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Old 12-09-2020, 09:31 PM   #1 (permalink)
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Theories of lift

I saw this last night.

It's why when people ask for explanations (not just descriptions) of why air on cars follows curved surfaces, why pressures vary (etc), it's best not to answer.

And when they say "It's easy - Bernoulli!" or "It's easy - Newton!" you'd best run a mile.

https://www.scientificamerican.com/a...ay-in-the-air/

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Old 12-14-2020, 01:44 PM   #2 (permalink)
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This was an interesting article and deserves a bump. Thanks for posting the link.
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The power needed to push an object through a fluid increases as the cube of the velocity. Mechanical friction increases as the square, so increasing speed requires progressively more power.
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Old 12-14-2020, 02:36 PM   #3 (permalink)
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Seconded. I ordered a copy of Mclean's book to see what he argues.
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Old 12-14-2020, 03:18 PM   #4 (permalink)
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Seconded. I ordered a copy of Mclean's book to see what he argues.
Please let us know how you find it in terms of understandings that help in car aero.
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Old 12-16-2020, 12:20 PM   #5 (permalink)
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Mclean

I attended his lecture on aircraft design in 1997, at the Oshkosh Annual Fly-In.
He has a different slant on aero for sure. 'adjacent-flow,' Coanda material. Inverted dynamics logic.
I just considered it informational. None of it was germane to road vehicle aerodynamics.
The numerical models under attack have been used for aeronautical design, with results within 99% of accuracy, basically for as long as they've been around.
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Old 12-16-2020, 01:29 PM   #6 (permalink)
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Quote:
Originally Posted by aerohead View Post
I attended his lecture on aircraft design in 1997, at the Oshkosh Annual Fly-In.
He has a different slant on aero for sure. 'adjacent-flow,' Coanda material. Inverted dynamics logic.
I just considered it informational. None of it was germane to road vehicle aerodynamics.
The numerical models under attack have been used for aeronautical design, with results within 99% of accuracy, basically for as long as they've been around.
Did you actually read the cited article? It doesn't seem so because it states:

Adding to the confusion is the fact that accounts of lift exist on two separate levels of abstraction: the technical and the nontechnical. They are complementary rather than contradictory, but they differ in their aims. One exists as a strictly mathematical theory, a realm in which the analysis medium consists of equations, symbols, computer simulations and numbers. There is little, if any, serious disagreement as to what the appropriate equations or their solutions are. The objective of technical mathematical theory is to make accurate predictions and to project results that are useful to aeronautical engineers engaged in the complex business of designing aircraft.

So, no one is arguing about the numerical models.

But by themselves, equations are not explanations, and neither are their solutions. There is a second, nontechnical level of analysis that is intended to provide us with a physical, commonsense explanation of lift. The objective of the nontechnical approach is to give us an intuitive understanding of the actual forces and factors that are at work in holding an airplane aloft. This approach exists not on the level of numbers and equations but rather on the level of concepts and principles that are familiar and intelligible to non-specialists.

That's where the discussion is - and it's one where you routinely dismiss Newtonian concepts in car aero.

Maybe read the article and reflect on it?
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Old 12-16-2020, 01:57 PM   #7 (permalink)
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The article has some real gems in it:
Quote:
..the theorem does not say how the higher velocity above the wing came about to begin with.
I don't even..

(The author could've probably found an Indian guy on Youtube to answer his questions if he tried.)
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Old 12-16-2020, 02:33 PM   #8 (permalink)
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read it

Quote:
Originally Posted by JulianEdgar View Post
Did you actually read the cited article? It doesn't seem so because it states:

Adding to the confusion is the fact that accounts of lift exist on two separate levels of abstraction: the technical and the nontechnical. They are complementary rather than contradictory, but they differ in their aims. One exists as a strictly mathematical theory, a realm in which the analysis medium consists of equations, symbols, computer simulations and numbers. There is little, if any, serious disagreement as to what the appropriate equations or their solutions are. The objective of technical mathematical theory is to make accurate predictions and to project results that are useful to aeronautical engineers engaged in the complex business of designing aircraft.

So, no one is arguing about the numerical models.

But by themselves, equations are not explanations, and neither are their solutions. There is a second, nontechnical level of analysis that is intended to provide us with a physical, commonsense explanation of lift. The objective of the nontechnical approach is to give us an intuitive understanding of the actual forces and factors that are at work in holding an airplane aloft. This approach exists not on the level of numbers and equations but rather on the level of concepts and principles that are familiar and intelligible to non-specialists.

That's where the discussion is - and it's one where you routinely dismiss Newtonian concepts in car aero.

Maybe read the article and reflect on it?
I did read it. To me it's just esoteric banter, with no actionable information, germane to road vehicles.
It's more 'philosophy' than workaday aerodynamics. And kinda intellectually dishonest, as they're relying on turning Popperian logic on it's head, with no way to prove the hypothetical issue, one way or another. Water 'memory' at the sub-molecular level.
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Old 12-16-2020, 02:44 PM   #9 (permalink)
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Quote:
Originally Posted by aerohead View Post
I did read it. To me it's just esoteric banter, with no actionable information, germane to road vehicles.
It's more 'philosophy' than workaday aerodynamics. And kinda intellectually dishonest, as they're relying on turning Popperian logic on it's head, with no way to prove the hypothetical issue, one way or another. Water 'memory' at the sub-molecular level.
I'll just repeat what I said in my first post:

It's why when people ask for explanations (not just descriptions) of why air on cars follows curved surfaces, why pressures vary (etc), it's best not to answer.

And when they say "It's easy - Bernoulli!" or "It's easy - Newton!" you'd best run a mile.
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Old 12-16-2020, 03:41 PM   #10 (permalink)
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Quote:
There is a second, nontechnical level of analysis that is intended to provide us with a physical, commonsense explanation of lift.
This sounds like a job for Adversarial Generative AI. Ask GPT-3, but be aware that Microsoft is a gatekeeper. We're back to the pre-personal computer days where a white-robed technician behind a glass wall intercedes with your queries.

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