Droplet impact on a smooth solid surface at atmospheric pressure was experimentally studied and physically interpreted. A particular emphasis of the study is on the effects of liquid viscosity on the transition between droplet deposition (or droplet spreading without breakup) and droplet disintegration (including droplet splash and receding breakup). Specifically, the critical Weber number separating droplet deposition from droplet disintegration decreases and then increases with increasing Ohnesorge number (). The splash in the low- region and the receding breakup in the high- region were analyzed qualitatively based on the unbalanced forces acting on the rim of the spreading or receding liquid film. A semiempirical correlation of droplet deposition/disintegration thresholds is proposed and well fits the experimental results from previous and present studies over a wide range of liquid viscosity.
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http://dx.doi.org/10.1021/acs.langmuir.1c01797 | DOI Listing |
Soft Matter
March 2022
Process System Engineering, Faculty of Engineering and Applied Science, University of Regina, Regina, SK, S4S 0A2, Canada.
The problem of terminating a droplet at the surface of a membrane in a crossflow field is an important topic in the context of controlled emulsification of fluids for use in pharmaceutical and other industries. Some of these industries struggle to produce emulsions of uniform sizes for their products requiring higher levels of precision. In this work, we comprehensively investigated one such technique in which droplets were produced membrane openings and were terminated a crossflow field.
View Article and Find Full Text PDFJ Colloid Interface Sci
May 2022
Department of Chemical Engineering, Stanford University, CA 94305, USA. Electronic address:
Hypothesis: Although wetting agents have been developed to limit tear film dewetting over contact lenses, systematic analyses correlating wetting agent properties to mechanisms of the tear film destabilization are not readily available. Clarifying destabilization characteristics across key physio-chemical variables will provide a rational basis for identifying optimal wetting agents.
Experiments: We employ an in-house, in vitro platform to comprehensively evaluate drainage and dewetting dynamics of five wetting agents across seventeen different formulations and two model tear film solutions.
Langmuir
September 2021
Departmental of Mechanical Engineering, The Hong Kong Polytechnic University, Hung Hom, Kowloon 852, Hong Kong.
Droplet impact on a smooth solid surface at atmospheric pressure was experimentally studied and physically interpreted. A particular emphasis of the study is on the effects of liquid viscosity on the transition between droplet deposition (or droplet spreading without breakup) and droplet disintegration (including droplet splash and receding breakup). Specifically, the critical Weber number separating droplet deposition from droplet disintegration decreases and then increases with increasing Ohnesorge number ().
View Article and Find Full Text PDFJ Colloid Interface Sci
January 2021
Department of Mechanical Engineering, York University, Toronto, ON M3J 1P3, Canada. Electronic address:
We studied experimentally the breakup of liquid bridges made of aqueous solutions of Poly(acrylic acid) between two separating solid surfaces with freely moving contact lines. For polymer concentrations higher than a certain threshold (~30 ppm), the contact line on the surface with the highest receding contact angle fully retracts before the liquid bridge capillary breakup takes place at its neck. This means that all the liquid remains attached to the opposing surface when the surfaces are separated.
View Article and Find Full Text PDFPest Manag Sci
October 2020
School of Mathematical Sciences, Queensland University of Technology, Brisbane, Australia.
Background: A key challenge for developing computer models of spray retention by plants is to accurately predict how spray drops behave when impacting leaf surfaces. One poorly understood outcome occurs when drops bounce or shatter on impact but leave behind a proportion of the liquid on the surface (designated as pinning). This process is studied via impaction experiments with two hard-to-wet leaf surfaces (fat-hen: Chenopodium album and barnyard grass: Echinochloa crus-galli L.
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