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Water compresses under a high gradient electric field

phys.org

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Re: Water compresses under a high gradient electric field

#21

Post by geoalchimista »

slimsag wrote: post #18
ahelwer wrote: post #2

"This is an unexpected phenomenon, contrary to what we thought we knew about nanopore transport. It took three years to work out what it was the simulations were showing us. After exploring many potential solutions, the breakthrough came when we realized that we should not assume water is incompressible. Now that we understand what's happening in the computer simulations, we are able to reproduce this phenomenon in t…

> I probably would have written it off as floating point shenanigans. Pretty sure anyone in actual scientific computing stays far, far away from floating point numbers and sticks to arbitrary precision ones instead.

Error analysis can tell you whether the roundoff error would grow exponentially with time steps for the algorithm you use. If you avoid this kind of conditions in scientific computing, then double precision floating point number would work perfectly fine.

And by the way, scientific computing is a diverse discipline, or a federation of disciplines. Say, there may be little overlap between the algorithms, tools, and environments that a physicist uses for scientific computing and those used by a bioinformatician. So I don't think it is universally true in scientific computing that arbitrary precision is preferable to double precision.

Re: Water compresses under a high gradient electric field

#22

Post by leovailati »

ahelwer wrote: post #2

"This is an unexpected phenomenon, contrary to what we thought we knew about nanopore transport. It took three years to work out what it was the simulations were showing us. After exploring many potential solutions, the breakthrough came when we realized that we should not assume water is incompressible. Now that we understand what's happening in the computer simulations, we are able to reproduce this phenomenon in t…

I found it counterintuitive that it was predicted in simulation and then confirmed with experiments, rather than the other way around.

Re: Water compresses under a high gradient electric field

#23

Post by felipemnoa »

leovailati wrote: post #22
ahelwer wrote: post #2

"This is an unexpected phenomenon, contrary to what we thought we knew about nanopore transport. It took three years to work out what it was the simulations were showing us. After exploring many potential solutions, the breakthrough came when we realized that we should not assume water is incompressible. Now that we understand what's happening in the computer simulations, we are able to reproduce this phenomenon in t…

I found it counterintuitive that it was predicted in simulation and then confirmed with experiments, rather than the other way around.

This is how lots of new science is discovered. One example is the Theory of Relativity. Sure it was not a software simulation per se but it was still simulated on paper. It was not confirmed by experiment until several years latter.

Re: Water compresses under a high gradient electric field

#24

Post by waiquoo »

leovailati wrote: post #22
ahelwer wrote: post #2

"This is an unexpected phenomenon, contrary to what we thought we knew about nanopore transport. It took three years to work out what it was the simulations were showing us. After exploring many potential solutions, the breakthrough came when we realized that we should not assume water is incompressible. Now that we understand what's happening in the computer simulations, we are able to reproduce this phenomenon in t…

I found it counterintuitive that it was predicted in simulation and then confirmed with experiments, rather than the other way around.

With nanopore experiments, it's not unusual to see unusual behavior that could possibly be explained by macromolecule interactions, contamination, or electrical interference. There are often more unknowns than knowns due to the scale of the system, novel materials, measurement precision, unique physics, etc etc... What usually happens is the undesired measurement gets filed away for 'later study'. Unless you have some theoretical framework or model that explains it, you may never go back. So probably the experimental part was previously dismissed as an error or contamination, but now it is interesting because there is an explanation

Re: Water compresses under a high gradient electric field

#26

Post by ahartmetz »

leovailati wrote: post #22
ahelwer wrote: post #2

"This is an unexpected phenomenon, contrary to what we thought we knew about nanopore transport. It took three years to work out what it was the simulations were showing us. After exploring many potential solutions, the breakthrough came when we realized that we should not assume water is incompressible. Now that we understand what's happening in the computer simulations, we are able to reproduce this phenomenon in t…

I found it counterintuitive that it was predicted in simulation and then confirmed with experiments, rather than the other way around.

That is how it's supposed to work. You build a theory based on known phenomena, then you look for any new phenoma it predicts and test them in experiments. Without the new phenomena, your theory is more likely to be just "overfitting" the data. A famous example of overfitting the data - adding more cruft to account for unexplained aspects - is this: https://en.wikipedia.org/wiki/Deferent_and_epicycle

Re: Water compresses under a high gradient electric field

#27

Post by CamperBob2 »

stephengillie wrote: post #8
fooker wrote: post #5

Does this also mean compressing/decompressing water can generate an electric field?

Probably, but it would take a lot of mechanical force. From the article: > The compression is only 3 percent, but that pressurizes the water—it's equivalent to 100 atmospheres Although, that's not uncommon for ice giants, so it might be causing part of Ouranos (aka Uranus) magnetic field. > The troposphere is thought to have a highly complex cloud structure; water clouds are hypothesised to lie in the pressure range…

Coincidentally, I just watched a great video by Ben Krasnow yesterday that suggests that the answer to fooker's question is indeed "Yes." There are other well-known principles along these lines, ranging from piezoelectricity to the Seebeck and Peltier effects, and it's almost more of a rule than an exception for such effects to behave symmetrically.

Glowing plasma created by a high speed jet of water: https://www.youtube.com/watch?v=_vTq8oGpqwM&list=LLaIdy5TkkQ...

He definitely has the "whole lot of mechanical force" thing going for him, considering that he's about 2 psi away from fragging himself with a hydraulic cylinder.

Re: Water compresses under a high gradient electric field

#28

Post by A_Person »

It's always surprised me how many people do not know that water is incompressible! For example, when someone is filling a scuba tank, it's common to put the tank in a large, often metal-sided container of water. When asked why, the shop staff member will typically say: "In the unlikely event of the tank blowing up, the water will absorb the force of the explosion." But in fact, water being incompressible, it will absorb approximately 0% of that force - which is then transmitted undiminished to the metal walls - which then explode like a giant hand grenade, promptly maiming or killing everyone standing nearby! The purpose of the water is instead, to absorb the heat from adiabatic compression, and keep the tank cool.

Re: Water compresses under a high gradient electric field

#29

Post by Retra »

stephengillie wrote: post #7
ChuckMcM wrote: post #4

That is a really neat effect. Basically if you can put a water molecule inside a flat field it lines itself up with that field and can be compressed. I would bet this has an impact on Graphene based desalination efforts as well.

This sounds akin to electrons forming Cooper pairs in atoms. https://en.wikipedia.org/wiki/Cooper_pair

How so?

Re: Water compresses under a high gradient electric field

#30

Post by politician »

A_Person wrote: post #28

It's always surprised me how many people do not know that water is incompressible! For example, when someone is filling a scuba tank, it's common to put the tank in a large, often metal-sided container of water. When asked why, the shop staff member will typically say: "In the unlikely event of the tank blowing up, the water will absorb the force of the explosion." But in fact, water being incompressible, it will abs…

> "...the breakthrough came when we realized that we should not assume water is incompressible..."

The shop staff was right, water is not incompressible (under important conditions that don't apply to their scenario!).

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