Icephobicity of Superhydrophobic Surfaces Under Atmospheric Icing, the Role of Surface Wettability on Impact Dynamics and Ice Growth Kinetics
Bibliographic record
Abstract
Le givrage atmospherique est un probleme difficile pour l'exploitation et la securite des aeronefs. Il se produit en vol lorsque des nuages de micrometriques gouttelettes d'eau en surfusion percutent et gelent sur les surfaces exposees, entrainant diverses defaillances et pertes d'efficacite. Ces gouttelettes, dans une phase liquide instable, possedent des diametres de l'ordre de 10 a 50 micrometres, peuvent etre refroidies a des temperatures inferieures a moins 20 C et percuter a des vitesses de dizaines de metres par seconde. Les systemes actuels de protection contre la glace reposent sur des technologies telles que des elements chauffants ou des fluides de degivrages. Ils sont energivores, toxiques et peu fiables dans des conditions severes. Recemment, le developpement de surfaces dites glaciophobes a attire l’attention pour exploiter leurs potentielles proprietes afin d'empecher l'accumulation de glace, de faciliter le deglacage ou d'ameliorer le degivrage thermique. Parmi ces surfaces, les revetements superhydrophobes, qui combinent des materiaux a faible energie de surface et une rugosite de surface elevee, ont ete proposes en raison de leur resistance a l’eau exceptionnelle. Il a ete demontre que ces surfaces hydrophobes conservent leurs proprietes dans certaines conditions de givrage, affichant une faible adherence a la glace, une repulsion des gouttes dans des environnements glacials ou facilitant la fonte et l'elimination de la glace. Cependant, l'adoption de surfaces glaciophobes pour des applications aerospatiales est entravee par un manque de connaissance de leur performance dans des conditions environnementales realistes. Les conditions de givrage des aeronefs necessitent des installations dediees d'essai en soufflerie givrante pour reproduire un environnement atmospherique realiste. Le comportement de mouillage et de glaciophobicite des revetements superhydrophobes sous l’effet combine de microgouttelettes, de temperatures glaciales et d'une vitesse d'impact elevee est encore largement inexplore. Par consequent, l'objectif de cette these est d'etudier le role de la mouillabilite et de la superhydrophobicite sur la glaciophobicite de surfaces specifiquement modifiees dans des conditions de givrage de microgouttelettes en surfusion telles que subies en vol. L’essentiel du travail experimental a ete realise sur une soufflerie de givre a petite echelle capable de reproduire des conditions de givrage quasi realistes necessaires pour tester la glaciophobicite des surfaces fabriquees. Nous avons etudie l'influence de la mouillabilite et de la rugosite de surface en examinant successivement la dynamique d'impact des gouttelettes, la cinetique de croissance de la glace et le comportement des surfaces nanotexturees.Abstract----------Atmospheric icing is a challenging problem for aircraft operation and safety. It occurs in flight when clouds of micrometric supercooled water droplets impact and freeze on exposed surfaces, potentially leading to diverse system malfunctions and efficiency losses. These droplets, in an unstable liquid phase, feature diameters in the range of 10 to 50 micrometers, can be cooled to temperatures below -20oC and impact at speeds of tens of meters per second. Current ice protection methods rely on technologies such as heaters or freezing-point depressant chemicals. These are energy-consumptive, environmentally damaging and prone to failure in severe weather. Recently, the development of so-called icephobic surfaces has attracted a lot of research to harness potential properties to prevent ice accretion, facilitate ice shedding or enhanced thermal de-icing. Among these surfaces, superhydrophobic coatings, which combine low surface energy materials and high surface roughness, have been proposed due to their exceptional water repellency. These water-repellent surfaces have been shown to maintain their properties under certain icing conditions, displaying low ice adhesion, droplet repellency in cold environment, or facilitating ice melting and removal. However, the adoption of icephobic surfaces in aerospace applications has been hindered by a lack of research related to their performance under realistic environmental conditions. Aircraft icing conditions require dedicated icing wind-tunnel testing facilities to reproduce realistic atmospheric environment. The wetting and icephobic behavior of superhydrophobic coatings under the combination of micrometric droplets, sub-zero temperatures, and high impact velocity is still largely unexplored. Therefore, the objective of this thesis is to investigate the role of wettability and superhydrophobicity on the icephobicity of engineered surfaces under supercooled water microdroplet icing conditions as experienced by aircraft. The core of the experimental work was performed on a small-scale icing wind-tunnel able to reproduce near-realistic icing conditions needed to test icephobicity of the desired surfaces. We investigated the influence of surface wettability and roughness by looking successively at the droplet impact dynamics, the ice growth kinetics and the behavior of nanotextured surfaces. In the first part of the study, we used ultra-high-speed imaging in the wind-tunnel to record in detail the impact dynamics of microdroplets at different levels of supercooling on four reference surfaces with wettability ranging from smooth near-superhydrophilic to micro/nanotextured superhydrophobic.
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.001 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.001 | 0.000 |
| Research integrity | 0.000 | 0.001 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".