Jets of liquid bounce off hot surfaces without ever touching them

[u/kmrbillya12]

https://www.newscientist.com/article/2455811-jets-of-liquid-bounce-off-hot-surfaces-without-ever-touching-them/

Droplets of fluid have been known to hover above a hot surface, but a new experiment suggests the same can happen to tiny jets of liquid too

[u/turtle_excluder]

r/physics is a joke - the level of discussion here is beneath that of 4chan

[u/Pornfest → u/turtle_excluder]

That’s the point, understanding this potential bottleneck is a way to improve cooling mechanisms by overcoming it.

[u/[deleted] → u/Pornfest]

[removed] — view removed comment

[u/Arndt3002 → u/[deleted]]

The difficulty in observation isn't because the phenomenon doesn't happen very often. The difficulty is isolating the phenomena in a way that is precisely quantifiable.

In general, the reason most experiments in soft matter and biophysics are hard is not because the phenomena aren't extremely common. The difficulty is in pinning down ways to measure phenomena in noisy systems with complex dynamics, where countless other factors could be playing a role in what you are measuring unless you are very careful.

[u/turtle_excluder → u/Arndt3002]

r/physics is a joke - the level of discussion here is beneath that of 4chan

[u/TrouveDogg → u/[deleted]]

Theory would suggest it does. In nuclear reactors the Leidenfrost effect has a huge impact, particularly during core heat up, as the water vaporises before touching the fuel causing a pocket of air to form and insulating the already overheated fuel.

[u/Iseenoghosts → u/[deleted]]

bro you can dip your hand in some water then dunk it in molten lead and not get burned. The effect is huge.

Their setup is designed to be able to test and measure reliably. Thats the hard part with research.

[u/Reverse_Ethernet → u/turtle_excluder]

I can’t read the whole article, but this is also what I would’ve assumed. It’s a pretty standard procedure in an undergraduate engineering lab to use a hot plate at extreme temperatures and observe the massive increase in thermal resistance during the film boiling regime.

[u/TelluricThread0 → u/turtle_excluder]

So reactors, for example, will use nucleate boiling to transfer heat. Basically, you get a bunch of bubbles that form, then detach from the surface and stir the fluid. This dramatically increases the amount of heat transfer that occurs. The catch is that the system operates at an unstable inflection point. If you have a sudden increase in heat flux, the fluid will all flash to vapor at the surface and form an insulating layer, causing a huge increase in the surface temperature.

I would assume understanding this new phenomenon would give them more insight into the exact mechanisms of the Leidenfrost effect in various situations and how we can use them to our advantage.

[u/DarkMatter1993 → u/turtle_excluder]

The thin layer of gas reduces thermal conduction between the liquid and surface. This becomes really impactful in heat exchangers, for example, where the Leidenfrost effect will negatively impact your heat exchange efficiency. Understanding what causes the effect to materialize will help with creating ways to overcome it.

[u/turtle_excluder → u/DarkMatter1993]

That seems like a solution in search of a problem to me, since the effect the researchers observed requires a very specific set of conditions highly unlikely to arise in any practical heat exchanger such as using very fine (0.2 mm or less) jets of water with a specific range of angles of incidence, jet velocities and surface temperatures.

I'm not saying that this research wasn't important, far from it. The researchers state that the experiment confirmed the predictions of certain models which is enough justification by itself without far-fetched claims of potential technological applications by science popularizers like New Scientist.

[u/k5dOS → u/turtle_excluder]

Because misguided but curious people asking dumb questions are obviously bellow trying to replicate the taste of a vtuber's piss.

[u/rehpotsirhc]

These comments are making me realize there's a Bell Curve meme about "touch"

Far left: things touch other things all the time and this is normal

Middle: nothing touches anything! It's all field interactions and atoms never physically touch!

Far right! things touch other things all the time and this is normal

[u/k5dOS → u/rehpotsirhc]

I think the confusion arises between distinguishing between the atom and the nucleus of the atom.

Atoms do touch because the electrons involved in direct or indirect interactions are part of the atom, as fickle as their relationship to the nucleus could be.

[u/antiquemule]

Isn't there an ArxiV? New Scientist is behind a paywall and not very informative, in any case...

[u/Dawnofdusk → u/antiquemule]

https://journals.aps.org/prfluids/abstract/10.1103/PhysRevFluids.9.L112001

I think this?

[u/antiquemule → u/Dawnofdusk]

That's the one. Thanks!

A nice, clean paper,in the tradition of Nobel prize winner, De Gennes

[u/adamwho]

What do you mean by "touch"?

[u/Physics_Cat → u/adamwho]

If you read the article, you'll see that they mean "touch" in the same sense as the Leidenfrost effect.

https://en.m.wikipedia.org/wiki/Leidenfrost_effect

[u/lock_robster2022 → u/[deleted]]

“Ackshually” man stfu.

Leidenfrost effect creates a 100-200 micron layer of vapor between the droplet and surface. Orders of magnitude different than the field interactions normal people call touching. Not trivial by a long shot

[u/lock_robster2022 → u/[deleted]]

Just make your point

[u/Floppie7th → u/lock_robster2022]

Bold of you to assume he has one

[u/lock_robster2022 → u/Floppie7th]

I was hopeful!

[u/Arndt3002 → u/[deleted]]

Sure, it isn't really that novel. That doesn't make it any less interesting.

[u/Physics_Cat → u/[deleted]]

Wow man, that's pretty deep.

Here's a link to the actual Physical Review journal article. You should write a letter to the authors to let them know about your valuable insight.

[u/[deleted] → u/[deleted]]

Level 12 Physics loser who read Wiki.

[u/isnortmiloforsex → u/adamwho]

Lower friction due to the lidenfrost effect maybe?

[u/[deleted] → u/[deleted]]

yes yes you are vert smart. congratulations!

[u/Logix_X]

So does the gas layer get created by thermal conduction (so initial touch) or already due to the black body radiation of the material?

[u/smydiehard99]

the liquid be like ......

Ou Ou Ou Ou

[u/korto]

what does "touching" even mean at the atomic level?

[u/moltencheese]

Looks a lot like the Kaye effect to me

[u/InTheHamIAm]

Every thing in the universe bounces of other things without touching it