Thursday, October 18, 2018

Clock this: Dandelion Seeds Have a Vortex Floating Above Their Filaments

     "Dandelion seeds fly using a method that researchers thought would not work in the real world, according to a study published on October 17, 2018, in Nature." Here is a dandelion head, also called a dandelion clock:



     "When some animals, airplanes, or seeds fly, rings of circulating air called vortices form in contact with their wings or wing-like surfaces. These vortices can help to maintain the forces that lift the animal, machine, or seed into the air. 



     Researchers thought that an unattached vortex would be too unstable to persist in nature. Yet the light, puffy seeds of dandelions use vortices that materialize just above their surfaces and lift the seed into the air.



     Dandelion seeds bear filaments that radiate out from a central stalk like the spokes on a bicycle wheel, a feature that seems to be the key to their flight. Many insects harbor such filter-like structures on their wings or legs, suggesting that the use of detached vortices for flight or swimming might be relatively common, says study co-author Dr. Naomi Nakayama, a plant scientist at the U. of Edinburgh.



      As far as vortex rings go, the dandelion's is unusual. Normally, such air bubbles stay attached to an object or totally separate and disappear. But the dandelion’s bubble separates and hangs out above the seed. “When you show it to a fluid dynamicist, it blows their mind,” says study coauthor Dr. Cathal Cummins.



     Researchers were curious about how these bristly seeds of the pappus (the seed plus the filaments) stayed in the air because they looked so different from the wing-like seeds of other plants, such as maple trees. Those structures act like the wings of a bird or airplane, generating pressure differences above and below the wing to fly. To find the answer, Dr. Nakayama and her colleagues put dandelion seeds in a vertical wind tunnel and used a laser to illuminate particles that helped to visualize the airflow around the seed.



     That’s when they saw the vortex floating above the seeds. The amount of open space between the spokes of the seeds seems to be the key to the stability of these detached vortices, says Dr. Cummins. Pressure differences between the air moving through the spokes and the air moving around the seed creates the vortex ring.



     Previous studies have found that dandelion seeds always have between 90 and 110 bristles, says Nakayama. She described it as “extremely consistent”, and that consistency turns out to be very important.



     When the team designed small silicon discs to imitate these spokes, they produced models with a range of openings: from solid discs to ones that were 92% air, like the structures on the dandelion seeds. When the researchers tested these model seeds in their wind tunnel, they found that only the discs that best approximated dandelion seeds could maintain the detached vortex.



     If the number of openings in the discs was even 10% off of those in dandelion seeds, the vortex destabilized. The seed looks inefficient for flight because it has so much open space, says Dr. Nakayama, but these openings are what allow the unattached vortex ring to remain stable."



     “It’s great to see an analysis of something we see every day but didn’t fully understand,” says Dr. Richard Bomphrey, a comparative biomechanist at the Royal Veterinary College. “To discover that there were aerodynamic mechanisms that we didn’t already know — despite the fact that we can fly things at Mach 9 — is always exciting.”



        Wow, hanging vortices in a common flower. Nature sure is dandy!
Steph

Zoë had her Peace Corps gong out service, hitting the gong thrice to represent three years of service. Proud of her and looking ahead to what she'll do next!




55 comments:

  1. When I was a kid we had the best dandelion garden in the area, which mysteriously ended exactly and squarely at our neighbors' yards on both sides. Nice to know the mechanism of flight we enjoyed watching and, in a small way, enabling with a brief puff.

    I suppose next you'll be telling us spiders use electricity to fly. Then Elon Musk will come out with the flying Tesla Spider, which will surely give everyone the vapors. Finally, he will have to change his name to Elon Bison, just to get along.

    Have you considered offering your posts to local newspapers? They are often hungry for content, and accelerating a little science for the masses would increase the public force, especially on issues of gravity.

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    1. [Dandy]Lions and Spiders and Bulls! Oh, my!

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    2. I enjoy dandelions in my yard. The neighbors? Not so much.

      I also enjoyed your cheeky links, eco. Thanks.

      As to local newspapers, I might reach out to The Washington Park Profile, a monthly newspaper here. It's about the only physical newspaper here that folks I know regularly read. {Well, there's Westword, but it is more into the dating and marijuana scene. Not sure dandelion seeds would fly there.}

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    3. I also don't enjoy the neighbors in my yard (smiling snarky emoji here).

      Why not try the Denver Post, isn't that the biggun for your part of the world? I think a lot of papers (even if they don't use paper) will take content, especially if it's free and reasonably well written.

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    4. Smiling snarky emoji ;-] is just what is needed there, eco.

      Maybe. Yes, the Post is the biggun here (though I don’t know anyone who still reads it. . .) I have many friends who were let go when The Rocky Mountain News folded. I never picked up the physical paper habit after that.

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  2. Replies
    1. You can never have too many geology jokes. Thanks, jan.

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  3. The Little Free Libraries in my neighborhood are great places to stop and talk about books.

    What a wonderful idea; sorry the founder has passed on:


    http://www.startribune.com/little-free-library-founder-dies-leaving-a-legacy-of-helping-cities-one-book-at-a-time/497938831/?c=n&clmob=y

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  4. Zoë had her Peace Corps gong out service where she rang the special gong three times representing her three years of service (Image newly added above). Now some travel throughout Africa and a job search in public health in the US. Exciting times ahead. Proud of Zoë for her service!

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    Replies
    1. Going, going gong? Congratulations to Zoë (how do you get the dots above the e?) and her proud mom.

      A noble path she wants to follow, I had a client who was in Peace Corps (Sierra Leone), then USDA Food and Nutrition Service for 2 decades, then back to Peace Corps as West Coast Regional Director. I think she's since left that position, but I haven't kept in touch since her renovation finished.

      Unfortunately the orange menace has significantly cut funding for Peace Corps, and probably USDA nutrition programs too. Has Zoë been burdened with having to explain his outrages, including the infamous s***hole countries comment?

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    2. eco, if I hold down the 'e' key on my phone or iPad, up pop choices for 'e" with various accents. Choose è or ê or ë; there are 11 choices.

      Yes, sadly, she has been asked that s***hole question more than once.

      Zoë is quite grateful for the opportunity to be of service. What a wonderful way to start life post-college.

      Every PCV I have met talks about their service within short order upon first meeting them. It has a profound effect on many lives around the world.

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    3. Ah, I have neither cell phone nor iPad, and holding down the "e" only gets me eeeeeeeeeeeeeeeeeeeeeeeeeeeeeee on my laptop. Or a very long tone on my land line.

      Another client was also in the PC, he's 75 now and has stayed in touch with his fellow PCV's for the 50+ years, including a current Congressman.

      We just submitted drawings to replace his (and his wife's) house - my first strawbale - that burned in last year's fires, and over the 20 years I've known him he speaks frequently and fondly of his time in Botswana, and still draws on memories of the people and their lives to guide him today.

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    4. Here you go, eco.

      On a PC:

      ë = CTRL + " then e, or Alt + 0235.

      On a Mac:

      Use the OPTION key. For the umlauted characters, hold down OPTION and push ‘u’. Release OPTION, then type the desired base letter (a, e, o, u, A, E, O, or U). The umlaut will appear over the letter you typed. (So to type ë, you should hold down OPTION, press e, then release OPTION and press e again.)

      Yes, I imagine the guiding goes on for many years. One thing Zoë learned is the art of the “3-minute conversation”—long enough to say a bit about what’s going on so you feel connected to the other person but not so long it keeps you from your meeting, class, or work.

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  5. Rectangular iceberg in Antarctica >>>

    https://amp.cnn.com/cnn/2018/10/24/asia/rectangular-iceberg-antarctica-intl-trnd/index.html

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    1. This comment has been removed by the author.

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    2. Hard to see how you get that from a hexagonal crystal lattice. Not likely Icy Ice.

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    3. jan, I see. But it is Ice icy, yes?

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    4. eco, those penguins are great! The music in the seagull video is delightful, too. Thanks for the great, edgy link.

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  6. Per the electric flying spiders, perhaps other species use hot air to balloon. I was measuring a house earlier this month, and the owners said "Oh by the way you should know that there are black widows in the garage."

    And since we have the topic of tool usage, a story about eating good in the neighborhood. The article fails to mention that most of the people in Texas have failed to evolve over the past 15,000 years.

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  7. eco, perhaps the black widows were there to date respectable Bay Area architects?

    As to the spears, as they were found 40 miles from Austin, perhaps some evolution has gone on there. . .

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    Replies
    1. An arborist friend showed me a male black widow hanging in the tree from which I also hang my laundry line.... I'm glad the venomous (and person attacking) critters in this land are not aggressive.

      I've driven 40 miles outside of Austin, the bubble doesn't extend nearly that far.

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    2. How big was the spider?

      I dressed up as a black widow spider one Halloween as a newly minted geologist. It was interesting.

      The Austin bubble is expanding, especially northward. My friend’s very progressive daughter and her circle of friends are about 20 mi north in Round Rock or 30 miles north in Georgetown, TX, where they can afford to buy houses.

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    3. Maybe 1/2" - 3/4". Hard to measure when you're running and screaming like a girl.

      I've driven to Austin from San Antonio, and then west to Dripping Springs. Seemed pretty empty, though that was a while ago.

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    4. . . .

      This map (from 2016) shows that Austin area growth, mostly northward.

      https://www.austinchamber.com/upload/images/ed/Map-population.jpg

      The archeological site on Buttermilk Creek where the spears were found is more northwest, hopefully protected from development.

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  8. Emerald green lion:

    https://www.cnn.com/style/amp/massive-emerald-found-in-zambia/index.html

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    Replies
    1. Not so much envious as dismayed that they plan to cut that beauty into smaller pieces.

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    2. Are you suggesting our geological heritage is more important than satisfying the whims of billionaires?

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    3. Wait, what Is our geological heritage, and how does cutting rocks harm it?

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    4. jan, good question.

      From M Brocx & V Semeniuk (Journal of the Royal Society of Western Australia, 90: 53-87, 2007) offer the following definition. >>>

      “Geoheritage encompasses global, national, statewide, and local features of geology, at all scales that are intrinsically important sites or culturally important sites offering information or insights into the evolution of the Earth; or into the history of science, or that can be used for research, teaching, or reference.”

      Wouldn’t it be lovely to have the green lion intact at a museum or in college earth sciences classes?

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    5. I'm glad you answered that; I was just making up words.

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    6. OK, so what is intrinsically or culturally important about that rock?

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    7. From an article in Newsweek:

      “The team said it had recovered several significant crystals at the location in recent months, but none with the combined size, color and clarity of the Lion Emerald. According to the company, as little as two dozen emeralds have been worthy of being christened with their own name.”

      The crystal has its own name!

      I often go to visit the football-sized rhodochrosite crystal “Alma King” at the Denver Museum of Nature and Science. I think it is better to keep such large, beautiful, high-clarity specimens in one piece for millions to enjoy. >>>

      https://www.historycolorado.org/node/4615

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    8. The rhodochrosite has me hankering for a southern jello mold topped with coconut shavings. Nothing says good eating like horse hooves.

      And if carved out just right the emerald would make an awesome St Patrick's Day beer mug.

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  9. Back to spiders: last night when I got home there was one of those wolf-like spiders trapped in my kitchen sink - I caught him in a glass and set him free in the yard.

    Tonight there was a (female) black widow on the floor; I fear I was not so merciful. Probably set my nightmares for a week...

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  10. Bromeliads on a wire:

    https://epod.usra.edu/blog/2018/11/bromeliads.html

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    Replies
    1. Is someone named Liana always divine?

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    2. Haha.

      Woody Vines sounds like a good name for someone, but I’m not sure who. Liana Divine works, too. . .

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  11. Replies
    1. Another reason to not use helium balloons �� ��. . .(jk, sort of)

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  12. “A giant thunderclap at dawn”

    >>>

    https://www.smithsonianmag.com/smart-news/early-giant-fossils-shows-how-dinos-went-two-legs-four-180970423/

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  13. Replies
    1. At the speed of the fastest spacecraft to date, that's only 24,000 years away.

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    2. Thanks, eco. I enjoyed both articles, though the Nature article was a bit of a slog.

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  14. Milestone: PEOTS just reached 180,000 hits.

    New post coming later today.

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  15. New post on "Cratonically Yours: Thinner Lithosphere and Crust in Western Antarctica Than in Eastern Antarctica" is now up.

    Happy Thursday!

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