5/20/2025 at 4:44:41 PM
by rbrownmh
5/20/2025 at 8:47:51 PM
Figure I'd drop this here - some other projects I'm working on currently:Seafloor LOD (infinite terrain generator): https://github.com/kanakawai-maui/seafloor-lod
Olelo Honua (free LLM-enabled translation tool): https://www.olelohonua.com/
by rbrownmh
5/20/2025 at 8:27:53 PM
For those of us who didn't know what these were, you can specify a 4 digit code that corrrelates with an airfoil shape, and here's how it works.by observationist
5/21/2025 at 8:57:32 AM
This is very fun - here's a small feature request: add the ability to define KFM airfoils.https://en.wikipedia.org/wiki/Kline–Fogleman_airfoil
I experiment with these airfoil designs and it would be very nice to have a smooth way to see the various efficiencies/inefficiencies of various dimensions of KFM airfoil.
by aa-jv
5/20/2025 at 5:00:27 PM
I have a background in fluid dynamics and may be interested in helping with this. Is there a way for me to contact you?by hbrav
5/20/2025 at 5:13:09 PM
Do you have Reddit by chance? Feel free to DM me u/Creative_Walrus_5197by rbrownrw8
5/20/2025 at 5:13:33 PM
(and I'll give you my email just want to avoid too much spam)by rbrownrw8
5/20/2025 at 5:27:52 PM
I've sent you a message.by hbrav
5/20/2025 at 8:10:54 PM
Oh damn that's trippy how you can move the camera haha I am the airfoil0990 chonker
by ge96
5/20/2025 at 7:05:09 PM
Unless you're planning to resolve the boundary layer and model separation (good luck...), you'd probably be better off using panel methods than NS. Look at XFoil or JavaFoil for available implementations.by addaon
5/20/2025 at 7:08:20 PM
Also, it looks like you might have a bug in generating the airfoil shape. An airfoil like the 8412, while extreme, is well-defined and constructible from NACA-style combination of thickness and camber forms; but you show it as having a "kink" on the bottom surface, which is definitely not correct.by addaon
5/20/2025 at 8:24:56 PM
841220 is interesting, if you want to see what a borg cube aerodynamics might look like.by observationist
5/20/2025 at 9:53:08 PM
841220 is, sadly, not a legal NACA airfoil designator.There are three major families of procedurally-defined NACA airfoils -- four-digit like the 2412, five-digit like the 23012, and the 6-series like the 64A012.
It looks like this site only expects the four-digit form, and is mis-parsing anything other than that -- which is a pity, because one of the uses of a tool like this is to get a sense of /why/ the 23012 is similar CLmax to the 2412, but with lower moment and a more sudden stall. If nothing else, input validation is necessary!
by addaon
5/20/2025 at 11:26:14 PM
Added validation and looking into fully supporting the 5 digit codes - thanks for the feedback!by rbrownmh
5/20/2025 at 8:36:08 PM
LOL and it's also completely verticalby rbrownmh
5/20/2025 at 8:40:17 PM
Good catch - I'll look into fixing this. thanks!by rbrownmh
5/20/2025 at 9:56:45 PM
Yep. If you're generating them yourself, you'll probably want to be careful to follow the NACA method for combining camber and thickness profiles -- basically, running a circle of thickness-profile-defined diameter along the camber line and unioning the areas. The alternative (which is these days sometimes called the Riblett approach) is just to define the airfoil as the camber line plus or minus half the thickness vertically at each point -- which often leads to better airfoils for many purposes, but will disagree with available NACA data, especially w.r.t. nose radius (and thus, critical angle for airfoils which stall near the nose).If the goal is to allow a user to compare the properties of different airfoils, there's a lot to get right to make sure they actually know what airfoils they're comparing. The alternative is to allow airfoil selection from one of these sites [1][2], which also allow a link to provide comparative analysis.
[1] https://m-selig.ae.illinois.edu/ads/coord_database.html [2] https://bigfoil.com/
by addaon
5/20/2025 at 11:27:51 PM
I may have fixed 8412 :)by rbrownmh
5/20/2025 at 8:38:28 PM
I just pushed an update using spalart-allmaras turbulence model (somewhere in between NS and panel methods). Also updated the controls to use arrow keys :)by rbrownmh
5/21/2025 at 5:21:46 PM
Notes re: CFD, Navier Stokes,"Deep Learning Poised to ‘Blow Up’ Famed Fluid Equations" https://news.ycombinator.com/item?id=31049608
https://github.com/chennachaos/awesome-FEM4CFD?tab=readme-ov...
>> Numerical methods in fluid mechanics: https://en.wikipedia.org/wiki/Numerical_methods_in_fluid_mec...
jax-cfd mentions phiflow
jax-cfd > Other awesome projects: https://github.com/google/jax-cfd#other-awesome-projects
PhiFlow: https://github.com/tum-pbs/PhiFlow/
We had a monochrome green aerodynamic simulation app literally on floppy disks in middle school in approximately 1999 that was still cool then. IIRC various keyboard keys adjusted various parameters of the 2d hull that was tested to eventually - after floppy disc noises - yield a drag coefficient.
TIL that the teardrop shape maximizes volume and minimizes drag coefficient, but some spoiler wings do generate downward lift to maintain traction at speed.
A competitive game with scores and a leaderboard might be effective.
...
Navier-Stokes for compressible and incompressible fluids, but it's a field of vortices with curl so SQG/SQR Superfluid Quantum Gravity / Relativity has Gross-Pitaevskii for modeling emergent dynamics like fluidic attractor systems in exotic states like superfluids and superconductors and supervacuum.
TIL the mpemba effect says that the phase diagram for water is incomplete because one needs the initial water temperature to predict the time to freeze or boil; those have to be manifold charts like HVAC.
There's a Gross-Pitaevskii model of the solar system; gravity results in n-body fluidic vortices which result in and from the motions of the planets and other local masses.
/?hnlog "CFD" :
From "FFT-based ocean-wave rendering, implemented in Godot" https://news.ycombinator.com/item?id=41683990 :
> Can this model a fluid vortex between 2-liter bottles with a 3d-printable plastic connector?
> Curl, nonlinearity, Bernoulli, Navier-Stokes, and Gross-Pitaevskii are known tools for CFD computational fluid dynamics with Compressible and Incompressible fluids.
> "Ocean waves grow way beyond known limits" (2024-09) https://news.ycombinator.com/item?id=41631177#41631975
Also, recently I learned that longitudinal waves in superfluids (and plasmas) are typically faster than transverse standing waves that we observe in fluid at Earth pressures.
by westurner