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ebah6 March 26, 2012 03:11

openFoam 2.1.x: creating AMI patches from a cylinder.
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Dear all,

I am inspiring my self from the pimpleDyMFoam/propeller tutorial to run a case.
But when I create the AMI from an .obj cylinder, the surface is all messed up.

Attached is my picture from paraFoam.

Can some help me out with this.

Thank you all.

linnemann March 26, 2012 07:19

We really need some more info.

How is the mesh created?

It looks like SHM, and if that is the case it looks like either your background mesh is too coarse or the refinement level on the AMI is too low.

On another note to improve stability during simulation it can be a good idea to keep the same refinementlevel on the ami/ggi's to avoid concave faces.

ebah6 March 26, 2012 07:44

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Thank you sir,

I did a lot of "gymnastic" to get the .obj file.
1) create mesh with Pointwise and export it as .cas (i.e fluent)
2) with ANSYS ICEM-CFD I converted it to .stl
3) the use blender to get the .obj extension.

I made a trial by using the .stl file and got the picture attached.

Regarding your suggestions refining the outer box and/or the AMI, I think just need to refine my hex box in the blockMeshDict. How about the the AMI refinement? where should do this?

Please, allow that I ask related question.
a) how do I go and determine the value of startFace in system/changeDictionary?
As of now, I have to run it twice: first I let it crash and give a number that I plug back in and re-run.
b) another issue I have being struggling all along is the inlet and outlet pressure and velocity boundary conditions. could suggest a combination?

My apologies if these questions are too basic, but I am newbie.

linnemann March 26, 2012 07:59

From the propeller tutorial.


            level      (4 4); // this is the refinement
            cellZone    innerCylinderSmall;
            faceZone    innerCylinderSmall;
            cellZoneInside  inside;

I can see you are making a VAWT simulation.

Here is a case I made you can use as inspiration with setup etc.

3D structured VAWT case

This is made using 1.6-ext but its a matter of changing the ggi's to ami's.

PS. VAWT are horrible energy producing devices, don't waste your time on them, other than pure interest.
Try to find a company that's willing to share real world produced energy data.

ebah6 March 26, 2012 13:27

Thank you very much sir.

ebah6 March 26, 2012 18:06

1 Attachment(s)
Hello again,

I have been using the same level of refinement as in the propeller tutorial. And I refined my outer block by 6 times but these right angle features still persist.
May be it is that my .stl geometriy is not good enough. Could you tell me what you used to create you geometries?
Also, if you have lead on the BC setup as I mentioned earlier.

Thank you for your patience.


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