Explaining pressure exchange

[Erina]

I came across this short illustrative demonstration of pressure exchange, but I can't explain what is going on:

https://imgur.com/FfWg4GU

How do I explain this please ?

[joigus]

Mmmm. I don't know. There are several things going on, and gravity is not helping.

I see it more as an illustration of osmotic pressure, or diffusion, than mechanical pressure. Also increase in entropy.

Pressure would be more like the balls pushing a wall. For that I would recommend computer simulation.

Some like this from Wikipedia:

 

[sethoflagos]

It's effectively a time reversed Coe and Clevenger test - the progressive fluidisation of a packed bed of buoyant particles rather than the more industrially significant progressive compaction of denser particulates from a suspension. 

I agree with joigus that it's not saying anything significant about pressure here. No measurements seem to be taken so I question whether it's actually saying anything about anything.

[J.C.MacSwell]

There's certainly mass exchange and pressure effects, including those resulting in buoyancy. I'm sure a case can be made there is plenty of "pressure exchange" depending on how you choose to define it.

[sethoflagos]

2 hours ago, J.C.MacSwell said:

There's certainly mass exchange and pressure effects, including those resulting in buoyancy. I'm sure a case can be made there is plenty of "pressure exchange" depending on how you choose to define it.

Could one choose to define 'pressure exchange' as an 'exchange of gravitational potential energy'?

Not clear on whether pressure is something that can be 'exchanged'. 'Propagated into another medium' for sure, but 'exchanged' usually tends to imply a conserved quantity, doesn't it?  

[Endy0816]

Possibly supposed to show pressure equalizing. A pressure exchanger is a real thing although that doesn't seem a very good example.

[ALine]

how dense are those beads? It could just be that they are floating up due to them being less dense than the water. 

However I could also not be understanding the question being asked.

[swansont]

8 hours ago, ALine said:

how dense are those beads? It could just be that they are floating up due to them being less dense than the water. 

Yes, that means they will float. But the downflow of water exerts a force as it strikes the beads, so initially the buoyancy can’t overcome this. But the flow rate near the beads decreases after the top fills up, so this force decreases, and then the beads can float upwards.

 

 

[studiot]

I can't access the OP post because it "values my privacy"   can we see what it says here please?

[joigus]

21 minutes ago, studiot said:

I can't access the OP post because it "values my privacy"   can we see what it says here please?

It doesn't really say anything. It's a video of some kind of analogical experiment.

https://i.imgur.com/FfWg4GU.mp4

I hope a direct link to the video helps (it's very short.)

Edited December 30, 2020 by joigus

[studiot]

18 minutes ago, joigus said:

I hope a direct link to the video helps (it's very short.)

Thanks for the attempted help.

Unfortunately your link is the same as the OP.

 

Here is what I get, I don't deal with outside sites that do this.

[joigus]

53 minutes ago, studiot said:

Thanks for the attempted help.

Unfortunately your link is the same as the OP.

 

Here is what I get, I don't deal with outside sites that do this.

I'm no expert, but some "nice" sites, after clicking the "more options" button, allow you to disable all the cookies. Others inform you of different kinds (session variables, tracking, and so on). Although it's always up to you, of course.

I'm sorry it didn't work for you. I thought a direct link to the video could work. I did disable the tracking cookies, if I remember correctly. What about just disagree? You will have to rely on the website's honesty, that that will disable all.

[ALine]

6 hours ago, swansont said:

Yes, that means they will float. But the downflow of water exerts a force as it strikes the beads, so initially the buoyancy can’t overcome this. But the flow rate near the beads decreases after the top fills up, so this force decreases, and then the beads can float upwards.

ah, thank you for the correction.

[J.C.MacSwell]

21 hours ago, sethoflagos said:

Could one choose to define 'pressure exchange' as an 'exchange of gravitational potential energy'?

Not clear on whether pressure is something that can be 'exchanged'. 'Propagated into another medium' for sure, but 'exchanged' usually tends to imply a conserved quantity, doesn't it?  

Technically of course no. One's force per area and the other force times distance.