scholarly journals The contact line behaviour of solid-liquid-gas diffuse-interface models

2013 ◽  
Vol 25 (9) ◽  
pp. 092111 ◽  
Author(s):  
David N. Sibley ◽  
Andreas Nold ◽  
Nikos Savva ◽  
Serafim Kalliadasis
Keyword(s):  
Contact Line ◽  
Diffuse Interface ◽  
Interface Models ◽  
Solid Liquid

Sharp-interface limit of the Cahn–Hilliard model for moving contact lines

2010 ◽  
Vol 645 ◽  
pp. 279-294 ◽  
Author(s):  
PENGTAO YUE ◽  
CHUNFENG ZHOU ◽  
JAMES J. FENG
Keyword(s):  
Contact Line ◽  
Diffusion Length ◽  
Slip Length ◽  
Sharp Interface ◽  
Diffuse Interface ◽  
Contact Lines ◽  
Sharp Interface Limit ◽  
Interface Models ◽  
Moving Contact ◽  
Moving Contact Lines

Diffuse-interface models may be used to compute moving contact lines because the Cahn–Hilliard diffusion regularizes the singularity at the contact line. This paper investigates the basic questions underlying this approach. Through scaling arguments and numerical computations, we demonstrate that the Cahn–Hilliard model approaches a sharp-interface limit when the interfacial thickness is reduced below a threshold while other parameters are fixed. In this limit, the contact line has a diffusion length that is related to the slip length in sharp-interface models. Based on the numerical results, we propose a criterion for attaining the sharp-interface limit in computing moving contact lines.

scholarly journals Contact-line behavior in boiling on a heterogeneous surface: Physical insights from diffuse-interface modeling

2020 ◽  
Vol 5 (3) ◽  
Author(s):  
Biao Shen ◽  
Jiewei Liu ◽  
Gustav Amberg ◽  
Minh Do-Quang ◽  
Junichiro Shiomi ◽  
...  
Keyword(s):  
Contact Line ◽  
Heterogeneous Surface ◽  
Diffuse Interface ◽  
Interface Modeling

scholarly journals Moving contact line on chemically patterned surfaces

2008 ◽  
Vol 605 ◽  
pp. 59-78 ◽  
Author(s):  
XIAO-PING WANG ◽  
TIEZHENG QIAN ◽  
PING SHENG
Keyword(s):  
Contact Line ◽  
Critical Value ◽  
Diffuse Interface ◽  
Patterned Surfaces ◽  
Fluid Interface ◽  
Two Phase ◽  
Stick Slip ◽  
Moving Contact Line ◽  
Moving Contact ◽  
Wetting Fluid

We simulate the moving contact line in two-dimensional chemically patterned channels using a diffuse-interface model with the generalized Navier boundary condition. The motion of the fluid–fluid interface in confined immiscible two-phase flows is modulated by the chemical pattern on the top and bottom surfaces, leading to a stick–slip behaviour of the contact line. The extra dissipation induced by this oscillatory contact-line motion is significant and increases rapidly with the wettability contrast of the pattern. A critical value of the wettability contrast is identified above which the effect of diffusion becomes important, leading to the interesting behaviour of fluid–fluid interface breaking, with the transport of the non-wetting fluid being assisted and mediated by rapid diffusion through the wetting fluid. Near the critical value, the time-averaged extra dissipation scales as U, the displacement velocity. By decreasing the period of the pattern, we show the solid surface to be characterized by an effective contact angle whose value depends on the material characteristics and composition of the patterned surfaces.

Sliding, pinch-off and detachment of a droplet on a wall in shear flow

2010 ◽  
Vol 644 ◽  
pp. 217-244 ◽  
Author(s):  
HANG DING ◽  
MOHAMMAD N. H. GILANI ◽  
PETER D. M. SPELT
Keyword(s):  
Shear Flow ◽  
Contact Line ◽  
Contact Angle Hysteresis ◽  
Stress Singularity ◽  
Local Maximum ◽  
Diffuse Interface ◽  
Moving Contact Line ◽  
Moving Contact ◽  
Effective Slip Length ◽  
Maximum Angle

We investigate here what happens beyond the onset of motion of a droplet on a wall by the action of an imposed shear flow, accounting for inertial effects and contact-angle hysteresis. A diffuse-interface method is used for this purpose, which alleviates the shear stress singularity at a moving contact line, resulting in an effective slip length. Various flow regimes are investigated, including steadily moving drops, and partial or entire droplet entrainment. In the regime of quasi-steadily moving drops, the drop speed is found to be linear in the imposed shear rate, but to exhibit an apparent discontinuity at the onset of motion. The results also include the relation between a local maximum angle between the interface and the wall and the instantaneous value of the contact-line speed. The critical conditions for the onset of entrainment are determined for pinned as well as for moving drops. The corresponding critical capillary numbers are found to be in a rather narrow range, even for quite substantial values of a Reynolds number. The approach to breakup is then investigated in detail, including the growth of a ligament on a drop, and the reduction of the radius of a pinching neck. A model based on an energy argument is proposed to explain the results for the rate of elongation of ligaments. The paper concludes with an investigation of detachment of a hydrophobic droplet from the solid wall.

scholarly journals THERMODYNAMICALLY CONSISTENT, FRAME INDIFFERENT DIFFUSE INTERFACE MODELS FOR INCOMPRESSIBLE TWO-PHASE FLOWS WITH DIFFERENT DENSITIES

2012 ◽  
Vol 22 (03) ◽  
pp. 1150013 ◽  
Author(s):  
HELMUT ABELS ◽  
HARALD GARCKE ◽  
GÜNTHER GRÜN
Keyword(s):  
Surface Diffusion ◽  
Sharp Interface ◽  
Diffuse Interface ◽  
Momentum Balance ◽  
Two Phase ◽  
Interface Models ◽  
Natural Energy ◽  
Soluble Species ◽  
Sharp Interface Models ◽  
Dissipation Inequalities

A new diffuse interface model for a two-phase flow of two incompressible fluids with different densities is introduced using methods from rational continuum mechanics. The model fulfills local and global dissipation inequalities and is frame indifferent. Moreover, it is generalized to situations with a soluble species. Using the method of matched asymptotic expansions we derive various sharp interface models in the limit when the interfacial thickness tends to zero. Depending on the scaling of the mobility in the diffusion equation, we either derive classical sharp interface models or models where bulk or surface diffusion is possible in the limit. In the latter case a new term resulting from surface diffusion appears in the momentum balance at the interface. Finally, we show that all sharp interface models fulfill natural energy inequalities.

Surfactant Self-Assemblies Near Contact Lines and their Effect on Wetting by Surfactant Solutions

1994 ◽  
Vol 366 ◽  
Author(s):  
B. Frank ◽  
S. Garoff
Keyword(s):  
Pattern Formation ◽  
Contact Line ◽  
Self Assembly ◽  
Surface Interactions ◽  
Contact Lines ◽  
Dynamic Wetting ◽  
Wetting Behavior ◽  
Wetting Properties ◽  
Surfactant Solutions ◽  
Solid Liquid

ABSTRACTSurfactant self-assembly at the liquid-vapor, solid-liquid, and solid-vapor interfaces controls the wetting behavior of advancing surfactant solutions. While different surfactants exhibit different static and dynamic wetting properties, we show that these behaviors can be understood through an examination of microscopic structures driven by surfactant-surface interactions. We examine surfactant solutions exhibiting complete and partial static wetting as well as spreading by dendritic pattern formation and unsteady, stick-jump behavior. In each case, the observed behavior is related to the structure of the surfactant assemblies in the vicinity of the contact line.

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