No one can explain WHY planes fly...

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Dan Thomas

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I think NASA* could do an experiment:
Build an "airless" wind tunnel. In other words a vacuum chamber.
Instead of air, particles of sand or something similar would be slung at the model in the tunnel.
This would eliminate most of the reduced pressure characteristics of air, but the inertia characteristics of particles would remain. I expect the reaction lift would only occur on the bottom.

A device called a "Wheel-a-brator" could hurl the airless sand. (used for industrial sand blasting)

* NASA could "throw" money at the model.
It wouldn't be anything similar to airflow. Air molecules repel each other somehow, which is why air is compressible. That sand (or the Wheel-a-brator's steel shot) doesn't repel anything. It wouldn't follow any streamlines.

In the '80s our shop had one of those shot blasters. Mighty aggressive cleaning. We used very small steel shot. The machine had a ten-horse motor driving a paddle wheel with paddles made of really hard, brittle steel.

See this: https://www.av8n.com/how/htm/airfoils.html#sec-fluid
 

BBerson

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Of course air is not the same as bullets. Air molecules somehow both stick together and repel each other. That's why some other odd experiments might provide some insights. Even your link said there would be some reaction from bullets:
"Bullets hit the bottom of the wing, transferring upward momentum to it"
 

lr27

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Pagobay:
If you are talking about pressure gradients, that brings in Bernoulli without using the name.
 

lr27

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There is no somehow about air molecules "sticking" together. They are shoved together by atmospheric pressure.
 

BJC

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There is no somehow about air molecules "sticking" together. They are shoved together by atmospheric pressure.
The air has pressure because of gravitational attraction to the Earth. I.e., Pressure is the result of the gasses that make up air being accelerated toward the Earth, it is not the cause of “air molecules being shoved together”.


BJC
 

PagoBay

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Pagobay:
If you are talking about pressure gradients, that brings in Bernoulli without using the name.
It is all about the math. If you don't need Bernoulli's equations (math) to determine lift, then nobody "brings in Bernoulli". Bernoulli is unnecessary, irrelevant, and gets factored out. Pun intended.

Starts by recognizing that an airfoil of any design is absolutely not a venturi. I presented only the key quotes that state things quite clearly. If more details are desired, please watch the Babinsky video or read the papers.
 

henryk

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somehow about air molecules
=DONT remember, thermic V average of N2,O2 molecules is circa
500 m/sec (1800 km/h) !

we all remember formula for Kinetic Energy ?
E=0.5 m V^2 ...

E kin. in one qm. of "cold air" is circa 150000 J (150 kJ !!!)

I think,it is the essential phactor of "wing flying" !

PS=iff NO thermic Velocity (and energy), the whole atmospheric air should be condenset into OCEAN of air.
 
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BBerson

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There is no somehow about air molecules "sticking" together. They are shoved together by atmospheric pressure.
Air molecules (and molecules in solids) are held close together by the ""electric" force.
See Feynman article link I posted a while back.
I said close together because they don't actually touch in any intuitive sense, even in solids.
 

Aerowerx

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Air molecules (and molecules in solids) are held close together by the ""electric" force.
See Feynman article link I posted a while back.
I said close together because they don't actually touch in any intuitive sense, even in solids.
I went through the article. I don't see where he says that the molecules of air are held together by an electrical force.

The only place he mentions anything held together by an electric force is the salt molecule, where the Sodium and Cholrine atoms are ions.
 

Aerowerx

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"vacuum PUMP" is not exactly pump =it only "build" empty
volumes into which air particles are selfdriwed .

VACUUM cant do any work !!!
=only kinetic energy of molecules can do the work...
That is true henryk.

Maybe I did not state it correctly. It is the kinetic energy of the molecules that does the work.

If you have air in a cylinder with a piston, push the piston in and the molecules get closer together. The kinetic energy is the same, and the temperature increases because of the increased collisions Pull the piston out and the temperature drops because of the decreased collisions.
 

Aerowerx

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Actually, when you get down to the molecular level you are in a gray area where Newtonian physics starts to not work.

The molecules of air are not hard little round steel balls. If they were, then there would be no liquid Nitrogen or liquid oxygen. Or ice cubes for that matter.
 

henryk

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then there would be no liquid Nitrogen or liquid oxygen.
=iff liquid Helium flows in steal tube,on the auter surface
momentary flow condenset liquid air (N2 +O2)...

the temperature increases because of the increased collisions
molecular collisions are similar to the equipoles of magnets
=no kinetic energy conversion into thermic energy...

atoms are "sours/accumulators" of thermic energy=the moore
particles in the volume=the higher temperature...

in isolated from infrared radiation vacuum vessel T=0 deg.Kelvin.
 

BBerson

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I don't see where he says that the molecules of air are held together by an electrical force.
It's in chapter 2-2. Click the yellow tab upper left to move to chapter 2.

excerpt: " This is the reason why the atoms, which are constituted out of plus and minus electric charges, feel very little force when they are separated by appreciable distance (aside from gravity). When they come close together, they can “see inside” each other and rearrange their charges, with the result that they have a very strong interaction. The ultimate basis of an interaction between the atoms is electrical. "
 

Aerowerx

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It's in chapter 2-2. Click the yellow tab upper left to move to chapter 2.

excerpt: " This is the reason why the atoms, which are constituted out of plus and minus electric charges, feel very little force when they are separated by appreciable distance (aside from gravity). When they come close together, they can “see inside” each other and rearrange their charges, with the result that they have a very strong interaction. The ultimate basis of an interaction between the atoms is electrical. "
Ah! I see.

But he is talking about atoms interacting with each other. I thought the discussion was about molecules. Unless there was ionization going on, a molecule would have no net charge, and therefore no "electrical" attraction or repulsion!
 
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