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Old   November 11, 2010, 02:27
Default Co-axial rotor help
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Jason Eason
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Does anyone know if any of the openfoam software simulate and co-axial helicopter? I have the both rotors, but I don't know if there is a way to rotate them in the opposite directions simultaneously. Any and all help would be greatly appreciated.
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Old   November 11, 2010, 03:20
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Masashi Ohbuchi
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Hi,

There is no dynamicFvMesh class suitable for your problem.
So, you have to make custom dynamicFvMesh class using examples from mixerGgiFvMesh that support only one rotating region.

Good luck!
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Old   November 11, 2010, 03:50
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Hi,

looks like a job for GGI this means you have to use the -DEV version of OpenFOAM.

The other solutions would be the overset Grid (but this piece of software is not available to ordonary people)http://web.student.chalmers.se/group...SlidesOFW5.pdf
or "immersed boundary method" that is currently under development.

If you use a debian/ubuntu based distribution you can get compiled binaries
https://launchpad.net/%7Ecae-team/+a...s_filter=lucid
otherwise you have to use svn and check out the -DEV version of OpenFOAM.
Takes a little more time, but not that complicated.

Or you try a virtual machine / live DVD/ live usbstick =>read
OpenFOAM-dev Live USB DVD, based on kubuntu
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Old   November 11, 2010, 16:46
Default Co-axial rotor
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Vojtech Betak
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Hi,

I have solved the same problem a year ago and I used MRFSimpleFOAM for the solution of it.

Vojta
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Old   November 12, 2010, 01:13
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Jason Eason
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Ohbuchi, How easy is it to modify that particular file? Is that 1 file all i need to modify?

Vojta, MRFSimpleFOAM is static, and only shows pressure on the rotors, I want to see airflow pressure changes. I've tried that before.

Thank you all for your quick replies and help.
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Old   November 13, 2010, 10:33
Default Co-axial counter rotating rotors simulation
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Masashi Ohbuchi
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Hi, 

I made custom library "myCoAxialGgiFvMesh" (see attached files), and ran sample case with co-axial counter rotating two rotors.

This implementation is simple extension of mixerGgiFvMesh, I've only introducied two rotating speed (rpm1 and rpm2) and modified movingPointMask.
And the rotating region's name must be fixed as "rotor1" and "rotor2".

In dynamicMeshDict, you should define two moving slider, "moving1"
and "moving2" as follows.


dynamicFvMeshLib "libtopoChangerFvMesh.so";
dynamicFvMesh myCoAxialGgiFvMesh;

myCoAxialGgiFvMeshCoeffs
{
coordinateSystem
{
type cylindrical;
origin (0 0 0);
axis (0 0 1);
direction (1 0 0);
}

rpm1 60;
rpm2 -60;

slider
{
moving1 ( ROTOR1.INLET ROTOR1.OUTLET );
moving2 ( ROTOR2.INLET ROTOR2.OUTLET );
static ( IN.OUTLET INTER.INLET INTER.OUTLET OUT.INLET );
}
}
Attached Images
File Type: jpg WS000074.jpg (30.3 KB, 38 views)
File Type: png WS000075.png (43.3 KB, 42 views)
Attached Files
File Type: gz myCoAxialGgiFvMesh.tar.gz (4.5 KB, 11 views)
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Old   November 14, 2010, 21:14
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Masashi Ohbuchi
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I'm sorry, but I've made some mistake in my code.
It's rotating in twice speed than specified. And it will not work in case of abs(rpm1)<>abs(rpm2).
The bug is in update() function of myCoAxialGgiFvMesh.C
Now I'm fixing it. and I will upload fixed version soon.
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Old   November 15, 2010, 01:35
Default updated library code
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Masashi Ohbuchi
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Here is bug-fixed library code.
I've introduced another movingPointMask for rotor2.
Attached Files
File Type: gz myCoAxialGgiFvMesh.tar.gz (3.3 KB, 12 views)
FrankFlow likes this.
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Old   November 16, 2010, 20:25
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Thank you, Ohbuchi-san, will will implement your program tonight.

Edit: Ohbuchi-san I've combined my to rotors into 1 file. Is it possible to make multiple cellSets from the cellSetDict file? How did you create two diiferent cellZones?
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Last edited by JulytoNovember; November 30, 2010 at 00:11. Reason: Update
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