Journal article
Contact Line Instability Caused by Air Rim Formation under Nonsplashing Droplets
Langmuir, v 34(17), pp 4962-4969
01 May 2018
PMID: 29620373
Featured in Collection : UN Sustainable Development Goals @ Drexel
Abstract
Drop impact is fundamental to various natural and industrial processes such as rain-induced soil erosion and spray-coating technologies. The recent discovery of the role of air entrainment between the droplet and the impacting surface has produced numerous works, uncovering the unique physics that correlates the air film dynamics with the drop impact outcomes. In this study, we focus on the post-failure air entrainment dynamics for We numbers well below the splash threshold under different ambient pressures and elucidate the interfacial instabilities formed by air entrainment at the wetting front of impacting droplets on perfectly smooth, viscous films of constant thickness. A high-speed total internal reflection microscopy technique accounting for the Fresnel reflection at the drop-air interface allows for in situ measurements of an entrained air rim at the wetting front. The presence of an air rim is found to be a prerequisite to the interfacial instability which is formed when the capillary pressure in the vicinity of the contact line can no longer balance the increasing gas pressure near the wetting front. A critical capillary number for the air rim formation is experimentally identified above which the wetting front becomes unstable where this critical capillary number inversely scales with the ambient pressure. The contact line instabilities at relatively low We numbers (We similar to O(10)) observed in this study provide insight into the conventional understanding of hydrodynamic instabilities under drop impact which usually require We >> 10.
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Details
- Title
- Contact Line Instability Caused by Air Rim Formation under Nonsplashing Droplets
- Creators
- Min Pack - Drexel UniversityPaul Kaneelil - Drexel UniversityHyoungsoo Kim - Princeton UniversityYing Sun - Drexel University
- Publication Details
- Langmuir, v 34(17), pp 4962-4969
- Publisher
- American Chemical Society; Washington, DC
- Number of pages
- 8
- Grant note
- CMMI-1401438; CBET-1705745 / National Science Foundation; National Science Foundation (NSF)
- Resource Type
- Journal article
- Language
- English
- Academic Unit
- College of Engineering
- Web of Science ID
- WOS:000431463500004
- Scopus ID
- 2-s2.0-85046274959
- Other Identifier
- 991019167632804721
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- Collaboration types
- Domestic collaboration
- International collaboration
- Web of Science research areas
- Chemistry, Multidisciplinary
- Chemistry, Physical
- Materials Science, Multidisciplinary