Study of Microdroplet Growth on Homogeneous and Patterned Surfaces Using Lattice Boltzmann Modeling

2019 ◽  
Vol 141 (6) ◽  
Author(s):  
Nilesh D. Pawar ◽  
Sunil R. Kale ◽  
Supreet Singh Bahga ◽  
Hassan Farhat ◽  
Sasidhar Kondaraju
Keyword(s):  
Contact Angle ◽  
Contact Line ◽  
Lattice Boltzmann ◽  
Growth Dynamics ◽  
Hydrophobic Surface ◽  
Droplet Growth ◽  
Patterned Surfaces ◽  
Hydrophobic Region ◽  
Hydrophilic Region ◽  
Contact Line Pinning

We present droplet growth dynamics on homogeneous and patterned surfaces (surface with hydrophilic and hydrophobic region) using two-dimensional thermal lattice Boltzmann method (LBM). In the first part, we performed 2D simulations on homogeneous hydrophobic surfaces. The result shows that the droplet grows at higher rate on a surface with higher wettability which is attributed to low conduction resistance and high solid–liquid contact area. In the later part, we performed simulations on patterned surface and observed that droplet preferentially nucleates on the hydrophilic region due to lower energy barrier and grows in constant contact line (CCL) mode because of contact line pinning at the interface of hydrophilic–hydrophobic region. As the contact angle reaches the maximum value of hydrophobic surface, contact line depins and droplet shows constant contact angle (CCA) growth mode. We also discuss the effect of characteristic width of hydrophilic region on growth of droplet. We show that contact angle of the droplet increases rapidly and reaches the contact angle of hydrophobic region on a surface with a lower width of the hydrophilic surface.

LATTICE BOLTZMANN SIMULATIONS OF CONTACT LINE PINNING

2007 ◽  
Vol 18 (04) ◽  
pp. 595-601 ◽  
Author(s):  
XINLI JIA ◽  
J. B. MCLAUGHLIN ◽  
G. AHMADI ◽  
K. KONTOMARIS
Keyword(s):  
Contact Angle ◽  
Contact Line ◽  
Lattice Boltzmann ◽  
Contact Angle Hysteresis ◽  
Contact Angles ◽  
Contact Lines ◽  
Lattice Boltzmann Simulations ◽  
Spatially Periodic ◽  
Contact Line Pinning ◽  
Geometrical Defects

Contact angle hysteresis is caused by contact line pinning by geometrical and/or chemical non-uniformities on a solid surface. For small contact angles, theories have been developed for the pinning of contact angles, and an analogy between geometrical and chemical defects has been established. This paper presents LBM results for the interaction of a contact line with a spatially periodic array of chemical defects. The results are for finite contact angles. Qualitative comparisons with existing theories for chemical defects and experimental results for geometrical defects are made for pinned contact lines.

Effect of Surface Wettability on Dropwise Condensation Using Lattice Boltzmann Method

2016 ◽  
Author(s):  
Nilesh D. Pawar ◽  
Sasidhar Kondaraju
Keyword(s):  
Heat Transfer ◽  
Contact Angle ◽  
Lattice Boltzmann Method ◽  
Lattice Boltzmann ◽  
Growth Dynamics ◽  
Surface Wettability ◽  
Droplet Growth ◽  
Nucleation Time ◽  
Boltzmann Method ◽  
Effect Of Surface

Understanding the condensation mechanism is crucial to enhance the heat transfer performance of numerous industrial applications such as power generations, fog harvesting, water desalination, cooling of nuclear reactor, and thermal management of electronic device. In the present study, simulations are performed to investigate the effect of surface wettability on droplet growth dynamics during dropwise condensation. To simulate droplet growth dynamics involving phase change heat transfer, thermal lattice Boltzmann method has been employed with two distribution function for fluid and temperature field. Simulations performed in this work are used to analyze the effect of surface wettability on nucleation time and the evolution of average droplet radius, height, base diameter, and contact angle of the droplet. It is observed that nucleation time increases exponentially with the contact angle. The growth rate of droplet is higher for smaller droplets compared to larger droplets.

Anomalous Contact Angle Hysteresis of a Captive Bubble: Advancing Contact Line Pinning

Langmuir ◽  
2011 ◽  
Vol 27 (11) ◽  
pp. 6890-6896 ◽  
Author(s):  
Siang-Jie Hong ◽  
Feng-Ming Chang ◽  
Tung-He Chou ◽  
Seong Heng Chan ◽  
Yu-Jane Sheng ◽  
...  
Keyword(s):  
Contact Angle ◽  
Contact Line ◽  
Contact Angle Hysteresis ◽  
Contact Line Pinning

scholarly journals On the microhydrodynamics of superspreading

2011 ◽  
Vol 670 ◽  
pp. 1-4 ◽  
Author(s):  
C. MALDARELLI
Keyword(s):  
Contact Angle ◽  
Aqueous Phase ◽  
Contact Line ◽  
Sessile Drop ◽  
Numerical Study ◽  
Dynamic Contact Angle ◽  
Hydrophobic Surface ◽  
Dynamic Contact ◽  
Spreading Rate ◽  
Spreading Rates

Droplets of an aqueous phase placed on a very hydrophobic, waxy surface bead-up rather than spread, forming a sessile drop with a relatively large contact angle at the edge of the drop. Surfactant molecules, when dissolved in the aqueous phase, can facilitate the wetting of an aqueous drop on a hydrophobic surface. One class of surfactants, superwetters, can cause aqueous droplets to move very rapidly over a hydrophobic surface, thereby completely wetting the surface (superspreading). A recent numerical study of the hydrodynamics of superspreading by Karapetsas, Craster & Matar (J. Fluid Mech., this issue, vol. 670, 2011, pp. 5–37) provides a clear explanation of how these surfactants cause such a dramatic change in wetting behaviour. The study shows that large spreading rates occur when the surfactant can transfer directly from the air/aqueous to the aqueous/hydrophobic solid interface at the contact line. This transfer reduces the concentration of surfactant on the fluid interface, which would otherwise be elevated due to the advection accompanying the drop spreading. The reduced concentration creates a Marangoni force along the fluid surface in the direction of spreading, and a concave rim in the vicinity of the contact line with a large dynamic contact angle. Both of these effects act to increase the spreading rate. The molecular structure of the superwetters allows them to assemble on a hydrophobic surface, enabling the direct transfer from the fluid to the solid surface at the contact line.

3D Lattice Boltzmann Simulation of Droplet Evaporation on Patterned Surfaces: Study of Pinning-Depinning Mechanism

2019 ◽  
Author(s):  
Boheng Dong ◽  
Fuxian Wang ◽  
Xinya Zhang ◽  
Xiang Jiang
Keyword(s):  
Contact Line ◽  
Lattice Boltzmann ◽  
Droplet Evaporation ◽  
Force Balance ◽  
Patterned Surfaces ◽  
Stick Slip ◽  
3D Space ◽  
Lattice Boltzmann Simulation ◽  
Evaporation Heat ◽  
Boltzmann Method

The liquid-vapor phase change lattice Boltzmann method is used to investigate the pinning-depinning mechanism of the contact line during droplet evaporation on the stripe-patterned surfaces in 3D space. Considering the curvature of the contact line and the direction of the unbalanced Young’s force, the local force balance theory near the stripe boundary is proposed to explain the steady state of the droplets on the stripe-patterned surfaces. An equation is proposed to evaluate the characteristic contact angle of the stabilized droplets. During the evaporation of the droplet, the stick-slip-jump behavior and the CCR-Mixed-CCA mode can be well captured by the lattice Boltzmann simulation. When the contact line is pinned to the stripe boundary, the contact line in the direction perpendicular to the stripes is slowly moving while the curvature of the contact line is gradually increasing. The gradually increasing curvature of the contact line accelerates the movement of the contact line, and the final contact line is detached from the stripe boundary. The research results provide theoretical support and guidance for the design, improvement and application of patterned surfaces in the field of micro-fluidic and evaporation heat transfer.

Measurement of Liquid Droplet Evaporation Rate under the Conditions of Intense Heating

2014 ◽  
Vol 698 ◽  
pp. 603-608 ◽  
Author(s):  
Evgenija Orlova ◽  
Dmitriy Feoktistov
Keyword(s):  
Contact Angle ◽  
Contact Line ◽  
Evaporation Rate ◽  
Liquid Droplet ◽  
Droplet Evaporation ◽  
Solid Substrate ◽  
Anodized Aluminum ◽  
Specific Evaporation Rate ◽  
Contact Line Pinning ◽  
Contact Diameter

This paper presents an experimental study of the evaporation of a sessile water-sodium chlorides solution drop to open atmosphere on the solid substrate (anodized aluminum) under the varying heat flux. The main parameters defining drop profile, i. e., contact diameter, contact angle, and height of the drop have been obtained. Specific evaporation rate has been calculated. According to the data analysis it was found, that the sessile water-sodium chlorides solution drop with the highest concentration (16.7%) evaporates in the "reverse depinning" mode. So, there is movement of the contact line in the direction of increasing the surface occupied by the drop. The sessile water and water-sodium chlorides solution drop with 4.8% and 9.1% concentration evaporates in the contact line pinning mode. The influence of the initial concentration of the evaporated solution on the contact angle and the specific evaporation rate was found out.

Self-Spreading of Lipid Bilayer on a Hydrophobic Surface Made by Self-Assembled Monolayer with Short Alkyl Chain

2016 ◽  
Vol 16 (4) ◽  
pp. 3426-3430
Author(s):  
Yuya Omori ◽  
Hiroyuki Sakaue ◽  
Takayuki Takahagi ◽  
Hitoshi Suzuki
Keyword(s):  
Fluorescence Microscopy ◽  
Lipid Bilayer ◽  
Alkyl Chain ◽  
Hydrophobic Surface ◽  
Bilayer Membrane ◽  
The Self ◽  
Self Assembled Monolayer ◽  
Hydrophobic Region ◽  
Hydrophilic Region ◽  
Surface Modified

Behaviors of self-spreading of lipid bilayer membrane on a glass surface modified with selfassembled monolayer (SAM) with short alkyl chain were observed with fluorescence microscopy. Hydrophobic surface made by SAM was found to hamper the self-spreading phenomenon but the lipid bilayer spread on a hydrophilic one where SAM was decomposed by oxidation. On a binary surface having a hydrophobic region and a hydrophilic one, the lipid bilayer spread on the hydrophilic region but it stopped at the boundary of the hydrophobic region.

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