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Bouncing off macro-textures: Merging simulation with experiment for better surface functionality

English title Bouncing off macro-textures: Merging simulation with experiment for better surface functionality
Applicant Karlin Ilya
Number 172640
Funding scheme Project funding (Div. I-III)
Research institution Institut für Energietechnik ETH Zürich
Institution of higher education ETH Zurich - ETHZ
Main discipline Fluid Dynamics
Start/End 01.07.2017 - 30.06.2021
Approved amount 388'657.00
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Keywords (4)

Fluid dynamics; Lattice Boltzmann methods; Hierarchical surface textures; Multiphase flows

Lay Summary (German)

Lead
Interaktion von Flüssigkeiten mit hierarchisch strukturierten Oberflächen: Grundlagen und Anwendungen
Lay summary

Die Erforschung des Wasserabstosseffekts beim Auftreten flüssiger Tropfen auf eine hydrophobe Oberfläche ist ein aktives Forschungsgebiet sowohl aus fundamental- als auch aus ingenieurwissenschaftlicher Perspektive und Quelle vieler neuartiger Anwendungen wie etwa selbst-reinigende, wasserabweisende und vereisungsfreie Oberflächen.

Die jüngste Zunahme von Interesse für dieses Gebiet besteht vorwiegend aus experimentellen Studien. Nebst der anspruchsvollen Fertigung von Oberflächen und deren Beschichtungen tragen diese Untersuchen aber wenig zum Verständnis der auftretenden Strömungsphänomene bei.

Dieses Projekt hat das Ziel, durch die Kombination von Modellierung hochentwickelter numerischer Algorithmen und experimenteller Herangehensweise, die Fluid-dynamischen Prozesse während der Interaktion von Tropfen mit komplexen Makro-strukturierten Oberflächen besser zu verstehen und quantitativ vorherzusagen, um dann neue strukturierte Oberflächen zu finden, welche die Kontakt-Zeit der Tröpfchen mit dem Substrat minimieren.

 

Direct link to Lay Summary Last update: 03.04.2018

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Abstract

Discovery and understanding of novel mechanisms of drops repellence from hydrophobic and super-hydrophobic surfaces constitutes an area of active research from both a fundamental fluidics perspective as well as a source of novel engineering ideas for various applications such as self-cleaning, water resistance and anti-icing. The current proposal aims at exploring both numerical and experimental approaches to discovering new surfaces that minimize the contact time by understanding the fluid dynamics of droplet surface interaction for complex macro-textured surfaces and the use of state-of-the-art surface engineering and coating techniques. The recent surge of interest on this topic [Bird et al., Nature 2013, Liu et al., Nature Physics 2014, Nature communications 2015, Schutzius et al., Nature 2015] has been predominantly experimental in nature. Apart from the demanding process of surface fabrication and coating, these investigations provide little insights into the associated flow phenomena mainly due to the hierarchy of scales (from millimeter to sub-micron scale) of the surface texture and difficulty to probe the flow inside the droplet. To that end, the present proposal aims at establishing the entropic lattice Boltzmann methods (ELBM) as a reliable tool for investigation of flow phenomena. We show as a part of preliminary research that ELBM can accurately predict the behavior of fluids on macro-textured surfaces and can accurately describe the interplay between kinetic energy, surface energy and viscous dissipation while also revealing the flow physics inside the droplet. Based on ELBM simulations we propose here detailed investigation of new surfaces that show large reduction in droplet contact time while at the same time being robust and effective in a wide range of parameters. Together with our National Collaborators we intend to fabricate and extensively study, through experimental and numerical investigations, these and other novel ideas of decorating a surface with macro patterns. This proposal further aims at extending the capabilities of ELBM in predicting multiphase flows with thermal interactions and phase change. The overall goal of this study is to advance the fundamentals underlying the reduction of the contact time of liquid drops with the substrate morphology (smooth to hierarchical) and wettability (hydrophobicity or icephobicity). Systematic tuning of the hierarchical texture along with functionalization will be used to retard the ice formation and minimize the ice adhesion on such surfaces under both stationary and dynamic (flow) conditions of the surrounding gas. In addition to their fundamental value, the results of the study will also help the future designs of superhydrophobic surfaces with significant reduction of contact times for various liquids.
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