for the flow configuration, the drag force coefficient, and the position of cavity detachment. It was found that for each radius of the edges, there exists a critical Weber number, below which the iterative solution process fails to converge, so a steady flow solution cannot be computed. This critical Weber number increases as the radius of the edge decreases. As the edge radius tends to zero, the critical Weber number tends to infinity, or a steady cavity flow cannot be computed at any finite Weber number in the case of sharp wedge edges. This shows some limitations of the model based on the Brillouin–Villat criterion of cavity detachment.

Molecular Dynamics Study of Anatase TiO2 Nanoparticles in Water and Vacuum Environments

2012 ◽  
Author(s):  
George Okeke ◽  
Robert B. Hammond ◽  
S. Joseph Antony
Keyword(s):  
Molecular Dynamics ◽  
Surface Tension ◽  
Surface Energy ◽  
Tio2 Nanoparticles ◽  
Anatase Tio2 ◽  
Particle Sizes ◽  
Metallic Oxides ◽  
Wide Range ◽  
Enhanced Properties ◽  
Dynamics Simulations

Nanoparticles are nanometer sized metallic oxides which possess enhanced properties that are desirable to a wide range of industries. In this study, we investigate structural and surface properties of anatase TiO2 nanoparticles in vacuum and water environments using molecular dynamics simulations. The particle sizes ranged from 2 to 6 nm and simulations were performed at 300 K. Surface energy of the particles in vacuum was seen to be higher than that of the particles in water by about 100% for the smaller particles (i.e. 2 and 3nm) and about 60% for the larger particles (i.e. 4 to 6 nm). Surface energy of the particles in both environments, is seen to increase to a maximum (optimum value) as the particle size increases after which no further significant increase is observed. In vacuum, studies carried out at temperatures ranging from 300–2500 K showed a high dependence of surface energy on temperature. The estimated surface tension of water is seen to agree quite well with that of experiments.

scholarly journals Production of a Biosurfactant by Cunninghamella echinulata Using Renewable Substrates and Its Applications in Enhanced Oil Spill Recovery

2018 ◽  
Vol 2 (4) ◽  
pp. 63 ◽  
Author(s):  
Patrícia de Souza ◽  
Nadielly Andrade Silva ◽  
Daniele Souza ◽  
Thayse Lima e Silva ◽  
Marta Freitas-Silva ◽  
...  
Keyword(s):  
Surface Tension ◽  
Soybean Oil ◽  
Corn Steep Liquor ◽  
Artemia Salina ◽  
Engine Oil ◽  
Variable Response ◽  
Cunninghamella Echinulata ◽  
Marine Sand ◽  
Wide Range ◽  
Steep Liquor

This study aimed to evaluate the production of a surfactant by Cunninghamella echinulata, using agro-industrial residues, corn steep liquor (CSL), and soybean oil waste (SOW). The study had a factorial design, using as a variable response to the reduction of surface tension. C. echinulata was able to produce biosurfactant in assay, CSL (8.82%) and SOW (2%). The results showed that the biosurfactant was successfully produced by C. echinulata and had attractive properties, such as a low surface tension (31.7 mN/m), a yield of 5.18 g/L at 120 h of cultivation, and an anionic profile. It also achieved a reduction in surface tension stability in a wide range of pH values, temperatures, and salinity values. The biosurfactant produced by C. echinulata showed an absence of toxicity to Artemia salina. The influence of the biosurfactant on the viscosity of engine oil, burnt engine oil, diesel, soybean oil post-frying, canola oil, and water was investigated. The results reveal a mechanism for the decrease of the viscosity using hydrophobic substrates and the new biosurfactant solution at 1.5% of the (CMC). This enables the formulation of a low-cost culture medium alternative, based on corn steep liquor and the reuse of soybean oil after frying to produce a biosurfactant. Additionally, performance of the biosurfactant isolated from C. echinulata showed an excellent ability to remove spilled oil, such as diesel (98.7%) and kerosene (92.3%) from marine sand.

scholarly journals Amphiphobic Nanostructured Coatings for Industrial Applications

Materials ◽  
2019 ◽  
Vol 12 (5) ◽  
pp. 787 ◽  
Author(s):  
Federico Veronesi ◽  
Giulio Boveri ◽  
Mariarosa Raimondo
Keyword(s):  
Surface Tension ◽  
Contact Angle ◽  
Photoelectron Spectroscopy ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Friction Reduction ◽  
Hybrid Coatings ◽  
Wetting Behavior ◽  
Wide Range ◽  
Solid Liquid

The search for surfaces with non-wetting behavior towards water and low-surface tension liquids affects a wide range of industries. Surface wetting is regulated by morphological and chemical features interacting with liquid phases under different ambient conditions. Most of the approaches to the fabrication of liquid-repellent surfaces are inspired by living organisms and require the fabrication of hierarchically organized structures, coupled with low surface energy chemical composition. This paper deals with the design of amphiphobic metals (AM) and alloys by deposition of nano-oxides suspensions in alcoholic or aqueous media, coupled with perfluorinated compounds and optional infused lubricant liquids resulting in, respectively, solid–liquid–air and solid–liquid–liquid working interfaces. Nanostructured organic/inorganic hybrid coatings with contact angles against water above 170°, contact angle with n-hexadecane (surface tension γ = 27 mN/m at 20 °C) in the 140–150° range and contact angle hysteresis lower than 5° have been produced. A full characterization of surface chemistry has been undertaken by X-ray photoelectron spectroscopy (XPS) analyses, while field-emission scanning electron microscope (FE-SEM) observations allowed the estimation of coatings thicknesses (300–400 nm) and their morphological features. The durability of fabricated amphiphobic surfaces was also assessed with a wide range of tests that showed their remarkable resistance to chemically aggressive environments, mechanical stresses and ultraviolet (UV) radiation. Moreover, this work analyzes the behavior of amphiphobic surfaces in terms of anti-soiling, snow-repellent and friction-reduction properties—all originated from their non-wetting behavior. The achieved results make AM materials viable solutions to be applied in different sectors answering several and pressing technical needs.

Sessile drop profiles: corrected methods for surface tension and spreading coefficients

1972 ◽  
Vol 330 (1583) ◽  
pp. 561-572 ◽  
Keyword(s):  
Surface Tension ◽  
Drop Size ◽  
Sessile Drop ◽  
Graphical Form ◽  
Drop Diameter ◽  
Maximum Height ◽  
Drop Height ◽  
Wide Range ◽  
Spreading Coefficients ◽  
Limiting Value

The height of a sessile drop first increases as the drop size increases and then diminishes to a limiting value for very large drops. The variation of sessile drop height with drop size has been calculated and is given in graphical form for a very wide range of drop size and of contact angle. These data are then used to derive correction factors so that the surface tension and the spreading coefficient may be obtained from equations which would normally apply with the limiting drop height. A comparison is made of these data with some empirical equations, developed by earlier workers, to express the drop height as a function of its size. It is shown that these equations apply over limited ranges of size only. The phenomenon of a sessile drop possessing some maximum height is shown to be a consequence of the capillary pressure at the apex changing with drop diameter in a different way from that at the base of the drop.

Strongly nonlinear interfacial dynamics in core–annular flows

1995 ◽  
Vol 290 ◽  
pp. 131-166 ◽  
Author(s):  
V. Kerchman
Keyword(s):  
Surface Tension ◽  
Blow Up ◽  
High Surface ◽  
Spatiotemporal Chaos ◽  
Interfacial Dynamics ◽  
Core Flow ◽  
The Core ◽  
Wide Range ◽  
Lens Formation ◽  
Annular Film

Nonlinear stability of a pressure driven core-annular flow is analysed, and a study of the large-amplitude interfacial dynamics is reported in the limit of a small ratio β of the annular clearance to the radius. An asymptotic nonlinear evolution equation for the annular film thickness is derived as a general case which involves shear coupling with the core flow. We discuss the effects of the surface tension parameter and viscosity stratification of various orders in β. The governing equation is investigated by solving it on extended intervals. Long-term simulations in a wide range of parameters reveal rich dynamics of wave patterns and coherent structures. Only in a narrow window of the small control parameters can it be described by the weakly nonlinear dissipative-dispersive equation, exhibiting behaviour of strictly bounded solutions which varies from a spatiotemporal chaos to the quasi-steady wavetrains. For sufficiently high surface tension, some pulses (to which the primary instabilities saturate) can coalesce into stable larger structures. This leads to the formation of solitary humps via cascade absorption. Substantial thickness non-uniformities can cause collapse of the perfect CAFF owing to the lens formation or extreme film thinning. Our critical value of the control parameter is in good agreement with the experimental data by Aul & Olbricht. Under strong coupling of the core flow with a less viscous annular film the interfacial evolution settles to a train of inverted pulses. Long-time behaviour in the intermediate range of parameters is diversified from regular pulse trains, to the formation of wide multi-peak structures or blow-up, depending on the apparent involvement of the core.

Deformation of a Droplet in a Channel Flow

2008 ◽  
Vol 5 (4) ◽  
Author(s):  
Ebrahim Shirani ◽  
Shila Masoomi
Keyword(s):  
Surface Tension ◽  
Channel Flow ◽  
Polymer Electrolyte Membrane ◽  
Droplet Deformation ◽  
Navier Stokes Equation ◽  
Droplet Shape ◽  
Viscous Forces ◽  
Electrolyte Membrane ◽  
Wide Range ◽  
Surrounding Fluid

Formation of droplets especially in microchannels, micro-electro-mechanical systems (MEMS) and polymer electrolyte membrane fuel cells and their effects on the performance of these devises, as well as scientific aspect of the droplet behavior in the fluid flow motion, makes the subject of the droplet deformation and motion an attractive problem. In this work, we numerically simulate the deformation of a drop of water attached to the wall of a channel flow using full two-dimensional Navier–Stokes equation and the volume-of-fluid method for capturing the interface. The effects of channel inlet velocity, the density and viscosity of the surrounding fluid, and the surface tension coefficient on the flow structures both inside and outside of the droplet as well as the deformation of the droplets are examined. Several test cases, which cover rather wide range of the Reynolds and capillary numbers, based on the surrounding fluid properties and the diameter of the droplet are performed. The Reynolds number, Re, range is from 24 to 1800 and the capillary number, Ca, is from 0.014 to 0.219. It is found that the droplet shape changes and depending on the capillary and Reynolds numbers, it eventually reaches an equilibrium state when there is balance between the surface tension, inertia, and the viscous forces. It is also found that the deformation of the droplet does not depend on the capillary numbers, when Ca is small, but it is a strong function of Ca, when it is large.

The electronic capacitor at a metal–electrolyte interface

1984 ◽  
Vol 62 (6) ◽  
pp. 1145-1158 ◽  
Author(s):  
G. A. Martynov ◽  
R. R. Salem
Keyword(s):  
Surface Tension ◽  
Work Function ◽  
Mercury Electrode ◽  
Electron Work Function ◽  
Potential Drop ◽  
Free Electrons ◽  
Left Hand ◽  
Zero Charge ◽  
Wide Range ◽  
The Right

A model for the dense part of electrical double layer is proposed using the concept that conduction electrons penetrate into a solution to form an electronic capacitor on the metal surface. The potential drop between the metal and solution, the charge of the metal, its surface tension, and the electron work function for a metal–solution interface are calculated within the framework of the model, and the formulae derived are compared with experiment. It is shown that for a metal–vacuum interface of 38 metals in the left-hand subgroups of the Mendeleev table the discrepancy between the theoretical and experimental values of surface tension and work function does not exceed the experimental error (i.e. it is less than 10%); for six metals in the right-hand subgroups and especially for semimetals the theoretical error is two to three times higher. The density of free electrons in a metal determined in terms of the concepts of the model is shown to vary monotonously with the element number for all 54 metals with available experimental data.A relationship, previously unknown, between surface tension and zero-charge potential is established, which enabled one to calculate the electronic capacitor charge for mercury (the theoretical value is 33 C/cm2, and the experimental value is 36–38 C/cm2). This paper also reports the calculated values of the integral capacity of a mercury electrode in water: the experimental value is 29 F/cm2 (at the zero-charge point), and the theoretical value is 28 F/cm2. The model predicts an increase of the capacity in the anodic region and a decrease in the cathodic region, in a good agreement with experiment. It should be stressed that although the theory includes only one fitting parameter, the density of free electrons in the metal, it correctly explains a wide range of phenomena.

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