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Title:The Ephemeral Jelly
Author(s):Hoque, Muhammad Jahidul
Contributor(s):Yan, Xiao; Miljkovic, Nenad
Subject(s):Mechanical Science and Engineering
Abstract:Though this jet-like internal flow pattern inside of a water droplet resembles a mushroom, it swims like a jellyfish. This microscopic phenomenon was observed when two micro-droplets coalesce. Internal droplet flow has remained a challenge to visualize for over a century due to the small length and time scales associated with the flows. In order to study droplet coalescence dynamics, we developed a droplet dispensing and visualization system. To track the internal flow front, and ethanol (20 wt%) water mixture was used as the working fluid. Due to the unequal evaporation rates between water and ethanol, a density gradient is developed at the liquid-gas interface of the droplets, resulting in a lower refractive index at the interface compared to that in the bulk liquid. Jet-like internal flow and vortex rings create a jellyfish-like structure inside the merging droplet. The chronophotograph demonstrates the previously unidentified jet-like flow that occurs during the coalescence of droplets having different sizes.
Issue Date:2020
Rights Information:Copyright 2020 Muhammad Jahidul Hoque
Date Available in IDEALS:2020-04-14

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