Re: In-compressible fluids
« Reply #20 on: August 24, 2018, 01:48:52 AM »
Since the cats out of the bag, check this thread for the history of that equation/nonsense.  Page 6 of this :  https://forum.tfes.org/index.php?topic=9809.msg159853#msg159853
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Re: In-compressible fluids
« Reply #21 on: August 24, 2018, 02:37:49 AM »
Since the cats out of the bag, check this thread for the history of that equation/nonsense.  Page 6 of this :  https://forum.tfes.org/index.php?topic=9809.msg159853#msg159853

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Re: In-compressible fluids
« Reply #22 on: August 24, 2018, 08:10:03 AM »
Gases are fluids, I know of no incompressible gases.
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Offline QED

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Re: In-compressible fluids
« Reply #23 on: August 24, 2018, 05:54:42 PM »
Gases are fluids, I know of no incompressible gases.

Yes. The thread is incorrectly named. Fluids comprise liquids and gases. gases are compressible, liquids are not, generally.

Re: In-compressible fluids
« Reply #24 on: August 24, 2018, 06:47:16 PM »
Gases are fluids, I know of no incompressible gases.

Yes. The thread is incorrectly named. Fluids comprise liquids and gases. gases are compressible, liquids are not, generally.

Right, so liquids are in the set of incompressible fluids, which is why it is titled as such.
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Offline Rushy

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Re: In-compressible fluids
« Reply #25 on: August 24, 2018, 07:33:16 PM »
Gases are fluids, I know of no incompressible gases.

Yes. The thread is incorrectly named. Fluids comprise liquids and gases. gases are compressible, liquids are not, generally.

This is incorrect. All fluids are compressible, this includes liquid and gasses. In fact, all states of matter are compressible. There's no such thing as matter that cannot be compressed. Equations that assume an incompressible fluid do so for the sake of simplicity, not a genuine reflection of reality. Under most circumstances, most liquids will compress very little, but it's still a non-zero amount.
« Last Edit: August 24, 2018, 07:34:49 PM by Rushy »

Re: In-compressible fluids
« Reply #26 on: August 24, 2018, 07:50:05 PM »

Right, so liquids are in the set of incompressible fluids, which is why it is titled as such.

Are you asking?  seems like you are asking, not stating a fact.  which is wrong BTW
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Re: In-compressible fluids
« Reply #27 on: August 24, 2018, 08:06:53 PM »

Right, so liquids are in the set of incompressible fluids, which is why it is titled as such.

Are you asking?  seems like you are asking, not stating a fact.  which is wrong BTW

If you assume we are talking about "theory", which is what we are talking about, liquids are assumed to be in-compressible - that is what the equation is demonstrating (however useless it is). Fluids are a set that contains both liquid and gas. If gases are compressible and liquids are in-compressible, then an in-compressible fluid is referring to liquids.
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Offline RonJ

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Re: In-compressible fluids
« Reply #28 on: October 17, 2018, 05:22:21 AM »
For several years I worked on the Woods Hole Oceanographic ship that carried the Alvin Submarine.  In college we were always taught that water is incomprehensible.  The guys who crewed the Alvin corrected me.  They said that the Alvin has some compensation equipment aboard that corrects for the 1/2 percent per thousand feet that water actually compresses at depth.  I was on several scientific expeditions where the Alvin was diving at 9 North on the underwater hydro thermal vents.  The compensation becomes significant there. 
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Offline Mora

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Re: In-compressible fluids
« Reply #29 on: November 09, 2018, 02:29:21 AM »
If the difference between reality and approximation is too small to measure, would you even be able to distinguish the two? If not, then we're arguing over nothing, but if so, it hardly makes a difference because whether it's 1100 K or 1115 K, the engine in your car continues to function normally.

Assumptions such as incompressible or inviscid are useful; if they weren't, we wouldn't use them. In fact, there are many instances where we don't use them. Non-dimensional analysis will tell you what assumptions are reasonable to make, and if you're completely intolerant of assumptions for whatever reason, there are other more complete equations that do not make those assumptions. They're just notoriously difficult to solve without using numerical methods.

To the OP, if you're interested in learning more about the sciences, I would start with /literally anything but/ Fluid Mechanics.