[HN Gopher] Airfoil (2024)
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Airfoil (2024)
Author : brk
Score : 321 points
Date : 2026-01-28 14:32 UTC (8 hours ago)
(HTM) web link (ciechanow.ski)
(TXT) w3m dump (ciechanow.ski)
| Lwrless wrote:
| https://news.ycombinator.com/item?id=39526057
| dang wrote:
| Thanks! Macroexpanded:
|
| _Airfoil_ - https://news.ycombinator.com/item?id=39526057 -
| Feb 2024 (296 comments)
| moralestapia wrote:
| I was just thinking the other day about how AI will pretty soon
| be able to create this kind of explainers on everything quite
| quickly.
|
| Amazing times!
| bayesnet wrote:
| It's kind of sad IMO. Bartosz has made a ton of these super
| interesting and meticulously designed explainers. Something
| thrown together with AI is much more likely to be made by
| someone who doesn't know what they're talking about, and I'm
| worried that the sheer volume will crowd out actually quality
| content like this.
| SecretDreams wrote:
| > and I'm worried that the sheer volume will crowd out
| actually quality content like this.
|
| It's a valid fear.
| hollowturtle wrote:
| Don't think so, and we should stop spread damaging narrative
| like this. I'd say it's already able to imitate this kind of
| explainers(badly) thanks to his training data. All the subtle
| teaching nuances, effort, know-how and visual creativity that
| people like Bartosz Ciechanowski put on this kind of work is
| not reproducible if not statistically imitating it
| dahauns wrote:
| And the usual corollary: Not just _thanks_ to his training
| data, but because training data of that kind and for this
| kind of topic - still - exists.
| hollowturtle wrote:
| Exactly and him not publishing any new post in 2025 makes
| me wonder...
| carlos-menezes wrote:
| Haven't people been saying this since 2023? Yet to see AI build
| this kind of stuff "quite quickly".
| _verandaguy wrote:
| It's been said before, but this prediction isn't amazing, imo.
|
| I look forward to Bartosz's articles because they're rock-solid
| sources of information and the visualizations are both easy-to-
| understand and surprisingly light on performance. It's all
| shockingly digestible.
|
| Honestly, as popular science writing goes, this is art as far
| as I'm concerned, and art is best when it comes from a place of
| passion and conviction, something AI will never be able to
| reproduce.
| estsauver wrote:
| I think it's actually already there. It's definitely possible
| to make these sorts of explainers with something like a Claude
| Code, you just have to spend a fair amount of time making sure
| that it's actually doing what you expect it to do. I think the
| biggest danger with something like a Claude Code is that you
| get something that looks functionally correct but that the
| details are suddenly wrong on. I wrote a little bit about this
| on my blog for some of the places that I've done visualizations
| actually, and I think it's remarkably easy to iterate on them
| now.
|
| https://estsauver.com/blog/scaling-visualizations
| moralestapia wrote:
| Hey, that's a pretty great article! Thanks for sharing.
|
| (I hope you don't get downvoted by Chichanowski's fanboys.
| Sad to see people being _against_ innovation, on this site of
| all places.)
|
| I think it's only a matter of time, AI history has been a
| cycle of "yeah, but it will never do this", then literal
| weeks later it does it, lol.
|
| We should think about how each part of the iteration cycle
| you describe can be improved. This is definitely a problem
| that can be solved!
| jkubicek wrote:
| Good rule of thumb: it should take less time to consume content
| than it does to create it.
|
| I don't know how long it takes Ciechanowski to create these
| explainers, probably a few months? It shows and it's well worth
| spending your time reading through his content meticulously.
|
| How long does it take for an LLM to crap out an equivalent
| explainer? 60 seconds? You should be spending less time than
| that reading it.
| tolerance wrote:
| In order to be taken serious I feel like statements like this
| need to be qualified with who the claimant is imagining to be
| responsible for generating the anticipated output. The 'A' in
| AI isn't for 'autonomous'.
|
| Bartosz Ciechanowski could generate an explainer like this
| using Claude _today_ if he wanted to. But would he? If someone
| like him had the mind to do it then they could instead. But
| where's it at? These types may hold themselves to a standard
| above this method. No shame in that.
| underdeserver wrote:
| Should be (2024).
| MarleTangible wrote:
| I was excited for a moment, and wondered why the RSS feed
| didn't work, but later realized that the article is from 2024.
| greenavocado wrote:
| Where can I find more articles where things are explained in this
| manner?
| burkaman wrote:
| https://ciechanow.ski/archives/
| ubj wrote:
| The author of the Airfoil article has made several similar
| tutorials on various topics:
|
| https://ciechanow.ski/archives/
|
| For machine learning, Distill.pub has some excellent hands-on
| tutorials. For example, here's one on momentum:
|
| https://distill.pub/2017/momentum/
| matsemann wrote:
| https://explorabl.es collects various
| lloeki wrote:
| https://ncase.me/projects/
|
| And going kinda meta, learning about the principles:
|
| https://worrydream.com/LadderOfAbstraction/
|
| https://vimeo.com/906418692
| colechristensen wrote:
| Ok that's long, one top line thing people tend to miss in these
| flying explanations is that airfoil shape isn't about some
| special sauce generating lift. A flat plate generates any amount
| of lift you want just fine. Airfoil design is about the ratio of
| lift to drag most importantly and then several more complex
| effects but NOT just generating lift. (stall speed, performance
| near and above the speed of sound, laminar/turbulent flow in
| different situations, what you can fit inside the wing, etc)
| Stevvo wrote:
| Umm no, at zero degrees AoA as the first diagram on the page
| shows, a flat plate does not generate lift. But nobody actually
| questions that a flat shape can generate lift; we all made
| paper planes as a kid.
| wat10000 wrote:
| There are about a million places incorrectly "explaining"
| that airfoils create lift because the top path is longer and
| this means the air has to go faster. A flat plate would not
| create lift in that case. The fact that paper airplanes
| obviously can fly somehow never stops people from repeating
| this.
| kqr wrote:
| Paper airplanes do not have barndoor wings, though. Most of
| them have stepped camber through the way they are folded.
|
| It's not finished but I started writing this to clarify:
| https://entropicthoughts.com/paper-airplane-aerodynamic-
| stab...
|
| Scroll down to "trim and angle of attack".
|
| (I hope there's nothing embarrassing in there. It's an old,
| early draft.)
| colechristensen wrote:
| Uncambered airfoils also don't generate lift at zero degrees.
| What constitutes "0" for curved airfoils is convenience. You
| want lift, you put a flat plate on an angle, anything fancier
| is for Lift/Drag, Thrust/Weight, etc.
| andrewla wrote:
| But every airfoil has an equilibrium angle of attack (not
| always stable with velocity) where it generates zero lift.
| The chordal angle of attack is for convenience because it
| depends only on airfoil geometry and not ambient velocity,
| but it isn't a fundamental physical property of the airfoil.
|
| If we treat the angle where zero lift is generated as the
| base angle for an airfoil, then all airfoils generate lift
| depending on their angle relative to that, including a flat
| plane. As the GP says, other properties are the dominant
| factor in airfoil geometry.
|
| When introducing airfoils I think it is more useful to start
| from a plane than a traditional airfoil shape; the math and
| intuitions are much clearer from there.
| colechristensen wrote:
| And with steady level flight symmetrical airfoils are flown
| at an angle, a cambered airfoil shape being flown at 0
| degrees angle of attack vs its chord line would be an
| unusual coincidence. Wings are mounted at a small angle
| relative to the direction of thrust and what one would
| define as a flat line on the fuselage.
| ge96 wrote:
| Was gonna say where is the debate of bernouli vs. AoA/pforce
| (p-factor), scatter blast shotgun hitting bottom of wing
| roncesvalles wrote:
| Exactly. Airfoil is an optimization. There is a common
| misconception that planes wouldn't get off the ground if you
| didn't have airfoil. No, most of the lift (depends on the plane
| but in the ballpark of 80-90%) comes from the overall shape of
| the wings. ~20% is from leading edge airfoil deflection
| dynamics.
|
| And if, say, airfoil was never discovered, we'd probably design
| the whole wing slightly differently to compensate for it, so
| the actual difference wouldn't even be 20%.
|
| Airfoil is about as important as winglets, and planes fly
| without winglets just fine. But nobody points to winglets and
| says that's the crucial bit that makes the whole thing work.
| colechristensen wrote:
| Two ratios dominate aircraft design. Lift/Drag, Thrust/Weight
|
| To get off the ground Lift > Weight, Thrust > Drag, or to
| simplify to stay aloft Lift = Weight, Thrust = Drag
|
| Bigger engines weigh more.
|
| To get off the ground you need an engine powerful enough to
| overcome the drag necessary to generate enough lift.
|
| That is what enabled powered flight especially at the
| beginning. Wing design with a good enough lift to drag ratio
| and engine+propeller design that had a good enough thrust to
| drag ratio to come together for more lift than the aircraft
| weighed.
| chrisweekly wrote:
| I was obsessed with fighter jets in my adolescence. My
| favorite plane was the F-15 Eagle; its thrust:weight ratio
| was greater than 1 -- meaning it could take off, point its
| nose straight up to vertical, and keep accelerating past
| mach 1. Amazing.
| hypertexthero wrote:
| The F-15C (and the F-16), yes.
|
| The F-15E was a different story, which I remember from
| flamewars at flightsim forums over how slow of a climber
| it was :)
| gf000 wrote:
| There is an interactive simulation on the page with a simple
| plane showing exactly this.
| carabiner wrote:
| HERE WE GO AGAIN...
| somat wrote:
| It is probably obvious, so obvious that no one starts with it?
| but it took me an absurdly long time to put together that an
| airplane lifts by moving air down.
|
| Admittedly there is an amazing amount of fluid-dynamic subtly
| on top of this simple Newtonian problem. But I am surprised
| that almost no one starts with "An airplane produces lift by
| moving air down, for steady flight it needs to move exactly as
| much air mass down as the plane weighs. here are the
| engineering structures that are used to do this and some
| mathematical models used to calculate it"
| ActorNightly wrote:
| To be more specific,
|
| You can't escape momentum exchange. To generate an upward
| force, the airplane must exert a downward force on the air
| molecules.
|
| An airfoil does this more efficiently than a flat plate,
| essentially using the top shape to create a low pressure area
| that sucks the air over the top downwards, imparting the
| downwards momentum, along with deflecting the air downward on
| the bottom surface. A flat plate pitched upwards "stalls" the
| air on the top surface, because the air has to travel forward
| some to fill the gap by the plate moving forward - so this
| creates a lot of drag as the plate is imparting more forward
| momentum on the air.
|
| The issue is that to analyze lift using momentum, you have to
| do statisitcal math on a grid of space around the airfoil,
| which is super complex. So instead, we use concept of pressure
| with static and dynamic pressure differences creating lift,
| because it makes sense to most people learning this, which then
| all gets rolled up into a plot of lift coefficient vs angle of
| attack.
|
| And as you dive deeper, you learn more analysis tools. For
| example, there is also another way to analyze performance of an
| airfoil more accurately, which is called vorticity. If you
| subtract the average velocity of the airflow around an airfoil,
| the vector field becomes a circle. In vector math, the total
| curl of the vector field is directly correlated to the
| effective lift an airfoil can produce. This method accounts for
| any shape of the airfoil.
|
| But under the hood its all momentum.
| colechristensen wrote:
| Nearly everything you wrote here is inspired by reality and
| mostly incorrect.
| mellisacodes wrote:
| wait what? this is goood!
| huqedato wrote:
| That's the missing course for the first year of any Aerospace
| Engineering faculty.
| random_duck wrote:
| I wish there was an infinite number of blogs that where this
| good.
| nntwozz wrote:
| Bartosz Ciechanowski, the gift that keeps on giving.
| nvitas wrote:
| He usually posts these brilliant explanations once or twice a
| year but nothing in 2025. I hope he finds the time to continue
| because the lessons are really really brilliantly told.
| darksaints wrote:
| This is absolutely amazing.
|
| For those of us programming nerds that want to play with
| aerodynamics, I can't recommend AeroSandbox enough. While the
| code is pretty obviously written for people who know their way
| around aerodynamics and not so much around programming, it is
| remarkably powerful. You can do all sorts of aerodynamic
| simulations and is coupled with optimization libraries that allow
| you to do incredible aerodynamic optimizations. It comes included
| with some pretty powerful open weight neural network models that
| can do very accurate estimates of aerodynamic characteristics of
| airfoils in a fraction of the time that top tier heuristic
| solvers (like xfoil) can do (which are already several orders of
| magnitude faster than CFD solvers).
|
| https://github.com/peterdsharpe/AeroSandbox
| Wistar wrote:
| Oh man. This guy. His work is simply some of the best explanation
| content I have ever seen
| robshippr wrote:
| This is so cool. I've become more interested in aerodynamics
| since I've started watching F1 and reading Adrian Newey's book.
| This is such a great post, especially the diagrams in the
| velocity section.
| seemaze wrote:
| I say it every time it pops up; I'm a huge fan of ciechanow.ski!
|
| They should receive an unlimited grant to produce educational
| content for the digital generation's benefit.
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(page generated 2026-01-28 23:00 UTC)