scholarly journals Toward droplet dynamics simulation in polymer electrolyte membrane fuel cells: Three-dimensional numerical modeling of confined water droplets with dynamic contact angle and hysteresis

2021 ◽  
Vol 33 (12) ◽  
pp. 122109
Author(s):  
Mohammad R. Hashemi ◽  
Pavel B. Ryzhakov ◽  
Riccardo Rossi
Keyword(s):  
Contact Angle ◽  
Numerical Modeling ◽  
Polymer Electrolyte Membrane ◽  
Three Dimensional ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Dynamics Simulation ◽  
Confined Water ◽  
Droplet Dynamics ◽  
Electrolyte Membrane

Dynamics of Droplet Motion Induced by Electrowetting

2016 ◽  
Author(s):  
Yi Lu ◽  
Aritra Sur ◽  
Dong Liu ◽  
Carmen Pascente ◽  
Paul Ruchhoeft
Keyword(s):  
Contact Angle ◽  
High Speed ◽  
Numerical Models ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
High Speed Photography ◽  
Droplet Dynamics ◽  
Droplet Shape ◽  
Moving Contact Line ◽  
Moving Contact

Electrowetting has drawn significant interests due to the potential applications in electronic displays, lab-on-a-chip devices and electro-optical switches, etc. Current understanding of electrowetting-induced droplet dynamics is hindered by the inadequacy of available numerical and theoretical models in properly handling the dynamic contact angle at the moving contact line. A combined numerical and experimental approach was employed in this work to study the spatiotemporal responses of a droplet subject to EW with both direct current and alternating current actuating signals. The time evolution of the droplet shape was measured using high-speed photography. Computational fluid dynamics models were developed by using the Volume of Fluid-Continuous Surface Force method in conjunction with a selected dynamic contact angle model. It was found that the numerical models were able to accurately predict the key parameters of the electrowetting-induced droplet dynamics.

Prediction of Droplet Tear-Off and Meniscus Formation in the Top-Spot Experiment Using TransAT

2010 ◽  
Author(s):  
Chidambaram Narayanan ◽  
Djamel Lakehal
Keyword(s):  
Fluid Dynamics ◽  
Contact Angle ◽  
Contact Line ◽  
Dynamic Contact Angle ◽  
Microfluidic Devices ◽  
Dynamic Contact ◽  
Design Tool ◽  
Dynamics Simulation ◽  
Simulation Tools ◽  
Multiphase Fluid

For the design and development of new microfluidic devices reliable modeling and simulation tools must be made available. Many extensions to conventional computational fluid dynamics are required, especially multiphase fluid dynamics simulation capability. A new dynamic contact angle model is presented here, which does not require the specification of a contact angle or contact-line velocity. The level-set method is used for interface capture. The model is tested for unit problems such as relaxation to equilibrium of a contact line. It is then applied to the problem of fluid filling in a prototypical microdevice to show its utility as a design tool.

An Experimental Method for Three-Dimensional Dynamic Contact Angle Analysis

2012 ◽  
Vol 26 (18-19) ◽  
pp. 2199-2215 ◽  
Author(s):  
Diogo Baptista ◽  
Lech Muszyński ◽  
Douglas J. Gardner ◽  
Eisso Atzema
Keyword(s):  
Contact Angle ◽  
Experimental Method ◽  
Three Dimensional ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Contact Angle Analysis

scholarly journals Dynamic Wetting of Photo-Responsive Arylazopyrazole Monolayers is Controlled by the Molecular Kinetics of the Monolayer

2022 ◽  
Author(s):  
Christian Honnigfort ◽  
Leon Topp ◽  
Natalia García Rey ◽  
Andreas Heuer ◽  
Björn Braunschweig
Keyword(s):  
Contact Angle ◽  
Time Scales ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Oxide Surfaces ◽  
Relaxation Processes ◽  
Phosphonic Acids ◽  
Additional Measure ◽  
Time Resolved ◽  
Droplet Dynamics

Smart surfaces that can change their wetting behavior on demand are interesting for applications such as self-cleaning surfaces or lab-on-a-chip devices. In order to functionalize aluminum oxide surfaces, we have synthesized arylazopyrazole phosphonic acids (butyl-AAP-C18PA) that represent a new class of photoswitchable molecules for these oxide surfaces. Butyl-AAP-C18PA monolayers were deposited on alpha-Al2O3(0001) and show reversible E/Z photo-switching with UV (Z) and green (E) light that can trigger contact angle changes of up to ~10°. We monitored these changes on the macroscopic level by recording the dynamic contact angle while the monolayer was switched in situ from the E to the Z state. On the molecular level, time-resolved vibrational sum-frequency generation (SFG) spectroscopy provided information on the kinetic changes within the AAP monolayer and the relevant characteristic time scales for E to Z switching and vice versa. In addition, vibrational SFG at different relative humidity indicates that the thermal stability of the Z configuration is largely influenced by the presence of water and that water can stabilize the Z state and, thus, hinder the AAP monolayer to switch into the E state when it is immersed in H2O. Having established the characteristic times for switching on the molecular scale from SFG spectroscopy, we additional measure the dynamic contact angle. Further, we reveal the time scales of the coupled substrate and droplet dynamics which we have extracted individually. For that, we report on a relaxation model, that can be solved analytically and which is verified via comparison with simulations of a Lennard Jones system and a comparison with experimental data. Indeed, our modelling of these coupled relaxation processes allows us to predict the non-trivial variation of the time-dependence of the contact angle when changing the size of the droplet. The observed slowing-down for E to Z switching upon the presence of the droplet is rationalized in terms of specific interactions of water with the exposed AAP moieties.

Investigation of behavior of the dynamic contact angle in a problem of convective flows

2017 ◽  
Vol 5 (4) ◽  
pp. 27-42
Author(s):  
O.N Goncharova ◽  
◽  
I.V. Marchuk ◽  
A.V. Zakurdaeva ◽  
◽  
...  
Keyword(s):  
Contact Angle ◽  
Dynamic Contact Angle ◽  
Dynamic Contact ◽  
Convective Flows

scholarly journals Morphological effect of side chain on H3O+ transfer inside polymer electrolyte membranes across polymeric chain via molecular dynamics simulation

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
JinHyeok Cha
Keyword(s):  
Fuel Cell ◽  
Ionic Conductivity ◽  
Polymer Electrolyte ◽  
Polymer Electrolyte Membrane ◽  
Dynamics Simulation ◽  
Polymeric Chain ◽  
Side Chains ◽  
Dynamic Simulations ◽  
Morphological Effect ◽  
Electrolyte Membrane

AbstractPerformance and durability of polymer electrolyte membrane are critical to fuel cell quality. As fuel cell vehicles become increasingly popular, membrane fundamentals must be understood in detail. Here, this study used molecular dynamic simulations to explore the morphological effects of perfluorosulfonic acid (PFSA)-based membranes on ionic conductivity. In particular, I developed an intuitive quantitative approach focusing principally on hydronium adsorbing to, and desorbing from, negatively charged sulfonate groups, while conventional ionic conductivity calculations featured the use of mean square displacements that included natural atomic vibrations. The results revealed that shorter side-chains caused more hydroniums to enter the conductive state, associated with higher ion conductivity. In addition, the hydronium path tracking showed that shorter side-chains allowed hydroniums to move among host groups, facilitating chain adsorption, in agreement with a mechanism suggested in earlier studies.

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