Editing Vortex ring (section)

==Other examples==

===Vortex ring state in helicopters===
{{main|Vortex ring state}}
[[File:Vortex ring helicopter.jpg|thumb|The curved arrows indicate airflow circulation about the rotor disc.  The helicopter shown is the [[RAH-66 Comanche]].]]
Air vortices can form around the [[helicopter rotor|main rotor]] of a [[helicopter]], causing a dangerous condition known as [[vortex ring state]] (VRS) or "settling with power".  In this condition, air that moves down through the rotor turns outward, then up, inward, and then down through the rotor again. This re-circulation of flow can negate much of the lifting force and cause a catastrophic loss of altitude.  Applying more power (increasing collective pitch) serves to further accelerate the downwash through which the main-rotor is descending, exacerbating the condition.

===In the human heart===
A vortex ring is formed in the left [[ventricle (heart)|ventricle]] of the [[human heart]] during cardiac relaxation ([[diastole]]), as a [[jet (fluid)|jet]] of [[blood]] enters through the [[mitral valve]]. This phenomenon was initially observed [[in vitro]]<ref>Bellhouse, B.J., 1972, ''Fluid mechanics of a model mitral valve and left ventricle'', Cardiovascular Research 6, 199–210.</ref><ref>Reul, H., Talukder, N., Muller, W., 1981, ''Fluid mechanics of the natural mitral valve'', Journal of Biomechanics 14, 361–372.</ref> and subsequently strengthened by analyses based on [[color Doppler mapping]]<ref>Kim, W.Y., Bisgaard, T., Nielsen, S.L., Poulsen, J.K., Pedersen, E.M., Hasenkam, J.M., Yoganathan, A.P., 1994, ''Two-dimensional mitral flow velocity profiles in pig models using epicardial echo Doppler Cardiography'', J Am Coll Cardiol 24, 532–545.</ref><ref>Vierendeels, J. A., E. Dick, and P. R. Verdonck, ''Hydrodynamics of color M-mode Doppler flow wave propagation velocity V(p): A computer study'', J. Am. Soc. Echocardiogr. 15:219–224, 2002.</ref> and [[magnetic resonance imaging]].<ref>Kim, W.Y., Walker, P.G., Pedersen, E.M., Poulsen, J.K., Oyre, S., Houlind, K., Yoganathan, A.P., 1995, ''Left ventricular blood flow patterns in normal subjects: a quantitative analysis by three dimensional magnetic resonance velocity mapping'', J Am Coll Cardiol 26, 224–238.</ref><ref>Kilner, P.J., Yang, G.Z., Wilkes, A.J., Mohiaddin, R.H., Firmin, D.N., Yacoub, M.H., 2000, ''Asymmetric redirection of flow through the heart'', Nature 404, 759–761.</ref> Some recent studies<ref>Kheradvar, A., Milano, M., Gharib, M. ''Correlation between vortex ring formation and mitral annulus dynamics during ventricular rapid filling'', ASAIO Journal, Jan–Feb 2007 53(1): 8–16.</ref><ref>Kheradvar, A., Gharib, M. ''Influence of ventricular pressure-drop on mitral annulus dynamics through the process of vortex ring formation'', Ann Biomed Eng. 2007 Dec;35(12):2050–64.</ref> have also confirmed the presence of a vortex ring during [[rapid filling]] phase of [[diastole]] and implied that the process of vortex ring formation can influence [[mitral annulus]] dynamics.

===Bubble rings===
Releasing air underwater forms [[bubble ring]]s, which are vortex rings of water with bubbles (or even a single donut-shaped bubble) trapped along its axis line.  Such rings are often produced by [[scuba diver]]s and [[dolphin]]s.<ref name="dolphin">{{cite web|author=Don White|title=Mystery of the Silver Rings|access-date=2007-10-25|url=http://www.earthtrust.org/delrings.html|url-status=dead|archive-url=https://web.archive.org/web/20071026021403/http://earthtrust.org/delrings.html|archive-date=2007-10-26}}</ref>

===Volcanoes===
[[File:Anello di fumo Etna da Zafferana.jpg|thumb|220px|right|Mount Etna vortex ring]]
{{Expand list|date=May 2012}}
Under particular conditions, some volcanic vents can produce large visible vortex rings.<ref name=ABCNews /><ref>[http://www.volcanodiscovery.com/photoglossary/smoke_ring.html Illustrated Volcano Glossary]</ref> Though a rare phenomenon, several volcanoes have been observed emitting massive vortex rings as erupting steam and gas condense, forming visible toroidal clouds:
*[[Mount Etna]],<ref>[http://news.bbc.co.uk/2/hi/science/nature/696953.stm Etna hoops it up] BBC News, 2003-03-31.</ref><ref>[http://www.swisseduc.ch/stromboli/etna/etna00/index-en.html Etna 2000] Stromboli Online, 2009-03-12.</ref><ref>[http://video.it.msn.com/watch/video/miracolo-etna-dal-cratere-anelli-di-fumo-perfetti/168go5fdp] {{Webarchive|url=https://web.archive.org/web/20120121235645/http://video.it.msn.com/watch/video/miracolo-etna-dal-cratere-anelli-di-fumo-perfetti/168go5fdp |date=2012-01-21 }} Smoke rings of Mount Etna video</ref> Italy ([[Sicily]])
*[[Stromboli]],<ref>{{cite web|url=https://www.volcanodiscovery.com/fr/photos/stromboli/0606/smokerings.html|title=Smoke rings from Stromboli volcano (June 2006)|website=www.volcanodiscovery.com}}</ref> Italy ([[Aeolian Islands]])
*[[Eyjafjallajökull]],<ref>[http://news.discovery.com/earth/iceland-volcano-smoke-ring.html Iceland Volcano Blows Spectacular Smoke Ring: Big Pics] Discovery News, 2010-05-10.</ref> [[Iceland]]
*[[Hekla]],<ref>{{cite web|url=https://www.telegraph.co.uk/earth/earthpicturegalleries/7498695/Iceland-volcano-eruption-volcanic-activity-in-the-land-of-fire-and-ice.html?image=11 |archive-url=https://web.archive.org/web/20100326135118/http://www.telegraph.co.uk/earth/earthpicturegalleries/7498695/Iceland-volcano-eruption-volcanic-activity-in-the-land-of-fire-and-ice.html?image=11 |url-status=dead |archive-date=March 26, 2010 |title=Environment |publisher=The Telegraph |date= |accessdate=2021-01-28}}</ref> [[Iceland]]
*[[Tungurahua]],<ref>{{cite web|url=http://www.earth-of-fire.com/article-les-volcans-fument-la-pipe-formation-de-vortex-toroidal-69760899.html|title=&quot; Les volcans fument la pipe&quot; - formation de vortex toroidal.|first=Bernard|last=Duyck|website=Earth of fire|access-date=2024-04-08|archive-date=2013-07-25|archive-url=https://web.archive.org/web/20130725215706/http://earth-of-fire.over-blog.com/article-les-volcans-fument-la-pipe-formation-de-vortex-toroidal-69760899.html|url-status=dead}}</ref> [[Ecuador]]
*[[Pacaya]],<ref>{{cite web|url=https://skagwaydelta.wordpress.com/2011/05/15/pacaya-volcano-blows-a-smoke-ring-in-farewell-guatemala-2005/|title=Pacaya Volcano blows a smoke-ring in farewell Guatemala 2005|date=May 15, 2011}}</ref> [[Guatemala]]
*[[Mount Redoubt]],<ref>{{cite web|url=https://www.flickr.com/photos/31220278@N05/3880927815/|title=Mt Redoubt Blowing Smoke Rings|date=August 30, 2009|via=Flickr}}</ref> United States ([[Alaska]])
*[[Mount Aso]],<ref>{{cite web|url=https://www.flickr.com/photos/mikelyvers/6890803977/|title=aso volcano smoke ring|date=February 17, 2012|via=Flickr}}</ref> Japan ([[Kyushu]])
*[[Whakaari / White Island|Whakaari (White Island)]],<ref>{{cite web|url=https://www.flickr.com/photos/mr_step/8510876313/|title=DSC_0350.jpg|date=February 21, 2013|via=Flickr}}</ref> New Zealand
*[[Gunung Slamet]],<ref>{{cite web |url=http://touch.metrotvnews.com/read/2014/09/11/290353#.VBJpsmYxW2c/ |title=''Cincin Raksasa'' Muncul di Atas Gunung Slamet - Daerah |website=touch.metrotvnews.com |access-date=17 January 2022 |archive-url=https://web.archive.org/web/20140912083101/http://touch.metrotvnews.com/read/2014/09/11/290353#.VBJpsmYxW2c/ |archive-date=12 September 2014 |url-status=dead}}</ref> [[Indonesia]] ([[Central Java]])
*[[Momotombo]],<ref>{{cite web|url=https://www.youtube.com/watch?v=sNIKDrUO29Y  |archive-url=https://ghostarchive.org/varchive/youtube/20211222/sNIKDrUO29Y |archive-date=2021-12-22 |url-status=live|title=Momotombo - Anillos de humo |publisher=YouTube |date=2015-12-05 |accessdate=2021-01-28}}{{cbignore}}</ref> [[Nicaragua]] ([[León, Nicaragua|León]])

===Separated vortex rings===
[[File:Photos-photos 1088103921 Floating.jpg|thumb|Pappus of the dandelion which produces a separated vortex ring in order to stabilize flight]]
There has been research and experiments on the existence of separated vortex rings (SVR) such as those formed in the wake of the [[Pappus (botany)|pappus]] of a [[Taraxacum|dandelion]]. This special type of vortex ring effectively stabilizes the seed as it travels through the air and increases the lift generated by the seed.<ref>{{Cite journal|last1=Ledda|first1=P. G.|last2=Siconolfi|first2=L.|last3=Viola|first3=F.|last4=Camarri|first4=S.|last5=Gallaire|first5=F.|date=2019-07-02|title=Flow dynamics of a dandelion pappus: A linear stability approach|journal=Physical Review Fluids|volume=4|issue=7|page=071901|doi=10.1103/physrevfluids.4.071901|bibcode=2019PhRvF...4g1901L|issn=2469-990X|hdl=11568/998044|s2cid=198429309 |url=https://research.utwente.nl/en/publications/f98244a1-97b0-4aa2-8a22-bcf113eb8d18 |hdl-access=free}}</ref><ref name=":0">{{Cite journal|last1=Cummins|first1=Cathal|last2=Seale|first2=Madeleine|last3=Macente|first3=Alice|last4=Certini|first4=Daniele|last5=Mastropaolo|first5=Enrico|last6=Viola|first6=Ignazio Maria|last7=Nakayama|first7=Naomi|date=2018|title=A separated vortex ring underlies the flight of the dandelion|journal=Nature|volume=562|issue=7727|pages=414–418|doi=10.1038/s41586-018-0604-2|pmid=30333579|bibcode=2018Natur.562..414C|s2cid=52988814|issn=0028-0836|url=http://eprints.gla.ac.uk/171858/7/171858.pdf}}</ref> Compared to a standard vortex ring, which is propelled downstream, the axially symmetric SVR remains attached to the pappus for the duration of its flight and uses drag to enhance the travel.<ref name=":0" /><ref>{{Cite journal|last=Yamamoto|first=Kyoji|date=November 1971|title=Flow of Viscous Fluid at Small Reynolds Numbers Past a Porous Sphere|journal=Journal of the Physical Society of Japan|volume=31|issue=5|page=1572|doi=10.1143/JPSJ.31.1572|bibcode=1971JPSJ...31.1572Y}}</ref> These dandelion seed structures have been used to create tiny battery-free wireless sensors that can float in the wind and be dispersed across a large area.<ref>{{Cite journal |last1=Iyer |first1=Vikram |last2=Gaensbauer |first2=Hans |last3=Daniel |first3=Thomas L. |last4=Gollakota |first4=Shyamnath |date=2022-03-17 |title=Wind dispersal of battery-free wireless devices |url=https://www.nature.com/articles/s41586-021-04363-9 |journal=Nature |language=en |volume=603 |issue=7901 |pages=427–433 |doi=10.1038/s41586-021-04363-9 |pmid=35296847 |bibcode=2022Natur.603..427I |s2cid=247499662 |issn=0028-0836|url-access=subscription }}</ref>