A separated vortex ring underlies the flight of the dandelion
File(s)
Accepted version
Author(s)
Type
Journal Article
Abstract
Wind-dispersed plants have evolved ingenious ways to lift their seeds1,2. The common dandelion uses a bundle of drag-enhancing bristles (the pappus) that helps to keep their seeds aloft. This passive flight mechanism is highly effective, enabling seed dispersal over formidable distances3,4; however, the physics underpinning pappus-mediated flight remains unresolved. Here we visualized the flow around dandelion seeds, uncovering an extraordinary type of vortex. This vortex is a ring of recirculating fluid, which is detached owing to the flow passing through the pappus. We hypothesized that the circular disk-like geometry and the porosity of the pappus are the key design features that enable the formation of the separated vortex ring. The porosity gradient was surveyed using microfabricated disks, and a disk with a similar porosity was found to be able to recapitulate the flow behaviour of the pappus. The porosity of the dandelion pappus appears to be tuned precisely to stabilize the vortex, while maximizing aerodynamic loading and minimizing material requirements. The discovery of the separated vortex ring provides evidence of the existence of a new class of fluid behaviour around fluid-immersed bodies that may underlie locomotion, weight reduction and particle retention in biological and manmade structures.
Date Issued
2018-10-18
Date Acceptance
2018-08-21
Citation
Nature, 2018, 562 (7727), pp.414-418
ISSN
0028-0836
Publisher
Nature Research
Start Page
414
End Page
418
Journal / Book Title
Nature
Volume
562
Issue
7727
Copyright Statement
© 2018 Springer Nature Limited. All rights reserved. The final publication is available at Springer via https://doi.org/10.1038/s41586-018-0604-2
Sponsor
Royal Society
The Royal Society
Leverhulme Trust
Identifier
https://www.nature.com/articles/s41586-018-0604-2
Grant Number
UF140640
UF140640
rpg-2015-255
Subjects
General Science & Technology
Publication Status
Published
Date Publish Online
2018-10-17