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Dandelion Seeds Fly Using ‘Impossible’ Method Never Before Seen in Nature

nature.com

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Re: Dandelion Seeds Fly Using ‘Impossible’ Method Never Before Seen in Nature

#21

Post by captain_perl »

wahern wrote: post #15
tines wrote: post #8

> Those structures act like the wings of a bird or aeroplane, generating pressure differences above and below the wing to fly. I thought we had settled this, airplane wings work by deflecting air downward, not by the Bernoulli effect, right?

They're different ways to describe the same phenomenon. "[B]oth 'Bernoulli' and 'Newton' are correct." https://www.grc.nasa.gov/www/k-12/airplane/bernnew.html

> They're different ways to describe the same phenomenon.

Well ... they're actually different ways to incorrectly describe the same phenomenon.

Wind tunnels are still used for aircraft design because we can't accurately model aerodynamics.

Re: Dandelion Seeds Fly Using ‘Impossible’ Method Never Before Seen in Nature

#22

Post by anigbrowl »

sova wrote: post #16

Does anybody have a link to a video of the lasers creating small vortices just above the dandelion surface?

Click through to the paper and you can view the figures and supplementary information for free. Protip: while it's frustrating to find a paywalled paper if you just want to know how it works the supplementary materials are usually unrestricted, better written, and easier to understand than the paper itself.

Re: Dandelion Seeds Fly Using ‘Impossible’ Method Never Before Seen in Nature

#23

Post by repiret »

pugworthy wrote: post #10

Something something "Bumblebees shouldn't be able to fly" something something. How is it we are shocked to find out we are sometimes wrong and not shocked that sometimes we get it right? My critique by the way is the headline, not the actual research. The headline is clickbait IMO, and just as I suppose some don't like my comment (not well thought out, emotional, etc.), the headline is the same. E.g., consider, "Curi…

I agree its a bad headline. Maybe "Dandelion Seeds Fly Using Method Not Previously Described in Nature", because: 1. Of course its been _observed_ before. As the video points out, just about every kid has observed it. The claim is really that nobody has previously understood the physics of it. 2. There's nothing impossible about it, clearly. Moreover, the article doesn't claim that people had previously analyzed the seeds behavior and came to the conclusion that it defies physics.

Re: Dandelion Seeds Fly Using ‘Impossible’ Method Never Before Seen in Nature

#25

Post by the8472 »

repiret wrote: post #23
pugworthy wrote: post #10

Something something "Bumblebees shouldn't be able to fly" something something. How is it we are shocked to find out we are sometimes wrong and not shocked that sometimes we get it right? My critique by the way is the headline, not the actual research. The headline is clickbait IMO, and just as I suppose some don't like my comment (not well thought out, emotional, etc.), the headline is the same. E.g., consider, "Curi…

I agree its a bad headline. Maybe "Dandelion Seeds Fly Using Method Not Previously Described in Nature", because: 1. Of course its been _observed_ before. As the video points out, just about every kid has observed it. The claim is really that nobody has previously understood the physics of it. 2. There's nothing impossible about it, clearly. Moreover, the article doesn't claim that people had previously analyzed the…

The vortex may not have been observed since air is mostly transparent.

Re: Dandelion Seeds Fly Using ‘Impossible’ Method Never Before Seen in Nature

#26

Post by marcosdumay »

saudioger wrote: post #20
mattdemon wrote: post #17

Wow, new parachute designs may be possible then! They will look scary, but can be more effective.

Ehhh, I imagine the seed/filament weight ratio is much closer than the human/filament weight ratio... if you blow this up to human size/weight proportions the filaments would likely need to be gigantic.

I don't think you can scale the filaments up. Scaling this up would mean adding small holes to a parachute and filaments around those... And then we would get into the task of folding something full of small filaments.

Re: Dandelion Seeds Fly Using ‘Impossible’ Method Never Before Seen in Nature

#27

Post by ehnto »

lordnacho wrote: post #12
aidos wrote: post #3

That was a lovely little diversion! There’s a brief 1 minute clip in the article that’s worth watching. I do have one question though, how is the air flowing up through? It the seed not falling for that to happen?

Yes, the seed is falling, but the vortex slows the fall enough for it to be useful in distributing the seed as far as possible.

Some seeds have a small leaf attached, making them spin as they fall and slowing their descent for the same purpose. It's not about flying, just about prolonging the time spent in a moving body of air.

Re: Dandelion Seeds Fly Using ‘Impossible’ Method Never Before Seen in Nature

#28

Post by namirez »

mattdemon wrote: post #17

Wow, new parachute designs may be possible then! They will look scary, but can be more effective.

Probably not! This phenomenon is not scale-independent. There is a parameter called the Reynolds number (Re for short) which is the ratio of intertial forces to viscous forces. For a dandelion seed Re is small which is the key to the stability of the vortex.

For a parachute, the Re number is much higher which makes the dynamics of the flow chaotic (called turbulence). There is a critical Re number beyond which There is no way keep the vortex stable, or as they call it, the vortex bursts.

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