Retraction of large liquid strips

2015 ◽  
Vol 778 ◽  
Author(s):  
Cunjing Lv ◽  
Christophe Clanet ◽  
David Quéré
Keyword(s):  
Surface Tension ◽  
Surface Energy ◽  
Surface Area ◽  
Driving Force ◽  
Large Scale ◽  
Horizontal Surface

We study the behaviour of elongated puddles deposited on non-wetting substrates. Such liquid strips retract and adopt circular shapes after a few oscillations. Their thickness and horizontal surface area remain constant during this reorganization, so that the energy of the system is only lowered by minimizing the length of the contour (and the corresponding surface energy); despite the large scale of the experiments (several centimetres), motion is driven by surface tension. We focus on the retraction stage, and show that its velocity results from a balance between the capillary driving force and inertia, due to the frictionless motion on non-wetting substrates. As a consequence, the retraction velocity has a special Taylor–Culick structure, where the puddle width replaces the usual thickness.

The nucleation of cavities at grain boundaries

1987 ◽  
Vol 45 ◽  
pp. 288-291
Author(s):  
P. J. Goodhew
Keyword(s):  
Surface Tension ◽  
Surface Energy ◽  
Grain Boundaries ◽  
Radiation Damage ◽  
Impurity Concentration ◽  
Driving Force ◽  
Nucleation And Growth ◽  
Phase Boundaries ◽  
Cavity Nucleation ◽  
Spherical Bubble

Cavity nucleation and growth at grain and phase boundaries is of concern because it can lead to failure during creep and can lead to embrittlement as a result of radiation damage. Two major types of cavity are usually distinguished: The term bubble is applied to a cavity which contains gas at a pressure which is at least sufficient to support the surface tension (2g/r for a spherical bubble of radius r and surface energy g). The term void is generally applied to any cavity which contains less gas than this, but is not necessarily empty of gas. A void would therefore tend to shrink in the absence of any imposed driving force for growth, whereas a bubble would be stable or would tend to grow. It is widely considered that cavity nucleation always requires the presence of one or more gas atoms. However since it is extremely difficult to prepare experimental materials with a gas impurity concentration lower than their eventual cavity concentration there is little to be gained by debating this point.

The Gating Mechanism of Mechanosensitive Channels in Droplet Interface Bilayers

2015 ◽  
Vol 1722 ◽  
Author(s):  
Joseph S. Najem ◽  
Eric Freeman ◽  
Sergei Sukharev ◽  
Donald J. Leo
Keyword(s):  
Surface Tension ◽  
Surface Area ◽  
Duty Cycle ◽  
Large Scale ◽  
Droplet Surface ◽  
Lipid Monolayer ◽  
Low Frequencies ◽  
Area Change ◽  
Gating Mechanism ◽  
Relative Change

ABSTRACTMscL, a large-conductance mechanosensitive channel, is a ubiquitous osmolyte release valve that aids bacteria in surviving abrupt hypo-osmotic shocks. The large scale of its tension-driven opening transition makes it a strong candidate to serve as a transducer in novel stimuli-responsive biomolecular materials. In the previous work, a low-threshold gain-of-function V23T mutant of MscL produced a reliable activation behavior in a droplet interface bilayer (DIB) with applied axial droplet compression. Near the maximal compression, the aqueous droplets deform and the resulting increase in surface area leads to an increase in tension in the water-lipid-oil interface. This increase in tension is the product of the relative change in the droplet surface area and the elastic modulus of the DPhPC lipid monolayer (∼120 mN/m). This paper, presents a study of the physical processes that cause MscL gating in the DIB. Analysis of video during compression and relaxation of the droplets is utilized to estimate the change in the surface area of the droplet and the variation on monolayer surface tension. The monolayer surface tension is proportional to the area change of the droplet normalized to the original surface area. The results demonstrate that the area change in the droplet is negligible at frequencies above 1 Hz, but is approximately 2% at frequencies in the range of 100 mHz. In addition, at low frequencies (∼0.2 Hz) bilayer thinning occurs at maximum compression, proving an increase in bilayer tension. However, this study also shows that gating at frequencies higher than 0.2 Hz could be achieved through the application of high duty cycle oscillation (∼75%). The relative change in monolayer area increases significantly at higher duty cycle oscillations where the compression stroke is much faster than the relaxation stroke.

Relations among recoil pressure, surface area, and surface tension in the lung

1981 ◽  
Vol 50 (5) ◽  
pp. 921-930 ◽  
Author(s):  
T. A. Wilson
Keyword(s):  
Surface Tension ◽  
Surface Energy ◽  
Total Energy ◽  
Surface Area ◽  
Lung Volume ◽  
Mechanical Energy ◽  
Energy Difference ◽  
Published Data ◽  
Recoil Pressure ◽  
Pressure Surface

The difference between energy stored in air- and saline-filled lungs is the sum of surface energy and the energy of tissue distortion caused by surface tension. The surface energy is zeta gamma dS, where gamma is surface tension and S is surface area. There is no corresponding relation between tissue energy and measurable variables. However, two equations can be obtained from the expression for the total energy difference. One is the statement that the total energy of the lung is minimum at equilibrium, and the other is the statement of conservation of mechanical energy as lung volume changes. The expression for tissue energy is eliminated between the two equations to obtain a single relation among the variables of interest: recoil pressure, surface area, and surface tension. Published data on recoil pressure and surface area of saline-filled, air-filled, and detergent-washed rabbit lungs are used in these equations to determine surface tension as a function of lung volume. The values of surface tension deduced from this analysis are lower than the values that would be obtained if the additional tissue forces in the air-filled lung were neglected. The contribution of tissue forces to the added recoil of the air-filled lung increases with increasing lung volume and accounts for approximately half the additional recoil at high lung volume.

The entrainment interface

1972 ◽  
Vol 51 (1) ◽  
pp. 97-118 ◽  
Author(s):  
O. M. Phillips
Keyword(s):  
Velocity Field ◽  
Turbulent Flow ◽  
Surface Area ◽  
Large Scale ◽  
Positive Curvature ◽  
Lagrangian Description ◽  
Eulerian Description ◽  
Entrainment Process ◽  
Necessary And Sufficient ◽  
Small Disturbances

A theory is developed to describe the evolution of the entrainment interface in turbulent flow, in which the surface is convoluted by the large-scale eddies of the motion and at the same time advances relative to the fluid as a result of the micro-scale entrainment process. A pseudo-Lagrangian description of the process indicates that the interface is characterized by the appearance of ‘billows’ of negative curvature, over which surface area is, on average, being generated, separated by re-entrant wedges (lines of very large positive curvature) where surface area is consumed. An alternative Eulerian description allows calculation of the development of the interfacial configuration when the velocity field is prescribed. Several examples are considered in which the prescribed velocity field in the z direction is of the general form w = Wf(x – Ut), where the maximum value of the function f is unity. These indicate the importance of leading points on the surface which are such that small disturbances in the vicinity will move away from the point in all directions. The necessary and sufficient condition for the existence of one or more leading points on the surface is that U [les ] V, the speed of advance of an element of the surface relative to the fluid element at the same point. The existence of leading points is accompanied by the appearance of line discontinuities in the surface slope re-entrant wedges, In these circumstances, the overall speed of advance of the convoluted surface is found to be W + (V2 – U2)½, where W is the maximum outwards velocity in the region; this result is independent of the distribution f.When the speed U with which an ‘eddy’ moves relative to the outside fluid is greater than the speed of advance V of an element of the front, the interface develops neither leading points nor discontinuities in slope; the amplitude of the surface convolutions and the overall entrainment speed are both reduced greatly. In a turbulent flow, therefore, the large-scale motions influencing entrainment are primarily those that move slowly relative to the outside fluid (with relative speed less than V). The experimental results of Kovasznay, Kibens & Blackwelder (1970) are reviewed in the light of these conclusions. It appears that in their experiments the entrainment speed V is of the order fifteen times the Kolmogorov velocity, the large constant of proportionality being apparently the result of augmentation by micro-convolutions of the interface associated with small and meso-scale eddies of the turbulence.

Facile and large-scale synthesis of poly(m-phenylenediamine) nanobelts with high surface area and superior dye adsorption ability

RSC Advances ◽  
2014 ◽  
Vol 4 (85) ◽  
pp. 45244-45250 ◽  
Author(s):  
Yun Meng ◽  
Liyuan Zhang ◽  
Liyuan Chai ◽  
Wanting Yu ◽  
Ting Wang ◽  
...  
Keyword(s):  
Surface Area ◽  
Large Scale ◽  
High Surface ◽  
High Surface Area ◽  
Dye Adsorption ◽  
High Adsorption ◽  
Adsorption Ability ◽  
Adsorption Performance ◽  
Large Scale Synthesis

PmPD nanobelts with high adsorption performance have been synthesized by using CTAP as oxidants.

Effects of Weld Strength Heterogeneity on Crack Driving Force in Stress and Strain Based Design Scenarios

2014 ◽  
Author(s):  
Stijn Hertelé ◽  
Noel O’Dowd ◽  
Matthias Verstraete ◽  
Koen Van Minnebruggen ◽  
Wim De Waele
Keyword(s):  
Driving Force ◽  
Large Scale ◽  
Limit State ◽  
Weld Strength ◽  
Force Response ◽  
Crack Driving Force ◽  
Key Factor ◽  
Weld Properties ◽  
Girth Welds ◽  
Strain Hardening Behavior

Weld strength mismatch is a key factor with respect to the assessment of a flawed girth weld. However, it is challenging to assign a single strength mismatch value to girth welds, which are generally heterogeneous in terms of constitutive behavior. The authors have recently developed a method (‘homogenization’) to account for weld strength property variations in the estimation of crack driving force response and the corresponding tensile limit state. This paper separately validates the approach for stress based and strain based assessments. Whereas homogenization is reliably applicable for stress based assessments, the strain based crack driving force response is highly sensitive to effects of actual heterogeneous weld properties. The sensitivity increases with increased weld width and decreased strain hardening behavior. For strain based design, a more accurate methodology is desirable, and large scale testing and/or advanced numerical modeling remain essential.

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