There's no such thing as a fluid that cannot be compressed.

Quote from: Rushy on August 21, 2018, 06:54:28 PMThere'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?

Quote from: timterroo on August 21, 2018, 07:27:12 PMQuote from: Rushy on August 21, 2018, 06:54:28 PMThere'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!

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!

Planes fall out of the sky all the time

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.

Quote from: timterroo on August 23, 2018, 01:37:54 AMIf 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

that's a rho, not a p. and U here is fluid flow velocity.

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

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

Quote from: Rushy on August 23, 2018, 11:53:31 PMRho 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_equationsI 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...QuoteIt'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. :-(

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. :-(

Quote from: timterroo on August 24, 2018, 12:52:35 AMI 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.