MERGED: Engineer debunks theory of flight
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MERGED: Engineer debunks theory of flight
Over to you.
I still think the Earth sucks....
Bernoulli eat your heart out..
I still think the Earth sucks....
Bernoulli eat your heart out..
Engineer debunks theory of flight
David Millward and Nick Collins London
January 27, 2012
AN ENGINEER has debunked one of the most common myths in science - why aircraft fly.
Aeroplanes fly because their wings cause the air pressure underneath to be greater than that above, lifting them into the air. For years engineers have been frustrated by a theory that wrongly explained the change in pressure.
The myth is common in textbooks, and even Einstein was rumoured to have subscribed to it.
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A Cambridge scientist was so fed up with it that he created a minute-long video to lay it to rest. The video, published on YouTube by Professor Holger Babinsky, seeks to explain in simple terms why the theory goes against the laws of physics.
According to the myth, the pressure change happens because the air on the curved upper surface of the wing has further to travel than that below the flat underneath surface, meaning it must travel faster to arrive at the other side of the wing at the same time.
The true explanation is nothing to do with the distance the air has to travel. The curvature of the wing causes the change in air pressure because it pulls some of the air upwards, which reduces pressure, and forces the rest beneath it, creating higher pressure.
Professor Babinsky explains that, although lift is caused by a pressure change between the top and bottom surfaces, it's due to the change in the shape of the air flow, rather than its speed. ''This is why a flat surface like a sail is able to cause lift,'' he says. ''In this case, the distance on each side is the same but it is slightly curved when it's rigged, acting like an aerofoil.''
Professor Babinsky filmed smoke passing across a wing. If traditional wisdom had been correct the smoke above and below should have reached the back at the same time. Actually, the plume above the wing reached the back much sooner.
Read more: Engineer debunks theory of flight
David Millward and Nick Collins London
January 27, 2012
AN ENGINEER has debunked one of the most common myths in science - why aircraft fly.
Aeroplanes fly because their wings cause the air pressure underneath to be greater than that above, lifting them into the air. For years engineers have been frustrated by a theory that wrongly explained the change in pressure.
The myth is common in textbooks, and even Einstein was rumoured to have subscribed to it.
Advertisement: Story continues below
A Cambridge scientist was so fed up with it that he created a minute-long video to lay it to rest. The video, published on YouTube by Professor Holger Babinsky, seeks to explain in simple terms why the theory goes against the laws of physics.
According to the myth, the pressure change happens because the air on the curved upper surface of the wing has further to travel than that below the flat underneath surface, meaning it must travel faster to arrive at the other side of the wing at the same time.
The true explanation is nothing to do with the distance the air has to travel. The curvature of the wing causes the change in air pressure because it pulls some of the air upwards, which reduces pressure, and forces the rest beneath it, creating higher pressure.
Professor Babinsky explains that, although lift is caused by a pressure change between the top and bottom surfaces, it's due to the change in the shape of the air flow, rather than its speed. ''This is why a flat surface like a sail is able to cause lift,'' he says. ''In this case, the distance on each side is the same but it is slightly curved when it's rigged, acting like an aerofoil.''
Professor Babinsky filmed smoke passing across a wing. If traditional wisdom had been correct the smoke above and below should have reached the back at the same time. Actually, the plume above the wing reached the back much sooner.
Read more: Engineer debunks theory of flight
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Lift Theory
Cop this for a load!!!!
Not going to make my own comments at this point, but I thought more that a few of you might find it interesting.
Of interest, is how quick the paper closed comments to the article.
Engineer debunks theory of flight
Cheers
Jas.
PS...mods sorry if this was raised elswhere, but I only read godzone
Not going to make my own comments at this point, but I thought more that a few of you might find it interesting.
Of interest, is how quick the paper closed comments to the article.
Engineer debunks theory of flight
Cheers
Jas.
PS...mods sorry if this was raised elswhere, but I only read godzone
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I always had a problem with Bernoulli's principle as far as lift is concerned. I thought that was one of those things they didn't teach in BAK courses anymore, it was more about downdraft providing the lift. I stand to be corrected, because I'd really love to hear other's opinions, or theories.
This could turn into a downwind turn argument
This could turn into a downwind turn argument
Grandpa Aerotart
Take a large spoon and dangle it, lightly held, between thumb and forefinger then slowly move it under a running tap...just let the water flow touch the curved surface and see what happens. You'll see a very strong demonstration of 'lift' but there is no movement of water down BOTH sides of the spoon...just the curved surface...but 'lift' is still produced.
Sails are NOT flat - they are 'cut' to have an aerofoil shape. As wind strength increases you manipulate various controls to flatten them and reduce lift to keep the boat upright - but they never end up 'flat' - even storm sails, designed for extreme wind strengths, are not flat.
Yes you can get a flat plate, give it an AoA, and get 'some lift' but efficient lift comes from accelerating air over a curved surface which produces reduced pressure - a static pressure delta - that sucks the wing up.
The spoon experiment above should prove to anyone which is the strongest force - suck or push.
Sails are NOT flat - they are 'cut' to have an aerofoil shape. As wind strength increases you manipulate various controls to flatten them and reduce lift to keep the boat upright - but they never end up 'flat' - even storm sails, designed for extreme wind strengths, are not flat.
Yes you can get a flat plate, give it an AoA, and get 'some lift' but efficient lift comes from accelerating air over a curved surface which produces reduced pressure - a static pressure delta - that sucks the wing up.
The spoon experiment above should prove to anyone which is the strongest force - suck or push.
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Well, maybe you should revisit Bernoulli's theory and re-read the article. Contemplate that for a while then watch the video. 
and yer steve, I also hope this one can stay civil.
and yer steve, I also hope this one can stay civil.
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Take a large spoon and dangle it, lightly held, between thumb and forefinger then slowly move it under a running tap...just let the water flow touch the curved surface and see what happens. You'll see a very strong demonstration of 'lift' but there is no movement of water down BOTH sides of the spoon...just the curved surface...but 'lift' is still produced.
Like this example of the Coanda Effect
effect......
Watch the flow after the spoon......
p.s. Thanks to You Tube etc.....
Cheers
p.p.s....All I know is that when the airspeed gets to be 'this', I pull back a little 'here' and the houses get smaller.....
I don't really care 'how'...I just am thankful that it 'does'.....;
effect......
Watch the flow after the spoon......
p.s. Thanks to You Tube etc.....
Cheers
p.p.s....All I know is that when the airspeed gets to be 'this', I pull back a little 'here' and the houses get smaller.....
I don't really care 'how'...I just am thankful that it 'does'.....
;
The curvature of the wing causes the change in air pressure because it pulls some of the air upwards, which reduces pressure, and forces the rest beneath it, creating higher pressure.
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Yawn...............
Any reputable test book will tell you that there are several theories that have been developed to predict the performance of an aerofoil. The Equation of Continuity (that's the one that uses Bernoulli's Theorem) is but one (the most used, granted). There are also Momentum Theory (I personally prefer this one), Circulation Theory and Dimensinal Analysis that I am aware of.
The Equation of Continuity just happens to be the easiest to understand and is therefore the most widely used.
Any reputable test book will tell you that there are several theories that have been developed to predict the performance of an aerofoil. The Equation of Continuity (that's the one that uses Bernoulli's Theorem) is but one (the most used, granted). There are also Momentum Theory (I personally prefer this one), Circulation Theory and Dimensinal Analysis that I am aware of.
The Equation of Continuity just happens to be the easiest to understand and is therefore the most widely used.
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Curvature of the Earth
A lot of military jets only get airborne because of the curvature of the Earth and excess thrust, therefore a lot of military runways are "humped" in the middle to reduce take-off length. 
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Nothing "sucks"
Quote - "that sucks the wing up."
Reduced pressure does not suck. It is always the higher pressure which is pushing. To accept suction as a force, you would have to accept that the less fluid there is on one side, the more work it can do. Take it to the point that if, on one side of the aerofoil or whatever there was a vacuum, you would have to believe the absence of something can do work.
Reduced pressure does not suck. It is always the higher pressure which is pushing. To accept suction as a force, you would have to accept that the less fluid there is on one side, the more work it can do. Take it to the point that if, on one side of the aerofoil or whatever there was a vacuum, you would have to believe the absence of something can do work.
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...........'griffo' thanks for yr post although I had to duck off to the loo only after a few short seconds of watching all that water flow.....wasteful it was too, some simply don't care about water conservation!
I recall doing such an experiment at school in a science class (yes that's about all I recall about school!).
A trick that dear old dad showed us as kids in the car was to stick ones hand out the window whilst moving along at speed & watch the change in lift as we either kept our hands flat against the wind on a shallow angle or curve/cup our hands, the latter produced far more a force upwards, dear old dad he was so clever & he was just a TV repair man!.
I'm with you 'griffo' ...............who cares???? I didn't invent the theory, I can't change it so I accept that when I haul back on the stick I go up along with the many tonnes of hardware strapped to my bum, I also get scared!
I subscribe to the theory that for every action there's an equal & opposite reaction, well so says Mr Newton & that's not the CH 9 guy either! So if it's good enuf for him it's good enuf for me
Now on with the theories!
Wmk2
.....wasteful it was too, some simply don't care about water conservation!I recall doing such an experiment at school in a science class (yes that's about all I recall about school!).
A trick that dear old dad showed us as kids in the car was to stick ones hand out the window whilst moving along at speed & watch the change in lift as we either kept our hands flat against the wind on a shallow angle or curve/cup our hands, the latter produced far more a force upwards, dear old dad he was so clever & he was just a TV repair man!
.I'm with you 'griffo' ...............who cares???? I didn't invent the theory, I can't change it so I accept that when I haul back on the stick I go up along with the many tonnes of hardware strapped to my bum, I also get scared!
I subscribe to the theory that for every action there's an equal & opposite reaction, well so says Mr Newton & that's not the CH 9 guy either!
So if it's good enuf for him it's good enuf for meNow on with the theories!
Wmk2
I never accepted the scientific explanation as rational.
After playing aerofoils with my hand out of the car window all those years as a kid, you can feel lift. It's almost as if you a compressing the molecules and creating a solid which supports more weight the faster you go, or the more you collect.
After playing aerofoils with my hand out of the car window all those years as a kid, you can feel lift. It's almost as if you a compressing the molecules and creating a solid which supports more weight the faster you go, or the more you collect.
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so after watching the video, the curved upper surface, accelerates the air over the top... lowering pressure.... so whats new? the only difference i can see from conventional wisdom is the air passing above reaches the trailing edge before the air passing below... but the principle remains the same of the air flowing faster over the top... 
