Talk:Vortex ring

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Diagrams[edit]

will try to create a simple diagram soon. this is a pretty hard physical construction to describe verbally. mnemonic 22:52, 2004 Jul 15 (UTC)

woot, finally did the diagram. not sure if i rendered from the best angle...✈ James C. 20:56, 2004 Aug 16 (UTC)


Added a link which includes some graphs showing where a helicopter will enter vortex ring state. I didn't check copyright status, but maybe someone else can see if maybe they ca plot similar graphs or so from scratch at least? Kim Bruning 12:19, 25 Jun 2005 (UTC)

More general introduction to vortex rings etc.[edit]

Hi Guys,

I've tried to add a more general intro to vortex rings and have put the helo-effect as a subheading. I also tried to intuitively explain how the ring may form, but I need some one in the know to check it.

thanksKghose 15:02, 20 October 2005 (UTC)[reply]


Vortex ring / Ground effect in fixed-wing VTOL aircraft[edit]

Hi,

While looking into flight test data on an early VTOL aircraft Short SC.1, I came across a research memorandum which refers to the losses in vertical thrust due to what is referred to there as "ground effect". This seemed fine, since this is how I would have described it, so I added the appropriate link to the article. Looking at ground effect however, I discovered that this refers to a net gain in lift experienced by some conventional aircraft wing types when flying close to the ground.

There is a potential confusion here, which I would like to sort out.
Is "vortex ring" specific to rotary wing aircraft?
Is "vortex ring" perhaps the U.S. term, "ground effect" the British term for the same thing?

Here is the reference: Discussion of ground effect w.r.t. the Short SC.1

Thanks TraceyR 19:55, 12 January 2007 (UTC)[reply]

Hello Tracey R. The article which you read may have been referring not necessarily to ground effect but of hot gas re-ingestion into the engine. As VTOL aircraft hover close to the ground, hot exhaust gases may be 'sucked' back into the engine intakes which would increase the temperature of the intake air and reduce thrust. Ground effect is an increase in lift that is experienced when an aircraft flies close to the ground, if I recall correctly (been a while since I've flown), within about the distance of a wing span. Oversimplifying the phenomenon, the air underneath the aircraft becomes a 'cushion' that the aircraft rests on increase the net lift. Vortex ring state is as has been described in the article and as far as I know is limited to rotary wing aircraft and is definitely not the same as ground effect or hot gas re-ingestion. Cheers, Angmi —Preceding signed but undated comment was added at 04:37, 20 September 2007 (UTC) Article cited on the SC.1 does not appear to discuss effects of hot gas re-ingestion.--Angmi (talk) 10:23, 13 April 2008 (UTC)[reply]

Merger proposal[edit]

I think that the page Vortex ring toys provides redundant information, and a new section in Vortex ring would better suit the proper formatting of wikipedia. Thusly, I have added merger templates to the start of both pages. What do y'all think? Mmoople (talk) 22:32, 21 March 2009 (UTC)[reply]

I'm not sure of the value of the Vortex ring toys article. It doesn't describe what such a toy is or does; the summary doesn't summarise the article's content; it's all opinion without sources. Really it's a candidate either for deletion or rewrite, rather than merger. A section in Vortex ring would be unjustified. Only after a total rewrite would a one-line mention that such toys exist (with a wikilink) be justified. --TraceyR (talk) 11:30, 25 March 2009 (UTC)[reply]
I removed some OR and added a reference to Vortex ring toys. I also favour to leave it where it is, and add a "see also" here. I removed the merge tags. -- Crowsnest (talk) 11:42, 11 April 2009 (UTC)[reply]

Keep Shafranov reference?[edit]

I cannot find any reference to Shafranov regarding the similarity of steady Euler flow to the MHD equations, but I did find a reference in a footnote in Saffman (Vortex Dynamics) to a 1986 paper, H.K. Moffatt, "On the existence of localized rotational disturbances which propagate without change of structure in an inviscid fluid", J. Fluid Mech. 173, 289-302. Since Hill's spherical vortex is a very specific vortex ring, and its relation to MHD tenuous (without a reference), it seems like this is a trivial inclusion, and should probably be axed. Markstock (talk) 00:59, 18 October 2010 (UTC)[reply]

Conserved quantities[edit]

Lord Kelvin says that:

Helmholtz’s investigation proves that the angular vortex velocity of the core varies directly as its length, or inversely as its sectional area.

Unfortunately it's not clear to me whether he's talking about two conserved quantities, (length divided by angular velocity; and length times cross-sectional area; implying a third that's angular velocity times cross-sectional area) or one, angular velocity times cross-sectional area divided by length. Documenting the conserved quantities of a vortex line would be a good addition to this page. There must also be some relationship between the conserved quantities and the properties of the fluid: pressure, temperature, density and perhaps specific heat capacity. Documenting any such relationships would also be constructive. 84.215.6.188 (talk) 14:08, 14 February 2011 (UTC)[reply]

Of course, the core of the vortex ring is a vortex tube whose vorticity is conserved; it is also a material line of the fluid; Batchelor (p275) says the length of such a line and "the local vorticity magnitude" remain in a constant ratio, each being inversely proportional to the cross-section of the vortex-tube; this gives us a single conserved quantity; the local vorticity magnitude is curl of fluid flow velocity, so can be construed as angular velocity; and vorticity is its integral over the vortex-tube's cross-section; so "area times angular velocity" is vorticity, which is a conserved quantity. The surface bounding a vortex-tube is a material surface, so contains a material volume, which must again be conserved (as mass is conserved), so circumference (length) of the vortex ring times cross-sectional area of its core is constant. We thus have two conserved quantities, a volume and a vorticity.
So that answers my question, albeit inferred from Batchelor; I can't see it stated overtly ! So I don't have a source to cite for my conclusions. 84.215.6.188 (talk) 15:28, 14 February 2011 (UTC)[reply]

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External links modified (January 2018)[edit]

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