Aerofoil advice please - Points and Splines

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looo
Posts: 3482
Joined: Mon Nov 11, 2013 5:29 pm

Re: Aerofoil advice please - Points and Splines

Postby looo » Sun Dec 08, 2019 8:28 am

I think it makes sense to start thinking about an airfoil workbench: ;)
https://github.com/looooo/freecad.airfoil

This currently provides methods to:
- import / export foils (.dat files)
- create parametric jukowsky / trefftz, vandevooren, naca airfoils
- create spline foils (2 splines with 9 poles for each side and tangential constraints at the leading edge) [1]
- modify splines (similar to the sketcher) [1]
- calibrate spline-foil given by points (calibrate y-positions and weights of poles. The x-position should be set manually if necessary)[2]

For the future, I will try to use libxfoil [3] to compute the forces acting at the foil. To interpolate the parameter-space (Ncrit, Ma, Re, alpha/cl -> cd, cm) I think about using a neural-network surrogate model.
Additionally, provide methods for drag-minimization (minimize drag for given input-parameters)

But it's still a long way to go, and some of you might disagree with some design limitations (like keeping the number of poles constant for a spline foil, using two splines for upper and lower side ...)

[1]
Bildschirmfoto von 2019-12-08 09-04-36.png
Bildschirmfoto von 2019-12-08 09-04-36.png (9.95 KiB) Viewed 618 times
[2] https://forum.freecadweb.org/viewtopic. ... 10#p343926
[3] https://github.com/montagdude/libxfoil
Last edited by looo on Mon Dec 09, 2019 8:53 am, edited 1 time in total.
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hammax
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Re: Aerofoil advice please - Points and Splines

Postby hammax » Sun Dec 08, 2019 9:42 am

Question:
Will this WB be a pure Python3 application?

And trying to understand theory of:
https://pages.mtu.edu/~shene/COURSES/cs ... ctlpt.html
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looo
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Re: Aerofoil advice please - Points and Splines

Postby looo » Sun Dec 08, 2019 1:45 pm

hammax wrote:
Sun Dec 08, 2019 9:42 am
Question:
Will this WB be a pure Python3 application?
Yes, py2 compatibility is a low priority for me. Theoretical it's possible but dependencies like pandas and scipy will stop py2 support.
a179308
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Re: Aerofoil advice please - Points and Splines

Postby a179308 » Sat Dec 28, 2019 9:37 pm

Hello
I've have started a Air Plane Design Workbench :https://github.com/FredsFactory/FreeCAD_AirPlaneDesign . Available to install in the addon manager, Air Plane Design Workbench V0.1 and V0.2 can create a wings based on panel and profil.
I integrate a NACA 4 and 5 digits in the workbench, and I work now to integrate the ability to translate the workbench.
If you want we can discuss about the integration of our idea in the workbench ?

Fred
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looo
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Re: Aerofoil advice please - Points and Splines

Postby looo » Sun Dec 29, 2019 9:08 am

a179308 wrote:
Sat Dec 28, 2019 9:37 pm
If you want we can discuss about the integration of our idea in the workbench ?
Yes, I think this makes sense. Does your workbench work with discrete airfoils (coordinates) or with bsplines?
a179308
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Re: Aerofoil advice please - Points and Splines

Postby a179308 » Sun Dec 29, 2019 3:28 pm

looo wrote:
Sun Dec 29, 2019 9:08 am
a179308 wrote:
Sat Dec 28, 2019 9:37 pm
If you want we can discuss about the integration of our idea in the workbench ?
Yes, I think this makes sense. Does your workbench work with discrete airfoils (coordinates) or with bsplines?
In fact twice, you can choose if you want to generate Spline or use simply wire based on points (dat file or NACA 3 or 4 digits). I will integrate in the UI some change to edit directly the points and in the next version you can access to all points by the "Geometry" property.
My main objective is to have at the end a parametric rib, and if it possible extract some information to use "PredimRc" : http://rcaerolab.eklablog.com/predimrc-p1144024


Frédéric
a179308
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Re: Aerofoil advice please - Points and Splines

Postby a179308 » Thu Jan 02, 2020 1:00 pm

a179308 wrote:
Sun Dec 29, 2019 3:28 pm
looo wrote:
Sun Dec 29, 2019 9:08 am
a179308 wrote:
Sat Dec 28, 2019 9:37 pm
If you want we can discuss about the integration of our idea in the workbench ?
Yes, I think this makes sense. Does your workbench work with discrete airfoils (coordinates) or with bsplines?
In fact twice, you can choose if you want to generate Spline or use simply wire based on points (dat file or NACA 3 or 4 digits). I will integrate in the UI some change to edit directly the points and in the next version you can access to all points by the "Geometry" property.
My main objective is to have at the end a parametric rib, and if it possible extract some information to use "PredimRc" : http://rcaerolab.eklablog.com/predimrc-p1144024


Frédéric
Hello
I looked at your idea and by combining 3 workbenchess (Image, AirPlaneDesign for generate the Rib and Curved Shapes),
I get this result:
Sirius_2009-Wing.FCStd
(362.66 KiB) Downloaded 54 times
The process is very simple :
0 -Workbench : Image, import 3views and scale it to the right dimension
1 - Workbench : Air plane design, create a rib
Capture d’écran 2020-01-02 à 13.30.14.png
Capture d’écran 2020-01-02 à 13.30.14.png (372.15 KiB) Viewed 402 times
2 - Create two sketch
Capture d’écran 2020-01-02 à 13.31.50.png
Capture d’écran 2020-01-02 à 13.31.50.png (203.84 KiB) Viewed 402 times
The result :
Capture d’écran 2020-01-02 à 13.33.58.png
Capture d’écran 2020-01-02 à 13.33.58.png (70.23 KiB) Viewed 402 times
3 - Workbench : Curved Shapes, "Create an Array" after select the rib and sketches. You can adjust the number of items, if you want a solid or a surface or only ribs.

Sirius_2009-Wing.FCStd
(362.66 KiB) Downloaded 54 times
Capture d’écran 2020-01-02 à 13.34.22.png
Capture d’écran 2020-01-02 à 13.34.22.png (124.43 KiB) Viewed 402 times
don't forget to recompute if you change your rib profile

Next step for me is to develop a wizard in the Air Plane Design Workbench to integrate this approach...

Fred