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Jan 08, 2013, 11:08 AM
Ascended Master
Sparky Paul's Avatar
Dr. Munk would tell us frequently that "thinking is painful"..
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Jan 09, 2013, 05:56 PM
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[QUOTE=ShoeDLG;23707327]I agree that, under a very specific condition, wing or rotor lift must be a pure Newtonian reaction to accelerating air downward.QUOTE]

An open question that has bothered me for some time. You may consider it only a matter of semantics.

I see lift as a reaction to the CONDITIONS created by the reactions to the normal accelerations of turning. The vertical component of that acceleration is a MEASURE of the lift contributions.

Dose this constitute basic Newtonian reaction?

( The rotor flowcfield is too complicated for me!)
Jan 10, 2013, 04:58 AM
Registered User
Everything can be reduced to basic Newtonian reaction (as long as we keep away from extremes of mass, scale and speed), but complex systems require complex explanations. You can't just say "that much air goes down, that much force pushes up", you have to consider every single reaction of every single rigid body collision, one molecule at a time. Then you can build a statistic model that works for volumes. But if you do that you MUST consider also pressure distribution, because it's essentially what describes gas molecules bouncing on each other. (see http://en.wikipedia.org/wiki/Kinetic_theory for an example)
Jan 10, 2013, 12:24 PM
Registered User
Quote:
Originally Posted by Brandano View Post
But if you do that you MUST consider also pressure distribution, because it's essentially what describes gas molecules bouncing on each other.
You are absolutly right. It is all about the pressure distribution.

I was just hoping to shake up some of the pragmatism.
Jan 10, 2013, 01:26 PM
An itch?. Scratch build.
eflightray's Avatar
Otherwise every time a plane flew over you, you would 'feel the pressure'.

Though I did get knocked off my pushbike once when an English Electric Lightning decided to go vertical just after take-off. My self and some friends would cycle out to Bitteswell Airfield to see what was happening, (I was about 14 at the time). The did testing, repairs and experimenting there.

Vaguely remember seeing an old four engine plane with a jet engine strapped on one side of the fuselage.
Last edited by eflightray; Jan 10, 2013 at 01:32 PM.
Jan 10, 2013, 03:07 PM
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aeronaut999's Avatar
Almost 1,000 posts and still going strong! Steve
Jan 10, 2013, 04:16 PM
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richard hanson's Avatar
You can measure pressure down -or whichever direction you prefer - when it comes to explaining lift - it is simply the pressure difference on the body in question - which counts . You can throw down all the air you want to measure - If air pressure is still the same on th other side of the rotor/wing/ fuselage , whatever -
- No lift
Feb 15, 2013, 09:41 PM
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aeronaut999's Avatar

a fine afternoon


Just spent a fine afternoon with my feet off the ground gravitationally attracting the earth upward... while simultaneously exerting an equal and opposite downward force on the earth with my downwash...

I mean... I went flying today. Did you notice anything unusual? No unusual accelerations? Good, I guess that means that these forces/ accelerations counterbalanced each other and the harmony of our dear planet was not disturbed. Although I do remember hearing something about some cosmic explosion in the skies over Russia. Oh dear... back to the drawing board...

S
Mar 23, 2013, 11:54 AM
Registered User

downwash is beautiful


This is the best one I've seen so far:
Mar 23, 2013, 05:49 PM
Launch the drones ...
Quote:
Originally Posted by richard hanson View Post
You can measure pressure down -or whichever direction you prefer - when it comes to explaining lift - it is simply the pressure difference on the body in question - which counts . You can throw down all the air you want to measure - If air pressure is still the same on th other side of the rotor/wing/ fuselage , whatever -
- No lift
Poor ole Newton ... he simply gets no respect these days.
Mar 23, 2013, 08:48 PM
Registered User
richard hanson's Avatar
Oh he gets respect but consider the heli which is throwing down down air -but the SAME air is recirculating back to upper side of blades - net pressure difference - zip- ergo lift does not occur.
It can happen.
Mar 24, 2013, 08:32 AM
Launch the drones ...
Quote:
Originally Posted by richard hanson View Post
Oh he gets respect but consider the heli which is throwing down down air -but the SAME air is recirculating back to upper side of blades - net pressure difference - zip- ergo lift does not occur.
It can happen.
Sheer nonsense - dude. Just my opinion, and NASA's as well.
Mar 24, 2013, 08:42 AM
Registered User
Someone should summarize the current debate going on in this thread in like 1000 words or less so it's easier for new posters to get in on it

I feel like it's gotten to the stage where if I contribute something that has already been addressed or is at too basic a level then I will get my head bitten off, but 67 is a lot of pages lol.
Mar 24, 2013, 09:55 AM
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richard hanson's Avatar
Quote:
Originally Posted by Tim Green View Post
Sheer nonsense - dude. Just my opinion, and NASA's as well.
Who is NASA?
Mar 24, 2013, 10:08 AM
Launch the drones ...
Quote:
Originally Posted by Nereth View Post
Someone should summarize the current debate going on in this thread in like 1000 words or less so it's easier for new posters to get in on it

I feel like it's gotten to the stage where if I contribute something that has already been addressed or is at too basic a level then I will get my head bitten off, but 67 is a lot of pages lol.
If you want to understand the cause of lift, try out NASA - they seem to know what they're talking about - the rocket scientists ought to know - right?

http://www.grc.nasa.gov/WWW/K-12/airplane/lift1.html

Enjoy.


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