scholarly journals Deformation of soap films pushed through tubes at high velocity

2010 ◽  
Vol 652 ◽  
pp. 529-539 ◽  
Author(s):  
BENJAMIN DOLLET ◽  
ISABELLE CANTAT
Keyword(s):  
Simple Model ◽  
High Velocity ◽  
Equilibrium Configuration ◽  
Hydraulic Diameter ◽  
Radius Of Curvature ◽  
Inertial Effects ◽  
Soap Films ◽  
Small Parameters ◽  
Tube Geometry

The behaviour of soap films pushed through tubes at large velocities, up to several metres per second, is investigated in this paper. The film shape deviates from its equilibrium configuration perpendicular to the walls and gets curved downstream. A simple model relates the radius of curvature of the film to the friction in the lubrication films touching the wall, and the scaling of Bretherton (J. Fluid Mech., vol. 10, 1961, pp. 166–188) holds up to surprisingly high velocities, at which the capillary and Weber numbers are no longer small parameters. The tube geometry is varied and accounted for through the notion of hydraulic diameter. A limit of stability of the films, beyond which they burst or evolve unsteadily, is predicted, and it quantitatively captures the observations. The new questions raised by our results on the dissipation in soap films are discussed, especially the role of Plateau borders and inertial effects.

scholarly journals Physical Processes in Nebular Shells and the Interpretation of Nebular Spectra

1983 ◽  
Vol 103 ◽  
pp. 219-227
Author(s):  
J. Patrick Harrington
Keyword(s):  
Charge Transfer ◽  
Simple Model ◽  
Stellar Wind ◽  
High Velocity ◽  
Planetary Nebulae ◽  
Geometrical Parameters ◽  
Stellar Winds ◽  
Physical Processes ◽  
Rapid Cooling ◽  
Particle Distributions

Computed models are now recognized as useful tools for interpretation of the spectra of planetary nebulae. However, even the most detailed models need geometrical parameters such as filling factors which are poorly determined by observations. Some effects may be seen more clearly by modeling the stratification than by just using total fluxes. A simple model for NGC 6720 is presented which reproduces the behavior of (Ne III) λ3869 observed by Hawley and Miller (1977), clearly showing the effects of charge transfer. The behavior of C II λ4267 remains puzzling. Finally, we comment on the interaction of high velocity stellar winds with nebular shells. Non-equilibrium particle distributions at the contact between the shocked stellar wind and the nebula may result in the rapid cooling of the shocked gas.

Thinning of Soap Films: The Role of Surface Viscoelasticity

1994 ◽  
Vol 162 (2) ◽  
pp. 323-330 ◽  
Author(s):  
A.A. Sonin ◽  
A. Bonfillon ◽  
D. Langevin
Keyword(s):  
Soap Films

scholarly journals A Simple Contact Mechanics Model for Highly Strained Aqueous Surface Gels

2021 ◽  
Author(s):  
A. L. Chau ◽  
M. K. Cavanaugh ◽  
Y.-T. Chen ◽  
A. A. Pitenis
Keyword(s):  
Simple Model ◽  
Contact Mechanics ◽  
Contact Lenses ◽  
Radius Of Curvature ◽  
Winkler Foundation ◽  
Surface Layers ◽  
Mechanics Model ◽  
Soft Surface ◽  
Simple Contact ◽  
Highly Strained

Abstract Background Soft, biological, and bio-inspired materials are often compositionally heterogeneous and structurally anisotropic, and they frequently feature graded or layered organizations. This design complexity enables exceptional ranges in properties and performance yet complicates a fundamental understanding of the contact mechanics. Recent studies of soft gel layers have relied on Hertzian or Winkler foundation (“bed-of-springs”) models to characterize the mechanics but have found neither satisfactory. Objective The contact mechanics of soft gel layers are not yet fully understood. The aim of this work is to develop a simple contact mechanics model tailored for compositionally-graded materials with soft surface layers under high strains and deformations. Methods Concepts from polymer physics, fluid draining, and Winkler foundation mechanics are combined to develop a simple contact mechanics model which relates the applied normal force to the probe radius of curvature, elastic modulus, and thickness of soft surface layers subjected to high strains. Results This simple model was evaluated with two examples of graded surface gel layers spanning multiple length-scales, including commercially available contact lenses and stratified hydrogels. The model captures the nonlinear contact mechanics of highly strained soft aqueous gel layers more closely than either Hertz or Winkler foundation theory while simultaneously enabling a prediction for the thickness of the surface gel layer. Conclusion These results indicate that this simple model can adequately characterize the contact mechanics of highly strained soft aqueous gel layers.

scholarly journals Electric potential differences across auroral generator interfaces

2013 ◽  
Vol 31 (2) ◽  
pp. 251-261 ◽  
Author(s):  
J. De Keyser ◽  
M. Echim
Keyword(s):  
Electric Field ◽  
High Altitude ◽  
Electric Fields ◽  
Electric Potential ◽  
Equilibrium Configuration ◽  
Potential Difference ◽  
Field Profile ◽  
Electric Potential Difference ◽  
Electric Field Profile

Abstract. Strong localized high-altitude auroral electric fields, such as those observed by Cluster, are often associated with magnetospheric interfaces. The type of high-altitude electric field profile (monopolar, bipolar, or more complicated) depends on the properties of the plasmas on either side of the interface, as well as on the total electric potential difference across the structure. The present paper explores the role of this cross-field electric potential difference in the situation where the interface is a tangential discontinuity. A self-consistent Vlasov description is used to determine the equilibrium configuration for different values of the transverse potential difference. A major observation is that there exist limits to the potential difference, beyond which no equilibrium configuration of the interface can be sustained. It is further demonstrated how the plasma densities and temperatures affect the type of electric field profile in the transition, with monopolar electric fields appearing primarily when the temperature contrast is large. These findings strongly support the observed association of monopolar fields with the plasma sheet boundary. The role of shear flow tangent to the interface is also examined.

scholarly journals VELOCITY SEGREGATION IN A CLUMP-LIKE OUTFLOW WITH A NON-TOP HAT VELOCITY CROSS-SECTION

2021 ◽  
Vol 57 (2) ◽  
pp. 269-277
Author(s):  
A. Castellanos-Ramírez ◽  
A. C. Raga ◽  
J. Cantó ◽  
A. Rodríguez-González ◽  
L. Hernández-Martínez
Keyword(s):  
Star Formation ◽  
Simple Model ◽  
Radial Velocity ◽  
Cross Section ◽  
High Velocity ◽  
Planetary Nebulae ◽  
Young Stars ◽  
Working Surface ◽  
Star Formation Regions ◽  
Analytic Models

High velocity clumps joined to the outflow source by emission with a “Hubble law” ramp of linearly increasing radial velocity vs. distance are observed in some planetary nebulae and in some outflows in star formation regions. We propose a simple model in which a “clump” is ejected from a source over a period τ0, with a strong axis to edge velocity stratification. This non-top hat cross section results in the production of a highly curved working surface (initially being pushed by the ejected material, and later coasting along due to its inertia). From both analytic models and numerical simulations we find that this working surface has a linear velocity vs. position ramp, and therefore reproduces in a qualitative way the “Hubble law clumps” in planetary nebulae and outflows from young stars.

The role of the wind in the destruction of an historic hut at Cape Adare in Antarctica

Polar Record ◽  
1996 ◽  
Vol 32 (180) ◽  
pp. 3-18 ◽  
Author(s):  
David L. Harrowfield
Keyword(s):  
High Velocity ◽  
Katabatic Wind ◽  
Storm Events ◽  
Antarctic Expedition ◽  
History Of

AbstractIn 1911 the Northern Party of Robert Falcon Scott's British Antarctic expedition (1910–1913), built a wooden hut at Cape Adare, a locality notorious for gusting, high-velocity winds. During the expedition, the hut suffered superficial damage from 18 storms estimated at force 11–12 on the Beaufort scale. Since then, storms during the intervening 84 years have virtually destroyed the hut. This paper outlines the wind and storm events recorded at Cape Adare and suggests that the topography of the Adare Peninsula forces the strong southeast wind to change to an eastsoutheast wind only on meeting high ground. By the time it reaches Ridley Beach, it assumes the character of a highvelocity katabatic wind. It is suggested that at Cape Adare topographically reinforced winds are largely responsible for the destruction of the historic hut. The reasons for this and a possible history of hut destruction is given.

scholarly journals CP VIOLATION AND MODULI STABILIZATION IN HETEROTIC MODELS

2002 ◽  
Vol 17 (22) ◽  
pp. 1465-1473 ◽  
Author(s):  
JOEL GIEDT
Keyword(s):  
Supergravity Models ◽  
Simple Model ◽  
Cp Violation ◽  
Scalar Potential ◽  
Background Values ◽  
Moduli Stabilization ◽  
Weakly Coupled ◽  
Potential Sources

The role of moduli stabilization in predictions for CP violation is examined in the context of four-dimensional effective supergravity models obtained from the weakly coupled heterotic string. We point out that while stabilization of compactification moduli has been studied extensively, the determination of background values for other scalars by dynamical means has not been subjected to the same degree of scrutiny. These other complex scalars are important potential sources of CP violation and we show in a simple model how their background values (including complex phases) may be determined from the minimization of the supergravity scalar potential, subject to the constraint of vanishing cosmological constant.

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