Meaningless aerodynamics and related physics discussion

[mjohnson]

Sooo... I got into an entirely unreasonably heated argument recently (of course at a bar) on "how planes fly".

I of course have my (as correct as it could be at a bar) opinion, but - how do planes fly?

[mjohnson]

Originally Posted by mjohnson

Sooo... I got into an entirely unreasonably heated argument recently (of course at a bar) on "how planes fly".

I of course have my (as correct as it could be at a bar) opinion, but - how do planes fly?

No, neither drunk or stoned ATM. This is an interesting thing for me regarding teaching reality.

(and it might possibly be driven by the 8yo's "why????" onslaught)

[pwd72s]

It's witchcraft.

[HobieMarty]

Air velocity and pressure creating lift, maybe?

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[island911]

Funny, while I've had applied aerodynamics during engineering school, the best explanation that I got was earlier as a kid, and was from an MJohnson who worked as a model maker at Boeing wind tunnel.

Something like, the air, being forced up and over the wing top creates a tunnel of vacuum along the length of the wing. -which also explains why elliptical wings and winglets work to 'pinch-off that tunnel of vacuum.

Hope that helps the 8 year old.

[917_Langheck]

Ask Bernoulli, he knows....


Actually, no one really knows, or so says Scientific American (glad this question came up so I can dispose of this piece of information and store a new bit of pedantic/unnecessary information):

https://www.scientificamerican.com/article/no-one-can-explain-why-planes-stay-in-the-air/

[93nav]

Originally Posted by 917_Langheck

Ask Bernoulli, he knows....


Actually, no one really knows, or so says Scientific American (glad this question came up so I can dispose of this piece of information and store a new bit of pedantic/unnecessary information):

https://www.scientificamerican.com/article/no-one-can-explain-why-planes-stay-in-the-air/

Bernoulli was a quack.

Anyone who has been involved with airplanes knows that money is what makes them fly. No money, no fly. The more money, the faster, higher and further they fly.

[917_Langheck]

Originally Posted by 93nav

Bernoulli was a quack.

Anyone who has been involved with airplanes knows that money is what makes them fly. No money, no fly. The more money, the faster, higher and further they fly.

LOL

Ok Mr. Grissom...

https://youtu.be/a7rGA0Zv8R4

[RobFrost]

Planes get lift by sending air downwards, it's simple Newtonian mechanics. There are two ways of looking at this, which are in a way the same thing.

A. Most wings have a convex top which forces the air to move faster round the outside of the circle. Whenever a fluid moves faster it has lower pressure, so the pressure difference from top to bottom of the wing manifests as lift.

And B. Wings usually have an upwards angle of attack to the direction of travel, I.e. the back of the wing is lower than the front.

Both a and b work by sending air downwards as the plane moves forwards. But a curved wing with a level angle of attack would still generate lift.

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[hbueno]

Originally Posted by RobFrost

Planes get lift by sending air downwards, it's simple Newtonian mechanics. There are two ways of looking at this, which are in a way the same thing.

A. Most wings have a convex top which forces the air to move faster round the outside of the circle. Whenever a fluid moves faster it has lower pressure, so the pressure difference from top to bottom of the wing manifests as lift.

And B. Wings usually have an upwards angle of attack to the direction of travel, I.e. the back of the wing is lower than the front.

Both a and b work by sending air downwards as the plane moves forwards. But a curved wing with a level angle of attack would still generate lift.

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That sums it up.

[jcommin]

Originally Posted by RobFrost

Planes get lift by sending air downwards, it's simple Newtonian mechanics. There are two ways of looking at this, which are in a way the same thing.

A. Most wings have a convex top which forces the air to move faster round the outside of the circle. Whenever a fluid moves faster it has lower pressure, so the pressure difference from top to bottom of the wing manifests as lift.

And B. Wings usually have an upwards angle of attack to the direction of travel, I.e. the back of the wing is lower than the front.

Both a and b work by sending air downwards as the plane moves forwards. But a curved wing with a level angle of attack would still generate lift.

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This got me thinking to my high school days and then I read this - That is what I remember.

[mjohnson]

I think I agree most with Mr. Frost... Air down = plane up. Works for rockets, too. Bumblebees, I guess we still don't know (JK, I'm aware that we figured that out)

(and thank god I'm not into planes or piloting, but according to some colleagues - money is an absolute requirement to keep those things airborne)

I'll stick with my kid's completely flat winged, rubber band powered, balsa and completely affordable things...

[IROC]

Originally Posted by RobFrost

Planes get lift by sending air downwards, it's simple Newtonian mechanics. There are two ways of looking at this, which are in a way the same thing.

A. Most wings have a convex top which forces the air to move faster round the outside of the circle. Whenever a fluid moves faster it has lower pressure, so the pressure difference from top to bottom of the wing manifests as lift.

And B. Wings usually have an upwards angle of attack to the direction of travel, I.e. the back of the wing is lower than the front.

Both a and b work by sending air downwards as the plane moves forwards. But a curved wing with a level angle of attack would still generate lift.

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^^^This! It's funny, but the answer to this question is more complicated than it seems (like most things). But, the above is correct.

One interesting thing I read once is that this act of "sending the air downwards" creates a pressure (or force) that can be measured on the ground. When a jet flies over your house, there is a pressure footprint below it as it flies. Logically, there must be. Mythbusters did a good episode on this. IIRC, they ended up putting an RC helicopter in the back of an enclosed 18-wheeler trailer. The question being - if the helicopter lifts off the bed of the trailer, does the truck weigh less than with the helicopter sitting on the bed? The answer was, no - the truck weighed the same. The pressure (force) created by the helicopter rotor sending the air downwards acted on the trailer bed, so the weight didn't change.

[masraum]

Originally Posted by RobFrost

Planes get lift by sending air downwards, it's simple Newtonian mechanics. There are two ways of looking at this, which are in a way the same thing.

A. Most wings have a convex top which forces the air to move faster round the outside of the circle. Whenever a fluid moves faster it has lower pressure, so the pressure difference from top to bottom of the wing manifests as lift.

And B. Wings usually have an upwards angle of attack to the direction of travel, I.e. the back of the wing is lower than the front.

Both a and b work by sending air downwards as the plane moves forwards. But a curved wing with a level angle of attack would still generate lift.

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That's also my understanding. It's not just what most of us previously learned about the lower pressure over the top due to increased speed. I took a class about 10 years ago, and that was news to me.

[Seahawk]

Pretty basic stuff:



Where it get really complicated is the multitude of wing designs for various types of aircraft.

[masraum]

Originally Posted by Seahawk

Pretty basic stuff:



Where it get really complicated is the multitude of wing designs for various types of aircraft.

I think they were looking for specifically how the lift is generated.

Growing up, this was the only thing that I'd heard.



But then about 2007, I took a course on a whim, and it included the following.
That course taught the following

Essentially that the downwash from the wing and Newtons third law caused the lift on the wing.

I've heard that it's not that simple and is a combination of Bernoulli and Newton that make the whole thing work.

[KFC911]

Mebbe ya just needed a few more drinks?

[blucille]

just don't ask about helicopters.

[URY914]

Wings on racecars are upside down.

[GH85Carrera]

Like a lot of kids, I got into model airplanes. I built a kit with the classes 0.049 engine on it and learned the basics of U-control. I moved up to a .35 and a balsa wood airplane. It had a wing shape that was the same top or bottom. My Air Force pilot father said it can't fly. But the power to weight ratio was more than enough to fly with ease and I had a lot of fun with it. And yes, even when the engine ran out of gas it would glide down just fine to a safe landing.