scholarly journals Fluid interfaces with very sharp tips in viscous flow

2020 ◽  
Vol 117 (51) ◽  
pp. 32238-32243
Author(s):  
Sylvain Courrech du Pont ◽  
Jens Eggers
Keyword(s):  
Viscous Flow ◽  
Electric Fields ◽  
External Flow ◽  
Opening Angle ◽  
Radius Of Curvature ◽  
Logarithmic Scale ◽  
Fluid Interfaces ◽  
Fluid Interface ◽  
Nonlocal Coupling ◽  
Analytical Technique

When a fluid interface is subjected to a strong viscous flow, it tends to develop near-conical ends with pointed tips so sharp that their radius of curvature is undetectable. In microfluidic applications, tips can be made to eject fine jets, from which micrometer-sized drops can be produced. Here we show theoretically that the opening angle of the conical interface varies on a logarithmic scale as a function of the distance from the tip, owing to nonlocal coupling between the tip and the external flow. Using this insight we are able to show that the tip curvature grows like the exponential of the square of the strength of the external flow and to calculate the universal shape of the interface near the tip. Our experiments confirm the scaling of the tip curvature as well as of the interface’s universal shape. Our analytical technique, based on an integral over the surface, may also have far wider applications, for example treating problems with electric fields, such as electrosprays.

Cavitation in lubrication. Part 1. On boundary conditions and cavity—fluid interfaces

1977 ◽  
Vol 80 (4) ◽  
pp. 743-755 ◽  
Author(s):  
M. D. Savage
Keyword(s):  
Surface Tension ◽  
Boundary Conditions ◽  
Fluid Pressure ◽  
Radius Of Curvature ◽  
Fluid Interfaces ◽  
Fluid Interface ◽  
Detailed Review ◽  
Lubrication Regime ◽  
Narrow Gaps ◽  
Small Disturbances

The flow of viscous lubricant in narrow gaps is considered for those geometries in which cavitation arises. A detailed review is presented of those boundary conditions which have been proposed for terminating the lubrication regime (i.e. those valid where the cavity forms). Finally it is shown that a uniform cavity-fluid interface remains stable to small disturbances provided that \[ \frac{d}{dx}\left(P+\frac{T}{r}\right) < 0, \] in which T and r represent the surface tension of the fluid and the radius of curvature of the interface respectively whilst dP/dx is the gradient of fluid pressure immediately upstream of the interface.

scholarly journals In situ assessment of the contact angles of nanoparticles adsorbed at fluid interfaces by multiple angle of incidence ellipsometry

Soft Matter ◽  
2014 ◽  
Vol 10 (36) ◽  
pp. 6999-7007 ◽  
Author(s):  
Antonio Stocco ◽  
Ge Su ◽  
Maurizio Nobili ◽  
Martin In ◽  
Dayang Wang
Keyword(s):  
Surface Coverage ◽  
Contact Angles ◽  
Fluid Interfaces ◽  
Angle Of Incidence ◽  
Fluid Interface ◽  
Colloidal Interactions ◽  
In Situ Assessment

Contact angles and surface coverage of nanoparticles adsorbing at the fluid interface are assessed by ellipsometry. Results reveal the competition between wetting and colloidal interactions.

Continuum and Molecular Dynamics Studies of the Hydrodynamics of Colloids Straddling a Fluid Interface

2021 ◽  
Vol 54 (1) ◽  
Author(s):  
Charles Maldarelli ◽  
Nicole T. Donovan ◽  
Subramaniam Chembai Ganesh ◽  
Subhabrata Das ◽  
Joel Koplik
Keyword(s):  
Molecular Dynamics ◽  
Characteristic Size ◽  
Two Dimensions ◽  
Annual Review ◽  
Publication Date ◽  
Fluid Interfaces ◽  
Particle Interactions ◽  
Fluid Interface ◽  
Interfacial Energies ◽  
Multiple Particle

Colloid-sized particles (10 nm–10 μm in characteristic size) adsorb onto fluid interfaces, where they minimize their interfacial energy by straddling the surface, immersing themselves partly in each phase bounding the interface. The energy minimum achieved by relocation to the surface can be orders of magnitude greater than the thermal energy, effectively trapping the particles into monolayers, allowing them freedom only to translate and rotate along the surface. Particles adsorbed at interfaces are models for the understanding of the dynamics and assembly of particles in two dimensions and have broad technological applications, importantly in foam and emulsion science and in the bottom-up fabrication of new materials based on their monolayer assemblies. In this review, the hydrodynamics of the colloid motion along the surface is examined from both continuum and molecular dynamics frameworks. The interfacial energies of adsorbed particles is discussed first, followed by the hydrodynamics, starting with isolated particles followed by pairwise and multiple particle interactions. The effect of particle shape is emphasized, and the role played by the immersion depth and the surface rheology is discussed; experiments illustrating the applicability of the hydrodynamic studies are also examined. Expected final online publication date for the Annual Review of Fluid Mechanics, Volume 54 is January 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

scholarly journals Interface deformations affect the orientation transition of magnetic ellipsoidal particles adsorbed at fluid–fluid interfaces

Soft Matter ◽  
2014 ◽  
Vol 10 (35) ◽  
pp. 6742-6748 ◽  
Author(s):  
Gary B. Davies ◽  
Timm Krüger ◽  
Peter V. Coveney ◽  
Jens Harting ◽  
Fernando Bresme
Keyword(s):  
Magnetic Field ◽  
Fluid Interfaces ◽  
Fluid Interface ◽  
Ellipsoidal Particles ◽  
Particle Monolayer

Magnetic ellipsoidal particles adsorbed at a fluid–fluid interface create dipolar interface deformations in response to a magnetic field, which affects their orientation and may lead to novel particle monolayer structures.

scholarly journals Particle and Particle-Surfactant Mixtures at Fluid Interfaces: Assembly, Morphology, and Rheological Description

2015 ◽  
Vol 2015 ◽  
pp. 1-17 ◽  
Author(s):  
Armando Maestro ◽  
Eva Santini ◽  
Dominika Zabiegaj ◽  
Sara Llamas ◽  
Francesca Ravera ◽  
...  
Keyword(s):  
Contact Angle ◽  
Equations Of State ◽  
Fluid Interfaces ◽  
Interfacial Behavior ◽  
Fluid Interface ◽  
Surfactant Mixtures ◽  
Interfacial Assembly ◽  
Shear Rheology ◽  
Properties Of Materials ◽  
Definition Of

We report here a review of particle-laden interfaces. We discuss the importance of the particle’s wettability, accounted for by the definition of a contact angle, on the attachment of particles to the fluid interface and how the contact angle is strongly affected by several physicochemical parameters. The different mechanisms of interfacial assembly are also addressed, being the adsorption and spreading the most widely used processes leading to the well-known adsorbed and spread layers, respectively. The different steps involved in the adsorption of the particles and the particle-surfactant mixtures from bulk to the interface are also discussed. We also include here the different equations of state provided so far to explain the interfacial behavior of the nanoparticles. Finally, we discuss the mechanical properties of the interfacial particle layers via dilatational and shear rheology. We emphasize along that section the importance of the shear rheology to know the intrinsic morphology of such particulate system and to understand how the flow-field-dependent evolution of the interfacial morphology might eventually affect some properties of materials such as foams and emulsions. We dedicated the last section to explaining the importance of the particulate interfacial systems in the stabilization of foams and emulsions.

scholarly journals Curvature dynamics and long-range effects on fluid–fluid interfaces with colloids

Soft Matter ◽  
2019 ◽  
Vol 15 (13) ◽  
pp. 2848-2862 ◽  
Author(s):  
A. Tiribocchi ◽  
F. Bonaccorso ◽  
M. Lauricella ◽  
S. Melchionna ◽  
A. Montessori ◽  
...  
Keyword(s):  
Long Range ◽  
Colloidal Particles ◽  
Fluid Interfaces ◽  
Fluid Interface ◽  
Fluid Mixture ◽  
Binary Fluid ◽  
Interface Curvature

The fluid–fluid interface curvature can provide new insights into local inhomogeneities of a binary fluid mixture containing colloidal particles.

scholarly journals Mechanically driven accumulation of microscale material at coupled solid–fluid interfaces in biological channels

2014 ◽  
Vol 11 (91) ◽  
pp. 20130922 ◽  
Author(s):  
T. I. Zohdi
Keyword(s):  
Shear Stress ◽  
Accumulation Rate ◽  
Critical Value ◽  
Rate Equations ◽  
Fluid Interfaces ◽  
Sectional Area ◽  
Fluid Interface ◽  
Cross Sectional ◽  
Initial Stage ◽  
Biological Channels

The accumulation of microscale materials at solid–fluid interfaces in biological channels is often the initial stage of certain growth processes, which are present in some forms of atherosclerosis. The objective of this work is to develop a relatively simple model for such accumulation, which researchers can use to qualitatively guide their analyses. Specifically, the approach is to construct rate equations for the accumulation at the solid–fluid interface as a function of the intensity of the shear stress. The accumulation of material subsequently reduces the cross-sectional area of the channel until the fluid-induced shear stress at the solid–fluid interface reaches a critical value, which terminates the accumulation rate. Characteristics of the model are explored analytically and numerically.

scholarly journals Self-diffusiophoresis induced by fluid interfaces

Soft Matter ◽  
2018 ◽  
Vol 14 (8) ◽  
pp. 1375-1388 ◽  
Author(s):  
P. Malgaretti ◽  
M. N. Popescu ◽  
S. Dietrich
Keyword(s):  
Physical Properties ◽  
The Self ◽  
Fluid Interfaces ◽  
Axially Symmetric ◽  
Fluid Interface ◽  
Two Fluid ◽  
Fluid Phases

The influence of a fluid–fluid interface on the self-phoresis of chemically active spherical colloids is analyzed for axially symmetric configurations. Distinct from the case of hard walls, motion of the particle either towards or away from the interface can be induced by tuning the physical properties of one of the two fluid phases.

Relationship between Kinematic Viscosity and Cluster Size in Multicomponent Metal Melts

2021 ◽  
Vol 410 ◽  
pp. 102-107
Author(s):  
Vladimir S. Tsepelev ◽  
Yuri N. Starodubtsev ◽  
Yekaterina A. Kochetkova
Keyword(s):  
Viscous Flow ◽  
Kinematic Viscosity ◽  
Transition State Theory ◽  
Cluster Structure ◽  
State Theory ◽  
Logarithmic Scale ◽  
Heating And Cooling ◽  
Metal Melts ◽  
Initial Stage ◽  
Temperature Dependences

We analyzed the temperature dependences of the kinematic viscosity and density of Fe73.5Cu1M3Si13.5B9 melts, where M = Nb, Mo, V, and Cr, in the temperature range from 1450 to 1950 K using the transition state theory. It is shown that the activation energy of viscous flow is proportional to the particle size on a natural logarithmic scale. The lowest viscosity and the highest free volume has the Nb melt. In melts with Mo, V, and Cr, the structural units of viscous flow upon heating and cooling are clusters about 0.6 nm in size. In a melt with Nb, at the initial stage of heating, the vibrations of individual atoms prevail, the movement of which creates viscosity. After heating the Nb melt above the critical temperature of 1770 K, the viscous flow is associated with clusters about 1 nm in size. At the cooling stage, the cluster structure of the Nb melt is retained up to a temperature of 1450 K.

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