In-compressible fluids
« on: August 21, 2018, 05:26:56 PM »
Some of the more well known folks here have come up the following formula for the momentum of an in-compressible fluid - which is quite interesting!



I have inquired about this equation, and the folks here have generously agreed to give us a demonstration of how this works, and how it can be used in FET.

Please, I welcome your input!
"noche te ipsum"

"If you can't explain it simply, you don't understand it well enough."  - Albert Einstein

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Offline Rushy

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Re: In-compressible fluids
« Reply #1 on: August 21, 2018, 06:54:28 PM »
There's no such thing as a fluid that cannot be compressed.

Re: In-compressible fluids
« Reply #2 on: August 21, 2018, 07:27:12 PM »
There's no such thing as a fluid that cannot be compressed.

If I have misunderstood the claim made for this formula, I apologize.

What does this formula claim to do, and how does it work?
"noche te ipsum"

"If you can't explain it simply, you don't understand it well enough."  - Albert Einstein

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Offline Rushy

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Re: In-compressible fluids
« Reply #3 on: August 21, 2018, 08:35:04 PM »
There's no such thing as a fluid that cannot be compressed.

If I have misunderstood the claim made for this formula, I apologize.

What does this formula claim to do, and how does it work?

Well, you claimed that: "Some of the more well known folks here have come up the following formula for the momentum of an in-compressible fluid" so I figured I would immediately point out that this can't possibly be the case, since there's no such thing as an "in-compressible fluid".

Re: In-compressible fluids
« Reply #4 on: August 21, 2018, 09:14:50 PM »
There's no such thing as a fluid that cannot be compressed.

If I have misunderstood the claim made for this formula, I apologize.

What does this formula claim to do, and how does it work?

Well, you claimed that: "Some of the more well known folks here have come up the following formula for the momentum of an in-compressible fluid" so I figured I would immediately point out that this can't possibly be the case, since there's no such thing as an "in-compressible fluid".

In fluid dynamics, liquids are often treated as in-compressible. If you prefer to claim that this formula is for compressible fluid, again I ask, please explain!
"noche te ipsum"

"If you can't explain it simply, you don't understand it well enough."  - Albert Einstein

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Offline Rushy

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Re: In-compressible fluids
« Reply #5 on: August 21, 2018, 09:50:36 PM »
In fluid dynamics, liquids are often treated as in-compressible. If you prefer to claim that this formula is for compressible fluid, again I ask, please explain!

Yes, in much of physics, things are treated as ideals that don't actually exist, which is why ideal gas equations are useless in reality. If this equation presupposes that we have something that doesn't actually exist, then perhaps you should wonder why anyone needs it. I'm not sure what else you're confused about.
« Last Edit: August 21, 2018, 09:53:29 PM by Rushy »

Re: In-compressible fluids
« Reply #6 on: August 22, 2018, 06:06:09 PM »
Some of the more well known folks here have come up the following formula for the momentum of an in-compressible fluid - which is quite interesting!



I have inquired about this equation, and the folks here have generously agreed to give us a demonstration of how this works, and how it can be used in FET.

Please, I welcome your input!

that is a well known derivation to a common equation.  you claim to be well versed in physics, but you dont recognize it?
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Re: In-compressible fluids
« Reply #7 on: August 23, 2018, 01:37:54 AM »
If you, or anyone else is unable to provide an explanation, a proof, an example, or even a brief description of the variables in play, then, by default, you accept defeat and we all move on.
"noche te ipsum"

"If you can't explain it simply, you don't understand it well enough."  - Albert Einstein

Re: In-compressible fluids
« Reply #8 on: August 23, 2018, 02:22:00 AM »
If you, or anyone else is unable to provide an explanation, a proof, an example, or even a brief description of the variables in play, then, by default, you accept defeat and we all move on.

Seriously?  We didn't create that, it's pretty well known.   Sorry you can't follow along
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Re: In-compressible fluids
« Reply #9 on: August 23, 2018, 11:04:18 PM »
If you, or anyone else is unable to provide an explanation, a proof, an example, or even a brief description of the variables in play, then, by default, you accept defeat and we all move on.

Seriously?  We didn't create that, it's pretty well known.   Sorry you can't follow along

Does the equation determine the momentum or is momentum the constant p in this equation? If momentum is the constant p, does the equation determine the expansion of some space as a factor of momentum? Could it be the expansion of something other than space? Like a prediction of a possible expansion at a given momentum? Does this account for time at all? If it determines momentum based on some other constant p, what is that constant, and then that opens up a whole host of other questions....
"noche te ipsum"

"If you can't explain it simply, you don't understand it well enough."  - Albert Einstein

Re: In-compressible fluids
« Reply #10 on: August 23, 2018, 11:06:53 PM »
If it determines the expansion of space, are there some other factors in there that might influence space? What is U in this equation and why is the expansion linear?
« Last Edit: August 23, 2018, 11:08:54 PM by timterroo »
"noche te ipsum"

"If you can't explain it simply, you don't understand it well enough."  - Albert Einstein

Re: In-compressible fluids
« Reply #11 on: August 23, 2018, 11:09:41 PM »
that's a rho, not a p.  and U here is fluid flow velocity.
shitposting leftists are never alone

Re: In-compressible fluids
« Reply #12 on: August 23, 2018, 11:18:24 PM »
that's a rho, not a p.  and U here is fluid flow velocity.

OK, so it's the expansion of fluid in 3 dimensional space with respect to its density? Is it possible to calculate this over time (t)?

Oh nevermind, I see it now... it's in dp/dt.
« Last Edit: August 23, 2018, 11:19:57 PM by timterroo »
"noche te ipsum"

"If you can't explain it simply, you don't understand it well enough."  - Albert Einstein

Re: In-compressible fluids
« Reply #13 on: August 23, 2018, 11:23:49 PM »
I think I need to rephrase that,

It would be "expansion of fluid in 3 dimensional space as a factor of density with respect to time (t)".
"noche te ipsum"

"If you can't explain it simply, you don't understand it well enough."  - Albert Einstein

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Offline Rushy

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Re: In-compressible fluids
« Reply #14 on: August 23, 2018, 11:53:31 PM »
Rho is a constant and it represents density, which is why the equation assumes an incompressible liquid, because if the liquid were compressible, then obviously its density cannot be a constant.

This is a mass continuity equation for Navier-Stokes equations. It's just taking all of the mass flow in the system and setting that equal to zero. Since we know a classical system obeys conservation of mass, this can be helpful in flow in/flow out problems in fluid mechanics.

https://en.wikipedia.org/wiki/Navier%E2%80%93Stokes_equations

I mean really you could have just reverse image searched the equation, since it was lifted from this exact Wikipedia page.

Re: In-compressible fluids
« Reply #15 on: August 24, 2018, 12:52:35 AM »
Rho is a constant and it represents density, which is why the equation assumes an incompressible liquid, because if the liquid were compressible, then obviously its density cannot be a constant.

This is a mass continuity equation for Navier-Stokes equations. It's just taking all of the mass flow in the system and setting that equal to zero. Since we know a classical system obeys conservation of mass, this can be helpful in flow in/flow out problems in fluid mechanics.

https://en.wikipedia.org/wiki/Navier%E2%80%93Stokes_equations

I mean really you could have just reverse image searched the equation, since it was lifted from this exact Wikipedia page.

I am pleasantly impressed! Thank you. I could have searched for the equation, yes. I learned much more by not searching for it, though. As I said in my rant, I'm 5 or 6 years out from having done any real serious math, and I only took one University Physics class, which I didn't complete (started my first 'real' full-time job just then... life choices, ya know?) So, this has been great.... Also, sorry for the divergence of topic here.... back on track...

Quote
It's just taking all of the mass flow in the system and setting that equal to zero.

I don't see that in this equation, the setting it equal to zero part... dp/dt is the derivative correct? God there's something I'm forgetting about the "dt"....

Sorry for sounding so elementary... getting old sucks. :-(
"noche te ipsum"

"If you can't explain it simply, you don't understand it well enough."  - Albert Einstein

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Offline Rushy

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Re: In-compressible fluids
« Reply #16 on: August 24, 2018, 01:10:25 AM »
Rho is a constant and it represents density, which is why the equation assumes an incompressible liquid, because if the liquid were compressible, then obviously its density cannot be a constant.

This is a mass continuity equation for Navier-Stokes equations. It's just taking all of the mass flow in the system and setting that equal to zero. Since we know a classical system obeys conservation of mass, this can be helpful in flow in/flow out problems in fluid mechanics.

https://en.wikipedia.org/wiki/Navier%E2%80%93Stokes_equations

I mean really you could have just reverse image searched the equation, since it was lifted from this exact Wikipedia page.

I am pleasantly impressed! Thank you. I could have searched for the equation, yes. I learned much more by not searching for it, though. As I said in my rant, I'm 5 or 6 years out from having done any real serious math, and I only took one University Physics class, which I didn't complete (started my first 'real' full-time job just then... life choices, ya know?) So, this has been great.... Also, sorry for the divergence of topic here.... back on track...

Quote
It's just taking all of the mass flow in the system and setting that equal to zero.

I don't see that in this equation, the setting it equal to zero part... dp/dt is the derivative correct? God there's something I'm forgetting about the "dt"....

Sorry for sounding so elementary... getting old sucks. :-(

Density is a constant, therefore its derivative with respect to time is zero. I can't believe that I need to explain that to you after you repeatedly told me that "I'd be willing to bet that I've studied more math than most people here"

Re: In-compressible fluids
« Reply #17 on: August 24, 2018, 01:11:52 AM »
I don't see that in this equation, the setting it equal to zero part... dp/dt is the derivative correct? God there's something I'm forgetting about the "dt"....

Sorry for sounding so elementary... getting old sucks. :-(

it's a statement about mass conservation.  all this says is that if the fluid is incompressible (ie the density of the fluid doesn't change over time), then the divergence anywhere in the flow is zero.  this implies that there are no sources or sinks of mass in the system.

shitposting leftists are never alone

Re: In-compressible fluids
« Reply #18 on: August 24, 2018, 01:16:07 AM »
I don't see that in this equation, the setting it equal to zero part... dp/dt is the derivative correct? God there's something I'm forgetting about the "dt"....

Sorry for sounding so elementary... getting old sucks. :-(

it's a statement about mass conservation.  all this says is that if the fluid is incompressible (ie the density of the fluid doesn't change over time), then the divergence anywhere in the flow is zero.  this implies that there are no sources or sinks of mass in the system.



This is helpful, thank you.
"noche te ipsum"

"If you can't explain it simply, you don't understand it well enough."  - Albert Einstein

Re: In-compressible fluids
« Reply #19 on: August 24, 2018, 01:41:18 AM »
I don't see that in this equation, the setting it equal to zero part... dp/dt is the derivative correct? God there's something I'm forgetting about the "dt"....

Sorry for sounding so elementary... getting old sucks. :-(

it's a statement about mass conservation.  all this says is that if the fluid is incompressible (ie the density of the fluid doesn't change over time), then the divergence anywhere in the flow is zero.  this implies that there are no sources or sinks of mass in the system.



Baby Thork would disagree :)
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