Shrinking instability of toroidal droplets

• Type of Material: Article
• Authors: Alexandros A. Fragkopoulos, Georgia Institute of Technology; Ekapop Pairam, King Mongkut’s Institute of Technology; Eric Berger, Georgia Institute of Technology; Phil Segre, Emory University; Alberto Fernández-Nieves, Georgia Institute of Technology
• Language: English
• Date: 2017-03-14
• Publisher: National Academy of Sciences
• Publication Version: Final Published Version
• Copyright Statement: © 2017 National Academy of Sciences
• Final Published Version (URL): http://dx.doi.org/10.1073/pnas.1619073114
• Title of Journal or Parent Work: Proceedings of the National Academy of Sciences
• ISSN: 0027-8424
• Volume: 114
• Issue: 11
• Start Page: 2871
• End Page: 2875
• Grant/Funding Information: We thank the National Science Foundation for financial support.
• Keywords: Stokes flow; PIV; liquid tori; hydrodynamic instabilities; stream function
• Research Categories: Physics, General

Abstract

Toroidal droplets are inherently unstable due to surface tension. They can break up, similar to cylindrical jets, but also exhibit a shrinking instability, which is inherent to the toroidal shape. We investigate the evolution of shrinking toroidal droplets using particle image velocimetry. We obtain the flow field inside the droplets and show that as the torus evolves, its cross-section significantly deviates from circular. We then use the experimentally obtained velocities at the torus interface to theoretically reconstruct the internal flow field. Our calculation correctly describes the experimental results and elucidates the role of those modes that, among the many possible ones, are required to capture all of the relevant experimental features.