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Modelling with many circles in a rectangle

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Old   October 31, 2007, 03:50
Default Dear Doug, Since I have only
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ZHOU Bin
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Dear Doug,
Since I have only several days to finish meshing, I would like to accept your advise, using hex for my case. I'll let you know my progress.
Thank you.
Zhou Bin
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Old   October 31, 2007, 04:43
Default Dear Doug, I am really impr
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Tommaso Lucchini
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Dear Doug,

I am really impressed by the capabilities of Blender and Calculix together and I would like to start using them as meshing tools.

Before starting, I have a couple of curisosities about them:

1) Are you using them for only 2d meshes or also 3d?
2) Which kind of geometries are you modelling?
3) Could you post a couple of images of some meshes?
4) What about the mesh quality (skewness/non-orthogonality)?

Thanks a lot,

Bye
Tommaso
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Old   October 31, 2007, 05:23
Default Doug, I forgot the last qu
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Tommaso Lucchini
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Doug,

I forgot the last question: have you ever tried meshing STL surfaces with Blender?

Thanks again,

Tommaso
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Old   October 31, 2007, 06:24
Default Dear Doug, When I install Cal
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Dear Doug,
When I install Calculix, and go ahead one by one according to the installation, but at step 8, after I type: cgx -b dummy.fbd.
the system tells me that: the input file dummy.fbd can not be opened.
I stop here and have done this for two days.
Kindly,
Zhou Bin
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Old   October 31, 2007, 07:40
Default Tommaso, Q1) Are you using
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Doug Baldwin
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Tommaso,

Q1) Are you using them for only 2d meshes or also 3d?

A1) Blender for 2-D compound curve surface, then extrude in Calculix for 3-D external flow.

Q2) Which kind of geometries are you modeling?

A2) Concave/convex surfaces, beginning to use what has been called manifolds for joining multiple meshes. The Python tool I posted in a separate thread works great for external flow over uniformly convex bodies of revolution.

Q3) Could you post a couple of images of some meshes?

A3) Everything I have done is private. I'm currently working overtime on one project. Perhaps in the next month I'll have free time to create a public example.

Q4) What about the mesh quality (skewness/non-orthogonality)?

A4) For highly curved surfaces where extrusion is not orthogonal, I can pass all meshCheck except nonOrthogonal warnings. I must iterate between Blender/Calculix/OpenFOAM to achieve this quality, and its becoming faster for me so that maybe in about 4-5 iterations I have a high quality mesh. Also, subsurf in Blender has generated one or two warped surfaces warnings. For flat surfaces with orthogonal extrusion, no errors or warnings.

Q5) STL?

Q5) I once imported an STL into Calculix, extruded it, then meshed it with hex. Looked kinda funny, even passed meshCheck, but I didn't run the solver. Blender has the ability to import/output an STL, which I have used on occasion as a template for creating a subsurf with square elements. I prefer square and hex.

Doug
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Old   October 31, 2007, 07:47
Default Zhou Bin, > input file dumm
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Zhou Bin,

> input file dummy.fbd can not be opened.

This is correct. Calculix needs a filename to start running. If you then create geometry in Calculix and Save, your geometry will be saved in dummy.fbd . This and more is covered in the tutorial that is provided with Calculix.

Doug
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Old   November 1, 2007, 17:16
Default Dear Doug, Here we have a fes
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Dear Doug,
Here we have a festival in Italy, so I'm sorry I could not reply you immediately.
Now I can see that this is not a problem, and I can go ahead. Thank you.
By the way, the geometry you post entitled "
Image of surface mesh" is quite well, and I'd like to use this way, but afterwards you post on Saturday, October 13, 2007 - 12:11 pm, the mesh is different.
Because at first the circle is made from rectangle, How you make another rectangle around the circle for mesh in your first case? Or just like the usual way?
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Old   November 1, 2007, 17:30
Default Dear zhoubin, are you worki
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Dear zhoubin,

are you working with OpenFOAM and Blender in Italy? Is it possible to know which is your company/university?

Thanks a lot,

Tommaso
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Old   November 2, 2007, 03:27
Default Dear Tommaso: I am a student
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Dear Tommaso:
I am a student here in Politecnico di Torino, nice to meet you.
Best regards,
Zhou Bin
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Old   November 2, 2007, 08:14
Default Zhou Bin, Good. The square
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Doug Baldwin
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Zhou Bin,

Good. The square around the square allows you to control the mesh at the boundary of the circle. That too is the way I'd do it. The simple technique is to set the Pivot to Midpoint, in Edit Mode select one square, then press the "E"-key to Extrude. Press <escape> so that the extruded square keeps the same dimensions as the original square, then press the "S"-key to scale the square about the midpoint pivot. I'm on travel through mid-next week. You should be able to locate a tutorial on Extrusion. The one trick not usually taught is <esc>, then S-key to scale the extrusion.

Doug
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Old   November 2, 2007, 11:26
Default Dear Doug, First have a nice
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Dear Doug,
First have a nice trip.
I'll show you what I have done during your trip next week.
Best regards,
Zhou Bin
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Old   November 18, 2007, 21:35
Default Dear Doug, OpenFOAM has a p
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Dear Doug,

OpenFOAM has a period of no function, and between this time, I have posted my current situation here.

Now, I want to tell you that I have solved the problem of 4 z just as you said. Really thank you.

After I select the boundary with the command qadd and qrem, I have many files, however, in the 4 files: boundary, cells, faces and points, I could not find the boundary I selected. But in the files I saved, which is named as "holewithin.fbb".

Do you generate the file "boundary" which can contain the selected boundary?

Best regards,

Zhou Bin
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Old   November 18, 2007, 21:47
Default Dear Doug, in the parent di
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Dear Doug,

in the parent directory of project, I input: checkMesh .project, but an information tells me: FOAM FATAL ERROR:Wrong number of arguments, expected 2 found 1.

I don't know if you have this kind of problem or not?

Best regards,

Zhou Bin
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Old   November 19, 2007, 09:38
Default I check the mesh from Calculix
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I check the mesh from Calculix to openfoam, but I get the following information:
root@openfoam:~/OpenFOAM/root-1.4.1/run# checkMesh .filter
/*---------------------------------------------------------------------------*\
| ========= | |
| \ / F ield | OpenFOAM: The Open Source CFD Toolbox |
| \ / O peration | Version: 1.4.1 |
| \ / A nd | Web: http://www.openfoam.org |
| \/ M anipulation | |
\*---------------------------------------------------------------------------*/

Exec : checkMesh .filter
Date : Nov 19 2007
Time : 14:17:22
Host : openfoam
PID : 6527

Usage: checkMesh <root> <case> [-parallel] [-fullTopology] [-cellDeterminant] [-pointNearness] [-latestTime] [-time time]


--> FOAM FATAL ERROR : Wrong number of arguments, expected 2 found 1


FOAM exiting

After several hours check, I still could not find the reason.
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Old   November 19, 2007, 12:01
Default Dear Zhou, you should run:
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Dear Zhou,

you should run:

checkMesh . filter

and not

checkMesh .filter

bye
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Old   November 20, 2007, 04:59
Default Dear Tommaso, Last night I
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Dear Tommaso,

Last night I had the same solution like you suggest, this morning I tried, and I got:

----------------------------------
Exec : checkMesh . filter
Date : Nov 20 2007
Time : 08:00:07
Host : openfoam
PID : 5462
Root : /home/zhou/OpenFOAM/root-1.4.1/run
Case : filter
Nprocs : 1
Create time


--> FOAM FATAL IO ERROR : cannot open file

file: /home/zhou/OpenFOAM/root-1.4.1/run/filter/system/controlDict at line 0.

Function: regIOobject::readStream(const word&)
in file: db/regIOobject/regIOobjectRead.C at line: 66.

FOAM exiting
------------------------------------

I'm searching and thinking about this problem.

Best regards,

Zhou Bin
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Old   November 20, 2007, 06:22
Default Dear Tommaso, I have solved t
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Dear Tommaso,
I have solved this problem, and I would like to post it here, hope it is useful for others:

I copy controlDict from icoFoam, then I change some parameters inside use "gedit ..."

Now it is ok.

Best regards,

Zhou Bin
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Old   November 27, 2007, 05:30
Default Dear Doug, I am very glad t
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Dear Doug,

I am very glad to tell someone else who has the similar model with me that:

after I use gmsh for meshing, I am impressed by the power of gmsh---- a powerful tool with simple platform.

I could control the mesh around each circle very easily and mesh them for one click.

Sincerely thank you for introducing me Blender for a long way.
Best regards,

Zhou Bin
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