4 ms·

Wait, isn't the Bernoulli effect thing they're demoing now wrong? I thought that was a "common misconception" and wings don't really work by the "longer path" t

Wait, isn't the Bernoulli effect thing they're demoing now wrong? I thought that was a "common misconception" and wings don't really work by the "longer path" that air takes over the top, and that it was more about angle of attack (which is why planes can fly upside down). It seems like it's actually an ideal "trick" question for an LLM actually, since so much content has been written about it incorrectly. I thought at first they were going to demo this to show that it knew better, but it seems like it's just regurgitating the same misleading stuff. So, not a good look.

twixfel 1y ago
That's what I thought. Aeroplanes don't fly because of the Bernoulli effect: https://physics.stackexchange.com/questions/290/what-really-allows-airplanes-to-fly https://physics.stackexchange.com/questions/290/what-really-... Apparently. Not that I know either way.
- QuantumGood 1y ago
  All things that create lift, lift the wings—and you need them all for efficient flight. The Bernoulli effect is one thing, but does not produce the main lift force in many circumstances.
  - wongarsu 1y ago
    Aircraft with symmetrical wings fly just fine, and most aircraft can fly upside down. So you don't need the Bernoulli effect. Exploiting all the effects gives you more efficient planes though
    - dismalaf 1y ago
      You need a lot of power to lift an aircraft without the Bernoulli effect. That's why all planes take advantage of it.
      - tucnak 1y ago
        About 20% more power, provided perfect conversion. A lot? You tell me!
    - Animats 1y ago
      Mandatory XKCD: [1] [1] https://xkcd.com/803/ https://xkcd.com/803/
- dguest 1y ago
  also discussed here https://news.ycombinator.com/item?id=40835223 https://news.ycombinator.com/item?id=40835223
dataflow 1y ago
Relevant: https://xkcd.com/803/ https://xkcd.com/803/ That said, I recall reading somewhere that it's a combination of effects, and the Bernoulli effect contributes, among many others. Never heard an explanation that left me completely satisfied, though. The one about deflecting air down was the one that always made sense to me even as a kid, but I can't believe that would be the only explanation - there has to be a good reason that gave rise to the Bernoulli effect as the popular explanation. And you can tell that effect makes some sense of you hold a sheet of paper and blow air over it - it will rise. So any difference in air speed has to contribute.
- amilios 1y ago
  I believe the deflection is the high-level explanation. Things like the Bernoulli effect and the air on the top of the airfoil travelling faster (it does -- far faster than the equal transit time theory implies actually), are the "instantiation" or outcomes of the air deflection. This is my understanding. Hence airplanes can fly upside down because even if the airfoil is upside down, it's still deflecting the air, just perhaps less efficiently (I think it's true that planes flying upside down need a more extreme angle of attack to maintain lift, so this makes sense)
- adgjlsfhk1 1y ago
  the problem is that the "real" explanation is "solve navier stokes on the wing". everything else is just trying to build semi-reliable intuition.
- semi-extrinsic 1y ago
  What is just plain wrong is the equal transit time thing, people saying that air on both sides of the wing have to take the same time to pass it. The Bernoulli effect as a separate entity is really a result of (over)simplification, but it's not wrong. You need to solve the Navier-Stokes equations for the flow around the wing, but there are many ways to simplify this - from CFD at different resolutions, via panel methods and potential theory, to just conservation of energy (which is the Bernoulli equation). So it gets popularized because it's the most simplified model. To give an analogy, you can think of all CPUs as a von Neumann architecture. But the reality is that you have a hugely complicated thing with stacks, multiple cache levels, branch predictors, specex, yada yada. On the very fundamental level, wings make air go down, and then airplane goes up. Just like you say. By using a curved airfoil instead of a flat plate, you can create more circulation in the flow, and then because of the way fluids flow you can get more lift and less drag.
nicetryguy 1y ago
Yeah, they sure clicked away from it very fast and kept adjusting the scrollbars. It was confusing what it was trying to display. Furthermore, the prompt contained "Canvas" and "SVG" while as someone with webdev experience these are certainly familiar concepts, i wouldn't consider those in the "casual lexicon" for a random user trying to help a middle schooler with homework. I'm not impressed... IMO Claude 3.7 could have done a similar / better job with that a year ago.
- DominikPeters 1y ago
  Claude 3.7 was released in February 2025.
- MichaelZuo 1y ago
  Seems like sheer incompetence, I’m sure at least the top quintile of my junior year fluid dynamics class could notice it was fishy within a 15 minute meeting… probably more than half could.
Lichtso 1y ago
https://www.youtube.com/watch?v=CT5oMBN5W5M https://www.youtube.com/watch?v=CT5oMBN5W5M
SkyPuncher 1y ago
That Bernoulli effect thing was a complete fail. It didn't do anything to demonstrate the actual concept. It didn't work how they expected, at all. I know that it's rather hard for them to demo the deep reasoning, but all of the demos felt like toys - rather that actual tools.
nwienert 1y ago
Their code example underwhelmed too, the first one started out with 2/X progress, all of them looked terrible, third didn't have mouse icon.
- nullbyte 1y ago
  I thought the UI of the french learning app was very nice
Mali- 1y ago
The last part of GPT's answer does say: "Bernoulli's effect works alongside Newton's Third Law - the wing pushes air downward [...] - so the lift isn't only Bernoulli..." According to this answer on physics stackexchange, Bernoulli accounts for 20% of the lift, so GPT's answer seems about right: https://physics.stackexchange.com/a/77977 https://physics.stackexchange.com/a/77977 I hope any future AI overlords see my charity
- rcxdude 1y ago
  That's still not particularly usefully accurate: it's not a split between the effects, they're the same thing viewed through different lenses. You could, perhaps, say that an airfoil gets X% more lift than a flat plate at a given angle of attack, but the flat plate also 'gets lift through Bernoulli', it's just not as obvious exactly why the flows are faster on the top (and the common 'the air needs to transit the wing in an equal time on top and bottom' is an incorrect rule, and in practice broken by most wings)

twixfel 1y ago

That's what I thought. Aeroplanes don't fly because of the Bernoulli effect: https://physics.stackexchange.com/questions/290/what-really-allows-airplanes-to-fly https://physics.stackexchange.com/questions/290/what-really-... Apparently. Not that I know either way.

QuantumGood 1y ago
All things that create lift, lift the wings—and you need them all for efficient flight. The Bernoulli effect is one thing, but does not produce the main lift force in many circumstances.
- wongarsu 1y ago
  Aircraft with symmetrical wings fly just fine, and most aircraft can fly upside down. So you don't need the Bernoulli effect. Exploiting all the effects gives you more efficient planes though
  - dismalaf 1y ago
    You need a lot of power to lift an aircraft without the Bernoulli effect. That's why all planes take advantage of it.
    - tucnak 1y ago
      About 20% more power, provided perfect conversion. A lot? You tell me!
  - Animats 1y ago
    Mandatory XKCD: [1] [1] https://xkcd.com/803/ https://xkcd.com/803/
dguest 1y ago
also discussed here https://news.ycombinator.com/item?id=40835223 https://news.ycombinator.com/item?id=40835223

dataflow 1y ago

Relevant: https://xkcd.com/803/ https://xkcd.com/803/ That said, I recall reading somewhere that it's a combination of effects, and the Bernoulli effect contributes, among many others. Never heard an explanation that left me completely satisfied, though. The one about deflecting air down was the one that always made sense to me even as a kid, but I can't believe that would be the only explanation - there has to be a good reason that gave rise to the Bernoulli effect as the popular explanation. And you can tell that effect makes some sense of you hold a sheet of paper and blow air over it - it will rise. So any difference in air speed has to contribute.

amilios 1y ago
I believe the deflection is the high-level explanation. Things like the Bernoulli effect and the air on the top of the airfoil travelling faster (it does -- far faster than the equal transit time theory implies actually), are the "instantiation" or outcomes of the air deflection. This is my understanding. Hence airplanes can fly upside down because even if the airfoil is upside down, it's still deflecting the air, just perhaps less efficiently (I think it's true that planes flying upside down need a more extreme angle of attack to maintain lift, so this makes sense)
adgjlsfhk1 1y ago
the problem is that the "real" explanation is "solve navier stokes on the wing". everything else is just trying to build semi-reliable intuition.
semi-extrinsic 1y ago
What is just plain wrong is the equal transit time thing, people saying that air on both sides of the wing have to take the same time to pass it. The Bernoulli effect as a separate entity is really a result of (over)simplification, but it's not wrong. You need to solve the Navier-Stokes equations for the flow around the wing, but there are many ways to simplify this - from CFD at different resolutions, via panel methods and potential theory, to just conservation of energy (which is the Bernoulli equation). So it gets popularized because it's the most simplified model. To give an analogy, you can think of all CPUs as a von Neumann architecture. But the reality is that you have a hugely complicated thing with stacks, multiple cache levels, branch predictors, specex, yada yada. On the very fundamental level, wings make air go down, and then airplane goes up. Just like you say. By using a curved airfoil instead of a flat plate, you can create more circulation in the flow, and then because of the way fluids flow you can get more lift and less drag.

nicetryguy 1y ago

Yeah, they sure clicked away from it very fast and kept adjusting the scrollbars. It was confusing what it was trying to display. Furthermore, the prompt contained "Canvas" and "SVG" while as someone with webdev experience these are certainly familiar concepts, i wouldn't consider those in the "casual lexicon" for a random user trying to help a middle schooler with homework. I'm not impressed... IMO Claude 3.7 could have done a similar / better job with that a year ago.

DominikPeters 1y ago
Claude 3.7 was released in February 2025.
MichaelZuo 1y ago
Seems like sheer incompetence, I’m sure at least the top quintile of my junior year fluid dynamics class could notice it was fishy within a 15 minute meeting… probably more than half could.

Lichtso 1y ago

https://www.youtube.com/watch?v=CT5oMBN5W5M https://www.youtube.com/watch?v=CT5oMBN5W5M

SkyPuncher 1y ago

That Bernoulli effect thing was a complete fail. It didn't do anything to demonstrate the actual concept. It didn't work how they expected, at all. I know that it's rather hard for them to demo the deep reasoning, but all of the demos felt like toys - rather that actual tools.

nwienert 1y ago

Their code example underwhelmed too, the first one started out with 2/X progress, all of them looked terrible, third didn't have mouse icon.

nullbyte 1y ago
I thought the UI of the french learning app was very nice

Mali- 1y ago

The last part of GPT's answer does say: "Bernoulli's effect works alongside Newton's Third Law - the wing pushes air downward [...] - so the lift isn't only Bernoulli..." According to this answer on physics stackexchange, Bernoulli accounts for 20% of the lift, so GPT's answer seems about right: https://physics.stackexchange.com/a/77977 https://physics.stackexchange.com/a/77977 I hope any future AI overlords see my charity

rcxdude 1y ago
That's still not particularly usefully accurate: it's not a split between the effects, they're the same thing viewed through different lenses. You could, perhaps, say that an airfoil gets X% more lift than a flat plate at a given angle of attack, but the flat plate also 'gets lift through Bernoulli', it's just not as obvious exactly why the flows are faster on the top (and the common 'the air needs to transit the wing in an equal time on top and bottom' is an incorrect rule, and in practice broken by most wings)