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Comment by WhatsName | Hacker News Reader

I recently wanted to design a flying wing/rc plane. Is there any FOSS to get reasonable results for aerodynamics?

Using a computational fluids model like OpenFOAM is overkill for reasonable estimates of aerodynamic performance and stability, provided you stick to normal-ish designs. The term you want to Google is "vortex lattice" and/or "potential flow" solvers, of which there are many open source softwares available specifically geared towards typical aircraft configurations, with simple, easy to use interfaces.

Some good ones to look at to get started with nice guis

- VSP Aero

- XFOIL (for 2D airfoil analysis only, also generates inputs for 3D VLM solvers)

- AVL

And some others if you want perhaps a little higher fidelity, and don't mind text/code interfaces:

-FreeWake

- Datcom (not technically a potential flow models, but a database)

To get the most value out of these softwares, you will need some background in aeronautics. You need to have an understanding of what a potential flow models can and cannot accurately model. It also helps to have knowledge about what forms aircraft stability/control and performance data is typically communicated in, as these softwares will use that terminology.

I used xfoil in my aerodynamics masters degree, it absolutely good enough for hobby applications

The 2D model alone maybe be sufficient for OPs needs, but I'd advocate for going at least a little further with some form of 3D model. The wing tip effects are significant enough to warrant some form of "next step" after the initial 2D analysis. Although simple algebraic relationships are likely good enough to satisfy this end.

However, the 3D tools above give you a little bit more, that I feel warrant their consideration by the op. These models can yield performance of wing-tail-body configurations that include wake effects. They also can give stability analysis in both longitudinal/lateral axes. The stability effects being especially important if OP wants to design a flying-wing, which are a tad more challenging to get right than just slapping a "good-enough" sized tail on a classic config plane.

For this type of problem, unless you are trying to set range or climb rate records, understanding lift and moment (and control derivatives) is more important than accurately modeling drag. Panel methods shine at this, and are both easier to use and much much faster than CFD — enough that wrapping them in optimizers is trivial. I personally prefer AVL, but there are other open source alternatives as well.

OpenFOAM I think is the go to for open source CFD, although I’ve never tried it myself. There’s also XFOIL which, since you’re talking about a flying wing, might be enough for your use case.

Even for a finicky flying wing, I think if you keep an eye on the way the pitching moment shifts with pitch, I don’t see why picking an airfoil shape for the frame and hand calcs couldn’t get you to a design that flies reasonably.

The usual way is to use a wing with known aerodynamics. Choose one on airfoiltools.com

This project might be exactly what you're looking for:

https://github.com/peterdsharpe/AeroSandbox

This guy seems to have a good handle on diy aero. Both air and water.

https://youtube.com/@rctestflight

Check out: https://ecalc.ch/wingdesigner.htm

Xflr5? OpenFOAM?

I've used neither but I hear others in the gliding and model airplane scene talk about those.

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