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Topic: Reworking established science, and perpetual motion machines  (Read 1 time) previous topic - next topic

PerryBebbington

As far as I know the laws of aerodynamics that keep planes aloft are well understood, although I only have an outline understanding of them. What do you think is not understood?

GoForSmoke

I'm thinking of the old NACA days before 1940. They didn't know higher than .5 mach so well, or maybe slower given airspeed gauges even later.

We know more about friction, boundaries and turbulence than before without changing a single physical law.
Go back a ways, NACA didn't knows Reynolds numbers. It wasn't until about 1929 that wings got decent with the Clark Y.

The air goes over the top of the wing faster than underneath, makes a pressure difference and if the air speed is calculated based on the speed of the plane and shape of the wing it turns out there's not enough lift.

But at the sharp trailing edge of the wing the slow underwing flow mixes with the fast overwing flow and makes a vortex that actually sucks air over the top of the wing and drives what is called circulation, air well in front of the wing moves up and into the effect. When air splits over top and  bottom of the wing, the bottom air reaches the vortex well after the top split air is rolling below and behind the plane.

The foil makes a vortex that throws a mass of air downwards hard enough to keep the plane up. The pressure difference and the throw down are the opposite and equal forces, there is never just one force/hand pushing/clapping.
1) http://gammon.com.au/blink  <-- tasking Arduino 1-2-3
2) http://gammon.com.au/serial <-- techniques howto
3) http://gammon.com.au/interrupts
Your sketch can sense ongoing process events in time.
Your sketch can make events to control it over time.

Robin2

The air goes over the top of the wing faster than underneath,
Why?


Quote
But at the sharp trailing edge of the wing the slow underwing flow mixes with the fast overwing flow and makes a vortex that actually sucks air over the top of the wing and drives what is called circulation, air well in front of the wing moves up and into the effect. When air splits over top and  bottom of the wing, the bottom air reaches the vortex well after the top split air is rolling below and behind the plane.equal forces, there is never just one force/hand pushing/clapping.
Do you have a reference for a text book or online source that explains that?


If you are (or were) a practicing aerodynamicist working for a state-of-the-art airplane maker I may be interested to discuss the matter further but there is no point in the blind leading the blind.

...R
Two or three hours spent thinking and reading documentation solves most programming problems.

CrossRoads

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

GoForSmoke

It is a measured fact that with a foil designed for lift given a positive angle of incidence the air over the top moves faster than underneath.

It is a measured fact that airplanes give air behind and below downward momentum. That's why it's dangerous to land too soon after a big plane lands, like a minute later if you're in a light plane and there's no wind.

You only get lift under certain conditions, the why includes those. It includes the paths that air takes around the wing. It includes the vortex

I had months of answers from 2 aerodynamicists, one finishing his PhD to go back to SA. I did a good bit of reading to be able to ask questions that got those answers. I had my own interests going back to 1968 when I learned to make gliders with 1910 concepts.

You can find the basics on the NASA site and more if you poke around but then you have your books.

See if you can find a usenet cache with Mark Drexler's explanation of lift, I did paraphrase but he has the degree.

Oh yeah, TKS Bob!  I had forgotten See How It Flies! He's Caltech and FAA.
1) http://gammon.com.au/blink  <-- tasking Arduino 1-2-3
2) http://gammon.com.au/serial <-- techniques howto
3) http://gammon.com.au/interrupts
Your sketch can sense ongoing process events in time.
Your sketch can make events to control it over time.

CrossRoads

"He's Caltech and FAA."

The author, not me. I'm just an instrument rated pilot and aircraft owner.

Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

CrossRoads

My airplane has a high wing, and uses 30 degrees of flap when landing.  When I come in and the engine is turning really slow (like 500-600 RPM), it is pretty quiet.  I'll approach the runway at an angle, like 3-5 degrees. When I get over the runway, and pull the noseup (by pulling the yoke back which tilts the stabilator and pushes the tail down), the pitch of the wings also goes up, and you can hear the air being pushed down by the tilted wing/lowered flap combination.
Designing & building electrical circuits for over 25 years.  Screw Shield for Mega/Due/Uno,  Bobuino with ATMega1284P, & other '328P & '1284P creations & offerings at  my website.

GoForSmoke

Yes, John Denker. Enough pedigree for Robin2 I hope?

I heard that you can make a small fortune with an airplane. You start with an airplane and a big fortune.

1) http://gammon.com.au/blink  <-- tasking Arduino 1-2-3
2) http://gammon.com.au/serial <-- techniques howto
3) http://gammon.com.au/interrupts
Your sketch can sense ongoing process events in time.
Your sketch can make events to control it over time.

Budvar10

Why?
The shape of wing profile is a key. The top surface is longer than the bottom surface in terms of the air flow. If the air flow is laminar then upper flow near to surface must be faster and this results in a pressure drop above top surface. This difference in air pressure causes the lift force.
Of course some types of airfoil have symmetrical shape. Here the same effect is reached by tilting the wing.

It is a physics for elementary school in at least Slovakia.


Arduino clone with ATmega1284P   http://forum.arduino.cc/index.php?topic=277260.0

Budvar10

Experiment:
Hold two sheets of paper flat approximately 3 cm apart. The distance is not very critical. Blow into the gap between them.
What will happen?
Arduino clone with ATmega1284P   http://forum.arduino.cc/index.php?topic=277260.0

GoForSmoke

https://www.grc.nasa.gov/www/k-12/airplane/lift1.html

Quote
HOW IS LIFT GENERATED?

There are many explanations for the generation of lift found in encyclopedias, in basic physics textbooks, and on Web sites. Unfortunately, many of the explanations are misleading and incorrect. Theories on the generation of lift have become a source of great controversy and a topic for heated arguments. To help you understand lift and its origins, a series of pages will describe the various theories and how some of the popular theories fail.

Lift occurs when a moving flow of gas is turned by a solid object. The flow is turned in one direction, and the lift is generated in the opposite direction, according to Newton's Third Law of action and reaction. Because air is a gas and the molecules are free to move about, any solid surface can deflect a flow. For an aircraft wing, both the upper and lower surfaces contribute to the flow turning. Neglecting the upper surface's part in turning the flow leads to an incorrect theory of lift.
https://www.grc.nasa.gov/WWW/k-12/airplane/right2.html

----------- time for F U N N ----------------

https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html

Quote
There are many theories of how lift is generated. Unfortunately, many of the theories found in encyclopedias, on web sites, and even in some textbooks are incorrect, causing unnecessary confusion for students.

The theory described on this slide is one of the most widely circulated, incorrect explanations. The theory can be labeled the "Longer Path" theory, or the "Equal Transit Time" theory. The theory states that airfoils are shaped with the upper surface longer than the bottom. The air molecules (the little colored balls on the figure) have farther to travel over the top of the airfoil than along the bottom. In order to meet up at the trailing edge, the molecules going over the top of the wing must travel faster than the molecules moving under the wing. Because the upper flow is faster, then, from Bernoulli's equation, the pressure is lower. The difference in pressure across the airfoil produces the lift.
IMO, wing AoA changes the paths start point, a symmetric wing won't have equal paths with positive AoA.


1) http://gammon.com.au/blink  <-- tasking Arduino 1-2-3
2) http://gammon.com.au/serial <-- techniques howto
3) http://gammon.com.au/interrupts
Your sketch can sense ongoing process events in time.
Your sketch can make events to control it over time.

GoForSmoke

The shape of wing profile is a key. The top surface is longer than the bottom surface in terms of the air flow. If the air flow is laminar then upper flow near to surface must be faster and this results in a pressure drop above top surface. This difference in air pressure causes the lift force.
Of course some types of airfoil have symmetrical shape. Here the same effect is reached by tilting the wing.

It is a physics for elementary school in at least Slovakia.

For elementary school when you went, with the math you knew then.

But a cambered wing has no lift without angle of attack, that's why wings are given angle of incidence to the fuselage.

Laminar flow? It is argued that the P-51 only came close and was a special effort I think the word laminar is taken differently. Did the Fokker Eindekker have laminar flow wings? They got enough right in Gottingen to fly.
1) http://gammon.com.au/blink  <-- tasking Arduino 1-2-3
2) http://gammon.com.au/serial <-- techniques howto
3) http://gammon.com.au/interrupts
Your sketch can sense ongoing process events in time.
Your sketch can make events to control it over time.

Robin2

See this e-book

Many thanks for the link. I will bookmark it.

To be honest its nearly 20 years since I was seriously interested in this subject so my appetite for more is somewhat limited.

...R

PS ... I have just realized that I spent far too much of my life thinking about this subject back then - and I am not going to waste any more time on it now. Sorry to have started this.
Two or three hours spent thinking and reading documentation solves most programming problems.

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